'HE UNIVERSITY OF CALIFORNIA 
 
 LIBRDRY OF THE UNIVERSITY OF CUIFORNK 
 
 LIBRII 
 
 HE UNIVERSITY OF CALIFORNIA LIBRARY OF THE UNIVERSITY OF CALIFORNIA LIBRAI 
 
 9i 
 
 
 IHE UNIVERSITY OF CALIFORNIA LIBRARY OF THE UNIVERSITY OF CALIFORNIA LIBRA 
 
IIVERSITY OF CUIFORNU 
 
 LIBRARY OF THE UNIVERSITY OF CALIFORNIA LIBRARY OF 
 
 >ibte? 
 
 J 
 
 IIVERSITY OF CALIFORNIA LIBRARY OF THE UNIVERSITY OF CALIFORNIA LIBRARY OF 
 
 \^/Tb 
 
 UVERSITV OF CHIFORNIA LIBRARY OF THE UNIVERSITY OF CHIFBRNU U8RRt OF 
 
' 
 1 OTthofhombic, 
 
 2 Monoclmic -Tncluxed Dispersion. 
 
 3 jVlono clinic - .Horizontal Dispersion. 
 
 r 
 
 s 
 
 - 
 
 
 r -iic 'Cro'ssed Dispersion.. 
 
 1 SPtcruUi-son, Wewtta vtn, Cl. 
 
A TEXT-BOOK 
 
 OF 
 
 MINERALOGY 
 
 WITH AN EXTENDED TREATISE ON 
 
 CRYSTALLOGRAPHY AND PHYSICAL MINERALOGY. 
 
 b\ 
 
 EDWARD SALISBURY DANA, 
 
 CURATOR OP MINERALOGY, YALE COLLEGE. 
 
 ON THE PLAN AND WITH THE CO-OPERATION 
 OP 
 
 PROFESSOR JAMES D. DANA 
 
 WITH UPWARDS OF EIGHT HUNDRED WOODCUTS ANO "oNE COLORED* 'fr-ATE. 
 
 NEWLY REVISED AND ENLARGED. 
 (HTH EDITION.) 
 
 ' NEW YORK: 
 
 JOHN WILEY & SONS, 
 15 ASTOR PLACE. 
 
 1885, 
 
PMYSIC8 
 
 PHYSICS DfiPT 
 
 COPTRIGHT BT 
 
 EDWARD S. DATTA, 
 
 1877. 
 
PREFACE. 
 
 THE preparation of a "Text-Book of Mineralogy" was undertaken in 
 1868, by Prof. J. D. Dana, immediately after the publication of the fifth 
 edition of the System of Mineralogy. The state of his health, however, 
 early compelled him to relinquish the work, and he was not able subsequently 
 to resume it. Finally, after the lapse of seven years, the editorship of the 
 volume was placed in the hands of the writer, who has endeavored to carry 
 out the original plan. 
 
 The work is intended to meet the requirements of class instruction. With 
 this end in view the Descriptive part has been made subordinate to the 
 more important subjects embraced under Physical Mineralogy. 
 
 The Crystallography is presented after the methods of Naumann ; his 
 system being most easily understood by the beginner, and most convenient 
 for giving a general knowledge of the principles of the Science. For use 
 in calculations, however, it is much less satisfactory than the method of 
 Miller, and a concise exposition of Miller's System has accordingly been 
 added in the Appendix. The chapter on the Physical Characters of Min- 
 erals has been expanded to a considerable length, but not more than was 
 absolutely necessary in order to make clearly intelligible the methods of 
 using the principles in the practical study of crystals. For a still fuller 
 discussion of these subjects reference may be made to the works of Schrauf 
 and of Groth, and for details in regard to the optical characters of mineral 
 species to the Mineralogy of M. DesCloizeaux. 
 
 The Descriptive part of the volume is an abridgment of the System of 
 Mineralogy, and to that work the student is referred for the history of each 
 upecies and a complete list of its synonyms ; for an enumeration of ob- 
 served crystalline planes, and their angles ; for all published analyses ; 
 
 665366 
 
IV PREFACE. 
 
 for a fuller description of localities and methods of occurrence, and also foi 
 an account of many species of uncertain character, not mentioned in the 
 following pages. 'A considerable number of changes and additions, how- 
 over, have been made in the preparation of the present work, made neces- 
 sary by the progress in the Science, and among these are included many 
 new species. The chemical formulas are those of modern Chemistry. The 
 new edition of Rammelsberg's Handbuch der Mineralchemie has been 
 often used in the preparation of the volume, and frequent references to him 
 will be found in the text. 
 
 The work has throughout been under the supervision of Prof. Dana, and 
 all the proofs have passed under his eye. Acknowledgments are also due 
 to Prof. G. J. Brush and Prof. J. P. Cooke for friendly advice on manj 
 points. 
 
 PREFACE TO THE REVISED EDITION. 
 
 IN this Revised Edition, the chief additions are contained in four sup- 
 plementary chapters, covering about fifty pages. Of these, two are devoted 
 to descriptions of new instruments and methods of research in Crystallog- 
 raphy and Physical Mineralogy; and the others to brief descriptions of 
 the minerals recently announced, and a concise statement of important 
 new facts in regard to the characters or occurrence of old species. A 
 number of new figures are introduced in illustration of these subjects. 
 The work has been repaged ; and a new index, much more complete than 
 the former one, has been added. 
 
 >!EW HAVEN, January, 1883. 
 
TABLE OF CONTENTS. 
 
 INTRODUCTION. 
 
 F A. R, r r i. 
 
 PHYSICAL MINERALOGY. 
 Section I. CRYSTALLOGRAPHY. 
 
 FAOB 
 
 DESCRIPTIVE CRYSTALLOGRAPHY 1-83 
 
 General Characters of Crystals 1 
 
 Descriptions of some of the Simpler Forms of Crystals 3 
 
 Systems of Crystallization 8 
 
 Laws with reference to the Planes of Crystals 10 
 
 I. Isometric System 14 
 
 II. Tetragonal System 25 
 
 III. Hexagonal System 31 
 
 IV. Orthorhombic System 41 
 
 V. Monoclinic System 47 
 
 VI. Triclinic System 50 
 
 MATHEMATICAL CRYSTALLOGRAPHY 51 
 
 Methods of Calculation in General . 53 
 
 Special Methods of Calculation in the different Systems 62 
 
 Measurement of the Angles of Crystals 83 
 
 COMPOUND OR TWIN CRYSTALS 88 
 
 IRREGULARITIES OF CRYSTALS 102 
 
 CRYSTALLINE AGGREGATES. Ill 
 
 PSEUDOMORPHOUS CRYSTALS 113 
 
 Section I. SUPPLEMENTARY CHAPTER. 
 Improved Instruments for the Measurement of the Angles of Crystals 115 
 
 Section II. PHYSICAL CHARACTERS OF MINERALS. 
 
 I. COHESION AND ELASTICITY i!9 
 
 Cleavage and Fracture 119 
 
 Hardness 1-0 
 
 Tenacity 121 
 
 II. SPECIFIC GRAVITY 123 
 
 III. LIGHT 125 
 
 Fundamental Principles of Optics 125 
 
 Distinguishing Optical Characters of Crystals of the different Systems 135 
 
 Isometric Crystals 135 
 
 Uniaxial Crystals 136 
 
 Biaxial Crystals 144 
 
 Diaphaneity ; Color 161 
 
 Lustre. . . 167 
 
Vi TABLE OF CONTENTS. 
 
 PAGE 
 
 IV. HEAT .................................................................... 168 
 
 V. ELECTRICITY MAGNETISM ................................................... 169 
 
 VI. TASTE AND ODOR ............................................ .............. 171 
 
 Section II. SUPPLEMENTARY CHAPTER. 
 
 I. COHESION AND ELASTICITY ................................................... 173 
 
 II. SPECIFIC GRAVITY .......................................................... 173 
 
 III. LIGHT ......................................... ........................ 177 
 
 Determination of Indices of Refraction .................................... 177 
 
 Polarization Instruments .................................... ........... 178 
 
 Discussion of the Various Explanations offered for Observed " Optical Anoma- 
 
 lies " of Crystals .................................................... 185 
 
 II. 
 CHEMICAL MINERALOGY. 
 
 Chemical Constitution of Minerals ____ . ........................................... 191 
 
 Dimorphism ; Isomorphism ...................................................... 199 
 
 Chemical Examination of Minerals : 
 
 In the Wet Way ........................................................ 202 
 
 In the Dry Way ; Blowpipe Analysis ..................................... 203 
 
 III. 
 DESCRIPTIVE MINERALOGY. 
 
 Classification of Mineral Species .................................................. 215 
 
 Description of Mineral Species .......................... * ........... . .......... 221-419 
 
 Supplementary Chapter ...................................................... 420-440 
 
 APPENDIX A. Miller's System of Crystallography .................................. 441 
 
 APPENDIX B. On the Drawing of Figures of Crystals .............................. 463 
 
 APPENDIX C. Catalogue of American Localities of Minerals ........................ 473 
 
 APPENDIX C. Supplementary Chapter ............................................ 503 
 
 GENERAL INDEX. . , 
 
INTRODUCTION. 
 
 THE Third Kingdom of Nature, the Inorganic, embraces all species nut 
 organized by living growth. Unlike a plant or animal, an inorganic spe- 
 cies is a simple chemical compound, possessing unity of chemical and physi- 
 cal nature throughout, and alike in essential characters through all diversity 
 of age or size. 
 
 The Science of Mineralogy treats of those inorganic species which occur 
 ready formed in or about the earth. It is therefore but a fragment of the 
 Science of Inorganic nature, and it owes its separate consideration simply 
 to convenience. 
 
 The Inorganic Compounds are formed by the same forces, and on the same principles, 
 whether produced in the laboratory of the chemist or in outdoor nature, and are strictly no 
 more artificial in one case than in the other. Calcium carbonate of the chemical laboratory 
 is in every character the same identical substance with calcium carbonate, or calcite, found 
 in the rocks, and in each case is evolved by nature's operations. There is hence nothing 
 whatever in the character of mineral species that entitles them to constitute a separate 
 division in the natural classification of Inorganic species. 
 
 The objects of Mineralogy proper are three-fold : 1, to present the true 
 idea of each species ; 2, to exhibit the means and methods of distinguishing 
 species, which object is however partly accomplished in the former ; 3, to 
 make known the modes of occurrence and associations of species, and their 
 geographical distribution. 
 
 In presenting the science in this Text Book, the following order is 
 adopted : 
 
 I. PHYSICAL MINERALOGY, comprising that elementary discussion with 
 regard to the structure and form, and the physical qualities essential to a 
 right understanding of mineral species, and their distinctions. 
 
 II. CHEMICAL AND DETERMINATIVE MINERALOGY, presenting briefly the 
 general characters of species considered as chemical compounds, also giving 
 the special methods of distinguishing species, and tables constructed for this 
 purpose. The latter subject is preceded by a few words on the use of the 
 blow-pipe. 
 
 III. DESCRIPTIVE MINERALOGY, comprising the classification and descrip- 
 tions of species and their varieties. The descriptions include the physical 
 and chemical properties of the most common and important of the minerals, 
 
Vlll INTRODUCTION. 
 
 with some account also of their association and geographical distribution. 
 The rarer species, and those of uncertain composition, are only very briefly 
 noticed. 
 
 Besides the above, there is also the department of Economic Mine] alogy, which is not hero 
 included. It treats of the uses of minerals, (1) as ores; (2) in jewelry ; and (3) in the coarser 
 arts. 
 
 The following subjects connected with minerals properly pertain to Geology : 1, Lithdo- 
 gical geology, or Lithohgy, which treats of minerals as constituents of rocks. 2, Chemical 
 geology, which considers in one of its subdivisions the origin of minerals, as determined, in 
 the light of chemistry, by the associations of species, the alterations which species are liable 
 to, or which they are known to have undergone, and the general nature, origin, and changes 
 of the earth's rock formations. Under chemical geology, the department which considers 
 especially the associations of species, and the order of succession in such associations, has 
 received the special name of the par agenesis of minerals ; while the origin of minerals or 
 rocks through alteration, is called metamorphism or pseudomorphism, the latter term being 
 restricted to those cases in which the crystalline form, and sometimes also the cleavage, of 
 a mineral is retained after the change. 
 
LITEKATUKE. 
 
 For a catalogue of mineralogical works, and of periodicals, and transactions of Scientific 
 Societies in which mineralogical memoirs have been and are published, reference is made to 
 the System of Mineralogy (1868), pp. xxxv-xlv., Appendix II. (18 T4), and Appendix III. 
 ^1882). The following works, however, deserve to be mentioned, as they will be found use- 
 ful as books of reference. 
 
 In CRYSTALLOGRAPHY 
 
 Naumann. Lehrbuch der reinen und angewandten Krystallographie. 2 vols., 8vo. 
 Leipzig, 1829. 
 
 Naumann. Anfangsgrtinde der Krystallographie. 2d ed., 292 pp., 8vo. Leipzig, 1854. 
 
 Naumann. Elemente dertheoretischen Krystallographie. ii83 pp., 8vo. Leipzig, 1856. 
 
 Miller. A Treatise on Crystallography. Cambridge, 1889. 
 
 Grailich. Lehrbuch der Krystallographie von W. H. Miller. 328 pp., 8vo. Vienna, 1856. 
 
 Kopp. Einleitung in die Krystallographie. 348 pp., 8vo. Braunschweig, 1862. 
 
 Von Lang. Lehrbuch der Krystallographie. 358pp., 8vo. Vienna, 18(>i5. 
 
 Quenstedt. Grundriss der bestimmenden und rechnenden Krystallographie. Tubingen, 
 1873. 
 
 Rose-Sadebeck. Elemente der Krystallographie. Cd ed., vol. i., 181 pp., 8vo. Berlin, 
 1873. Vol. ii., Angewandte Krystallographie. 284 pp., 8vo. Berlin, 1876. 
 
 Schrauf. Lehrbuch der Physikalischen Mineralogie. Vol. i., Krystallographie. 251 
 pp., 8vo., 1866 ; vol. ii., Die angewandte Physik der Krystalle. 426 pp. Vienna, 1868. 
 
 Grroth. Physikalische Krystallographie. 527pp., 8vo. Leipzig, 1876. 
 
 Klein. Einleitung in die Krystallbercchnung. 39o pp., 8vo. Stuttgart, 1876. 
 
 Mallard. Traite de Cristallographie geometrique et physique, vol. i. Paris, 1876. 
 
 Bauerman. Text-Book of Systematic Mineralogy. Vol. i., 367 pp , 12mo. London. 
 1881. 
 
 LieUsch. Geometrische Krystallographie. 464 pp., 8vo. Leipzig, 1881. 
 
 Tschcrmak. Lehrbuch der Mineralogie. Lief. I., II., pp. 1-308. Vienna, 1881-82. 
 _ In PHYSICAL MINERALOGY the works of Schrauf (1868), and Grotli (1870), and TschermaJc, 
 titles as in the above list. Reference is also made to the works on Physics, mentioned on 
 p. 160. In addition to these, on pp. Ill, 122, 160, 167, 171, 190, a few memoirs of especial 
 importance on the different subjects are enumerated. 
 
 In CHEMICAL MINERALOGY : ftammelsbera^Haridbuch der Mineral chemie, 2d ed., Leipzig, 
 1875. In Determinative Mineralogy, Brush, New York, 1878. 
 
 In DESCRIPTIVE MINERALOGY : among recent works those of Brooke and Miller (2d ed. of 
 Phillips' Min.), London, 1852; Quenstedt, 3d ed., Tubingen, 1877; Schrctuf, Atlas der 
 Krystallformen, Lief. I.-V., 1871-1878 ; Grotli (Tabellarische Uebersicht der Mineralien, 
 etc.), 2d ed., 1882; v. Kokscharof, Materialien zur Mineralogie Russ lands, vol. i., 1865, 
 vol. viii., 1881 ; Des Cloizeaux, vol. i., 1862, vol. ii., Paris, 1874; Dana, System of Miner- 
 alogy, 1888, App. I., 1872, App. II., 1874, App. III., 1882; Blum, 4th ed., 1874; Nau- 
 mann-Zirkel, llth ed., 1881. 
 
 The following publications are devoted particularly to Mineralogy : 
 
 Jahrbuch fiir Mineralogie ; G. Leonhard and H. B. Geinitz, Editors ; after 1879, E. W. 
 Benecke, C. Klein, and H. Rosenbusch. 
 
 Mineralogische Mittheilungen ; commenced 1872, G. Tschermak, Editor ; since 1878, 
 published as the Mineralogische und Petrographische Mittheilungen. 
 
 Mineralogical Magazine and Journal of the Mineralogical Society ; London, and Truro, 
 Cornwall. Commenced 1875. 
 
 Zcitschri-ft fiir Krystallographie ; P. Groth. Editor ; Leipzig. Commenced 1876. 
 
 Bulletin de la Societe Mineralogique de France. Commenced 1878. 
 
 ABBKEYIATIONS. 
 
 For abbreviations of the names of Mineralogical works, of Journals, publications of 
 Scientific Societies, etc., see System Min., 5th ed., pp. xxxv.-xlv., App. III., p. viii. 
 The following abbreviations are used in the Description of Species. 
 
 B.B. Before the Blowpipe (p. 210). Obs. Observations on occurrence, etc. 
 
 Comp. Composition. O.F. Oxidizing Flame (p. 204). 
 
 Diff. Differences, or distinctive characters. Pyr. Pyrognostics. 
 
 G. Specific Gravity. Q. Ratio. Quantivalent Ratio (p. 198). 
 
 Germ. German. R.F. Reducing Flame (p. 204). 
 
 H. . Hardness. Var. Varieties. 
 
 An asterisk (*), appended to the name of a mineral species in the Descriptive part of this 
 work, indicates that additional facts in regard to it are mentioned in the Supplementary 
 Chapter, pp. 420 to 440. 
 
 ix 
 
I. 
 
 PHYSICAL MINERALOGY. 
 
 THE grand departments of the science here considered are the following 
 1. STRUCTURE. Structure in Inorganic nature is a result of mathemati- 
 cal symmetry in the action of cohesive attraction. The forms produced 
 are regular solids called crystals ; whence morphology is, in the Inorganic 
 kingdom, called CRYSTALLOLOGY. It is the science of structure in this king - 
 dom of nature. 
 
 2. PHYSICAL PROPERTIES OF MINERALS, or those depending on relations to 
 light, heat, electricity, magnetism ; on differences as to density or specific 
 gravity, hardness, taste, odor, etc. 
 
 Crystallology is naturally divided into, I. CRYSTALLOGRAPHY, which treats 
 of the forms resulting from crystallization ; II. CRYSTALLOGENY, which de- 
 scribes the methods of making crystals, and discusses the theories of their 
 origin. Only the former of these two subjects is treated of in this work. 
 
 SECTION L v. ,_;FGS^; * 
 
 CRYSTALLOGRAPHY. 
 
 Crystallography embraces the consideration of (1) normally formed or 
 regular crystals ; (2) twin or compound crystals ; (3) the irregularities of 
 crystals ; (4) crystalline aggregates ; and (5) pseudomorphous crystals. 
 
 1. GENERAL CHARACTERS OF CRYSTALS. 
 
 (1) External form. Crystals are bounded by plane surfaces, 
 called simply planes or faces, symmetrically arranged in refer- 
 ence to one or more diametral lines called axes. In the an- 
 nexed figure the planes 1 and the planes i are symmetrically 
 arranged with reference to the vertical axis c c ; and also the 
 planes of each kind with reference to the three transverse axes. 
 
 (2) Constancy of angle in, the same species. The crystals of 
 
 any species are essentially constant in the angle of inclination w 
 between like planes. The angle between 1 and i, in a given 
 species, is always essentially the same, wherever the crystal is found, and 
 whether a product of natfcre or of the laboratory. 
 
CRYSTALLOGRAPHY. 
 
 (3) Difference of angle of different species. The crystals of different 
 species commonly differ in angles between corresponding planes. The 
 angles of crystals are consequently a means of distinguishing species. 
 
 (4) Diversity of planes. While in the crystals of a given species there 
 is constancy of angle between like planes, the forms of the crystals may be 
 exceedingly diverse. The accompanying figures are examples of a few of 
 
 the forms of the species zircon. There is hardly any limit to the number of 
 forms which may occur ; yet for each the angles between like planes are 
 essentially constant. 
 
 Crystals occur of all sizes, r frpm the merest microscopic point to a yard or more in diame- 
 ter. , A single crystal pir qnart$, now at Milan, is three and a quarter feet long, and five and a 
 half in /circumference 5 ^Tnji'VtS weight is estimated at eight hundred and seventy pounds. 
 A single davity in a vein of quartz near the Tiefen Glacier, in Switzerland, discovered in 
 1867, h?,s r affoide(?. fifni(ky Tjivartz crystals weighing in the aggregate about 20,000 pounds ; a 
 co^.d^r^Vjle.iiuVnber'.cC? r ttfe- P slRgle r crystals having a weight of 200 to 850 pounds, or even 
 more/ One of the gigantic beryls from Acworth, New Hampshire, measures four feet in 
 length, and two and a half in circumference; and another, at Graf ton, is over four feet long, 
 and thirty-two inches in one of its diameters, and does not weigh less than two and a half 
 tons. But the highest perfection of form and transparency are found only in crystals of 
 small size. 
 
 In its original signification the term crystal was applied only to crystals of quartz (f. 1), 
 which the ancient philosophers believed to be water congealed by intense cold. Hence the 
 term, from Kpv<Tra\\os t ice. 
 
 (5) Symmetry in the position of planes. The planes on the crystals 
 of any species, however numerous, are arranged in accordance with certain 
 laws of symmetry and numerical ratio. If one of the simpler forms be 
 taken as a primary QY fundamental form, all other planes will be secondary 
 planes, or modifications of the fundamental form. It should be observed, 
 however, that the forms called primary and fundamental in crystallographic 
 description, are in general merely so by assumption and for convenience 
 of reference. (See also p. 12.) 
 
 Cleavage. Besides external symmetry of form, crystall zation produces 
 also regularity of internal structure, and often of fracture. This regular- 
 ity of .fracture, or tendency to break or cleave along certain planes, is called 
 cleavage. The surface afforded by cleavage is oijpi smooth and brilliant. 
 The directions of cleavage are those of least cohesive force in a crystal ; it 
 
CRYSTALLOGRAPHY. 3 
 
 is not to be understood that the cleavage lamellae are in any sense present 
 before they are made to appear by fracture. 
 
 In regard to cleavage, two principles may be here stated : (a) In any 
 species, the direction in which cleavage takes place is always pa rallel to 
 some plane which either actually occurs in the crystals or may exist there 
 in accordance with the general laws which will be stated hereafter. 
 
 (b) Cleavage is uniform as to ease parallel to all like planes ; that is, if 
 it may be obtained parallel to one plane of a kind (as 1, f. 1), it may be ob- 
 tained with equal facility parallel to each of the other planes 1 ; and will 
 afford planes of like lustre. This is in accordance with the symmetry of 
 crystallization. It will be evident from this that the angles between planes 
 of like cleavage will be constant : thus, a mass of calcite under the blow of 
 a hammer will separate into countless rhombohedrons, each of which aiforda 
 on measurement the angles 74 55' arid 105 5'. In a shapeless mass of 
 marble the minute grains have the same regularity of cleavage structure. 
 See further, p. 119. 
 
 2. DESCRIPTIONS OF SOME OF THE SIMPLER FORMS OF CRYSTALS. 
 
 PRELIMINARY DEFINITIONS. Angles. In the descriptions of crystals three 
 kinds of angles may come under consideration, solid, plane, arid inter/a- 
 cial. The last are the inclinations between the faces or planes of crystals. 
 
 Axes. The crystallographic axes are imaginary lines passing through 
 the centre of a crystal. They are assumed as axes in order to describe, by 
 reference to them, the relative positions of the different planes. One of 
 the axes is called the vertical, and the others the lateral ; the number of 
 lateral axes is either two or three. The axes have essentially the same re- 
 lative lengths in all the crystals of a species ; but those of different species 
 often differ widely 
 
 Diametral planes. The planes in which any two axes lie are called the 
 axial or diametral planes or sections ; they are the coordinate places of an- 
 alytical geometry. They divide the space about the centre into sectants; 
 into eight sectants, called octants, if there are but two lateral axes, as is 
 generally the case ; but into twelve sectants if there are three, as in hexa- 
 gonal crystalline forms. 
 
 Diagonal planes are either diagonal to the three axes, as those through 
 the centre connecting diagonally opposite solid angles of a cube, oi diag- 
 onal to two axes, and passing through the third, as those connecting diag- 
 onally opposite edges of the cube. 
 
 Similar planes and edges are such as are similar in position, and of like 
 angles with reference to the axes or axial planes. Moreover, in the case of 
 similar edges, the two planes by whose intersection the edges are formed, 
 meet at the same angle of inclination. For example, all the planes and 
 edges of the tetrahedron (f. 9), regular octahedron (f. 11), cube (f. 14), 
 rhombic dodecahedron (f. 19), are similar. In the rhombohedron (f. 16) 
 there are two sets of similar edges, six being obtuse and six acute. 
 
 Solid angles are similar when alike in plane angles each for each, and 
 when formed by the meeting of planes of the same kind. 
 
 A combination-edge fc&the edge formed by the meeting or intersection of 
 two planes. 
 
CRYSTALLOGRAPHY. 
 
 Truncations, bevelments. In a crystal, an edge or angle h said to be re* 
 placed when the place of the edge or angle is occupied bj one or more 
 planes ; and in the case of the replacement of an edge, the replacing 
 planes make parallel intersections with the including planes, that is. with 
 the direction of the replaced edge (f. 43). 
 
 A replacement of an edge or angle is a truncation when the replacing 
 plane makes equal angles with the including planes. Thus, in f. 6, i-i 
 truncates the edge between / and / 
 
 An edge is said to be bevelled when it is replaced by two similar planes, 
 that is, by planes having like inclinations to the adjoining planes. Thus, 
 in f. 5, the edge between 3, 3, is bevelled by the two planes 3-3, 3-3, the right 
 3-3 and 3 having the same mutual inclination as the left 3-3 and 3. So, 
 in f. 192, p. 43, the edge between /and /is bevelled by the planes 1-2, i-2. 
 Truncations and bevelments of edges take place only between similar 
 planes. Thus 1, /, and 3, 3, are similar planes in fig. 5. The edge i|i might 
 be truncated or bevelled, for the same reason ; but not the edge between 1 
 and 1, since 1 and 1 are dissimilar planes. 
 
 A zone is a series of planes in which the combination-edges or mutual 
 intersections zxz parallel. Thus, in fig. 3, the planes 1, 3, /make a vertical 
 zone; so in f. 8, the planes between 1 and i-i make a zone, and this zone 
 actually continues above and below, around the crystal ; in f. 5, the planes 
 3, 3-3, 3-3, 3 are in one zone ; and i-i, /, i-i, /, in another. On the true 
 meaning of zones, see p. 53. 
 
 The above explanations are preliminary to the descriptions of the forms 
 of all crystals. 
 
 A. FORMS CONTAINED UNDER FOUR 
 
 EQUAL TRIANGULAR PLANES. A. Regu- 
 lar tetrahedron (f. 0). Edges six ; solid 
 angles four. Faces equilateral trian- 
 gles, and plane angles therefore 60. 
 Interfacial angles 70 31/ 44". Named 
 from reTjoa/a?, four times, and e'S/ja, 
 face. 
 2. Sphenoid (f. 10). Faces isosceles triangles, not equilateral. Plane and 
 
 interfacial angles varying ; the latter of two kinds, (a) two terminal, (b) four 
 
 lateral. Named from <r$P ) a wedge. 
 
 B. FORMS CONTAINED UNDER EIGHT TRIANGULAR PLANES. The solids 
 here included are called octahedrons, from OKTCLKIS, eight times, and eSpa, 
 face. They have twelve edges ; and six solid angles. One of the axes, 
 when they differ in length, is made the vertical axis ; and the others are 
 the lateral axes. The solid angles at the extremities of the vertical axes are 
 the vertical or terminal solid angles ; the other four are the lateral. The 
 four edges meeting in the apex of the terminal solid angle are the terminal 
 edges ; the others, the lateral or basal edges. 
 
 1. Regular Octahedron (f. 11). Faces equilateral triangles. Interfacial 
 angles 109 28' 16" ; angle between the planes over the apex of a solid 
 angle 70 31' 44" ; angle between edges over a solid angle 90. The three 
 axes are equal, and hence either may be made the vertical. Lines connect- 
 ing the centres of opposite faces are called the octahedral or trigonal inter- 
 
CRYSTALLOGRAPHY. 
 
 tixf,8 / and those connecting the centres of opposite edges the dodecaheJlral 
 or r/iombic interaxes. 
 
 2. Square Octahedron (f. 12, f. 12A). Faces equal isosceles triangles, 
 not equilateral. The four terminal edges are equal arid similar ; aiid so 
 also the four lateral. 
 
 12A 
 
 The lateral axes are equal / the vertical axis may be longer or shorter 
 than the lateral. 
 
 3. The rhoinbic octahedron (f. 13) differs from the square octahedron in 
 having a rhombic base, arid consequently the three axes are unequal. The 
 basal edges are equal and similar ; but, owing to the unequal lengths of 
 the lateral axes, the terminal edges are of two kinds, two being shorter 
 and more obtuse than the other two. 
 
 C. FORMS CONTAINED UNDER six EQUAL PLANES. The forms here in- 
 cluded have the planes parallelograms ; the edges are twelve in number 
 Aind equal ; the solid angles eight. 
 
 1. Cube (f . 14). Faces equal squares, and plane angles therefore 90. 
 The twelve edges similar as well as equal ; the eight solid angles similar and 
 equal. Intel-facial angles 90. The three axes equal and intersecting at 
 right angles. 
 
 Lines connecting the apices of the solid angles are the octahedral or tri- 
 gonal interaxes, and those connecting the centres of opposite edges the 
 dodecahedral ox rhombic interaxes. If the cubic axis (=edge of the cube) 
 = 1, then the dodecahedral interaxes = 1/2 =1.414:21; and the octahedral 
 interaxes == \/3 1.73205. Arid if the dodecahedral axis = 1, then the 
 octahedral = 1.224745. 
 
 U 
 
 If a cube is placed with the apex of one angle vertically over that diagonally opposite, that 
 Is, with an octahedral interaxis vertical, the parts are all symmetrically arranged around 
 tni& vertical axis. In this position (f. 15) the cube has three planes inclined toward one apex, 
 and three toward the other ; it has three terminal edges meeting at each apex ; and six late- 
 ral edges situated symmetrically, but in a zigzag, around the vertical axis. If lines are 
 drawn connecting the centres of the opposite lateral edges, and these are taken as the lateral 
 axes, the lateral axes, three in number, will lie in a plane at right angles to the vertical, and 
 will intersect at the centre at angles of 60. The cube placed in this position would then have 
 
6 CRYSTALLOGRAPHY. 
 
 one vertical and three equal lateral axes ; and as the lateral ax as correspond tojbhe dodeca 
 hedral interaxes of a cube, the ratio of a lateral axis to the vertical is 1 : 1.224745. 
 
 2. Rhombohedron (f. 16 to 18). Faces equal rhombs. The twelve edges 
 of two kinds ; six obtuse, and six acute. Solid angles of two kinds ; two 
 symmetrical, consisting each of three equal plane angles ; the other six un- 
 eymmetwcal, the plane angles enclosing them being of two kinds. 
 
 The rhombohedron resembles a cube that has been either shortened, or 
 lengthened, in the direction of one of the octahedral axes, the former mak- 
 ing an obtuse rhombohedron, the latter an acute; and it is in position when 
 this axis is vertical, the parts being situated symmetrically about this axis, 
 as in the second position of the cube above described. In an obtuse rhom- 
 bohedron (f. 16, 17), the terminal solid angles are bounded by three obtuse 
 plane angles, and the other six, which are the lateral, by two acute and one 
 obtuse ; the six terminal edges (three meeting at each apex) are obtuse, and 
 the six lateral edges are acute. Conversely, in an acute rhombohedron (f. 
 18) the terminal angles are made up of acute plane angles, and the lateral 
 of two obtuse and one acute ; the six terminal edges are acute, and the six 
 lateral obtuse. The axes are a vertical, and three lateral ; the lateral axes 
 connect the centres of opposite lateral edges and intersect at angles of 60. 
 The cube in the second position (f. 15) corresponds to a rhombohedron 
 of 90, or is intermediate between the obtuse and the acute series. 
 
 D. FORMS CONTAINED UNDER TWELVE EQUAL PLANES. 1. 
 llhonibic Dodecahedron (f. 19). Faces rhombs, with the 
 plane angles 109 28' 16", 70 31' 44". Edges twenty-four, 
 all similar; interfacial angle over each edge 120. Solid 
 angles of two kinds : (a) six acute tetrahedral, being formed 
 of four acute plane angles; and (b) eight obtuse trihedral, 
 being formed of three obtuse plane angles. Angle between 
 planes over apex of tetrahedral solid angle, 90 ; angle between 
 edges over the same 109 28' 16". The axes three, equal, 
 rectangular, and therefore identical with those of the regular octahedron 
 and cube. The dodecahedral interaxes connect the centres of opposite 
 faces ; and the octahedral the apices of the trihedral solid angles. Named 
 from &wSe/ca, twelve, and e'Spa, face. 
 
 2. Pyramidal dodecahedron, or Quartzoid. (Called 
 also Dihexagonal Pyramid, Isosceles Dodecahedron.) 
 Faces isosceles triangles, and arranged in two pyramids 
 placed base to base (f . 20). Edges of two kinds : twelve- 
 equal terminal, and six equal basal; axes, a vertical, differ-' 
 ing in length in different species; and three lateral, equal, 
 situated in a plane at right angles to the vertical, and in- 
 tersecting one another at angles of 60, as in the rhombo- 
 hedron. 
 
 E. PRISMS. Prismatic forms consist of at least two sets 
 of planes, the basal planes being unlike the lateral. The bases are always 
 equal ; and the lateral planes parallelograms. The vertical axis is unequal 
 to the lateral, (a) Three-sided prism. A right (or erect) prism, having 
 its^ bases equal equilateral triangles, (b) Four-sided prisms. Four sided 
 prisms are either right (erect), or'oblique/the former having the vertical axis 
 
CRYSTALLOGRAPHY. 
 
 at right angles to the base or to the plane of the lateral axes, and the latter 
 oblique. 
 
 1. Square or Tetragonal Prism (f. 21, ,22V Base a square; lateral 
 planes equal. Edges of two kinds : (a) eight basal, equal, each contained 
 between the base and a lateral plane ; (b) fan? lateral, contained between the 
 equal lateral planes. Interfacial angles all 90, plane angles 90. Solid 
 angles eight, of one kind. Axes : a vertical, differing in length indifferent 
 species, and longer or shorter than the lateral ; two lateral, equal, at right 
 angles to one another and to the vertical, and connecting either the centres 
 of opposite lateral planes (f. 21) or edges (f. 22). The cube is a square 
 prism with the vertical axis equal to the lateral. 
 
 22 
 
 24 
 
 ii 
 
 2. Eight Rhombic Prism (f. 23). Base a rhomb ; lateral planes equal 
 parallelograms. Edges of three kinds : (a) eight basal, equal, and rectan- 
 gular as in the preceding form ; (b) two lateral, obtuse ; and (c) two lateral, 
 acute. Solid angles of two kinds ; (a) obtuse at the extremities of the ob 
 tuse edge, and (b) acute at the extremities of the acute edge. Axes rect- 
 angular, unequal ; a vertical ; a longer lateral, the maorodiagonal axis 
 (named from yua/c/>o9, large), and a shorter lateral, the brachydiagonal axis 
 (named from /3pa^u9, short). 
 
 3. Eight Rectangular Prism (f. 24). Base a rectangle, and in conse- 
 quence of its unequal sides, two opposite lateral planes of the prism are 
 broader than the other two. Edges all rectangular, but of three kinds : 
 (a) four longer basal ; (b) four shorter basal ; (a) four lateral. Axes con- 
 necting the" centres of opposite faces, rectangular, unequal ; a vertical, a 
 macrodiagonal, and a brachy diagonal, being like those of the right rhom- 
 bic prism. In the rectangular prism, either of the faces may be made the 
 basal, and either axis, consequently, the vertical. 
 
 4. Oblique Prisms. Figs. 25 and 26 represent prisms oblique in the 
 direction of one axis. As seen in them, the vertical axis c is oblique to the 
 lateral axis , called the dinodiagonal axis ; but b, the orthodiagonal axis, 
 is at right angles to both c and d. Similarly, the axial sections cb, # are 
 mutually oblique in their inclinations, while ca, cb and ca, ba are at right 
 angles. The dinodiagonal section ca is called the section or plane of sym- 
 metry. 
 
 The form in f. 25 is sometimes called an oblique rhombic prism. The 
 edges are of two kinds as to length, but of four kinds as to interfacial angles 
 over them : (a) four basal obtuse ; (b) four basal acute ; (c) two lateral ob- 
 tuse : (d) two lateral acute. The prism is in position when placed with the 
 dinodiagunal section vertical. 
 
 Figs. 27 and 28 show the doubly oblique, or oblique rhomboidal prism, 
 in which all the axes, and hence all the axial sections, are oblique to each 
 
CRYSTALLOGRAPHY. 
 
 other. All these cases will receive further attention in the description of 
 actual crystalline forms. 
 
 25 26 27 28 
 
 The prisms (in f. 21, 24, 26, 28) in which the planes are parallel to tho 
 three diametral sections, are sometimes called (Jiainetral prisms. This 
 term also evidently includes the cube. The planes which form these 
 diametral prisms are often called pinacoids. The terminal plane is the 
 basal pinacoid, or simply base ; also, in f. 24 the plane (lettered ^-1) parallel 
 to the macrodiagonal section is called the macropinacoid, and the plane (i-i) 
 parallel to the brachy diagonal the Irachypinacoid. In f. 26 the plane (i-i) 
 parallel the\tb ortho-diagonal section is called the orthopinacoid, and the 
 plane (i-i) parallel to the clinodiagonal section the chnopinacoid. The 
 word pinacoid is from the Greek TrtWf, a board. 
 
 (c). SIX-SIDED PRISM. The Hexagonal prism. 
 Base an equilateral hexagon. Edges of two 
 kinds : (a) twelve basal, equal and similar, (b) six 
 lateral, equal and similar ; interfacial angle 
 over the former 90, ove.r the latter 120. Solid 
 angles, twelve, similar. Axes: a vertical, of 
 different length in different species ; three late- 
 ral equal, intersecting at angles of 60, as in the 
 rhombohedron, and the dihexagonal pyramid or 
 quartzoid, connecting the centres either of the lateral edges (f . 29), or lateral 
 faces (f. 30). 
 
 3. SYSTEMS OF CRYSTALLIZATION. 
 
 The systems of crystallization are based on the mathematical relations of 
 the forms ; the axes are lines assumed in order to exhibit these relations, 
 they mark the degree of symmetry which belongs to each group of forms, 
 and which is in fact the fundamental distinction between them. The num- 
 ber of axes, as has been stated, is either three or four the number being 
 four when there are three lateral axes, as occurs only in hexagonal forms. 
 
 Among the forms with three axes, all possible conditions of the axes exist 
 both as to relative lengths and inclinations ; that is, there are (as has been 
 exemplified in the forms which have been described), (A) among ortho- 
 metric kinds, or those with rectangular axial intersections ; (a) the three 
 axes equal ; (b) two equal, and the other longer or shorter than the two ; (c) 
 the three unequal ; and (B) among clinometrio kinds, one or more of the 
 intersections may be oblique (in all of these the three axes are unequal). 
 The systems are then as follows : 
 
 A. Axes three ; orthometric. 
 
 1. ISOMETRIC SYSTEM. Axes equa". Examples,, cube, regular octahe- 
 dron, rhombic dodecahedron 
 
CRYSTALLOGRAPHY. 9 
 
 ^ 2. TETRAGONAL SYSTEM. Lateral axes equal ; the vertical a varying axis 
 Ex., square prism, square octahedron. 
 
 3. OBTHORUOMBIO SYSTEM. Axes unequal. Ex., right rhombic prism< 
 rectangular prism, rhombic octahedron. 
 
 B. Axes three; clinometric. 
 
 1. MONOCLINIC SYSTEM. Axes unequal ; one of the axial intersection 
 oblique, the other two rectangular. Ex., the oblique prisms (f. 25, 26). 
 
 2. TRICLINIG SYSTEM. Axes unequal ; three of the axial intersections ob- 
 lique. Ex., oblique rhomboidal prism (f. 27, 28). 
 
 C. Axes four. HEXAGONAL SYSTEM. Three lateral axes eqnal, intersect- 
 ing at angles of 60. The vertical axis of variable length. Example, 
 hexagonal prisms (f. 29, 30). 
 
 The so-called Diclinic system (two oblique axes) is not known to occur, for the single sub- 
 stance, an artificial salt, supposed to crystallize in this system has been shown by von Zepha- 
 rovich to be triclinic. Moreover, von Lang, Quenstedt, and others have shown mathemati- 
 cally that there can be only six distinct systems. 
 
 The six systems may also be arranged in the following groups: 
 
 1. Isometric (from ttro?, equal, and /uerpoi/, measure), the axes being all 
 equal; including: I. ISOMETRIC SYSTEM. 
 
 2. Isodiametric, the lateral axes or diameters being equal; including: 
 II. TETRAGONAL SYSTP:M ; III. HEXAGONAL SYSTEM. 
 
 3. Anisometric (from aVt<ro?, unequal, etc.), the axes being unequal ; in- 
 cluding : IV. ORTHORHOMBIO SYSTEM; V. MONOCLINIG SYSTEM ; VI. TRI- 
 CLINIC SYSTEM. 
 
 A further study of these different systems will show that in group 1 
 the crystals are formed or developed alike in all three axial directions; in 
 group 2 the development is alike in the several lateral directions, but un- 
 like vertically-; and in group 3 the crystals are formed unlike in all three 
 directions. These distinctions are of the highest importance in relation to 
 the physical characters of minerals, especially their optical properties, and 
 are often referred to beyond. 
 
 The numbers (in Roman numerals) here connected with the names of the system are often 
 used in place of the names in the course of this Treatise. 
 
 The systems of crystallization have been variously named by different authors, as follows : 
 
 1. ISOMETRIC. Teasularof Mohs and Haidinger ; Isometric of Hausmann ; Teaser al of Nau- 
 xnaun ; Regular of Weiss and Rose ; Cubic of Dufrenoy, Miller, Des Cloizeaux ; Monometric of 
 the earlier editions of Dana's System of Mineralogy. 
 
 2. TETRAGONAL. Pyramidal of Mohs ; Viergliedriege, or Zwei-und-einaxige, of Weiss ; 
 Tetragonal of Naumann ; Monodimetric of Hausmann ; Quadratic of von Kobell ; Dimetric of 
 early editions of Dana's System. 
 
 3. HEXAGONAL. Rhombohedral of Mohs ; Sechsgliedrige, or Drei-und-einaxige of Weiss; 
 Hexagonal of Naumann ; Monotrimetric of Hausmann. 
 
 4. ORTHORHOMBIC. Prismatic, or Orthotype, of Mohs; Ein-und-einaxige of Weiss; 
 Rhombic and Anisometric of Naumann ; Trimetric and OrtJwrJiombic of Hausmann ; Trimtt- 
 ric of earlier editions of Dana's System. 
 
 5. MONOCLTNIC. Hemiprismatic and Hemiorthotype of Mohs ; Zwei-und-ringUederige of 
 Weiss; Monodinohcdral of Naumann ; Clinorhombic of v. Kobell, Hausmann, Des Cloizeaux; 
 Augitic of Haidinger ; Oblique of Miller; Monosymmetrio of Grobh. 
 
 6. TRICLINIC. Tetarto-prismatic of Moha ; Ein-und-dngliederige of Weiss ; Tndinohedral 
 of Naumanu ; Clinorhomboidal of v. Kobell ; Anorthic of Haidinger and Miller ; Anortluc, 01 
 Doubly Oblique, of Des Cloizeaux ; Asymmetric, of Groth. 
 
10 
 
 CE FSTALLOGK APHT. 
 
 4. LAWS WITH REFERENCE TO THE PLANES OF CRYSTALS- 
 
 The laws with reference to the positions of the planes of crystals are two; 
 first, the law of simple mathematical ratio; sevoudly,tkelaw of symmetry. 
 
 1. THE LAW OP SIMPLE MATHEMATICAL RATIO. 
 
 The cry stall ographic axes afford the means, after the methods oJ analyti- 
 cal geometry, of expressing with precision the relative positions of the 
 planes of crystals, and so exhibiting the mathematical ratios pertaining to 
 crystallization. These axes, as has been stated, are supposed to pass through 
 the centre of the crystal, and every plane must intersect one, two, or three 
 of them. The position of a plane is obviously determined by the position 
 
 of the points in which it meets these axes. 
 Thus the plane ABC, f . 31, meets the 
 three axes at the points A, B, and C, and 
 its position is determined by the dis- 
 tances O A, O B, O C, intercepted be- 
 tween these points and the centre O. 
 Similarly the plane A B D meets the 
 axes in the points A, B, and D, and its 
 position is determined by the distances 
 O A, O B, O D ; and in the same manner 
 with any other plane. On the crystals 
 of a given species the occurring planes 
 have exact numerical relations to each 
 other, and it is to show these relations 
 that certain lengths of the axes are 
 assumed as units. Thus, in the case 
 already given if O C, O B, O A, or more 
 briefly c, #, #, are the lengths of the 
 axes* (strictly speaking semi-axes) for a 
 given species, then the position of the 
 
 first plane is expressed by Ic : 15 : 10 ; that of the second by 2c : 15 : \a 
 (if OD=2OC), and still another plane might be 2c : 25 : 1, and so on. 
 Consequently the general position of any plane may be expressed by 
 me : no : rafy or more simply me : nb : #, as every plane is for simplicity 
 supposed to meet one of the axes at the unit distance. In the first case 
 mentioned above, m =1 and n 1 ; but in general m and n may vary in 
 value from zero to infinity. The law of simple mathematical ratio, how- 
 ever, requires that m and n, which express the ratios in the lengths of the 
 axes, should be invariably rational numbers, and in general they are either 
 whole numbers or simple fractions. 
 
 This principle may be stated as follows : 
 
 The position of the planes in a given crystal is related in some simple 
 ratio to the relative lengths of the axes. 
 
 * The vertical axis is throughout called c, see p. 53. 
 
 f It is more usual, and analytically more correct,Jbo write this expression ra : nb : me ; 
 but as the usual symbols take the form m-n, the order of the terms used here and elsewhere 
 La more convenient. 
 
CRYSTALLOGRAPHY. 
 
 11 
 
 This subject will become clear in the subsequent study of die different 
 crystalline forms; in passing, however, reference maybe made 
 to f. 32 (zircon) as a single example. The planes lettered 1 
 and 3 have respectively the positions, Ic : lb : la, and 3c : Ib : la, 
 and in the second case the vertical axis has exactly three times 
 the length of that of the former ; any such multiples as 2.93 or 
 3.07 are crystallographically impossible. It is this principle 
 which makes crystallography an exact mathematical science. 
 Some apparent exceptions, such as occasionally occur, do not at 
 all set aside this rule. 
 
 The expression me : nb : a is called the symbol of a plane, as it expresses 
 its exact mathematical position, and the values of 7n and n are called its 
 parameters. If a plane intersects two of the axes, but not the third, it 
 is parallel to it, and mathematically it is said to cut it at infinity (oo ) ; 
 hence the general expression for a plane parallel to the vertical axis c (as in 
 f . 33) will be GO c : nb : a, or GO c : b : na, according as a or b is taken as 
 the unit ; for a plane parallel to the lateral axis b (as in f. 34), it will be 
 mo : oo b : a ; ^if parallel to the lateral axis a (as in f. 35), mo : b : oo a. 
 
 If a plane is parallel to two axes, b and#, that is, intercepts these axes at 
 
 33 
 
 34 
 
 "' 
 
 
 
 
 /\ 
 
 / "., 
 
 
 
 >1 
 
 / / 
 
 ~^""i 
 
 
 y 
 
 1 
 
 / / to/' 
 
 ^_2 r , 
 
 _-.-- 
 
 
 
 
 V 
 
 V 
 
 an infinite distance, its position is expressed by c : oo b : oo a, as is illus- 
 trated by f. 36 ; again, its position is expressed by oo c : I : oo 0, if parallel 
 to G and a ; and by oo c : oo b : a, if parallel to c, b. These may also be 
 written Oc : fl : <z, etc. 
 
 The following important principle 
 should be kept in mind. The relative 
 not the absolute position of any plane 
 has to be regarded, and hence all 
 planes parallel to each other are 
 crystallographically identical. A 
 plane on the angle of the cube is the 
 same, if the mutual inclinations re- 
 main unchanged, whether large or 
 small, for, though the actual distances 
 cut off on the axes may differ in each 
 case, the ratios of these axes are iden- 
 tical. Again, in f. 37, the three planes, 
 4c : 45 : 20, and 2c : 25 : a, and c : 
 b : \a are identical, for the ratios 
 of the three axes are the s^me 
 throughout, the planes being of course 
 parallel. Similarly the symbol Ic : %b : %a may 
 
 be written Zc : b : 
 
|2 CRYSTALLOG EAPHY. 
 
 and c : oo I : oo a is the same as Oc : I : a. It will be seen that this priii. 
 eiple makes it right to regard every plane as meeting one of the axes at 
 the unit distance from the centre, which, as before stated, reduces the 
 general expression of any plane mcinb: ra to the simpler form me : nb : a } 
 or me : b : na. 
 
 The principle, which has just been stated, also makes it evident that when 
 the axes are all equal, they are not necessarily considered in naming the 
 position of any plane ; when the lateral axes alone are equal, a certain 
 length of the vertical axis must be assumed for each species ; and when all 
 the axes are unequal, certain lengths for two of the axes, expressed in 
 terms of the third axis, must in every case be adopted. 
 
 Hence the fundamental form of any species may be regarded as that 
 octahedron whose axes correspond in relative lengths with the axes <?, &, a 
 adopted for the species. The faces of this octahedron intersect the axes at 
 distances from the centre equal to. we, nb, na (or c : b : a) respectively, and. 
 since the ratio of the coefficients which expresses the position of these 
 planes is 1 : 1 : 1, this form is also called the unit octahedron. But the 
 form is not necessarily fundamental ; for it is frequently more or less arbi- 
 trarily assumed, and the structure or genesis of the crystals of a species may 
 point to other forms, having very different axial relations, as will appear 
 from facts stated beyond. 
 
 MODELS. For clear illustration of the axes and axial ratios of planes it is well to have 
 models of the axes made of rods of wood mortised and glued together at the crossing at centre. 
 The rods may be half an inch in diameter and 10 or 12 inches long ; for the Isometric system, 
 three equal rods, say 12 inches long ; for the Tetragonal system, two of 12 inches for the 
 lateral axes and one of 8 or 14 inches for the vertical ; for the Orthorhombic, one of 16 inches 
 for axis b, one of 10 inches for axis c, and one of 14 inches for axis a. (Either axis may be 
 made the vertical by way of change.) 
 
 For the Clinometric systems, make a second model like that for the Orthorhombic system, 
 but with the rods but loosely mortised and tied together, so as to admit of a little movement 
 at centre. Then, the model when in its more natural position will be that of the orthorhom- 
 bic system, the intersections being all rectangular. But by pushing the front rod a down in 
 the plane of ea, making it thus oblique to c while at right angles to 6, the model will repre- 
 sent the monoclinic axes ; if all the intersections of the rods are oblique, the model will 
 represent the axes of the Triclinic system. 
 
 Now by taking a large piece of thick pasteboard, and placing it in different positions with 
 reference to the three axes, the relations to the various planes may be readily illustrated . 
 
 Models of the various forms of crystals are also of the highest importance ; and the best 
 for general illustration are those made of plate glass, some of them having the positions of 
 the axes within indicated by threads, and others consisting of one form inside of another to 
 show their mutual relations. Such glass models (first made by Professor Dana, in 1835, 
 and recommended in the first edition of his Mineralogy) are now manufactured of great per- 
 fection at Siegen, in Germany. 
 
 Pasteboard models, likewise useful aids to the study of crystallography, are easily made 
 from the outlines of the faces of the various forms, which have been prepared by various 
 authors. 
 
 Models cut in hard wood representing the actual forms of the various mineral species are 
 very valuable, when accurately made. They not only show the relations of different planes, 
 but may also be advantageously used to give the student practice in the mathematical cal- 
 culations of the axes and parameters, the angles being measured by him as on an actual 
 crystal. Such models have the advantage of being of convenient size, and symmetrically 
 foimed, which are conditions not often realized in the crystals furnished by nature. 
 
 2. LAW OP SYMMETRY. 
 
 .* 
 
 The symmetry of crystals is based upon the law that either : 
 
CRYSTALLOGRAPHY. 13 
 
 T. All parts of a crystal similar in position with reference to the ove* 
 are similar in planes or modification, or 
 
 II. Each half of the similar 'parts of a crystal, alternate or symmetri- 
 cal in position or relation to the other half, may he alone similar in its 
 planes or modifications. 
 
 The forms resulting according to the first method are termed holohe- 
 dral forms, from 0X05, all, %pa, face ; and those' according to the second, 
 hemihedral, from ijfjLia-vs, half. 
 
 According to the law of full or holohedral symmetry, each sectant in one 
 of the rectangular systems (a) should have the same planes both as to num- 
 ber and kind ; and (b) whatever the kinds, in each sectant there should be 
 as many of each kind as are geometrically possible. But in hemihedrism, 
 either fa) planes of a kind occur only in half of the sectants ; or else (b) 
 half the full number occur in all the sectants. 
 
 In the isometric system, for example, if one solid angle of a cube has 
 upon it a plane equally inclined to the diametral sections, so will each of the 
 other angles (or sectants) (f. 39-42). 
 
 If one of the twelve edges of the cube has a plane equally inclined to the 
 enclosing cubic faces (or diametral planes) the others will have the same 
 (f. 43-46). 
 
 Again, one of the solid angles of a cube being replaced by six planes, as 
 in f. 70, this law requires that the same six planes should appear on all the 
 other sol id angles. 
 
 But under the law of hemihedrism these planes may occur on half the 
 solid angles of the cube, and not on the other half, as in f . 87, or half the 
 full number of planes may occur on all the angles, as in f. 101. This subject 
 is further elucidated in the discussion of the hemihedral forms belonging 
 to each system of crystallization. 
 
 HEMIHEDRISM is of various kinds : 
 
 1. Holomorphic, in which the occuring planes pertain equally to both 
 the upper and lower (or opposite) ranges of sectants, as in all ordinary hemi- 
 hedral forms. 
 
 2. Hemimorphic, in which the planes pertain to either the upper or the 
 lower range, and not to both, and hence the planes are only half enough of 
 the kind to enclose a space, whence the term hemimorphic, from 
 
 half, and fio pcfrrj, form. 
 
 The holomorphic forms may be either : 
 
 A. Hemiholohedral, HALF the sectants having the FULL number of planes, 
 or 
 
 B. Holohemihedral, ALL the sectants having HALF the whole number of 
 planes. 
 
 Again, as to the relative positions of the sectants containing the planes, 
 the forms may be : 
 
 a. Vertically-direct, in which the sectants of the upper and of the lower 
 ranges are alternate, but the upper not alternate with reference to the lower, 
 
14 CRYSTALLOGRAPHY. 
 
 and, accordingly, each plane above is in the same vertical zone with a lika 
 plane below ;*" as in forms described on pp. 34, 35. 
 
 b. Vertically-alternate, in which the sectants of the upper and lower 
 ranges are alternate, and also the upper are alternate with reference to the 
 lower, and, accordingly, each plane above is not in the same vertical zone 
 with alike plane below; as in the tetrahedron (f. 9), rhombohedron (f. 16), 
 and gyroidal forms (f. 182). 
 
 c. Vertically -oblique, in which the sectants of the upper and lower ranges 
 are adjacent, but the upper are situated diagonally with reference to the 
 lower, being on the opposite side of a transverse diametral or diagonal 
 plane ; as in hemihedrons of monoclinic habit under the orthorhombic 
 system (p. 45). 
 
 Tetartohedrism. Mathematically the rhombohedron is a hemihedron un- 
 der the hexagonal system, consequently the forms that are hemihedral to the 
 rhombohedron are tetartohedrons, or quarter-forms. See p. 39. 
 
 Tetartohedral forms, or those with one-fourth of the normal number of 
 planes, have also been observed in the Isometric system. The term mero- 
 fiedrism, from pepos, part, and eSpa, face, has been used in place of hemi- 
 hedrism, to include both this and tetartohedrism. 
 
 I. ISOMETRIC SYSTEM. 
 A. Holohedral Forms. 
 
 In the ISOMETRIC SYSTEM the axes are equal, so that either one may be the 
 vertical axis, and each may be called a. It has already been shown that the 
 general expression for any plane meeting the axes c, b,a is me : nb : a ; and 
 in this system it will be ma : na : a, or, since the axes are equal, simply 
 m : n : 1. Now it has been shown also that according as a plane intersects 
 the several axes at different points, or is parallel to one or more of them, 
 this fact is indicated by the values given for m and n in each case (p. 11). 
 Hence expressions for all the forms geometrically possible in this system 
 will be obtained if to m and n, in the general expression ma \na\ a, succes- 
 sive values are given. These values inay be in this system, 0, 1, a number 
 greater than 1, or GO . In this way are derived :- 
 
 1. m 
 
 2. m 
 
 3. m 
 
 4. 1 
 
 5. oo 
 
 6. oo 
 
 7. oo 
 
 n 
 
 ***' JLU tiJio w vy arc uerivcu . 
 
 \m-ri\ when m and n have both different values greater 
 than unity. 
 
 1 \m-m\ when m > 1, n = m. 
 
 1 [m] when m > 1, n = 1. 
 
 1 [1] when m and n = 1. 
 
 1 \i-ri\ when m = oo , n > 1. 
 
 1 [i] when m = oo , n = 1. 
 
 1 [ZT] when m and n = <x> 
 
 In lettering the planes of the several forms only the essential part of the symbol is used: tha 
 cube is // (hexahedron) ; the octahedron 1(=1 1 : 1) the dodecahedron i (oo : 1 : 1), ( i 
 stands for infinity) ; m is used for the planes m : 1 : ] ; m-m for m : m : 1 ; i-n for <x : n : 1 
 
ISOMETRIC SYSTEM. 
 
 15 
 
 m-n for m : n : 1. These symbols are the same as those of Naumann, except that he wrote 
 30 instead of i for infinity, and introduced also the letter (octahedron) as the sign of the 
 system ; co oo of his system^r^; 0=1 ; GO 0=i ; m 0=m ; m mm-m, oo n=i-n, 
 and m n=m-n. 
 
 Each of these expressions, appearing at first sight possibly a little 
 obscure, may be translated into simple language. 
 
 Cube. The cube with the symbol oo : oo : 1, is composed of planes each 
 one of which is parallel to two of the axes, and meets the third at its unit 
 point (see f . 36). It is evident that there are six such planes, one at each 
 extremity of the three axes, and the figure or crystal which is enclosed by 
 these six planes has already been described (p. 5) as the cube (f. 38). 
 
 Octahedron. The symbol 1:1:1 comprises all those planes which meet 
 the three axes at the same distance, that is, cut off the unit length of each. 
 It is evident that there must be eight such planes, one in each octant, and 
 they together form the regular octahedron (f. 42), which has already been 
 described, p. 4. 
 
 Dodecahedron.- The symbol oo : 1 : 1 includes those planes which inter- 
 cept two of the axes at* the same unit distance, and are parallel to the 
 third. There can be twelve planes answering to these conditions, and they 
 form together the dodecahedron (f . 45, see also p. 6). 
 
 These three forms, the cube, octahedron, and dodecahedron, are those 
 most commonly occurring in this system, and it is important that their rela- 
 tion should be thoroughly understood. The transitions between these forms, 
 as they modify one another, are exhibited in the following figures : 
 
 38 
 
 Figs. 38 and 42 represent the cube and octahedron, and 39, 40, 41, the 
 intermediate forms. Slicing off from the eight angles of a cube piece after 
 piece, such that the planes made are equally inclined to H, or the cubic faces, 
 the cube is finally converted into the regular octahedron ; and the last 
 disappearing point of each face of the cube is the apex of each solid angle 
 of the octahedron. The axes of the former, therefore, of necessity conned 
 the apices of the solid angles of the latter. 
 
 The form in f. 40 is called a cubo-oatahedron. H/\ 1=125 15' 52". 
 
 If the twelve edges of the cube are truncated (for all will be truncated if 
 one is) it affords the form in f . 43 ; then that of f . 44 ; then the dodecahe- 
 
16 
 
 CRYST ALLOGRAPHS 
 
 dron, f. 45 ; the axes of the cube becoming, in the transition, the axes con 
 necting the tetrahedral solid angles of the dodecahedron ; H /\ i = 135. If 
 the twelve edges of the octahedron (f. 42) are truncated, the form in f. 47 
 results ; and by continuing the replacement, finally the dodecahedron again 
 is formed (f. 45). 1 A i = 144 44' 8". The last point of the face of the 
 octahedron, as it disappears, is the apex of the trihedral solid angle of the 
 dodecahedron. 
 
 These forms are thus mutually derivable. The process may be reversed, 
 the cube being derivable from the dodecahedron by the truncation of the 
 tetrahedral solid angles of the latter (compare in succession f. 45, 44, 43, 
 38) ; and the octahedron by the truncation of the trihedral solid angles 
 (compare f. 45, 47, 42). These remarks are important as showing the rela- 
 tions between these forms, though it is of course not intended to be under- 
 stood that they are in any sense derived from each other in this manner in 
 nature. 
 
 The three axes (or cubic axes) connect the centres of opposite faces in the 
 cube the apices of opposite solid angles in the octahedron ; the apicea 
 of opposite tetrahedral solid angles in the dodecahedron. 
 
 The eight trigonal or octahedral interaxes connect the centres of opposite 
 faces in the octahedron / the apices of opposite solid angles in the cube ; 
 the apices of opposite trihedral solid angles in the dodecahedron. 
 
 The twelve rhombic or dodecahedral interaxes connect the centres of op- 
 posite faces in the dodecahedron / the centres of opposite edges both in the 
 cube and the octahedron. 
 
 In a vertical section, containing each of these kinds of axes, the octahe 
 dral interaxis intersects one of the three cubic axes at the angles 54 44' 8 
 and 125 15' 52", and one of the 
 dodecahedral interaxes, at the an- *8 
 
 gles 35 15' 52" and 144 44' 8". 
 
 There remain four other holohe- 
 dral forms belonging to the system 
 as contained in the list on page 14. 
 
 Trisoctahedrons. The sy m bol 
 m : 1 : 1 is of that solid each of 
 whose planes meets two of the axes 
 at the unit distance, and the third 
 axis at some distance which is a 
 multiple of this unit length. It will 
 be evident, as in f. 48, that there 
 are three such planes in each of the 
 eight sectants, and hence the total 
 number of planes by which the solid 
 is bounded is twenty-four. The 
 resulting solid is called a trigonal 
 trisoctahedron, and one, having 
 77Z- f, is shown in f. 49. 
 
 It will be found a very valuable practice for the student to construct the figures of the 
 successive crystalline forms in this way, laying off the proper lengths of the several axes and 
 
ISOMETRIC SYSTEM. 
 
 The symbol m:m:l belongs to all the planes which 
 meet one axis at the unit distance, and the others at equal 
 distances which are multiples of the former. As seen in the 
 preceding case, there will be three such planes in each of 
 the eight sectants, and the total number consequently will 
 be twenty-four. The solid is seen in f. 50, and is called a 
 tetragonal trisoctahedron, or a trapezohedron. 
 
 Both these forms are called trisoctahedrons, from rpi?, three times, and 
 octahedron, because in each a three-sided pyramid occupies 
 the position of the planes of the regular octahedron. They 
 are closely related to each other ; starting with the form 
 rn : 1 : 1, if m is diminished till it equals unity, then the 
 symbol becomes 1:1:1, that is, it has passed into the octa- 
 hedron. If m becomes less than unity, the symbol may be, 
 for example, :!:!, which is identical, as has been ex- 
 plained (p. 11) with 1:2:2 (2-2), and this is the symbol of 
 the second trisoctahedron. This explains why, in the first list comprising 
 all the possible forms, m was in no case made less than unity. 
 
 _ Trigonal-trisoctahedron.li\ this form the solid angle's are of two 
 
 kinds : the trigonal or octahedral, and the octagonal or cubic. The edo-es are 
 
 thirty-six m number, twenty-four of one kind, forming the octahedral or 
 
 trihedral solid angles, and twelve edges meeting at the extremities of the 
 
 Each of the twenty-four planes is an isosceles triangle. 
 
 52 53 
 
 In combination with the cube, the form 2 appears as a replacement of 
 each of the solid angles by three planes equally inclined on the edges; this 
 is seen in f. 52. With the octahedron, it appears as a bevelment of its 
 twelve edges, as shown in f. 53. It also replaces the eight trigonal solid 
 angles of a dodecahedron by three planes inclining on the faces. "The more 
 commonly occurring examples of this form are 2 (=2 : 1 : 1), also 4 (=| 
 : 1 : 1), and 3 (3 : 1 : 1). 
 
 The Tetragonal-trisoctahedron or trapezohedron, has three kinds of solid 
 angles : six cubic, whose truncations are cubic faces (f. 56) ; eight octahe- 
 dral, whose truncations are octahedral faces (f. 56) ; twelve dodecahedral, 
 truncated by the dodecahedral planes (f. 60). It has forty-eight edges ; 
 twenty-four of one kind, those of the trihedral or octahedral solid angles, 
 and the remaining twenty-four, also of one kind, meeting in the cubic solid 
 angles. Each of the twenty-four faces is a quadrilateral. 
 
 In combination with the cube it is seen in f. 55, 56, appearing as a re 
 placement of each of the solid angles by three planes equally inclined on 
 2 
 
18 
 
 CRYSTALLOGR APH Y. 
 
 the faces of the cube. Figs. 56, 57, 58, 59, 60, 62, also show it in com 
 bination with the octahedron and dodecahedron. The most commonly 
 occurring of this series is 2-2 ( = 2 : 2 : 1), f . 54 ; as seen in f. 59, it truncates 
 the twenty-four edges of the dodecahedron. On the other hand the form 
 
 57 58 
 
 54 
 
 55 
 
 56 
 
 60 
 
 01 
 
 f~f would replace the trihedral solid angles by planes inclined on the edges, 
 while 3-3 replaces (f. 62), the tetrahedral solid angles of the dodecahedron, 
 by planes also inclined on the edges. 
 
 Tetrahexahedron. The symbol oo : n : 1 (i-n) belongs to all the planes 
 which are parallel to one axis, meet a second at the unit distance, and the 
 third at some multiple of that. There are twenty-four planes which satisfy 
 these conditions, and they form the tetrahexahedron / f. 64, 65, represent two 
 varieties of tetrahexahedrons. It will be seen that the planes are so 
 arranged that a square pyramid corresponds to each of the six faces of the 
 cube ; and hence the name from rer/oa/ct?, four times, ef, six, and e8pa, 
 face, it being a 4x6-faced solid. The tetrahexahedron has six tetrahe- 
 dral solid angles and eight hexahedral or octahedral solid angles. There are 
 twenty-four edges of one kind forming the former solid angles, and twelve 
 edges occupying the position of the cubic edges. Each of the twenty-four 
 faces is an isosceles triangle. In combination with the cube it produces a 
 bevelment of its twelve edges, as represented in f. 64. 
 
 64 
 
 65 
 
 60 
 
 The tetrahexahedron, in f. 65, lettered *-2, has the symbol oo : 2 : 1 ; and 
 that of f. 66, lettered i-3, oo : 3 : 1. Some of the other occurring kinds are 
 those with the ratios, 2 : 3, 3 : 4, 4 : 5, etc., etc. 
 
 The relation of the tetrahexahedron to the octahedron is shown in f. 67 
 By comparing this figure with f. 42, it is seen that the planes a'fe replace 
 
ISOMETKIC SYSTEM. 
 
 19 
 
 tK 1 H i th S oc ^ edron b ^ Places inclined on its edges. Its rela- 
 lion to the dodecahedron is presented in f. 68, which is a dodecahedron 
 (planes * being the dodecahedral plar.es, see f. 45) with the tateffiSSS 
 angles replaced by four planes inclined each on an i 
 
 The tetrahexahedron is called a Jluoroid, by Haidinger, the form beine 
 
 U0rite ' * " ^ ^^^ 
 
 In accordance with considerations already presented it is evident that n 
 m the symbols, may always be written as a whole number, for the svmbo 
 oo : | : 1 is identical with oo : 1 : 2. Moreover it is seen that when /is T 
 the form passes into the cube (oo : co : 1), and as n diminishes and becomes 
 unity, it passes into the dodecahedron (oo : 1 : 1) 
 
 Hexoctahedron. The general form m : n includes the largest number 
 of similar planes geometrically possible in this system. This symbol 
 requires six p anes in each octant, as will be seen by a method of con- 
 struction similar to that in f. 48, and consequently the whole solid has 
 forty-eurht planes. It is hence called a hexakisoctahedron Ufa*, six 
 tomes otcrco, e^ght, and efya, face, i.e., a 6 x 8-faced solid) or hexoctahedron. 
 The form is shown in f. 69, where it will be seen that there are ^^differ- 
 ent kinds of edges, and three kinds of solid angles; each of the fortv- 
 eight planes is a scalene triangle. 
 
 When modifying the cube it appears as six planes replacing each of the 
 solid angles, f . 70. It replaces the eight angles of the octahedron, and the 
 
 70 71 
 
 form 3-f bevels the twenty-four edges of the dodecahedron (f. 71). Other 
 hexoctahedrons, differing in their angles, may replace the six acute solid an- 
 gles of the dodecahedron by eight planes, or the eight obtuse by s? a; planes. 
 The hexoctahedron of f. 69, 70, 71 is that whose planes have the axial 
 ratio 3 : J : 1. Others have the ratio 4 : 2 : 1, 2 : 4 : 1 (=6 -4-3} 5 4 1 
 1=15 : 5 : 3), 7 : J : 1 (=21 : 7 : 3), etc. 
 
 72 73 
 
 Amalgam. 
 
 Magnetite. 
 
20 
 
 CRYSTALLOGRAPHY. 
 
 The preceding figures show dodecahedrons variously modified. In 
 f. 72, /, or a, are faces of the dodecahedron ; Hoi the cube ; 1 of the octa- 
 hedron ; i-3 of a tetrahexahedron (f. 66) ; 2-2 of the trapezohedron of f . 54- 
 59 ; 3-f of the hexoctahedron of f. 69,' 70. In f. 73, i, O, and 1 are as in 
 f. 72; 3-3 is the trapezohedron of f . 61, 62 ; and 5-f (either side of 3-3) a 
 hexoctahedron. 
 
 The hexoctahedron is called the adamantoid by Haidinger, in allusion 
 to its being a common form of crystals of diamond. It is the hexakisocta- 
 hedron of Naumann. 
 
 B. Hemihedral Forms. 
 
 Of the kinds of hemihedral forms mentioned on page 13, the hemiho- 
 lohedral, in which only half of the sectants are represented in the form, 
 produces what are called inclined hemihedrons / and the holohemihedral, in 
 which all the sectants are represented by half the full number of planes, 
 parallel hemihedrons. In the former the sectants to which the, occurring 
 planes belong are diagonally opposite to those without the same planes ; and 
 hence no plane has another opposite and parallel to it ; on the contrary, 
 opposite planes are oblique to one another, and hence the name of inclined 
 hemihedrons applied to them. They are also called tetrahedral forms, the 
 tetrahedron being the simplest form of the number, and its habit character- 
 istic of them' all; while the latter are called pyritohedral, because observed 
 in the species pyrite. The complete symbols of the inclined hemihedrons 
 are written in the general form %(m : n : 1), of the parallel hemihedrons 
 in the form \ [m : n : 1] ; also written ic(m : nil) and ir(m : n : 1) re- 
 spectively. 
 
 a. Inclined or Tetrahedral Hemihedrons. 1. Tetrahedron, or H.emi- 
 octahedron. J(l : 1 : 1). 
 
 As has been shown, the form 1(1 : 1 : 1) embraces eight planes, and when 
 holohedrally developed it produces the octahedron ; in accordance, how- 
 ever, with the law of hemihedrism, half of the eight possible planes may 
 
 74 
 
 75 
 
 76 
 
 76A 
 
 77 
 
 78 
 
 79 
 
 80 
 
 occur in alternate octants; thus in two opposite sectants above, and rhu 
 two diagonally opposite below, as shown by the shaded planes in f . 74. 1 f 
 
ISOMETKIC SYSTEM. 
 
 21 
 
 these four shaded plane* are suppressed, while the other four of the octa- 
 hedron are extended, the resulting form is the regular tetrahedron, f. 76. 
 SEif^W ? tahed 7 m / d ^trahedron maybe better understood 
 .75. If, as just remarked, the planes shaded in f. 74 are suppressed 
 while the others are extended, it will be seen in f. 75 that the two lat 
 pairs intersect m edges parallel respectively to the basal edges of the 
 octahedron, and the complete tetrahedron is the result. The axes it is im- 
 portant to observe, connect the middle points of the opposite ed^es 
 
 E urtlier than this, since either set of four planes may go to form the solid 
 two tetrahedrons are evidently possible, and they may be distinguished 
 by calling the first, f. 76, positive, and the second negative, f. 76 A 
 These terms are of course only relative. The plus and the minus tetrahe- 
 drons may occur in combination, as in f. 79 ; and though there are here pre- 
 sent the eight planes which in holohedral forms make the octahedron, and 
 though they should happen to be equally developed so as to give the same 
 shape the crystal would still be pronounced tetrahedral, since the planes 
 1 and 1 are physically different. An example of this occurs in crystals 
 Ql boracite, where the planes of one tetrahedron are polished while those of 
 the other are without lustre. 
 70 Jhe / plane angles of the tetrahedron are 60, and the interfacial angles 
 
 The combinations of the cube and tetrahedron are shown in f. 77 and 78 
 and the dodecahedron and tetrahedron in f. 80. As the octahedron results 
 geometrically from slicing off successively the solid angles of the cube by 
 planes of equal inclination on the cubic faces, so also the tetrahedron may 
 be made mechanically by slicing off similarly half these solid angles 
 
 81 
 
 82 
 
 84 
 
 Hem-tmsoctahedrom, \(m : m : l)and \(m : 1 : 1). In the same manner 
 as with the tetrahedron, the form m-m, when hemihedral, may have half its 
 twenty-four planes present, viz., those in the two opposite sectants above 
 and the alternate sectants below. When these twelve planes are extended, 
 the others being suppressed, they form the solid represented in f. 81 ; the 
 symbol properly being J( m-m), or here (2-2). The faces, as will be ob 
 served, are trigonal, and the solid is sometimes called a cuproid. There is 
 the same distinction to be made here between the plus and the minus forms 
 afiwith the tetrahedrons. Figs. 82, 83, 84 show combinations of -fi(m-ra) 
 with the plus tetrahedron, the dodecahedron, and the tetrahexahedron. 
 
 bimilarly the form m, when hemihedral, according to the same principle 
 rosults in the solid, f. 85. It is called the deltohedron by Haidinger ; it has 
 trapezoidal faces. ^ In f. 86, + J(f) is shown in combination with -f-|(2-2). 
 Here also the distinction between the plus and minus forms is to be made in 
 the same manner as that already explained. 
 
22 
 
 CRYSTALLOGRAPHY. 
 
 Inclined or tetrahedral Hemi-hexoctahedron $(m : n : 1). The form m-n 
 when developed according to the law of inclined hemihedrism, that is, 
 when of its forty-eight faces, half are present, viz., all in half the whole 
 
 85 
 
 87 
 
 88 
 
 number of sectants, produces the solid seen in f. 87. There is here also a 
 plus solid, and a minus solid, corresponding to the 4- and tetrahedron. 
 In f. 88 it is in combination with the plus tetrahedron. 
 
 If the same method of inclined hemihedrism be applied to the remain- 
 ing solids of this system, the cube, dodecahedron, and tetrahexahedron, that 
 is, if in each case the parts in two opposite sectants above, and the two diag- 
 onally opposite sectants below, be conceived to be extended, the other half 
 being suppressed, it will be seen that the solid reproduces itself ; the hemi- 
 hedral form of the cube is the cube, and so of the others. 
 
 The following figures represent some other combinations of these forms. 
 
 89A 
 
 90 
 
 Sphalerite. 
 
 Sphalerite. 
 
 Tetrahedrite. 
 
 In f . 89, the cuproid 3-3 is combined with the faces 7 of a dodecahedron. 
 The form 3-3 resembles closely that of f. 81, but in its combination with 
 the dodecahedron it does not truncate an edge of the dodecahedron, like 2-2 
 in f. 83. Fig. 89A contains the same planes combined with the plus tetra- 
 hedron, hexagonal planes 1, the minus tetrahedron, triangular planes 1, and 
 thefacesof the cube//. The presence of the plane //facilitates the com- 
 parispn of the form with f. 55, 56, 57, p. 18, the plane 3-3 having the same 
 position essentially with 2-2. Fig. 90 has as its most prominent planes those 
 of f . 81 , but the position given it is relatively to f. 81 that of the minus 
 hemihedron ; and there are also the small planes 2-2 about the angles, 
 which are those of the minus hemihedron. //, are planes of the cube ; 
 1, those of the tetrahedron ; i, those of the dodecahedron ; i-3 those of a 
 etrahexahedron (H, i^i-3 all holohedral) ; and f the planes of a deltohe- 
 dron similar to f. 85, and occurring with 2-2 in f. 86. 
 
ISOMETRIC SYSTEM. 
 
 23 
 
 b. Parallel or pyritohedral hemihedrons. According to the second l 
 of hemihedrism, half the whole number of planes of any form may be pre 
 sent in all the sectants. In the resulting solids each plane has another par 
 allel to it. This method of heiniheclrisin obviously produces distinct forms 
 only in those cases where there is an even number of planes in each octant. 
 
 Pentagonal Dodecahedron, or Ilemi-tetrahexahedron, -J(oo mil). If 
 of the twenty -four planes of the form i-n(cc : n : 1), only half are present ; 
 viz., one of each pair in the manner indicated by shading in f. 91, these 
 being extended while the others are suppressed, the solids in f. 92 and f. 93 
 result. The parallelism of each pair of opposite planes will be seen in these 
 figures. These two possible forms, seen in the figures, are distinguished by 
 calling one plus (arbitrarily),-f-J[^-2], and the other minus, [*-2], These 
 solids are very common in the species pyrite, and are hence called pyritolie- 
 drons ; they are also called pentagonal dodecahedrons, in allusion to their 
 pentagonal faces. The regular dodecahedron of geometry belongs to this 
 class, but is an impossible form in nature, since for it n must have an irra- 
 
 tional value, viz., 
 
 see 
 
 p. 10. 
 
 In combination with the cube the form -f -J{i-2] is seen in f. 94 and f. 95, 
 and in f. 96, 97, with the octahedron, and in f. 98, with the cube and octa- 
 hedron. 
 
 01 92 93 94 
 
 96 
 
 Parallel hemi-hexoctahedron, J[m : n : 1]. When of the forty-eight 
 planes of the form m-n, only half are present, viz., the three alternate 
 
 101 
 
 planes in each octant as indicated by the shading in f. 99, the solid in 
 f. 100 results. This solid is called a diploid by Haidinger. It is also called 
 
24 
 
 CRY STALLOQRAPHY. 
 
 a dyakis-dodecahedron. In f . 101 it is shown in combination with the cube 
 and in f . 102 with the octahedron. 
 
 Figs. 103, 104, 105, of the species pyrite, represent various combina- 
 tions of parallel hemihedrons with the cubic and other faces. In f. 103 
 there are planes of twohemi-tetrahexahedrons (pentagonal dodecahedrons) 
 t-2, *-* ; and of two diploids 4-2, 3-f , along with planes of the octahedron, 
 1 and of the trapezohedron 2-2. In f. 104 the dominant form is the dode- 
 cahedron, 7; it has the faces of the cube, H\ of the octahedron, 1 ; of the 
 
 103 
 
 Pyrite. 
 
 Pyrite. 
 
 Pyrite. 
 
 trapezohedron, 2-2 ; and of the parallel hemihedrons, i-*2 and 4-2. Fig. 
 105 represents a map of one angle of a cube, showing at centre the octahe- 
 dral face 1, and around it the faces of the cube 7/, of the trapezohedron 
 2-2, the trigonal trisoctahedron 2, and the parallel hemihedrons, i-2, 2-J, 
 3-f. The axial ratio for 2-f is 2 : f : 1 (or 6:4: 2), and for 3-J, 3 : | : 1 
 (or 6 : 3 : 2). 
 
 Prominent distinctive characters. The student, in order to facilitate his 
 study of Isometric forms in nature, should be thoroughly familiar with the 
 following points, from the study of models or natural crystals ; (1) The 
 isometric character of the symmetry, the planes being alike in grouping in 
 the direction of the three axes. (2) The forms of the faces and solid an- 
 gles of the octahedron, the dodecahedron, the trapezohedron 2-2, the pen- 
 tagonal dodecahedron *-2. (3) The fact that the following are common an- 
 gles in the system 135 (=HA); ; 109 28' (angle of octahedron), 70 32' 
 (angle in octahedron and tetrahedron) ; 120 (angle of dodecahedron); 125 
 16' ( HAl); 144 44' (=HA2-2:= lAi); 153 ^6 r (=HA*^); 161 34' (=H 
 A^-3). A list of the angles belonging to the various forms of this system is 
 given on p. 67. (4) Cleavage may be cufric, octahedral, or dodeca/iedral ; 
 and sometimes two of these kinds, and occasionally the three, occur in the 
 same species, but always with great difference of facility between their,. 
 Galenite is an example of easy cubic cleavage ; flnorite of easy octahedral ; 
 sphalerite (blende) of easy dodecahedral. 
 
 Plzr<t*(>f symmetry. ~lL\\e'se\Q\\ kinds of solids described on pp. 15 to 19, 
 include all the holohedral forms possible in this system, as is evident from 
 their geometrical development. In them exists the/highest degree of sym 
 metry possible in any geometrical solids. 
 
 In' the cube, as lias already been stated, all planes, solid angles, and edges 
 are equal and similar. The three diametral planes, passing each through 
 two of the axes, arp the chief planes of symmetry, every part of the crystal 
 
TETRAGONAL SYSTEM. 
 
 on one side of the plane having its equal and symmetrical part on the oppo- 
 site side. Further than this, each of the six planes passing through the 
 diagonal edges of the cube, and consequently parallel to the dodecahedral 
 planes, are also planes of symmetry. There are hence in this system nin* 
 planes of symmetry. 
 
 II. TETRAGON AL S YSTEM. 
 
 In the TETRAGONAL SYSTEM, there are three rectangular axes ; but while 
 the two lateral axes are equal, the remaining vertical axis is either longer or 
 shorter than they are ; there are consequently to be considered the lateral 
 axes (a) and the vertical axis (o). 
 
 The general geometrical expression for the planes of crystals becomes for 
 this system mo : na : a, and, if this be developed in the same way as the cor- 
 responding expression in the Isometric system, all the forms* geometrically 
 possible are derived. 
 
 1. me : na : a \in-ri\ when m >1, n >1. 
 
 o j G : a : a [1] when wt=l 
 
 ' \ mo : a : a 
 
 3 \ 
 
 \ mo : oo a : a [tn-i] when m^l, n=<x> 
 
 [m] when 
 
 [i- 
 
 G : oo a : a [!-*] when m=l, n= oo . 
 
 4. oo c : na : a \i-n\ when m=<x> , n >1. 
 
 5. QO o : a i a [/] when w&=oo, %=1. 
 
 6. oc <? : oo & : # [t**] when m=ao , n=ao . 
 ^ j (c 1 : oo a : QO a) [0] when m=0, 7* = 1. 
 
 j or Go* : a : a. 
 
 [n lettering the planes the^abridged symbols are used; here, as before, i=oo , and the unit 
 term is omitted as unnecessary, me : oo : a = m-i, etc. These are the same as the symbols 
 of Naumann, except that he wrote oo , and added P as the sign of the systems which are not 
 isometric; QP=0 ; oo Px> i-i ; ooP=/; oo Pn-i-n ; mP^m-i\ mP=m ; P-l; and 
 iP/i=m-/i. 
 
 A. Holohedral Forms. 
 
 Basal plane. There are two similar planes corresponding to the sym- 
 bol G : QO a : oo a (or Oc : a : a), parallel to both the lateral axes ; each is 
 called the basal plane. They do not inclose a space, and consequently they 
 can occur onlv in combination with other planes. 
 
 Prisms. The planes having the symbol oo o : oo a : a are parallel to the 
 vertical and one of the lateral axes. There are four such planes, one at 
 each extremity of the two lateral axes, and, in combination with the plane 
 O, they form the square prism, which has been called the diametral prism, 
 seen in f. 106. 
 
 For the symbol oo G : a : a, the planes are parallel to the vertical axis, 
 
 * The word form has been freely used in the preceding pages ; from this point on. how- 
 ever, it needs to be more exactly denned. In a crystallographic sense it includes all th 
 planes geometrically possible, nerer less than two, which have the same general symbol. 
 
26 
 
 CRYSTALLOGRAPHY. 
 
 and meet the others at equal distances. There are. as in the t 
 case, four such planes. They form, in combination with the plane 6>, 
 that square prism which is seen in f. 107, and may be called the unit 
 prism. Both the prisms i-i and / are alike in their degree of symmetry. 
 Each has four similar vertical edges, and eight similar basal edges unlike 
 
 the vertical. There are also in each case eight similar solid angles. 
 
 108 
 
 109 
 
 i-2 
 
 -^ 
 
 -* 
 
 \i l i 
 
 . \ 
 
 12 
 
 ^ --J 
 
 110 
 
 '212 
 
 The form i-n (oo c : na : a) is another prism, but in this each plane meets 
 one of the lateral axes at the unit distance, and the other at some multiple 
 of its unit distance. As is evident in the accompanying horizontal section 
 (f. 113), this general symbol requires eight similar planes, two in each 
 quadrant, and the complete form is shown in f. 109. The sixteen basal 
 edges are all similar; the vertical edges are of two kinds, four axial X, and 
 four diagonal T (f. 109). The regular octagonal prism with eight similar 
 vertical edges, each angle being 135, is crystallographically impossible. 
 
 Ill 
 
 112 
 
 
 \\ 
 
 i 
 
 /i 
 
 I 
 
 i 
 
 :-J< 
 
 The planes / truncate the edges of the diametral prism i-i, as in f. 108. 
 Similarly the planes i-i truncate the vertical edges of /. The prism i-n be- 
 vels the edges of i-i, as in f. 110, where i-n=i-%. 
 
 The relation of the two square prisms, i-i and /, may be further illus- 
 trated by the figs. Ill and 112. In f. 112 the sections of the two prisms 
 are shown with the dotted lines for the axes, and in f. Ill there are the 
 two forms complete, the one (/) within the other (i-i). The unit prism /is 
 sometimes called the prism of the first series, and the prism i-i that of the 
 second series. 
 
 Octahedrons or Pyramids. The forms m-i and m both give rise to 
 square octahedrons, corresponding to the two kinds of square prisms. In 
 m-i the planes are parallel to one lateral axis and meet the vertical axie 
 at variable distances, multiples (denoted by m) of the unit length. The 
 total number of such planes, for a given value of m, is obviously eight, and 
 
TETRAGONAL SYSTEM. 
 
 the form is shown in f. 114 and 115. These planes replace the basal 
 edges of the form shown in f. 106, and m varies in value from to oo. 
 When m=0 the four planes above and below coincide with the two basal 
 
 114 
 
 116 
 
 planes; as m increases, there arises a series, or zone, of planes, with mu- 
 tually parallel intersections (f. 116) ; and when m=ao , the octahedral planes 
 m-i coincide with the planes i-i. The value of m in a particular species 
 depends upon the unit value assumed for the vertical axis c. 
 
 The same form replaces the vertical angles of the prism 7, as in f. 117. 
 
 The octahedrons of the m series meet both of the lateral axes at equal 
 distances and the vertical axis at variable distances. It is clear that the 
 whole number of planes for this form, when the value of mis given, is also 
 eight, one in each octant. When m=l the solid in f. HS^is obtained, 
 which is sometimes called the unit octahedron. As m decreases, the octahe- 
 drons become more and more obtuse, till m 0, when the eight planes coin- 
 cide with the two basal planes. As m increases from unity, on the other 
 hand, the octahedrons or pyramids become more and more acute, and when 
 #2,= oo they coincide with the prism I\ this series forms another zone of 
 planes. These octahedrons replace the basal edges in the form f. 107, as 
 seen in f. 119, and as the octahedron is more and more developed it passes 
 to f . 120, and finally to f . 118. 
 
 124 
 
 The same form replaces the solid angles of the form f. 106. as seen in 
 f, 121, and this too gradually passes into f. 122 and f. 114. 
 
28 
 
 CRYSTALLOGRAPHY. 
 
 The relation of the octahedrons 1 and I-i (m andm-i) is the same as that 
 of the prisms /and i-i (compare f. 112). Similarly, too, they are often 
 called octahedrons (or pyramids) of the first (m) and second (m-i) series. 
 
 As will be seen in f. 123, ~L-i truncates the pyramidal edges' of the octahe- 
 dron 1, and, conversely, the edges of the octahedron 2-i are truncated by 
 the octahedron 1 (f. 124). 
 
 Octagonal pyramids. The form m-n (me : 
 na : a) in this system has, as in the preceding sys- 
 tem, the highest number of similar planes which 
 are geometrically possible ; in this case the num- 
 ber is obviously sixteen, two in each of the eight 
 sectants, as in f. 125, where ra=l, ra=2. These 
 sixteen similar planes together form the octagonal 
 pyramid (strictly double pyramid) or zirconoid, 
 f. 126. It has tw r o kinds of terminal edges, the 
 axial X and the diagonal Y ; the basal edges are 
 all similar. It is seen (}n-n=~L- < 2) in f. 127 in 
 combination with the diametral prism, and in f. 128 with 1, where it bevel* 
 the vertical edges. 
 
 126 
 
 Other tetragonal forms are illustrated in 
 figures 2 to 8, of zircon crystals, on p. 2 ; 
 f. 8 is the most complex, and besides 3-3 
 shows also the related zirconoids 4-4 and 5-5. 
 
 Several series of forms occur in f . 129, of 
 vesuvianite. In the unit series of planes 
 there are the octahedrons (or pyramids) 1, 2, 
 3, and the prism /; in the diametral series 
 1-*, i-i ; of octagonal prisms, 2-2, i-3 ; of zir- 
 conoids 2-2, 3-3, 5-5, 4-2, f -3, the whole num- 
 ber of planes being 154. 
 
 B. Ilemihedral Forms. 
 
 Among hemihedral forms there are two divisions, as in the isometric 
 system : 
 
 1. Hemiholohedral, having the full number of planes in half the sectants 
 (a) Vertically-alternate, or sphenoidal forms. The planes occur in two 
 sectants situated in a diagonal line at one extremity, and two in the trans- 
 verse diagonal at the other. 
 
TETRAGONAL SYSTEM. 
 
 29 
 
 With octahedral planes \(mc : a : a) the solid is a tetrahedron (f. 130, 
 131) called a sphenoid, having the same relation to the square prism of 
 
 130 
 
 132 
 
 f. 106 that the regular tetrahedron has to the cube. Fig. 130 is the positive 
 sphenoid or +1, and 131 the negative, or 1. The form \(mc : oo a : a) 
 is similar. Fig. 132 represents the sphenoid in combination with the prism 
 
 If the planes of each sectant are the two of the octagonal pyramid 
 \(mc : na : a) (f. 126), the form is a dipioid (f. 133). It is in combination 
 with the octahedron 1-i in f . 134. 
 
 (b) Vertically -direct, or the planes occuring in two opposite sectanta 
 above, and in two on the same diagonal below. The result is a horizontal 
 prism, or forms resembling those of the orthorhombic system. Character- 
 izes crystals of edingtonite. 
 
 (c) Vertically-oblique. Planes occurring in two adjacent octants above, 
 and in two diagonally opposite below, producing monoclinic forms, as in a 
 hydrous ammonium sulphate. 
 
 2. Holohemihedral, all the sectants having half the full number of planes. 
 As the largest number of planes of a kind is two, half the full number is 
 in all cases one. Hemihedrism may occur in the forms m-n (f. 126, 127), 
 or zirconoids, and in the forms i-n (f. 109), or the octagonal prism. 
 
 The following are the kinds : 
 
 (a) Vertically-direct. The occurring plane of the sectants, the right 
 one in the upper series, and that in the same vertical zone below, as indi- 
 cated by the shading in f. 135 ; or else the left one above, and that in the 
 same vertical zone below, f. 136. 
 
 135 
 
 () Vertically-alternate. The occurring plane the right above, and that 
 in the alternate zone below, as indicated in f. 137 ; or else the l?ft above, 
 and that in the alternate zone below, f. 138. 
 
 As the right of the two planes above is in the same vertical zone with the 
 left of the two below (supposing the lower end made the upper), the two 
 kinds of the first division will be the rl m-n ; and the Ir m-n (in f. 136 on 
 the angles of the prism i-i) ; and the two of the second division the rr 
 and the U m-n (in f . 138, on the angles of the prism i-i). 
 
CRYSTALLOGRAPHY. 
 
 140 
 
 Wernerite. 
 
 Wulfenite. 
 
 The completed form for the first methods has parallel faces, and is like' the 
 ordinary square octahedron in shape, because the upper and lower planes 
 belong to the same vertical zone. But in the second it is gyroidal ; the 
 upper pyramid has its faces in the same vertical line with an edge of the 
 lower, as represented in f. 139, the form II m-n. 
 
 The first of these methods occurs in octagonal prisms, producing a square 
 prism, either r i-n, or I i-n. 
 
 Fig. 140 represents a com- 
 bination of the octahedron 1-?* 
 with the unit-octahedron 1, and 
 two hemihedral forms, one of 
 them Ir 1-2, the other rl 3-3. 
 The plane 1 shows the posi- 
 tion of the octant ; 3-3 is to 
 the right of 1, and 1-2 to the 
 left. In f. 141, which is a top 
 view of a crystal of wernerite, 
 there occurs I 3-3 large, along 
 with r 3-3 small, indicating 
 hemihedrism, and, judging 
 from that of the allied species 
 sarcolite, it is of the square oc- Scheelite. 
 
 tahedral kind, rl 33 and Ir 3-3. 
 Fig. 142 contains the hemihedral prism I i-^ , com- 
 bined with the unit-octahedron 1, and the basal 
 plane O. 
 
 Variable elements in this system. In the tetragonal system two ele- 
 ments are variable, and in any given case must be decided before the rela- 
 tions of the forms can be definitely expressed. 
 
 (a) The position of the lateral axes. These axes are equal, but there are 
 two possible positions for them, for in a given square octahedron they may 
 be either diagonal or diametral; in other words, given an octahedron, as in 
 f. 115, 116, the prismatic planes may be made diametral (i-i), and the octahe- 
 dron so belong to the m-i series, or the prismatic planes may be made diag- 
 onal, that is / (QO c : a : a\ when the corresponding octahedrons belong 
 to the_m series. The ratio of the lateral axes for the two cases is obviously 
 1:1/2, or 1:1.4142 + . 
 
 (1) The length of the vertical axis. Among the several occurring octa- 
 hedrons, one must be assumed as the unit, and the others referred to it. In 
 f. 143, of zircon, the octahedron 1 is made the unit, and by measur- 
 ing the basal angle it is found mathematically, as explained later, 
 that the length of the vertical axis is 0.85 times that of the lateral 
 axes. The octahedron 3 has then the symbol 3c : a : a as referred 
 to this unit. If the latter octahedron had been taken as the fun- 
 damental form, the length of the vertical axis would have been 
 3 x 0.85 times that of the lateral axes, and the symbol of the first 
 plane would have been \c : a : a. Which form is to be taken as 
 the unit or fundamental, that is, what length of the vertical axis c is to be 
 adopted, depends upon various considerations. in general that form is 
 
HEXAGONAL SYSTEM. 31 
 
 assumed as fundamental which is of most common occurrence or to whieb 
 the cleavage is parallel ; or which best shows the morphological relations 
 of the given species to others related to it in chemical composition, or which 
 gives the simplest symbols for the occurring forms of a species. 
 
 Prominent characteristics of ordinary tetragonal forms. The promi- 
 nent distinguishing characteristics of tetragonal forms are : (1) A symme- 
 trical arrangement of the planes in fours or eights. (2) The frequent oc- 
 currence of a square prism diagonal to a square prism, the one making with 
 the other an angle of 135. (3) The occurrence of bevelling planes on the 
 lateral edges of the square prism. (4) A resemblance of the octahedrons 
 to the regular octahedron, in having a square base, but a dissimilarity in 
 that the angles over the basal edges do not equal those over the terminal. (5) 
 Cleavage may be either basal, square-prismatic, or octahedral; prismatic 
 cleavage, when existing, is alike in two directions, parallel to the lateral 
 faces of one of the square prisms, and is always dissimilar to the basal cleav- 
 age; the basal, or the lateral, is sometimes indistinct or wanting: the pris- 
 matic may occur parallel to the lateral planes of both square prisms, but 
 when so, that of one will be always unlike in facility that of the other. 
 
 Planes of symmetry. There are five planes of symmetry in the tetra- 
 gonal system : one principal plane of symmetry normal to the vertical axis, 
 and four others, intersecting in this axis ; these four are in two pairs, the 
 planes of each pair normal (90) to each other, and diagonal (45) to those 
 of the other. 
 
 III. HEXAGONAL SYSTEM. 
 
 The HEXAGONAL SYSTEM includes two grand divisions : 1. The HEXA- 
 GONAL proper, in which (1) symmetry is by sixes, and multiples of six ; 
 (2) hemihedral forms are of the kind called vertically-direct ; and (3) 
 cleavage and all physical characters have direct relations to the holohedral 
 hexagonal form. 
 
 2. The RHOMBOHEDRAL, in which (1) symmetry is by threes and multi- 
 ples of three, rhombohedral forms being hemihedral in mathematical rela- 
 tion to the hexagonal system, and of the kind called vertically-alternate ; 
 (2) cleavage, and many other physical characters, usually partake of the 
 hemihedrism. 
 
 While the rhombohedron is mathematically a hemihedral form under 
 the hexagonal system, and is properly so treated in a system of mathema- 
 tical crystallography, it is not so genetically, or in its fundamental relations. 
 Moreover, it has its own hemihedral forms, which, under the broad hexago- 
 nal system, are tetartohedral. 
 
 The holohedral forms, all of which belong to the Hexagonal division, 
 are here first described ; and then the hemihedral forms, which include, be- 
 sides a few under the hexagonal division, the whole of the Rliombohedral 
 division. 
 
 A. Holohedral Forms : HEXAGONAL DIVISION. 
 
 The general expression for planes of this system is me : na : a : pa, where 
 there are to be considered the vertical axis, c, and three equal lateral axes, a. 
 
32 
 
 CRYSTALLOGKAPHY. 
 
 It is evident, however, that the position of any plane is determined by its 
 intersections with two of the lateral axes, as its direction with the third 
 follows directly from them. (Compare f. 146.) Consequently, in writn.g 
 the symbol of any plane it is necessary to take into consideration only 
 the vertical axis, and two of the lateral axes adjacent to each other. 
 
 The various holohedral forms possible in this system are derived after 
 the analogy of those of the tetragonal system. The parameters for all the 
 lateral axes are given below for sake of comparison. It is to be noted here 
 that m may be either < 1, or > 1 ; n is always > 1 and < 2, while p > 2 
 
 and< oo ; further than this it is always true that $=-;' 
 
 me \na\a\ (pa) \m-n\ when m ^ 1, n > 1 and < 2. 
 
 me: a: a: (oo 0) 
 e : : : (oo 0) 
 oo c: na : a: (pa) 
 ooc:20:0: (20) 
 oo c : a : a : (oo 0) 
 00 : : : (0) 
 
 The abridged symbols need no explanation beyond that which has been given on p. 25 ; 
 mPnm-n ; &Pn=i-n, etc. 
 
 Basal planes. The form 0=0c : a : a includes the two basal planes 
 bove and below, parallel to the plane of the lateral axes. 
 
 [m-ri] 
 
 M 
 [1J 
 
 [**] 
 
 [t-2] 
 
 ta 
 
 when 
 when 
 when 
 when 
 when 
 when 
 when 
 when 
 
 m 
 
 in 
 
 'HI 
 
 tu- 
 rn 
 m 
 m 
 m 
 
 >. 
 
 1, 
 1, 
 1, 
 1, 
 
 GO, 
 00, 
 
 > 
 o, 
 
 n> 
 
 n = 
 
 n = 
 n> 
 
 n = 
 n = 
 
 n = 
 
 1 
 2. 
 1. 
 1. 
 1 
 2. 
 1. 
 1. 
 
 and 
 and 
 
 < 2. 
 
 144 
 
 147 
 
 Prisms. ^The form jT=oo G : a : a comprises the six planes parallel to 
 the vertical axis, and meeting the two adjoining lateral axes at equal dis- 
 tances. These six planes with the basal plane form the hexagonal unit 
 prism, f. 144. The form t'-2=oo0 : 20 : a includes the six planes which 
 are parallel to the vertical axis but meet one of the lateral axes at the unit 
 distance, and the other two at double that distance. These plai.os with the 
 basal plane form the diametral prism, f. 145. The relations ol the two 
 prisms / and i-2 are shown in f. 146. In f. 14T, it will be seen that the one 
 prism truncates the vertical edges of the other. The faces of the ^-2 
 inake an angle of 150 with the faces of /. These two prisms have an inti- 
 mate connection with each other, and together form a regular twelve-sided 
 prism, a prism which is crystallographically impossible except as the result 
 of the combination of these two different forms. 
 
HEXAGONAL SYSTEM. 33 
 
 The form i-2 is a special case of the general form i-n or oo c : na : a. 
 When n is some number less than 2, and greater than 1, there must be tw<j 
 planes answering the given conditions in each sectant, and twelve in all, 
 Together they form the dihexagonal, or twelve-sided, prism. This prism 
 bevels tiie edges of the prism 7, and the vertical edges are of two kinds, 
 axial and diagonal. The values of n must lie between 1 and 2 ; some of 
 the occurring forms are *-|-, 2-|> etc. 
 
 Hexagonal pyramids, or Qaartzoids. The symbol l=c : a : a belongs 
 to the twelve planes of the unit pyramid, f. 148, while the general form 
 m mc : a : a includes all the pyramids in this series where the length of 
 the vertical axis is some multiple of the assumed unit length. As in the 
 tetragonal system, when m diminishes, the pyramids become more and 
 more obtuse, and the form passes into the basal plane when m is zero; 
 while as m increases, the pyramids become more and more acute, and finally 
 coincide with the prism /. These pyramids consequently replace the basal 
 edges between O and 7, f. 149, and with them form a vertical zone of planes. 
 
 The pyramids of the m-2 series have the same relation to those of them 
 series, just described, that the prism ?'-2 has to the prism /. They replace 
 the basal edges between i-"2 and O (f. 145), and as the value of m varies, 
 give rise to a series or zone of planes between these limits. 
 
 The pyramids of both the first (m) and the second (m-2) series are well 
 shown in f. 150, of apatite. In the first series there are the pyramids ^, 1, 
 and 2 ; and in the second series the pyramids 1-2, 2-2, and 4-2. The cor 
 
 149 
 
 responding prisms /and -2 are also shown, and the zones between each of 
 them and the basal plane O are to be noticed. Attention may also be 
 called to the fact, exemplified here, that the pyramid 2-2 truncates the ver- 
 tical edges of the pyramid 2 ; also 1-2 truncates the vertical edges of 1 ; 
 while the latter form (1) also truncates the vertical edges of f-2, as is seen 
 in f. 147. 
 
 Di hexagonal pyramids, or BeryUoids. The general form mo : na : a 
 gives the largest number of similar planes possible in this system, which ia 
 here obviously twenty-four, that is, two in each of the twelve sextants. 
 These pyramids correspond to the prisms of the i-n series, and form the 
 dihexagonal pyramids, or beryl loids, as in f. 151. 
 
 The berylloid has three kinds of edges : the axial edges X (L 151, 152), 
 connecting' the apex with the extremity of one of the axes ; the diagonal 
 edges Y, and the basal edges Z 
 3 
 
34 
 
 CRYSTALLOGRAPHY. 
 
 in the upper pyramid, one of these two planes for each sectant may be 
 distinguished as the right, and the other the left, as lettered in f. 152 ; ^and 
 the sa7ne, after inverting the crystal, for those of the other pyramid. It is to 
 be observed that in a given position of the form, as that of f. 151, the right 
 
 153 
 
 154 
 
 of the upper pyramid will be over the left of the lower pyramid, and the 
 reverse. Fig. 153 represents the planes of such a form m-n combined with 
 the unit prism 7, and the planes are lettered , r, in accordance with the 
 above. In f. 154, of a crystal of beryl, the prism I is combined with tho 
 pyramids 1, 2, 2-2, and the berylloid 3-f . 
 
 B. Ilemihedral Forms. 
 
 I. VERTICALLY DIRECT. The planes of the upper range of sectants being 
 in the same vertical zone severally with those below. 
 
 (A). Ilemiholohedral. Ilalf the sectants having the full number of 
 planes : 
 
 1. Trigonal pyramids. The diametral pyramid ra-2 is some- 155 
 times thus hemihedral, as in the annexed figure (f. 155) of a crys- 
 tal of quartz, in which there are only three planes, 2-2 7 at each 
 o.xtremity, and each of those above is in the same zone with one 
 below. The completed form would be an equilateral and symme- 
 trical double three-sided pyramid. 
 
 2. Trigonal prisms. The occurrence of three out of the six 
 planes of the prism /, or fc-2, produces a three-sided prism. The 
 
 is thus hemihedral in tourmaline (f. 156, a top view of a crystal), and the 
 prism -2 in quartz. Both these forms properly belong to the Rhombo- 
 hedral division. 
 
 3. Ditrigonal prisms. An hexagonal prism hemihedral to the dihexago- 
 nal prism occurs in quartz and tourmaline, the hexagonal prism sometimes 
 having only the alternate vertical edges bevelled, as in f. 185, and f. 186, 
 p. 40. 
 
 (B\ Ilolohemihedral. All the sectants having half the full number of 
 planes : 
 
 1. Uemi-dihexagonal pyramids. Each sectant has one out of the twi 
 planes of the dihexagonal pyramid (f. 151, 153) ; this is indicated by 
 
 prism 
 
HEXAGONAL SYSTEM. 
 
 35 
 
 the shading in f. 157. The occurring plane may be the right above and 
 left below, or left above and right below, and the form accordingly 
 
 156 
 
 157 
 
 158 
 
 Tourmaline. 
 
 Apatite. 
 
 either rl m-n, or IT m-n. Examples of the first of these occur in f. 158, 
 representing a crystal of apatite, the planes 0(3-f), and o'(k-Q being of 
 this kind. This method of hemihedrism occurs only in forms that are 
 true hexagonal ; it is often called pyramidal hemihedrism, 
 
 II. VERTICALLY ALTERNATE, the planes of the upper range of sectants 
 being in zones alternate with those below. 
 
 (A) Ilemiholohedral forms, or those in which half the sectants have the 
 full number of planes as in the 
 
 RHOMBOHEDRAL DIVISION. 
 
 1. Rhombohedro'ns,and their relation to Hexagonal forms. The rhom- 
 bohedron is derivable from the hexagonal p} r ramid by a suppression of the 
 alternate planes and the extension of the others. In f. 159, if the shaded 
 planes in front and the opposite ones behind are suppressed, while the others 
 are extended, a rhombohedron will be derived. This is further shown 
 in f. 160, where the hexagonal pyramid is represented within the rhom- 
 bohedron. Another similar rhombohedron, complementary to this, would 
 result from the suppression of the other alternate half of the planes. One 
 of these rhombohedrons is called minus, and the other plus (f. 161, 162). 
 The form in f. 148 is made up, under the rhombohedral system, of +R 
 and R (or +1 and 1) combined, as in the annexed figure (f. 163), of a 
 crystal of quartz. 
 
 159 
 
 160 
 
 Fig. 164 shows the combination of the rhombohedron with the prism /; 
 in f. 165 the former is more developed, and it finally passes into the com 
 
36 
 
 CKYSTALLOG RAPHY. 
 
 plete rhombohedron, f. 161. In f. 166 the rhombohedral planes occur on 
 the alternate angles of the diagonal prism i-2. 
 
 The symbol of the unit rhombohedron as referred to the hexagonal sys- 
 tem is (0 : a : a), a second rhombohedron may be |(20 : a : a) and so on ; 
 it is, however, more simple to write only +7? or 7?, and +27? or 27-?, and 
 so on ; or, where there is no confusion with the symbols of hexagonal forms, 
 as -f 1. 1, and +m, m. 
 
 163 
 
 164 
 
 Quartz. 
 
 166 
 
 This hemihedrism resulting in the rhombohedron is analogous, in the 
 alternate 'positions of the planes above and below, to that producing the 
 tetrahedron in the isometric system. But owing to the fact that there are 
 three lateral axes instead of two, the rhombohedron has its opposite faces 
 parallel, nnlike the tetrahedron. 
 
 In f. 167 the planes 7? belong to 
 the rhombohedron -fl ; -f to the 
 rhombohedron H-f , having the verti- 
 tical axis ; O is the basal plane, 
 or mathematically the rhombohe- 
 dron 0, the vertical axis being 
 00. / is the hexagonal prism 
 oo : 1 : 1, or more properly a rhom- 
 bohedron with an infinite axis, 000. 
 
 Cinnabar. 
 
 ^ -I tne 
 
 are rhombohedral, but belong to the 
 
 minus series ; J has the vertical 
 Calcite. axis|0; 4.40; 2, 20; f, |0, 
 
 this last being complementary to 
 
 +f, and the same identical form, except that all the parts 
 are reversed. Fig. 168, A-E represent different rhombo- 
 hedrons of the species calcite : A., the rhombohedron 1 ; 
 7?, 4; C, 2 ; 7?, f; E, 4 ; having respectively for 
 the vertical axis, 10, -J^ 20, |0, 40, with 0=0.8543, the lat- 
 eral axes being made equal to unity. In f. 169 the 
 rhombohedron 2 (or 27?) is combined with 1 (or R\ 
 the latter truncating the terminal edges of the former. 
 
 In relation to the series of + and rhombohedrons it 
 is important to note that, since the position of \lt is that 
 of the vertical edge of -f 7?, in combination with it, it truncates these 
 edges. Similarly +J7? truncates the same edges of %R, and so on. 
 
HEXAGONAL SYSTEM. 
 
 37 
 
 Also + R truncates the edges of -27?, and - R the edges of + 2R (f. 169) 
 2/ truncates the edges of +47?, and so on. 
 
 2. Scalenohedrons ; forms hemihedral to the dihexagonal pyramid. As 
 the rhombohedron is a hemihedral hexagonal pyramid or -quartzoid, so a 
 seal enohed ron is a hemihedral dihexagonal pyramid or berylloid. The 
 method of hemihedrism is similar by tlie suppression of the planes of the 
 alternate sectauts, as indicated by the shading in f . 170 (analogous to f. 159) 
 and the extension of those of the other sectants. A scalenohedron is 
 
 173 
 
 174 
 
 represented in f. 171, a hexagonal double pyramid with a zig-zag basal out- 
 line, and three kinds of edges ; the shorter terminal edge X, the longer 
 terminal edge Y, and the basal edge Z; the lateral axes terminate in the 
 middle of the edges Z. There are plus and minus scalenohedrons, as 
 there are plus and minus rhombohedrons, and they bear the same rela- 
 tion to each other. 
 
 The relations of the form to replacements of the rhom- 175 
 bohedron are illustrated in the other figures. Fig. 172 repre- 
 sents a rhombohedron (+1 or R) with its basal edges bevel- 
 led ; and this bevelment, continued to the obliteration of the 
 planes 7?, produces the scalenohedron shown by the dotted 
 lines. The scalenohedron in f. 171, 172 has the vertical axis 
 equal to 3c', or three times as long as that of 7?, the lateral 
 axes of both being equal ; and hence it is that the planes are 
 lettered I 3 , the 1 referring to the rhombohedron and the 
 index 3 being the multiple that gives the value of the vertical 
 axis of the scalenohedron, 
 
 In f. 173 there are two scalenohedrons of the same series, 
 viz., I 6 , I 8 , combined with the rhombohedrons R (or +1) and 
 + 4. Fig. 174 shows the scalenohedron I 3 combined with 
 the rhom bohedron 4 (or 47); and 175, the same with the rhombohe- 
 dron 5 ( + 5R). 
 
 Other scalenohedrons replace the basal angles of a rhombohedron by 
 two similar planes (f. 176); or bevel the terminal edges; or replace the 
 terminal solid angles by six planes, two to each terminal edge, or to each 
 
38 
 
 CRYSTALLOGRAPHY. 
 
 \hombohedral face ; a? id they will be relatively + or -, according to theii 
 position in one or the other set of sectants, as has been explained. Fig. 177 
 represents the top view of a crystal of tourmaline. It contains the rhombo 
 
 176 
 
 Tourmaline. 
 
 hedral planes, 72, f, ^, , , , 2, along with the scalenohedrons *, 
 3 5 i B ,l|, 1% and also two others bevelling the terminal edges of the 
 rhombohedron R. 
 
 The scalenohedrons i 2 , -J 3 , i 5 , bevel the basal edges of the rhombohedron -J; and 
 consequently the lengths of the axes are respectively 2, 3, 5 times that of the rhombohedron 
 , and hence, equal Ic, fc, 7*5. Every scalenohedron corresponds to a bevelment of the 
 basal edges of some rhombohedron and that particular one whose lateral edges are parallel 
 to those of the scalenohedron. The symbols for them accordingly are made up of the 
 symbol of the rhombohedron and an index which expresses the relation of its vertical axis 
 as to length to that of the rhombohedronj according to a method proposed by Naumann. 
 (See p. 72.) 
 
 Hexagonal pyramids of the m-2 or diagonal series occur in 
 many rhombohedral species ; as f. 178 of corundum, which 
 contains 4-2(^,4-2,^-2 (for 9-2 on the figure read f-2, Klein), 
 along with the rhombohedron 1, and the basal plane ; also 
 f. 167, in which is the pyramid 2-2. Ilemihedral forms of the 
 same pyramids (of the kind described on p. 34) are met with in 
 rhombohedral species, but only such as have also tetartohedral 
 modifications. Ilemihedral forms of the hexagonal and dihex- 
 Corundum. a g Ona ] p r i sms (p. 34.) are a l so characteristic of some rhombohedral 
 species, and of those that have either tetartohedral or hemimorphic modifi- 
 cations. 
 
 Fig. 179 illustrates the relative positions of the zones of 
 the + and rhombohedrons, and diagonal pyramids m-2 
 alternating with regions of -r- and scalenohedrons in the 
 scheme of the rhombohedral system. The figure is supposed 
 to be a top view. It is similar to f. 152, p. 34, and like that 
 contains the upper planes of the dihexagonal pyramid ; but 
 these are divided between a plus and a minus scalenohedron, 
 those planes marked + being the former, and the others ( ) the 
 latter. The three lateral axes are lettered each bb. The posi- 
 tion of the + mR zone of planes (or plus rhombohedrons) relative 
 to the scalenohedrons is shown by the lettering + It ; of tho 
 mR zones (or minus rhombohedrons) by R. The position of 
 the vertical zone of m-2, or diametral pyramidal planes, is 
 indicated by the letter d. The order of succession, beginning 
 
 with one of the plus interaxial sectants (the one in the medial line below) and numbering it 
 
 I. is as follows : 
 
HEXAGONAL SYSTEM. 
 
 !(1) Plus scalenohedrons, or planes of the general form +m n . 
 (2) Zone of plus rhombohedrons, +mR. 
 (3) Plus scalenohedrons, or planes of the general form +m n . 
 (4) Zone of diagonal pyramids, m-2. 
 
 5(5) \Iinus scalenohedrons, or planes of the general form m n . 
 (6) Zone of minus rhombohedrons, mil. 
 (7). Minus scaleiiohedrons, m". 
 (8) Zone of diagonal pyramids, m-2. 
 
 5(9) Plus scalenohedrons, +m n . 
 (10) Zone of plus rhombohedrons, +mR. 
 (11) Plus scalenohedrons, +m n . 
 (12) Zone of diagonal pyramids. 
 
 And so on around, as the figure illustrates. In the lower pyramid the order of succession If 
 the same ; but the plm planes are directly below the minus of the above view of the uppet 
 pyramid. 
 
 The plw scalenohedrons have the pyramidal edge over the +mR section, the more 
 obtuse of the two (or edge Y) ; and the minus scalenohedrons have that edge the less obtuse 
 (or edge Jf), and that over the mR section the more obtuse (or edge Y). 
 
 B. Holokemikedral forms, or those in which all the sectants have half 
 the full number of planes (as shown by the shading in f. 180). 
 
 Gyroidal, or trapezohedral forms. Of the planes, in f. 181 there would 
 occur only those lettered r, r, above and below ; or those lettered I, I, and, 
 unlike f. 157, the planes above and below are not in the same zone. The 
 
 180 
 
 181 
 
 form is consequently gyroidal, the planes being inclined around the prism, 
 both above and below, and in the same direction at the two extremities. 
 It is also called plagihedraL The symbol for the planes is rr m-n, or 
 U m-n, according as the occurring planes of the two in the same sector are 
 the right or the left. Fig. 182 is an example of U 6-f in the species quartz. 
 
 C. Tetartohedral Forms. 
 
 These forms are hemihedral to the Rhombohedron. 
 
 (A) Holomorphic forms, like the preceding hemihedral, the planes occur- 
 ring equally in the upper and lower range of sectants. 
 
 1. Rhombohedral tetartohedrism. Occurring planes the alternate of 
 those mentioned on page 35, that is, the alternate planes r of one base, 
 and I of the other. They are the r of three alternate sectants above, and 
 
40 CRYSTALLOGRAPHY. 
 
 the I of three sectants below alternate with these. A form of ^ this kina 
 consists of six equal planes, equally spaced, and hence, equal in inclina- 
 tions, and is therefore, in the completed state, a rhombohedron. It occurs 
 in menaccanite or titanic iron, and in quartz (f. 183, planes 13 --if). 
 
 2. Gyroidal or tmpezohedral tetartohedrism. Occurring planes the 
 alternate of those lettered r or I in f. 153, p. 34, that is, the alternate planes 
 r, or alternate Z, of both bases. 
 
 183 184 185 
 
 Quartz. 
 
 Quartz. 
 
 In f. 185, the planes o\ o n , <? m , o {v , o* (4-f , 5-f, 6-f, 8-f, 3-, the first 
 f Otti* rtj^A, the last left) are examples. The upper and lower of a kind adjoin 
 the same diametral plane, but are on opposite sides of it, and therefore the 
 three sectants containing planes below are alternate with the three above. 
 The solid made of these six planes (f. 184) has trapezoidal faces, and is 
 called a trigonotype by Naumann. 
 
 The tetartohedral planes on quartz and cinnabar have a remarkable con- 
 nection with the circular polarization which is characteristic of them 
 both, and which is further explained elsewhere (p. 142). 
 
 (B) HemimorphiG forms / the planes occurring either in the upper or 
 the lower range of sectants and not in both. 
 
 There are two kinds of forms: (1) the hemi-rhombohedron, and (2) the 
 hemi-scalenohedron. Fig. 186 illustrates each of these 
 forms. The form R is properly hem i lied ral at the two 
 extremities, its planes being very large at one, and 
 quite small at the other. So with \. Another rhom- 
 bohedron, 2, occurs only at the upper extremity. 
 Again, ^ is a hemi-scalenohedron, the upper six planes 
 being present, but not the lower. 
 
 The prism /in this figure is hemihedrcd, as explained 
 on p. 34. It is not tetartohedral to the hexagonal 
 system in the ordinary view. But since in a vertical 
 zone +m/?, oo R, mR, the oo R may be regarded as 
 the infinite term of either the -\-inR series, or else tlie 
 same of the mR series; and as this view accords with 
 the tetartohedral character of the m,R series in till such 
 crystals, it might be ranked among tetartohedral forms. 
 From the same point of view, the ditrigonal prisms in tourmaline and 
 
ORTHORHOMBIC SYSTEM. 41 
 
 quartz are tetartohedral, since they may be regarded as either plus or minus 
 tetartohedral scalenohedrons, with an infinite vertical axis. 
 
 Variable elements. In the hexagonal system the same elements are vari- 
 able as in the tetragonal (see p. 30). In" other words, the position of the 
 vertical axis is fixed, but (1) a certain length must be assumed as the unit 
 in a given species, and also (2) the position of the lateral axes must be fixed, 
 for, as in f. 144:, 145, either of the hexagonal prisms may be made I and 
 the other i-2. 
 
 The general characteristics of this system which the student must be 
 acquainted with are : (1) The planes constantly occur in threes or sixes, 
 or their multiples ; (2) The frequency of the angles 120 and 150 in the 
 prismatic series ; (3) The rhombohedral cleavage, common in species be- 
 longing to the rhombohedral division. It is also important to note that 
 many forms apparently hexagonal really belong to the orthorhombic system, 
 being produced by twinning parallel to the vertical prism ; e.g., the appar- 
 ently hexagonal prisms of aragonite. The close relation of the two systems 
 is spoken of elsewhere (p. 46). 
 
 The planes of symmetry for the holohedral forms are analogous to those 
 in the tetragonal system ; that is, one principal plane of symmetry normal 
 to the vertical axis, and six others intersecting in this axis. These last 
 belong to two sets, the planes of the one cutting each other .at angles of 
 60, and diagonal to those of the other. 
 
 IY._ORTI10RI10MBIC SYSTEM. 
 
 In the ORTHORHOMBIC SYSTEM the three axes are unequal c, , a ; of these 
 c is the vertical axis, b is made the longer of the two lateral axes, or the 
 macrodiagonal axis, and a the shorter lateral, or braehydiagonal, axis.* 
 
 The different occurring forms, deduced as before from the general ex- 
 oression, are: 
 
 ( me : nb : a [m-n] (ccc:nb:a 
 
 \ me : b : na [m-fa] \ <x> c : b : na 
 
 \mc:b:a \_m] oo c : b : a [/] 
 
 ( c : b : a [1] oo c : b : oo a [i-i] 
 
 ( me : oo b : a [//v4] oo c : oo b : a [i-i] 
 
 ( me : b : oo a [m>$] Qc : b : a [O] 
 
 The abridged y mbols need very little explanation additional to that given on p. 25. As 
 before, only the essential part of the symbol is given ; m is written first, and refers in a]l 
 oases to the vertical axis (c), and n refers to one of the lateral axes, whether the longer (b) 
 or the shorter (d) is indicated by the sign p'aced over it, as tl or n. When n~ oo, this is 
 indicated by the hitherto used, and the sign is placed over it, I, or $, with the same signi- 
 Tneso correspond to the symbols used by Naumann, as follows: 0=0 P', i-l= 
 
 m-i mP=m m-tl=mP/l, etc. 
 
 * For the relation of the axes thus lettered to those of Dana's System of Mineralogy and 1 , 
 of other auth :>rs, seep. 53. 
 
CRYSTALLOGRAPHY. 
 
 A. Holohedral forms. 
 
 Pinacoids. The final case mentioned in the above enumeration em 
 braces, as before, the two basal planes, or basal pinacoids ; the one pre- 
 ceding it includes the two planes parallel to the vertical and macrodiagonal 
 axes (<; and &), called the macropinacoids, and the next above includes the 
 planes parallel to the vertical and brachydiagonal axes (c and cc), called the 
 brachypiiiacoids. These three sets of planes together form the solid in 
 f. 188, which is called the diametral prism. In consequence of the ine- 
 quality of the different pairs of planes there are only four similar edges in 
 any set; thus four similar vertical edges; four macrodiagonal basal edges, 
 two above and two below, between and i-i ; and similarly four brachy- 
 diagonal basal edges between and i-i / the eight solid angles are all 
 similar. 
 
 187 
 
 188 
 
 Prisms. The form oo c : b : 0, or /, includes the four planes of the unit 
 prism which, in combination with O, is seen in f. 187. In this case the 
 eight basal edges are similar, being made in each case by a similar pair of 
 planes O and /. Of the vertical edges there are two pairs, those at 
 the_extremity of the axis #, which are obtuse, and those at the extremity 
 of $, which are acute. Similarly, there are two sets of basal solid angles, 
 four in each; for though each solid angle is formed by the meeting of 
 the same three planes, the angles are different in the two cases. The 
 form / replaces the four similar vertical edges of f. 188 ; the macro- 
 pinacoids i-l truncate the obtuse vertical edges of the prism 7J and the 
 brachypinacoids i-l truncate the acute vertical edges of /, as shown in f. 189. 
 There are two other series of prisms with symbols oo c : nb : a and 
 oo c : b : na. In the latter series the axis b is made the unit ; the reason for 
 this will be obvious when the relations of the two forms are explained. 
 
 The prism / meets both axes a and 
 
 190 191 at their unit lengths, as in f. 187. 
 
 If, now, the prismatic planes meet 
 the longer lateral axis (b) at a greater 
 distance, a prism is formed such as 
 that in f. 190, whose symbol is i5,or 
 QO c : %b : a. This is a macrodiago- 
 nal prism ; and others might have 
 the symbols i-$ (oo c : 35 : a), i-4 (<x- c : 45 : #), and so on, or in general i-n. 
 If n becomes less than unity, the case shown in f. 191 arises, where the 
 inner prism has n=\, and the symbol is^'-I (oo e : ^b : a), still retaining a as 
 the unit axis. For convenience of reference, however, the principle before 
 explained (p. 11) is made use of, and the plane is called oo c : b : 2a, or 2-2; 
 
ORTHOKHOMBIC SYSTEM. 
 
 these expressions and those before given being identical, except that in 
 the latter case b is the unit axis. By this method the use of any fractions 
 less than unity is avoided. The inner prism ^-J, indicated by dotted lines 
 in f. 191, then becomes the outer prism or i-%. The prisms of the general 
 form i-n, are called brachydiagonal prisms. 
 
 The prisms i-n bevel the front and rear (obtuse) edges of the prism /, 
 f. 192, and the prisms i-n bevel the side (acute) edges as in f. 193. Further, 
 the former, i-n, replace the edges between i-i and I (f. 194), while the i-n 
 prisms replace the edges between i-l and 1 (f. 194). 
 
 This series of planes (f. 194), from i-l to i-l, is another example of a 
 zone; all the planes make parallel intersections with each other, being alike 
 in that they are parallel to the vertical axis. 
 
 192 
 
 194 
 
 1 
 
 
 
 t* 
 
 12 
 
 1 
 
 J 
 
 
 uJ 
 
 Domes. The form me : oo b : a includes the four planes which are 
 parallel to the macrodiagonal axis, and meet the vertical axis at variable 
 distances, multiples of the unit length (see f. 34, p. 11). An example of 
 them in combination with i-l, the brachypinacoid, is shown in f. 195. 
 These planes are called macrodomes (see also f. 196). 
 
 195 
 
 196 
 
 197 
 
 If 
 
 If 
 
 The form me : b : cca includes four analogous planes, which differ in 
 this respect, that they are parallel to the brachydiagonal axis, and are hence 
 called brachydomes (see f. 35, p. 11). In this case, the longer lateral axis 
 is taken as the unit. Fig. 197 shows two such brachydomes, \-l and 24, 
 in combination with other forms. (See also f. 198.) The word dome, used 
 here and above, is derived from SO/A/}, or domus, a house, the form resem- 
 bling the roof of a house. 
 
 The combination of l-l with \-l is shown in f. 199, form ing a rectangular 
 cctahedron, and in f. 21)0 they are shown replacing the solid angles formed 
 by / and O, as in f. 188. As either of the three directions may be made 
 the vertical, it is evident that these domes differ from vertical prisms only 
 in position. 
 
CRYSTALLOGRAPHY. 
 
 200 
 
 The occurrence of these domes in combination with the other forms, 0, 
 i-l, i-ly /, affords an illustration of the law of symmetry that all similar 
 
 parts must be modified alike. Thus in f. 
 187, as has been shown, there are two sets 
 of solid angles, four in each ; one set is 
 replaced by the four planes of the form 
 m-l, and if one is, all must be ; and the 
 other set (lateral) is replaced by the four 
 planes of the form m-i, f. 200. 
 
 Octahedrons (or Pyramids). The sym- 
 bol c : b : a (1) belongs to the unit octahedron (f. 201). It replaces the 
 edges between the prism /and the basal plane O (f. 20:4). It also replaces 
 
 201 
 
 202 
 
 203 
 
 the eight similar solid angles of the diametral prism, as in f. 203. This 
 is a special case of the form mo : b : a, in which m may have values vary- 
 ing from to oo . Fig. 208, of sulphur, shows a zone "of such planes, of 
 the general symbol mo : b : a, with ra=x> for /; also, ra=l, m=$, ra=-J. 
 m |, and finally m=Q, for the basal plane O. 
 
 204 
 
 206 
 
 207 
 
 The general form in this system, consisting of eight similar planes, may 
 le written either me : nb : a (m-n) or mo :b:na (m-n). The relation be- 
 tween the two is the same as that between the prisms i-i; and i-h. Thus, 
 in f. 204, one plane of the octahedron 2c : 2b : a (2-2) is Driven, and also one 
 plane of another octahedron or pyramid, whose symbol is 2c : b : a ('2). If 
 n becomes less ^than unity, as -, the plane has the symbol 2c : %b : a (2-J). 
 In order to avoid this use of fractions the symbols written ^4c : b : 2a, 
 that is, 4-5. The plane is shown in f. 205, in its two positions correspond- 
 ing to 20 \\l\a, and c : b : 2a, the two being crystallographically iden- 
 
ORTHORHOMBIC SYSTEM. 
 
 Thus there are two series of pyramidal planes : a macrodiagonal (m-n\ 
 where the shorter axis is taken as the unit, and a 
 br achy diagonal (m-7i), where the unit is the longer 
 lateral axis; and between the two lie the unit 
 octahedron (1) and those of the m series, just as 
 the prism / lies between the prisms i-n and i-n. 
 The macrodiagonal planes 1-2 and 2-2 are shown 
 in f. 206 and f. 2_07. It is also seen in f. 207 that 
 the planes 2-2, 24, 2-2 all make parallel intersec- 
 tions with each other and with i-t, being an 
 example of a zone where the ratios of the ver- 
 tical axes are the same. Further orthorhombic 
 forms are displayed in f. 208, of sulphur, already 
 referred to. The full symbol of the plane 1-5 is 
 c : b : 3a. 
 
 B. Hemihedral Forms. 
 
 Sulphur. 
 
 The hemihedral forms that have been ohserved are of two kinds : 1, 
 The vertically -oblique (p. 14), producing monoolinic forms; and 2, the 
 hemimorphic, in which the planes of the octahedrons or domes of one base 
 have no corresponding planes at the opposite extremity. The former kind 
 
 211 
 
 Humite. 
 
 Humite. 
 
 Calaminc. 
 
 is illustrated in f. 209, of the species chondrodite (var. hnmite, type 111). 
 Fig. 210 represents the.holohedral form of the same; the planes f-i, 14, 
 24, are of macrodomes ; %-%, |--, f-, 4-, of brachy domes ; and the others of 
 various octahedrons, mostly in two vertical zones, the unit zone (me : b : a\ 
 and the 1 : 2 zone (ma : %b : a). In f. 209 the alternate of the macro- 
 domes and of the octahedral planes of the 1 : 2 zone are absent in the 
 upper half of the form, and are present without those with which they 
 alternate in the lower half. The crystal consequently resembles one under 
 the monoclinic system. 
 
 Datolite was formerly cited as a hemihedral orthorhombic species, but it 
 has been found to be really monoclinic. Furthermore, it has been recently 
 shown by the author, by reference to the optical properties, that the ehon 
 
46 CRYSTALLOGRAPHY. 
 
 drodite of the second and third types (see p. 327) is not orthoihombic but 
 monodinic, and this must be true also of humite.* 
 
 Hernimorphic forms characterize the species topaz and ealamine. The 
 latter (in f. 211) has only the planes of a hernioctahedron at one extremity, 
 and planes of hemidomes at the other. For the pyro-electric properties of 
 such forms, see p. 169. 
 
 Variable elements. In the orthorhombic system the lengths of the three 
 axes are variable, though their position is fixed, and after these are fixed 
 the choice of one for the vertical axis must be arbitrarily made. In other 
 words, given an orthorhombic crystal, the three rectangular directions are 
 fixed, but two assumptions must be made which will mathematically deter- 
 mine the length of two of the axes in terms of the third. For instance, 
 in a crystal, if certain occurring domes are adopted as the unit planes \-l 
 and l-, this will determine "the relative lengths of the three axes, for 
 which two measurements will be necessary ; or, if an occurring octahe- 
 dron is assumed as the unit octahedron (1,) this alone will obviously fix the 
 axes ; but here, also, two independent measurements are necessary in order 
 to enable us to calculate their length, as is explained later, p. 74. Hav- 
 ing determined upon the relative lengths of the axes, one of these must be 
 made the vertical axis (c\ and then, of the two remaining, the shorter will 
 be the brachydiagonal (a), and the longer the macrodiagonal axis (). 
 
 In deciding these arbitrary points, the following serve as guides : The 
 habit of the crystals; the relations of the given species to those allied in 
 composition; the cleavage, which is regarded as pointing to tluit form 
 which is properly fundamental ; and other considerations. How arbitrary 
 the choice generally is is well shown by the fact that, in a considerable 
 number of species belonging to this system, different lengths of axes, as 
 also cliff- -rent positions for them, have been adopted by different authors. 
 "Where an optical examination can be made of an orthorhombic crystal, 
 the results show what the true position of the axes is, in accordance with 
 the principles proposed by Schrauf. This subject is alluded to again in its 
 proper place (p. 151). 
 
 The general characteristics of the crystals of this system, are not so 
 marked as those of the preceding systems. The kind of symmetry should 
 be well understood, though, as remarked on p. 50, crystals which are in 
 appearance orthorhombic maybe really monoclinic; the true test of the 
 system is to be found in the three rectangular axial directions. A pris- 
 matic habit is very common, the prisms (except the diametral prism) not 
 being square, also the prominence of some of the most commonly occur- 
 ring macrodomes and brachy domes ; a prismatic cleavage is common, 
 and often a cleavage exists parallel to one of the pinacoids (e.g., i-l) 
 and not to the other, which could not be true in the tetragonal system ; 
 similarly the planes i-l, i-l are sometimes physically different, e.g., in 
 regard to lustre. 
 
 As has already been remarked, forms apparently hexagonal are common 
 among certain species belonging to this system ; this is true in those cases 
 
 * Since the above paragraph was put into type, Des Cloizeaux has announced that an opti- 
 cal investigation by him has proved that humite crystals, of types II. and III., are really 
 monoclinic^ as suggested above. The figures are allowed to remain, however, since they illus- 
 trate the form which this method of hemihediism would produce. 
 
MONOCLINIC SYSTEM. 47 
 
 where the prism has an angle approximating to 120. It is immediately 
 evident, as is explained more thoroughly in the chapter on compound 
 crystals, that if three individual crystals are united each by a prismatic 
 face, when the prismatic angle is near 120, they will form together 
 a six-sided prism, approximating more or less closely to a regular hexa 
 gonal prism. Similarly, under the same circumstances, the correspond 
 ing pyramids will thus together form a more or less symmetrical hexagonal 
 pyramid. This is illustrated by the accompanying 
 figures of witherite, where the prismatic angle is 118, 
 30'. It need hardly be added that this is true in 
 general, not only of the vertical prism, but also of a 
 macrodome or brachydome, having an angle near 120. 
 The optical relations connected with this subject are 
 alluded to elsewhere, p. 151. 
 
 Planes of Symmetry. The three diametral planes 
 are planes of symmetry in this system, and they are the only ones. 
 
 X 
 
 212 
 
 V. MOKOCLINIC SYSTEM. 
 
 In the MONOCLTNIC SYSTEM the three axes are un- 
 equal in length, and while two of them have rectan- ' 
 gular intersections, the third is oblique. The position 
 usually adopted for these axes is as shown in f. 214, 
 where the vertical axis, c, and lateral axis, J, make 
 retangular intersections, The same is true of b and 
 #, while c and d are oblique to one another. 
 
 The following is an enumeration of the several 
 distinct forms possible in this system, deduced, as be- 
 fore, from the general expression : 
 
 214 
 
 m-n 
 -\-m-n 
 m-n 
 -f m-n 
 
 m,c : oo b : a 
 + me : oo b : a 
 j QO c : n b : a 
 \ oo c : b : na 
 x> c : b : a 
 oo c I oo b i a 
 oo c : b : QO a 
 Oc :b : a 
 
 [ m 
 
 [ + 7H 
 
 [i-n 
 
 -*] 
 i* 
 
 ( me : nb : a 
 \ +mc : nb : a 
 j me : b : na 
 ( +mc : b : na 
 j mo : b : a 
 ( c : b : a 
 
 )+mc : b : a \_-\-in\ 
 
 + c:b:a [+1] 
 
 mo '. b '. oo a \m-i\ 
 
 The abridged symbols correspond to those in the orthorhombic system, explained on p. 42. 
 The only point to be noted is that where n or i relates to the clinodiagonal axis, d, this i3 
 indicated by an accent placed over it, as m-l, m-n ; but in m-i, and m-n, etc. , i and n refer 
 to the orthodiagonal axis. Naumann wrote these mPcc , and mPri, or else with the 
 accent across the initial letter P. The minus signs are used in the same way as by Naumann 
 (see p. 76). 
 
 Pinacoids. As in the orthorhombic system, there are three pairs of 
 pinacoidal planes : the base O=Qc : b : a\ the ortbopinacoid, parallel to the 
 
CRYSTALLOGRAPHY. 
 
 216 
 
 / 1 
 
 
 / 
 
 ii 
 
 1 1 
 
 / -, 
 
 )- 
 
 
 7 
 
 217 
 
 ortho-axis (5) oo c : <x> "b : a, or i-i ; and the clinopinacoid, parallel to the in 
 olined axis (#), QO c : b : oo a, or i-l. 
 
 In the solid (f. 216) or diametral prism formed of these three pairs of 
 planeo, the four vertical edges are similar, and this is also true of the four 
 edges between O and i-l. On the other hand, the four remaining edges are 
 of two sets ; that is, the edge in front above is similar to the edge be- 
 hind and below, for the angles are equal 
 and inclosed by similar planes ; but these 
 edges are not similar to the remaining 
 two. since, though the planes are the 
 same, the inclosed angles are unequal to 
 the former. Further, there are two sets 
 of solid angles, two in front and two dia- 
 gonally opposite behind, being alike ob- 
 tuse angles, and the other four alike and acute. 
 
 Prisms. In consequence of the similarity of the vertical edges of the 
 diametral prism, they must all be replaced if one is ; this is done by the 
 
 unit prism /(oo c : b : a), in f. 215, 217. 
 
 Of the other prisms, each obviously consist-- 
 ing of four planes, there are two series, the 
 orthodiagonal, i-n, and clinodiagonal, i-n, 
 bearing the same relation to each other as 
 the macro- and brachy-diagonal prisms in 
 the orthorhombic system, in fact, tbe same 
 explanation may be made use of here. Fig. 
 217, of a crystal of datolite from Toggiana. 
 shows the pinacoid planes, as also the unit 
 prism, /, and the clinodiagonal prism, i-b. 
 
 Clinodomes. The form m-l (me : l> : GO a] 
 includes the four planes parallel to the clino- 
 diagonal axis, and meeting the others at variable distances. They are analo- 
 gous to the brachydomes of the orthorhombic system. There are four of 
 these planes, because the two axes, c and &, make rectangular intersections. 
 This is also seen in f. 218, since, as has been remarked, the four clino- 
 diagonal edges in f. 21g are similar, and hence are simultaneously replaced 
 by these clinodomes. 
 
 220 
 
 7 
 
 Orthodomes. Of the general form, me : oo b : a, there are two sets oi 
 planes, two in each (hemi-orthodo'mes), both of which are alike in that they 
 are parallel to the orthodiagonal (b} axis (see f. 219). They are unlike, how- 
 ever, in that two are opposite an obtuse angle, and two opposite the acute 
 angle. Consequently these two pairs of planes are distinct, and must occur 
 
MONOCLINIC SYSTEM. 
 
 ra 22o thepl r - 
 
 tiated by f. 220, where, as has been remarked, the obtuse edges, above i 
 
 S21 
 
 233 
 
 front, and below behind are similar, and are hence replaced by planes of 
 
 ^"-)> io simi^an^ 
 
 di8 ' inc tf of plus and minus belongs to 
 
 }, f , and the signs are used in the same way. & For 
 
 each form there are only four similar planes. 
 
 The m series is that of the unit octahedrons,- properly hemi-octahe- 
 kZ; in f e 99? Jra , ra Vo m > ai | d ' The f de ' P of +T and -1 
 Three pinatoS ' U * Sam6 plaileS "* in coinb lati with the 
 
 0n ?> +m ~ n > ~ m ~ n > and +m -> ~^-^ ^ ive each fo r simi- 
 ft - V u ear 6Xact1 ^ the 8ame relation to ea h otli er as the m-n 
 fhoinbic system, so that no additional explanation is 
 needed here in regard to them. 
 
 (f * ^i ? dat lite maj be referred to for illustrations of the 
 1 " ^ 11Ch > V ? been 1Jamed - Tllere are here tliree different 
 omes f ., 2-^ and 4-^ each comprising four planes; a minus hemi- 
 
 + 2i^ l t PP , Slte the btUSe ^4-Afid also a 'plus orthodomo, 
 tese two planes are quite distinct, though numerically the symbols ;.re 
 e sanie) ; moreover, of hemi-octahedrons of the unit series, there are -4 
 -4, +2, +t, + l, + f, +|; also of orthodiagonalpyramids, -4-2, 
 6-3, also +2-2, and of clinodiagonal planes, -8-S, and +12-| A 
 1 study of a few such figures, especially with the help of models, will 
 give the student a clear idea of the symmetry of this system. It will be 
 that all the planes above in front are repeated below behind, and 
 e below in front appear again above behind. More important than 
 tnis, it will be seen that the clinodiagonal diametral plane divides the crys- 
 tal into two symmetrical halves, right and left; in other words, as remarked 
 later, it is a plane of symmetry. 
 
 Ilemihedral forms occur of a hemimorphic character, in which the planes 
 
 the opposite extremities of the vertical axis are unlike ; thus, the 
 
 * one or more hemi-pyrarnidsmay occur at one extremity, without 
 
 4iose corresponding at the other, as in tartaric acid, ammonium tartrate, etc. 
 
 With many monocliriic crystals the obliquity is obvious at sight ; but with 
 
 many others it is slight, and can be determined only by exact measurements 
 
50 
 
 CRYSTALLOGRAPHY. 
 
 In datolite it is only six minutes. The character of the symmetry exhibits 
 f urthe the obliquity. But, as seen above, both + and - planes of he same 
 value do occurtogether, and though they are real y distinct yet : they may 
 give a monoclinic crystal the aspect of w orthorhomfoc crystal 
 other hand, true orthorhombic crystals may be hemihedral, and thus may be 
 monoclinic in the character of the symmetry (p. 45). 
 
 Variable elements. In the monoclinic system, the only element which is 
 fixed is the position of the orthodiagonal axis (b) at right angles to the plane 
 in which the other axes must lie. The lengths of these axes must obviously 
 be assumed in the same way as in the preceding system; but, further than 
 this, their position in the given plane, and the angle they make with each 
 other, are both arbitrary; in other words, any plane m the zone at righl 
 ano-les to the clinopinacoid may be taken as the base (O) and any othei 
 as "the orthopinacoid (i-i). The existence of a prismatic cleavage, or one 
 parallel to a plane in the orthodiagonal zone often points to the^planes which 
 are really to be considered fundamental. In many cases it is considered 
 desirable to assume an angle near 90 as the angle of obliquity, so as to show 
 the degree of divergence from the rectangular type. It need hardly be 
 added that authorities differ widely both as to the position and lengths 
 given to the axes of the same species. 
 
 ' Plane of symmetry. Monoclinic crystals have but one plane o sym- 
 metry the diametral plane in which the vertical and clinodiagonai axes 
 lie, that is, the plane parallel to the clinopinacoids. The maximum num- 
 ber of similar planes for any form is four, and it will be noticed that 
 there is no single form which alone can enclose a space, or form a geo 
 *,rical solid. 
 
 YL TRICLINIC SYSTEM. 
 
 In the TRICLINIC SYSTEM the three axes are unequal, and their intersections 
 are mutually oblique. In consequence of this fact, there is no plane 
 symmetry. " Only diagonally opposite octants are similar; there can conse- 
 quently be onlv two planes of anyone kind. There are no truncations or 
 bevelments, and no Intel-facial angles of 90, 135, or 120. The prisms 
 are all hemiprisms, and the octahedrons tetarto-octakedrons. 
 
 The lateral axes are called the macrodiagonal (b), and the Irachydiago- 
 nal (a). In f . 225 the diametral prism (made up of three pairs of < 
 
 224 
 
 planes) is represented, and in f . 224 the unit pram. To the latter u added 
 Fin f 226) one plane -1 on two diagonally oppose edges, which are two 
 out of the eight of the unit octahedron (f. 227). Tins octahedron, as will 
 
MATHEMATICAL CKTSTALLOGKAPHY. 
 
 51 
 
 he seen, is made up of four sets of different planes. The different kinds 
 of planes are distinguished by the long or short mark over the n (n or n} 
 and also by giving those which occur in the right-hand octants, in front, 
 an accent ; those above (in the obtuse octants) are minus, and the others 
 plus. The form m-n consequently may be -m-n', or m-n, -{-m-n, 01 
 +m-n; and similarly with m-n. In f. 228 the unit prism is combined with 
 a hernidorne and a vertical plane parallel to the brachydiagonal section. 
 ^ The forms, although oblique in every direction, may still be closely 
 similar to monoclinic forms of related species. 
 
 Anorthite. 
 
 Axinite. 
 
 The annexed figures are of triclinic species. In f. 229, of anorthite, of 
 the feldspar group, the form is very similar to those of the monoclinid 
 feldspar, orthoclase ; in orthoclase, on the brachydiagonal (clinodiagonal) 
 section is 90, whence it is monoclinic, while in anorthite this angle is 85 
 50', or 4 10' from 90, and this is the principal source of the diversity of 
 angle and form. 
 
 Fig. 230 represents one of the crystalline forms of axinite, nearly all of 
 which fail of any special monoclinic habit. 
 
 MATHEMATICAL CRYSTALLOGRAPHY. 
 
 Introductory remarks on the proper symbol of each plane of a general 
 crystalline form. Hitherto the symbol me : nb : a has been employed to 
 express the general position of all the planes comprising any crystalline 
 form, and it has been shown that there are in some cases forty-eight similar 
 planes answering to the general symbol, and in other cases only two. In 
 order, however, to express the exact position of each individual plane be- 
 longing to such a form, it becomes necessary to resort to the methods of 
 analytical geometry. As shown in f. 231, the portions of the axes, when 
 the centre is the starting point, which lie above, to the right, and in front 
 of the centre, are called plus (-H); the corresponding portions of the axes 
 measured from the centre below, to the left, and behind, are called, for the 
 
52 
 
 CRYSTALLOGRAPHY. 
 
 sake of distinction, minus (-). The planes of the firs quadrant (see also 
 f. 232) are all positive (+); the planes of the second positive (+) wi th 
 reference to the axes o and a, but negative (-) with reference to b ; in the 
 
 231 
 
 232 
 
 third both lateral axes are negative (-) ; in the fourth quadrant the planes 
 are positive in regard to c and ft, but negative w \ th respect to a. Ihe 
 lower quadrants are respectively similar, except that the vertical axis is 
 always q negative. The symbols for each plane of the orthorhombic 
 octahedron (f. 231), taken in the same order, will be as follows . 
 
 Above. +c: + & : 
 Below, -c: + b: 
 
 c : -I : 
 <?:-&: 
 
 ; +c : -I : -a; 
 ; -*:-:. -a 5 
 
 : -a. 
 
 The hexoctahedron (ma : wa : a) may be taken as another example. The 
 general symbol of the form of f. 247, p. 64, is 3-f (3 : fa : a), but the 
 symbol of each plane is distinct. The same principle applies here as in the 
 other case. Several of the planes in f. 247 are numbered to allow < 
 convenient reference to them as examples, the appropriate symbols are 
 written below; the order in the symbols is the same as that uniformly used 
 in the work: 1st, the vertical axis (c) ; 2d, the lateral axis extending right 
 and left (b) ; and 3d, the lateral axis, in front and behind (a). 
 
 1 = 3a : f a : a 
 
 2 = f a : 3a : a 
 
 3 = a : 3a : f a 
 
 4 = a : f a : 3a 
 
 5 = d : a : 3a 
 
 c la 
 
 6 = 3a : a : f a 
 
 7 = 3a : f a : a 
 
 8 = 3a : a : %a 
 
 9 =. \a\ 3a : a 
 
 10 = 3a : } : , and so on. 
 
 It will be evident from these examples that to express the position of 
 an individual plane the numbers expressing its relations to the three axes 
 must all be regarded, each with its appropriate sign ; m other words, the 
 values of m, n, r, in the general form, me : nb : ra, must all be given, one 
 of them being unity; m always refers to the vertical axis, c; n to the 
 lateral axis, b: r to the lateral axis, a ; as has already been remarked, a 
 is usually made the unit axis. In the example last given the axes, being 
 all equal, are all called a. 
 
MATHEMATICAL CRYSTALLOGRAPHY. 
 
 53 
 
 Reference must be made here to the method of lettering the axes adopted in this work 
 The usage of the majority of authors is followed, and the subject is illustrated in the fol- 
 lowing table. 
 
 Isometric. 
 
 Common usage. 
 This work 
 (Weiss, Rose. 
 Miller's School, 
 Mohs, Naumann, 
 Dana (System 1868) 
 
 Tetrng. (Hexag.) Othorhombic, Triclinic. Monoclinic. 
 
 vert. lat. vert, macrodiag. brachydiag. vert, ortfcodiag clinodiag 
 
 I 
 
 It is certainly very desirable to indicate to which axis each letter refers by tho mark 
 placed above it ; in doing which, we follow Klein's EMeitung in dieKrystattberechnung. 
 
 DETERMINATION OP PLANES BY ZONES. 
 
 The subject of zones has been briefly explained on page an varous 
 examples have been pointed out. The principle is one of the highest im- 
 portance, both practically, since it gives the means of determining the 
 symbols of many planes without calculation, and also theoretically. The 
 law of zones, which states simply that the planes of a crystal lie in zones, 
 is one of the most important of the science, and second only to that of the 
 rationality of the indices. The planes of a crystal thus may be said to be 
 connected together by these zones, a single plane often lying in a large 
 number of zones. 
 
 Parallelism in the combination edges, or mutual intersections of planes, 
 is based upon some common geometrical ratio, and this common ratio bp 
 longs to the symbols of all the planes of the zone. 
 
 All planes which lie in the same zone will give exactly 
 parallel reflections with the reflective goniometer, as explained 
 on p. 87. This is the only decisive test, and when possible 
 should be made use of, since combination-edges often appear 
 parallel when the planes forming them are not really in the 
 same zone. Furthermore, inasmuch as parallel intersections 
 are observed between planes of a zone only when they actually 
 intersect, the goniometer may often serve to detect the ex- 
 istence of zones not otherwise manifest. 
 
 In f. 194, p. 43, the planes i-i, i-2, 7, 2, i-l, all 
 lie in a vertical zone, and they are all obviously 
 alike in this, that they are parallel to the vertical 
 axis ; in other words, the common value c oo be- 
 longs to them all. Again, in the zone O, \-l, 14, Acanthite. 
 *-, etc. (f. 197, p. 43), the planes are alike in that 
 
 they are all parallel to the br achy diagonal axis ; in other words, & = oo is 
 true of all of them. Still again, the pyramidal planes J, 1, 2 (f. 150, p. 33), 
 are also in a zone between O and /, and here the ratio 1 : 1 for the lateral 
 axes applies to all ; also, 1-2, 2-2, 4-2, are in a zone from O to i- 2, and for 
 them the lateral axes have the ratio 1 : 2. In the case of an oblique zone, 
 as i-l, 3-3, 2-2, 1, etc. (f. 233), this fact is less evident on inspection, but is 
 equally true, as will be seen later. The common ratio in this case is m r. 
 
 Since all the planes of a zone have a comrron ratio, which has been 
 
54 CRYSTALLOGRAPHY. 
 
 shown to be true in several examples but also admits of rigid proof, 
 it is evident that a plane which lies in two zones has its position deter- 
 mined by that fact, since it must answer to two known conditions. In 
 other words, the algebraic equation of a zone is known when the parame- 
 ters of two of its planes are given, for they are sufficient to determine the 
 common ratio, and by combining them the zone equation is obtained ; and 
 further, when the equations of two zones are given, combining them will 
 give the equation, that is, the parameters, of the plane common to both. 
 
 The general equation, derived from Analytical Geometry, for any plane 
 mo : nb : ra, making parallel intersections with the planes m'c : rib : r'a 
 and m"c : ri'b : r"a is, 
 
 M N R 
 
 H -i = 0; in which, 
 
 m n r 
 
 M= m'm"(rtr"-ri f r')', N = n'n" (r'm"-r"m'}\ R = r'r" (m'n"-m"ri). 
 
 By substituting the values of the parameters of two given planes for m' , 
 n', r', and m", n" , r" in the zone equation, a Derived equation is obtained 
 which expresses the relations between m, n, r of all the planes of the zone. 
 The form of the general zone equation is so symmetrical that the calcula- 
 tions are in any case quickly and easily made by a method analogous to 
 that used in Miller's system (as suggested by Prof. J. P. Cooke). If we 
 write the parameters in parallel lines, repeating the first two terms, we 
 have 
 
 m' , n' \S r' \/ ' \s n' 
 trJ' , n" A r" A m" A n" 
 
 and it will be seen that the coefficients J/", N, R are found by multiplying 
 together the parameters in the manner which the scheme indicates. 
 
 M= m'm" (ri r"r'n"). N= n'n" (r'm"m'r"). R r'r" (m'ri'n'm"). 
 
 Take, for example, the zone of planes between i-l and 1 (f. 233). For 
 i-t, m' = *', n' 1, r' = i ; for 1, m" = 1, n" 1, r" = 1 ( i = oo ) ; hence 
 the scheme becomes 
 
 * > * V * V * 
 
 i , i A i A i / 
 
 and for the several values of the coefficients 
 
 This reduces the zone equation torn = r (after dividing by $ = oo 2 ), and 
 to this all the planes of the zone conform. So also for the zone of 1-2, /, 
 3-}, 14,^etc., in f. 23i. The parameters of the plane / and 14 arranged as 
 above give 
 
 1 i 1 1 
 
 and the values of Jf, ty R are ^ 2 , -a 2 and -H" 2 respectively. Hence the 
 zone equation becomes 
 
 1 3 1 
 
 I . Q . 
 
 m n r ' 
 
 
MATHEMATICAL CRYSTALLOGRAPHY. 
 
 55 
 
 797 
 
 and if r = 1, the general formula n = y is derived. Between i : 1 : 1 (/) 
 
 and 1 : i : 1 (1-1} the values of n are positive, as with the series of planes 
 i:l-i:l-; 6c:^:a; 5:*:l;4:f:l; 3:f:l; 
 2:2:1; f : 3 : 1, etc., 1:^:1. Between 1 : * : 1 234 
 and % the values of n are negative, that is, are 
 measured on the back half of the axis b ; as, for 
 example, |- : 4 : 1 ; J : 3:1; : 2:1; -|: 
 1:1. As the zone continues on from : 1:1 
 to 1 : - 1 : i (l-), and i : 1 : 1 (7), the unit 
 axis is changed, making n = 1. The zone equa- 
 tion then becomes r = r, the values of r being 
 
 ?/2/"^~ -L 
 
 positive between -| : 1 : 1 and 1 : 1 : i, and 
 negative between 1 : 1: i and i : 1 : 1. 
 The successive planes are f: 1:2; f- : 1:3; 
 
 4 
 
 | ) 
 
 1 4. 1 1 L. a 4 1 1 3 1 O. t). "I . Ockf 
 
 . l.rr, -L. A it * j .^ -- "t j y J- . o , .j . . .4, 6t i. 
 
 oth figures 233 and 234 are illustrations of this zone. 
 
 If the student will select a variety of examples of zones from the figures in the descriptive 
 part of this work, and will apply the zone equation as given above to them, paying special 
 attention to the signs of the parameters of each plane, he will soon find that the apparent 
 difficulties of the subject disappear. 
 
 EXHIBITION OP THE ZONE-RELATIONS OP DIFFERENT PLANES BY MEANS OP METHODS OP 
 
 PROJECTION. 
 
 The relations of the different planes of a crystal are to some extent exhi- 
 bited graphically in such figures as have been already given. Other meth- 
 ods, however, are used which have special advantages. The two most 
 important are briefly mentioned here. 
 
 1. Queiistedtfs method of projection. In this method the planes of a 
 crystal are projected upon a horizontal plane, usually 
 that of the base (O). Every plane is regarded as pass- 
 ing through the unit-length of the axis which is taken 
 as the vertical ; these planes consequently appear as 
 straight lines intersecting each other on the plane of 
 projection. 
 
 The following are examples. In f. 235, of galenite, 
 there are present the planes of the cube, octahedron, 
 dodecahedron, and tetragonal trisoctahedron |-|. In 
 the projection (f. 236) the plane of the paper is taken 
 as that of the cubic plane, the two equal lateral axes (a) 
 are shown in the dotted lines, and the vertical axis is perpendicular to the 
 plane of the paper at their point of intersection. Any arbitrary length of 
 the lateral axes, as ca, is taken as the unit. One of the cubic planes coin- 
 cides with the plane of the paper, and the others, since they are supposed 
 to pass through the unit point of the vertical axis, coincide with the projec- 
 tions of the lateral axes, and are marked Zf, //. 
 
 The octahedral planes (1) appear as lines connecting the unit lengths of 
 the equal lateral axes ; of the dodecahedral planes, four pass each through 
 
56 
 
 CRTS TALLOGEAPH Y. 
 
 the extremity of one lateral axis, and parallel to the other, and four others 
 are diagonal lines passing through the centre ; they are marked * in the 
 figure. The other planes, f-f, when passing through the unit point of the 
 vertical axis, are represented by the symbols 1 : f : 1, and 1 : 1 : f, and 
 1 : f : }, in the first quadrant, and similarly in the other three. 
 
 The projection of the first of these planes is the line joining the points x 
 (ex = f of ca j )and a? : that of the second plane is the line joining the points 
 a 1 and y (cy = f of # : ); that of the third plane is the line joining the points 
 s 1 and 2* (c2 l = cz f of ca). The same method is followed in the other 
 quadrants, the twelve lines, lightly drawn, in the figure are the projections 
 of the twelve corresponding planes of the form f-J. 
 
 Fig. 237. 238, give another example (topaz) from 
 the orthorhombic system. The dotted lines, as before 
 (f. 238), show the lateral axes on which the relative 
 unit lengths of b and a belonging to this species have 
 been marked off (b = 1.892, a = 1). The four lines 
 passing through these unit points, a and Z>, are the pro- 
 jections of the unit octahedron 1. The unit prism, /, 
 is projected in lines parallel to these, and passing 
 through the centre. The prism i-% also passes through 
 the centre, but the direction is that of a line joining 
 the unit length of the axis b with two times that of d. 
 The symbol of the octahedron *( = %c : b : a), becomes, 
 on supposing the plane to pass through the unit point 
 of the vertical axis c : f b : \a* and it is consequently projected in the lines 
 
MATHEMATICAL CRYSTALLOGRAPHY. 
 
 57 
 
 joining the points t(ct = l of cb\ and s (cs = | of ca). The symbol of the 
 plane f 2 (= f c : b : 2#) becomes, on the same condition, c : \b : f 0, and ita 
 projection lines consequently connect the points t (ct = | of <#) and u (cu 
 f of ca). The same method is followed in the other systems ; in the 
 hexagonal there are on the plane of projection three equal lateral axes 
 cutting each other at angles of 60. 
 
 it will be seen from these examples that planes in a zone all pass 
 through the same point of intersection; as in f. 234, O, f-f, 1, *(*), and, 
 f. 237, /, a-2, i-i (c) ; this is also true mathematically of the planes O, 1, f , 
 /, whose projections are parallel. This principle, which follows immediately 
 from the fact stated above that planes in a zone have a common ratio for two 
 of the axes, is very important. If a given plane lie in two zones its projection 
 must necessarily pass through the two points of intersections which belong 
 to each of these respectively, and consequently its position is determined. 
 The plane on f. 237 which has no written symbol for instance, lying in 
 the zone with f and f , and the zone with 1 and f-2, must, when projected, 
 pass through the intersection point (f. 238) s of the former zone, and also 
 through v that of the second zone. The plane itself, then, is one which 
 meets the vertical axis at its unit length, the axis b obviously at an infinite 
 distance, and the axis a at a distance J of its unit length ; hence, the sym- 
 bol is G : oo b : \a, or f c : oo b : a (f -?,) in the form it is usually written. In 
 many cases the ratios of the lateral axes are obvious at sight, as here ; in 
 every case, however, the position of the zonal point, and of the two points 
 of intersection on the axes, admits of exact determination by a series of 
 simple equations. 
 
 These equations it is unnecessary to add here ; reference for them may 
 be made to Quenstedi's Crystallography, or that of Klein, mentioned on 
 p. 59. This method is of so general use and of so easy application that 
 every student should be familiar with it. Its advantages are that it leads 
 tu a clearer comprehension of the relations of the different forms, showing 
 immediately all the zones in which they lie, and in many cases without the 
 
58 
 
 CRYSTALLOGRAPHY. 
 
 72 
 
 use of equations suffices to determine the symbols of an unknown plane, 
 and that more simply than by the use of the zonal equation. The general 
 principles contained in the method have been made by its proposer (Quen- 
 stedt) the basis of an ingenious and philosophical system of Crystallograpny 
 (Grundriss der bestimmenden und reclmenden Krystallographie von Fr. 
 Aug. Qnenstedt, Tubingen, 1873). 
 
 2. Spherical projection of Neumann ami Miller. In this subject, as 
 viewed by Miller, a crystal is situated within a sphere so that the centres of 
 the two coincide. If now perpendiculars, or normals, be drawn from this 
 centre to each pb.ne, and be produced, they will meet the surface of the 
 sphere, and these normal points will determine the position of each plane. 
 If, then, this sphere is regarded as projected upon a horizontal plane it will 
 appear as a circle, and the various normal points will occupy each its pro- 
 per position on or within this circle. This will be made more clear by an 
 example. If the crystal (f. 237) be supposed to occupy the centre of a 
 sphere, and if the terminal plane coincide with the plane of the paper, a 
 normal to the plane O will meet the sphere of projection at the central 
 point (f. 239) ; the planes i-i at the points indicated, and so of the other 
 
 planes 1, f, i-2, etc. 
 
 Two principles here are of 
 fundamental importance: 1st, all 
 planes of a zone have their nor- 
 mals in the same great circle, as 
 i-i, f , f 4, etc. ; and 2d, the an- 
 gles between these normal points 
 are the supplements of the an- 
 gles between the actual planes. 
 These having been stated, it will 
 be clear at once that the calcula- 
 tion of the angles between dif- 
 ferent planes, i.e., their normals, 
 becomes merely a matter of solv- 
 ing a series of spherical triangles 
 in which some parts are given 
 and others obtained by calcula- 
 tion. Upon this basis a system 
 of crystallography was construct- 
 ed by Miller in 1839, which, as further developed by Grail ich, Schrauf, 
 von Lang and Maskelyne, has every advantage over that of Nauinaun 
 in the matter of facility of calculation as in some other even more import- 
 ant respects. 
 
 The method of construction of the circle of projection, for a given crystal, is in most cases 
 very simple. The position of the crystal is commonly so taken that the prismatic zone is 
 represented by the circumference of the circle, and the position of the normal-points of all 
 prismatic planes lie upon it. The normal-points of the pinacoid planes are at 90 from one 
 another (the macropinacoid is not present on the crystal, f 2:J7). The two corresponding 
 diameters, at right angles to each other, which are properly the projections of two great cir- 
 cles, intersect at the centre the normal-point of the basal plane, ; these diameters repre- 
 sent respectively the macrodome (m-l) and brachydome (*$) zones of planes. The several 
 positions of the normal-points of the prismatic planes are determined by laying off the sup- 
 plement angles of each with a protractor ; that of 2 is 43 25', and of /, 62 8i', from the 
 
MATHEMATICAL CRYSTALLOGRAPHY. 5Jj 
 
 normal-point of i-i. The lines drawn between 2, 0, and -2 (behind), and 7, <9, /(behind) 
 represent the zones of the m-2 and m pyramids respectively. The position of the normal- 
 points of a dome or pyramid upon its respective zonal line (great circle) is formed by laying 
 off from the centre a distance equal to the tangent of half the supplement angle of the given 
 plane on 0, taking the radius as unity. For example, A $-1 120 27', hence the position 
 of the required normal-point will be about (.5040) of the radius measured from 0. 
 
 It is in general necessary to determine in this way the normal-points of but very few of 
 the planes, since those of the others are given by the zonal connection between the planes. 
 Thus in this case, having determined in the way explained the positions of the points i-i, i-%, 
 /, and f-i, no further calculation is needed; the point of intersection of the great circle 
 joining i-i. 4, and i-l, and that joining/, 0, /, is the normal-point of $; also the point of 
 intersection of the great circle -2, f-i, -2 with /, 0, /, is the normal-point of 1, and with 
 -2, 0, *-2 that of f-1 
 
 The method explained is the same for all the orthometrio systems ; for the clinometric sys- 
 tems the same principle is made use of, though the application is not quite so simple, since 
 the basal plane does not fall at the centre of the circle. 
 
 In the system of Miller the general form of the symbol is hkl, in which k, &, and I are 
 always whole numbers, and, the reciprocals of Naumann's symbols. To translate the latter 
 into the former it is only necessary to take the reciprocals and reduce the result to three 
 whole numbers and write them in the proper order. In general, for m-n (me : nb : ), 
 h : k : I = mn : m : n. the latter expression being written in its simplest form, and, if neces- 
 sary,- fractional forms must be reduced to whole numbers by multiplication. Conversely, 
 
 from hkl is obtained m = -, n = , and hence, = m-n. This applies to all the sys- 
 L/C IK 
 
 terns except the hexagonal, where a special process is required. See Appendix (p. 441). 
 
 METHODS OF CALCULATION. 
 
 In mathematical crystallography there are three problems requiring 
 solution: 1st, The determination of the elements of the crystallization of 
 a species, that is, the lengths and mutual inclination of the axes ; 2d, The 
 determination of the mutual interfacial angles of like or unlike known 
 planes ; and 3d, The determination of the symbols, that is, values of the 
 parameters m and n for unknown planes. 
 
 This whole subject has been exhaustively discussed by Naumann in his several works on 
 crystallography. (For titles, see p. iv.) The long series of formulas deduced by him cover 
 almost every case which can arise. In the present place the matter is treated briefly, since 
 for all ordinary problems in crystallography the amount of mathematics required is very 
 small. This is especially true in view of the fact that a large part of unknown planes can 
 be determined by the zonal equation already given. When complicated problems do arise, 
 the me hods of spherical trigonometry (based on the spherical projection of Miller) offer, in 
 the opinion of most crystallographers. the simplest and shortest mode of solution. It is be- 
 lieved that the student who has mastered the elements of the subject, after the method of 
 Naumann here followed, will, if he desire t<> go further, find it to his advantage to turn to the 
 system of Miller, referred to on p. 58 (See also Appendix. ) The formulas given under 
 the different systems in the following pages are mostly those of Naumann, and it has been 
 deemed desirable to explain at length, in most cases, the methods by which these formulas 
 are deduced. If the student will follow these explanations through, he will find himself in 
 a position to solve more difficult problems involving similar methods. Spherical triangles 
 are employed in most cases, as early used by Hausmann (1813), by Naumann (1829), and 
 others ; and carefully explained by Von Kobelf in 1867 (Zur Berechnung der Krystallformen). 
 The same methods have been elaborated by Klein (Einleitung in die Krystallberechnung, 
 Stuttgart, 1875). 
 
 THE RATIO OP THE TANGENTS IN RECTANGULAR ZONES. 
 
 Tangent principle. In any rectangular zone of planes, that is, a zone 
 lying between two planes at right angles to each other, one of them being 
 a diametral plane, the tangents of the supplement angles made with thk 
 
CRYSTALLOGRAPHY. 
 
 240 
 
 diametral plane are proportional to the lengths of the axis corresponding 
 to it. 
 
 Examples of rectangular zones are afforded by the zones between i-i and 
 i-i, also 1 and O, f. 130, and / and O, in f. 208 ; still again between / and 
 O, in f. 167; / and O, also i-2 and O, in f. 150. In f. 217, the zone be- 
 tween i-i and i-i, and O and i-i, as also the zones between i-i and any one of 
 the orthodomes, are rectangular zones, but not the zones between the basal 
 and vertical planes (except i-i), nor those between i-i and a clinodome. 
 The truth of the above law is evident from the accompanying figures. 
 If the angles between the planes e l , #, / (f. 240) and 
 the basal plane are given, their supplements are the 
 angles with the basal diametral section a 1 , a 2 , a 3 , respec- 
 tively (f. 241). The tangents of these angles are the 
 respective lengths of the vertical axis, corresponding 
 to each plane, as seen in the successive triangles. In 
 each case we have b tan a = c, and hence, tan a 1 : tan 
 a 2 : tan a 3 = c l : & : c 3 . 
 
 By the law stated on p. 10, the ratio of the axes must 
 have some simple numerical value. In other words, if 
 c l be taken as the unit, (? and <? must bear some simple 
 ratio to it (denoted generally by m). In general, if a 1 , 
 a 2 , a 3 are the supplement angles of three planes of a 
 vertical zone upon a basal plane, then, 
 
 tan a 1 : tan a 2 : tan a 3 = m l c : m z G : m*c = m 1 : m 2 : m 8 . 
 
 This is true as well for the pyramidal planes p l , p 2 , p 3 , 
 and the domes d 1 , d 2 , d? (f. 240). This principle is 
 most commonly applied to a vertical zone, where the 
 angles on the basal plane are known, and the value of 
 m for each is required ; it applies, however, in the same 
 way, to any rectangular zone. 
 
 For a prismatic zone, if the supplement angles on i-i 
 are given = y l , T 2 , etc., then, 
 
 tan 7 1 : tan T 2 : tan 7 s = 
 
 = n : n : n 
 
 These relations may perhaps be made more clear by a little further 
 explanation. Suppose a plane to pass through the vertical axis at 
 right angles to the given zone 0, e\ e'\ 3 , and intersecting it in the 
 dotted line (see also f. 241). A similar section may be made with the 
 planes d 1 , d', <f, or with ;/, ^ 2 , p 3 . From the section (f. 241), the 
 -jit relation of the vertical axes to the tangents of the basal angles is at 
 I once obvious. It will be seen here that a 1 , n 2 , etc. , are not only the 
 supplements of the interfacial angles measured on 0, but are also 
 
 equal to the angles measure 1 on i-l diminished by 90, and this is true in general. It will 
 be also seen that the angles a 1 , a 9 , etc., may be obtained from the angles of the planea 
 measured on each other. Thus, given e } f\0 = 180 Q a 1 , and given tf'A* 2 , obviously a 2 ( 
 plement of <? 2 A 0) = a 1 + (180 - e 1 
 
 (sup- 
 
 USE OF SPHERICAL TRIGONOMETRY. 
 
 The use of a spherical triangle often simplifies very much the operation 
 
MATHEMATICAL CRYSTALLOGRAPHY. 
 
 of calculating the various angles and axial ratios. The following example 
 will exemplify the principle involved. Fig. 242 represents a square octa- 
 hedron of zircoii. If we take the front 
 solid angle of the octahedron as a cen- 
 tre, and from it imagine three arcs to 
 be described with any radius one on 
 the octahedral plane BA, another on 
 the basal section CA, and a third on 
 the diametral section CB, it is evi- 
 dent that a spherical triangle will be 
 formed. In other words, the point a 
 is imagined to be the centre of a 
 sphere and the triangle ABC is that 
 portion of its surface included between the three planes in question. 
 In this triangle (f. 243) the successive parts are as follows : 
 
 (7= the angle between the basal and vertical diametral sections; 
 
 here 90. 
 
 a = the inclination of the vertical edge on the lateral axis. 
 j?= the semi- vertical angle of the octahedron (= i-JT). 
 h (the hypothenuse) = the plane angle of the octahedral face. 
 A = the semi- basal angle (= -JZ). 
 # = the inclination of the basal edge on the lateral axis. 
 
 En the case given, ~b = 45, since in this, the tetragonal system, the 
 lateral axes are equal and the basal edge makes an angle of 45 with each. 
 Now if either A. or B (that is, JTor Z) is given by measurement, two parts 
 in the triangle will be known and the others can be rea lily calculated as 
 they may be required. Other examples will be found in the pages which 
 follow. 
 
 In the majority of cases the spherical triangles obtained in the manner described are 
 right-angled, and the problems resolve themselves into the solution of right-angled spherical 
 triangles. In performing these operations practically, the student may be assisted by the 
 following graphic method (used by Prof. Cooke, of Harvard University). It is based upon 
 Napier's rules, which are familiar to every student : 
 
 In a right-angled spherical triangle the sine of any part is equal to the product of the 
 cosines of the opposite parfcs, or the product of the tangents of the adjacent parts. Here it 
 is to be remembered that for the two angles and hypothenuse the complements are to be 
 taken. 
 
 The problems are represented graphically as follows : In the case given, suppose that the 
 basal angle (Z) on the given octahedron has been measured and found to be 84 19 46", that 
 is, the angle A = +Z = 42 9 53", and hence 90 A = 47 50' 7". Then the parts of the 
 triangle may be written, commencing with (7, 
 
 90 (C7) 
 (90 - A) 
 
 (90 - B) 
 
 (90 - h). 
 
 If B is required, we have (for zircon) sin (90 - B) = cos 45 x cos 47 50' 7* ; 
 whence B = 61 39' 47", 
 
 and the vertical angle (X) is 123 19 34". 
 
 Also, sin 45 = tan a x tan 47 50' 7", 
 
 tan a = 0.640373 = c t the vertical axis. 
 
62 CEYSTALLOGEAPHY. 
 
 For convenience, some of the more important formulas for the solution of spherical 
 triangles are here added. 
 In spherical right triangles G = 90. 
 
 sin a sin b 
 
 Sin A = - r sin B = - r 
 
 sm h sm h 
 
 tan b tan a 
 
 Cos A cos B = j- 
 
 tan h tan h 
 
 tan a tan b 
 
 Tan A = - tan B = - 
 
 sin b sin a 
 
 cos B cos A 
 
 Sin ^4 = r sm J9 = 
 
 cos b cos a 
 
 cos h ~ cos a cos b 
 cos 7i cot A cot .Z? 
 
 In oblique-angled spherical triangles : 
 
 (1) Sin A : sin 5 = sin a : sin 5 ; 
 
 (2) Cos a = cos b cos c + sin b sin c cos A 
 
 (3) Cot & sin c = cos c cos A + sin J. cot B 
 
 (4) Cos A = cos Z? cos G + sin 2? sin C cos a. 
 
 In calculation it is often more convenient to use, instead of the latter formulas, those 
 especially arranged for logarithms, which will be found in any of the many books devoted 
 to mathematical formulas. 
 
 Cosine formula. General equation for the inclination of two planes in 
 the orthometric systems. 
 
 Representing the parameters of any plane by c : b : a, and also of any 
 other plane by G' : b' : a', and placing W for the supplement of their 
 mutual inclination, 
 
 __ aa'lb'+cc'aa'+Wcc' 
 
 ~ 
 
 In using this equation, the actual values of the parameters are to be sub- 
 stituted for the letters. For the planes m-n, m'-ri, in the same octant, in 
 which the parameters would be me : nb : a, and m'c : n'b : a y 
 
 me, nb, a are substituted severally for c, J, a. 
 m'c, rib, a " " "</, &', a'. 
 
 I. ISOMETEIC SYSTEM. 
 
 The equality of the axes in the Isometric system makes it unnecessary to 
 consider them in the calculations. The most commonly occurring prob- 
 lems are the determination of the symbols in the various forms, i-n, ra, 
 m-m, m-n (f. 51, 54, 65, 69). These cases will be considered in succession. 
 In all but the last, but a single measurement is necessary. 
 
 1. Form i-n, tetrahexahedron. The edges are of two kinds (p. 18), as 
 A add C in f. 24:4 ; a measurement of either is sufficient to determine the 
 value of n. (a) Given the angle of the edge A. Suppose a plane tc 
 
MATHEMATICAL CRYSTALLOGRAPHY. 
 
 63 
 
 pass through the edge A and the adjoining axis, ac, also a second plane 
 through the two lateral axes, and imagine a spherical triangle con- 
 structed, as explained on p. 61. 
 This triangle (see f. 244A) is right 
 angled at C, and the other angles 
 are -JJ., (half the measured angle of 
 the crystal) and 45, respectively. 
 Hence, if v is the inclination of the 
 plane on the lateral axis, ac, 
 
 cos v = cos \A 1/2, 
 
 and tan v = na = n. 
 
 (b) Suppose the angle of the edge C 
 
 to be given. In the plane triangle 
 
 (abc) of the section in f. 244, C -h 
 
 45 + v 180, or v = 135-! \C, 
 
 and, as before, tan v = n. If the angle of two opposite planes, meeting at 
 
 the extremity of an axis, were given, half this angle would be the angle v. 
 
 For a series of tetrahexahedrons the tangent law may be applied, since 
 
 they form a zone between two cubic planes ; the dodecahedron falls in this 
 
 zone, being a special case of the tetrahexahedron where n = 1. The angle 
 
 between a plane i-n and the adjoining cubic face (H) is equal to v + 90, 
 
 hence, cot H=n. 
 
 2. Form m, trigonal trisoctahedron. The edges are of two kinds, A 
 and B. (a) If the angle over B is given, suppose a diagonal plane to 
 pass through the vertical axis and the edge A, 
 meeting the planes, as indicated in the iigure. 
 A right-angled plane triangle is formed, of which 
 the basal angle is equal to \B, and the base is 
 the diagonal line x. Then x tan \B = the 
 vertical side of the triangle (raa),but x = V-J- when 
 a 1, whence tan \B^/\ = ma or m,. (b) If 
 the given angle is that of the edge A, place 
 a spherical triangle (ma), as indicated in the 
 figure. In this triangle O= 90 (for the diagonal 
 plane is perpendicular to the plane m), and the 
 other angles are respectively %A (half the mea- 
 sured angle) and 60 ; hence, the side opposite 
 \A (= the angle p) is obtained. Further, the 
 angle of the two dotted diagonals (the octahe- 
 dral and dodecahedral axes) is 35 16' (p. 16), 
 whence, \B = 144 44' p, and, as before, 
 tan \B^\ = m. See further the following case. The general equations 
 are thus : 
 
 (a) 
 
 tan 
 
 = cos 
 
 = 144 44'- 
 
 3. Form m-m, tetragonal trisoctahedron. Suppose (a} that the angle of 
 the edge B is given. In the spherical triangle 1, in f. 246, C 90, and 
 
64 
 
 CRYSTALLOGRAPHY. 
 
 each of the other angles equals \B. Hence, one of the equal sides 
 (= angle v) is obtained, and tan v m. (b) If the angle C is given, 
 9AR the triangle 2, in f . 246, is employed ; 
 
 here one angle is = 90, a second 
 = HO, and the third =<?, half 
 the measured angle of the edge C. 
 The side of the triangle the angle 
 p is calculated, and, as in the preced- 
 ing case, f = 144 44' p, then 
 
 The planes m-m, 1, m, form a 
 zone between the cubic and dodeca- 
 hedral planes as f. 461, p. 244, to 
 which the tangent law may be often 
 conveniently applied. The form m 
 passes into the octahedron 1 when 
 m 1, and when m is less than 
 unity it becomes m-m, as explained 
 on p. 17. 
 
 Since these planes form a rectangular zone the tangent of the supple- 
 ment angles between them and a cubic plane are proportional to the values 
 of m for the given forms ; only by applying this principle for m-m, the 
 
 index (= :!:!) will be obtained, which is equivalent to m-m 
 m m 
 
 (= 1 : m : m). 
 
 The general equations for the form m-m are : 
 
 (a) cos v = cot \B ; tan v = m. 
 
 (b) cos p = cot \C A/i; f = 144 44'-/> ; tan 
 
 = m + 1. 
 
 4. Form m-n, hexoctahedron. The edges of 
 the hexoctahedron are of three kinds, A, B, C 
 (f. 247), and two measurements are, in general, 
 needed in order to deduce the values of m 
 and n. 
 
 (a) Given A and B. In the oblique-angled 
 spherical triangle I (f. 247), the three angles 
 are \A, %B, and 45. In this triangle, the 
 side opposite %A (= angle v) is calculated, and 
 from it are obtained the values of m and n, 
 as follows : 
 
 cosi> = 
 
 4- cos IB 
 
 sin 
 
 tan 
 
 sin v = m ; tan v n. 
 
 (5) Given A and C. In the oblique-angled triangle II (f. 247), the three 
 angles are equal respectively to %A, \C, and 60 The side oppDsite \A 
 (= angle p) is calculated. But the angle between the diagonals, that is, 
 the octahedral and dodecahedral axes, is 35 16', and the third angle of 
 the triangle is f, the inclination of the edge C on the dodecahedral axis ; 
 
MATHEMATICAL CRYSTALLOGRAPHY. 
 
 65 
 
 hence, J = 144 44' p. Again, in the right-angled triangle III (f. 247), one 
 angle %C\ and the adjacent side = , whence the other side, 8 (the in- 
 clination of the edge B on the dodecahedral axis), is obtained ; v =135 S, 
 and from this, as above, and from the angle /o, are deduced the values oi 
 n and n. The formulas are : 
 
 = 135 b ; tan v = n ; 
 
 tan = m. 
 
 (c 
 
 ) Given B and C. K the right-angled triangle, III (f. 247), the two 
 les are given, equal respectively to \B and %G. From the triangle is 
 deduced the side opposite $C (= angle 8 denned before), and from it is 
 obtained i/, and from v and \B, the values of m and n, as in the first case 
 The formulas are : 
 
 cos = 
 
 - * ; 
 
 v = 135 8 ; tan v=n\ tan J.Z? sin v = m. 
 
 If, instead of m-n, the form is 
 
 m 
 
 248 
 
 -p only one measurement is needed, 
 
 and the process is simplified. 
 
 When the angles of any plane m-n on two cubic planes are given, their 
 supplements will be the angles of the plane upon the corresponding 
 diametral sections, and from them the values of m-n may be readily calcu- 
 lated. Thus (in f . 248), the angles of a given plane on a cubic plan at 
 a 9 will be the supplement of its angle upon the 
 section a 1 a*, that is, the angle B in the spherical 
 triangle ; similarly, the angle of a cubic plane at 
 a* will be the supplement of its angle on the 
 section #V, the angle A in the spherical triangle. 
 In this same triangle C = 90. Hence, the sides 
 opposite A. and B^ that is, the inclinations of the 
 two edges on the adjacent axis, may be calculated, 
 and this axis being equal to unity, their tangents 
 will give the corresponding lengths of the other 
 axes. These lengths may not be the values of m 
 and n in the form in which the symbol is generally 
 written, where the unit axis is always the shortest, 
 but the latter are immediately deducible. For ex- 
 ample, if the angles here mentioned for the plane numbered 4 (in f. 247) had 
 been measured, the values of the axes obtained by calculation, when the 
 front axis is the unit, would be -J and -J respectively, and the symbol, hence, 
 1 : i : 1, which is equivalent to 1 : f : 3, or m-n = 3-J for the general form. 
 
 Hem ihedral forms. For each hemihedral form the formulas are iden- 
 tical with those already given for the corresponding holohedral, so far as 
 the edges of the two are the same. For example, in comparing f. 69 and 
 f. 87 it is seen that the edges A and C are the same in both, while B of 
 the holohedral form differs from B' of the hemihedral. The formulas re* 
 
66 CRYSTALLOGRAPHY. 
 
 quired to cover these additional cases are given belotv, they are obtained 
 in a manner similar to those in the preceding pages. 
 
 Form J(m), f. 85. Given E'. 
 
 cos e = 2 cos \B'\/\ ; f = 35 16'+ e ; tan 
 Form J(m-m), f. 81. Given j'. 
 
 tan i^V2 = m. 
 Form J(m-n), f. 87. (a) Given J/ and B f . 
 
 cos 
 
 cos \A' 
 
 = - - = 
 
 cos a = - f-p- : cos p = -. =-=57 ; m = x ; n = - - 
 
 sm %A ' sm -J^ ' cot a cotp cot a + cot ,^. 
 
 (J) Given ^?' and C'. 
 
 sn 
 
 
 tan (8 + 45) = rc; - - tan f = m. 
 
 Form iO'-n], f. 92. Given ^1". 
 
 tan \A!' n. 
 Form [m-n], f. 100. (a) Given ^!" and B" . 
 
 cos -i^.'' n cos \A" 
 
 = <*os v ; tan p = n ; - , p,, = m. 
 
 sin j cos 
 
 (1) Given ^1" and 67" 
 
 i xr/* ^ zi COB (H <508 44'' 
 
 2 cos (7 v- = sm O cos#=: 
 
 sin \A" v 2 
 
 tan (45 + 0) = m ; sin (45 + ^) tan 4"= 
 () Given B" and 67". 
 
 1 /T//4/T fi 
 
 2 cos J67"V-J = sin 6^ ; cos S = 
 
 sn 
 
 tan (45 -f S) = n; sin (45 -f 5) tan \B' = m. 
 
 The various combinations of holohedral and hemihedral forms which 
 may occur are unlimited, and it would be unwise to attempt here to show 
 
 C 8 - C S 
 
MATHEMATICAL CRYSTALLOGRAPHY. 67 
 
 the methods of working them out. It is only necessary to remark that the 
 solution can generally be readily obtained by the use of one or two spheri- 
 cal triangles in the way shown in the preceding cases. 
 
 The calculation of the intcrfacial angles between two known forms can 
 often be performed by the formulas already given, or by similar methods 
 For the more general cases, reference must be made to the cosine formula, 
 p. 62. 
 
 Interfacial Angles. I. Holohedral Forms. 
 
 The following are some of the angles among the more common of 
 Isometric holohedral forms; adjacent planes are to be understood, unless 
 it is stated otherwise. The angles A, B, C\ above, are those over the 
 edges so lettered in the figures referred to (see pp. 15-19), or over the 
 corresponding edges in related forms : 
 
 fff\H= 90, f. 38 1 A 2-2 = 160 32', f. 58 e-| A *-|, 4 = 133 49' 
 
 H A 1 = 125 16', f. 40, 41 1 A 3-3 = 150 30, f. 57 f A *-, 6 r ,= 157 23 
 
 H A = 135, f. 43, 45. 1 A \ = 169 49 2 A *-2, A,= 143 8, f. 65 
 
 #A *-f = 146 19 1 A 2 = 164 12. f. 53 -2 A i-2, G,= 143 8 
 
 H A i-2 = 153 26, f . 64 1 A 3 = 158 e-2 A fr#, ov. top, = 126 52 
 
 H A *-3 = 161 34 1 A 34 = 157 45 i-2 A -3 = 171 52 
 
 H A H = 133 19 1 A 4-2 = 151 52 i-2 A 2-2 = 155 54 
 
 H A 14 = 136 45 1 A 5- = 151 25 i-3 A *-3, A,= 154 9, f. 66 
 
 //A 2-2 = 144 44, f. 55 i A = 120 f. 45 3 A *-3, C,= 126 52 
 
 .# A 3-3 = 154 46 i A &', ov. top,= 90 2 A 2, -4,= 152 44, f. 51 
 
 H A f, ov. 1,= 115 14 * A *'-f = 167 42 2 A 2, .,= 141 3 
 
 ^ A 2, u = 109 28, f. 52 i A *-2 = 161 34, f . 68 3 A 3, 4,= 142 8 
 
 H A 3, " = 103 16 t A '-3 = 153 26 3 A 3, B,= 153 28 
 
 tf A 3-| = 143 18, f. 70 i A 2-2 = 150 8-f, 4,= 158 13, f, 69 
 
 # A 4-2 = 150 48 A 3-| = 160 54 3-2, #, = 149 
 
 ff A 5-| = 147 41 t A 3-3 = 148 31 3-$, 6 Y ,= 158 13 
 
 1 A 1 = 109 28, f. 42 A 4-i = 166 6 4-2, A,= 162 15 
 
 1 A 1. top,= 70 32 t A 5- = 162 58* 4-2, B,~ 154 47 
 
 1 A = I* 4 44, f 47 2-2 A 2-2, B,= 131 49, f. 54 4-2, tf,= 144 3 
 
 1 A H = 143 11 2-2 A 2-2, <7,= 146 27 5-|, .4,= 152 20 
 
 1 A i-2 = 140 16, f. 67 2-2 A 2-2, ov. top. =109 28 5-f,, #,= 160 32 
 
 1 A -3 = 136 54 3-3 A 3-3, B,= 144 54, f. 61 5-|, C,= 152 20 
 
 1 A H = 168 41 3-3 A 3-3, (7,= 129 31 
 
 II. Hemihedral Forms. 
 The following are the angles for the corresponding hemihedral forms : 
 
 1 A 1 = 70 32', f. 76, 76A 3-3 A 3-3, C,= 134 2' t-3 A *-3, #,= 107 27f 
 
 f A i^, -4,= 162 39i 3-1- A 3-^, A,- 158 13, f. 87 4-2 A 4-2, A,= 128 15 
 
 I A f #,= 82 10 3-| A 3-^ -B,= HO 55^ 4-2 A 4-2, #,= 154 47| 
 
 9 A 8. .4.= 152 44, f. 85 8- A 3-f, C',= 158 13 4-2 A 4-2, C,= 131 49 
 
 2 A2 'R = 9o 4-2 A 4-2, A, = 162 15 3-| A 3-;S ^1,= 115 23, f. IOC 
 
 3 A 3, A, = 142 8 4-2 A 4-2, B, = 124 51 3-f A 3-|, JB, = 149 
 
 3 A 3, 1?,= 99 5 4-2 A 4-2, (7,= 144 3 3-f A 8-f, O,= 141 47 
 
 H A H. X= 93 22 i'-$ A *-f, -4,= H2 37 5-f A -fr, -4,= 119 8* 
 
 M A l-i' ^= 160 15 *-| A M, (7,= 117 29 5-f A 6-fr, -B,= 160 33 
 
 2-2 A 2-2, 4= 109 28, f. 81 *-2 A , 4,= 126 52, f. 92, 93 5-f A 5-^, 6',= 131 5 
 2-2 A 2-2, C,= 146 26* J-2 A -2, 6',= 113 35 
 
 8-8 A 3-3, #,= 124 7 *-3 A -3, -4,= 143 8 
 
 In the forms -}, 2 (f. 92), 3, 4, A is the angle at the longer edge, 
 and C that at either of the others. 
 
68 
 
 CRYSTALLOGRAPHY. 
 
 II. TETRAGONAL SYSTEM. 
 
 In the Tetragonal system, as has been fully explained (p. 30), the \cngfh of 
 the vertical axis is variable, and must be determined for each species. If the 
 length of c is known, then it may be required to determine the symbols of 
 certain planes by means of measured angles. These two problems are in a 
 measure complementary to each other, and the same methods will give a 
 solution to either case. (For figures of the forms see pages ^7 and 28.) 
 The calculation of the interfacial angles can be performed by similar 
 methods or by the cosine formula. 
 
 1. Form m. The edges are of two kinds, pyramidal X, and basal Z. 
 If either angle is known, the angle a, which is the inclination of the edge 
 X on the lateral axis, may be calculated by the spherical triangle, as in 
 f. 242, 243. (Compare the explanation of this case, p. 62.) Obviously in 
 the plane right-angled triangle formed by the two axes and the edge X, 
 tan a = me (since a = 1). If c is known, then m is determined ; and, con- 
 versely, a value being assumed for m, in the special case, c is given by tho 
 calculation. The general formulas are : 
 
 cot |X= sin a, or tan \Z V~% = tan a ; then tan a = me. 
 
 2. Form m-i. (a) Given the angle Z, me is found immediately ; the 
 
 solution is obvious, for in the section indicated by 
 the dotted line (f. 249), \Z = a, and the tangent of 
 this angle is equal to the vertical axis, (b) Given 
 the angle Y. A spherical triangle placed as in 
 f. 249, has one angle = | Y, a second = 45, and 
 the third =90, whence the side opposite | Y is 
 calculated, which is the complement of a. 
 
 The general formulas, which may serve to de- 
 duce the value of ra, when c is given, or the con- 
 verse, are : 
 
 cos J J*"Vlf = sin a, or tan \Z tan a, and tan a = mo. 
 
 If a series of square octahedrons m, or m-i, occur in a vertical zone, their 
 symbols may be calculated in both cases alike by the law of the tangents, 
 the angles of the planes on O, or on /, or i-i, respectively, being given. 
 (See p. 60.) 
 
 3. Form i-n.For the angle of the edge X(f. 109, p. 26), at the extrem- 
 ity of a lateral axis, tan -J JT = n. From tlie angle of the other edge Y, 
 we have X = 135- \Y; and hence, tan (135- Y) = n. 
 
 4. Form m-n. The edges are of three kinds, X, Y, Z(L 250), and two 
 angles ^must be given in the general case to determine m and n. 
 
 (a) Given Xand Z. A spherical triangle having its vertices on the edgea 
 Xand Z, and the lateral axis, as 1, f. 250, will have two of its angles equal 
 to |X, |Z, respectively, and the third equal to 90. The solution of this 
 triangle gives the sides, viz., a and v, the inclinations of the edges X and 
 
MATHEMATICAL CRYSTALLOGRAPHY. f>9 
 
 Z, respectively, on the lateral axis. The tangents of these angles give the 
 values of in and n. The formulas are as follows : 
 
 cos 
 
 sin 
 
 = cos a, tan a = m<? ; - 
 
 ' 
 
 sin 
 
 = cos v, tan v = n. 
 
 (J) Given F and Z. In a second triangle placed as indicated (2, f. 250), 
 two of the angles are ^F^and ^Z respectively, 
 and the third is 90. The solution of this second 
 triangle gives S, the inclination of the edge Z 
 on the diagonal axis, from which, in the plane 
 triangle we have v = 135 S, and from v is ob- 
 tained n. Still again from the triangle 1 (f. 250), 
 and its solution used in the preceding case, having 
 given Z and v, a is obtained, and from it in ; 
 as by the following formulas : 
 
 C08 ^,T = cos 8, v = 135-S, tan v = n ; 
 sm \Zi 
 
 tan 
 
 sin i/ = tan a = me. 
 
 (<i) Given ^Tand Y. A third triangle, numbered 3 in the figure, has two 
 of the angles equal toJ"and \ Y respectively, and the third is 45. Solv- 
 ing this oblique-angled triangle, the angle of the inclination of the edge T 
 cm the vertical axis is obtained, and its complement is the angle e, the in- 
 clination of the edge J"on the diagonal axis; from e and ^ F are obtained, 
 by triangle 2, 8, and thence, as above, n; and finally, from X and v, is 
 obtained a, and from that the value of m. The simplified formulas are as 
 follows : 
 
 cos 
 
 cos 
 
 n\ ; sin a = n cot \X, tan a me. 
 
 Pyramids of the general symbol 1-n, m-m, etc., are especial cases of the 
 preceding, the processes being for them, however, somewhat simplified. A 
 single measurement is sufficient. 
 
 III. HEXAGONAL SYSTEM. 
 
 In the Hexagonal system there are three equal lateral axes (a) inter 
 secting at angles of 60, and a fourth vertical axis (<?) at right angles to 
 the plane of the others. Taking a = 1, there remains but one unknown 
 quantity in the elements of a cr} r stal, that is the length of c, and a 
 single measurement is sufficient to determine this. The relations of the 
 three lateral axes have been explained on p. 32. 
 
 The hexagonal system is closely allied to the tetragonal, and optically 
 they are identical, as is shown beyond. 
 
 Sch ran f refers all hexagonal forms to two lateral axes crossing at right 
 
70 CRYSTALLOGRAPHY. 
 
 angles and a vertical axis, in order to show this relation. Accoi ding to him,, in 
 this system, the axes are c : aV3 : a ; in the tetragonal they are c : a : a. 
 Miller's school, on the contrary, employ three equal axes, making equal 
 angles with each other, and each normal to a face of the fundamental rhom- 
 bohedron. In each of these methods a holohedral form, for instance a 
 hexagonal pyramid, is considered as made up of two sets of forms, having 
 different indices. 
 
 A. Holohedral Forms. 
 
 1. Form m : hexagonal pyramid, first series. Suppose a spherical trian- 
 gle, inscribed in f. 148, p. 33, having its vertices upon the edges X and Z, 
 and the corresponding lateral axis respectively, similar to the triangle of 
 f. 242. This will be a right-angled triangle. 
 
 (a) When the angle of the edge X is given, then f , the inclination of the 
 edge X upon the adjoining lateral axis, is calculated : 
 
 sin f = cot \X V3, and tan f = mo, or = c, the vertical axis, when m = 1. 
 
 (b) Given the angle Z. 
 
 tan Z V% = me, or = c when m = 1. 
 
 2. Form m-% : hexagonal pyramid, second series. These pyramids bear 
 the same relation to those of the m series as the m-i octahedrons to m octa- 
 hedrons of the tetragonal system. (Compare f. 112, 146.) The methods of 
 calculation are similar (f. 249.) The edges are of two kinds, vertical I^and 
 basal Z. 
 
 (a) Given the angle Y. 
 
 2 cos -J Y = sin %Z, and tan \Z me, or c when m = 1. 
 
 (b) Given the angle Z. Then simply 
 
 tan \Z me. 
 
 3. Form i-n : dihexagonal prism. The vertical edges are of two kinds, 
 axial X, and diagonal Y ', the solution in either case is by means of a plane 
 triangle, in a cross-section analogous to that of f. 146. 
 
 (a) Given X. 
 
 tan 
 
 2-n 
 (b) Given Y. 
 
MATHEMATICAL CRYSTALLOGRAPHY. 
 
 71 
 
 4. Form m-n : dihexagonal pyramid. The edges (f. 251) are of three 
 kinds, X and Y terminal, and Z basal; measurements of 
 two of these are required to give the values of m and 
 n ; this is analogous to the calculation for the form m-n 
 in the preceding system. 
 
 (a) Given JTand Z. In a spherical triangle having its 
 vertices on the edges X and Z, and the adjoining lat- 
 eral axis respectively, two angles are given. If v = the 
 inclination of the edge Z upon the lateral axis (the side 
 of the spherical triangle opposite the angle \X ), then 
 
 008 v = 
 
 
 ' n ~~ * = tan (" ~~ 
 
 tan 
 
 su v = mc ' 
 
 (b) Given T and Z. The right-angled spherical triangle has its vertices 
 on the eo!ges T^and Z and the diagonal axis. If 8 = the inclination of 
 the edge Zupon this diagonal lateral axis, then : 
 
 cos 8 = 
 
 ; but n - \ = tan (120- 5) 
 
 also 
 
 (150 S) = v; and, as before, tan \Z sin v = mc. 
 
 (e) Given X and Y. In the oblique-angled spherical triangle, with its 
 vertices upon the edges X and Y and the vertical axis, the three angles 
 are known, viz., JT, T", and 30, hence : 
 
 2 -n 
 
 cos 
 
 COS 
 
 Further, if f = the angle of inclination of the edge JTupon a lateral 
 axis, that is, the complement of the same edge upon the vertical axis (the 
 side of the spherical triangle opposite the angle 
 
 sin f = n - cot JT, and tan f = mo. 
 
 m 
 
 If the pyramid m-n takes the form m- , as determined by its zonal 
 
 m-\ 
 
 relations, the calculations are simplified, since one unknown quantity 
 only, m, has to be determined, and one measurement is sufficient. 
 
 B. Rhombohedral Division. 
 
 The relation of the rhombohedrons and scalenohedrons to the true hexa- 
 gonal forms has been made clear in another place. The rhornbohedron is 
 the hemihedral form of the hexagonal pyramid m, and its symbol is writ- 
 
72 
 
 CRYSTALLOGRAPHY. 
 
 ten , or usually mR. The sealenohedron is the corresponding hemihe 
 
 2i 
 
 dral form of the twelve-sided pyramid, and its symbol is written $(m-ri) or 
 in' It"'. The latter symbol, proposed by Naumann, has reference to the 
 rhombohedron whose lateral edge corresponds to the edge Z of the given 
 Bcalenohedron. 
 
 The formulas given by Naumann for reducing the symbol \(m-ri) to the 
 form m'R"' are as follows : 
 
 n " 2 n 
 
 For the converse, to reduce m'R"' to the form 
 
 m = m'n' and n = 
 
 n' + 1 
 
 1. Rhombohedrons^ mR. The methods of calculation are simple, and 
 will be understood from f. 252. The edges are of 
 two kinds, JTand Z, and their relation is such that 
 the corresponding angles are the supplements of 
 each other. 
 
 Given the angle of the edge X. A spherical 
 triangle is placed, as indicated by ABG,\\\ f. 252, 
 with its vertices respectively on the edge JT, the 
 vertical axis, and the diagonal of the rhoinbohe- 
 
 dral face. In this triangle A = 
 and 0= 90, but cos a = 
 
 , B = 60 
 cos 
 
 sin B sin 60' 
 
 here a is the inclination of the diagonal line 
 upon the vertical axis, that is, the complement of 
 a, its inclination upon the basal section. Now in the plane triangle abc, 
 where ac = the lateral axis = 1, ab = Vf, hence, tan a V$= me, or = c, 
 the vertical axis of the rhombohedron, when m = 1. 
 The general formulas are then : 
 
 cos 
 
 sm a = 
 
 tan a * 
 
 Obviously, when the angle of R (or mR) upon the basal plane can be 
 measured, the supplement of this is the angle a. Similarly the angle R A 1 
 90 = a. 
 
 In a series of rhombohedrons in a vertical zone, the tangent law can be 
 advantageously applied. Attention must also be called to the zonal relations 
 of certain -f and rhombohedrons, remarked on p. 36 ; these relations 
 may be conveniently shown by means of Quenstedt's method of projection. 
 
 2 kcalenohedrons, mlP.As seen in f. 171, p. 37, the edges are of three 
 kinds, JL, Y, Z, and two angles, must in general be measured to allow of 
 
MATHEMATICAL CRYSTALLOGRAPHY. 73 
 
 the determination of m and n. The methods of calculation are not alto- 
 gether simple. The following equations are from Naumann. 
 
 (a) Given Xand Y. 
 
 also, 
 
 tan Z 
 
 cos f = -- > and cot f V3 = me. 
 ny 3 
 
 tanjZ 
 
 n i found from tLl = ; further, sin \Z = cos i X 
 
 n-l c' 
 
 (c) Given l^and Z. 
 
 2ft sinjZ tan \Z 
 
 cos P : -^/T' and cot 
 
 If m, that is the inscribed rhombohedron, is known, one measnrome?it 
 will give the value of n. Z' = basal edge of the inscribed rhombohedrou 
 (care must be taken to note whether < is'obtuse or acute). 
 
 (d) Given X sin = 2 cos iX cos \ 
 
 tan (0-J2P) cot 4Z r = 
 (*) Given JT. sin = 2 cos ^F cos 
 
 (/) Given Z. tan JZ, cot JZ X = n. 
 
 If 7i is known. From X, we have sin %Z = - - cos -JX ; then, as 
 
 n-\- 1 
 
 under (a). From Y, sin Z = cos %Y, and then as above. From Z, 
 
 Yl/ J. 
 
 cos f ' is obtained as under (a), and then inc. 
 
 IY. OKTHORHOMBIO SYSTEM. 
 
 Of the three rectangular axes in the Orthorhombic system, one is always 
 taken equal to unity, in this work the shortest (&). This leaves two 
 inknovvn quantities to be determined for each species, namely, the lengths 
 
74 
 
 CRYSTALLOGRAPHY. 
 
 of the axes c and #, expressed in terras of the unit axis d, and for this 
 end two independent measurements are required. The simpler cases are 
 considered here. 
 
 Calculation of the Lengths of the Axes. 
 
 Let a = the inclination of the edge Z to the axis d (f. 253). 
 B = the inclination of the edge X to the axis d. 
 7 = the inclination of the edge Y to the axis b. 
 
 From the plane triangle formed by each edge and the axes adjacent 
 (f 253, 254) the following relations are deduced, when d = 1 : 
 
 tan = c and _tan a = b. 
 tan a = b, and b tan 7 = 4 
 tan /3 = 4 ail d c cot 7 = b. 
 
 (1) Given a and /3, 
 
 (2) Given a and 7, 
 
 (3) Given and 7, 
 
 255 
 
 The angles a, 0, 7 are often given direct by measurement; for, obviously 
 (f. 254, 255), 
 
 a = the semi -prismatic angle I A /(over *-t). 
 
 # = the semi-basal angle of 14 A 14. 
 
 7 = the semi-basal angle of 1-2 A 1-L 
 
 Also /A t = a + 90 ; 14 A ^4 = /3 + 90 ; It A <9 = 180-/3, etc. 
 
 From the octahedron (f. 253), the angles a, & 7 are calculated immedi- 
 ately by the following formulas, and from them the length of the axes aa 
 above. 
 
 (a) Given X and Z (spherical triangle I, f. 253), 
 
 sin sin 
 
 () Given JTaiid Z (spherical triangle II, f. 253), 
 
 (c) Given Xand ^(spherical triangle 111, f. 253), 
 
 sin ft = 
 
 cos 
 sin 
 
MATHEMATICAL CRYSTALLOGRAPHY. 75 
 
 If any one of the angles a, ft, or 7 is given, as from the measurement of 
 aprism or dome, and also any one of the angles of the octahedral edges X, 
 Y, or Z, a second of the former angles may be calculated, and from the 
 two the axes are obtained as before. The formulas, derived from the 
 same spherical triangles, are as follows : 
 
 (1) Given Xand a, sin ft = cot Xtan a. 
 
 X and ft, tan a = tan X sin ft. 
 X and 7, cos ft = cot %X cot 7. 
 
 (2) Given J^and a, sin 7 = cot ^l^cot a. 
 
 Y and ft, cos 7 = cot -J Z cot . 
 
 Y and 7, cot a = tan -J I 7 sin 7. 
 
 (3)* Given Z and a, tan 7 = tan Z cos a. 
 
 Z and ft, cos a = cot -J Z tan 7. 
 
 Z and 7, sin a = cot Z tan /. 
 
 Calculation of the values of m and ft. 
 
 The above formulas cover all the ordinary cases, the only change that is 
 required in them is to write for <?, b,a, in equations (1), (2), (3), above, c', 5', #', 
 the lengths of the axes for the given form, noting that a' = me, and so on. 
 
 1. Prisms, i-n or i-n. As remarked, the semi-prismatic angle (over i-l) 
 is the angle a (f. 254), and tan a = nb. If the calculated value of ?i is 
 greater than unity, tne form is written oo c : nb : a (i-n) ; if less than unity 
 the form is written oo c : b : na (i-n), b being the unit axis. Thus 
 (oo c : ^b : a) becomes i 2 (oo <? : b : 2#). 
 
 2. Domes, m-i and m-i. No further explanation is needed (f. 255) ; here 
 tan ft = me, or b tan 7 = me. 
 
 3. Octahedrons, m. Here the angle a is always known (it being the 
 same as for the unit-octahedron where tan a = #), and hence a single meas- 
 ured angle, X, Y, or Z will give the values of either ft or 7 for the given 
 form, and tan ft = mc 9 b tan 7 = me. 
 
 4. Forms m-n or m-h. The measurement of the angles X, Y, Z will 
 give the values of a, ft, and 7 belonging to the given form, and tan ft = me, 
 tan a = nb, etc. 
 
 Here, as in the prisms, if n is less than unity, when the axis a is the unit, 
 the symbol is transposed, and the axis b made the unit, thus 2<? : $b : a (2 J) 
 becomes 4c : b : 2a (4-2). 
 
 If the angle between the form m-n (or m-n) and either of the pinacoide 
 can be measured, the method of calculation is essentially the same (Com- 
 pare f. 24S) ; for 
 
 m-n A O (base) = supplement of the angle -J-Z; 
 
 m-n A i-l (macropinacoid) = supplement of the angle \Y \ and 
 
 m-n A i-l (brachypinacoid) = supplement of the angle 
 
 The method of calculation of planes in a rectangular zone by means of 
 the tangents of their supplement basal angles tinds a wide application in 
 this system. It applies not only to the main zones O to i-l (maerodomes), 
 
CRYSTALLOGRAPHY. 
 
 O to i-l (brachydomes), i-l to i-l (vertical prisms), and / to (unit octahe- 
 drons), but also to any z.me of octahedrons m-n (or m-n) between O and i n 
 (or i-n), and any transverse zone from i-l to //&-, and i-l to m-l. 
 
 V. MONOCLINIC SYSTEM. 
 
 In the Monoclinic system the number 
 of unknown quantities is three, viz., the 
 lengths of the axes c and &, expressed in 
 terms of the unit clinodiagonal axis , and 
 the oblique angle ft (also called 6*), between 
 the basal and vertical diametral sections, 
 that is, between the axes c and d. Three 
 independent measurements are needed to 
 determine these crystallographic elements. 
 
 The angle ft is obtuse in the upper front 
 quadrants, and acute in the lower front 
 quadrants; the planes in the first mentioned 
 quadrants are distinguished from those be- 
 low by the minus sign. The unit octahe- 
 dron is made up of two hemi-octahedrons 
 (1 and +1), as shown in f. 256. 
 
 Calculation of the Lengths of the Axes, 
 and the Angles of obliquity. 
 Represent (see f. 256) the inclination of the 
 
 Edge X on the axis c by /*-. X on d by v. Y on c by p. 
 X' " c " /*'. X' on d by v. Z on d by <r. 
 
 For the relation of the axes in terms of these angles we have : 
 (1) In the oblique-angled plane triangle, in the clinodiagonal section 
 
 sin v 
 
 a : o = sin /* : sm V, or, c = 
 
 tan ju = 
 
 a sin 
 
 B . 
 c a cos ft 
 
 8111 /X- 
 
 tan u! = 
 
 when a = 1. 
 a sin ft 
 
 c sin ft 
 
 tan v = - ^ .=. 
 a c cos ft 
 
 tan v' = 
 
 c+a cos /3* 
 
 c sin ft 
 a + c cos/3 
 
 2 sin v sin i/ 
 
 sin (/A /*/)* " sin (v v') * 
 
 Further, p + v + ft = 180 /// + i/= ft. 
 
 (2) In the right-angled triangle of the orthodiagonal section, b cot p 
 
MATHEMATICAL CRYSTALLOGRAPHY. 77 
 
 (3) In the basal section, d tan <r = b. 
 
 The above formulas serve to determine the lengths of the axes, and the 
 angle of obliquity, or, if these are known, to determine the values of m and 
 n by substituting mo for c 9 etc. 
 
 The angles p, v, />, <r, etc., must, in general, be determined by calculatioD 
 from measured angles. 
 
 Let the inclination of a plane in the positive quadrant on the clinodi- 
 agonal section be denoted by X\ that on the orthodiagonal section by Y; 
 that on the basal section by Z. Let also the corresponding inclinations of 
 a plane in the negative quadrants be indicated by X.\ Y', Z ', respectively 
 (see f. 256). 
 
 It is to be noted, when the piriacoids are present, that 
 
 + 1 A = ISO Z; -f 1 A i-i = ISO Y\ + 1 A i-l = 180-X; 
 - 1 A O = ISO - Z ; 1 A*-t == ISO - Y' ; - 1 A i4 = 180-X'. 
 
 The same is true for the corresponding angles of the general form 
 m-n, or m-n. 
 Also, when 1 (f. 256) alone are present (or m-n} note that 
 
 + 1 A -1 (orthodiag.)= Y+ Y> i 
 (basal) = Z+Z. 
 
 An}'- three of these angles will serve to give for the unit form ( 1) the 
 length and obliquity of the axes, or, when these are known, two of these 
 angles are sufficient to deduce the values of ra and n for any unknown 
 form. 
 
 In the first case, as one of the three measured angles must be either 
 Y+ Y' or Z + Z ', the formulas given above do not immediately apply. 
 
 For example, if X, X.' and Y-+- Y' are given. Placing a spherical 
 triangle, abc, in f. 256, with its vertices on the edges X, X r , and Y, 
 in this the three angles will equal X, X and Y+ Y respectively ; here 
 the side, ac, opposite the angle ( Y+ Y) is calculated, which gives the value 
 of fjb + //, also the side, fo," opposite A' '; then, again, in the right-angled 
 spherical triangle, where bo and X are known, /A is obtained, thus p' is 
 known and also /#. The lengths of the axes follow from the formulas 
 given above. 
 
 The following are some of the cases which may occur: 
 
 (a) Given O, and i4. O/\i-i (front)= 180- /9, behind = ft. 
 
 (b) Given 0, - 1-t, and -I- l-i. O^- l-i = 180 v'; 0/\+ l-i = 180 
 
 - 2 sin v sin v , ^ OAf 
 
 v. By the formula given above, tan p = ^ , _^ , , also, p 180 
 
 __ (/3 + z/). Thus ft, p, and j/ are known, and from them the relation of the 
 axes d and c is deduced. 
 
 (c) Given i-i, 1-* and + l-i. i-i A \4 = 180 /,*-* A + 1-* = 180 
 - /i. As before, tan ft = 2 f in ^ sin ^ and v = i 80 - (^ + /*). 
 
 Bill (U- tt 
 
78 
 
 CRYSTALLOGRAPHY. 
 
 (d) Given the prism I and (f. 257). In the spherical triangle ABC : 
 C= 90 (inclination of base on cli lodiagonal section), BOl\I, A = 
 J(/A Z). Hence, the sides CA and CB are calculated ; CA = ft (or, as 
 
 in this case, 180 fi) CB <r, which gives the ratio 
 
 of the lateral axes, d and b. 
 
 (e) Given i-i, 1-i and O. 0/\i-i (behind) = /?, and 
 sin p tan [(0Al-t) - 90] = tan p. 
 
 (f) Given +1 and 1, form as in f. 256. The 
 angles between the planes -f- 1 and 1 and the diame- 
 tral sections are indicated by the letters X^ Y, etc., as 
 before explained (p. 77). The relations between these 
 angles and the angles //,, v, p, etc., are given in the fol- 
 lowing formulas, deduced by means of spherical triangles: 
 
 COS IL = 
 
 cos Y 
 
 COS V = 
 
 cos Z 
 
 also, 
 
 , COS Z 
 
 cos v = . ^ 
 sm X 
 
 cos a- = -- ^ 
 in Z 
 
 cos X 
 sin 
 
 tan <r 
 -; - 
 sin v 
 
 tan 
 
 sin //, 
 
 tan X'= 
 
 tan a- 
 sin v' 
 
 , tan Z = , 
 
 sin p sin a- 
 
 tan Z = 
 
 tan j/ 
 sin <r 
 
 (<7) Given the prism / and 1 (or -f 1). The i 
 /A/, lA/, lA 1 are measured. In the spherical 
 triangle ABD (f. 258), the angle A = i(/A /), B = 
 1 A f, D i( 1 A 1) = X, from which the sides AD 
 = v' + (180 - ) and AB are calculated. Then in the 
 second triangle, ABC, G 90, AB is known, also A; 
 ence, #Z? = <rand CA = 180 - & are calculated. Thus 
 ' and p' and y3 become known, and the relation of d to 
 c ; also from <r follows the ratio of d to b. 
 
 Calculation of the values of m and n. 
 
 In general, it may be said that the methods of calculation are the same 
 as those already given. In each case the values of /*, i/, p, <r are to be 
 obtained, and tnose introduced into the axial equations (1, 2, 3) given 
 above sjive the values of me, nb, etc., from which m and n are derived. 
 When in the general form m-n (me : nb : a) n is found to be less than 
 unity, then b is made the unit axis and the form is written m-h (me : 
 b : na\ thus 2c : b : a becomes 4c : b : 2a (4-fc), the same is true for i-n 
 and }rh. 
 
 1. Hemi-octahedrons, m-n.- -Two measurements are needed, giving 
 
MATHEMATICAL CRYSTALLOGRAPHY. 79 
 
 two of the angles X, Y, Z, etc., from which are derived p (or v), p (or a\ 
 and from the proper formulas in and n. 
 
 The following hemi-octahedrons require one measurement only : m\ 
 m-m, m-m, l-n, 1-n. Further, it is to be noted in regard to 
 them that the forms m have the same ratio of the lateral axes as 1, 
 that is, the same value of <r. 
 
 Forms I-n, and m-m, have the same ratio of the axes c and d as the 
 unit form 1, that is, the same values of p, v (jj,', v'). 
 
 Forms m-m, 1-n, have the same ratio of the axes c and b with 
 1, that is, the same value of p. 
 
 2. Form *'-?& (or i-n). If, as before, X, Y represent the inclinations of 
 the given prism on the clinodiagonal and orthodiagonal sections respect- 
 ively, it is to be noted that : 
 
 X + Y = 90. 
 Similarly to f. 257, we obtain, in general, for any form, i-n, 
 
 sin # tan X , - . ^ b cot X 
 
 n = c 7 ; and for ^-n, n : -5-. 
 
 b sin/3 
 
 Since i-i A i-l = 90, the tangent law can be applied in this zone advan- 
 tageously. If X 1 , Y 1 are the corresponding angles for the unit prism /, 
 then for i-n, 
 
 tan X tan Y 1 , - . ; tan X 1 tan Y 
 
 n=- ^rr= ^F, and for ir-n, n ^-=7 ^T' 
 
 tanJT 1 tan Y 9 tan X tan Y 1 
 
 3. Forms m-i, hemi-orthodomes. For each form the corresponding 
 values of /*, v (/LI/, v') are to be obtained by measurement or else calculated, 
 and from them the value of me obtained from the formulas (1), mo = 
 sin v 
 
 , - ~ L -" t5 Lv/ 
 
 sin fju 
 
 4. Forms m-i, clinodomes. Similarly as with the prisms, when JTand 
 Z denote the angles with the clinodiagonal and basal sections, 
 
 X +Z=90. 
 For any form m-\, 
 
 bcotX 
 
 c sin p 
 Or by the tangent law, X 1 being the corresponding angle for 1-i, 
 
80 CRYSTALLOGRAPHY. 
 
 TRICLINIC SYSTEM. 
 
 The triclinic system is characterized by its entire want of symmetry : 
 The inclinations of all the diametral planes, and hence, the inclination of 
 the axes, are oblique to one another. There are, then, five unknown quan- 
 tities to be determined in each case, viz., the three angles of obliquity of 
 the axes, and the lengths of the axes b and c, d being made = 1. 
 
 The axes are lettered as in the orthorhombic system : c = the vertical 
 axis, b = the macrodiagonaLaxis, and a the brachydiagonal axis. 
 
 Xet (f. 259) a = angle between the axes c and b\ 
 ft = angle between the axes c and a ; 
 <y = angle between the axes b and d. 
 Also, let A = angle of inclination of the diame- 
 tral planes meeting in the axis a ; J3 = angle of 
 inclination for those intersecting in the axis $, and 
 G = the angle of those meeting in c. 
 
 The macrodiagonal (m-n) and brachydiagonal 
 (m-n) planes are indicated as in the orthorhombic 
 system, also the planes opposite the acute angle 
 (ft) are called + , and those opposite the corre- 
 spending obtuse angle ; furthermore, the planes 
 in front, to the right (and behind, to the left) are distinguished by an accent, 
 as m-n'. 
 
 In the fundamental octahedron formed by four sets of planes, these are, 
 taken in the usual order (f. 227), 1', 1, +1', + 1, and below, + 1', 
 + 1, 1 , 1. 
 
 In the determination of any individual crystal belonging to this system, 
 the axial directions as well as unit values have to be assumed arbitrarily ; 
 in many cases (e.g., axinite) the custom of different authors has varied 
 much. Two points are to be considered in making the choice : 1, the cor- 
 respondence in form with related species, even if these be not triclinic, as, 
 for example, in the feldspar family ; and 2, the ease of calculation, which 
 is much facilitated if, of the planes chosen as fundamental, the pinacoids 
 are all, or at least in part, present. 
 
 In general, the methods of calculation are not simple. Some of the 
 most important relations are given here (from Naumann). In actual 
 practice, problems which arise may be solved by some of the following 
 formulas, or by means of a series of appropriate spherical triangles, used 
 as in the preceding pages, and by which, from the measured angles, the 
 required elements of the forms may be obtained. 
 
 In addition to the angles already defined, let, as follows (f. 259), 
 
 -5T= inclination of a plane on the brachydiagonal section ; 
 jT= " " macrodiagonal " 
 
 Z= . basal 
 
 Let the inclination of the edge, 
 
 X on c = /A, JTon c = />, Z on d -= <r, 
 
 X on d = v y Y on b = TT, Z on b = T, 
 
MATHEMATICAL CRYSTALLOGRAPHY. 81 
 
 When the three pinacoids are present, the angles A, j5, C are given by 
 measurement. These angles are connected with the axial angles by the 
 following equations : 
 
 cos A 4- cos B cos C Q cos B + cos C cos A 
 
 cos a = - : jj. - ; cos $ = - : 7r - - - -. - ; 
 sm B sin C sin C &m A 
 
 cos C + cos A cos B 
 
 COS 7 = - : - - A ; -- j> - 1 
 
 sin A sin B 
 also, 
 
 sin a : sin ft : sin 7 = sin A : sin B : sin C. 
 
 The relations between the angles a, ft, 7, and the angles /x, v, etc., are as 
 follows : 
 
 2 sin p sin p 2 sin TT sin TT' 
 tan a = . f- - = . T ^r-. 
 sin (p p) sm (TT TT ) 
 
 ~ 2 sin A sin a' 2 sin v sin i/ 
 tan 8 = 
 
 . 
 sin (/A /A) sin (v z^) 
 
 2 sin T sin r r 2 sin a sin 0-' 
 tan 7 = ; -. - 7 = . -, jr . 
 sm (T T ) sm (<r <7 ) 
 
 Also, 
 
 a + 7T + /!> = /3 + /4 + z/ = 7-}-<r + T= 180. 
 
 The relations between JT, F. Z, and A, B, C, and ^, v, etc., are given 
 by the following formulas, in which the stun and difference of X and F, 
 etc., are calculated, and from them the angles X, Y, etc., themselves are 
 obtained : 
 
32 CRYSTALLOGRAPHY. 
 
 cos Y + cos X cos C cos Z 4- cos X cos A 
 
 COS /A = - : - =i^ : - 7> - * COS V = 
 
 " 
 
 COS = 
 
 : - =i^ : - 7> - * : ^FF : - i 
 
 sin X sin C sin JT sin A 
 
 cos JT + cos l^cos C cos Z -f- cos I 7 ' cos ./? 
 
 7T = 
 
 T * 
 
 sin ;r sin c sin ;r sin B 
 
 cos JT + cos Z cos ^4 cos !F 4- cos Z cos ./? 
 
 COS <T = - : - ~ - 5 - ~ A - J COS T = - ; - ^ -- - . 
 
 sin Z sin ^1 sin Z sin JJ 
 
 Further, sin JT : sin Y =. sin p 
 
 sin T" : sin Z = sin T 
 sin Z : sin X sin p 
 
 sin /. 
 sin 7T. 
 sin <r. 
 
 The following equations give the relations of the angles /LI, v, p, etc to 
 the axes and axial angles : 
 
 a sn c sn 
 
 tan j. = - ^ ; tan v = 
 
 3 - -5. 
 
 a cos p a c cos /3 
 
 J sin a c sin a 
 
 tan p = - j -- ; tan IT = 1 - . 
 
 c b cos a o c cos a 
 
 # sin 7 5 sin / 
 
 tan T = j - - ; tan a- = ---- T - . 
 
 a cos 7 a o cos 7 
 
 Also, ein T 
 
 sin /> 
 sin v 
 
 sin o- = d : b, 
 sin TT = b : c, 
 sin JJL = c : d. 
 
 For any form 
 
 ra-tt A ?;4 = 180 F; i-nAi- = J80 X; m- A O = 180 Z. 
 For a vertical heraiprism, X+ Y+C= 180, 
 
 d : b = sin Y . sin a : sin X : sin 0. 
 For a macrodiagonal hemidorae, Y+ Z + B = 180, 
 d : c ==. sin Y . sin a : sin Z . sin 7. 
 For a brachydiagonal hemidome, X+Z +A = 180, 
 2 : c sin 2T sin : sin Z sin 7. 
 
 By writing me for c y nb for 0, etc., these formulas will answer also for 
 the determination of m and n. It is supposed in the above that the 
 measured edge is parallel to the axis of the given hemiprism, etc. ; when 
 this is not the case the relations are a little less simple. 
 
MATHEMATICAL CRYSTALLOGRAPHY. 
 
 83 
 
 MEASUREMENT OF THE ANGLES OF CRYSTALS.* 
 
 The angles of crystals are measured by means of instruments which aie 
 called goniometers. 
 
 The simplest form of these instruments is the hand -goniometer, repre- 
 sented in f. 260. It consists of an arc, graduated to half degrees, or finer, 
 
 and two movable arms. In the instrument figured, one of the arms, ao, 
 has the motion, forward and backward by means of slits gJt, ik; the other 
 arm, cd, has also a similar slit, and in addition it turns around the centre of 
 the arc as an axis. The planes whose inclination is to be measured are 
 applied between the arms ao, co 9 and the latter adjusted so that they and 
 the surfaces of the planes are in close contact. This adjustment must be 
 made with care, and when the instrument is held up to the light none must 
 pass through between the arm and the plane. The number of degrees read 
 off on the arc between k and the left edge of d (this edge being in the line 
 of the centre, o, of the arc) is the angle required. The motion to and fro by 
 means of the slits is for the sake of convenience in measuring small or 
 imbedded crystals. In a much better form of the instrument the arms are 
 wholly separated from the arc ; and the arc is a delicately graduated circle 
 to which the arms are adjusted after the measurement. 
 
 The hand-goniometer is useful in the case of large crystals, and those 
 whose faces are not well polished ; the measurements with it, however, are 
 seldom within a quarter of a degree of accuracy. In the finest specimens 
 of crystals, where the planes are smooth and lustrous, results far more 
 accurate may be obtained by means of a different instrument, called the 
 reflecting goniometer. 
 
 Reflecting Goniometer. This instrument was devised by Wollaston, in 
 1809, but it has been much improved in its various parts since his time, 
 especially by Mitscherlich. The principle on which it is constructed may 
 be understood by reference to the following figure (f. 261), which repre 
 gr.nts a crystal, whose angle, abe. is required. 
 
 The eye at P, looking at the face of the crystal, $<?, observes a reflected 
 
84 
 
 CRYSTALLOGRAPHY. 
 
 image oi m, in the direction of Pn. The crystal may now be so changed in 
 its position, that the same image is seen reflected by 
 the next face and in the same direction, Pn. To 
 effect this, the crystal must be turned around, until 
 abd has the present direction of be. The angle dbc, 
 measures, therefore, the number of degrees through 
 which the crystal must be turned. But dbc, subtracted 
 from 1 80, equals the required angle of the crystal, 
 abc. The crystal is, therefore, passed in its revolution 
 
 through an angle which is the supplement of the required angle. This 
 
 angle evidently may be measured by attaching the crystal to a graduated 
 circle, which should turn with the crystal. 
 
 The accompanying cut (f. 262) represents a reflecting goniometer made 
 
MATHEMATICAL CRYSTALLOGRAPHY. 85 
 
 by Oertling, in Berlin. It will suffice to make clear the general character 
 of the instrument, as well as to exhibit some of the refinements added for 
 the sake of greater exactness. 
 
 The circle, 6 y , is graduated, in this case, to twenty minutes, and by means 
 of the vernier at v the readings may be made to minutes and half min- 
 utes. The crystal is attached by means of wax to the little plate at k ; 
 this may be removed for convenience, but in its final position it is. as here, 
 at the extremity of the axis of the instrument. This axis is moved by 
 means of the wheel, n ; the graduated circle is moved by the wheel, m. 
 These motions are so arranged that the motion of n is independent, its axis 
 being within the other, while on the other hand the revolution of m moves 
 both the circle and the axis to which the crystal is attached. This ar- 
 rangement is essential for convenience in the use of the instrument, as 
 will be seen in the course of the following explanation. 
 
 The screws, c, d, are for the adjustment of the crystal, and the slides, 
 a, >, serve to centre it. 
 
 The method of procedure is briefly as follows : The crystal is attached 
 by means of suitable wax at &, and adjusted so that the direction of the 
 combination-edge of the two planes to be measured coincides with the axis 
 of the instrument ; the wheel, n, is turned until an object (e.g., a window- 
 bar) reflected in one plane is seen to coincide with another object not 
 reflected (e.g.^ a chalk line on the floor), the position of the graduated circle 
 is observed, and then both crystal and circle revolved together by means 
 of the wheel, m, till the same reflected object now seen in the second plane 
 again coincides with the fixed object (that is, the chalk line) ; the angle 
 through which the circle has been moved, as read off by means of the 
 vernier, is the supplement angle between the two planes. 
 
 In order to secure accuracy, several conditions must be fulfilled, of 
 which the following are the most important : 
 
 1. The position of the eye of the observer must remain perfectly 
 stationary. 
 
 2. The object reflected and that with which it is brought in coincidence, 
 should be at an equal distance from the instrument, and this distance 
 should not be too small. 
 
 3. The crystal must be accurately adjusted j this is so when the line 
 seen reflected in the case of each plane and that seen directly with which 
 it is in coincidence are horizontal and parallel. It can be true only when 
 the intersection edge of the two planes measured is exactly in the direction 
 of the axis of the instrument, and perpendicular to the plane of the circle. 
 
 4. The crystal must be centered as nearly as possible, or, in other words, 
 the same intersection -edge must coincide with a line drawn through the re- 
 volving axis. This condition will be seen to be distinct from the preced- 
 ing, which required only that the two directions should be the same. The 
 error arising when this condition is not satisfied diminishes as the object 
 reflected is removed farther from the instrument, and becomes zero if the 
 object is at an infinite distance. 
 
 The first and second conditions are both satisfactorily fulfilled by 
 the use of a telescope, as , f. 262, with slight magnifying power. This 
 is arranged for parallel light, and provided with spider lines in its 
 focus. It admits also of some adjustments, as seen in the figure, but 
 
86 CRYSTALLOGRAPHY. 
 
 when used it must be directed exactly toward the axis of the goniometer. 
 This telescope has also a little magnifying glass (g, f. 262) attached to it, 
 which allows of the crystal itself being seen when mounted at k. This 
 latter is used for the first adjustments of both planes, and then slipped 
 aside, when some distant, object which has been selected must be seen 
 in the field of the telescope as reflected, first by the one plane and 
 then by the other as the wheel n is revolved. When the final adjustments 
 have been made so that in each case the object coincides with the centre of 
 the spider-cross of the telescope, and when further the edge to be measured 
 has been centered, the crystal is ready for measurement. 
 
 This telescope, obviously, can be used only when the plane is smooth and 
 large enough to give distinct and brilliant reflections. In many cases 
 sufficient accuracy is obtained without it by the use of a window-bar and 
 a white chalk line on the floor below for the two objects ; the instrument in 
 this case is placed at the opposite end of the room, with its axis parallel to 
 the window ; the eye is brought very close to the crystal and held motionless 
 during the measurement. 
 
 The best instruments are provided with two telescopes. The second 
 stands opposite the telescope, t (see figure), the centres of both telescopes 
 being in the same plane perpendicular to the axis of the instrument. 
 This second telescope has also a hair cross in the focus, and this, when 
 illuminated by a brilliant gas burner (the rest of the instrument being 
 protected from the light by a screen) will be reflected in the successive 
 faces of the crystal. The reflected cross is brought in coincidence with the 
 cross in the first telescope, first for one and then for the other plane. As 
 the lines are delicate, and as exact coincidence can take place only 
 after perfect adjustment, it is evident that a high degree of accuracy is 
 possible. 
 
 Still more than before, however, are well-polished crystals required, so 
 that in the majority of cases the use of the ordinary double telescopes is 
 impossible, very often, however, the second telescope may be advantage- 
 ously replaced by another having an adjustable slit in its focus, as proposed 
 by Websky, allowing of being made as narrow as is convenient ; or, as sug- 
 gested by Schraufj^the spider-lines of the second telescope may be re- 
 placed by a piece of tin-foil, in which two fine cross lines have been cut; 
 these are illuminated by a gas-burner. By these methods the reflected 
 object is a bright line or cross, instead of the dark spider-lines, and it is 
 visible in the first telescope even when the planes are extremely minute, 
 or, on the other hand, somewhat rough and uneven ; the image is naturally 
 not perfectly distinct, but sufficiently so to admit of good measurements 
 (0.<7., within two or three minutes). 
 
 The third and fourth conditions are the most difficult to fulfil absolutely. 
 In the cheaper instruments the contrivance to accomplish the end often 
 consists of a jointed arm so placed as to have two independent motions at 
 right angles to each other. In the best instruments the greatest care and 
 attention is paid to this point, and a great variety of ingenious contrivances 
 have been devised to overcome the various practical difficulties arising. 
 
 The cut (f. 262) shows one of these in its simpler form. The crystal ia 
 approximately adjusted by the hand, and then the operation completed by 
 means of the screws c and d. These give two motions at right angles tc 
 
MATHEMATICAL CRYSTALLOGRAPHY. 87 
 
 each other, and the arrangement is such that the motions are made on the 
 surface of a spherical segment of which the crystal itself occupies the 
 centre, so that it is not thrown entirely out of the axis of the instrument 
 by the motions of the screws. The adjustment having been accurately 
 made, the edge is centered by means of two sliding carriages, a, &, moving 
 at right angles to each other ; here they are moved by hand, but in better 
 instruments by line screws. The edge must be first centered as carefully as 
 practicable, then the complete adjustments made, and finally again centered, 
 as before, to remove the excentricity caused by the movement of the ad- 
 justment screws. The successful use of the most elaborate instruments is 
 only to be attained after much patient practice. 
 
 Theoretical discussions of the various errors arising in measurements and 
 the weight to be attached to them have been given by Kuppfer (Preis- 
 schrift iiber genaue Messung der Winkel an Krystallen, 1825), also by 
 Naumann, Grailich, Schrauf, and others (see literature, p. iv). 
 
 It has been stated that when the two planes have been adjusted in the 
 goniometer so that their combination-edge is parallel to the axis of the 
 instrument, the reflections given by them will be parallel. It is evident 
 from this that any other planes on the crystal which are in the same zone 
 with the two mentioned planes will also give, as the circle is revolved, 
 reflections parallel to these. This means gives the test referred to on 
 p. 53, leading on the one hand to the discovery of zones not indicated by 
 parallel intersections, and on the other hand showing, in regard to supposed 
 zones, whether they are so in fact or not. 
 
 The degree of accuracy and constancy in the angles of crystals as they are given by nature 
 is an important subject. Crystallography as a science is based upon the assumption that the 
 forms made by nature are perfectly accurate, and whenever exact measurements are possible, 
 supposing the crystals to have been free from disturbing influences, it has been found that 
 this assumption is warranted by the facts ; in other words, the more accurate the measure- 
 ments th>; more closely do the angles obtained agree with those required by theory. An 
 example may illustrate this : On a crystal of sphalerite (zinc-blende), from the Binnenthal, 
 exact measurements were made by Kokscbarow to test the point in question. He found for 
 the angle of the tetrahedron 70 31' 48", required 70 3 31' 44" ; for the octahedral angle 
 109 3 27 42", required 109 28' 16'; and for the angle between the tetrahedron and cube 
 125 15' 52", required 125 15' 52". The crystallographic works of the same author, as well 
 as those of many other workers in the same field, contain many illustrations on the same 
 subject. At the same time variations in angle do occasionally occur, from a change in 
 chemical composition, and from various disturbing causes, such as heat and pressure (see 
 further, p. 107). Further than this, it is universally true that exact measurements are in 
 comparatively few cases possible. Many crystals are large and rough, and admit of only 
 approximate results with the hand goniometer; others have faces which are more or less 
 polished, but which give uncertain reflections. This is due in some cases to striations, in 
 others to the fact that the surfaces are curved or more or less covered with markings 01 
 etchings, like those common on the pyramidal planes of quartz. In all such cases there is a 
 greater or less discrepancy between the measured and calculated angles. 
 
 The important point to be noted always is the degree of accuracy attainably or, in other 
 words, the probable error. The true result to be accepted is always to be obtained by the 
 discussion of all the measurements in accordance with the methods of least squares. This 
 method involves considerable labor, and in most cases it is sufficient to take the arithmetical 
 mean, noting what degree of weight is to be attached to each measurement. It is to be noted 
 that where measurements vary largely the probable error in the mean accepted will be con- 
 siderable ; moreover an approximate measurement may not be the more accurate because it 
 happens to agree closely with the theoretical angle. 
 
 For the determination of the symbols of planes, measurement accurate within 30', or even 
 1, a>-e generally sufficient. 
 
 When planes are rough and destitute of lustre the angles can best be obtained with the 
 
88 
 
 C R YSTALLOGR APHT. 
 
 reflecting goniometer, the reflections of the light from an object like a candle-flame, being ' 
 taken in place of more distinct images. 
 
 For" imbedded crystals, and often in other cases, measurements may be very advantage- 
 ously made from impressions in some material, like sealing-wax. Angles thus obtained ought 
 to be accurate within one degree, and suffice for many purposes. It is sometimes of advan- 
 tage to attach to the planes to be measured, when quite rough, fragments of thin glass, from 
 which reflections can be obtained; this must, however, be done with care, to avoid consider- 
 able error. 
 
 COMPOUND, OR TWIN CRYSTALS. 
 
 TWIN CRYSTALS are those in which one or more parts regularly arrranged 
 are in reverse position with reference to the other part or parts. They 
 often appear externally to consist of two or more crystals symmetrically 
 united, and sometimes have the form of a cross or star. They also exhibit 
 the composition in the reversed arrangement of part of the planes, in the 
 striae of the surface, and in re-entering angles ; in other cases the compound 
 structure is detected only by polarized light. The following figures are 
 examples of the simpler kinds. Fig. 263 is a twinned octahedron with 
 
 264 
 
 264A 
 
 Spinel. 
 
 Cassiterite. 
 
 re-entering angles. Fig. 263A represents the regular octahedron divided 
 into two halves by a plane parallel to an octahedral face ; the revolving of 
 the upper half around 180 produces the twinned form. Fig. 264 consists 
 of a square prism, with pyramidal terminations, twinned parallel to a 
 diagonal plane between opposite solid angles, as illustrated in f. 264A, 
 a representation of the simple form. A revolution of one of the two 
 halves of f. 264A 180 about an axis at right angles to the diagonal plane 
 outlined in the figure, would produce the form in fig. 264. 
 
 Crystals which occupy parallel positions with reference to each other, 
 that is, those whose similar axes and planes are parallel, are not properly 
 called twins ; the term is applied only where the crystals are united in their 
 reversed position in accordance with some deducibfe mathematical law. In 
 conceiving of them we imagine first the two individuals or portions of the 
 same individual to be in a parallel position, and then a revolution of 180 
 to take place about a certain line, as axis, which will bring them into the 
 twinning position. 
 
 An exception to the principle in regard to parallel axes is afforded in the case of hemihe- 
 dral crystals, in some of which a revolution of 180 has the effect of producing an apparent!} 
 holohedral form, the axes of the parts revolved remaining parallel. 
 
TWIN CRYSTALS. 89 
 
 In some cases (e.g.. hexagonal forms), a revolution of 60 would produce the twinned 
 form, but in treating of the subject it is better to make the uniform assumption of a revolu- 
 tion of iU J , which will answer in all cases. 
 
 It is not to be supposed that twins have actually been formed by such a revolution of the 
 parts of crystals, for the twin is the result of regular molecular growth or enlargement, like 
 th.Hu 01 the simple crystal. This reference to a revolution, and an axis of revolution,, is only 
 a convenient means of describing the forms. But while this is true, it is important to ob- 
 serve that the Itiics deduced to explain the twinning of a crystal have, from a molecular 
 standpoint, a real existence. The measurements of Schrauf on twins of cerussite (Tsch. 
 Min. Mitth., 1873, 209) show the complete corresj iondence between the actual angles and 
 those required in accordance with the law of twinning. 
 
 Twinning axis. The line or axis about which the revolution of 180 is 
 supposed to take place is called the t winning-axis (Zwillingsaxe, Germ.) t 
 or axis of revolution. 
 
 The following law has been deduced in regard to this axis, upon which 
 the theory of the whole subject depends : 
 
 The twinning axis is always a possible crystallographic line, usually 
 either an axis or a normal to some possible crystalline plane. 
 
 Twinning-plane. The plane normal to the axis of revolution is called 
 the twinning-plane (Zwillingsflache, Germ.}. The axis and plane of twin- 
 ning bear the same relation to both individuals in their reversed position ; 
 consequently (except in some of hemihedral and triclinic forms) the twin- 
 ned crystals are symmetrical with reference to the twinning-plane. 
 
 Composition-ydane. The plane by which the reversed crystals are united 
 is the composition-plane or -face (Zusammensetzungsflache, Germ.}. This 
 and the twinning-plane very commonly coincide; this is true of the simple 
 examples given above (f. 263, 264) where the plane about which the revolu- 
 tion is conceived as having taken place (normal to the twinning axis), and 
 the plane by which the semi-individuals are united, are identical. When 
 not coinciding the two planes are generally at right angles to each other, 
 that is, the composition face is parallel to the axis of revolution. Examples 
 of this are given beyond (p. 99). Still again, where the crystals are not 
 regularly developed, and where they interpenetrate, and, as it were, exer- 
 cise a disturbing influence upon each other, the contact surface may be 
 interrupted, or may be exceedingly irregular. In such cases the axis and 
 
 Elane of twinning have, as always, a definite position, but the composition- 
 ice has lost its significance. 
 
 Thus in quartz the interpenetrating parts have 
 often no rectilinear boundary, but mingle in the most 
 irregular manner throughout the mass, and showing 
 this composite irregularity by abrupt variations of the 
 planes at the surface. Fig. 265 exhibits by its shaded 
 part the parts of the plane 1 that appear over the 
 surface of the plane R, owing to the interior composi- 
 tion. This internal structure of quartz, found in almost 
 all quartz crystals, even the common kinds, is well 
 brought out 'by means of polarized light ; also, by 
 etching with hydrofluoric acid, the plane 1 and R 
 becoming etched unequally on the same amount of 
 exposure to the acid. 
 
 The twinning-plane is, with rare exceptions, a pos- 
 sible occurring plane on the given species, and usually one of the more 
 
90 CKYSTALLOGBAPHY. 
 
 frequent or fundamental planes. The exceptions occur only in the triclinic 
 and monoclinic systems, where the twinning axis is sometimes one of the 
 oblique crystal lographic axes, and then the plane of twinning normal to it 
 is obviously not necessarily a crystal lographic plane, this is conspicuous in 
 albite. In these cases the composition-face is often of more significance 
 than the twinning-plane, the former being distinct and parallel to the 
 axis, in accordance with the principle stated above. 
 
 With reference to the composition-face, the twinning may be described as taking place (1) 
 by a revolution on an axis at right angles to the 'composition-face, (2) on an axis parallel 
 to it and vertical, (3) by an axis parallel to it and horizontal; whether the revolution 
 takes place with the right or left half of the crystal, the twin is right- or left-handed. 
 
 One further principle is of theoretical importance in the mathematical 
 explanation of the forms. The twinning axis may, in many cases, be ex- 
 changed for another line at right angles with it, a revolution about which 
 will also satisfy the conditions of producing the required form. An exam- 
 ple of this is furnished by f. 318, of orthoclase ; the composition-face is 
 parallel to i-i, the axis of revolution also parallel to this plane, and (a) nor- 
 mal to i4, which is then consequently the twinning-plane, though the axis 
 does not coincide with the crystallographic axis, or (b) it may coincide with 
 the vertical axis, and then the twinning-plane normal to it is not a crys- 
 tallographic plane. In other simpler cases also, the same principle holds 
 good, generally in consequence of the possible mutual interchange of the 
 planes of twinning and composition. In most cases the true twinning-plane 
 is evident, since it is parallel to some plane on the crystal of simple mathe- 
 matical ratio. 
 
 An interesting example of the above principle is furnished by the species staurolite. 
 Fig. 307, p. 98, shows a prismatic twin observed by the author among crystals from Fannin 
 Co., Ga. The measured angle for i-i A *'-*' was 70 30' ; the twinning-axis deduced from 
 this may be the normal to the plane 4-f, which would then be the twinning-plane. Instead 
 of this axis, its complementary axis at right angles to it may be taken, which will equally 
 well produce the observed form. Now in this species it happens that the planes -3 and i-'$ 
 (over i-l) are almost exactly at right angles (90 8') with each other, and hence, according to 
 this latter supposition,^'- 3 becomes the twinn ng-plane, and the axis of revolution is normal 
 to it. Hence, either i- \ or i-3 may be the twinning-plane, either supposition agrees closely 
 with the measured angle, which could not be obtained with great accuracy. The former 
 method of twinning (f-f ) conforms to the other twins observed on the species, and hence it 
 may be accepted. What is true hi this case, however, is not always true, for it will seldom 
 happen that of the two complementary axes each is so nearly normal to a plane of the crystal. 
 In most cases one of the two axes conforms to the law in being a normal to a possible plane, 
 and the other does not, and hence there is no doubt as to which is the true twinning axis. 
 
 Contact-twins and Penetration-twins. In contact-twins, when normally 
 formed, the two halves are simply connate, being united to each other bj 
 the composition-face ; this is illustrated by f. 263, 264. In actually occur- 
 ring crystals the two parts are seldom symmetrical, as demanded by theory, 
 but one may preponderate to a greater or less extent over the other; in 
 some cases only a small portion of the second individual in the reversed 
 position may exist. Yery great irregularities are observed in nature in this 
 respect. Moreover, the re-entering angles are often obliterated by the ab- 
 normal developments of one or other of the parts, and often only an indis- 
 
TWIN CRYSTALS. 
 
 91 
 
 tinct line on some of the faces marks the division between the twc 
 individuals. 
 
 Penetration-twins are those in which two or more complete crystals 
 interpenetrate, as it were crossing through each other. Normally, the 
 crystals have a common centre, which is the centre of the axial system fo f 
 both ; practically, however, as in contact-twins, great irregularities occur. 
 
 Examples of these twins are 
 
 given in the annexed figures, 266 267 
 
 f. 266, of fluorite, and f. 267, of 
 hematite. Other examples occur 
 in the pages following, as, for 
 instance, of the species staurolite, 
 f . 309 to 312, the crystals of which 
 sometimes occur in nature with 
 almost the perfect symmetry de- 
 manded by theory. It is obvi- 
 ous that the distinction between 
 contact and penetration-twins is 
 
 not a very important one, and the line cannot always be clearly drawn 
 between them. 
 
 Paragenio and Metagenic twins. The distinction of paragenic and 
 metagenic twins belongs rather to crystallogeny than crystallography. Yet 
 the forms are often so obviously distinct that a brief notice of the dis- 
 tinction is important. 
 
 In ordinary twins, the compound structure had its beginning in a nucleal 
 compound molecule, or was compound in its very origin ; and whatever 
 inequalities in the result, these are only irregularities in the development 
 from such a nucleus. But in others, the crystal was at first simple ; and 
 afterwards, through some change in itself or in the condition of the mate- 
 rial supplied for its increase, received new layers, or a continuation, in a 
 reversed position. This mode of twinning is metagenic, or a result subse- 
 quent to the origin of the crystal ; while the ordinary 
 mode is paragenio. One form of it is illustrated in 
 f. 268. The middle portion had attained a length 
 of half an inch or more, and then became genicu- 
 lated simultaneously at either extremity. These 
 geniculations are often repeated in rutile, and the 
 ends of the crystal are thus bent into one another, and 
 occasionally produce nearly regular prismatic forms. 
 
 This metagenic twinning is sometimes presented 
 by the successive layers of deposition in a crystal, 
 as in some quartz crystals, especially amethyst, the 
 inseparable layers, exceedingly thin, being of oppo- 
 site kinds. So calcite crystals are sometimes made 
 up of twinned layers, which are due to an oscillatory 
 process of twinning attending the progress of the 
 crystal. In a similar manner, crystals of the triclinic feldspars, albite, 
 etc., are often made up of thin plates parallel to i-%, by oscillatory compo- 
 sition, and the face O, accordingly, is finely striated parallel to the edge 
 
 Rutile. 
 
92 CRYSTALLOGRAPHY. 
 
 Repeated twinning. In the preceding paragraph one case of repeated 
 twinning has been mentioned, that of the feldspars ; it is a case of parallel 
 repetition or parallel grouping of the successive crystals. Another kind is 
 that which is illustrated by f. 295, 297, 311, where the successively 
 reversed individuals are not parallel. In this case the axes may, however, 
 lie in a zone, as the prismatic twins of aragonite, or they may be inclined 
 to each other, as in f. 311, of staurolite. In all such cases where the repeti- 
 tion of the twinning tends to produce circular forms, as f. 281, of rutile, the 
 number of individuals is equal to the number of times the angle between 
 the two axial systems is contained in 360. For example, five-fold twins 
 occur in the tetrahedrons of gold and sphalerite, since 5 x 70 32' (the tetra- 
 hedral angle) = 360 (approx.). A compound crystal, when there are three 
 individuals, is called a Trilling (Drilling, Germ.), where there are four 
 individuals, a Fourling (Yierling, Germ.), etc. (See also on p. 186.) 
 
 Compound crystals in which twinning exists in accordance with two laws 
 at once are of rare occurrence; an excellent example is afforded by stauro- 
 lite, f. 312. They have also been observed on albite (f. 333), orthoclase, 
 chalcocite, and in other less distinct cases. 
 
 JZxamples of different methods of Twinning* 
 
 ISOMETRIC SYSTEM. With few exceptions the twins of this system are ol 
 one kind, the twinning axis an octahedral axis, and the twinning plane 
 consequently an octahedral plane inmost cases also the latter coincides 
 
 Galenite. Sphalerite. Galenite. 
 
 with the composition-face. Fig. 263 shows this kind as applied to tiie 
 simple octahedron, it is especially common with the spinel group of min- 
 erals ; similarly, f. 269, a more complex form, and also, f. 270, a dodeca- 
 hedron twinned ; all these are contact twins. Fig. 271 is a penetration 
 twin following the same law ; the twinning being* repeated, and the form 
 flattened parallel to an octahedral face. Fig. 266, p. 91, shows a twin oi 
 
 * A complete enumeration of the different methods of twinning observed under the differ- 
 ent systems, with detailed descriptions and many figures, will be found in Vol. II. of Rose- 
 Sadebeck's Crystallography (Angewandte KrystaUographie, 284 pp., 8vo, Berlin, 1876). 
 
TWIN CRYSTALS. 
 
 93 
 
 fluorite, two interpenetrating cubes ; f. 272 exhibits a dodecahedral twin 
 of sodalite occurring in nature of almost ideal symmetry, and f. 273 is a 
 tetrahedral twin of the species tetrahedrite ; the same law is true for all. 
 
 Sodalite. 
 
 Tetrahedrite. 
 
 Haiiynite. 
 
 Figs. 274, 275, 276, are twins whose axes are parallel ; these forms are 
 possible only with hernihedral crystals. The twinning axis is here a dode- 
 cahedral axis and the twinning plane a dodecahedral plane. The same 
 
 275 
 
 276 
 
 277 
 
 Pyrite. 
 
 Magnetite. 
 
 method of composition is often seen in dendritic crystallizations of native 
 gold and copper, in which the an^le of divergence of the branches is 60 
 and 120, the interfacial angles of a dodecahedron. The brownish-black 
 mineral in the mica from Pennsbury, Pa., is magnetite in this form (f. 277), 
 as first observed by G. J. Brush. 
 
 TETRAGONAL SYSTEM. The most common method is that where the t win- 
 ning-plane is parallel to 1-i. It is especially characteristic of rntile and 
 cassiterite. This is illustrated in f. 264 and similarly in f. 278. Fig. 268 
 shows a similar twin of rutile, and in f. 281 to 283 the twinning according 
 to this law is repeated. In f. 281 the vertical axes of the successive six 
 individuals lie in a plane, and an enclosed circle is the result ; in f. 282 the 
 successive vertical axes form a zig-zag line ; there are here four individuals, 
 
CRYSTALLOGRAPHY. 
 
 add four more behind, the last (VIII) uniting with the first (I), and let it 
 be developed vertically, and the complex form produced results in the 
 scalenohedron twin of f. 283. In chalcopyrite, the octahedron 1, which is 
 
 279 
 
 Cassiterite. 
 
 Chalcopyrite. 
 
 Scheelite. 
 
 very near a regular octahedron in angle, may be the twinning-plane, and 
 forms are thus produced very similar to f. 263. With hemihedral forms 
 twinning may take place as shown in f. 280, where the axis of revolution 
 
 Entile. 
 
 Rutile. 
 
 is a diagonal axis, and the plane of twinning the prism /. It is not always 
 indicated by a re-entering angle, but is sometimes only shown by the 
 oblique striations in two directions meeting in the line of contact. 
 
 Rutile. 
 
 Pyrrhotite. 
 
 Another mode of twinning is that occurring in leucite, observed by vom 
 Rath, who showed the species to be tetragonal. The twinning-plane is here 
 2-t. (Jahrb. Min., 1873, 113.) 
 
TWIN CRYSTALS. 
 
 SYSTEM.- -In the holohedral division of this system twins are 
 
 rare. 
 
 plane 
 
 nearl 
 
 is tridymite 
 
 t or. 
 
 885 
 
 gles to each other (O A 1 = 135 8'). Another example 
 (see p. 288), where the twinning-plane is either the pyramid 
 
 Galcite. 
 
 Calcite. 
 
 Chabazite. 
 
 In the species of the rhombohedral division twins are numerous ; the 
 ordinary methods are the following: the twinning-plane the rhombohe- 
 dron R, f. 285 ; the rhombohedron -27?, f. 288 ; the rhombohedron \R, 
 f. 286. The last mentioned method is common in masses of calcite, where by 
 its frequent repetition it gives rise to thin lamellae ; these are observed 
 often in crystalline limestones. (See p. 173.) 
 
 288 
 
 Pyrargyrite. 
 
 The twinning-plane may also be the basal plane, the axis of revolution 
 consequently the vertical axis. This is illustrated in f. 287, a complex 
 penetration twin of chabazite, also f. 267 (hematite), and in f. 289, 290. 
 It is also common with quartz, the two crystals sometimes distinct, and 
 joined by a prismatic plane, sometimes interpenetrating each other very 
 irregularly, as shown in f. 265. 
 
 * G. vom Rath, Pogg. Ann., cxxxv. 437 ; clii 1. 
 
96 
 
 CRYSTALLOGRAPHY. 
 
 ORTHORHOMBIO SYSTEM. In the orthorhombic system twins are exceed 
 ingly common, and the variety of methods is very great. These may, how 
 ever, be brought into two groups, according as the twinning-plane is (1) a 
 prismatic plane, vertical or horizontal, or (2) an octahedral plane. The 
 twinning is very often repeated, and always in accordance with the law 
 already stated, that the number of individuals is determined by the number 
 of times that the angle of the two axial systems is contained in 360 
 
 (a) Twinning parallel to a prism whose angle is approximately 120. 
 
 1. Pris7ti vertical. The principal examples are aragonite, / A 1 = 116 
 10'; cerussite, 7 A 1= 117 13'; witherite, /A 7 118 30'; bromlite, 
 / A 7 = 118 50' ; chalcocite, 7 A 7 = 119 35' ; stephanite, 7 A / = 115 
 39'; dyscrasite, 7A7= 119 59'. Figs. 291, 292, represent twins of ara- 
 gonite in accordance with this law. Figs. 293, 294, show cross-sections of 
 the two prisms of the preceding figures, in the latter the form is hexagonal, 
 though not regularly so. Fig. 295 is a cruciform twin of the same species. 
 
 291 
 
 Aragonite. 
 
 Aragonite. 
 
 295 
 
 Aragonite. 
 
 2. Prism horizontal ; that is, a macrodome. Examples: arsenopvrite, 
 14 A 14 = 120 46' ; leadhillite, 14 A 14 = 119 20' ; 
 humite, type 1. 
 
 3. Prism horizontal ; that is, a brachydome. 
 Examples : manganite, 1-2 A 1-2 = 122 5<) ! (f. 2l6) ; 
 chrysoberyl, 3 I A 3-2 (f. 300) =120 13' ; columbite, 
 2-2 A 2-2 = 117 20'. 
 
 In all these cases there is a strong tendency toward 
 repetition of the twinning, by which forms often stel- 
 late, sometimes apparently hexagonal, result. These 
 forms are illustrated in the following figures : f. 297 
 is of witherite; f. 298 9 crystal of Leadh llite, in its 
 twinned form of very rhombohedral spi*cr. Figs. 
 299 and 300 are both chrysoberyl, where 3-i is the 
 twinning-plane ; six-rayed twins are very common in 
 this species. 
 
 The genesis of these forms is further illustrated by the following cross- 
 
 Manganite. 
 
TWIN CRYSTALS. 
 
 97 
 
 sections. Fig. 301 shows a cross-section of a cerussite twin, and f. 302 one 
 of the crystal of leadhillite figured above (f. 298). 
 
 Witherite. 
 
 Leadhillite. 
 
 Chrysoberyl. 
 
 Chrysoberyl. 
 
 In f. 303, three rhombic prisms, /, of aragonite, are combined about their 
 acute angles, the dotted lines showing the outlines of the prisms, and the 
 
 f*-*+mr*n ~\ 1.1* J - . A.* C i1_ _ 1- _ 1 _1 1 1 /* f\r\ t f* 
 
 cross lining the direction of the brachydiagonal ; and in f. 304, four are 
 similarly united. In f. 305, three similar prisms, /, are combii 
 
 are combined about the- 
 
 301 
 
 Cerussite. 
 
 obtuse angle. This twin combination may take the form of a hexagonal 
 prism, with or without re-entering angles ; of a three-rayed twin, like f. 
 301, and if a penetration-twin, of a composite prism, like-f. 306 (the num- 
 bering of the parts showing the relation), or a six-rayed twin. In all these 
 cases the stellate form depends on the extension of the individuals beyond 
 the normal limits. 
 
 (b) Prismatic angle approximately that of the regular octahedron, 109 
 28'. An example is furnished by the species staurolite (f. 307), where th 
 7 
 
CRYSTALLOGKAPHY. 
 
 \ 
 
 tw inning-plane is H|, and the corresponding prismatic angle is 109 14' 
 
 (over*-*, or 70 46' over i-l). 
 
 307 308 Another example is furnished 
 
 by marcasite, whose prismatic 
 angle is 106 5'. The twins 
 are generally compound, the 
 repetition with the t winning- 
 plane sometimes parallel, 
 sometimes oblique, see p. 247. 
 In f. 308 the compound crys- 
 tal consists of five individuals, 
 Marcasite since five times 73 55' is ap- 
 
 proximately equal to 360. 
 
 Staurolite. 
 
 nearly rectangular 
 phillipsite, p. 345. 
 
 2. The twinning-plane may be also an octahedral plane. An excellent 
 example is furnished by staurolite, where the twinning-plane isf-f (f. 310). 
 The crystals cross at angles of nearly 120 and 60, hence the form in f. 
 311, consisting of three individuals (trilling) forming a six-rayed star. In 
 f. 312 both this method of twinning: and that mentioned above are ( 
 
 com- 
 
 312 
 
 Staurolite. 
 
 Staurolite. 
 
 Staurolite. 
 
 Staurolite. 
 
 bined. There are thus for the species staurolite three methods of twin- 
 ning, parallel to *"-}, to f-, and to f-". If the occurring prism is made *-}, 
 then the three twinning-planes become /, 1-i, 1, or fundamental planes, as 
 is usually true. 
 
 MONOCLINIC SYSTEM. The following examples comprise the more com- 
 monly occurring methods of twinning in this system. 
 
 (a) The twinniug-plane is the orthopinacoid (i-i). This is true in the 
 se of the common twins of orthoclase (f. 318), called the CarUbad twins. 
 
 case 
 
 The axis of revolution is normal to i-i (see also p. 90), while the two 
 crystals are united by the clinopinacoid, which is consequently the compo- 
 sition-face. These twins may be either right- or left-handed (f. 318 or 
 f. 319), according as the right or left half of the simple form (f. 317) has 
 been revolved. 
 
TWIN CRYSTALS. 
 
 Fig. 313, of pyroxene, is another familiar example ; so also f. 314, of which 
 f. 315 is the simple form. Fig. 320 is a twin of scolecite, where the twin 
 structure is shown by the striafions on the clinopinacoid. 
 
 313 
 
 315 
 
 Pyroxene. 
 
 Ainpbibole. 
 
 Scolecite. 
 
 A form of penetration-twin, with i-i the twinning-plane, is shown in 
 f. 321 (from von Lang). The mode of combi- 
 nation and cross-penetration of the two crystals 321 
 1 , 2, is illustrated in f. 322 ; it is a medial section 
 of f. 321 from front to back. 
 
 Malachite. 
 
 (b) The twinning-plane may also be the 
 basal plane. This is common with orthoclase 
 ff. 324); also with gypsum (f. 323). It has 
 also been observed by the author in chondro- 
 dite, type II and III, from Brewster, N. Y., see 
 p. 305. 
 
 (c) Figs. 325, 326. 327 show another method 
 of twinning of orthoclase parallel to the clino- 
 dome, 24. These twins are peculiar in that 
 they form nearly rectangular prisms, since 
 
 O A 24 = 135 3^'. They are common among the orthoclase crystals from 
 Baveno, and hence are called Baveno twins. This method of twinning is 
 also common with the amazon-stone of Pike's Peak. 
 
 The union of four crystals of this kind produces the form represented in 
 f. 325 ; and the same, by penetration, develops the penetration-twin of 
 f. 327 (from v. Rath), which apparently consists of four pairs of twins, but 
 may be regarded as made by the cross-penetration of the crystals of two 
 pairs, or of the four of f. 325. 
 
 Forms like f. 325 may have one of the four parts undeveloped and so 
 consist of three united crystals, and also the other parts, as in such com- 
 pound twins generally, may be very unequal. 
 
 Twins corresponding to those of the orthorhombic system, where tho 
 twinning-plane is a prism whose angle is nearly 120, have been observed 
 by VODI Rath in hurnite, types II and III. 
 
 TRIOIJNIC SYSTEM. In the twins of the triclinic system, the three axes 
 
100 
 
 CEYSTALLOGEAPHY. 
 
 may be axes of revolution, in which case the t winning-planes are not occur- 
 ring crystallographic planes ; or, the pinacoid planes may be the planes of 
 twinning and' the normals to them the axes of revolution. Some of the 
 eases are illustrated in the following figures of albite. In f. 329 the 
 brachr^pinacoid (i-Z) is the twinning-plane ; f . 328 is the same, but it is a 
 penetration-twin ; this is the most common method of twinning with thia 
 species. 
 
 323 
 
 324 
 
 Orthoclase. 
 
 Orthoclase. 
 
 In f. 332 the vertical axis is the twinn ing-axis. Fig. 333 (from G. Hose) 
 is a double twin, the two halves of which are like f. 328, but they are 
 twinned together like f. 332. It happens in albite that the plane angles 
 
 on i-l, made by the edges /A O and /A 1 differ but 37' (the former being 
 116 26', the latter 115 55'), and hence it is that in the twin O and 1 fall 
 nearly into one plane. 
 
CRYSTALS. 
 
 101 
 
 Composition parallel to <9, where the revolution is on a horizontal axis 
 normal to the shorter diagonal of O, is ex- 
 emplified in f. 334 (from G. Rose). Both 
 right- and left-handed twins of this kind 
 occur; also double twins in which this 
 method is combined with twinning (like 
 that in f . 329, 330), parallel to i-l. 
 
 A thorough discussion of the method of 
 twinning in the triclinic system lias been 
 given by Schrauf in his monograph of the 
 species brochantite (Ber. Ak., Wien, Ixvii., 275, 1873). 
 
 Albite. 
 
 REGULAR GROUPING OF CRYSTALS. 
 
 Connected with the subject of twin crystals is that of the parallel posi- 
 tion of associated crystals of the same species, or of different species. 
 Crystals of the same species occurring together are very commonly 
 in parallel position. In this way large crystals are sometimes built up of 
 smaller individuals grouped together with corresponding planes parallel. 
 This parallel grouping is often seen in crystals as they lie on the support- 
 ing rock. On glancing the eye over a surface covered with crystals, a 
 reflection from one face will often be accompanied with reflections from the 
 corresponding face in each of the other crystals, showing that the crystals 
 are throughout similar in their positions. 
 
 Crystals of different species often show the same tendency to parallelism 
 in mutual position. This is true most frequently of species which, from 
 similarity of form and composition, are said to be isomorphous (see p. 199). 
 Crystals of albite, implanted on a surface of orthoclase, are sometimes an 
 example of this ; crystals of hornblende and pyroxene, and of various kinds 
 of mica are also at times observed associated in parallel position. 
 
 The same relation of position also occasionally occurs where there is no 
 connection in composition, as the crystals of rutile on tabular crystals of 
 hematite, the vertical axes of the former coinciding with the lateral axes 
 of the latter. Breithaupt has figured crystals of calcite, whose rhombo- 
 
 hedral faces ( \E] had a series of quartz crystals upon them, all in 
 parallel position (f. 335) ; and Frenzel and vom Rath have described the 
 same association where three such quartz crystals, one on each rhornbo- 
 hedral face, entirely enveloped the calcite, and uniting with re-entering 
 
102 CRYSTALLOGRAPHY. 
 
 angles formed pseudo-twins (rather trillings) of quartz aftei calcite. The 
 author has described a similar occurrence from u Specimen Mountain," in 
 the Yellowstone Park ; the form is shown in f. 336. (Am. J. ScL, III., 
 xii., 1876.) 
 
 IRREGULARITIES OF CRYSTALS. 
 
 The laws of crystallization, when unmodified by extrinsic causes, should 
 produce forms of exact symmetry ; the angles being not only equal, but 
 al^p the homologous faces of crystals and the dimensions in the directions 
 r &xefe; r '' THis symmetry is, however, so uncommon, that it can 
 l F fre^ considered" Bother than an ideal perfection. Crystals are very 
 Sml often the fundamental forms are so completely dis- 
 guised, that an intimate familiarity with the possible irregularities is re- 
 quired in order to unravel their complexities. Even the angles may 
 occasionally vary rather widely. 
 
 The irregularities of crystals may be treated of under several heads: 1, 
 Imperfection* of surface / 2, Variations of form and dimensions / 3, 
 Variations of angles / 4, Internal imperfections and impurities. 
 
 I. IMPERFECTIONS IN THE SURFACES OF CRYSTALS. 
 
 1. Striations or angular elevations arising from oscillatory combina- 
 tions. The parallel lines or furrows on the surfaces of crystals are called 
 stricBj and such surfaces are said to be striated. 
 
 Each little ridge on a striated surface is enclosed by two narrow planes 
 more or less regular. These planes often correspond in position to differ- 
 ent planes of the crystal, and we may suppose these ridges to have been 
 formed by a continued oscillation in the operation of the causes that give 
 rise, when acting uninterruptedly, to enlarged planes. By this means, the 
 surfaces of a crystal are marked in parallel lines, with a succession of nar- 
 row planes meeting at an angle and constituting the ridges referred to. 
 
 This combination of different planes in the fonna- 
 337 tion of a surface has been termed oscillatory com- 
 
 bination. The horizontal striae on prismatic crystals 
 of quartz are examples of this combination, in 
 which the oscillation has taken place between the 
 prismatic and pyramidal planes. As the crystals 
 lengthened, there was apparently a continual effort 
 to assume the terminal pyramidal planes, which effort 
 was interruptedly overcome by a strong tendency to 
 an increase in the length of the prism. In this 
 manner, crystals of quartz are often tapered to a 
 point, without the usual pyramidal terminations. 
 Magnetite. Other examples are the striation on the cubic faces 
 
 of pyrite parallel with the intersections of the cube 
 
 with the planes of the pyritohedron ; also the striations on magnetite 
 (f. 337) due to the oscillation between the octahedron and dodecahedron. 
 
IRREGULARITIES OF CRYSTALS. 103 
 
 Prisms of tourmaline are very commonly bounded vertically "by three convex 
 surfaces, owing to an oscillatory combination of the planes /and i-%. 
 
 Faces of crystals are often marked with angular elevations more or less 
 distinct, due sometimes also to oscillatory combination. Octahedrons of 
 fluorite are common which have for each face a surface of minute cubes, 
 proceeding from an oscillation between the cube and octahedron. This is 
 a common cause of drusy surfaces with the crystals of many minerals. 
 
 2. Striationsfrom oscillatory composition. The striations of the plane 
 O of albite and other triclinic feldspars, and of the rhombohedral surfaces 
 some calcite, have been attributed, on p. 91, to oscillatory twinning. 
 
 3. Markings from erosion and other causes. It is not uncommon that 
 the faces of crystals are uneven, or have the crystalline structure developed 
 as a consequence of etching by some chemical agent. Cubes of galenite 
 are often thus uneven, and crystals of lead sulphate or lead carbonate are 
 someiimes present as evidence with regard to the cause. Crystals of numer- 
 ous other species, even of corundum, spinel, quartz, etc., sometimes show the 
 same result of partial change over the surface often the incipient stage in 
 a process tending to a final removal of the whole crystal. Interesting in- 
 vestigations have been made by various authors on the action of solvents on 
 different minerals, the actual structure of the crystals being developed in 
 this way. These are referred to again in another place (p. 12^). 
 
 The markings on the surfaces of crystals are not, however, always to be 
 ascribed to etching. In most cases etchings, as well as the minute angular 
 elevations upon the planes, are a part of the original molecular growth of 
 the crystal, and often serve to show the successive stages in its history. 
 They are the imperfections arising from an interrupted or disturbed de- 
 velopment of the form, the perfectly smooth and even crystalline faces 
 being the result of completed action free from disturbing causes. Ex- 
 amples of the marking referred to occur on the crystals of most minerals, 
 and conspicuously so on the pyramidal planes of quartz. 
 
 The development of this subject belongs rather to crystallogeny refer- 
 ence may, however, be made here to the memoirs of Scharff, bearing on 
 this subject, especially one entitled " LJeber den Quarz, II., die Ueber- 
 gangsflachen," Frankfort, 1874; also to the Crystallography of Sadebeck 
 (for title free Introduction). 
 
 It follows from the symmetry of crystallization that like planes should 
 be physicaUy alike, that is in regard to their surface character ; it thus 
 often happens that on all the crystals of a species from a given locality, or 
 perhaps from all localities, the same planes are etched or roughened alike. 
 For example, on crystals of datolite from Bergen Hill, the plane 2-i 
 is almost uniformly destitute of lustre ; there is much uniformity on the 
 crystals of quartz in this respect. 
 
 4. Curved surfaces may result from (a) oscillatory combination ; or (b) 
 some independent molecular condition producing curvatures in the laminae 
 of the crystal ; or (c) from a mechanical cause. 
 
 Curved surfaces of the first kind have been already mentioned, p. 102. 
 A singular curvature of this nature is seen in f. 339, of calcite ; and another 
 in the same mineral in the lower part of f. 338, in which traces of a scaleno- 
 hedral form are apparent which was in oscillatory combination with the 
 prismatic form. 
 
104 
 
 CRYSTALLOGRAPHY. 
 
 Curvatures of the second kind sometimes have all the faces convex. This 
 is the case in crystals of diamond (f. 340), some of which are almost 
 spheres. The mode of curvature, in which all the faces are equally oon- 
 vex, is less common than that in which a convex surface is opposite and 
 parallel to a corresponding concave surface. Hhombohedrons of sideritc 
 (see p. 403) are usually thus curved. The feathery curves of frost on win- 
 dows and the flagging stones of pavements in winter are other examples of 
 curves of the second kind. The alabaster rosettes from the Mammoth 
 Cave, Ky., are similar. 
 
 339 
 
 340 
 
 
 Caleitc. 
 
 Calcite. 
 
 Diamond. 
 
 V. 
 
 A third kind of curvature is of mechanical origin. In many species 
 
 crystals appear as if they had been broken 
 transversely into many pieces, a slight dis- 
 placement of which has given a curved form 
 to the prism. This is common in tourmaline 
 and beryl. The beryls of Monroe, Conn., 
 often present these interrupted curvatures, 
 as represented in f. 341. 
 
 Crystals not unfrequently occur with a 
 deep pyramidal depression occupying the 
 
 Beryl, Monroe, Conn, 
 
 place of each plane, as is often observed in common salt, alum, and sulphur. 
 This is due in part to their rapid growth. 
 
 II. VARIATIONS IN THE FORMS AND DIMENSIONS OF CRYSTALS. 
 
 The simplest modification of form in crystals consists in a simple varia- 
 tion in length or breadth, without a disparity in similar secondary planes 
 The distortion, however, extends very generally to the secondary planes, 
 especially when the elongation of a crystal takes place in the direction of a 
 diagonal, instead of the crystallographic axes. In many instances, one or 
 more planes are obliterated by the enlargement of others, proving a sor,rce 
 of much perplexity to the student. The'interfacial angles remain constant, 
 unaffected by these variations in form. These changes in form often give 
 rise to what is called by Sadebeck pseudo-symmetry / the distorted forms 
 of one system appearing similar to the normal forms of another. (Compare 
 the descriptions of the following figures.) As most of the difficulties in the 
 
 * See p. 188 for another use of this word. 
 
IRREGULARITIES OF CRYSTALS. 
 
 105 
 
 study of crystals arises from these distortions, this subject is one of great 
 importance. 
 
 Figs. 342 to 353 represent examples from the isometric system. 
 
 A cube lengthened or shortened along one axis becomes a right square 
 prism, and if varied in the direction of two axes is changed to a rectangu- 
 lar prism Cubes of pyrite, galenite, iluorite, etc., are generally thus dis- 
 torted, it is very unusual to find a cubic crystal that is a true symmetrical 
 cube. In some species the cube or octahedron (or other isometric form) is 
 lengthened into a capillary crj stal or needle, as happens in cuprite and 
 pyrite. 
 
 An octahedron flattened parallel to a face, or in the direction of a trigonal 
 interaxis, is reduced to a tabular crystal (f. 342). If lengthened in the 
 same direction, it takes the form in f. 343 ; or if still farther lengthened 
 to the obliteration of A', it becomes an acute rhombohedron (same figure). 
 
 343 
 
 344 
 
 When an octahedron is extended in the direction of a line between two 
 opposite edges, or that of a rhombic interaxis, it has the general form of 
 a rectangular octahedron; and still farther extended, as in f. 344, it is 
 changed to a rhombic prism with dihedral summits (spinel, fluorite, magne- 
 tite). The figure represents this prism lying on its acute edge. 
 
 The dodecahedron lengthened in the direction of a diagonal between the 
 
 345 
 
 346 
 
 obtuse solid angles, that is, that of a trigonal interaxis, becomes a six- 
 sided prism with three-sided summits, as in f. 345 ; and shortened in the 
 same direction is a short prism of the same kind (f. 346). Both resemble 
 rhombohedral forms and are common in garnet and zinc blende. When 
 lengthened in the direction of one of the cubic axes, it becomes a square 
 prism with pyramidal summits (f. 347), and shortened along the same axis 
 if is reduced to a square octahedron, with truncated basal angles (f. 348). 
 
106 
 
 CRYSTALLOGRAPHY. 
 
 The trapezohedron is still more disguised by its distortions. When elon- 
 gated in the line of a trigonal interaxis, it assumes the form in f. 349 ; and 
 still farther lengthened, to the obliteration of some of the planes, becomes 
 a scalene dodecahedron (f. 350). This has been observed in flnor spar. 
 Only twelve planes are here present out of the twenty -four. Threads oi 
 native gold from Oregon, are strings of crystals presenting the form of this 
 very acute rhombohedron, with the other planes of the trapezohedron 2-2 
 (the scalenohedral and the terminal obtuse rhombohedral) quite small at 
 the extremities. 
 
 If the elongation of the trapezohedron takes place along a cubic axis, it 
 becomes a double eight-sided pyramid with four-sided summits (f. 351) ; or 
 if these summit planes are obliterated by a farther extension, it becomes a 
 complete eight-sided double pyramid (f. 352). 
 
 349 
 
 350 
 
 A scaleno-dodecahedron of calcite is shown distorted in f. 353, which ap- 
 pears, however, to be an eight sided prism, bounded laterally by the planes 
 R, 1 s , I 3 , and R, and their opposites, and terminated by the remaining planes. 
 The following figures of quartz (f. 35-t, 355) represent distorted forms of 
 this mineral, in which some of the pyramidal faces by enlargement dis- 
 place the prismatic faces, and nearly obliterate some of the other pyramidal 
 faces ; see also f. 336. 
 
 353 
 
 354 
 
 355 
 
 Calcite. 
 
 Quartz. 
 
 Quartz. 
 
 Fig. 356 is a distorted crystal of apatite ; the same is shown in f. 357 
 with the normal symmetry. The planes between O and the right / are 
 enlarged, while the corresponding planes below are in part obliterated. 
 
IRREGULARITIES OF CRYSTALS. 
 
 107 
 
 By observing that similar planes are lettered alike, the correspondence of 
 the two figures will be understood. 
 
 In deciphering the distorted crystalline forms it must be remembered 
 that while the appearance of the crystals may be entirely altered, the angles 
 remain the same ; moreover, like planes are physically alike, that is, alike 
 in degree of lustre, in striations, and so on. 
 
 356 
 
 357 
 
 Apatite. 
 
 Apatite. 
 
 In addition to the variations in form which have just been described, still 
 greater irregularities are due to the fact that, in almost all cases, crystals in 
 nature are attached either to other crystals or to some rock surface, and in 
 consequence of this are only partially developed. Thus quartz crystals are 
 generally attached by an extremity of the prism, and hence have only one 
 set of pyramidal planes ; perfectly formed crystals, as those from Ilerkiraer 
 Co., N". Y., having the double pyramid complete, are rare. The same 
 statement may be made for nearly all species. 
 
 III. VARIATIONS IN THE ANGLES OF CRYSTALS. 
 
 The greater part of the distortions described occasion no change in the 
 mterfacial angles of crystals. But those imperfections that produce con- 
 vex, curved, or striated faces, necessarily cause such variations. Further- 
 more, circumstances of heat or pressure under which the crystals were 
 formed may sometimes cause not only distortion in form, but also some 
 variation in angle. The presence of impurities at the time of crystallization 
 may also have a like effect. 
 
 Still more important is the change in the angles of completed crystals 
 which is caused by subsequent pressure on the matrix in which the} 7 were 
 formed, as, for example, the change which may take place during the more 
 or less complete metaiuorphism of the enclosing rock. 
 
 The change of composition resulting in pseudomorphous crystals (see 
 p. 113) is generally accompanied by an irregular change of angle, so that 
 the pseudomorphs of a species vary much in angle. 
 
 In general it is safe to affirm that, with the exception of the irregularities 
 
108 CRYSTALLOGRAPHY. 
 
 arising from imperfections in the process of crystallization, or from 
 changes produced subsequently, variations in the angles are rare, and the 
 constancy of angle alluded to on p. 87 is the universal law.* 
 
 In cases where a greater or less variation in angle has heen observed in 
 the crystals of the same species from different localities, the cause for this 
 can usually be found in a difference of chemical composition. In the case 
 of isomorphous compounds it is well known that an exchange of correspond- 
 ing chemically equivalent elements may take place without a change of 
 form, though usually accompanied with a slight variation in the funda- 
 mental angles. 
 
 The effect of heat upon the form of crystals is alluded to upon p. 168. 
 
 IY. INTERNAL IMPERFECTIONS AND IMPURITIES. 
 
 The transparency of crystals is often destroyed by disturbed crystalliza- 
 tion, or by impurities taken up from the solution during the process of 
 crystallization. These impurities may be simply coloring ingredients, or they 
 may be inclosed particles, fluid or solid, visible to the eye or under the 
 microscope. The coloring ingredients mav vary in the course of formation 
 of the crystals, and thus layers of different colors result ; the tourmaline 
 crystals of Chesterfield, Mass., have a red centre and blue exterior ; others 
 from Elba are sometimes light-green below and black at the extremity ; 
 many other examples might be given. 
 
 The subject of the fluid and solid inclosures in crystals is one to which 
 much attention has been directed of late years. Attention was early called 
 to its importance by Brewster, who described the presence of fluids in 
 quartz, topaz, beryl, chrysolite, and other minerals. In later years the mat- 
 ter has been more' thoroughly studied by Sorby, Zirkel, Vogelsang, Fischer, 
 Rosenbusch, and many others. (See Literature, p. 111.) 
 
 Many crystals contain empty cavities ; in others the cavities are filled 
 sometimes with water, or with the salt solution in which the crystal was 
 formed, and not infrequently, especially in the case of quartz, with liquid 
 carbonic acid, as first proved by Vogelsang, and recently followed out by 
 Hartley. These liquid inclosures are marked as such, in many cases, by 
 the presence in the cavity of a movable bubble. 
 
 The solid inclosures are almost infinite in their variety. Sometimes they 
 are large and distinct, and can be referred to known mineral species, as the 
 scales of hematite to which the peculiar character of aventui ine feldspar is 
 due. Magnetite is a very common impurity for many minerals, appearing, 
 for example, in the Pennsbury mica; quartz is also often mechanicairy 
 mixed, as in staurolite and gmelinite. On the other hand, quaitz crystals 
 very commonly inclose foreign material, such as chlorite, tourmaline, rutile, 
 hematite, asbestos, and many other minerals. 
 
 * Referen e must be made here to the discussion by Scacchi of the principle of " Polysym- 
 metry." (Atti Accad. Napoli, i., 1864.) See also Hirschwald, Zur Kritik des Leucitsystema, 
 Tsch. Mia. Mitth., 1875, 227. See further the discussion on pp. 185 et seq. 
 
IRREGULARITIES OF CRYSTALS. 
 
 100 
 
 The inclosures may also consist of a heterogeneous mass of material ; as 
 the granitic matter seen in orthoclase crystals in a porphyritic granite ; or 
 the feldspar, quartz, etc., sometimes inclosed in 
 large coarse crystals of beryl, occurring in granite 
 veins. 
 
 An interesting example of the inclosure of one 
 mineral by another is afforded by the annexed 
 figures of tourmaline, enveloping orthoclase (E. II. 
 Williams, Am. J. Sci., III., xi., 273, 1876). Fig. 
 358 shows the crystal of tourmaline ; and cross-sec- 
 tions of it at the pL-ints indicated (a, &, c) are given 
 by f. 359, 360, 361. The latter show that the^f eld- 
 spar increases in amount in the lower part of the 
 crystal, the tourmaline being merely a thin shell. 
 Similar specimens from the same locality (Port 
 Henry, Essex Co., N". Y.) show that there is no ne- 
 cessary connection between the position of the tour- 
 maline and that of the feldspar. 
 
 Similar occurrences are those of trapezohedrons 
 of garnet, where the latter is a mere shell, enclosing 
 calcite, or sometimes epidote. Analogous cases 
 have been explained by some authors as being due to partial pseudomorph 
 ism, the alteration progressing from the centre outward. 
 
 The microscopic crystals observed as inclosures may sometimes be 
 referred to known species, but more generally their true nature is doubtful. 
 The term microlites, proposed by Yogelsang, is often used to designate the 
 
 362 
 
 366 
 
 minute inclosed crystals; they are generally of needle-like form, some 
 times quite irregular, and often very remarkable in their arrangement and 
 groupings ; some of them are exhibited in f. 367 and f. 368, as explained 
 
no 
 
 CRYSTALLOGRAPHY. 
 
 below. Trichite and belonite are names introduced by Zirkel ; the former 
 name is derived from Opi& hair, the forms, like that in f. 362, are common 
 in obsidian. Where me minute individuals belong to known species they 
 are called, for example, feldspar microlites, etc. 
 
 Crystallites is an analogous term which is intended by Vogelsang to cover 
 those minute forms which have not the regular exterior form of crystals, 
 but may be considered as intermediate between amorphous matter and true 
 crystals. Some of the forms, figured by Yogelsang, are shown in f. 363 to 
 366 ; they are often observed in glassy volcanic rocks, and also in furnace 
 slags. A series of names have been given to varieties of crystallites, such 
 as globulites, margarites, etc.* 
 
 The microscopic inclosures may also be of an irregular glassy nature ; a 
 kind that exists in crystals which have formed from a melted mass, as lavas 
 or the slag of iron furnaces. 
 
 In general, it may be said that while the solid inclosures occur sometimes 
 quite irregularly in the crystals, they are more generally arranged with 
 some evident reference to the symmetry of the form, or planes of the 
 crystals. Examples of this are shown in the following figures: f. 367 ex 
 
 867 
 
 368 
 
 Augite. 
 
 Leucite. 
 
 Calcite. 
 
 hibits a crystal of augite, inclosing magnetite, feldspar and nephelite 
 microlites, etc., and f. 368 shows a crystal of leucite, a species whose 
 crystals very commonly inclose foreign matter. Fig. 369 shows a section 
 of a crystal of calcite, containing pyrite. 
 
 Andalusite. 
 
 ^ Another striking example is afforded by andalusite, in which the inclosed 
 impurities are of considerable extent and remarkably arranged. Fig. 370 
 shows the successive parts of a single crystal, as dissected by B. Horsford 
 
 * Die Krystalliten von Hermann Vogelsang. Bonn, 1875. 
 
CRYSTALLINE AGGREGATES. 
 
 of Springfield, Mass. ; 371, one of tie four white portions; and 372 the 
 central black portion. 
 
 372 
 
 LITERATURE. 
 
 Some of the most important works on the subject are referred to here, but for a complete 
 Ust of the literature up to 1873, reference may be made to Uosenbusch (see below). 
 
 Blum, Leonhard, 8eyfert, and Sochting, die Einschliisse von Mineralien in krystallisirten 
 Mineralien. (Preisschrift.) Haarlem, 1854. 
 
 Brewster. Many papers published mostly in the Philosophical Magazine, and the Edinburgh 
 Phil. Journal, from 1822-1856. 
 
 Fischer. Kritische-microscopische mineralogische Studien. Freiburg in Br 64 pp 1869 
 Ite Fortsetzung, 64 pp., 1871 ; 2te Forts., 90 pp., 1873. 
 
 Kosmnnn. Ueber das Schillem und den Dichroismus des Hypersthens Jahrb Min 1869 
 368 (ibid. p. 532, 1871, p. 501). 
 
 Rosenbusch. Microscopische Physiographic der petrographisch wichtigen Mineralien 
 395 pp., Leipzig, 1873 
 
 Schrauf. Studien an der Mineralspecies Labradorit. Ber. Ak. Wien, lx., Dec., 1869. 
 
 Sorby. ' On the microscopical structure of crystals, indicating the origin of minerals and 
 rocks. Q. J. Geol. Soc., xiv., 453, 1858, (and many other papers). 
 
 Sorby and Butler. On the structure of rubies, sapphires, diamonds, and some other minerals 
 Proc. Roy. Soc., No. 109, 1869. 
 
 Vogelsang. Die Krystalliten. 175 pp., Bonn, 1875. 
 
 Vogelsang and Oeusler. Ueber die Natur der Fliissigkeitseinschlusse in gewissen Minera- 
 lion. Pogg. Ann., cxxxvii., 56, 1869 (ibid. p. 257). 
 
 Zirkel. Die microscopische Beschaff enheit der Mineralien und Gesteine. 502 pp. , Leipzig, 
 1873. 
 
 CRYSTALLINE AGGREGATES. 
 
 The greater part of the specimens or masses of minerals that occur, may 
 be described as aggregations of imperfect crystals. Even those whose 
 structure appears the most purely impalpable, and the most destitute in- 
 ternally of anything like crystallization, are probably composed of crystal- 
 line grains. Under the above head, consequently, are included all the 
 remaining varieties of structure in the mineral kingdom. 
 
 The individuals composing imperfectly crystallized individuals, may be: 
 
 1. Columns, or fibres, in which case the structure is columnar. 
 
 2. Thin lamina!, producing a lamellar structure. 
 
 3. Grains, constituting a granular structure. 
 
 1. Columnar Structure. 
 
 A mineral possesses a columnar structure when it is made up of slender 
 columns or fibres. There are the following varieties of the columnar struc 
 ture : 
 
 Fibrous ; when the columns or fibres are parallel. Ex. gypsum, asbeatua 
 Fibrous minerals have often a silky lustre. 
 
112 CRYSTALLOGRAPHY. 
 
 Reticulated : when the fibres or columns cross in various directions, and 
 produce an appearance having some resemblance to a net. 
 
 Stellated or stellular: when they radiate from a centre in all directions, 
 and produce star-like forms. Ex. stilbite, wavellite. 
 
 Radiated, divergent : when the crystals radiate from a centre, without 
 producing stellar forms. Ex. quartz, stibnite. 
 
 2. Lamellar Structure. 
 
 The structure of a mineral is lamellar when it consists of plates or 
 leaves. The laminae may be curved or straight, and thus give rise to the 
 curved lamellar, and straight lamellar structure. Ex. wollastonite (tabular 
 spar), some varieties of gypsum, talc, etc. When the laminae are thin and 
 easily separable, the structure is said to be foliaceous. Mica is a striking 
 example, and the term micaceous is often used to describe this kind of 
 structure. 
 
 3. Granular Structure. 
 
 The particles in a granular structure differ much in size. When coarse, 
 the mineral is described as coarsely granular ; when fine, finely granular 
 and if not distinguishable by the naked eye, the structure is termed im- 
 palpable. Examples of the first may be observed in granular crystalline 
 limestone, sometimes called saccharoidal ; of the second, in some varieties 
 of hematite ; of the last, in chalcedony, opal, and other species. 
 
 The above terms are indefinite, but from necessity, as there is every 
 degree of fineness of structure in the mineral species, from perfectly im- 
 palpable, through all possible shades, to the coarsest granular. The term 
 phanero-crystdlline has been used for varieties in which the grains are dis- 
 tinct, and crypto-crystalline, for those in which they are not discernible. 
 
 Granular minerals, when easily crumbled in the fingers, are said to be 
 friable. 
 
 4. Imitative /Shapes. 
 
 Reniform : kidney shape. The structure may be radiating or concentric, 
 
 Botryoidal: consisting of a group of rounded prominences. The name 
 is derived from the Greek fiorpvs, a bunch of grapes. Ex. limonite, chal- 
 cedony. 
 
 Mammillary : resembling the botryoidal, but composed of larger prom- 
 inences. 
 
 Globular : spherical or nearly so ; the globules may consist of radiating 
 fibres or concentric coats. When attached, as they usually are, to the sur- 
 face of a rock, they are described as implanted globules. 
 
 Nodular : in tuberose forms, or having irregular protuberances over the 
 surface. 
 
 Amygdaloidal ; almond-shaped, applied usually to a greenstone contain- 
 ing almond-shaped or sub-globular nodules. 
 
PSEUDOMOKPHOUS CRYSTALS. 113 
 
 Coralloidal : like coral, or consisting of interlaced flexuous branchings 
 of a white color, as in some aragonite. 
 
 Dendritic : branching tree-like. 
 
 Mossy : like moss in form or appearance. 
 
 Filiform or Capillary : very slender and long, like a thread or hair ; 
 consists ordinarily of a succession of mimite crystals. 
 
 Acicular : slender and rigid like a needle. 
 
 Reticulated : net-like. 
 
 Drusy : closely covered with minute implanted crystals. 
 
 Stalactitic : when the mineral occurs in pendant columns, cylinders, or 
 elongated cones. 
 
 Stalactites are produced by the percolation of water, holding mineral 
 matter in solution, through the rocky roofs of caverns. The evaporation 
 of the water produces a deposit of the mineral matter, and gradually forms 
 a long pendant cylinder or cone. The internal structure may be imper- 
 fectly crystalline and granular, or may consist of fibres radiating from the 
 central column, or there may be a broad cross-cleavage. 
 
 Common stalactites consist of calcium carbonate. Chalcedony, gibbsite, 
 brown iron ore, and many other species, also present Stalactitic forms. 
 
 The term amorphous is used when a mineral has not only no crystalline 
 form or imitative shape, but also does not polarize the light even in its minute 
 particles, and thus appears to be destitute wholly of a crystalline structure 
 internally, as most opal. Such a structure is also called colloid or jelly- 
 like, from the Greek for glue. Whether there is a total absence of crystal- 
 line structure in the molecules is a debated point. The word is from a, 
 privative, and popfj)?), shape. 
 
 PSEUDOMORPHOUS CRYSTALS. 
 
 Every true mineral species has, when crystallized, a form peculiar to 
 itself ; occasionally, however, crystals are found that have the form, both 
 as to angles and general habit, of a certain species, and yet differ from it 
 entirely in chemical composition. Moreover it is often seen that, though 
 in outward form complete crystals, in internal structure they are granular, 
 or waxy, and have no regular cleavage. 
 
 Such crystals are called pseudomorphs, and their existence is explained 
 by the assumption, often admitting of direct proof, that the original min- 
 eral has been changed into the new compound, or has disappeared through 
 Borne agency, and its place been taken by another chemical compound to 
 which the form does not belong. 
 
 Pseudomorphs have been classed under several heads. 
 
 1. Pseudomorphs by substitution. 
 
 2. Pseudomorphs by simple deposition, (a) incrustation or (b) in/Ut^a* 
 tion. 
 
 3. Pseudomorphs by alteration and these may be altered 
 
 a) without a change of composition, by paramorphism ; 
 
 b) by the loss of an ingredient ; 
 
 v by the assumption of a foreign substance ; 
 by a partial exchange of constituents. 
 8 
 
114 CRYSTALLOGRAPHY. 
 
 1. The first class of pseudomorphs, by substitution, embrace those cases 
 where there has been a gradual removal of the original material and a 
 corresponding and simultaneous replacement of it by another, without, 
 however, any chemical reaction between the two. A common example of 
 this is a piece of fossilized wood, where the original fibre has been replaced 
 entirely by silica. The first step in the process was the filling of all the 
 pores and cavities by the silica in solution, and then as the woody fibre by 
 gradual decomposition disappeared, the silica further took its place. Other 
 examples are quartz after fluorite, calcite, and many other species, cassiterite 
 after orthoclase, etc. 
 
 2. Pseudomorphs by incrustation, form a less important class. Such 
 are the crusts of quartz formed over fluorite. In most cases the removal 
 of the original mineral has gone on simultaneously with the deposit of the 
 second, so that the resulting pseudomorph is properly one of substitution. 
 In pseudomorphs by infiltration, a cavity made by the removal of a crystal 
 has been filled by another mineral. 
 
 3. The third class of pseudomorphs, by alteration* include a considerable 
 proportion of the observed cases, of which the number is very large. Con- 
 clusive evidence of the change which has gone on is often furnished by a 
 kernel of the original mineral in the centre of the altered crystal ; e.g., a 
 kernel of cuprite in a pseudomorphous octahedron of malachite ; also of 
 chrysolite in a pseudomorphous crystal of serpentine ; of corundum in 
 fibrolite, or spinel (Genth). 
 
 (a) An example of paramorphism is furnished by the change of aragonite 
 to calcite at a certain temperature ; also the paramorphs of rutile after 
 arkansite from Magnet Cove. 
 
 (V) An example of the pseudomorphs in which alteration is accompanied 
 by a loss of ingredients is furnished by crystals of limonite in the form of 
 siderite, the carbonic acid having been removed ; so also calcite after 
 gay-lussite ; native copper after cuprite. 
 
 (c) In the change of cuprite to malachite, e.g., the familiar crystals from 
 Chessy, France, an instance is afforded of the assumption of an ingredient, 
 viz., carbonic acid. Pseudomorphs of gypsum after anhydrite occur, where 
 there has been an assumption of water. 
 
 (d) A partial exchange of constituents, in other words, a loss of one and 
 gain of another, takes place in the change of feldspar to kaolin, in which 
 the potash silicate disappears and water is taken up ; pseudomorphs of 
 chlorite after garnet, pyromorphite after galenite, are other examples. 
 
 The chemical processes involved in such changes open a wide field for 
 investigation, in which Bischof, Delesse and others have done much. 
 
SECTION L SUPPLEMENTARY CHAPTER. 
 
 IMPROVEMENTS IN THE INSTRUMENTS FOR THE MEASUREMENT OF THE 
 ANGLES OF CRYSTALS (sec pp. 83-87). 
 
 Reflecting Goniometer. A form of reflecting goniometer, well adapted for 
 accurate measurements, and at the same time thoroughly practical, is shown 
 in f. 372A. It is made on the Babinet type, with a horizontal graduated 
 circle; the instruments of the Mitscherlich type, alluded to on p. 86, having 
 a vertical circle. The horizontal circle has many advantages, especially 
 when it is desired to measure the angles of large crystals or those which are 
 
 372A. 
 
 attached to a large piece of rock. This particular form of instrument here 
 figured is made^by K. Fuess,* in Berlin (Alte Jacobstrasse 108), and has 
 
 * The author is indebted to R. Fuess for the electrotypes from which this and the fol- 
 lowing figures (372A, B, c, D, also, f. 412c, D, E, F, H, K, L}have been primtcd. 
 
 115 
 
116 IMPROVEMENTS IN GONIOMETERS. 
 
 many improvements suggested by WEBSKY (Zeitschr. Kryst.. iv., 545. 1880. 
 See also Liebisch, Bericht iiber die wissenschaftlichen Instruments auf der 
 Berliner Gewerbeausstellung im Jab re 1879, pp. 330-332). 
 
 The instrument stands on a tripod with leveling screws. The central 
 axis, 0, has within it a hollow axis, h, with which turns the plate, d, carry- 
 ing the verniers and also the observing telescope, the upright support of 
 which is shown at B. Within b is a second hollow axis, e, which carries 
 the graduated circle, /, above, and which is turned by the screw-head, g ; 
 the tangent screw, a, serves as a fine adjustment for the observing telescope, 
 B, the screw, c, being for this purpose raised so as to bind b and e together. 
 The tangent screw, J3, is a fine adjustment for the graduated circle. Again, 
 within e is the third axis, h, turned by the screw-head, i, and within It is the 
 central rod, s, which carries the support for the crystal, with the adjusting 
 and centering contrivances mentioned below. The rod, s, can be raised or 
 lowered by the screw, h, so as to bring the crystal to the proper height, that is 
 up to the axis of the telescope ; when this has been accomplished, the clamp 
 at p, turned by a set-key, binds s to the axis, li. The movement of h can 
 take place independently of g, but after the crystal is ready for measurement 
 these two axes are bound together by the set-screw, I. The signal telescope 
 is supported at C, firmly attached to one of the legs of the tripod. The crys- 
 tal is mounted on the plate, u, with wax, the plate is clamped by the screw, 
 v. The centering apparatus consists of two slides at right angles to each 
 other (one of these is shown in the figure) and the screw, a, which works it ; 
 the end of the other corresponding screw is seen at a'. The adjusting 
 arrangement consists of two cylindrical sections, one of them, r, shown in 
 the figure, the other is at r 1 '; the cylinders have a common centre. 
 
 The circle is graduated to degrees and quarter degrees, and the vernier gives 
 the readings to 30", but by estimate they can be obtained to 10". The signals 
 provided are four in number, each in its own tube, to be inserted behind the 
 collimator lens ; these are : (1) the ordinary telescope with the hair cross, to 
 be used in the case of the most perfect planes ; (2) the commonly used signal,* 
 proposed by Websky, consisting of two small opaque circles, whose distance 
 apart can be adjusted by a screw between them ; the light passing between 
 these circles enters the tube in a form resembling a double concave lens ; 
 also (3) an adjustable slit ; and, finally, (4) a tube with a single round open- 
 ing, very small. There are four observing telescopes of different angular 
 breadth of field and magnifying power, and hence suitable for planes varying 
 in size and in degree of polish. A Nicol prism is also added. 
 
 The methods to be employed, both in making the preliminary adjust- 
 ments required by every instrument before it can be used, and in the actual 
 measurement of the angles of crystals, have been described by Websky (1. c.) 
 with a fullness and clearness which leaves nothing to be desired, and refer- 
 ence must be here made to this memoir. 
 
 Microscope- Goniometer of Hirschwald. For the measurement of the angles 
 of crystals whose planes are destitute of polish, HIRSCHWALD has devised a 
 "microscope-goniometer" (Jahrb. Min., 1879, 301, 539; 1880, i., 156. 
 See also Liebisch, 1. c., pp. 336, 377) ; the actual construction has been made 
 by Fuess. The instrument consists of a Wollaston goniometer with a center- 
 ing telescope and a vertical microscope. The principle upon which the use 
 of the instrument is based is this : that a plane seen through a microscope 
 
 * See Websky, Z. Kryst., iii., 241. 
 
CONTACT-LEVER GONIOMETER OF FUESS. 
 
 ir 
 
 will be in focus over its entire extent only when the plane is exactly at right 
 angles to the axis of the microscope. The microscope stands vertically above 
 the crystal, and is supported on a double slide, which allows of its being 
 moved parallel and perpendicular to the axis of the goniometer, so that it is 
 possible to see successively every portion of a crystal face fastened to the 
 goniometer, and at the proper focal distance. The slide perpendicular to the 
 axis of the goniometer carries a vernier, so that the position of the microscope 
 can be measured on the fixed scale to a half millimeter. The micrometer 
 screw of the microscope is arranged so that the raising or lowering of the 
 microscope can be measured to 0-004 mm. The spider line in the eye-piece, 
 parallel to the axis of rotation of the goniometer, is so adjusted that when the 
 slide just mentioned stands at the zero of its scale, it lies exactly in the 
 vertical plane through the axis. The horizontal centering telescope is placed 
 opposite the crystal support, and moves on a slide parallel to the axis of the 
 graduated circle. Its spider lines are so adjusted that their centre exactly 
 coincides with this axis. The apparatus for centering and adjusting the 
 crystal consists of a vertical disk allowing of motion in any direction perpen- 
 dicular to the axis of rotation, and a spherical segment moved by four arms 
 (Petzval support). In use the edge of the two planes to be measured is 
 brought by means of the spider line of the microscope parallel to the axis of 
 rotation of the goniometer, and there centered, by means of the telescope, so 
 that as the crystal is turned this edge remains in the centre of the spider line 
 of the centering telescope ; then the two planes which form this edge are, by 
 successive adjustments by help of the microscope, brought each successively 
 into an exactly horizontal position as the circle is revolved. The angle 
 (normal angle) between the two planes is obtained in the usual manner. 
 Hirschwald calculates that, with a sufficiently delicate arrangement of lenses, 
 for planes whose width is 5 mm., the theoretical error of measurement is 2' 40"; 
 for those with a width of 10 mm., the error is only 1'. The improved sup- 
 port for the crystal is so arranged that when the edge is exactly adjusted and 
 one of the two planes carefully placed with the microscope, the second plane 
 must be for its whole 
 extent in the proper 
 position as soon as this 
 is true for a single 
 point of the plane. 
 
 Contact-lever Goni- 
 ometer of Fucss. An- 
 other form of goniom- 
 eter has been invented 
 by FUESS (see Liebisch, 
 1. c., pp. 337-339) 
 which aims to accom- 
 plish the same end as 
 that of Hirschwald 
 the exact measurement 
 of the angle between 
 two unpolished surfaces 
 but in this case the 
 adjustment is accom- 
 plished by mechanical 
 means. The essential arrangement is shown in f. 372s, 372c. It consists 
 of a Wollaston goniometer, G, supported upcn a perfectly even unpolished 
 
118 
 
 IMPROVEMENTS IX GONIOMETERS. 
 
 372c. 
 
 L.,.,. .^^ LJ 
 
 glass plate, A. The contact-lever is carried by B, which rests on the glass 
 plate by two pegs, o, and by the screw, n, with a graduated head turn- 
 ing in connection with the index, y. Two arms, F F. go down from 
 B, carrying the nut in which the screw, r, turns ; this screw moves B 
 in a direction at right angles to the axis of the goniometer. The arm, 
 D, contains the nut for the adjusting screw, m (similar to n), which 
 belongs immediately to the lever system. On the arm C is attached the 
 knife edge, I, which meets the edge, c, fastened to the arm, i ; this arm, /, 
 
 turns about , and is supported by the 
 screw, m. The adjustable ball, #. sup- 
 ported on t, is to be placed so that the 
 ivory index rests with the least pos- 
 sible pressure on the crystal-face at 
 K (see also f. 372c). The contact- 
 lever, E, whose longer arm marks on 
 the scale, 8, lies between I and c ; its 
 head, d, is so to be adjusted that the 
 lever resting on the lower edge, c, has 
 a slight excess of weight on the side of the goniometer, so that it touches both 
 edges. A perceptible play of the long arm corresponds to a raising or lower- 
 ing of the ivory index of 0-0005 mm. If the plane has a width of 1 mm., the 
 degree of accuracy attainable is theoretically 2'. 
 
 In the preliminary centering and adjusting the work is facilitated by the 
 arrangement shown in f. 372D. It consists of a plate, p, 372D 
 
 which rests on A by the three set-screws, s. Two arms, 
 with set-screws, t, resting on the side of the supporting 
 plate, make possible, similar to r, a movement parallel to 
 this side. An index finger, I, is supported above the plate, 
 p. The screws, s and t, are now set so that the sharp edge 
 of I is exactly in the prolongation of the axis of rotation 
 of the goniometer, which is necessarily parallel to the 
 upper and side surfaces of the supporting plate. By the 
 help of this arrangement, the approximate centering and adjusting of the 
 crystal-edge can be readily accomplished, and also the parallelism between 
 the crystal-face and the supporting plate be proved. 
 
 Measurement of the Angles of microscopic Crystals. BERTRAKD (C. E., 
 Ixxxv., 1175, 1877 ; Bull. Soc. Min., i., 22, 96, 1878) has described a 
 method for obtaining the interfacial angles of microscopic crystals, which may 
 be briefly alluded to here. It is based on the geometrical principle that if the 
 plane angles are known which the projections of a plane make with three 
 perpendicular co-ordinate axes, the angular inclination of the plane to the 
 three axes can be calculated. The crystal to be measured is fastened on a 
 small cube of glass held in a pincer arrangement, on a secondary microscope 
 stage ; this stage is, like the principal stage below it, movable about a ver- 
 tical axis, and besides has by means of screws a motion in two perpendicular 
 directions in a horizontal plane. The method of obtaining the desired angles 
 is very ingenious, but too complex to allow of explanation here; reference 
 must "be made to the original paper. With crystals of from 1-20 to 1-30 mm., 
 Bertrand obtained results accurate within 6', and he states that the method 
 can be extended to crystals which have a magnitude of only 1-100 mm. 
 
SECTION IL 
 PHYSICAL OHAEAOTEES OF MLN"EEALS. 
 
 THE physical characters of minerals are those which relate : L, tc 
 Cohesion and Elasticity, that is : cleavage and fracture, hardness, and ten- 
 acity ; IL, to the Mass and Volume, the specific gravity ; III., to Light, 
 the optical properties of crystals ; also color, lustre, etc. ; IV., to Heat ; 
 V., to Electricity and Magnetism ; VI., to the action on the Senses, aa 
 taste, feel, etc. 
 
 I. COHESION AND ELASTICITY.* 
 
 By cohesion is understood the attraction existing between the molecules 
 of a body, in consequence of which they offer resistance to a force tend- 
 ing to separate them, as in breaking or scratching. This principle leads to 
 some of the most universally important physical characters of minerals, 
 cleavage, fracture, and hardness. 
 
 Elasticity, on the other hand, is the force which tends to bring the 
 molecules of a body back into their original position, from which they have 
 been disturbed. Upon elasticity depends, for the most part, the decree 
 of tenacity possessed by different minerals. 
 
 A. CLEAVAGE AND FKACTURE. 
 
 1. Cleavage. Most crystallized minerals have certain directions in 
 which their cohesive power is weakest, and in which they consequently, 
 yield most readily to an exterior force. This tendency to break in the 
 direction of certain planes is called cleavage, and being most intimately 
 connected with the crystalline form it has already been necessary to define 
 it, and to mention some of its most important features (p. 2). Cleavage 
 differs (a) according to the ease with which it is obtained, and (b) accord- 
 ing to its direction, crystallographically determined. 
 
 (a) Cleavage is called perfect or eminent when it is obtained with great 
 ease, affording smooth, lustrous surfaces, as in mica, topaz, calcite. Inferior 
 degrees of cleavage are spoken of as distinct, indistinct or imperfect, inter- 
 rupted, in traces, difficult. These terms are sufficiently intelligible without 
 further explanation. It may be noticed that the cleavage of a species ia 
 sometimes better developed in some of its varieties than in others. 
 
 (b) Cleavage is also named according to the direction, crystallographically 
 defined, which it takes in a species. When parallel to the basal section (O) 
 it is called basal, as in topaz; parallel to the prism, as in amphibole, it is 
 called prismatic ; also macrodiagonal, orthodiagonal, etc., when parallel 
 to the several diametral sections ; parallel to the faces of the cube, octa- 
 
 * SP.P. fnrthpr rvn n 172 
 
120 PHYSICAL CHARACTERS OF MINERALS. 
 
 hedron, dodecahedron, or rhombohedron, it is called cubic, as galenite; 
 octahedral, as fluorite ; dodecahedral, as sphalerite ; rhombohedral, as 
 calcite. 
 
 Intimately connected with the cleavage of crystallized minerals are the divisional planes in- 
 vestigated by Reusch (see Literature, p. 122). He has found that by pressure, or by a sudden 
 blow, divisional planes are in many cases produced which are analogous to the cleavage 
 planes. The first he calls Gleitflachen, or planes in which a sliding of the molecules upon 
 each other takes place. Thus, for example, if two opposite dodecahedral edges of a cubic 
 cleavage mass of rock-salt are regularly filed away, and the mass then subjected to pressure 
 in this direction, a Gleitflache is obtained parallel to the dodecahedral face. 
 
 The figures, on the other hand, obtained by a blow on a rounded steel point, placed perpen- 
 dicular to the natural or cleavage face of a crystal, are called by him. fracture-figures (Schlag- 
 fi'^uren). The divisional-planes in this case appear as cracks diverging from the point where 
 the blow has been made. For instance, on a cubic face of rock-salt two planes, forming a 
 rectangular cross, are obtained ; on biaxial mica, a six-rayed (sometimes three rayed) stai 
 results from the blow, one ray of which is always parallel to the brachydiagoual axis of the 
 prism. 
 
 2. Fracture. The term fracture is used to define the form or kind of 
 surface obtained by breaking in a direction other than that of the cleavage 
 in crystallized minerals, and in any direction in massive minerals. When 
 the cleavage is highly perfect in several directions, as the cubic cleavage of 
 galenite, fracture is often not readily obtainable. 
 
 Fracture is defined as : 
 
 (a) Conchoidal ; when a mineral breaks with curved concavities, more 
 or less deep. It is so called from the resemblance of the concavity to the 
 valve of a shell, from concha, a shell ; flint. 
 
 (b) Even when the surface of fracture, though rough, with numerous 
 small elevations and depressions, still approximates to a plane surface. 
 
 (c) Uneven, / when the surface is rough and entirely irregular. 
 
 (d) Hackley ; when the elevations are sharp or jagged ; broken iron. 
 Other terms also employed are earthy, splintery, etc. 
 
 B. HARDNESS. 
 
 By the hardness of a mineral is understood the resistance which it offers 
 to abrasion. The degree of hardness is determined by observing the ease 
 or difficulty with which one mineral is scratched by another, or by a file or 
 knife. 
 
 In minerals there are all grades of hardness, from that of a substance 
 impressible by the finger-nail to that of the diamond. To give precision 
 to the use of this character, a scale of hardness was introduced by MOIIS. 
 It is as follows : 
 
 1. Talc; common laminated light-green variety. 
 
 2. Gypsum ; a crystallized variety. 
 
 3. Calcite transparent variety. 
 
 4. Fluorite ; crystalline variety. 
 
 5. Apatite; transparent variety. 
 (5.5. Scapolite; crystalline variety.) 
 
 6. Feldspar (orthoclase) ; white cleavable variety. 
 
 7. Quartz; transparent. 
 
HAKDNESS TENACITY. 121 
 
 8. Topaz / transparent. 
 
 9. SwppTwre: cleavable varieties. 
 10. jDiamond. 
 
 If the mineral under trial is scratched by the file or knife as easily as 
 apatite, its hardness is called 5 ; if a little more easily than apatite and 
 not so readily as fluorite, its hardness is called 4.5, etc. For minerals as 
 hard or harder than quartz, the file will not answer, and the relative hard- 
 ness is determined by finding by experiment whether the given mineral will 
 scratch, or can be scratched by, the successive minerals in the scale. 
 
 It need hardly be added that great accuracy is not attainable by the above 
 methods, though, indeed, for all mineralogical purposes exactness is quite 
 unnecessary. 
 
 The interval between 2 and 3, and 5 and 6, in the scale of Mohs, being 
 a little greater than between the other numbers, Breithaupt proposed a 
 Bcale of twelve minerals ; but the scale of Mohs is now universally accepted. 
 
 Accurate determinations of the hardness of minerals have been made by 
 FranJcenheim, Franz, Grailich and Pekarek, and others (see Literature, 
 p. 122), with an instrument called a sderometer. The mineral is placed on 
 a movable carriage with the surface to be experimented upon horizontal ; 
 this is brought in contact with a steel point (or diamond-point), fixed on a 
 support above; the weight is then determined which is just sufficient to 
 move the carriage and produce a scratch on the surface of the mineral. 
 
 By means of such an instrument the hardness of the different faces of a 
 given crystal has been determined in a variety of cases. It has been found 
 that different planes of a crystal differ in hardness, and the same plane dif- 
 fers as it is scratched in different directions. In general, the hardest plane 
 is that which is intersected by the plane of most complete cleavage. And 
 of a single plane, which is intersected by cleavage planes, the direction 
 perpendicular to the cleavage direction is the softer, those parallel to it the 
 harder. 
 
 This subject has been recently investigated by Exner (p. 122), who has given the form of 
 the curves of hardness for the different planes of many crystals. These curves are obtained as 
 follows : the least weight required to scratch a crystalline surface in different directions, 
 for each 10 or 15, from to 180, is determined with the sclerometer ; these directions 
 are laid off as radii from a centre, and the length of each is made proportional to the weight 
 fixed by experiment, that is, to the hardness thus determined ; the line connecting the 
 extremities of these radii is the curve of hardness for the given plane. 
 
 C. TENACITY. 
 
 Solid minerals may be either brittle, sectile, malleable, flexible, or elastic. 
 
 (a) Brittle / when parts of a mineral separate in powder or -grains on 
 attempting to cut it ; calcite. 
 
 (b) Sectile ; when pieces may be cut off with a knife without falling to 
 powder, but still the mineral pulverizes under a hammer. This character 
 is intermediate between brittle and malleable ; gypsum. 
 
 (c) Malleable ; when slices may be cut off, and these slices flattened out 
 under a hammer ; native gold, native silver. 
 
 (d) Flexible ; when the mineral will bend, and remain bent after the 
 bending force is removed ; talc. 
 
122 PHYSICAL CHARACTERS CF MINERALS. 
 
 (e) Elastic / when after being bent, it will spring back to its original 
 position ; mica. 
 
 The elasticity of crystallized minerals is a subject of theoretical rather 
 than practical importance. The subject has been acoustically investigated 
 by Savart with very interesting results. Reference may also be made to 
 the investigations of Neumann, and later those of Voigt and Groth. The 
 most important principle established by these researches is, as stated by 
 Groth, that in crystals the elasticity (coefficient of elasticity) differs in 
 different directions, but is the same in all directions which are crystallo- 
 graphically identical ; hence he gives as the definition of a crystal, a solid 
 in which the elasticity is a function of the direction. 
 
 Intimately connected with the general subjects here considered, of cohesion in relation 
 to minerals, are the figures produced by etching on crystalline faces (Aetzfiguren, Germ.), 
 investigated by Leydolt, and later by Baumhauer, Exner, and others. This method of investi- 
 gation is of high importance as revealing the molecular structure of the crystal ; reference, 
 however, must be made to the original memoirs, whose titles are given below, for the full 
 discussion of the subject. 
 
 The etching is performed mostly by solvents, as water in some cases, more generally the 
 ordinary mineral acids, or caustic alkalies, also by steam and hydrofluoric acid; the latter is 
 especially powerful in its action. The figures produced are in the majority of cases angular 
 depressions, such as low triangular, or quadrilateral pyramids, whose outlines run parallel to 
 some of the crystalline edges. In some cases the planes produced can be referred to occur- 
 ring crystallographic planes. They appear alike on similar planes of crystals, and hence 
 serve to distinguish different forms, perhaps in appearance identical, as the two sets of planes 
 in the ordinary double pyramid of quartz ; so, too, they reveal the compound twinning struc- 
 ture common on some crystals, as quartz (p. 89) and aragonite. 
 
 Analogous to the etching-figures are the figures produced on the faces of some crystals by 
 the loss of water (Verwitterungsfiguren, Germ,) This subject has been investigated by Pape 
 (see below). 
 
 LITERATURE. 
 Cohesion / Hardness. 
 
 FrankenJieim. De Crystallorum Cohaesione, 1829 ; also in Baumgarfcner's Zeitschrift fiii 
 Physik, ix., 94, 194. 1831. 
 
 Frankenheim. Ueber die Anordnung der Molecule in Krystallen ; Pogg. xcvii., 337. 1836. 
 
 Sohncke. Ueber die Cohasion des Steinsalzes in krystallographisch verschiedenen Rich- 
 tungen; Pogg. cxxxvii., 177. 1809. 
 
 Pranz. Ueber die Hiirte der Mineralien und ein neues Verfahren dieselbe zu rnessen ; 
 Pogg. Ixxx., 37. 1850. 
 
 Grailwh und Pekdrek. Ber. Ak. Wien, xiii., 410. 1854. 
 
 Exner. Ueber die Harte der Krystallflachen ; 166 pp. Wien, 1873. 
 
 Elasticity. 
 
 Savart. Pogg. Ann., xvi., 206. 
 
 Neumann. Pogg. Ann., xxxi., 177. 
 
 Voigt. Pogg. Ann. Erg. Bd., vii, i, 177, 1875. 
 
 Groth. Pogg. Ann., clvii., 115, 787. 1876. 
 
 Bauer. Untersuchung iiber den Glimmer und verwandte Minerale ; Pogg. cxxxviii., 337, 
 
 Reusch. Ueber die Kornerprobe am Steinsalz u. Kalkspath. Pogg. cxxxii., 441, 1867; 
 am zwei-axigen Glimmer, Pogg. Ann. cxxxvi, 430, 632 ; am krystallirten Gyps, ibid., p. 135. 
 
SPECIFIC GRAVITY 123 
 
 Baumhauer. Ueber Aetzfiguren und die Erscheinungen des Asteiismus an Krystallen ; 
 Pogg. Ann. cxxxviii., 163 ; cxxxix., 349 ; cxL, 271 ; cxlv., 459 ; sliii., 621 ; Ber. Ak. Miinchen, 
 
 Darnell. Quarterly Journal of Science, i., 24. 1816. 
 
 Exner. An Losungsfiguren in Krystallen; Ber. Ak. Wien, Ixix., 6. 1874. 
 Hirschwald. Aetzfiguren an Quarz-Krystallen ; Pogg. cxxxvii. , 548. 1869. 
 Knop. Jahrb. Min., 1872, 785. 
 
 Ley dolt. Ueber Aetzungen ; Ber. Ak. Wien, xv., 58; xix., 10. 
 
 Pape. Ueber das Verwitterungs-Ellipsoid wasserhaltiger Krysteille; Pogg. cxxiv., 339: 
 CKXV. , 513. 1865. 
 
 II. SPECIFIC GKAVITY.* 
 
 The specific gravity of a mineral is its weight compared with that of an- 
 other substance of equal volume, whose gravity is taken at unity. In the 
 case of solids or liquids, this comparison is usually made with water. If a 
 cubic inch of any mineral weighs twice as much as a cubic inch of water 
 (water being the unit), its specific gravity is 2, if three times as much, its 
 specific gravity is 3, etc. 
 
 The direct comparison by weight of a certain volume of water with an 
 equal volume of a given solid is not often practicable. By making use, 
 however, of a familiar principle in hydrostatics, viz., that the weight lost 
 by a solid immersed in water is equal to the weight of an equal volume of 
 water, that is of the volume of water it displaces, the determination of the 
 specific gravity becomes a very simple process. 
 
 The weight of the solid out of water (w) is determined by weighing in 
 the usual manner ; then the weight in water is found (w'), when the loss by 
 immersion or the difference of the two weights (w w') is the weight of a 
 volume of water equal to that of the solid ; finally the quotient of the first 
 weight (w) by that of the equal volume of water as determined (w w') 
 is the specific gravity (G). 
 
 Hence, 
 
 For example, the weight of a fragment of quartz is found to be 4.534 
 grams. Its weight in water = 2.817 grains, and therefore the loss oi 
 weight, or the weight of an equal volume of water = 1.717. Consequent!} 
 
 4 534 
 the specific gravity is equal to T-^T^J or 2.641. 
 
 The ordinary method for obtaining the specific gravity of firm, solid 
 minerals is first to weigh the specimen accurately on a good chemical bal- 
 ance, then suspend it from one pan of the balance by a horse-hair, silk 
 thread, or better still by a fine platinum wire, in a glass of water con- 
 veniently placed beneath. The platinum wire may be wound around the 
 specimen, or where the latter is small it may be made at one end into a 
 little spiral support. While thus suspended, the weight is again taken with 
 the same care as before. 
 
 The water employed for this purpose should be distilled, to free it from 
 all foreign substances. Since the density of water varies with its tempera- 
 ture, a particular temperature has to be selected for these experiments, in 
 
 * SPP fnrthpr nn r 1 73 
 
124 PHYSICAL CHARACTERS OF MINERALS. 
 
 order to obtain uniform results: 60 F. is the most convenient, and has 
 been generally adopted. But the temperature of the maximum density of 
 water, 39.2 F. (4 C.), has been recommended as preferable. For minerals 
 soluble in water some other liquid, as alcohol, benzene, etc;., must be em- 
 ployed, whose specific gravity (g) is accurately known ; from the com- 
 parison with it, the specinc gravity (G) of the mineral as referred to water 
 is determined, as by the formula : 
 
 G= 
 
 w w* 
 
 A very convenient form of balance is the spiral balance of Jolly, where the weight is mea- 
 Bured by the torsion of a spiral brass wire. The readings, which give the weight of the min- 
 eral in and out of water, are obtained by observing the coincidence of the index with its 
 image reflected in the mirror on which the graduation is made. 
 
 A form of balance in which weights are also dispensed with, the specinc gravity being read 
 off from a scale without calculation, has recently been described by Parish (Am. J. Sci., III., 
 x., 352). "Where great accuracy is not required, it can be very conveniently used. 
 
 If the mineral is not solid, but pulverulent or porous, it is best to reduce 
 it to a powder and weigh it in a little glass bottle (f. 373) 
 373 called a pygnometer. This bottle has a stopper which 
 
 fits tightly and ends in a tube with a very fine opening. 
 The bottle is filled with distilled water, the stopper in- 
 serted, and the overflowing water carefully removed with 
 a soft cloth. It is now weighed, and also the mineral 
 whose density is to be determined. The stopper is then 
 removed and the mineral in powder or in small fragments 
 inserted, with care, so as not to introduce air-bubbles. 
 The water which overflows on replacing the stopper is 
 the amount of water displaced by the mineral. The 
 weight of the pygnometer with the enclosed mineral is 
 determined, and the weight of the water lost is obviously 
 the difference between this last weight and that of the 
 bottle and mineral together, as first determined. The specific gravity of 
 the mineral is equal to its weight alone divided by the weight of the equal 
 volume of water thus determined. 
 
 Where this method is followed with sufficient care, especially avoiding 
 any change of temperature in the water, the results are quite accurate. 
 Other methods of determining the specific gravity will be found described 
 in the literature notices which follow. 
 
 It has been shown by Rose that chemical precipitates have uniformly a 
 higher density than belongs to the same substance in a less finely divided 
 state. This increase of density also characterizes, though to a less extent, 
 a mineral in a fine state of mechanical subdivision. This is explained 
 by the condensation of the water on the surface of the powder. 
 
 It may also be mentioned that the density of many substances is altered 
 by fusion. The same mineral in different states of molecular aggregation 
 may differ somewhat in density. Furthermore, minerals having the same 
 chemical composition have sometimes different densities corresponding Co the 
 different crystalline forms in which they appear (see p. 199). 
 
LIGHT. 125 
 
 For all minerals in a state of average purity the specific gravity is one of 
 the most important and constant characteristics, as urged especially by 
 Breithaupt. Every chemical analysis of a mineral should be accompanied 
 by a careful determination of its density. 
 
 Practical suggestions. The fragment taken should not be too large, say from two to five 
 grams for ordinary cases, varying somewhat with the density of the mineral. The substance 
 must be free from impurities, internal and external, and not porous. Care must be taken to 
 exclude air-bubbles, and it will often be found well to moisten the surface of the specimen 
 before inserting it in the water, and sometimes boiling is necessary to free it from air. If it 
 absorbs water this latter process must be allowed to go on till the substance is fully satu- 
 rated. No accurate determinations can be made unless the changes of temperature are 
 rigorously excluded and the actual temperature noted. 
 
 In a mechanical mixture of two constituents in known proportions, when the specific 
 gravity of the whole and of one are known, that of the other can be readily obtained. This 
 method is often important in the study of rocks. 
 
 LITERATURE. SPECIFIC GRAVITY. 
 
 Beudant. Pogg. Ann., xiv., 474. 1828. 
 
 Jenzsch. Ueberdie Bestimmung der specifischen Gewichte ; Pogg. xcix., 151. 1856. 
 
 Jotty. Ber. Ak. Miinchen, 1864, 162. 
 
 Gadoliti. Eine einfache Methode zur Bestimmung des specifischen Gewichtes der Minera- 
 lien; Pogg., cvi., 213. 1859. . 
 
 G. Ilosc. Ueber die Fehler, welche in der Bestimmung des specifischen Gewichtes del 
 Korper entstehen, wenn man dieselben im Zustande der feinsten Vertheilung wagt ; Pogg. 
 Ixxiii., Ixxv , 403. 1848. 
 
 Scheerer. Ueber die Bestimmung des specifischen Gewichtes von Mineralien ; Pogg. Ann. , 
 Ixvii., 120, 1846. Journ. pr. Ch., xxiv., 139. 
 
 kchiff. Ann. Ch. Pharm., cviii., 29. 1858. 
 
 Schroder. Neue Beitrage zur Volumentheorie ; Pogg. cvi., 226. 1859. 
 
 ; Die Volumconstitution einiger Mineralien ; Jahrb. Min , 1873, 561, 932 ; 1874, 
 
 399, etc. 
 
 Tschermak. Ber. Ak. Wien, 292, 1863. 
 
 Websky. Die Mineralien nach den fur das specifische Gewicht derselben angenommenen 
 and gefundenen Werthen ; 170 pp. Breslau, 1868. 
 
 III. LIGHT.* 
 
 Before considering the distinguishing optical properties of crystals of the 
 different systems, it is desirable to review briefly some of the more im- 
 portant principles of optics upon which the phenomena in question 
 depend. 
 
 Nature of light. In accordance with the undulatory theory of Huy- 
 ghens, as further developed by Young and Fresnel, light is conceived to 
 consist in the vibrations, transverse to the direction of propagation, of the 
 particles of imponderable, elastic ether, which it is assumed pervades all 
 space as well as all material bodies. These vibrations are propagated with 
 great velocity in straight lines and in all directions from the luminous 
 point, and the sensation which they produce on the nerves of the eye is 
 called light. 
 
 The nature of the vibrations will be understood from f. 374. If AE 
 represents the direction of propagation of the light-ray, each particle of 
 ether vibrates at right angles to this as a line of equilibrium. The vibra- 
 
126 PHYSICAL CHARACTERS OF MINERALS. 
 
 tiou of the first particle induces a similar movement in the adjacent par- 
 ticle ; this is communicated to the next, and so on. The particles vibrate 
 successively from the line AB to a distance corresponding to bb' ', called the 
 amplitude of the vibration, then return to b and pass on to ", and so 
 
 on. Thus at a given instant there are particles occupying all positions, 
 from that of the extreme distance ', or <?', from the line of equilibrium to 
 that on this line. In this way the wave of vibration moves forward, while 
 the motion of the particles is only transverse. In the figure the vibrations 
 are represented in one plane only, but in ordinary light they take place in 
 all directions about the line AS. The distance between any two particles, 
 which are in like positions, of like phase, as b' and c' 9 is called the wave- 
 length and the time required for this completed movement is called the 
 time of vibration. The intensity of the light varies with the amplitude of 
 the vibrations, and the color depends upon the length of the waves ; the 
 wave-lengths of the violet rays are shorter than those of the red rays. 
 
 Two waves of like phase, propagated in the same direction and of equal 
 intensity, on meeting unite to form a wave of double intensity (double 
 amplitude). If the waves differ in phase by half a wave-length, or an odd 
 multiple of this, they interfere and extinguish each other. For other rela- 
 tions of phase they are also said to interfere, forming a new resultant wave, 
 differing in phase and amplitude from each of the component waves ; if 
 they are waves of white light, their interference is indicated by the appear- 
 ance of the successive colors of the spectrum. The propagation of the 
 vibration -waves of light is sometimes compared to the effect produced 
 when a pebble is thrown in a sheet of quiet water a series of concentric 
 circular waves are sent out from the point of agitation. These waves con- 
 sist in the transverse vibration of the particles of water, the waves move 
 forward, but the water simply vibrates to and fro vertically. 
 
 The waves of light are propagated forward, in an analogous manner, in 
 all directions from the luminous point, and the surface wfiich contains all 
 the particles which commence their vibrations simultaneously is called the 
 wave-surface (Wellenflache, Germ.). 
 
 If the propagation of light goes on with the same velocity in all direc- 
 tions in a homogeneous medium, the wave-surface is obviously that of a 
 sphere and the medium is said to be isotrope. If it takes place with dif- 
 ferent velocities in different directions in a body, the wave-surface is some- 
 times an ellipsoid, but never spherical, as Is shown later ; such a body ia 
 called anisotrope. 
 
 All the phenomena of optics are explained upon the supposition of waves 
 of light, whose change of direction accompanies refraction, whose interfer- 
 ence produces the colored bands of the diffraction spectra, etc. For the 
 full discussion of the subject reference must be made to works on optics. 
 
REFRACTION JF LIGHT. 
 
 127 
 
 Refraction. A ray of light passing through a homogeneous medium is 
 always propagated in a straight line without deviation. When, however, 
 the light-ray passes from one medium to another, which is of different 
 density, it suffers a change of direction, which is called refraction. For in- 
 stance, in f. 375, if ca is a ray of light passing from air into water, its path 
 will be changed after passing the surface at 
 a, and it will continue in the direction ab. 
 Conversely, if a ray of light, ba, pass from 
 the denser medium, water, into the rarer 
 medium, air, at #, it will take the direction 
 ac. 
 
 If now mao is a perpendicular to the sur- 
 face at #, it will be seen that the angle cam, 
 called the angle of incidence (i) of the ray 
 ca is greater than the angle bao, called the 
 angle of refraction (/*), and what is observed 
 in this case is found to be universally true, 
 and the law is expressed as follows : 
 
 A ray of light in passing from a rarer 
 to a denser medium is refracted TOWARDS 
 the perpendicular if from a denser to a rarer medium it is refracted 
 AWAY FROM the perpendicular. 
 
 A further relation has also been established by experiment : however 
 great or small the angle ot' incidence, cam (?'), m&y be, there is always a 
 constant relation between it and the angle of refraction, gam (7'), for two 
 given substances, as here for air and water. This is seen in the figure where 
 af and da are the sines of the two angles, and their ratio ( nearly) is 
 the same as that of the sine of any other angle of incidence to the sine of 
 its angle of refraction. This principle is expressed as follows: 
 
 The sine of the angle of incidence bears a constant ratio to the sine of 
 the angle of refraction. 
 
 This constant ratio between these two angles is called the index of refrac- 
 tion^ or simply n. In the example given for air and water - - = 1.335, 
 
 and consequently the value of the index of refraction, or n, is 1.335. 
 
 The following table includes the values of n for a variety of substances. 
 For all crystallized minerals, except those of the isometric system, the index 
 of refraction has more than one value, as is explained in the pages which 
 follow. 
 
 Ice 1.308 
 
 Water 1.335 
 
 Fluorite 1.436 
 
 Alum 1.457 
 
 Chalcedony 1.553 
 
 Eock-salt 1.557 
 
 Quartz 1.548 
 
 Calcite 1.654 
 
 Aragonite 1.693 
 
 Boracite 1.701 
 
 Garnet 1.815 
 
 Zircon 1.961 
 
 Blende 2.260 
 
 Diamond.. .... 2.419 
 
 In the principle which has been stated, = n, twc points are to be 
 
 snip 
 
128 PHYSICAL CHAEACTEKS OF MINERALS. 
 
 noted. First, if the angle i = 0, then sin i = 0, and obviously also r = 0, 
 i:i other words, when the ray of light coincides with the perpendicular no 
 refraction takes place, the ray proceeding onward into the second medium 
 without deviation. 
 Again, if the angle i = 90, then sin i = 1, and the equation above be- 
 
 comes - = n. or sin r = . As n has a fixed value for every substance. 
 sin r n 
 
 it is obvious that there will also be a corresponding value of the angle r 
 for the case mentioned. From the above table it is seen that for water 
 
 sin r = ij-s^, and r = 48 35' ; for diamond, sin r = , and r 24 25'. 
 
 2.4:2 
 
 In the example employed above, if the angle bao (r) 48 35', the line ac 
 will coincide with #/*, supposing the light to go from b to a. If r is greater 
 than 48 35', the ray no longer passes from the water into the air, but suffers 
 total reflection at the surface a. This value of r is said to be the limiting 
 value for the given substance. The smaller it is the greater the amount of 
 light reflected, and the greater the apparent 'brilliancy of the substance in 
 question. This is the explanation of the brilliancy of the diamond. 
 
 Determination of the index of refraction* By means of a prism, as 
 375 MNP in f. 376, it is possible to determine 
 
 the value of w, or index of refraction of a 
 given substance. The full explanation of 
 this subject belongs to works on optics, but 
 a word is devoted to it here. If the material 
 is solid, a prism must be cut and polished, 
 with its edge in the proper direction, and 
 
 _ having not too small an angle. If the refrac- 
 
 M p tive index of a liquid is required, it is placed 
 
 within a hollow prism, with sides of plates of glass having both surfaces 
 parallel. 
 
 The angle of the prism, MN P (a), is, in each case, measured in the 
 same manner as the angle between two planes of a crystal, and then the 
 minimum amount of deviation (8) of a monochromatic ray of light passing 
 from a slit through the prism is also determined. The amount of deviation 
 of a ray in passing through the prism varies with its position, but when the 
 prism is so placed that the ray makes equal angles with the sides of the 
 prism (i i\ f. 376), both when entering and emerging, this deviation has 
 & fixed minimum value. 
 
 If S = the minimum deviation of the ray, and 
 
 a = the angle of the prism, then n = sm ^ a - /. 
 
 sin %a 
 
 In determining the value of n for different colors, it is desirable to employ 
 rays of known position in the spectrum. 
 
 Double refraction. Hitherto the existence of only one refracted ray has 
 been assumed when light passes from one medium to another. But it is 
 a well-known fact that there are sometimes two redacted rays. The most 
 familiar example of this is furnished by the minerat calcite, also called on 
 account of this property " doubly-refracting spar." 
 
 If mnop (f. 377) be a cleavage piece of calcite. and a ray of light meets 
 
 * See further on p. 177. 
 
REFLECTION, DISPERSION AND DIFFRACTION OF LIGHT. 129 
 
 it at J, it will, in passing through, be divided into two rays, be, Id 
 Similarly a line seen through a piece of calcite ordi- 
 narily appears double. 377 
 
 It will be seen, however, that the same property is " 
 
 enjoyed by the great majority of crystallized minerals, 
 though in a less striking degree. 
 
 Reflection. When a ray of light passes from one 
 medium to another, for example, from air to a denser 
 substance, as has been illustrated, the light will be par- 
 tially transmitted and refracted by the latter, in the 
 manner illustrated, but a portion of it (the ray ag, in f. 375), is always 
 reflected back into the air. The direction of the reflected ray is known 
 in accordance with the following law : 
 
 The angles of incidence and reflection are equal. In f. 375 the angle 
 cam is equal to the angle mag. 
 
 The relative amount of light reflected and transmitted depends upon the 
 angle of incidence, and also upon the transparency of the second medium. 
 If the surface of the latter is not perfectly polished, diffuse reflection will 
 take place, and there will be no distinct reflected ray. 
 
 Still another important principle, in relation to the same subject, remains 
 to be enunciated : The rays of incidence, reflection, and refraction all lie 
 in the same plane. 
 
 Dispersion. Thus far the change in direction which a ray of light suffers 
 on refraction has alone been considered. It is also true that the amount 
 of refraction differs for the different colors of which ordinary white light 
 is composed, being greater for blue than for red. In consequence of this 
 fact, if a ray of ordinary light pass through a prism, as in f. 376, it will 
 not only be refracted, but it will also be separated into its component colors, 
 thus forming the spectrum. 
 
 This variation for the different colors depends directly upon their wave- 
 lengths ; the red rays have longer waves, and vibrate move slowly, and 
 hence suffer less refraction than the violet rays, for which the wave-lengths 
 are shorter and the velocity greater. 
 
 Interference of light ; diffraction. When a ray of monochromatic light 
 is made to pass through a narrow slit, or by the edge of an opaque body, 
 it is diffracted^ and there arise, as may be observed upon an appropriately 
 placed screen, a series of dark and light bands, growing fainter on the outer 
 limits. Their presence, as has been intimated, is explained in accordance 
 with the undulatory theory of light, as due to the interference, or mutual 
 reaction of the adjoining waves of light. If ordinary light is employed, 
 the phenomena are the same and for the same causes, except that the bands 
 are successive spectra. Diffraction gratings, consisting of a series of ex- 
 tremely fine lines very closely ruled upon glass, are employed for the same 
 purpose as the prism to produce the colored spectrum. The familiar 
 phenomena of the colors of thin plates and of Newton's rings depend upon 
 the same principle of the interference of the light waves. This subject is 
 one of the highest irm^tence in its connection with the optical properties 
 of crystals, since thejpTOnomena observed when they are viewed, under 
 certain circumstances, in polarized light are explained in an analogous 
 manner. (Compare the colored plate, frontispiece.) 
 9 
 
130 
 
 PHYSICAL CHARACTERS OF MINERALS. 
 
 Polarization by reflection. By polarization is understood, in general, 
 that change in the character of reflected or transmitted light which dimin- 
 ishes its power of being further reflected or transmitted. In accordance 
 with the undulatory theory of light a ray of polarized light is one whose 
 vibrations take place in a single plane only. 
 
 Suppose (f. 378) mn and op to be two parallel mirrors, say simple 
 polished pieces of black glass ; a ray of light, AB, 
 will be reflected from mn in the direction BC, 
 and meeting op^ will be again reflected to D. 
 When, as here, the two mirrors are in a parallel 
 position, the plane of reflection is clearly the 
 same for both, the angles of incidence are equal, 
 and the rays AB and CD are parallel. The ray 
 CD is polarized, although this does not show 
 itself to the eye direct. 
 
 Now let the mirror, op, be revolved about BC 
 as an axis, and let its position otherwise be un- 
 changed, so that the angles of incidence still 
 remain equal, it will be found that the reflected 
 ' ray, CD, loses more and more of its brilliancy as 
 the revolution continues, and when the mirror, 
 op* occupies a position at right angles to its 
 
 former position, the amount of light reflected will be a minimum, the 
 planes of reflection being in the two cases perpendicular to one another. 
 
 If the revolution of the mirror be continued with the same conditions as 
 before, and in the same direction, the reflected ray will become brighter 
 and brighter till the mirror has the position indicated by the dotted line, 
 o'p', when the planes of reflection again coincide, and the reflected ray, CD' , 
 is equal in brilliancy to that previously obtained for the position CD. 
 
 The same diminution to a minimum will be seen if the revolution is con- 
 tinued 90 farther, and the reflected ray again becomes as brilliant as before 
 when the mirror resumes its first position op. 
 
 In the above description it was asserted that, when the planes of inci- 
 dence of the mirrors were at right angles to each other, the amount of light 
 reflected would be less than in any other position, that is a minimum. For 
 one single position of the mirrors, however, as they thus stand perpendicular 
 to each other, that is for one single value of the. angle of incidence, the 
 light will be practically extinguished, and no reflected ray will appear 
 from the second mirror. 
 
 The angle of incidence, ABH, for this case is called the angle of polar- 
 ization, and its value varies for different substances. It was shown further 
 by Brewster that : 
 
 The angle of polarization is that angle whose tangent is the index of 
 refraction of the reflecting substance, i.e., tan i = n. 
 
 Exactly the same phases of change would have been observed if the 
 upper mirror had been revolved in a similar manner. The first mirror is 
 often called the polarizer, the second the analyzer. 
 
 This change which the light suffers in this case, in consequence of re- 
 flection, is called polarization. 
 In order to give a partial explanation of this phenomenon and to make 
 
POLARIZATION OF LIGHT. 
 
 the same subject intelligible as applied to other cases in which polarisation 
 occurs, reference must be made to the commonly received theory of the 
 nature of light already defined. 
 
 The phenomena of light are explained, as has been stated, on the assump- 
 tion that it consists of the vibrations of the ether, the vibrations being 
 transverse, that is in a plane perpendicular, to the direction in which the 
 light is propagated. These vibrations in ordinary light take place in all 
 directions in this plane at sensibly the same time ; strictly speaking, the 
 vibrations are considered as being always transverse, but their directions 
 are constantly and instantaneously changing in azimuth. Such a ray of light 
 is alike on all sides or all around the line of propagation, AH, f. 374. 
 A ray of completely polarized light, on the other hand, has vibrations in 
 one direction only, that is in a single plane. 
 
 These principles may be applied to the case of reflection already de- 
 scribed. The ray of ordinary light, AB, has its vibrations sensibly simul- 
 taneous in all directions in the plane at right angles to its line of propaga- 
 tion, while the light reflected from each mirror has only those vibrations 
 which are in one direction, at right angles to the plane of reflection 
 supposing that the mirrors are so placed that the angle of incidence 
 (ABH) is also the angle of polarization. 
 
 If the mirror occupy the position represented in f. 378, the ray of light, 
 BC\ after being reflected by the first mirror, mn, contains that part of the 
 vibrations whose direction is normal to its plane of reflection called the 
 plane of polarization. This is also true of the second mirror, and when 
 they are parallel and their planes of reflection coincide, the ray of light is 
 reflected a second time without additional change. 
 
 If, however, the second mirror is revolved in the way described (p. 130), 
 less and less of the light will be reflected by it, since a successively smaller 
 part of the vibrations of the ray J?6 y take place in a direction normal to 
 its plane of reflection. And when the mirrors are at right angles to each 
 other, after a revolution of op 90 about the line -Z?6 y as an axis, no part of 
 the vibrations of the ray j&6 r are in the plane at right angles to the reflec- 
 tion-plane of the second mirror, and hence the light is extinguished. 
 
 By reference to f. 375 this subject may be explained a little more broadly. 
 It was seen that of the ray ca, meeting the surface of the water at a, part is 
 reflected and part transmitted in accordance with the laws of reflection 
 and refraction. It has been shown further that the reflected ray is polar- 
 ized, that is, it is changed so that the vibrations of the light take place in 
 one direction, at right angles to the plane of incidence. It is also true that 
 the refracted ray M polarized, it containing only those vibrations which 
 were lost in the reflected ray, that is, those which coincide with the plane 
 of incidence and reflection. 
 
 It was stated that the vibrations of the polarized reflected ray take place 
 at right angles to the plane of polarization. This is the assumption which 
 is commonly made ; but all the phenomena of polarization can be equally 
 well explained upon the other supposition that they coincide with this 
 plane. 
 
 The separation of the ray of ordinary light into two rays, one reflected 
 the other refracted, vibrating at right angles to each ether, takes place most 
 completely when the reflected and refracted rays are 90 from one another, 
 
132 PHYSICAL CHARACTERS OF MINERALS. 
 
 as proved by Brewster. From this fact follows the law already stated 
 that the tangent of the angle of polarization is equal to the index of re- 
 fraction. The angle of polarization for glass is about 54 35'. 
 
 This separation is in no case absolutely complete, but varies with differ- 
 ent substances. In the case of opaque substances the vibrations belonging 
 to the refracted ray are more or less completely absorbed (compare remarks 
 on color, p. 168). Metallic surfaces polarize the light very slightly. 
 
 Polarization by means of thin plates of glass. It has been explained 
 that the light which has been transmitted and refracted is always at least 
 in part polarized. It will be readily understood from this fact that when a 
 number of glass plates are placed together, the light which passes through 
 them all will be more and more completely polarized as their number is 
 increased. This is a second convenient method of obtaining polarized 
 light. 
 
 Polarization by means of tourmaline plates. The phenomena of polar- 
 ized light may also be shown by means of tourmaline plates. If from 
 a crystal of tourmaline, which is suitably transparent, two sections be 
 obtained, each cut parallel to the vertical axis, it will be found that 
 these, when placed together with the direction of their axes coinciding, 
 allow the light to pass through. If, however, one section is revolved upon 
 the other, less and less of the light is transmitted, until, when their axes are 
 at right angles (90) to each other, the light is (for the most part) extin- 
 guished. As the revolution is continued, more and more light is obtained 
 through the sections, and after a revolution of 180, the axes being again 
 parallel, the appearance is as at first. A further revolution (270) brings 
 the axes again at right angles to each other, when the light is a second time 
 extinguished, and so on around. 
 
 The explanation of these phenomena, so far as it can be given here, is 
 analogous to that employed for the case of polarization by re- 
 flection. Each plate so affects the ray of light that after 
 having passed through it there exist vibrations intone direction 
 only, and that parallel to the vertical axis, the other vibrationy 
 being absorbed. If now the two plates are placed in the same 
 position, abdc, and efgh (f. 379), the light passes through both 
 in succession. If, however, the one is turned upon the other, 
 only that portion of the light can pass through which vibrates 
 still in the direction ac. This portion is determined by the 
 resolution of the existing vibrations in accordance with the 
 principle of the parallelogram of forces. Consequently, when the sections 
 stand at right angles to each other (f. 380) the amount of 
 380 ^ transmitted light is nothing (not strictly true), that is, the 
 light is extinguished. 
 
 The tourmaline plates, which have been described, are 
 mounted in pieces of cork and held in a kind of wire 
 pincers (f. 381). The object to be examined is placed 
 between them and supported there by thp spring in the 
 wire. In use they are held close to the eye, and in 
 this position the object is viewed in converging polarized light. 
 
 Polarization by means of Nicol prisms. The most convenient method 
 of obtaining polarized light is by means of a Nicol prism of calcite. A 
 
POLARIZATION OF LIGHT. 
 
 133 
 
 cleavage rhombohedron of calcite (the variety Iceland- spar is universally 
 used in consequence of its transparency) is obtained, having four large and 
 two small rhotnbohedral faces opposite each other. Iii place of the latter 
 
 382 
 
 planes two new surfaces are cut, making angles of 68 (instead of 71) with 
 
 the obtuse vertical edges; these then form the terminal faces of the prism. 
 
 In addition to this, the prism is cut through in the direction RH (f. 382), 
 
 the parts then polished and cemented together again with 
 
 Canada balsam. A ray of light, , entering the prism 
 
 is divided into two rays polarized at right angles to each 
 
 other. One of these, be, on meeting the layer of balsam 
 
 (whose refractive index is greater than that of calcite) 
 
 suffers total reflection (p. 128), and is deflected against the 
 
 blackened sides of the prism and extinguished. The other 
 
 passes through and emerges at e, a completely polarized 
 
 ray of light, that is. a ray with vibrations in one direction 
 
 only, and that the direction of the shorter diagonal of the 
 
 prism (f. 383). 
 
 It is evident that two Nicol prisms can be used together 
 in the same way as the two tourmaline plates, or the two 
 mirrors ; one is called the polarizer, and the other the 
 analyzer. The plane of polarization of the Nicol prisms 
 has the direction PP (f. 383) at right angles to which the 
 vibrations of the light take place. A ray of light pass- 
 ing through one Nicol will be extinguished by a second 
 when its plane of polarization is at right angles to that of 
 the first prism ; in this case the Nicols are said to be 
 crossed. The Nicol prisms have the great advantage over the tourmaline 
 plates, that the light they transmit is uncolored and more completely 
 polarized. 
 
 Either a tourmaline plate or a Nicol prism 
 may also be used in connection with a reflecting 
 mirror. The light reflected by such a mirror 
 vibrates in a plane at right angles to the plane of 
 incidence (plane of polarization) ; that trans- 
 mitted by the Nicol prism vibrates in the direc- 
 tion of the shorter diagonal (f. 383). Hence, 
 when the plane of this diagonal is at right angles 
 to the plane of polarization of the mirror, the re- 
 flected ray will pass through the prism ; but when the two planes mentioned 
 coincide, the planes of vibration are at right angles and the reflected ray is 
 extinguished by the prism. 
 
134 
 
 PHYSICAL CHARACTERS OF MINERALS. 
 
 Polariscopes* TheNicol prisms, when ready for use, are mounted in an 
 upright instrument, called a polariscope. Sometimes parallel, and some- 
 times converging, light is required in the investigations for which the instru- 
 ment is used. Fig. 384 shows the polarization-microscope of Norrenberg 
 
 384 
 
 385 
 
 as altered and improved by Groth (see 
 Literature, p. 160). The Nicol prisms 
 are at d and r, and are so mounted as 
 to admit of a motion of revolution in- 
 dependent of the other parts of the in- 
 strument. The lense e causes the light 
 from the ordinary mirror, a, to pass as a 
 cone through the prism d, and the lenses 
 at h converge the light upon the plate 
 to be examined placed at i. The other 
 lenses (o) above act as a weak microscope, 
 having a field of vision of 130. The 
 stage (7 and &), carrying the object, admits 
 of a horizontal revolution. The distance 
 between the two halves of the instrument 
 is adjusted by the screws in and n. 
 
 When parallel light is required, a similar instrument is employed, which 
 has, however, a different arrangement of the lenses, as shown in f. 385. 
 The objects for which these instruments, as well as the tourmaline plates, 
 are employed, will be found described in the following pages. 
 
 The Nicol prisms are often used as an appendage to the ordinary com- 
 pound microscope, and in this form are important as enabling us to examine 
 very minute crystals in polarized light. t 
 
 See further on pp. 178, 179. 
 
 f See pp. 182 et seq. 
 
OPTICAL CHARACTERS OF ISOMETRIC CRYSTALS. 135 
 
 DISTINGUISHING OPTICAL CHARACTERS OF THE CRYS- 
 TALS OF THE DIFFERENT SYSTEMS. 
 
 It has already been remarked that all crystallized minerals group them- 
 selves into three grand classes, which are distinguished by their physical 
 properties, as well as their geometrical form : 
 
 A. Isometric, in which the crystals are developed alike in all the several 
 axial directions. 
 
 J3. Isodiametric, including the tetragonal and hexagonal systems, whose 
 crystals are alike in the directions of the several lateral axes, 'but vertically 
 the development is unlike that laterally. 
 
 C. Anisometrlc, embracing the three remaining systems, where the crys- 
 tals are developed in the three axial directions dissimilarly. 
 
 Between these classes there are many cases of gradual transition in crystalline form, and, 
 similarly and necessarily, in optical character. The line between uniaxial and biaxial 
 crystals, for instance, cannot be considered a very sharply denned one.* 
 
 A. ISOMETRIC CRYSTALS. 
 General Optical Character. 
 
 All isometric crystals are alike in this respect that they simply refract, 
 but do not doubly refract the light they transmit. They are optically 
 isotrope. This follows directly from the symmetry of the crystallization. 
 In the language of Fresnel, the elasticity of the light-ether is throughout 
 them the same, and the light is propagated in every direction with the 
 same velocity. There is, consequently, but one value of the index of refrac- 
 tion. The wave-surface is spherical. This class also includes all trans- 
 parent amorphous substances, like glass. 
 
 Optical Investigation of Isometric Crystals. 
 
 In consequence of their isotropic character, isometric crystals exhibit no 
 special phenomena in polarized light. Sections of isometric crystals may 
 be always recognized as such by the fact that they behave as an amorphous 
 substance in polarized light; in other words, when the Nicol prisms are 
 crossed they appear dark, and a revolution of the section in any plane pro- 
 duces no change in appearance. Similarly they appear light when placed 
 between parallel Nicols. Some anomalies are mentioned on p. 158. 
 
 Isometric crvstals have but a single index of refraction, and that may be 
 determined in "the way described by means of a prism cut with its edge iu 
 any direction whatever. 
 
 Crystals of the second and third classes are optically anisotrope. 
 
136 PHYSICAL CHARACTERS OF MINERALS. 
 
 B. UNIAXIAL CRYSTALS. 
 General Optical Character. 
 
 In the isodiametric crystals, those of the tetragonal and hexagonal sys- 
 tems, there is crystallographically one axial direction, that of the vertical 
 axis, which is distinguished from the other lateral directions which are 
 among themselves alike. So also the optical investigations of these crystals 
 show that with reference to the action of light there exists a similar kind 
 of symmetry. Light is propagated in the direction of the vertical axis with 
 a velocity different from that with which it passes in any other direction, 
 but for all directions at right angles to the vertical axis, or all directions 
 making the same angle with it, the velocity of propagation is the same. 
 In other words, the elasticity of the ether in the direction of the vertical 
 axis is either greater or less than that in directions normal to it (analogous 
 to the crystallographical relation c ? a\ while in the latter directions it is 
 everywhere alike. 
 
 Optic axis. Let a ray of light pass through 
 the crystal in the direction of the vertical axis, 
 ab, in f. 386, its vibrations must take place in 
 the plane at right angles to this axis ; but in all 
 directions in this plane the elasticity of the ether 
 is the same, hence for such a ray the crystal must 
 act as an isotrope medium ; and the ray is con- 
 sequently not doubly refracted and not polarized. 
 This direction is called the OPTIC AXIS.* 
 
 Double refraction. If, on the other hand, the 
 ray of light passes through the crystal in any other direction, it is divided 
 into two rays, or doubly refracted (see f. 377), and this in consequence of 
 the difference in the elasticity of the ether in the plane in which the vibra- 
 tions take place. Of these two rays, one follows the law of ordinary 
 refraction, and this is called the ordinary ray ; the other does not conform 
 to this law, and is called the extraordinary ray. Both these rays are polar- 
 ized, and in planes at right angles to each other ; the vibrations of the 
 extraordinary ray take place in the plane passing through the incident ray 
 and vertical axis, called the principal section, those of the ordinary ray 
 are in a plane at right angles to this. 
 
 Wave-surface of the ordinary ray. The meaning of the statement that 
 the ordinary ray follows the law of the simple refraction is this : the index 
 of refraction (to) of the ordinary ray has invariably the same value, what- 
 ever be the direction in which the light passes through the crystal ; the 
 amount of deviation from the perpendicular is always in accordance with 
 
 the law = n (&). In other words, the ordinary ray is propagated in 
 all directions in the medium with the same velocity ; and hence the wave- 
 
 * It will be understood that, the optic axis is always a direction, not a fixed line in the 
 crystals. 
 
OPTICAL CHARACTERS OF UNIAXIAL CRYSTALS. 
 
 137 
 
 surface is that of a sphere. Moreover, the ordinary ray always remains in 
 the plane of incidence. 
 
 Wave-surface of the extraordinary ray. For the extraordinary ray the 
 law of simple refraction does not hold good. If experiments be made upon 
 any nniaxial crystal, it will be found that the two rays are most separated 
 when (1) the light falls PERPENDICULAR to the vertical axis. As its inclina- 
 tion toward the axis is diminished, the extraordinary ray approaches the 
 ordinary ray, and coincides with it when (2) the light passes through PAR- 
 ALLEL to the vertical axis. The index of refraction of the extraordinary ray 
 varies in value, being most unlike w for the first case supposed when the 
 vibrations of the extraordinary ray are parallel to the axis (when it is 
 called e), and is equal to o> for the second case supposed. The velocity of 
 this ray is then variable in a corresponding manner. The wave-suri'ace of 
 the extraordinary ray is an ellipsoid of rotation. Moreover it ordinarily 
 does not remain in the plane of incidence. 
 
 Two cases are now possible : the index (&>) of the ordinary ray may be (1) 
 greater than that of the extraordinary ray (e), in which case the velocity 01 
 the light in the direction of the vertical axis is less than that in any othei 
 direction ; or (2) a> may be less than e, and in this case the velocity of pro- 
 
 Eagation for the light has its maximum parallel to the vertical axis. The 
 ormer are called negative, the latter positive crystals. The fact alluded 
 to here should be noted that the value of the refractive index is inversely 
 proportional to the velocity of the light, or elasticity of the ether, in the 
 given direction. 
 
 Negative crystals ; Wave-surface. Forcalcite o> =1/654:, e = 1-483, it is 
 hence one of the class of negative crystals. The former value (o>) belongs 
 to the ray vibrating at right angles to the vertical axis, and the latter value 
 (e) to the ray with vibrations parallel to the axis. As has been stated, the 
 refractive index for the extraordinary ray increases from 1.483 to 1.654, as 
 the ray becomes more and more nearly 
 parallel to the vertical axis. Fig. 387 illus- 
 trates graphically the relation between the 
 two indices of refraction, and the correspond- 
 ing velocities of the rays ; ab represents the 
 direction of the vertical axis, that is, the optic 
 Also ma, mb represent the velocity 
 
 887 
 
 axis. 
 
 of the light parallel to this axis, correspond- 
 ing to the greater index of refraction (1'654). 
 The circle described with this radius will 
 represent the constant velocity of the ordi- 
 nary ray in any direction whatever. Let 
 further md, me represent the velocity of the extraordinary ray passing at 
 right angles to the axis, hence corresponding to the smaller index :>f 
 refraction (1-483). The ellipse, whose major and minor axes are cd 
 and ab, will express the law in accordance with which the velocity of the 
 extraordinary ray varies, viz., greatest in the direction md, least in the 
 direction ab in which it coincides with the ordinary ray. For any inter- 
 mediate direction, hgm, the velocity will be expressed by the length of the 
 'iue, km. 
 Now let this figure be revolved about the axis ab ; there will be geneiated 
 
138 
 
 PHYSICAL CHARACTERS OF MINERALS. 
 
 a circle within an oblate ellipsoid of rotation (f. 388). The surface of the 
 
 sphere is the wave-surface of the ordinary ray, 
 388 and that of the ellipsoid of the extraordinary 
 
 ray ; the line of their intersection is the optic 
 axis. 
 
 In f. 377, p. 147, the ray of light is shown 
 divided into two by the piece of calcite ; of 
 these, bd, which is the more refracted, is the 
 ordinary ray, and J<?, which is less refracted, is 
 the extraordinary ray. 
 
 Positive crystals ; Wave-surface. .For 
 quartz o> = 1'548, e 1*558. The index of 
 refraction for the ordinary ray (o>) is less than that of the extraordinary ray 
 (e) ; quartz hence belongs to the class of positive crystals. The value of e 
 (1*558) for the extraordinary ray corresponds to the direction of the ray at 
 right angles to the vertical axis, when its vibrations are parallel to this axis. 
 As the direction of the ray changes and becomes more and more nearly par- 
 allel to the axis, the value of its index of re- 
 fraction decreases, and when it is parallel to the 
 latter, it has the value 1-548. The extraordin- 
 ary ray then coincides with the ordinary, and 
 there is no double refraction; this is, as be- 
 fore, the line of the optic axis. The law for 
 both rays can be represented graphically in 
 the same way as for negative crystals. In 
 f. 389, amb is the direction of the optic axis; 
 let ina, tnb represent the velocity of the ordin- 
 ary ray, which corresponds to the least re- 
 fractive index (1-548), the circle afbe will 
 express the law for this ray, viz., the velocity 
 the same in every direction. Moreover, let 
 md, mo represent the velocity of the extraor- 
 dinary ray, at right angles to the axis, which corresponds to the maximum 
 refractive index (1'558) ; the ellipse, adbc, will express the law for velocity 
 of the extraordinary ray, viz., least in the direction md, and greatest in the 
 direction ab, when it is equal to that of the ordinary ray, and varying 
 uniformly between these limits. If the figure be revolved as before, thore 
 will be generated a sphere, whose surface is the wave-surface of the ordin- 
 ary ray, and within it a prolate ellipsoid w r hose surface represents the 
 wave-surface of the extraordinary ray. 
 
 The following list includes examples of both classes of uniaxial crystals : 
 
 Negative crystals ( ), 
 Calcite. 
 Tourmaline, 
 Corundum, 
 Beryl, 
 Apatite. 
 
 Positive crystals (+), 
 Quartz, 
 Zircon, 
 Hematite, 
 Apophyllite, 
 Cassiterite. 
 
 It may be remarked that in some species both + and varieties have 
 
OPTICAL CHARACTERS OF UNIAXIAL CRYSTALS. 139 
 
 been observed. Certain crystals of apophyllite are positive for one 
 end of the spectrum and negative for the other, and consequently for some 
 color between the two extremes it has no double refraction. 
 
 These principles make the explanation of the use of tourmaline plates and calcite prisxm 
 as polarizing instruments (p. 150) more intelligible. 
 
 The two rays into which the single ray is divided on passing through a uniaxial crystal are, 
 as has been said, both polarized, the ordinary ray in a plane passing through the vertical 
 axis and the extraordinary ray perpendicular to this. In a tourmaline plate of the proper 
 thickness, cut parallel to the axis c, the ordinary ray is absorbed (for the most part) and the 
 extraordinary ray alone passes through, having its vibrations in the direction of the vertical 
 axis. 
 
 In the calcite prism, of the two refracted and polarized rays, the ordinary ray is disposed of 
 artificially in the manner mentioned (p. 151), and the extraordinary ray alone passes through, 
 vibrating as already remarked, in the direction of the axis c, or, in other words, of the 
 shorter diagonal of the Nicol prism . 
 
 The relation of these phenomena to the molecular structure of the crystal is well shown 
 by the effect of pressure upon a parallelepiped of glass Glass, normally, exhibits no colored 
 phenomena in polarized light, since the elasticity of the ether is the same in ail directions, 
 and there is hence no double refraction. But if the block be placed under pressure, exerted 
 on two opposite faces, the conditions are obviously changed, the density is the same in the 
 both lateral directions but differs from that in the direction of the axis of pressure. The sym- 
 metry in molecular structure becomes that of a uniaxial crystal, and, as would be expected, 
 on placing the block in the polari scope, a black cross with its colored rings is observed, exactly 
 as with calcite. Similarly when glass has been suddenly and unevenly cooled its molecular 
 structure is not homogeneous, and it will be found to polarize light, although the phenomena, 
 for obvious reasons, will not have the regularity of the case described. 
 
 It may be added here that recent investigations by Mr. John Kerr have shown that electri- 
 city calls out birefringent phenomena in a block of glass. (Phil. Mag., 1., 337.) 
 
 Optical Investigation of Uniaxial Crystals. 
 
 Sections normal or parallel to the axis in polarized light. Suppose a 
 section to be cut perpendicular to the vertical axis (axial section), it has 
 already been shown that a ray of light passing through the crystal in this 
 direction suffers no change, consequently, such a section examined in 
 parallel polarized light, in the instrument (f. 385), appears as a section of 
 an isometric crystal. 
 
 If the same section be placed in the other instrument (f. 384, p. 152), 
 arranged for viewing the object in converging light, or in the tourmaline 
 tongs, a beautiful phenomenon is observed ; a symmetrical black cross 
 when the Nicola or tourmaline plates are crossed with a series of concentric 
 rings, dark and light, in monochromatic light, but in white light, showing 
 the prismatic colors in succession in each ring. This is shown without the 
 colors in f. 390, the arrangement of the colors in the elliptical rings of the 
 colored plate (frontispiece) is similar. 
 
 This cross becomes white when the Nicols or tourmalines are in a par- 
 allel position, and each band of color in white light changes to its comple- 
 mentary tint (f. 391). These interference figures are seen* in this form 
 only in a plate cut perpendicular to the vertical axis, and marks the uni- 
 zxial character of the crystal. 
 
 The explanation of this phenomenon can be only hinted at in this place 
 
 * Uniaxial crystals which produce circular polarization exhibit interference figures which 
 differ somewhat from those described. Some anomalies are mentioned on p. 158. See also 
 pp. 185 et seq. 
 
PHYSICAL CHARACTERS OF MINERALS. 
 
 All the rays of light, whose vibrations coincide with the vibration-planes 
 of either of the crossed Nicols, must necessarily be extinguished. This 
 gives rise to the black cross in the centre, with its arms in the direction of 
 The planes mentioned. All other rays passing through the given plate 
 obliquely will be doubly refracted, and after passing through the second 
 Nicol, thus being referred to the same plane of polarization, they will 
 
 interfere^ and will give rise to a series of concentric rings, light and dark 
 in homogeneous light, but in ordinary light showing the successive colors of 
 the spectrum. In regard to the interference of polarized rays, the fact must 
 be stated that that can take place only when they vibrate in the same plane ; 
 two rays vibrating at right angles to each other cannot interfere. These 
 interference phenomena are similar to the successive spectra obtained by 
 diffraction gratings alluded to on p. 129. It is evident that, in order to 
 observe the phenomena most advantageously, the plate must have a suitable 
 thickness, which, however, varies with the refractive index of the substance 
 The thicker the plate the smaller the rings and the more they are crowded 
 together ; when the thickness is considerable, only the black brushes are 
 seen. 
 
 Section parallel (or sharply inclined) to the axis. If a section of a uni- 
 axial crystal, cut parallel or inclined to the vertical axis, be examined in 
 parallel polarized light, it will, when its axis coincides with the direction 
 of vibration of one of the Nicol prisms, appear dark when the prisms are 
 crossed. If, however, it be revolved horizontally on the stage of the polaii- 
 scope (I, I, f. 384) it will appear alternately dark and light at intervals of 45, 
 dark under the conditions mentioned above, otherwise more or less light, the 
 maximum of light being obtained when the axis of the section makes an 
 angle of 45 D with the plane of the Nicol. Between parallel Nicols the 
 phenomena are the same except that the light and darkness are reversed. 
 When the plate is not too thick the polarized ray, after passing the upper 
 Nicol, will interfere, and in white light, the plate will show bright colors, 
 which change as one of the Nicols or the plate is revolved. 
 
 Examined in converging light, similar sections, when very thin, show in 
 white light a series of parallel" colored bands. 
 
 Determination of the indices of refraction o> and e. One prism will 
 
OPTICAL CHARACTERS OF UNIAXIAL CRYSTALS. 141 
 
 Buffice for the determination of both indices of refraction, and its edge may 
 be either parallel or perpendicular to the vertical axis. 
 
 (a) If parallel to the vertical axis, the angle of minimum deviation for 
 each ray in succession must be measured. The extraordinary ray vibrates 
 parallel to, and the ordinary ray at right angles to, the direction of the edge 
 of the prism. For convenience it is better to isolate each of the rays in 
 succession, which is done with a single Nicol prism. If this is held before 
 the observing telescope with its shorter diagonal parallel to the refracting 
 edge of the prism, the ordinary ray will be extinguished and the image of 
 the slit observed will be that due to the extraordinary ray. If held with its 
 plane of vibration at right angles to the prismatic edge, the extraordinary 
 ray will be extinguished and the other alone observed. From the single 
 observed angle, for the given color, the index of refraction can be calculated, 
 &> or e, by the formula given on p. 128, the angle of the prism being known. 
 
 (b) If the refracting edge of the prism is perpendicular to the vertical 
 axis of the crystal, the same procedure is necessary, only in this case the 
 ordinary ray will vibrate parallel to the prismatic edge, and the extraordi- 
 nary ray at right angles to it. The two rays are distinguished, as before, by 
 a Nicol prism. 
 
 Determination of the positive or negative character of the double refrac- 
 tion. The most obvious way of determining the character of the double 
 refraction (to > e or co > e) is to measure the indices of refraction in accord- 
 ance with the principles explained in the preceding paragraphs. It is not 
 always possible, however, to obtain a prism suitable for this purpose, and in 
 an} 7 case it is convenient to have a more simple method of accomplishing 
 the result. 
 
 To do this, use may be made of a very simple principle : the + or 
 character of a given crystal is determined by observing the effect produced 
 when an axial section from it is combined in the polariscope with that of a 
 crystal of known character. 
 
 For instance, calcite is negative, and if it be placed in conjunction with 
 the section of a positive crystal, the whole effect observed is the same as that 
 which would be produced if the original plate were diminished in thickness, 
 while, if combined with a negative crystal, it is as if the plate were made 
 thicker. It has already been remarked that, as the axial plate of a crystal 
 increases in thickness, the number of rings visible in the field of the polari- 
 scope increases, and they become more crowded together ; but, if the section 
 is made thinner, the successive rings widen out and become less numerous. 
 One or the other of these effects is produced by the use of the intervening 
 section. 
 
 In the case of uniaxial crystals, however, the method which is practically 
 most simple is that suggested by Dove the use of an axial plate of mica of 
 a certain thickness. The section required is a cleavage piece of such a 
 thickness that the two rays in passing through suffer a difference of phase 
 which is equal to a quarter wave-length, or an odd multiple of this. 
 
 Suppose that the section of the crystal to be examined, cut perpendicular 
 to the axis, is brought between the crossed Nicols in the polariscope ; the 
 black cross and the concentric colored rings are of course visible. Let now, 
 while the given section occupies this position, the mica plate be placed upon 
 it, with the plane of its optic axes (determined beforehand, and the direction 
 
142 PHYSICAL CHARACTERS OF MINERALS. 
 
 marked by a line for convenience) making an angle of 45 with the vibra- 
 tion-planes of the ]^icols ; the black cross disappears and there remain only 
 two diagonally situated dark spots in the place of it. Moreover, the colored 
 curves in the two quadrants with these spots are pushed farther away from 
 the centre than the others. The effect produced is represented in f. 392 
 and f. 393. If the line joining these two dark spots stands at right angles 
 
 to the axial plane of the mica, the crystal is positive (f. 392), if this line 
 coincides with the axial plane, the crystal is negative (f. 393). The explana- 
 tion of this eff'v-t is not so simple as to allow of being introduced here ; the 
 effect of the mica is to produce circular polarization of the light which it 
 transmits. 
 
 With both uniaxtal and biaxial crystals the student will find it of great assistance always 
 to have at his side a good section of a positive and a negative crystal. By comparing the 
 phenomena observed in the section under examination with those shown by crystals of known 
 character, he will often be saved much perplexity. 
 
 For the investigation of the absorption phenomena of uniaxial crystals 
 see p. 165. 
 
 CIRCULAR POLARIZATION. 
 
 In what has been said of polarized light, in the preceding pages, it has 
 been assumed that a polarized ray was one whose vibrations took place in 
 a single plane, so that the plane of polarization at ri^ht angles to this was a 
 fixed plane. Such a ray is said to be linearly polarized. There are some 
 uniaxial crystals, however, which have the power to rotate the plane of polari- 
 zation ; the ray is said to be circularly polarized. They manifest this in the 
 phenomena observed when an axial section is examined in the polariscope. 
 
 An axial section of a nniaxial crystal normally exhibits, in converging 
 
 r)larized light, a black cross with a series of concentric colored circles, 
 390, p. 140. If, however, a section of quartz be cut perpendicular to the 
 axis and viewed between the crossed Nicols, the phenomena observed are 
 different from tl.ese: the central portion of the black cross has disap- 
 peared, and instead, the space within the inner ring is brilliantly colored. 
 Furthermore, when the analyzing Nicol is revolved, this color changes 
 from blue to yellow to red, and it is found that in some cases this 
 
CIRCULAR POLARIZATION. 143 
 
 change is produced by revolving the Nicol to the right, and in other cases 
 to the left. To distinguish between these the first are called right-handed 
 rotating crystals, and the others left-handed. The relations here involved 
 will be better understood if the quartz section is viewed in parallel mono- 
 chromatic light. Under these circumstances a similar plate of calcite 
 appears dark when the Nicols are crossed, but with quartz the maximum 
 darkness is only obtained when the analyzer has been revolved beyond its 
 first position a certain angle ; this angle increasing with the thickness of 
 the section, and also varying with the color of the light employed. 
 
 For a section 1 mm. thick in red light, a rotation of the analyzer of 19 
 is required to produce the maximum darkness. For yellow light the 
 rotation is 24 with a plate of the same thickness ; with blue, 32, and so on. 
 The rotation of the analyzer with some crystals is to the right, with others 
 to the left. 
 
 The explanation of these facts lies in the fact stated above, that the 
 quartz rotates the plane of vibration of the polarized light, and the angle of 
 rotation is different for rays of different wave-lengths. Furthermore, this 
 rotation of the plane of vibration results from the fact that in quartz, even 
 in the direction of its axis, double refraction takes place. The oscillations 
 of the particles of ether take place not in straight lines but in circles, and 
 they move in opposite directions for the two rays, ordinary and extraor- 
 dinary. 
 
 An axial section of a quartz crystal can never appear dark between 
 crossed Nicols in ordinary light, since there is no point at which all the 
 colors are extinguished ; on the contrary, it appears highly colored. The 
 color depends upon the thickness of the section, and is the same as that 
 observed in the centres of the rings in converging polarized light. If sec- 
 tions of a right-handed and left-handed crystal are placed together in the 
 polariscope, the centre of the interference figure is occupied with a four- 
 rayed spiral curve, called from the discoverer Airy's spiral. Twins of 
 quartz crystals are not uncommon, consisting of the combination of right- 
 and left-handed individual, which sometimes show the spirals of Airy. 
 
 It is a remarkable fact, discovered by Herschel, that the right- or left- 
 handed optical character of quartz is often indicated by the position of the 
 trapezohedral planes on the crystals. When a given trapezohedral plane 
 appears as a modification of the prism, to the right above and left below, 
 the crystal is optically right-handed ; if to the left above and right below, 
 the crystal is left-handed. In f . 394 the plane is, as last remarked, left above 
 and right below, and the crystal is hence left-handed. Cinnabar has been 
 shown by Des Cloizeaux to possess the same property as quartz; and this is 
 true also of some artificial salts, also solutions of sugar, etc. 
 
 In twins of quartz, the component parts may be both right-handed or 
 both left-handed (as in those of Dauphiny and the Swiss Alps) ; or one may 
 be of one kind and the other of the other. Moreover, successive layers of 
 deposition (made as the crystal, went on enlarging, and often exceedingly 
 thin) are sometimes alternately right- and left-handed, showing a constant 
 oscillation of polarity in the course of its formation ; and, when this is the 
 case, and the layers are regular, cross-sections, examined by polarized light, 
 exhibit a division, more or less perfect, into sectors of 120, parallel to the 
 plane /?, or intc sectors of 6u. If the layers are of unequal thickness 
 
144 
 
 PHYSICAL CHARACTERS OF MINERALS. 
 
 there are broad areas of colors without sectors. In f. 395 (by Des Cloizeaux. 
 from a crystal from the Dept. of the Aude), half of each sector of 60 is 
 
 395 
 
 -i 
 
 right-handed, and the other half left (as shown by the arrows), and the dark 
 radii are neutral bands produced by the overlapping of layers of the twc 
 kinds. These overlapping portions often exhibit the phenomenon of Airy'e 
 spiral. 
 
 0. BIAXIAL CRYSTALS. 
 General Optical Character. 
 
 As in the crystalline systems, thus far considered, so also in the anisome- 
 tric systems, the orthorhombic, monoclinic, and triclinic, there is a strict corre- 
 spondence between the molecular structure, as exhibited in the geometrical 
 form of the crystals, and their optical properties. In the crystals of these 
 systems there is no longer one axis around about which the elasticity of the 
 light-ether, that is, the velocity of the light, is everywhere alike. On the 
 contrary, the relations are much less simple, and less easy to comprehend. 
 There are two directions in which the light passes through the crystal 
 without double refraction these are called the optic axes, and hence the 
 crystals are biaxial but in every other direction a ray of light is separated 
 
 into two rays, polarized at right angles to 
 each other. Neither of these conforms to 
 the law of simple refraction. The subject 
 was first developed theoretically by Fresnel, 
 r and his conclusions have since been fully 
 
 j^"* 8 verified by experiment. 
 
 -A Axes of elasticity. In regard to the 
 
 elasticity of the ether in a biaxial crystal 
 there are %(1) a maximum value, (2) a 
 minimum value, and (3) a mean value, and 
 these values in the crystal are found in 
 directions at right angles to each other. 
 In f. 396, GO 1 represents the axis (c) of least elasticity, A A' of greatest 
 elasticity (a), and BB' of mean elasticity (b). A ray passing in the direo- 
 
 A'. 
 
 c f 
 
OPTICAL CHARACTERS OF BIAXLAL CRYSTALS. 
 
 145 
 
 Hon CO' vibrates in a plane at right angles, that is, parallel to BB' and 
 AA'. Similarly for the ray BB' the vibrations are parallel to AA' and 
 CO', and for the ray AA' parallel to BB' and CO'. Between these 
 extreme values of the axes of elasticity, the elasticity varies according to a 
 regular law, as will be seen in the following discussion. The form of the 
 wave-surface for a biaxial crystal may be determined by fixing its form 
 for the planes of the axes a, b, and c. 
 
 Wave-surface. First consider the case of rays in the plane of the axe* 
 BB' and CC' (f. 397X A ray pass- 
 ing in the direction BB' is separated 397 
 into two sets of vibrations, one paral- 
 lel to A A', corresponding to the 
 greatest elasticity, moving more 
 rapidly than the other set, parallel 
 to CC', which correspond to the 
 least elasticity. The velocities of the 
 two sets of vibrations are made pro- 
 portional to the lengths of the lines 
 mn, and mo respectively, in f. 397. 
 Again, for a ray in the same plane, 
 parallel to CC', the vibrations are 
 (1) parallel to AA', and propagated 
 faster (greatest elasticity) than the 
 other set; (2) parallel to BB' (mean 
 elasticity). Again, in f. 397, on the 
 line CO', mn", and mq" are made 
 proportional to these two velocities ; 
 here mn = mn" ^ and for a ray in the 
 same plane in any other direction, there will be one set of vibrations 
 parallel to AA', with the same velocity as before, and another set at right 
 angles with a velocity between mo and mq", determined by the ellipse 
 whose semi-axes are proportional to the 
 mean and least axes of elasticity. 
 
 Fig. 397 then represents the section of 
 the wave-surface through the axes CO' 
 and BB'. The circle nn" shows the 
 constant velocity for all vibrations par- 
 allel to A A', and the ellipse the variable 
 values of the velocity for the other set of 
 vibrations at right angles to the first. 
 
 Again, for a ray in the plane A A', 
 BB', the method of the construction 
 is similar. The vibrations will in every 
 case take place in the plane at right 
 angles to the direction of the ray, which 
 plane must always pass through the axis 
 CC' of least elasticity. Hence for every 
 direction of the ray in the plane men- 
 tioned, one set of vibrations will always 
 be parallel to CC', and hence be propagated with a constant velocity 
 10 
 
146 
 
 PHYSICAL CHARACTERS OF MINERALS. 
 
 = mo', f . 398), and hence this is expressed by the circle oo'. The other set 
 of vibrations will be at right angles to CC', and the velocity with which 
 they are propagated will vary according as they are parallel to A A 
 (= mn, f. 398), "or parallel to BB' (= mq'), or some intermediate value for 
 an intermediate position. The section of the wave-surface is consequently 
 a circle within an ellipse. 
 
 Finally, let the ray pass in some direction in the plane CC', A A, of least and 
 greatest elasticity, the section of the wave-surface is also a circle and ellipse. 
 
 Suppose the ray passes in the direction 
 
 Sarallel to AA, the vibrations will be 
 L) parallel to CC', and (2) parallel to 
 BB', those (1) parallel to CC' (least axis 
 of elasticity) are propagated more slowly 
 than those (2) parallel to BB (axis of 
 mean elasticity). In f. 399, on the line 
 AA' , lay off mo and mq' proportional to 
 these two values. 
 
 Again, for a ray parallel to CC' the 
 vibrations will take place (1) parallel to 
 AA, and (2) parallel to BB', the former 
 will be propagated with greater velocity 
 than those latter. These two values of 
 the velocity in the direction CC' are 
 represented by mn" and mq" (= mq'). 
 For any intermediate position of the ray 
 in the same plane there will always be 
 one set of vibrations parallel to BB' 
 (mq f = mq", f. 399, hence the circle). The other set at right angles to these 
 
 will be propagated with a velocity va- 
 rying according to the direction, from 
 that corresponding to the least axis 
 of elasticity (represented by mo' , f . 399), 
 to that of the greatest axis of elasticity 
 
 f 
 
 Optic axes. It is seen that the cir- 
 cle, representing the uniform velocity 
 of vibrations parallel to b, and the 
 ellipse representing the varying value 
 of the velocity for the vibrations at 
 right angles to these, intersect one an- 
 other at P, P', f. 399. The obvious 
 meaning of this fact is that, for the 
 directions mP, and mP', making 
 equal angles with the axis CC', the 
 velocity is the same for both sets of 
 vibrations ; these are not separated 
 from each other, the ray is not doubly 
 refracted, and not polarized. 
 These two directions are called the OPTIC AXES. All anisometric crj stale 
 have, as has been stated, two optic axes, and are hence called biaxial. 
 
OPTICAL CHARACTERS OF BIAXIAL CRYSTALS. 147 
 
 The complete wave-surface of a biaxial crystal is constructed from the 
 three sections given in f. 397, 398, 399. It is shown graphically in f. 400, 
 where the lines PP, and P' P' are the two optic axes. 
 
 Bisectrices^ or Mean-lines. As shown in f . 399, the optic axes always lie 
 in the plane of greatest (a) and least (c) elasticity, and the value of the optic 
 axial angle is known when the axes of elasticity are given as stated below. 
 The axis of elasticity which, as the line 6 y 6", f. 399, bisects the acute angle 
 is called the acute bisectrix, or first nwan-line (erste Mittellinie, Germ.), and 
 that bisecting the obtuse angle, the obtuse bisectrix, or second mean-line 
 (zweite Mittellinie, Gen/i.). 
 
 Positive and negative crystals. When the acute bisectrix is the axis of 
 least elasticity (c), it is said to be positive, and when it is the axis of greatest 
 (a) elasticity, it is said to be negative. Barite is positive, mica negative. 
 
 Indices of refraction. It has been seen that in uniaxial crystals there 
 are two extreme values for the velocity with which light is propagated, and 
 corresponding to them, and inversely proportional to them, two indices of 
 refraction. Similarly for biaxial crystals, where there are three axes of elasti- 
 city, there are three indices of refraction a maximum index a, a minimum 7, 
 and a mean value /3 ; a is the index for the rays propagated at right angles 
 to a, but vibrating parallel to a ; is the index for rays propagated perpen- 
 dicularly to b, by vibrations parallel to b ; 7 is the index for rays propagated 
 
 perpendicularly to c, but vibrating parallel to c- a =,=, y = . 
 
 u b 
 
 If a, ft, and 7 are known, the value of the optic axial angle (2 V) can be 
 calculated from them by the following formula : 
 
 cos = 
 
 dispersion of the optic axes. It is obvious that the three indices oi 
 refraction may have different values for the different colors, and as the angle 
 of the optic axes, as explained in the last paragraph, is determined by these 
 three values, the axial angle will also vary in a corresponding manner. 
 
 This variation in the value of the axial angle for rays of different wave 
 lengths is called the dispersion of the axes, and the two possible cases are 
 distinguished by writing p > v when the angle for the red rays (p) is greater 
 than for the blue (violet, v), and p < v when the reverse is true. 
 
 In the properties thus far mentioned, the three systems are alike ; in 
 details, however, they differ widely. 
 
 Practical Investigation of Biaxial Crystals. 
 
 Interference figures. A section cut perpendicular to either axis will 
 show, in converging polarized light, a system of concentric rays analogous 
 to those of uniaxial crystals, f. 390, but more or less elliptical. There is, 
 moreover, no black cross, but a single black line, which changes its position 
 as the Nicols are revolved. 
 
148 PHYSICAL CHARACTERS OF MINERALS. 
 
 If a section of a biaxial crystal, cut, perpendicularly to the first, that ifc 
 acute, bisectrix, is viewed in the polariscope, a different phenomenon is 
 observed. 
 
 There are seen in this case, supposing the plane of the axes to make an angle 
 of 45 with the planes of polarization of the crossed Nicols, two black hyper- 
 b^las, marking the position of the axes, a series of elliptical curves surround:- 
 ing the two centres and finally uniting, forming a series of lemniscates. 
 If monochromatic light is employed, the rings are alternately light and 
 dark ; if white light, each ring shows the successive colors of the spectrum. 
 If one of the Nicol prisms be revolved, the dark hyperbolic brushes gradu- 
 ally become white, and the colors of the rings take the complementary tints 
 after^ a revolution of 90. Since the black hyperbolic brushes mark the 
 position of the optic axes, the smaller the axial angle the nearer together 
 are the hyperbolas, and when the angle is very small, the axial figure 
 
 observed closely resembles the simple cross of a uniaxial crystal. On the 
 other hand, when the axial angle is large the hyperbolas are far apart, and 
 may even be so far apart as to" be invisible in the field of the polariscope. 
 
 When the plane of the axes coincides with the plane of vibration foi 
 either Nicol, these being crossed, an unsymmetrical black cr>ss is observed, 
 and also a series of elliptical curves. Both these figures are well exhibited 
 on the frontispiece ; the one gradually changes into the other as the 
 crystal-section is revolved in the horizontal plane, the Nicols remaining 
 stationary. 
 
 A section of a biaxial crystal cut perpendicular to the obtuse bisectrix 
 will exhibit the same figures under the same conditions in polarized light, 
 when the angle is not too large. This is, however, generally the case, and 
 in consequence the axes suffer total reflection on the inner surface of the 
 section, and no axial figures are visible. This is sometimes the case also 
 
OPTICAL CHARACTERS OF BIAXIAL CRYSTALS. 
 
 119 
 
 with a section cut normal to the acute bisectrix, when the angle is large. 
 A micrometer scale in the polariscope, f. 384, allows of an approximate 
 measurement of the axial angle ; the value of each division of the scale 
 being known. 
 
 Measurement of the axial angle* The determination of the angle made 
 by the optic axes is of the highest importance, and the method of proce- 
 dure offers no great difficulties. Fig. 401 shows the instrument recom- 
 mended for this purpose by DesCloizeaux ; its general features will be 
 understood without detailed description ; some improvements have been 
 introduced by Groth, which make the instrument more accurate and con- 
 venient of use. The section of the crystal, cut at right angles to the bisec- 
 trix, is held in the pincers at c, with the plane of the axes horizontal, 
 making an angle of 45 with the plane of vibration of the Nicols (NN). 
 There is a cross- wire in the focus of the eye-piece, and as the pincers hold 
 ing the section are turned by the screw F, one of the axes, that is one black 
 hyperbola, is brought in coincidence with 
 the vertical cross-wire, and then, by a 
 further revolution of F, the second. The 
 angle which the section has been turned 
 from one axis to the second, as read oif 
 at the vernier H on the graduated circle 
 above, is the apparent angle for the axes 
 of the given crystal as seen in the air 
 (aca, f. 402). It is only the apparent 
 angle, for, owing to the refraction suffered 
 on passing from the section of the crystal 
 to the air, the true axial angle is more 01 
 less increased, according to the refractive 
 index of the given crystal. 
 
 This being understood, the fact already 
 stated is readily intelligible, that when the axial angle exceeds a certain 
 limit, the axes will suffer total reflection (p. 128), and they will be no longer 
 visible at all. When this is the case, oilf or some other medium with high 
 refractive power is made use of, into which the axes pass when no longer 
 visible in the air. In the instrument described a small receptacle holding 
 the oil is brought between the tubes, as seen in the figure, and the pincers 
 holding the section are immersed in this, and the angle measured as before. 
 
 In the majority of cases it is only the acute axial angle that it is practi- 
 cable to measure ; but sometimes, especially when oil is made use of, the 
 obtuse angle can also be determined from a second section normal to the 
 obtuse bisectrix. 
 
 If E = the apparent semi-axial angle in air (f. 402). 
 j H a = the apparent semi-acute angle in oil. 
 ( H = " ' " obtuse " " " 
 
 V a = the real (or interior) semi-acute angle (f. 402). 
 V = u " " " semi-obtuse " (f. 402). 
 n = index of refraction for the oil. 
 ft = the mean refractive index for the given crystallized substance. 
 
 * See further on p. 180. 
 
 4- Almond oil which has been decolorized by exposure to the light, is commonly employed. 
 
150 PHYSICAL CHARACTERS OF MINERALS. 
 
 sin E = n sin H a ; sin V a = sin H a ; sin V = -= sin H . 
 
 
 
 These formulas give the true interior angle from the measured apparent 
 angle when the mean refractive index (ft) is known. 
 
 If, however, it is possible to measure both the acute and obtuse apparent 
 angles, the true angle, and also the value of ft, can be determined from 
 them. For sin V = cos V a , hence : 
 
 sin H n sin E 
 sin V n ' 
 
 a 
 
 In measuring this angle, if white light is employed, the colors being 
 separated, the position of the hyperbolas is a little uncertain ; hence it is 
 always important to measure the angle for monochromatic light, red and 
 yellow and blue particularly. This is especially essential where the disper- 
 sion of the axes is considerable. 
 
 Determination of the indices of refraction* The values of the three 
 indices of refraction, a, ft, 7, for biaxial crystals, may be determined from 
 three prisms cut with their refracting edges parallel respectively to the 
 three axes of elasticity o, b, and c. In each case, after the angle of the 
 prism has been measured, the angle of minimum deviation must be meas- 
 ured for that one of the two refracted rays whose vibrations are parallel 
 to the edge of the prism ; the formula of p. 128 is then employed. 
 
 It is possible, however, to obtain the values of a, ft, and 7 with (wo 
 prisms ; in this case one of the prisms must be so made that its vertical edge 
 is parallel to one axis of elasticity, while the line bisecting its refracting 
 angle at this edge is parallel to a second. In the case of such a prism the 
 minimum deviation of the ray is obtained for both rays, that having its 
 vibrations parallel to the prism-edge, and that vibrating at right angles to 
 this, that is parallel to the bisector of the prismatic angle. 
 
 Of the three indices of refraction, ft is one which it is most important to 
 determine, since by means of it, in accordance with the above formulas, 
 the true value of the axial angle can be calculated from its apparent value 
 in air. The prism to give the value of ft should obviously have its refract 
 ing edge parallel to the mean axis of elasticity b, that is at right angles to 
 the plane of the optic axes. 
 
 Determination of the positive or negative character of biaxial crystals. 
 The question of the positive or negative character of a biaxial crystal is 
 determined from the values of the indices of refraction, where these can be 
 obtained. If c, the axis of least elasticity, is the acute bisectrix, the crystal 
 is optically positive ; if a, the axis of greatest elasticity, is the acute bisec- 
 trix, the crystal is optically negative ; in the former case the value of b is 
 nearer that of c than of a, in the second case the reverse of this is true. 
 
 There is, however, a more simple method of solving the problem, as was 
 remarked also in regard to uniaxial crystals. The methods are similar. 
 
 The quarter-undulation mica plate may be employed just as with uniaxiaJ 
 crystals, but its use is not very satisfactory excepting when the axial diver- 
 gence is quite small. In this case it can be employed to advantage, the 
 
 "- See further on pp. 177 et seq. 
 
DISTINGUISHING OPTICAL CHARACTERS OF OETHOKHOMBIC CRYSTALS. 151 
 
 plane of the axes of the crystal investigated being made to coincide with 
 the vibration-plane of one of the Nicols. The more general' method is the 
 employment of a wedge-shaped piece of quartz ; this is so cut that one sur- 
 face coincides with the direction of the vertical axis, and the other makes 
 an angle of 4 to 6 with it. By this means a section of varying thickness is 
 obtained. The section to be examined normal to the acute bisectrix is 
 brought between the crossed Nicols of the polariscope (f. 384), and with its 
 axial plane making an angle of 45 with the polarization-plane of the 
 JNicol prisms ; that is, so that' the black hyperbolas are visible. The quartz 
 wedge is now introduced slowly between the section examined and the 
 analyzer; in the instrument figured a slit above gives an opportunity to 
 insert it. The quartz section is introduced first, in a direction at right 
 angles to the axial plane, that is, to the line joining the hyperbolas, of the 
 plate investigated ; and second, parallel to the axial plane, that is, in the 
 direction of the line joining the hyperbolas. In one direction or the other 
 it will be seen, when the proper thickness of the quartz wedge is reached, 
 that the central rings appear to increase in diameter, at the same time 
 advancing from the centre to the extremities. 
 
 The effect, in other words, is that which would have been produced by 
 the thinning of the given section. If the phenomenon is observed in the 
 first case when the axis of the quartz is parallel to the axial plane, that is 
 to the obtuse bisectrix, it shows that this bisectrix must have an opposite 
 sign to the quartz, that is, the obtuse bisectrix is negative, and the acute 
 bisectrix positive. If the mentioned change in the interference figures 
 takes place when the axis of the quartz is at right angles to the axial plane, 
 then obviously the opposite must be true and the acute bisectrix is negative. 
 
 The same effect may be obtained by bringing an ordinary quartz section 
 of greater or less thickness, cut normal to the axis, between the analyzer and 
 the crystal examined, and then inclining it, first in the direction of the 
 axial plane, and again at right angles to it. The method of investigation 
 with the quartz wedge can be applied even in those cases where the axial 
 angle is too large to appear in the air. 
 
 For the investigation of the absorption phenomena of biaxial crystals, 
 see p. 165. 
 
 DISTINGUISHING OPTICAL CHARACTERS OP ORTHORHOMBIC CRYSTALS. 
 
 In the Orthorhomlic System, in accordance with the symmetry of the 
 crystallization, the three axes of elasticity coincide with the three crystallo- 
 graphic axes. Further than this, there is no immediate relation between 
 the two sets of axes in respect to magnitude, for the reason that, as has been 
 stated, the choice of the crystallographic axes is arbitrary, and has been 
 made, in most cases, without reference to the optical character. 
 
 Schrauf has proposed that the crystallographic vertical axis (c) should be 
 always made to coincide with the acute bisectrix, which would be very 
 desirable, especially, as urged by him, in showing the true relations between 
 the orthorLombic and hexagonal systems. Of course, this suggestion can 
 be carried out only in those species in which the optical character is known. 
 
 Schrauf (Phys. Min., p. 302, 303) has shown there is a close analogy between certain 
 
152 
 
 PHYSICAL CHARACTERS OF MINERALS. 
 
 orthorhombic crystals whose prismatic angle is near 120 (compare remarks on twins, p 96; 
 and the crystals of the hexagonal system. With these the acute bisectrix is uniformly parallel 
 to the prismatic edge, and normal to the six-sided basal plane, analogous to the one optic axis ot 
 true hexagonal forms. Moreover, he shows that the nearer the prismatic angle approaches 
 120, the less the difference between the three axes of elasticity, and the nearer the approach 
 to the uniaxial character. 
 
 By the combination of thin plates of a biaxial mica optical phenomena may, under some 
 conditions, be observed in polarized light which are similar to those shown by uniaxial crys- 
 tals. Similarly twins of chrysoberyl (p. 97) have been described which in spots gave the 
 axial image of uniaxial crystals. This subject has been investigated by Reusch (Pogg. 
 cxxxvi., 626, 637, 1869), and later by Cooke (Am. Acad. Sci., Boston, p, 35, 1874). 
 
 Practical Optical Investigation of OrtJwrhombic Crystals. 
 
 Determination of the plane of the optic axes. The position of the 
 three axes of elasticity in an orthorhombic crystal is always known, since 
 they must coincide with the crystallographic axes ; but the plane of the optic 
 axes, that is, of the axes of greatest (a) and least (c) elasticity, must in each 
 case be determined. This plane will be parallel to one of the three diame- 
 tral or pinacoid planes. In order to determine in which the axes lie, it is 
 necessary to cut sections parallel to these three directions ; one of these three 
 sections will in all ordinary cases show, in converging polarized light, the 
 interference figures peculiar to biaxial crystals. It is evident, too, that two 
 of the three sections named determine the character of the third, so that 
 the plane of the optic axes and the position of the acute bisectrix can be in 
 practice generally told from them. 
 
 Measurement of the axial angle, p *. v. From the section showing the 
 axial figures, that is, normal to the acute bisectrix, the axial angle can be 
 measured in the manner which has been described (p. 149). If it is prac- 
 ticable to determine also the obtuse axial angle, from a second section nor- 
 mal to the obtuse bisectrix, it will be possible to calculate the true axial 
 angle from these data, and also the mean index of refraction (0). 
 
 There is further to be determined the dispersion of the axes. Whether 
 
 the axial angle for red rays is greater or 
 less than for blue (p > v, or p < v) can be 
 seen immediately from the figure of the 
 axes, as in f. 1, 15, in the colored plate, 
 (frontispiece). It is obviously true in this 
 case, from f. la, as also f. 15, that the angle 
 for the blue rays is greater than that for 
 the red (p < v), and so in general. This 
 same point is also accurately determined, 
 of course, by the measured angle for the 
 two monochromatic colors. 
 
 In all cases the same line will be the 
 bisectrix of the axial angle for both blue 
 and red rays, so that the position of the 
 respective axes is symmetrical with refer- 
 ence to the bisectrix. In f. 403, the dis- 
 persion of the axes is illustrated, where p < v ; it is shown also that the 
 lines, IP IP and .Z? 2 ^, bisect the angles of both red (pOp) and blue 
 (vOv') rays. It also needs no further explanation that fora certain relatioD 
 
DISTINGUISHING OPTICAL CHARACTERS OF MONOCLINIC CRYSTALS. 
 
 153 
 
 >f the refractive indices of the different colors, the acute bisectrix of the 
 axial angle for red rays may be the obtuse bisectrix for the angle for blue 
 rays. 
 
 Indices of refraction, etc. The determination of the indices of refrac- 
 tion and the character (-1- or ) of the acute bisectrix is made for ortho- 
 rhombic crystals in the same way as for all biaxial crystals (p. 150). It is 
 merely to be mentioned that, since the axes of elasticity always coincide 
 with the crystallographic axes, it will happen not infrequently that crystals 
 without artificial preparation will furnish, in their prismatic or dome series, 
 prisms whose edges are parallel to the axes of elasticity, and consequently 
 at once suitable for the determination of the indices of refraction. 
 
 DISTINGUISHING OPTICAL CHARACTERS OP MONOCLINIC CRYSTALS. 
 
 Position of the axes of elasticity. In crystals belonging to the mono- 
 clinic system one of the axes of elasticity always coincides with the ortho- 
 diagonal axis &, and the other two lie in the plane of symmetry at right 
 angles to this axis. Here obviously three cases are possible, according 
 to which two of the axes, a, b, or c, lie in the plane of symmetry. 
 
 Corresponding to these three positions of the axes of elasticity, there may 
 occur three kinds of dispersion of these axes, or dispersion of the bisectrices. 
 This dispersion arises from the fact that, while the position of one axis of 
 elasticity is always fixed, the position of the other two is indeterminate and 
 for the same crystal may be different for the different colors, so that the 
 bisectrices of the different colors may not coincide. 
 
 Uispersion of the bisectrices. 1. The bisectrices, that is, the axes of 
 greatest and least elasticity, lie in the plane of sym- 
 metry, while the orthodiagonal axis b coincides with b. 
 The optic axes here suffer a dispersion in this plane 
 of symmetry, and, as already stated, they do not lie 
 symmetrically with reference to the acute bisectrix. 
 "This is illustrated in f. 404, where MM is the bisec- 
 trix for the angle, vOv', and BB for the angle pOp'. 
 This kind of dispersion is called by DesCloizeaux 
 inclined (dispersion inclinee). 
 
 2. The second case is that where the plane of the 
 optic axes is perpendicular to the plane of symmetry, 
 and the acute bisectrix stands at right angles to the 
 orthodiagonal axis b. In other words, the acute 
 bisectrix and the axis of mean elasticity both lie in 
 the plane of syinmetry. In this case also dispersion 
 of the axes may take place, and in this way the 
 
 plane of the optic axes for all the colors lies parallel to the orthodiagonal, 
 but these planes may have different inclinations to the ve *tical axis. This 
 is called horizontal dispersion by DesCloizeaux. 
 
 3. Still again, in the third place, the plane of the optic axes lies perpen 
 iicular to the plane of symmetry ; but in this Case the acute bisectrix is 
 parallel to the crystallographic axis b, so that the obtuse bisectrix and axis 
 of mean elasticity lie in the plane of symmetry. The dispersion which 
 
 P' 
 
154 
 
 PHYSICAL CHARACTERS OF MINERALS. 
 
 results in this case is called by DesCloizeaux crossed (dispersion tournante 
 or eroisee). 
 
 Dispersion as shown in the interference figures. If an axial section 
 of a monoclinic crystal be examined in converging polarized light, the kind 
 of dispersion which characterizes it will be indicated by the nature of the 
 interference figures observed ; the three cases are illustrated by the figures 
 upon the frontispiece, taken from DesCloizeaux. (frontispiece). 
 
 Figs. 1#, Ib represent the interference figures for an orthorhombic crystal 
 (nitre), characterized by the symmetry in the size of the rings, and the 
 distribution of the colors. Figs. 2a, 25 (diopside), 3<z, 3b (orthoclase), 4&, 4 
 (borax), are examples of the corresponding figures for monoclinic crystals, 
 characterized as such more or less distinctly by the want of symmetry in 
 the size of the rings about the two axes, and the irregularity in the arrange- 
 ment of the colors. 
 
 (1) Inclined dispersion. Where the axes are not symmetrically situated 
 with reference to the acute bisectrix. The relation of the two axial figures 
 is illustrated by f. 405. In f. 2#, 2b this kind of dispersion is indicated by 
 
 405 
 
 the position of the red and blue at the centres of the rings, and on the 
 borders of the hyperbolas, compare f. 1#, \b of the normal figure, where 
 there is no dispersion of the bisectrices. 
 
 (2) Horizontal dispersion, where the planes of the optic axes for the 
 different colors make different angles with the axis. This is illustrated by 
 f. 406. The effect upon the interference figures is seen in f. 3#, 3b of the 
 plate, by comparing the colors within the rings (f. 3#), and on the borders 
 of the hyperbolas (f. 3b), with f. la, Ib. 
 
 (3) Grossed dispersion, where the acute bisectrix coincides with the 
 crystallographic axis b. This is illustrated in f. 407, and the interference 
 figures belonging to this kind of dispersion are seen in f. 4a, 4b of the plate, 
 compared as before with 1#, 1&, and with the other figures. 
 
 Practical Optical Investigation of Monoclinic Crystals. 
 
 Determination of the position of the axes of elasticity, tf^at is, the direc- 
 tions of vibration. Stauroscope. The position of one axis of elasticity is 
 alone known, since, as has been stated, it coincides with the crystallographic 
 axis b. In order to determine the position of the other axes in the plane of 
 symmetry, where they necessarily lie, use is made of an instrument, first 
 proposed by von Kobell, called the STAUROSCOPE. The principle of this 
 instrument is very simple. Suppose that the two Nicols in the polari- 
 Bcope (f. 385) have their planes of polarization crossed, causing the maxi- 
 mum extinction of light. Now, if a section of any biaxial crystal is brought 
 
DISTINGUISHING OPTICAL CHARACTERS OF MONOCLINIO CRYSTALS. 155 
 
 between them, obviously, if the position of its two rectangular axes of 
 elasticity, which are its two directions of vibration, coincide with those of 
 the two Nicols, it will produce no change in appearance : the field of the 
 polariscope, which was dark before, remains dark. But suppose, on the 
 other hand, that it is placed in any other position ii, the plane, so that its 
 two rectangular directions of vibration do not coincide with those of the 
 Nicols, the field is no longer dark, but more or less light. The reason foi 
 this is, that the light from the lower Nicol meeting the crystal plate is 
 separated, according to the law of the parallelogram of forces, into two sets 
 of vibrations, which are again resolved by the analyzing Nicol, and only one 
 set extinguished by it. If, however, the plate be gradually changed in posi- 
 tion, that is, revolved horizontally, until its vibration-directions (axes of 
 elasticity) coincide with those of the Nicols, then, as at first, the light is ex- 
 tinguished. If the angle is measured which it is necessary to revolve the 
 section to accomplish the result just remarked, that will be the angle be- 
 tween the direction of one of the axes of elasticity'of the plate in its original 
 position and the vibration-plane of the Nicol. 
 
 In figure 408, let the two larger rectangular arrows represent the vibration- 
 directions for the two Nicols, and between the two 
 prisms suppose a section of a monoclinic crystal, 408 
 
 abed, to be placed so that one edge of a known crys- 
 tallographic plane (<?<?., i-i) coincides with one of 
 these lines. The field of the microscope, dark before, 
 since the prisms were crossed, is no longer so, and 
 becomes dark again, as explained, only when the 
 crystal is revolved so that its vibration-directions 
 (the smaller dotted arrows) coincide with those of d ,- 
 the Kicols, which is indicated by the maximum 
 extinction of the light. The crystal has then the 
 position a'b'e'd'. The angle (f. 408), which it 
 has been necessary to revolve the plate to obtain 
 the effect described, is the angle which one of the axes of elasticity in the 
 given plate makes with the given crystallographic edge i-i. 
 
 The preceding explanations cover everything that is essential in the 
 Stauroscope ; but a variety of improvements have been introduced, which 
 practically make the measurements by means of the instrument much more 
 easy and accurate. 
 
 It will be seen that the most important feature is the point where the 
 maximum extinction of the light occurs ; this, however, is not easy for the 
 eye to decide upon, and if the trial is made, it will be found that the change 
 produced by a revolution of several degrees is hardly perceptible. To 
 overcome this difficulty, vou Kobell proposed to introduce a section of cal- 
 cite just below the analyzer, because its interference figure gives a better 
 opportunity to judge of a change in the intensity of the light. A still better 
 plan is to introduce a composition plate of calcite, as proposed by Brezina, 
 giving a peculiar interference figure, a very slight change in which destroys 
 its symmetrv, and it takes its normal form only when the planes of polariza 
 tion of the two Nicols are exactly at right angles. Supposing this to be the 
 case, when the crystal has been introduced the interference figure is disturbed, 
 it returns to its normal appearance only when the crystal has been revolved 
 
156 
 
 PHYSICAL CHARACTERS OF MINERALS. 
 
 to the point where the vibration-directions of the Nicola and crystal section 
 exactly coincide.* 
 
 It will be observed again, that it is essential that the direction of the 
 known edge of the crystal should be exactly parallel to the vibration-direc- 
 tion of one of the Nicols. This condition, in the case of bmall crystals 
 especially, is hard to fulfil, and to accomplish it most satisfactorily Groth 
 has proposed to use the plate shown in f. 409. 
 
 The plate of glass, v, held in its present position by the spring, has one 
 edge polished, which adjoins u, and the direction 
 of this is made to coincide exactly with the line 
 joining the opposite zero points of the gradua- 
 tion. The crystal section is attached to this plate 
 over the hole seen in v, and with a plane of 
 known crystallographic position, either O, i-i or 
 a plane in that zone or a corresponding edge, 
 coinciding with the direction of the polished edge 
 of the plate. Whether this coincidence is exact 
 can be tested by the reflective goniometer. In 
 order to eliminate any small error, Groth pro- 
 poses to measure the divergence from the exact 
 coincidence, and then to make a corresponding 
 correction, for which he furnishes a series of tables. 
 
 After the adjustment of the crystal section on the plate, the latter is 
 inserted in its place, the whole plate, , k, occupying the position indicated 
 in f. 385, and the Nicols so adjusted that the plane of vibration of one 
 coincides with the line to 180. The angle of revolution of the plate, I, 
 is obtained from the graduated scale on Tc. 
 
 It is not always easy to make the adjustment of the Nicols alluded to, 
 but the error arising when the vibration-plane of the Nicol does not coincide 
 with the line to 180 is easily eliminated. This is accomplished by remov- 
 ing the plate v, and, without disturbing the crystal section, restoring it to 
 its place in an inverted position. The measured angle, if before too great, 
 will now be as much too small, and the arithmetical mean of the two 
 measurements will be the true angle. 
 
 Reference further may be made to Groth, Fogg. Ann., cxliv., 34, 1871. 
 Determination of the plane of the optic axes. The investigation of a 
 section of a monoclinic crystal parallel to the plane of symmetry determines 
 the position of the two remaining axes of elasticity, but it does not fix the 
 relative position of the greatest and least axes of elasticity, that is, the plane 
 of the optic axes. To solve the latter point, sections normal to each of the 
 three axes must be examined in converging polarized light, and one of 
 them will show the characteristic interference figures. The section parallel 
 to the plane of symmetry is first to be examined, and if it does not show 
 the axes even in oil, one or both of the other sections spoken of must be 
 employed. 
 
 A.mal angle, dispersion, etc. The method of measuring the axial angle 
 has been already explained, and if this is determined for the different colors 
 it will determine the dispersion of the axes p . v. 
 
 The dispersion of the axes of elasticity has been shown to be always 
 indicated by the character of interference figures ; its amount, where con- 
 
 * See p. 180 for a description of the Calderon plate. 
 
EFFECT OF HEAT UPON THE OPTICAL CHARACTERS OF CRYSTALS. 157 
 
 tidcrable. may be determined by making the stauroscopic measurements for 
 different colors. 
 
 The remaining points to be investigated, the indices of refraction, and 
 the 4- or character of the crystal, need no further explanation beyond 
 that which has been given, pp. 150, 151. 
 
 DISTINGUISHING OPTICAL CHARACTERS OF TRICLINIC CRYSTALS. 
 
 The crystals of the triclinic system are characterized by their entire want 
 of crystallographic symmetry, the position and inclination of the axes being 
 entirely arbitrary, and it follows from this that there is no necessary connec- 
 tion between them and the rectangular axes of elasticity. More than one of 
 the three kinds of dispersion mentioned on p. 154 may occur in a single 
 crystal, and the interference figures will indicate the existence of both. 
 
 The practical investigation of triclinic crystals optically involves great 
 difficulty; in general a series of successive trials are required to determine 
 the position of the axes of elasticity. When these are found, the axial sec- 
 tions can be prepared and the axial angle determined, and the other points 
 settled as with other biaxial crystals. 
 
 EFFECT OF HEAT UPON THE OPTICAL CHARACTERS OF CRYSTALS. 
 
 In addition to the ordinary investigation of crystal-sections in the polari- 
 scope, it is often important to determine the influence of heat upon the 
 optical character of crystals. The axial angle may be measured at any 
 required temperature by the use of a metal air-bath. This is placed at C\ 
 (f. 401), and extends beyond the instrument on either side, so as to allow 
 of its being heated with gas burners ; a thermometer inserted in the bath 
 makes it possible to regulate the temperature as may be desired. This bath 
 has two openings, closed with glass plates, corresponding to the two tubes 
 carrying the lenses, and the crystal-section, held as usual in the pincers, is 
 seen through these glass windows. 
 
 The conclusions of DesCloizeaux (see Literature) as to the influence of 
 heat upon the optical characters of crystals are as follows : 
 
 (1) Uniaxial crystals appear to be uninfluencqdfcy a heating of from 10 
 to 190 C. (2) biaxial crystals of the orthorhowNk system suffer a greater 
 or less change in axial angle. (3) Biaxial crystals of the monoclinic system 
 suffer a change in axial angle, and in addition also in the plane of the axes 
 when it is not the plane of symmetry. Triclinic crystals also show a little 
 change in the position of the axes. 
 
 A striking example of the change in axial divergence is furnished by 
 gypsum. At ordinary temperatures the axes lie in the plane of symmetry 
 (i-l) ; at 80 G. they unite in a line making an angle of 37 28' with a normal 
 to O ; and with an increased temperature they again separate in a plane 
 perpendicular to i-l. DesCloizeaux found that the feldspars, when heated 
 up to a certain point, suffer a change in the position of the axes, and if the 
 heat becomes greater and is long continued, they do not return again to their 
 original position, but remain altered. Weiss* has made use of this principle 
 
 * Zur Konntniss der Feldspathbildung ; Haarlem Soc. Verhandl. , xxv. , 1866. 
 
158 PHYSICAL CHARACTERS OF MINERALS. 
 
 to determine at what temperature certain feldspathic rocks were formed 
 This constant change of axial angle upon heating is true also of brookite, 
 zoisite, and other minerals. The investigations of Pfaff show that the opti- 
 cal properties of some uniaxial crystals also are affected by heating, though 
 to no great extent. Pogg., cxxiii., 179, cxxiv., 448, etc. 
 
 ANOMALIES EXHIBITED BY SOME CRYSTALS IN THEIR OPTICAL PHENOMENA.* 
 
 There are a considerable number of crystals of the three classes, which, 
 from a variety of causes, exhibit irregularities in their optical characters ; 
 some of the more important cases are mentioned here. 
 
 Isometric crystals. Boradte, and also senarmontite, sometimes exhibit 
 interference figures resembling closely those of biaxial crystals. In the 
 case of boracite this is explained by DesCloizeanx as due to the presence 
 of enclosed crystals of parasite formed by alteration. Perofskite is also 
 strongly doubly refracting, and in polarized light appears to be biaxial, 
 although, as shown by Kokscharow, it is isometric in crystallographic rela- 
 tions. The irregularities are supposed by him to be caused by the want of 
 homogeneity in the internal structure of the crystals. 
 
 The properties of double refraction possessed by some substances, crystal- 
 lized and non-crystallized, which are normally isotrope, are explained by 
 Biot to be due to lamellar polarization. This is analogous to the produc- 
 tion of polarized light by means of a series of thin plates (see p. 132). 
 Alum crystals have often the lamellar structure, which causes these pheno- 
 mena. 
 
 Analcite and leucite have been included in the list of isometric crystals, 
 which exhibit anomalous optical characters ; but the most accurate crystal- 
 lographic determination has referred both species to the tetragonal system. 
 Tension or compression at the time of crystallization may cause isotropic 
 crystals to polarize light ; Schrauf has described a uniaxial diamond, and 
 it was long since shown by Brewster that some diamonds give evidence in 
 polarized light of compression about interior cavities. 
 
 Uniaxial crystals. A want of homogeneity in the crystals, as shown by 
 DesCloizeaux, may causefuniaxial crystals to exhibit in polarized light a 
 variety of abnormal phenomena. In some cases the axial figures resemble 
 those of biaxial crystals, the cross in the middle of 'the field (f. 390) not 
 being closed, but separated into two hyperbolas, lying near each other. 
 Beryl, zircon, vesuvianite, and apatite are examples. That such crystals 
 are nevertheless uniaxial is proved by the fact that the opening of the cross 
 is independent of the position of the Nicols, and is not altered if the section 
 is turned in a horizontal plane. If this is not true, or if, when the section 
 is heated (p. 157) the distance between the hyberbolas is altered, it is a 
 proof that the irregularity is not due to lamellar polarization, but that the 
 two indices of refraction are not exactly equal, and consequently that the 
 crystal is riot strictly uniaxial. In such cases a revision of the crystallo- 
 graphical elements is desirable. 
 
 The axial figure shown by a section of apophyllite is peculiar, exhibiting 
 
 * For a discussion of this subject in the light of recent (1882) investigations, see pp. 
 185 et seq. 
 
ANOMALIES EXHIBITED BY SOME CRYSTALS IN OPTICAL PHENOMENA. 
 
 a series of rings alternately dark violet, and yellow. The explanation ia 
 fonnd in the fact previously stated, that it is positive for red rays, negative 
 for blue, and does not doubly refract yellow light. 
 
 Among biaxial crystals irregularities in the optical phenomena are often 
 observed. They are due in part to want of homogeneity, in part to twin 
 structure, and also to other causes. In brookite the planes of the axes for 
 red and blue rays are at right angles to each other, and hence the axial 
 figures vary much from those normally observed ; in titanite the axial angle 
 for the two colors is widely different, and this also gives rise to an axial 
 figure of abnormal appearance. 
 
 Irregular structure, due to twinning, is a frequent cause of peculiar opti- 
 cal phenomena ; crystals, in external form apparently simple, often show 
 themselves to be made up of irregular banded layers in twinned position, 
 when examined in polarized light ; this is true of many minerals. 
 
 In some crystals, as occasionally in the epidote froni the Untersulzbach- 
 thal in the Tyrol, the biaxial figures may be observed immediately, without 
 the use of the polariscope. This is due to the complex twinned structure 
 of. the crystal, a thin lamella in reverse position being enclosed in the 
 interior, so that the parts of the crystal on either side act as polarizer and 
 analyzer. 
 
 Practical Suggestions in regard to the Preparation and iise of Crystal Sections made for 
 
 Optical Examination. 
 
 The most important task is the preparation of a plate for examination in the Stauroscope, 
 or for the observation of the axial interference-figures. In this we are often assisted by the 
 cleavage, which sometimes makes it possible to obtain the require I section without the labor 
 of cutting it. This is conspicuously the case with mica ; also with topaz and anhydrite, and 
 other minerals. Sometimes the natural surfaces need to be made smooth and polished. 
 Furthermore natural crystals sometimes occur in a tabular form, thin and transparent enough 
 to answer the purpose ; this is true of the crystals of wulfenite from Utah. In most cases, 
 however, the section must be actually cut. The means required in such cases vary with the 
 hardness of the mineral under examination. For the hardest minerals diamond powder is 
 made use of in grinding; it is employed after the manner of the lapidary. (It may be men- 
 tioned here that the investigator will generally find it for his interests, both as regards time, 
 money, and accuracy of results, to employ a lapidary to do this work for him.) The diamond 
 powder is applied to a thin wheel of soft iron or copper, rotating on a lathe. 
 
 For minerals which are not so extremely hard, good emery may be used instead of diamond 
 powder. It is merely necessary to apply the emery and water to the edge of the wheel as it 
 revolves, the mineral being held firmly against. A neater and more advantageous method, 
 where the amount of material is small, is the use of a fine saw, or better wire, mounted in a 
 frame, and used with either diamond powder or emery moistened with water or oil. The 
 crystal may be mounted in wax or otherwise, if very small ; sometimes a holder made of cork 
 is convenient. 
 
 The direction in which the slice is to be cut is of the highest importance, and can often be 
 indicated tit first by a scratch across a plane of a crystal. In many cases it is more simple to 
 grind on a surface in the proper direction, and this can be easily accomplished by holding the 
 crystal against a fine-grained emery wheel rotating on a lathe. It can be held either in the 
 fingers, or cemented to a small piece of glass, for instance with Canada balsam. 
 
 Another way, more simple as demanding no instruments, is to make use of a flat piece of 
 plate glass, not too small, on which the crystal is ground with moistened emery, being care- 
 fully moved about with the hand. In some cases a file, or even a knife, may be used, where 
 the mineral in hand is soft. 
 
 Whatever method of grinding is adopted, it is necessary to exercise great care to bring the 
 artificial surface into exactly the proper direction. This can be determined only as its inclina 
 tions to existing crystalline planes, or cleavage surfaces, are measured, and practically it ia 
 necessary often to stop the v ork and test what has been done. The parallel intersections 
 
160 PHYSICAL CHARACTERS OF MINERALS. 
 
 will often show the degree of correctness in the work. For purposes of measurement it ia 
 necessary to polish the artificial plane, or instead, a small piece of thin glass may be cementod 
 on where the crystal is too small for the use of the hand-goniometer. It is of course necessary 
 to know, before starting, the angle which the new plane will make with the natural planes 
 which are already present. When one plane in the required direction has been obtained, it 
 is a comparatively simple process to obtain a second parallel to it, though care must be exer- 
 cised to attain accuracy. 
 
 The required section having been cut, it remains only to polish the surfaces. The means 
 required differ so widely, according to the hardness of the mineral, that no fixed rule can be 
 given. The most commonly used polishing powder is the English red, or colcothar, which 
 may be used on the plate of glass, or leather surface, or on a revolving wheel covered with a 
 soft cloth. In other cases oxide of tin or fine chalk is used ; and again the simple plate of 
 ground pJass will answer the purpose without the use of any other means. As a rule, the 
 hardest minerals take the polish most readily. Sometimes the only method practicable is to 
 use small fragments of thin glass, adhering with balsam, by which transparency is obtained 
 without polish, though errors are easily introduced by this means when sufficient care is not 
 exercised. 
 
 The preparation of prisms for the measurement of the indices of refraction is practically 
 much more difficult than that of a simple section, but in general the methods are the same. 
 
 It is often advisable to examine a mineral microscopically when a slice in a particular direc- 
 tion is not needed. In such cases use can be made of the methods employed in making rock 
 slices. A revolving wheel of soft iron, vertical or horizontal, is employed, on the lateral sur- 
 face of which the substance is ground with the use of emery moistened with water. A thin 
 slice, or thin fragment broken off, is taken to commence with. First one surface is ground 
 smooth and polished. The piece is then cemented to a little plate of thick glass with balsam, 
 and the other side ground down parallel to the first, the grinding being continued until the 
 required degree of transparency is obtained. Obviously when the section becomes thin and 
 fragile, the coarse emery must be replaced with fine, and a considerable degree of care exer- 
 cised. The section obtained is generally removed to another slip of glass and mounted with 
 balsam under a thin glass cover. 
 
 The microscopic investigation of minerals, by means of thin slices, is of the highest import- 
 ance, aside from optical investigations. Every chemical analysis should be preceded by such 
 an examination to test the purity of the material in hand. Where a transparent section can- 
 not be obtained, a single polished surface, examined by reflected light, will often suffice to 
 decide the same point. 
 
 The valuable investigations of Vogelsang, Fischer, Rosenbusch, and others, referred to on 
 pp. 108 to 111, show how many minerals, which at first glance seem perfectly pure, are found 
 to enclose impurities considerable in variety and amount. 
 
 LITERATURE. OPTICAL CHARACTERS OF CRYSTALS. 
 
 Brewster. Treatise on Optics, and many minor papers in Ed. Phil. Mag., etc. 
 
 Beer. Einleitung in die hohere Optik ; Braunschweig, 1853. 
 
 Dove. Darstellung der Farbenlehre und optische Studien ; Berlin, 1853. 
 
 Grailich. Krystallographisch-optische Untersuchungen ; Wien, 1858. 
 
 Grailich u. von Lang. Untersuchungen iiber das physikalische Verhalten krystallisirtet 
 Korper; Ber. Ak. Wien, xxvii. 3; xxxii., xxxiii., and other papers. 
 
 DesGloizeaux. Memoire sur les proprietes birefringentes en Mineralogie, Ann. d. Mines; 
 V., xi., 1857; xiv., 1858. 
 
 Memoire sur 1'emploi du microscope polarisant, etc. ; Paris, 1864. 
 
 Nouvelles Recherches stir les proprietes optiques des Cristaux, etc., et sur lea 
 
 rariations que ces proprietes eprouvent sous I'influence de la chaleur ; C. R., Ixii., 987, 1866. 
 
 Schrauf. Lehrbuch der physikalischen Mineralogie ; vol. ii., Wien, 1868. 
 
 MuUer-Pouillet. Lehrbuch der Physik ; vol. i., Braunschweig, 1875. 
 
 Wuttner. Lehrbuch der Experimental-Physik ; vol. ii. Die Lehre vom Licht ; Leipzig, 
 1871. 
 
 Itosenhmch. Microscopische Physiographic der petrographisch wichtigen Mineralien, pp. 
 56-107 ; Stuttgart, 1873. 
 
 Qroth, Physikalische Krystallographie ; Leipzig, 1876. 
 
 Von Kobdl. Ueber ein neues Polariskop Siauroskop ; Pogg., xcv., 320, 1855. 
 
 Brezina. Eine neue Modification des Stauroskops, etc. ; Pogg., cxxviii., 448, 1866 ; cxxx., 
 141, 1867. 
 
 Qroth. Ueber Apparate und Beobachtungsmethoden fur krystallographisch-optisch 
 Untersuchungen ; Pogg., cxliv., 34, 1871. 
 
DIAPHANEITY COLOR LUSTRE. 
 
 DIAPHANEITY; COLOR; LUSTRE. 
 
 There are certain characteristics belonging to all minerals alike, crystal- 
 lized and ri on-crystallized, in their relation to light. These are : 
 
 1. DIAPHANEITY ; depending on the power of transmitting light. 
 
 2. COLOR ; depending on the kind of light reflected or transmitted. 
 
 3. LUSTRE ; depending on the power and manner of reflecting light. 
 
 1. DIAPHANEITY. 
 
 The amount of light transmitted by a solid varies in intensity, or, in other 
 words, of the light received more or less may be absorbed. The amount 
 of absorption is a minimum in a perfectly transparent solid, as ice, while it 
 is greatest in one which is opaque, as iron. The following terms are adopted 
 to express the different degrees in the power of transmitting light : 
 
 Transparent : when the outline of an object seen through the mineral is 
 perfectly distinct. 
 
 Subtransparent) or semi-transparent: when objects are seen, but the 
 outlines are not distinct. 
 
 Translucent : when light is transmitted, but objects are not seen. 
 
 Subtranslucent : when merely the edges transmit light or are trans- 
 lucent. 
 
 When no light is transmitted, the mineral is said to be opaque. This is 
 properly only a relative term, since no substance fails to transmit some 
 light, if made sufficiently thin. Magnetite is translucent in the Pennsbury 
 mica. The recent researches of Prof. A. W. Wright have fchown that by 
 means of the electrical current the metals may be volatilized and deposited 
 again on the sides of the surrounding glass tube. The layers thus formed 
 are perfectly continuous, but so thin as to be transparent. By transmitted 
 light the layer of gold thus obtained appears green, and that of silver a 
 beautiful blue. 
 
 The property of diaphaneity occurs in the mineral kingdom, in every 
 degree from nearly perfect opacity to a perfect transparency, and many 
 minerals present, in their numerous varieties, nearly all the different shades. 
 
 The absorption of light in its relation to the axes of elasticity is spoken 
 of on p. 165. 
 
 2. COLOR. 
 
 Cause of color. The color of a substance depends upon its power of 
 absorbing certain portions of the light, that is, certain rays of the spec trum ; 
 a yellow mineral, for instance, absorbs all the rays of the spectrum with the 
 exception of the yellow. In general the color which the eye perceives ia 
 the result of the mixture of those rays which are not absorbed. All min- 
 erals may be divided into two classes : (1) those whose color is essential and 
 belongs to the finest particles mechanically made; (2) those whose color ia 
 non-essential and in the fine powder is different from what it is in the mass 
 
PHYSICAL CHARACTERS OF MINERALS. 
 
 Streak. It is obvious from these distinctions that the color of the 
 powder, or the streak, as it is called, is often a very important quality 
 in distinguishing minerals. The streak is obtained by scratching the sur- 
 face of the mineral with a knife or file, or still better, if not too hard, by 
 rubbing it on an unpolished porcelain surface. 
 
 To the first class, mentioned above, belong the metals, and many 
 metallic minerals ; for instance, the streak of the black manganese oxides is 
 black ; that of hematite, which is red by transmitted light, is red, and so 
 on. To the second class belong the silicates, and in fact the large part 
 of all minerals. With them the color is often quite unessential, being gen- 
 erally due to small admixtures of some metallic oxide, to some carbon com- 
 pound, or some foreign substance in a finely divided state. Most of these 
 nave a white or light-colored streak. For example, the streak of black, 
 green, red, and blue tourmaline varies little from white. 
 
 VARIETIES OP COLOR. 
 
 The following eight colors have been selected as fundamental, to facilitate 
 the employment of this character in the description of minerals : white, 
 gray, black, blue, green, yellow, red, and brown. 
 
 \/ a. Metallic Colors. 
 
 1. Copper-red: native copper. 2. Bronze-yellow : pyrrhotite. 3. Brass- 
 yellow : chalcopyrite. 4. Gold-yellow. 5. Silver-white : native silver, less 
 distinct in arsenopy rite. 6. Tin-white: mercury, cobaltite. 7. Lead-gray : 
 galenite, molybdenite. 8. Steel-gray: nearly the color of fine-grained 
 steel on a recent fracture ; native platinum, and palladium. 
 
 b. Non-metallic Colors. 
 
 A. WHITE. 1. Snow-white : Carrara marble. 2. Reddish-white : some 
 varieties of calcite and quartz. 3. Yellowish-white : some varieties of cal- 
 cite and quartz. 4. Grayish-white : some varieties of calcite and quartz. 
 5. Greenish-white : talc. 6. Milk-white : white, slightly bluish ; some 
 chalcedony. 
 
 B. GRAY. 1. Bluish-gray: gray, inclining to a dirty blue color. 2. 
 Pearl-gray : gray, mixed with red and blue ; cerargyrite. 3. Smoke-gray : 
 gray, with some brown ; flint. 4. Greenish-gray : gray, with some green ; 
 cat's eye, some varieties of talc. 5. Yellowish-gray : some varieties of 
 compact limestone. 6. Ash-gray : the purest gray color ; zoisite. 
 
 C. BLACK. 1. Grayish-black: black, mixed with gray (without any 
 green, brown, or Jalue tints) ; basalt, Lydian stone. 2. Velvet-black : pure 
 bla<&; obsidian, black tourmaline. 3. Greenish-black: angite. 4 Brown- 
 ish-black : brown coal, lignite. 5. Bluish-black : black cobalt. 
 
 D. BLUE. 1. Blackish-blue : dark varieties of azurite. 2. Azure-Hue : 
 a clear shade of bright blue ; pale varieties of azurite, bright varieties of 
 
DIAPHANEITY COLOR LUSTBE. 
 
 azulite. 3. Violet-Hue: blue, mixed with red; amethyst, fluorito.- 4- 
 Lavender Jdue : blue with some red and much gray. 5. Prussian-Hue 
 jr Berlin blue : pure bine; sapphire, eyanite. 6. Smalt-blue: some varie- 
 ies of gypsum. 7. Indigo-blue : bine with black and green ; bine tourma- 
 ine. 8. Sky-blue : pale blue with a little green ; it is called mountain 
 )lue by painters. 
 
 E. G-KEEN. 1. Verdigris-green : green inclining to blue ; some feldspar 
 amazon-stone). Celandine-green: green with blue and gray ; some vane- 
 ies of talc and beryl. It is the color of the leaves of the celandine (Cheli- 
 lonium rnajus). 3. Mountain-green : green with much blue ; beryl. 4. 
 Leek-green : green with some brown ; the color of leaves of garlic ; dis- 
 inctly seen in prase, a variety of quartz. 5. Emerald-green : pure deep 
 rreen ; emerald. 6. Apple-green : light green with some yellow ; chryso- 
 )rase. 7. Grass-green : bright green with more yellow ; green diallage. 
 :. Pistachio-green : yellowish green with some brown ; epidote. 9. Aspa- 
 wgus-green : pale green with much yellow ; asparagus stone (apatite). 
 .0. Blackish-green : serpentine. 11. Olive-green: dark green with much 
 >rown and yellow; chrysolite. 12. Oil-green: the color of olive oil; 
 >eryl, pitchstone. 13. Siskin-green : light green, much inclining to yellow; 
 irani te. 
 
 F. YELLOW. 1 . Sulphur-yellow : sulphur. 2. Straw-yellow : pale yel- 
 ow ; topaz. 3. Wax-yellow : grayish yellow with some brown ; blende, 
 >pal. 4. Honey-yellow : yellow with some red and brown ; calcite. 5. 
 ^emon-yellow : sulphur, orpiment. 6. Ochre-yellow : yellow with brown ; 
 ellow ochre. 7. Wine-yellow: topaz and fluorite. S. Cream-yellow: 
 ome varieties of lithomarge. 9. Orange-yellow : orpiment. 
 
 G. RED. 1. Aurora-red: red with much yellow; some realgar. 2. 
 r lyacinth-red : red with yellow and some brown ; hyacinth garnet. 3. 
 ^rick-red: poly halite, some jasper. 4. Scarlet-red: "bright red with a 
 inge of yellow ; cinnabar. 5. Blood-red: dark red with some yellow ; 
 yrope. 6. Flesh-red: feldspar. 7. Carmine-red: pure red; ruby sap- 
 hire. 8. Rose-red : rose quartz. 9. Crimson-red : ruby. 10. Peach- 
 lossom-red: red with white and gray; lepidolite. 11. Columbine-red: 
 eep red with some blue ; garnet. 12. Cherry-red : dark red with some 
 lue and brown : spinel, some jasper. 13. Brownish-red: jasper, limonite. 
 
 H. BUOWN. 1. Reddish-brown : garnet, zircon. 2. Clove-brown : brown 
 rith red and some blue ; axinite. 3. Hair-brown : wood opal. 4. JSroc- 
 oli-brown : brown, with blue, red, and gray ; zircon. 5. Chestnut-brown : 
 ure brown. 6. Yellowish-brown : jasper. 7. Pinchbeck-brown: yellow- 
 ;h-brown, with a metallic or metallic-pearly lustre; several varieties of 
 lie, bronzite. 8. Wood-brown : color of old wood nearly rotten ; some 
 pecimens of asbestus. 9. Liver-brown : brown, with some gray and green ; 
 isper. 10. Blackish-brown ; bituminous coal, brown coal. 
 
 c. Peculiarities in the Arrangement of Colors. 
 
 Play of Colors. An appearance of several prismatic colors in rapid 
 Liccessioii on turning the mineral. This property belongs in perfection to 
 lie diamond ; it is also observed in precious opal, and is most brilliant by 
 an die-light. 
 
164 PHYSICAL CHARACTERS OF MINERALS. 
 
 Change of Colors. Each particular color appears to pervade a larger 
 space than in the play of colors, and the succession produced by tinning the 
 mineral is less rapid ; Ex. labradorite. 
 
 Opalescence. A milky or pearly reflection from the interior of a speci- 
 men. Observed in some opal, and in cat's eye. 
 
 Iridescence. Presenting prismatic colors in the interior of a crystal. 
 The phenomena of the play of colors, iridescence, etc., are sometimes to be 
 explained by the presence of minute foreign crystals, in parallel positions ; 
 more generally, however, they are caused by the presence of fine cleavage 
 lamellse, in the light reflected from which interference takes place, analogous 
 to the well-known Newton's rings. 
 
 Tarnish. A metallic surface is tarnished, when its color differs from 
 that obtained by fracture ; Ex. bornite. A surface possesses the steel tar- 
 nish, when it presents the superficial blue color of tempered steel ; Ex. 
 columbite. The tarnish is irised, when it exhibits fixed prismatic colors ; 
 Ex. hematite of Elba. These tarnish and iris colors of minerals are owing 
 to a thin surface film, proceeding from different sources, either from a 
 change in the surface of the mineral, or foreign incrustation ; hydrated iron 
 oxide, usually formed from pyrite, is one of the most common sources of it, 
 and produces the colors on anthracite and hematite. 
 
 Asterism. This name is given to the peculiar star-like rays of light 
 observed in certain directions in some minerals by reflected or transmitted 
 light. This is seen in the form of a six-rayed star in sapphire, and is also 
 well shown in mica from South Burgess, Canada. In the former case it 
 has been attributed by Yolger to a repeated lamellar twinning ; in the 
 other case, by Rose, to the presence of minute inclosed crystals, which are 
 a uniaxial mica, according to DesCloizeaux. Crystalline planes, which 
 have been artificially etched, also sometimes exhibit asterism. In general 
 the phenomenon is explained by Schrauf as caused by the interference of 
 the light, due to fine striations or some other cause. 
 
 (Upon the above subjects, see Literature, p. 167.) 
 
 PHOSPHORESCENCE. 
 
 Phosphorescence,* or the emission of light by minerals, may be produced 
 in different ways : \>y friction, by heat, or by exposure to light. 
 
 By friction* Light is readily evolved from quartz or white sugar by 
 the friction of one piece against another, and merely the rapid motion of a 
 feather will elicit it from some specimens of sphalerite. Friction, however, 
 evolves light from a few only of the mineral species. 
 
 By heat. Fluorite is highly phosphorescent at the temperature of 300 F. 
 Different varieties give off light of different colors ; the chlorophane variety, 
 an emerald-green light ; others purple, blue, and reddish tints. This phos- 
 phorescence may be observed in a dark place, by subjecting the pulverized 
 mineral to a heat below redness. Some varieties of white limestone or 
 marble emit a yellow light. 
 
 * This subject has been investigated by Becquerel, Ann. Ch. Phys., III., lv., 5-119, 1859 ; 
 Faster, Mitth. nat. Ges. Bern, 1807, 62: and Hahn, Zeitsch. Ges. nab. Wiss. Berlin, II., 
 Ix, 1,181, 1874. 
 
DIAPHANEITY COLOK LUSTRE. 
 
 165 
 
 By the application of heat, minerals lose their phosphorescent properties. But on passing 
 electricity through the calcined mineral, a more or less vivid light is produced at the time of 
 the discharge, and subsequently the specimen when heated will often emit light as before. 
 The light is usually of the same color as previous to calcination, but occasionally is quite 
 different. It is in general less intense than that of the unaltered mineral, but is much 
 increased by a repetition of the electric discharges, and in some varieties of fluorite it may 
 be nearly or quite restored to its former brilliancy. It has also been found that some varie- 
 ties of fluorite and some specimens of diamond, calcite, and apatite, which are not naturally 
 phosphorescent, may be rendered so by means of electricity. Electricity will also increase 
 the natural intensity of the phosphorescent light. 
 
 Light of the sun. The only substance in which an exposure to the light 
 of the sun produces very apparent phosphorescence is the diamond, and 
 some specimens seem to be destitute of this power. This property is most 
 striking after exposure to the blue rays of the spectrum, while in the red 
 rays it is rapidly lost. 
 
 PLEOCHKOISM. 
 
 Dichroism, Trichroism. In addition to the general phenomena of color, 
 which belong to all minerals alike, some of those which are crystallized 
 show different colors under certain circumstances. This is due to the fact 
 that in them the absorption of parts of the spectrum takes place unequally 
 in different directions, and hence their color by transmitted light depends 
 upon the direction in which they are viewed. This phenomenon is called 
 in sreneral pleochroism. 
 
 lu uniaxial crystals it has been seen that, in consequence of their crystal- 
 lographic symmetry, there are two distinct values for the velocity of light 
 transmitted by them, according as the vibrations take place, parallel or at 
 Tight angles to the vertical axis. Similarly the crystal may exert different 
 degrees of absorption upon the rays vibrating in these two directions. For 
 example, a transparent crystal of zircon looked through in the direction of 
 the vertical axis appears of a pinkish-brown color, while in a lateral direc- 
 tion the color is asparagus-green. This is because the rays (extraordinary) 
 vibrating parallel to the axis are absorbed with the exception of those 
 which together give the green color, and those vibrating laterally (ordinary) 
 are absorbed except those which together appear pinkish-brown. 
 
 Again, all crystals of tourmaline in the direction of the vertical axis are 
 opaque, since the ordinary ray, vibrating normal to the axis c, is absorbed, 
 while light-colored varieties, looked through laterally, are transparent, for 
 the extraordinary ray, vibrating parallel to c, is not absorbed ; the color 
 differs in different varieties. Thus, all uniaxial crystals may be dichroio^ 
 or have two distinct axial colors. 
 
 Similarly all biaxial crystals may be trichroic. For the rays vibrating in 
 the directions of the three axes of elasticity may be differently absorbed. 
 For diaspore the three axial colors are azure-blue, wine-yellow, and violet- 
 blue. It will be understood that, while these three different colors are pos- 
 sible, they may not exist ; or only two may be prominent, so that a biaxial 
 mineral may be called dichroic. 
 
 In order to investigate the absorption-properties of any uniaxial or biaxial 
 crystal, it is evident that sections must be obtained which are parallel to the 
 
166 
 
 PHYSICAL CHARACTERS OF MINERALS. 
 
 several axes of elasticity. Suppose that f. 410 represents a rectangular solid 
 with its sides parallel to the three axes of elasticity of 
 a biaxial crystal. In an orthorhombic crystal the faces 
 are those of the three diametral planes or pinacoids ; 
 in a monoclinic crystal one side coincides with the clino 
 pinacoid, the others are to be determined for each 
 species. The light transmitted by this solid is examined 
 by means of a single Nicol prism. Suppose, first, that 
 the light transmitted by the parallelopiped (f. 410) in 
 the direction of the vertical axis is to be examined. 
 When the shorter diagonal of the Nicol coincides with 
 the direction of the axis b, the color observed belongs 
 to that ray vibrating parallel to this direction ; when it coincides with the 
 axis a, the color for the ray with vibrations parallel to a is observed. In 
 the same way the Nicol separates the different colored rays vibrating 
 parallel to c and a respectively, when the light passes through in the direc- 
 tion of b. 
 
 So also finally when the section is looked through in the direction of the 
 axis a, the colors for the rays vibrating parallel to b and c, respectively, are 
 obtained. It is evident that the examination in two of the directions named 
 will give the three possible colors. 
 
 For epidote, according to Klein, the colors for the three axial directions 
 
 are : 
 
 Vibrations parallel to fe, brown (absorbed). 
 " *' a, yellow. 
 
 o Vibrations parallel to * 
 *>> t. it 
 
 
 
 Vibrations parallel to f, green. 
 
 a, yellow. 
 f , green, 
 t, brown (absorbed). 
 
 The colors observed by the eye alone are the resultants of the double set 
 oi vibrations, in which the stronger color predominates ; thus, in the above 
 example, the plane, normal to c is brown, to b, yellowish-green, to a, green. 
 In any other direction in the crystal, the apparent color is the result of a 
 mixture of those corresponding to the three directions of vibrations in differ- 
 ent proportions. Dichroite is a striking example of the phenomenon of 
 pleochroism. 
 
 An instrument called a dichroscope has been contrived by Haidinger for 
 examining this property of crystals. An oblong rhombohedron of Ice- 
 land spar has a glass prism of 18 cemented to each extremity. It is placed 
 
 411 
 
 in a metallic cylindrical case, as in the figure, having a convex lens at one 
 end, and a square hole at the other. On looking through it, the square hole 
 appears double ; one image belongs to the ordinary and the other to the 
 extraordinary ray. When a pleochroic crystal is examined with it, by trans- 
 mitted light, on revolving it, the two squares, at intervals of 90 in the revo 
 
DIAPHANEITY COLOR LUSTRE. 167 
 
 lution, have different colors, corresponding to the direction of the vibrations 
 of the ordinary and extraordinary ray in calcite. Since the two images are 
 situated side by side, a very slight difference of color is perceptible. 
 
 LITERATURE. PLEOCHROISM, ASTERISM, ETC. 
 
 Haidinger. Ueber den Pleochroismus der Krystalle ; Pogg. Ixv., 1, 1845. 
 
 TJeber das Schillern der Krystallflachen ; Pogg. Ixx., 574, 1847; Ixxi., 321; 
 
 Ixxvi., 99, 1849. 
 
 JReusch. Ueber das Schillern gewisser Krystalle : Pogg. cxvi., 392, 1862; cxviii., 256. 
 1863; cxx.,95, 1863. 
 
 v. Kobell. Ueber Asterismus; Ber. Ak. Miinchen, 1863, 65. 
 
 HamJwfer. Der Asterismus des Calcites ; Ber. Ak. Miinchen, 1869. 
 
 Vogelsang. Sur le Labradorite colore ; Arch. Neerland., iii., 32, 1868. 
 
 Schrauf. Labradorit; Ber. Ak., Wien, lx., 1869. 
 
 Kosmann. Ueber das Schillern und den Dichroismus des Hypersthens ; Jahrb. Min., 1869, 
 368, 532 ; 1871, 501. 
 
 Hose. Ueber den Asterismus der Krystallen ; Ber. Ak. Berlin, 1862, 614 ; 1869, 344 
 
 3. LUSTRE. 
 
 The lustre of minerals varies with the nature of their surfaces. A varia- 
 tion in the quantity of light reflected, produces different degrees of intensity 
 of lustre ; a variation in the nature of the reflecting surface producer 
 different kinds of lustre. 
 
 A. The kinds of lustre recognized are as follows : 
 
 1. Metallic : the lustre of metals. Imperfect metallic lustre is expressed 
 by the term sub-metallic. 
 
 2. Adamantine: the lustre of the diamond. When also sub-metallic, it 
 is termed metallic-adamantine. Ex. cerussite, pyrargyrite. 
 
 3. Vitreous: the lustre of broken glass. An imperfectly vitreous lustre 
 is termed sub-vitreous. The vitreous and sub-vitreous lustres are- the most 
 common in the mineral kingdom. Quartz possesses the former in an emi- 
 nent degree ; calcite, often the latter. 
 
 4. Itesinous : lustre of the yellow resins. Ex. opal, and some yellow 
 varieties of sphalerite. 
 
 5. Pearly: like pearl. Ex. talc, brucite, stilbite, etc. When united with 
 sub-metallic, as in hypersthenite, the term metallic-pearly is used. 
 
 6. Silky : like silk ; it is the result of a fibrous structure. Ex. fibrous 
 calcite, fibrous gypsum. 
 
 B. The degrees of intensity are denominated as follows: 
 
 1. Splendent : reflecting with brilliancy and giving well-defined images. 
 Ex. hematite, cassiterite. 
 
 2. Shining : producing an image by reflection, but not one well defined. 
 Ex. celestite. 
 
 3. Glistening : affording a general reflection from the surface, but no 
 image. Ex. talc, chalcopyrite. 
 
 4. Glimmering: siffording imperfect reflection, and apparently from 
 points over the surface. Ex. flint, chalcedony. 
 
 A mineral is said to be dull when there is a total absence of lustre. Ex. 
 chalk, the ochres, kaolin 
 
168 PHYSICAL CHARACTERS OF MINERALS. 
 
 The true difference between metallic and vitreous lustre is due to the 
 effect which the different surfaces have upon the reflected light ; in general, 
 the lustre is produced by the union of two simultaneous impressions made 
 upon the eye. If the light reflected from a metallic surface be examined 
 by a Nicol prism (or the dichroscope of Haidinger), it will be found that 
 both rays, that vibrating in the plane of incidence and that whose vibra- 
 tions are normal to it, are alike, each having the color of the material, only 
 differing a little in brilliancy ; on. the contrary, of the light reflected by a 
 vitreous substance, those rays whose vibrations are at right angles to the 
 plane of incidence are more or less polarized, and are colorless, while those 
 whose vibrations are in this plane, having penetrated somewhat into the 
 medium and suffered some absorption, show the color of the substance 
 itself. A plate of red glass thus examined will show a colorless and a red 
 image. Adamantine lustre occupies a position between the others. 
 
 The different degrees and kinds of lustre are often exhibited differently by unlike faces of 
 the same crystal, but always similarly by like faces. The lateral faces of a right square 
 prism may thus differ from a terminal, and in the right rectangular prism the lateral faces 
 also may differ from one another. For example, the basal plane of apophyllite has a pearly 
 lustre wanting in the prismatic planes. The surface of a cleavage plane in foliated minerals, 
 very commonly differs in lustre from the sides, and in some cases the latter are vitreous, 
 while the former is pearly. As shown by Haidinger, only the vitreous, adamantine, and 
 metallic lustres belong to faces perfectly smooth and pure. In the first, the index of refrac- 
 tion of the mineral is 1 '3 1 '8 ; in the second, 1-9 2 '5 ; in the third, about 2 '5. The pearly 
 lustre is a result of reflection from numberless lamellae or lines within a translucent mineral, 
 as long since observed by Breithaupt. 
 
 IY. HEAT. 
 
 The expansion of crystallized minerals by heat depends, as directly as 
 their optical properties, on the symmetry of their molecular structure as 
 shown in their crystalline form. The same three classes as before are dis- 
 tinguished : 
 
 A. Isometric crystals, where the expansion is in all directions alike. 
 
 B. Isodiametric crystals, of the tetragonal and hexagonal systems. Ex- 
 pansion vertically unlike that laterally, but in all lateral directions alike. 
 
 C. Anisometric, of the orthorhombic, monoclinic, and triclinic systems. 
 Expansion unlike in the three axial directions. The expansion by heat in 
 the case of crystals may serve to alter the angles of the form, but it has 
 been shown that the zone relations and the crystalline system remain con- 
 stant. 
 
 Mitscherlich found that in calcite there was a diminution of 8' 37" in the angle of the 
 rhombohedron, on passing from 32 to 212 F. , the form thus approaching that of a cube, as 
 the temperature increased. Dolomite, in the same range of temperature, diminishes 4' 4(5"; 
 and in aragonite, between 63 and 212 F., the angle of the prism diminishes 2' 46", and 
 1-* : \-l increases 5' 30" ; in gypsum, / : i-l is increased 5' 24", /: 1, 4' 12", and \-i : i-i is 
 diminished 7' 24". In some rhombohedrons, as of calcite, the vertical axis is lengthened 
 (and the lateral shortened), while in others, like quartz, the reverse is true. The variation 
 is such either way that the double refraction is diminished with the increase of heat ; for 
 calcite possesses negative double refraction, and quartz, positive. 
 
 The conductive power of a crystal depends, - as does expansion, on the 
 symmetry of its crystalline form ; this is also true of its power of trans- 
 
ELECTRICITY MAGNETISM. 169 
 
 mitting or absorbing heat. It follows, moreover, from the analogous nature 
 of heat and light, that heat rays are polarized by reflection, and by transmission 
 in anisotrope media, in the same way as the rays of light. These subjects, 
 considered solely in their relation to Mineralogy, are of minor importance ; 
 they belong to works on Physics, and reference may be made to those 
 whose titles are given in the Introduction, as also to the works of Schrauf 
 and Groth. 
 
 The change in the optical properties of crystals produced by heat has 
 already been noticed (p. 151). 
 
 Y. ELECTRICITY MAGNETISM. 
 
 The electric and magnetic characters of crystals, as their relations to heat, 
 bear but slightly upon the science of mineralogy, although of high interest 
 to the student of physics. 
 
 Frictional electricity. The development of electricity by friction is a 
 familiar fact. All minerals become electric by friction, although the 
 degree to which this is manifested depends upon their conducting or non- 
 conducting power. There is no line of distinction among minerals, divid- 
 ing them \\\^Q positively electric and negatively electric; for both kinds of 
 electricity may be presented by different varieties of the same species, and 
 by the same variety in different states. The gems are positively electric 
 only when polished ; the diamond alone among them exhibits positive elec- 
 tricity whether polished or not. The time of retaining electric excitement 
 is widely different in different species, and topaz is remarkable for continu- 
 ing excited many hours. 
 
 Pressure also develops electricity in many minerals ; calcite and topaz 
 are examples. 
 
 Pyro-electricity. A decided change of temperature, through heat or 
 cold, develops electricity in a large number of minerals, which are hence 
 called pyro-electric. This property is most decided, and was first observed 
 in a series of minerals which are hemimorphic or hemihedral in their 
 development. The electricity in these minerals is of opposite character in 
 the parts dissimilarly modified. Thus in tourmaline and calamine, the 
 crystals of which are often differently modified at the two extremities, posi- 
 tive and negative electricity are developed at these extremities or poles 
 respectively. When the extremity becomes positive on heating it has been 
 called the analogue pole, and when it becomes negative, it has been called 
 the antilogue. The names were given by Rose and Riess, who investigated 
 these phenomena. For a change of temperature in the opposite direction, 
 that is, cooling, the reverse electrical effect is observed. 
 
 Boracite, on whose crystals the -f- and tetrahedrons often occur, shows 
 by heating the positive electricity for the faces of one tetrahedron and the 
 negative for those of the other. 
 
 Further investigations by Hankel and others (see Literature) have ex- 
 tended the subject and shown that the phenomena of pyro-electricity belong 
 to the crystals of a large number of species. Moreover, it is not, as once 
 supposed, essentially connected with hemihedral development. The num- 
 ber of poles, too, may be more than two, that is, the points at which posi 
 
170 PHYSICAL CHARACTERS OF MINERALS. 
 
 tive and negative electricity is developed. Thus for prelmite there Is a 
 large series of such poles, distributed over the surface of a crystal. The 
 investigations of Hankel have shown in general, that in crystals not hemi- 
 hedrally developed, the same electricity is developed at both extremities of 
 the same axis, and the distinction between positive and negative electricity 
 is only shown by reference to the different crystallographic axes; on sym- 
 metrically formed crystals of the isodiametric class the electricity is the 
 same in all lateral directions, that is, on all prismatic planes, while different 
 at the extremities of the vertical axis. 
 
 Thermo-electricity. When two different metals are brought into con- 
 tact, a stream of electricity passes from one to the other. If one is heated 
 the effect is more decided and is sufficient to deflect more or less vigorously 
 the needle of a galvanometer. According to the direction of the current 
 produced by the different metallic substances, they are arranged in a 
 thermo-electrical series; the extremes are occupied by antimony (+) and 
 bismuth ( ), the electrical stream passing from bismuth to antimony. 
 
 This subject is so far important for mineralogy, as it was shown by 
 Bunsen that the natural metallic sulphides stand further off in the series 
 than antimony and bismuth, and consequently by them a stronger stream 
 is produced. The thermo-electrical relations of a large number of minerals 
 was determined by Flight (Ann. Ch. Pharm., cxxxvi.). 
 
 It was early observed that some minerals have varieties which are both 
 4- and . This fact was made use of by Rose to show a relation between 
 the plus and minus hemihedral varieties of pyrite and cobaltite. The later 
 investigations of Schrauf and Dana have shown, however, that the same 
 peculiarity belongs also to glaucodot, tetradymite, skutterudite, danaite, and 
 other minerals, and it is demonstrated by them that it cannot be dependent 
 upon crystalline form, but, on the contrary, upon chemical composition. 
 
 MAGNETISM. The magnetic properties of crystals are theoretically of 
 interest, since they, too, like the optical and thermic, are directly dependent 
 upon the form ; hence, with relation to magnetism they group themselves 
 into the same three classes before referred to. 
 
 All substances are divided into two classes, the paramagnetic and dia- 
 magnetic, according as they are attracted or repelled by the poles of a mag- 
 net. For purposes of experiment the substance in question, in the form of 
 a rod, is suspended between the poles of the magnet, being movable on a 
 horizontal axis. If of the first class, it will take a position parallel, and if 
 of the second class, transverse, to the magnetic axis. 
 
 By the use of a sphere it is possible to determine the relative amount of 
 magnetic induction in different directions of the same substance. Experi- 
 ment has shown that in isometric crystals the magnetism is alike in all 
 directions ; in those optically uniaxial, that there is a direction of maximum 
 and, normal to it, one of minimum magnetism ; in biaxial crystals, that 
 there are three unequal axes of magnetism, the position of which may be 
 determined. 
 
 A few minerals have the power of exerting a sensible influence upon the 
 magnetic needle, and are hence said to be magnetic. This is true of mag- 
 netite and pyrrhotite (magnetic pyrites) in particular, also of franklinite, 
 almandite, and other minerals, containing considerable iron protoxide (FeO). 
 When such minerals in one part attract and in another repel the poles of 
 
TASTE AND ODOK. 171 
 
 the magnet, they are said to possess polarity . This is true of the variety of 
 magnetite called in popular language loadstone. 
 
 LITERATURE. ELECTBICITY.* 
 
 Hankel. Ueber die Thermo-Electricitat der Krystalle; Pogg., xlix., 493; i, 237, 1840; 
 Ixi. , 281. 
 
 Rose u. Ries. Ueber die Pyro-Electricitat der Mineralien ; Ber. Ak. Berlin, 1843. 
 
 Ueber den Zusammenhang zwischen der Form und der elektrisohen Polaritat del 
 
 KrystaJUe ; Ber. Ak. Berlin, 1836. 
 
 v. Kcbell Ueber Mineral-Eleetricitat ; Pogg., cxviii., 594, 1863. 
 
 Bunsen. Thermo-Ketten von grosser Wirksamkeit ; Pogg., cxxiii., 505, 1864. 
 
 FriedeL Sur les proprietes pyro-electrique desCristaux bons conducteurs de I'electricite : 
 Aim. Ch. Phys., IV., xvii., 79, 1869.' 
 
 Hose. Ueber den Zusammenhang zwischen hemiedrischer Krystallform und thermo-elek- 
 trischem Verhalten beim Eisenkies und Kobaltglanz ; Pogg., cxh'i., 1, 1871. 
 
 Schrauf u. E. S. Dana. Ueber die thermo-elektrischen Eigenschaften von Mineral varie- 
 taten; Ber. Ak. Wien, Ixix., 1874 (Am. J. Sci., IIT., viii., 255). 
 
 Hankel. Ueber die thermo-elektrischen Eigenschaften des Boracites ; Sachs. Ges. Wiss., 
 vi., 151, 186o; ibid., viii., 323, 1866; Topaz, ix., 1870, 359; 10 Abhandlung, 1872, 21; cal- 
 otte, beryl, etc., 1876. 
 
 On MAGNETISM reference may be made to Faraday (Experimental Researches) ; Tyndall, 
 Phil. Mag. ; Knoblauch and Tyndall, Pogg., Ixxxi., 481, 498 ; Ixxxiii., 384 ; Pflucker, Pogg., 
 Ixxii., 315; IxxvL, 576; Ixxvii., 447; Ixxxvi., 1; Grailich u. von Lang, Ber. Ak., Wien, 
 xxxii., 43 ; xxxiii., 439, etc., etc. 
 
 VI. TASTE AKD ODOR. 
 
 In their action upon the senses a few minerals possess taste, and others 
 under some circumstances give off odor. 
 
 TASTE belongs only to soluble minerals. The different kinds of taste 
 adopted for reference are as follows : 
 
 1. Astringent / the taste of vitriol. 
 
 2. Sweetish astringent / taste of alum. 
 
 3. Saline ; taste of common salt. 
 
 4. Alkaline taste of soda. 
 
 5. Cooling / taste of saltpeter. 
 
 6. Bitter ; taste of epsom salts. 
 
 7. Sour : taste of sulphuric acid. 
 
 ODOK. Excepting a lew gaseous and soluble species, minerals in the dry 
 unchanged state do not give off odor. By friction, moistening with the 
 breath, and the elimination of some volatile ingredient by heat or acids, 
 odors are sometimes obtained which are thus designated : 
 
 1. Alliaceous j the odor of garlic. Friction of arsenical iron elicits this 
 odor; it may also be obtained from arsenical compounds, by means of heat. 
 
 2. Horse-radish odor / the odor of decaying horse-radish. This odor is 
 strongly perceived when the ores of selenium are heated. 
 
 3. Sulphureous j friction elicits this odor from pyrite and heat from 
 many sulphides. 
 
 4. Bituminous ; the odor of bitumen. 
 
 5. Fetid / the odor of sulphuretted hydrogen or rotten eggs. It is eli- 
 cited by friction from some varieties of quartz and limestone. 
 
 6. Argillaceous / the odor of moistened clay. It is obtained from sep- 
 
 * Spft also on r>. 190. 
 
172 PHYSICAL CHARACTERS OF MINERALS. 
 
 pentine and some allied minerals, after moistening them with the breath ; 
 others, as pyrargillite, afford it when heated. 
 
 The FEEL is a character which is occasionally of some importance ; it is 
 said to be smooth (sepiolite), greasy (talc), harsh, or meagre, etc. Some 
 minerals, in consequence of their hygroscopic character, adhere to the to 
 when brought in contact with it. 
 
SECTION IL SUPPLEMENTARY CHAPTER. 
 
 I. COHESION AND ELASTICITY (pp. 119 to 122). 
 
 THE etching-figures (Aetzfiguren) produced by the action of appropriate 
 solvents upon the surfaces of crystals have been further investigated in the 
 case of a considerable number of minerals, and the results have in some 
 cases served to throw light upon the question as to which crystalline system 
 a given species belongs. See the investigations of BAUMHAUEE of the 
 etching-figures of lepidolite, tourmaline, topaz, calamine, Jahrb. Min., 1876, 
 i. ; pyromorphite, mimetite, vanadinite, ib., 1876, 411 ; of ad nl aria, albite, 
 fluorite, ib., 1876, 602 ; of leucite, Z. Kryst., i.,257, 1877; quartz, ib., ii., 
 117, 1878; mica (zinnwaldite), ib., iii., 113, 1878; bora-cite, ib., iii., 337, 
 1879; perofskite, ib., iv., 187, 1879; nephelite, ib., vi., 209, 1882. (For 
 earlier papers giving results of etching experiments on muscovite, garnet, 
 linnaeite, biotite, epidote, apatite, gypsum, in Ber. Ak. Miinchen, 1874, 
 245 ; 1876, 99.) On the etching-figures of alum, see FR. KLOCKE, Z. 
 Kryst., ii., 126, 1878 ; of the different micas, F. J. WIIK, Oefv. Finsk. Vet. 
 Soc., xxii., 1880. 
 
 On the artificial twins (twinning-plane ^R) of calcite produced by 
 simple pressure with a knife-blade on the obtuse edge of a cleavage frag- 
 ment, see BAUMHAUER, Zeitschr. Kryst., iii., 588. 1879 ; BREZINA, ib., iv., 
 518, 1880. The fragment should have a prismatic form, say 6-8 mm. in 
 length and 3-6 mm. in breadth, and be placed with the 
 obtuse edge on a firm horizontal support. The blade 
 of an ordinary table-knife is then applied to the other 
 obtuse edge, as at a (f. 412A), and pressed gradually and 
 firmly down. The result is that the portion of the crys- 
 tal lying between a and b is reversed in position, as if 
 twinned parallel to the horizontal plane %R. The 
 twinning surface, gee, is perfectly smooth, and the 
 re-entrant angle corresponds very exactly with that required by theory 
 (Brezina). Earlier observations by Pfaff and Keusch have shown that 
 twin lamellae ( %R) may be produced in a cleavage mass of calcite of 
 prismatic form, by simple pressure exerted perpendicular to a straight ter- 
 minal plane. Such twinning lamellae are often observed in thin sections of 
 a crystalline limestone when examined in polarized light under the micro- 
 scope. 
 
 On the application of the fracture-figures (Schlagfiguren) in the optical 
 examination of the mica species see Bauer, ZS. G. Ges.. xxvi., 137, 1874 
 (for earlier papers see p. 122) ; Tschermak, Z. Kryst., ii., 14, 1877. On 
 the occurrence of Gleitflaclien on galena see Bauer, Jahrb. Min., 1882, i., 
 183. 
 
 II. SPECIFIC GRAVITY (pp. 123, 124). 
 
 Use of a Solution of high Specific Gravity. A solution of mercuric 
 iodide in potassium iodide (Hg 2 I in KI) affords a means of readily ob- 
 taining the specific gravity of any mineral not acted upon by it chemically, 
 
 173 
 
174 SPECIFIC GRAVITY. 
 
 and for which G. < 3-1 ; and also of separating from each other minerals of 
 different densities, when intimately mixed in the form of small fragments. 
 The solution is called the Sonstadt solution, having been first proposed 
 by E. SOXSTADT in 1873 (Chem. News, xxix., 127) ; its application for the 
 above objects was proposed by CHURCH in 1877 (Min. Mag., i., 237) ; and 
 the method elaborated by THOULET in 1878 (0. R., Feb. 18, 1878 ; Bull. 
 Soc. Min., ii., 17, 189, 1879), and later by GOLDSCHMIDT (J. Min., Beil.- 
 Bd.,i., 179, 1881). 
 
 The solution is prepared (Goldschmidt) as follows : The KI and HgJ 
 are taken in the ratio of 1:1-239, and introduced into a volume of water 
 slightly greater than is required to dissolve them (say 80 cc. to 500 gr. of 
 the salts) ; the solution is then filtered in the usual way and afterward evap- 
 orated down in a porcelain vessel, over a water-bath, until a crystalline scum 
 begins to form, or when a fragment of tourmaline (G. =3-1) floats ; on cooling, 
 the solution has its maximum density. If the mercuric iodide is not quite 
 pure a small quantity in excess of that required by the above ratio must be 
 taken. The highest specific gravity for the solution obtained by Gold- 
 schmidt was 3-196, a solution in which fluorite floats. This maximum is 
 not quite constant, varying with the moisture of the atmosphere and with 
 the temperature. 
 
 The method of using the solution for obtaining the specific gravity of 
 small fragments of any mineral is, according to Goldschmidt, as follows : The 
 fragments are introduced into a tall beaker, say 40 cc. capacity, with a por- 
 tion of the concentrated solution ; then water is added drop by drop (or r, 
 dilute solution of the same for high densities) from a burette, until the frag- 
 ments, after being agitated, are just suspended, and remain so without either 
 rising or falling. This process requires care and precision, since the princi- 
 pal error to which the method is liable is involved here. The solution is now 
 introduced into a little glass flask, graduated say to hold just 25 cc., and this 
 amount having been exactly measured off, the weight is taken ; then the 
 solution is poured back into the original beaker and the fact noted whether 
 the fragments still remain suspended ; then introduced again into the flask 
 and weighed, and so a third time. The average result of the three weigh- 
 ings, diminished by the known weight of the flask and divided by 25, gives 
 the specific gravity. The exact measurement of the 25 cc. is a matter of 
 importance, and is most easily accomplished by adding at first a little more 
 than enough and then removing the excess by a capillary tube or a piece of 
 filter paper ; the reading is best taken from the lower edge of the meniscus. 
 It is not necessary to clean and dry the flask each time. The weighing need 
 not be very accurate, as an error of 25 mgr. only involves a change of a unit 
 in the third decimal place (-001). The describer readily obtained results 
 accurate to three decimals. The advantages of the method are that it is 
 readily applicable in the case of small fragments (dust is to be avoided), it is 
 easily used, and any want of homogeneity in the mineral makes itself at once 
 apparent. 
 
 This solution is also most useful in affording a means of separating me- 
 chanically different minerals when intimately mixed together ; as, for example, 
 in a fine-grained rock. For this purpose the rock must first be pulverized 
 in a steel mortar, then put through a sieve, or better, through several, so as 
 to obtain a series of sets of fragments of different size ; the dust is rejected. 
 The fragments should be examined under the microscope, to see that they are 
 homogeneous ; the largest fragments satisfying this condition will give the 
 best results. 
 
SPECIFIC GRAVITY. 
 
 175 
 
 According to Thoulet the best method of procedure is to first determine the 
 density of the fragments approximately by inserting typical ones in a series 
 of samples of the solution of gradually Increasing density. This point deter- 
 mined, some 60 cc. of the concentrated solution are introduced 
 into the tube, A, and 1 or 2 grams of the weighed fragments (f 
 added. Then the tightly-fitting rubber cork with the tube, 
 F, is inserted ; the tube, F, is connected by a rubber tube with 
 an air pump, and the air bubbles are in this way removed from 
 the powder. The heavy parts of the mixture fall to the bottom, 
 and are removed by opening the stop-cock at (7, and are washed 
 out by use of the tube, B ; the other fragments float. Now a 
 quantity of distilled water is added in order so to dilute the solu- 
 tion as to cause the next heavier portions to sink, as determined 
 by the equation 
 
 tr, = 
 
 - A) 
 
 A 1 
 
 I 
 
 where v = volume of the solution, D its specific gravity, Vi the 
 volume of the water, and A the density desired. The cock 
 at D is shut and that at C opened and air blown through the 
 side tube, so as to mix the solution thoroughly ; then the original 
 operation is repeated, and so on. 
 
 GOLDSCHMIDT recommends the following method of procedure. 
 The separation is conducted in a small slender beaker of about 
 40-50 cc. capacity. Instead of the series of standard solutions 
 (the density of which is liable to alter) a series of minerals of y 
 
 known specific gravity are used as indicators ; by means of them it 
 is easy to determine the limits as to density which are required to make the 
 separation desired, the constituent minerals having been determined by the 
 microscope. For example, suppose it to be desired to separate augite, horn- 
 blende, oligoclase, and orthoclase ; labradorite and albite are taken as indica- 
 tors. Augite falls at once in the concentrated solution ; if diluted till the lab- 
 radorite sinks, all the hornblende goes down ; before or with the albite the 
 oligoclase sinks, and the orthoclase is left suspended. By the use of the 25 cc. 
 flask, the exact specific gravity in each case can be obtained if desired. The 
 operation of separation goes on as follows : The rock powder and the indicators 
 are inserted with say 30 cc. of the concentrated solution into the beaker spoken 
 of, then the whole is stirred vigorously and allowed to settle, and the lighter part 
 decanted off. The heavier part which has settled is removed with a jet from 
 a wash bottle, without disturbing the lighter fragments adhering to the upper 
 part of the beaker. The latter are subsequently removed, washed, dried, 
 again washed in the solution, and added to the rest for the further separation. 
 If the separations accomplished in this way are not complete, they may be 
 repeated most conveniently with the Thoulet apparatus. Under favorable 
 conditions, and if the manipulation is skilful, the separation can be accom- 
 plished with considerable exactness. For the best results the process must be 
 repeated several times. 
 
 THOULET recommends also (1. c.) this method of determining the specific 
 gravity of small fragments of minerals. A float of wax (inclosing any suit- 
 able solid body) is made with a specific gravity of from 1 to 2. The frag- 
 
176 SPECIFIC GRAVITY. 
 
 ments of the mineral are lightly pressed into the wax float, and this intro- 
 duced into the Sonstadt solution, of such strength that the float remains in 
 
 equilibrium at any level. If P, V, D are respectively the weight, volume, 
 
 / p \ 
 
 and density of the float alone I V = j and JP, v, d the same values for the 
 
 fragments alone ( v = - J and finally A the density of the liquid in which 
 the loaded float is in equilibrium ; then 
 
 ni 
 
 has proposed (Bull. Soc. Min., iii., 46, 1880) the following method 
 for separating different minerals intimately mixed, which is applicable in 
 cases where their density is greater than that of the Sonstadt solution. Lead 
 chloride and zinc chloride, m appropriate proportions, are fused together (at 
 400 C.) and by this means a transparent or translucent solution is obtained 
 of high specific gravity. Briefly, the method of procedure is as follows : A 
 conical tube of glass is taken, of about 12 to 15 cc. capacity ; this will allow of 
 the treatment of 4 or 5 grams of the mixed minerals. The chlorides of lead 
 and zinc, in approximately the proper proportions, are placed in the glass tube 
 and this, surrounded by sand, inserted in a platinum crucible. On the ap- 
 plication of heat the zinc chloride fuses first, but finally a homogeneous mix- 
 ture of the two liquids is obtained. Now, little by little, the mineral frag- 
 ments are introduced and the liquid stirred ; then on allowing it to stand for 
 a moment the heavier particles sink to the bottom and the lighter ones float. 
 The tube is now removed from its sand bath and cooled rapidly. When 
 solidified but still hot the glass may be plunged into cold water, in which 
 case it will be broken and the fragments can be removed, so that the fused 
 mass within can be obtained free. Subsequently the fragments in the upper 
 and lower parts of the mass can be separated by solution in water to which a 
 little acetic acid has been added. The author has operated on minerals vary- 
 ing from wolframite (G. = 7-5) to beryl (G. = 2-7), and in some samples 
 of sand has separated as many as 12 constituent minerals. 
 
 D. KLEIN- (Bull. Soc. Min., iv., 149, 1881) has proposed to use one of the 
 boro-tungstate salts in the place of the Sonstadt solution for the separation 
 of minerals whose specific gravity is as high as 3-6. The most suitable salt 
 for this purpose is the cadmium compound, JLCdaBaWQC^ + ie aq. It dis- 
 solves at 22 C. in about -fa its weight of water, and crystallizes out both 
 on evaporation and cooling. At 75 C. it melts (best over a water-bath) in 
 its water of crystallization to a yellow liquid, on the surface of which a 
 spinel crystal (G. =3 -55) floats. By the application of the Thoulet appara- 
 tus (see above), so arranged as to allow of the application of heat, solutions 
 of any specific gravity, hot or cold, from 1 to 3-6, can be obtained. A num- 
 ber of common minerals (e. g. chrysolite, epidote, vesuvianite, some varie- 
 ties of amphibole and mica) can be separated by the use of this liquid, while 
 the Sonstadt solution is inapplicable. The fragments under examination 
 must be free from the carbonates of calcium or magnesium, which decom- 
 pose the boro-tungstate of cadmium. 
 
TOTAL KEFLECTROMETEE. 177 
 
 III. LIGHT (pp. 125-168). 
 
 Measurement of Indices of Refraction. 
 
 For the determination of the indices of refraction of crystallized minerals, 
 various improvements have been made in former methods and some new 
 methods devised. 
 
 Use of the Horizontal Goniometer. The ordinary method for determining 
 the index of refraction, requiring the observation of the angle of minimum 
 deviation (d) of a light-ray on passing through a prism of the given mate- 
 rial, having a known angle (<*), and with its edge cut in the proper Direc- 
 tion, has already been mentioned (p. 128). The two measurements required 
 in this case can be readily made with the horizontal goniometer of Fuess, 
 described on p. 115. In this instrument the collimator is stationary, being 
 fastened to a leg of tho tripod support, but the observing telescope with, the 
 verniers moves freely. In the use for this object the graduated circle is to be 
 clamped, and the screw attachments connected with the axis carrying the 
 support, and the vernier circle and observing telescope are to be loosened. 
 The method of observation requires no further explanation (see also pp. 
 141, 150). 
 
 Total Reflectrometer.J?. KOHLRAUSCH has shown (Wied. Ann., iv., 1,1878) 
 that the principle of total reflection (p. 128) may be made use of to deter- 
 mine the index of refraction in cases where other methods are inapplicable. 
 No prism is required, but only a small fragment having a single polished 
 surface ; this may be cut in any direction for an isotrope medium ; it should 
 be parallel to the vertical axis in a uniaxial crystal, and perpendicular to the 
 acute bisectrix with a biaxial crystal. The arrangements required are, in 
 their simplest form, a wide-mouthed bottle filled with carbon disulphide 
 (refractive index 1-0) ; the top of this is formed by a fixed graduated circle, 
 and a vertical rod, with a vernier attached, passes through the plate and car- 
 ries the crystal section on its extremity, immersed in the liquid. The angle 
 through which the crystal surface lying in the axis is turned is thus meas- 
 ured in the same way as in f. 412H, by the vernier on the stationary gradu- 
 ated circle. The front of the bottle is made of a piece of plate glass, and 
 through this passes the horizontal observing telescope, arranged for parallel 
 light. The rest of the surface of the bottle is covered with tissue-paper, 
 through which the diffuse illumination from say a sodium flame has access ; 
 the rear of the bottle is suitably darkened. When now the observer looks 
 through the telescope, at the same time turning the axis carrying the crystal 
 section, he will finally see, if the source of illumination is in a proper oblique 
 direction, a sharp line marking the limit of the total reflection. The angle 
 is then measured off on the graduated circle, when this line coincides with 
 one of the spider lines of the telescopo. Now the crystal is turned in the 
 opposite direction, and the angle again read off. Half the observed angle 
 (2a) is the angle of total reflection ; if n is the refractive index of the car- 
 bon disulphide, then the required refractive index is equal to 
 
 n sin a. 
 
 Under favorable conditions the results are accurate to four decimal places. 
 This method is limited, of course, to substances whose refractive index is less 
 than that of the liquid medium with which the bottle is filled. With a sec- 
 
 19 
 
178 MEASUREMENT OF INDICES OF REFRACTION. 
 
 tion of a uniaxial crystal, whose surface is most conveniently parallel to 
 the vertical axis, the method is essentially the same. The section is so 
 placed that in it the direction normal to the optic axis is horizontal. The 
 light will be here separated into two rays, having separate limiting surfaces, 
 and with a Nicol prism it is easy to determine which of them corresponds 
 to the vibrations parallel and perpendicular, respectively, to the optic axis. 
 For biaxial crystals the surface should be normal to the acute bisectrix. This 
 will give by actual observation the values of a and y, and if %E, the appa- 
 rent axial angle in air, is known, then /?, the mean index can be calculated 
 (see p. 150). Instead of carbon disulphide the Sonstadt solution, with 
 n = 1-73, can be employed. The total reflectrometer of Kohlrausch has been 
 adapted in practical form to the horizontal goniometer (f. 372A) of Fuess 
 (see Liebisch, Ber. Ges. Nat. Fr. Berlin, Dec. 16, 1879). Klein has sug- 
 gested some improvements ( J. Min., 1879, 880), and Bauer (J. Min., 1882, 
 i., 132) has shown how the method can be simply applied to the instrument 
 for the measurement of the optic axial angle (f. 412n), and without its 
 modification in any important respect. 
 
 QUINCKE (abstract in Z. Kryst., iv., 540) has described another method 
 for obtaining the refractive index of a substance on the principle of total 
 reflection. In a word, it consists in observing on a spectrometer the limit- 
 ing angle of total reflection for a plane section of the substance to be inves- 
 tigated, brought with oil of cassia between two flint glass prisms. 
 
 SORBY (Proc. Eoy. Soc., xxvi., 384; Min. Mag., i., 97, 194; ii., 1, 103) 
 has developed the method of obtaining the refractive index of a transparent 
 medium, first described by Duke de Chaulnes (1767), and has shown that 
 under suitable conditions it allows of determinations being made with con- 
 siderable accuracy. This method consists in observing the distance (d) which 
 the focal distance of the objective is changed when a plane-plane plate of 
 known thickness (t) is introduced perpendicular to the axis of the microscope 
 between the objective and the focal point here 
 
 Sorby makes use of a glass micrometer, upon which two systems of lines 
 perpendicular to each other are ruled. The micrometer screw at g, in the 
 Kosenbusch microscope (f. 412K, p. 181), makes it possible to measure the 
 distance through which the tube is to be raised and lowered down to -001 
 mm. ; consequently both t and d can be obtained with a high degree of 
 accuracy. 
 
 BAUER has shown that the indices of refraction may be obtained with con- 
 siderable accuracy from measurements, in the plane of the axes, of the distances 
 between the black rings in the interference figures as seen in homogeneous 
 light. The relation between these distances and the optical axes of elasticity 
 was established by Neumann (Pogg. Ann., xxxiii., 257, 1834). Bauer has 
 made use of this method in the case of muscovite (Ber. Ak. Berlin, 1877, 704). 
 He has also developed the same method as applied to uniaxial crystals and 
 employed it in the case of brucite (ib., 1881, 958). 
 
 Polarization Instruments. 
 Polariscope. The earlier forms of polari scope for converging and for par- 
 
POLARIZATIOX INSTRUMENTS POLABI8COPE. 
 
 179 
 
 412c. 
 
 412E. 
 
 ol of?*' aS arran ed by Groth and constructed bv Fuess, are shown in fi<rs. 
 384, 38o, p. 134. The more 
 recently constructed instru- 
 ments (see Liebisch, 1. c., p. 
 342 et seq.), with some impor- 
 tant improvements, are shown 
 in f. 412c and f. 412D. The 
 lower tube, /, containing the 
 analyzer, has about it a collar, 
 /' (see details, figure 412F), 
 with a triangular projection 
 on the upper edge ; this fits 
 into one of two correspond- 
 ing triangular depressions 
 (0 and 45) in the surround- 
 ing tube, g. This serves to 
 fix the position of the tube, 
 that is, of the vibration-plane 
 of the enclosed Kicol, with ref- 
 erence to the fixed arm, B, to 
 which the verniers are at- 
 tached, so that the principal 
 section of the Nicol either co- 
 incides with, or makes an 
 angle of 45 with the line 
 of the verniers. The circle, t, 
 is graduated to 1, and with 
 the vernier gives readings to 
 2' ; the section to be examined 
 is supported at k. A similar 
 collar, u, surrounds the upper 
 tube, v, by which the posi- 
 tion of the micrometer (at r) 
 (this micrometer consists of 
 two lines at right angles, one 
 of which is graduated) can also 
 be fixed relatively to the ver- 
 nier so that the graduated line 
 of the micrometer is perpendic- 
 ular to the plane through the 
 axis of the instrument and the 
 zero of the vernier. The tube 
 above carrying the Nicol has 
 at s a graduated circle which 
 shows the relative directions of 
 the vibration -planes of the two 
 Nicols. The lenses at n and o 
 
 412F. 
 
 are arranged so that they may be used all together, when strongly converging 
 light is needed, or the small 'lenses may be removed, so that three combina- 
 tions are possible. A small screw at a makes it possible to adjust the position 
 of the glass micrometer so that it shall always be in the focus of the lenses at 
 o, a point which varies according to the combination of lenses employed. 
 
180 
 
 POLARIZATION INSTRUMENTS. 
 
 Slauroscope Calderon's Plate. The stauroscope is essentially the same in- 
 strument as that mentioned in f. 385. Instead, however, of employing the 
 Brezina interference-plate of calcite, a double plate is used, as suggested by Cal- 
 deron (Z. Kryst , ii., 68). This plate is, in fact, an artificial twin, andismade 
 as follows : A calcite rhombohedron is cut through along the shorter diagonal ; 
 from each half a wedge-shaped portion is cut away and the two surfaces thus 
 produced, after being polished, are cemented together. A plane-plane plate is 
 then cut from this (compare figure) by grinding 
 away the angles as indicated ; this platens divided 
 into two halves by the line of separation of the 
 artificial twin. Such a plate is very sensitive, and 
 allows of very exact observations. It is placed at m 
 (f. 4l2o), and when the arrangements are completed 
 
 I--"' --;' the dividing line of the calcite exactly coincides with 
 
 a vibration-plane of one of the two Nicols. A diaphragm is placed above 
 with holes of varying size according to the minuteness of the crystal to be 
 examined. The stauroscopic determinations made by Calderon showed an 
 error of only 3' to 7'. 
 
 Axial-angle Instrument (see p. 148). The instrument for the measure- 
 ment of the angle of the optic axes is in principle essentially that of Des 
 Cloizeaux, but in the details of the construction various improvements have 
 
 been introduced (see f. 412H). The same arrangement of adjustable collars 
 at u' and/ is employed as in the other instruments, to fix the position of the 
 principal sections of the Nicols relatively to the plane passing through the axis 
 of the observing telescope and the axis 'of rotation, Instead of the straight 
 rod in f. 401, in the pincers at the extremity of which the crystal section is 
 
POLARIZATION MICROSCOPE. 
 
 181 
 
 -N 
 
182 
 
 POLARIZATION INSTRUMENTS. 
 
 held, there is here an arrangement consisting of two concentric tubes, turn- 
 ing independently, but so as to be clamped at e. The adjustable disk hav- 
 ing a horizontal motion at F, and the spherical segment at H (Petzval 
 support) allow cf the section being both centered and adjusted. 
 
 Polariscope of Adams- Schneider. A polariscope of peculiar construction, 
 giving a very large field of view, and at the same time allowing of the meas- 
 urement of the axial angle, was proposed in 1875 by ADAMS (Phil. Mag.. IV., 
 1., p. 13, 1875; V., viii., 275). The same instrument has been further devel- 
 oped by SCHNEIDER (Carl. Rep., xv., 744), and is also described by BECKE 
 (Min. Petr. Mitth., ii., 430, 1879). The peculiarity of the instrument con- 
 sists in this, that the middle plano-convex lenses which ordinarily are fixed 
 to the upper and lower lens systems, respectively (see 0, 0, 0, and n, n, n, in 
 f. 412c), are here separated from the others in a common support, and to- 
 gether form a sphere. The course of the light-rays will be always the same, 
 however the sphere is rotated about its fixed centre. Between the semi- 
 spherical lenses a space is left, and here is introduced the section to be ex- 
 amined, which, turning with the surrounding lenses, can obviously be made 
 to take any desired position with reference to the axis of the instrument. An 
 appropriate arrangement makes it possible to measure the angle through 
 which the section must be rotated to bring first one and then the second 
 optic axis in coincidence with the axis of the instrument. The advantages 
 of the instrument consist in the fact that the field of view is very large, and 
 at the same time it allows of placing the section in any desired position rela- 
 tively to the axis. Moreover, the angle measured is the apparent angle for 
 the glass of which the lenses are made, so that the axes are visible in cases 
 where this would not be the case, because of total reflection, either in air or 
 in oil. 
 
 Polarization- Microscope. The investigation of the form and optical prop- 
 erties of minerals when in microscopic form, as they occur, for example, in 
 rocks of fine crystalline structure, has been much facilitated by the use 
 of instruments specially adapted for this purpose. The most serviceable 
 polarizing microscope, for general use, is that described by Rosenbusch ( Jahrb. 
 Min., 1876, 504), and made by R. Fuess, of Berlin. A sectional view is 
 given in f. 412K. The essential arrangements are as follows : The coarse ad- 
 justment of the tube carrying the eye-piece and objective is accomplished by 
 412L the hand, the tube sliding freely 
 
 in the support, p. The fine ad- 
 justment is made bv the screw, 
 g\ the screw-head is graduated 
 and turns about a fixed index 
 attached to p, by this means 
 the distance through which the 
 tube is raised or lowered can 
 be measured to 0*001 mm.; 
 this is important in determin- 
 ing the indices of refraction 
 by the De Chaulnes-Sorby meth- 
 od (see p. 178). The polarizing 
 prism (Razumovsky) is placed 
 below the stage at r, in a sup- 
 port, with a graduated circle, so 
 that the position of its vibration-plane can be fixed. The analyzing prism 
 is placed above the eye-piece in a support, s, which may be removed at 
 
POLARIZATION MICROSCOPE. 183 
 
 pleasure ; the edge of this is graduated and a fixed mark on the plate, /", makes 
 it possible to set the vibration-plane in any desired position. When both prisms 
 are set at the zero mark, their vibration -planes are crossed (_L); when either 
 is turned 90, the planes are parallel (||). The stage is made to rotate about 
 the vertical axis, but otherwise is fixed ; its edge is graduated, so that the 
 angle through which it is turned can be measured to |. Three adjustment 
 screws, of which one is shown at n, n, make it possible to bring the axis of 
 the object glass in coincidence with axis of rotation of the stage (see fur- 
 ther the detailed drawing at the side). 
 
 This instrument is especially applicable to the study of the form and opti- 
 cal properties of minerals as they are found in thin sections of rocks (on the 
 method of preparing see p. 159), although it can also be used with small in- 
 dependent crystals and crystalline sections or fragments. The more impor- 
 tant points to which the attention is to be directed, more particularly in the 
 case of minerals in sections of rocks, are : (1) crystalline form, as shown in 
 the outline ; (2) direction of cleavage lines ; (3) index of refraction ; (4) 
 light absorption in different directions, i. e., dichroism or pleochroism ; (5) 
 the isotrope or anisotrope character, and if the latter, the direction of the 
 planes of light-vibration this will generally decide the question as to the 
 crystalline system ; (6) position of the axial plane and nature of the axial 
 interference figures when they can be observed, and the positive or negative 
 character of the double refraction ; (7) inclosures, solid, liquid or gaseous. 
 
 In regard to these several points a few general remarks may be made.* 
 
 (1) Crystalline Form. In most rocks well defined crystals are rather the exception than 
 the rule. It will be consequently only in occasional sections (e. g. more commonly in vol- 
 canic rocks) that a clear crystalline outline is observed. The form of this outline will de- 
 pend upon the direction in which the section is cut, and will vary as it varies ; this fact 
 will explain why in a given rock section so many widely different forms of a given mineral 
 are observed ; this irregularity is increased by the fact that the crystals may be more or 
 less distorted. For the recognition of the form, consequently, considerable familiarity 
 with the various outlines likely to occur in the case of a given species is very desirable. 
 
 The angles between any two crystalline directions is obtained by first bringing one of 
 them in coincidence with a spider line in the eye-piece, the adjustment at N' having been 
 previously made, and then noting the angle through which the crystal, i. e., the stage, 
 must be rotated to bring the other direction in coincidence with the same spider line. 
 
 (2) Cleavage. The process of grinding involved in the making of a thin section tends to 
 develop the cleavage lines. Here are to be noted, (1) the direction of cleavage (measured 
 as above), depending on the direction in which the section is cut ; and (2) the character of 
 the cleavage. For example, a basal section of a crystal of amphibole shows the cleavage 
 lines parallel to the prism (12H); a vertical section shows one set of vertical and parallel 
 
 * For the full development of this subject, see the works of ROSENBUSCH and ZIRKEL 
 (titles on p. 111.) ; also the following : 
 
 BORICKY, E. Elemente einer neuen chemisch-mikroskopischen Mineral- und Gesteins- 
 analyse, 72 pp. 4to, Frag, 1877. 
 
 COHEN, E. Sammlung von Mikrophotographieen zur Yeranschaulichung der mikroskop- 
 ishen Structur von Mineralien und Gesteinen, aufgenommen von J. Grimm in O-fienburg, 
 1, 2, 3, 4, 5 Lfg., Stuttgart, 1881-82. 
 
 DOELTER. Die Bestimmung der petrographisch wichtigeren Mineralien durch das Mikro- 
 skop ; Eine Anleitung zur mikroskop. Gesteins-Analyse, 33 pp. 8vo, Vienna, 1876. 
 
 FOUQUE, F. and MICHEL-LEVY, A. Mineralogie micrographique, roches eruptives Fran- 
 9aises, 509 pp. 4to, Paris, 1879. 
 
 RUTLEY, F. The Study of Rocks, 319 pp. 12mo, London, 1879. 
 
 THOULET. Contributions a 1'ttude des proprietes physiques et chemiques des mineraux 
 microscopiques, 77 pp. 8vo, Paris. 
 
 HAWES, G. W. The Mineralogy and Lithology of New Hampshire (Geology of New 
 Hampshire, vol. iiU, 262 pp. 4to, with 12 plates. " Pages 8-18 of this work give an excel- 
 lent summary of microscopic methods of investigation, as applied to rocks and minerals. 
 
184 POLARIZATION INSTRUMENTS. 
 
 cleavage lines. On the other hand, a basal section of a crystal of pyroxene shows the pris- 
 matic cleavage, here less perfect than in the amphibole, and at an angle of 87 and 93 ; 
 a vertical section again shows only one set. Also a basal section of mica shows no cleav- 
 age lines, but a vertical section shows a series of very fine parallel lines corresponding to 
 tha highly perfect basal cleavage. 
 
 (3) The index of refraction is obtained by the method of the Duke de Chaulnes, as devel- 
 oped by Sorby (see p. 178). 
 
 (4) Pleochroism. To examine the pleochroism of a mineral section, the lower prism is 
 inserted and set at 0, so that its vibration-plane coincides with the direction to 180 on 
 the stage. If now the section be placed on the stage and the latter rotated, the absorption 
 of the light vibrating in the same plane with the prism can be observed. For example, a 
 vertical section of biotite is dark when the direction of the cleavage lines is || with the above 
 named line (0 to 180 of stagey for the light which it transmits has vibrations in this plane 
 only, and these are strongly absorbed ; on the contrary, when the stage is rotated 90 the 
 section becomes light, because the light vibrating || to this direction, is but slightly ab- 
 sorbed ; on the other hand, a basal section shows no difference of light absorption. 
 
 (5) Isotrope or Anisotrope, etc. Supposing the prisms in position and placed with their vi- 
 bration-planes perpendicular, a section of an amorphous substance, as glass, will remain 
 dark in all positions as it is rotated upon the stage, for it has sensibly the same light-elastic- 
 ity in all directions, since no one direction has any advantage over another. 
 
 A section of an isometric mineral will also remain dark as it is revolved between the 
 crossed prisms. A section of a tetragonal or hexagonal crystal parallel to the base will also 
 remain unchanged between crossed prisms ; a vertical section, or one inclined to the base, 
 will be dark only when the directions of the spider lines coincide with the vertical and trans- 
 verse directions ; in other words, the extinction directions are || and JL to the prism. A 
 section of an orthorhombic crystal will have its directions of extinction coincident with the 
 crystallographic axes. A section of a monoclinic crystal cut parallel to any direction in the 
 orthodiagonal zone will have its extinction directions parallel to the clinodiagonal axis and 
 perpendicular ; that is, if prismatic in habit. || and J_ to the prism, hence in this position 
 it cannot be distinguished from an orthorhombic crystal. On the other hand, in the case of 
 a section cut in any other plane, the position of the' extinction directions will depend upon 
 the individual crystal. For the exact determination of these directions with reference to 
 any crystallographic lines present, the method of the stauroscope must be employed. For 
 minute s?ctions a quartz plate (JL vertical axis) is sometimes inserted (ZZ at it in f. 41 2K); 
 this gives for a proper position of the upper prism a field of uniform delicate color (say 
 violet). A section of an anisotrope mineral placed on the stage will have the same color only 
 when its extinction directions are || and 1 to the vibration plane of the lower prism (rr, in 
 f. 412K). A special eye-piece (see f . 412K) provided with a Calderon plate is also sometimes 
 employed. 
 
 (6) If the eye-piece is removed, and at the same time suitable lenses added, two at T (f. 
 41 SK) and one above, strongly converging light is obtained. In many cases wh' n the sec- 
 tion is cut in the proper direction, the axial interference figures can be seen as distinctly as 
 in the ordinary polariscope. A {-undulation mica plate mr.kes it possible in such cases to 
 determine the + or character of the double refraction. On the use of microscope for the 
 observation of the optic axes, see v Lasaulx, J. Min., 1878, 377, and Z. Kryst., ii., 256 ; Ber- 
 tram!, Bull. Soc. Min., 1878, 27 ; Klein, Nachr. Gcs. Wiss. Gottingen, 1878, 461 ; Laspeyres, 
 Z. Kryst, iv.. 460. 
 
 (7) For a description of the various inclosures often observed in sections of minerals, and 
 the method of studying them, reference must be made to the works referred to above. 
 
 When it is desired to observe the effect of increased temperature on the mineral sections or 
 their enclosures (e.g. liquid CO?) the air bath (f. 41 SL) heated by the lamp, L, and provided 
 with a delicate thermometer, is employed. This fits into the stage at T, and the section is 
 placed above at ss. 
 
 Microscope of Bertrand. Bertrand (Bull. Soc. Min., iv., 97-100, 1880) 
 has devised a form of microscope especially adapted for mineraloencal work, 
 and allowing of the determination of the form and optical properties of min- 
 erals in crystals or sections so small that they cannot be employed in the or- 
 dinary polariscopes. The tube carrying the eye-piece and objective has the 
 ordinary coarse and fine adjustments ; the former is accomplished by a rack 
 and pinion movement, and is measured by a scale and vernier; the latter is 
 madn by a so row with a graduated head situated similarly to that in the Eo- 
 senbusch microscope. An opening in the tube above the objective allows of 
 
CAUSE OF OPTICAL ANOMALIES OF CRYSTALS. 185 
 
 the introduction of a little slide carrying a small lens, whose vertical position 
 can be adjusted by an appropriate rack and pinion turned by a screw head ; 
 this auxiliary lens may either magnify the interference figures of the crystal 
 section or else the section itself, when the position of the former is properly 
 adjusted. The objective can be centered by horizontal screws, and immedi- 
 ately above it a quartz wedge, or quarter-undulation plate of mica, can be in- 
 troduced for the determination of the character of the double refraction. 
 The stage has two movements in directions at right angles to each other, for 
 each of which a special scale with a vernier is supplied ; also, the stage ro- 
 tates in a horizontal plane, and is supplied with a graduation to allow of the 
 measurement of the angle of rotation. The lower polarizing prism is supplied 
 with several lenses for producing strongly converging light, and by a screw 
 can be moved in a vertical direction. In addition, a small goniometer with 
 oil bath is provided, which can be placed upon the stage, and which allows 
 of the measurement of the optic axial angle of the section under examination. 
 The special advantages of this instrument, as shown by the observations of the 
 inventor with it, as also those of Des Oloizeaux, are that it allows of all the 
 necessary optical determinations even in crystals or crystal sections which are 
 extremely minute. 
 
 On the Cause of the so-called Optical Anomalies of Crystals. 
 
 [The following paragraphs contain a brief statement of the results of some of the more 
 important of recent investigations bearing upon the subject of the "Optical Anomalies" of 
 crystals. It will be seen that the main point at issue is as to the true explanation of the 
 phenomena of double-refraction, observed in many crystallized minerals of apparent iso- 
 metric form (as garnet, fluorite, boracite, analcite, etc. \ and analogous variations from the 
 theoretical optical character in crystals apparently tetragonal, hexagonal, etc. (as vesuvi- 
 anite, zircon, corundum, beryl, etc.). Are these "optical anomalies" a proof that the appa- 
 rent symmetry of the observed form is only pseudo-symmetry, being due to the complex 
 twinning of parts of lower grade of symmetry than that which the crystal as a whole simu- 
 lates? In other words, do the optical properties actually belong to the inherent molecular 
 structure of the parts of the crystal ? Or, does the geometrical form of the whole really 
 represent the true symmetry of the crystal, and are these phenomena (of double-refraction 
 in isometric crystals, for example) due to secondary causes, such as internal tension pro- 
 duced during the growth of the crystal, and so on ? 
 
 In regard to this subject, it may be remarked that it is beyond question, on the one hand, 
 that pseudo-symmetry is to some extent a law of nature, for the crystals of many minerals, 
 of unquestioned orthorhombic character simulate hexagonal forms (e. g., aragonite) ; on the 
 other hand, it is equally certain that the phenomena of double-refraction may be produced 
 in colloid or crystalline isotrope media by a state of tension, and similarly that uriiaxial 
 crystals may be made biaxial by pressure, and so on. Which of these two explanations is 
 to be applied in the large number of cases now under discussion cannot be regarded as 
 settled, although the writer inclines to the opinion that the second explanation, more fully 
 detailed later, will be found to hold true in the case of the majority. This does not seem, 
 however, to be the place nor the time for a full review of the testimony which has been ac- 
 cumulated on both sides of the question.] 
 
 There are a considerable number of minerals, the crystals of which exhibit 
 optical phenomena which are not in accordance with the apparent symme- 
 try of the crystalline form. Cases of this kind were observed by Brewster 
 (1815 and later), and investigated by him with a remarkable acuteness con- 
 sidering the imperfect instruments then available. For example, alum, anal- 
 cite, boracite, diamond, fluorite, halite were shown by Brewster to exert an 
 effect on polarized light not in accordance with their apparent isometric 
 form. With the improved methods and means of investigation at the dis- 
 posal of mineralogists in recent times, the list of minerals whose crystals ex- 
 hibit " optical anomalies" has been very largely increased. 
 
186 CAUSE OF OPTICAL ANOMALIES OF CRYSTALS. 
 
 In explanation of these anomalies, various hypotheses have been advanced. 
 BEEWSTEE explained them in the case of diamond as due to local tension 
 connected with solid or gaseous inclosures. In 1841 BIOT published his 
 memoir on lamellar polarization (0. R. xii., 967 ; xiii., 155, 391, 839), and 
 explained the optical characters of the minerals named above, as also the 
 tetragonal apophyllite, as due to that cause. The idea advanced by him was 
 that the crystal was made up of thin lamellae, which exerted on transmitted 
 light an effect analogous to that of a bundle of parallel glass plates. VOLGEB 
 (1854-5) attempted to show that in the case of boracite the anomalous opti- 
 cal properties were due to the presence of a doubly-refracting anisotrope 
 mineral, parisite, derived from alteration ; much later (1868) this view was 
 accepted by Des Cloizeaux. MAEBACH (Pogg. Ann., xciv., 412, 1855) dis- 
 cussed the question more broadly, and concluded that the phenomena ob- 
 served were due to the presence in the normal substance of abnormal aniso- 
 trope portions, which last owed their existence to a tension produced at the 
 time the crystal was formed. It was further shown by VON REUSCH (ib. cxxxii., 
 618, 1867) that the hypothesis of Biot was not sufficient to explain the observed 
 facts in the case of alum. He also took up the view of Marbach, and follow- 
 ing out much the same idea as that of Marbach, reached the conclusion that 
 the anisotrope characters of isometric crystals were due to the condition of 
 internal tension existing within the crystal. As bearing upon the question 
 he proved by experiment that by suitable pressure, in the case for example 
 of alum crystals, the double-refraction could be removed. The influence of 
 pressure in causing double refraction was early investigated by F. E. NEU- 
 MANN (Pogg. Ann., liv.. 449, 1841), and by PFAFF (ib., cvii., 333 ; cviii., 
 578, 1859). The subject has also been discussed by HIESCHWALD (Min. 
 Mitth., 1875, 227). 
 
 More recently the idea of internal molecular tension as a cause of anoma- 
 lous optical characters has been developed by Klocke, Jannettaz, Klein, Ben 
 Saude and others, as more particularly described later. 
 
 In 1876 MALLAED published his most important memoir (Ann. Min., 
 VII. , x., 60-196) upon this subject, in which he not only gave a very large 
 number of new facts of a similar nature, but also advanced a new explana- 
 tion which has been warmly accepted by some mineralogists. He regards 
 all the indications of double-refraction observed in apparent isometric crys- 
 tals, and analogous variations from the normal character in crystals of other 
 systems, as proof that the form is only apparently isometric, tetragonal, and 
 so on (pseudo-isometric, pseudo-tetragonal, etc.), the union of several indi- 
 vidual crystals giving rise to an external form of a higher grade of symmetry 
 than that which they themselves possess. On his view, an apparent iso- 
 metric cube may, in fact, be a combination of six uniaxial crystals (count- 
 ing two parallel as one, in fact only three independent), each having the 
 form of a square pyramid, united so that their bases form the sides of the 
 cube, and their vertices are combined at the centre. Again, an apparent 
 regular octahedron may be made up of eight uniaxial triangular pyramids, 
 similarly placed ; a dodecahedron of twelve rhombic pyramids (boracite), or 
 perhaps of forty-eight triclinic triangular pyramids, the bases of four com- 
 bining to form a rhombic face. In most of these cases the optic axis coin- 
 cides with the axis of the pyramid. 
 
 Mallard thus includes among pseudo-isometric species : alum, analcite, 
 boracite, fluorite, garnet, senarmontite ; among pseudo-tetragonal species : 
 apophyllite, mellite, octahedrite, rutile, vesuvianite, zircon ; among pseudo- 
 
CAUSE OF OPTICAL ANOMALIES OF CRYSTALS. 187 
 
 hexagonal species : apatite, beryl, corundum, perminite, ripidolite, tourma- 
 line ; pseudo-orthorhombic species: harmotome, topaz; pseudo-monoclinic : 
 orthoclase. 
 
 Many observations similar to those of Mallard have been made by BER- 
 TRAXD (in Bull. Soc. Min., 1878-1882), who applies the same method of 
 explanation to them. For explanation, Bertrand has described crystals of 
 garnet which were biaxial, with an angle of about 90 ; a hexoctahedron 
 being made up, in his view, of forty-eight triangular pyramids, four to each 
 pseudo-rhombic pyramid. Each pyramid is biaxial, with the acute negative 
 bisectrix nearly normal to the base/ and the axial plane coincides with the 
 direction of the longer diameter of the rhombic face. Further, apparent 
 tetrahedral crystals of romeite are regarded as formed of four rhombohedrons 
 of 120, placed with their vertices at a common point. Also in the case of 
 rorneite the octahedrons are, in his view, formed by the grouping of eight 
 rhombohedral crystals of 90 about a central point. "The above will serve as 
 illustrations. Bertrand has extended his observations over a considerable 
 number of specias, and the explanation given by Mallard of the optical phe- 
 nomena just described is strongly supported by him, as against the Mar- 
 bach-Reusch theory of molecular tension, more minutely described below. 
 Bertrand urges (Bull. Soc. Min., v., 3, 1882) that a true doubly-j-efracting 
 crystal, whether simple or a complex twin, can always be distinguished from 
 a crystal normally isotrope, but modified through internal tension or any 
 other cause. The difference, he states, is to be seen in parallel polarized 
 light, where the former will show a distinctness and uniformity of character 
 which does not belong to the latter ; still more clearly in converging light, 
 where the truly doubly-refracting crystal shows throughout the same char- 
 acters, each fragment into which the section may be broken giving the iden- 
 tical uniaxial or biaxial figures with the whole ; on the other hand, this can- 
 not be true of the different parts of a crystal made doubly-refracting through 
 some cause, as contraction, and so on. As illustrations of these facts, he 
 appeals to boracite, garnet, pharmacosiderite, etc., stating that, as the re- 
 sult of his observations, they fall into the former class. He speaks further of 
 octahedrons of boracite formed of twelve biaxial crystals, and of romeite 
 formed of eight uniaxial crystals, as showing that the internal structure is 
 independent of the external form ; as bearing further upon this point, it is 
 stated that the imperfect crystals of the garnet rock of Jordansmuhl show 
 the same twinning of biaxial individuals as do isolated crystals of garnet, 
 whose external form is complete. But reference must be made to the obser- 
 vations alluded to beyond, which do not entirely support the conclusions of 
 Bertrand. 
 
 This subject has been discussed by GRATTAROLA, who includes calcite, 
 quartz, nephelite, barite, etc., in the list of species which have an apparent 
 symmetry higher than that which really belongs to them ; his conclusions, 
 however, are not based upon observations (Dell' unita cristallonomica in 
 Mineralogia, Florence, 1877). 
 
 In many other cases, besides those mentioned above, observers have, on the 
 basis of variation in angles, or of optical characters, reached the conclusion 
 that the species in question really belongs to a system of lower symmetry than 
 that to which it has been ordinarily referred. For example, see'Des Cloizeaux 
 on microcline and milarite ; Rumpf on apophyllite (Min. Petr. Mitth., ii., 
 369); Becke on chabazite (ib., ii., 391), and hessite (ib., iii., 301); 
 Schrauf on brookite (Ber. Ak. Wien, Ixxiv., 535 and Z. Kryst., i., 274) and 
 
188 CAUSE OF OPTICAL ANOMALIES OF CRYSTALS. 
 
 other species ; Brezina on autunite (Z. Kryst., iii., 273); Tschermak on the 
 micas (Z. Kryst., ii., 14) and corundum (Min. Petr. Mitth., ii., 362) ; and 
 many other cases. These last named observations, however, do not generally 
 admit of being explained on the hypothesis of Mallard. In many of them the 
 conclusions reached are beyond doubt correct, in others the question must be 
 regarded as still undecided. 
 
 TSCHERMAK proposes the term mimetic for those forms ("mimetische For- 
 men"), which imitate a higher grade of symmetry by the grouping (twinning) 
 of individuals of a lower grade of symmetry, as for example, aragonite ; also, 
 chabazite, which, according to Becke, is apparently rhombohedral, but, in 
 fact, formed by a complex twinning of triclinic individuals (this conclusion, 
 however, is not universally accepted). He also uses the term pseudo-sym- 
 metry to describe the phenomena in general (ZS. G. Ges., xxxi., 6o7, 1879, and 
 Lehrb. Min., p. 89 et seq., 1881). 
 
 The explanation of the optical phenomena referred to above, which was 
 presented by Marbach and later developed by Reusch, has been recently still 
 further elaborated by Klocke (J. Min., 1880, i., 53, 158), Klein, Jannettaz, 
 Ben Saude. KLOCKE'S first observations were made upon artificial crystals of 
 alum. He found that each crystal (contrary to earlier statements) showed 
 doubly refracting properties as strongly normal to an octahedral plane as in 
 other directions. A section parallel to this plane was divided into six sectors 
 by radial lines passing from the angles to the centre ; the directions of extinc- 
 tion in each sector being || (parallel) and J_ (perpendicular) to its outer edge, 
 these directions consequently coinciding for each pair of opposite sectors. 
 These sectors behaved as if made up of bands in a state of tension parallel to 
 their longer direction ; a similar result was obtained by subjecting a six-sided 
 octahedral and isotrope alum section to pressure perpendicular to two of its 
 edges. He found further that all the sections of the same crystal, independ- 
 ent of the crystallographic orientation, were alike as regards the direction of 
 the tension, and that all crystals made at the same time, that is, under the 
 same conditions, yielded identical results ; but this was not true of crystals 
 made at different times. Further it was found that the distortion peculiar to 
 the crystal exerted an essential effect upon the number and arrangement of 
 the optical sectors, and that the position which the crystal occupied in the 
 vessel during its formation was also an important factor. 
 
 Later the same author (J. Min., 1881, ii., 249) has extended his observa- 
 tions to some of the species exhibiting pseudo-symmetry. He shows, among 
 other results, that pressure exerted normal to the vertical axis of a section of a 
 tetragonal or hexagonal crystal which has been cut J_ c ( vert. ), changes the uni- 
 axial interference figure into a biaxial, and with substances optically positive, 
 the plane of the optic axes is parallel, and with negative substances normal, 
 to the direction of pressure. This was observed on sections of vesuvianite 
 and apophyllite which exhibited uniaxial portions. Many sections are divided 
 into four optical fields (biaxial) with the axial plans perpendicular to the 
 edge. The behavior of each field in a section of apophyllite consequently is 
 (optically +, see above) as if in a state of tension parallel to the adjacent com- 
 bination-edge with the prism; but with vesuvianite (optically ) the direc- 
 tion of tension is perpendicular. This explanation is supported by the fact 
 that pressure exerted in the proper direction serves, in accordance with the 
 above principles, respectively to increase or diminish the axial angle. The 
 author also succeeded in obtaining axial interference figures visible in con- 
 verging polarized light in gelatine sections when under pressure ; the same 
 phenomenon in parallel light had been earlier observed. 
 
CAUSE OF OPTICAL ANOMALIES OF CRYSTALS. 189 
 
 On the observations of JANNETTAZ, showing the effect of internal tension 
 in causing double-refraction, see Bull. Soc. Min., ii., 124; ii., 191; iii, 20. 
 
 The results of the observations of KLEI^ (J. Min., 1880, ii., 209 ; 1881, 
 i., 239) on boracite have an important bearing upon this subject. As stated 
 above, it is included by Mallard among the pseudo-isometric species. Basing 
 his results more especially upon the examination of crystals of dodecahedral 
 habit, Mallard concluded that the apparent simple form is made up of twelve 
 rhombic pyramids whose basal planes form the twelve faces of the dodecahe- 
 dron. Baumhauer, on the basis of results of etching experiments, more par- 
 ticularly on crystals of octahedral habit, concluded that the species was or- 
 thorhombic, the apparent simple form being made up of six individuals whoso 
 bases would coincide with the cubic planes (p. 187). The observations of 
 Klein show that the structure of the crystals of different habits vary some 
 agreeing with the scheme of Mallard some with that of Baumhauer ; he 
 shows, however, very conclusively (as it seems to the writer) that this appa- 
 rently complicated structure is probably due to internal tension produced 
 during the growth of the crystals. Crystallographically there is no variation 
 in angle from the requirements of the isometric system to be observed. In 
 regard to the optical characters, he shows that the interior optical structure 
 does not correspond to the exterior planes ; that the etching figures do not 
 correspond to the optical limits; that a change of temperature alters the 
 relative position of the optical fields without influencing the form of the 
 etching figures ; that the differently orientired optical portions lose their 
 sharp limits, they change their position relatively, some disappearing in part 
 or whole, and others appearing.* Klein has also made a series of optical 
 studies on garnet (Nachr. Ges. Wiss. Gottingen, June 28, 1882), and after a 
 review of the whole subject decides in favor of the true isometric character of 
 the species ; the double-refraction phenomena observed being due to secondary 
 causes. 
 
 BE^ SAUDE (J. Min., 1882, i., 41) has investigated analcite, and arrived at 
 the conclusion that with it also the abnormal optical characters are to be ex- 
 plained by internal molecular tension. He shows that the crystals are formed 
 of different optical parts, in combinations of 30 with the cube and trapezo- 
 hedron together, and 24 for the trapezohedron alone, the form of which 
 changes as the outer surfaces of the crystals change. The structure can be 
 explained in this way, as made up of pyramids going from each plane to the 
 middle of the crystal having the plane as its base, with as many sides as there 
 are edges to the plane ; as the outer form changes the optical structure 
 changes correspondingly ; every edge corresponds to an optical boundary, and 
 every plane to an optical field. All these double-refraction phenomena are 
 explained as due to secondary causes. Moreover, the author has proved that 
 gelatine cast into the form of the natural crystals has on solidifying an analo- 
 
 *A memoir by Mallard (Bull. Soc. Min., v., 144, 1882) upon the effect of heat upon bo- 
 racite crystals was received just as these pages were going to press. Mallard details the 
 results of numerous experiments, and concludes that the effect of heat does not modify the 
 form of the ellipsoid of elasticity, nor the position of the six different orientations which it 
 can have ; it only modifies the choice made by each of the crystal sections between the six 
 orientations. From this it is concluded that this ellipsoid is in fact characteristic of the 
 crystalline reseau of the species, and that the apparent isometric symmetry is due to the 
 method of grouping alluded to. Analogous results were obtained with crystals of potas- 
 sium sulphate (orthorhombic, pseudo-hexagonal like aragonite), and the conclusion is drawn 
 from this that a perfect analogy exists between the so-called pseudo-isometric crystals and 
 the pseudo- hexagonal. 
 
190 RECENT PAPERS ON HEAT AND ELECTRICITY. 
 
 gous optical structure, showing the same sections, the same directions of light- 
 extinction, and under favoring conditions the same position of the optic axes. 
 Ben Saude has also examined perofskite (Gekronte Preisschrift der Universitiit 
 Gottingen, 1882) from the same standpoint, with reference to the etching- 
 figures and optical phenomena. Ho concludes that it is to be referred to the 
 isometric system, and that the double refraction is to be explained as caused 
 by changes* in the original position of equilibrium produced in the growth of 
 the crystals. This conclusion, however, is at variance with the results of 
 the observations of others. 
 
 References to some important Recent Papers upon the Subjects of Heat and Electricity. 
 
 A. Arzruni. Ueber den Einfluss der Temperatur auf die Brechungsexponentcn der 
 natiirlichen Sulfate des Baryum, Strontium und Blei, Zeitsch. Kryst. i., 165, 1877. 
 
 J. Beckenkamp. Ueber die Ausdehnung monosymmetrische'r und asymmctrischer 
 Krystalle durch die Warme, Z. Kryst., v., 436, 1881. 
 
 H. Dufet. Influence de la temperature sur la double refraction du gypse, Bull. Soc. 
 Min., iv., 113, 1881 ; Influence de la temperature sur les indices principaux du gypse, ib., 
 iv., 191. 
 
 L. Fletcher. Ueber die Ausdehnung der Kristalle durch die Warme, Zeitschr. Kryst., 
 iv., 336. 
 
 Jannettaz. Memoire sur la propagation de la chaleur dans les corps cristallises, Bull. 
 Soc. Geol., IV., xxix., 5 ; Note sur la conductibiiite des corps cristallises pour la chaleur, 
 etc., ib., III., i., 117 ; Sur les proprittes thermiques des cristaux, ib., p. 252; see also ib., ii., 
 
 &264; iii., 499; iv., 1, 553 ; ix. ; Sur un appareil a conductibiiite thermique, Bull. Soc. 
 in., i., 119. 
 
 Joubert. Sur le pouvoir rotatoire du Quartz et sa variation avec la temperature, C. R., 
 Ixxxvii., 497, 1878. 
 
 F. von Lang. Ueber die Abhangigkeit der circularpolarization des Quarzes A'on der 
 Temperatur, Ber. Ak. Wien., Ixxi., 707, 1875. GfFosse und Lage der optischen Blast icitat- 
 saxen beirn Gypse, Ber. Ak. Wien., Ixxvi., 793, 1877. 
 
 0. J. Lodge. On a method of measuring the absolute thermal conductivity of crystals 
 and other rare substances, Phil. Mag., V., v., 110, 1878. 
 
 C. Pttpe. Die. Warmeleitung im Kupfervitriol, Wied. Ann., i., 126, 1877. 
 
 W. C. Rontgen. Ueber eine Variation der Senarmont'schen Methode zur Bestimmung der 
 Isothermenflachen in Krystallen, Pogg. Ann., cli., 603, 1874. Ueber eine Methode zur 
 Erzeugung von Isothermen auf Krystallen, Zeitschr. Kryst., iii., 17, 1878. 
 
 L. Sohncke. Ueber den Einfluss der Temperatur auf das optische Drehvermogcn des 
 Quarzes und des Chlorsauren Natrons, Weid. Ann., iii., 516, 1878. 
 
 S. P. Thompson and 0. J. Lodge. On unilateral conductivity in tourmaline crystals, 
 Phil. Mag., V., viii., 18, 1879. 
 
 Jacques et Pierre Curie. Dcveloppement par compression de 1'electricite polaire dans 
 les cristaux hemiedres a faces inclinees, C. E., xci., 294. 383, 1880; Lois du degagement 
 de 1'electricite par pression dans la tourmaline, ib., xcii., 186, 1881; Surlesphenomeneselec- 
 triques de la tourmaline et des cristaux hemiedres a faces inclinees, ib., xcii., 350; Les 
 cristaux hemiedres a faces inclinees comme sources constantes d'electricite, ib., xciii., 204. 
 
 C. Friedel. Sur la pyroelectricite dans la topaze, la blende et le quartz. 
 
 TF G. Hankel. Elektrische Untersuchungen (I. Thermoelektricitat, II. Aktinolektrici- 
 tat, III. Piezoelectricitat), Abhandl. K. Sachs Ges. Wiss., xii., 459,1881. Ueber eine 
 direct e Umwandlungder Schwingungen der strahlenden Warme in Electricitat, Ber. Sachs 
 Ges. Wiss., April 23, 1880, or Wied. Ann., x., 618. On the thermo-electrical properties of 
 various minerals see earlier papers (p. 171), and also (gypsum, diopside, orthoclase, albite, 
 pericline), Wied. Ann., i., 276. 
 
PA.RT II. 
 
 CHEMICAL MINERALOGY. 
 
 MINERALS are either the uncombined elements in a native state, or com 
 pounds of these elements formed in accordance with chemical laws. It is 
 the object of Chemical Mineralogy to determine the chemical composition 
 of each species ; to show the chemical relations of different species to each 
 other where such exist ; and also to explain the methods of distinguishing 
 different minerals by chemical means. It thus embraces the most import- 
 ant part of Determinative Mineralogy. 
 
 CHEMICAL CONSTITUTION OF MINERALS. 
 
 In order to understand the chemical constitution of minerals, some 
 knowledge of the fundamental principles of Chemical Philosophy is 
 required ; and these are here briefly recapitulated. 
 
 Chemical elements. Chemistry recognizes sixty-four substances which 
 cannot be decomposed, or divided into others, by any processes at present 
 known ; these substances are called the chemical elements. Of these 
 oxygen, hydrogen, and nitrogen are iixed gases; chlorine and fluorine are 
 generally gases, but may be condensed to the liquid state ; bnomine is a 
 volatile liquid ; and the rest, under ordinary conditions, quicksilver excepted, 
 are solids. Of these last carbon, phosphorus, arsenic, sulphur, boron, (tel- 
 lurium), selenium, iodine, silicon, generally rank as non-metallic elements, 
 and the others as metallic.* 
 
 Molecules / Atoms. By a molecule is understood the smallest portion of a 
 substance which possesses all the properties of the matter itself ; it is the 
 smallest division into which the substance can be divided without loss or 
 change of character. The molecule of water is the smallest conceivable 
 particle which can exist alone, and which has all the properties of water. 
 An atom is the smallest mass of each element which enters into combina- 
 tion with others to form the molecule. Thus two chemical units, or atoms, 
 of hydrogen unite with one atom of oxygen to form i\iQ physical unit, or 
 molecule, of water. 
 
 Atomic weights. The relative weights of the chemical units, or atoms, 
 of the different elements are their atomic weights. For the sake of uni- 
 
 * Recent investigations have added a considerable number of supposed new elements 
 to the list on the following page. 
 
192 CHEMICAL MINERALOGY. 
 
 formity the atom of hydrogen, the lightest of all the elements, has been 
 adopted as the standard or unit. The absolute weight of the atoms cannot 
 be determined ; but their relative weight can in many cases be fixed beyond 
 question. When the elements are gases, or form gaseous compounds, the 
 atomic weights are determined directly. Thus in hydrochloric acid gas 
 there are equal volumes of hydrogen and chlorine, or, chemically expressed, 
 one atom of hydrogen combines with one atom of chlorine ; by analysis it 
 is found that in 100 parts there are 2*74 by weight of hydrogen, and 97*26 
 of chlorine ; hence if hydrogen be taken as the unit, the atomic weight of 
 chlorine is 35*5, since 2-94 : 97*26 = 1 : 35-5. 
 
 Where the elements, or their compounds, are not gases, the atomic weights 
 are determined more or less indirectly, and are sometimes not entirely free 
 from doubt. The analysis of rock-salt gives us, in 100 parts, 60*68 parts of 
 chlorine, and 39*32 parts of sodium ; now if, as is believed, the number of 
 units of each element involved is the same, or in other words, if the mole- 
 cule consists of one atom each of chlorine and sodium, then the atomic 
 weights will be as 60*68 : 39*32 ; or 35*5 : 23, since that of chlorine = 35*5. 
 Hence the atomic weight of sodium is 23, when referred, like chlorine, to 
 that of hydrogen as the unit. There is an assumption in such cases as to 
 the number of units of each element involved which may introduce doubt, 
 so that other methods are applied which need not be here detailed. 
 
 The following table gives the atomic weights of the elements. The symbols 
 used to represent an atom of each element are shown in the table ; in most 
 cases they are the initial letter or letters of the Latin name. When more than 
 one atom is involved in the formation of a compound, it is indicated by a 
 small index number placed below, to the right : as Sb 2 O 3 , which signifies 2 
 of antimony to 3 of oxygen. The quantity by weight of any element enter- 
 ing into a compound is always expressed either by the atomic weight or 
 some multiple of- it ; hence the atomic weights are strictly the combining 
 weights of the different elements. 
 
 ATOMIC WEIGHTS. 
 
 Aluminum 
 
 Al 
 
 27-3 
 
 Cobalt 
 
 Co 
 
 59 
 
 Antimony 
 
 Sb 
 
 122 
 
 Columbium (Niobium) 
 
 Cb (Nb) 
 
 94 
 
 Arsenic 
 
 As 
 
 75 
 
 Copper 
 
 Cu 
 
 63-4 
 
 Barium 
 
 Ba 
 
 137 
 
 Didymium* 
 
 D 
 
 96-5 
 
 Bismuth 
 
 Bi 
 
 208 
 
 Erbium 
 
 E 
 
 112-6 
 
 Boron 
 
 B 
 
 11 
 
 Fluorine 
 
 F 
 
 19 
 
 Bromine 
 
 Br 
 
 80 
 
 Gallium 
 
 Ga 
 
 69*8 
 
 Cadmium 
 
 Cd 
 
 112 
 
 Glucinum (Beryllium) 
 
 G (Be) 
 
 9 
 
 Caesium 
 
 Cs 
 
 133 
 
 Gold 
 
 Au 
 
 196 
 
 Calcium 
 
 Ca 
 
 40 
 
 Hydrogen 
 
 H 
 
 1 
 
 Carbon 
 
 C 
 
 12 
 
 Indium 
 
 In 
 
 113-4 
 
 Cerium* 
 
 Ce 
 
 92 
 
 Iodine 
 
 I 
 
 127 
 
 Chlorine 
 
 Cl 
 
 35-6 
 
 Iridium 
 
 Ir 
 
 198 
 
 Chromium 
 
 Cr 
 
 52 Iron 
 
 Fe 
 
 56 
 
 * By the determination of the specific heats of cerium, didymium, and lanthanum, Dr. 
 Hillebrand has shown recently that the oxides of the three metals are sesquioxides (Ce a Ot, 
 DiaOs, La u O 3 ), and corresponding to them the atomic weights should be Ce = 138, Di = 
 144*8, La = 139. (Pogg. Ann., clviii., 71, 1876.) 
 
CHEMICAL CONSTITUTION OF MINERALS. 193 
 
 Lanthanum La 92 '5 
 
 Lead Pb 207 
 
 Lithium Li 7 
 
 Magnesium Mg 24 
 
 Mg 
 Mn 
 
 Manganese Mn 55 
 
 Mercury Hg 200 
 
 Molybdenum Mo 96 
 
 Nickel Ni 59 
 
 Nitrogen N 14 
 
 Osmium * Os 200 
 
 Oxygen O 16 
 
 Palladium Pd 106 
 
 Phosphorus P 31 
 
 Platinum Pt 198 
 
 Potassium K 39 
 
 Rhodium Bo 104 
 
 Rubidium Rb 85 '4 
 
 Ruthenium Ru 104 
 
 Selenium Se 79 
 
 Silver Ag 108 
 
 Silicon Si 28 
 
 Sodium Na 23 
 
 Strontium Sr 88 
 
 Sulphur S 32 
 
 Tantalum Ta 182 
 
 Tellurium Te 128 
 
 Thallium Tl 204 
 
 Thorium Th 231 
 
 Tin Sn 118 
 
 Titanium Ti 50 
 
 Tungsten W 184 
 
 Uranium U 240 
 
 Vanadium V 51 '4 
 
 Yttrium Y 61 '7 
 
 Zinc Zn 65 
 
 Zirconium Zr 90 
 
 Atomicity ; Quantivalence. The combining power of each element is 
 measured by the number of hydrogen atoms with which it combines in 
 forming a chemical compound. In hydrochloric acid (HC1), one atom of 
 hydrogen combines with one of chlorine ; in water (H 2 O), two atoms of 
 hydrogen combine with one of oxygen ; in ammonia (H 3 N), three atoms of 
 hydrogen combine with one of nitrogen ; and in marsh gas (H 4 C), four 
 atoms of hydrogen are required to enter into combination with one carbon 
 atom. 
 
 By the examination of compounds of all the elements we are able to fix 
 the combining power, or quantivalence, of each, expressed in hydrogen 
 units. All those elements which combine with one atom of hydrogen, or 
 an element which (like chlorine) has the same quantivalence, are called 
 monads ; those which require two of hydrogen, or two other monad atoms, 
 in forming the compound, are called dyads / those uniting with three atoms 
 of hydrogen are called triads / and similarly tetrads, pentads, hexads, and 
 heptads. 
 
 The adjective terms univalent, bivalent, trivalent, quadrivalent, etc., are 
 also employed with similar meaning. Atoms having the same decree of 
 quantivalence are said to be equivalent / this is true of Na and K, both 
 monads, and they may replace each other in similar compounds; but it 
 requires two sodium atoms to be equivalent to one calcium atom, since the 
 latter is a dyad. 
 
 The degree of quantivalence may vary for many of the elements in 
 different compounds ; for example, in FeO or FeS, iron (Fe) is bivalent, 
 since it satisfies or is combined with simply a dyad ; in FeS 2 , it is quadri- 
 valent, since it is united to two atoms of a dyad; and, similarly, in [Fe 2 ]O 3 
 it is sexivalerit (for the double atom). 
 
 Perissads ; Artiads. Those elements whose atoms have an odd qu anti- 
 valence (I, III, Y, or Y II), are called perissads / those whose quantivalence 
 is even (II, IY, YI) are called artiads. These terms, perissad and artiad, 
 are derived from irepia-a-o^ and a/mo?, the words for odd and even in 
 ancient arithmetic. The following table gives the division of the ele- 
 ments into these two classes, and shows, also, the quantivalence of each ele- 
 ment : - g 
 
194 
 
 CHEMICAL MINERALOGY. 
 
 PERISSADa 
 
 Monads: 
 Hydrogen. 
 
 Fluorine. 
 
 Chlorine, T, III. V, VII. 
 Bromine, I, III, V, VII. 
 Iodine, I, III, V, VIL 
 
 ABTIADS. 
 
 Lithium. 
 Sodium, 
 Potassium, 
 
 Rubidium. 
 Caesium. 
 
 Silver, 
 Thallium, 
 
 I, III. 
 
 i, in, v. 
 
 i, in. 
 i, in. 
 
 Triads : 
 
 Nitrogen, I, III, V. 
 Phosphorus. I, III, V. 
 Arsenic, I, III, V. 
 Antimony, III, V. 
 Bismuth, III, V. 
 
 Boron. 
 
 Gold, I, III 
 
 Pentads : 
 
 Columbium. 
 Tantalum. 
 
 Vanadium, in, V. 
 
 Dyads: 
 Oxygen. 
 
 Sulphur, II, IV, VI. 
 Selenium, II, IV, VI. 
 Tellurium, II, IV, VI. 
 
 Calcium, II, IV. 
 Strontium, II, IV. 
 Barium, II, IV. 
 
 Magnesium. 
 
 Zinc. 
 
 Cadmium. 
 
 Glucinum. 
 
 Yttrium. 
 
 Cerium. 
 
 Lanthanum. 
 
 Didymium. 
 
 Erbium. 
 
 Mercury [Hg a ] n , II. 
 
 Copper [Ouj",II. 
 
 Tetrads : 
 
 Carbon, II, IV. 
 
 Silicon. 
 
 Titanium, II, IV. 
 Tin, II, IV. 
 
 Thorium, 
 Zirconium. 
 
 Platinum, 
 Palladium, 
 
 Lead, 
 Indium. 
 
 II, IV. 
 
 n, iv. 
 n, iv. 
 
 Hexad* : 
 
 Molybdenum, II, TV, VI. 
 
 Tungsten, IV, VI. 
 
 Ruthenium, II, IV, VI. 
 
 Rhodium, II, IV, VI. 
 
 Iridium, II, IV, VI. 
 
 Osmium, II, IV, VI. 
 
 Aluminum, IV, [A1 S ] VI . 
 
 Chromium, II, IV, VI. 
 
 II, IV, VI. 
 II, IV, VI. 
 II, IV. 
 II, IV. 
 II, IV. 
 
 Iron, 
 Cobalt, 
 Nickel, 
 Uranium, 
 
 The general divisions of chemical compounds now accepted are as fol- 
 lows. 
 
 1. Binaries, where the atoms are directly united. Examples are given 
 by the compounds of a positive (basic) element with oxygen (Na 2 O, CaO, 
 CO 2 ), called oxides / those with sulphur, chlorine, bromine, iodine, etc., 
 called sulphides, chlorides, etc. Binary compounds of a negative element 
 with hydrogen (as HC1, HBr) form acids. 
 
 2. Ternaries, where the atoms are united by means of a third atom, as 
 oxygen, sulphur, etc., as CaSO 4 , Mg 2 SiO 4 , etc. 
 
 Among minerals there are three classes of compounds : (1) The Native 
 Elements ; (2) Binary compounds, including the sulphides, oxides, chlorides, 
 iodides, fluoride 's / (3) Ternary compounds, including sulph-arsenites, etc., 
 hydrates (hydrated oxides), silicates, mostly salts of the acids II 4 SiO 4 and 
 H 2 SiO 3 , tantalates, colurnbates, phosphates, arsenates, sulphates, chromates, 
 carbonates, etc. The full enumeration of these compounds, with their gen- 
 eral chemical formulas, are given in the synopsis which precedes the 
 Descriptive Mineralogy. 
 
 The position of water in the composition of minerals. Many minerals 
 lose water, especially upon the application of heat. With some of these it 
 is given off upon mere exposure to dry air at ordinary temperature, and 
 such crystals are said to effloresce ; others lose water when they are placed 
 in a desiccator over sulphuric acid, or when they are subjected to a slightly 
 
CHEMICAL CONSTITUTION OF MINERALS. 195 
 
 elevated temperature; with others, again, a greater heat is required; and 
 with a few silicates water is yielded only upon long continued heating at a 
 very high temperature. It is evidently possible that either, (1) the mineral 
 contains water as such, or (2) the water is formed by the process of decom- 
 position caused by the application of heat. In the cases first mentioned, 
 where water is readily given off, it is believed that the water actually exists 
 as such in the compound. It is found that many salts take up water when 
 they crystallize, and in some cases the amount of water depends upon the 
 temperature at which the salt is formed ; this water is called water of 
 crystallization. For example: manganous sulphate has three definite 
 amounts of this water of crystallization, according to the temperature at 
 which it has been formed. When crystallized below 7, its composition is 
 MnSO 4 + 7H 2 O; between 7 and 20, MnSO 4 4-5H 2 O ; and between 20 
 and 30, MnSO 4 + 4H 2 O. 
 
 In those cases where a very high temperature is required to make a loss 
 of water, it is quite certain the water has no place as such in the original 
 constitution, but, on the contrary, that the mineral contains basic hydrogen, 
 replacing the other basic elements. In some cases, where part of the water 
 is yielded at a low and the rest at a very high temperature, this shows that 
 a difference exists in regard to the part which the water plays in the two 
 cases ; for example, crystallized sodium phosphate yields readily 24 equiva- 
 lents of water, while the remaining 1 molecule is given off only at a tem- 
 perature between 300 and 400 ; from this it is concluded that in the 
 latter case the elements forming the water exist actually in the salt, and 
 that its composition is : 
 
 The part played by the water in the silicates is in most cases still unde- 
 cided, though in many species the hydrogen is undoubtedly basic. The 
 latter is doubtless true of many of the so-called hydrous silicates. The views 
 commonly held in regard to them will be gathered from the descriptive part 
 of this work. 
 
 Chemical formulas for minerals. A chemical formula expresses the 
 relative amounts of the different elements present in the compound, in 
 terms of their atomic weights or, in other words, more strictly the number 
 of atoms of each element in a given molecule with or without the expression 
 of their probable grouping. 
 
 Empirical formulas simply state in the briefest form the result of the 
 analysis, giving the number of atoms of each element present without any 
 theoretica ^Considerations. For example, the empirical formula of epidote 
 is Si 6 Al 3 Ca 4 tI 2 26 . 
 
 The object of the rational formulas is to express not only the number of 
 atoms of each element present, but also their probable method of grouping, 
 and relation to each other, in the molecule. These are called typical for- 
 mulas when the attempt is made to arrange the atoms in accordance with the 
 type of water, or some other type. 
 
 In the rational formulas of the old chemistry the oxygen (or sulphur) 
 was apportioned to the several elements, according to their combining 
 power, and the basic and acid oxides, or sulphides, thus obtained were writ- 
 ten consecutively. For example, the formula of wollastonite (calcium sili- 
 
196 CHEMICAL MINERALOGY. 
 
 cate), according to the old dualistic method, was written CaO, SiO 2 , and 
 of anhydrite (calcium sulphate), CaO, SO 3 . The principles of the new 
 chemistry have set aside these rational formulas ; but as others consistent 
 with the new principles now adopted have not in all cases been accepted, 
 it is customary to give the formulas of minerals empirically. For those 
 above the empirical formulas are CaSiO 3 and CaSO 4 . 
 
 Relation between the old and new systems. The points of difference 
 between the old and new chemistry have already been hinted at. The 
 principal changes which have been introduced by the latter are : (1) The 
 doubling of all the atomic weights, except those of the monad elements, 
 and also of bismuth, arsenic, antimony, nitrogen, phosphorus, and boron, 
 whose oxides are now written Bi 2 O 8 , instead of BiO 8 , etc. Corresponding 
 to this change, binary compounds involving the monad elements are writ- 
 ten : H 2 O instead of HO, Na 2 O for NaO, N^S, etc., also CaCl 2 instead CaCl, 
 SiF 4 instead of SiF 2 , and so on. (2) The method of viewing the composi- 
 tion of ternary compounds these being now regarded not as compounds 
 of an oxide and a so-called acid, but as compounds for the most part of 
 the several elements concerned, and hence a metal in a compound is 
 believed to be replaced by another metal, not one oxide by another. Hence 
 we say calcium carbonate, or carbonate of calcium instead of carbonate of 
 lime, and write the formula CaCO 3 , not CaO, CO 2 ; and so in the other 
 cases. 
 
 Replacing power of the different elements. It has been mentioned 
 that the replacing power of the* elements is in proportion to their combining 
 power, that is, to their quanti valence. For example, one atom of Mg or 
 of Ba may replace one atom of Ca, all being dyads ; but two atoms of Na 
 (monad) are required to replace one of Ca ; similarly three dyad atoms are 
 equivalent, or may replace, one hexad atom, thus, 3Ca = [A1 2 ]. 
 
 The relation of the different oxides may be understood from the follow- 
 ing scheme, in which the above principle is made use of. The line A 
 below contains the different kinds of oxides. B the same divided each by 
 its number of atoms of oxygen (that is, severally, for the successive terms, 
 by 1, 3, 2, 5, 3, 7, 4), by which division they are reduced to the protoxide 
 form. C the basic elements alone : 
 
 A RO R2O 3 RO 2 R 2 O 5 RO 3 R 2 O 7 RO 4 
 B RO R*O R*O R*O R*O R*O R*O 
 C R R* R* R2 R* K* R* 
 
 According to the above law the R, R f , R*, etc., in the last line, are mutu- 
 ally replaceable, 1 for 1, though varying in atomic weight from 1 to J. 
 They represent different states in which elements may exist, and have, to a 
 certain extent, independent element-like relations. In some cases, as in 
 iron, four of these states are represented in a single element, the compounds 
 (1) FeO, FeS, (2) Fe 2 O 3 , (3) FeS 2 , (4) FeO 3 , containing this metal in foni 
 states Fe, Fe, Fe, Fe*. 
 
 The use of the fractions can be avoided by multiplying, instead of divid- 
 ing, thus, Fe 1 of Fe 2 O 8 replaces Fe of FeO, we might have said, 2Fe of 
 Fe 2 O 3 replaces 3Fe of FeO (Fe 2 O 8 , Fe 3 O 8 ), and so for the others. 
 
 These different states of the elements are best designated in the symbols 
 
CHEMICAL CONSTITUTION OF MINERALS. 197 
 
 by the Greek letters a, /3, etc., thus avoiding all ccnf usion. The above 
 lines A, B, C then become 
 
 A aRO 3RO 2?RO 5SRO 3eRO 7RO 
 
 R aRO 0RO 7 RO SRO eRO fRO 7?RO 
 
 aR 0B 7R SR eR fB *;R 
 
 By means of this system all the different oxides may be reduced to the 
 common protoxide form, and thus the true relations of the silicates may be 
 clearly expressed. This is exhibited in the formulas for the silicates given 
 in Dana's System of Mineralogy (1868). 
 
 Calculation of a formula from an analysis. The result of an analysis 
 gives the proportions, in a hundred parts of the mineral, of either the ele- 
 ments themselves, or of their oxides or other compounds obtained in the 
 chemical analysis. In order to obtain the atomic proportions of the ele- 
 ments : Divide the percentages of the elements by the respective ATOMIC 
 WEIGHTS ; or, for those of the oxides : Divide the percentage amounts of 
 each by their MOLECULAR WEIGHTS ; then, find the simplest ratio in whole 
 numbers for the numbers thus obtained. 
 
 Examples. AJI analysis of bournonite from Meiseberg gave Rammels- 
 berg : Lead (Pb) 42*88, copper (Cu) 13-06, antimony (Sb) 24-34, and sul- 
 phur (S) 19*76 = 100*04. Dividing each amount by its atomic weight we 
 obtain : 
 
 The atomic ratio is hence : Pb : On : Sb : S = -207 : -206 : -217 : -6175 ; 
 that is, 1*005 : 1 : 1-053 : 2*998, or in whole numbers, 1:1:1:3. The 
 empirical formula is consequently CuPbSbS 3 . 
 
 An analysis of epidote from Untersulzbach gave Ludwig : 
 
 SiO A1O FeO 3 FeO CaO II 2 O 
 
 37-83 22-63 15-02 0-93 23*27 2-05 = 101-73. 
 
 From the results of the analysis given in this form, the percentage 
 amount of each element may be calculated in the usual way ; we obtain : 
 Si 17-65, Al 12-06, Fe 10-51, FeO 0-72, Ca 16-62, H 0.23, O 43*64. The 
 number of atoms of each element may be calculated from the last given 
 
 percentages by dividing each by the atomic weight, that is = '630 
 
 1 9'Ofi ** 
 
 f or Si, - 0-22 for Al (= A1 2 ), etc. Or, the percentage amounts of each 
 
 oo 
 oxide may be divided by its molecular weight, and the result will be the same ; 
 
 37*83 
 for SiO 2 , the molecular weight is 60 (28 + 2x16), hence, -^- = '630 aa 
 
 before ; also for Al, 103 (= 2 x 27'5 + 3 x 16), and -j^- = 0-22, etc. The 
 atomic proportions thus obtained are : 
 
198 CHEMICAL MINERALOGY. 
 
 Si &1 Fe Fe Ca H O 
 
 0-630 0-220 0-094 0-013 0-415 0-230 2-727, or simply 
 
 6 2-99 4-07 2-2 25-79, or again, 
 
 63 4 2 26. 
 
 The empirical formula is consequently Si 6 Al 3 Ca 4 H 2 O 26 . As in the above 
 case, it is necessary, when very small quantities only of certain elements 
 are present, to neglect them in the final formula, reckoning them in with 
 the elements which they replace, that is, with those of the same quanti va- 
 lence. The degree of correspondence between the analysis and the formula 
 deduced, if the latter is correctly assumed, depends entirely upon the accuracy 
 of the former. 
 
 Quantivalent Ratio. In the chemical constitution of most minerals 
 there exists a strong distinction between the basic and acidic elements, and 
 this relation, in the case of substances of complex character, is often fixed 
 when otherwise the composition is exceedingly varied. In the dualistic 
 formulas of the old chemistry this relation was expressed in the " oxygen- 
 ratio" which gave the ratio between the number of oxygen atoms belong- 
 ing respectively to the bases, protoxide and sesquioxide, and to the acid. 
 The expression, "oxygen-ratio," is not in harmony with the present method 
 of viewing chemical compounds, and the term has consequently been, to 
 some extent, abandoned ; the same relation, however, between the different 
 classes of elements still exists, but the ratio must be regarded as that exist- 
 ing between the total quanti valences of each group of elements, and hence 
 may be called the QUANTIVALENT RATIO.* 
 
 The old formula for all the members of the garnet family is 3R, fi, 38i 
 = 3RD, KO 3 , 3SiO 2 , and the oxygen ratio for & : S : Si = 1 : 1 : 2, or for 
 bases to silica, 1 : 1. Here II may be either Ca, Mg, Fe, Mn, or Cr, and R 
 either akl, Fe, Or. This formula, however, written according to the new 
 system (the quantivalence being expressed by Roman numerals over the 
 symbols), is : 
 
 II VI IV II II VI IV 
 
 ja ; or R^Cy Si s , 
 
 to indicate that the oxygen is regarded as all linking oxygen. The ratio 
 of the total quantivalences for each class of elements, dyads and hexads 
 (basic), and the tetrad silicon (acidic), is: 3 xll : VI : 3 xIY, or, Q. ratio 
 for R : R : Sif = 6 : 6 : 12, that is, 1 : 1 : 2. 
 
 The same ratio for (R-f-ffc) : Si = 1 : 1, both of which are identical with 
 the previously given oxygen ratio. 
 
 * This relation was brought out by Prof. Dana in 1867 (Am. J. Sci., xliv.. 89, 252, 308), 
 and it forms the basis of all the formulas, according to the new system, in Dana's System of 
 Yfineralogy, 1868. Prof. Cooke has discussed the same subjecc (Am. J. Sci., II., xlvii.. 880, 
 1869), he calls the ratio, the Atomic Ratio ; the latter term, however, is generally usrd in n 
 different sense, hence the expression Quantivalent Ratio employed here. 
 
 f Throughout this work the letter R, unless otherwise indicated, represents a bivalent 
 metal, and R either Fe, Al, <3r, Mn, where the quantivalence of the double atom is six. ID 
 ft few cases, to indicate further relations, the sign of the quantivalence is sometimes emDloved 
 
DIMORPHISM ISOMORPHISM. 199 
 
 Thus the oxygen ratio of the old system becomes the quantivalent ratio 
 of the new, " a term, too, which has a wider meaning and bearing than that 
 which it replaces." This principle of the ratio between the total quanti- 
 valences is an important one, and fundamental in the character of chemical 
 compounds. This is well shown in the example here given, where, for a 
 family of minerals of so varied composition as the garnets, it remains con- 
 stant in all varieties. Its importance is even more marked in the many 
 silicates where R replaces 311 (as in spodumene in the pyroxene family). 
 
 The quantivalent ratio is obtained by multiplying the quantivalence of 
 each class of elements present by their number of atoms; or by dividing 
 the percentage amount of each element by the atomic weight and multiply 
 by its quantivalence. When the basic or acid oxides are given, divide 
 the percentage amount of each by the molecular weight, and multiply as 
 before by the number expressing the quantivalence, and the result is the 
 total quantivalence for the given element. 
 
 DIMORPHISM. ISOMORPHISM. 
 
 A chemical compound, which crystallizes in two forms genetically dis- 
 tinct, is said to be dimorphous ; if in three, trimorphous^ or in general 
 pleomorphous. The phenomenon is called DIMORPHISM, or PLEOMORPHISM. 
 
 On the other hand, chemical compounds, which are of dissimilar though 
 analogous composition, are said to be isomorphous when their crystalline 
 forms are identical, or at least very closely related (sometimes called homceo- 
 morphous). This phenomenon is called ISOMORPHISM. 
 
 An example of pleomorphism is given by the compound calcium carbon- 
 ate (CaCO 3 ), which is trirnorphous : appearing as calcite, as aragonite, and 
 as baryto-calcite. As calcite* it crystallizes in the rhombohedral system, 
 and, unlike as its many crystalline forms are, they may be all referred to 
 the same fundamental rhombohedron, and, what is more, they have all the 
 same cleavage and the same specific gravity (2'7), and, of course, ..the same 
 optical characters. As aragonite, calcium carbonate appears in orthorhom- 
 bic crystals, whose optical characters are entirely different from those of 
 calcite, as will be understood from the explanations made in the preceding 
 chapter. Moreover, the specific gravity of aragonite (2'9) is higher than 
 that of calcite (27). Again, as baryto-calcite^ calcium carbonate crystal- 
 lizes in a morioclinic form. 
 
 The explanation of the phenomenon of pleomorphism in this case and 
 an analogous explanation must answer for all such cases is to be found, 
 not as was once proposed in a slight variation of chemical composition, but 
 in the different conditions in which the same compound has been formed. 
 Thus Rose has shown that the calcium carbonate precipitated from a solu- 
 tion by the alkaline carbonates in the cold has the form of calcite, whereas, 
 if the precipitation takes place at a temperature of 100 0., it takes the 
 form of aragonite. Moreover, he found that aragonite on heating fell to 
 powder, andlhough no loss of weight took place, the specific gravity (2'9) 
 became that of calcite (2'7). 
 
 Many other examples of pleomorphism may be given : Silica (S5O 2 ) is 
 trimorphous ; appearing as quartz, rhombohedral, G = 2'66 ; as tridymite. 
 
200 CHEMICAL MINERALOGY. 
 
 hexagonal, G = 2'3 ; and as asmanite, orthorhombic, G = 2*24. Titanic 
 oxide (TiO 2 ) is also trimorphous, the species being called rutile, tetragonal 
 (c = -6442), G = 4-25 ; octahedrite (c = 1-778), G = 3'9 ; and IrooUte, 
 orthorhombic or mouoclinic, G = 4*15. Carbon appeal's in two forms, in 
 diamond and graphite. Other familiar examples are pyrite and marcasite 
 (FeS 2 ) ; acanthite and argentite (A^ 2 S) ; sphalerite and wiirtzite (ZnS) ; 
 sulphur natural, orthorhombic, if artificial and crystallizing from a molten 
 condition, mouoclinic. The relation in form of the species mentioned, 
 and also of those of other dimorphous groups, will be found in Part III., 
 Descriptive Mineralogy. 
 
 Isomorphism is well illustrated by the group of rhombohedral carbonates, 
 with the general formula RCO S . Here R may be Ca, Mg, Fe, Mn, or Zn ; 
 or further, in the same species, the R may be represented by both Ca and 
 Mg in varying proportions, as remarked on the following page, or both Ca 
 and Fe, etc. The group is as follows : 
 
 Calcite. Dolomite. Magnesite. Bhodochrosite. Siderite. Smithsonite. 
 
 CaCO s 2'CO s MgC0 8 MnCO s FeCO 3 ZnCO 8 
 
 105 5' 106 15' 107 29' 106 51' 107 0' 107 40'. 
 
 Ankerite (parankerite), breunerite, mesitite, and pistomesite belong to 
 the same group. All the above species have an analogous composition, and 
 all crystallize in the rhombohedral system, the angle of the fundamental 
 form varying somewhat in the different cases. 
 
 Mitscherlich, who, by a series of experimental researches, established the 
 principle of isomorphism, expressed it as follows : Substances, which are 
 analogous chemical compounds, have the same crystalline form, or are 
 ISOMORPHOUS. 
 
 Some of the more important isomorphous groups are mentioned below, 
 for the description of the different species reference must be made to 
 Part III. 
 
 Isometric system. (1) The SPINEL group, having the general formula 
 RRO 4 , including spinel MgAlO 4 , magnetite FeFeO 4 , chromite FeOrO 4 . also 
 franklinite, galmite. etc. (2) The ALUM group, for example, potash-alum 
 K 2 AlS 4 O lb H-24aq, etc. (3) The GARNET group, having the general formula 
 
 Tetragonal system. RUTILE group, RO 2 ; including rutile TiO 2 , and cas- 
 siterite SnO 2 . The SCHEELJTE group ; including scheelite CaWO 4 , stolzite 
 PbWO 4 , wulfenite PbMO 4 . 
 
 Hexagonal system. APATITE group ; apatite 3Ca 3 P 2 O 8 -hCa(Cl, F) 2 , pyro- 
 
 inorphite 3Pb 3 P 2 O 8 + PbCl 2 , mimetite 3Pb 3 As2O 8 -f PbCl 2 , and vanadinite 
 3Pb 3 Y 2 O 8 -h PbCl 2 . COKUNDDM group, iiO 8 ; corundum A1O 3 , hematite 
 FeO 3 , menaccanite. 
 
 Rhombohedral system. CALcrrE group, RCO 3 , already mentioned. 
 
 Orthorhombic system. ARAGONITE group, RCO 3 ; aragonite CaCO 3 , 
 witherite BaCO 3 , strontianite SrCO 3 , cerussite JPbCO 8 . BARITE group, RSO 4 ; 
 barite BaSO 4 , celestite SrSO 4 , anhydrite CaSO 4 , anglesite PbSO 4 . CHRYSO- 
 LITE group, general formula, 
 
DIMORPHISM ISOMORPHISM. 201 
 
 Monoclinic system. COPPERAS group ; melanterite FeSO 4 4-7aq; bieberite 
 CoSO 4 -j-7aq, etc. Pyroxene group, RSiO 3 , etc. 
 
 Monodinia and Tridinic. Feldspar group. 
 
 The above enumeration includes only the more prominent arntng the 
 isornorphous groups. In many other cases a close relationship exists among 
 gpecies, both in form and composition, as brought out in Dana's System of 
 Mineralogy (1854), and as also to some extent exhibited in the grouping of 
 the species in the descriptive part of this work. 
 
 (1) It will be observed in the above that a replacement of an element in a 
 compound by one or more other elements, chemically equivalent, may take 
 place without any essential change of the crystalline form. Besides this a 
 part of one element may be similarly replaced. This is illustrated in the 
 case of the rhombohedral carbonates : calcite has the composition CaCO 8 , 
 and magnesite MgCO 3 ; but in dolomite the place of the basic element is 
 taken by Ca and Mg in equal proportions, so that the formula may be 
 written (JCa+Mg)CO 3 , or more properly CaMgC 2 O 6 . But besides this 
 compound there are others where the ratio of Ca to Mg is 3 : 2, also 2 : 1, 
 and 3 : 1, etc. Further than this the Ca or Mg may be in part replaced by 
 Mn, Fe, orZn. 
 
 The mineral ankerite is one in which Ca, Mg, Fe (Mn), all enter, and in 
 different proportions. Boricky has shown that the composition of the 
 ankerite group of compounds is expressed bv the formula : CaCO 3 -hFeCO 3 
 + a<CaMgC 2 O 6 ), where x may be i, 1, f, f, f, 2, 3, 4, 5, 10. This and all 
 similar cases are examples of isomorphous replacement. 
 
 It is not essential that the replacing elements in an isomorphous series 
 should have the same quantivalence, although this is generally true. For 
 example, spodumene is isomorphous with the pyroxene group, though in it 
 the bivalent element is replaced bv a sexivalent (3R, = Ki. So, too, menac- 
 
 II IV 
 
 canite was included in the corundum group, since here RRO 3 is isomor- 
 phous with !K) 3 . This relation of the elements, which are not equivalent, 
 is brought out by the method of viewing the oxides presented on p. 174. 
 
 (2). Minerals which crystallize in different systems may yet be isomor- 
 phous, when the difference between their geometrical form is slight ; this 
 is conspicuously true of the members of the feldspar family. 
 
 (3). Minerals may be closely related in form, although there is no ana- 
 logy whatever between their chemical composition ; many such cases have 
 been noted, e.g., axinite and glauberite, azurite and epidote. 
 
 Two substances may be both homoeomorphous and correspondingly 
 dimorphous ; and they are then described as isodimorphom. Titanic oxide 
 (TiO 2 ), and stannic oxide (SnO 2 ), are both dimorphous, and they are also 
 homceomorphous severally in each of the two forms. This is an example 
 of ixodimorphism. 
 
 There are also cases of isotrimorphism. Thus there are the following 
 related groups ; the angle of the rhombohedral forms here given is R : It \ 
 of the orthorhoinbic and monoclinic 1 : /(for baryto-calcite 2-S on 2-&): 
 
 RJiomboJiedral. OrtkorJiombic. Monodinic. 
 
 RC0 3 Calcite, 105 5'. Aragonite, 11<> 10'. Barytocalcite, 95 8'. 
 
 BSO 4 Dreelite, 93-94. Anglesite, 103 38'. Glauberite, 83-83 30'. 
 
 RS0 4 +nRCO 3 Susannite, 94. Leadhillite, 103 16'. Lanarkite, 84. 
 
202 CHEMICAL MINERALOGT. 
 
 Calcite, aragonite, and barytocalcite form an undoubted case of trimor 
 phism, as has already been shown. Dreelite, anglesite, and glauberite 
 constitute another like series, and moreover it is closely parallel in angle 
 with the former. In the third line we have the snlphato-carbonate susan- 
 nite near dreelite in angle, leadhillite (identical with susannite in composi- 
 tion) near anglesite, and lanarkite, another sulphato-carbonate, near glau- 
 berite, forming thus a third parallel line. The sulphuric acid in these sul- 
 phato-carbonates dominates over the carbonic acid, and gives the form of 
 the sulphates enumerated in the second line of the table. 
 
 CHEMICAL EXAMINATION OF MINERALS. 
 
 The chemical characters of minerals are ascertained (a) by the action of 
 acids and other reagents ; (b) by means of the blowpipe assisted by a few 
 chemical reagents ; (c) by chemical analysis. The last method is the only 
 one by which the exact chemical composition of a mineral can be deter- 
 mined. It belongs, however, wholly to chemistry, and it is unnecessary to 
 touch upon it here except to call attention to the remarks already made 
 (p. 160) upon the essential importance of the use of pure material for analysis. 
 
 The various tests and reactions of the wet and dry methods are important, 
 since they often make it possible to determine a mineral with very little 
 labor, and this with the use of the minimum amount of material. 
 
 a. Examination in the Wet Way. 
 
 The most common chemical reagents are the three mineral acids, hydro- 
 chloric, nitric, and sulphuric. In testing the powdered mineral with these 
 acids, the important points to be noted are: (1) the degree of solubility, 
 and (2) the phenomena attending entire or partial solution ; that is, whether 
 a gas is evolved, producing effervescence, or a solution is obtained without 
 effervescence, or ail insoluble constituent is separated out. 
 
 Solubility. In testing the degree of solubility hydrochloric acid is most 
 commonly used, though in the case of sulphides, and compounds of lead 
 and silver, uitric acid is required. Less often sulphuric acid, and aqua 
 regia (nitro-hydrochloric acid), are resorted to. 
 
 Many minerals are completely soluble without effervescence : among these 
 are some of the oxides, hematite, limonite, gothite, etc., some sulphates, 
 many phosphates and arseniates, etc. 
 
 Solubility with effervescence takes place when the mineral loses a gaseous 
 ingredient, or when one is generated by the mutual decomposition of acid 
 and mineral. Most conspicuous here are the carbonates, all of which dissolve 
 with effervescence, giving off carbonic acid (properly carbon dioxide, CO 2 ), 
 though some of them only when pulverized, or again, on the addition of 
 heat. In applying this test dilute hydrochloric acid is employed. Sul- 
 phuretted hydrogen (H 2 S) is evolved by some sulphides, when dissolved hi 
 hydrochloric acid: this is true of sphalerite, stibnite, greenockite, etc. 
 Chlorine is evolved by oxides of manganese and also chromic and vanadic 
 acid salts, when dissolved in hydrochloric acid. Nitric peroxide is given 
 off by many metallic minerals, and also some of the lower oxides (cuprite, 
 etc.), when treated with nitric acid. 
 
CHEMICAL EXAMINATION OF MINKBALS, 
 
 203 
 
 The separation of an insoluble ingredient takes pla ce : With many sili- 
 cates, the silica separating sometimes as a fine powder, and again as a jelly ; 
 in the latter case the mineral is said to gelatinize (sodalite, analcite). In 
 order to test this point the finely pulverized silicate is digested with strong 
 hydrochloric acid, and the solution afterward slowly evaporated nearly to 
 dryness. With a considerable number of silicates the gelatinization takes 
 place only after ignition ; while others, which ordinarily gelatinize, are 
 rendered insoluble'by ignition. 
 
 With many sulphides a separation of sulphur takes place when they are 
 treated with nitric acid. Compounds of titanic and tungstic acids are 
 decomposed by hydrochloric acid with the separation of the oxides named. 
 The same is true of salts of molybdic and vanadic acids, only that here the 
 oxides are soluble in an excess of the acid. 
 
 Compounds containing silver, lead, and mercury give with hydrochloric 
 acid insoluble residues of the chlorides. These compounds are, however, 
 soluble in nitric acid. 
 
 When compounds containing tin are treated with nitric acid, the stannic 
 oxide separates as a white powder. A corresponding reaction takes place 
 under similar circumstances with minerals containing arsenic and antimony. 
 
 Insoluble minerals. A large number of minerals are not sensibly 
 attacked by any of the acids. Among these may be named the following 
 oxides: corundum, spinel, chromite, diaspore, rutile, cassiterite, quartz; 
 also cerargyrite ; many silicates, titanates, tantalates, and columbates ; also 
 the sulphates (barite, celestite, anglesite); many phosphates (xenotime, 
 lazulite, childrenite, ainblygonite), and the borate, boracite. 
 
 b. ^Examination of Minerals by means of the Blowpipe. 
 
 Blowpipe. The simplest form of the blowpipe is a tapering tube of 
 brass (f. 413, 1), with a minute aperture at the 
 extremity. A chamber is advantageously 
 added (f. 413, 2) at o, to receive the condensed 
 moisture, and an ivory mouth-piece is often 
 very convenient. In the better forms of the 
 instrument (see f. 413, 3), the tip is made of 
 solid platinum (/"), which admits of being 
 readily cleaned when necessary. Operations 
 with the blowpipe often require an un inter- 
 mitted heat for a considerable length of time, 
 and always longer than a single breath of the 
 operator. It is therefore requisite that breath- 
 ing and blowing should go on together. This 
 may be difficult at first, but the necessary skill 
 or tact is soon acquired. 
 
 Blowpipe-flame. The best and most con- 
 venient source of heat for blowpipe purposes 
 is ordinary illuminating gas. The burner is a 
 simple tube, flattened at the top, and cut off a 
 little obliquely ; it thus furnishes a flame of convenient shape. A similar 
 
204 CHEMICAL MINKRALOGY. 
 
 jet may also be used in conjunction with the ordinary Bunsen burner, it 
 being so made as to slip down within the outer tube, and cut off the supply 
 of air, thus giving a luminous flame. The gas flame required need not be 
 more than an inch and a half in height. In place of the gas, a lamp fed 
 with olive oil will answer, or even a good candle. 
 
 The jet of the blowpipe is brought close to the gas flame on the higher 
 Bide of the obliquely terminated burner. The arm of the blowpipe is 
 inclined a little downward, and the blast of air produces an oblique conical 
 flame of intense heat. This blowpipe flame consists of two cones : an inner 
 of a blue color, and an outer cone which is yellow. The heat is most 
 intense just beyond the extremity of the blue flame, and the mineral is held 
 at this point when ite fusibility is to be tested. 
 
 The inner flame is called the .REDUCING FLAME (R.F.) ; it is characterized 
 by the excess of the carbon or hydrocarbons of the gas, which at the high 
 temperature present tend to combine with the oxygen of the mineral 
 brought into it, or in other words, to reduce it. The best reducing flame 
 is produced when the blowpipe is held a little distance from the gas flame ; 
 it should retain the yellow color of the latter. 
 
 The outer cone is called the OXIDIZING FLAME (O.F.) ; it is characterized 
 by the excess of the oxygen of the air over the carbon of the gas to be com- 
 bined with it, and has hence an oxidizing effect upon the assay. This 
 flame is best produced when the jet of the blowpipe is inserted a very little 
 in the gas flame ; it should be entirely non-luminous. 
 
 Supports. Of other apparatus required, the most essential articles are 
 those which serve to support the mineral in the flame ; these supports are : 
 (1) charcoal, (2) platinum forceps, (3) platinum wire, and (4) glass tubes. 
 
 (1) Charcoal is especially useful as a support in the case of the examina- 
 tion of metallic minerals, where a reduction is desired. It must not crack 
 when heated, and should not yield any considerable amount of ash on com- 
 bustion ; that made from soft wood (pine or willow) is the best. Pieces of 
 convenient size for holding in the hand are employed ; they should have a 
 smooth surface, and a small cavity should be in it made for the mineral. 
 
 (2) A convenient kind of platinum forceps is represented in f. 414 ; it 
 is made of steel with platinum points. These open by means of the pins 
 
 414 
 
 ; other forms open by the spring of the wire in the handle. Care must 
 taken not to heat any substance (e.g., metallic) in the forceps, which when 
 fused might injure the platinum. 
 
 (3) Platinum wire is employed with the use of fluxes, as described in 
 another place. 
 
 (4) The glass tubes required are of two kinds : closed tubes, having only 
 one open end, about four inches long ; and open tubes, having both ends 
 open, four to six inches in length. Both kinds can be easily made by the 
 student from ordinary tubing (best of rather hard glass), having a bore of 
 1 to J of an inch. 
 
CHEMICAL EXAMINATION OF MINERALS. 205 
 
 In the way of additional apparatus, the following articles are useful ; they 
 need no special description : hammer, small anvil, three-cornered file, mag- 
 net, pliers, pocket-lens, and a small mortar, as also a few of the test-tubel, 
 etc., used in the laboratory. 
 
 Chemical reagents. The commonest reagents employed are the fluxes^ 
 TIZ., soda (sodium carbonate) ; salt of phosphorus (sodium-ammonium 
 phosphate); and borax (sodium biborate). The method of using them is 
 spoken of on p. 208. 
 
 Nitrate of cobalt in solution is also employed. It is conveniently kept 
 in a small bulb from which a drop or two may be obtained as it is needed. 
 This is used principally as a test for aluminum or magnesium with infusible 
 minerals, as remarked beyond. The fragment of the mineral held in the 
 forceps is first ignited in the blowpipe name, a drop of the cobalt solution 
 is placed on it, and then it is heated again ; the presence of either constitu- 
 ent named is manifested by the color assumed by the ignited mineral. It 
 is also used as a test for zinc. Potassium bisulphate and calcium fluoride 
 (fluorite) in powder, metallic magnesium (foil or wire), and tin foil, are 
 other reagents, the use of which is explained later. Test-papers are also 
 needed, viz., blue litmus paper, and turmeric paper. 
 
 The wet reagents required are : the ordinary acids, and most important 
 of these hydrochloric acid, generally diluted one-half for use, and also 
 barium chloride, silver nitrate, ammonium molybdate. 
 
 The blowpipe investigation of minerals includes their examination, (1) in 
 the platinum-pointed forceps, (2) in the closed tube, (3) in the open tube, 
 (4) on charcoal, and (5) with the fluxes. 
 
 (1) Examination in the forceps. The most important use of the plati- 
 num-pointed forceps is to hold the fragment of the mineral while its fusi- 
 bility is tested. 
 
 The following practical points must be regarded : (1) Metallic minerals, which when fused 
 may injure the platinum, should be examined on charcoal ; (2) the fragment taken should be 
 thin, and as small as can conveniently be held ; (3) when decrepitation takes place, the heat 
 must be applied slowly, or, if this does not prevent it, the mineral may be powdered and a 
 paste made with water, thick enough to be held in the forceps or on the platinum wire ; or 
 the paste may, with the same end in view, be heated on charcoal ; (4) the fragment whose 
 fusibility is to be tested must be held in the hottest part of the flame, just beyond the 
 extremity of the blue cone. 
 
 In connection with the trial of fusibility, the following phenomena may 
 be observed : (a) a coloration of the flame ; (b) a swelling up (stilbite), or 
 an exfoliation of the mineral (vermiculite) ; or (c) a glowing without fusion 
 (calcite) ; and (d) an intumescence, or a spirting out of the mass as it fuses 
 (scapolite). The color of the mineral after ignition is to be noted ; and the 
 nature of the fused mass is also to be observed, whether a clear or blebby 
 glass is obtained, or a black slag, or whether magnetic or not, etc. 
 
 The ignited fragment, if nearly or quite infusible, may be moistened 
 with the 5 cobalt solution and again ignited (see above) ; also, if not too 
 fusible, it may, after treatment in the forceps, be placed upon a strip of 
 moistened turmeric paper, in which case an alkaline reaction shows the 
 presence of the alkaline earths. 
 
 . All grades of fusibility exist among minerals, from those 
 
206 CHEMICAL MINERALOGY. 
 
 which fuse in large fragments in the flame of the candle (stibnite, see 
 below), to those which fuse only on the thinnest edges in the hottest blow- 
 pipe flame (bronzite) ; and still again there are a considerable number 
 which are entirely infusible (e.g., corundum). 
 
 The following scale of fusibility, proposed by von Kobell, is made use 
 of : 1, stibnite ; 2, natrolite ; 3, almandine garnet ; 4, actiiiolite ; 5, ortho- 
 clase ; 6, bronzite. 
 
 A little practice with these minerals will show the student what degree 
 of fusibility is expressed by each number, and render him quite independent 
 of the table; he will thus be able also to judge of his power to produce a 
 hot flame by the blowpipe, which requires practice. 
 
 Flame coloration. When coloration is produced it is seen on the exterior 
 portion of the flame, and is best observed when shielded from the direct light. 
 
 The presence of soda, even in small quantities, produces a yellow flame, which (except in 
 the spectroscope) more or less completely masks the coloration of the flame due bo other sub- 
 stances ; phosphates and borates give the green flame in general best when they have been 
 pulverized and moistened with sulphuric acid ; moistening with hydrochloric acid makes the 
 coloration in many cases (barium, strontium) more distinct. 
 
 The colors which may be produced, and the substances to whose presence 
 they are due, are as follows : (1) yellow, sodium / (2) violet, potassium ; 
 
 (3) purple-red, lithium red, strontium / yellowish-red, calcium (lime) ; 
 
 (4) yellowish-green, barium, molybdenum ; emerald-green, copper / bluish- 
 green, phosphorus (phosphates) ; yellowish-green, boron (borates) ; (5) blue, 
 azure-blue, copper chloride ; light-blue, arsenic ; greenish-blue, antimony. 
 
 (2) Heating in the closed tube. The closed tube is employed to show 
 the effect of heating the mineral out of contact with the air. A small frag- 
 ment is taken, or sometimes the powdered mineral is inserted, though in 
 this case with care not to soil the sides of the tube. The phenomena which 
 may be observed are as follows : decrepitation, as shown by fluorite, calcite, 
 etc. ; glowing, as exhibited by gadolinite ; phosphorescence, of which fluorite 
 is an example ; change of color (limonite), and here the color of the mineral 
 should be noted both when hot, and again after cooling; fusion ; giving off 
 oxygen, as mercuric oxide ; yielding water at a low or high temperature, 
 which is true of all hydrous minerals ; yielding acid or alkaline vapors, 
 which should be tested by inserting a strip of moistened litmus or turmeric 
 paper in the tube ; yielding a sublimate, which condenses in the cold part 
 of the tube. 
 
 Of the sublimates which form in the tube, the following are those with 
 which it is most important to be familiar: Sublimate yellow, sulphur; 
 dark brown-red when hot, and red or reddish-yellow when cold, arsenic 
 sulphide; brilliant black, arsenic (also giving off a garlic odor); black 
 when hot, brown-red when cold, formed near the mineral by strong heating, 
 antimony oxy sulphide ; dark-red, selenium (also giving the odor of decay- 
 ing horseradish) ; sublimate consisting of small drops with metallic lustre, 
 teU-urium ; sublimate gray, made up of minute metallic globules, mercury ; 
 sublimate black, lustreless, red when rubbed, mercury sulphide. 
 
 (3) Heating in the open tube. The small fragment is placed in the tube 
 about an inch from the lower end, the tube being inclined sufficiently to 
 prevent the mineral from slipping out. The current of air, passing through 
 
CHEMICAL EXAMINATION OF MINEEALS. 207 
 
 the tube during the heating process, has an oxidizing effect. The special 
 phenomena to be observed are the formation of a sublimate and the odor 
 of the escaping gases. The acid or alkaline character of the vapors are 
 tested in the same way as with the closed tube. Fluorides, when heated in 
 the open tube with previously fused salt of phosphorus, yield hydrofluoric 
 acid, which gives an acid reaction with test-paper, has a peculiar pungent 
 odor, and corrodes the glass. 
 
 The sublimates which may be formed, as far as they differ from those 
 already mentioned, as obtained in the closed tube, are as follows : Subli- 
 mate, white and crystalline, volatile, arsenous oxide ; white, near the min- 
 eral crystalline, fusible to minute drops, yellowish when hot, nearly color 
 less when cold, molybdic oxide / sublimate white, yielding dense white 
 fumes, at first mostly volatile, forming on the upper side ot the tube, and 
 afterward generally non-volatile on the under side of the tube, antimonous 
 and antimonic oxides ; sublimate dark brown when hot, lemon-yellow 
 when cold, fusible, bismuth oxide; sublimate gray, fusible to colorless 
 drops, tellurous oxide / sublimate steel-gray, the upper edge appearing red, 
 selenium / sublimate bright metallic, mercury. 
 
 The odors which may be perceived are the same as those mentioned in 
 the following article. 
 
 (4) Heating alone on charcoal. The substance to be examined is placed 
 in a shallow cavity ; it may simply be a small fragment, or, where the 
 mineral decrepitates, it may be powdered, mixed with water, and thus the 
 material employed as a paste. The points to be noticed are : 
 
 (a) The odor given off after short heating. In this way the presence of 
 eulphur, arsenic (garlic odor), and selenium (odor of decayed horseradish), 
 may be recognized. 
 
 (6) Fusion. In the case of the salts of the alkalies the fused mass is 
 absorbed into the charcoal ; this is also true, after long heating, of the car- 
 bonates and sulphates of barium and strontium. 
 
 (c) The infusible residue. This may (1) glow brightly in the O.F., indi- 
 cating the presence of calcium, strontium, magnesium, zirconium, zinc, or 
 tin. " (2) It may give an alkaline reaction after ignition : alkaline earths. 
 (3) It may be magnetic, showing the presence of iron. 
 
 (d) The sublimate. By this means the presence of many of the metals 
 may be determined. The color of the sublimate, both near the assay (N), 
 and at a distance (D) ; as also when hot and when cold is to be noted. 
 
 The most important of the sublimates, with the metals to which they are 
 due, are contained in the following list : Sublimate, steel-gray (N)^ and 
 dark gray (D), in R.F. volatile with a blue flame, selenium (also giving a 
 peculiar odor) ; white (N) and red or deep yellow (D), in RF. volatile with 
 green flame, tellurium ; white (N) and grayish (D), arsenic (giving also a 
 peculiar alliaceous odor); white (N) and bluish (D), antimony (also giving 
 off dense white fumes). Reddish-brown, silver ; dark orange-yellow when 
 hot, and lemon- yellow when cold (N), also bluish-white (D), bismuth / dark 
 lemon-yellow when hot, sulphur-yellow when cold, lead; red-brown (N) 
 and orange-yellow (D), cadmium ; yellow when hot, white on cooling, sine 
 (the sublimate becomes green if moistened with cobalt solution and again 
 ignited); faint yellow when hot, white on cooling, tin (the sublimate 
 'Become? bluish-green when ignited after being moistened with the cobalt 
 
208 CHEMICAL MINERALOGY. 
 
 solution, in the RF. it is reduced to metallic tin) ; yellow, sometime? crys 
 talline when hot, white when cold (N), bluish (D), molybdenum (i;j O.F 
 the sublimate volatilizes, leaving a permanent stain of the oxide, in RF. 
 gives an azure blue color when touched for a moment with the flame). 
 
 (5) Treatment with, the fluxes. The three fluxes have been mentioned 
 oil p. 205. They are used either on charcoal or with the platinum wire. 
 If the latter is employed it must have a small loop at the end ; this is heated 
 to redness and dipped into the powdered flux, and the adhering particles 
 fused to a bead ; this operation is repeated until the loop is filled. Some- 
 times in the use of soda the wire may at first be moistened a little to cause 
 it to adhere. When the bead is ready it is, while hot, brought in contact 
 with the powdered mineral, some of which will adhere to it, and then the 
 heating process may be continued. Very little of the mineral is in general 
 required, and the experiment should be commenced with a minute quantity 
 and more added if necessary. The bead must be heated successively in 
 the reducing and oxidizing flames, and in each case the color noted when 
 hot and when cold. The phenomena connected with fusion, if it takes 
 place, must also be observed. 
 
 Minerals containing sulphur or arsenic, or both, must be first roasted, that is, heated on 
 charcoal, first in the oxidizing and then in the reducing flame, till these substances have been 
 volatilized. If too much of the mineral has been added and the bead is hence too opaque to 
 show the color, it may, while hot, be flattened out with the hammer, or drawn out into a 
 wire, or part of it may be removed and the remainder diluted with more of the flux. 
 
 BORAX. The following list enumerates the different colored beads 
 obtained with borax, and also the metals to the presence of whose oxides 
 the colors are due : 
 
 Colorless / silica, aluminum, the alkaline earths, etc. (both O.F. and 
 RF.) ; also silver, zinc, cadmium, lead, bismuth, and nickel, O.F., and also 
 RF., after long heating, but when first heated, gray or turbid ; K.F., man- 
 ganese. 
 
 Yellow / in O.F., titanium, tungsten, and molybdenum, also zinc and 
 cadmium, when strongly saturated and hot / vanadium (greenish when 
 hot) ; iron, uranium, and chromium, when feebly saturated. 
 
 lied to brown ; in O.F., iron, hot (on cooling, yellow) ; O.F., chromium, 
 hot (yellowish-green when cold) ; O.F., uranium, hot (yellow when cold) ; 
 nickel, manganese, cold (violet when hot). 
 
 Red ; RF., copper, if highly saturated, cold (colorless when hot). 
 
 Violet / O.F., nickel, hot (red-brown to brown on cooling) ; O.F., man- 
 ganese. 
 
 Blue; O.F. arid E.F., cobalt, both hot and cold; O.F., copper, cold 
 (when hot, green). 
 
 Green O.F., copper, hot (blue or greenish-blue on cooling), R.F., bottle- 
 green ; O.F., chromium, cold (yellow to red when hot), RF., emeral d -green ; 
 O.F., vanadium, cold (yellow when hot), RF., chrome-green, cold (brown- 
 ish when hot) ; RF., uranium, yellowish-green (when highly saturated). 
 
 SALT OF rnospHORUS. This flux gives for the most part reactions similar 
 to those obtained with borax. The only cases enumerated here are those 
 which are distinct, and hence those where the flux is a good test. 
 
 With silicates this flux forms a glass in which the bases of the silicate 
 
CHEMICAL EXAMINATION OF MINERALS. 209 
 
 are dissolved, but the silica itself is left insoluble. It appears as a skeleton 
 readily seen floating about in the melted bead. 
 
 The colors of the beads and the metals to whose oxides these are due, are : 
 
 Blue ; K.F., tungsten, cold (brownish when hot) ; R.F., columbium, cold 
 and when highly saturated (dirty-blue when hot). Both these give .colorless 
 beads in the O.F. 
 
 Green; R.F., uranium, cold (yellowish-green when hot); O.F., molyb- 
 denum, pale on cooling, also R.F., dirty-green when hot, green when cold. 
 
 Violet ; RF., columbium (see above) ; E.F., titanium cold (yellow when 
 hot). 
 
 SODA is especially valuable as a flux in the case of the reduction of the 
 metallic oxides ; this is usually performed on charcoal. The finely pulver- 
 ized mineral is intimately mixed with soda, arid a drop of water added to 
 form a paste. This is placed in a cavity in the charcoal, and subjected to 
 a strong reducing flame. More soda is added as that present sinks into the 
 coal, and, after the process has been continued some time, the remainder 
 of the flux, the assay, and the surrounding coal are cut out with a knife, 
 and the whole ground up in a mortar, with the addition of a little water. 
 The charcoal is carefully washed away and the metallic globules, flattened 
 out by the process, remain behind. Some metallic oxides are very readily 
 reduced, as lead, while others, as copper and tin, require considerable skill 
 and care. 
 
 The metals obtained may be: iron, nickel, or cobalt, recognized by their 
 being attracted by the magnet ; or copper, marked by its red color ; bis- 
 muth and antimony, which are brittle ; gold or silver ; antimony, tellurium, 
 bismuth, lead, zinc, cadmium, which volatilize more or less completely and 
 may be recognized by their sublimates (see p. 207) ; arsenic and mercury 
 are also reduced, but must be heated with soda in the closed tube in order 
 to collect the sublimates. The metals obtained may be also tested with 
 borax on the platinum wire. 
 
 By means of soda on charcoal the presence of sulphur in the sulphates 
 may be shown, though they do not yield it upon simple heating. When 
 soda is fused on charcoal with a compound of sulphur (sulphide or sulphate), 
 sodium sulphide is formed, and if much sulphur is present the mass will 
 have the hepar (liver-brown) color. In any case the presence of the sulphur 
 is shown by placing the fused mass on a clean surface of silver, and adding 
 a drop of water ; a black or yellow stain of silver sulphide will be formed. 
 Illuminating gas often contains sulphur, and hence, when it is used, the 
 soda should be first tried alone on charcoal, and if a sulphur reaction ia 
 obtained (due to the gas), a candle or lamp must be employed in the place 
 of the gas. 
 
 It is also useful in the case of many minerals to test their fusibility or 
 infusibility with soda, generally on the platinum wire. Silica forms if not 
 in excess a clear glass with soda, so also titanic acid. Salts of barium and 
 strontium are fusible with soda, but the mass is absorbed by the coal. 
 Many silicates, though alone difficultly fusible, dissolve in a little soda to a 
 clear glass, but with more soda they form an infusible mass. Manganese, 
 when present even hi minute quantities, gives a bluish-green color to the 
 soda bead. 
 
210 CHEMICAL MINERALOGY. 
 
 CHARACTERISTIC REACTIONS OP THE MOST IMPORTANT ELEMENTS AKD ov SOME o? 
 
 THEIR COMPOUNDS. 
 
 The following list contains the most characteristic reactions, both before 
 the blowpipe (B.B.) and in some cases in the wet way, of the different ele- 
 ments and their oxides. It is desirable for every student to be familiar 
 with them. Many of them have already been briefly mentioned in the 
 preceding pages. It is to be remembered that while the reaction of a 
 single substance may be perfectly distinct if alone, the presence of other 
 substances may more or less entirely obscure these reactions ; it is conse- 
 quently obvious that in the actual examination of minerals precautions have 
 to be taken, and special methods have to be devised, to overcome the diffi- 
 culty arising from this cause. These will be gathered from the pyrognostic 
 characters given (by Prof. Brush) in connection with the description of 
 each species in the Third Part of this work. 
 
 For many substances the most satisfactory and delicate tests are those 
 which have been given by Bunsen in his important paper on Flame-reac- 
 tions (Flammenreactionen, Ann. Ch. Pharm., cxxxviii., 257, or Phil. Mag., 
 IY., xxxii., 81). The methods, however, require for the most part much 
 detailed explanation, and in this place it is only possible to make this gen- 
 eral reference to the subject. 
 
 Alumina. B.B. ; the presence of alumina in most infusible minerals, 
 containing a considerable amount, may be detected by the blue color which 
 they assume when, after being heated, they are moistened with cobalt solu- 
 tion and again ignited. Very hard minerals (e.g.) corundum) must be first 
 finely pulverized. 
 
 Antimony. B.B. ; antimonial minerals on charcoal give dense white 
 inodorous fumes. Antimony sulphide gives in a strong heat in the closed 
 tube a sublimate, black when hot, brown-red when cold. See also p. 207. 
 
 In nitric acid compounds containing antimony deposit white antimonic 
 oxide (Sb 2 O 5 ). 
 
 Arsenic. B.B. ; arsenical minerals give off fumes, usually easily recog- 
 nized by their peculiar garlic odor. In the open tube they give a white, 
 volatile, crystalline sublimate of arsenious oxide. In the closed tube arsenic 
 sulphide gives a sublimate dark brown-red when hot, and red or reddish- 
 yellow when cold. The presence of arsenic in minerals is often proved by 
 testing them in the closed tube with sodium carbonate and potassium cyan- 
 ide. Strong heating produces a sublimate of metallic arsenic, proper pre- 
 cautions being observed. 
 
 Baryta. B.B. ; a yellowish-green coloration of the flame is given by all 
 baryta salts, except the silicates. 
 
 In solution the presence of barium is proved by the heavy white precipi 
 tate formed upon the addition of dilute sulphuric acid. 
 
 Bismuth. B.B. ; on charcoal alone, or with soda, bismuth gives a very 
 characteristic orange-yellow sublimate (p. 207). Also when treated with 
 equal parts of potassium iodide and sulphur, and fused on charcoal, a beauti- 
 ful red sublimate of bismuth iodide is obtained. 
 
 Boracic acid. Borates. B.B. ; many compounds tinge the flame intense 
 yellowish-green, especially if moistened with sulphuric acid. For silicates 
 
CHARACTERISTIC REACTIONS OF THE DIFFERENT ELEMENTS. 211 
 
 the best method is to mix the powdered mineral with one part powdered 
 tiuorite and two parts potassium bisnlphate. The mixture is moistened 
 and placed on platinum wire. At the moment of fusion the green coloi 
 appears, but lasts but a moment (ex. tourmaline). 
 
 Heated in a dish with sulphuric acid, and alcohol being added and 
 ignited, the flames of the latter will be distinctly tinged green. 
 
 Cadmium. B.B. ; on charcoal cadmium gives a characteristic sublimate 
 of the reddish-brown oxide (p. 207) 
 
 Carbonates. Effervesce with dilute hydrochloric acid ; many require to 
 be pulverized, and some need the addition of heat. 
 
 Chlorides. B.B. ; if a small portion of a chloride is added to the bead of 
 salt of phosphorus, saturated with copper oxide, the bead is instantly sur- 
 rounded with an intense purplish flame. 
 
 In solution they give with silver nitrate a white curdy precipitate, which 
 darkens in color on exposure to the light ; it is insoluble in nitric acid, but 
 entirely so in ammonia. 
 
 Chromium. B.B. ; chromium gives with borax and salt of phosphorus an 
 emerald-green bead (p. 208). 
 
 Cobalt. B.B. ; a beautiful blue bead is obtained with borax in both 
 flames from minerals containing cobalt. Where sulphur or arsenic is present 
 it should first be roasted off on charcoal. 
 
 Copper. B.B. ; on charcoal the metallic copper can be reduced from 
 most of its compounds. With borax it gives a green bead in the oxidizing 
 flame, and in the reducing an opaque red bead (p. 208). 
 
 Most metallic compounds are soluble in nitric acid. Ammonia produces 
 a green precipitate in the solution, which is dissolved when an excess is 
 added, the solution taking an intense blue color. 
 
 Fluorine. B.B. ; heated in the closed tube fluorides give off fumes of 
 hydrofluoric acid, which react acid with test-paper and etch the glass. 
 Sometimes potassium bisulphate must be added (see also p. 207). 
 
 Heated gently in a platinum crucible with sulphuric -acid, most com- 
 pounds give off hydrofluoric acid, which corrodes a glass plate placed 
 over it. 
 
 Iron. B.B. ; with borax iron gives a bead (O.F.) which is yellow while 
 hot, but is colorless on cooling; K.F., becomes bottle-green (see p. 208). 
 On charcoal with soda gives a magnetic powder. Minerals which contain 
 even a small amount of iron yield a magnetic mass when heated in the 
 reducing flame. 
 
 Lvad. B.B. ; with soda on charcoal a malleable globule of metallic lead 
 is obtained from lead compounds ; the coating has a yellow color near the 
 assay and farther off a white color (carbonate) ; on being touched with the 
 reducing flame both of these disappear, tinging the flame azure blue. 
 
 In solutions dilute sulphuric acid gives a white precipitate of lead sul- 
 phate ; when delicacy is required an excess of the acid is added, the solution 
 evaporated to dryness, and water added, the lead sulphate, if present, will 
 then be left as a residue. 
 
 Lime. B.B. ; it imparts a yellowish-red color to the flame. In the pres- 
 ence of other alkaline earths the spectroscope gi ves a sure means of detecting 
 even when in small quantities. Many lime salts give an alkaline reaction 
 with test-paper after ignition. 
 
212 CHEMICAL MINERALOGY. 
 
 In solutions containing lime salts, even when dilute, ammonium oxalate 
 throws down a white precipitate of calcium oxalate. 
 
 Lithia. B.B. ; lithia gives an intense red to the outer flame; in very small 
 quantities it is evident in the spectroscope. 
 
 Magnesia. B.B. ; moistened, after heating, with cobalt nitrate and again 
 ignited, a pink color is obtained from infusible minerals. 
 "" Manganese. B.B. ; with borax manganese gives a bead violet-red (O.F.), 
 and colorless (R.F.). 'With soda (O.F.) it gives a bluish-green bead ; this 
 reaction is very delicate and may be relied upon, even in presence of almost 
 any other metal. 
 
 Mercury. B.B. ; in the closed tube a sublimate of metallic mercury is 
 yielded when the mineral is heated with soda. Mercuric sulphide gives a 
 black lustreless sublimate in the tube, red when rubbed (p. 207). 
 
 Molybdenum. B.B. ; on charcoal molybdenum gives a copper- red stain 
 (O.F.) which becomes azure-blue when for a moment touched with the R.F. 
 (p. 208). 
 
 Nickel. B.B. ; with borax nickel oxide gives a bead which (O.F.) is violet 
 when hot and red-brown on cooling ; (R.F.) the glass becomes gray and 
 turbid from the separation of metallic nickel, and on long blowing colorless. 
 
 Nitrates. Detonate when heated on charcoal. Heated in a tube with 
 sulphuric acid give off red fumes of nitric peroxide. 
 
 Phosphates. B.B. ; most phosphates impart a green color to the flame, 
 especially after having been moistened with sulphuric acid, though this test 
 may be rendered unsatisfactory by the presence of other coloring agents. 
 If they are used in the closed tube with a fragment of metallic magnesium or 
 sodium, and afterward moistened with water, phosphuretted hydrogen ia 
 given off, recognizable by its disagreeable odor. 
 
 A few drops of a neutral or acid solution, containing phosphoric acid, 
 produces in a solution of ammonium molybdate with nitric acid a pulveru- 
 lent yellow precipitate. 
 
 Potash. B.B. ; potash imparts a violet color to the flame when alone. 
 It is best detected in small quantities, or when soda or lithia is present, by 
 the aid f the spectroscope. 
 
 Selenium. B.B. ; on charcoal selenium fuses easily, giving off brown 
 fumes with a peculiar disagreeable organic odor (see also p. 207). 
 
 Silica. B.B. ; a small fragment of a silicate in the salt of phosphorus 
 bead leaves a skeleton of silica, the bases being dissolved. 
 
 If a silicate in a fine powder is fused with sodium carbonate and the mass 
 then dissolved in hydrochloric acid and evaporated to dryness, the silica is 
 made insoluble, and when strong hydrochloric acid is added and then water, 
 the bases are dissolved and the silica left behind. 
 
 Many silicates, especially those which are hydrous, are decomposed by 
 strong hydrochloric acid, the silica separating as a powder or as a jelly 
 (see p. 203). 
 
 Silver. B.B. ; on charcoal in O.F. silver gives a brown coating (p. 207). 
 A globule of metallic silver may generally be obtained by heating on char- 
 coal in O.F., especially if soda is added. Under some circumstances it ia 
 desirable to have recourse to cupellation. 
 
 From a solution containing any salt of silver, the insoluble chloride ia 
 thrown down when hydrochloric acid is added. This precipitate is insoluble 
 
DETERMINATIVE MINERALOGY. 213 
 
 In acid or water, but entirely so in ammonia. It changes color on exposure 
 to the light. 
 
 Soda. B.J3. ; gives a strong yellow flame. 
 
 ^ Sulphur, sulphides, sulphates. B.B. ; in the closed tube some sulphides 
 give off sulphur, others sulphurous oxide which reddens a strip of moistened 
 litmus paper. In small quantities, or in sulphates, it is best detected by 
 fusion on charcoal with soda. The fused mass, when sodium sulphide has 
 thus been formed, is placed on a clean silver coin and moistened ; a distinct 
 black stain on the silver is thus obtained (the precaution mentioned on 
 p. 209 must be exercised). 
 
 A solution in hydrochloric acid gives with barium chloride a white in 
 soluble precipitate of barium sulphate. 
 
 Tellurium. B.B. ; tellurides heated in the open tube give a white or 
 grayish sublimate, fusible to colorless drops (p. 207). On charcoal they 
 give a white coating and color the R.F. green. 
 
 Tin. B.B ; minerals containing tin, when heated on charcoal with soda 
 or potassium cyanide, yield metallic tin in minute globules (see also p. 209). 
 
 Titanium. B.B. ; titanium gives a violet color to the salt of phosphorus 
 bead. Fused with sodium carbonate and dissolved with hydrochloric acid, 
 and heated with a piece of metallic tin or zinc, the liquid takes a violet 
 color, especially after partial evaporation. 
 
 Tungsten. B.B. ; tungsten oxide gives a blue color to the salt of phos- 
 phorus bead (R.F.). Fused and treated as titanic acid (see above) with the 
 addition of zinc instead of tin, gives a fine blue color. 
 
 Uranium. B.B. ; salt of phosphorus bead, in O.F., a greenish-yellow 
 bead when cool. In E.F. a hue green on cooling (p. 209). 
 
 Vanadium. B.B. ; the characteristic reactions of vanadium with the 
 fluxes are given on p. 208. 
 
 Zinc. B.B. ; on charcoal compounds of zinc give a coating which is yel- 
 low while hot and white on cooling, and moistened by the cobalt solution 
 and again heated becomes a line green (p. 207). 
 
 Zirconia. A dilute hydrochloric acid solution, containing zirconia, im- 
 parts an orange-yellow color to turmeric paper, moistened by the solution. 
 
 Students who desire to become thoroughly acquainted with the use of the 
 blowpipe should provide themselves with a thorough and systematic book 
 devoted to the subject. The most complete American book is that by Prof. 
 Brush (Manual of Determinative Mineralogy, with an introduction on blow- 
 pipe analysis, New York, 1875). Other standard works are those of Ber 
 zelius (The use of the Blowpipe in Chemistry and Mineralogy, translated into 
 English by Prof. J. D. Whitney, 1845), and Plattner (Manual of Qualita- 
 tive and Quantitative Analysis with the Blowpipe, translated by Prof. H. 
 B. Cornwall, 1872). The work of Prof. Brush has been freely used in the 
 preparation of the preceding notes upon blowpipe methods and reactions. 
 
 DETERMINATIVE MINERALOGY 
 
 Determinative Mineralogy may be properly considered under the general 
 head of Chemical Mineralogy, since the determination of minerals dependi 
 
CHEMICAL MINERALOGY. 
 
 moetly upon chemical tests. But crystallographic and all physical chaiactere 
 have also to be used. 
 
 There is but one satisfactory way in which the identity of an unknown 
 mineral may in all cases be fixed beyond question, and that is by the use of 
 a complete set of determinative tables. By means of such tables the mineral 
 in hand is referred successively from a general group into a more special 
 one, until at last all other species have been eliminated, and the identity 
 of the one given is beyond doubt. 
 
 A careful preliminary examination of the unknown mineral should, how- 
 ever, always be made before final recourse is had to the tables. This 
 examination will often suffice to show what the mineral in hand is, and in 
 any case it, should not be omitted, since it is only in this way that a practi- 
 cal familiarity with the appearance and characters of minerals can be gained. 
 
 The student will naturally take note first of those characters which are 
 at once obvious to the senses, that is : the color, lustre, feel, general struc 
 ture, fracture ! , cleavage, and also crystalline form, if distinct ; also, if the 
 specimen is not too small, the apparent weight will suggest something as to 
 the specific gravity. The above characters are of very unequal importance. 
 Structure, if crystals are not present, and fracture are generally unessential 
 except in distinguishing varieties ; color and lustre are essential with 
 metallic, but generally very unimportant with unmetallic minerals. Streak 
 is of importance only with colored minerals and those of metallic lustre 
 (p. 162). Crystalline form and cleavage are of the highest importance, but 
 usually require careful study. 
 
 The first trial should be the determination of the hardness (for which end 
 the pocket-knife is often sufficient in experienced hands). The second trial 
 should be the determination of the specific gravity. Treatment of the 
 powdered mineral with acids may come next ; by this means (see p. 202) 
 the presence of carbonic acid is detected, and also other results obtained 
 (p. 203). Then should follow blowpipe trials, to ascertain the fusibility, 
 the color given to the flame, if any, the character of the sublimate given off 
 and the reactions with the fluxes and other points as explained in the pre 
 ceding pages. 
 
 How much the observer learns in the above way, in regard to the nature 
 of his mineral, depends upon his knowledge of the characters of minerals in 
 general, and upon his familiarity with the chemical behavior of the vari- 
 ous elementary substances (pp. 210 to 4 213) with reagents, and before the 
 blowpipe. If the results of such a preliminary examination are sufficiently 
 definite to suggest thac the mineral in hand is one of a small number oJ 
 species, reference may be made to their full description in Part 111. of this 
 work for the final decision. 
 
 A number of minor tables, embracing under appropriate heads minerals 
 which have some striking physical characters, are added in the Appendix. 
 They will in many cases aid the observer in reaching a conclusion. In 
 addition to these tables, an extended table is also given for the systematic 
 determination of the more important minerals, those described in full in 
 the following pages. 
 
T III.* 
 
 DESCRIPTIVE MINERALOGY, 
 
 THE following is the system of classification employed in the arrangement 
 of the species in this work. It is identical with that adopted in Dana's 
 System of Mineralogy, 1868, to which treatise reference may be made for 
 the discussion of the principles upon which it is based. In ^ general only 
 the more prominent species are enumerated under the successive heads. 
 The native elements are grouped as follows : 
 SERIES I. The more basic, or electro-positive elements. 
 
 1. GOLD GROUP. Gold, silver (also hydrogen, potassium, 
 
 sodium, etc.). 
 
 2. IKON GROUP. Platinum, palladium, mercury, copper, iron, 
 
 zinc, lead (also cobalt, nickel, chromium, manganese, 
 calcium, magnesium, etc.). 
 
 3. TIN GROUP. Tin (also titanium, zirconium, etc.). 
 SERIES II. Elements generally electro-negative. 
 
 1. ARSENIC GROUP. Arsenic, antimony, bismuth, phosphorus, 
 
 vanadium, etc. 
 
 2. SULPHUR GROUP. Sulphur, tellurium, selenium. 
 
 3. CARBON-SILICON GROUP. Carbon, silicon. 
 SERIES III. -Elements always negative. 
 
 1. Chlorine, bromine, iodine. 
 
 2. Fluorine. 
 
 3. Oxygen. 
 
 CLASSIFICATION OF MINERAL SPECIES. 
 
 I. NATIVE ELEMENTS. 
 
 Gold : silver. Platinum ; palladium ; iridosmine, IrOs, etc. ; itercuiy ; 
 amalgam, AgHg, etc. ; copper ; iron. Arsenic ; antimony ; bismuth, 
 Tellurium ; sulphur. Diamond ; graphite. 
 
216 DESCRIPTIVE MINERALOGY. 
 
 II. SULPHIDES, TELLURIDES, SELENIDES, ARSEN- 
 IDES, ANTIMONIDES, BISMUTHIDES. 
 
 1. BINARY COMPOUNDS. SULPHIDES AND TELLURIDES of METALS 
 OF THE SULPHUR AND ARSENIC GROUPS. 
 
 (a) Realgar group. Composition US. Monoclinic. Realgar. 
 (If) Orpiment group. Composition R^Sg. Ortliorhombic. Orpirnent; 
 stibnite ; bismuthinite. 
 
 (c) Tetradymite group. Tetradymite Bi 2 (Te,S) 3 . 
 
 (d) Molybdenite group. Composition RS 2 . Molybdenite. 
 
 2. BINARY COMPOUNDS. SULPHIDES, TELLIJRIDES, ETC., OF METALS 
 OF THE GOLD, IRON, AND TIN GROUPS. 
 
 A. BASIC DIVISION. Dyscrasite; domeykite. 
 
 B. PROTO DIVISION. Composition RS (or RgS), RSe, RTe. 
 
 (a) Galenite group. Isometric ; holohedral. Argentite ; galenite ; 
 
 clausthalite ; bornite ; alabandite. 
 (o) Blende group. Isometric ; tetrahedral. Sphalerite. 
 
 (c) Chalcocite group. Orthorhombie. Chalcoeite ; acanthite ; hes- 
 
 site ; stromeyerite. 
 
 (d) Pyrrhotite group. Hexagonal. Cinnabar ; millerite ; pyrrho- 
 
 tite (Fe 7 S 8 ) ; greenockite ; niccolite. 
 
 C. DEUTO OR PYRITE DIVISION. Composition RS 2 , et3. 
 
 (a) Pyrite group. Isometric. Pyrite ; linnaeite ; smaltite ; cobal- 
 
 tite ; gersdorftite. Chal copy rite. 
 
 (b) Marcasite group. Ortliorhombic. Marcasite ; arsenopyrite ; 
 
 sylvanite. 
 
 (c) Nagyagite. (d) Covellite. 
 
 3. TERNARY COMPOUNDS. SULPHARSENITES, SULPHANTIMONITES, 
 
 SULPHOBISMUTHITES. 
 
 (a) GROUP I. Atomic ratio, R : As(Sb) : S = 1 : 2 : 4. Formula 
 
 R(As,Sb) 2 S 4 = RS -h(As,Sb) 2 S 8 . Miargyrite ; sartorite ; zink- 
 
 enite. 
 (J) SUB GROUP. At. Ratio, R : As(Sb) : S = 3 : 4 : 9. Formula 
 
 R3(As,Sb,Bi) 4 S 9 = 3RS + 2(As,Sb,Bi) 2 S 3 . Jordanite ; schir- 
 
 merite etc 
 
 (c) GROUP II. At. Ratio, R : (As, Sb) : S = 2 : 2 : 5. Formula 
 
 R2(Sb,As) 2 S 5 = 2RS + (Sb,As) 2 S 3 . Jamesonite ; duf renoysite, 
 
 (d) GROUP III. At. Ratio, R : (As,Sb) : S = 3 : 2 : 6. Formula 
 
 R3(As,Sb) 2 S 6 = 3RS + (As,Sb^S 8 . Pyrargyrite, proustite ; 
 bournonite ; boulangerite. 
 
CLASSIFICATION OP SPECIES. 217 
 
 (e) GROUP IV. At. Katio, K : (As,Sb,Bi) : S = 4 : 2 : 7. Formula 
 E 4 (As,Sb,Bi) 2 S 7 = 4ES + (As,Sb,Bi) 2 S 8 . Tetrahedrite ; ten- 
 nantite. 
 (/) GROUP Y. At. Eatio, E : (As,Sb) : S = 5 : 2 : 8. Formula 
 
 E 5 (As,Sb) 2 S 8 = 5ES + (As,Sb) 2 S 3 . Stephanite ; geocronite 
 P ;>lybasite. Enargite. 
 
 III. CHLORIDES, BROMIDES, IODIDES. 
 
 1. ANHYDEOUS CHLOEIDES. Composition mostly E(C1. Br, I) : 
 also Kj(Cl,Br,I) (calomel), and EC1 6 (molysite). 
 
 Halite ; svlvite ; cerargyrite ; embolite ; bromyrite. 
 
 2. HYDROUS CHLOEIDES. Carnallite. Tachhydrite. 
 
 3. OXYCHLOEIDES.Atacamite ; inatlockite. 
 
 IV. FLUORIDES. 
 
 1. ANHYDROUS FLUOEIDES. Fluorite ; sellaite. Cryolite. 
 
 2. HYDEOUS FLUOEIDES. -Paclmolite ; ralstonite. 
 
 V. OXYGEN COMPOUNDS. 
 
 I. OXIDES. 
 
 1. OXIDES OF METALS OF THE GOLD, IRON, AND TIN GROUPS. 
 
 A. ANHYDROUS OXIDES. (a) PROTOXIDES. Binary compounds of 
 
 oxygen with a univalent or bivalent element. Formula EO or (E^O). 
 Cuprite ; zincite ; tenorite. 
 
 (&) SESQUIOXIDES. Binary compounds of oxygen with a sexivalent ele- 
 ment. Formula RO 3 . Corundum; hematite. This group also includes 
 menaccanite and perofskite. 
 
 (c) COMPOUNDS OF PROTOXIDES AND SESQUIOXIDES. Ternary compounds 
 of oxygen with a bivalent and a sexivalent element. Formula EEO 4 = EG 
 
 Spinel Group. Isometric. Spinel ; gahnite \ magnetite ; franklinite ; 
 chromite. Orthorhombic. Chrysoberyl. 
 
 (d) DEUTOXIDES. Binary compounds of oxygen with a quadrivalent ele- 
 ment. Formula EO 2 . 
 
 TETRAGONAL. Rutile Group. Cassiterite ; rutile ; octatedrite ; haus- 
 mannite ; braunnite. Orthorhombic. Brookite ; pyrolusite. 
 
 B. HYDROUS OXIDES. Turgite. Diaspore ; gothite ; manganite. 
 lamonite. Brncite ; gibbsite. -Psilomelane. 
 
218 DESCRIPTIVE MINERALOGY. 
 
 2. OXIDES OF METALS OF THE ARSENIC AND SULPHUR GROUPS. 
 Isometric. Arsenolite ; senarmontite. Orthorhombie. Claudetite ; 
 
 valentinite ; bismite, etc. 
 
 3. OXIDES OF THE CARBON-SILICON GROUP. Quartz ; tridymite ; as- 
 manite; opal. 
 
 t 
 
 II. TERNARY OXYGEN COMPOUNDS. 
 1. SILICATES. A. ANHYDROUS SILICATES. 
 
 (a) BISILICATES. Salts of meta-silicic acid, H^SiOs. Quantivalent ratio 
 for basic elements and silicon, 1 : 2. General formula RSiO 3 . This may 
 be written : R \\ O 2 || SiO, to indicate that part only of the oxygen is regarded 
 as linking oxygen, or, taking into account the quantivalence of the various 
 basic elements that may be present, RS, aR, /3R [ O 2 j SiO. 
 
 (a) Amphibole group. Pyroxene section (/A / = 86-88). Orthorhom- 
 bic. Enstatite ; hypersthene. Monoclinic. Wollastonite ; pyroxene ; 
 acmite ; segirite. Triclinic. Rhodonite ; babingtonite. Spodumene ; 
 petal ite. 
 
 (b) Amphibole section (I ^I 123-125). Orthorhombic. Anthophyl- 
 lite, kupfl'erite. Monoclinic, amphibole ; arf vedsonite. 
 
 Beryl. Eudialjte. Pollucite. 
 
 (/8) UNISILICATES. Salts of the normal silicic acid, H 4 SiO 4 . Quantivalent 
 ratio for basic elements and silicon, 1 : 1. General formula RgSiO,,. This 
 may be written : Eg | O 4 j Si, to show that all the oxygen is regarded as 
 linking oxygen, or, R$>,aR, /3R . || O 4 j| Si. The latter formula shows that, 
 though elements of different quantivalence may be present, the same uni- 
 silicate type still exists. The excess of silica sometimes present in both 
 bisilicates and unisilicates, as well as other deviations from the ordinary 
 types, are remarked upon in the pages which follow. 
 
 (a) Chrysolite group. Orthorhoinbic, /A 1= 91-95 ; A 14 = 124- 
 129. Chrysolite, forsterite, tephroite, monticellite, etc. 
 
 (b) Willemite group. Hexagonal, R A R = 116-117. Willemite, diop- 
 tase, phenacite. 
 
 (c) Isometric. Helvite. Danalite, R ? SiO 4 +RS. 
 
 (a) Garnet group. Isometric. Q. ratio for R : R : Si = 1 : 1 : 2. Gen- 
 eral formula RjffcSisO^. 
 
 (e) Vesuvianite group. Tetragonal. Zircon, vesuvianite. 
 
 (/ ) Epidote group. Anisometric. Epidote ; allanite ; zoisite ; gadoli- 
 nite ; ilvaite. 
 
 (a) Triclinic. Axinite. Danburite. (A) lolite. 
 
 Qc) Mica group. /A 1 =120. Cleavage basal perfect; optic axis o? 
 acute bisectrix normal to the cleavage-plane. Phlogopite ; biotite ; lepido 
 melane ; muscovite ; lepidolite. 
 
 (1) Scapolite group. Tetragonal. Sarcolite ; ineiomU ; wernerite ; 
 ekebergite. 
 
 (m) Hexagonal. Nephelife. Isometric. Sodalite ; hailynite ; nosite ; 
 leucite. 
 
CLASSIFICATION OF SPECIES. 219 
 
 Feldspar group. Monoclinic or triclinic. /A /near 120 ; Q. ratio for 
 E : S = 1 : 3. Anorthite ; labradorite ; andesite ; hyalophanc ; oligo- 
 clase ; albite ; orthoclase (microcline). 
 
 (7) SUBSILICATES. (a) Q. ratio for bases to silicon, 4: : 3. Chondrodite 
 Tourmaline. 
 
 (b) Q. ratio for bases to silicon, 3 : 2. Genlenite. Andalusite ; nbrolite ; 
 cyanite (A18iO 6 ). Topaz ; euclase ; datolite. Guarinite ; titanite ; keil- 
 hauite ; tscheffkinite. 
 
 (e) Q. ratio for bases to silicon, 2 : 1. Staurolite. 
 
 B. HYDROUS SILICATES GENERAL SECTION. 
 
 BISILICATES. Fectolite ; laumontite ; okenite. Chrysocolla ; alipite, etc. 
 UNISILICATES. Calamine ; prehnite. Thorite. Pyrosmalite. Apophyl- 
 
 lite. 
 
 SUBSILICATES. Allopliane. 
 
 ZEOLITE SECTION. 
 
 Thomsonite 
 Chabazite 
 heulandite. 
 
 nite ; natrolite ; scolecite ; mesolite. Levynite. Analcite. 
 ; gmelinite ; herschelite. Phillipsite. Harmotome. Stilbite ; 
 
 MARGAROPHYLLITE SECTION. 
 
 BISILICATES. Talc. Pyrophyllite. Sepiolite ; glaucoriite. 
 
 UNISILIOATES. Serpentine group. Serpentine ; deweylite ; geiithite. 
 
 Kaolinite group. Kaolinite ; pholerite ; halloysite. 
 
 Pinite group. Tinite, etc. ; palagonite. 
 
 Hydro-mica group. Fahluuite ; margarodite ; damounte ; paragonite ; 
 cookeite. Hisingerite. 
 
 Chlorite group. Yermiculites, Q. ratio of bases to silicon, 1:1. Fyro- 
 Bclerite; jefferisite, etc. Penninite. Eipidolite ; prochlorite. Chloritoid ; 
 margarite. Seybertite. 
 
 2. TANTALATES, COLUMBATES. 
 
 Pyrochlore. Tantalite ; columbite; yttrotantalite ; samarskite; euxe- 
 nite ; seschynite, etc. 
 
 3. PHOSPHATES, ARSENATES, VANABATES. 
 
 ANHYDEOUS. Xenotime Y 3 P 2 O 8 ; pncherite. Descloizite. 
 
 Zto^^.-Formnla B 3E,(P^8,V)|O 8 +E(01,FV Apatite; pyromor- 
 pliite ; mimetite ; vanadinite. ../it, ^ \ 
 
 ' Wagnerite; monazite. Triphylite ; triplite.-Arnblygcmte (hebromte) 
 
220 DESCRIFflVE MINERALOGY. 
 
 HYDROUS. Pharmacolite ; brushite. Yivianite ; erythrite. Libethinito ; 
 olivenite. Liroconite ; pseudomalachite. Clinoclasite. Lazulite ; scoro 
 dito ; wavellite ; pharraacosiderite. Childreiiite. Turquois ; cacoxenite. 
 Torbernite ; autunite. 
 
 Hydrous antimonate. Bindheimite. 
 
 4. EQUATES. 
 
 Sassolite ; sussexite ; ludwigite. Boracite ; ulexite ; priceite. War- 
 wickite. 
 
 5. TUNGSTATES, general formula KW 4 ; MtLYMATES, 
 
 CHRtMATES, RCr* 4 . 
 
 Wolframite ; scheelite ; st*lzite. Wulf enite. Crac^ite ; phenicechrite. 
 
 6. SULPHATES. 
 
 ANHYDROUS. General formula KSO 4 . Orthorhombic I^I = 100-105. 
 Barite ; celestite ; anhydrite ; anglesite ; zinkosite ; leadhillite. 
 Caledonite. Dreelite ; susamrite ; connellite. Glanberite ; lanarkite. 
 HYDROUS SULPHATES. Mirabilite. Gypsum. Polyhalite. Epsomite. 
 Copperas group. Chalcanthite, CuSO 4 + 5aq, also the other vitriols, 
 " 
 
 Copiapite. Aluminite. Liuarite ; brochantite, etc. 
 TELLURATES. Montanite, Bi 2 TeO 6 + 2aq. 
 
 7. CARBONATES. 
 
 ANHYDROUS. Calcite group. Rhombohedral. General formula, KCO 3 . 
 Calcite ; dolomite ; magnesite ; siderite ; rhodochrosite ; smithsonite. 
 
 Aragonite group. Orthorhombic. Aragonitc ; witherite ; strontianite ; 
 cerussite ; baryto-calcite. Phosgenite. 
 
 HYDROUS CARBONATES. Gay lussite, Hydromagnesite. Hy drozincite ; 
 malachite ; azurite. Bismutite, etc. 
 
 VI. HYDROCARBON COMPOUNDS. 
 
I. NATIVE ELEMENTS. 
 
 GOLD. 
 
 Isometric. The octahedron and dodecahedron the most commcn forms. 
 Crystals sometimes acicular through elongation of octa- 415 
 
 hedral or other forms ; also passing into filiform, reti- 
 culated, and arborescent shapes ; and occasionally 
 spongiform from an aggregation of filaments ; edges of 
 crystals often salient (f. 415). Cleavage none. Twins : 
 twinning-plane octahedral. Also massive and in thin 
 laminae. Often in flattened grains or scales, and rolled 
 masses in sand or gravel. 
 
 H.=2-5-3. G.^15-6-19'5 ; 19-30-19-34, when quite 
 pure, G-. Kose. Lustre metallic. Color and streak 
 various shades of gold-yellow, sometimes inclining to silver-white. Very 
 ductile and malleable. 
 
 . Composition, Varieties Gold, but containing silver in different proportions, and some- 
 times also traces of copper, iron, bismuth (maldonite), palladium, rhodium. Var. 1. Ordinary. 
 Containing (HO to 16 p. c. of silver. Color varying, accordingly, from deep gold-yellow to 
 pale yellow; G.=19-15'5. 2. Argentiferous ; Electrum. Color pale yellow to yellowish- 
 white ; G. = 15 "5-12 '5. Ratio for the gold and silver of 1 : 1 corresponds to 35 "5 p. c. of silver, 
 2 : 1, to 21 -6 p. c. 
 
 The average proportion of gold in the native gold of California, as derived from assays of 
 several hundred millions of dollars' worth, is 880 thousandths ; while the range is mostly 
 between 870 and 890 (Prof. J. C. Booth, of U. S. Mint). The range in the metal of Australia 
 is mostly between 900 and 960, with an average of 1)25. The gold of the Chaudiere, Canada, 
 contains usually 10 to 15 p c. of silver ; while that of Nova Scotia is very nearly pure. The 
 Chilian gold afforded Domeyko 84 to 96 per cent, of gold and 15 to 3 per cent, of silver. 
 (Ann. d. Mines, IV. vi.) 
 
 Pyroguostic and other Chemical Characters. B.B. fuses easily. Not acted on by fluxes. 
 Insoluble in any single acid ; soluble in nitro-hydrochlorio acid (aqua-regia). 
 
 D-ff. Readily recognized by its malleability and specific gravity. Distinguished by it 
 insolubility ra nitric acid from pyrite and chalcopyrite. 
 
 Observations. Native gold is found, when in titu, with comparatively small exceptions, 
 in the quartz veins that intersect metamorphic rocks, and to some extent in the wall rock of 
 these veins. The metamorphic rocks thus intersected are mostly chloritic, talcose, and 
 argillaceous schist of dull green, dark gray, and other colors ; also, much less commonly, 
 mica and hornblendic schist, gneiss, dioryte, porphyry ; and still more rarely, granite. A 
 " laminated quartzyte, called itacolumyte, is common in many gold regions, as those ot -brazil 
 and North Carolina, and sometimes specular schists, or slaty rocks containing much foliated 
 gpecular iron (hematite), or magnetite in grains. 
 
 The gold occurs in the quartz in strings, scales, plates, and in masses which are sometim 
 an agglomeration of crystals ; and the scales are often invisible to the naked eye, massive 
 quartz that apparently contains no gold frequently yielding a considerable percentage 1 
 assayer It is always very irregularly distributed, and never in continuous pure bands 
 metal, like many metallic ores. It occurs both disseminated through the mass of the quartz 
 and in its cavities. The associated minerals are : pyrite, which far exceeds in quantity all 
 others, and is generally auriferous; next, chalcopyrite, galenite, sphalente, arse nopyrite, 
 each frequently auriferous ; often tetradymite and other tellurium ores, native bismuth, st 
 nite, magnetite, hematite ; sometimes barite, apatite, fluorite, siderite, chrysocolla. ^ 
 
 The gold of the world has been mostly gathered, not directly from the quartz veins, 01 
 
222 DESCRIPTIVE MINERALOGY. 
 
 from the gravel or sands of rivers or valleys in auriferous regions, or the slopes of mountain! 
 or hills, whose rocks contain in some part, and generally not far distant, auriferous veins , 
 such mines are often called aMuvial washings ; in California placer-digyings. Most of the gold 
 of the Urals, Brazil, Australia, and all other gold regions, has come from such alluvial wash- 
 ings. The alluvial gold is usually in flattened scales of different degrees of fineness, the size 
 depending partly on the original condition in the quartz veins, and partly on the distance to 
 which it has been transported. Transportation by running water is an assorting process ; tht 
 coarser particles or largest pieces requiring rapid currents to transport them, and dropping 
 first, and the finer being carried far away sometimes scores of miles. A cavity in the rocky 
 slopes or bottom of a valley, or a place where the waters may have eddied, generally proves 
 in such a region to be a pocket full of gold. 
 
 In the auriferous sands, crystals of zircon are very common ; also garnet and cyanite in 
 grains; often also mouazite, diamonds, topaz, magnetite, corundum, iridosmine, platinum. 
 The zircons are sometimes mistaken for diamonds. 
 
 Gold exists more or less abundantly over all the continents in most of the regions of crystal- 
 line rocks, especially those of the semi-crystalline schists ; and also in some of the large 
 islands of the world where such rocks exist. In Europe, it is most abundant in Hungary and 
 in Transylvania ; it occurs also in the sands of the Rhine, the Reuss, the Aar, the Rhone, and 
 the Danube ; on the southern slope of the Pennine Alps, from the Simplon and Monte Rosa 
 to the valley of Aosta ; in Piedmont ; in Spain, formerly worked in Asturias ; in many of the 
 streams of Cornwall ; near Dolgelly and other parts of North Wales ; in Scotland ; in the 
 county of Wicklow, Ireland ; in Sweden, at Edelfors. 
 
 In Asia, gold occurs along the eastern flanks of the Urals for 500 miles, and is especially 
 abundant at the Beresov mines near Katharinenburg (lat. 56 40' N.) ; also obtained at Petro- 
 pavlovski (60 N.) ; Nischne Tagilsk (50 N.) ; Miask, near Slatoust and Mt. IJmen (55 N., 
 where the largest Russian nugget was found), etc. Asiatic mines occur also in the Cailas 
 Mountains, in Little Thibet, Ceylon, and Malacca, China, Corea, Japan, Formosa, Sumatra, 
 Java, Borneo, the Philippines, and other East India Islands. 
 
 In Africa, gold occurs at Kordofan, between Darfour and Abyssinia ; also, south of the 
 Sahara in Western Africa, from the Senegal to Cape Palmas ; in the interior, on the Somat, 
 a day's journey from Cassen ; along the coast opposite Madagascar, between 22 D and 35 S., 
 supposed by some to have been the Ophir of the time of Solomon. 
 
 In South America, gold is found in Brazil; in New Granada ; Chili ; in Bolivia ; sparingly 
 in Peru. Also in Central America, in Honduras, San Salvador, Guatemala, Costa Rica, and 
 near Panama ; most abundant in Honduras. 
 
 In North America, there are numberless mines along the mountains of Western America, 
 and others along the eastern range of the Appalachians from Alabama and Georgia to Labra- 
 dor, besides some indications of gold in portions of the intermediate Archean region about 
 Lake Superior. They occur at many points along the higher regions of the Rocky Mountains, 
 in Mexico, an$ in New Mexico, in Arizona, in the San Francisco, Wauba, Yuma, and other 
 districts ; in Colorado, abundant, but the gold largely in auriferous pyrite ; in Utah, and 
 Idaho, and Montana. Also along ranges between the summit and the Sierra Nevada, in the 
 Humboldt region and elsewhere. Also in the Sierra Nevada, mostly on its western slope 
 (the mines of the eastern being principally silver mines). The auriferous belt may be said to 
 begin in the Californian peninsula. Near the Tejon pass it enters California, and beyond for 
 180 miles it is sparingly auriferous, the slate rocks being of small breadth ; but beyond this, 
 northward, the slates increase in extent, and the mines in number and productiveness, and 
 they continue thus for 200 miles or more. Gold occurs also in the Coast ranges in many 
 localities, but mostly in too small quantities to be profitably worked. The regions to the 
 north in Oregon and Washington Territory, and the British Possessions farther north, as also 
 our possessions in Alaska, are at many points auriferous, and productively so, though to a 
 less extent than California. 
 
 In eastern North America, the mines of the Southern United States produced before the 
 California discoveries, in 1849, about a million of dollars a year. They are mostly confined 
 to the States of Virginia, North and South Carolina, and Georgia, or along a line from the 
 Rappahannock to the Coosa in Alabama. But the region may be said to extend north to 
 Canada ; for gold has been found at Albion and Madrid in Maine ; Canaan and Lisbon, N. H. ; 
 Bridgewater, Vermont ; Dedham, Mass. Traces occur also in Franconia township, Mont- 
 gomery Co. , Pennsylvania. In Canada, gold occurs to the south of the St. Lawrence, in the 
 oil on the Chaud^re, and over a considerable region beyond. In Nova Scotia, mines are 
 worked near Halifax and elsewhere. 
 
 In Australia, which is fully equal to California in productiveness, and mach superior in the 
 purity of the metal, the principal gold mines occur along the streams in the mountains of 
 N. S. Wales (S. E. Australia), and along the continuation of the same range in Victoria 
 (8. Australia). 
 
NATIVE ELEMENTS. 223 
 
 SILVER. 
 
 Isometric. Cleavage none. Twins : twinning-plane octahedral. Com- 
 monly coarse or fine filiform, reticulated, arborescent ; in the latter, the 
 branches pass off either (1) at right angles, and are crystals (usually octa- 
 hedrons) elongated in the direction of a cubic axis, or "else a succession of 
 partly overlapping crystals ; or (2) at angles of 60, they being elongated in 
 the direction of a dodecahedral axis. Crystals generally obliquely pro- 
 longed or shortened, and thus greatly distorted. Also massive, and in 
 plates or superficial coatings. 
 
 H. 2-5-3. G.=lp-l-ll-l, when pure 10-5. Lustre metallic. Color 
 and streak silver-white ; subject to tarnish, by which the color becomes 
 grayish-black. Ductile. 
 
 Comp., Var. Silver, with some copper, gold, and sometimes platinum, antimony, bismuth, 
 mercury. 
 
 Ordinary, (a} crystallized ; (b) filiform, arborescent ; (c) massive. Auriferous. Contains 
 10 to 30 p. c. of gold ; color white to pale brass-yellow. There is a gradual passage to argen- 
 tiferous gold. Cupriferous. Contains sometimes 10 p. c. of copper. 
 
 Fyr., etc. B.B. on charcoal fuses easily to a silver- white globule, which in O.F. gives a 
 faint dark- red coating of the oxide ; crystallizes on cooling. Soluble in nitric acid, and 
 deposited again by a plate of copper. 
 
 Obs. Native silver occurs in masses, or in arborescent and filiform shapes, in veins travers- 
 ing gneiss, schist, porphyry, and other rocks. Also occurs disseminated, but usually invisibly, 
 in native copper, galenite, chalcocite, etc. 
 
 The mines of Kongsberg, in Norway, have afforded magnificent specimens of native silver. 
 The principal Saxon localities are at Freiberg, Schneeberg, and Johanngeorgenstadt ; the 
 Bohemian, at Przibram, and Joachimsthal. It also occurs in small quantities with other ores, 
 at Andreasberg, in the Harz ; in Suabia ; Hungary ; at Allemont in Dauphiny ; in the 
 Ural near Beresof ; in the Altai, at Zmeoff ; and in some of the Cornish mines. 
 
 Mexico and Peru have been the most productive countries in silver. In Mexico it hai 
 been obtained mostly from its ores, while in Peru it occurs principally native. In Durango, 
 Sinaloa, and Sonora, in Northern Mexico, are noted mines affording native silver. 
 
 In the United States it is disseminated through much of the copper of Michigan, occasion- 
 ally in spots of some size, and sometimes in cubes, skeleton octahedrons, etc. , at various 
 mines. In Idaho, at the ' k Poor Man's lode," large masses of native silver have been ob- 
 tained. In Nevada, in the Comstock lode, it is rare, and mostly in filaments ; at the Ophir 
 mine rare, and disseminated or filamentous ; in California, sparingly, in Silver Mountain dis* 
 trict, Alpine Co. ; in the Maris vein, in Los Angeles Co. ; in the township of Ascot, Canada. 
 
 PLATINUM. 
 
 Isometric. Rarely in cubes or octahedrons. Usually in grains ; occa- 
 sionally in irregular lumps, rarely of large size. Cleavage none. 
 
 H.=4-4-5. G.=16-19; 17-108, small grains, 17-608, a mass, Breith. 
 Lustre metallic. Color and streak whitish steel-gray ; shining. Opaque. 
 Ductile. Fracture hackly. Occasionally magneti-polar. 
 
 Comp Platinum combined with iron, iridium, osmium, and other metals. The amount 
 
 of iron varies from 4-20 p. c. 
 
 Pyr., etc. Infusible. Not affected by borax or salt of phosphorus, except in the state of 
 tine dust, when reactions for iron and copper may be obtained. Soluble only in heated nitro- 
 hydrochloric aoid. 
 
224 DESCRIPTIVE MINERALOGY". 
 
 Diff. Distinguished by its malleability, high specific gravity, infusibility, and entire insol 
 ability in the ordinary acids. 
 
 Obs- Platinum was first found in pebbles and small grains in the alluvial deposits of thi 
 river Pinto, in the district of Choco, near Popayan, in South America, where it received ita 
 name platina,, from plata, silver. In the province of Antioquia, in Brazil, it has been found 
 in auriferous regions in syenite (Boussingault). 
 
 In Russia, it occurs at Nischne Tagilsk, and Goroblagodat, in the Ural, in alluvial material. 
 Formerly used as coins by the Russians. Russia affords annually about 800 cwt. of platinum, 
 which is neariy ten times the amount from Brazil, Columbia, St. Domingo, and Borneo. 
 Platinum is also found on Borneo ; in the sands of the Rhine ; at St. Aray, val du Drac ; 
 county of Wicklow, Ireland ; on the river Jocky, St. Domingo ; in California, but not abun- 
 dant : in traces with gold in Rutherford Co., North Carolina ; at St. Francois Beauce, etc., 
 Canada East. 
 
 PLATINIRIDIUM. Platinum and iridium in different proportions. Urals ; Brazil. 4 
 
 PALLADIUM. 
 
 Isometric. In minute octahedrons, Haid. Mostly in grains, sometimes 
 composed of diverging fibres. 
 
 H.=4-5-5. G.=ll-3-ll-8, Wollaston. Lustre metallic. Color whitish 
 steel-gray. Opaque. Ductile and malleable. 
 
 Comp. Palladium, alloyed with a little platinum and iridium, but not yet analyzed. 
 
 Obs. Palladium occurs with platinum, in Brazil, where quite large masses of the metal 
 are sometimes met with ; also reported from St. Domingo, and the Ural. 
 
 Palladium has been employed for balances ;>al8o for the divided scales of delicate apparatus, 
 for which it is adapted, because of its not blackening from sulphur gases, while at the same 
 time it is nearly as white as silver. 
 
 IRIDOSMINE. Osmiridium. 
 
 Hexagonal. Rarely in hexagonal prisms with replaced basal edges. 
 Commonly in irregular flattened grains. 
 
 H.=6-T. G.=19-3-21-12. Lustre metallic. Color tin-white, and light 
 steel-gray. Opaque. Malleable with difficulty. 
 
 Comp., Var. Iridium and osmium in different proportions. Two varieties depending on 
 these proportions have been named as species, but they are isomorphous, as are the metals 
 (G. Rose). Some rhodium, platinum, ruthenium, and other metals are usually present. 
 
 Var. 1. N&wjanskite, Haid. ; H.=7; G.=18'8-19'5. In flat scales ; color tin-white. Over 
 40 p. c. of Iridium. Probably IrOs. 
 
 2. tfls&er*kil$, Haid. In flat scales, often six-sided, color grayish-white, steel-gray. G. 
 20-21 2. Not over 30 p. c of iridium. One kind from Nischne Tagilsk afforded Berzelius 
 TrOs 4 =Iridium 19-9, osmium 801=100 ; G. =21 '118. Another corresponded to the formula 
 IrOs 8 . 
 
 Pyr., etc. At a high temperature the sisserskite gives out osmium, but undergoes no 
 further change. The newjanskite is not decomposed and does not give an osmium odor until 
 fused with nitre. 
 
 Diff. Distinguished from platinum by its superior hardness. 
 
 Obs. Occurs with platinum in the province of Choco in South America ; in the Ural moun- 
 tains ; in Australia. It is rather abundant in the auriferous beach-sands of northern Cali- 
 fornia, occurring in small bright lead -colored scales, sometimes six-sided. Also traces in the 
 g old-washings on the rivers du Loup and des Plantes, Canada. 
 
 MERCURY. Quicksilver. Gediegeu Quecksilber, Germ. 
 
 Isometric. Occurs in small fluid globules scattered through its ganglia 
 G.= 13.568. Lustre metallic. Color tin- white. Opaque. 
 
NATIVE ELEMENTS. 225 
 
 Oomp. Pure mercury (Hg) ; with sometimes a little silver. 
 
 Pyr., etc. B.B., entirely volatile. Dissolves readily in nitric acid. 
 
 Obs. Mercury in the metallic state is a rare mineral ; the quicksilver of commerce is ob- 
 tained mostly from cinnabar, one of its ores. The rooks affording the metal and its ores are 
 mostly clay shales or schists of different geological ages. 
 
 Its most important mines are those of Idria in Garniola, and Almaden in Spain. It ia 
 found in small quantities in Carinthia, Hungary, Peru, and other countries ; in California, 
 especially in the Pioneer mine, in the Napa Valley. 
 
 AMALGAM. 
 
 Isometric. The dodecahedron a common form, also the cube and octa 
 hedron in combination (see f. 40, 41, etc., p. 15). Cleavage : dodecahedral 
 in traces. Also massive. 
 
 H. 3-3-5. G.= 13.75-1 4. Color and streak silver- white. Opaque. 
 Fracture conchoidal, uneven. Brittle, and giving a grating noise when 
 cut with a knife. 
 
 Oomp. Both Ag Hg (= Silver 35'1, mercury, 64 '9), and Ag^Hgs (= Silver 26 '5, and mer- 
 cury, 73 '5), are here included. 
 
 Pyr., etc, B.B., on charcoal the mercury volatilizes and a globule of silver is left. In the 
 closed tube the mercury sublimes and condenses on the cold part of the tube in minute glo- 
 bules. Dissolves in nitric acid. 
 
 Obs, From the Palatinate at Moschellandsberg. Also reported from Rosenau in Hungary, 
 Sala in Sweden, Allemont in Dauphine, Almaden in Spain. 
 
 ARQUERITE. Composition Ag, 2 Hg=silver 86'6, mercury, 13-4=100. Chili KONQS- 
 BERQITE, AgisHg (?) Kongsberg, Norway. 
 
 COPPER. 
 
 Isometric. Cleavage none. Twins: twinning-plane octahedral, very 
 common. Often filiform and arborescent ; the latter with the branches 
 passing off usually at 60, the supplement of the dodecahedral angle. Also 
 massive. 
 
 H.= 2-5-3. G. =8-838, Whitney. Lustre metallic. Color copper-red. 
 Streak metallic shining. Ductile and malleable. Fracture hackly. 
 
 Oomp. Pure copper, but often containing some silver, bismuth, etc. 
 
 Pyr., etc. B.B., fuses readily ; on cooling, becomes covered with a coating of black oxiae. 
 Dissolves readily in nitric acid, giving off red nitrous fumes, and producing a deep azure- blue 
 solution upon the addition of ammonia. 
 
 Obs. Copper occurs in beds and veins accompanying its various ores, and is most abundant 
 in the vicinity of dikes of igneous rocks. It is sometimes found in loose masses imbedded in 
 the soil. 
 
 Found at Turinsk, in the Urals, in fine crystals. Common in Cornwall. In Brazil, Chili, 
 Bolivia, and Peru. At Walleroo, Australia. 
 
 This metal has been found native throughout the red sandstone (Triassico-Jurassic) region 
 of the eastern United States, in Massachusetts, Connecticut, and more abundantly in New 
 Jersey, where it has been met with sometimes in fine crystalline masses. No known locality 
 exceeds in the abundance of native copper the Lake Superior copper region, near Keweenaw 
 Point, where it exists in veins that intersect the trap and sandstone, and where masses of 
 immense size have been obtained. It is associated with prehnite, ditolite, analcite, laumon- 
 tite, pectolite, epidote, chlorite, wollastonite, and sometimes coats amygdules of calcite, 
 etc., in amygdaloid. Native copper occurs sparingly in California. Also on the Gila rivei 
 in Arizona ; i large drift masses in Alaska. 
 IK 
 
226 DESCRIPTIVE MINERALOGY. 
 
 IRON.* 
 
 Isometric. Cleavage octahedral. 
 
 /H.=4-5. G.=7-3-7'8. Lustre metallic. Color iron-gray. Stre'-ak shin- 
 ing. Fracture hackly. Malleable. Acts strongly on the magnet. r 
 
 Obs. The occurrence of masses of native iron of terrestrial origin has been several' ttime, 
 reported, but it is not yet placed beyond doubt. The presence of metallic iron in grains iii 
 basaltic rocks has been proved by several observers. It has also been noticed in other related 
 rocks. The so-called meteoric iron of Ovifak, Greenland, found imbedded in basalt, is con- 
 sidered by some authors to be terrestrial 
 
 Meteoric iron usually contains 1 to 20 per cent of nickel, besides a small percentage of 
 other metals, as cobalt, manganese, tin, copper, chromium ; also phosphorus common as a 
 phosphuret (schreibersite), sulphur in sulphurets. carbon in some instances, chlorine. Among 
 large iron meteorites, the Gibbs meteorite, in the Yale College cabinet, weighs 1,635 Ibs. ; it 
 was brought from Eed River. The Tucson meteorite, now in the Smithsonian Institution, 
 weighs 1,400 Ibs. ; it was originally from Sonora. It is ring-shaped, and is 49 inches in its 
 greatest diameter. Still more remarkable masses exist in northern Mexico ; also in South 
 America; one was discovered by Don Rubin de Celis in the district of Chaco-Gualamba, 
 whose weight was estimated at 32.000 Ibs. The Siberian meteorite, discovered by Pallas, 
 weighed originally 1,600 Ibs. and contained imbedded crystals of chrysolite. Smaller masses 
 are quite common. 
 
 Zmc.- -Native zinc has been reported to occur in Australia; and more recently Mr. W. 
 D. Marks reports its discovery in Tennessee, under circumstances not altogether free from 
 doubt 
 
 LEAD. Native lead occurs very sparingly. It has been found in the Urals, in Spain, 
 Ireland, etc. Dr. Genth speaks of its discovery in the bed rock of the gold placers at Camp 
 Creek, Montana. 
 
 TIN is probably only an artificial product. 
 
 ARSENIC. 
 
 Ehombohedral 72 A i2 = 85 41', O A R = 122 9', c = 1-3779, Miller. 
 Cleavage: basal, imperfect Often grannlar massive; sometimes reticu- 
 lated, renifonn, and stalactitic. Structure rarely columnar. 
 
 H.==3*5. G.=5'93. Lustre nearly metallic. Color and streak tin-white, 
 tarnishing soon to dark-gray. Fracture uneven and line granular. 
 
 Comp. Arsenic, often with some antimony, and traces of iron, silver, gold, or bismuth. 
 
 Pyr. B.B., on charcoal volatilizes without fusing, coats the coal with white arsenous oxide, 
 and affords the odor of garlic ; the coating treated in R.F. volatilizes, tinging the flame blue. 
 
 Obs. Native arsenic commonly occurs in veins in crystalline rocks and the older schists, 
 and is often accompanied by ores of antimony, red silver ore. realgar, sphalerite, and other 
 metallic minerals. 
 
 The silver mines of Saxony afford this metal in considerable quantities ; also Bohemia, the 
 Harz. Transylvania, Hungary. Norway, Siberia ; occurs at Chanarcillo, and elsewhere in 
 Chili ; and at the mines of San Augustin, Mexico. In the United States it has been 
 observed at Haverhiii and Jackson, N. H., at Greenwood, Me. 
 
 ANTIMONY, 
 
 Rhombohedral. J2 A J2 = 87 35', Hose ; A R = 123 32' ; c = 1-3068. 
 2 A 2 = 89 25'. Cleavage : basal, highly perfect ; J distinct. Generally 
 massive, lamellar ; sometimes botryoidal or renif orm with a granular texture. 
 
 * The asterisk in this and similar cases indicates that the species is mentioned again in 
 the Supplementary Chapter, pp, 420 to 440. 
 
NATIVE ELEMENTS. 
 
 227 
 
 H.=3-3'5. G. 6-646-6-72. Lustre metallic. Color and streak tin- 
 white. Very brittle. 
 
 Comp, Antimony, containing sometimes silver, iron, or arsenic. 
 
 py r ,_B.B., on charcoal fuses, gives a white coating in both O. and B.F. ; if the blowing 
 be intermitted, the globule continues to glow, giving off white fumes, until it is finalty crusted 
 over with prismatic crystals of aatimonous oxide. The white coating tinges the R.F. bluish- 
 ereen Crystallizes readily from fusion. 
 
 Occurs near Sahl in Sweden ; at Andreasberg in the Harz ; at Przibram ; at Allemont in 
 Dauphiny; in Mexico; Chili; Borneo; at South Ham, Canada; at Warren, N. J., rare; at 
 Prince William antimony mine, N. Brunswick, rare. 
 
 ALLEMONTITE. Arsenical antimony, SbAs 3 . Color tin-white or reddish-gray. Occ 
 Allemont ; in Bohemia ; the Harz. 
 
 BISMUTH. Gediegen Wismuth, Germ. 
 
 Hexagonal. R A R = 87 40', G. Rose ; A R = 123 36' ; 6 = 1-3035. 
 Cleavage : basal, perfect ; 2, 2, less so. Also in reticulated and arbores- 
 cent shapes ; foliated and granular. 
 
 H.= 2-2-5. G.= 9-727. Lustre metallic. Streak and color silver-white, 
 with* a reddish hue ; subject to tarnish. Opaque. Fracture not observable. 
 Sectile. Brittle when cold, but when heated somewhat malleable. 
 
 Oomo Var. Pure bismuth, with occasional traces of arsenic, sulphur, tellurium. 
 
 Pvr etc. B B., on charcoal fuses and entirely volatilizes, giving a coating orange-yellow 
 while hot, and lemon-yellow on cooling. Dissolves in nitric acid ; subsequent dilution caus< 
 a white precipitate. Crystallizes readily from fusion. K^-H-I* 
 
 Diff. Distinguished by its reddish color, and high specific gravity, from the other 
 
 m Obs 8 ^-Bismuth occurs in veins in gneiss and other crystalline rocks and clay slate .accom- 
 panying various ores of silver, cobalt, lead, and zinc. Abundant at the silver and cobalt 
 mines of Saxony and Bohemia ; also fouud in Norway, and at Fahlun in Sweden. At Wheal 
 Sparnon, and elsewhere in Cornwall, and at Carrack Fe in Cumberland ; at the Atlas maie 
 Devonshire ; at Meymac, Correze ; at San Antonio, Chili ; Mt. Illampa (Sorata), in B la , 
 
 At Lafce'a mine in Monroe, and near Seymour, Conn., in quartz ; occurs also at Brewer'i 
 mine, Chesterfield district, South Carolina ; in Colorado. 
 
 TELLURIUM.* 
 
 Hexagonal, R A R = 86 57', G. Rose ; A * - 123 4', t = 1-8308. 
 In six-sided prisms, with basal edges replaced. Cleavage : lateral perfect, 
 basal imperfect. Commonly massive and granular. 
 
 H.=2-2-5. G.=6-l-6'3. Lustre metallic. Color and streak tm-wmt< 
 Brittle. 
 
 Oomp According to Klaproth, Tellurium 92'55, iron 7-20, and gol 
 
 ad 
 
 thename ft***.) ; also at the 
 
 Red Cloud mine, near Gold Hill, Boulder Co., Colorado 
 
228 
 
 DESCRIPTIVE MINERALOGY. 
 
 NATIVE SULPHUR. 
 
 1-23 : 1. A 1 
 
 Orthorhombic. /A 7 = 101 46', O/\1-l = 113 6': c : I : d = 2-34-4 
 
 41'; O A! = 108 19'. 
 
 Cleavage: /, and 1, imperfect. Twins, 
 composition -face, I, sometimes producing cruci- 
 form crystals. Also massive, sometimes con 
 sisting of concentric coats. 
 ^ H.= 1:5-2-5. G. =2-072, of crystals from 
 Spain. Lustre resinous. Streak sulphur-yel- 
 low, sometimes reddish or greenish. Trans- 
 parent subtranslucent. Fracture conchoidal, 
 more or less perfect. Soctile. 
 
 Comp. Pure sulphur; but often contaminated with clay or bitumen. 
 
 Pyr., etc. Burns at a low temperature with a bluish flame, with the strong odor of sul- 
 phurous oxide. Becomes resinously electrified by friction. Insoluble in water, and not 
 acted on by the acids. 
 
 Obs. Sulphur is dimorphous, the crystals being monoclinic when formed at a moderately 
 high temperature (125 C., according to Frankenheim). 
 
 The great repositories of sulphur are either beds of gypsum and the associate rocks, or the 
 regions of active and extinct volcanoes. In the valley of Noto and Mazarro, in Sicily at 
 Coml, near Cadiz, in Spain ; Bex, in Switzerland ; Cracow, in Poland, it occurs in the former 
 situation ; also Bologna, Italy. Sicily and the neighboring volcanic isles ; the Solfatara, near 
 Naples ; the volcanoes of the Pacific ocean, etc., are localities of the latter kind. Abundant 
 in the Chilian Andes. 
 
 Sulphur is found near the sulphur springs of New York, Virginia, etc., sparingly': in many 
 coal deposits and elsewhere, where pyrite is undergoing decomposition ; at the hot springs 
 and geysers of the Yellowstone park ; in California, at the geysers of Napa valley, Sonoma 
 Co. ; in Santa Barbara in good crystals ; near Clear lake, Lake Co. ; in Nevada, in Humboldt 
 Co., in large beds ; Nye and Esmeralda Cos., etc. 
 
 ,^, h f.f ulp . bur mines of Sicily ' the crater of Vulcano, the Solfatara near Naples, and thebeda 
 of California, afford large quantities of sulphur for commerce. 
 
 DIAMOND.* 
 
 Isometric. Often tetrahedral in planes, 1, 2, and 3-f. Usually with 
 418 419 420 
 
 curved faces, as in f. 419 (3-f) ; f. 420 is a distorted form. Cleavage : 
 octahedral, highly perfect. Twins : twinning-plane, octahedral ; f . 418, is 
 
NATIVE ELEMENTS. 229 
 
 an elliptic twin of f. 419, the middle portion between two opposite sets oi 
 six planes being wanting. Rarely massive. 
 
 II.. 10. G. 3.5295, Thompson. Lustre brilliant adamantine. Color 
 white or colorless : occasionally tinged yellow, red, orange, green, blue, 
 brown, sometimes black. Transparent ; translucent when dark colored. 
 Fracture conchoid al. Index of refraction 2-4. Exhibits vitreous electricity 
 when rubbed. 
 
 Oomp. Pure carbon, isometric in crystallization. 
 
 Var. ] . Ordinary, or crystallized. The crystals often contain numerous microscopic cavi- 
 ties, as detected by Brewster ; and around these cavities the diamond shows evidence, by 
 polarized light, of compression, as if from pressure in the included gas when the diamond 
 was crystallized. The coarse varieties, which are unfit, in consequence of imperfections, for 
 use in jewelry, are called bort ; they are sold to the trade for cutting purposes. 
 
 2. Massive. In black pebbles or masses, called carbonado, occasionally 1,000 carats in weight. 
 H =10 ; G. =3-012-3-416. Consists of pure carbon, excepting 0'27 to 2'07 p. c. (Brazil). 
 
 3. Anthracitic. Like anthracite, but hard enough to scratch even the diamond.^ In glo- 
 bules or mammillary masses, consisting partly of concentric layers; fragile ; G =1'66; com- 
 position, Carbon 97, hydrogen 0*5, oxygen 15. Cut in facets and polished, it refracts and 
 disperses light, with the white lustre peculiar to the diamond. Locality unknown, but sup- 
 posed to come from Brazil. 
 
 Pyr., etc. Burns, and is wholly consumed at a high temperature, producing carbomo 
 dioxide. It is not acted on by acids or alkalies. 
 
 Diff. Distinguished by its extreme hardness, brilliancy of reflection, and adamantine lustre. 
 
 Oba, The diamond often occurs in regions that afford a laminated granular quartz rock, 
 
 called itacolumyte, which pertains to the talcose series, and which in thin slabs is more or 
 less flexible. This rock is found at the mines of Brazil and the Urals ; and also in Georgia 
 and North Carolina, where a few diamonds have boen found. It has also been detected in a 
 species of conglomerate, composed of rounded siliceous pebbles, quartz, chalcedony, etc., 
 cemented by a kind of ferruginous clay. Diamonds are usually, however, washed out from 
 the soil. The Ural diamonds occur in the detritus along the Adolfskoi rivulet, where worked 
 for sold, and also at other places. In India the diamond is met with at Purteal, between 
 Hyderabad and Masulipata m, where the famous Kohinoor was found . The locality on Borneo 
 is at Pontiana, on the west side of the Ratoos mountain. Also found in Australia. 
 
 The diamond region of South Africa, discovered in 18(57, is the most productive at the 
 present time. The diamonds occur in the gravel of the Vaal river, from Potchefstrom, cap- 
 ital of the Transvaal Republic, down its whole course to its junction with the Orange river, 
 and thence along th-3 latter stream for a distance of 60 miles. In addition to this the dia- 
 monds are found also in the Orange River Republic, in isolated fields or Pans, of which Du 
 Toit's Pan is the most famous. The number of diamonds which have been found at the Ciipo 
 is very laro-e, and some of them are of considerable size. It has been estimated that the valuo 
 of those obtained from Maroh, 1867, to November, 1875, exceeded sixty millions of dollars. 
 As a consequence of this production the market value of the stones has been much dunin- 
 
 In the United States a few crystals have been met with in Rutherford Co., N. C., and Hall 
 Co., Ga. ; they occur also at Portis mine, Franklin Co., N. C. (Genth) ; one handsome one, 
 over % in. in diameter, in the village of Manchester, opposite Richmond, Va. In California, 
 at Cherokee ravine, in Butte Co. ; also in N. San Juan, Nevada Co., and elsewhere in the 
 gold washings. Reported from Idaho, and with platinum of Oregon. 
 
 The largest diamond of which we have any knowledge is mentioned by Tavermer as i 
 possession of the Great Mogul. It weighed originally 900 carats, or 2769 3 grains, but was 
 reduced by cutting to 861 grains. It has the form and size of half a hen's egg. It was found 
 in 1550, in the mine of Colone. The Pitt or Regent diamond weighs but 136 2o carats, pi 
 41 9i o-rains but is of unblemished transparency and color. It is cut in the form ot a bril 
 liant, and its value is estimated at 125,000. The Kohinoor measured, on its arrival m fing 
 land about If inches in its greatest diameter, over f of an inch in thickness, and weighe 
 ISiV, carats, and was cut with many facets. It has since been recut, and reduced to a dia 
 meter of 1-V by 1* nearly, and thus diminished over one-third in weight. It is supposed by 
 Mr. Tennant to have been originally a dodecahedron, and he suggests that the great Russian 
 diamond and another large slab weighing 130 carats were actually cut from the original do< 
 cahedron. Tavernier gives the original weight at 787| carats. The Rajah of Mattan has in 
 his possession a diamond from Borneo, weighing 367 carats. The mines of Brazil were not 
 known to afford diamonds till the commencement of the eighteenth century. 
 
230 DESCRIPTIVE MINERALOGY. 
 
 GRAPHITE. Plumbago. 
 
 Hexagonal. In flat six-sided tables. The basal planes (0) are often 
 striated "parallel to the alternate edges. Cleavage : basal, perfect. Com- 
 monly in imbedded, foliated, or granular masses. Rarely in globular con- 
 cretions, radiated in structure. 
 
 H.=l-2. G.= 2-09-2-229. Lustre metallic. Streak black and shining. 
 Color iron-black -dark steel-gray. Opaque. Sectile ; soils paper. Thin 
 laminae flexible. Feel greasy. 
 
 Var. (a) Foliated ; (b) columnar, and sometimes radiated ; (c) scaly, massive, and slaty ; 
 (d) granular massive ; (e) earthy, amorphous, without metallic lustre except in the streak ; 
 (/) in radiated concretions. 
 
 Comp. Pure carbon, with often a little iron sesquioxide mechanically mixed. 
 
 Pyr., etc. At a high temperature it burns without flame or smoke, leaving usually somo 
 red oxide of iron. B.B. infusible; fused with nitre in a platinum spoon, deflagrates, con- 
 verting the reagent into potassium carbonate, which effervesces with acids. Unaltered by 
 acids. 
 
 Dift See molybdenite, p. 233. 
 
 Obs. Graphite occurs in beds and imbedded masses, laminae, or scales, in granite, gneiss, 
 mica schists, crystalline limestone. It is in some places a result of the alteration by heat of 
 the coal of the coal formation. Sometimes met with in greenstone. It is a common furnace 
 product 
 
 Occurs at Borrowdale in Cumberland ; in Glenstrathfarrar in Invernesshire ; at Arendal in 
 Norway; in the Urals, Siberia, Finland ; in various parts of Austria; Prussia; France. 
 Large quantities are brought from the East Indies. 
 
 In the United States, the mines of Sturbridge, Mass., of Ticonderoga and Fishkill, N. Y., 
 of Brandon, Vt., and of Wake, N. C., are worked; and that of Ashford, Conn., formerly 
 afforded a large amount of graphite. It occurs sparingly at many other localities. 
 
 The name black lead, applied to this species, is inappropriate, as it contains no l^ad. The 
 name graphite, of Werner, is derived from ypd<j>w, to write. 
 
 Nordenskiuld makes the graphite of Ersby and Storgard monodinie. 
 
II. SULPHIDES, TELLURIDES, SELENIDES, ARSEN- 
 IDES, BISMUTHIDES. 
 
 1. BINARY COMPOUNDS. SULPHIDES AND TELLUKIDES OF THE METALS 
 OF THE SULPHUR AND AKSENIO GROUPS. 
 
 REALGAR,* 
 
 Monoclinic. 6" = 66 5', /A 7= 74 26', Marignac, Scacchi, A 14 
 138 21' ; c:b: d = 0-6755 : 0-6943 : 1. Habit pris- 
 matic. Cleavage : i-l, O rather perfect ; I, i-i in 
 traces. Also granular, coarse or fine ; compact. 
 
 H.=l'5-2. G.=3'4-3-6. Lustre resinous. Color 
 aurora-red or orange-yellow. Streak varying from 
 orange-red to aurora-red. Transparent translu- 
 cent. Fracture conchoidal, uneven. 
 
 Comp, AsS= Sulphur 29.9, arsenic 70*1=100. 
 
 Pyr,, etc. In the closed tube melts, volatilizes, and gives a 
 transparent red sublimate ; in the open tube, sulphurous fumes, 
 and a white crystalline sublimate of arsenous oxide. B.B. on 
 
 jharcoal burns with a blue flame, emitting arsenical and sulphurous odors. Soluble in caustia 
 alkalies. 
 
 Obs. Occurs with ores of silver and lead, in Upper Hungary ; in Transylvania ; at Joachims- 
 thal ; Schneeberg ; Andreasberg ; in the Binnenthal, Switzerland, in dolomite ; at Wiesloob 
 in Baden ; near Julamerk in Koordistan ; in Vesuvian lavas, in minute crystals. 
 
 ORPIMENT.* 
 
 Orthorhombic. 7 A 1 = 100 40', O A 14 = 126 30', Mohs. c : I : d == 
 1-3511 : 1-2059 : 1. Cleavage : i-l highly perfect, i-l in traces, i-l longi- 
 tudinally striated. Also, massive, foliated, or columnar; sometimes reui- 
 form. 
 
 H. = 1-5-2. G. = 3-48, Haidinger. Lustre pearly upon the faces ot per- 
 fect cleavao-e ; elsewhere resinous. Color several shades of lemon-yellow. 
 Streak yellow, commonly a little paler than the color. Subtransparent-- 
 Biibtranshicent. Sub-sestUe. Thin laminae obtained by cleavage flexible 
 but not elastic. 
 
 Oomp. As 2 S 3 = Sulphur 39, arsenic 61=100. 
 
 Pvr., etc. In the closed tube, fuses, volatilizes, and gives a dark yellow sublimate ; other 
 reactions the same as under realgar. Dissolves in nitro-hydrochloric acid and caustic alkalies. 
 
 Obs Orpiment in small crystals is imbedded in clay at Tajowa, in Upper Hungary, 
 usually in foliated and fibrous masses, and in this form is found at Kapmk at Moldawa, and 
 at Felsbbanya ; at Hall in the Tyrol it is found in gypsum ; at St. Gothard m dolomite ; at 
 
232 
 
 DESCRIPTIVE MINERALOGY. 
 
 the Solfatara near Naples. Near Julamerk in Koordistan. Occurs also at Acobambillo, Pent 
 Small traces are met with in Edenville, Orange Co. , N. Y. 
 
 The name orpiment is a corruption of its Latin name auripigmentum, " golden paint" 
 which was given in allusion to the color, and also because the substance was supposed to con- 
 tain gold. 
 
 DIMORPHITE of Scaccbi may be, according to Kenngott, a variety of orpiment. 
 
 STIBNITE, Antimonite. Gray Antimony. Antimony Glance. Antimonglanz, Germ. 
 
 Orthorhombic. /A 1= 90 54/, O A 14 = 134 16', Krenner ; c\l:d = 
 
 1-0259 : 1-0158 : 1. O A 1 = 124 
 423 423 
 
 45'; A 1-2 = 134 
 
 Lateral planes deeply striated 
 longitudinally. Cleavage : i-l highly 
 perfect. Often columnar, coarse or 
 tine ; also granular to impalpable. 
 
 H.=2. G. =4-516, Haiiy. Lustre 
 metallic. Color and streak lead- 
 gray, inclining to steel-gray : sub- 
 ject to blackish tarnish, sometimes 
 iridescent. Fracture small sub-con- 
 choidal. Sectile. Thin laminae a 
 little flexible. 
 
 Comp. Sb 2 S 3 = Sulphur 28 2, antimony 71 8=100. 
 
 Pyr., etc, In the open tube sulphurous and antimonous fumes, the latter condensing as a 
 white sublimate which B.B. is non-volatile. On charcoal fuses, spreads out, gives sulphurous 
 and antimonous fumes, coats the coal white ; this coating treated in R.F. tinges the flame 
 greenish -blue. Fus. =1. When pure perfectly soluble in hydrochloric acid. 
 
 Diff Distinguished by its perfect cleavage ; also by its extreme fusibility and other blow- 
 pipe characters. 
 
 Ob-. Occurs with spathic iron in beds, but generally in veins. Often associated with 
 blende, barite, and quartz. 
 
 Met with in veins at Wolfsberg. in the Harz ; at Briiunsdorf, near Freiberg ; at Przibram ; 
 in Hungary; at Pereta, in Tuscany; in the Urals; in Dumfriesshire; in Cornwall. Also 
 found in different Mexican mines. Also abundant in Borneo. 
 
 In the United States, it occurs sparingly at Carmel, Me. ; at Cornish and Lyme, N. H. ; 
 at u Soldier's Delight," Md. ; in the Humboldt mining region in Nevada ; also in the mines 
 of Aurora, Esmeralda Co., Nevada. Also found in New Brunswick, 20 m. from Fredericton, 
 S. W. side of St. John R. 
 
 This ore affords much of the antimony of commerce. The crude antimony of the shops is 
 obtained by simple fusion, which separates the accompanying rock. From this product most 
 of the pharmaceutical preparations of antimony are made, and the pure metal extracted. 
 
 LIVING STONITE (Barcena). Resembles stibnite in physical characters, but has a red 
 streak, and contains, besides sulphur and antimony, 14 p. c. mercury. Huitzuco, State of 
 Guerrero, Mexico, gee p. 430. 
 
 BISMUTHINITE. Bismuth Glance. Wismuthglanz, Germ. 
 
 Cleavage : brachydiagonal 
 In acicular crystals. Also 
 
 Orthorhombic. /A / = 91 30', Haidinger. 
 perfect ; macrodiagonal less so ; basal perfect, 
 massive, with a foliated or fibrous structure. 
 ^ H. = 2. G. = 6-4-6-459 ; 7'2 ; 7-16, Bolivia, Forbes. Lustre metallic. 
 Streak and color lead-gray, inclining to tin-white, with a yellowish or irides- 
 cent tarnish. Opaque. 
 
SULPHIDES, TELLUKIDES, SELENIDES, ETC. 233 
 
 Comp. Bi 2 S 3 = Sulphur 18'75, bismuth 81 '25=100 ; isomorphous with stibnite. 
 
 Pyr,, etc. In the open tube sulphurous fumes, and a white sublimate which B.B. fuses 
 into drops, brown while hot and opaque yellow on cooling. On charcoal at first gives sul- 
 phurous fumes, then fuses with spirting, and coats the coal with yellow bismuth oxide. 
 Fus. =1. Dissolves readily in hot nitric acid, and a white precipitate falls on diluting with 
 water. 
 
 Obs. Found at Brandy Gill, Carrook Fells, in Cumberland ; near Redruth; at Botallack 
 near Land's End ; at Borland Mine, Gwennap ; with childrenite, near Callington ; in Saxony; 
 at Riddarhyttan, Sweden; near Sorata, Bolivia. Occurs in Rowan Co., N. C., at the Barn- 
 hardt vein ; at Haddam, Ct. ; Beaver Co., Utah. 
 
 GUANAJUATITE ; F'renzelite. Fernandez, 1873 ; Castillo, 1873 ; Frenzel, 1874. A bismuth 
 selenide, Bi 2 Se 3 ; sometimes with part of the selenium replaced by sulphur, that is, Bi 2 (Se,S) 3 , 
 with Se : S 3 : 2, which requires Selenium 23 '8, sulphur 6 '5, bismuth 697=100. Isomor- 
 phous with stibnite and bismuthinite (Schrauf). Guanajuato, Mexico. SILAONITB from 
 Guanajuato is Bi 3 Se (Fernandez). See p. 428. 
 
 TETRADYMITB, Tellurwismuth, G&rm. 
 
 Hexagonal. Of\R = 118 38', .# A 72 = 81 2' ; c = 1-5865. Crystals 
 often tabular. Cleavage : basal, very perfect. Also massive, foliated, or 
 granular. 
 
 H. = l'5-2. G.=7'2-7-9. Lustre metallic, splendent. Color pale steel- 
 gray. Kot very sectile. Laminae flexible. Soils paper. 
 
 Comp., Var. Consists of bismuth and tellurium, with sometimes sulphur and selenium. 
 If sulphur, when present, replaces part of the tellurium, the analyses for the most part afford 
 the general formula Bi 2 (Te, S) 3 . Var. I. Free from sulphur. Bi 2 Te 3 = Tellurium 48-1, 
 bismuth 51 "9; G. =7-868, from Dahlonega, Jackson; 7-642, id., Balch. 2. Sulphurous. 
 Containing 4 or 5 p. c. sulphur. G.=7-500, crystals from Schubkau, Wehrle. 
 
 Pyr. In the open tube a whit/; sublimate of tellurous oxide, which B.B. fuses to colorless 
 drops. On charcoal fuses, gives white fumes, and entirely volatilizes ; tinges the R. F. bluish- 
 green ; coats the coal at first white (tellurous oxide), and finally orange-yellow (bismuth 
 oxide) ; some varieties give sulphurous and selenous odors. 
 
 Diflf. Distinguished by its easy fusibility ; tendency to foliation, and high specific gravity. 
 
 Obs. Occurs at Schubkau, near Schemnitz ; at Retzbanya ; Orawicza; at Tellemark in 
 Norway; at Bastnaes mine, near Riddarhyttan, Sweden. 
 
 In the United States, associated with gold ores, in Virginia ; in North Carolina, Davidson 
 Co. , etc. Also occurs in Georgia, 4 m. E. of Dahlonega, and elsewhere ; Highland, Montana 
 T. ; Red Cloud mine, Colorado, rare ; Montgomery mine, Arizona. 
 
 JOSEITE. _ A bismuth telluride, in which half the tellurium is replaced by sulphur and 
 uelenium ; Brazil. 
 
 WEHRLITE. Composition probably Bi(Te, S). G. =8-44. Deutsch Pilsen, Hungary. 
 
 MOLYBDENITE.* Molybdanglanz, Germ. 
 
 In short or tabular hexagonal prisms. Cleavage : eminent, parallel to 
 base of hexagonal prisms. Commonly foliated, massive, or in scales: also 
 tine granular. 
 
 PL 1-1-5, being easily impressed by the nail. G.=4-44-4-8. Lustre 
 metallic. Color pure lead-gray. Streak similar to color, slightly inclined 
 to green. Opaque. Laminae very flexible, not elastic. SectiJe, and almost 
 malleable. Bluish-gray trace on paper. 
 
234 DESCRIPTIVE MINERALOGY. 
 
 Comp. MoS a = Sulphur 41'0, molybdenum 59'0=100, 
 
 Pyr., etc. In the open tube sulphurous fumes. B.B. in the forceps infusible, imparts a 
 yellowish-green color to the tiame ; on charcoal the pulverized mineral gives in O. F. a strong 
 odor of sulphur, and coats the coal with crystals of molybdic oxide, which appear yellow 
 while hot, and white on cooling ; near the assay the coating is copper-red, and if the white 
 coating be touched with an intermittent R. F., it assumes a beautiful azure-blue color. 
 Decomposed by nitric acid, leaving a white or grayish residue (rnolybdic oxide). 
 
 Diff. Distinguished from graphite by its color and streak, and also by its behavior (yield- 
 ing sulphur, etc. ) before the blowpipe. 
 
 Obs Molybdenite generally occurs imbedded in, or disseminated through, granite, gneiss, 
 zircon-syenite, granular limestone, and other crystalline rocks. Found in Sweden ; Norway ; 
 Russia. Also in Saxony ; in Bohemia ; Rathausberg in Austria ; near Miask, Urals ; Chessy 
 in France ; Peru ; Brazil ; Calbeck Fells, and elsewhere in Cumberland ; several of the Cornish 
 mines ; in Scotland at East Tulloch, etc. 
 
 In Maine, at Blue Hill Bay and Camdage farm. In Conn,, at Haddam. In Vermont, at 
 Newport. In N. Hampshire, at Westmoreland ; at Llandaff ; at Franconia. In Mass., at 
 Shutesbury ; at Brimfield. In N. York, near Warwick. In Penn., in Chester, on Chester 
 Creek ; near Concord, Cabarrus Co., N. C. In California, at Excelsior gold mine, in Excel- 
 aior district. In Canada, at several places. 
 
 2. BINARY COMPOUNDS. SULPHIDES, TELLURIDES, ETC., OF METALS 
 OF THE GOLD, IRON, AND TIN GROUPS. 
 
 A. BASIC DIVISION. 
 
 DYSCRASITE. Antimonial Silver. Antimon-Silber, Germ. 
 
 Orthorhornbic. /A 1 = 119 59' ; A 14 130 41' ; c : I : d = 1-1633 : 
 1-7315:1; O A 1 = 126 40' ; A l- = 146 6'. Cleavage : basal distinct : 
 \-l also distinct ; / imperfect. Twins : stellate forms and hexagonal 
 prisms. Prismatic planes striated vertically. Also massive, granular ; par- 
 ticles of various sizes, weakly coherent. 
 
 H.= 3-5-4. G.= 9-44-9 -82. Lustre metallic. Color and streak silver- 
 white, inclining to tin-white ; sometimes tarnished yellow or .blackish. 
 Opaque. Fracture uneven. 
 
 Comp. Ag 4 Sb= Antimony 22, silver 78=100. Also Ag 6 Sb= Antimony 15 '66, silver 84*34, 
 and other proportions. 
 
 Pyr., etc. B. B. on charcoal fuses to a globule, -coating the coal with white antimonous 
 oxide, and finally giving a globule of almost pure silver. Soluble in nitric acid, leaving anti- 
 monous oxide. 
 
 Obs. Occurs near Wolfach in Baden, Wittichen in Suabia, and at Andreasberg ; also at 
 AUemont in Daupbine, Casalla in Spain, and in Bolivia, S. A. 
 
 DOMEYKITE, Arsenikkupfer, Germ. 
 
 Reniform and botryoidal ; also massive and disseminated. 
 
 H.:= 3-3-5. G.= T-7'50, Portage Lake, Genth. Lustre metallic but dull 
 on exposure. Color tin-white to steel-gray, with a yellowish to pinchbeck- 
 brown, and, afterward, an iridescent tarnish. Fracture uneven. 
 
TELLURIDES, SELENIDE8, ETC. 235 
 
 Comp. Cu 3 As=Arsenic 28 -3, copper 71 7=100. 
 
 Pyr., etc. In the open tube fuses and gives a white crystalline sublimate of arsenoua 
 oxide. B.B. on charcoal arsenical fumes and a malleable metallic globule, which, on treat- 
 ment with soda, gives a globule of pure copper. Not dissolved in hydrochloric acid, but 
 soluble in nitric acid. 
 
 Obs From the mines of Chili. In N, America, found on the Sheldon location, Portage 
 Lake ; and at Michipicoten Island, in L. Superior. 
 
 ALGOPONITE. Composition, Cu 6 As = Arsenic 16 '5, copper 83*5. Chili ; also Lake Superior. 
 
 WHITNEVITE. CuAs=Arsenic 11*6, copper 88 '4 =100. Houghton, Mich., also Calif ornia, 
 Arizona. 
 
 B. PROTO DIVISION. 
 
 (a) Galenite Group. Isometric ; holohedral. 
 
 ARGENTITE. Silver Glance. Vitreous Silver. Silberglanz, Germ. 
 
 Isometric. Cleavage : dodecahedral in traces. Also reticulated, arbores- 
 cent, and filiform ; also amorphous. 
 
 H.=:2-2-5. G.= 7-196-7-365. Lustre metallic. Streak and color black- 
 ish lead-gray ; streak shining. Opaque. Fracture small sub-conchoidal, 
 ineven. Malleable. 
 
 Comp Ag 2 S=Sulphur 12 '9, silver 87 '1=100. 
 
 Pyr., etc. In the open tube gives off sulphurous oxide. B.B. on charcoal fuses with intu- 
 mescence in O.F., emitting sulphurous fumes, and yielding a globule of silver. 
 
 Diff. Distinguished from other silver ores by its malleability. 
 
 Obs. Found in the Erzgebirge ; in Hungary ; in Norway, near Kongsberg ; in the Altai ; 
 in the Urals at the Blagodat mine ; in Cornwall ; in Bolivia ; Peru ; Chili ; Mexico, etc. 
 Occurs in Nevada, at the Comstock lode, and elsewhere. 
 
 OLDIIAMITE from the Busti meteorite is essentially CaS. 
 
 NAUMANNITE. A silver selenide, containing also some lead. Color iron-black. From 
 the Harz. 
 
 EUCAIRITE. A silver-copper selenide, (Cu, Ag) 2 Se. Color silver-white to gray. Sweden ; 
 Chili. 
 
 CROOKESITE. 
 
 Massive, compact ; no trace of crystallization. 
 
 H.=2-5-3. &.=6-90. Lustre metallic. Color lead-gray. Brittle. 
 
 Comp (Cu 2 ,Tl,Ag) Se=Selenuim 33 -28, copper 45-76. thallium 17-25, silver 3'71.100. 
 
 Pyr., etc. B.B. fuses very easily to a greenish-black shining enamel, coloring the flame 
 strongly green. Insoluble in hydrochloric acid ; completely soluble in nitric acid. 
 
 Obs. From the mine of Skrikerum in Norway. Formerly regarded as selenide of copper 
 or berzelianite. 
 
 GALENITE. Galena. Bleiglanz, Germ. 
 
 Isometnc ; habit cubic (see f. 38, 39, etc., p. 15). Cleavage, cubic, per- 
 fect ; octahedral in traces. Twins: twinning-plane, the octahedral plane, 
 f. 425 (f. 263, p. 88); the same kind of composition repeated, f. 426, anJ 
 
236 
 
 DESCRIPTIVE MINERALOGY. 
 
 flattened parallel to 1. Also reticulated, tabular ; coarse or fine granular ; 
 sometimes impalpable ; occasionally fibrous. 
 
 424 
 
 426 
 
 II.=2-5-2-75. G.=7'25-7'7. Lustre metallic. Color and streak pure 
 lead-gray. Surface of crystals occasionally tarnished. Fracture flat sub- 
 chonchoidal, or even. Frangible. 
 
 Comp., Var PbS = Sulphur 13 "4, lead 86 -6 = 100. Contains silver, and occasionally selen- 
 ium, zinc, cadmium, antimony, copper, as sulphides ; besides, also, sometimes native silver 
 and gold ; all galenite is more or less argentiferous, and no external characters serve to dis- 
 tinguish the relative amount of silver present. 
 
 Pyr. In the open tube gives sulphurous fumes. B.B. on charcoal fuses, emits sulphurous 
 fumes, coats the coal yellow, and yields a globule of metallic lead. Soluble in nitric acid. 
 
 Diff. Distinguished in all but the finely granular varieties by its perfect cubic cleavage. 
 
 Obs. Occurs in beds and veins, both in crystalline and uncrystalline rocks. It is often 
 associated with pyrite, marcasite, blende, chalcopyrite, arsenopyrite, etc., in a gangue of 
 quartz, calcite, barite, or fluorite, etc. ; also with cerussite, anglesite, and other salts of lead, 
 which are frequent results of its alteration. It is also common with gold, and in veins of 
 silver ores. Some prominent localities are : Freiberg in Saxony, the Harz, Przibram and 
 Joachimsthal, Styria ; and also Bleiberg, and the neighboring localities of Carinthia, Sala in 
 Sweden, Leadhills and the killas of Cornwall, in veins; Derbyshire, Cumberland, and the 
 northern districts of England ; in Nertschinsk, East Siberia; in Algeria; near Cape of Good 
 Hope ; in Australia ; Chili ; Bolivia, etc. 
 
 Extensive deposits of this ore in the United States exist in Missouri, Illinois, Iowa, and 
 Wisconsin. Other important localities are : in New York, Rossie, St. Lawrence Co. ; 
 Wurtzboro, Sullivan Co. ; at Ancram. Columbia Co. ; in Ulster Co. In Maine, at Lubec. In 
 New Hampshire, at Eaton and other places. In Vermont, at Thetford. In Connecticut, at 
 Middletown. In Massachusetts, at Newburyport, at Southampton, etc. In Pennsylvania, at 
 Phenixville and elsewhere. In Virginia, at Austin's mines in Wythe Co., Walton's gold mine 
 in Louisa Co., etc. In Tennessee, at Brown's Creek, and at Haysboro, near Nashville. In 
 Michigan, in the region of Chocolate river, and Lake Superior copper districts, on the 
 N. shore of L. Superior, in Neebing on Thunder Bay, and around Black Bay. In Cali- 
 fornia, at many of the gold mines. In Nevada, abundant on Walker's river, and at Steam- 
 boat Springs, Galena district. In Arizona, in the Castle Dome, Eureka, and other districts. 
 In Colorado, at Pike's Peak, etc. 
 
 CLAUSTHALITB. Selenblei, Germ. 
 
 Isometric. Occurs commonly in fine granular masses ; some specimens 
 foliated. Cleavage cubic. 
 
 H.=2'5-3. Gr.= 7-6-8-8. Lustre metallic. Color lead -gray, somewhat 
 bluish. Streak darker. Opaque. Fracture granular and shining. 
 
 Comp., Var. PbSe = Selenium 27'6, lead 72'4=100. Besides the pure selenide of lead, 
 there are others, often arranged as distinct species, which contain cobalt, copper, or mercury 
 in place of part of the lead, arid sometimes a little silver or iron. 
 
SULPHIDES, TKLLURIDES, SELENIDES, ETC. 237 
 
 Pyr. Decrepitates in the closed tube. In the open tube gives selenous fumes and a red 
 sublimate. B. B. on charcoal a strong selenous odor ; partially fuses. Coats the coal near 
 the assay at first gray, with a -reddish border (selenium), and later yellow (lead oxide) ; when 
 pure entirely volatile ; with soda gives a globule of metallic lead. 
 
 Obs Much resembles a granular galenite; but the faint tinge of blue and the B.B 
 selenium fumes serve to distinguish it. 
 
 Found at Glausthal, Tilkerode, Zorge, Lehrbach, etc., in the Harz ; at Rehjsberg in Sax 
 ony ; at the Rio Tinto mines, Spain ; Cacheuta mine, Mendoza, S. A. 
 
 ZORGITE and LEHKBACIIITE occur with clausthalite in the Harz. Zorgite is a lead-copper 
 eelenide. Lehrbachite is a lead-mercury selenide. 
 
 BEBZELIANITE. Cu 2 Se= Selenium 38 '4, copper 61 '6=100. Color silver -white. From 
 Sweden, also the Harz. 
 
 ALTAITE. Composition PbTe= Tellurium 38 '3, lead 61 '17. Isometric. Color tin-white. 
 From Savodinski in the Altai ; Stanislaus mine, Cal. ; Red Cloud mine, Colorado ; Province 
 of Coquimbo, Chili. 
 
 TIEMANNITE (Selenquecksilber, Germ.). A. mercury selenide, probably HgSe. Massive. 
 Found in the Harz ; also California. 
 
 BORNITE. Erubescite. Purple Copper Ore. Buntkupfererz, Germ. 
 
 Isometric. Cleavage : octahedral in traces. Massive, structure granular 
 or compact. 
 
 H. 3. G-.=4-4-5*5. Lustre metallic. Color between copper-red and 
 pinchbeck-brown; speedily tarnishes. Streak pale grayish- black, slightly 
 shining. Fracture small conchoidal, uneven. Brittle. 
 
 Oomp. For crystallized varieties FeCu 3 S 3 , or sulphur 28 '06, iron 16'36, copper 55 '58=100. 
 Other varieties are : Fe 2 Cu 3 S 4 , FeCu 5 S 3 , and so on. The ratio of R (Cu or Fe) to S has the 
 values 5 : 4, 4 : 3, 3 : 2, 7 : 3 (Rammelsberg). Analysis, CoUier, from Bristol, Ct. Sulphur 
 25-83, copper 61 '79, iron 11 '77, silver tr. =99-39 (R : 8=3 : 2). 
 
 Pyr., etc. In the closed tube gives a faint sublimate of sulphur. In the open tube yields 
 sulphurous oxide, but gives no sublimate. B.B. on charcoal fuses in R.F. to a brittle mag- 
 netic globule. The roasted mineral gives with the fluxes the reactions of iron and copper, 
 and with soda a metallic globule. Soluble in nitric acid with separation of sulphur. 
 
 Diff. Distinguished by its copper-red color on the fresh fracture. 
 
 Obs. Found in the mines of Cornwall ; at Rose Island in Killarney, Ireland ; at Mount 
 Catini, Tuscany; in the Mansfeld district, Germany; and in Norway, Siberia, Silesia, and 
 Hungary. It is the principal copper ore at some Chilian mines; also common in Peru, Boli- 
 via, and Mexico. At Bristol, Conn., it has been found abundantly in good crystals. Found 
 massive at Mahoopeny, Penn., and in other parts of the same State; also at Chesterfield, 
 Mass. ; also in New Jersey. A common ore in Canada, at the Acton and other mines. 
 
 ALABANDITE (Manganglanz, Germ.). MnS= Sulphur 36*7, manganese 63.3=100. Isomet- 
 ric. Cleavage cubic. Color black. Streak green. From Transylvania, etc. 
 
 GKUNAUITE. A sulphide containing nickel, bismuth, iron, cobalt, copper. From 
 Griinau, 
 
 (5) Blende Group. Isometric ; tetrahedral. 
 
 SPHALERITE or ZINC BLENDE. Black-Jack, Engl. Miners. 
 
 Isometric: tetrahedral. Cleavage: dodecahedral, highly perfect. Twins: 
 twinning-plane 1, as in f. 429. Also botryoidal, and other imitative shapes ; 
 sometimes fibrous and radiated ; also massive, compact. 
 
 H.= 3-5-4. G.= 3-9-4-2. 4-063, white, New Jersey. Lustre resinous 
 to adamanite. Color brown, yellow, black, red, green ; white or yellow 
 
238 
 
 DESCRIPTIVE MINERALOGY. 
 
 when pure. Streak white reddish-brown. Transparent translucent, 
 Fracture conchoidal. Brittle. 
 
 427 
 
 428 
 
 Comp., Var. ZnS Sulphur 33, zinc 67=100. But often having- part of the zinc replaced 
 by iron, and sometimes by cadmium; also containing in minute quantities, thallium, indium, 
 and gallium. Var. 1. Ordinary. Containing little or no iron ; colors white to yellowish- 
 brown, sometimes black ; G. =3 9-4*1. 2. Ferriferous; Marmatite. Containing 10 p. c. 01 
 more of iron; dark-brown to black ; G.=8*9-4*2. The proportion of iron sulphide to zinc 
 sulphide varies from 1 : 5 to 1 : 2. 3. Cudmiferous ; Przibramite. The amount of cadmium 
 present in any blende thus far analyzed is less than 5 per cent. Each of the above varieties 
 may occur (a) in crystals ; (b) firm, fibrous, or columnar, at times radiated or plumose ; (c) 
 cleavable, massive, or foliated ; (d) granular, or compact massive. 
 
 Pyr., etc. In the open tube sulphurous fumes, and generally changes color. B.B. on 
 charcoal, in R.F., some varieties srive at first a reddish- brown coating of cadmium oxide, and 
 later a coating of zinc oxide, which is yellow while hot and white after cooling. With cobalt 
 solution the zinc coating gives a green color when heated in O.P. Most varieties, after 
 roasting, give with borax a reaction for iron. With soda on charcoal in R.F. a strong green 
 zinc flame. Difficultly fusible. 
 
 Dissolves in hydrochloric acid, during which sulphuretted hydrogen is disengaged. Some 
 specimens phosphoresce when struck with a steel or by friction. 
 
 Diff. Generally to be distinguished by its perfect cleavage, giving angles of 60 and 120 ; 
 by its resinous lustre, and also by its infusibility. 
 
 Obs. Ocouis in both crystalline and sedimentary rocks, and is usually associated with 
 galenite ; also with barite, chalcopyrite, fluorite, siderite, and frequently in silver mines. 
 
 Derbyshire. Cumberland, and Cornwall, afford different varieties ; also Transylvania; Hun- 
 gary ; the Harz; Sahla in Sweden; Ratieborzitz in Bohemia; many Saxon localities. 
 Splendid crystals in dolomite are found in the Binnenthal. 
 
 Abounds with the lead ore of Missouri, Wisconsin, Iowa, and Illinois. In JV. York, Sulli- 
 van Co., near Wurtzboro' ; in St. Lawrence Co., at Cooper's falls, at Mineral Point; at the 
 Ancram lead mine in Columbia Co. ; in limestone at Lockport and other places. In Mass., 
 at Sterling ; at the Southampton lead mines ; at Hatfield. In N. Hamp., at the Eaton lead 
 mine ; at Warren, a large vein of black blende. In Maine, at the Lubec lead mines, etc. 
 In Conn., at Roxbury, and at Lane's mine, Monroe. In N. Jersey, a white variety at Frank- 
 lin. In Penn., at the Wheatley and Perkiomen lead mines ; near Friedensville, Lehigh Co. 
 In Virginia, at Austin's lead mines, Wythe Co. In Michigan, at Prince vein, Lake Superior. 
 In Illinois, near Rosiclare ; near Galena, in stalactites, covered with pyrite, and galenite 
 In Wisconsin, at Mineral Point. In Tennessee, at Haysboro', near Nashville. 
 
 Named blende because, while often resembling galena, it yielded no lead, the word in Ger 
 meaning blind or deceiving. Sphalerite is from (npoAepos, treacherous. 
 
 (c) Chalcocite Group. Orthorhombic. 
 HESSITE.* Tellursilber, Germ. 
 
 Orthorhombic, and resembling chalcocite. Cleavage indistinct Mas 
 fli ve ; compact or fine grained ; rarely coarse-granular. 
 
SULPHIDES, TELLURIDES, SELENIDES, ETC. 
 
 239 
 
 H.=2-3-5. G. 8-3-8*6. Lustre metallic. Color between lead-gray 
 and steel-gray. Sectile. Fracture even. 
 
 Comp Ag 2 Te= Tellurium 37 '2, silver 62 '8 =100. Silver sometimes replaced in part by 
 gold. 
 
 Pyr. In the open tube a faint white sublimate of tellurous oxide, which B.B. fuses to 
 colorless globules. On charcoal fuses to a black globule ; this treated in R.F. presents on 
 cooling white dendritic points of silver on its surface ; with soda gives a globule of silver. 
 
 Obs. Occurs in the Altai, in Siberia, in a talcose rock ; at Nagyag in Transylvania, and at 
 Retzbanya in Hungary ; Stanislaus mine, Calaveras Co. , Cal. ; Red Cloud mine, Colorado ; 
 Province of Coquimbo, Chili. 
 
 PETZITE. Differs from hessite in that gold replaces much of the silver. H. 2*5. G.= 
 8 '72-8 '83, Petz; 9-0*4, Kiistel. Color between steel-gray and iron-black, sometimes with 
 pavonine tarnish. Streak iron-black. Brittle. Analysis by Genth, from Golden Rule mine, 
 tellurium 32'68, silver 41-8H, gold 25 -60 = 10014. Occurs at Nagyag, Stanislaus mine, 
 California, and several localities in Colorado. 
 
 TAPALPITE (Tellurwismuthsilber). Composition (Ramm.), Ag 2 Bi. 2 Te.,S(Ag 2 S + 2BiTe). 
 Granular. Color gray. Sierra de Tapalpa, Mexico. 
 
 ACANTHITE. 
 
 Orthorhombic. /A / = 110 54' ; O A l-l = 124 42', Dauber ; i : I : d 
 = 1-4442 : 1-4523 : 1. A l- = 135 10' ; A 1 = 119 42'. Twins : 
 parallel to l-l. Crystals usually slender-pointed prisms. Cleavage indis- 
 tinct. 
 
 H.=2-5 or under. G.=7'16-7'33. Lustre metallic. Color iron-black 
 or like argentite. Fracture uneven, giving a shining surface. Sectile. 
 
 Comp Ag 2 S, or like argentite. Sulphur 12 9, silver 87-1=100. 
 
 Pyr. Same as for argentite, p. 235. 
 
 Obs. Pound at Joachimsthal ; also near Freiberg in Saxony. 
 
 CHALCOCITB. Chalcosine. Vitreous Copper. Copper Glance. Kupferglanz, Germ. 
 
 Orthorhombic. /A /= 119 35', A I-l = 120 57'; r : I : a = 1*6676 : 
 1-7176 : 1 ; A 1 = 117 24' ; A \-l = 135 52'. Cleavage : /, indistinct. 
 Twins : t winning-plane, /, producing hexagonal, or stellate forms (left half 
 430 431 432 433 
 
 Bristol, Ct. 
 
 \ 
 
 Bristol, Ct Bristol, Ct. 
 
 of f. 432) ; also 4-, a cruciform twin (f. 432), crossing; at angles of 111 
 and 69 ; f. 433, a cruciform twin, having O and I of one crystal parallel 
 respectively to i4 and O of the other. Also massive, structure granular, 
 or compact and impalpable 
 
240 
 
 DE8CEIPTTVE MINERALOGY. 
 
 H.=2*5-3. G. 5-5-5*8. Lustre metallic. Color and streak blackish 
 lead-gray : often tarnished blue or green ; streak sometimes shining. Frac- 
 ture conchoidal. 
 
 Comp. Cu 2 S= Sulphur 20 '2, copper 79-8=100. 
 
 Pyr,, etc. Yields nothing volatile in the closed tube. In the open tube gives off sulphur- 
 ous fumes. B.B. on charcoal melts to a globule, which boils with spirting; with soda ia 
 reduced to metallic copper. Soluble in nitric acid. 
 
 Obs. Cornwall affords splendid crystals. The compact and massive varieties occur in 
 Siberia, Hesse, Saxony, the Bunat, etc. ; Mt. Catini mines in Tuscany ; Mexico, Peru. 
 Bolivia, Chili. 
 
 In the United States, it has been found at Bristol, Conn. , in large and brilliant crystals. 
 In Virginia, in the United States copper mine district, Orange Co. Between Newmarket and 
 Taneytown, Maryland. In Arizona, near La Paz ; in N. W. Sonora. In Nevada, in Washoe, 
 Humboldt. Churchill, and Nye Cos. 
 
 HARRISITE of Shepard, from Canton mine, Georgia, is chalcocite with the cleavage of 
 galenite (pseudomorphous, Gentli). 
 
 STROMEYERITE, Silberkupferglanz, Germ. 
 
 Orthorhombic : isomorphous with chalcocite. 
 massive, compact. 
 
 H.=:2-5-3. G.=6-2-6-3. Lustre metallic. 
 Streak shining. Fracture subconchoidal. 
 
 /A 7= 119 35'. Also 
 Color dark steel-gray. 
 
 Comp, AgCuS=Ag 2 S+Cu a S=Sulphur 15'7, silver 53-1, copper 31 '2-100. 
 
 Pyr., etc. Fuses, but gives no sublimate in the closed tube. In the open tube sulphurous 
 fumes. B.B. on charcoal in O.F. fuses to a semi-malleable globule, which, treated with the 
 fluxes, reacts strongly for copper, and cupelled with lead gives a silver globule. Soluble in 
 nitric acid. 
 
 Obs, Found at Schlangenberg, in Siberia ; at Rudelstadt, Silesia ; also in Chili ; at Com- 
 bavalla in Peru ; at Heintzelman mine in Arizona. 
 
 STERNBERGITE."5 An iron-silver sulphide, AgFe 2 S 3 . Johanngeorgenstadt and Joachimsthal. 
 
 Ehombohedral. 
 
 434 
 
 (d) Pyrrhotite Group. Hexagonal. 
 
 CINNABAR. Zinnober, Germ. 
 
 E A E = 92 36', R/\O = 127 6' ; c = 1-1448. Ac- 
 cording to DesCloizeaux, tetartohedral, like quartz. 
 Also granular, massive ; sometimes forming super- 
 ficial coatings. 
 
 Cleavage: /, very perfect. Twins: twinning- 
 plane O. 
 
 H=2-2-5. G=8'998, a cleavable variety from 
 Neumarktel. Lustre adamantine, inclining to metal- 
 lic when dark-colored, and to dull in fjiable 
 varieties. Color cochineal-red, often inclining to 
 brownish-red and lead-gray. Streak scarlet, sub 
 transparent, opaque. Fracture subconchHdal. un- 
 even. Sectile. Polarization circular. 
 
 Comp HgS (or Hg 3 S 3 )= Sulphur 13-8, mercury 86 '2=100. Sometimes impurt Prom clay 
 uon sesquioxide, bitumen. 
 
SULPHIDES, TELLURIDES, 8ELENIDES, ETC. 241 
 
 Pyr. In the closed tube a black sublimate. Carefully heated in the open tube gives RU! 
 phurous fumes and metallic mercury, condensing in minute globules on the cold walls of the 
 Cube. B.B. on charcoal wholly volatile if pure. 
 
 Obs. Cinnabar occurs in beds in slate rocks and shales, and rarely in granite or porphyry. 
 It has been observed in veins, with ores of iron. The most important European beds of this 
 ore are at Almaden in Spain, and at Idria in Carniola. It occurs at Reichenau and Windisch 
 Kappel in Cariiithia ; in Transylvania ; at Ripa in Tuscany ; at Schemnitz in Hungary ; in 
 the Urals and Altai ; in China abundantly, and in Japan ; San Onof re and elsewhere in Mexico ; 
 in Southern Peru ; forming extensive mines in California, in the coast ranges the principal 
 mines are at New Almaden and the vicinity, in Santa Clara Co. Also in Idaho, in limestone, 
 abundant. 
 
 This ore is the source of the mercury of commerce, from which it is obtained by sublima 
 tion. When pure it is identical with the manufactured vermilion of commerce. 
 
 METACINNABARITE (Moore). A black mercury sulphide (HgS). Rarely crystallized 
 H.=3. G.=7-75. Lustre metallic. Redington mine, Lake Co., Cal. 
 
 (TUADALCAZARITE. Essentially HgS, with part (ifs) of the sulphur replaced by selenium, 
 and part of the mercury replaced by zinc (Hg : Zn=6 : 1, Peterben ; 12 : 1, Ramm.). Massive. 
 Color -deep black. Guadalcazar, Mexico. LEVIGLIANITE is a ferruginous variety from 
 Levigliani, Italy. 
 
 MILLERITE.* Capillary Pyrites. Haarkies ; Nickelkies, Germ. 
 
 Ehombohedral. E A R = 144 8 ', Miller. c = 0-32955. 6>A72 = 15910'. 
 
 Cleavage : rhombohedral, perfect. Usual in capillary crystals. Also in 
 columnar tufted coatings, partly serai-globular and radiated. 
 
 H.= 3-3-5. G.=4r-6-5'65. Lustre metallic. Color brass-yellow, inclin- 
 ing to bronze-yellow, with often a gray iridescent tarnish. Streak bright. 
 Brittle. 
 
 Comp. NiS= Sulphur 35 6, nickel 64 "4=100. 
 
 Pyr., etc. In the open tube sulphurous fumes. B.B. on charcoal fuses to a globule. When 
 roasted, gives with borax and salt of phosphorus a violet bead in 0. F. , becoming gray in R.F. 
 from reduced metallic nickel. On charcoal in R.F. the roasted mineral gives a coherent 
 metallic mass, attractable by the magnet. Soluble in nitric acid. 
 
 Obs. Found at Joachimsthal ; Przibram ; Riechelsdorf ; Andreasberg ; several localities 
 in Saxony ; Cornwall. 
 
 Occurs at the Sterling mine, Antwerp, N. Y. ; in Lancaster Co., Pa., at the Gap mine ; 
 with dolomite, and penetrating calcite crystals, in cavities in limestone, at St. Louis, Mo. 
 
 BEYRICHITE (Lube). Formula Ni 5 S 7 Sulphur 43-6, nickel 56'4=100. Color lead-gray. 
 Occurs in radiated groups with millerite in the Westerwald. 
 
 PYRRHOTTTE. Magnetic Pyrites. Magnetkies, Germ. 
 
 Hexagonal. O A 1 = 135 8' ; c = 0-862. Twins : twinning-plane 1 
 (f . 435). Cleavage : O, perfect ; I, less so. Commonly 435 
 
 massive and amorphous; structure granular. 
 
 H.=3-5-4:-5. G.=4-4:-4-68. Lustre metallic. 
 Color between bronze-yellow and copper-red, and 
 subject to speedy tarnish. Streak dark grayish- 
 black. Brittle. Magnetic, being attractable in 
 fine powder by a magnet, even when not affecting 
 an ordinary needle. 
 
 Comp. (1) Mostly Pe,S 8 =Sulphur 39-5, iron 60-5=100 ; but varyingto Fe 8 S 9 ,Fe 9 S,o and 
 Fei Sj i. Some varieties contain 3-6 p. c. nickel. Horbachite contains (Wagner) 12 p. c. Ni. 
 Pyr., etc. Unchanged in the closed tube. In the open tulre gives sulphurous oxide. On 
 Ifi 
 
242 DESCRIPTIVE MINERALOGY. 
 
 charcoal in R.F. fuses to a black magnetic mass ; in O.F. is converted into iron sesqui Dxide, 
 which with fluxes gives only an iron reaction when pure, but many varieties yield small 
 amounts of nickel and cobalt. Decomposed by muriatic acid, with evolution of sulphuretted 
 hydrogen. 
 
 Dift. Distinguished by its magnetic character, and by its bronze color on the fresh fracture. 
 
 Obs. Occurs in Norway ; in Sweden ; at Andreasberg ; Bodenmais in Bavaria ; N. Tagilsk ; 
 in Spain ; the lavas of Vesuvius ; Cornwall. 
 
 In N. America, in Vermont, at Stafford, Corinth, and Shrewsbury ; in many parts of 
 Massachusetts ; in Connecticut, in Trumbull, in Monroe ; in N. York, near Natural Bridge 
 in Diana, Lewis Co. ; at O'Neil mine and elsewhere in Orange Co. In N. Jersey, Morris Co., 
 at Hurdstown. In Pennsylvania, at the Gap mine, Lancaster Co. , niccolif erous. In Tennes- 
 see, at Ducktown mines. In Canada, at St. Jerome ; Elizabeth town, Ontario (f. 435), etc. 
 
 The niccoliferous pyrrhotite is the ore that affords the most of the nickel of commerce. 
 
 TKOILITE. According to the latest investigations of J. Lawrence Smith, composition 
 FeS, iron proto-sulphide ; that is, iron 63 '6, sulphur 36 '4= 100. Occurs only in iron meteor- 
 ites. DAUBRiiELiTE (Smith). Composition Cr Q S 3 . Observed in the meteoric iron of Northern 
 Mexico ; occurring on the borders of troilite nodules. Similar to shepardite, Haidingei 
 (=schreiber8ite, Shepard), described by Shepard (1846) as occurring in the Bishopville, S. C., 
 meteoric iron. 
 
 SCUREIBERSITE also solely a meteoric mineral. Contains iron, nickel, and phosphorus. 
 
 WURTZITE (Spiauterite). ZnS, like sphalerite, but hexagonal in crystallization. Bolivia. 
 
 GREENOCKITE. 
 
 Hexagonal ; hemimorphic. A 1 = 136 24' ; c = 0-8247. Cleavage : 
 /, distinct ; 0, imperfect. 
 
 H.=3-3'5. G.^4'8-4'999. Lustre adamantine. Color honey-yellow; 
 citron-yellow ; orange-yellow veined parallel with the axis ; bronze- 
 yellow. Streak-powder between orange-yellow and brick red. Nearly 
 transparent. Strong double refraction. Not thermoelectric, Breithaupt. 
 
 Oomp. CdS (or Cd 3 S 3 )=Sulphur 22-2, cadium 77'8. 
 
 Pyr., etc. In the closed tube assumes a carmine -red color while hot, fading to the original 
 yellow on cooling. In the open tube gives sulphurous oxide. B. B. on charcoal, either alone 
 or with soda, gives in B.F. a reddish-brown coating. Soluble in hydrochloric acid, evolving 
 sulphuretted hydrogen. 
 
 Obs. Occurs at Bishoptown, in Renfrewshire, Scotland ; also at Przibram in Bohemia ; 
 on sphalerite at the Ueberoth zinc mine, near Friedensville. Lehigh Co., Pa., and atGranby, 
 Mo. 
 
 NICCOLITE. Copper Nickel. Kupfernickel, Rothnickelkies, Germ. 
 
 Hexagonal. O A 1 = 136 35' ; c : 0-81944. Usually massive, structure 
 nearly impalpable ; also reniform with a columnar structure ; also reticu- 
 lated and arborescent. 
 
 H.=5-5'5. G.=7-33-7'671. Lustre metallic. Color pale copper-red, 
 with a gray to blackish tarnish. Streak pale brownish-black. Opaque. 
 Fracture" uneven. Brittle. 
 
 Comp. NiAs (or Ni 3 As 3 )= Arsenic 56 "4, nickel 43-6=100; sometimes part of the arsenic 
 replaced by antimony. 
 
 Pyr., etc. In the closed tube a faint white crystalline sublimate of arsenous oxide. In the 
 open tube arsenous oxide, with a trace of sulphurous oxide, the assay becoming yellowish- 
 green. On charcoal gives arsenical fumes and fuses to a globule, which, treated with borax 
 glass, affords, by successive oxidation, reactions for iron, cobalt, and nickel. Soluble in 
 nitro-hydrochloric acid. 
 
 Diff Distinguished by its color from other similar sulphides, as also by its pyrognostica 
 
243 
 
 Obs. Occurs at several Saxon mines, also in Thuringia, Hesse, and Styria, and at Alle- 
 mont in Dauphiny ; occasionally in Cornwall ; Chili ; abundant at Mina de la Rioja, in the 
 Argentine Provinces. Found at Chatham, Conn., in gneiss, associated with smaltite. 
 
 BHKITHAUPTITE. Composition NiSb= Antimony 07 '8, nickel 32 '2=: 100. Color light 
 copper-red. Andreasberg. 
 
 ARITE. AJC. antimoniferous niccolite, containing 28 p. c. Sb. Basses-Pyrenees ; Wolfach, 
 Baden. 
 
 0. DEUTO OR PYBITE DIVISION. 4 
 (a) Pyrite Group. 
 
 FYRITE.* Iron Pyrites. Schwefelkies, Eisenkies, Germ. 
 
 Isometric ; pjritohedral. The cube the most common form ; the pyrito- 
 hedron, f. 92, p. 23, and related forms, f. 94, 95, 96, also very common. 
 See also f. 103, 104, 105, p. 24. Cubic faces often striated, with striationa 
 of adjoining faces at right angles, and due to oscillatory combination of the 
 cube and pyritohedron, the striae having the direction of the edges between 
 and i-2. Crystals sometimes acicular through elongation of cubic and 
 other forms. Cleavage : cubic and octahedral, more or less distinct. Twins: 
 twining-plane /, f. 276, p. 93. Also reniform, globular, stalactitic, with a 
 crystalline surf ace ; sometimes radiated subfibrous. Massive. 
 
 436 437 438 
 
 Kossie. 
 
 H.=6-6-5. G.=4-83-5-2. Lustre metallic, splendent to glistening. 
 Color a pale brass-yellow, nearly uniform. Streak greenish or brownish- 
 black. Opaque. Fracture conchoidal, uneven. Brittle. Strikes fire with 
 steel. 
 
 Comp. Var. FeS 2 = Sulphur 53'3, iron 46-7=100. Nickel, cobalt, and thallium, and also 
 copper, sometimes replace a little of the iron, or else occur as mixtures ; and gold is some- 
 times present, distributed invisibly through it. 
 
 Pyr etc. In the closed tube a sublimate of sulphur and a magnetic residue, 
 charcoal gives off sulphur, burning with a blue flame, leaving ^ a residue which reacts Ills a 
 pyrrhotite. Insoluble in hydrochloric acid, but decomposed by nitric acid. 
 
 Diff. Distinguished from chaJcopyrite by its greater hardness, since it cannot be cut with 
 a knife ; as also by its pale color ; from marcasite by its specific gravity and 
 malleable like gold . , , 
 
 Obs. Pyrite occurs abundantly in rocks of all ages, from the oldest crystalline rocks to the 
 
244 
 
 DESCRIPTIVE MUSTERA^OGT. 
 
 most recent alluvial deposits. It usually occurs in small cubes, also in irregular spheroidal 
 nodules and in veins, in clay slate, argillaceous sandstones, the coal formation, etc. The 
 Cornwall mines, Alston-Moor, Derbyshire, Fahlun in Sweden, Kongsberg in Norway, Elba, 
 Traversella in Piedmont, Peru, are well-known localities. 
 
 Occurs in New England at many places : as the Vernon slate quarries ; Roxbury, Conn. , etc. 
 In N. York^ at Rossie, at Schoharie ; iu Orange Co. , at Warwick and Deerpark, and many 
 otherplaces. In Pennsylvania, at Little Britain, Lancaster Co. ; at Chester, Delaware Co."; 
 in Carbon, York, and Chester Cos. ; at Cornwall, Lebanon Co., etc. In Wisconsin, near 
 Mineral Point. In N. Car., near Greensboro', Guilford Co. Auriferous pyrite is common at 
 the mines of Colorado, and many of those of California, as well as in Virginia and the States 
 south. 
 
 This species affords a considerable part of the iron sulphate and sulphuric acid of commerce 
 and also much of the sulphur and alum. The auriferous variety is worked for gold in many 
 gold regions. 
 
 The name #yn'te is derived from TrOp, fire, and alludes to the sparks from friction. 
 
 HAUERITE. Composition MnS 2 = Sulphur 53-7, manganese 46 '3 =100. Isometric. Color 
 reddish-brown. Kalinka, Hungary. 
 
 CHALOOPYRITE,* Copper Pyrites. Kupferkies, Genn. 
 
 Tetragonal ; tetrahedral. A I-i = 135 25'; c = 0-98556 ; O A 1 =' 125 
 40' ; 1 A 1, pyr., = 109 53' ; 1 A 1 (f. 440) = 71* 20' and 70 7'. Cleav- 
 age : %-i sometimes distinct ; 0, indistinct. Twins : twinning-plane I-i ; 
 the plane 1 (see p. 94). Often massive. 
 
 440 
 
 H.=3'5-4. G. 4*l-4'3. Lustre metallic. Color brass-yellow ; subject 
 to tarnish, and often iridescent. Streak greenish-black a little shining. 
 Opaque. Fracture conchoidal, uneven. 
 
 Comp.CuFeS 2 = Sulphur 34-9, copper 34 '6, iron 30'5=100. Some analyses give other 
 proportions ; bub probably from mixture with pyrite. There are indefinite mixtures of the 
 two, and with the increase of the latter the color becomes paler. 
 
 This species, although tetragonal, is very closely isomorphous with pyrite, the variation 
 from the cubic form being slight, the vertical axis being '98556 instead of 1. 
 
 Traces of selenium have been noticed by Kersten in an ore from Reinsberg near Freiberg. 
 Thallium is also present in some kinds, and more frequently in this ore than in pyrite. 
 
 Pyr., etc. In the closed tube decrepitates, and gives a sulphur sublimate ; in the open 
 tube sulphurous oxide. B.B. on charcoal gives sulphur fumes and fuses to a magnetic glo 
 bule. The roasted ore reacts for copper and iron with the fluxes ; with soda on charcoal 
 gives a globule of metallic iron with copper. Dissolves in nitric acid, excepting the sulphur, 
 and forms a green solution ; ammonia in excess changes the green color to a deep blue. 
 
 Diff, Distinguished from pyrite by its inferior hardness, it can be easily scratched with 
 the knife ; and by its deeper color. Not malleable like gold, from which it differs also in 
 being decomposed by nitric acid. 
 
SULPHIDES, TELLUKIDES, SELENIDESj ETC. 245 
 
 Obs. Cbalcopyrite is the principal ore of copper at the Cornwall mines. Occurs at Frei- 
 berg ; in the Bannat ; Hungary ; and Thuringia ; in Scotland ; in Tuscany ; in South Australia ; 
 in fine crystals at Cerro Blanco, Chili. 
 
 A common mineral in America, some localities are : Stafford, Vt. ; Rossie, Ellenville, N. Y. ; 
 Pheuixville, etc., Penn. The mines in North Carolina and eastern Tennessee afford large 
 quantities. Occurs in Gal. , in different mines along a belt between Mariposa Co. and Del NorU 
 Co., on west side of, and parallel to, the chief gold belt ; occurring massive in Calaveras Co.; 
 in Mariposa Co., etc. In Canada, in Perth and near Sherbrooke; extensively mined at 
 Bruce mines, on Lake Huron. 
 
 Named from %aA/cos, brass, and pyrites, by Henckel, who observes in his Pyritology (1725) 
 that chalcopyrite is a good distinctive name for the ore. 
 
 CUBANITE is CuFe a S 4 , or CuFe 2 S 3 (Scheidhauer). Occurs massive at Barracanao, Cuba; 
 Tunaberg, Sweden. 
 
 BARKHARDTITE, from North Carolina. Composition uncertain, perhaps Cu 4 Fe 2 S 6 . It may 
 be partly altered from chalcopyrite. 
 
 STANNITE (Zinnkies, Germ.}. A sulphide containing 26 p. c. tin; also copper, iron, and 
 zinc. Massive. Color steel-gray. Chiefly from Cornwall, also Zmnwald. 
 
 UNNJEITE. Kobaltnickelkies, Germ. 
 
 Isometric. Cleavage : cubic, imperfect* Twins : twinning-plane octa- 
 hedral. Also massive, granular to compact. 
 
 U.=:5'5. G.=4*8-5. Lustre metallic. Color pale steel-gray, tarnishing 
 copper-red. Streak blackish-gray. Fracture uneven or subconchoidal. 
 
 Comp, Co 3 S 4 (or 2CoS+CoS 2 )= Sulphur 42'0, cobalt 58-0=100; but having the cobalt 
 replaced partly by nickel or copper, the proportions varying very much. The Miisen ore 
 (siegenite) contains 30-40 p. c. of nickel. 
 
 Pyr., etc. The variety from Miisen gives, in the closed tube, a sulphur sublimate ; in the 
 open tube, sulphurous fumes, with a faint sublimate of arsenous oxide. B.B. on charcoal 
 gives arsenical and sulphurous odors, and fuses to a magnetic globule. The roasted mineral 
 gives with the fluxes reactions for nickel, cobalt, and iron. Soluble in nitric acid, with separa- 
 tion of sulphur. 
 
 Diff. Distinguished by its color, and isometric crystallization. 
 
 Obs, In gneiss, at Bastnaes, Sweden ; at Miisen, near Siegen, in Prussia ; at Siegen 
 (siegenite), in octahedrons ; at Mine la Motte, in Missouri, mostly massive, also crystalline , 
 and at Mineral Hill, in Maryland. 
 
 SMALTITE.* Speiskobalt, Germ. 
 
 Isometric. Cleavage : octahedral, distinct ; cubic, in traces. Also mas- 
 sive and in reticulated and other imitative shapes. 
 
 H. 5-5-6. G.=6'4: to 7*2. Lustre metallic. Color tin-white, inclining, 
 when massive, to steel-gray, sometimes iridescent, or grayish from tarnish. 
 Streak grayish-black. Fracture granular and uneven. Brittle. 
 
 Comp., Var. For typical kind (Co,Fe,Ni)As 2 =: (if Co, Fe, and Ni be present in equal 
 parts) Arsenic 72 '1, cobalt 94, nickel 9 '5, iron 9 -0=1 00. It is probable that nickel is never 
 wholly absent, although not detected in some of the earlier analyses ; and in some kinds it is 
 the principal metal. The proportions of cobalt, nickel, and iron vary much. 
 
 The following analyses will serve as examples of the different varieties : 
 
 As Co Ni Fe Cu 
 
 1. Schneeberg 70'37 13'95 1'79 11-71 1'39 S 0'66, BiO-01=99'8S Hofmana 
 
 2. Allemont (chloanthite) 7 I'll 18 '71 6-82 S 2 '29 =98 "93 Raminelsberg. 
 
 8. Kiechelsdorf 6042 10 "80 25'87 0'80 S 2-11 = 100. 
 
 4. Schneeberg 74 '80 879 12 '86 7 "33 S 0-85 =99 '63 Karstedt. 
 
246 DESCRIPTIVE MINERALOGY. 
 
 Pyr., etc. In the close tube gives a sublimate of metallic arsenic ; in the open tube a 
 white sublimate of arsenous oxide, and sometimes traces of sulphurous oxide. B.B. on char- 
 coal gives an arsenical odor, and fuses to a globule, which, treated with successive portions 
 of borax-glass, affords reactions for iron, cobalt, and nickel. 
 
 Obs. Usually occurs in veins, accompanying ores of cobalt or nickel, and ores of silvei 
 and copper ; also, in some instances, with niccolite and arsenopyrite ; often having a coating 
 of annabergite. 
 
 Occurs at Schneeberg, etc., in Saxony ; at Joachimsthal ; also at Wheal Sparnon in Corn- 
 wall ; at Riechelsdorf in Hesse ; at Tunaberg in Sweden ; Allemont in Dauphine. Als& in 
 crystals at Mine La Motte, Missouri. At Chatham, Conn. , the chloanthite (chathamite) occura 
 in mica slate, associated generally with arsenopyrite and sometimes with niccolite. 
 
 SPATHIOPYRITJS is closely allied to smaltite, with which it occurs at Bieber in Hessen. 
 
 SKUTTERUDITE (Tesseralkies, (?mw.). CoAs 3 =Arsenic79-2, cobalt 20'8=100. Isometric. 
 Skutterud, Norway. 
 
 COBALTITE. Glance Cobalt. Kobaltglanz, Germ. 
 
 Isometric ; pyritohedral. Commonly in pyritohedrons (f. 92, 95, etc., 
 p. 23). Cleavage : cubic, perfect. Planes striated. Also massive, 
 granular or compact. 
 
 Ii. = 5-5. G.= 6-6-3. Lustre metallic. Color silver- white, inclined to 
 red ; also steel-gray, with a violet tinge, or grayish-black when containing 
 much iron. Streak grayish-black. Fracture uneven and lamellar. Brittle. 
 
 Comp., Var. CoAsS (or CoS a +CoAs-.)= Sulphur 19 '3, arsenic 45 '2, cobalt 35'5=100. The 
 cobalt is sometimes largely replaced by iron, and sparingly by copper. 
 
 Pyr., etc. Unaltered in the closed tube. In the open tube, gives sulphurous fumes and 
 a crystalline sublimate of arsenous oxide. B.B. on charcoal gives off sulphur and arsenic, 
 and fuses to a magnetic globule ;' with borax a cobalt-blue color. Soluble in warm nitric acid, 
 separating arsenous oxide and sulphur. 
 
 Diflf. Distinguished by its reddish-white color ; also by its pyritohedral form. 
 
 Ob 1 ?. Occurs at Tunaberg. Hokansbo, in Sweden ; also at Skutterud in Norway. Other 
 localities are at Querbach in Silesia, Siegen in Westphalia, and Botallack mine, in Cornwall. 
 The most productive mines are those of Vena in Sweden. 
 
 This species and smaltite afford the greater part of the smalt of commerce. It is also 
 employed in porcelain painting. 
 
 GERSDORFFITE. Nickelarsenikkies, Arseniknickelglanz, Germ. 
 
 Isometric ; pyritohedral. Cleavage : cubic, rather perfect. Also lamel- 
 lar and granular massive. 
 
 H.=5-5. G. 5.6-6-9. Lustre metallic. Color silver-white steel- 
 gray, often tarnished gray or grayish-black. Streak grayish-black. Frac- 
 ture uneven. 
 
 Comp., Var. Normal, NiAsS (or NiS 2 +NiAs 2 )- Arsenic 45 '5, sulphur 19 '4, nickel 35 -1 = 
 100. The composition varies in atomic proportions rather widely. 
 
 Pyr., etc. In the closed tube decrepitates, and gives a yellowish-brown sublimate of 
 arsenic sulphide. Jn the open tube yields sulphurous fumes, and a white sublimate of arsen- 
 ous oxide. B.B. on charcoal gives sulphurous and garlic odors and fuses to a globule, which, 
 with borax-glass, gives at first an iron reaction, and, by treatment with fresh portions of tho 
 flux, cobalt and nickel are successively oxidized. 
 
 Decomposed by nitric acid, forming a green solution, with separation of sulphur and arsen- 
 ous oxide. 
 
 Obs. Occurs at Loos in Sweden ; in the Harz ; at Schladming in Styria; Kamsdorf in 
 Lower Thuringia ; Haueisen, Voigbland ; near Ems. Also found as an incrustation at 
 Phenixville, Pa. 
 
SULPHIDES, TELLTTKIDE8, SELENIDES, ETC. 247 
 
 ULLMANNITE. NiSbS (NiS 2 +NiSb 2 )= Antimony 57'2, sulphur 15 '1, nickel 27 '7=100. 
 Generally contains also some arsenic. Color steel-gray. Siegen, Harzgerode, etc. 
 
 COKYNITE. M(As,Sb)S, but the arsenic (38 p. c. ) in excess of the antimony. Olsa, Corin- 
 thia. WOLFACIIITE (Petersen), from Wolfach, Baden, is similar in composition, bub is 
 orthorhombic in form. 
 
 LAURITE. An osmium-ruthenium sulphide. Analysis (Wohler) Sulphur 31 '79 [Osmium 
 3-03], Ruthenium 05. 18=100. Occurs in minute octahedrons from the platinum - washfc iga 
 of Borneo ; as also those in Oregon. 
 
 Marcasite Group. Orthorhombic. 
 
 MAROASITE. White Iron Pyrites. Strahlkies, etc., Germ. 
 
 Orthorhombic. /A 1= 106 5', A 14 = 122 26', Miller ; I : I : & = 
 1-5737 : 1-3287 : 1. A 1 = 116 55' ; O A l-i 
 = 130 10'. Cleavage: /rather perfect; \4 
 in traces. Twins : t winning-plane 7, sometimes 
 consisting of five individuals (see f. 308, p. 98) ; 
 also l-l. Also globular, reniform, and other 
 imitative shapes structure straight columnar ; 
 often massive, columnar, or granular. 
 
 II. 6-65. G.= 4-678-4- 847. Lustre metallic. Color pale bronze-yel- 
 low, sometimes inclined to green or gray. Streak grayish- or brownish- 
 black. Fracture uneven. Brittle. 
 
 Comp,, Var. FeS 2 , like py rite = Sulphur 53 "3, iron 46-7=100. 
 
 The varieties that have been recognized depend mainly on state of crystallization ; as the 
 Radiated (Strahlkies) : Radiated ; also the simple crystals. Cockscomb (Kammkiex} : Aggre- 
 gations of flattened crystals into crest-like forms. Spear (Speerkies) : Twin crystals, with 
 reentering angles a little like the head of a spear in form. Capillary (Ilaarkies) : In capil- 
 lary crystallizations, etc. 
 
 Fyr. Like pyribe. Very liable to decomposition ; more so than pyrite. 
 
 Diff. Distinguished from pyrite by its paler color, especially marked on a fresh surface ; 
 
 by its tendency to tarnish ; by its inferior specific gravity. 
 
 ' Qbs. Occurs near Carlsbad in Bohemia ; at Joachimsthal, and in several parts of Saxony ; 
 
 in Derbyshire ; near Alston Moor in Cumberland ; near Tavistock in Devonshire, and iu 
 Cornwall. 
 
 At Warwick, N. Y. Massive fibrous varieties abound throughout the mica slate of New 
 England particularly at Cummington, Mass. Occurs at Lane's mire, in Monroe, Conn. ; in 
 Trumbull ; at East Haddam ; at Haverhill, N. H. ; Galena, 111., in stalactites. In Canada in 
 
 Marcasite is employed in the manufacture of sulphur, sulphuric acid, and iron sulphate, 
 though less frequently than pyrite. 
 
 ARSENOPYRITB, or MISPICKEL. Arsenical Pyrites. Arsenikkies, Germ. 
 
 Orthorhombic. 1 A 1= 111 53', O A 14 = 119 37' ; c : I : & = 1'7588 : 
 1-4793:1. 6>Al = 115 12', O A l- = 130 4'. Cleavage: 7 rather 
 distinct ; O, faint traces. Twins : twinning-plane /, and 1 4. Also colum- 
 nar, straight and divergent ; granular, or compact. 
 
 H.= 5-5-6. G. 6-6-6-4; 6'269, Franconia, Kenngott. Lustre metallic. 
 
248 
 
 DESCRIPTIVE MINERALOGY. 
 
 Color silver- white, inclining to steel-gray. Streak dark grayish-black. Frac 
 ture uneven. Brittle. 
 
 443 
 
 444 
 
 445 
 
 Franconia, N. H. Franconia, N. H., and Kent, N. Y. 
 
 Danaite. 
 
 Comp., Var. FeAsS =FeS 3 +FeAs 2 = Arsenic 46 K), sulphur 19-6, iron 34 '4=100. Part o 
 the iron sometimes replaced by cobalt ; a little nickel, bismuth, or silver are also occasionally 
 present. The cobaltic variety, called danaite (after J. Freeman Dana), contains 4-10 p. c. of 
 cobalt. 
 
 Pyr., etc. In the closed tube at first gives a red sublimate of arsenic sulphide, then a 
 black lustrous sublimate of metallic arsenic. In the open tube gives sulphurous fumes and a 
 white sublimate of arsenous oxide. B.B. on charcoal gives the odor of arsenic. The varieties 
 containing- cobalt give a blue color with borax-glass when fused in O.F. with successive por- 
 tions of flux until all the iron is oxidized. Gives fire with steel, emitting an alliaceous odor. 
 Decomposed by nitric acid with separation of arsenous oxide and sulphur. 
 
 Diff. Distinguished by its form from smaltite. Leucopyrite (lollingite) do not give 
 decided sulphur reactions. 
 
 Obs. Found principally in crystalline rocks, and its usual mineral associates are ores of 
 silver, lead, and tin ; pyrite, chalcopyrite, and spalerite. Occurs also in serpentine. 
 
 Abundant at Freiberg ; at Reichenstein in Silesia ; at Schladming ; Andreasberg ; Joachims- 
 thai ; at Tunaberg in Sweden ; at Skutterud in Norway ; in Cornwall ; in Devonshire at the 
 Tarnar mines. 
 
 In New Hampshire, in gneiss, at Franconia (danaite) ; also at Jackson and at Haverhill. 
 In Maine, at Blue Hill, Corinna, etc. In Vermont, at Brookfield, Waterbury, and Stockbridge. 
 In Mass., at Worcester and Sterling. In Conn., at Monroe, at Mine Hill, Roxbury. In New 
 Jersey, at Franklin. In N.Tork, massive, in Lewis, Essex Co., near Edenville, and else- 
 where in Orange Co. ; in Carmel ; in Kent, Putnam Co. In California, Nevada Co., Grass 
 valley. In S. America, in Bolivia ; also, niccoliferous var., between La Pas and Yungas in 
 Bolivia (anaL by Kroeber). 
 
 LOLLINGITE is FeAs 2 (^Arsenic 72'8, iron 27 -2), and LEUCOPYBITE is Fe 2 As 3 (^Arsenic 
 66'S, iron 33 -2). They are both like arsenopyrite in form. Found, the former at Lolling ; 
 Schladming ; Satersberg, near Fossum, Norway ; the latter at Reichenstein ; Geyer (geyerite) 
 near Hiittenberg, Carinthia. 
 
 GLAUCODOT (Co,Fe)S 2 -f-(Co,Fe)As 2 , with Co : Fe=2 : 1 = Sulphur 19 '4, arsenic 45 -5, cobalt 
 23 '8, iron 11-3=100. Form like arsenopyrite. Huasco, Chili; Hakansbo, Sweden. 
 
 ALLOCLABITE R 4 (As,Bi) 7 S6, with R=Bi,Co,Ni,Fe,Zn. Orawicza, Hungary. 
 
 SYLVANITB. Graphic Tellurium. Schrifterz, Schrift-Tellur, Germ. 
 
 Moiioclinic. C = 55 21 J', /A 1= 94 26', O A 14 = 121 21' ; c : b : 
 d = 1-7732 : 0-889 : 1, Kokscharof. Cleavage : *4 distinct. Also massive ; 
 imperfectly columnar to granular. 
 
 H.=l'5-2. Gr. 7-99-S-33. Lustre metallic. Streak and color pure steel- 
 gray to silver-white, and sometimes nearty brass-yellow. Fracture uneven, 
 
 Comp., Var. (Ag,Au)Te 2 = (if Ag : Au=l : 1) Tellurium 55 -8, gold 28-5, silver 15 ?= 100. 
 Antimony sometimes replaces part of the tellurium, and lead part of the other metals. 
 
8ULPHABSENITES, SULPHANT1MONITES, ETC. 249 
 
 Pyr., etc. In the open tube gives a white sublimate which near the assay is gray ; when 
 treated with the blowpipe flame the sublimate fuses to clear transparent drops. B.B. on 
 charcoal fuses to a dark gray globule, covering the coal with a white coating, which treated 
 in R.F. disappears, giving a bluish-green color to the flame; after long blowing a yellow, 
 malleable metallic globule is obtained. Most varieties give a faint coating of the oxides oi 
 lead and antimony on charcoal. 
 
 Obs. Occurs at Offenbanya and Nagyag in Transylvania. In California, Calaveras Co., at 
 the Melones and Stanislaus mines ; Bed Cloud mine, Colorado. 
 
 Named from Transylvania, the country in which it occurs, and in allusion to syhaiiium, one 
 of the names at first proposed for the metal tellurium. Called graphic because of a resem- 
 blance in the arrangement of the crystals to writing characters. 
 
 Schrauf has stated that, according to his measurements, sylvanite is orthorhombic. 
 
 CALAVERITE (Genth.) has the composition AuTe 4 = Tellurium 55'5, gold 44-5=100. M-aa- 
 Bive. Color bronze-yellow. Stanislaus mine, Cal. ; Red Cloud mine, Colorado. 
 
 NAGYAGITE.* Blattererz, Blattertellur, Germ. 
 
 Tetragonal. A l-i = 127 37' ; o = 1-298. A 1 = 118 37'. Cleav- 
 age: basal. Also granularly massive, particles of 
 various sizes ; generally foliated. 
 
 H.=1-1'5. G.= 6-85-7-2. Lustre metallic, splen- 
 dent. Streak and color blackish lead-gray. Opaque. 
 Sectile. Flexible in thin laminae. 
 
 Comp. Uncertain, perhaps B(S,Te) 9 , withR=Pb,Au (Ramm.). Analysis, Schonlein, Te 
 30-52, S 8-07, Pb 50'78, Au 9'11, Ag 0'53, Cu 0-99=100. 
 
 Pyr., etc. In the open tube gives, near the assay, a grayish sublimate of antimonate and 
 tellurate, with perhaps some sulphate of lead ; farther up the tube the sublimate consists of 
 antirnonous oxide, which volatilizes when treated with the flame, and tellurous oxide, which 
 at a high temperature fuses into colorless drops. B.B. on charcoal forms two coatings : one 
 white and volatile, consisting of a mixture of antimonite, tellurite, and sulphate of lead ; and 
 the other yellow, less volatile, of oxide of lead quite near the assay. If the mineral is treated 
 for some time in 0. F. a malleable globule of gold remains ; this cupelled with a little assay 
 lead assumes a pure gold color. Decomposed by nitro-hydrochloric acid. 
 
 Obs. At Nagyag and Offenbanya in Transylvania, in foliated masses and crystalline plates. 
 
 COVELLITE (Kupferindig, Germ.). Composition CuS= Sulphur 33 -5, copper 66'5=100. 
 Hexagonal Commonly massive. Color indigo-blue. Mansfeld, etc. ; Vesuvius, on lava ; 
 
 MELONITE (Genth.). A nickel telluride, formula probably Ni 2 Te 3 tellurium 76 '5, nickel 
 23-5=100. Hexagonal. Cleavage basal eminent. Color reddish- white. Streak dark-gray. 
 Occurs mixed with other tellurium minerals at the Stanislaus mine, Cal. 
 
 3. TERNAKY COMPOUNDS. SULPHAKSENITES, SULPHANTIMONITES, 
 
 SULPHOBISMUTHITES.* 
 
 (a) GROUP I. Formula R(As,Sb) 2 S 4 =ES + (As,Sb) 2 S 8 . 
 MIARGYRITB. 
 
 Monoclinic. O= 48 14'; /A 7= 106 31', O A 14 = 136 8' ; c : I : d 
 = 1-2883 : 0-9991 : 1, iSTaumann. Crystals thick tabular, or stout, or short 
 prismatic, pyramidal. Lateral planes deeply striated.. Cleavage : f-t-, 1-a 
 imperfect. 
 
 * The species of this group contain as bases chiefly copper, lead, and silver. They can bo 
 most readily distinguished by their behavior before the blowpipe. Attention may be calle 
 to the group of lead sulphantimonites, zinkentte, plagionite, (jamesonite) boulangente mene- 
 'lUnite, geocronite, for which the prognostics are nearly similar, and which are mosl 
 ***tinguished by their specific gravity. 
 
250 DESCRIPTIVE MINERALOGY. 
 
 H.=: 2-2*5. G.=5*2-5*4r. Lustre submetallic-adamantine. Color iron 
 black. Streak dark cherry-red. Opaque, except in thin splinters, which, 
 by transmitted light, are deep blood-red. Fracture subconchoidal. 
 
 Comp. AgSbS 2 (orAg 2 S + Sb 2 S 3 )=:Sulphur 21 '8, antimony 41 -5, silver 36 '7=100. 
 
 Pyr., etc. In the closed tube decrepitates, fuses easily, and gives a sublimate of antimony 
 sulphide ; in the open tube sulphurous and antimonoue fumes, the latter as a white sublimate*. 
 B.B. on charcoal fuses quietly, with emission of sulphur and antimony fumes, to a gray bead, 
 which after continued treatment in O.F. leaves a bright globule of silver. If the silver globule 
 be treated with phosphorus salt in O.F., the green glass thus obtained shows traces of coppei 
 when fused with tin in B. F. 
 
 Decomposed by nitric acid, with separation of sulphur and antimonous oxide. 
 
 Obs. At Braiinsdorf , near Freiberg in Saxony ; Felsobanya (kenngottite) ; Przibram in 
 Bohemia ; Clausthal (hy par gy rite) ; Guadalajara in Spain ; at Parenos, and the mine Sta. M. 
 de Catorce, near Potosi ; also at Molinares, Mexico. 
 
 SARTORITB. SCLEKOCLASE. 
 
 Orthorhombic. 7 A 1= 123 21', O A 14 = 131 3' ; c : I : a = 1-1483 : 
 
 1'8553 : 1. Crystals slender. Cleavage : 
 447 quite distinct. 
 
 H.=3. G.=5-393. Lustre metallic. 
 Color dark lead-gray. Streak reddish- 
 brown. Opaque. Brittle. 
 
 Comp. PbAs. 2 S 4 (PbS+AR 2 S 3 )=Sulphur 26 '4, 
 arsenic 30 '9, lead 42-7=100. 
 
 Fyr,, etc. Nearly the same as for dufrenoy- 
 site (q. v.), but differing in strong decrepitation. 
 Obs. From the Binnen valley with dufrenoy- 
 site and binnite. As the name Scleroclase is 
 inapplicable, and the mineral was first an- 
 nounced by Sartorius v. Waltershausen, the species may be appropriately called Sartorite. 
 It is the binnite of Heusser. 
 
 ZINKENITE. 
 
 Orthorhombic. If\ 1= 120 39', Rose. Usual in twins, as hexagonal 
 prisms, with a low hexagonal pyramid at summit. Lateral faces longitudi- 
 nally striated. Sometimes columnar, fibrous, or massive. Cleavage not 
 distinct. 
 
 H.= 3-3-5. G. = 5-30-5-35. Lustre metallic. Color and streak steel- 
 gray. Opaque. Fracture slightly uneven. 
 
 Comp. PbSb 2 S 4 (or PbS + SboS 3 ) = Sulphur 22'1, antimony 42'2, lead 35 '7=100. 
 
 Pyr., etc. Decrepitates and fuses very easily ; in the closed tube gives a faint sublimate 
 of sulphur and antimonous sulphide ; in the open tube sulphurous fumes and a white subli- 
 mate of oxide of antimony. B. B. on charcoal is almost entirely volatilized, giving a coating 
 which on the outer edge is white, and near the assay dark-yellow ; with soda in R. F. yields 
 globules of lead. 
 
 Soluble in hot hydrochloric acid with evolution of sulphuretted hydrogen and separation of 
 lead chloride on cooling. 
 
 Resembles stibnite and bournonite, but may be distinguished by its superior hardness and 
 specific gravity. 
 
 Obs. Occurs at Wolfsberg in the Harz. 
 
 CHALCOSTIBITE (Kupferantimonglanz, Germ.). Composition CuSbS 2 (or Cu 2 S f SboS s ) 
 Sulphur 25 '7, antimony 48 '9, copper 25 -4 Color lead -gray to iron-gray. Wolfsberg in the 
 Harz. 
 
 EMPLECTITE (Kupferwismuthglanz, Germ.). Composition CuBiS 2 (or Cu,S+Bi 2 S 3 )=Sul- 
 phur 19*1, bismuth 62*0, copper 18'9=100. Color grayish to tin-white. Schwarzenberg, 
 S-txony; Copiapo, Chili. 
 
SULPHARSENITES, SULPHANTIMONITES, ETC. 251 
 
 BERTHIERITE. Composition approximately FeSb 2 S 4 (orFeS4-Sb 2 S 3 )=Sulr;hur30-0, anti- 
 mony 57 '0, iron 13-0=100. Color dark steel-gray. Auvergne ; Braunsdorf, Saxony; Corn- 
 
 wall, etc. ; San Antonio, Cal. 
 
 (b) SUB-GBOUP. Formula K 3 ( As,Sb,Bi) 4 S 9 = 3RS + 2(As,Sb,Bi) 2 S 3 . 
 
 PLAGIONITE. Composition (Rose) Pb 4 Sb 6 S 13 (or 4PbS + 3Sb 2 S 3 )= Sulphur 21;1, antimony 
 37'0, lead 41 '9. Monoclinic. Gr. =5 '4. Found at Wolfsberg in the Harz. 
 
 JORDANITE (v. Rath). Composition Pb 3 As 4 S9 (or 3PbS+2As 2 S 3 ) = Sulphur 23-8, arsenic 
 24 - 8, lead 51 '4. Orthorhombic. Resembles sartorite, but distinguished by its black streak, 
 its six-sided twins, and by not decrepitating B.B. Binnenthal, Switzerland. 
 
 BINNITE. Composition probably Cu 6 As 4 S 9 (or 3Cu 2 S+2As 2 S 3 ) = Sulphur 29*7, arsenic 31 '0, 
 copper 39 '3 = 100. Isometric. Streak cherry -red. Binnenthal in dolomite (dufrenoysite of 
 v. Walter shausen). 
 
 KLAPJIOTHOLITE (Petersen). Composition Cu 6 Bi 4 Sb 9 (or 3Cu 2 S-f-2Bi 2 S 3 ). Orthorhombic. 
 Cleavage i-l distinct. Color steel-gray. G.=4'6. Wittichen, Baden. 
 
 ScmitMEiUTE (Gentfi). Composition R 3 Bi 4 S 9 (or 3RS + 2Bi 2 S 3 ), with R=Ag 2 : Pb 2 : 1. 
 This requires sulphur 1(>'4, bismuth 47'3, silver 24 '5, lead 11 '8=100. Massive, disseminated 
 in quartz. Color lead-gray. Red Cloud mine, Colorado. 
 
 (G) GKOUP II. Formula 
 
 JAMESONITE. Federerz, Germ. 
 
 Orthorhombic. /A 1= 101 20' and 78 40'. Cleavage basal, highly 
 perfect; /and i-l less perfect. Usually in acicnlar crystals. Also fibrous 
 massive, parallel or divergent ; also in capillary forms ; also amorphous 
 massive. 
 
 H.=:2-3. G.=5'5-5-8. Color steel-gray to dark lead-gray. Streak 
 gray. 
 
 Comp. Pb 2 Sb 2 S 5 (or 2PbS + Sb 2 S 3 ) ; more strictly 2PbS=2 (or Pb,Fe)S. If Fe : Pb=l : 
 4, Sulphur 21-1, antimony 32 '2, lead 43 '7, iron 3'0=100. Small quantities of zinc, bis- 
 muth, silver, and copper are also sometimes present. 
 
 Fyr. Same as for zinkenite. 
 
 Diff. Distinguished from other related species by its perfect basal cleavage. 
 
 Obs. Jamesonite occurs principally in Cornwall, in Siberia, Hungary, at Valentia, d' Alcan- 
 tara in Spain, and Brazil. 
 
 The feather ore occurs at Wolfsberg in the Eastern Harz ; also at Andreasberg and Glaus- 
 thai ; at Freiberg and Schemnitz ; at Pf affenberg and Meiseberg ; in Tuscany, near Bottino ; 
 at Chonta in Peru. 
 
 DUFRBNOYSITB. 
 
 Orthorhombic. 7 A 7= 93 39', A 14 = 121 30', c : I : & = 1-6318 : 
 1*0658 : 1. Usual in thick rectan- 
 gular tables. Cleavage: perfect. 
 Also massive. 
 
 H.=:3. G.=5-549-5-569. Lustre 
 metallic. Color blackish lead-gray. 
 Streak reddish-brown. Opaque. Brit- 
 tle. 
 
 Comp. Pb 2 As 2 S 5 (or 2PbS+2As 3 S,)=Sul- 
 phur 22-10, arsenic 20'72, lead 57-18=100. 
 
 Fyr., etc. Easily fuses and gives a subli- 
 mate of sulphur and arsenous sulphide ; in 
 the open tube a smell of sulphur only, with a sublimate of sulphur in upper part ot tube, and 
 
252 
 
 DESCRIPTIVE MINERALOGY. 
 
 of arsenous oxide below. On charcoal decrepitates, melts, yields fumes of arsenic and 8 
 globule of lead, which on cupellation yields silver. 
 
 Obs From the Binnenthal in the Alps, in crystalline dolomite, along with sartorite, Jordan- 
 
 ite, binnite, etc. 
 
 Damour, who first studied the arsenic-sulphides of the Binnenthal, analyzed the massive 
 ore and named it dufrenoysite. He inferred that the crystallization was isometric from some 
 associated crystals, and so published it. This led von Waltershausen and Heusser to call the 
 isometric mineral dufrenoysite, and the latter to na.ne the orthorhombic species binnite. "Von 
 Waltershausen, after studying the prismatic mineral, made out of the species ameuomeUtn and 
 sclerodase, yet partly on hypothetical grounds. Recently it has been found that three ortho- 
 rhombic minerals exist at the locality, as announced by vom Rath, who identifies one, by speci- 
 fic gravity and composition, with Dam our' s dufrenoysite ; another he makes sclerodase of von 
 Waltershausen (sartorite, p. 250) ; and the other he names jorda-nite (p. 251). The isometric 
 mineral was called binnite by DesCloizeaux. 
 
 FREIESLEBENITE. Schilfglaserz, Germ. 
 
 Monoclinic. O = 87 46', /A 1= 119 12', A 14 = 137 10' (B. & M.) ; 
 cil:d = 1-5802 : 1-7032 : 1. A \4 = 123 55'. 
 449 Prisms longitudinally striated. Cleavage : / perfect. 
 
 H. = 2-2-5. G. = 6-6-4. Lustre metallic. Color and 
 streak light steel-gray, inclining to silver-white, also 
 blackish lead-gray. Yields easily to the knife, and is 
 rather brittle. Fracture subconchoidal uneven. 
 
 Comp Pb 2 AgsSb 3 S e , Ramm. (or 7RS+3Sb 2 S 3 , with7RS=4PbS 
 + 3 Ag 2 S) = Sulphur 18'8, antimony 20'9, lead 30'5, silver 23 -8 =100. 
 Pyr In the open tube gives sulphurous and antimonial fumes, 
 the latter condensing as a white sublimate. B. B. on charcoal fuses 
 easily, giving a coating on the outer edge white, from antimonous 
 oxide, and near the assay yellow, from oxide of lead ; continued 
 blowing leaves a globule of silver. 
 
 Obs. Occurs at Freiberg in Saxony and Kapnikin Transylvania; at 
 Ratieborzitz ; atPrzibram ; at Felsbbanya; at Hiendelencina in Spain. 
 According to v. Zepharovich, the mineral from Przibram and 
 
 Braunsdorf, and part of that from Freiberg, while identical in composition with freies- 
 lebenite, has an ortharhombic form. It is called by him DIAPHORITE. 
 
 BRONGNIARDITE. Composition Ag 2 PbSb 2 S 5 (or PbS-f-Ag 2 S+SbgS 3 )r=Sulphur 194, anti- 
 mony 29-5, silver 2(M, lead 25'0=100. Isometric ; in octahedrons, also massive. Color gray- 
 ish-black. Mexico. 
 
 COSALITE ( Genth). Composition Pb 2 Bi 2 S 5 (or 2PbS+Bi 2 S 3 )= Sulphur 16 -1, bismuth 42'2, 
 lead 41-7=100. Color lead-gray. Soft and brittle. Cosala, Sinaloa, Mexico. Identical 
 (Frenzel) with Hermann's retebanyite. 
 
 PYROSTILPNITE (Feuerblende, Germ.}. In delicate crystals; color hyacinth-red. Con- 
 tains 62 - 3 p. c. silver, also sulphur and antimony. Freiberg ; Andreasberg ; Przibram. 
 
 RITTINGERITE. In minute tabular crystals. Color black Streak orange-yellow. Con- 
 tains sulphur, antimony, and silver. JoachimsthaL 
 
 (d) GBOUP IIL Formula :Rj(As,Sb) 2 S 6 =: 3ES + (As,Sb) 2 S 3 . 
 
 PYRARGYRTTE. Ruby Silver. Dark Red Silver Ore. Dunkles RothgiUtigerz, Germ. 
 
 Rhombohedral. Opposite extremities of crystals often unlike. R A R 
 = 108 42' (B. & M.) ; Of^B = 137 42' ; c = 0'788. A I 3 = 112 33', 
 6>A1 7 = 100 U', Rl\\ = \ 21'. Cleavage: R rather imperfect. 
 
STJLPHARSENITES, SULPHANTIMONITES, ETC. 
 
 253 
 
 Twins: composition-face^; or basal plane, as in f. 290, p. 95; also 
 It and /. Also massive, structure 
 
 450 
 
 451 
 
 granular, sometimes impalpable. 
 ' Ii.=2-2-5. G.=5-7-5-9. Lustre 
 metallic-adamantine. Color black, 
 sometimes approaching cochineal-red. 
 Streak cochineal-red. Translucent 
 opaque. Fracture conchoidal. 
 
 Comp. Ag 3 SbS 3 (or 3Ag 2 S+Sb a S 3 )=Sul- 
 phur 17-7, antiiuony 22 '5, silver 59-8 = 100. 
 
 Pyr., etc. In the closed tube fuses and gives 
 a reddish sublimate of antimonous sulphide ; 
 in the open tube sulphurous fumes and a white sublimate of antimonous oxide. B.B. on 
 charcoal fuses with spirting to a globule, gives off antimonous sulphide, coats the coal white, 
 and the assay is converted into silver sulphide, which, treated in O.F., or with soda in B.F., 
 gives a globule of fine silver. In case arsenic is present it may be detected by fusing the 
 pulverized mineral with soda on charcoal in R.F. 
 
 Decomposed by nitric acid with separation of sulphur and antimonous oxide. 
 
 Obs. Occurs principally with calcite, native arsenic and galenite, at Andreasberg ; also in 
 
 Saxony, Hungary, Norway, at G-audalcanal in Spain, and in Cornwall. In Mexico abundant. 
 In Chili; in Nevada, at Wash oe in DaneyMine; abundant about Austin, Reese river; at 
 Poor Man lode, Idaho. 
 
 PROUSTITE. Light Red Silver Ore. Lichtes Rothgultigerz, Germ. 
 
 48', 
 
 9' c = 0-78506. 
 
 Khombohedral. 
 Also granular massive. 
 
 H. 2-2-5. G.= 5 -422-5-56. Lustre adamantine. Color cochineal-red. 
 Streak cochineal-red, sometimes inclined to aurora-red. Subtransparent- 
 subtranslncent. Fracture conchoidal uneven. 
 
 Comp.-Ag 3 AsS 3 (or 3Ag 2 S+As 2 S 3 ) = Sulphur 19-4, arsenic 15'1, silver 65 "5=100. 
 
 Pyr., etc. In the closed tube fuses easily, and gives a faint sublimate of arsenous sulphide ; 
 in the open tube sulphurous fumes and a white crystalline sublimate of arsenous oxide. B.B. 
 on charcoal fuses and emits odors of sulphur and arsenic; by prolonged heating in O.F., or 
 with seda in R.F., gives a globule of pure silver. Some varieties contain antimony. 
 
 Decomposed by nitric acid, with separation of sulphur and arsenous oxide. 
 
 Obs. Occurs at Freiberg and elsewhere in Saxony ; at Joachimsthal ; Wolfach m Baden ; 
 Chalanches in Dauphin^ ; Guadalcanal in Spain ; in Mexico : Peru ; Chili, at Chanarcillo, in 
 magnificent crystals. In Nevada, in the Daney mine, and in Comstock lode, but rare ; in 
 veins about Austin, Lander Co. ; in microscopic crystals in Cabarrus Co., N. C., at the 
 McMakin mine : in Idaho, at the Poor Man lode. 
 
 BOURNONITE. Radelerz, Germ.(= Wheel Ore). 
 
 Orthorhombic. I^ 1= 93 40', O A 14 = 136 IT (Miller) ; I I : & == 
 0-95618 : 1-0662 : 1. O A 1-5 = 133 26', O A 1 = 127 20', A 1-t = 13b 
 6'. Cleavao-e: i>l imperfect ; i4 and O less distinct. Twins: twinnmg- 
 plane face 1; crystals often cruciform (f. 453), crossing at angles of 93 
 40' and 86 20' ; hence, also, cog-wheel shaped. Also massive ; granular, 
 compact. 
 
254 
 
 DESCRIPTIVE MINERALOGY. 
 
 H.= 2-5-3. G.= 5-7-5-9. Lustre metallic. Color and streak steel-gray, 
 inclining to blackish lead-gray or iron-black. Opaque. Fracture con- 
 choidal or uneven. Brittle. 
 
 452 
 
 Oomp., Var. CuPbSbS 3 Ramm. (or 3RS+Sb 2 S 3 , with3RS=2PbS+Cu 2 S)=Suhphur 19 6, 
 antimony 25 0, lead 42-4, copper 13-0=100. 
 
 Pyr., etc. In the closed tube decrepitates, and gives a dark-red sublimate. In the open 
 tube gives sulphurous oxide, and a white sublimate of antimonous oxide. B.B. on charcoal 
 fuses easily, and at first coats the aoal white, from antimonous oxide ; continued blowing 
 gives a yellow coating of lead oxide; the residue, treated with soda in R.F., gives a globule 
 of copper. 
 
 Decomposed by nitric acid, affording a blue solution, and leaving a residue of sulphur, and 
 a white powder containing antim >ny and lead. 
 
 Obs. Occurs in the Harz ; at Kapnik in Transylvania; at Servoz in Piedmont; Brauns- 
 dorf and Gersdorf in Saxony, Olsa in Corinthia, etc. ; in Cornwall ; in Mexico ; at Huasco- 
 Alto in Chili ; at Machacamarca in Bolivia ; in Peru. 
 
 STYLOTYPITB. An iron-silver-copper bournonite ; Copiapo, Chili. 
 
 BOULANGERITE. 
 
 In plumose masses, exhibiting in the fracture a crystalline structure ; 
 also granular and compact. 
 
 H.= 2-5-3. G. 5.75-6-0. Lustre metallic. Color bluish lead-gray; 
 often covered with yellow spots from oxidation. 
 
 Comp. Pb 3 Sb 2 S 6 (or 3PbS+Sb 2 S 3 )=Sulphur 18'2, antimony 23'1, lead 587=100. 
 
 Pyr. Same as for zinkenite. 
 
 Obs Quite abundant at Molieres, department of Gard, in France ; also found at Nasaf jeld 
 in Lapland ; at Nertschinsk : Ober-Lahr in Sayn-Altenkirchen ; Wolfsberg in the Harz ; near 
 Bottino in Tuscany. 
 
 EPIBOULANGERITE. Probably a decomposition product of boulangerite (Websky) ; it con- 
 tains more sulphur and less antimony. Altenberg, Silesia. 
 
 WITTICHENITE. Composition Cu 3 BiS 3 (or 3Cu Q S + Bi 2 Ss)= Sulphur 19'4, bismuth 43.1, 
 copper 38-5 = 100. Color steel-gray. Wittichen, Baden. 
 
 KOBELLITE. Pb 3 BiSbS 6 (or 3PbS + (Bi,Sb) 2 S 3 ) Ramm. = Sulphur 16'8, antimony 10'7, bis- 
 muth 18 2, lead 54-3 = 100. Color lead-gray to steel-gray. Hvena, Sweden. 
 
 AIKINITE (NadUerz, Germ.). CuPbBiS 3 (or Cu 2 S+2PbS+Bi 2 S 3 )=Sulphur 167, bismuth 
 86-2, lead 30-0, cooper 111 = 100. In acicular crystals, also massive. Color blackish lead- 
 gray. Beresof, Urals ; Gold Hill, North Carolina. 
 
SULPHAKSENITES, SULPHANTIMONITES, ETC. 
 
 255 
 
 (e) GEOUP IT. Formula E 4 (As,Sb,Bi) 2 S 7 =4rRS + (As,Sb,Bi) 2 S 3 , 
 
 TETRAHEDRITE.* Gray Copper Ore. Fahlerz; Antimon- and Quecksilberfalilerz, Germ 
 
 Isometric ; tetrahedral. Twins : twinning-plane octahedral, producing, 
 when the composition is repeated, the form in f. 456. Also massive ; gran- 
 ular, coarse, or fine ; compact or crypto-crystalline. 
 
 454 
 
 456 
 
 Color between lisrht flint- 
 
 color ; sometimes 
 
 H.=3-4-5. G.=4-5-5-56. Lustre metallic. 
 gray and iron-black. Streak generally same as the 
 inclined to brown and cherry-red. Opaque ; sometimes subtranslucent in 
 very thin splinters, transmitted color cherry-red. Fracture subconchoidal 
 uneven. Rather brittle. 
 
 Comp., Var.-Cu 8 Sb 2 S 7 (or 4Cu 2 S+ Sb 2 S 3 ), with part of the copper (C^) often replaced by 
 iron (Fe) zinc (Zn), silver (Ag a ), or quicksilver (Hg), and rarely cobalt (Co and part of the 
 antimony by arsenic, and rarely bismuth. Katio Ag 2 +Cu 2 : Zn+Fe generally =2.1. . 
 are^thus: ^ arsenio-antimonial series; C. A bismuthic arsenio-anti. 
 
 mortal; besides an arsenical, in which arsenic replaces all the antimony, and which is made 
 into a distinct species named tennantite. 
 
 Var 1 Ordinary Containing little or no silver. Color steel-gray to dark-gray. 
 
 2. Argentiferous; Freibergite. Light steel-gray, sometimes iron-black. 
 
 3. Mercuriferous ; Schwatzite. Color gray to iron-black. 
 
 The following analyses will serve as examples of these varieties : 
 
 Ag 
 
 0'60 Ni Col-64=98 '59 Eammelsberg. 
 
 Zn 
 
 3 -50 
 
 3-89 10.48 Pb 0'78=:100-00 
 0-69 - Hg 17-27, Pb 0'21 Bi 0'81=100 
 v. Rath. 
 
 S Sb As Cu Fe 
 
 ID Miisen 25 '46 19 -15 4'93 39 -88 3 "43 
 
 (2) Meiseberg 24 '80 25 "56 30 '47 3 "52 
 
 (3) Kotterbach 22 "53 19 "34 2 -94 35 '34 0'S7 
 
 Pyr., etc. Differ in the different varieties. In the closed .. 
 red sublimate of antimonous sulphide ; when containing mercury, 
 appears at a low red heat ; and if much arsenic, a sublimate of arsenous 
 In the open tube fuses, gives sulphurous fumes and a white sublimate of - . 
 
 arsenic is present a crystalline volatile sublimate condenses with the antimo ny it the 
 ore contains mercury it condenses in the tube in minute metallic globules. B.B. 01 
 fuses gives a coating of antimonous oxide and sometimes arsenous acid 
 oxide; the arsenic may be detected by the odor when the coating is 
 zinc oxide assumes a green color when heated with cobalt solution 
 gives with the fluxes reactions for iron and copper; with soda yields 
 copper To determine the presence of a trace of arsenic by th< 
 
 fc f e 
 
 gives wiiiu. ijii UUACS icdvu^iio iv... rr f j . - ~A n - if io Vipsfr t,n fuse 
 
 copper. To determine the presence of a trace of arsenic by the ^*^J; * ' ^ 
 mineral on charcoal with soda. The presence of mercury is best ascertained by ti 
 
256 DESCRIPTIVE MINEKJLLOGY. 
 
 pulverized ore in a closed tube with about three times its weight of dry soda, the metal 
 subliming and condensing in minute globules. The silver is determined by cupellation. 
 
 Decomposed by nitric acid, with separation of sulphur, and antimonous and arsenous oxides, 
 
 Obs. The Cornish mines, near St. Aust. ; at Andreasberg and Clausthal in the Harz ; 
 Kremnitz in Hungary ; Freiberg in Saxony ; Przibram in Bohemia ; Kahl in Spessart ; Kap- 
 nik in Transylvania ; Dillenburg in Nassau ; and other localities. The ore containing mer- 
 cury occurs in Schmolnitz, Hungary ; at Schwatz in the Tyrol ; and in the valleys of Angina 
 and Costello in Tuscany. 
 
 Found in Mexico, at Durango, etc. ; at various mines in Chili ; in Bolivi* ; at the Kellogg 
 mines, Arkansas ; at Newburyport, Mass. In California in Mariposa Co. ; in Shasta Co. In 
 Nevada, abundant at the Sheba and De Soto mines, Humboldt Co. ; near Austin in Lander 
 Co. ; in Arizona at the Heintzelman mine, containing ! p. c. of silver ; at the Sana Rita mine. 
 
 EJONITE (Brauns). A bismuth tetrahedrite from Cremenz. Einfischthal, Switzerland. 
 
 MALINOWSKITE. A tetrahedrite containing 9-13 p. c. lead, and 10-13 p. c. silver. District 
 of Eocuay, Peru. (5th Append. Min. Chili.) 
 
 TENNANTITE.* Graukupfererz, Germ. 
 
 Isometric ; holohedral, Phillips. Cleavage : dodecahedral imperfect. 
 Twins as in tetrahedrite. Massive forms unknown. 
 
 H.:=3-5-4. G.= 4-37-4-53. Lustre metallic. Color blackish lead-gray 
 to iron-black. Streak dark reddish-gray. Fracture uneven. 
 
 Comp. Cu*As 2 S 7 (or 4Cn 2 S-4-A8 2 S 3 ), with Cu 2 replaced in part by Fe, Ag 2 , etc., as in tetra- 
 hedrite, with which it agrees in crystalline form. 
 
 Fyr. In the closed tube gives a sublimate of arsenous sulphide. In the open tube givea 
 sulphurous fumes, and a sublimate of arsenous oxide. B.B. on charcoal fuses with intumes- 
 cence and emission of arsenic and sulphur fumes to a dark-gray magnetic globule. The 
 roasted mineral gives reactions for copper and iron with the fluxes; with soda on charcoal 
 gives metallic copper with iron. 
 
 Obs. Found in the Cornish mines. Also at Skutterud in Norway, and in Algeria. 
 
 JULIANITE (Websky) is near tennantite. G.=5-12. Budelstadt, Silesia. 
 
 MENEGIIINITE has the composition Pb 4 Sb2S 1 (4PbS4-Sb 2 S3)= Sulphur 17 '3, antimony 16*8, 
 iead 63 '9 =100. Kesembles boulangerite, Bottino, Tuscany ; Schwarzenberg, Saxony. 
 
 (/) GROUP Y. Formula E 8 (As,Sb) 8 S 8 =5ES + (AB,Sb) 1 S 8 . 
 
 STEPHANITE. Sprodglaserz, Germ. 
 
 Orthorhombic. 1 A 1 = 115 39', O A I-l = 132 32f ' ; c : I : & = 1-0897 
 : 1-5844:1. O Al = 127 51', 0Al-S = 145 34. Cleav- 
 age: 2- and i-l imperfect. Twins: twinning-plane I ; 
 forms like those of aragonite frequent. Also massive, 
 compact, and disseminated. 
 
 H.= 2-2-5. G.=6-269, Przibram. Lustre metallic. 
 Color and streak iron-black. Fracture uneven. 
 
 Comp. Ag 5 SbS 4 (or 5 Ag 2 S+Sb 2 S,)=: Sulphur 16 '2, antimony 15'3, 
 silver 68 '5 =100. 
 
 Pyr. In the closed tube decrepitates, fuses, and after long heating 
 gives a faint sublimate of antimonous sulphide. In the open tube fuses, 
 giving off antimonial fumes and sulphurous oxide. B.B. on charcoal 
 fuses with projection of small particles, coats the coal with antimonous 
 oxide, which after long blowing is colored red from oxidized silver, and a globule of metallic 
 silver is obtained. 
 
 Soluble in dilute heated nitric acid, sulphur and oxide of antimony being deposited. 
 
BTJLPHAR8ENITES, 8TJLPHANTIMONITES, ETC. 257 
 
 Obs. At Freiberg and elsewhere in Saxony ; at Przibram in Bohemia ; in Hungary ; at 
 Indreasberg ; at Zacatecas in Mexico ; and in Peru. In Nevada, an abundant silver ore in 
 ihe Corastock lode ; at Ophir and Mexican mines in fine crystals ; in the Reese river and 
 EEumboldt and other regions. In Idaho, at the silver mines. 
 
 GEOCRONITE. Composition Pb 3 Sb.S 6 (or 5PbS-t-Sb 2 S 3 )= Sulphur 16*7, antimony 15'9, lead 
 57 '4 100 (also contains a little arsenic). Color light lead-gray. Sala, Sweden; Merido, 
 Spain ; Val di Castello, Tuscany. 
 
 POLYBASITB. 
 
 Orthorhombic, DesCl. 7 A / nearly 120, A 1 = 121 30'. Crystals 
 usually short tabular prisms, with the bases triangularly striated parallel 
 to alternate edges. Cleavage : basal imperfect. Also massive and dis- 
 seminated. 
 
 H.=2-3. G.=6*214. Lustre metallic. Color iron-black; in thin crys- 
 tals cherry-red by transmitted light. Streak iron-black. Opaque except 
 when quite thin. Fracture uneven. 
 
 Comp. AggSbSe (or 9Ag 2 S+Sb 2 S 3 ), if containing silver without copper or arsenic, Sulphur 
 14 '8, antimony 9*7, silver 95 5=100. But with Ag 2 replaced in part by Cu a (ratio Ag : Cu= 
 1 : 4 to 1 : 11), and Sb replaced by As (ratio 1:1, etc.). 
 
 Pyr., etc. In the open tube fuses, gives sulphurous and antimonial fumes, the latter 
 forming a white sublimate, sometimes mixed with crystalline arsenous oxide. B.B. fuses 
 with spirting to a globule, gives off sulphur (sometimes arsenic), and coats the coal with anti- 
 monous oxide ; with long-continued blowing some varieties give a faint yellowish-white coat- 
 ing of zinc oxide, and a metallic globule, which with salt of phosphorus reacts for copper, 
 and cupelled with lead gives pure silver. 
 
 Decomposed by nitric acid. 
 
 Obs. Occurs in Mexico ; at Tres Puiitos, Chili ; at Freiberg and Przibram. In Nevada, 
 at the Reese mines ; in Idaho, at the silver mines of the Owhyhee district. 
 
 POLYARGYRITE. Isometric. Cleavage cubic. Malleable. Comp. 12Ag 2 S+Sb a Ss. Wol- 
 fach, Baden. 
 
 ENARGITE. 
 
 Orthorhombic. /A 7 = 97 53', O A 14 = 136 37' (Dauber) ; c : I : d = 
 0-94510 : 1-1480 : 1. O A 1-* = 140 20', A 1 = 128 35'. Cleavage : 1 
 perfect ; *4, i-l distinct ; indistinct. Also massive, granular or columnar. 
 
 II. =3. G. 4-43-4-45 ; 4-362, Kenngott. Lustre metallic. Color gray- 
 ish to iron-black ; streak grayish-black, powder having a metallic lustre. 
 Brittle. Fracture uneven. 
 
 Comp. Cu 3 As 4 = Sulphur 32 '5, arsenic 191, copper 48-4=100, usually containing also a 
 little antimony, and zinc, and sometimes silver. 
 
 Fyr. In the close-! tube decrepitates, and gives a sublimate of sulphur ; at a higher tem- 
 perature fuses, and gives a sublimate of arsenous sulphide. In the open tube, heated gently, 
 the powdered mineral gives off sulphurous and arsenous oxides, the latter condensing to a 
 sublimate containing some antirnonous oxide. B. B. on charcoal fuses, and gives a faint coat- 
 ing of arsenous oxide, antimonous oxide, and zinc oxide ; the roasted mineral with the fluxea 
 gives a globule of metallic copper. 
 
 Soluble in nitro-hydrochloric acid. 
 17 
 
258 DESCRIPTIVE MINERALOGY. 
 
 Obs. From Morococha, Cordilleras of Peru ; Famatina Mts.. Argentine Republic ; from 
 Chili; mines of Santa Anna, N. Granada ; at Cosihuirachi in Mexico ; Brewster's gold mine, 
 Chesterfield district, S. Carolina ; in Colorado ; at Willis's Gulch, near Black Hawk ; southen 
 Utah ; Morning Star mine, Cal. 
 
 FAMATINITE (titelsner). An antiinonial euargite. Massive. Color reddish gray. Fama- 
 tina Mts. , Argentine Republic ; Cerro de Pasca, Peru. 
 
 LUZONITE. Similar to enargite in composition, but unlike inform, according to Weisbach. 
 Mancayan Island, Luzon. 
 
 CLARITE (Sandberger}. Also similar to enargite in composition, but in form monoclinic, 
 and having a perfect cleavage parallel to the clinopinacoid. Schapbaeh, Black Forest. 
 
 ETIGENITE. Composition S 32-24, As 12-78, Cu 4068, Fe 14'20=100. Orthorhombio. 
 Color steel-gray. Neugliick mine, Wittichen, 
 
COMPOUNDS OF CHLORINE, B-ttOMINE, IODINE. 
 
 259 
 
 IIJ. COMPOUNDS OF CHLORINE, BROMINE, IODINE 
 
 1. ANHYDROUS CHLORIDES, ETC. 
 
 HALITE!. COMMON SALT. Kochsalz, Steinsalz, Germ. 
 
 Isometric. Usually in cubes ; rarely in octahedrons ; faces of crystals 
 sometimes cavernous, as in f. 458. Cleavage : cubic, 
 perfect. Massive and granular, rarely columnar. 
 
 H.=2-5. G.= 2 -1-2-257. Lustre vitreous. Streak 
 white. Color white, also sometimes yellowish, red- 
 dish, bluish, purplish; often colorless. Transparent 
 translucent. Fracture conchoidal. Eather brittle. 
 Soluble ; taste purely saline. 
 
 Oomp. NaCl= Chlorine 60 '7, sodium 39 '3 = 100. Commonly 
 mixed with some calcium sulphate, calcium chloride, and magne- 
 sium chloride, and sometimes magnesium sulphate, which render 
 it liable to deliquesce. 
 
 Pyr., etc. In the closed tube fuses, often with decrepitation ; when fused on the platinum 
 loop colors the flame deep yellow. 
 
 Diff. Distinguished by its taste, solubility, and perfect cubic cleavage. 
 
 Obs. Common salt occurs in extensive but irregular beds in rocks of various ages, associ- 
 ated with gypsum, polyhalite, calcite, clay, and sandstone ; also in solution, and forming 
 
 mines of Europe are at Wieliczka, in Poland; at Hall, in the Tyrol; Stass- 
 furt in Prussian Saxony ; and along the range through Reichenthal in Bavaria, Hallein in 
 Salzburg Hallstadt, Ischl, and Ebensee, in upper Austria, and Aussee in Styria ; in Transyl- 
 vania ; Wallachia, G-alicia, and upper Silesia ; Vic and Dieuze in France ; Valley of Cardona 
 and elsewhere in Spain, forming hills 300 to 400 feet high ; Bex in Switzerland ; and North- 
 wich in Cheshire, England. It also occurs near Lake Oroomiah, the Caspian Lake., etc. In 
 Vle-eria in Abyssinia in India in the province of Lahore, and in the valley of Cashmere ; 
 xn China and Asiatic Russia ; in South America, in Peru, and at Zipaquera and Nemocon. 
 
 In the United States, salt has been found forming beds with gypsum, in Virginia, Wash- 
 ino-ton Co in the Salmon River Mts. of Oregon ; in Louisiana. Brine springs are very 
 numerous m the Middle and Western States. These springs are worked at Salina and Syra- 
 cuse N Y in the Kanawha Valley, Va. ; Muskingum, Ohio; Michigan, at Sagmaw and 
 elsewhere '; and in Kentucky. Vast lakes of salt water exist in many parts of the world 
 Lake Timpanogos in the Rocky Mountains, 4,200 feet above the level of the sea, now called 
 the Great Salt Lake, is 2,000 square miles in area. L. Gale found in this water 20'196 per 
 cent of sodium chloride in 1852 ; but the greater rainfall of the last few years has dimin- 
 ished the proportion of saline matter. The Dead and Caspian Seas are salt, and the waters 
 of the former contain 20 to 26 parts of solid matter in 100 parts. . 
 
 HUANTAJAYTTE.-Composition 20Nad + AgCl. Occurs in white cubes m the mine of Sao 
 Simon, Cerro de Huantajaya, Peru. 
 
260 DESCRIPTIVE MINERALOGY. 
 
 SYLV1TE. 
 
 Isometric. Cleavage cubic. Also compact. 
 
 H.=2. G.=l'9-2. White or colorless. Yitieous. Soluble; tasle like 
 that of common salt. 
 
 Comp. KC1= Chlorine 47 '65, potassium 52 -35 = 100. But often containing impurities. 
 
 Pyr., etc. B.B. in the platinum loop fuses, and gives a violet color to the outer flame. 
 Added to a salt of phosphorus bead, which has been previously saturated with copper oxide, 
 colors the O.F. deep azure-blue. Water completely dissolves it. 
 
 Obs. Occurs at Vesuvius, about the fumaroles of the volcano. Also at Stassfurt ; at Leo- 
 poldshall (leopoldite) ; at Kalusz, Galicia. 
 
 CERARGYRITE. Kerargyrite. Horn Silver. Silberhornerz, Germ. 
 
 Isometric. Cleavage none. Twins: twimiing-plane octahedral. Usually 
 massive and looking like wax ; sometimes columnar, or bent columnar ; 
 often in crusts. 
 
 H.=1-1'5. G.=5'552. Lustre resinous, passing into adamantine. Color 
 pearl-gray, grayish-green, whitish, rarely violet-blue, colorless sometimes 
 when perfectly pure; brown or violet-brown on exposure. Streak shin- 
 ing. Transparent feebly subtranslucent. Fracture somewhat conchoidal. 
 Sectile. 
 
 Comp. AgCl=Chlorine 247, silver 75-3=100. 
 
 Pyr., etc. In the closed tube fuses without decomposition. B.B. on charcoal gives a 
 globule of metallic silver. Added to a bead of salt of phosphorus, previously saturated with 
 copper oxide, and heated in O.F. , imparts an intense azure -blue to the flame. A fragment 
 placed on a strip of zinc, and moistened with a drop of water, swells up, turns black, and 
 finally is entirely reduced to metallic silver, which shows the metallic lustre on being pressed 
 with the point of a knife. Insoluble in nitric acid, but soluble in ammonia. 
 
 Obs. Occurs in veins of clay slate, accompanying other ores of silver, and usually only in 
 the higher parts of these veins. It has also been observed with ochreous varieties of brown 
 iron ore ; also with several copper ores, with calcite, barite, etc. 
 
 The largest masses are brought from Peru, Chili, and Mexico. Also occurs in Nicaragua 
 near Ocotal ; in Honduras. It was formerly obtained in the Saxon mining districts of 
 Johanngeorgenstadt and Freiberg, but is now rare. Found in the Altai; at Kongsberg in 
 Norway ; in Alsace ; rarely in Cornwall, and at Huelgoet in Brittany. In Nevada, about 
 Austin, Lander Co., abundant ; at mines of Comstock lode. In Arizona, in the Willow Springs 
 dist. , veins of El Dorado canon, and San Francisco dist. In Idaho, at the Poor Man lode. 
 
 Named from Kt/jac, horn, and ap^upof, silver. 
 
 CALOMEL (Quecksilberhornerz, Germ.). Composition HgCl Chlorine 15*1, mercury 84*9 
 = 100. Color white, grayish, brown. Spain. 
 
 SAL AMMONIAC (Salmiak, Germ.}. Ammonium chloride, NH 4 C1= Ammonium 33 '7, chlo- 
 rine 66 '3 =100. Vesuvius, Etna, and many volcanoes. 
 
 NANTOKITE (Breithaupt). Composition CuCl=Chlorine 35 '9, copper 641=100. Cleavage 
 cubic. Color white. Nantoko, Chili. 
 
 EMBOLITE. Ag(Cl,Br) ; the ratio of Cl : Br varying from 3 : 1 to 1 : 3. Color grayish- 
 green. At various mines in Chili ; also Mexico ; Honduras. 
 
 BKOMYRITE, Bromargyrite (Bromsilber, Germ.). Silver bromide, AgBr=Bromine 42'6, 
 silver 57 '4=100. Color when pure bright yellow, slightly greenish. Chili ; Mexico. 
 
 IODYRITE, lodargyrite (lodsilber, Germ.). Silver iodide, Agl = Iodine 54'0, silver 46 '0= 
 100. Color yellow. Mexico ; Chili ; Spain ; Cerro Colorado mine in Arizona. 
 
 TOCORNALITE (Domeyko). Composition AgI-{-HgI. Amorphous. Color pale yellow. 
 Chanarcillo, Chill 
 
 CHLOROCALCITE (Scacchi). From Vesuvius, contained 58*76 p. c. CaCl* ; with also KC1, 
 NaCl,MgCl 2 . CHLORALLUMINITE, CIILORMAGNESITE, and CHLOKOTHIONITE are also from 
 Vesuvius. 
 
COMPOUNDS OF CHLORINE, BROMINE, IODINE. 261 
 
 COTUNNITE. Lead chloride, PbCl 2 = Chlorine 25 '5, lead 74 '5=100. Soft. White. Vera- 
 vins. PSEUDOCOTUNNITE (Scacchi), Vesuvius. 
 
 MOLYSITE. Composition FeCl 6 = Chlorine 65-5, iron 34-5=100. Vesuvius. 
 
 2. HTDKOUS CHLOKIDES. 
 
 CARNALLITE. 
 
 Massive, granular ; flat planes developed by action of water, but no dis- 
 tinct traces of cleavage ; lines of striae sometimes distinguished, which 
 indicate twin- composition. 
 
 Lustre shining, greasy. Color milk-white, but often reddish from mix- 
 ture of oxide of iron. Fracture conchoidal. Soluble. Strongly phosphor 
 escent. 
 
 Comp. KMgCl 3 .6aq=KCl-|-MgCl2 + 6aq=Magnesium chloride 34 '2, potassium chloride 
 26-9, water 38 -9 100. 
 
 The brown and red color of the mineral is due partly to iron sesquioxide, which is in hex- 
 agonal tables, and partly to organic matters (water-plants, infusoria, sponges, etc.). 
 
 Pyr., etc. B.B. fuses easily. Soluble in water, 100 parts of water at 18'75 C. taking up 
 64-5 parts. 
 
 Obs. Occurs at Stassfurt, where it forms beds in the upper part of the salt formation, 
 alternating with thinner beds of common salt and kieserite, and also mixed with the common 
 salt. Its beds consist of subordinate beds of different colors, reddish, bluish, brown, deep red, 
 sometimes colorless. Sylvite occurs in the carnallite. Also found at Westeregeln ; with salt 
 at Maman in Persia. Its richness in potassium makes it valuable for exploration. 
 
 TACHHYDRITE. Composition CaMg a Cl 6 + 12aq=CaCl 2 +2MgCl 2 + 12aq (Ramm.)= Chlorine 
 40'3, magnesium 9*5, calcium 7 '5, water 427=100. Color yellowish. Deliquescent. Stass- 
 furt. 
 
 KREMERSITE. Probably 2NH 4 Cl-f-2KCl4-FeCl 6 +3aq. Vesuvius. 
 
 ERYTHROSIDERITE, also from Vesuvius, is 2KCl+FeCl 6 +2aq. 
 
 3. OXYCHLOKIDES. 
 
 ATACAMITB. 
 
 29'; 
 
DESCRIPTIVE MINERALOGY. 
 
 Comp.--CuCl 2 +3H 2 CuO 2 = Chlorine 16-64, copper 59'45, oxygen 11-25, water 12'66=100. 
 Also other compounds with more water (18 and 22$ p. c.). 
 
 Pyr., etc. In the closed- tube gives off much water, and forms a gray sublimate. B.B. or, 
 charcoal fuses, coloring the O.F. azure-Blue, with a green edge, and giving two coatings, 
 one brownish and the other grayish-white ; continued blowing yields a globule of metallic 
 copper ; the coatings touched with the R.F. volatilize, coloring the flame azure -blue. In acide 
 easily soluble. 
 
 Obs. Occurs in different parts of Chili ; in the district of Tarapaca, Bolivia ; at Tocopilla 
 in Bolivia ; with malachite in South Australia ; Serro do Bembe, near Ambriz, on the west 
 coast of Africa ; at the Bstrella mine in southern Spain ; at St. Just in Cornwall. 
 
 TALLINGITE. Composition CuCl 2 +4H 2 CuO a +4aq. In thin crusts. Color blue. Botal- 
 lack mine, Cornwall. 
 
 ATELITE. Composition CuCl 2 +2H 2 Cu0 2 + aq. Formed from tenorite. Vesuvius. 
 
 PERCYLITE. An oxychloride of lead and copper. Occurs in minute sky-blue cubes. 
 Sonora, Mexico ; So. Africa. 
 
 MATLOCKITE. Composition PbCl a +PbO= Lead chloride 55-5, lead oxide 44*5=100. Crom- 
 ford, near Matlock, Derbyshire. 
 
 MENDIPITE. Composition PbCl a +2PbO=Lead chloride 38*4, lead oxide 61'6=100. In 
 columnar masses, often radiated. Color white. Mendip Hills, Somersetshire; Brillon, 
 Westphalia. 
 
 SCHWAIITZEMBERGITE. Composition Pb(I,Cl) 2 +2PbO. Color yellow. Desert of Ata- 
 cama. 
 
 DAUBREITE. Composition (Bi 2 O 3 )4BiCl3=Bi 2 O 8 76-16, BiCls 23'84=100. Amorphous. 
 Structure earthy, sometimes fibrous. Color yellowish-gray. H.=2'5. G. =6 "4-6 '5. From 
 the mine Constancia, Cerro de Tanza, Bolivia (Domeyko). 
 
FLTTOBINE COMPOUNDS. 
 
 263 
 
 IV. FLUORINE COMPOUNDS. 
 
 1. ANHYDKOUS FLUOKIDES. 
 
 FLUORITE or FLUOR SPAR* Flusspath, Germ. 
 
 Isometric; forms usually cubic (see f. 39, 40, 41, 52, 55, etc., pp. 1G 
 to 19). Cleavage : octahedral, perfect. Twins : 
 twinning-plane, 1, f. 266, p. 91. Massive. 
 Rarely columnar ; usually granular, coarse or 
 fine. Crystals often having the surfaces made 
 up of small cubes, or cavernous with rectangular 
 ca vities. 
 
 [.=4. G.:=3-01-3-25. Lustre vitreous ; 
 bometimes splendent ; usually glimmering in the 
 massive varieties. Color white, yellow, green, 
 rose, and crimson-red, violet-blue, sky-blue, and 
 brown : wine-yellow, greenish and violet-blue, 
 most common ; red, rare. Streak white. Trans- 
 parent subtranslucent. Brittle. Fracture of fine massive varieties flat- 
 conchoidal and splintery. Sometimes presenting a bluish fluorescence. 
 Phosphoresces when heated. 
 
 Comp., Var. Calcium fluoride, CaF 2 = Fluorine 48'7, calcium 51 '3=100. Berzelius found 
 -5 of calcium phosphate in the fluorite of Derbyshire. The presence of chlorine was detected 
 early by Scheele. Kersten found it in fluor from Marienberg and Freiberg. The bright 
 colors, as shown by Kenngott, are lost on heating the mineral ; they are attributed mainly to 
 different hydrocarbon compounds by Wyrouboff, the crystallization having taken place from 
 aqueous solution. 
 
 Var. Ordinary ; (a) cleavable or crystallized, very various in colors ; (b) coarse to fine 
 granular ; (c) earthy, dull, and sometimes very soft. A soft earthy variety from Ratofka, 
 Russia, of a lavender-blue color, is the ratofkite. The finely-colored fluorites have been 
 called, according to their colors, false ruby, topaz, emerald, amethyst, etc. The colors of the 
 phosphorescent light are various, and are independent of the actual color ; and the kind 
 affording a green color is (d) the chloropliane. 
 
 Pyr., etc. In the closed tube decrepitates and phosphoresces. B.B. in the 1 
 
 on charcoal fuses, coloring the flame red, to an enamel which reacts alkaline to test paper. 
 With soda on platinum foil or charcoal fuses to a clear bead, becoming opaque on cooling ; 
 with an excess of soda on charcoal yields a residue of a difficultly fusible enamel, while most 
 of the soda sinks into the coal ; with gypsum fuses to a transparent bead, becoming opaque 
 on cooling. Fused in an open tube with fused salt of phosphorus gives the reaction for fluor- 
 ine. Treated with sulphuric acid gives fumes of hydrofluoric acid which etch glass. Phoe- 
 
264 
 
 DESCRIPTIVE MINERALOGY. 
 
 phorescence is obtained from the coarsely powdered spar below a red heat. At a high tem- 
 perature it ceases, but is partially restored by an electric discharge. 
 
 Diff. Recognized by its octahedral cleavage, its etching power when heated in the glasa 
 tube, etc. 
 
 Obs. Sometimes in beds, but generally in veins, in gneiss, mica slate, clay slate, and also 
 in limestones, both crystalline and uncrystalline, and sandstones. Often occurs as the gangue 
 of metallic ores. In the North of England, it is the gangue of the lead veins. In Derby- 
 shire it is abundant, and also in Cornwall. Common in the mining district of Saxony ; fine 
 near Kongsberg in Norway. In the dolomites of St. Gothard it occurs in pink octahedrons 
 
 Some American localities are : Trumbull and Plymouth, Conn. ; Muscolonge Lake, Jeffer- 
 son Co., N.Y., in gigantic cubes ; Rossie, St. Lawrence Co. ; near the Fianklin furnace, N. J. ; 
 Gallatin Co., 111. ; Thunder Bay, Lake Superior; Missouri. 
 
 SELLAITE (Striiver). Magnesium fluoride, MgF 2 . Tetragonal. Colorless. Occurs with 
 anhydrite at Gerbulaz in Savoy. 
 
 YTTKOCERITE. Composition 2(9CaF 2 +2YF 2 +CeF 2 )+3aq (Ramm.). Color violet-blue, 
 white. Near Fahlun, Sweden ; Amity, N. Y. ; Paris, Me. ; etc. 
 
 FLUOCERITE. Contains (Berzelius) -GeOs 82 '64, YO 1'12. Sweden. 
 
 FLUELLITE. Contains (Wollaston) fluorine and aluminum. Cornwall. 
 
 CRYPTOHALITE. Fluosilicate of ammonium. Vesuvius. Also observed at Vesuvius, 
 kydrofluorite, HF, and proidonite, SiF 4 (Scacchi). 
 
 CRYOLITE.* 
 
 Triclinic (DesCloizeanx and Websky). Form approaching very closely 
 in appearance and angles to the cube and cnbo- 
 octahedron of the isometric system. General habit 
 as in f. 460 ; P(O] A T(I) = 90 2', P(O] A M(l') 
 = 90 24', M/\ T(I/\ T) = 91 57' ; also I (14') A $L 
 (/') = 124 30', I (14') A T(l) = 124 14' (angles by 
 Websky). Twins common. Cleavage parallel to 
 the three planes P, M, T; in crystals most com- 
 plete parallel to T 7 , in masses parallel to P. Com- 
 monly massive, cleavable. 
 
 H.=2-5. O. = 2-9-3-077. Lnstre vitreous; slightly 
 pearly on O. Color snow-white ; sometimes reddish 
 or brownish to brick-red and even black. Sub- 
 transparent translucent. Immersion in water in- 
 creases the transparency. Brittle. 
 
 Comp. Na 6 AlF 12 (or 6NaF+AlF 6 )= Aluminum 13-0, sodium 32-8, fluorine 54-2=100. 
 
 Pyr., etc. Fusible in the flame of a candle. B.B. in the open tube heated so that the 
 flame enters the tube, gives off hydrofluoric acid, etching the glass ; the water which con- 
 denses at the upper end of the tube reacts for fluorine with Brazil-wood paper. In the for- 
 ceps fuses very easily, coloring the flame yellow. On the charcoal fuses easily to a clear bead, 
 which on cooling becomes opaque ; after long blowing, the assay spreads out, the sodium 
 fluoride is absorbed by the coal, a suffocating odor of fluorine is given off, and a crust of 
 alumina rerc ains, which, when heated with cobalt solution in O. F. , gives a blue color. Soluble 
 in sulphuric acid, with evolution of hydrofluoric acid. 
 
 Diff. Distinguished by its extreme fusibility, and its yielding hydrofluoric acid in the open 
 tube. 
 
 Obs, Occurs in a bay in Arksut-fiord, in West Greenland, at Evigtok, where it constitutes 
 a large bed or vein in gneiss. It is used for making soda, and soda and alumina salts ; also 
 in Pennsylvania, for the manufacture of a white glass which is a very good imitation of 
 porcelain. 
 
 CHIOLITE. G. =2-84-2-90. Na 3 AlF 9 (or 3NaF+AlF 6 ). CHODNEFFITE. G.=3-01. Na*AJ 
 P,o (or4NaF + A!F 6 ) Ramm. The two minerals are alike in physical characters, occurring 
 In minute tetragonal pyramids ; both from Miask. 
 
FLUORINE COMPOUNDS. 
 
 265 
 
 2. HYDKOUS FLUORIDES. 
 
 PAOHNOLTTB. Thomsenolibe.* 
 
 Monoclinic. with the lateral axes equal (" clino-qnadratic " Norden* 
 kiold). 6:b:d = 1-044 : 1 : 1 ; C7 = 92 30'. Prisms slender 
 a little tapering ; / horizontally striated. Cleavage : basal 
 very perfect. Also massive, opal or chalcedony-like. 
 
 li. = 2'5-4. G.=2'929-3-008, of crystals. Lustre vitreous, 
 of a cleavage-face a little pearly, of massive waxy. Color 
 white, or with a reddish tinge. Transparent to translucent. 
 
 Comp.-Na 2 Ca 2 AlF 12 + 2aq, or 2XaF + 2CaF 2 + A1F 6 4- 2aq = 
 51 28 aluminum 12*28, calcium 17'99, sodium 103o, water 8'10=100. ^ 
 
 Pvr. etc. Fuses more easily than cryolite to a clear glass. The massive 
 decrepitates remarkably in the flame of a candle. In powder easily decom- 
 posed by sulphuric acid. . 
 
 Obs. Found incrusting the cryolite of Greenland, and a result of its 
 alteration The crystals often have an ochre-colored coating, especially the 
 terminal portion: they are sometimes quite large, and have much tne 
 appearance of cryolite. The mineral was first described by Knop, and though his ^scnptic n 
 of the crystals does nob agree with that given above, there seems to be no doubt that the 
 material was .the same, which has since been investigated by Hagemann (dimetnc packnohte 
 ^thomsenolite), Wohler (pyroconite) and Koemg, as urged by the latter. 
 
 Knop originally described two varieties of the mineral, to which he gave the name pachno. 
 lite The variety, A, appeared in large, cuboidal crystals, with cleavage planes parallel to the 
 faces intersLting at angles of approximately 9(P . These cleavage planes seemed to be con- 
 
 b.^ the possibility that the crystals of 
 
 r reall 
 
 wd obtained theangles quoted on the preceding page, were really 
 variety A of palhnolite. The crystallographic relation of the two species is not 
 
 GEARKSUTITE, all from Greenland; and PROSOPITE from 
 related to those which precede, but whose exact nature 
 
 RLSTON (Brwh).-An hydrous aluminum fluoride, containing also a little magnet 
 andtodium! Ocfurs in minute regular octahedrons on the cryolite from Greenland. 
 
266 
 
 DESCRIPTIVE MINERALOGY. 
 
 V. OXYGEN COMPOUNDS. 
 
 1. OXIDES OF METALS OF THE GOLD, IKON, OR TIN GROUPS. 
 
 A. ANHYDROUS OXIDES, (a) PROTOXIDES, RO(or R 8 O). 
 
 CUPRITE. Bed Copper Ore. Rothkupfererz, Germ. 
 
 Isometric (see figures on p. 17). Cleavage: octahedral. Sometimes 
 
 cubes lengthened into capillary forms. Also 
 461 massive, granular; sometimes earthy. 
 
 H.^3-5-4. G.=5-85-6-15. Lustre ada- 
 mantine or submetallic to earthy. Color red, 
 of various shades, particularly cochineal-red : 
 occasionally crimson-red by transmitted light 
 Streak several shades of brownish-red, shin 
 ing. Subtransparent subtranslueent. Frac- 
 ture conchoidal, uneven. Brittle. 
 
 Comp., Var. Cu 2 0=Oxygenll-2, copper 88 '8 100 
 Sometimes affords traces of selenium. Chalcotrichitt 
 is a variety which occurs in capillary or acicular crys- 
 tallizations, which are cubes elongated in the direction 
 of the octahedral axis. It also occurs earthy; Tilt 
 Ore (Ziegelerz Germ.). Brick-red or reddish-brown 
 and earthy, often mixed with red oxide of iron ; some- 
 times nearly black. 
 
 Fyr., etc. Unaltered in the closed tube. B.B. in the forceps fuses and colors the flame 
 emerald-green; if previously moistened with hydrochloric acid, the color imparted to the 
 flame is momentarily azure-blue from copper chloride. On charcoal first blackens, then fuses, 
 and is reduced to metallic copper. With the fluxes gives reactions for copper oxide. Soluble 
 in concentrated hydrochloric acid. 
 
 Obs. Occurs in Thuringia ; on Elba, in cubes ; in Cornwall ; in Devonshire ; in isolated 
 crystals, in litbomarpe, at Chessy, near Lyons, which are generally coated with malachite, 
 etc. At the Somerville, and Flemington copper mines, N. J. ; at Cornwall, Lebanon Co., 
 Pa. ; in the Lake Superior region. 
 
 HTDFOCUPRITE (Oenth). A hydrous cuprite. Occurs in orange-yellow coatings on 
 mrgnetite. Cornwall, Lebanon Co., Pa. 
 
 ZINCITE. Eed Zinc Ore. Rothzinkerz, Germ. 
 
 Hexagonal. O A 1 = 118 V ; c = 1-6208. In quartzoids with truncated 
 summits, and prismatic faces I. Cleavage : basal, eminent ; prismatic, 
 sometimes distinct. Usual in foliated grains or coarse particles and masses ; 
 also granular. 
 
 H. 4-4-5. G. =5-43-5-7. Lustre subadamantine. Streak orange-yel- 
 low. Color deep red, also orange-yellow. Translucent subtranslucent. 
 Fracture subconchoidal. Brittle. 
 
 Comp. ZnO= Oxygen 19 '74, zinc 80*26=100; containing manganese as an unessential 
 ingredient. The red color is due probably to the presence of manganese sesquioxide, cer- 
 tainly not to scales of hematite. 
 
OXYGEN COMPOUNDS ANHYDROUS OXIDES. 
 
 267 
 
 Pyr., etc. Heated in the closed tube blackens, but on cooling resumes the original color 
 B. B, inf usib .e ; with the fluxes, on the platinum wire, gives reactions for manganese, and on 
 charcoal in R. F. gives a coating of zinc oxide, yellow while hot, and white on cooling. The 
 coating, moistened with cobalt solution and treated in R.F., assumes a green color. Soluble 
 in acids without effervescence. 
 
 Obs. Occurs with franklinite and also with calcite at Stirling Hill and Mine Hill, Sussex 
 Co.,N. J. 
 
 CALCOZINCITE. Impure zincite (mixed with CaC0 3 , etc.). Stirling Hill, N. J. 
 
 TENORITE.* MELACONITE. Schwarzkupfererz (Kupferschwarze), Germ. 
 
 Orthorhombic (tenorite), crystals from Vesuvius. Earthy; massive; 
 pulverulent (melaconite) ; also in shining flexible scales ; also rarely in 
 cubes with truncated angles (pseudomorphous ?). 
 
 H.=3. G. 6-25, massive (Whitney). Lustre metallic, and color steel or 
 iron-gray when in thin scales ; dull and earthy, with a black or grayish- 
 black color, and ordinarily soiling the fingers when massive or pulverulent. 
 
 Comp CuO=Oxygen 20 '15, copper 79 '85 =100 
 
 Pyr., etc. B.B. in O.F. infusible; other reactions as for cuprite (p. 244). Soluble in 
 hydrochloric and nitric acids. 
 
 Obs. Found on lava at Vesuvius in minute scales ; and also pulverulent (Scacchi, who 
 uses the name melaconise for the mineral). Common in the earthy form (mdaconite) about 
 copper mines, as a result of the decomposition of chalcopyrite and other copper ores. Duck- 
 town mines in Tennessee, and Keweenaw Point, L. Superior. 
 
 PERICLASITE. Essentially magnesium oxide, MgO, or more exactly (Mg,Fe)0, where 
 Mg : Fe=20 : 1, or 30 : 1. Mt. Somma. 
 
 BUNSENITE. NiO. Found at Johanngeorgenstadt. The compound MnO has been found 
 recently in Wermland, in masses of a green color, and with cubic cleavage. See mangano- 
 site, p. 431. 
 
 MASSICOT (Bleiglatte). PbO, but generally impure. Baden weiler, Baden. Mexico. 
 Austin's mines, Va. 
 
 HYDRARGYRITE. HgO ; with BOUDOSITE, AgCl + HgCl, at Los Bordos, Chili. 
 
 ~ 
 
 (fy SESQUIOXIDES. GENERAL FORMULA 
 CORUNDUM.* 
 
 EhombohedraL E A R = 86 4', O A \(R) = 122 26' ; (122 25', Kok- 
 gcharof) ; c = 1-363. Cleavage : basal, some- 
 times perfect, but interrupted, commonly im- 
 perfect in the blue variety ; rhombohedral, often 
 perfect. Large crystals usually rough. Twins : 
 composition-face It. Also massive granular or 
 impalpable ; often in layers from composition 
 parallel to /?. 
 
 H.=9. G.=3-909-4-16. Lustre vitreous; 
 sometimes pearly on the basal planes, and occa- 
 sionally exhibiting a bright opalescent star of 
 BIX rays in the direction of the axis. Color blue, 
 >-ed, yellow, brown, gray, and nearly wlite; 
 Btreak uncolored. Transparent translucent. 
 Fracture conchoidal uneven. Exceedingly 
 tough when compact. 
 
 Comp., Var Pure alumina AlO 3 =Oxygen 46 '8, aluminum 53'2=100. There are threr 
 
268 
 
 DESCRIPTIVE MINERALOGY. 
 
 subdivisions of the species prominently recognized in the arts, and until eaily in this century 
 regarded as distinct species ; but which actually differ only in purity and state of crystalliza- 
 tion or structure. 
 
 YAK. 1. SAPPHIRE Includes the purer kinds of fine colors, transparent to translucent, 
 useful as gems. Stones are named according to their colors ; true Ruby, or Oriental Ruby, 
 red; Toprut, yellow ; 0. Emerald,. green; 0. Amethyst, purple. 
 
 2. CORUNDUM. Includes the kinds of dark or dull colors and not transparent, colors light 
 blue to gray, brown, and black. The original adamantine spar from India has a dark gray- 
 ish smoky-brown tint, but greenish or bluish by transmitted light, when translucent, and 
 either in distinct crystals often large, or cleavable-massive. It is ground and u^ed as a polish- 
 ing material, and being purer, is superior in this respect to emery. It was thus employed in 
 ancient times, both in India and Europe. 
 
 3. EMERY, Schmirgel, Germ. Includes granular corundum, of black or grayish-black 
 color, and contains magnetite or hematite intimately mixed. Feels and looks much like a 
 black fine-grained iron ore, which it was long considered to be. There are gradations from the 
 evenly fine-grained emery to kinds in which the corundum is in distinct crystals. This last 
 is the case with part of ihat at Chester, Massachusetts. 
 
 Pyr., etc. B.B. unaltered ; slowly dissolved in borax and salt of phosphorus to a clear 
 glass, which is colorless when free from iron ; not acted upon by soda. The finely pulverized 
 mineral, after heating with cobalt solution, gives a beautiful blue color. Not acted 
 upon by acids, but converted into a soluble compound by fusion with potassium bisulphate 
 or soda. Friction excites electricity, and in polished specimens the electrical attraction, con- 
 tinues for a considerable length of time. 
 
 Diff. Distinguished by its hardness, scratching quartz and topaz ; its infusibility and its 
 high specific gravity. 
 
 Obs. This species is associated with crystalline rocks, as granular limestone or dolomite, 
 gneiss, granite, mica slate, chlorite slate. The fine sapphires are usually obtained from the 
 beds of rivers, either in modified hexagonal prisms or in rolled masses, accompanied by grains 
 of magnetic iron ore, and several species of gems. The emery of Asia Minor, according to 
 Dr. Smith, occurs in granular limestone. 
 
 Sapphires occur in Ceylon ; the East Indies ; China. Corundum, at St. Gothard ; in Pied- 
 mont ; Urals ; Bohemia. Emery is found in large boulders on some of the Grecian islands ; 
 also in Asia Minor, near Ephesus, etc. In N. America, in Massachusetts, at Chester, corun- 
 dum and emery in a large vein ; also in Westchester Co. , N. Y. In New York, at Warwick 
 and Amity. In Pennsylvania, in Delaware Co., and Chester Co. In western N. Carolina^ 
 at many localities in large quantities, and sometimes in crystals of immense size. In Georgia^ 
 in Cherokee Co. In California, in Los Angeles Co. ; in the gravel on the Upper Missouri 
 .River in Montana. 
 
 HEMATITE. Specular Iron. Eisenglanz, Rotheisenerz, Germ. 
 
 Rhombohedral. 7? A 7? = 86 10', A E = 122 30'; c = 1-3591. 
 O A f 2 = 118 53', O A I 3 = 103 32, R A f 2 = 154 V. Cleavage : par- 
 allel to R and Of often indistinct. Twins: twinning-plane R ; also 
 
 ' 468 469 
 
 Elba. 
 
 Elba. 
 
 Vesuvius. 
 
 (f . 267, p. 91). Also columnar granular, botryoidal, and stalactitic shapes ; 
 also lamellar, laminae joined parallel to O, and variously bent, thick or 
 thin ; also granular, friable or compact. 
 
OXYGEN COMPOUNDS ANHYDROUS OXIDES. 269 
 
 H. 5'5-6'5. G.=4-5-5'3; of some compact varieties, as low as 4*2. 
 Lustre metallic and occasionally splendent ; sometimes earthy. Color dark 
 steel-gray or iron-black ; in very thin particles blood-red by transmitted 
 light ; when earthy, red. Streak cherry-red or reddish-brown. Opaque, 
 except when in very thin laminae, which are faintly translucent and blood- 
 red. Fracture subconchoidal, uneven. Sometimes attractable by the 
 magnet, and occasionally even magnet ipolar. 
 
 Comp., Var. Iron sesquioxide, Fe0 3 = Oxygen 30, iron 70=100. Sometimes containing 
 titanium and magnesium. 
 
 The varieties depend on texture or state of aggregation, and in some cases the presence v ' 
 impurities. 
 
 Var. 1. Specular. Lustre metallic, and crystals often splendent, whence the name specular 
 iron, (b) When the structure is foliated or micaceous, the ore is called micaceous hematito 
 (Eisenglimmer). 2. Compact columnar ; or fibrous. The masses of ten long radiating ; lustre 
 submetallic to metallic ; color brownish-red to iron-black. Sometimes called rtd hematite, 
 the name hematite among- the older mineralogists including the fibrous, stalactitic, and other 
 solid massive varieties of this species, limonite, and turgite. 3. Red Ochreous. Bed and 
 earthy. Often specimens of the preceding are red ochreous on some parts. Reddle and red 
 chalk are red ochre, mixed with more or less clay. 4. Glay Iron-stone ; Argillaceous hematite. 
 Hard, brownish-black to reddish-brown, heavy stone ; often in part deep-red ; of submetallic 
 to unmetallic lustre ; and affording, like all the preceding, a red streak. It consists of iron 
 sesquioxide with clay or sand, and sometimes other impurities. 
 
 Pyr., etc. B.B. infusible; on charcoal in R.F. becomes magnetic; with borax in O.F. 
 gives a bead, which is yellow while hot and colorless on cooling ; if saturated, the bead 
 appears red while hot and yellow on cooling ; in R.F. gives a bottle-green color, and if treated 
 oil charcoal with metallic tin, assumes a vitriol-green color. With soda on charcoal in R.F. 
 is reduced to a gray magnetic metallic powder. Soluble in concentrated hydrochloric acid. 
 
 Diff. Distinguished from magnetite by its red streak, also from limonite by the same 
 means, as well as by its not containing water ; from turgite by its greater hardness and by 
 its not decrepitating B.B. It is hard; and infusible. 
 
 Obs. This ore occurs in rocks of all ages. The specular variety is mostly confined to crys- 
 talline or metamorphic rocks, but is also a result of igneous action about some volcanoes, aa 
 at Vesuvius. Traversella in Piedmont ; the island of Elba, afford fine specimens ; also St. 
 Gothard, of ten in the form of rosettes (Eisenrose , and Cavradi in Tavetsch; and near Limogei, 
 France. At Etna and Vesuvius it is the result of volcanic action. Arendal in Norway, Long- 
 ban in Sweden, Framont in Lorraine, Dauphiny, also Cleator Moor in Cumberland, are other 
 localities. 
 
 In N. America, widely distributed, and sometimes in beds of vast thickness in rooks of the 
 Archgean age, as in the Marquette region in northern Michigan ; and in Missouri, at the Pilot 
 Knob and the Iron Mtn. ; in Arizona and Nftw Mexico. Some of the localities, interesting 
 for their specimens, are in northern New York, etc.; Woodstock and Aroostook, Me.; at 
 Hawley, Mass. ; at Piermont, N. H. 
 
 This ore affords a considerable portion of the iron manufactured in different countries. The 
 varieties, especially the specular, require a greater degree of heat to melt than other ores, 
 but the iron obtained is of good quality. Pulverized red hematite is employed in polishing 
 metals, and also as a coloring material. The fine-grained massive variety from England 
 (bloodstone), showing often beautiful conchoidal fracture, is much used for burnishing metals. 
 Eed ochre is valuable in making paint. 
 
 MARTITE is iron sesquioxide under an isometric form, occurring in octahedrons or dodeca- 
 hedrons like magnetite, and supposed to be pseudomorphous, mostly after magnetite. H. 
 6-7. G. =4 -809-4 -832, Brazil, Breith. ; 5 '33, Monroe, N. Y., Hunt. Lustre submetallic. 
 Color iron-black, sometimes with a bronzed tarnish. Streak reddish-brown or purplish-brown. 
 Fracture couchoidal. Not magnetic, or only feebly so. The crystals are sometimes imbed- 
 ded in the massive sesquioxide. They are distinguished from magnetite by their red streak, 
 and very feeble, if any, action on the magnetic needle. 
 
 Found in Vermont at Chittenden; in the Marquette iron region south of L. Superior; 
 Bass lake, Canada West; Digby Neck, Nova Scotia; at Monroe, N. Y. ; in Moravia, neaj 
 Schonberg, in granite. 
 
 MENACCANITE.* ILMENIFE. Titanic Iron Ore. Titaneisen, Germ. 
 Khombohedral ; tetartohedral to the hexagonal type. It A R = 85 30' 
 
270 
 
 DESCRIPTIVE MINERALOGY. 
 
 56" (Koksch.), c = 1-38458. Angles nearly as 
 
 cleavage parallel with 
 
 in hematite. Often a 
 
 a the terminal plane, but 
 
 ue to planes of composition. Crystals 
 usually tabular. Twins : twinning-plane O ; 
 sometimes producing, when repeated, a form 
 resembling f. 468. Often in thin plates or 
 lamina} ; massive ; in loose grains as sand. 
 
 II. 5-6. G.=4r'5-5. Lustre submetallic. 
 Color iron-black. Streak submetallic, powder 
 black to brownish-red. Opaque. Fracture con- 
 choidal. Influences slightly the magnetic needle. 
 
 Comp., Var. (Ti,Fe) 2 3 (or hematite, with part of the iron replaced by titanium), the pro 
 portion of Ti to Fe varying. Mosander assumes the proportion of FeO : TiO 2 to be always 
 1:1, and that in addition variable amounts of Fe0 3 are present in the different varieties. 
 The extensive investigations of Rammelsberg have led him to write the formula like Mosan- 
 der (FeO,TiO 2 )+nFeO 3 (notice here that FeO,TiO 2 =tt0 3 ). This method has the advantage 
 of explaining the presence of the magnesium, occurring sometimes in considerable amount, it 
 replacing the iron (FeO). The first formula given requires the assumption of Mg 2 3 . Friedel 
 and Guerin have recently discussed the same subject (Ann. Ch. Phys., V., viii., 38, 1876). 
 
 Sometimes contains manganese. The varieties recognized arise mainly from the proportions 
 of iron to titanium. No satisfactory external distinctions have yet been made out. 
 
 The following analyses will illustrate the wide range in composition : 
 
 TiO* FeO 3 FeO MnO 
 
 1. IlmenMts., Ilmenite W-92 10 '74 37 '86 2 "73 
 
 2. Snarum 10 '02 77" 17 8-52 
 
 3. Warwick, N. Y. 57'71 26 '82 0'90 
 
 MgO 
 
 1-14=99-39, Mosander. 
 
 1-33, AlO a 1-46=98-50, Ramm. 
 13-71=9914, Ramm. 
 
 Pyr., etc. B.B. infusible in O.F. although slightly rounded on the edges in R. F. With 
 borax and salt of phosphorus reacts for iron in O.F., and with the latter flux assumes a more 
 or less intense brownish-red color in R.F. ; this treated with tin on charcoal changes to a 
 violet-red color when the amount of titanium is not too small. The pulverized mineral, 
 heated with hydrochloric acid, is slowly dissolved to a yellow solution, which, filtered from 
 the undecomposed mineral and boiled with the addition of tin-foil, assumes a beautiful blue 
 or violet color. Decomposed by fusion with sodium or potassium bisulphate. 
 
 Diff. Resembles hematite, but has a submetallic, nearly black, streak. 
 
 Obs. Some of the principal European localities of this species are : Krageroe, Egersnnd, 
 Arendal, Norway; Uddewalla, Sweden ; Ilmen Mts. (ilmenite) ; Iserwiese, Riesengebirge (iaer- 
 ine) ; Aschaffenburg ; Eisenach ; St. Cristophe (orichtonite). 
 
 Occurs in Warwick, Amity, and Monroe, Orange Co., N. Y. ; also near Edenville ; at Ches- 
 ter and South Royalston, Mass. ; at Bay Sb. Paul in Canada; also with labradorite at Chateau 
 Richer. Grains are found in the gold sands of California. 
 
 PEROFSKTTE.* 
 
 Isometric, Eose (fr. Ural). Habit cubic, with secondary planes incom- 
 pletely developed ; in cubes, octahedrons, and cubo-octahedrons, from 
 Arkansas. Twins: twinning-plane octahedral, Magnet Cove, Ark.; also 
 like f. 276, p. 93, Achmatovsk. Cleavage : parallel to the cubic faces 
 rather perfect. 
 
 IT.r=5-5. G.=4'02-4:'04:. Lustre metallic adamantine. Color pale 
 ye* low, honey-yellow, orange-yellow, reddish-brown, grayish-black to iron- 
 black. Streak colorless, grayish. Transparent to opaque. Double refract- 
 ing. 
 
OXYGEN COMPOUNDS. ANHYDROUS OXIDES. 271 
 
 Oomp. (Ca+Ti)0 3 =KO 3 =Titanic oxide 59'4, lime 40'6=100. 
 
 Pyr., etc. In the forceps and on charcoal infusible. With salt of phosphorus in O.F. dis 
 solves easily, giving a bead greenish while hot, which becomes colorless on cooling; in R.F. 
 the bead changes to grayish-green, and on cooling assumes a violet-blue color. Entirely de- 
 composed by boiling sulphuric acid. 
 
 Obs. Occurs at Achmatovsk, in the Ural ; in the valley of Zermatt ; at Wildkreuzjoch 
 in the Tyrol. Also at Magnet Cove, Arkansas. 
 
 DesCloizeaux has found that the yellow crystals from Zermatt have a complex twinned 
 structure, and are optically biaxial. Kokscharof, in his latest investigations, has shown that 
 the Russian specimens also exhibit phenomena in polarized light analogous to those of biaxial 
 crystals, though irregular. He proves, however, that crystallographically the crystals ex- 
 amined by him were unquestionably isometric, and adds also that almost all the Russian 
 perofskite crystals are penetration -twins. The latter fact explains the commonly observed 
 striations on the cubic planes, as also the incompleteness in the development of the other 
 forms. He refers the optical irregularities to the want of homogeneity in the crystals. Des- 
 Cloizeaux speaks of inclosed lamellae of a doubly-refracting substance analogous to the para- 
 site in boracite crystals (p. 170). 
 
 HYDROTITANITE. A decomposition-product of perofskite crystals from Magnet Cove, 
 Arkansas. Form retained but color changed to yellowish-gray (Koenig). 
 
 (c) COMPOUNDS OP PROTOXIDES AND SESQUIOXIDES,* KBO 4 (or RO+RO 3 ). 
 Spinel Group. Isometric (Octahedral). 
 
 SPINEL. 
 
 Isometric. Habit octahedral. Faces of octahedron sometimes convex. 
 Cleavage : octahedral. Twins : twinning-plane 1. 
 
 H.=8. G.=3-5-4'l. Lustre vitreous ; splendent 471 
 
 nearly dull. Color red of various shades, passing into 
 blue, green, yellow, brown, and black; occasionally 
 almost white. Streak white. Transparent nearly 
 opaque. Fracture conchoidal. 
 
 Comp., Var. The spinels proper have the formula MgA10 4 (=MgO 
 4-rtl0 3 ), or in other words contain chiefly magnesium and aluminum, 
 with the former replaced in part by iron (Fe), calcium (Ca), and man- 
 ganese (Mn) ; and the latter by iron (Fe). There is hence a grada- 
 tion into kinds containing little or no magnesium, which stand as 
 distinct species, viz., Hercynite and Gahnite. MgA10 4 Alumina 
 
 ^ma^esw. Magnesia Spinel. Clear red or reddish; transparent to translucent; 
 
 sometimes subtranslucent. Gk =3 '52-3 '58. Composition MgAlO 4 , with little or no Fe, and 
 sometimes chromium as a source of the red color. 2. Ceywnite, or Iron-Magnesia Spinel. 
 Color dark-green, brown to black, mostly opaque or nearly so. 0. =8 -8-8-6. Composition 
 M"Al0 4 + FeM0 4 . Sometimes the Al is replaced in part by Fe. 3. Pic-otite. Contains over 
 7 p. c. of chromium oxide. Color black. Lustre brilliant. G.=4'08. The original was 
 from a rock occurring about L. Lherz, called Lherzolite. 
 
 Pyr., etc. B B. alone infusible ; the red variety turns brown, and even black and 
 opaque as the temperature increases, and on cooling becomes first green, and then nearly 
 colorless and at last resumes the red color. Slowly soluble in borax, more readily in salt of 
 phosphorus, with which it gives a reddish bead while hot, becoming faint chrome-green on 
 
 * The compounds here considered are sometimes regarded as salts of the acide. HatlO* 
 that is, as aluminates, ferrates, etc. 
 
272 
 
 DESCRIPTIVE MINERALOGY. 
 
 cooling. The black varieties give reactions for iron with the fluxes. Soluble with difficulty 
 in concentrated sulphuric acid. Decomposed by fusion with sodium or potassium bisulphate. 
 
 Diff. Distinguished by its octahedral form, hardness, and inf usibility ; magnetite is 
 attracted by the mag-net, and zircon has a higher specific gravity. 
 
 ' Obs Spinel occurs imbedded in granular limestone, and with calcite in serpentine, gneiss, 
 and allied rocks. It also occupies the cavities of masses ejected from some volcanoes, e.g., 
 Mt. Somma. 
 
 Fine spinels are found in Ceylon ; in Siam, as rolled pebbles in the channels of rivers. 
 Occur at Aker in Sweden ; also at Monzoni in the Fassathal. 
 
 From Amity, N. Y., to Andover, N. J., a distance of about 30 miles, is a region of granular 
 limestone and serpentine, in which localities of spinel abound ; numerous about Warwick, 
 and at Monroe and Cornwall. Franklin, Sterling, Sparta, Hamburgh, and Vernon, N. J., 
 are other localities. At Antwerp, Jefferson Co., N. Y. ; at Bolton and elsewhere in Mass. 
 
 HERCYNTTE. FeAlO 4 (or FeO+AlO 3 ). Color black. Massive. Bohemia. 
 
 JACOBSITE (Damour). RfK) 4 , or (Mn,Mg) (Fe,Mn)0 4 . Color deep black. Occurs in dis- 
 torted octahedrons (magnetic) in a crystalline limestone at Jacobsberg, Sweden. 
 
 GAHNITE. Zinc Spinel. 
 
 Isometric. In octahedrons, dodecahedrons, etc., like spinel. 
 
 H.=7'5-8. G.=4-4'6. Lustre vitreous, or somewhat greasy. Color 
 dark green, grayish-green, deep leek-green, greenish-black, bluish-black, 
 yellowish- or grayish-brown ; streak grayish. Subtranslucent to opaque. 
 
 Comp., Var. Zn:MO 4 = Alumina 61 -3, oxide of zinc 38'7=100 ; with little or no magnesium. 
 The zinc sometimes replaced in small part by manganese or iron (Mn,Fe), and the aluminum 
 in part by iron (Fe). 
 
 Var. 1. A utomolite, or Zinc GaJmite; with sometimes a little iron. G. =4'l-4'6. Colors as 
 above given. 2. Dysluite, or Zinc-Manganese-Iron Gahnite. Composition (Zn,Fe,Mn) 
 (Al,Fe)O 4 . Color yellowish-brown or grayish-brown. G. =4-4 "6. Form the octahedron, or 
 the same with truncated edges. 3. Kreittonite, or Zinc- Iron OaJinite. Composition (Zn, 
 Fe,Mg)(Al,Fe,O 4 . Occurs in crystals, and granular massive. H.=7-8. G. =4 '48-4 "89. 
 Color velvet to greenish-black ; powder grayish-green. Opaque. 
 
 Pyr., etc. Gives a coating of zinc oxide when treated with a mixture of borax and soda 
 on charcoal. Otherwise like spinel. 
 
 Obs. Automolite is found at Fahlun, Sweden ; Franklin, N. Jersey ; Canton mine, Ga. ; 
 Dysluite at Sterling, N. J. ; Kreittonite at Bodenmais in Bavaria. 
 
 MAGNETITE. Magnetic Iron Ore. Magneteisenstein, Magneteisenerz, Germ. 
 
 Isometric. The octahedron and dodecahedron the most common forms. 
 
 475 
 
 Achmatovsk. Haddam. 
 
 Fig. 75 is a distorted dodecahedron. Cleavage : octahedral, perfect tc 
 
OXYGEN COMPOUNDS. ANHYDROUS OXIDES. 273 
 
 imperfect. Dodecahedral faces commonly striated parallel to the longer 
 diagonal. Twins : twinning-plane, 1 ; also in dendrites, branching at angles 
 of 60 (f. 277, p. 93). Massive, structure granular particles of various 
 sizes, sometimes impalpable. 
 
 II.=:5'5-6'5. G.=4'9-5'2. Lustre metallic submetallic. Color iron- 
 black ; streak black. Opaque ; but in mica sometimes transparent or 
 | nearly so ; and varying from almost colorless to pale smoky-brown and 
 black. Fracture subconchoidal, shining. Brittle. Strongly magnetic, 
 sometimes possessing polarity. 
 
 Comp., Var. FeFe0 4 (or Fe 8 4 )=FeO+Fe0 3 =Oxygen 27'6, iron 72'4=100 ; or iron ses- 
 quioxide 68-97, iron protoxide 31-03=100. The iron sometimes replaced in small part by 
 magnesium. Also sometimes titaniferous. 
 
 From the normal proportion of Fe to Fe, 1:1, there is occasionally a wide variation, and 
 thus a gradual passage to the sesquioxide Fe0 3 ; and this fact may be regarded as evidence 
 that the octahedral Fe0 3 , martite, is only an altered magnetite. 
 
 Pyr., etc. B. B. very difficultly fusible. In O.F. loses its influence on the magnet. With 
 the fluxes reacts like hematite. Soluble in hydrochloric acid.' 
 
 DifF. Distinguished from other members of the spinel group, as also from garnet, by its 
 being attracted by the magnet, as well as by its high specific, gravity. Also, when massive, 
 by its black streak from hematite and limonite. 
 
 Obs. Magnetite is mostly confined to crystalline rocks, and is most abundant in metamor- 
 phic rocks, though found also in grains in eruptive rocks. In the Archaean rocks the beds are 
 of immense extent, and occur under the same conditions as" those of hematite. It is an ingre- 
 dient in most of the massive variety of corundum called emery. The earthy magnetite is 
 found in bogs like bog-iron ore. 
 
 Extensive deposits occur at Arendal, Norway ; Dannemora and the Taberg in Smaoland ; 
 in Lapland. Fahlun in Sweden, and Corsica, afford octahedral crystals. 
 
 In N. America, it constitutes vast beds in the Archaean, in the Adirondack region, in 
 Northern N. York ; also in Canada ; at Cornwall in Pennsylvania, and at Magnet Cove, 
 Arkansas. Also found in Putnam Co, (Tilly Foster Mine), N. Y., etc. In Conn., at Haddam. 
 In Penn., at Chester Co. ; in mica at Pennsbury. In California^ in Sierra Co. ; in Plumaa 
 Co., and elsewhere. In M. Scotia, Digby Co., Nichol's Mt. 
 
 MAGNESIOFEKRITB (ma.gnoferrite). MgFe0 4 . In octahedrons; resembling magnetite. 
 Vesuvius. 
 
 FRANKLJNITE. 
 
 Isometric. Habit octahedral. Cleavage: octahedral, indistinct. Also 
 massive, coarse or fine granular to compact. 
 
 H.=5-5-6-5. G.=5-069. Lustre metallic. Color iron-black. Streak 
 dark reddish-brown. Opaque. Fracture conchoidal. Brittle. Acts slightly 
 on the magnet. 
 
 Comp. (Fe,Zn,Mn) (Fe,Mn)O 4 , or corresponding to the general formula of the spinel 
 group, though varying much in relative amounts of iron, zinc, and manganese. Analysis, 
 Sterling Hill, N. J., *Fe0 3 67 '42, A1O 3 0'65, FeO 15 -65, ZnO 6-78, MnO 9'53=100'12, Seyms. 
 Q. ratio for B : R=l : 1 nearly. In a crystal from Mine Hill, N. J., Seyms found 4' 44 p. c. 
 MnO 3 . 
 
 The evolution of chlorine in the treatment of the mineral is attributed by v. Kobell to the 
 presence of a little Mn0 3 (0.80 p. c.) as mixture, which Rammelsberg observes may have 
 come from the oxidation of some of the protoxide of manganese. 
 
 Pyr., etc. B.B. infusible. With borax in O.F. gives a reddish amethystine bead (man- 
 ganese), and in R.F. this becomes bottle-green (iron). With soda gives a bluish-green man- 
 ganate, and on charcoal a faint coating of zinc oxide, which is much more marked when a 
 mixture of borax and soda is used. Soluble in hydrochloric acid, with evolution of a smali 
 amount of chlorine. 
 
 Diff. Resembles magnetite, but is only slightly attracted by the magnet ; it also reacti 
 for zinc on charcoal B.B. 
 
 18 
 
274 
 
 DESCRIPTIVE MINERALOGY. 
 
 Obs. Occurs in cubic crystals near Eibach in Nassau ; in amorphous masses at Altenberg, 
 near Aix la Chapelle. Abundant at Hamburg, N. J., near the Franklin furnace; also at 
 Stirling Hill, in the same region. 
 
 CHROMITE.* Chromic Iron. Chromeisenstein, Germ. 
 
 Isometric. In octahedrons. Commonly massive ; structure fine granu- 
 lar or compact. 
 
 H.=5-5. G.=4-321-4-568. Lustre submetallic. Streak brown. Color 
 between iron-black and brownish-black. Opaque. Fracture uneven. 
 Brittle. Sometimes magnetic. 
 
 Comp. Fe6r0 4 , or (Fe,Mg,Cr) (Al,Fe,<3r)0 4 . Fe6r0 4 =Iron protoxide 32, chromium ses- 
 quioxide 68=100. Magnesia is generally present, and in amounts varying from 6-24 p. c. 
 
 Pyr., etc. B. B. in O. F. infusible ; in R. F. slightly rounded on the edges, and becomes 
 magnetic. With borax and salt of phosphorus gives beads, which, while hot, show O7ily a 
 reaction for iron, but on cooling become chrome-green ; the green color is heightened by 
 fusion on charcoal with metallic tin. Not acted upon by acids, but decomposed by fusion 
 with potassium or sodium bisulphate. 
 
 Diff. Distinguished from magnetite by the reaction for chromic acid with the blowpipe. 
 
 Obs. Occurs in serpentine, forming veins, or in imbedded masses. It assists in giving the 
 variegated color to verde-antique marble. Also occurs in meteorites. 
 
 Occurs in Syria ; Shetland ; in Norway ; in the Department du Var in France ; in Silesia 
 and Bohemia ; in the Urals; in New Caledonia. At Baltimore, Md., in the Bare Hills ; at 
 Cooptown. In Pennsylvania, in Chester Co. ; at Wood's Mine, near Texas, Lancaster Co. , 
 etc. Chester, Mass. In California, in Monterey Co., etc. 
 
 This ore affords the chromium oxide, used in painting, etc. The ore employed in England 
 is obtained mostly from Baltimore, Drontheim in Norway, and the Shetland Isles. 
 
 CHROMPICOTITE (Petersen). A magnesian chromite. Color black. New Zealand. 
 
 URANINITE* (Pitchblende ; Uranpecherz, Oerm.}. 
 Saxony, etc. 
 
 Massive. Black. 
 
 OHRYSOBBRYL. 
 
 Orthorhombic. /A I 129 38', O A l-l = 129 1 .' ; <J : I : a = 1-2285 : 
 
 2-1267 : 1. i-l A 1 = 136 52', i-l A 
 2-2 = 12_8 52', i4 A l- = 120 7'. 
 Plane *4 vertically striated ; and 
 sometimes also i4, and other verti- 
 cal planes. Cleavage : 14 quite 
 distinct ; i-l imperfect ; i-l more 
 so. Twins : twinning-plane 3-, as 
 in f. 477 (see p. 97), made up of 6 
 parts by the crossing of 3 crystals. 
 H.=8'5. G.=3-5-3-84. Lustre 
 vitreous. Color asparagus-green, 
 grass- green, emerald-green, green- 
 ish-white, and yellowish-green, 
 sometimes raspberry or columbine-red by transmitted light. Streak uncol- 
 ored. Transparent translucent. Sometimes a bluish opalescence inter- 
 nally. Fracture conchoidal, uneven. 
 
 Norway, Me. 
 
 Alexandrite. 
 
OXYGEN COMPOUNDS. ANHYDROUS OXIDES. 
 
 275 
 
 Var. 1. Ordinary. Color pale green, being colored by iron. G.=3.597, Haddam ; 3 '734. 
 Brazil; 3 '689, Ural, Rose; 3 '835, Orenburg-, Kokscharof. 2. Alexandrite. Color emerald- 
 green, but columbine-red by transmitted light. G-.=3'644, mean of results, Kokscharof. 
 Supposed to be colored by chrome. Crystals often very large, and in twins, like f. 477, 
 either six-sided or six-rayed. 
 
 Comp. BeiVIO 4 = Alumina 80'2, glucina 19 '8 100. Iron is also often present, though not 
 in the transparent varieties. Isomorphous with chrysolite. 
 
 Pyr., etc. B. B. alone unaltered ; with soda, the surface is merely rendered dull. With 
 borax or salt of phosphorus fuses with great difficulty. With cobalt solution, the powdered 
 mineral gives a bluish color. Not acted upon by acids. 
 
 Diff. extinguished by its extreme hardness, greater than that of topaz ; and its infusi- 
 bility ; also characterized by its tabular crystallization, in contrast with beryl. 
 
 Obs. In Brazil and also Ceylon ; at Marchendorf in Moravia ; in the Ural; in the Mourno 
 Mts., Ireland; at Haddam, Ct. ; at Norway, Me. 
 
 When transparent, and of sufficient size, chrysoberyl is cut with facets, and forms a beauti- 
 ful yellowish-green gem. If opalescent, it is usually cut en cabochon. 
 
 (d) DEUTOXIDES, 
 
 fiutile Group. Tetragonal. 
 
 OASSITERITE. Tin Stone. Zinnstein, Zinnerz, Germ. 
 
 Tetragonal. O A 1-& = 146 5' ; c = 0-6724. 1 A 1, pyr., = 121 40'; 
 /Al = 133 34'; l-aAl-fc, pyr., = 133 31'. Cleavage: 1 and i-i hardly 
 distinct. Twins: f. 478, twinning-plane 1--&; prewiring often complex 
 forms through the many modifying planes ; sometimes repeated parallel to 
 all the eight planes 1-*; also f. 480, a mefcagenic twin. Often in reniform 
 shapes, structure fibrous divergent ; also massive, granular or impalpable. 
 
 H.=6-7. Gr.:=6'4-7'l. Lustre adamantine, and crystals usually splen- 
 dent. Color brown or black ; sometimes red, gray, white, or yellow. 
 Streak white, grayish, brownish. Nearly transparent opaque. Fracture 
 Biibconchoidal, uneven. Brittle. 
 
 Var. 1. Ordinary, Tin- stone. In crystals and massive. G. of ordinary cryst. 6 '96; of 
 colorless, from Tipuani R., Bolivia, 6 '832, Forbes. 2. Wood Tin (Holz-Zinn, Germ.). In 
 botryoidal and reniform shapes, concentric in structure, and radiated fibrous internally 
 
276 
 
 DESCRIPTIVE MINERALOGY. 
 
 although very compact, with the color brownish, of mixed shades, looking somewhat like drj 
 wood in its colors. G-. of one variety 6*514. Stream tin is nothing but the ore in the state 
 of sand, as it occurs along the beds of streams or in the gravel of the adjoining region. 
 It has been derived from tin veins or rocks, through the wear and decomposition of the rocka 
 and transportation by water. 
 
 Comp. Sn0 2 = Tin 78 '6, oxygen 21 '4 100. 
 
 Pyr., etc. B.B. alone unaltered. On charcoal with soda reduced to metallic tin, and 
 gives a white coating. With the fluxes sometimes gives reactions for iron and manganese, 
 and more rarely for tantalic oxide. Only slightly acted upon by acids. 
 
 Diff. -Distinguished by its high specific gravity, its infusibility, and by its yielding metallic 
 tin B.B. from some varieties of garnet, sphalerite, and black tourmaline, to which it has 
 some resemblance. Specific gravity (6 '5) higher than that of rutile (4). 
 
 Obs Tin ore is met with in veins traversing granite, gneiss, mica schist, chlorite or clay 
 schist, and porphyry. Occurs in Cornwall ; in Devonshire ; in Bohemia and Saxony ; at 
 Limoges ; also in G-alicia ; Greenland ; Sweden, at Finbo ; Finland, at Pitkaranta. In the 
 E. Indies ; in Victoria and New South Wales ; in large quantities in Queensland. In Bolivia, 
 S. A. ; in Mexico. 
 
 In the United States, rare : in Maine, at Paris ; in 2f. Hamp., at Lyme ; in California, in 
 San Bernardino Co. ; in 2da7u>, near Boonville. 
 
 RUTILE. 4 
 
 Tetragonal. O A I-i = 147 12|', c = 0-6442. 1 A 1, pyr., = 123 7J', 
 /A 1 = 132 20'. Cleavage: /and i-i, distinct; 1, in traces. Vertical 
 planes usually striated. Crystals often acicular. Twins : (1) twinning-plane 
 l-i (see p. 94). (2) 3-, making a wedge-shaped crystal consisting of two 
 individuals. (3) 1-i and 3-i in the same crystal (fr. Magnet Cove, liessen- 
 berg). Occasionally compact, massive. 
 
 481 
 
 t3 
 
 483 
 
 Graves Mtn., Ga. 
 
 H.=6-6-5. G.= 4-18-4-25. Lustre metallic- adamantine. Color red- 
 dish-brown, passing into red ; sometimes yellowish, bluish, violet, black ; 
 rarely grass-green. Streak pale brown. Subtransparent opaque. Frac- 
 ture subconchoidal, uneven. Brittle. 
 
 Comp., Var Titanic oxide, Ti0 2 = Oxygen 39, titanium 61 =100. Sometimes a little iron 
 is present. 
 
 Pyr., etc. B.B. infusible. With salt of phosphorus gives a colorless bead, which in R.F. 
 assumes a violet color on cooling. Most varieties contain iron, and give a brownish -yellow 
 or red bead in R.F., the violet only appearing after treatment of the bead with metallic tin 
 on charcoal. Insoluble in acids ; made soluble by fusion with an alkali or alkaline carbonate. 
 The solution containing an excess of acid, with the addition of tin-foil, gives a beautiful 
 riolet-color when concentrated. 
 
OXYGEN COMPOUNDS. ANHYDKOUS OXIDES. 
 
 277 
 
 Diff. Characterized by its peculiar sub-adamantine lustre, and brownish-red color. Differs 
 horn V armaline, vesuvianite, augite in being entirely unaltered when heated alone B.B. 
 Spec; Re gravity about 4, cassiterite 6 '5. 
 
 O T oa. -Rutile occurs in granite, gneiss, mica slate, and syenitic rocks, and sometimes in 
 granula^ limestone and dolomite. It is generally found in imbedded crystals, often in masses 
 of quartz or feldspar, and frequently in acicular crystals penetrating quartz. Very commonly 
 implanted in regular position upon crystals of hematite, as from Cavradi in the Tavetschthal. 
 Occurs in Norway; Finland ; Saualpe, Carinthia; in the Urals ; in the Tyrol ; at St. Gothard 
 near Freiberg ; at Ohlapian in Transylvania. 
 
 In Maine, at Warren. In Vermont, at Waterbury and elsewhere. In Mass. , at Barre , 
 Shelburne; Sheffield. In Conn., at Lane's mine, Monroe. In N. York, in Orange Co.; 
 Edenville ; Warwick. In Penn., Chester Co. In N. Car., at Crowder's Mountain. In 
 Georgia, in Habersham Co. ; in Lincoln Co., at Graves' Mountain. In Arkansas, at Magnet 
 Cove. 
 
 Titanium oxide is employed for a yellow color in painting porcelain, and also for giving the 
 requisite tint to artificial teeth. 
 
 Binnenthal. 
 
 OCTAHEDRITE.* Anatase. 
 
 Tetragonal. Al-i = 119 22'; c = 1 '77771. Commonly octahedral 
 or tabular. 1 A 1, pyr., = 
 97 51'. 7M = 158 18'. 
 Cleavage: 1 and 0, per- 
 fect. 
 
 H.=5-5-6. G.=3-82- 
 3-95 ; sometimes 4-11-4-16 
 after heating. Lustre 
 metallic-adamantine. Col- 
 or various shades of brown, passing into indigo-blue, 
 and black ; greenish-yellow by transmitted light. 
 Streak uncolored. Fracture subconchoidal. Brittle. 
 
 Comp. Like rutile and brookite, pure titanic oxide. 
 
 Pyr., etc. Same as for rutile. 
 
 Obs. Abundant at Bourg d'Oisans, in Dauphiny ; also in the Bin- 
 nenthal (including here Kenngott's wiserinfi, f. 484, as shown by Klein, Jahrb. Min., 1875, 
 337); at Pfitsch Joch, Tyrol; near Hof in the Fichtelgebirge ; Norway; the Urals; in 
 Devonshire, near Tavistock ; at Tremadoc, in North Wales ; in Cornwall ; in Brazil in quartz. 
 In the U. States, at Smithfield, R. I. 
 
 HAUSMANNITE. Mn 3 O 4 =2MnO,Mn0 2 . Tetragonal, A 1-i =130 25'. Color brownish- 
 black. Thuringia ; Harz, etc. 
 
 BKAUNITE. 2(2MnO,MnO 2 )+MnO 2 ,SiO,. Tetragonal, 0Al-=135 26'. Color dark 
 brownish-black. Thuringia ; Norway, etc. 
 
 MINIUM (Mennige, Germ.). PbaO 4 =PbO a +2PbO. Badenweiler; Wythe Co., Va., etc. 
 
 BROOKITE* 
 
 Orthorhombic (?). /A 7=99 50' (-100 50') : O A 1-^ = 131 42'; 
 i : I : d = 1-1620 : 1*1883 : 1. Cleavage : /, indistinct ; O, still more so. 
 
 H.=5-5-6. G.=4-12-4-23, brookite; 4-03-4-085, arkansite. Hair-brown, 
 yellowish, or reddish, with metallic adamantine lustre, and translucent 
 
278 
 
 DESCKIKnVE MINERALOGY. 
 
 (brookite); also ircm-black, opaque, and submetallic (arkaneite). Streak 
 uneolored grayish, yellowish. Brittle. 
 
 487 
 
 488 
 
 Arkansas. 
 
 if 
 
 EUenville, N. Y. 
 
 Miask, TJral. 
 
 Comp. Pure titanic oxide, Ti0 2 , like rutile and octahedrite. 
 
 Pyr., etc. Same as for rutile. 
 
 Obs. Brookite occurs at Bourg d'Oisans in Dauphiny ; at St. Gothard ; in the Urals, near 
 Miask ; in thick black crystals (arkansite f. 486) at Magnet Cove, Arkansas, sometimes altered 
 to rutile by paramorphism ; at Ellenville, Ulster Co., N. Y. ; at Paris, Maine. 
 
 Schrauf has announced (Atlas Min., Reich. IV.) that he has found brookite to be monodinie 
 (and isomorphous with wolframite). He distinguishes three types having different axial 
 relations. The measurements of v. Rath, however, seem to show that in part it must be 
 orthorhombio. 
 
 EUMANITE. From Chesterfield, Mass., may be identical with brookite. 
 
 Orthorhombic. 
 
 PYROLUSITE.* Polianite. 
 
 IM = 93 40', O A 14 = 142 11' ; t : I : & = 0-776 : 
 1*066 : 1. Cleavage /and i-4. Also columnar, often 
 divergent ; also granular massive, and frequently in 
 renifonn coats. Often soils. 
 
 H.=2-2-5. G.=4-82. Turner. Lustre metallic. 
 Color iron-black, dark steel-gray, sometimes bluish. 
 Streak black or bluish-black, sometimes submetallic. 
 Opaque. Rather brittle. 
 
 Comp. MnO 2 =Manganese 63'2, oxygen 36*8-100. 
 
 Fyr., etc B.B. alone infusible; on charcoal loses oxygen. A manganese reaction with 
 borax. Affords chlorine with hydrochloric acid. 
 
 Diflf. Hardness less than that of psilomelane. Differs from iron ores in its reaction for 
 manganese B. B. Easily distinguished from psilomelane by its inferior hardness, and usually 
 by being crystalline. 
 
 Obs. Occurs extensively at Elgersberg near Ilmenau in Thuringia ; at Vorderehrensdorf in 
 Moravia ; at Platten in Bohemia, and elsewhere. Occurs in the United States in Vermont, 
 at Brandon, etc. ; at Con way, Mass. ; at Winchester, N. H. ; at Salisbury and Kent, Conn. 
 In California, on Red island, bay of San Francisco. In New Brunswick, near Bathurst. In 
 Nova Scotia, at Walton ; Pictou, etc. 
 
 Pyrolusite and manganite are the most important of the ores of manganese. Pyrolusite 
 parts with its oxygen at a red heat, and is extensively employed for discharging the brown 
 and green tints of glass. It hence received its name from irvp, fire, and /i'u, to wash. 
 
 C.REDNERITE. Cu 3 Mn 2 O 9 , or 3CuO+2MnO s . Foliated. Color black. Thuringia. 
 
OXYGEN COMPOUNDS. HYDKOUS OXIDES. 
 
 279 
 
 B. HYDKOUS OXIDES. 
 
 TURGITE. 
 
 Compact fibrous and divergent, to massive ; often botryoidal and sta- 
 lactitic like limonite. Also earthy, as red ochre. 
 
 H.=5-6. G.=: 3-56-3-74, from Ural; 4-29-4-49, fr. Hof; 4-681, fr. 
 Horhausen ; 4-14, fr. Salisbury. Lustre submetallic and somewhat satin- 
 like in the direction of the fibrous structure; also dull earthy. Color 
 reddish-black, to dark red ; bright-red when earthy ; botryoidal surface 
 often lustrous, like much lirnonite. Opaque. 
 
 Comp. H 2 Fe,O 7 =Iron sesquioxide 94 '7, water 5 '3 100. 
 
 Pyr., etc. Heated in a closed tube, flies to pieces in a remarkable manner ; yields water. 
 Otherwise like hematite. 
 
 Diff. Distinguished from hematite and limonite by its superior hardness, the color of its 
 streak, and B.B. its decrepitation. 
 
 Obs. A very common ore of iron. Occurs at the Turginsk copper mine near Bosgolovsk, 
 in the Ural ; near Hof in Bavaria, and Siegen in Prussia ; at Horhausen. In the U. S. it 
 occurs at Salisbury, Ct. 
 
 DIASPORE. 
 
 Orthorhombic. I A 1= 93 42f, A l-l =147 
 0-64425 : 1-067 : 1. i-lM-l = 121 7^, a A 1-2 = 104 
 14J', i-lM = 116 54^. Crystals usually thin, flattened 
 parallel to i-l, sometimes acicular; commonly implanted. 
 Cleavage : i4 eminent ; i-2 less perfect. Occurs foliated 
 massive and in thin scales; sometimes stalactitic. 
 
 H. = 6-5-7. G.= 3-3-3-5. Lustre brilliant and pearly on 
 cleavage-face ; elsewhere vitreous. Color whitish, grayish- 
 white, greenish-array, hair-brown, yellowish, to colorless ; 
 sometimes violet-blue in one direction, reddish plumb-blue 
 in another, and pale asparagus-green in a third. When thin, 
 translucent subtranslucent. Very brittle. 
 
 Comp H 2 A10 4 = Alumina 85'1, water 14'9=100 ; a little phosphorus 
 pentoxide is often present. 
 
 Pyr., etc. In the closed tube decrepitates strongly, separating into pearly white scales, 
 and at a high temperature yields water. The variety from Schemnitz does not decrepitate. 
 Infusible ; with cobalt solution gives a deep blue color. Some varieties react for iron with 
 the fluxes. Not attacked by acids, but after ignition becomes soluble in sulphuric acid. 
 
 Diff, Distinguished (B.B.) by its decrepitation and yielding water ; as also by the reaction 
 for alumina with cobalt solution. Resembles some varieties of hornblende, but is harder. 
 
 Obs. Commonly found with corundum or emery. Occurs in the Ural ; at Schemnitz ; 
 at Broddbo near Fahlun ; in Switzerland ; in Asia Minor, and the Grecian islands ; in Chester 
 Co., Pa. ; at the emery mines of Chester, Mass. ; N. Carolina. 
 
 IHaspore was named by Haiiy from diaarreipcj, to scatter, alluding to the usual decrepitation 
 before the blowpipe. 
 
iz 
 
 iz 
 
 280 DESCRIPTIVE MINERALOGY. 
 
 GOTHITE. 
 
 Orthorhombic. I^I= 94 52' (B. & M.) ; A 14 = 146 33' ; c : I : d 
 = 0-66 : 1*089 : 1. in prisms longitudinally striated, and 
 often flattened into scales or tables parallel to the shorter 
 diagonal. Cleavage : brachydiagonal, very perfect. Also 
 fibrous; foliated or in scales; massive; reniform; stalac- 
 titic. 
 
 H. =5-5-5. G.=4-0-4*4. Lustre imperfect adamantine. 
 Color yellowish, reddish, and blackish-brown. Often blood- 
 red by transmitted light. Streak brownish-yellow ochre- 
 yellow. 
 
 Var. 1. In thin scale-like or tabular crystals, usually attached by one 
 edge. 2. In acicular or capillary (not flexible) crystals, or slender prisms, often radiately 
 grouped : the Needle- Ironstone (Nadeleuemteiii). It passes into (b) a variety with a velvety 
 surface : the Przibramite (Sammelblende) of Przibram is of this kind. Other varieties are 
 columnar or fibrous, scaly-fibrous, or feathery columnar ; compact massive, with a flat con- 
 choidal fracture ; and sometimes reniform or stalactitic. 
 
 Comp. H 2 FeO4=H 6 Fe06 + 2Fe0 3 Iron sesquioxide 89'9, water 10-1 = 100. 
 
 Pyr., etc. In the closed tube gives off water and is converted into red iron sesquioxide. 
 With the fluxes like hematite ; most varieties give a manganese reaction, and some treated 
 in the forceps in O.F., after moistening in sulphuric acid, impart a bluish-green color to the 
 flame (phosphoric acid). Soluble in hydrochloric acid. 
 
 Obs. Found with the other iron oxides, especially hematite or limonite. Occurs at Eiser 
 feld ; in Nassau ; at Zwickau in Saxony ; in Cornwall ; in Somersetshire, at the Providence 
 iron mines. In the U. States, near Marquette, L. Superior; in Penn., near Easton; in 
 California, at Burns Creek, Mariposa Co. 
 
 Named Gothite after the poet-philosopher G-othe; and Pyrrliosiderite from nvppog, fire-red, 
 and cidrjpos, iron. 
 
 MANGANITE. 
 
 Orthorhombic. 7 A 1= 99 40', O A l-l 147 9J' ; c : I : d 0-6455 : 
 1-185 : 1. Twins: twinn ing-plane 1-2 (f. 296, p. 96). Cleavage: i-l very 
 perfect, 1 perfect. Crystals longitudinally striated, and often grouped in 
 bundles. Also columnar; seldom granular; stalactitic. 
 
 Ii.=4. G. =4-2-4-4. Lustre submetallic. Color dark steel-gray iron- 
 black. Streak reddish-brown, sometimes nearly black. Opaque ; minute 
 splinters sometimes brown by transmitted light. Fracture uneven. 
 
 Comp. H 2 Mn0 4 =H 8 Mn06 + 2Mn0 3 =Manganese sesquioxide 89 "8 (=Mn 62 '5, O 27 '3), 
 
 Pyr., etc In the closed tube yields water ; otherwise like braunite. 
 
 Obs Occurs in veins traversing porphyry, at Ilefeld in the Harz ; in Thuringia ; Undenaea 
 in Sweden; Christiansand in Norway; Cornwall, at various places; also in Cumberland, 
 Devonshire, eta In Nova Scotia, at Cheverie, etc. In New Brunswick, at Shepody moun- 
 tain, Albert Co., etc. 
 
 LIMONITE. Brown Hematite. Brauneisenstein, Germ. 
 
 Usually in stalactitic and botryoidal or mammillary forms, having a fibrous 
 or subfibrous structure; also concretionary, massive; and occasionally 
 earthy. 
 
OXYGEN COMPOUNDS. HYDROUS OXIDES. 281 
 
 H. = 5-5*5. G. =3-6-4:. Lustre silky, often subraetallic ; sometimes dull 
 and earthy. Color of surface of fracture various shades of brown, com- 
 monly dark, and none bright ; sometimes with a nearly black varnish-like*" 
 exterior ; when earthy, brownish-yellow, ochre-yellow. Streak yellowish- 
 brown. 
 
 Var.- (1) Compact. Submetallic to silky in lustre ; often stalactitic, botryoidal, etc. (2) 
 OcJireous or earthy, brownish-yellow to ochre-yellow, often impure from the presence of clay, 
 sand, etc. (3) Bog ore. The ore from marshy places, generally loose or porous in texture, 
 often petrifying leaves, wood, nuts. etc. (4) Brown day -ironstone, in compact masses, often 
 in concretionary nodules, having a brownish-yellow streak, and thus distinguishable from the 
 clay- ironstone of the species hematite and siderite ; it is sometimes (a) pisolitic, or an aggre- 
 gation of concretions of the size of small peas (Bohnerz, Qerm.}\ or (b) oolitic. 
 
 Comp. H 6 Fe 2 09=H 6 Fe06 + Fe03=Iron sesquioxide 85 '6, water 14'4=100. In the bog 
 ores and ochres, sand, clay, phosphates, manganese oxides, and humic or other acids of organic 
 origin are very common impurities. 
 
 Fyr., etc. Like gothite. Some varieties give a skeleton of silica when fused with salt of 
 phosphorus, and leave a siliceous residue when attacked by acids. 
 
 Diff. Distinguished from hematite by its yellowish streak, inferior hardness, and its reac- 
 tion for water. Does not decrepitate, B.B., like turgite. 
 
 Obs. Limonite occurs in secondary or more recent deposit*, in beds associated at times 
 with barite, siderite, calcite, aragonite, and quartz ; and often with ores of manganese ; also 
 'as a modern marsh deposit. It is in all cases a result of the alteration of other ores, through 
 exposure to moisture, air, and carbonic or organic acids ; and is derived largely from the 
 change of pyrite, siderite, magnetite, and various mineral species (such as mica, augite, horn- 
 blende, etc. }, which contain iron in the protoxide state. 
 
 Abundant in the United States. Extensive beds exist at Salisbury and Kent, Conn. , also 
 in the neighboring towns of N. Y., and in a similar situation north; at Richmond and Lenox, 
 Mass. ; in Vermont, at Bennington, etc. 
 
 Limonite is one of the most important ores of iron. The pig iron, from the purer varieties, * 
 obtained by smelting with charcoal, is of superior quality. That yielded by bog ore is what 
 is termed cold short, owing to the phosphorus present, and cannot therefore be employed in 
 the manufacture of wire, or even of sheet iron, but is valuable for casting. The hard and 
 compact nodular varieties are employed in polishing metallic buttons, etc. 
 
 MELANOSIDERITE. Near limonite, but containing 7 '39 p. c. SiO -2, perhaps as an impurity. 
 Cooke regards it as a very basic silicate of iron. G. 3*39. Westchester, Penn. 
 
 XANTHOSIDERITE. H 4 Fe05=FeO 3 81 '6, H 2 18'4100; or H 6 Fe0 8 (Ramm.). In fine 
 needles. Color yellow, brown. Ilmenau ; the Harz. 
 
 BEAUXITE. Occurs in concretionary grains. Color whitish to brown. Composition doubt- 
 ful, perhaps Al(Fe)O 3 +2aq. Beaux, near Aries, France; near Lake Wochein, Styria (woch&i- 
 nite) ; French Guiana. 
 
 BRUOITE.* 
 
 Khombohedral. K/\R = W 22*', O/\ = 119 39*'; c = 1-52078 
 (Hessenberg). Crystals often broad tabular. Cleavage: basal, eminent 
 
 492 493 
 
 Low's Mine, Texas. Wood's Mine, Texas. 
 
 folia easily separable, nearly as in gypsum. Usually foliated massive, 
 Also fibrous, fibres separable and elastic. 
 
232 DESCRIPTIVE MINERALOGY. 
 
 H. = 2-5. G. = 2-35-2-44. Lustre pearly on a cleavage-face, elsewhere 
 between waxy and vitreous ; the fibrous silky. Color white, inclining to 
 gray, blue, or green. Streak white. Translucent subtranslncent. Sectile. 
 Thin laminae flexible. 
 
 Comp. H 2 Mg0 2 Magnesia 69, water 31 = 100. 
 
 Var. 1. Foliated. 2. Fibrous ; called nemalite, containing 4 or 5 p. c. of FeO. 
 
 Pyr., etc. In the closed tube gives off water, becoming opaque and friable, sometimes 
 turning gray to brown. B.B. infusible, glows with a bright light, and the ignited mineral 
 reacts alkaline to test paper. With cobalt solution gives the violet-red color of magnesia. 
 The pure mineral is soluble in acids without effervescence. 
 
 DifF. Distinguished by its infusibility. Differs from talc in its solubility in acids. 
 
 Obs. Brucite accompanies other magnesian minerals in serpentine, and has also been found 
 in limestone. Occurs at Swinaness in Unst, Shetland Isles ; in the Urals ; at Goujot in 
 France ; near Filipstadt in Wermland. It occurs at Hoboken, N. J. ; in Richmond Co. , N. Y. ; 
 at Brewster, N. Y. ; at Texas, Pa. The fibrous variety (nemalite) occurs at Hoboken, and 
 at Xettes in the Vosges. 
 
 GIBBSITE. 
 
 Monoclini.c (DesCl.). In small hexagonal crystals with replaced lateral 
 edges. Planes vertically striated. Cleavage : basal or eminent. Occa- 
 sionally in lamello-radiate spheroidal concretions. Usually stalactitic, or 
 small mammilla^ and incrusting, with smooth surface, and often a faint 
 fibrous structure within. 
 
 H.=: 2-5-3-5. G. = 2-3-2-4. Color white, grayish, greenish, or reddish- 
 white ; also reddish-yellow when impure. Lustre of O pearly ; of other 
 faces vitreous ; of surface of stalactites faint. Translucent ; sometimes 
 transparent in crystals. A strong argillaceous odor when breathed on. 
 Tough. 
 
 Var. 1. In crystals : the original hydraryillite. 2. Stalactitic ; gibbsite. 
 
 Comp. H 8 A10 6 Alumina 65-5, water 34-5 = 100. 
 
 Pyr., etc. In the closed tube becomes white and opaque, and yields water. B.B. infusible, 
 whitens, and does not impart a green color to the flame. With cobalt solution gives a deep- 
 blue color. Soluble in concentrated sulphuric acid. 
 
 Diff. --Resembles chalcedony in appearance, but is softer. 
 
 Obs. The crystallized gibbsite occurs near Slatoust in the "Oral; at Gumuchdagh, Asia 
 Minor; on corundum at Unionville, Pa.; in Brazil. The stalactitic occurs at Richmond, 
 Mass.; at the Clove mine, Duchess Co., N. Y.; in Orange Co., N. Y. 
 
 Rose's hydrargillite (Urals, 1839) is identical with gibbsite (Torrey, 1822), and must receive 
 this name. An uncertain mineral from Richmond afforded Hermann 38 p. c. of phosphoric 
 acid, but a phosphate, if it really occurs there, is not gibbsite. 
 
 PYROCHROITE. H 2 MnO 2 =Manganese protoxide 79 '8, water 20-2=100. Foliated. Color 
 white. Mine of Paisberg. Filipstadt, Sweden. 
 
 HYDROTALCITE from Snarum, Norway, and VOLKNERITE from the Urals, contain alumina, 
 magnesia, and water with more or less carbon dioxide. Probably mixtures, containing 
 brucite, gibbsite, etc. HOUGHITE from Oxbow and Rossie, N. Y., is a similar mineral 
 derived from the alteration of spinel. NAMAQUALITE (Church}. A related mineral; from 
 Namaqualand, So. Africa. 
 
 FSILOMELANE.* 
 
 Massive and botryoidal. Reniform. Stalactitic. 
 
 H.=r5-6. G.=3-7-4-7. Lustre submetallic. Streak brownish-black, 
 Binning. Color iron-black, passing into dark steel-gray. Opaque. 
 
OXYGEN COMPOUNDS. HYDROUS OXIDES. 283 
 
 Oomp. Somewhat doubtful. Contains manganese oxide, with varying amounts of baryta, 
 and potash (lithia), and also water. General formula, according to Rammelsberg, R 5 9 =RG 
 +4Mn0 2 , where R is Ka 2 , Ba or Mn. Analyses: 
 
 O MnO BaO K 2 O H 2 O 
 
 1. Thuringen 11-48 6576 16 '59 5-25 CuO 0-59, CoO 0'79, CaO 0'51=100-7S 
 
 Olschewsky. 
 
 2. Ilmenau 15 '82 77'23 0'12 5'29 CaO 0'91, CuO 0'40=99-77 Clausbruch. 
 
 Pyr., etc. In the closed tube most varieties yield water, and all lose oxygen on ignition; 
 with the fluxes reacts for manganese. Soluble in hydrochloric acid, with evolution of 
 chlorine. 
 
 Ob*. This is a common ore of manganese. It occurs in Devonshire and Cornwall ; at 
 Ilefeld in the Harz ; also at Johanngeorgenstadt ; Schneeberg ; Ilmenau ; Siegen, etc. It 
 forms mammillary masses at Chittenden, Irasburg, and Brandon, Vt. 
 
 WAD. 
 
 The manganese ores here included occur in amorphous and reniform 
 masses, either earthy or compact, and sometimes incrusting or 'as stains. 
 They are mixtures of different oxides, and cannot be considered chemical 
 compounds or distinct mineral species. 
 
 H.=0-5-6. G.=3-4-26 ; often loosely aggregated, and feeling very light 
 to the hands. Color dull black, bluish or brownish-black. 
 
 Comp., Var. Perhaps H 2 Mn 2 5 =:2Mn0 2 +aq (Rammelsberg), but in all cases mixed with 
 Other ingredients. 
 
 Varieties : (A) Manganesian ; (B) Cobaltiferous ; (C) Cupriferous. 
 
 A. BOG MANGANESE. Consists mainly of manganese dioxide and water, with some iron 
 sesquioxide, and of hen silica, alumina, baryta. 
 
 B. ASBOLITE, or Earthy Cobalt, is wad containing cobalt oxide, which sometimes amounts 
 to 32 p. c. LithiopTwritt, heterogenite, and rabdionite belong near here. 
 
 C. LAMPADITE, or Cupreous Manganese. A wad containing 4 to 18 p. c. of copper oxide, 
 and often cobalt oxide also. It graduates into black copper (Melaconite). G. =3' 1-8*2. 
 
 Pyr., etc. Wad reacts like psilomelane. Earthy cobalt gives a blue bead with salt of 
 phosphorus, and when heated in R. F. on charcoal with tin, some specimens yield a red opaque 
 bead (copper). Cupreous manganese gives similar reactions, and three varieties give a strong 
 manganese reaction with soda, and evolve chlorine when treated with hydrochloric acid. 
 
 Obs. The above ores are results of the decomposition of other ores partly of oxides, and 
 partly of manganesian carbonates. Wad or bog manganese is abundant in the counties of 
 Columbia and Dutchess, JS". Y. There are large deposits of bog manganese at Blue Hill Bay, 
 Dover, and other places in Maine. 
 
 Earthy cobalt occurs at Rieehelsdorf in Hesse ; Saalf eld in Thuringia ; at Nertschinsk in 
 Siberia ; at Alderly Edge in Cheshire. 
 
 CHALCOPHANITE. Rhombohedral. In druses of minute tabular crystals ; also in stalacti- 
 tic aggregates. H. =2 '5. G. 3 "907. Lustre metallic. Color bluish-black. Analysis gave 
 MnO a 59*94, MnO 6 "58, ZnO 21-70, FeO 3 0'25, H a O 11-58=100-05. Composition 2Mn0 2 -H 
 (Mn,Zn)0 + 2aq. If half the water were basic, the formula might be written 2RMn0 3 +aq, 
 where R = Mn,Zn and H-,. B.B. becomes of a copper color, hence the name fcoAxof, brass, 
 bronze, and <paivG), to appear). Stirling Hill, N. J. (Moore.} 
 
284 
 
 DESCKIFIIVE MINEBALOGY. 
 
 8. OXIDES OF ELEMENTS OF THE ARSENIC AND SULPHUB GROUTS, SERIES II 
 
 VALENTINITE. Weisspiesglaserz, Germ. 
 
 Orthorhombic. 7A 7= 136 58'; A l-l = 105 35'; c : I : a = 3*5868 : 
 2*5365 : 1. Often in rectangular plates with the lateral 
 edges bevelled, and in acicular rhombic prisms. Cleav- 
 age : /, highly perfect, easily obtained. Also massive ; 
 structure lamellar, columnar, granular. 
 
 H. 2-5-3. G.=5-566, crystals from Braunsdorf. 
 Lustre adamantine, i-l often pearly ; shining. Color 
 snow-white, occasionally peach-blossom red, and ash-gray 
 to brownish. Streak white. Translucent subtrans- 
 
 Comp. Sb 2 O 3 := Oxygen 16 '44, antimony 83 "56 = 100. 
 Ob*. Found at Przibram in Bohemia ; at Felsobanya in Hungary ; 
 Braunsdorf in Saxony. Also at South Ham, Canada East. 
 
 SENARMONTITE.^ Same composition as the above, but crystallizes in isometric octahe- 
 drons. G. =5 "2-5 '3. Perneck, Hungary; Cornwall; Haraclas in Algeria ; S. Ham, Canada. 
 
 CLAUDETITE ; ARSENOLITE. Both As 2 O 3 . The loriner is orthorhonibic, the latter iso- 
 metric. They thus correspond to the two forms of Sb 2 O 3 (see above). Claudetite (G. =3-85) 
 occurs in thin plates at the San Domingo mines, Portugal. Arsenolite (G.=3'698) occurs 
 usually in capillary crystals, also stalactitic ; earthy. Andreasberg ; JoacLimsthal ; Corn- 
 wall ; Ophir mine, Nevada ; California. 
 
 Bi SMITE (Wismuthocker, Germ ). Bi 2 O 3 . Occurs massive, earthy. Schneeberg; Joachims 
 thai; Cornwall. KARELINITE. 3BiO+BiS. Massive. Color lead-gray. G.=6'60. Savo- 
 dinsk mine in the Altai. 
 
 MOLYBDITE (Molybdanocker, Germ.}. Composition Mo0 3 . In radiated crystallizations, as 
 an incrustation, etc. Occurs with molybdenite. At Westmoreland, New Hampshire ; Chester, 
 Penn. ; Virginia City, Nevada. ILSEMANNITE, near the above. Bleiberg. Carinthia. 
 
 TUNGSTITE. WO 3 . Pulverulent and earthy. Cornwall; Monroe, Ct. MEYMACITE 
 (Carnot). A hydrated tungstite. Meymac, Correze. 
 
 KERMESITE (Antimonblende, Germ.). Composition Sb 2 S 2 0=2SboS 3 +Sb 2 3 . In capillary 
 crystals. Color cherry-red. Braunsdorf, Saxony ; Allemont ; South Ham, Canada East. 
 
 CERVANTITE. SbO 2 =Sb 2 3 + Sbi06. Color yellow. Besults from alteration of stibnite. 
 Spain ; Tuscany ; Hungary, etc. ; South Ham, Canada. 
 
 3. OXIDES OF THE CARBON-SILICON GJROUP, SEEIES II. 
 
 QUARTZ. 4 
 
 Rhombohedral, and for the most part hemihedral to the rhombohedron 
 (or tetartohedral to the hexagonal prism). R/\R = $ 15', Ot\R = 128 
 13' ; c = 1-0999. iASJ-2 = 142 V,R A -l,ov.*, = 103 34', R A -1, adj., 
 = 133 44/, R A i, ov. 2-2, = 113 8'. Cleavage : R, 1, and i very indis- 
 tinct: sometimes effected by plunging a heated crystal in cold water. 
 Crystals sometimes very short, but general habit prismatic ; the crystals 
 
OXYGEN COMPOUNDS SILICA. 
 
 285 
 
 much elongated, sometimes fine acicular; usually implanted by one 
 extremity of the prism. Prismatic faces * commonly striated horizontally, 
 and thus distinguishable, in distorted crystals, from the pyramidal. Crys- 
 tals often grouped by juxtaposition, not proper twins. Frequently in radi- 
 ated masses with a surface of pyramids, or in druses having a surface of 
 pyramids or short crystals. Twins : twinning-plane, (1), the basal plane 
 6 (f. 506) ; very generally penetration-twins, as illustrated in f. 265, p. .89. 
 (2) The pyramid 1-2, truncating the ed.o-e between -\-R and 7^, divergence 
 of axes 84 33', Other methods of twinning rare, parallel to i, to ./?, to 
 
 503 
 
 501 
 
 502 
 
 \R, etc. (Jenzsch). Also in pseudo-trillings on calcite, with 2-2 as the 
 approximate twinning-plane (see f. 336, p. 101). 
 
 Massive; coarse or fine granular to flint-like or crypto-crystalline 
 Sometimes mammillary, stalactitic, and in concretionary forms. 
 
 505 
 
 506 
 
 H.=:7. G. 2-5-2-8 ; 2-6413-2-6541 (Beudant). Lustre vitreous, some 
 times inclining to resinous ; splendent nearly dull. Colorless when pure ; 
 often various shades of yellow, red, brown, green, blue, black, 
 white, of pure varieties ; if impure, often the same as the color, but much 
 paler. Transparent opaque. Fracture perfect conchoidal subconchoi- 
 dal. Tough brittle friable. Polarization circular, see pp. 142-144 
 
286 DESCRIPTIVE MINERALOGY 
 
 Comp. Pure silica, or Si0 2 =Oxygen 53*33, silicon 46'67=:100. In massive varieties often 
 mixed with a little opal-silica. Impure varieties contain iron sesquioxide, calcium carbonate, 
 clay, sand, and various minerals. 
 
 Var. I, Crystallized (pheuocrystalline), vitreous in lustre. 2. Flint-like, massive, or cryp- 
 
 tocrystalline. The first division includes all ordinary vitreous quartz, whether having crys- 
 talline faces or not. The varieties under the second are in general acted upon somewhat more 
 by attrition, and by chemical agents, as fluohydric acid, than those of the first. In all kinds 
 made up of layers, as agate, successive layers are unequally eroded. 
 
 A. PHENOCRYSTALLINE OR VITREOUS VARIETIES. 
 
 1. Ordinary Crystallized ; Rock Crystal. Cv^loufess quartz, or nearly so, whether in dis- 
 tinct crystals or not. 
 
 2. Asteriated ; Star quartz (Stern quartz, Germ.). Containing within the crystal whitish 
 or colored radiations along the diametral planes. 
 
 3. Amethystine; Amethyst. Clear purple, or bluish- violet. The color is supposed to ba 
 due to manganese. 
 
 4. Hose. Rose-red or pink, but becoming paler on exposure. Common massive, and then 
 usually much cracked. Lustre sometimes a little greasy. Fuchs states that the color is due 
 to titanic oxide. It may come in part from manganese. 
 
 5. YeUow ; False Topaz. Yellow and pellucid, or nearly so ; resembling somewhat yellow 
 topaz, but very different in crystallization and in absence of cleavage. 
 
 6. Smoky \ Cairngorm Stone. Smoky -yellow to smoky -brown, and often transparent ; but 
 varying to brownish-black, and then nearly opaque in thick crystals. The color is due to 
 organic compounds, according to Forster. 
 
 7. Milky. Milk-white and nearly opaque. Lustre often greasy, and then called Greasy 
 quartz. 
 
 8. Gaffs Eye (Katzenauge, Germ.). Exhibiting opalescence, but without prismatic colors, 
 an effect due to fibres of asbestus. 
 
 9. Aventurine. Spangled with scales of mica or other mineral. 
 
 10. Impure from the presence of distinct minerals distributed densely through the mass. 
 The more common kinds are those in which the impurities are : (a) ferruginous, either red or 
 yellow iron oxide; (b) chloritic, some kind of chlorite ; (c) actinolitic ; (d) micaceous; (e) are- 
 naceous, or sand. Quartz crystals also occur penetrated by various minerals, as topaz, corun- 
 dum, chrysoberyl, garnet, different species of the hornblende and pyroxene groups, rutile, 
 hematite, gothite, etc., etc. 
 
 Containing liquids in cavities. These liquids are seen to move with the change of position 
 of the crystal, provided an air-bubble be present in the cavity. The liquid is either water 
 (pure, or a mineral solution), carbon dioxide, or some petroleum-like or other compound. 
 
 B. CRYPTOCRYSTALLINE VARIETIES. 
 
 1. CJialcedony. Having the lustre nearly of wax, and either transparent or translucent. 
 Color white, grayish, pale-brown to dark-brown, black ; tendon-color common ; sometimes deli- 
 cate blue. Also of other shades, and then having other names. Often mammillary, botryoi- 
 dal, stalactitic, and occurring lining or filling cavities in rocks. It is true quartz, with some 
 disseminated opal. 
 
 2. Carnelian. A clear red chalcedony, pale to deep in shade ; also brownish-red to brown, 
 the latter kind reddish-brown by transmitted light. 
 
 3. Chrysoprase. An apple-green chalcedony, the color due to the presence of nickel 
 oxide. 
 
 4. Prase. Translucent and dull leek-green ; so named from Kpacov, a leek. Always regarded 
 as a stone of little value. The name is also given to crystalline quartz of the same color. 
 
 5. Plasma. Rather bright-green to leek-green, and also sometimes nearly emerald-green, 
 and subtranslucent or feebly translucent ; sometimes dotted with white. Heliotrope, or 
 Blood-stone, is the same stone essentially, with small spots of red jasper, looking like drops of 
 blood. 
 
 6. Agate. A variegated chalcedony. The colors are either banded or in clouds, or due to 
 visible impurities, a. Banded. The bands are delicate parallel lines, of white, tendon-like, 
 wax-like, pale and dark-brown, and black colors, and sometimes bluish and other shades. 
 They follow waving or zigzag courses, and are occasionally concentric circular, as in the eye- 
 agate. The bands are the edges of layers of deposition, the agate having been formed by a 
 deposit of silica from solutions intermittently supplied, in irregular cavities in rocks, and 
 
OATGEN COMPOUNDS SILICA. 287 
 
 deriving their concentric waving courses from the irregularities of the walls of the cavitj 
 Owing also to the unequal porosity, agates may be varied in color by artificial means, ft. Ir 
 regularly clouded. The colors various, as in banded agate. 7. Colors due to visible impurities, 
 including Moss-agate, filled with brown moss-like or dendritic forms distributed through the 
 mass ; Vendritic Agate, containing brown or black dendritic markings. There is also Agatized 
 wood : wood petrified with clouded agate. 
 
 7. Onyx, Like agate in consisting of layers of different colors, but the layers are in even 
 planes, and the banding therefore straight, and hence its use for cameos, the head being cut 
 in one color, and another serving for the background. The colors of the best are perfectly 
 well defined, and either white and black, or white, brown and black alternate. 
 
 8. Sardonyx. Like onyx in structure, but includes layers of carnelian (sard) along with 
 others of white or whitish, and brown, and sometimes black colors. 
 
 9. Jasper. Impure opaque colored quartz, (a) Red iron sesquioxide being the coloring 
 matter, (b) Brownish, or ochre-yellow, colored by hydrous iron sesquioxide, and becoming red 
 when so heated as to drive off the water, (c) Dark-green and brownish-green, (d) Grayish- 
 blue. (<?) Blackish or brownish-black. (/) /Striped or riband jasper (Bandjaspis, Germ.), 
 having the colors in broad stripes, (g) Egyptian jasper, in nodules which are zoned in brown 
 and yellowish colors. Porcelain jasper is nothing but baked clay, and differs from true jasper 
 in being B.B. fusible on the edges. Red porphyry, or its base, resembles jasper, but is also 
 fusible on the edges, being usually an impure feldspar. 
 
 10. Agate-Jasper. An agate consisting of jasper with veinings and cloudings of chalcedony. 
 
 11. Siliceous sinter. Irregularly cellular quartz, formed by deposition from waters contain- 
 ing silica or soluble silicates in solution. 
 
 12. Flint (Feuerstein, Germ.). Somewhat allied to chalcedony, but more opaque, and of 
 dull colors, usually gray, smoky-brown, and brownish-black. The exterior is often whitish, 
 from mixture with lime or chalk, in which it is imbedded. Lustre barely glistening, sub- 
 vitreous. Breaks with a deeply conchoidal fracture, and a sharp cutting edge. The flint of 
 the chalk formation consists largely of the remains of infusoria (Diatoms), sponges, and other 
 marine productions. The coloring matter of the common kinds is mostly carbonaceous 
 matter. 
 
 I'd. Hornstone (Hornstein, Germ.). Resembles flint, but more brittle, the fracture more 
 splintery. Chert is a term often applied to hornstone, and to any impure flinty rock, includ- 
 ing the jaspers. 
 
 14. Basanite, Lydian Stone or Touchstone. A velvet-black siliceous stone or flinty jasper, 
 used on account of its hardness and black color for trying the purity of the precious metals. 
 The color left on the stone after rubbing the metal across it indicates to the experienced eye 
 the amount of alloy. It is not splintery like hornstone. 
 
 Pyr., etc. B.B. unaltered ; with borax dissolves slowly to a clear glass ; with soda dis- 
 solves with effervescence ; unacted upon by salt of phosphorus. Insoluble in hydrochloric 
 acid, and only slightly acted upon by solutions of fixed caustic alkalies. When fused and 
 cooled it becomes opal-silica, having G.=2'2. 
 
 Diflf. Quartz is distinguished by its hardness scratching glass with facility ; infusibilitQ 
 not fusing before the blowpipe ; insolubility not attacked by water or the acids ; uncleava- 
 bility one variety being tabular, but proper cleavage never being distinctly observed. To 
 these characteristics the action of soda B.B. may be added. 
 
 Obs Quartz occurs as one of the essential constituents of granite, syenite, gneiss, mica 
 schist, and many related rocks ; as the principal constituent of quartz-rock and many sand- 
 stones ; as an unessential ingredient in some trachyte, porphyry, etc. ; as the vein-stone in 
 various rocks, and for a large part of mineral veins ; as a foreign mineral in the cavities of trap, 
 basalt, and related rocks, some limestones, etc. , making geodes of crystals, or of chalcedony, 
 agate, carnelian, etc.; as imbedded nodules or masses in various limestones, constituting the 
 flint of the chalk formation, the hornstone of other limestones these nodules sometimes 
 becoming continuous layers ; as masses of jasper occasionally in limestone. It is the principal 
 material of the pebbles of gravel beds, and of the sands of the sea- shore and sand beds every- 
 where. Silica also occurs in solution (but mostly as a soluble alkaline silicate) in heated 
 natural waters, as those of the Geysers of Iceland, New Zealand, and California, and the 
 Yellowstone Park, and very sparingly in many cold mineral waters. 
 
 Switzerland, Dauphiny, Piedmont, the Carrara quarries, and numerous other foreign locali- 
 ties, afford fine specimens of rock crystal. Amethysts are brought from India, Ceylon, and 
 Persia, also Transylvania. The amygdaloids of Iceland and the Faroe Islands, afford magni- 
 ficent specimens of chalcedony; also Hiittenberg and Loben in Carinthia, etc. The finest 
 carnelians and agates are found in Arabia, India, Brazil, Surinam, Oberstein, and Saxony. 
 Cat's eye, in Ceylon, the coast of Malabar, and also in the Harz and Bavaria. Heliotrope, is. 
 Bucharia, Ta-tary, Siberia. 
 
288 DESCRIPTIVE MINERALOGY. 
 
 In New York, quartz crystals are abundant in Herkimer Co. Fine dodecahedral crystals, 
 at the beds of specular iron in St. Lawrence Co. In Antwerp, Jefferson Co. , at Diamond 
 Island and Diamond Point, Lake George, Pelham and Chesterfield, Mass. , Paris and Perry, 
 Me., Benton, N. H., Sharon, Vt., Meadow Mount, Md., and Hot Springs, Ark., are other 
 localities of quartz crystal. For other localities, see the catalogue of localities in the latter 
 part of this volume. 
 
 Rose quartz, at Albany and Paris, Me., Ac worth, N. H., and elsewhere ; smoky quartz, at 
 Goshen, Mass., Richmond Co., N. Y., Pike's Peak, Colorado, etc. ; amethyst, at*Keweenaw 
 Point and Thunder Bay, etc., Lake Superior; also at Bristol, Rhode Island, near Greensboro, 
 N. C. ; Specimen Mountain, Yellowstone Park. Crystallized green quartz, at Providence, 
 Delaware Co., Penn. ; at Ellen ville, N. Y. Chalcedony and agates about Lake Superior, the 
 Mississippi, and the streams to the west, etc. Red jasper is found in pebbles on the banks of 
 the Hudson at Troy ; red and yellow, near Murphy's, Calaveras Co. , Gal. Heliotrope occupies 
 veins in slate at Bloomingrove, Orange Co. , N. Y. 
 
 Several varieties of this species have long been employed in jewelry. The amethyst haa 
 always been esteemed for its beauty. Cameos are in general made of onyx, which is well 
 fitted for this kind of miniature sculpture. Jasper admits of a brilliant polish, and is often 
 formed into vases, boxes, knife-handles, etc. It is also extensively used in the manufacture 
 of Florentine mosaics. The carnelian is often rich in color, but is too common to be much 
 esteemed ; when first obtained from the rock they are usually gray or grayish-red ; they 
 receive their fine colors from an exposure of several weeks to the sun's rays, and a subsequent 
 heating in earthen pots. The colors of agate, when indistinct, may be brought out by boil- 
 ing in oil, and afterward in sulphuric acid ; the latter carbonizes the oil absorbed by the 
 porous layers, and thus increases the contrast of the different colors. 
 
 TRIDYMITE.* 
 
 Hexagonal. 1 A 1 = 124 3' (basal) ; 1 A 1 = 127 35' (terminal) ; c = 
 1*6304 (v. Hath). Cleavage O, imperfect. Crys- 
 507 ^ tals minute, commonly tabular (f. 507), formed 
 
 by the prism and basal plane ; also frequently in 
 twins and trillings with (1) -J-, and (2) j- as the 
 twinning-planes. Double refraction positive. 
 
 H.:=7. G.=2-282-2-326. Lustre vitreous, on 
 the face pearly. Colorless, becoming white on weathering. Fracture con- 
 choidal. 
 
 Comp. Pure silica, or Si0 2 , like quartz. 
 
 Pyr. B. B. infusible. Fuses in soda with effervescence, forming a colorless glass. Soluble 
 in a boiling saturated solution of sodium carbonate. 
 
 Obs. First found in cavities in the trachyte from Cerro St. Cristoval, near Pachuca, 
 Mexico. Also in the trachyte of the Siebengebirge, and in related rocks from many localities. 
 Forming on one occasion the mass of white volcanic ashes, from the island Vulcano. Also 
 in microscopic crystals inclosed in opal, and in quartz. 
 
 ASMANITE (Maskdyne). A third form of silica, crystallizing in the orthorhombic system, 
 " isomorphous with brookite." H. =5'5. G.=2-245. Found in very minute crystalline 
 grains, generally rounded, in the meteoric iron of Breitenbach. 
 
 OPAL. 
 
 Massive, amorphous; sometimes small reniform. stalactitic, or large 
 tuberose. Also earthy. 
 
 H.=5-5-6-5. Gr,=l-9-2'3. Lustre vitreous, frequently subvitreoue ; 
 often inclining to resinoua, and sometimes to pearly. Color white, yellow, 
 
OXYGEN COMPOUNDS SILICA. 289 
 
 red, brown, green, gray, generally pale ; dark colors arise from foreign 
 admixtures ; sometimes a rich play of colors, or different colors by refracted 
 and reflected light. Streak white. Transparent to nearly opaque. 
 
 Oomp. Silica, SiO 2 , as for quartz, the opal condition being one of lower degrees of hard- 
 ness and specific gravity. Water is usually present, but it is regarded as unessential. It 
 varies in amount from 2 to 21 p. c. ; or, mostly, from 3-9 p. c. 
 
 Var. 1. Precious Opal. Exhibits a play of delicate colors, or, as Pliny says, presents vaiioua 
 refulgent tints in succession, reflecting now one hue and now another. Seldom larger than a 
 hazel-nut. Doubly refracting (biaxial), Behrens. 
 
 3. Fire-opal. Hyacinth-red to honey-yellow colors, with fire-like reflections somewhat irised 
 on turning. 
 
 3. Oirasol. Bluish-white, translucent, with reddish reflections in a bright light. 
 
 4. Common Opal. In part translucent ; (a) milk-white to greenish, yellowish, bluish; (b) 
 Resin-opal (Wachsopal, Pechopal, Germ.), wax-, honey- to ochre-yellow, with a resinous 
 lustre ; (c) dull olive-green and mountain-green ; (d) brick-red. 
 
 5. Cacholong. Opaque, bluish-white, porcelain-white, pale-yellowish or reddish ; often 
 adheres to the tongue, and contains a little alumina. 
 
 6. Opal-agate. Agate-like in structure, but consisting of opal of different shades of color. 
 
 7. Jasp-opal. Opal containing some yellow iron sesquioxide and other impurities, and hav- 
 ing the color of yellow jasper, with the lustre of common opal. 
 
 8. Wood-opal (Holzopal, Germ.). Wood petrified by opal. 
 
 9. Hyalite. Clear as glass and colorless, constituting globular concretions, and also crusts 
 with a globular, renif orm, botryoidal> or stalactitic surface ; also passing into translucent, 
 and whitish. 
 
 10. Fiorite, Siliceous Sinter. Includes translucent to opaque, grayish, whitish, or brownish 
 incrustations, porous to firm in texture ; sometimes fibrous -like or filamentous, and, when so, 
 pearly in lustre, formed from the decomposition of the siliceous minerals of volcanic rocks 
 about fumaroles, or from the siliceous waters of hot springs. It graduates at times into 
 hyalite. Geyserite constitutes concretionary deposits about the Iceland and Yellowstone 
 (pealite) geysers, presenting white or grayish, porous, stalactitic, filamentous, cauliflower- 
 like forms; also compact-massive, and scaly - massi ve ; H. =5; rarely transparent, usually 
 opaque ; sometimes falling to powder on drying in the air. 
 
 11. Float-stone. In light concretionary or tuberose masses, white or grayish, sometimes 
 cavernous, rough in fracture. So light, owing to its spongy texture, as to float on water. 
 The concretions sometimes have a flint-like nucleus. 
 
 12. Tripolite. Formed from the siliceous shells of Diatoms and other microscopic species, 
 as first made known by Ehrenberg, and occurring in deposits, often many miles in area, either 
 uncompacted, or moderately hard. Infusorial Earth, or Earthy Tripolite, a very fine-grained 
 earth looking often like an eartny chalk, or a clay, but harsh to the feel, and scratching glass 
 when rubbed on it. 
 
 Pyr., etc. Yields water. B.B. infusible, but becomes opaque. Some yellow varieties, 
 containing iron, turn red. 
 
 Oba. Occurs filling cavities and fissures or seams in igneous rocks, porphyry, and some 
 metallic veins. Also imbedded, like flint, in limestone, and sometimes, like other quartz 
 concretions, in argillaceous beds ; also formed from the siliceous waters of some hot springs ; 
 also resulting from the mere accumulation, or accumulation and partial solution and solidifi- 
 cation, of the siliceous shells of infusoria which consist essentially of opal-silica. 
 
 Precious opal occurs in Hungary ; in Honduras ; and Mexico. Fire opal occurs at Zimapaii 
 in Mexico ; Faroe ; near San Antonio, Honduras. Common opal is abundant at Telkebanya 
 in Hungary; in Moravia; in Bohemia ; Stenzelberg in the Siebengebirge ; Faroe, Iceland; 
 the Giant's Causeway, at many localities. In U. S., hyalite occurs sparingly in N. York, at 
 the Phillips ore bed, Putnam Co. ; in Georgia, in Burke and Scriven Cos.; in Washington Co., 
 good fire opal. At the Geysers on the Fire Hole river, Yellowstone Park, geyserite is abundant. 
 
 The precious opal, when large, and exhibiting its peculiar play of colors in perfection, is a 
 gem of high value. It is cut with a convex surface. 
 
 MELANOPHLOGITE (Lasauix). Occurs in minute, colorless, cubes coating sulphur crystal! 
 from Girgeuti, Sicily. Contains SiO 2 86 '3 p. c., SO 3 7 , H 2 O 2 '9 ; chemical nature doubt* 
 ful. Turns black upon ignition, hence the name. 
 
 19 
 
290 
 
 DESCRIPTIVE MINERALOGY. 
 
 II. TEENAEY OXYGEN COMPOUNDS. 
 
 1. SILICATES. A. ANHYDROUS SILICATES. 
 a. BISILICATES. GENERAL FORMULA RSiO 3 . 
 
 (a) Amphibole Group. Pyroxene Section. 
 ENSTATTTE. BRONZITE. Protobaetite. 
 
 Orthorhombic. 
 
 508 
 
 1 A 1= 88 16' and 91 44:' (Breitenbach meteorite, v. 
 Lang}-, c:t>:d = 0-58853 : 1-03086 : 1. Cleavage: /, 
 easy ; i-i, i-i, less so. Sometimes a fibrous appearance 
 on the cleavage-surface. Also massive and lamellar. 
 
 H.=5-5. G.=3-l-3-3. Lustre a little pearly on 
 cleavage-surfaces to vitreous ; often metalloidal in the 
 bronzite variety. Color grayish- white, yellowish-white, 
 greenish- white, to olive-green and brown. Streak 1111- 
 colored, grayish. Double refraction positive ; optic- 
 axial plane brachydiagonal ; axes very divergent. 
 
 Bamle Norway Comp., Var. MgSiO s = Silica 60, magnesia 40 = 1 00 ; also (Mg, Fe) 
 
 SiO 3 . 
 
 Var. 1. With little or no iron; Emtatite. Color white, yellowish, grayish, or greenish- 
 white; lustre pearly- vitreous ; G. =3 '10-3 '13. Chladnite, which makes up 90 p. c. of the 
 Bishopville meteorite, belongs here and is the purest kind ; Victorite (Meunier), from the 
 Deesa (Chili) meteoric iron is probably identical. 
 
 2. Ferriferous ; Bronzite. Color grayish -green to olive-green and brown; lustre of cleav- 
 age-surface adamantine pearly to subtnetallic or bronze-like. The ratio of Mg : Fe varies 
 from 11 : 1 to 3 : 1. Analysis of bronzite from Leiperville by Pisani, Si0 2 57-08, A1O 3 0'28, 
 FeO 5-77, MgO 35 -59, H 2 O 0-90=99-62. 
 
 Pyr., etc. B.B. almost infusible, being only slightly rounded on the thin edges ; F.=6. 
 Insoluble in hydrochloric acid. 
 
 Diff. Distinguished by its infusibility from varieties of amphibole, which it resembles. 
 
 Obs. Occurs near Aloysthal in Moravia ; in the Vosges ; at Kupf erberg in Bavaria ; at 
 Baste in the Harz (Protobastite) ; in the chrysolite bombs in the Eifel ; in immense crystals 
 with apatite, near Bamle, Norway. In Pennsylvania, at Leiperville and Texas ; at Brewster, 
 N. Y. Bronzite is quite common in meteorites. 
 
 DesCloizeaux first defined the limits of this species, as here laid down. 
 
 Named from 'fva-rdr-ns, an opponent, because so refractory. The name bronzite has priority, 
 but a bronze lustre is not essential, and is far from universal. 
 
 HYPERSTHENB. 
 
 Orthorhombic. /A 1= 91 32, DesCloizeaux (Mt. Dor6); 91 40' 
 T. Eath (amblystegite). Cleavage : i-l perfect, 1 and i-l distinct but inter 
 rupted. Usually foliated massive. 
 
 H.=5-6. Gr.= 3-392. Lustre somewhat pearly on a cleavage-surface, 
 and sometimes a little metalloidal ; often with a peculiar iridescence due 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 291 
 
 509 
 
 to the presence of minute enclosed tabular crystals (brookite?) in parallel 
 position (Kosmann). Color dark brownish -green, gray- 
 ish-black, greenish- black, pinchbeck-brown. Streak 
 S*ayish, brownish-gray. Translucent to nearly opaque, 
 rittle. Optic-axial plane brachydiagonal ; axes very 
 divergent; bisectrix negative. 
 
 if 
 
 Me. Dora. 
 
 Comp. (Mg-,Fe}Si0 3 with Fe : Mg 1 : 5, 1:3, etc. If Fc to 
 Mg=l : 2 the formula requires SiO 2 54 -2, FeO 21-7, MgO 24-1 = 100. 
 
 Pyr., etc. B.B. fuses to a black enamel, and on charcoal yields a 
 magnetic mass. Partially decomposed by hydrochloric acid. 
 
 Obs. Hypersthene occurs at Isle St. Paul, Labrador in Canada ; 
 at the Isle of Skye ; in Greenland ; Norway ; Ronsberg in Bohemia ; 
 the Tyrol ; Elfdalen in Sweden ; Laacher See (amblystegite] ; Voigt- 
 land ; in trachyte of Mt. Dore, Auvergne. 
 
 In chemical composition, emtatite (and bronzite), and hypersthene 
 belong together, since they grade insensibly into each other ; and in 
 crystalline form they are identical. The essential difference between 
 
 them, according to DesCloizeaux, lies in the axial dispersion which is uniformly p < v f 01 
 enstatite, and p > v f or hypersthene. 
 
 DIACLASITE. Near bronzite ; differs in optical characters. (Mg,Fe,Ca)Si0 3 . Harzburg; 
 Guadarrama, Spain. 
 
 WOLLASTONITE. Tabular Spar. Tafelspath, Gem. 
 
 Monoclinic. O= 69 48', I A 1 = 87 28', A 2-i = 137 48' ; c : I : d 
 = 0-4338 : 0-89789 : 1. Fig. 510 in the pyroxene or normal position, but 
 wi" 1 "* 1 the edge O fi-i the obtuse edge ; f. 511 in the position given the crys- 
 tals u\ authors who make i-i the plane O, and 24 the plane"/. O A 1-^ 
 = 160 30', A l-i = 154 25', i-i A - 2 = 132 54', i-i A 2 = 93 52'. 
 Rarely in distinct tabular crystals. Cleavage : most distinct ; i-i less 
 so ; l-i and l-i in traces. Twins : twinning-plane i-i. Usually cleav- 
 able massive, with the surface appearing long fibrous, fibres parallel or 
 reticulated, rather strongly coherent 
 
 510 
 
 511 
 
 H.= 4-5-5. G.== 2-78-2 '9. Lustre vitreous, inclining to pearly upon 
 the faces of perfect cleavage. Color white, inclining to gray, yellow, red, 
 or brown. Streak white. Subtransparent translucent. Fracture uneven, 
 sometimes *ery tough. Optic-axial plane i-i ; divergence 70 40' for the 
 red rays ; bisectrix of the acute angle negative ; inclined to a normal to i-i 
 57 48', and to a normal to O 12/De801. 
 
292 
 
 DESCRIPTIVE MINERALOGY. 
 
 Comp. CaSi0 3 =Silica 517, lime 48 '3=100. 
 
 Pyr., etc. In the matrass no change. B.B. fuses easily on the edges; with some soda, a 
 blebby glass, with more, swells up and is infusible. With hydrochloric acid gelatinizes ; most 
 varieties effervesce slightly from the presence of calcite. 
 
 Diff. Differs from asbestus, and tremolite in forming a jelly with acids, as also by its more 
 vitreous fracture ; fuses less readily than natrolite and scolecite ; when pure does not effer- 
 vesce with acids like the carbonates. 
 
 Obs. Wollastonite is found in regions of granite and granular limestone ; also in basalt and 
 lavas. Occurs in Hungary ; in Finland ; and in Norway ; at Gockum in Sweden ; in the 
 Harz ; at Auerbach, in granular limestone ; at Vesuvius. In the U. S., in H. York, at Wills- 
 borough ; at Lewis ; Diana, Lewis Co. In Penn. , Bucks Co. At the Cliff Mine, Keweenaw 
 Point, Lake Superior. In Canada, at Grenville. 
 
 PYROXENE. 
 
 Monoclinic. O = 73 59', /A / = 87 5', A 24 = 131 IT ; c : b : d 
 = 0-5412 : 0-91346 : 1. 0/\I= 100 57', A l-i = 155 51', O A l-i 
 = 148 35', 0A -1 = 146 9', 6>Al = 137 49', -1 A -1 = 131 24'. 
 Cleavage : / rather perfect, often interrupted ; i-i sometimes nearly per- 
 
 517 
 
 lit 
 
 519 
 
 feet ; i-i imperfect ; sometimes easy. Crystals usually thick and stout. 
 
 Twins: t winning-plane i-i (f. 521). Often coarse lamellar, in large masses, 
 
 parallel to O or i-i. Also granular, particles coarse or line ; and fibrous, 
 
 fibres often fine and long. 
 
 H.=5-6. G. = 3-23-3-5. Lustre 
 vitreous, inclining to resinous ; 
 some pearly. Color green of 
 various shades, verging on one 
 side to white or grayish- white, 
 and on the other to brown and 
 black. Streak white to gray and 
 grayish-green. Transparent 
 opaque. Fracture conchoidal 
 uneven. Brittle. In crystals 
 from Fassa, optic-axial plane i-\\ 
 divergence 110 to 113; bisec- 
 
 inclined 51 6' to a normal to i4 and 22 C 
 
 trix of the acute angle positive, 
 55' to a normal to O, DesCl. 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 293 
 
 Comp., Var A bisilicate, having the general formula RSi0 3 , where E may be Ca,Mg, 
 Fe,Mn, sometimes also Zn,Kao,Na 2 . Usually two or more of these bases are present. The 
 first three are most common ; but calci im is the only one that is present always and in large 
 percentage. Besides the substitutions of the above bases for one another, these same basea 
 are at times replaced by Al,Fe,Mn, though sparingly, and the silicon occasionally by alumi- 
 num. 
 
 The varieties proceeding from these isomorphous substitutions are many and diverse ; and 
 there are still others depending on the state of crystallization. The foliated and fibrous 
 kinds early received separate names, and for a while were regarded as distinct species. Fibrous 
 or columnar forms are very much less common than in hornblende, and lamellar or foliated 
 kinds more common. The crystals are rarely long and slender, or bladed, like those of that 
 species. 
 
 The most prominent division of the species is into (A) the non-aluminous ; (B) the alumi- 
 nous. But the former of these groups shades imperceptibly into the latter. These two groups 
 are generally subdivided according to the prevalence of the different protoxide elements. 
 Yet here, also, the gradation from one series to another is in general by almost insensible 
 shades as to composition and chemical characters, as well as all physical qualities. 
 
 I. CONTAINING LITTLE OH NO ALUMINA. 
 
 1. Lime-Magnesia Pyroxene; MALACOLITE. Diopside, Alalite, White Coccolite. Color 
 white, yellowish, grayish- white to pale green. In crystals: cleavable and granular massive. 
 Sometimes transparent and colorless. G. =3'2-3'38. Formula, CaMgSi 2 O 6 Silica 55 '6, mag- 
 nesia 18 '5, lime 25-9. Sometimes Ca : Mg=l : 2 ; less than 4 p. c. of iron are present. 
 
 2. Lime- Magnesia- Iron Pyroxene ; SAIILITE. Color grayish -green to deep green and black ; 
 sometimes grayish and yellowish-white. In crystals ; also cleavable and granular massive 
 G. =3 25-3-4. Named from Sala in Sweden, one of its localities, where the mineral occurs 
 in masses of a grayish-green color, having a perfect cleavage parallel to the basal plane (0). 
 Formula (Ca,Mg,Fe)SiO 3 . The ratio of Ca : Mg : Fe varies much, =3 : 3 : 1, 2 : 2 : l,etc. The 
 ratio=4 : 3 : 1, corresponds to silica 53'7, magnesia 13 4, lime 24*9, iron protoxide 8'0=lO(X 
 
 DIALLAGE. Part of the so-called diallage, or thin foliated pyroxene, belongs here, and the 
 rest under the corresponding division of the aluminous pyroxenes. Color grayish-green to 
 bright grass-green, and deep green; lustre of cleavage surface pearly, sometimes metalioidal 
 or brassy. H.=4. G-.=3'2-3'35. Composition near the preceding ; analysis by vom Rath, 
 Neurode, Si0 2 53 '60, A10 3 1'99, FeO 8 '95, MnO 0'28, MgO 13'08, CaO 21'0(>, H.O p-8t>=99'82. 
 With this variety belongs part also of what has been called hypersthene and bronzite the part 
 that is easily fusible. Common especially in serpentine rocks. Named from dici'Mayy, dif- 
 ference, in allusion to the dissimilar cleavages. 
 
 3. Iron- Lime Pyroxene. HEDENBERGITE. Color black. In crystals, and also lamellar 
 massive ; cleavage easy parallel to i-i. G-. =3 '5-3 -58. Formula CaFeSi.jO 8 (Mg being absent) 
 ^Silica 4839, lime 2218, iron protoxide 29 '43 =100. Asteroite is a similar pyroxene con- 
 taining also Mn (Igelstrom), Sweden. 
 
 4. Lime-Iron-Manganese-Zinc Pyroxene ; JEPFERSONITE. Color greenish-black. Crystals 
 often very large (3-4 in. thick), with the angles generally rounded, and the faces uneven, as 
 if corroded. G.=3'36. Analysis, Franklin, N. J., by Pisani, SiO a 45-95, itt0 3 0-85, FeO 
 8-91, MnO 10-20, ZnO 1015, CaO 21-55, MgO 3 -61, ign 0'35=101-57. 
 
 II. ALUMINOUS. 
 
 Aluminous Lime-Magnesia Pyroxene; LEUC AUGITE (Dana). Color white or grayish. 
 Analysis, Bathurst, C., by Hunt, SiO, 51 '50, A1O 3 6-15, FeO 3 0'35, MgO 17 '69, CaO 23 '80 
 H.O 1-10= 100-59. Looks like diopside. H.=6-5. G.=319. Hunt. Named from Aewco;, 
 white. 
 
 Aluminous \time-Magnesia.-Iron Pyroxene; FASSAITE, AUGITE. Color clear deep-green to 
 greenish-black and black ; in crystals, and also massive ; subtranslucent to opaque. G. 
 =3 25-3 -5. Contains iron, with calcium and magnesium, also aluminum. Analysis of augite 
 from Montreal by Hunt, SiO 2 49-40, A10 3 G"70, ^eO 3 7'83, MgO 13-06, CaO 21 '88, Na 2 0'74, 
 H a O 0-50=100- 11. 
 
 a. Fassaitd (or Pyrgom). Includes the green kinds found in metamorphic rocks. Named 
 from the locality at Fassa in Piedmont, which affords deep-green crystals, sometimes pistachio- 
 green, like the epidote of the locality. 
 
 b. Augite. Includes the greenish or brownish-black and black kinds, occurring mostly in 
 eruptive rocks, but also in metamorphic. Named from av-yq, lustre. 
 
294 
 
 DESCRIPTIVE MINERALOGY. 
 
 Pyr., etc. Varying widely, owing to the wide variations in composition in the different 
 varieties, and often by insensible gradations. Fusibility, from the almost infusible dialiage 
 to 3 '75 in diopside ; 8 "5 in sahlite ; 3 in jeffersonite and augite ; 2 '5 in hedenbergite. Va- 
 rieties rich in iron afford a magnetic globule when fused on charcoal, and in general their 
 fusibility varies with the amount of iron. Jeffersonite gives with soda on charcoal a reaction 
 for zinc and manganese ; many others also give with the fluxes reactions for manganese. Most 
 varieties are unacted upon by acids. 
 
 Diff. See Amphibole, p. 297. 
 
 Obs. Pyroxene is a common mineral in crystalline limestone and dolomite, in serpentine, 
 and in volcanic rocks ; and occurs also, but less abundantly, in connection with granitic rocks 
 and metamorphic schists. The pyroxene of limestone is mostly the white and light-green or 
 gray varieties ; that of most other metamorphic rock, sometimes white or colorless, but 
 usually green of different shades, from pale green to greenish- black, and occasionally black; 
 that of serpentine is sometimes in fine crystals, but often of the foliated green kind called 
 diallage ; that of eruptive rocks is the black to greenish-black augite. 
 
 Prominent foreign localities are : malacolite (diopaide], Traversella, Ala in Piedmont ; Sala, 
 Tunaberg. Sweden ; Pargas ; Achmatovsk ; etc. Sahlite, Sala ; Arendal ; Degeroe ; Schwarzen- 
 berg; etc. Hedenbergite, Tunaberg; Arendal Augite, Fassathal ; Vesuvius; etc. inmost 
 dolerytio igneous rocks. 
 
 In N. America common (see list of localities at the close of the volume). Some localities 
 are: In Ma&s., at the Bolton quarries. In Conn., at Canaan. In N. York, at Warwick, Mon- 
 roe, Edenville, Diana. In N. Jersey, in Franklin. In Perm., near Attleboro'. In Canada, 
 at Bytown, at Calumet I. , at Grenville. 
 
 . ACMITE. Monoclinic. In slender pointed crystals (hence name) in quartz. H. =6. G-. = 
 3 -2-3 '53. Color brownish to reddish-brown, in the fracture blackish-green. Opaque. Frac- 
 ture uneven. Brittle. RSiO 3 ,R=Na 2 ,Fe, or Fe(Fe=3R); analysis by Rammelsberg, SiO a 
 51-66, FeO 3 28'28, FeO 5 '23, MnO 0-69, Na 2 12 46, K 3 O 0'43, TiO I'll, ign 0'39=100'25. 
 Kongsberg, Norway. 
 
 ^GIBITE. Near pyroxene in form, but contains alkalies. H. =5-5-6. G.=3'45-3'58. 
 Color greenish-black. Subtranslucent to opaque. Analysis Ramm., Brevig, SiO-> 50 '25, A10 S 
 1-22, FeO 8 22-07, FeO 8-80, MnO 1'40, CaO 5 '47. MgO 1-28, Na.O 9 29, K 2 O 94 =100 '72. 
 Also from Magnet Cove, Arkansas. 
 
 RHODONITE. 
 
 Triclinic, but approximately isomorphous with pyroxene. Cleavage : 1 
 perfect ; 'O less perfect. Usually massive. 
 
 H.=5*5-6-5. Gr.= 3-4-3-68. Lustre vitreous. Color 
 light brownish-red, flesh-red, sometimes greenish or 
 yellowish, when impure ; often black outside from ex- 
 posure. Streak white. Transparent opaque. Frac- 
 ture conchoidal uneven. Very tough when massive. 
 
 Comp., Var. MnSiO 3 = Silica 45*9, manganese protoxide 54 -1 = 
 100. Usually some Fe and Ca, and occasionally Zn replace part of the 
 Mn. Ordinary, (a) Crystallized. Either in crystals or foliated. 
 The ore in crystals from Paisberg, Sweden, was named Paisbergite 
 under the idea that it was a distinct species, (b) Granular massive. 
 Calciferous ; BUSTAMITE. Contains 9 to 15 p. c. of lime replacing 
 part of the manganese. Often also impure from the presence of cal- 
 cium carbonate, which suggests that part of the lime replacing the manganese may have come 
 from partial alteration. Grayish-red. Zinciferous ; FOWLEHITE. In crystals and foliated, 
 the latter looking much like cleavable red feldspar ; the crystals sometimes half an inch to an 
 inch through. JA 7=86 30', Torrey. G.= 3 '44, Thomson. 
 
 Pyr., etc. B.B. blackens and fuses with slight intumescence at 2*5 ; with the fluxes givea 
 reactions for manganese ; fowlerite gives with soda on charcoal a reaction for zinc. Slightly 
 acted upon by acids. The calciferous varieties often effervesce from mechanical admix- 
 ture with calcium carbonate. In powder, partly dissolves in hydrochloric acid, and the in 
 soluble part becomes of a white color. Darkens on exposure to the air, and sometimes 
 becomes nearly black. 
 Obs. Occurs at Longban, near Ptiilipstadt in Sweden ; also in the Harz ; in the district of 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 295 
 
 Katherinenberg in the Ural ; in Cornwall, etc. Occurs in Warwick, Mass. ; Blue Hill Bay, 
 Maine ; near Hinsdale, N. H. ; fowlerite (keatingine) at Hamburg and Sterling, New Jersey. 
 
 Named from podov, a rose, in allusion to the color. 
 
 BABINGTONITE. Triclinic. 9RSi0 3 +FeSi 3 9 , with R=Fe(Mn) : Ca(Mg)=2 : 3 (Eamm.). 
 Analysis, Rammelsberg, SiO 2 51 '22, Fe0 3 H'OO, FeO 10 '26, MnO 7 "91, MgO 077, Cap 
 19*32, ign=0-44 IGO'92. Color greenish-black. Arendal; Nassau; Devonshire; Baveno. 
 
 SPODUMENE.* 
 
 Monoclinic. 6"= 69 40' 7A/= 87, A 24 = 130 30'. Crystals 
 large. Cleavage: i-i very perfect; / also perfect; 
 14 in traces ; in striae on i-\. Twins : twinning-plane 
 i-i. Also massive, with broad cleavage surface. 
 
 H.:=6-5-7. G.:= 3- 13-3-19. Lustre pearly. Cross 
 fracture vitreous. Color grayish-green, passing into 
 greenish-white and grayish- white, rarely faint-reddish. 
 Streak mi colored. Translucent subtranslucent. Frac- 
 ture uneven. 
 
 Oomp 3RSi0 3 +4AlSi 3 9 ; R=Li 2 mostly. Silica 64 '2, alu- 
 mina 29-4, lithia 6 -4= 100. Sometimes Li : Na(K) = 20 : 1, Ramm. 
 
 Pyr., etc. B. B. becomes white and opaque, swells up, imparts 
 a purple red color (lithia) to the flame, and fuses at 3 5 to a clear 
 or white glass. The powdered mineral, fused with a mixture of 
 potassium bisulphate and fluor on platinum wire, gives a more in- 
 tense lithia reaction. Not acted upon by acids. 
 
 Diflf. Distinguished by its perfect orthodiagonal, as well as 
 prismatic, cleavage ; has a higher specific gravity and more pearly 
 lustre than feldspar or scapolite. Gives a red flame B.B. 
 
 Obs. Occurs on the island of Tito, Sweden; near Sterzing and 
 
 Lisens in the Tyrol; at Killiney Bay, near Dublin, and at Peterhead in Scotland. At Goshen, 
 Mass. ; also at Chesterfield and Norwich, Mass. ; at Windham, Maine ; at Winchester, N. H. ; 
 at Brookfield, Ct. 
 
 PETALITE. 3Li 2 Si 2 O 5 +4A]Si 6 15 --Silica 77'97, alumina 17'79, lithia 3'57, soda 067= 
 100. Ramm. Q. ratio Li : Al : Si=l : 4 : 20, or for bases to silicon^! ; 4. H.=6-6'5. O. 
 Colorless; white. Uto, Sweden; Elba (castorite) ; Bolton, Mass. 
 
 Norwich, Mass. 
 
 Ampliibole Section. 
 
 ANTHOPHYLLITE. 
 
 Orthorhombic. 7A/= 125 to 125 25'. Cleavage: 14 perfect, 1 lesa 
 so, i-l difficult. Commonly lamellar, or fibrous massive ; fibres often very 
 slender. 
 
 H.=5'5. Gr.= 3-1-3-2. Lustre somewhat pearly upon a cleavage sur- 
 face. Color brownish-gray, yellowish-brown, brownish-green, sometimes 
 submetallic. Streak nncolored or grayish. Translucent to subtranslucent. 
 Brittle. Double refraction positive; optical axes in the brachydiagonal 
 section. 
 
296 
 
 DESCRIPTIVE MINERALOGY. 
 
 Oomp (Fe,Mg)Si0 3 , Fe : Mg=l : 3=Silica 55 -5, magnesia 27*8, iron protoxide IQ'7 
 
 100. 
 
 Pyr., etc. B.B. fuses with great difficulty to a black magnetic enamel; with the fluxes 
 gives reactions for iron ; unacted upon by acids. 
 
 Obs. Occurs near Kongsberg in Norway, and near Modum. Also at Hermannschlag, 
 Moravia. 
 
 Anthophyllite Taears the same relation to the Amphibole Group that enstatite and hyper- 
 sthene do to the Pyroxene Group. 
 
 KUPFPERITE. Probably MgSiO 3 , with a little Fe. 1 A 7=124 30', hence an enstatite-Jiorn- 
 blende. Color emerald-green (chrome). Tunkinsk Mts. , Miask. Analysis of a similar min- 
 eral from Perth, Canada, Thomson, Si0 2 57-60, A10 3 3 "20, FeO 210, MgO 29" 30, CaO 3 -55, 
 ign. 3-55=99 30. 
 
 AMPHIBOLE.* HORNBLENDE. 
 
 Monoclinic. O= 75 2', I/\ 1= 124 30', 0Al-i = 164 1.0', c : I : d 
 =0-5527 : 1*8825 : 1. Crystals sometimes stout, often long and bladed. 
 Cleavage : / highly perfect ; i-i, i-l sometimes distinct. Lateral planes 
 often longitudinally striated. Twins: i winning-plane i-i^ as in f. 527 (simple 
 form f. 526), and 530. Imperfect crystallizations : fibrous or columnar, 
 coarse or fine, fibres often like flax ; sometimes lamellar ; also granular 
 massive, coarse or fine, and usually strongly coherent, but sometimes 
 friable. 
 
 525 
 
 528 
 
 530 
 
 H.=5-6. G.=2'9-3'4. Lustre vitreous to pearly on cleavage-faces; 
 fibrous varieties often silky. Color between black and white, through vari- 
 ous shades of green, inclining to blackish-green. Streak uncolored, or paler 
 than color. Sometimes nearly transparent ; usually subtranslucent opaque. 
 Fracture subconchoidal, uneven. Bisectrix, in most varieties, inclined about 
 60 to a normal to O, and 15 to a normal to i-i\ and double refraction 
 negative. 
 
 Comp., Var. General formula RSi0 3 , as for pyroxene. Aluminum is present in most 
 amphibole, and when so it usually replaces silicon. R may correspond to two or more of the 
 basic elements Mg,Ca,Fe,Mn,Na 2 ,K 2 ,H.,; and ft to 7\:1, Fe or Mn. Fe sometimes replaces 
 silicon, like Al. Much amphibole, especially the aluminous, contains some fluorine. The base 
 calcium is absent from some varieties, or nearly so. 
 
 The varieties of amphibole are as numerous as those of pyroxene, and for the same reasons; 
 and they lead in general to similar subdivisions. 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 297 
 
 I. CONTAINING LITTLE on NO ALUMINA. 
 
 Magnesia-. Lime Amphibole ; TREMOLITE. Grammatite. Colors white to dark-gray. Iq 
 distinct crystals, either long bladed or short and stout ; long and thin columnar, or fibrous ; 
 also compact granular massive. 1 A /=124 30'. H. =5"0-6'5. G. =29-3*1. Sometimes 
 transparent and colorless. Contains magnesia and lime with little or no iron ; formula (Ca. 
 Mg)Si0 3 , Ca : Mg=l : 3 = Silica 57*70, magnesia 28 85, lime 13'35 = 100. Named Tremoltteby 
 Pini, from the locality at Tremola in Switzerland. 
 
 NEPHRITE. In part a tough, compact, fine grained tremolite, having a tinge of green or 
 blue, and breaking with a splintery fracture and glistening lustre. H. =6-6*5. G. =2 96-3*1. 
 Named from a supposed efficacy in diseases of the kidney, from ve^pdf, kidney. It occurs 
 usually associated with talcose or magnesian rocks. Nephrite or jade was brought in the 
 form of carved ornaments from Mexico or Peru soon after the discovery of America. A simi- 
 lar stone comes from China and New Zealand. 
 
 A nephrite-like mineral, called bowenite, from Smithfield, R. I., having the hardness 5-5 is 
 serpentine in composition. The jade of de Saussure is the saussurite (see under ZOISITE) 
 of the younger de Saussure. Another aluminous jade has been called jadeite (q. v.) by 
 Damour. 
 
 Magnesia- Lime -Iron Amphibole; ACTINOLITE. Strahlstein, Germ. Color bright-green 
 and grayish -green. In crystals, either short or long-bladed, as in tremolite ; columnar or 
 fibrous; granular massive. G. =3-32. Sometimes transparent. Contains magnesia and 
 lime, with some iron protoxide, but seldom more than 6 p. c. ; formula (Ca,Mg. Fe)Si0 3 . 
 The variety in long bright-green crystals is called glassy actinolite ; the crystals break easily 
 across the prism. The fibrous and radiated kinds are often called asbestiform actinolite and 
 radiated actinolite. Actinolite owes its green color to the iron present. 
 
 Iron-Magnesia Amphibole ; CUMMINGTONITE. Color gray to brown. Usually fibrous or 
 fibro-lamellar, often radiated. G. =3 '1-3 '32. Contains much iron, with some magnesia, and 
 little or no lime. Formula (Fe,Mg)SiO 3 . Named from the locality, Cummington, Mass, 
 
 ASBKSTUS. Tremolite, actinolite, and other varieties of amphibole, excepting those (Con- 
 taining much alumina, pass into fibrous varieties, the fibres of which are sometimes very 
 long, fine, flexible, and easily separable by the fingers, and look like flax. These kinds, like 
 the corresponding of pyroxene, are called asbestus (fr. the Greek for incombustible). The 
 colors vary from white to green and wood- brown. The name amianthus is now applied usu- 
 ally to the finer and more silky kinds. Much that is so called is chrysolite, or fibrous serpen- 
 tine, it containing 12 to 14 p. c. of water. Mountain leather is a kind in thin flexible sheets, 
 made of interlaced fibres ; and mountain cork (Bergkork) the same in thicker pieces ; both 
 are so light as to float on water, and they are often hydrous. Mountain wood (Bergholz, 
 Holzasbest, Germ ) is compact fibrous, and gray to brown in color, looking a little like dry 
 wood. 
 
 II. ALUMINOUS. 
 
 Aluminous Magnesia- Lime Amphibole. (a) EDENITE. Color white to gray and pale-green, 
 and also colorless ; G. =3 '0-3-059, Ram in. Resembles an thophyllite and tremolite. Named 
 from the locality at Edenville, N. Y. (for analysis, see below.) To this variety belong various 
 pale-colored amphiboles, having less than five p. c. of oxide of iron. 
 
 (b) SMARAGDITE Saussure. A thin -foliated variety, of a light grass-green color, resembling 
 much common green diallage. According to Boulanger it is an aluminous magnes a-lime 
 amphibole, containing less than 3 p. c. iron protoxide, and is hence related to edenite and 
 the light green Pargas mineral. DesCloizeaux observes that it has the cleavage, and appar- 
 ently the optical characters, of amphibole. H.=5; G.=3. It forms, along with whitish or 
 gree*nish saussurite, a rock. 
 
 irgasite is usually made to include green and bluish-green 
 in stout lustrous crystals, or granular; and liornblende the greenish-black and black kinds, 
 whether in stout crystals or long bladed, columnar, fibrous, or massive granular. But no 
 line can be drawn between them. Pargasite occurs at Pargas, Finland, in bluish -green and 
 grayish-black crystals. 
 
 Composition shown by the following analyses by Rammelsberg ; (1) from Edenville ; (3) 
 Wolfaborg, Bohemia ; (3) Brevig. 
 
298 DESCRIPTIVE MINERALOGY. 
 
 Si0 3 A1O 8 Fe0 3 FeO MnO MgO CaO Na,O K 2 () H 2 0(ign) 
 
 (1) 51-67 5-75 2-86 23M7 12-42 0-75 0'84 0-46^98-12 
 
 (2) 41-98 14-31 5-81 7'18 14-06 12-55 1-64 1'54 0'26=99'10 
 
 (8) 43-28* 6-31 6-62 2172 1-13 3-62 9 '68 314 2 -65 "48 =98 63 
 
 * With I'Ol TiO 2 . 
 
 Pyr., etc. The observations under pyroxene apply also to this species, it being impossible 
 to distinguish the varieties by blowpipe characters alone. 
 
 Diflf. Distinguished from pyroxene (and tourmaline) by its distinct prismatic cleavage, 
 yielding an angle of 124. Also in colored varieties by its dichroism, when examined in thin 
 sections. Fibrous and columnar forms are much more common than with pyroxene, lamellar 
 and foliated forms rare. Crystals often long, slender, or bladed. Differs from the fibrous 
 zeolites in not gelatinizing with acids. 
 
 Isomorphous and Dimorphous relations to Pyroxene. The analogy in composition between 
 pyroxene and hornblende has been abundantly illustrated. They have the same general 
 formula ; and under this formula there is but one difference of any importance, viz. , that 
 lime is a prominent ingredient in all the varieties of pyroxene, while it is wanting, or nearly 
 so, in some of those of hornblende. The analogy between the two species in crystallization, 
 or their essential isomorphism, was pointed out by G. Rose in 1831, who showed that the 
 forms of both were referable to one and the same fundamental form. The prism / of horn- 
 blende corresponds in angle to e'-2 of pyroxene. Calculating from the angle I A /in pyroxene, 
 87 5', the angle of i-2 is precisely 124 J 30 , or the angle /A /in hornblende. But while thus 
 isomorphous in axial relations or form, they are also dimorphous. For ( 1 ) the cleavage in 
 pyroxene is parallel to the prism of 87 5', and in hornblende to that of 124|. (2) The occur- 
 ring secondary planes of the latter are in general diverse from those of the former, so that the 
 crystals differ strikingly in habit or system of modifications. Moreover, in pyroxene colum- 
 nar and fine fibrous forms are uncommon ; in hornblende, exceedingly common. (3) The 
 several chemical compounds under pyroxene have one-tenth higher specific gravity than the 
 corresponding ones under hornblende. 
 
 Vom Rath has described the occurrence of minute crystals of hornblende in parallel posi- 
 tion upon crystals of pyroxene (Vesuvius), and in consequence of the relation between the two 
 fonns, thus brought out, suggests a change in the commonly accepted fundamental form of 
 the latter. ( Jahrb. Min., 1876.) This association of crystals of the two species in parallel 
 position is not uncommon. 
 
 Obs. Amphibole occurs in many crystalline limestones, and metamorphic granitic and 
 schistose rocks, and sparingly in serpentine, and volcanic or igneous rocks. Tremolite, the 
 magnesia-lime variety, is especially common in limestones, particularly magnesian or dolomi- 
 tic ; actinolite, the magnesia lime-iron variety, in steatitic rocks; and brown, dark-green, 
 and black hornblende, in chlorite schists, mica schist, gneiss, and in various other rocks 
 (syenyte, dioryte, etc.), of which it forms a constituent part. Asbestus is often found in con- 
 nection with serpentine. Hornblende is often disseminated in black prismatic crystals through 
 trachyte, and also through other igneous rocks, especially the feldspathic kinds. 
 
 AuBsig and Teplitz in Bohemia, Tunaberg in Sweden, and Parg-as in Finland, afford fine 
 specimens of the dark-colored hornblendes. Actinolite in the Zillerthal; tremolite at St. 
 Gothard, in granular limestone or dolomite ; the Tyrol ; the Bannat, etc. Asbestus is found 
 in Savoy, Salzburg, the Tyrol; in the island of Cor.-ica. Some localities in the U. S. are : 
 Carlisle, Pelham, etc., Mass., cummingtonite at Cummington. In Conn., white crystals of 
 tremolite in dolomite, Canaan. In N. York, Willsboro', St. Lawrence Co. ; Warwick ; with 
 pyroxene at Edenv'le; near Amity ; in Rossie ; the variety pargaxite in large white crystals 
 at Diana, Lewis Co. In Penn., actinolite at Mineral Hill, in Delaware Co.; at Unionville. 
 In Maryland, actinolite and asbestus at the Bare Hills ; assbestus at Cooptown. 
 
 HEXAGONITE. Described as a new mineral by Goldsmith, but shown by Koenig to be only 
 a variety of tremolite. From Edwards. St. Lawrence Co., N. Y. 
 
 ARFVEDSONITE:^ Near hornblende, but contains alkalies. Analysis, Ramm., Greenland. 
 SiO a 51-22, A1O 3 tr.. F-e0 3 2375, FeO 7 -80, MuO 112, CaO 2'08, MgO 0-90, Na 2 O 10-58, 
 K,O 68, ign 0'16=98'29. Greenland ; Brevig ; Arendal. 
 
 CROCIDOLITE. Composition uncertain, near arfvedsonite. Analysis, Stromeyer, SiO 2 
 51-22, FeO 34 -08, MnO O'lO, MgO 2 -48, CaO 0'03, Na.O 7'07, H.O 4'80=99-?8. Fibrous, 
 asbestus-like. Sometimes altered to " Faserquarz." Color lavender-blue or leek-green. 
 Orange river, So. Africa. Vosges Mts. 
 
 GASTALDTTE. Monoclinic. Cleavage prismatic, lf\l = 124 25' (like amphibole). H. = 
 6-7. G.=3'044. Color dark-blue to azure-blue Streak greenish-blue. Q. ratio R : ft : Si 
 =1:2:6; formula R 3 M,Si.O.7, with R=Fe.Mg.Ca Na,. Analysis, Struver, SiO 2 5855, 
 A1O 3 21-40, FeO 9 '04, MgO 8 92, CaO 2 03, Na.O 4-77, K,0 tr=9971. Occurs in chlorite 
 late in the valleys of Aosta and Looano. 
 
 GLAUCOPHAN E.- Monoclinic. Cleavage prismatic, 2 A /=124 51'. H. =6'5. G. 3 -0907 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 299 
 
 Color blue, bluish-black. Q. ratio for bases to silicon 1 : 2. Analysis from Zermatt by 
 Bodewig, SiO, 57-81, A10 3 12'03, Fe0 3 2-17, FeO 5 '78, MgO 13'07, CaO 2'20, Na.O 7'33 
 ^100-45. Also from island of Syra. 
 WICHTISITE, Finland. Perhaps identical with glaucophane. 
 
 BERYL.* 
 
 Hexagonal. 6>Al = 150 3'; c = 0499. Habit prismatic, the prism 
 often vertically striated. Cleavage : basal imperfect ; lateral indistinct. 
 Occasionally coarse columnar and 
 large granular. 
 
 H. = 7-5-8. G. = 2-63-2-76. 
 Lustre vitreous, sometimes resin- 
 ous. Color emerald -green, pale 
 green, passing into light-blue, yel- 
 low, and white. Streak white. 
 Transparent subtranslucent. 
 Fracture conchoidal, uneven. Brit- 
 tle. Double refraction feeble; 
 axis negative. 
 
 Haddam, Ct. 
 
 Siberia. 
 
 Var. This species is one of the few that 
 occur only in crystals, and that have no es- 
 sential variations in chemical composition. There are, however, two prominent groups depend- 
 ent on color, the color varying as chrome or iron is present ; but only the merest trace of either 
 exists in any case. The crystals are usually oblong prisms. 1. Emerald. Color bright 
 emerald-green, owing to the presence of chromium. Hardness a little less than for beryl, 
 according to the lapidaries. 2. Beryl. Colors those of the species, excepting emerald-green, 
 and due mainly to iron. The varieties of beryl depending on color are of importance in the 
 arts, when the crystals are transparent enough to be of value as gems. The transparent 
 bluish-green lands are called aquamarine; also apple -green ; greenish-yellow to iron-yel- 
 low and honey -yellow. Davidsonite is nothing but greenish-yellow beryl from near Aberdeen ; 
 and gouhenite is a colorless or white variety from Goshen, Mass. 
 
 Comp Be 3 MSi 6 O 18 Silica 60-8, alumina 19'1, glucina 14-1=100. 
 
 Pyr,, etc. B. B. alone unchanged or becomes clouded ; at a high temperature the edges 
 are rounded, and ultimately a vesicular scoria is formed. Fusibility =5 '5 (Kobell). Glass 
 with borax clear and colorless for beryl, a fine green for emerald. Slowly soluble with salt 
 of phosphorus without leaving a siliceous skeleton. A yellowish variety from Broddbo and 
 Finbo yields with soda traces of tin. Unacted upon by acids. 
 
 Diff. Distinguished from apatite by its hardness, not being scratched by a knife, also 
 harder than green tourmaline ; from chrysoberyl by its form, and from euclase and topaz by 
 its imperfect cleavage ; never massive. 
 
 Obs. Emeralds occur in clay slate, in isolated crystals or in nests (not in veins), near Muso, 
 etc. , in N. Granada ; in Siberia. Transparent beryls (aquamarines) are found in Siberia, 
 Hindostan, and Brazil. Beautiful crystals also occur at Elba ; Ehrenfriedersdorf ; Schlacken- 
 wald ; at St. Michael's Mount in Cornwall ; Limoges in France ; in Sweden ; Fossuni in Nor- 
 way ; and elsewhere. 
 
 Berylf? of gigantic dimensions have been found in the United States, in N. Hamp.^ at 
 Acworth and Grafton, and in Mass.. at Royalston ; but they are mostly poor in quality. A 
 crystal from Grafton, according to Prof. Hubbard, measures 45 in. by 24 in its diameter, and 
 a single foot in length by calculation weighs l,07o Ibs., making it in all nearly 2^ tons. 
 Other localities are in Mass., at Barre; at Goshen ; at Chesterfield. In Conn., at Haddam; 
 Middletown ; at Madison. In Penn. , at Leiperville and Chester ; at Mineral Hill. 
 
 EUDIALYTE. RhombohedraL Color rose-red. Exact composition uncertain. Analysis, 
 Damour, SiO 2 50'38, ZrO a 15-60, Ta.O 6 0'35, FeO 6 '37, MnO 1-61, CuO 9 23, Na 2 O 13-10, 
 Cl T48, H,O 1-25=99 -37. West Greenland. EUCOLITE is similar, but contains also some 
 of the cerium metals. Norway. 
 
 POLLUCITE.* 3R.AlSi 4 O 12 -t-2aq with R = mostly Cs(Na,Li). If Na : Cs=l : 2, then 
 SiO, 42 0, AJO. 18-2, Cs.O 33 4, Na a O 3'7, H 2 2-1=100. Isornetric. Colorless. Island oi 
 Elba with castcrite. 
 
300 
 
 DESCRIPTIVE MINERALOGY. 
 
 Orthorhombic. 
 533 
 
 ft. UNISILICATES. GENERAL FORMULA 
 Chrysolite Group. 
 
 CHRYSOLITE.* Olivine. Peridot. 
 
 /A 1= 94 2'; A 14 =128 28'; c : I: a -= 1-2588 : 
 
 534 
 
 1-0729 : 1. A 1-i = 130 26J'. 
 A i-2, ov. 4, = 130 2 r . Cleavage : 
 *- rather distinct. Massive and 
 compact, or granular; usually in 
 imbedded grains. 
 
 H. = 6-7. G.= 3-33-3-5. Lustre 
 vitreous. Color green commonly 
 olive-green, sometimes yellow, 
 brownish, grayish- red, grayish- 
 green. Streak usually uncolored, 
 rarely yellowish. Transparent 
 translucent. Fracture conchoidal. 
 
 Comp., Var. (Mg.Fe) 2 SiO 4 , with traces at times of Mn, Ca, Ni. The amount of iron 
 varies much. If Mg : Fe=12 : 1, the formula requires Silica 41 '39, magnesia 50-90, iron 
 protoxide 7 71 =100 ; Mg : Fe=9 : 1, 6 : 1, etc., and in hyalosiderite 2 : 1. 
 
 Pyr., etc. B.B. whitens, but is infusible ; with the fluxes gives reactions for iron. Hya- 
 losiderite and other varieties rich in iron fuse to a black magnetic globule. Some varieties 
 give reactions for titanium and manganese. Decomposed by hydrochloric acid with separa- 
 tion of gelatinous silica. 
 
 Diff. Distinguished by its infusibility. Commonly observed in small yellow imbedded grains. 
 
 Obs. A common constituent of some eruptive rocks ; and also occurring in or among meta- 
 morphic rocks, with talcose schist, hypersthene rocks, and serpentine ; or as a rock formation ; 
 also a constituent of many meteorites (e.g., the Pallas iron). 
 
 Occurs in eruptive rocks at Vesuvius, Sicily, Hecla, Sandwich Islands, and most volcanic 
 islands or regions ; in Auvergne ; at Unkel, on the Rhine ; at the Laacher See ; in dolerite or 
 basalt in Canada. Also in labradorite rocks in the White Mountains, IS'. H. (hyalosiderite) ; in 
 Loudon Co., Va. ; in Lancaster Co., Pa., at Wood's Mine. 
 
 The following are members of the Chrysolite Group : 
 
 FORSTERITE. Mg 2 SiO 4 . Like chrysolite in physical characters. Vesuvius. BOLTONITE, 
 essentially the same. Bolton, Mass. 
 
 MONTICKLLITE, from Mt. Somma, and BATRACIIITE, from the Tyrol, are (Ca,Mg) 2 SiO 4 , 
 with Ca : Mg=l : 1. H. =5-5 '5. G. =3'03-8-25. Monticellibe also occurs in large quantities 
 (v. Rath) on the Pesmeda Alp, Tyrol, altered to serpentine and fassaite. 
 
 FAYALTTE. Fe a SiO 4 . G. =4-4 14. Color black. In volcanic rocks at Fayal, Azores ; 
 Mourne M'.ts., Ireland. 
 
 HORTONOLITE. (Fe,Mg),SiO 4 , with Fe : Mg=3 : 2. O'Neil mine, Orange Co., N. T. 
 
 TEPHROITE- Mn 2 SiO 4 . G. =4-4 '12. Color reddish-brown. Sterling Hill, N. J.; Sweden. 
 
 ROEPPERITE. An iron-manganese-zinc chrysolite. H.=5*5-6. G. =3 '95-4 '08. Color 
 dark-green to black. Stirling Hill, N. J. 
 
 KNEBELITE. (Fe,Mn),Si0 4 , with Fe : Mn=l : 1. G.=4-12. Color gray. Dannemora. 
 
 LEUCOPHANITE.* Composition given by the analysis (Ramm.) SiO 2 47*03, A10 3 1 '03, BoO 
 10-70, CaO 23-37, MgO 0'17, Na,O 11-26, K,O 0'30, F 6-57=100-43. Orthorhombic. G.= 
 2 "97. Color greenish-yellow. Occurs in syenite on the island of Lamoe, Norway. 
 
 MELIPHANITE (Melinophan). Composition given by the analysis (Rarnm.) SiO 2 43 66, 
 AlO,(FeOs) 1-57, BeO 11 '74, CaO 26-74, MgO (HI, Na 2 8-55, K,O 1'40, H 2 0'30, F 5'73 
 =99-80. G.=3'018. Orthorhombic. Color yellow. Fredriksvarn, Norwa/. 
 
 WOHLERITE. Composition given by the analysis (Ramm. ) SiO 2 28-43, CboO 6 14-41, ZrO 1 
 19 -63, CaO 26-18, FeO(MnO) 2 "50, Na 2 7' 78=98 -93. Monoclinic. G. =3 '41. Color light- 
 yellow. Near Brevig, Norway. 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 301 
 
 Willemite Group. 
 
 WILLEMITE. 
 
 Ehombohedral. R A E = 116 V, A E = 142 IT ; c = 0-67378. Cleav- 
 age: -2 easy in N". Jersey crystals; easy in those of Moresnet. Also 
 massive and in disseminated grains. Sometimes fibrous. 
 
 H.=5-5. G.=3-89-4-18 ; 4'27, transparent crystals 535 
 
 (Cornwall). Lustre vitreo-resinous, rather weak. Color 
 whitish or greenish-yellow, when purest; apple-green, 
 flesh-red, grayish-white, yellowish-brown ; often dark- 
 brown when impure. Streak uncolored. Transparent 
 to opaque. Brittle. Fracture conchoidal. Double 
 refraction strong ; axis positive. 
 
 \ 
 
 Var. The crystals of Moresnet and New Jersey differ in occurring 
 forms. The latter are often quite large, and pass under the name of 
 troostite ; they are commonly impure from the presence of man- 
 ganese and iron. 
 
 Comp.Zn 2 Si0 4 = Silica 27-1, zinc oxide 72 "9 =100. 
 
 Pyr., etc. B.B. in the forceps glows and fuses with difficulty to 
 a white enamel ; the varieties from New Jersey fuse from 3 '5 to 4. 
 The powdered mineral on charcoal in R.F. gives a coating yellow 
 
 while hot and white on cooling, which, moistened with solution of cobalt, and treated in O. 
 I\, is colored bright green. With soda the coating is more readily obtained. Decomposed 
 by hydrochloric acid with separation of gelatinous silica. 
 
 Obs From Vieille-Montagne near Moresnet ; also at Stolberg ; at Raibel in Carinthia; 
 at Kucsaina in Servia, and in Greenland. In New Jersey, at both Franklin and Stirling in 
 such quantity as to constitute an important ore of zinc. It occurs intimately mixed with 
 zincite and franklinite, and is found massive of a great variety of colors, from pale honey- 
 yellow and light green to dark ash-gray and flesh-red ; sometimes in crystals (troostite). 
 
 DIOPTASE. Emerald-Copper. 
 
 Ehombohedral; tetartohedral. 72 A 72 =126 24'; <9 A 72 = 148 38'; 
 c= 0-5281. Cleavage: R perfect. Twins: twinning- 
 plane R. Also massive. 536 
 
 H.=5. G.=3-27S-3-348. Lustre vitreous. Color 
 emerald-green. Streak green. Transparent subtrans- 
 lucent. Fracture conchoidal, uneven. Brittle. Double 
 refraction strong, positive. 
 
 Comp Q. ratio for Cu : Si : H=l : 2 : 1 ; formula H 2 CuSi0 4 
 (Ramm.) = Silica 38 '1, copper oxide 50-4, water 11-5 = 100. 
 
 Pyr., etc. In the closed tube blackens and yields water. B.B. 
 decrepitates, colors tne flame emerald-green, but is infusible. With 
 the fluxes gives the reactions for copper. With soda on charcoal a 
 globule of metallic copper. Decomposed by acids with gelatinization. 
 
 Obs. Dioptase occurs disposed in well-defined crystals and amor- 
 phous on quartz, occupying seams in a compact limestone west of the 
 hill of Altyn-Tubeh in the Kirghese Steppes ; also in the Siberian 
 gold-washings. From Chase Creek, near Clifton, Arizona, in fine 
 crystals, on a "mahogany ore," consisting of limonite and copper oxide. 
 
 PHENACITE. Be. 2 Si0 4 . Rhombohedral. Colorless. Resembles quartz. Takovaja ; Miask j 
 Durango, Mexico. 
 
302 DESCRIPTIVE MINERALOGY. 
 
 FRIEDELITE. Rhombohedral. 0/\R=\tf\ R A 12=123 42'. Cleavage: easy. 
 H. 4.75. G. 3.07. Also massive, saccharoidal. Color rose-red. Translucent. Double 
 refraction strong, axis negative. Analysis, Si0 2 36.12, MnO (FeO tr) 53 '05, MgO, CaO 2-96, 
 H 2 O 7*87=100 This corresponds to the formula Mn 4 Si3Oio+2H 2 O. If the water is basic, 
 as in dioptase, with which it seems to be related in form, the formula is H 4 Mn 4 Si 3 Oi',= 
 R,Si0 4 . This requires SiO 2 30 "00, MnO 56 -80, H 2 O 7" 20= 100. f Occurs with diallogite and 
 alabandite at the manganese mine of Adervielle, Hautes-Pyrenees. (Bertrand, C. R. , May, 
 1876.) 
 
 HELVITE.* 
 
 Isometric : tetrahedral. Cleavage : octahedral, in traces. 
 
 H.=6-6'5. G.=3'l-3'3. Lustre vitreous, inclining to resinous. Color 
 honey-yellow, inclining to yellowish-brown, and siskin-green. Streak un- 
 colored. Subtranslucent. Fracture uneven. 
 
 Comp. Q. ratio for R : Si=l : 2 ; for Mn + Fe : Be=l : 1 ; formula 3(Be,Mn,Fe) 2 Si0 4 + 
 (Mn.Fe)S (Ramm.). Analysis by Teich, Lupikko, Finland, SiO 2 30'31, BeO 10-51, MnO 
 37-87, FeO 10-37, CaO 4-72, ign 0'22, S 5 95=99-95. 
 
 Pyr., etc. Fuses at 3 in R.F. with intumescence to a yellowish-brown opaque bead, becom- 
 ing darker in R.F. With the fluxes gives the manganese reaction. Decomposed by hydro- 
 chloric acid, with evolution of sulphuretted hydrogen, and separation of gelatinous silica. 
 
 Obs. Occurs in gneiss at Schwarzenberg in Saxony ; at Breitenbrunn. Saxony ; at Horte- 
 kulle near Modum, and also at Brevig in Norway, in zircon-syenite. 
 
 DANALITE.* 
 
 Isometric. In octahedrons, with planes of the dodecahedron ; the dode- 
 cahedral faces striated parallel to the longer diagonal. 
 
 H.=5'5-6. G.=3*427. Lustre vitreo-resinous. Color flesh-red to gray. 
 Streak similar, but lighter. Translucent. Fracture subconchoidal, uneven. 
 Brittle. 
 
 Comp. 3(Be,Fe,Mn,Zn) a SiO 4 +(Fe,Mn,Zn)S. Analysis : J. P. Cooke, Rockport, SiO 2 
 81-73, FeO 27'40, MnO 628, ZnO 17'51, BeO 13'83. S 5'48=102'23. By subtracting from 
 the analysis oxygen 2'74, equivalent to the sulphur, the sum is 99-49. 
 
 Pyr., etc. B.B. fuses readily on the edges to a black enamel. With soda on charcoal gives 
 a slight coating of zinc oxide. Perfectly decomposed by hydrochloric acid, with evolution of 
 sulphuretted hydrogen and separation of gelatinous silica. 
 
 Obs. Occurs in the Rockport granite, Cape Ann, Mass. , small grains being disseminated 
 through this rock ; also near Gloucester, Mass. 
 
 EaLTTiTE (Kieselwis:nuth, Germ.). Isometric, tetrahedral; in minute crystals often 
 aggregated together. H. =4-5-5. GK =6-106. Color grayish-white to brown. Comp. A uni- 
 silicate of bismuth, Bi 4 Si 3 Oi 2 . Schneeberg. Agricolite. Composition similar, but form 
 monoclinic. Occurs in globular masses having a radiated structure, and in indistinct groups 
 of crystals. Schneeberg (color hair-brown) and Johanngeorgenstadt (color wine -yellow). 
 
 BISMDTOPERRITE. Cryptocrystalline; generally massive. H.=35. G.=4-47. Color 
 olive-green. Analysis (Frenzel) Si0 2 24 '05, FeOs 33-12, Bi 2 O 8 42 83=100. Schneeberg. 
 HypocJdorite is hornstone mixed with the above mineral and other impurities. 
 
 Garnet O~roup. 
 GARNET.* Granat, Germ. 
 
 leometric; dodecahedron, f. 537, and the trapezohedron 2-2, f. 538, 
 Uio most common forms; octahedral form very rare. Distorted form? 
 
OXYGEN COMPOUNDS ANHTDKOCS SILICATES. 
 
 303 
 
 shown in f. 345-352, pp. 105, 106. Cleavage : dodecahedral, sometimes quite 
 distinct. Twins: twinning-plane octahedral. Also massive; granular, 
 coarse, or fine, and sometimes friable ; lamellar, lamellae thick and bent. 
 Also very compact, crypto-crystalline like saussurite. 
 
 539 
 
 H.=6*5-7'5. G.=3*15-4'3. Lustre vitreous resinous. Color red, 
 brown, yellow, white, apple-green, black ; some red and green colors often 
 bright. Streak white. Transparent subtranslucent. Fracture subcon- 
 choidal, uneven. Brittle, and sometimes friable when granular massive; 
 very tough when compact cryptocrystalline. Sometimes doubly refracting 
 in consequence of lamellar structure, or in some cases from alteration. 
 
 Comp., Var. Garnet is a unisilicate of elements in the sesquioxide and protoxide states, 
 having- the general formula R 3 ftSi 3 Oi2. There are three prominent groups, based on the 
 nature of the predominating sesquioxide. 
 
 I. ALUMINA GARNET, in which aluminum (Al) predominates. 
 
 II. IRON GARNET, in which iron (Fe) predominates, usually with some aluminum. 
 
 III. CHROME GARNET in which chromium (r) is most prominent. 
 
 There are the following varieties or subspecies, based on the predominance of one or another 
 of the protoxides : 
 
 A. GROSSULARITE, or Lime- Alumina garnet. B. PYROPE, or Magnesia- Alumina garnet. 
 C. ALMANDITE, or Iron- Alumina garnet. D. SPESSARTITE, or Manganese- Alumina garnet. 
 E. ANDRADITE, or Lime-Iron garnet, including 1, ordinary; 2, manganesian, or Sothoffite ; 
 3, yttriferous, or Ytter-garnet. F. BREDBERGITE, or Lime- Magnesia- Iron garnet. G. 
 OUVAROVITE, or Lime- Chrome gar net. Excepting the last, these subdivisions blend with one 
 another more or less completely. 
 
 A. Lime- Alumina garnet ; GROSSULARITE. Cinnamon stone. A silicate mainly of aluminum 
 and calcium ; formula mostly Ca 3 AlSi 3 Oi2 = Silica 40*0, alumina 22'8, lime 37-2=100. But 
 some calcium often replaced by iron, and thus graduating toward the Almandite group. Color 
 (a) white ; (b) pale green ; (c) amber- and honey-yellow ; (d) wine-yellow, brownish-yellow, 
 cinnamon-brown; rarely (e) emerald-green from the presence of chromium. G. =3 '4-3*75. 
 
 B. Mr gnesia- Alumina garnet ; PYROPE. A silicate of aluminum, with various protoxide 
 bases, among which magnesium predominates much in atomic proportions, while in small pro- 
 portion in other garnets, or absent. Formula (Mg,Ca,Fe,Mn)3^:lSi30i 2 . The original pyrope 
 is the kind containing chromium. In the analysis of the Arendal magnesia-garnet, Mg : Ca : 
 Fe+Mn=3 : 1 : 2; SiO, 42'45, A10 3 22 '47, FeO 9 29, MnO 6 '27, MgO 13 "43, CaO 6 '53= 
 100-44 Wacht. G. =3 '157. The name pyrope is from 7rvpw7r<fr, fire-like. 
 
 C. Iron- Alumina garnet; ALMANDITE. A silicate mainly of aluminum and iron <Fe); 
 formula FegAlSiaOn^ Silica 36-1, alumina 206, iron protoxide 43-3=100; or Mn may re- 
 place some of the Fe, and Fe part of the Al. Color fine deep-red and transparent, and then 
 called precious garnet ; also brownish-red and translucent or subtranslucent, common garnet; 
 black, and then referred to var. melanite. Part of common garnet belongs to the Andraditt 
 group, or is iron garnet. 
 
304 DESCRIPTIVE MINERALOGY. 
 
 D. Manganese- Alumina garnet; SPESSARTITE. Color dark hyacinth-red (fr. Spessart), 
 sometimes with a shade of violet, to brownish-red. G. =3'7-4'4. Analysis, Haddam, Ct., 
 Si0 2 36-16, A1 2 O 3 19-76, FeO ll'lO, MnO 32'18, MgO 0'22, CaO 0-58 = 100, Ramm. 
 
 E. Lime-Iron garnet ; ANDRADITE. Aplome. Color various, including wine-, topaz-, 
 and greenish-yellow (topazolite), apple-green, brownish red, brownish-yellow, grayish-green, 
 dark green, brown, grayish-black, black. G. =3. 64-4. 
 
 Comp. Ca 3 FeSi 3 Oi2, this includes : (a) Topazolite, having the color and transparency of 
 topaz, and also sometimes green ; although resembling essonite, Damour has shown that it 
 belongs here. (b) Colophonite, a coarse granular kind, brownish-yellow to dark reddish- 
 brown in color, resinous in lustre, and usually with iridescent hues ; named after the resin 
 eolopliony. (c) Melanite (named from f^e'tag, black), black, either dull or lustrous; but all 
 black garnet is not here included. Pyreneite is grayish-black melanite ; the original afforded 
 Vauquelin 4 p. c. of water, and was iridescent, indicating incipient alteration, (d) Dark green 
 garnet, not distinguishable from some allochroite, except by chemical means. 
 
 F. Lime- Magnesia Iron garnet ; BREDBERGITE. A variety from Sala, Sweden, is here 
 included. .Formula (Ca,Mg) 3 FeSi 3 Oi 2 =:Si]ica 372, iron sesquioxide 33'1, magnesia 12-4, 
 lime 17'3=100. It corresponds under Iron garnet nearly to aplome under Alumina garnet. 
 
 G. Lime- Chrome garnet ; OUVAROVITE. A silicate of calcium and chromium. Formula 
 Ca s 6rSi 3 Oi 2 . In the Ural variety, a fourth of the chromium oxide is replaced by aluminum 
 oxide; that is, Al : Or=l : 3 nearly. Color emerald-green. H.=7'5. G. =3 '41-3 -52. B.B. 
 infusible; with borax a clear chrome-green glass. Named after the Russian minister, Uvarof. 
 
 Pyr., etc. Most varieties fuse easily to a light-brown or black glass ; F. =3 in almandite, 
 spessartite, grossularite, and allochroite ; 3'5inpyrope; but ouvarovite is almost infusible, 
 F.=6. Allochroite and almandite fuse to a magnetic globule. Reactions with the fluxes 
 vary with the bases. Almost all kinds react for iron ; strong manganese reaction in spessar- 
 tite, and less marked in other varieties ; a chromium reaction in ouvarovite, and in most py- 
 rope. Some varieties are partially decomposed by acids ; all except ouvarovite are decomposed 
 after ignition by hydrochloric acid, and generally with separation of gelatinous silica. Decom- 
 posed on fusion with alkaline carbonates. 
 
 Diff. Ordinary garnets are distinguished from zircon by their fusibility B.B., but they fuse 
 less readily than vesuvianite ; the vitreous lustre, absence of prismatic structure, and usually 
 the form, are characteristic; it has a higher specific gravity than tourmaline. 
 
 Obs, Garnet crystals are very common in mica schist, gntiss, syenitic gneiss, and horn- 
 blende and chlorite schist ; they occur often, also, in granite, syenite, crystalline limestones, 
 sometimes in serpentine, and occasionally in trap and volcanic tufa and lava. 
 
 Some localities are : Cinnamon-stone (Exsonite), Ceylon ; Mussa-Alp in Piedmont. 
 Qrossularite, Siberia; Tellemark, Norway; Ural. Almandite, Ceylon, Pegu, Brazil, and 
 Greenland. Common garnet in large dodecahedrons, Sweden ; Arendal and Kongsberg in 
 Norway, and the Zillerthal. Melanite at Vesuvius and in the Hautes- Pyrenees (Pyreneite). 
 Aplome at Schwarzenberg in Saxony. Spessartite at Spessart in Bavaria, Elba, at St. Marcel, 
 Piedmont. Pi/rope in Bohemia, also at Zoblitz in Saxony. Ouvarovite an the Urals. 
 
 In N. America in Maine, Phippsburg, Rumford, Windham, at Brunswick, etc. In N. Hamp.^ 
 Warren. In Mass., at Carlisle; massive at Newbury ; at Chesterfield. In Conn., trapezo- 
 hedrons, -1 in. , in mica slate, at Reading and Monroe ; Haddam. In N. York, at Roger's 
 Rock; Crown Point, Essex Co.; at Amity. In N. Jersey, at Franklin. In Penn., in Chester 
 Co., at Pennsbury ; near Knauertown, at Keims' mine ; at Chester, brown; in Leiperville, 
 red; near Wilmington. In California, in Los Angeles Co., in Mt. Meadows; ouvarovite at 
 New Idria ; pyrope, near Santa Fe, New Mexico. In Canada, at Marmora, at Grenville ; 
 chrome -garnet in Orford, Canada. 
 
 The cinnamon- stone from Ceylon (called hyacinth) and the precious garnet are used as geins 
 when large, finely colored, and transparent. The stone is cut quite thin, on account of the 
 depth of color, with a pavilion cut below, and a broad table above bordered with small facets. 
 An octagonal garnet measuring 8 lines by 6^ has sold for near $700. Pulverized garnet is 
 sometimes employed as a substitute for emery. 
 
 Vesuvianite Group. 
 ZIRCON* 
 
 Tetragonal. A 14 = U7 22' ; c = 0-640373, Haidiuger. /A 1 = 
 132 10 . Faces of pyramids sometimes convex. Cleavage: / imperfect, 
 1 less distinct. Also in irregular forms and grains. 
 
OXYGEN COMPOUNDS ANHYDKOUS SILICATES. 
 
 305 
 
 H.=7'5. G.=4'05-4'75. Lustre adamantine. Colorless, pale yellow- 
 ish, grayish, yellowish-green, brownish-yellow, reddish-brown. Streak mi- 
 colored. Transparent to sub translucent and opaque. Fracture conchoidal, 
 brilliant. Double refraction strong, positive. 
 
 542 
 
 545 
 
 546 
 
 Saualpe. 
 
 McDoweU Co., N. C. 
 
 Var. The colorless and yellowish or smoky zircons of Ceylon have there been lot>g called 
 jargons in jewelry, in allusion to the fact that, while resembling the diamond in lustre, they 
 were comparatively worthless ; and thence came the name zircon. The brownish, orange, and 
 reddish kinds were called distinctively hyacinths a name applied also in jewelry to some topaz 
 and light- colored garnet. 
 
 Comp. ZrSiO 4 = Silica 33, zirconia 67=100. Klaproth discovered the earth zirconia in 
 this species in 1789. 
 
 Pyr., etc. Infusible ; the colorless varieties are unaltered, the red become colorless, while 
 dark-colored varieties are made white ; some varieties glow and increase in density by igni- 
 tion. Not perceptibly acted upon by salt of phosphorus. In powder is decomposed when 
 fused with soda on the platinum wire, and if the product is dissolved in dilute hydrochloric 
 acid it gives the orange color characteristic of zirconia when tested with turmeric paper. Not 
 acted upon by acids except in fine powder with concentrated sulphuric acid. Decomposed 
 by fusion with alkaline carbonates and bisulphates. 
 
 Diff. Distinguished by its adamantine lustre, hardness, and infusibility ; the occurrence of 
 square prismatic forms is also characteristic. 
 
 Obs. Occurs in crystalline rocks, especially granular limestone, chloritic and other schists ; 
 gneiss, syenite ; also in granite ; sometimes in iron-ore beds. 
 
 Found in alluvial sands in Ceylon ; in the gold regions of the Ural ; at Arendal in Norway ; 
 at Fredericksvarn, in zircon-syenite ; in Transylvania ; at Bilin in Bohemia. 
 
 In N. America, in N. York, at Moriah, Essex Co. , and in Orange Co. ; in Warwick ; near 
 Amity ; at Diana in Lewis Co. ; also at Rossie. In N. Jersey, at Franklin ; at Trenton in 
 gneiss. In N. Car., in Buncombe Co.; in the sands of the gold washings of McDowell Co. 
 In California, in the auriferous gravel of the north fork of the American river, and else- 
 where. In Canada, at Grenville, etc. 
 
 VESUVTANITE.* IDOCRASE. 
 
 Tetragonal. O A 1-* = 151 45'; c = 0-537199 (v. Kokscharof). O Al 
 = 142 46i' 1 A 1, ov. 1-t, = 129 21'. Cleavage : / not very distinct, 
 Btill less so. Columnar structure rare, straight and divergent, or irregular. 
 Sometimes granular massive. Prisms usually terminating in the basal piano 
 O ; rarely in a pyramid or zirconoid ; sometimes the prism nearly wanting, 
 and the form short pyramidal with truncated summit and edges. 
 20 
 
306 
 
 DESCRIPTIVE MINERALOGY. 
 
 XL =6-5. G. = 3-349-3-45. 
 
 548 
 
 651 
 
 2 /:: 
 
 Sandford, Me. 
 
 Lustre vitreous ; often inclining to re 
 inous. Color brown to green, 
 and the latter frequently bright 
 and clear ; occasionally sulphur- 
 yellow, and also pale blue ; some- 
 times green along the axis, 
 and pistachio-green transversely. 
 Streak white. Subtransparent 
 faintly subtranslucent. Fracture 
 subconchoidal -uneven. Double 
 refraction feeble, axis negative. 
 
 Oomp., Var, Q. ratio f or R : R : Si= 
 4:3:7 (according to the latest investi- 
 gations of Rammelsberg). R=Ca (also 
 Mg, Fe, or H 2 ,K 2 ,Na 2 ); ft=Al and also Fe. 
 If we neglect the water the empirical for- 
 
 mula is R 8 ft. 2 Si 7 O..8, where the quantivalent ratio of bases to silicon is 1 : 1. The ratio of 
 R : R varies much, which, as stated by Rammelsberg. is the explanation of the different 
 varieties. Analyses by Rammelsberg. (1) Monzoni ; (2) Wilui, Siberia. 
 
 (1) 
 (2) 
 
 SiO a 
 37-82 
 38-40 
 
 16-08 
 13-72 
 
 Fe0 3 
 
 3-75 
 
 5-54 
 
 FeO 
 
 2-91 
 
 MgO 
 
 2-11 
 6-88 
 
 CaO 
 
 3/3-34 
 
 35-04 
 
 NaO(K 2 O) 
 016 
 0-66 
 
 H 2 O 
 
 2-08= 99-75 
 
 0.82=101-06. 
 
 Pyr., etc B.B. fuses at 3 with intumescence to a greenish or brownish glass. Magnus 
 states that the density after fusion is 2 '93-2 945. With the fluxes gives reactions for iron, 
 And a variety from St. Marcel gives a strong manganese reaction. Cyprine gives a reaction for 
 copper with salt of phosphorus. Partially decomposed by hydrochloric acid, and completely 
 when the mineral has been previously ignited. 
 
 Diff. Resembles some brown varieties of garnet, tourmaline, and epidote, but its tetragonal 
 form and easy fusibility distinguish it. 
 
 Obs. Vesuvianite was first found among the ancient ejections of Vesuvius and the dolo- 
 mitic blocks of Somma. It has since been met with most abundantly in granular limestone ; 
 also in serpentine, chlorite schist, gneiss, and related rocks. It is often associated with lime- 
 garnet and pyroxene. It has been observed imbedded in opal. 
 
 - Occurs at Vesuvius ; at Ala, in Piedmont ; at Monzoni in the Fassathal ; near Christiansand, 
 Norway ; on the Wilui river, near L. Baikal ; in the Urals, and elsewhere. 
 . In N. America, in Maine, at Phippsburg and Rumford, abundant ; Sandford (f. 551). In 
 N. York, at Amity. In 2f. Jersey, at Newton. In Canada, at Calumet Falls ; at Grenville. 
 
 MELILITE from Capo di Bove, and HUMBOLDTILTTE from Mt. Somma, are similar in com- 
 
 jition. Analysis of the melilite by Damour. SiO > 38 '34, A10 3 861, Fe0 3 10 '02, CaO 32 "05, 
 6*71, Na 2 O 2-12, K,O 1-51=99-36. Tetragonal. Color honey-yellow. 
 
 Epidote Group. 
 
 The species of the Epidote Group are characterized by high specific 
 gravity, above 3 ; hardness above 5 ; fusibility B,B. below 4 ; anisometric 
 crystallization, and therefore biaxial polarization ; the dominant prismatic 
 angle 112 to 117 ; fibrous forms, when they occur, always brittle ; colors 
 .white, gray, browir yellowish -green, and deep green to black, and some- 
 times reddish. 
 
 The prismatic angle in zoisite and other orthorhombic species is I A /; but in epidote it ia 
 the angle over a horizontal edge between the planes and i-i, the orthodiagonal of epidote 
 corresponding .to the vertical axis of zoisite, as explained under the latter species. 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 307 
 
 EPIDOTE. Pistazite. 
 
 Monoclinic. 6 r = 89 27' ; *-2 A i-2 = 63 8', <9 A 14 = 122 C 23'; c : I : a 
 = 0-43436 : 0-30719 : 1. O M-i = 154 3', O f\ -l-i = 154 15', ^ A -1 
 = 104 48', i-iM = 104 15'. Crystals usually lengthened in the direc- 
 tion of the orthodiagonal, or parallel to i-i; sometimes long acicular. 
 Cleavage: i-i perfect; 1-i less so. Twins : twinning-plane I-ij also i-i. 
 Also fibrous, divergent, or parallel ; also granular, particles of various sizes, 
 sometimes fine granular, and forming rock-masses. 
 
 552 
 
 553 
 
 H. = 6-7. G.=3*25-3'5. Lustre vitreous, on i-i inclining to pearly or 
 resinous. Color pistachio-green or yellowish-green to brownish-green, 
 greenish-black, and black ; sometimes clear red and yellow ; also gray and 
 grayish- white. Pleochroism often distinct, the crystals being usually least 
 yellow in a direction through \-i (see p. 166). Streak 1111 colored, grayish. 
 Subtransparent opaque ; generally subtranslucent. Fracture uneven. 
 Brittle. 
 
 Var. Epidote has ordinarily a peculiar yellowish-green (pistachio) color, seldom found in 
 other minerals. But this color passes into dark and light shades black on one side, and 
 brown on the other. Most of the brown and nearly all the gray epidote belongs to the species 
 Zoisite ; and the reddish-brown or reddish-black, containing much oxide of manganese, to 
 the species Piedmontite, or Manganepidot ; while the black is mainly of the species Allanite^ 
 or Ceriurn-epidote. 
 
 Comp. Quantivalent ratio for Ca : R : Si =4 : 9 : 12, and H : Ca=l : 4. The formula is 
 then H-iCa^sSicO^G. R is Fe or Al, the ratio varying from 1 : 2 to 1 : 6. Analysis, Unter- 
 eulzbach, Tyrol, by Ludwig : SiO 2 37 '8:3, A1O 3 22'63, FeO 3 15 '05, FeO 0"93, CaO 23 '27, H.,0 
 2 -05 =100 '76. As first shown by Ludwig, epidote contains about 2 p. c. water, which is 
 given off only at high temperatures. 
 
 Pyr., etc. In the closed tube gives water at a high temperature. B. B. fuses with intumes- 
 cence at 3-3 '5 to a dark brown or black mass which is generally magnetic. Reacts for iron 
 and sometimes for manganese with the fluxes. Partially decomposed by hydrochloric acid, 
 but when previously ignited, gelatinizes with acid. Decomposed on fusion with alkaline car- 
 bonates. 
 
 Diff. Distinguished often by its peculiar yellowish-green color ; yields a magnetic globule, 
 B.B. Prismatic forms often longitudinally striated, but they have not the angle, cleavage, 
 or brittleness of trernolite. 
 
 Obs. Epidote is common in many crystalline rocks, as syenite, gneiss, mica schist, horn- 
 blendic schist, serpentine, and especially those that contain the ferriferous mineral horn- 
 blende. It often accompanies beds of magnetite or hematite in such rocks. It is sometimes 
 found in geodes in trap ; and also in sandstone adjoining trap dikes, where it has been 
 formed by metamorphism through the heat of the trap at the time of its ejection. It also 
 occurs at times in nodules in different quartz-rocks or altered sandstones. It is associated 
 often with quartz, pyroxene, feldspar, axinite, chlorite, etc., in the Piedmontese Alps. 
 
 Beautiful crystallizations come from Bourg d'Oisans, Ala, and Traversella, in Piedmont , 
 Zcrmatt and elsewhere in Switzerland ; Monzoni in the Fassathal ; the Untersulzbachthal and 
 Zillerthal in the Tyrol. 
 
 In N. America, occurs in Mass., at Chester ; at Athol ; at Rome. In Conn., at Haddaxn. 
 
308 
 
 DESCRIPTIVE MINERALOGY. 
 
 555 
 
 In N. York, at Amity ; near Monroe, Orange Co. ; at Warwick. In N. Jersey, at Franklin, 
 In Penn., at E. Bradford. In Michigan, in the Lake Superior region. In Canada, at Sfc, 
 Joseph. 
 
 PIEDMONTITE (Manganepidot, Germ.). A manganese epidote ; formula, HsCaiRsSieOae, 
 with R principally Mn (also Al,Fe). Color reddish-brown. St. Marcel, Aosta valley, Pied- 
 mont. 
 
 ALLANITE. 
 
 Monoclinic, isomorphous with epidote. C = 89 1' ; A 14 = 122 50J', 
 
 a-2 A a-2 = C3 58' ; c : I : d = 
 0-483755 : 0-312187 : 1. Crystals 
 either short, flat tabular, or long 
 and slender, sometimes acicnlar. 
 Twins like those of epidote. Cleav- 
 age : i-i in traces. Also massive, 
 and in angular or rounded grains. 
 
 H.=5-5-6. GL=: 3-0-4-2. Lustre 
 siibmetallic, pitchy, or resinous 
 occasionally vitreous. Color pitch- 
 
 brown to black, either brownish, greenish, grayish, or yellowish. Streak 
 
 gray, sometimes slightly greenish or brownish. Subtranslucent opaque. 
 
 Fracture uneven or subconchoidal. Brittle. Double refraction either dis- 
 
 tinct, or wanting. 
 
 Allanite (Cerine). In tabular crystals or plates. Color black or brownish-black. 
 G. =3 50-3 '95; found among specimens from East Greenland, brought to Scotland by C. 
 Giesecke. Bucklandite is anhydrous allanite in small black crystals from a mine of magnetite 
 near Arendal, Norway. Referred here by v. Rath on the ground of the angles and physical 
 characters. 
 
 Orthite. Including, in its original use, the slender or acicular prismatic crystals, often a 
 foot long, containing some water. But these graduate into massive forms, and some orthites 
 are anhydrous, or as nearly so as much of the allanite. The name is from bp66s, straight. 
 The tendency to alteration 'and hydration may be due to the slenderuess of the crystals, and 
 the consequent great exposure to the action of moisture and the atmosphere. II. =5-6. 
 G. =2 '80-3- 75. Lustre vitreous to greasy. 
 
 Comp. Not altogether certain, as analyses vary considerably, some showing the presence 
 of considerable water. According to Rammelsberg the Q. ratio for bases to silicon 1 : 1 
 (epidote^l^ : 1). Allanite has then the garnet formula, R 3 RSi 3 Oi 2 , where R=Ce(La,Di), 
 Fe(Mn), Ca(Mg), and occasionally Y,Na 2 ,K 2 , etc.; R=A1 or Fe. Analysis, allanite (Ramm.), 
 Fredrikshaab, Si0 2 33'78, A10 3 14'03, FeO 3 6 -36, FeO 13'63, CeO 12-63, LaO(DiO) 5 '07, CaO 
 1212, H 2 O 1-78=100. 
 
 Pyr., etc. Some varieties give water in the closed tube. B.B. fuses easily and swells up 
 (F. 2*5) to a dark, blebby, magnetic glass. With the fluxes reacts for iron. Most varieties 
 gelatinize with hydrochloric acid, but if previously ignited are not decomposed by acid. 
 
 Obs. Occurs in albitic and common feldspathic granite, syenite, zircon- syenite, porphyrj, 
 white limestone, and often in mines of magnetic iron. Allanite occurs in Greenland ; at 
 Criffel in Scotland ; at Jotun Fjeld in Norway ; at Snarum, near Dresden ; near Schmiede- 
 feld in the Thiiringerwald. Cerine occurs at Bastnas in Sweden. Orthite occurs at Finbo 
 and Ytterby in Sweden ; also at Krageroe, etc. , in Norway ; at Miask in the Ural. 
 
 In Mass., at the Bolton quarry. In Conn., at Haddam. In N. York, Moriah, Essex Co.; 
 at Monroe, Orange Co. In _ZV". Jersey ', at Franklin. In Penn. , at E. Bradford in Chester Co. ; 
 at Easton. Amherst Co., Va. In Canada, at St. Paul's, C. W. 
 
 MUROMONTITE and BODENITE from Marienberg, Saxony ; and MICHAELSONITE from 
 Brevig, are minerals related to allanite. 
 
 ZOISITE. 
 
 Orthorhombic. /A 1 = lld 40', O A l-l = 131 If ; c : I : d = 1-1493 
 * 1 '6 21 25 : 1. Crystals lengthened in the direction of the vertical axis, and 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 309 
 
 550 
 
 vertically deeply striated or furrowed. Cleavage: i-$ very perfect. 
 monly in crystalline masses longitudinally furrowed. 
 Also compact massive. 
 
 H. = 6-6-5. G.=3-ll-3-3S. Lustre pearly on i-l\ 
 vitreous on surface of fracture. Color grayish-white, 
 gray, yellowish, brown, greenish-gray, apple-green; 
 also peach-blossom-red to rose-red. Streak uricolored. 
 Transparent to sub translucent. Double refraction 
 feeble, optic-axial plane i-i ; bisectrix positive, normal 
 to i-i ; DesCl. 
 
 Com 
 
 r. LIME-ZOISITE. 1. Ordinary. Colors gray to Avhite 
 rown. 2. Rose-red, or Thulite. G. =3'1 24; fragile; dichro- 
 
 Var. 
 
 and brown. 
 
 ism strong, especially in the direction of the vertical axis ; in this 
 direction reddish, transversely colorless ; from Norway, Piedmont. 
 Saussurite, which forms with smaragdite the euphotideof the Alps, 
 is a lime -soda zoisite. 
 
 Comp. A lime-epidote, with little or no iron, and thus differing from epidote. Q. ratio 
 as in epidote, H : Ca=l : 4, and Ca : It : Si=4 : 9 : 12, whence the formula H. 2 Ca4R s Si 6 O2 e> . 
 Analysis, Ramm., Goshen (G.=3'341) SiO> 40'06,rUO 3 3067, Fe0 3 2 '45. CaO 23'91, MgO 
 0'49, HaO 2'25=99 83. The amount of iron sesquioxide varies from to 6'33 p. c. ; if much 
 more is present, amounting to a sixth atomically of the protoxide bases, the compound 
 appears to take the monoclinic form of epidote, instead of the orthorhombic of zoisite. 
 
 Pyr., etc, B.B. swells up and fuses at 3-3 '5 to a white blebby mass. Not decomposed by 
 acid ; when previously ignited gelatinizes with hydrochloric acid. 
 
 Obs Occurs at Saualpe in Carinthia ; Baireuth in the Fichtelgebirse ; Sterzing, Tyrol; 
 Lake Geneva ; Schwarzwald ; Arendal, etc. In the United States, found in Vermont, at 
 Willsboro and Montpelier. In Mass., at Goshen, Chesterfield, etc. In Penn., in Chester Co.; 
 at Unionville, white (Unionite). In Tenn., at the Ducktown copper mines. 
 
 JADEITE is one of the kinds of pale green stones used in China for making ornaments, and 
 passing under the general name of jade or nephrite. Mr. Pumpelly remarks that the fdtmi 
 is perhaps the most priced of all stones among the Chinese. In composition mainly a silicate 
 of aluminum and sodium. In its high specific gravity like zoisite. 
 
 GADOLINITE. Monoclinic (DesCl.). Color greenish-black. Contains yttrium, cerium, and 
 generally beryllium ; though the last is sometimes absent, through alteration (DesCl.). 
 Sweden ; Greenland ; Norway. 
 
 MOSANDRITE. A silicate containing titanium, cerium, and calcium. Brevig, Norway. 
 
 ILVAITB. Lievrite. Yenite. 
 
 Orthorhombic. 2/\ 7 ^112 38', A 1-i = 146 24' ; c : I 
 1-5004 : 1. Of\l = 141 24', O A 2-i = 138 29'. Lateral 
 faces usually striated longitudinally. Cleavage : parallel 
 to the longer diagonal, indistinct. Also columnar or com- 
 pact massive. 
 
 H.:=5-5-6. G.=3-7-4'2. Lustre submetallic. Color 
 iron-black, or dark grayish-black. Streak black, inclining 
 to green or brown. Opaque. Fracture uneven. Brittle. 
 
 Comp. Q. ratio, for R+R : Si : H=9 : 8 : 1, and for bases, including 
 hydrogen, to silicon 5 : 4 (Stadeler). Sipocz by the analysis of entirely 
 unaltered crystals (G. 4'037) from Elba confirms the conclusions of 
 Stadeler in regard to the presence of chemically combined water, and 
 adopts the same formula, viz.: H 2 Ca2Fe4FeSi 4 Oi8. This requires : 
 Silica 29 '34, iron sesquioxide 19*56, iron protoxide 35 21, lime 13 '69, 
 water 2 '20 100 ; manganese protoxide is also sometimes present in small quantities, 
 mflsberg considered the water as due to alteration. 
 
 = 0-66608 : 
 557 
 
 Rani 
 
310 
 
 DESCRIPTIVE MINERALOGY 
 
 Pyr., etc. B.B. fuses quietly at 2 '5 to a black magnetic bead. With the fluxes reacts foi 
 iron. Some varieties give also a reaction for manganese. Gelatinizes with hydrochloric a<;id. 
 
 Obs. Found in Elba, and at the mine of Temperino in Tuscany. Also at Fossum and at 
 Skeen in Norway ; in Siberia ; near Andreasberg ; near Predazzo, Tyrol ; at Schneeberg ; at 
 Hebrun in Nassau ; at Kangerdluarsuk in Greenland. 
 
 Reported as formerly found at Cumberland, R. I.; also at Milk Row quarry, Somerville, 
 Mass. 
 
 ARDENNITE (Dewalquite). Near ilvaite in form. Habit prismatic; vertically striated. 
 Composition given by the analyses, Lasaulx and Bettendorf, SiO 2 29 '60, A10 3 23 '50, MnO 
 2/5-88, Fe0 3 1'08, CaO 1'81, MgO 3'38, V,O 5 9'20, ign. 4 04=99'09. Color dark rosin-brown. 
 In thin splinters transparent. Other varieties, of a bright sulphur-yellow color (but opaque 
 and dull), contain arsenic (9-33 p. c. As 2 O 6 ) instead of vanadium. Between these two ex- 
 tremes are a series of compounds containing both arsenic and vanadium. Lasaulx regards 
 the arsenic-ardennite as having come from the other through alteration. Locality, Ottrez ir> 
 the Ardennes, Belgium. ROSCOELITE (p. 367) is another silicate containing vanadium. 
 
 AXINITE. 
 
 Triclinic. Crystals usually broad, and acute-edged. Making m = 0, 
 P = 'I,u = l',a (brachyd.) : I (macrod.) : c = 0-49266 : 1 : 0-45112. Cleav 
 age: i-i (v) quite distinct; in other directions indistinct. Also massive, 
 lamellar, lamellae, often curved ; sometimes granular. 
 
 558 
 
 V 
 Dauphiny. 
 
 Dauphiny. 
 
 Cornwall. 
 
 H.=6-5-Y. G.=3'271, Haidinger ; a Cornish specimen. Lustre highly 
 glassy. Color clove-brown, plum-blue, and pearl-gray; exhibits trichroism, 
 different colors, as cinnamon -brown, violet-blue, olive-green, being seen in 
 different directions. Streak uncolored. Transparent to subtranslucent. 
 Fracture conchoidal. Brittle. Pyroelectric, with two axes, the analogue (L) 
 and antilogue (T) poles being situated as indicated in f. 558 (G. Kose). 
 
 Comp. Analyses vary. If it contains 2 p. c. water (Ramm.), and if B 2 replaces Al, then 
 it is a unisilicate with the formula RTftsSisO^s, R=Fe,Mn,Ca,Mg, and K 2 , while ft=B 2 ,Al 
 (B 2 : ^1=1 : 2). Analysis (Ramm.), Oisans. Dauphine, SiO 2 43'46, B,O 3 5'61, A1O 3 IG'33, 
 Fe0 3 2-80, FeO 6-78, MnO 2-62, CaO 2019, MgO 1-73, K 2 0-11, H 2 1-45=101 -08. 
 
 Pyr., etc. B.B. fuses readily with intumescence, imparts a pale green color to the O.F. , 
 and fuses at 2 to a dark green to black glass ; with borax in O. F. gives an amethystine Dead 
 (manganese), which in R.F. becomes yellow (iron). Fused with a mixture of potassium bisul- 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 311 
 
 phate and fluor on the platinum loop colors the flame green (boron). Not decomposed by 
 acids, but when previously ignited, gelatinizes with hydrochloric acid. 
 
 Obs. Axinite occurs near Bourg d'Oisans in Dauphiny ; at Santa Maria, Switzerland; at 
 Kongsberg ; in Normark in Sweden ; in Cornwall ; in Devonshire, near Tavistock ; at Phips- 
 burg, Maine ; at Wales, Maine ; at Cold Spring, N. Y. 
 
 DANBURITE.* Triclinia CaB 2 Si 2 8 =Silica 48'8, boron trioxide 28-5, lime 227=100. 
 Occurs with feldspar in imbedded masses of yellow color in dolomite, at Danbury, Ct. 
 
 and 
 
 561 
 
 IOLITE. Cordierite. Dichroite. 
 
 Orthorhombic. In stout prisms often hexagonal. /A 1 = 119 10' 
 60 50', O A \-l =150 49'. Cleavage : i-l distinct ; i-l 
 and indistinct. Crystals often transversely divided 
 or foliated parallel with O. Twins : twinning-plane 
 I. Also massive, compact. 
 
 H.=7-7'5. Gr.=2-56-2-67. Lustre vitreous. Color 
 various shades of blue, light or dark, smoky-blue ; pleo- 
 chroic, being often deep blue along the vertical axis, 
 and brownish -yellow or yellowish-gray perpendicular to 
 it. Streak uncolored. Transparent translucent. Frac- 
 ture subconchoidal. 
 
 Comp. Q. ratio for bases and silicon 4 : 5 or 1 : 1. The state of oxidation of the iron ia 
 still unascertained, and hence there is uncertainty as to the proportion between the protoxides 
 and sesquioxides. The ratio usually deduced for R : ft : Si is 1 : 3 : 5. The formula R,ft.jSi 3 
 O], which corresponds to this ratio, =, if R=Mg,Fe and Mg : Fe=2 : 1, Silica 49 '4, 
 alumina 33'9, magnesia 8'8, iron protoxide 7 '9=10*0. 
 
 Pyr., etc B.B. loses transparency and fuses at 5-5 '5. Only partially decomposed by 
 acids. Decomposed on fusion with alkaline carbonates. 
 
 Obs. lolite occurs in granite, gneiss, hornblendic, chlorite and hydro-mica sohist, and allied 
 rocks, with quartz, orthoclase or albite, tourmaline, hornblende, andalusite, and sometimes 
 beryl. Also rarely in volcanic rocks. Occurs at Bodenmais, Bavaria ; at Ujordlersoak in 
 Greenland ; at Krageroein Norway ; Tunaberg in Sweden ; Lake Laach. At Haddam, Conn.; 
 at Brirnfield, Mass. ; also at Richmond, N . H. 
 
 Alt. The alteration of iolite takes place so readily by ordinary exposure, that the mineral 
 is most commonly found in an altered state, or enclosed hi the altered iolite. For the dis- 
 tinguishing characters of the different kinds of altered iolite, see FINITE, FAHLUNITE, 
 etc., under HYDROUS SILICATES. 
 
 Mica Group* 
 
 The minerals of the Mica group are alike in having (1) the prismatic 
 angle 120 ; (2) eminently perfect basal cleavage, affording readily very 
 thin, tough laminae ; (3) potash almost invariably among the protoxide 
 bases and alumina among the sesquioxide ; (4) the crystallization approxi- 
 mately either hexagonal or orthorhombic, and therefore the optic axis, or 
 optic-axial plane, at right angles (or nearly so) to the cleavage surface. 
 
 Sodium is sparingly present in some micas, and is characteristic of the hydrous species 
 paragon! te (p. 354). Lithium, rubidium, and caesium occur in lepidolite, and lithium in soina 
 biotite. Fluorine is often present, probably replacing oxygen. Titanium is found sparingly 
 in several kinds, and is a prominent ingredient of one species, astrophylli te. It is usually 
 regarded as in the state of titanium dioxide replacing silica ; but it is here made basic. 
 
312 
 
 DESCRIPTIVE MINERALOGY. 
 
 The species of the Mica group graduate into the hydrous micas of the Margarodite group 
 (p. 331) ; and through these they also approach the foliated species of the Talc and Chlorite 
 groups, especially the latter. 
 
 PHLOGOPITE.* 
 
 Orthorhombic. 7A/=120, and habit hexagonal. Prisms usually 
 oblong six-sided prisms, more or less tapering, with irregular 
 562 sides ; rarely, when small, with polished lateral planes. 
 Cleavage basal, highly eminent. Not known in compact 
 massive forms. 
 
 H.=2-5-3. G. 2-78-2-85. Lustre pearly, often sub- 
 metallic, on cleavage surface. Color yellowish-brown to 
 brownish-red, with often something of a copper-like reflec- 
 tion ; also pale brownish-yellow, green, white, colorless. 
 Transparent to translucent in thin folia. Thin laminae 
 tough and elastic. Optical-axial divergence 3-20, rarely 
 less than 5. 
 
 Comp. The bases include magnesium and little or no iron. Q. ratio 
 R : Si=l : 1. Formula probably (Ramm.) K 2 Mg 6 AlSi 6 O2o= Silica 4073, 
 alumina 13-93, magnesia 32 57, potash 12 '77 100. 
 
 Pyr,, etc. In the closed tube gives a little water. Some varieties 
 give the reaction for fluorine in the open tube, while most give little or 
 no reaction for iron with the fluxes. B. B. whitens and fuses on the thin 
 edges. Completely decomposed by sulphuric acid, leaving the silica in 
 thin scales. 
 
 Obs. Phlogopite is especially characteristic of serpentine and crystalline limestone or 
 dolomite. 
 
 Occurs in limestone in the Vosges. Includes probably the mica found in limestone at Alt- 
 Kemnitz, near Hirschberg ; that of Baritti, Brazil, of a golden-yellow color, having the optical 
 angle 5 30' and parallel to the shorter diagonal (Grailich) ; and a brown mica from limestone 
 of Upper Hungary, affording Grailich the angle 4 '-5. 
 
 Occurs in New York, at Gouverneur ; at Pope's Mills. St. Lawrence Co. ; at Edwards ; 
 Warwick; Natural Bridge; at Sterling Mine, Morris Co., N. J. ; Newton, N. J.; at St. Je- 
 rome, Canada; at Burgess, Canada West. 
 
 ASPIDOLITE (v. Kobell). Approaches in composition a soda-phlogopite. Green. Foliated. 
 Zillerthal, Tyrol. 
 
 MANGANOPHYLLITE. Q. ratio f or R : R : Si=3 : 1 : 4 (nearly). Foliated like the micas. 
 Color bronze-red. Analysis, Igelstrom, Si0 2 38-50, A1O 3 ll'OO, FeO 378, MnO 21'40, CaO 
 3-20, MgO 15-01, K 2 O(Na 2 O) 5 -51, igu. 1'60=100. Paisberg, Sweden. 
 
 BIOTITE.* 
 
 Hexagonal (?). R A R = 62 57' (crystals f r. Vesuvius, Hessenberg) ; c = 
 4:*911126. Habit often monoclinic. Prisms commonly tabular. Cleavage : 
 
 basal highly eminent. Often in disseminated 
 scales, sometimes in massive aggregations of 
 cleavable scales. 
 
 H.=2-5-3. G.=2-7-3'l. Lustre splendent, 
 and more or less pearly on a cleavage surface, 
 and sometimes submetallic when black ; lateral 
 surfaces vitreous when smooth and shining. 
 Colors usually green to black, often deep black 
 in thick crystals, and sometimes even in thin 
 laminae, unless the laminae are very thin ; such 
 thin laminae green, blood-red, or brown bv transmitted light ; rarely white. 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 313 
 
 Streak uncolored. Transparent to opaque. Optically uniaxial. Some- 
 times biaxial with slight axial divergence, from exceptional irregularities; 
 but the angle not exceeding 5 and seldom 1. 
 
 Oomp., Var. Biotite is a magnesia-iron mica, part of the aluminum (Al) being replace^ 
 by iron (Fe), and Fe and Mg existing among the protoxide bases. Black is the prevailing color, 
 but brown to white also occur. The results of analyses vary much, and for the rea-on already 
 stated the non- determination, in most cases, of the degree of oxidation of the iron ; and 
 the exact atomic ratio for the species and its limits of variation are therefore not precisely 
 understood. The Q. ratio of bases to silicon is generally 1:1, that is the formula in general 
 ~,SiO 4 , where R=K,(Na 2 ,Li 2 )Fe,Mg(Ca), or iVl,Fe^3R=R). 
 
 Analyses : 1, Ballyellin ; 2, Vesuvius ; 3, Portland, Conn. : 
 
 SiO 2 A1O 3 FeO 3 FeO CaO MgO K 2 Na 2 Li 2 O ign 
 
 (1) 35-55 17-08 23-70 5'50 368 9-45 0'35 4'30=99'61, Haughton. 
 
 (2) 40-91 17*79 3-00 7 '03 0'30 19 "04 9 96 =98-03, Chodnew. 
 
 (3j|35'61 20-03 0-13 21 '85 119MnO 5'23 9-69 0-52 93 1'87, F 0'76, Ti0 2 1'46, 
 
 01 tr. =99 -27, Hawes. 
 
 The above analyses give the ratio of unisilicates, when the water is neglected ; in others 
 the ratio of 1 : 1 is obtained only when the water is brought into account. 
 
 Pyr., etc. Same as phlogopite, but with the fluxes it gives strong reactions for iron. 
 
 Obs. A common constituent of many volcanic rocks. Fine specimens obtained at Vesu- 
 vius ; L. Baikal; Zillerthal; Pargas ; Miask ; Sala. Also from Greenwood Furnace, N. Y.j 
 Moriah, N. Y. ; Easton, Penn. ; Topsham, Me., etc. 
 
 The biotite of Vesuvius, according to the optical examination of Hintze, is monodinic. 
 (See also Tschermak, Min. Mitth., 1876, 187.) 
 
 LEPIDOMELANE. 
 
 Hexagonal (?). In small six-sided tables, or an aggregate of minute scales. 
 Cleavage : basal, eminent, as in other micas. 
 
 H.=3. G.r=3-0. Lustre adamantine, inclining to vitreous, pearly. 
 Color black, with occasionally a leek-green reflection. Streak grayish- 
 green. Opaque, or translucent in very thin laminae. Somewhat brittle, or 
 but little elastic. Optically uniaxial ; or biaxial with a very small axial 
 angle. 
 
 Oomp, An iron-potash mica. Q. ratio for bases and silicon 1:1; f or R : R, mostly 1 : 3, 
 but varying to 1 to more than 3 ; of doubtful limits, on account of the doubts as to the state 
 of the iron in most of the analyses. Differs from biotite in the smaller proportion of prot- 
 oxides and little Al and Mg, but appears to agree with it in optical characters. 
 
 Pyr., etc, B.B. at a red heat becomes brown and fuses to a black magnetic globule. 
 Easily decomposed by hydrochloric acid, depositing silica in scales. Analysis, Cooke, Rock- 
 port, Mass., SiO., 39-91, A10 3 16'73, FeO 3 12'07, FeO 17-48, MnO 0-54, MgO 0-62, K 2 O 10'66, 
 Na 2 O(Li 2 O) 0-59, H 2 O 1'50, F0'45=100. 
 
 Obs. Occurs at Persberg in Wermland, Sweden ; at Abborf orss in Finland ; in Ireland, in 
 Donegal and Leinster Cos. ; at Ballyellin, etc. From Cape Ann, Mass. (Annite). 
 
 ASTKOPHYLLITE. Usually in tabular prisms. Color bronze-yellow. Analysis, Pisani, SiOi 
 33-22, TiO, 7-66, A1O 3 4'32, FeO 3 4'05, FeO 25'48, MnO 10 70, MgO 1'37, CaO 1'22, Na a O 
 8-71, K 2 O 6-29, HiO 2-01=99'03. Brevig, Norway ; El Paso County, Colorado. 
 
 MUSCOVITE. Kaliglimmer, Germ.* 
 
 
 
 Monoclinic (Tschermak). 1 1\ I =120. Cleavage: basal eminent, 
 occasionally also separating in fibres parallel to a diagonal. Twins : often 
 observable "by internal markings, or by polarized light ; composition parallel 
 
314 DESCRIPTIVE MINERALOGY. 
 
 to 1 consisting of six individuals thus united ; sometimes a union of / to 
 i4. Folia often aggregated in stellate, plumose, or globular forms ; or in 
 scales, and scaly massive. 
 
 564 565 566 
 
 Miask, Ural. Binnenthal. 
 
 H.= 2-2-5. G.=2'75-3'l. Lustre more or less pearly. Color white, 
 gray, brown, hair-brown, pale green, and violet, yellow, dark olive-green, 
 rarely rose-red ; often different for transmitted and reflected light, and dif- 
 ferent also in vertical and transverse directions. Streak uncolored. Trans- 
 parent to translucent. Thin laminae flexible and elastic, very tough. Double 
 refraction strong; optic-axial angle 44: -78 ; the axial plane makes an angle 
 of 88 20' (Tschermak) with the base. 
 
 Ooinp. The quantivalent ratio for bases and silicon is generally 4 : 5 (1 . !), rarely 3 . 4, 
 etc. Water is generally present, sometimes as much as 5 p. c.; and the kinds containing 
 from 3 to 5 p. c. water have been referred to the species margarodite (p. 353). If the 
 
 i 
 water is regarded as chemically combined, that is, as basic, the Q. ratio for R : R : Si is then 
 
 =1 : 3 : 4 (B : Si=l : 1), also 1:6:8, 1:2:4, 1:3:5, etc. B, here is potassium (K) 
 mostly, but also hydrogen (H). R=aluminum mostly, also iron. Fluorine is often present, 
 but at most not more than about 1 p. c. Analysis, Smith and Brush, Monroe, Ct., SiO. 46 '50, 
 :MO 3 33-91. Fe0 3 2'69, MgO 0'90 Na 2 O 2'70, K.O 7*32, H,O 4 "63, F 0'82, Cl 0'31=99-?8. 
 
 Pyr., etc. In the closed tube gives water, .which with brazil-wood often reacts for tluorine. 
 B.B. whitens and fuses on the thin edges (F. =5-7, v. Kobell) to a gray or yeilow glass. With 
 fluxes gives reactions for iron and sometimes manganese, rarely chromium. Not decomposed 
 by acids. Decomposed on fusion with alkaline carbonates. 
 
 Obs. Muscovite is the most common of the micas. It is one of the constituents of granite, 
 gneiss, mica schist, and other related rocks, and is occasionally met with in granular lime- 
 stone, trachyte, basalt, iava; and occurs also disseminated sparingly in many fragmental 
 rocks. Coarse lamellar aggregations often form the matrix of topaz, tourmaline, and other 
 mineral species in granitic veins. 
 
 Siberia affords lamina of mica sometimes exceeding a yard in diameter ; and other remark- 
 able foreign localities are Finbo in Sweden, and Skutterud in Norway. Fuchsite or chromium 
 mica occurs at Greiner in the Zillerthal, at Passeyr in the Tyrol, and on the Dorfner Alp, as 
 well as at Schwarzenstein. 
 
 In N. Hamp., at Acworth, Grafton, etc., in granite, the plates at times a yard across and 
 perfectly transparent. In Maine, at Paris ; at Buckfield. In Mass. , at Chesterfield ; at Goshen. 
 In Conn., in Portland ; near Middletown. In N. York, near Warwick; Edenville ; in the 
 town of Edwards, In Pcnn., at Pennsbury ; at Unionville ; Delaware Co., at Middletown. 
 In Maryland, at Jones's Falls. In western North Carolina, where it is mined. 
 
 I LEPIDOLITE.* Lithia Mica. Lithionglimmer, Germ. 
 
 
 
 Orthorhombic. /A 1 = 120. Forms like those of mnscovite. Cleav- 
 age : basal, highly eminent. Also massive scaly-granular, coarse or tine. 
 
 H.= 2-5-4. G.= 2-84-3. Lustre pearly. Color rose-red, violet-gray, 01 
 
OXYGEN COMPOUNDS. ANHYDROUS SILICATES. 
 
 315 
 
 lilac, yellowish, grayish-white, wliite. Translucent. Optic-axial angle 
 70-78 ; sometimes 45-GO. 
 
 i 
 Comp. Q. ratio for bases and silicon mostly 1 : l ; and for R : R : Si=l : 3 : 6, or 1 : 4 
 
 : 8 ; the formula in the latter case is R 6 Al 4 Sii 2 O39. R includes potassium, also lithium, 
 rubidium, and caesium ; and, in the Zinnwald mica, thallium has been detected. Fluorine is 
 present, and the ratio to oxygen mostly 1 : 12. Analysis, Reuter, from Rozena, SiO 2 50 '43, 
 510 3 28-07, Mn0 3 0'88, MgO 1'42, K,O 10'59, Na.O 1-46, Li,O 1-23, P 4'8(5=98'94. 
 
 Pyr., etc. In the^closed tube gives water and reaction for fluorine. B. B. fuses with in- 
 tumescence at 2-2-5 to a white or grayish glass, sometimes magnetic, coloring the flame 
 purplish-red at the moment of fusion (lithia). With the fluxes some varieties give reactions 
 for iron and manganese. Attacked but not completely decomposed by acids. After fusion, 
 gelatinizes with hydrochloric acid. 
 
 Obs Occurs in granite and gneiss, especially in granitic veins, and is associated some- 
 times with cassiterite, red, green, or black tourmaline, amblygonite, etc. Found near Uto 
 in Sweden ; at Zinnwald in Bohemia ; Penig, etc. in Saxony ; in the Ural ; at Rozena in 
 Moravia ; on Elba ; at St. Michael's Mount in Cornwall. In the United States, at Paris and 
 Hebron, Me. ; near Middletown, Conn. 
 
 Named lepidolite from Ae/r/f, scale, after the earlier German name Sc?iuppenstein, alluding 
 to the scaly structure of the massive variety of Rozena. 
 
 CRYOPHYLLITE (Cooke). Q. ratio R : ft : Si=3 : 4 : 14, with R=Fe,K 2 ,Li 2 (Na,Rb,Cs,) a 
 and R-= Al. Orthorhombic. In scales like the micas. Color by transmitted light emerald 
 green. Cape Ann, Mass. 
 
 Sea/polite Group. 
 
 group, the quantivalent ratio varies from 
 2 : 4 and 1 : 2 : 6, but the species are 
 
 In the species of the Scapolite 
 1 : 1 : 2, 1 : 2 : 3, 1 : 3 : 4, to 1 : 
 
 closely alike in the square-prismatic forms of their crystals, in the small 
 number and the kinds of occurring planes, and in their angles. The species 
 are white, or grayish-white, in color, except when impure, and then rarely 
 of dark color ; the hardness 5-6'5. G. = 2'5-2'8. The alkali-metal present, 
 when any, is sodium, with only traces of potassium. An increase in the 
 amount of alkali is accompanied by an increase in the silica. 
 
 MEIONITE.* 
 
 Tetragonal : O A l-i = 156 18' ; c 0-439. Sometimes hemihedral in 
 the planes 3-3, the alternate being wanting. Cleavage : i-i 
 and / rather perfect, but often interrupted. 
 
 H.=5'5-6. G.=2*6~2'T4. Lustre vitreous. Colorless 
 to white. Transparent to translucent ; often much cracked 
 within. 
 
 Comp. Q. ratio f or R : R : Si=l : 2 : 3 ; formula RsRjSiaOae. If R= 
 Ca : Na 2 = 10 : 1, and R=:A:1 ; this is equivalent to Silica 41-6, alumina 
 31*7, lime 24 '1, soda 2'6 = 100. Neminar has found that meionite loses 
 1 p. c. water at a very high temperature, so that R must be also replaced 
 by Hi ; his analysis gives approximately the ratio 1 : 2 : 3. 
 
 Pyr., etc. B. B. fuses with intumescence at 3 to P, white blebby glass. 
 Decomposed by acid without gelatinizing (v. Rath). 
 
 Obs. Occurs in small crystals in geodes, usually in limestone blocks, on Monte Somma, 
 near Naples. 
 
316 
 
 DESCRIPTIVE MINERALOGY. 
 
 WERNERITE,* Scapolite. 
 
 Tetragonal: O A 1-i = 156 14J' ; c = 04398. Often hemihedrai in 
 planes 3-3 and i-2 (p. 30). Cleavage: i-i and /rather 
 distinct, but interrupted. Also massive, granular, or 
 with a faint fibrous appearance ; sometimes columnar, 
 II. =5-6. G.= 2-63-2-8. Lustre vitreous to pearly 
 externally, inclining to resinous ; cleavage and cross- 
 fracture surface vitreous. Color white, gray, bluish, 
 greenish, and reddish, usually light. Streak uncolored. 
 Transparent faintly subtranslucent. Fracture sub- 
 conchoidal. Brittle. 
 
 Comp Q. ratio for R : R : Si=l : 3 : 4 (R+R : Si=l : 1); 
 
 formula RRSi 2 O 8 =Ca(Na 2 )AlSi 2 O e . Analysis, v. Rath. Pargas, Si0 2 45 '46, A10 3 30'96, CaO 
 17-22, Na 2 O 2-29, K 2 1-31, H 2 1-29=98 '53. Some varieties vary widely from the above 
 ratio. 
 
 Pyr., etc. B.B. fuses easily with intumescence to a white blebby glass. Imperfectly de- 
 composed by hydrochloric acid. 
 
 Diff. Recognized by its square form ; resembles feldspar when massive, but has a charac- 
 teristic fibrous appearance on the cleavage surface ; it is also more fusible, and has a highei 
 specific gravity. 
 
 Obs. Occurs in rnetamorphic rocks ; sometimes ia beds of maguetite accompanying lime- 
 stone. Some localities are : Arendal, Norway ; Wermland ; Pargas, Finland ; L. Baikal, etc. 
 In the following those of the wernerite and ekebergite are not yet distinguished. In Ma*9., 
 at Bolton; Westfield. In Conn., at Monroe. In N. York, in Warwick; in Orange and 
 Essex Co., etc. In N. Jersey, at Franklin and Newton. In Canada, at Gr. Calumet Id. ; 
 at Hunterstown ; Grenville. 
 
 The following are other members of the scapolite group : 
 
 SARCOLifE. Q. ratio for R : R : Si=l : 1 : 2. In minute flesh-red crystals at Mt 
 Somma. 
 
 PARANTHITE. Q. ratio=l : 3 : 4. EKEBERGITE. Q. ratio=l : 2 : 4|, containing 6-8 p. 
 c. soda. MIZZONITE. Q. ratio^l : 2 : 5, containing 10 p. c. soda. In crystals at Mt. Somma, 
 DIPYRE. Q. ratio=l : 2 : 6, and for Ca : Na^l : 1. MARIALITE. Q. ratio=l : 2 : 6, and 
 for Ca : Na 2 =l : 2. 
 
 Hexagonal. 
 569 
 
 Nephelite Group. 
 
 NEPHELITE. Nepheline. 
 
 A 1 = 135 55' ; c = 0'839. Usual forms six-sided and 
 twelve-sided prisms with plane or modified sum- 
 mits. Fig. 569, summit planes of a crystal. Cleav- 
 age: /distinct, O imperfect. Also massive, com- 
 pact ; also thin columnar. 
 
 II. =5 5-6. G.= 2.5-2-65. Lustre vitreous- 
 greasy ; a little opalescent in some varieties. Color- 
 less, white, or yellowish ; also when massive, dark- 
 green, greenish or bluish-gray, brownish and brick- 
 red. "Transparent opaque. Fracture subcon- 
 choidal. Double refraction feeble ; axis negative, 
 
 Vesuvius. 
 
 Var. 1. Glassy, or Sommite. Usually in small crystals 01 
 grains, with vitreous lustre, first found on Mt. Somma, in the 
 
 region of Vesuvius. Davyne and cawlinite belong 1 
 
 i. ElcBolile. In large coarse crystals, or massive, with a greasy lustre. 
 
 here. 
 
OXYGEN COMPOUNDS. ANHYDROUS SILICATES. 317 
 
 Comp. Somewhat uncertain, as all analyses give a little excess of silica beyond what ii 
 required for a unisilicate. Assuming that nephelite is a true unisilicate, the Q. ratio for 
 
 R : R : Si=l : 3 : 4, and the formula is (Na,K) 2 A-lSi 2 8 (Ramm. ); some of the Na 2 being 
 replaced by Ca. Analysis, Scheerer, Vesuvius, SiO 2 44'03, A1O 3 38 '28, Fe0 3 (MnO 3 ) 0'05, 
 CaO 1-77. Na 2 O 15'44, K 2 O 4-94, H 2 0-21=100-32. The variety Elceolite has the same 
 composition. 
 
 Pyr., etc. B.B. fuses quietly at 3 '5 to a colorless glass. Gelatinizes with acids. 
 
 Diff Distinguished by its gelatinizing with acids from scapolite and feldspar, as also from 
 apatite, from which it differs too in its greater hardness. Massive varieties have a character- 
 istic greasy lustre. 
 
 Obs Nephelite occurs both in ancient and modern volcanic rocks, and also metamorphic 
 rocks allied to granite and gneiss, the former mostly in glassy crystals or grains (sommite), the 
 latter massive or in stout crystals (elceolite). Nephelite occurs in crystals in the older lavas of 
 Somma ; at Capo di Bove, near Rome ; in doleryte of Katzenbuckel, near Heidelberg, etc. 
 Eleeolite is found in Norway ; in the Ilmen Mts. ; Urals ; at Litchfield, Me. ; in the Ozark 
 Mts. , Arkansas. 
 
 Named nepkeline by Haiiy (1801), from ve^ety, a cloud, in allusion to its becoming cloudy when 
 immersed in strong acid ; elceolite (by Klaproth), from EACUOV, oil, in allusion to its greasy lustre. 
 
 GIESECKITE is shown by Blum to be a pseudomorph after this species (see p. 330). 
 
 C AN CRIN IT E.'^ Hexagonal, and in six- and twelve-sided prisms, sometimes with basal edges 
 replaced; also thin columnar and massive. H. =5-6. G. =2'42-2'5. Color white, gray, 
 yellow, green, blue, reddish; streak uncolored. Lustre subvitreous, or a little pearly or 
 greasy. Transparent to translucent. 
 
 COMP. Same as for nephelite, with some RC0 3 and water. Analysis, Whitney, Litchfield, 
 Me., SiO, 37-42, A10 3 27'70, CaO 3D1, Na.O 20'9S, K,0 0'67, C0 2 5'95. H 2 2'82, FeO 3 
 (MnO 3 ) 0-86=100-31. 
 
 PYR., ETC. In the closed tube gives water. B.B. loses color, and fuses (F.=2) with intu- 
 mescence to a white blebby glass, the very easy fusibility distinguishing it readily from 
 nephelite. Effervesces with hydrochloric acid, and forms a jelly on heating, but not before. 
 
 OBS. Found at Miask in the Urals ; at Barkevig, Norway ; at Ditro in Transylvania 
 (ditroyte) ; at Litchfield, Me. 
 
 SODALITE. 
 
 Isometric. In dodecahedrons. Cleavage : dodecahedral, more or less 
 distinct. Twins : see f. 272, p. 93. Also massive. 
 
 H.= 5:5-6. G.= 2 '136-2*4:01. Lustre vitreous, sometimes inclining to 
 greasy. Color gray, greenish, yellowish, white ; sometimes blue, lavender- 
 blue, light red. Subtransparent translucent. Streak uncolored. Frac- 
 ture conchoidal uneven. 
 
 Comp. 3Na 2 AlSi. 2 8 +2NaCl=Silica 371, alumina 31 '71, soda 25 -55, chlorine 7 "31 =101 '65, 
 fiome varieties contain considerably less chlorine. 
 
 Pyr., etc, In the closed tube the blue varieties become white and opaque. B.B. fuse* 
 with intumescence, at 3*5-4, to a colorless glass. Decomposed by hydrochloric acid, with 
 (separation of gelatinous silica. 
 
 Obs. Occurs in mica slate, granite, pyenite, trap, basalt, and volcanic rocks, and is often 
 associated with nephelite (or eleeolite) and eudialyte. Found in West Greenland ; on Monte 
 Somma; in Sicily; at Miask, in the Ural; near Bre^ig, Norway. A blue variety occurt 
 at Litchfield, Me., and at Salem, Mass. 
 
 MICROSOMMITE. Occurs in very minute hexagonal crystals in masses of leucitic lava 
 ejected from Mt. Somma. Composition : a unisilicate of potassium, calcium, and aluminum, 
 with small quantities of sodium chloride and calcium sulphate. 
 
318 DESCRIPTIVE MINERALOGY. 
 
 HAUYNITE. 
 
 Isometric. In dodecahedrons, octahedrons, etc. Cleavage : dodecahe- 
 dral distinct. Commonly in rounded grains often looking like crystals 
 with a fused surface. 
 
 H.= 5*5-6. G.=2'4-2'5. Lustre vitreous, to somewhat greasy. Coloi 
 bright blue, sky-blue, greenish-blue ; asparagus-green. Streak slightly 
 bluish to colorless. Subtransparent to translucent. Fracture flat conchoi- 
 dal to uneven. 
 
 Comp. 2Na 2 (Ca)AlSi20 8 +CaSO4 ; if in the silicate Na 2 is replaced by Ca, the atomic 
 ratio here being 5 : 1, this gives Silica 34 '13, alumina 2918, lime 10'62, soda 14-69, sulphur 
 trioxide=100. A little potassium is also often present. 
 
 Pyr., etc. In the closed tube retains its color. B.B. in the forceps fuses at 4 '5 to a white 
 glass. Fused with soda on charcoal affords a sulphide, which blackens silver. Decomposed 
 by hydrochloric acid with separation of gelatinous silica. 
 
 Obs. Occurs in the Vesuvian lavas, on Somma ; in the lavas of the Campagna, Rome ; in 
 basalt at Niedermendig and Mayen, L. Laach, etc. 
 
 NOSITE (Nosean). A <?rf<z-hauynite ; 2Na 2 AlSi208 + Na^S0 4 , with also a little calcium. 
 Isometric ; often granular massive. Common as a microscopic ingredient of most phonolytes. 
 Lake Laach, etc. 
 
 LAPIS-LAZULI (Lasurstein, Germ.). Not a homogeneous mineral according to Fischer and 
 Vogelsang. The latter calls it u a mixture of granular calcite, ekebergite, and an isometric, 
 ultramarine mineral, generally blue or violet." Much used as an ornamental stone. 
 
 LEUCITE.* 
 
 Tetragonal, according to v. Rath, c = 0*52637. Usual form as in 
 f. 570, closely resembling a trapezohedron. Twins : 
 t winning-plane 2-i ; crystals often very complex, con- 
 sisting of twinned lamellae, as indicated by the stria- 
 tions on the planes. Often disseminated in grama ; 
 rarely massive granular. 
 
 H.=:5-5-6. 5.:=2'44:-2-56. Lustre vitreous. Color 
 white, ash-gray or smoke-gray. Streak nn colored. 
 Translucent opaque. Fracture conchoidal. Brittle. 
 Optically uniaxial ; double refraction weak, negative 
 (from Aquacetosa), positive (from Frascati). 
 
 Comp. Formula K- 2 AlSi 4 Oi 2 = Silica 55 '0, alumina 23 '5, potash 
 21-5=100. Q. ratio for K : M : Si=l : 3 : 8, for bases to silicon 1 : 2. 
 
 Pyr., etc. B.B. infusible ; with cobalt solution gives a blue color (alumina). Decomposed 
 by hydrochloric acid without gelatinization. 
 
 Diff. Distinguished from analcite by its infusibility and greater hardness. 
 
 Obs. Leucite is confined to volcanic rocks, and is common in those of certain parts of 
 Europe ; also found in those of the western United States. At Vesuvius and some other 
 parts of Italy it is tJ ickly disseminated through the lava in grains. It is a constituent in the 
 nephelin-doleryte of Merches in the Vogelsberg ; abundant in trachyte between Lake Laacb 
 and Andernach, on the Rhine. 
 
 The question as to whether the crystals of leucite belong to the isometric or the tetragonal 
 system has excited much discussion. Hirschwald (Tsch. Min Mitth., 1875, 227) shows that 
 while implanted crystals are sometimes distinctly tetragonal, others, especially those which 
 are imbedded, are as clearly isometric, while between the two there exist many transition 
 cases. He claims that the mineral is in fact isometric, but having a polysymmetric develop- 
 ment, there existing a wide variation from the isometric type. The question cannot be con 
 idered as entirely decided. 
 
OXYGEN COMPOUNDS. ANHYDROUS SILICATES. 319 
 
 Feldspar Group* 
 
 The feldspars are characterized by specific gravity below 2*85 ; hardness 
 to 7 , fusibility 3 to 5 ; oblique or cliiiohedral crystallization ; 
 
 6 to 7 , fusibility 3 to 5 ; oblique or cliiiohedral crystallization ; prismatic 
 angle near 120 ; two easy cleavages, one basal, the other brachy diagonal, 
 inclined together either 90, or very near 90 ; cleavage a prominent fea- 
 ture of many massive kinds, and distinct in the grains of granular varieties, 
 giving them angular forms ; close isomorphism, and a general resemblance 
 in the systems of occurring crystalline forms ; transition from granular 
 varieties to compact, hornstone-like kinds, called felsites, which sometimes 
 occur as rocks ; often opalescent, or having a play of colors as seen in a 
 direction a little oblique to i-\ ; often aventurine, from the dissemination 
 of microscopic crystals of foreign substances parallel for the most part to 
 the planes O and /. 
 
 The bases in the protoxide state are calcium, sodium, potassium, and in 
 one species barium ; the sesquioxide base is only aluminum ; the quantivalent 
 ratio of H : R is constant, 1:3; while that of the silicon and bases varies 
 from 1 : 1 to 3 : 1, the amount of silicon increasing with the increase of the 
 alkali metals, and becoming greatest when alkalies are the only protoxides. 
 
 The included species are as follows : 
 
 Crystallization. Approx. Q. ratio R,ft,Si 
 
 ANORTHITE Lime feldspar Triclinic 
 
 LABRADOKITE Lime-soda feldspar " 1 
 
 HYALOPIIANB Baryta-potash feldspar Monoclinic 1 
 
 ANDESITE Soda-lime feldspar Triclinic 1 
 
 OLIQOCLASE " " " *. 1 
 
 ALBITE Soda feldspar 1 
 
 ORTHOCLASE Potash feldspar Monoclinic 1 
 
 To the above list should be added, according to DesCloizeaux, the Iridinic, potash feldspar, 
 MICROCLINE, which has the composition of orthoclase. 
 
 The above ratios are only approximate, for the analyses show a wide variation in the 
 amount of silicon, and an exactly proportionate variation in the amount of a'kali ; the two 
 elements vary in most cases, as has been long recognized, according to a simple law. There 
 seems hence to be a gradual transition between the successive species ; but this is due, in part, 
 to mixtures produced by contemporaneous crystallization (compare pert/lite, p 326, and the 
 description of microcUne, p. 326). 
 
 The unisilicate ratio of 1 : 1 tor bases and silicon is found in anorthite only, as shown above. 
 With Ca alone, as in this species, the Q. ratio for :A:1 and Si is 3 : 4; with Na 2 alone, 3 : 12; 
 and for kinds containing combinations of the two, exact combinations of these ratios, wNa a : 
 
 , 4:in+12n 
 TiCa, giving the ratio 3 : 
 
 An explanation of the above fact, and of the variation in ratio shown by analyses, was offered 
 by Hunt, and has since been developed by Tschermak. The existence of two distinct triclinio 
 feldspars is assumed: anorthite CaAlSi 2 8 , and albite Na 2 AlSi 6 Oio, and the other species 
 (sometimes embraced under the general term PLAGIOCLASE) are regarded as due to uomcr> 
 plious mixtures of these two members irt different proportions. They have then the general 
 
 formula j ^a.AlSieO'e)' Forlabradc ^ te the ratio of m : tt is mostly 3 : 2, also 3 : 1, etc.; 
 for andesite the ratio of m : n varies about 1 : 2, and f or oligoclase the ratio of m : n is 3 : 10, 
 also 1 : 3, etc. In accordance with the above formula, if Ca : Na=6 : 1, then Al : Si= 
 1 : 2-308; for Ca : Na=3 : 1, Al : Si=l : 1'257; for Ca : Na=l : 1, Al : Si=l : 3'33 ; for 
 Ca : Na=l : 3, Al : Si=l : 4'4 ; for Ca : Na=i : 6, Al : Si=l : 5. 
 
 This method of vie wing the feldspar species has the advantage of explaining the wide varia- 
 tion in their composition, and is generally accepted among German mineralogists. DesCloi- 
 eeaux regards his observations upon the optical characters of the feldspars (see p. 298) ai 
 showing that they are in fact distinct species, and not indeterminate isomorphous mixtures 
 
320 
 
 DESCRIPTIVE MINERALOGY. 
 
 Optical properties of the triclinic feldspars. The following table contains the more import' 
 ant optical properties of the feldspar species as determined by DesCloizeaux (C. K,., Feb. 8. 
 1875, and April 17, 1876). Bx= Bisectrix. 
 
 Acute bisectrix. ... ... 
 
 ANOBTHITE. 
 always 
 
 LABKADOBITE. 
 always + 
 
 OLIGOCLASE. 
 generally 
 
 ALBITE. 
 always 4- 
 
 MlCBOCLINE. 
 
 always 
 
 Angle made by the+Bx. 
 with a normal to i-l (g) 
 Same, with normal to 
 0(p) 
 
 Position of 
 the Bx. has 
 no simple 
 relation to 
 the planes 
 
 30 40' 
 56 
 
 sometimes + 
 18 10' 
 68 
 
 15 
 
 78 35' 
 
 15 26' 
 
 Angle made by the line 
 in which the plane of 
 . the optic-axes cuts i-l, 
 with edge i-l/0(g' /p). 
 Same, with edge i-l I 
 (a 1 m) 
 
 observed 
 on the crvs- 
 tals. 
 
 27-28 
 3725'-36~25' 
 
 Line parallel 
 to the edge 
 0\i-l. 
 
 U U 
 
 20 
 96 28' (front) 
 
 5 6' 
 
 Ordinary dispersion. . . . 
 Parallel or perpendicular 
 to plane of polariza- 
 tion. 
 
 Optic-axial angle (in air) 
 for red rays. 
 
 p < *(-Bx.) 
 Inclined. 
 
 84 58' 
 
 p > ?(+Bx.) 
 Crossed; also 
 slight in- 
 clined. 
 
 88 15' 
 
 p < 0(4- Bx.) 
 Crossed; also 
 slight ill" 
 dined. 
 
 89 35' 
 
 p < ?(4-Bx.) 
 Inclined ; 
 probably also 
 slight hori- 
 zontal. 
 
 80 39' 
 
 P < 0(4- Bx.) 
 Horizontal 
 (-Bx.) also 
 inclined 
 
 (+BX.) 
 
 87 54' 
 
 for blue rays 
 
 85 59' 
 (Somma) 
 
 87 48' 
 (Labrador) 
 
 88 C 31' 
 (Sunstone, 
 Tvedestrand) 
 
 81 59' 
 (Roc tourne) 
 
 Amazonst'ne, 
 Mursinsk. 
 
 The axial divergence is quite constant for albite, labradorite, and anorthite, but varies for 
 oligoclase even in different sections taken from the same specimen. Andesine (q. v.) ia 
 regarded by DesCloizeaux as an altered oligoclase. 
 
 DesCloizeaux gives the following method of distinguishing between the feldspars by optical 
 means : It is necessary to obtain a transparent plate parallel to the easiest cleavage ( 0). 
 Such sections obtained from crystals or lamellar masses of albite, oligoclase, labradorite, and 
 the majority of those of microcline, show hemitropic bauds, more or less close together, 
 arranged along the plane parallel to the second cleavage (i-l) for orthoclase and microline 
 in simple crystals, two sections placed in opposite positions serve to produce the same effect. 
 These sections are thus brought between the crossed Nicols of a polarization-microscope. 
 
 (1) For orthoclase the maximum extinction takes place when the two sections are parallel 
 to their plane of contact ; the edge 0/i-l being in the plane of polarization of the micro- 
 scope. 
 
 (2) For microcline, the whole structure consists of a multitude of very fine parallel bands ; 
 the section may show microcline alone, either hemitropic or not hemitropic, or microcline and 
 orthoclase ; the extinction can take place at 30 54' between the adjoining bands of the same 
 plate of the macle (microcline alone), at 30 54' between the two plates of the made (micro- 
 cline in bands), or at 15 C 27' between the adjoining bands (microcline and orthoclase). In the 
 last case the whole of two lamellae of the macle show at the same time an extinction oblique 
 to the plane of composition, belonging to the microcline, and one parallel to this plane for the 
 orthoclase. 
 
 (3) For albite, the extinction between two bands takes place at an angle of 6 32'. 
 
 (4) For oligoclase, the extinction is simultaneous in the two bands, and when the plane of 
 composition coincides with the plane of polarization of the polariscope, it shows that the 
 structure is homogeneous. 
 
 (5) For labradorite, the extinction takes place at 10 24' between the alternate lines of the 
 hemitropic lamellae. 
 
 It follows from this tha* a plane normal to the plane of the axes cuts the base along a line 
 making with the edge Q/i-l the following angles: 
 
 in orthoclase, 
 15 27' in microcline, 
 3 16' in albite, 
 5 12' in labradorite. 
 
 A variation of one or two degrees from the above mean angles was observed in some 
 pcoimens. See further on p. 426. 
 
OXYGEN COMPOUNDS ANHYDEOUS SILICATES. 321 
 
 Diff. The feldspars are distinguished from other species by the characters already stateu. 
 prominent among which are : cleavage in two directions, nearly or quite at right angles tc 
 each other ; also hardness, etc. 
 
 The triclinic feldspars can in most cases be distinguished from orthoclase by the fine stria- 
 ;ion due to repeated twinning. This striation can often be seen by the unaided eye upon the 
 cleavage face (0). And its existence can always be surely tested by the examination of a thin 
 section in polarized light, the alternate bands of color showing the same fact. 
 
 The separation of the different triclmic species can be surely made by complete analysis 
 only, or at least by the determination of the amount of alkali present. The degree of fusi- 
 bility, the color of the flame, and the effect produced by digestion in acids, are often import- 
 ant aids. In the hands of a skilled observer the optical examination may give decisive results. 
 
 ANORTHITE. Indianite. 
 
 Triclinic. i : I : a = 0-86663 : 1-57548 : 1. /A 1' = 120 
 (over 24) = 94 10', O f\ ! = 114 6', O A I '= 110 
 40', A 24 = 98 46' ; a = 93 13^', j3 = 115 55J', 
 7 = 91 Hi' Cleavage : 0, i4 perfect, the latter 
 least so. Twins similar to those of albite. Also mas- 
 sive. Structure granular, or coarse lamellar. 
 
 H.=6-7. G. 2-66-2-78. Lustre of cleavage 
 planes inclining to pearly ; of other faces vitreous. 
 Color white, grayish, reddish. Streak uncolored. 
 Transparent translucent. Fracture conchoidal. 
 Brittle. 
 
 Var. Anorthite was described from the glassy crystals of Som- 
 
 ma. Indianite is a white, grayish, or reddish granular anorthite from India, first described 
 in 1802 by Count Bournon. 
 
 Oomp Q. ratio for R : Al : Si=l : 3 : 4. Formula CaAlSi 2 8 = Silica 43-1, alumina 36-8, 
 lime 20-1=100. The alkalies are sometimes present in very small amounts. 
 
 Pyr., etc. B.B. fuses at 5 to a colorless glass. Decomposed by hydrochloric acid, with 
 separation of gelatinous silica. 
 
 Obs. Occurs in some granites; occasionally in connection with gabbro and serpentine 
 rocks ; in some cases along with corundum ; in many volcanic rocks. Found in the old lavas 
 in the ravines of Monte Somma ; Pesmeda-Alp, Tyrol ; in the Faroe islands ; in Iceland ; 
 near Bogoslovsk in the Ural, etc. 
 
 BYTOWNITE has been shown by Zirkel to be a mixture. Bytown, Canada. 
 
 LABRADORITE. 
 
 Triclinic. lhf = 121 ' 37', r\i-l 93 20', O l\ 1 110 50', 
 = 113 34' ; Marignac. Twins : similar to those of albite. Cleavage : O 
 easy ; i-l less so ; /traces. Good crystals rare ; generally massive granular, 
 and in grains cleavable ; sometimes cryptocrystalline or hornstone-like. 
 , H. 6. G.=2-67-2'76. Lustre of O pearly, passing into vitreous; 
 elsewhere vitreous or subresinous. Color gray, brown, or greenish, some- 
 times colorless and glassy; rarely porcelain-white; usually a change of 
 colors in cleavable varieties. Streak uncolored. Translucent subtrans- 
 lucent. 
 
 Comp., Var Q. ratio for R : Al : Si=l : 3 : 6, but varying somewhat (see p. 319). 
 Formula RAlSi 3 Oi ; here R=Ca and Na 2 . The atomic ratio for Na : Ca~ 2 : 3 generally, 
 this corresponds to Silica 52-9, alumina 30 '3, lime 12 '3, soda 4'5=100. 
 
 Var. 1. Cleavable. (a) Well crystallized to (b) massive. PJay of colors either -wanting, M 
 
 21 
 
322 DESCRIPTIVE MINERALOGY. 
 
 in some colorless crystals ; or pale ; or deep ; blue and green are the predominant colors ; but 
 yellow, fire-red, and pearl-gray also occur.' By cutting very thin slices, parallel to i-i, from 
 the original labradorite, they are seen under the microscope to contain, besides striae, great 
 numbers of minute scales, like the aventurine oligoclase, which are probably gothite or hema- 
 tite. These scales produce an aventurine effect which is quite independent of the play of 
 colors which arises from the interference of the rays of light reflected by innumerable inter- 
 nal lamellae (ReuxGh). The various forms of minerals (micropktkites, microphyllites, etc. ) en- 
 closed in the labradorite, and their relation to it in position, have been thoroughly investigated 
 by Schrauf (Ber. Ak., Wien, Dec., 1869). 
 
 Pyr,, etc. B. B. fuses at 3 to a colorless glass. Decomposed with difficulty by hydrochloric 
 acM generally leaving a portion of undecomposed mineral. 
 
 Otys. Labradorite is a constituent of some rocks, both metamorphic and igneous; e.g., 
 diabase, doleryte, basalt, etc. The labradoritic metamorphic rocks are most common among 
 the fcibmationb of the Archaean or pre-Silurian era. Such are part of those of British America, 
 northern New York, Pennsylvania, Arkansas; those of Greenland, Norway, Finland, Sweden, 
 and pifobably of the Vosges. Being a feldspar containing comparatively little silica, it occurs 
 mainly in rocks which include little or no quartz (free silica). 
 
 Kiev/ .has furnished fine specimens ; also Labrador. It is met with in many places in 
 Car-iia East. Occurs at Essex Co., N. Y. ; also in St. Lawrence, Warren, Scoharie, and 
 (*ren Cos. In Pennsylvania, at Mineral Hill, Chester Co. ; in the Witchita Mts., Arkansas, 
 etc.' 
 
 Labradorite was first brought from the Isle of Paul, on the coast of Labrador, by Mr. Wolfe, 
 a Moravian missionary, about the year 1770, and was called by the early mineralogists Labra- 
 dor stone (LabradoTistdri), and also chatoyant, opaline, or Labrador feldspar. Labradorite 
 receives a fine polish, and owing to the chatoyant reflections, the specimens ar often highly 
 beautiful. It is sometimes used in jewelry. 
 
 MASKELYNITE. Occurs in transparent, isometric, grains in the meteorite of Shergotty. 
 Same composition as labradorite. 
 
 ANDESITE. Andesine. 
 
 Triclinic. Approximate angles from Esterel crystals (DesCl.) : A i-l, 
 left, S7-88, O A /= 111-112, O/\T = 115, I l\i-l = 119-120, /' Ai-l 
 =120, ^A2-i = 101-102. Twins: resembling those of albite. Sel- 
 dom in crystals. Cleavage more uneven than in albite. Also granular 
 massive. 
 
 II. =5- 6. G.^2'61-2'74:. Color white, gray, greenish, yellowish, flesh- 
 red. Lustre subvitreous, inclining to pearly. 
 
 Comp. Q. ratio 1:3:8, but varying to 1 : 3 : 7. General formula KAlSi 4 Oi 2 ; R=Na 2 and 
 Ca in the ratio 1 : 1 to 3 : 1 ; if the ratio is 1 : 1, the formula corresponds to Silica 59 '8, alu- 
 mina 25-5, lime 7'0, soda 7-7=100. 
 
 Pyr., etc. Andesite fuses in thin splinters before the blowpipe. Saccharite melts only on 
 thin edges ; with borax forms a clear glass. Imperfectly soluble in acids. 
 
 Obs. Occurs in many rocks, especially some trachytes. The original locality was in the 
 Andes, at Marmato ; also in the porphyry of TEsterel, France ; in the Vosges Mts. ; at Vap- 
 nefiord, Iceland, in honey-yellow transparent crystals, etc. In North America, found at 
 Chateau Richer, Canada, forming with hypersthene and ilmenite a wide-spread rock ; color 
 flesh-red. 
 
 Andesite is regarded by DesCloizeaux as an altered oligoclase, but many careful analyse! 
 point to a feldspar having the composition given above. 
 
 HYALOPHANE. 
 
 Monoclinic, like orthoclase, and angles nearly the same. 6 r =6-i16', 
 f A /= 118 41', A l-i = 130 55'. Cleavage : O perfect, iA somewhat 
 less so. In small crystals, single, or in groups of two or three. 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 323 
 
 II. 6-6*5. G.=2'SO, transparent ; 2'905, translucent. Lustre vitreous 
 like that of adularia. Color white, or colorless ; also flesh-red. Trans- 
 parent to translucent. 
 
 Comp. Q. ratio f or R : R : Si=l : 3 : 8. Formula (Ba,K 2 )AlSi 4 12 . Analysis of hyalo- 
 phane from the Binnenthal by Stockar-Escher, Si0 2 52'67, A10 3 21-12, MgO 0'04. CaO 0'4G, 
 BaO 15-05, Na 2 214, K 2 O 7-82, H 2 O "58 = 99 "88. 
 
 Pyr., etc. B.B. fuses with difficulty to a blebby glass. Unacted upon by acids. 
 
 Obs Occurs in a granular dolomite near Imfeld, in the Binnenthal, Switzerland ; also i\i 
 Jakobsberg in Sweden. 
 
 OLIGOCLASE. 
 
 Triclinic. /A T = 120 42', A H ov. 24' = 93 50', A 1= 110 55', 
 A T = 114 40'. Cleavage : O, i-l perfect, the 
 latter least so. Twins : similar to those of albite. 
 Also massive. 
 
 H. = 6-7. G.=2-56-2-72; mostly 2-65-2-69. 
 Lustre vitreo-pearly or waxy, to vitreous. Color 
 usually whitish, with a faint tinge of grayish- 
 green, grayish-white, reddish-white, greenish, 
 reddish ; sometimes aventnrine. Transparent, 
 subtranslucent. Fracture conchoidal to uneven. 
 
 Comp., Var. Q. ratio for R : Al : Si 1 : 3 : 9, though 
 with some variations (see p. 297). Formula RAlSi^Ou, with 
 R=Na2(K 2 ),Ca The rat'O of 3 : 1 for Na : Ca corresponds in 
 this formula to Silica 61-9, alumina 24'1, lime 5 "2, soda 8 '8=100. 
 
 Var. 1. Cleavable ; in crystals or massive. 2. Compact massive ; oUgodase-felsite; includes 
 part, at least, of the so-called compact feldspar orfelsite, consisting of the feldspar in acorn- 
 pact, either fine granular or flint-like state. 3. Aventurine oUgockise, or sunstone. Color 
 grayish-white to reddish-gray, usually the latter, with internal yellowish or reddish fire-like 
 reflections proceeding from disseminated crystals of probably either hematite or gothite. 4. 
 Moonstone pt. A whitish opalescence. 
 
 Pyr., etc. B.B. fuses at 3'5 to a clear or enamel-like glass. Not materially acted upon by 
 acids. 
 
 Obs. Occurs in porphyry, granite, syenite, serpentine, and also in different eruptive rocks. 
 It is sometimes associated with orthoclase in granite, or other gTanit s-like rocks. Among its 
 localities are Pargas in Finland ; Schaitansk, Ural ; in protogine of the Mer-de-Glace, in the 
 Alps ; in fine crystals at Mt. Somma ; as sunstone at Tvedestrand, Norway ; in Iceland, 
 colorless, at Hafnefjord (Jiafnefiordite). In the United States, at Unionville, Pa. ; also at 
 Haddam, Ct. ; Mineral Hill, Delaware Co., Pa. ; at the emery mine, Chester, Mass. 
 
 Named in 1826 by Breithaupt from oA/yw;, little, and /c/liw, to cleave. 
 
 TSCHERMAKITE (v. Kobell). Supposed to be a magnesia-feldspar, but the conclusion 
 was probably based on the analysis of impure material. Later investigations (Hawes, Pisani) 
 make it an oligoclase. Occurs with kjerulfine from Bamle, Norway. 
 
 ALBITE.* 
 
 Triclinic, 7 A I = 120 47', O A i-l = 93 36', A T = 114 42', A / 
 .= 110 50', O A 24' = 136 50', O A 2-2 = 133 14'. Cleavage: 0, i-l 
 perfect, the first most so ; 14 sometimes distinct. Twins: twinning-planc 
 i-iy axis of revolution normal to i-i, this is the most common method, and 
 its repetition gives rise to the fine striations (p. 91) upon the plane <?, which 
 are so characteristic of the triclinic feldspars ; twinning-plane, 24 (f. 578) 
 
324 
 
 DESCRIPTIVE MINERALOGY. 
 
 analogous to the Baveno twins of orthoclase ; also twinning-axis, the vertical 
 axis (f. 575) ; twinning-axis, the raacrodiagonal axis* (J), ihepericline twins. 
 Double twins not uncommon. True simple crystals very rare. Also mas- 
 give, either lamellar or granular ; the laminae sometimes divergent ; granulai 
 varieties occasionally quite fine to impalpable. 
 
 579 
 
 Pericline. 
 
 Middletown, Ct. 
 
 H.=6-7. G.= 2 -59-2-65. Lustre pearly upon a cleavage face ; vitreous 
 in other directions. Color white, also occasionally bluish, gray, reddish, 
 greenish, and green ; sometimes having a bluish opalescence or play of colors 
 on O. Streak uncolored. Transparent subtranslucent. Fracture uneven. 
 Brittle. 
 
 Comp., Var. Q. ratio Na : Al : Si=l : 3 : 12. Formula Na 2 AlSi 6 O 16 =Silica68'6, alumina 
 19-6, soda 11-8=100. A small part of the sodium is replaced usually, if not always, by 
 potassium, and also by calcium (here Na 2 by Ca). But these differences are not externally 
 apparent. 
 
 Var. 1. Ordinary, (a) In crystals or cleavable massive. The angles vary somewhat, 
 especially for plane T. (b) Aventurine ; similar to aventurine oligoclase and orthoclase. (c) 
 Moonstone ; similar to moonstone under oligoclase and orthoclase. Peristerite is a whitish 
 adularia-like albite, slightly iridescent, having Gr. =2*626 ; named from ireptarepd, pigeon, the 
 colors resembling somewhat those of the neck of a pigeon, (d) Pericline is in large, opaque, 
 white crystals, short and broad, of the forms in f. 577 (f. 334, p. 101) ; from the chlorite schists 
 of the Alps. Lamellar ; cleavelandite, a white kind found at Chesterfield, Mass. 
 
 Pyr., etc. B.B. fuses at 4 to a colorless or white glass, imparting an intense yellow to the 
 flame. Not acted upon by acids. 
 
 Obs. Albite is a constituent of several rocks, as dioryte, etc. It occurs with orthoclase in 
 some granite. It is common also in gneiss, and sometimes in the crystalline schists. Veins 
 of albitie granite are often repositories of the rarer granite minerals and of fine crystalliza- 
 tions of gerne. including beryl, tourmaline, allanite, columbite, etc. It occurs also in some 
 trachyte, in phonolyte, in granular limestone in disseminated crystals, as near Modane in 
 .Savoy. Some localities for crystals are : Schneeberg in Passeir, in simple crystals ; Col du 
 Bonhomme ; St. Gothard, and elsewhere in the Alps; Penig, etc., Saxony; Arendal ; Green- 
 land ; Island of Elba. 
 
 In the TJ. S. , in Maine, at Paris. In MOM. , at Chesterfield ; at Goshen. In Conn. , at 
 Haddam ; at Middletown. In N. York, at Granville, Washington Co. ; at Moriah, Essex Co. 
 in Penn., at Unionville, Delaware Co. 
 
 The name Albite is derived from albus, white, in allusion to its color, and was given the 
 upecies by Gahn and Berzelius in 1814. 
 
 * Vom Rath has recently shown this to be the true method of twinning in this case, and 
 hence that the explanation of Rose (given on p. 101) is incorrect. 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 325 
 
 ORTHOCLASE. 
 
 Monoclinic. C= 63 53', /A/= 118 48', A 14 = 153 28'; c : fl : d 
 = 0-844 : 1-5183 : 1. 6> A l-i = 129 41', 6> A 2-* = 99 38', O A 2 98 
 4'. Cleavage : (9 perfect; i-l less distinct; ^' faint; also imperfect in the 
 direction of one of the faces I. Twins: twinning-plane, i-i (Carlsbad 
 twins) f. 582, but the clinopinacoid (i-i) the composition-face (see p. 98) ; 
 twinning-plane the base (O) f. 583 ; also the clinodorne, 2-i (Baveno twins), 
 as in f. 588, in which the prism is made up of two adjoining planes O and 
 two i-i, and is nearly square, because A i-i = 90, and A 24 = 135 3' ; 
 /A /= 169 28' ; also the same in a twin of 4 crystals, f . 587, each side of 
 the prism then an O (see also p. 99). Often massive, granular ; sometimes 
 lamellar. Also compact crypto-crystalline, and sometimes flint-like or 
 jasper-like. 
 
 580 
 
 581 
 
 582 
 
 Loxoclase. 
 
 H.=6-6-5. G. = 2-44-2-62, mostly 2-5-2-6. Lustre vitreous; on cleav- 
 age-surface sometimes pearly. Color white, gray, flesh-red, common; 
 greenish-white, bright-green. Streak nncolored. Transparent to trans- 
 lucent. Fracture conchoidal to uneven. Optic-axial plane sometimes in 
 the orthodiagonal section and sometimes in the clinodiagonal ; acute bisec- 
 trix always negative, normal to the orthodiagonal. 
 
 Oomp., Var. Q. ratio for K : Al : Si=l : 3 : 12. Formula K 2 AlSi 6 O 16 =Silica 64'7, alu- 
 mina 18'4, potash 16'9 = 100; with sodium sometimes replacing- part of the potassium. The 
 orthoclase of Carlsbad contains rubidium. The varieties depend mainly on structure, varia- 
 tions in angles, the presence of soda, and the presence of impurities. 
 
 The amount of sodium detected by analyses varies greatly, the variety sanidin, (see below) 
 sometimes containing 6 per cent. The variations in angles are large, and they occur some- 
 times even in specimens of the same locality. The crystal] ization is normally monocJinic, 
 and the variations are simply irregularities. There are also large optical variations in ortho- 
 clase, on which see DesCl. Min., i., 329. 
 
 Var. 1. Ordinary. In crystals, or cleavable massive. Adularia (adular). Transparent, 
 cleavable, usually with pearly opalescent reflections, and sometimes with a play of colors like 
 labradorite, though paler in shade. Moonstone belongs in part here, the rest being al bite and 
 oligoclase. Sunstone, or aventurine feldftpar : In part orthoclase, rest albite or oligoclase 
 (q. v.). Amazonstone: Bright verdigris-green, and cleavable, mostly mixtures of orthoclase 
 and microcline (Dx.). Koenig concludes that the coloring matter of the Pike's Peak amazon- 
 etone is an organic compound of iron, which has been infiliTated into the mass. 
 
 Sanidin of Nose, or glassy feldspar (including much of the Ice-spar, part of which is anor- 
 
326 DESCRIPTIVE MINERALOGY. 
 
 thit?). Occurs in transparent glassy crystals, mostly tabular (whence the name from cavi^, a 
 board), in lava, pumice, trachyte, phonolite, etc. Proportion of soda to potash varies from 
 1 : 20 to 2 : 1. Mhyacolite is the same ; the name was applied to glassy crystals from Mt. 
 Somma (Eisspath, 'Wern.). 
 
 Ghesterlite. In white crystals, smooth, but feebly lustrous, implanted on dolomite in Ches- 
 ter Co. , Penn., and having wide variations in its angles. It contains but little soda. Accord- 
 ing to DesCloizeaux the chesterlite consists of a union of parallel bands of orthoclase and a 
 triclinic feldspar of the same composition, which he calls microcline (see below). 
 
 Loxodase. In grayish- white or yellowish crystals, a little pearly or greasy in lustre, often 
 large, feebly shining, lengthened usually in the direction of the clinodiagonal. A 7=112" 
 80', 0A/' = 112 50', jAi'^120 20', 0/\i-l (cleavage angle) =90 D , Breith. G.=2'6-2'62, 
 Plattner. The analyses find much more soda than potash, the ratio being about 3:1, but 
 how far this is due to mixture with albite has not been ascertained. From Hammond, St. 
 Lawrence Co., N. Y. Named from A.o|J>, transverse, and /cAaw, / cleave, under the idea that 
 the crystals are peculiar in having cleavage parallel to the orthodiagonal section. Perthite. 
 A flesh-red aventurine feldspar, consisting of interlaminated albite and orthoclase, as shown 
 by Breithaupt. From Perth, Canada East. 
 
 COMPACT ORTHOCLASK or ORTHOCLASE-HELSITE. This crypto-crystalline variety is com- 
 mon and occurs of various colors, from white and brown to deep red. There are two kinds 
 (a) fhe jasper-like, with a subvitreous lustre ; and (b) the ceratoid or wax-like, with a waxy 
 lustre. Some red kinds look closely like red jasper, but are easily distinguished by the fusi- 
 bility. The orthoclase differs from the albite felsite in containing much more potash than 
 soda. The Swedish name Halleflinta means false flint. 
 
 Pyr., etc. B.B. fuses at 5 ; varieties containing much soda are more fusible. Loxoclase 
 fuses at 4. Not acted upon by acids. 
 
 Obs. Orthoclase is an essential constituent of many rocks ; here are included granite, 
 gneiss, and mica schist; also syenite, trachyte, phonolyte, etc., etc. 
 
 Fine crystals are found at Carlsbad in Bohemia ; Katherinenburg, Siberia ; Arendal, Nor- 
 way ; Baveno in Piedmont ; in Cornwall ; in the Urals ; the Mourne mountains, Ireland, etc.; 
 in the trachyte of the Drachenf els on the Rhine. In the U. States, orthoclase is found in 
 N. Hamp., at Acworth. In Conn., at Haddam and Middletown. In N. York, at Rossie ; 
 in the town of Hammond ; in Lewis Co. ; near Natural Bridge ; in Warwick ; and at Amity 
 and Edenville. In Penn., in crystals at Leiperville, Delaware Co., etc. In N. Car., at 
 Washington Mine, Davidson Co.; beautiful Amazonstone at Pike's Peak, Col. Massive ortho- 
 clase is abundant at many localities. 
 
 MICROCLINE.* A triclinic potash feldspar. The name microcline was originally given by 
 Breithaupt to a whitish or reddish feldspar from the zircon-syenite of Fredericksvarn and 
 Brevig, Norway, on the ground that it was triclinic. It was shown by DesCloizeaux that this 
 feldspar was merely a variety of orthoclase remarkable for its large amount of soda. Recently 
 the latter author has proposed to retain this name for a feldspar found in the midst of gran- 
 ites, pegmatite, and gneiss, which is shown both by the angle between its cleavage planes, 
 and also by its optical properties, to be really triclinic. 
 
 Form generally like that of orthoclase. Cleavage basal and clinodiagonal, and also easy 
 parallel to both prismatic faces (1 and 1") ; for the optical properties see p. 298. Often asso- 
 ciated with orthoclase in regular parallel bands, especially in the amazonstone ; albite is also 
 hometimes present, though irregularly. Analysis of a "pure microcline " from Magnet Cove 
 byPisani. GK=2'54. 
 
 Si0 2 A10 3 FeO 3 KoO NaoO ign. 
 
 6430 19-70 0-74 15 "60 0'48 0'35 =101 '17 
 
 The association of orthoclase and microcline was observed in specimens from the Ilmen 
 Bits.; Urals ; Arendal ; Greenland; Labrador; Leverett,Mass.; Delaware, Chester Co., Penn.; 
 Pike's Peak, Col. The purest microcline was that of a greenish color from Magnet Cove, 
 /brk. ; it enclosed crystals of asgirite, and was not mixed with orthoclase. 
 
 SUBSILICATES. 
 
 Humite or Chondrodite Groivp, including three snb-species : 
 
 L Humite j II. Chondrodite ; III. Clinohumite. 
 
 The existence of three types of forms among the crystals of humite (Vesuvius) was early 
 tthown by Scacchi ; they have since then been further investigated by vom Rath (Pogg. Erg., 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 327 
 
 Bd. -v., 321, 1871 ; ibid., vi., 385, 1873). The chemical identity of the species humite and 
 chondrodite was shown by llamrnelsberg ; later Kokscharof proved that the crystals of chon- 
 drodite from Pargas, Finland, were identical in form and angles with Scacchi's type II, of 
 humite, and the same has also been shown of the Swedish crystals by vom Rath. In 1870 
 the author described crystals of chondrodite from Brewster, N. Y. , belonging to each of the 
 three types of humite ; he showed, moreover, then and later (Feb., 1876), that contrary to 
 what had been previously assumed, the crystals of both type II. and type III. were monoclinic, 
 not orthorhombic. DesCloizeaux and Klein have since proved (Jahrb. Min., 1876, No. 0) 
 the monoclinic character of type III. of the Vesuvian humite, and the former that of the, 
 Swedish crystals (type II.) ; he, moreover, proved the orthorhombic character of the crystals 
 of type I. , Vesuvius. In accordance with these facts DesCloizeaux has proposed that the three 
 types be regarded as distinct species, with the names given above. 
 
 I. HUMITE.* In eluding type L, Scacchi, Vesuvius. Also rare crystals from Brewster, N. Y. 
 The latter large, coarse, and having suffered more or less alteration. 
 
 Orthorhombic. Holohedral. i-2 (o 2 ) A i -2 130 19' ; 6> (J.) A 34 (^ 3 ) = 
 
 16' ; 6> A 3-2 (e 5 ) = 103 47' ; 6> A l-S ( e 3 ) = 126 
 
 , v, /x ^ -* (y 3 ) = 121 44'. Twins : twinning-plane -|-2, also -f-2, in both 
 cases the angle of the horizontal prism is nearly 120. Optic-axial plane 
 parallel to the base, acute bisectrix positive, normal to i-l. Dispersion 
 almost zero. 2Ha = 7S 18' -79 for red rays. (DesCl.) 
 
 102 48' ; O A 14 (**) = 124 
 21' O A 1-2 (V 3 ) = 121 
 
 Vesuvius. 
 
 Brewster. 
 
 Brewster. 
 
 El. CHONDRODITE.* Including type II. of Scacchi, Vesuvius ; also crystals from Finland, 
 Sweden, and with few exceptions those of Brewster, N. Y. 
 
 Monoclinic. Ar\i= 122 29' ; A A # = 109 5' ; Ah#' = 108 58' ; 
 A:n*=W3 12'; A A?i 2 ' = 103 9'; A A r 1 = 135 20' ; ^A/* = 125' 
 50'; C A r* = 146 24'; 6 y A n 2 = 135 40' : C f\n j = 135 41'. 
 
 The letters (those employed by Scacchi) correspond to the following 
 symbols 
 
 A=O i = l-l <?=:<2-i ri*=-2 r l = r*= -S 
 
 Twins : twinning plane \-i (?) and %-i (?), (both having a prismatic 
 angle nearly 120) ; also the basal plane O (Brewster, IN". Y., f. 593). 
 Optic-axial plane makes an angle of 26 with the base; acute bisectrix 
 
328 
 
 DESCRIPTIVE MINERALOGY. 
 
 positive, normal to the cliriopinacoid (C}. 2Ha=:88 48' for red rays, 
 Brewster, K Y. (E. S. D.). 2Ha=86 14'-87 20' (red rays), Sweden, (DesCl.) 
 
 The above angles are those given by DesCloizeaux, the author's own measurements on the 
 crystals from Brewster (not yet completed), point to a smaller variation from the rectaugu'ar 
 type. DesCloizeaux makes the plane e 2 '=i-i, and ^=7, r' 2 =l, r*= 1. 
 
 fc 
 
 Brewster. 
 
 Brewster. 
 
 Vesuvius. 
 
 IIL CLINOHUMITE. Including type III. of Scacchi, Vesuvius ; also rare finely polished 
 red crystals from Brewster, N. Y. 
 
 Monoclinic. A A <? = 133 40' ; A A p = 133 40' ; A A ** = 125 13' ; 
 A ?/i = 114 55' ; ^ A m 2 = 92 58' ; Af\n = 132 14' ; A A ^ 2 = 122 C 
 57'; ^.A^ 4 = 9723'; ^1 A n*' = 97 23 r ; A A-/- 3 = 131 23 ; ^A7> 4 
 
 47' ; 
 
 =132 56 X 6 r A r 4 = 137 25 X . DesCloizeaux. 
 
 These letters (those employed by Scacchi) correspond to the following 
 symbols : 
 
 A=O =4 n= 
 
 C =i4 
 
 r 8 = 8-2 
 
 DesCloizeaux makes the plane e*' i-i, ^ = /, and r 4 = 1, and r 5 = 1. 
 Twins: twinning-plane J-^; also the basal plane (Brewster). Optic-axial 
 plane makes an angle of 7i with the base, Brewster (Dana) ; same angle 
 for Vesuvian crystals equals 12 28' (Klein), about 11 (DesCl.X Acute 
 bisectrix positive, normal to clinopinacoid. 2Ha=84 40'-85 15', yellow 
 (Kl.).=84 38'-85 4' white crystals, and =86 40'-87 14' brown crystals 
 (DesCl.). Sections of crystals often shows a complex twinned structure. 
 
 In other physical and in chemical characters these three sub-species are 
 hardly to be distinguished. 
 
 H.:=6-6-5. G.=3-118-3-24. Lustre vitreous resinons. Color of 
 crystals yellowish-white, citron -yellow, honey -yellow, hyacinth-red, brownish 
 (Vesuvius); also deep garnet-red (Brewster)." Color of the mineral occur- 
 ring massive and in rounded imbedded grains (chondrodite at least in part) 
 as of crystals, also sometimes olive-green, apple-green, gray, black. Streak 
 white, or slightly yellowish, or grayish. Transparent subtransluceut 
 Fracture subconchoidal uneven. 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 329 
 
 Comp. The chemical investigations of Rammelsberg and vom Rath have served to show 
 a considerable variation in composition in the different varieties, but do not give decidedly 
 different formulas to the three types of Scacchi, that is, the three minerals described above. 
 
 In general Q. ratio for Mg : Si=4 : 3 (!$ : 1), and the formula then MgeSiaOu ; or, as pre- 
 ferred by Rammelsberg, Mg : Si=5 : 4 (1 : 1), and the formula is then Mg 3 Si 2 O B . In all 
 cases part of the magnesium is replaced by iron, and part of the oxygen by fluorine (F 2 ), the 
 amount varying from 2 to 8J p. c., but certainly not dependent (v. Rath and Ramm.) upon 
 the three types. 
 
 Analyses : 
 
 I. Humite, Vesuvius, 
 
 II. Chondrodite, Vesuvius, 
 
 II. Chondrodite, Brewster, 
 
 II. Chondrodite, Sweden, 
 
 III. Clinohumite, Vesuvius, 
 
 SiO 2 
 35-63 
 33-26 
 3410 
 33-96 
 36-82 
 
 Chondrodite (?), N. Jersey, 33 -97 
 
 FeO 
 
 5-12 
 2-30 
 
 7-28 
 6-83 
 5-48 
 3-48 
 
 MgO 
 54-45 
 57-92 
 53-72 
 53-51 
 54-92 
 56-97 
 
 F 
 2-43 
 5-04 
 4-14 
 4-24 
 2-40 
 7-44 
 
 CaO 0-23 A10 3 0'82=99-68, v. Rath. 
 CaO 0-74 A1O 3 1'06=1 00-32, Ramm. 
 
 A1O 3 0-48=99-72, Hawes. 
 
 3 0-72=99-26, v. Rath. 
 3 0-24=99-86, v. Rath. 
 =101-68, Ramm. 
 
 Pyr., etc. B.B. infusible ; some varieties blacken and then burn white. Fused with salt 
 of phosphorus in the open tube gives a reaction for fluorine. With the fluxes a reaction for 
 iron. Gelatinizes with acids. Heated with sulphuric acid gives off silicon fluoride. 
 
 Diff. Distinguishing characters are : infusibility ; gelatinizing with acids ; fluorine reac- 
 tion with sulphuric acid. 
 
 Obs. The localities of the crystallized minerals have already been mentioned. 
 
 The granular Chondrodite (?) occurs mostly in limestone. It is found in Finland and 
 in Sweden ; at Taberg in Wermland ; at Boden in Saxony ; on Loch Ness in Scotland ; at 
 Achmatovsk in the Ural, etc. Abundant in the counties of Sussex, N. J. , and Orange, N. Y., 
 where it is associated with spinel. In N. Jersey, at Bryam ; at Sparta ; at Vernon, Lockwood, 
 and Franklin. In N. York, in Orange Co. , in Warwick, Monroe, etc. ; near Edenville ; at 
 the Tilly Foster Iron Mine, Brewster, Putnam Co. In Mass. , at Chelmsf ord. In Penn. , near 
 Chadsford. In Canada, in limestone at St. Crosby ; St. Jerome ; St. Adele ; Grenville, etc., 
 abundant 
 
 TOURMALINE.* Turmalin, Germ. 
 
 Khombohedral. fif\R = 103, O Ml = 134 3' ; = 0-89526. J A J =. 
 596 597 598 599 600 
 
 Gouverneur, N. Y. St. Lawrence Co. , N. Y. 
 
 154: 59', i A i = 133 8', *-2 A g = 155 14', i-2 A i 3 = H2 26'. Usually 
 
330 DESCRIPTIVE MINERALOGY. 
 
 hemihedral, being often unlike at the opposite extremities, or hernimorphic, 
 and the prisms often triangular. Cleavage : 72, J. and *-2, difficult. 
 Sometimes massive compact; also columnar, coarse or fine, parallel or 
 divergent. 
 
 11.=: 7-7*5. G. 2'94-3'3. Lustre vitreous. Color black, brownish- 
 black, bluish-black, most common ; blue, green, red, and sometimes of rich 
 shades ; rarely white or colorless ; some specimens red internally and green 
 externally ; and others red at one extremity, and green, blue, or black at 
 the other. Dichroic (p. 165). Streak uncolored. Transparent opaque ; 
 greater transparency across the prism than in the line of the axis. Frac- 
 ture subconchoidal uneven. Brittle. Pyroelectric (p. 169). 
 
 Var. 1. Ordinary. In crystals, (a) Rubellite ; the red sometimes transparent, (b) Indi- 
 colite ; the blue, either pale or bluish -black ; named from the indigo-blue color, (c) Brazilian 
 Sapphire (in jewelry) ; Berlin-blue and transparent ; (d) Brazilian Emerald^ Chrysolite (or 
 Peridot) of Brazil ; green and transparent, (e) Peridot of Ctylon ; honey-yellow. (/) Ach- 
 roite ; colorless tourmaline, from Elba, (g) Aphrizite; black tourmaline", from Krageroe, 
 Norway, (h) Columnar and black ; coarse columnar. Resembles somewhat ho>nblende, but 
 nas a more resinous fracture, and is without distinct cleavage or anything like a fibrous 
 appearance in the texture. 
 
 Comp. Q. ratio of all varieties for R : Si=3 : 2 (Rammelsberg), consequently the general 
 
 nil ii 
 
 formula is R 3 (R 6 ,R)SiO 6 . R may represent here H, K, Na, Li ; also R=Mg(Ca).Fe,Mn, and 
 R=A1,B.2 ; further than this the Si is often in part replaced by F 2 . Rammelsberg distin- 
 guishes two groups, where the Q. ratio for B : iVl : Si 3 : G : 8, and (2) with the Q. ratio for 
 B : Al : Si=l : 3 : 3. In the first group fall most of the yellow, brown, and black varieties, 
 
 ii i 
 
 the bivalent elements (Mg,Fe) predominating, the general formula being R 3 (Re)RnSi 4 2 o. 
 The second group includes the colorless, red, and slightly green kinds, the univalent elements 
 
 appearing most prominent, especially lithium. The general formula is R 6 (R 3 )RbSiuO4 5 . 
 
 Several distinct varieties are made under these groups, which will be sufficiently illustrated 
 by the following analyses, by Rammelsberg. I. Gouverneur, brown.; G. =3*049. II. Haddam, 
 black; G.=3"136. III. Goshen, bluish-black; G.=3 203. IV. Paris, Me., red; G.=3'019. 
 V. Chesterfield, Mass., green; G.=3'069. 
 
 SiO 2 B 2 3 A10 3 FeO MnO MgO CaO Na 2 O K 2 O Li 2 O F H 2 O 
 
 I. 38-85 (8-35) 31'32 114 1489 1-60 1-28 0-26 2'31=100'00 
 
 II. 37-50 (9-02) 30-87 8'54 8-60 1-33 1'GO 0'73 1-81 = 100-00 
 
 III. 36-22 10-65 33-35 11-95 1'25 0'63 1-75 0'40 0'84 082 2-21 = 100-82 
 
 IV. 38-19 9-97 42-63 1-94 0'39 0-45 2'60 0"68 1-17 1-18 2 00=100'20 
 
 V. 38-46 9-73 36-80 6-38 078 1-68 2-47 0'47 0-72 0'55 2-31 = 100-55 
 
 Fyr., etc. I. fuse rather easily to a white blebby glass or slag ; II. fuse with a strong heat 
 to a blebby slag or enamel ; III. fuse with difficulty, or, in some, only on the edges ; IV. fuse 
 on the edges, and often with great difficulty, and some are infusible ; V. infusible, but becom- 
 ing white or paler. With the fluxes many varieties give reactions for iron and manganese. 
 Fused with a mixture of potassium bisulphate and fluorite gives a strong reaction for boracic 
 acid. By heat alone tourmaline loses weight from the evolution of silicon fluoride and per- 
 haps also boron fluoride ; and only after previous ignition is the mineral completely decom- 
 posed by fluohydric acid. Not decomposed by acids (Ramm. ). After fusion perfectly decom- 
 posed by sulphuric acid (v*. Kobell). 
 
 Diff. Distinguished by its form, occurring commonly in three-sided, or six-sided prisms ; 
 absence of cleavage (unlike hornblende). It is less easily fusible than garnet or vesuvianite. 
 B.B. (see above) gives a green flame (boron). 
 
 Obs. Tourmaline is usually found in granite, gneiss, syenite, mica, chloritic or talcose schist, 
 dolomite, granular limestone, and sometimes in sandstone near dykes of igneous rocks. The 
 variety in granular limestone or dolomite is commonly brown. 
 
 Prominent localities are Katherinenburg in Siberia ; Elba ; Windisch Kappell in Carinthia ; 
 Rozena ; Airolo, Switzerland ; St. Gothard. In Great Britain. Bovey Tracey in Devon ; 
 Cornwall, at different localities ; Aberdeen in Scotland, etc. 
 
 In the U. States, in Maine, at Paris and Hebron. In Mass., at Chesterfield ; at Goshen, blue. 
 In N. Hamp. t Graf ton ; Acworth, etc. In Conn., at Monroe and Haddam, black, in 2f. York, 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 331 
 
 aear Gouverneur; near Port Henry, Essex Co., enclosing orthoclase (see p. 109) ; Pierrepont; 
 near Edenville. In Penn. , near Unionville; at Chester; Middletown, and elsewhere. In 
 Canada, at G. Calumet Id. ; at Fitzroy, C. W. ; at Hunterstown, C. E. ; at Bathurst an 
 EJmsley, C. W. 
 
 GEIILENITE. Tetragonal. Color grayish-green. Q. ratio for R : R : Si=3 : 3 : : 4, or 3 ! : 2 
 for bases and silicon. Formula Ca 3 RSi 2 10 , with ft=rVl : Fe=5 : 1 ; this requires Silica 29'9, 
 *iumina 21 '5, iron sesquioxide 6'6. lime 4 '20=100. Mt. Monzoni, Fassathal, Tyrol. 
 
 ANDALUSITE. 
 
 Orthorhombic. /A 7= 90 48', OM-l= 144 32' ; i : I : d = 0-71241 
 : 1-01405 : 1. Cleavage : 7 perfect in crystals from 
 Brazil ; i-l less perfect ; i-l in traces. Massive, im 
 
 603 
 
 - 
 
 perfectly columnar, sometimes radiated, and granular. 
 H. f-5 ; in some opaque kinds 3-6. G.=3'05- 
 3-35, mostly 3-1-3-2. Lustre vitreous ; often weak. 
 Color whitish, rose-red, flesh-red, violet, pearl-gray, 
 reddish-brown, olive-green. Streak uncolored.^ Trans- 
 parent to opaque, usually subtranslucent. Fracture 
 uneven, subconchoidal. 
 
 Var. 1. Ordinary. H. 7-5 on the basal face, if not elsewhere. 
 2. Ghiastolite (made), Sterling, Mass. Stout crystals having the 
 axis and angles of a different color from the rest, owing to a regu- 
 lar ar-angement of impurities through the interior, and hence ex- 
 haling a colored cross, or a tesselated appearance in a transverse 
 section. H.=3-7'5, varying much with the degree of impurity. 
 The following figure shows sections of some crystals (see also p. 110). 
 
 it \ 
 
 Comp. Q. ratio for R : Si=3 : 2 ; AlSi0 6 =Silica 36 -9, alumina 63 -I =100. Sometimes a 
 
 Ut pyr!^et 3 c! P RB 81 infusible. With cobalt solution gives a blue color. Not decomposed by 
 acids Decomposed on fusion with caustic alkalies and alkaline carbonates. 
 
 Diff. Distinguishing characters: inf usibility ; hardness; and the form, being n< 
 of a square t>rism, unlike staurolite. , . 
 
 Obs. Most common in argillaceous schist, or other schists imperfectly crystalline s ; also 
 gneiss, mica schist, and related rocks. Found in Spain, in Andalusia, and thence th( 
 of the species ; in the Tyrol, Lisens valley; in Saxony, at Braunsdorf, and elsewhere. In 
 Ireland. In Brazil, province of Minas Geraes (transparent). Common m crystalline i 
 New England and Canada; good crystals have been obtained in Delaware Co., renn., ew. 
 also in California; in Mass., at Sterling (chiaslolite). 
 
 FIBROLITE. Bucholzite. Sillimanite. 
 
 Orthorhombic. /A I 96 to 98 in the smoothest crystals ; usually large;, 
 the faces I striated, and passing into i-z. Cleavage : irt very perfect, b 
 liant. Crystals commonly long and slender, 
 massive, sometimes radiating. 
 
 Also fibrous or columnar 
 
332 DESCRIPTIVE MINERALOGY. 
 
 H.=6-7. G.= 3*2-3-3. Lustre vitreous, approaching subadamantine 
 Color hair-brown, grayish-brown, grayish-white, grayish-green, pale olive 
 green. Streak uncolored. Transparent to translucent. 
 
 Var. 1. SUlimanite In long, slender crystals, passing into fibrous, with the fibres separ- 
 able. 2. Fibrolile. Fibrous or fine columnar, firm and compact, sometimes radiated ; gray 
 ish- white to pale brown, and pale olive-green or greenish- gray. Bucholzite and monrolite are 
 here included ; the latter is radiated columnar, and of the greenish color mentioned. 
 
 Comp. AlSiOs, as for andalusite^ Silica 36 "9, alumina 63 '1 = 100. 
 
 Fyr., etc. Same as given under andalusite. 
 
 Dift Distinguished from tremolite by its infusibility ; also by its brilliant diagonal cleav- 
 age, in which and in its specific gravity it differs from cyanite. 
 
 Obs. Occurs in gneiss, mica schist, and related metamorphic rocks. In the Fassathal, 
 Tyrol (bucMzite) ; at Bodenmais in Bavaria, etc. In the United States, at Worcester, Mass. 
 Near Norwich, Conn. ; at Chester, near Saybrook (sillimanite). In N. York, in Monroe, 
 Orange Co. (monrolite). In Penn. , at Chester on the Delaware; in Delaware Co., etc. In 
 Delaware, at Brandywine Springs. In N. Carolina, with corundum. 
 
 Fibrolite was much used for stone implements in western Europe in the " Stone age." 
 
 W6RTHITE, a hydrous fibrolite ; WESTANITE (Sweden) is related in composition. 
 
 CYANITE.* Kyanite. Disthene. 
 
 Triclinic. In flattened prisms ; O rarely observed. Crystals oblong, 
 usually very long and blade-like. Cleavage : i-l distinct ; i-i less so ; O 
 imperfect. Also coarsely bladed columnar to subfibrous. 
 
 H.=5-7'25, the least on the lateral planes. G.=3'45-3'7. Lustre vit- 
 reous pearly. Color blue, white, blue along the centre of the blades or 
 crystals with white margins ; also gray, green, black. Streak uncolored. 
 Translucent transparent. 
 
 Var. The white cyanite is sometimes called RTiattizite. 
 
 Comp. AlSiO 5 = Silica 36'9, alumina 63*1=100, like andalusite and fibrolite. 
 
 Fyr., etc. Same as for andalusite. 
 
 Diff, Unlike the amphibole group of minerals in its infusibility ; occurrence in thin-bladed 
 prisms characteristic. 
 
 Obs. Occurs principally in gneiss and mica slate. Found at St. G-othard in Switzerland ; 
 at Greiner and Pfitsch in the Tyrol; also in Styria ; Carinthia ; Bohemia. In Mass., at 
 Chesterfield, etc. In Conn., at Litchfield ; at Oxford. In Vermont, at Thetford. 
 in Chester Co. ; and Delaware Co. In JW. Carolina. 
 
 TOPAZ. 3 * 
 
 Orthorhombic. /A 1 = 124 IT, A 1-i = 138 3' ; c : I : a =0-90243 
 : 1-8920 : 1. O A 1 = 134 25', 1 A 1, inacr., = 141 0'. Crystals usually 
 hemihedral, the extremities being unlike; habit prismatic. Cleavage; 
 basal, highly perfect. Also firm columnar ; also granular, coarse or fine. 
 
 H.=8. G-. =3-4-3-65. Lustre vitreous. Color straw-yellow, wine- 
 yellow, white, grayish, greenish, bluish, reddish ; pale. Streak uncolored 
 Transparent subtranslucent. Fracture subconchoidal, uneven. Pyro- 
 
OXYGEN COMPOUNDS ANHYDROUS SILICATES. 
 
 333 
 
 electric. Optic-axial plane i-l ; divergence very variable, sometimes differ- 
 ing much in different parts of the same crystal ; bisectrix positive, noimal 
 to O. 
 
 600 
 
 610 
 
 ' } i 
 Trumbull, Ct. 
 
 Schneckenstein. 
 
 O=l : 5 = 
 
 Oomp. AlSiOs, with part of the oxygen replaced by fluorine (F 2 ) ; ratio of F 2 
 Silicon 15-17, almninum 29 '58, oxygen 34'67, fluorine 20'58=100. 
 
 Pyr., etc. B.B. infusible. Some varieties take a wine-yellow or pink tinge when heated. 
 Fused in the open tube with salt of phosphorus gives the reaction for fluorine. With cobalt 
 solution the pulverized mineral gives a fine blue on heating. Only partially attacked by sul- 
 phuric acid. 
 
 Diff. Distinguishing characters: hardness, greater than that of quartz; inf usibility ; 
 perfect basal cleavage. B.B. yields fluorine. 
 
 Obs. Topaz occurs in gneiss or granite, with tourmaline, mica, and beryl, occasionally 
 with apatite, fluorite, and tin ore ; also in talcose rock, as in Brazil, with euclase, etc., or 
 in mica slate. Fine topazes come from, the Urals; Kamschatka ; Brazil; in Cairngorm, 
 Aberdeenshire ; at the tin mines of Bohemia and Saxony. Physalite (a coarse variety), occurs 
 at Fossum, Norway ; also in Durango, Mexico ; at La Paz, province of Guanaxuato. In the 
 United States, in Conn., at Trumbull. In N. Car., at Crowder's Mountain. In Utah, in 
 Thomas's Mts. ; from gold washings of Oregon. 
 
 EUCLASE.* 
 
 Monoclinic. C = 79 44'= O A i4, If\ f= 115 0', A 14 = 146 45' ; 
 c:b:d = 1-02943 : 1-5446 : 1 = 1 : 1-50043 : 0-97135. 
 Cleavage : i-4 very perfect and brilliant ; O^ i-i much 
 less distinct. Found only in crystals. 
 
 H. 7'5. G.= 3-098 (Haid.)/ Lustre vitreous, some- 
 what pearly on the cleavage-face. Colorless, pale moun- 
 tain-green, passing into blue and white. Streak un- 
 colored. Transparent ; occasionally subtransparent. 
 Fracture conchoidal. very brittle. r # a 12 
 
 Comp. Q. ratio for H : Be : Al : Si=l : 2 : 3 : 4, for R : Si=3 : 2 
 (H 2 =R, and 3R-:M), formula, H 2 Be a AlSi 2 Oi = Silica 41 '20, alumina 
 85-22, glucina 17 '39, water 619=100. 
 
 Pyr., etc. In the closed tube, when strongly ignited, B.B. gives off 
 water (Damour). B.B. in the forceps cracks and whitens, throws out 
 points, and fuses at 5 '5 to a white enamel. Not acted on by acids. 
 ; Obs. Occurs in Brazil, at Villa Rica ; in southern Ural, near the river Sanarka. 
 
334 
 
 DESCRIPTIVE MINERALOGY. 
 
 DATOLITE. Humboldtite. 
 
 Monoclinic. C= 89 54'= (below) A i-i, /A 7 = 115 3', A 14 = 
 162 27' ; c:b:d = 0-49695 : 1-5712 : 1. (9 A - 2-*' = 135 13', A 1 ^ 
 149 33', /A /front = 115 3', 24 A 24, ov. 6>, = 115 21', i-t A *-&, ov. f ?. 
 = 76 18', 44 A 44, ov. #, = 76 88. Cleavage : O distinct. Also botry- 
 oidal and globular, having a columnar structure ; also divergent and radi- 
 ating ; also massive, granular to compact. 
 
 612 
 
 613 
 
 Bergen Hill. 
 
 Bergen Hill. 
 
 Arendal. 
 
 H.=5-5-5. G.=2-8-3 ; 2-989, Arendal,. Haidinger. Lustre vitreous, 
 rarely subresinous on a surface of fracture ; color white ; sometimes gray- 
 ish, pale-green, yellow, red, or amethystine, rarely dirty olive-green or 
 honey-yellow. Streak white. Translucent; rarely opaque white. Frac- 
 ture uneven, subconchoidal. Brittle. Plane of optic-axes 4; angle of 
 divergence very obtuse ; bisectrix makes an angle of 4 with a normal to i-i 
 
 Var. 1. Ordinary. In crystals, glassy in aspect. Usual forms as in figures. 2. Cojnpact 
 
OXYGEN COMPOUNDS ANHYDKOUS SILICATES. 
 
 335 
 
 massive. White opaque, breaking with the surface of porcelain or Wedgewood ware. From 
 the L. Superior region. 3. Botryoidal ; Botryolite. Radiated columnar, having a botryoidal 
 surface, and containing more water than the crystals. The original locality of both the crys- 
 tallized and botryoidal was Arendal, Norway. Haytorite is datolite altered to chalcedony, 
 from the Hay tor Iron Mine, England. 
 
 Comp Q. ratio f or H : Ca : B : Sir=l : 2 : 3 : 4, like euclase: formula HoCa 2 B a SiaOio 
 Silica 37-5, boron trioxide 21-9, lime 35-0, water 5 '6 = 100. Botryolite contains 10 -64 p. c. water. 
 
 Pyr., etc. In the closed tube gives off much water. B.B. fuses at 2 with intumescence to 
 a clear glass, coloring the flame bright green. Gelatinizes with hydrochloric acid. 
 
 Diff. Distinguishing characters: glassy lustre; usually complex crystallization; B.B. 
 fuses easily with a green flame ; gelatinizes with acids. 
 
 Obs. Datolite is found in trappean rocks ; also in gneiss, dioryte, and serpentine ; in me- 
 tallic veins ; sometimes also in beds of iron ore. Found in Scotland ; at Arendal ; at Andreas- 
 berg ; at Baveno near Lago Maggiore ; at the Seisser Alp, Tyrol ; at Toggiana in Modena, in 
 serpentine. In good specimens at Roaring Brook, near New Haven ; also at many other 
 localities in the trap rocks of Connecticut ; in N. Jersey, at Bergen Bill ; in the Lake Superior 
 region, and on Isle Royale. San Carlos, Inyo Co., Cal., with garnet and vesuvianite. 
 
 TITANITE.* SPHENE. 
 
 Monoclinic. C 60 17' = A i-i ; /A I = 113 31', A l-l = 159 
 39'; c : b : d 0-56586 : 1-3251 : 1. Cleavage: / sometimes nearly per- 
 fect ; i-i and 1 much less so ; rarely (in greenovite) 2 easy, 2 less so ; 
 sometimes hemimorphic. Twins : twinning-plane i-i ; usually producing 
 thin tables with a reentering angle along one side ; sometimes elongated, 
 as in f. 623. Sometimes massive, compact ; rarely lamellar. 
 
 Lederite. SpinthSre. Schwarzensteiu. 
 
 H.=5-5-5. G.=3-4-3-56. Lustre adamantine resinous. Color brown, 
 gray, yellow, green, and black. Streak white, slightly reddish in greenovite 
 
336 
 
 DESCRIPTIVE MINERALOGY. 
 
 Transparent opaque. Brittle. Optic-axial plane i-l ; bisectrix positive, 
 closely normal to l-i (x) ; double refraction strong ; axi{ " 
 
 very c 
 
 53-56 for the red rays, 46-45 for the blue ; DesCl. 
 
 divergence 
 
 Oomp., Var. Q. ratio for Ca : Ti : Si 1 : 2 : 2, or making the Ti basic (Ti=2R), U : Si 
 =3:2; formula (equivalent to RSi0 5 ) CaTiSiO s = Silica 30'61, titanic oxide 40'82, lime 28 -57 
 =100. 
 
 Var. Ordinary, (a) Titanite ; brown to black, the original being thus colored, also opaque 
 or subtranslucent. (b) Sphene (named from a^v,awedge) ; of light shades, as yellow, green- 
 ish, etc. , and often translucent ; the original was yellow. Manganesian ; Greenomte. Red 
 or rose- colored, owing to the presence of a little manganese. In the crystals there is a great 
 diversity of form, arising from an elongation or not into a prism, and from the occurrence of 
 the elongation in the direction of different diameters of the fundamental form. 
 
 Pyr., etc. B.B. some varieties change color, becoming yellow, and fuse at 3 with intu- 
 mescence, to a yellow, brown, or black glass. With borax they afford a clear yellowish-green 
 glass. Imperfectly soluble in heated hydrochloric acid ; and if the solution be concentrated 
 along with tin, it becomes of a fine violet color. With salt of phosphorus in R.F. gives a 
 violet bead ; varieties containing much iron require to be treated with the flux on charcoal 
 with metallic tin. Completely decomposed by sulphuric and fluohydric acids. 
 
 Diff. The resinous lustre is very characteristic ; and its commonly occurring wedge-shaped 
 form. B.B. gives a titanium reaction. 
 
 Obs. Titanite occurs in imbedded crystals, in granite, gneiss, mica schist, syenite, chlorite 
 schist, and granular limestone ; also in beds of iron ore, and volcanic rocks, and often asso- 
 ciated with pyroxene, hornblende, chlorite, scapolite, zircon, etc. Found at St. Gothard, and 
 elsewhere in the Alps ; in the protogine of Chamouni (pittite, Saus. ) ; at Ala, Piedmont 
 (liqurile) ; at Arendal, in Norway ; at Achmatovsk, Urals ; at St. Marcel in Piedmont (green- 
 ovite, Duf .) ; at Schwarzenstein. Tyrol ; in the Untersulzbachthal in Pinzgau ; near Tavistock ; 
 near Tremadoc, in North Wales. 
 
 Occurs in Canada, at Grenville, Elmsley, etc. In Maine, at Sanford. In Mass., at Bol- 
 ton ; at Pelham. In N. York, at Gouverneur ; at Diana, in dark-brown crystals (lederite} ; 
 in Orange Co.; near Edenville ; near Warwick. In N. Jersey, at Franklin. In Penn. t Bucks 
 Co., near Attleboro'. 
 
 GUABINITE. Same composition as titanite, but orthorhombic (v. Lang and Guiscardi) in 
 crystallization. Color yellow.- Mt. Somma. 
 
 KEILHAUITE (Yttrotitanite). Near sphene in form and composition, but containing alu- 
 mina and yttria. Arendal, Norway. 
 
 TSCHEFFKINITE. Analogous to keilhauite in composition, containing, besides titanium, 
 also cerium (La,Di). Occurs massive, llmen Mts. 
 
 STAUROLITE. 
 
 Orthorhombic. /A 1 = 129 20', A 1-t = 124 46' ; c : I : a, = 1-4406 
 M1233 : 1. Cleavage: i-l distinct, but interrupted; 1 in traces. Twins 
 
 627 
 
 629 
 
 630 
 
 cruciform : twinning-plane *-f (f. 628) ; f -J (f. 629) ; and J-f (f. 630). Fig, 
 
OXYGEN COMPOUNDS HYDROUS SILICATES. 
 
 337 
 
 831 is a drilling according to the last method of twinning, and in f. 632 both 
 methods are combined. See also 
 
 p. 90 and p. 98. 
 with rough surfaces. 
 
 Crystals often 
 Massive 
 forms unobserved. 
 
 H.=7-7;5. G. = 3-4-3-8. Sub- 
 | vitreous, inclining to resinous. 
 Color dark reddish-brown ^ to 
 brownish-black, and yellowish- 
 brown. Streak uncolored to 
 grayish. Translucent nearly or 
 quite opaque. Fracture conchoidal. 
 
 Oomp., Var.-Q. ratio, according to Rammelsberg, for R : R : Si=2 : 9 : 6 (where R is Fe 
 and Mg P and also includes H a , withH 2 : E=l : 3). Formula H 2 R 3 AlePi 6 O 3; (if Mg : ^=1:3) 
 -Silica 30-37 alumina 51 92, iron protoxide 13 '66, magnesia 2 53, water I "52= 00. The 
 kon was first taken as Fe0 3 , but Mitscherlich showed that it was really FeO. Staurolite 
 often includes impurities, especially free quartz, as first shown by Lechartier, and since then 
 by Fischer, Lasaulx, and Rammelsberg. This is the cause of the variation in the amount of 
 silica appearing in most analyses, there being sometimes as much as 50 p. c. 
 
 Pvr.; etc. B B. infusible, excepting the man ganesian variety, which fuses easily to a black 
 magnetic glass. With the fluxes gives reactions for iron, and sometimes for manganese. 
 Imperfectly decomposed by sulphuric acid. 
 
 Diff. Always in crystals ; the prisms obtuse, having an angle of l^i) . 
 
 Obs.-Usually found in mica schist, argillaceous schist, and gneiss ; often associated with 
 garnet cyanite, and tourmaline. Occurs with cyanite in paragomte schist at Mt Campione, 
 Switzerland ; at the Greiner mountain, and elsewhere in the Tyrol ; in Brittany ; in Ireland. 
 Abundant throughout the mica slate of New England. In Maine, at Windham, and elsewhere. 
 In Mass., at Chesterfield, etc. In Penn. In Georgia, at Canton ; and in Fannm Co. 
 
 SCIIORLOMITE.-Q. ratio for Ca+Fe+Ti : Si=2 : 1, nearly. Analysis by Ramm ,., Arkan- 
 gas Si0 3 26-09, KoTaiH4, Fe0 3 20-11, FeO 1-57, CaO 29'38, MgO 1 -86=99-85. Color black. 
 Fracture conchoidaJL Magnet Cove, Arkansas ; Kaiserstuhlgebirge in Breisgau. 
 
 HYDROUS SILICATES. 
 
 L GENERAL SECTION. A. BISILIOATES. 
 PBOTOLITB. 
 
 Monoclinic, isomorphous with wollastonite, Greg. Cleavage : i-i (orthoa.) 
 perfect. Twins : twinning-plane i4. Usually in close aggregations oJ 
 cular crystals. Fibrous massive, radiated to stellate. 
 
 H _5 G.=2-68-2-T8. Lustre of the surface of fracture silky or sub 
 vitreous. Color whitish or grayish. Subtranslucent to opaque. Tough. 
 For Bergen mineral optic-axial plane parallel to orthodiagonal, and very 
 nearly normal to i-i ; acute bisectrix positive, parallel to orthodiagonal, and 
 obtuse bisectrix nearly normal to cleavage-plane or t-* ; axial angle >u, 
 through cleavage-plates, 143-H5 ; DesCl. 
 
 Var.- Almost always columnar or fibrous, and divergent, the fibres of ten 5 or 3 ^ 8 lo ^, 
 and sometimes, as in Ayrshire, Scotland, a yard. Resembles in aspect fibrous varieties oJ 
 natrolite, okenite, thomsonite, treuioUte, and wollastonite. 
 
 22 
 
338 
 
 DESCRIPTIVE MINERALOGY. 
 
 Comp. Q. ratio for H : Na : Ca : Si=l : 1 . 4 : 12, and for R : Si (where R includes C% 
 and H a ,Na a ') = l : 2, like wollastonite ; hence formula HNaGa 2 Si 3 Oj Silica 54 '2, lime 33'8, 
 soda 9'3, water 2-7=100. If the H does not belong with the bases, then the formula may be 
 (Ramm.) NaoCa 4 Si 6 Oi 7 +aq. 
 
 Pyr., etc. In the closed tube yields water. B.B. fuses at 2 to a white enamel. Gela- 
 tinizes with hydrochloric acid. Often gives out a light when broken in the dark. 
 
 Obs. Occurs mostly in trap and related rocks, in cavities or seams ; occasionally in meta- 
 morphia rocks. Found in Scotland, near Edinburgh; in Ayrshire; and at Tali ver, etc., L 
 Skye ; at Mt. Baldo and Mt. Monzoni in the Tyrol ; in Wermland ; at Bergen Hill, N. J. ; 
 compact at Isle Royale, L. Superior. 
 
 LAUMONTITE. Caporcianite. 
 
 Monoclinic. 0= 68 40', I/\I= 86 16', O A 14 = 151 9' ; c : I : d = 
 0*516 : 0-8727 : 1. Prism with very oblique terminal plane 
 %-ij the most common form. Cleavage : i-\ and ./perfect; 
 -t imperfect. Twins: twinning-plane i-i. Also columnar, 
 radiating or divergent. 
 
 H.=3'5-4. G. = 2-25-2-36. Lustre vitreous, inclining 
 to pearly upon the faces of cleavage. Color white, passing 
 into yellow or gray, sometimes red. Streak uncolored. 
 Transparent translucent; becoming opaque and usually 
 pulverulent on exposure. Fracture scarcely observable, 
 uneven. Not very brittle. Double refraction weak ; optic- 
 axial plane i-\\ divergence 52 24' for the red rays; bisec- 
 trix negative, making an angle of 20 to 25 with a normal 
 to i-i ; JDesCl. 
 
 Oomp Q. ratio for R : R : Si : H 1 : 3 : 8 : 4 ; and R : Si=l : 2 (3R=R). R=Ca, R 
 =A1, and the formula is hence CaAlSi 4 Oi 2 +4aq- Silica 50'0, alumina 2T8, lime 11'9, water 
 16-3=100. 
 
 Pyr., etc. Loses part of its water over sulphuric acid, bat a red heat is needed to drive 
 off all. B.B. swells up and fuses at 2*7-3 to a white enamel. Gelatinizes with hydrochloric 
 acid. 
 
 Obs. Laumontite occurs in the cavities of trap or amygdaloid ; also in porphyry and sye 
 nite, and occasionally in veins traversing clay slate with calcite. Its principal localities are 
 at the Faroe Islands ; Disko in Greenland ; in Bohemia, at Eule ; St. Gothard in Switzer- 
 land ; the Fassathal ; the Kilpatrick hills, near Glasgow. Nova Scotia affords fine specimens ; 
 also Lake Superior, in the copper region, and on I. Royale ; also Bergen Hill, N. J. 
 
 OKENITE. Formula H 2 CaSi 2 O 8 +aq, having half the water basic = Silica 50 'G, lime 26 '4, 
 water 17 '0=1 00. Commonly fibrous. Color white, Faroe Is.; Disco, Greenland; Iceland. 
 
 GYROLITE. Occurs in radiated concretions at the Isle of Skye ; Nova Scotia. Formula 
 perhaps H.2Ca 2 Si 3 O 9 +aq. CENTRALLASSITE. Related to okenite, but contains 1 molecule 
 more water. In trap of Nova Scotia. 
 
 CHRYSOCOLLA.* Kieselkupfer, Germ. 
 
 Cryptocrystalline ; often opal-like or enamel-like in texture ; earthy. 
 Incrusting, or filling seams. Sometimes botryoidal. 
 
 H.=2-4. G. 2-2-238. Lustre vitreous, shining, earthy. Color moun- 
 tain-green, bluish-green, passing into sky-blue and turquois-blue; brown to 
 impure. Streak, when p^ure, white. Translucent opaque, 
 Rather sectile ; translucent varieties brittle. 
 
 black when 
 Fracture conchoidal. 
 
OXYGEN COMPOUNDS HYDROUS SILICATES. 
 
 339 
 
 Comp.-- Composition varies much through impurities, as with other amorphous substances, 
 esulting from alteration. As the silica has been derived from the decomposition of othei 
 ilicates it is natural that an excess should appear in many analyses. True chrysocolla cor- 
 esponds to the Q ratio for Cu : Si : H, 1:2: 2=CuSiO 3 +2aq= Silica 34-2, copper oxide 
 15-3, water 20 "5 = 100. But some analyses afford 1:2:3, and 1:2:4. Impure chrysocolla 
 nay contain, besides free silica, various other impurities, the color varying from bluish-green 
 ;o brown and black, the last especially when manganese or copper is present. 
 
 Pyr., etc, In the closed tube blackens and yields water. B.B. decrepitates, colors the 
 3ame emerald-green, but is infusible. With the fluxes gives the reactions for copper. With 
 joda and charcoal a globule of metallic copper. Decomposed by acids without gelatinization. 
 
 Diff Color more bluish-green than that of malachite, and it does not effervesce with 
 icids. 
 
 Obs. Accompanies other copper ores, occurring especially in the upper part of veins. 
 Found in most copper mines in Cornwall ; at Libethen in Hungary ; at Falkenstein and 
 Sehwatz in the Tyrol; in Siberia; the Bannat; Thuringia; Schneeberg, Saxony; Kupfer- 
 oerg, Bavaria; South Australia ; Chili, etc. In Somerville and Schuyler's mines, New Jersey ; 
 it Morgantown, Pa. ; at Cornwall, Lebanon Co. ; 'Nova Scotia, at the Basin of Mines ; also 
 in Wisconsin and Michigan. 
 
 DKMIDOFPITE ; CYANOCHALCITE ; RESANITE ; near chrysocolla. 
 
 CATAPLEiiTE.-Analysis (Ramm.), SiO a 39'78, Zr0 2 40-12, CaO 3 '45, Na a O 7-59, H 2 9'24 
 e=100'18. Hexagonal Color yellowish-brown, Lamoe, near Brevig, Norway. 
 
 B. UNISILICATES. 
 
 CALAMINE. Galmei; Kieselzinkerz, Germ. 
 
 Orthorhombic ; hemimorphic-hemihedral. 
 148 31', Daubar ; c : I : a = 6124 : 1-2850 
 
 7A 7= 104 
 : 1. Cleav- 
 
 13', 0A1-I 
 
 age : 7, perfect ; O, in traces. Also stalactitic, mammil- 
 lated, botryoidal, and fibrous forms; also massive and 
 granular. 
 
 H.=4-5-5, the latter when crystallized. G.=3'16-3'9. 
 Lustre vitreous, O subpearly, sometimes adamantine. Color 
 white ; sometimes with a delicate bluish or greenish shade ; 
 also yellowish to brown. Streak white. Transparent 
 translucent. Fracture uneven. Brittle. Pyroelectric. 
 
 |; Zn 2 Si0 4 H-aq=: Silica 25 '0, 
 
 Comp. Q. ratio f or R : Si : H=l : 1 
 
 zinc oxide 67 "5, water 7 "5 =100. 
 
 Pyr., etc. In the closed tube decrepitates, whitens, and gives off 
 water. B.B. almost infusible (P. =6); moistened with cobalt solution 
 
 gives a green color when heated. On charcoal with soda gives a coating which is yellow while 
 hot, and white on cooling. Moistened with cobalt solution, and heated in O.F., this coating 
 assumes a bright green color. Gelatinizes with acids even when previously ignited. Decom- 
 posed by acetic acid with gelatinization. Soluble in a strong solution of caustic potash. 
 
 Diff. Distinguishing characters: gelatinizing with acids; infusibility ; reaction for zinc. 
 
 Obs. Calamine and smithsonite are usually found associated in veins or beds in stratified 
 calcareous rocks accompanying blende, ores of iron, and lead, as at Aix la Chapelle; Bleiberg 
 hi Carinthia ; Retzbanya ; Schemnitz. At Roughten G-ill in Cumberland ; at Alston Moor j 
 near Matlock in Derbyshire ; at Castleton ; Lead hills, Scotland. 
 
 In the United States occurs with smithsonite in Jefferson county, Missouri. At Stirling 
 Hill, N. J. In Pennsylvania, at the Perkiomen and Phenixville lead mines; at Bethlehem; 
 at Friedensville. Abundant in Virginia, at Austin's mines. 
 
340 
 
 DESCRIPTIVE MINERALOGY 
 
 PREHNITE. 
 
 Orthorhombic. / A 1= 99 56', O A 14 = 146 11J' ; c : I : & = 0-66963 
 : 1*19035 : 1. Cleavage: basal, distinct. Tabular crystals often united by 
 O, making broken forms, often barrel-shaped. Usually reniform, globular, 
 and stalactitic with a crystalline surface. Structure imperfectly columnar 
 or lamellar, strongly coherent ; also compact granular or impalpable. 
 
 H.=6-6'5. G.=2-S-2-953. Lustre vitreous; O weak pearly. Color 
 light green, oil-green, passing into white and gray ; often fading on expo- 
 sure. Subtransparent translucent ; streak uncolored. Fracture uneven. 
 Somewhat brittle. 
 
 Comp. Q. ratio f or R : R : Si : H=2 : 3 : 6 : 1, whence, if the water is basic, for bases 
 and silicon, 1:1; formula H 2 Ca 2 AlSi 3 O ia or Ca 3 AlSi 3 Ou+aq= Silica 43 '6, alumina 24-9, 
 lime 27-1, water 4 "4=100. 
 
 Pyr., etc. In the closed tube yields water. B. B. fuses at 2 with intumescence to a blebby 
 enamel-like glass. Decomposed by hydrochloric acid without gelatinizing. ( 'oupholite, which 
 often contains dust or vegetable matter, blackens and emits a burnt odor. 
 
 Diff. B. B. fuses readily, unlike beryl and chalcedony. Its hardness is greater than that of 
 the zeolites. 
 
 Obs. Occurs in granite, gneiss, syenite, dioryte, and trappean rocks especially the last. 
 At Bourg d'Oisans in Isere ; in the Fassathal, Tyrol ; Ala in Piedmont ; Joachimsthal in 
 Bohemia ; near Andreasberg ; Arendal, Norway ; ^Edelfors in Sweden ; in Dumbartonshire ; 
 in Renfrewshire. 
 
 In the United States, in Connecticut ; Bergen Hill, N. J. ; on north shore of Lake Superior ; 
 in large veins in the Lake Superior copper region. 
 
 CHLORASTROLITE and ZONOCHLORITE from Lake Superior are mixtures, as shown by 
 Hawes. 
 
 VILLARSITE. Probably an altered chrysolite. Formula R 2 SiO 4 +|aq (or aq) R=Mg : Fe 
 =11 : 1. Traversella. 
 
 CERITE, Sweden, and TRITOMITE, Norway, contain cerium, lanthanum, and didymium. 
 THORITE and ORANGITE contain thorium. Norway. 
 
 PARATHORITE. In minute orthorhombic crystals, imbedded in danburite at Danbury, Ct. 
 Chemical nature unknown. 
 
 PYROSMALITE. Analysis by Ludwig, SiO 3 34'66, FeO 27-05, MnO 25-60, CaO 0-52, MgO 
 0'93, H..O8-31, 014-88=101-85. In hexagonal tables. Color blackish-green. Nya-Koppai- 
 berg, etc. , Sweden. 
 
 APOPHYLUTE.* 
 
 Tetragonal. A 1-i = 128 38'; c = 1-2515. Crystals sometimes nearly 
 
 cylindrical or barrel- 
 shaped. Twins : twin- 
 ning-plane the octahe- 
 dron 1. Cleavage : 
 highly perfect; / less 
 so. Also massive and 
 lamellar. 
 
 H.= 4-5-5. G.=2-3- 
 2-4. Lustre of O pearly ; 
 of the other faces vitre- 
 ous. Color white, or 
 grayish ; occasionally 
 with a greenish, yellow- 
 ish, or rose- red tint, flesh 
 rarely opaque. Brittle. 
 
 red. Streak uncolored. Transparent 
 
OXYGEN COMPOUNDS HYDKOU8 SILICATES. 
 iSrfne 2'10=100 m It may be taken as a unisilicate if part of the silica is considered 
 
 ^ 
 
 flame violet (pota 8 h), and fuses to a white vesicular enamel. F. - 
 
 ^^^^-, - p- 
 
 Of 
 
 , BaO 36-84, CaO tr, Na,O t,, 
 
 ^ ^ ta .e Ha,, 
 
 Bases mostly in sesquioxide state (Al,Mn,Fe). 
 
 SUBSILICATES. 
 
 ALLOPHANE. 
 
 Amorphous. In incrustations, usually thin, with a mammillary surface, 
 and hyalite-like ; sometimes stalactitic. Occasionally almost P^erulen 
 
 H 3 Q -1-85-1-89 Lustre vitreous to subresmous ; bright and 
 waxv internally. Color pale sky-blue, sometimes greenish to deep green, 
 brown TOllowJ or colorless. Streak uncolored. Translucent. Fracture 
 imperfectly conchoidal and shining, to earthy. Very brittle. 
 
 nosdy=3 : 2 : 6 (or 5) ; AlSiO 6 +6aq, or AlSi0 6 +5aq= 
 35-63 = 100. Plumbattophane, from Sardinia, contains a 
 
 the blue variety is due to traces of chrysocolla, the green to mala- 
 B.B. crumbles, but is infusible. Gives 
 
 CoLLTKiTiS. A hydrous silicate of aluminum. Clay-like i 
 En Sp? A NM rom SUesia, and UBANOIILE , from WoUendorf , Bavaria, are silicates oo 
 tainiug uranium. 
 
342 
 
 DESCRIPTIVE MINERALOGY. 
 
 II. ZEOLITE SECTION. 
 
 THOMSONITE. Comptonne. 
 
 /A 1= 90 40' ; O A 14 = 144 9' ; c : I : a =0-7225 : 
 1-0117 : 1. Cleavage: i-l easily obtained ; i- less sc , 
 O in traces. Twins : cruciform, having the vertical 
 axis in common. Also columnar, structure radiated ; 
 in radiated spherical concretions ; also amorphous and 
 compact. 
 
 H. 5-5-5. G. 2-3-2-4. Yitreous, more or less 
 pearly. Snow-white ; impure varieties brown. Streak 
 nncolored. Transparent translucent. Fracture uneven. 
 Brittle. Pyroelectric. Double refraction weak ; optic- 
 axial plane parallel to O\ bisectrix positive, normal 
 to i-l ; divergence 82-82i for red rays, from Dumbarton ; DesCl. 
 
 Var. Ordinary, (a) In regular crystals, usually more or less rectangular in outline. (1} 
 Tn slender prisms, often vesicular to radiated, (c) Radiated fibrous, (d) Spherical concre- 
 itons, consisting of radiated fibres or slender crystals, (e) Massive, granular to impalpable, 
 and white to reddish-brown. Ozarkite is massive thomsonite ; rauite (Norway) is related. 
 
 Comp. Q. ratio for R( = Ca,Na a ) : R(A1) : Si : H=1 : 3 : 4 : 2, Ca : Na 2 =2 : 1, or 3 : 1 ; 
 formula 2(Ca,Na 2 )AlSi 2 O i< -f-5aq. Analysis, Rammelsberg, Dumbarton, Si0 2 38'09, A10 3 
 31-62, CaO 12-60, Na.O 4'62, H,O 13-40=100-20. 
 
 Pyr., etc. At a red heat loses 13 - 3 p. c. of water, and the mineral becomes fused to 
 white enamel. B. B. fuses with intumescence at 2 to a white enamel. G-elatinizes with 
 hydrochloric acid. " 
 
 Obs. Found in cavities in lava and other igneous rocks ; and also in some metamorphic 
 rocks, with elasolite. Occurs near Kilpatrick, Scotland ; in the lavas of Somma (comptonitfi) ; 
 in Bohemia ; in Sicily ; in Faroe ; the Tyrol, at Theiss ; at Monzoni, Fassathal ; at Peter's 
 Point, Nova Scotia ; at Magnet Cove, Arkansas (ozarkite). 
 
 NATROLITE. Mesotype. Nadelzeolith, Germ. 
 
 Orthorhombic. 1 A 7= 91, O A 14 = 144 23'; c : I : d = 0-35825 
 
 640 
 
 1'0176 : 1. Crystals usually slender, often acicular ; fre- 
 quently interlacing ; divergent, or stellate. Also .fibrous, 
 radiating, massive, granular, or compact. 
 
 H.=5-5-5. G. =2-17-2-25 ; 2-249, Bergen Hill, 
 Brush. Lustre vitreous, sometimes inclining to pearly, 
 especially in fibrous varieties. Color white, or colorless ; 
 also grayish, yellowish, reddish to red. Streak uncolored. 
 Transparent translucent. Double refraction weak ; op- 
 tic-axial plane i-%\ bisectrix positive, parallel to edge 
 ///; axial divergence 94~96, red rays, for Auvergne 
 crystals ; 95 12 X for brevicite ; DesCl. 
 
 Comp. Q. ratio for R : R : Si : H=l : 3 : 6 : 2 ; and for R : Si= 
 2 : 3(R=Na 2 ,3R=R) ; formula Na a AlSi 3 10 +2aq= Silica 47'29, alumina 26 '90, soda 16-30, 
 water 9 -45 =100. 
 
 Pyr., etc. In the closed tube loses water, whitens and becomes opaque. B.B. fuses quietlj 
 at 2 to a colorless glass. Fusible in the lame of an ordinary stearine or wax candle. Geia 
 tinizes with acids. 
 
OXYGEN COMPOUNDS HYDROUS SILICATES. 
 
 34) 
 
 Ditf, Some varieties resemble pectolite, thomsonite, but distinguished B.B. 
 
 Obs. Occurs in cavities in amygdaloidal trap, basalt, and other igneous rocks ; and some 
 times in seams in granite, gneiss, and syenite. It is found in Bohemia ; in Auvergne ; Fassa 
 thai, Tyrol ; Kapnik ; at Glen Farg in Fifeshire ; in Dumbartonshire. In North America, 
 occurs in the trap of Nova Scotia ; at Bergen Hill, N. J. ; at Copper Falls, Lake Superior. 
 
 SCOLECITE. Poonahlite. 
 
 Monoclinic. C= 89 6', /A 1= 91 36', O A 14 = 161 16*' 
 = 0-34:85 : 1-0282 : 1. Crystals long or short prisms, or 
 acicular, rarely well terminated, and always compound. 
 Twins: twinn ing-plane i-i. Cleavage: /nearly perfect. 
 Also in nodules or massive; fibrous and radiated. 
 
 IL 5-5-5. G. 2-16-2-4. Lustre vitreous, or silky 
 when fibrous. Transparent to subtranslucent. Pyro- 
 electric, the free end of the crystals the antilogne pole. 
 Double refraction weak ; optic-axial plane normal to i-l ; 
 divergence 53 41', for the red rays ; bisectrix negative, 
 aralFel to i-l ; plane of the axis of the red rays and their 
 isectrix inclined about 17 8' to i-i, and 93 3' to I-i. 
 
 641 
 
 pa 
 bis 
 
 Comp, Q. ratio f or R : R : Si : H=l : 3 : 6 : 3 ; forR(3R=R) : Si=2 : 3, as innatrolite ; 
 R=Ca,R=^l; formula Ca^lSi 3 10 +3aq= Silica 45 '85, alumina 2G'13, lime 1423, water 
 13-76=100. 
 
 Pyr., etc. B.B. sometimes curls up like a worm (whence the name from er/cwXij^, a worm, 
 which gives scolecite, and not scolesite or scolezite) ; other varieties intumesce but slightly, and 
 all fuse at 2-2 '2 to a white blebby enamel. Gelatinizes with acids like natrolite. 
 
 Diff. Characterized by its pyrognostics. 
 
 Obs. Occurs in the Berufiord, Iceland ; also at Staffa ; inSkye, atTalisker ; nearPoonah, 
 
 Hindostan (Poonahlite} ; in Greenland ; at Pargas, Finland, etc. 
 
 MESOLITE. (Ca,3S"a 2 )AlSi 3 O 10 +3aq (5 p. c. Na a O). Near scolecite. Iceland ; Nova Scotia. 
 
 LEVYNITE Rhombohedr il. Q. ratio forR : R : Si : H=l : 3 : 6 : 4. Analysis, Damour, 
 Iceland, SiO 2 4576, A1O 3 23'56, CaO 10 57, Na 2 O 1'36, K 2 O 1'64, H 2 17'33=100-22. Ire- 
 land ; Faroe ; Iceland. 
 
 ANALCITE.* 
 
 Isometric (?) . Usually in trapezohedrons (f. 54, p. 18). Cleavage, 
 cubic, in traces. Also massive granular. 
 
 H.=5-5-5. G.=2-22-2-29 ; 2-278, Thomson. Lustre vitreous. Color- 
 less ; white ; occasionally grayish, greenish, yellowish, or reddish- white. 
 Streak white. Transparent nearly opaque. Fracture subconchoidal, 
 uneven. Brittle. 
 
 2. For 
 
 Gelati- 
 
 Comp.-Q. ratio for R : R : Si : H=l : ?, : 8 : 2, R=Na Q , R= A1=3R ; R : Bi=J : 
 mulaNa 2 AlSi 4 12 -f2aq=Silica54-47, alumina 23 '29, soda 14'07, water 817=100. 
 
 Pyr., etc. Yields water in the closed tube. B.B. fuses at 2'5 to a colorless glass, 
 nizes with hydrochloric acid. 
 
 Diff. Distinguishing characters : crystalline form ; absence of cleavage ; fusion B.B. 
 vut intumescence to a clear glass (unlike chabaziteX 
 
 Obs. Some localities are : the Tyrol ; the Kilpaorick Hills in Scotland ; the Faroe Islands ; 
 Iceland ; Aussig, Bohemia ; Nova Scotia ; Bergen Hill, New Jersey ; the Lake Superior 
 
 region. 
 
 ^Schrauf has found that the analcite oi rrieueck, Bohemia, is properly tetragonal ; the 
 simplest crystals showing evidence of repeated twinning. 
 
DESCRIPTIVE MINERALOGY. 
 
 FAUJASITE. An octahedral zeolite from the Kaiserstuhlgebirge. Analysis, Damour, Sid 
 46-12, A1O 3 16-81, CaO 4 "79, Na 2 O 5 "09, H 2 O 27 '02 =99 -83. 
 
 EUDNOPHITE. Near analcite. In syenite near Brevig, Norway. 
 
 PILINITE. In slender needles (orthorhombic) ; white ; lustre silky. Analysis SiO 2 55 *70, 
 AlO 3 (FeO 3 ) 18-64, CaO 19.51, Li 2 O (1-18), H 2 4 "97=100. In granite of Striegau, Silesia 
 
 CHABAZITE* 
 
 Khornbohedral. E A E = 94 46', Ot\fi = 129 15' ; c = 1'06. Twins : 
 twinning-plane O, very common, and usually in compound twins, as in 
 f. 644 ; also -Z2, rare. Cleavage rhombohedral, rather distinct. 
 
 643 
 
 Haydenite. 
 
 H.=4-5. G.=2-08-2-19. Lustre vitreous. Color white, flesh-red ; 
 streak uncolored. Transparent translucent. Fracture uneven. Brittle. 
 Double refraction weak ; in polarized light, images rather confused ; axis 
 in some crystals (Bohemia) negative, in others (from Andreasberg) posi- 
 tive ; DesCl. 
 
 Var. 1. Ordinary. The most common form is the fundamental rhombohedron, in which 
 the angle is so near 90 that the crystals were at first mistaken for cubes. Acadialite, from 
 Nova Scotia (Acadia of the French of last century), is only a reddish chabazite ; sometimes 
 nearly colorless. In some specimens the coloring matter is arranged in a tesselated manner, 
 or in layers, with the angles almost colorless. 2. Phacolite is a colorless variety occurring in 
 twins of mostly a hexagonal form, and often much modified so as to be lenticular in shape 
 (whence the name, from *a/cos, a bean} ; the original was from Leipa in Bohemia; li/\R 
 =94 24', fr. Oberstein, Breith. 
 
 Comp. Making part of the water basic (at 300 C. loses 17-19 p. c.) Rammelsberg writes 
 the formula (I^KhCaAzlSisOis+eaq, where the Q. ratio f or R : ft : Si =2 : 3 : 10, R-H,,Na 2 , 
 Ca; or (3R=ft), R : Si=l : 2. The formula corresponds to Silica 50 '50, alumina 17 '26, lime 
 9-43, potash 1'98, water 20'83=100. 
 
 Pyr., etc. B.B. intumesces and fuses to a blebby glass, nearly opaque. Decomposed by 
 hydrochloric acid, with separation of slimy silica. 
 
 Diff. Its rhombohedral form, resembling a cube, is characteristic ; is harder, and does not 
 effervesce with acids like calcite ; is unlike fluorite in cleavage ; fuses B. B. with intumes- 
 cence to a blebby glass, unlike analcite. 
 
 Obs. Chabazite occurs mostly in trap, basalt, or amygdaloid, and occasionally in gneiss, 
 syenite, mica schist, hornblendic schist. At the Faroe Islands, Greenland, and Iceland ; at 
 Aussig in Bohemia ; Striegau, Silesia. In Nova Scotia, wine-yellow or flesh-red (the last the 
 acadiatite), etc.; at Bergen Hill, N. J.; at Jones's Falls, near Baltimore (haydenite}. 
 
 SEEBACHITE (Bauer) from Richmond, Victoria, is, according to v. Rath, identical with 
 phaooUte ; and he suggests the same may be true of HERSCHELITE, from Aci Castello, Sicily. 
 
OXYGEN COMPOUNDS HYDROUS SILICATES. 
 
 345 
 
 GMELINITE. 
 
 lihombohedral. E A E = 112 26', O A E = O A-l = 140 3 3' ; <J 
 0'7254. Crystals usually 
 
 hexagonal in aspect ; some- 645 646 
 
 times habit rhombohedral ; 
 i often horizontally stri- 
 ated. Cleavage: ^ perfect. 
 Observed only in crystals, 
 and never as twins. 
 
 II.=4-5. GL=2-04-2-17. 
 Lustre vitreous. Colorless, 
 yellowish-white, greenish- 
 white, reddish- white fiesli- 
 red. Transparent to trans- 
 lucent. Brittle. 
 
 C. Blornidon, etc. 
 
 C. Blomidon. 
 
 Comp. Q. ratio f or R : R : Si : H=l : 3 : 8 : 6, R Ca(Na^,K 2 ), R=A1. Formula (Ca,Na 2 ) 
 A-lSi 4 O 12 +6aq. Analysis by Howe, Bergen Hill, SiO 2 48'6~7, A1O 3 18-72, Fe0 3 O'lO, CaO 
 2-60, Na 2 O 9-14, H 2 O 21-35=100-58 (Am. J. Sci., III., xii., 270, 1876). 
 
 Pyr., etc. In the closed tube crumbles, gives off much water. B. B. fuses easily to a white 
 enamel. Decomposed by hydrochloric acid with gelatinization. 
 
 Diff. Closely resembles some chabazite, but differs decidedly in angle. 
 
 Obs Occurs at Andreasberg; in Translyvania ; in Antrim, Ireland ; near Larne ; at Talisker 
 in Skye; at Cape Blomidon and other localities in Nova Scotia (ledererite) ; in fine crystals of 
 varied habib at the Bergen Hill tunnel of 1876. 
 
 PHILLIPSITE.* 
 
 Orthorhombic. /A 7= 91 12' ; 1 A 1 = 121 20', 120 
 Marignac. Faces 1 and i-l striated parallel to 
 the edge between them. Simple crystals un- 
 known. Commonly in cruciform crystals, consist- 
 ing of two crossing crystals, each a twinned 
 prism (f. 64-7). Crystals either isolated, or 
 grouped in tufts or spheres that are radiated 
 within and bristled with angles at surface. 
 
 II. =4-4-5. G. =2-201. Lustre vitreous. 
 Color white, sometimes reddish. Streak un- 
 colored. Translucent opaque. 
 
 Comp Q. ratio for R : R : Si : H=l : 3 : 8 : 4, R=Ca 
 and K^Naa) ; Ca : K 2 =3 : 1, 2 : 3, etc. Formula RMSi 4 Oi 2 
 +4aq. Analysis by Ettling, Nidda. Hessen, SiO 2 4813, 
 A1O 3 21-41, CaO 8*21, K 2 O 5'20, Na 2 O 0'70, H 2 10 78= 
 100-48. 
 
 Pyr. etc. B.B. crumbles and fuses at 3 to a white enamel. 
 Gelatinizes with hydrochloric acid. 
 
 D-ff. Resembles harmotome, but distinguished B.B. 
 
 Obs. At the Giant's Causeway, Ireland ; at Capo di Bove, 
 near Rome ; in Sicily ; Annerode, near Giessen ; in Silesia ; 
 Bohemia ; on the west, coast of Iceland. 
 
 Streiig (Jahrb. Min., 1876, 585) shows that the forms are 
 exactly analogous to those of harmotome, and suggests that 
 it may be also monoclinic. 
 
 44', and 88 40', 
 
 647 
 
 C. di Bove. 
 
346 
 
 DESCRIPTIVE MINERALOGY. 
 
 HARMOTOME. 
 
 Monoclinic (DesCloizeaux). 
 
 Cleavage 
 
 /, O, easy. Simple crystals un- 
 known. Occurring in penetra- 
 tion-twins. Unknown massive, 
 H. =4-5. G. =2-44-2-45. 
 Lustre vitreous. Color white ; 
 passing into gray, yellow, red, 
 or brown. Streak white. Sub- 
 transparent translucent. Frac- 
 ture uneven, imperfectly con- 
 choidal. Brittle. 
 
 Comp. Q. ratio for R : ft : Si : H 
 = 1:3:10:5; here R=Ba mostly, 
 also K 2 ; ft=iU. Formula RAlSi 5 O M 
 +5aq. If one -fifth of the water is 
 
 chemically combined (Rammelsberg), then the formula corresponds to HiRAlSi 5 O )5 +4aq. 
 Both formulas give Silica 45-91, alumina 15 70, barvta 20-06, potash 3 '34, water 14-99 = 100. 
 Pyr., etc. B.B. whitens, then crumbles and fuses at 3*5 without intumescence to a white 
 translucent glass. Some varieties phosphoresce when heated. Decomposed by hydrochloric 
 acid without gelatinizing. 
 
 Diff. Characterized by its crystallization in twins ; the presence of barium separates it 
 from other species. 
 
 Obs. Ilarmotome occurs in amygdaloid, phonolyte, trachyte ; also on gneiss, and in some 
 metalliferous veins. At Strontian in Scotland ; at Andreasberg ; at Rudelstadt in Silesia , 
 Schiffenberg, near G-iessen, etc. ; Oberstein ; in the gneiss of upper New York City. 
 
 DesCloizeaux, who has shown the monoclinic character of the species by optical means, has 
 adopted a different position for the crystals (!=/, etc.). 
 
 Strontian. 
 
 STILBITE.* Desmine. 
 
 Orthorhombic. /A 1 = 94 16', 1 A 1, front, = 119 16', side, 114 0'. 
 Cleavage : i-l perfect, i-l less so. Forms as in f. 650 ; 
 more common with the prism flattened parallel to i-i 
 or the cleavage-face, and pointed at the extremities. 
 Twins: cruciform, twinning-plane. 1-^, rare. Common 
 in sheaf -like aggregations ; divergent or radiated ; some 
 times globular and thin lamellar-columnar. 
 
 11..-= 3-5-4. G.=2-094-2-205. Lustre of i-l pearly 
 of other faces vitreous. Color white ; occasionally 
 yellow, brown, or red, to brick-red. Streak uncolored. 
 Transparent translucent. Fracture uneven. Brittle. 
 
 it 
 
 \[ I Var. 1. Ordinary. Either (a) in crystals, flattened and pearly 
 
 v ./ \ / parallel to the plane of cleavage, or sheaf -like, or divergent groups ; 
 
 >Ny "^ V or (b) in radiated stars or hemispheres, with the radiating individual* 
 
 \___,s showing a pearly cleavage surface. Sphcerostiibite, Beud, is in spheres, 
 
 radiated within with a pearly fracture, rather soft externally. 
 
 Comp Q. ratio for R : ft : Si : H=l : 3 : 12 : G ; R^Ca(Na 2 ),ii Al. Formula RrVlSi 6 O 18 
 
 4 6aq. If two parts of water are basic (Ramm. ) the ratio becomes (R=Ca,H 2 ,Na.,) 3 : 3 : 13 
 : 4, or R : Si=l : 2, and the formula is H,RAlSi 6 Oi8+4aq. Analysis, Petersen, Seisser Alp, 
 SiO 2 55-61, A1O 3 15-62, CaO7'33, Na 2 O 2 -01, K 2 O 0'47, H 2 O 18'19=9fl-23. 
 Pyr., etc. B.B. exfoliates, swells up, curves into fan-like or vermicular forms, and fuses 
 
OXYGEN COMPOUNDS HYDROUS SILICATES. 347 
 
 to a white .enamel. F. =2-2'5. Decomposed by hydrochloric acid, without gelatinizing. The 
 sphcerostttbite gelatinizes, but Heddle says this is owing to a mixture of mesolite with the stil- 
 bite. 
 
 Diff. Prominent characters: occurrence in sheaf -like forms, and in the rectangular 
 tabular crystals ; luscre on cleavage-face pearly ; does not gelatinize with acids. 
 
 Obs. Stilbite .occurs mostly in cavities in amygdaloid. It is also found in some metal- 
 liferous veins, and in granite and gneiss. The Faroe Islands, Iceland, and the Isle of Skye ; 
 in Dumbartonshire, Scotland ; at Andreasberg ; Arendal in Norway ; in the Syhadree 
 Mts., Bombay ; near Fahlun, in Sweden. In North America, at Bergen Hill, New Jersey ; 
 at the Michipicoten Islands, Lake Superior ; Nova Scotia, etc. 
 
 The name stilbite is from an'A/fy, lustre; and dexmine from ^toyz??, a bundle. The species 
 stilbite, as adopted by Haiiy, included Strahlzeolith Wern. (radiated zeolite, or the above), 
 and Blatterzeolith Wern. (foliated zeolite, or the species heulaudite beyond). The former wap 
 the typical part of the species, and is the first mentioned in the description ; and the lattei 
 he added to the species, as he observes, with much hesitation. In 1817, Breithaupb separated 
 the two zeolites, and called the former ties'/nine and the latter euzeolite, thus throwing aside 
 entirely, contrary to rule and propriety, Haiiy's name stilbite^ which should have been accepted 
 by him in place of desmine. it being the typical part of his species In 1822, Brooke (ap- 
 parently unaware of what Breithaupt had done) used stilbite for the first, and named the other 
 heuldndit*. In this he has been followed by the French and English mineralogists, while the 
 Germans have unfortunately followed Breithaupt. 
 
 EPISTILBITE (Reixsite). Composition like heulandite, but form orthorhombic. Iceland; 
 Faroe ; Poonah, India, etc. ; Bergen Hill, N". J. 
 
 FORESITE. Resembles stilbite in form. Q. ratio for B : R : Si : H 1 : 6 : 12 : 6. Formula 
 RAl 3 Si 6 Oi9-f-6aq. (R = Na 2 : Ca=i : 3). Occurs hi crystalline crusts on tourmaline, in cavities 
 in granite. Island of Elba. 
 
 HEULANDITE. Stilbit, Germ. 
 
 Monoclinic. O = 88 35', /A 1= 136 4', O A 14 = 156 45' ; c : I : d = 
 1-065 : 2-4785 : 1. Cleavage : clinodiagonal (i4) emi- 
 nent. Also in globular forms ; also granular. 651 
 
 H.=3'5 4. G.=2*2. Lustre of i-l strong pearly ; of 
 other faces vitreous. Color various shades of white, 
 passing into red, gray, and brown. Streak white. 
 Transparent subtranslucent. Fracture subconchoidal, 
 uneven. Brittle. Double refraction weak ; optic-axial 
 plane normal to i-l ; bisectrix positive, parallel to the 
 horizontal diagonal of the base ; DesCl. 
 
 Comp. Q. ratio for R : R : Si : H=l : 3 : 12 : 5 ; R=Ca(Na 2 ). 
 Formula Ca^lSieOi 6 4-5 aq, or if 2H O be basic (Ramm.) then the 
 ratio becomes 1:1:4 (R=Ca and H 2 ), and the formula H 4 CaAlSi 6 
 Ois+Baq. Both require Silica 59-06, alumina 16*83, lime 7 -88, soda 
 1-46, water 14-77=100. 
 
 Pyr. B.B. same as with stilbite. 
 
 Diff. Distinguished by its crystalline form. Pearly lustre of i-\ a prominent character. 
 
 Obs. Heulandite occurs principally in amygdaloidal rocks. Also in gneiss, and occasionally 
 in metalliferous veins. Occurs in Iceland ; the Faroe Islands ; the Vendayah Mountains, 
 Hindostan. Also in the Kilpatrick Hills, near Glasgow ; in the Fassa Valley, Tyrol ; An- 
 dreasberg; Nova Scotia, etc. ; at Bergen Hill, New Jersey ; on north shore of Lake Superior ; 
 at Jones's Falls, near Baltimore (Levy's beaumontite). 
 
 For the relation of the synonymes see stilbit, above. 
 
 BREWSTERITE. Q. ratio same as for heulandite, but R is here Ba or Sr (Ca). Formula 
 requires SiO 2 53 -5, A1O 3 15 "3, BaO 7 -6, SrO 10 '2, H 2 O 13 '4= 100. Monoclinic. Strontian in 
 Argyleshire, etc. 
 
348 DESCRIPTIVE MINERALOGY. 
 
 III. MARGAROPHYLLITE SECTION. 
 BISILICATES. 
 
 The Margarophyllites are often foliated like the micas, and the name 
 alludes to the pearly folia. Massive varieties are, however, the most com- 
 mon with a large part of the species, and they often have the compactness 
 of clay or wax. Talc, pyrophyllite, serpentine, are examples of species pre- 
 senting both extremes of structure ; while pinite occurs, as thus far known, 
 only in the compact condition. The true Margarophyllites are below 5 in 
 hardness ; greasy to the feel, at least when finely powdered. 
 
 TALC. 
 
 Orthorhombic. /A 7 = 120. Occurs rarely in hexagonal prisms and 
 plates. Cleavage : basal, eminent. Foliated massive, sometimes in globu- 
 lar and stellated groups; also granular massive, coarse or fine ; also com- 
 pact or cryptocrystalline. 
 
 H.=l-l*5. (r.=2'565-2'8. Lustre pearly. Color apple-green to white, 
 or silvery-white ; also greenish-gray and dark green ; sometimes bright 
 green perpendicular to cleavage surface, and brown and less translucent at 
 right angles to this direction ; brownish to blackish-green and reddisli when 
 impure. Streak usually white ; of dark green varieties, lighter than the 
 color. Subtransparent subtranslucent. Sectile. Thin laminse flexible, 
 but not elastic. Feel greasy. Optic-axial plane i-l ; bisectrix negative, nor- 
 mal to the base ; DesCl. 
 
 Var. Foliated, Talc. Consists of folia, usually easily separated, having a greasy feel, and 
 presenting ordinarily light green, greenish -white, and white colors. Gr. =2 '55-2 '78. (a) 
 Massive, Steatite or Soapstone (Speckstein, Germ. ). Coarse granular, gray, grayish-green, and 
 brownish-gray in colors. H. =1-2 '5. (b) Fine granular or cryptocrystalline. and soft enough 
 to be used as chalk, as the French cJialk (Craie de Brianq&ri), which is milk-white, with a 
 pearly lustre. 
 
 Comp. Q. ratio forMg : Si=2 : 5, or 3 : 4, with a varying amount of water in both talc and 
 steatite, from a fraction of a per cent, to 7 p. c. If the water is basic, the ratio becomes for 
 K : Si=l : 2, (R=Mg(Fe)and H 2 ), and the formula is H 2 Mg s Si 4 O 12 (Ramm.) = Silica 63'49, 
 magnesia 31*75, water 4*76 = 100 ; the analyses show generally 1 or 2 p. c. of FeO. 
 
 Pyr., etc. In the closed tube B.B., when intensely ignited, most varieties yield water. In 
 the platinum forceps whitens, exfoliates, and fuses with difficulty on the thin edges to a white 
 enamel. Moistened with cobalt solution, assumes* on ignition a pale red color. Not decom- 
 posed by acids. 
 
 Diff. Recognized by its extreme softness, unctuous feel, and usually foliated structure. 
 Inelastic though flexible. Yields water only on intense ignition. 
 
 Obs. Talc or steatite is a very common mineral, and in the latter form constitutes exten- 
 sive beds in some regions. It is often associated with serpentine and dolomite, and frequently 
 contains crystals of dolomite, breunerite, asbestus, actinolite, tourmaline, magnetite. Steatite 
 is the material of many pseudomorphs, among which the most common are those after pyroxene, 
 hornblende, mica, scapolite, and spinel. The magnesian minerals are those which commonly 
 afford steatite by alteration ; while those, like scapolite and nephelite, which contain soda and 
 no magnesia, most frequently change to pinite-like pseudomorphs. liensstlaerite and 
 vyraUolite are pseudomorphous varieties. 
 
 Applfi-green talc occurs near Salzburg ; in the Valais ; also in Cornwall, near Lizard Point, 
 with serpentine ; in Scotland, with serpentine, at Portsoy and elsewhere ; etc. In N. 
 America, some localities are: Vermont, at Bridgewater; Grafton, etc. In New Hampshire, 
 at Pelham, etc. In R. Inland, at Smithfield. In N. York, near Amity. In Penn., at Texas; 
 at Chestnut Hill, on the SchuylkilL In Maryland, at Cooptown. 
 
OXYGEN COMPOUNDS HYDROUS SILICATES. 349 
 
 PYROPHYLLITE. Agalmatolite or Pagodite pt. 
 
 Orthorliombic. Not observed in distinct crystals. Cleavage: basal 
 eminent. Foliated, radiated lamellar; also granular, to compact or cry pto- 
 crystalline ; the latter sometimes slaty. 
 
 H. = i-2. G.=2-75-2-92. Lnsfcreof folia pearly, like that of talc; of 
 massive kinds dull or glistening. Color white, apple-green, grayish and 
 brownish-green, yellowish to ochre-yellow, grayish- white. Subtransparent 
 to opaque. Laminae flexible, not elastic. Feel greasy. Optic-axial angle 
 large (about 108) ; bisectrix negative, normal to the cleavage-plane. 
 
 Var. (I) Foliated, and often radiated, closely resembling talc in color, feel, lustre, and 
 structure. (2) Compact, massive, white, grayish, and greenish, somewhat resembling com- 
 pact steatite, or French chalk. This compact variety, as Brush has shown, includes part of 
 what has gone under the name of agalmatolite, from China ; it is used for slate-pencils, and 
 is sometimes called pencil-stone. 
 
 Comp. Q. ratio for Al : Si=l : 2, also in other cases 3 : 8, Formula for the first case = 
 AlSi 3 O 9 +aq (Bamm.). Analysis, Chesterfield, S. C., by Genth, SiO a 64 '82, A1O 8 28'48, FeO 8 
 0-96, MgO 0-33, CaO 0'55, H,O 5-25=100';J9. 
 
 Pyr., etc. Yields water. B.B. whitens, and fuses with difficulty on the edges. The 
 radiated varieties exfoliate in fan-like forms, swelling up to many times the original volume 
 of the assay. Heated with cobalt solution gives a deep bide color (alumina). Partially decom- 
 posed by sulphuric acid, and completely on fusion with alkaline carbonates. 
 
 Obs. Compact pyrophyllite is the material or base of some schistose rocks. The foliated 
 variety is often the gangue of cyanite. Occurs in the Urals ; at Westana, Sweden; near Ottrez 
 in Luxembourg ; in Chesterfield Dist., S. C. ; in Lincoln Co., Ga. ; in Arkansas. The compact 
 pyrophyllite of Deep River, N. C. , is extensively used for making slate pencils. 
 
 PIHLITE (cymatolite), near pyrophyllite. 
 
 SEPIOLITE.* Meerschaum, Germ. L'Ecume de Mer, Fr. 
 
 Compact, with a smooth feel, and fine earthy texture, or clay-like. 
 
 H.=2-2'5. Impressible by the nail. In dry masses floats on water. 
 Color grayish- white, white, or with a faint yellowish or reddish tinge. 
 Opaque. 
 
 Comp. Q. ratio for R : Si : H=l : 3 : 1, corresponding to Mg 2 Si 3 8 + 2aq ; or, if half the 
 water is basic, 1:2: i=H 2 Mg 2 Si s O 9 + aq=Silica 60-8, magnesia 27'1, water 121=100. The 
 amount of water present is somewhat uncertain. 
 
 Pyr., etc. In the closed tube yields first hygroscopic moisture, and at a higher temperature 
 gives much water and a burnt smell. B. B. some varieties blacken, then burn white, and fuse 
 with difficulty on the thin edges. With cobalt solution a pink color on ignition. Decomposed 
 by hydrochloric acid with gelatinization. 
 
 Obs. Occurs in Asia Minor, in masses in stratified earthy or alluvial deposits at the plains 
 of Eskihi-sher ; a]so found in Greece ; at Hrubsohitz in Moravia ; in Morocco ; at Vallecas in 
 Spain, in extensive beds. 
 
 The word meerschaum is German for sea-froth, and alludes to its lightness and color. Sepio- 
 Ute, Glocker, is from or/xia, cuttle-fish, the bone of which is light and porous, and also a pro- 
 duction of the sea. 
 
 APHRODITE. 4MgSi0 3 +3aq. Resembles sepiolite. Longban, Sweden. 
 
 SMECTITE. Fuller's earth pt. A greenish clay from Styria. 
 
 MONTMORILLONITE. A rose-red clay containing more alumina than smectite, from Mont- 
 morillon, France. 
 
 CELADONITE. A variety of "green earth" from Mt. Baldo, near Verona. 
 
 GLAUCONITE. Green earth pt. A hydrous silicate of iron and potassium, but alwayi 
 impure. Constitutes the green sand of the chalk and other formations (e.g in New Jersey). 
 
 STILPNOMELANK. la foliated plates, or aa a velvety coating. Eiwentially a hydrous iton 
 
350 DESCRIPTIVE MINERALOGY. 
 
 (Fe) silicate. Color black to yellowish-bronze. Silesia; Weilburg; Nassau; Sterling iron 
 mine; Antwerp, N. Y. (chalcodite}. 
 
 CHLOROPAL. Compact, earthy. Color greenish -yellow. A hydrated iron silicate. Formula 
 FeSi 3 9 4-5aq. Andreasberg"; Steinberg near Gottingen ; Nontron (nontronite\ France, etc. 
 
 AERIKITE. Perhaps related to chloropal (Lasaulx). Color blue. Spain. 
 
 UNISILICATES. 
 Serpentine Group. 
 
 SERPENTINE.* 
 
 Orthorhombic (?). In distinct crystals, but only as psendomorphs. Some- 
 times foliated, folia rarely separable ; also delicately fibrous, the fibres often 
 easily separable, and either flexible or brittle. Usually massive, fine granu- 
 lar to impalpable or cryptocrystalline ; also slaty. 
 
 H.=2-5-4, rarely 5'5. Gr. 2'5-2'65 ; some fibrous varieties 2-2-2-3 ; 
 retinalite, 2'36-2*55. Lustre subresinous to greasy, pearly, earthy ; resin- 
 like, or wax-like ; usually feeble. Color leek-green, blackish-green, oil 
 and siskin-green, brownish-red, brownish-yellow ; none bright ; sometimes 
 nearly white. On exposure, often becoming yellowish-gray. Streak white, 
 slightly shining. Translucent opaque. Feel smooth, sometimes greasy. 
 Fracture corichoidal or splintery. 
 
 Var. Many unsustained species have been made out of serpentine, differing in structure 
 (massive, slaty, foliated, fibrous), or, as supposed, in chemical composition. 
 
 MASSIVE. (1) Ordinary massive, (a) Precious or Noble Serpentine (E&zr Serpentin, Germ.) 
 is of a rich oil-green color, of pale or dark shades, and translucent even when in thick pieces ; 
 and (b) Common Serpentine, when of dark shades of color, and subtranslucent. The former 
 has a hardness of 2 5-3; the latter often of 4 or beyond, owing to impurities. Bowenitt 
 (Smithfield, R. I.), is a jade-like variety with the hardness 5'5. 
 
 FOLIATED. Marmolite is thin foliated ; the laminse brittle but easily separable, yet gradu- 
 ating into a variety in which they are not separable. G. =2 '41 ; lustre pearly ; colors green- 
 ish-white, bluish- white, or pale asparagus-green. From Hoboken, N. J. 
 
 FIBROUS. Chrysotile is delicately fibrous, the fibres usually flexible and easily separating ; 
 lustre silky, or silky metallic ; color greenish -white, green, olive-green, yellow, and brownish ; 
 G. =2'219. Often constitutes seams in serpentine. It includes most of the silky amianthus 
 of serpentine rocks. The original chrysotile was from Eeichenstein. 
 
 Any serpentine rock cut into slabs and polished is called serpentine marble. 
 
 Comp Q. ratio for Mg : Si : H=3 : 4 : 2, corresponding to Mg 3 SioO 7 +2aq= Silica 43 '48, 
 magnesia 43 '48, water 13*04. But as chrysolite is especially liable to the change to serpen- 
 tine, and chrysolite is a unisilicate, and the change consists in a loss of some Mg 1 , and the 
 addition of water, it is probable that part of the water takes the place of the lost Mg, so that 
 the mineral is essentially a hydrated chrysolite of the formula H 2 Mg 3 Si 2 O8 + aq. The rela- 
 tion in ratio to kaolinite and pinite corresponds with this view of the formula. 
 
 Pyr.j eto. In the closed tube yields water. B B. fuses on the edges with difficulty. F. 
 6. Gives usually an iron reaction. Decomposed by hydrochloric and sulphuric acids. Chry- 
 sotile leaves the silica in fine fibres. 
 
 Diff. Distinguishing characters : compact structure ; softness, being easily cut with a 
 knife ; low specific gravity ; and resinous lustre. 
 
 Obs. Serpentine often constitutes mountain masses. It frequently occurs mixed with 
 more or less of dolomite, magnesite, or calcite, making a rock of clouded green, sometimes 
 veined with white or pale green, called verd antique, or ophiolite. It results from the altera- 
 tion of other rocks, frequently chrysolite rocks. Crystals of serpentine (pseudomorphous) 
 occur in the Fass? valley, Tyrol; near Miask; Katharinenberg, and elsewhere; in Norway, 
 
OXYGEN COMPOUNDS HYDROUS SILICATES. 351 
 
 at bnarum, etc. Precious serpentines corne from Sweden ; the Isle of Man ; Corsica ; 
 Siberia ; Saxony, etc. In N. America, in Vermont, at New Fane; Roxbury, etc. In Mass., 
 at Newburyport and elsewhere. In Conn., near New Haven and Milford, at the verd-antique 
 quarries. In JV. York, at Brewster, Putnam Co. ; at Antwerp, Jefferson Co. ; in Gonver- 
 neur, St. Lawrence Co. ; in Orange Co. ; Richmond Co. In N. Jersey, at Hoboken. Iu 
 Penn.. at Texas, Lancaster Co. ; also in Chester Co. ; in Delaware Co. In Maryland, at 
 Bare Hills ; at Cooptown, Harf ord Co. 
 
 The following are varieties of serpentine : retinalite, G-renville, C. W. ; vorhaiLserite, Tyrol ; 
 porcellophite ; bowenite, Smithfield, R. I. ; antigorite, Piedmont ; wttliamzite, Texas, Pa. ; 
 marmoiite, Hoboken ; picrolite ; metaxite ; refdanskite (containing Ni) ; aquacreptite. 
 
 BASTITE or SCHILLER SPAR. An impure serpentine, a result of the alteration of a foliated 
 pyroxene. Baste ; Todtmoos in the Schwarzwald. ANTILLITE is similar. 
 
 DEWEYLITE (Gymnite). HMg4Si30, 2 +4aq. Occurs with serpentine at Middlefield and 
 Texas, Penn. HYDROPHITE (Jenkinsite), near deweylite, but Mg replaced in part by Fe. 
 
 CEROLITE. H 2 Mg2Si 2 07+aq. Silesia. LIMBACHITE from Limbach, and ZOBLITZITH 
 from Zoblitz, are varieties of cerolite. 
 
 GENTHITE. Nickel-Gymnite. 
 
 Amorphous, with a delicately hemispherical or stalactitic surface, in 
 crusting. 
 
 H.=3-4: ; sometimes (as at Michipicoten) so soft as to be polished 
 under the nail, and fall to pieces in water. G.= 2-409. Lustre resinous. 
 Color pale apple-green, or yellowish. Streak greenish- white. Opaque to 
 translucent. 
 
 Comp. Q. ratio for R : Si : H=2 : 3 : 3, or the same as for deweylite ; formula H 4 (Ni, 
 Mg) 4 Si 3 O 12 , being a nickel-gymnite. Analysis: Genth, Texas, Pa., Si0 2 35 '30, MO 30'04, 
 FeO 0-24, MgO 14'60, CaO 26, H 2 O 19 '09 =100 -19. 
 
 Pyr., etc In the closed tube blackens and gives off water. B.B. infusible. With borax 
 in O.F. gives a violet bead, becoming gray in R.F. (Nickel). Decomposed by hydrochloric 
 acid without gelatinizing. 
 
 Obs From Texas, Lancaster Co. , Pa. , in thin crusts on chromic iron ; from Webster, 
 Jackson Co., N. C.; on Michipicoten Id., Lake Superior. 
 
 ALTPITE and PIMELITE, an apple-green silicates containing some nickel. GARNIERITK 
 and NOUMEITE, from New Caledonia are similar, aud have been shown by Liversidge to be 
 mixtures. 
 
 Kaolinite Group. 
 KAOLINITE. 
 
 Orthorhombic. lt\ T 120. In rhombic, rhomboidal, or hexagonal 
 scales or plates ; sometimes in fan-shaped aggregations ; usually constitut- 
 ing a clay-like mass, either compact, friable, or mealy ; base of crystals 
 lined, arising from the edges of superimposed plates. Cleavage : basal, 
 perfect. Twins : the hexagonal plates made up of six sectors. 
 
 H. = 1-2-5. G.=2'4-2*63. Lustre of plates pearly ; of mass, pearly to 
 dull earthy. Color white, grayish-white, yellowish, sometimes brownish, 
 bluish, or reddish. Scales transparent to translucent. Scales flexible, 
 inelastic ; usually unctuous and plastic. 
 
 Var 1. Argilttform. Soft, clay-like ; ordinary kaolinite ; under the microscope, if not 
 without, showing that it is made up largely of pearly scales. The constituent of most, if not 
 
352 DESCRIPTIVE MINERALOGY. 
 
 all, pure kaolin. 2. Fariniform. Mealy, hardly coherent, consisting of pearly augula 
 scales. 3. Indurated; Lithomarge (Steinmark, Germ.). Firm and compact; H.=2-2'5 
 When pulverized, often shows a scaly texture. 
 
 Comp. Q. ratio for ft : Si : H=3 : 4 : 2 ; formula AlSio0 7 +2aq, or making part of thi 
 water basic, H 2 AlSi 2 8 +aq= Silica 46-4, alumina 39 '7, water 13-9 = 100. 
 
 Pyr., etc. Yields water. B.B. infusible. Gives a blue color with cobalt solution. Insol 
 nble in acids. 
 
 Diff. Characterized by its unctuous, soapy feel ; alumina reaction B B. 
 
 Obs. Ordinary kaolin is a result of the decomposition of aluminous minerals, especially 
 the feldspars of granitic and gneissoid rocks and porphyries. In some regions where thes* 
 rocks have decomposed on a large scale, the resulting clay remains in vast beds of kaolin 
 usually more or less mixed with free quartz, and sometimes with oxide of iron from some o 
 the other minerals present. 
 
 Occurs at Cache-Apres in Belgium ; also in Bohemia ; in Saxony. At Yrieix, near Limoges 
 is the best locality of kaolin in Europe, it affords material for the famous Sevres porcelaii 
 manufactory. 
 
 In the U. States, kaolin occurs at Newcastle and Wilmington, Del. ; at various localities ii 
 the liinonite region of Vermont (at Branford, etc.) ; Massachusetts ; Pennsylvania; Jackson 
 ville, Ala.; Edgefield, S. C.; near Augusta, Ga. 
 
 PHOLERITE, HALLOYSITE, clays allied to kaolinite. 
 
 SAPONITE. A soft magnesian silicate ; occurs in cavities in trap. 
 
 Pinite Group. 
 
 FINITE. 
 
 Amorphous ; granular to cryptocrystalline ; usually the latter. Also ir 
 crystals, and sometimes with cleavage, but only because pseudomorphs, th< 
 form and cleavage being those of the minerals from which derived. Rarely 
 a submicaceous cleavage, which may belong to the species. 
 ( H.= 2-5-3*5. G.=2'6-2*85. Lustre feeble, waxy. Color grayish-white 
 grayish -green, pea-green, dull green, brownish, reddish. Translucent 
 opaque. Acts like a gum on polarized light ; DesCl. 
 
 Comp., Var. Pinite is essentially a hydrous alkaline silicate. Being a result of alteration, 
 and amorphous, the mineral varies much in composition, and numerous species have beer 
 made of the mineral in its various conditions. The varieties of pinite here admitted agree 
 closely in physical characters, and in the amount of potash and water present. Average com- 
 position : Silica 46, alumina 30, potash 10, water 6 ; formula (Ramm.) HeKaAloSisOao. The 
 mineral is related chemically, as it is also physically, to serpentine ; and it is an alkali- alumina 
 serpentine, as pyrophyllite is an alumina talc. 
 
 The different kinds are either pseudomorphous crystals after (1) iolite ; (2) nephelite ; (3) 
 scapolite ; (4) some kind of feldspar; (5) spodumene ; or (6) other aluminous mineral; or (7) 
 disseminated masses resembling indurated talc, steatite, lithomarge, or kaolinite, also a result 
 of alteration ; or (8) the prominent or sole constituent of a metamorphic rock, which is some- 
 times a pinite schist (analogous to, and often much resembling, t'tkose schist, and still more 
 closely related to pyrophyllite schixt). Some prominent varieties are : 
 
 PINITE. Speckstein [fr. the Pini mine at Aue, near Schneeberg]. Occurs in granite, and 
 is supposed to be pseudomorphous after iolite. 
 
 G-IESECKITK. In 6-sided prisms, probably pseudomorphous after nephelite. It =3 5. 
 G. =2'78-2'85. Color grayish-green, olive-green, to brownish. Brought by (iieseoke from 
 Greenland. Also of similar characters from Diana, N. Y. 
 
 AGALMATOLITE. Like ordinary massive pinite in its amorphous compact texture, lustre, 
 and other physical characters, but contains more silica, so as to afford the formula of a bisili- 
 cate, or nearly, and it may be a distinct species. Agalmatolite was named from (ryaA/xo, an 
 image, and payodite from pagoda, the Chinese carving the soft atone into miniature pagodas 
 
OXYGEN COMPOUNDS HYDROUS SILICATES. 353 
 
 Images, etc. Part of the so-called agalmatolite of China is true pinite in eompo&iUon, anothei 
 part is compact pyrophyllite (p. 349), and still another steatite (p. 348). 
 
 Other minerals belonging in or near the pinite group are : dyssyntribite (=gieseckite) ; 
 parophite ; wilsonite ; polyargite ; rosite ; killinite ; gigcmto'ite ; hygrophiiite ; gumbelite ; 
 rcstormelite. Also cataspilite ; biharite ; palagonite. 
 
 Hydro-mica Group. 
 
 FAHLUNITE. 
 
 In six- or twelve-sided prisms, but derived from pseudomorphism alter 
 iolite. Cleavage : basal sometimes perfect. 
 
 H.=3'5-5. G.=2'6-2'8. Lustre of surface of basal cleavage pearly to 
 waxy, glimmering. Color grayish-green, to greenish-brown, olive- or oil- 
 green ; sometimes blackish-green to black ; streak colorless. 
 
 Var. This species is a result of alteration, and considerable variation in the results of 
 analyses should be expected. The crystalline form is that of the original iolite, while the 
 basal cleavage when distinct is that of the new species fahlunite. 
 
 Comp Q. ratio for R : R : Si : H=l : 3 : 5 : 1 ; whence the formula H 4 R2R-2Si 5 20 , the 
 
 water being considered as basic, and as entering to make up the deficiency of bases in the 
 unisilicate. In some kinds, the same with the addition of H 2 O. The Q. ratio of iolite, the 
 original of the species, is 1:3:5. Analysis by Wachtmeister, from Fahlun, Si0 2 44-60, 
 MO, 30-10, FeO 3'86, MnO 2'24, MgO 6 "75, CaO 1-35, K 2 1'98, H 2 O 9'35, F tr=100-23. 
 
 Pyr., etc. Yields water. B.B. fuses to a white blebby glass. Not acted upon by acids. 
 Pyrargillite is difficultly fusible, but is completely decomposed by hydrochloric acid. 
 
 Obs. Fahlunite (and tridasite) from Fahlun, Sweden. The following are identical, or 
 nearly so : Esmarkite and praseolite, Brevig ; raumite, Raumo, Finland ; cMorophyttite^ Unity, 
 Me. ; pyrargttlite, Helsingfors ; polychroilite, Krageroe, and aspasiolite, Norway ; huronitc, 
 Lake Huron ( Weissite, Fahlun). 
 
 MARGARODITE. 
 
 Like muscovite or common mica in crystallization, and in optical and 
 other physical characters, except usually a more pearly lustre, and the color 
 more commonly whitish or silvery. 
 
 Comp. Q. ratio for R : R : Si : H mostly 1:6:9:2; whence the formula H b R 2 Al 4 Si 9 03o, 
 the water being basic. Sometimes Q. ratio 1 : 9 : 12 : 2 ; but this division belongs with 
 damourite, if the two are distinguishable. This species appears to be often, if not always, a 
 result of the hydration of muscovite, there being all shades of gradation between it and that 
 species. Muscovite has the Q. ratio for bases and silicon of 4 : 5, or nearly. Analysis, Smith 
 and Brush, Litchfield, Ct., Si0 2 44'GO, A1 2 O 3 36'23,Fe 2 O 3 l-34,MgO 0'37, CaO 0'50, Na 2 04'lO, 
 K 2 6 20, H a O 5-26, F tr. =--100-60. 
 
 For pyrognostics and localities, see muscovite, p. 313. 
 
 GILBERTITE. Essentially identical with margarodite ; tin mines, Saxony. 
 
 DAMOURITE. 
 
 An aggregate of fine scales, mica-like in structure. 
 
 H.=:2-3. G. = 2-792. Lustre pearly. Color yellow or yellowish-white. 
 Optic-axial divergence 10 to 12 degrees ; for sterlingite 70. 
 
 Comp. A hydrous potash-mica, like margarodite, to which tt is closely related. Q. ratio 
 23 
 
354 DESCRIPTIVE MINERALOGY. 
 
 for R : 51 : Si : H=l : 9 : 12 : 2, or 1 : 1 for bases to silicon, if the water is basic. Formula 
 H 4 K 2 Al s SieO 24 . Analysis, Monroe, from Sterling, Mass, (sterlingite) , Si0 2 43 '87, A1O 3 36 '45. 
 FeO 3 3-36, K 2 O 10 86, H 2 O 5'19=99'73. 
 
 It is the gangue of cyanite at Pontivy in Brittany; and the same at Horrsjoberg, Werm- 
 land. Associated with corundum in North Carolina ; with spodumene, at Sterling, Mass. 
 
 PARAGONITB. Pregrattite. Cossaite. 
 
 Massive, sometimes consisting distinctly of fine scales ; the rock slaty 01 
 schistose. Cleavage of scales in one direction eminent, mica-like. 
 
 H.=2'5-3. G. 2779, paragonite; 2 895, pregrattite, (Ellacher. Lustre 
 strong pearly. Color yellowish, grayish, grayish-white, greenish, light apple- 
 green. Translucent ; single scales transparent. 
 
 i 
 
 Comp. A hydrous sodium mica. Q. ratio f or R : R : Si : H 1 : 9 : 12 : 2, or 1 : 1 for 
 bases and silicon, if the water be made basic. Formula B^Na^lsSieOs^K : Na=l : 6)= 
 Silica 46-60, alumina 39-96, soda 6 "90, potash 1'74, water 4*80=100. 
 
 Pyr. B.B. the paragonite is stated to be infusible. The pregrattite exfoliates somewhat 
 like vermiculite (a property of some clinochlore and other species), and becomes milk-white 
 on the edges. 
 
 Obs. Paragonite constitutes the mass of the rock at Monte Campione, in the region of 
 St. Gothard, containing cyanite and staurolite, called paragonitic or talcose schist. The 
 pregrattite is from Pregratten in the Pusterthal, Tyrol ; co^saite, from mines of Borgofranco, 
 near Ivrea. 
 
 IVIGTITE. Occurs in yellow scales, also granular, with cryolite from Greenland. 
 
 EUPHYLLITE. Associated with tourmaline and corundum at Unionville, Penn. Q. ratio 
 for R : R- : Si : H=l : 8 : 9 : 2. Average composition, Silica 41 -6, alumina 42 - 3, lime 1'5, 
 potash 3 2, soda 5-9, water 5 "6 = 100. 
 
 EPHESITE, LESLEYITE. Hydro-micas, perhaps identical with damourite. Occur with 
 corundum, and impure from admixture with it. 
 
 (ELLACHEBITE. A hydro-mica, containing 5 p. c. baryta. Pfitschthal, Tyrol. 
 
 COOKEITE. A hydrous lithium mica. From Hebron and Paris, Me., apparently a pro- 
 duct of the alteration of ru belli te. 
 
 HISINQERITE. 
 
 Amorphous, compact, without cleavage. 
 
 II. =3. G.=3-045. Lustre greasy, inclining to vitreous. Color black 
 to brownish-black. Streak yellowish-brown. Fracture conchoidal. 
 
 Comp. Q. ratio for R+ft : Si : H=2 : 3 : 3 ; formula R 6 : R 2 Si 3 Oi8-f4aq (with one-third 
 of the water basic). R=Fe,H 2 ; ft=Fe. Analysis, Cleve, from Solberg, Norway, Si0 2 35'33, 
 Fe0 8 32-14, FeO 7-08, MgO 3'60, H 2 O 22'04=100;19. 
 
 Pyr., etc. Yields much water. B. B. fuses with difficulty to a black magnetic slag. With 
 the fluxes gives reactions for iron. In hydrochloric acid easily decomposed without gelatin- 
 izing. 
 
 Obs. Found at Longban, Tunaberg, Sweden ; Riddarhyttan ; at Degero (degeroite), near 
 Helsingfors, Finland. 
 
 EKMANNITE. Foliated, also radiated. Color green, resembles chlorite. Analysis, Igel- 
 Btrom, SiO 2 34'80, FeO 8 4'97, FeO 35'78, MiiO 11 '45, MgO 2-99, H 2 10'51=100. With 
 magnetite at Grythyttan, Sweden. 
 
 NEOTOCITE. Uncertain alteration-products of rhodonite ; amorphous. Contains 20-30 
 p. c. MnO. Paisberg, near Filipstadt, Sweden ; Finland, etc. 
 
 GILLINGITE ; Sweden. JOLLYTE ; Bodenmais, Bavaria. 
 
OXYGEN COMPOUNDS HYDROUS SILICATES. 355 
 
 Vemni&Mte Group.* 
 
 The VERMICULITKS have a micaceous structure. They are all unisilicates, 
 having the general quantivalent ratio R-J-R : Si : 11=: 2 : 2 : 1, the water 
 being solely water of crystallization. The varieties differ in the ratio 
 of the bases present in the protoxide and sesquioxide states.* 
 
 JEFFERISITE. 
 
 Orthorhombic (?). In broad crystals or crystalline plates. Cleavage : basal 
 eminent, affording easily very thin folia, like mica. Surface of plates often 
 triangularly marked, by the crossing of lines at angles of 60 and 120. 
 
 H.=l*5. G.=:2'30. Lustre pearly on cleavage surface. Color dark 
 yellowish-brown and brownish-yellow; light yellow by transmitted light. 
 Transparent only in very thin folia. Flexible, almost brittle. Optically 
 biaxial ; DcsCl. 
 
 Comp. Q. ratio for R : R : Si : H=2 : 3 : 5 : 2|, and R-l-R : Si : H=2 : 2 : 1 ; whence 
 R 4 RaSi 6 O !i +5aq. Analysis: Brush, Westchester, SiO 2 37-10, A10 3 17'57, Fe0 3 10'54, FeO 
 1-26, MgO 19-65, CaO 0'56, Na a O tr., K 2 O 0'43, H 2 O 13-76=100'87. 
 
 Pyr., etc. When heated to 300 C. exfoliates very remarkably (like vermiculite) ; B.B. in 
 forceps after exfoliation becomes pearly-white and opaque, and ultimately fuses to a dar* 
 gray mass. With the fluxes reactions for silica and iron. Decomposed by hydrochloric acid. 
 
 Obs. Occurs in veins in serpentine at Westchester, Pa. Plates often several inches across. 
 
 PYROSCLERITE. Q. ratio for R : ft : Si : H=4 : 2 : 6 : 3, and for R+ft : Si : H=2 : 2 : 1. 
 
 Silica 38-0, alumina 14-8, magnesia 34-6, water 11'7 = 100. Color green. Elba. CHONICRITE, 
 also Elba, has the ratio 3:2:5:2. 
 
 VERMICULITE. Q. ratio for R : ft : Si : H=:4 : 2 : 6 : 3. Milbury, Mass. CULSAGEEITE. 
 Q. ratio R : R : Si : H=2 : 1 : 1 : 1. Jenk's mine, N. C. HALLITE, same ratio=2 : 1 : 3 : 2. 
 East Nottingham, Chester Co., Penn. PELIIAMITE, same ratio=6 : 4 : 10 : 5. Pelham, 
 Mass. Similar mineral from Lenni, Delaware Co., Pa., above ratio=6 : 4 : 10 : 5. In all of 
 the above R=Mg mostly, and R=A1 and Fe. 
 
 KERRITE. Q. ratio=6 : 3 : 10 : 10 ; and MACONITE, Q. ratio 3 : 6 : 8 : 5, are both from 
 Culsagee mine, Macon Co., N. C. VAALITE, Q. ratio=6 : 3 : 10 : 4. South Africa. 
 
 DIABANTITE, Hawes (diabantachronnyn, Liebe). Fills cavities in amygdaloidal trap. 
 Color dark green. Q. ratio for R : ft : Si : H=;4 : 2 : 6 : 3, but iron a more prominent ingre- 
 dient than in pyrosclerite (see above). Analysis : Hawes, Farmington, Ct., f SiOj 33 '68, A1O S 
 10-84, FeO 3 2-86, FeO 24-33, MnO 0'38, CaO 073, MgO 16'52, Na 2 0-33, H 2 O 10'02=99-69. 
 
 SUBSILICATES. 
 
 Chlorite Group. 
 PENNINITE. Kammererite. 
 
 Khombohedral. R A R = 65 36', O A R = 103 55 ; c = 3-4951. 
 Cleavage; basal, highly perfect. Crystals often tabular, and in crested 
 groups. Also massive, consisting of an aggregation of scales ; also com- 
 pact cryptocry stall in e. 
 
 * These relations were brought out by Cooke. Proc. Amer. Acad., Boston, 187 i, 35; 
 ibid., 1875, 453. 
 
356 
 
 DESCRIPTIVE MINERALOGY. 
 
 652 
 
 653 
 
 H.=2-2-5 ; 3, at times, on edges. G.=2-6-2-85. Lustre of cleavage 
 
 surface pearly ; of lateral plates 
 vitreous, and sometimes brilliant. 
 Color green, apple-green, grass- 
 green, grayish-green, olive-green; 
 also reddish, violet, rose-red, 
 pink, grayish-red ; occasionally 
 yellowish and silver- white; violet 
 crystals, and sometimes the 
 green, hyacinth-red by trans- 
 mitted light along the vertical 
 axis. Transparent to subtranslucent. Laminae flexible, not elastic. Double 
 refraction feeble ; axis either negative or- positive, and sometimes positive 
 and negative in different laminse of the same plate or crystal. 
 
 Comp. Q. ratio for bases and silicon 4 : 3, but varying 1 from 4 : 3 to 5 : 4. Exact deduc- 
 tions from the analyses cannot be made until the state of oxidation of the iron in all cases is 
 ascertained. Analysis: Schweizer, from Zermatt, Si0 2 33'07, A10 3 9 -69, FeO 11 '36, MgO 
 32-34, H 2 12-58=99-08. 
 
 Pyr., etc. In the closed tube yields water. B.B. exfoliates somewhat and is difficultly 
 fusible. With the fluxes all varieties give reactions for iron, and many varieties react for 
 chromium. Partially decomposed by acids. 
 
 Obs. Occurs with serpentine in the region of Zermatt, Valais, near Mt. Rosa ; at Ala, 
 Piedmont ; at Schwarzenstein in the Tyrol ; at Taberg in Wermland ; at Snarum. Kam- 
 mererite is found near Miask in the Urals; at Haroldswick in "Dnst, Shetland Isles. Abun- 
 dant at Texas, Lancaster Co., Pa., along with clinochlore, some crystals being imbedded in 
 clinochlore, or the reverse. 
 
 The following names belong here : tabergite ; pscvdopfiite, compact, massive (allophite} ; 
 loganite. 
 
 Delessite, euralite, aphrosiderite, chlorophceite are chloritic minerals, occurring under simi- 
 lar conditions, in amygdaloid, etc 
 
 RIPIDOLITE. Clinochlore. Klinochlor, Germ. 
 
 Monoclinic. C = 62 51' = A i-i, 1 A / = 125 37', A 44 = 108 
 
 14' : c : I : d = 1-47756 : 
 
 6- r >4 655 1-73195 : 1. Cleavage : 
 
 eminent ; crystals often tab- 
 ular, also oblong ; frequent- 
 ly rhombohedral in aspect, 
 the plane angles of the 
 base being 60 and 120. 
 Twins: twinning-plane 3 , 
 making stellate groups, as in 
 f. 656, 657, very common. 
 Crystals often grouped in 
 rosettes. Massive coarse scaly 
 granular to fine granular and 
 earthy. 
 
 H.=2-2-5. G.=2-65-2-78. 
 
 Lustre of cleavage-face somewhat pearly. Color deep grass-green to olive- 
 green ; also rose-red. Often strongly dichroic. Streak greenish- white to 
 uncoJored. Transparent to translucent. Flexible and somewhat elastic. 
 
 Achmatovsk. 
 
 Achmatovsk. 
 
OXYGEN COMPOUNDS HYDKOTJS SILICATES. 
 
 357 
 
 Westchester. 
 
 Comp. Q. ratio for R : R : Si : H=5 : 3 : 6 : 4 ; corresponding to Mg 5 7VlSi 3 Ou-t-4aq=.: 
 Silica 82-5, alumina 18 '6, magnesia 36-0, 
 water 12 -9 = 100. Sometimes part of the Mg 
 is replaced by Fe. 
 
 Pyr., etc. Yields water. B.B. in the 
 platinum forceps whitens and fuses with 
 difficulty on the edges to a grayish-black 
 glass. With borax a clear glass colored by 
 iron, and sometimes chromium. In sul- 
 phuric acid wholly decomposed. The variety 
 from Willimantic, Ct., exfoliates in worm- 
 like forms, like vermicuiite. 
 
 Obs. Occurs in connection with chloritic 
 and talcose rocks or schist, and serpentine. 
 Found at Achmatovsk ; Schwarzenstein ; 
 Zillerthal, etc. ; red (kotschubeite) in the dis- 
 trict of Ufaleisk, Southern Ural ; at Ala, Piedmont ; at Zermatt ; at Marienberg, Saxony. 
 In the U. S. , at Westchester and Unionville, and Texas, Pa. ; Brewster, N. Y. 
 
 Named ripidolUe from pints, a fan, in allusion to a common mode of grouping of the crys- 
 tals. 
 
 LEUCHTENBERGITE. A prochlorite with the protoxide base almost wholly magnesia. 
 Slatoust, Urals. 
 
 PROCHLORITE. 
 
 Hexagonal (?). Cleavage : basal, eminent. Crystals often implanted hy 
 their sides, and in divergent groups, fan-shaped, or 
 spheroidal. Also in large folia. Massive granular. 
 
 H. = l-2. GL = 2-78-2-96. Translucent to opaque; 
 transparent only in very thin folia. Lustre of 
 cleavage surface feebly pearly. Color green, 
 grass-green, olive-green, blackish-green ; across the 
 axis by transmitted light sometimes red. Streak 
 un colored or greenish. Laminae flexible, not. elastic. 
 Double refraction very weak ; one optical negative 
 axis (Dauphiny) ; or two very slightly diverging, apparently normal to 
 plane of cleavage. 
 
 Comp. Q. ratio for R : ft : Si : H=12 : 9 : 14 : 9 ; for bases and silicon 3 : 2. Average 
 compositi on = Silica 26 -8, alumina 19'7, iron protoxide 27 '5, magnesia 15 '3, water 10-7=100. 
 
 Pyr., etc. Same as for ripidolite. 
 
 Obs. Like other chlorites in mode of occurrence. Sometimes in implanted crystals, as at 
 St. Gothard, etc. ; in the Zillerthal, Tyrol; Traversella in Piedmont; in Styria, Bohemia. 
 Also massive in Cornwall, in tin veins (where it is called peach] ; at Arendal in Norway. 
 
 CRONSTEDTITE. Q. ratio R : ft : Si : H=3 : 3 : 4 : 8. Przibram; Cornwall. 
 
 STRIGOVITE. Q. ratio=3 : 2 : 4 : 2. In granite of Striegan, Silesia. GROCHAUITE same 
 locality. 
 
 MARGARITE. Perlglimmer, Germ. 
 
 Orthorhombic (?) ; hemihedral, with a rnonoclinic aspect. /A /= 119- 
 120. Lateral planes horizontally striated. Cleavage : 
 basal, eminent. Twins : common, composition-face 
 /, and forming, by the crossing of 3 crystals, groups 
 of 6 sectors. Usually in intersecting or aggregated 
 laminae ; sometimes massive, with a scaly structure. 
 
 H.=3-5-4-5. GK=2-99, Hermann. Lustre of 
 base pearly, laterally vitreous. Color grayish, red- 
 dish-white, yellowish. Translucent, subtranslucent. Laminae rather brittle 
 
358 DESCRIPTIVE MINERALOGY. 
 
 Optic-axial angle very obtuse ; plane of axes parallel to the longer diagonal ; 
 
 dispersion feeble. 
 
 f 
 
 Comp. Q. ratio for R : R- : Si : H=l : 6 : 4 : 1 ; whence, if the water be basic, for bases 
 and silicon =2 : 1, formula RRSiOe ; that is, H 2 CaAl 2 Si2O, 2 . Analysis, Smith, Chester, Mass., 
 SiO, 32-21, A1O 3 48-87, FeO s 2-50, MgO 0'32, CaO 10'02, Na 2 O(K 2 0) 1*91, H 2 O 4'61, Li.,0 
 0-32, MnO 0-20 = 100-96. 
 
 Pyr., etc. Yields water in the closed tube. B.B. whitens and fuses on the edges. 
 
 Obs. Margarite occurs in chlorite from the Greiner Mts. ; near Sterzing in the Tyrol ; at 
 different localities of emery in Asia Minor and the Grecian Archipelago ; with corundum in 
 Delaware Co., Pa.; at Unionville, Chester Co., Pa, (corunddlite} ; in Madison Co. 
 }) and elsewhere in North Carolina ; at the emery mines of Chester, Mass. 
 
 CHLORITOID. 
 
 Monoclinic, or triclinic. I/\ I' about 100 ; (or cleavage surface) on 
 lateral planes 93-95, DesCl. Cleavage : basal perfect : parallel to a 
 lateral plane imperfect. Usually coarsely foliated massive ; folia oftei 
 curved or bent, and brittle ; also in thin scales or small plates disseminatec 
 through the containing rock. 
 
 H.:= 5*5-6. G.= 3*5-3*6. Color dark gray, greenish-gray, greenish- 
 black, grayish-black, often grass-green in very thin plates ; strongly dichroic. 
 Streak uncolored, or grayish, or very slightly greenish. Lustre of surface 
 of cleavage somewhat pearly. Brittle. 
 
 Var. 1. The original chloritoid (or chloritspath) from Kossoibrod, near Katharinenburg in 
 he Ural. 2. The Simiondine, from St. Marcel. 3. Masonite, from Natic, R. I., in very 
 proad plates of a dark grayish-green color. The Canada mineral is in small plates, one-fourth 
 in. wide and half this thick, disseminated through a schist (like phyllite), and also in nodules 
 of radiated structure, half an inch through. That of Gumuch-Dagh resembles sismondine, is 
 dark green in thick folia and grass-green in very thin. 
 
 Comp. Q. ratio for R : ft : Si : H 1 : 3 : 2 : 1, for most analyses. Analysis by v. Kobell, 
 Bregratten, SiO, 26'19, A10 3 38'30, Fe0 3 6 00, FeO 21 11, MgO 3'30, H 2 O 5 '50=100 "40. 
 
 Pyr., etc In a matrass yields water. B.B. nearly infusible ; becomes darker and magne- 
 tic. Completely decomposed by sulphuric acid. The masonite fuses with difficulty to a dark 
 green enamel. 
 
 Obs. The Kossoibrod chloritoid is associated with mica and cyanite ; the St. Marcel occurs 
 in a dark green chlorite schist, with garnets, magnetite, and pyrite ; the Rhode Island, in an 
 argillaceous schist ; the Chester, Mass. , in talcose schist, with emery, diaspore. etc. 
 
 PhyUite (said ottrelite) closely resembles chloritoid, though the analyses hitherto made show 
 a wide discrepancy, perhaps from want of purity in the material analyzed. Occurs in small, 
 oblong, shining scales or plates, in argillaceous schist. Color blackish gray, greenish-gray, 
 black. Phyllite occurs in the schist of Sterling, Goshen, Chesterfield, Plainfield, etc., in 
 Massachusetts, and Newport, R. I. (newportite). Ottrelite is from a similar rock near Ottrez. 
 
 SEYBERTITE. Orthorhombic. I,\l = 120. In tabular crystals, sometimes hexagonal; 
 also foliated massive ; sometimes lamellar radiate. Cleavage : basal perfect. Structure thin 
 foliated, or micaceous parallel to the base. H. =4-5. G. =3-3-1. Lustre pearly submetallic. 
 Color reddish-brown, yellowish, copper-red. Folia brittle. Analysis. Brush, Amity, Si0 2 
 20-24, riJO 3 39-13, FeO 3 3'27, MgO20'84, CaO 13'69, H 2 O 1-04, Na 2 O,K 2 O) 1*43, ZrO 3 0-?5= 
 100-39. Amity, N. Y. (clintonite) ; Fassathal (brandmte}; Slatoust (xanthophyttite}. 
 
 CORUNDOPHILITE. A chlorite with the Q. ratio=l : 1 : 1 : f . Occurs with ccrundum at 
 Asheville. N. C.; Chester, Mass. 
 
 DUDLEYITE. Alteration product of margarite. Clay Co., N. C. ; Dudleyville, Ala. 
 
 WILLCOXITE. Near margarite. Decomposition product of corundum. Q. ratio f or R : R : 
 Si : H=3 : 6 : 5 : 1. 
 
 THURLNGITE. Q. ratio 2:3:3:2. Contains principally iron (Fe and Fe). Hot Springs, 
 Arkansas ; Harper's Ferry (owenite). Pattersonite from Unionville, Pa. , near thuringite. 
 
OXYGEN COMPOUNDS. TANTALATES, COLUMBATE8. 
 
 359 
 
 2. TANTALATES, COLUMBATES. 
 
 PYROCHLORE.* 
 
 Isometric. Commonly in octahedrons. Cleavage: octahedral, some- 
 times distinct, especially in the smaller crystals. 
 
 H.=5-5'5. G. 4-2-4-35. Lustre vitreous or resinous. Color brown, 
 dark reddish- or blackish-brown. Streak light brown, yellowish- brov//i. 
 Subtranslucent opaque. Fracture conchoidal. 
 
 Comp. A columbate of calcium, cerium, and other bases in varying 1 amounts. Analysis, 
 by Rammelsberg. Brevig, Cb 2 O 5 58 '27, TiO 2 5 '38, ThO 2 4 '96, CeO 5 '50, CaO 10 "93, FeO;U0 2 ) 
 5-53, Na 2 O 5 31, F 3 '75, H 2 1-53 = 101-16. 
 
 Obs. Occurs in syenite at Friederichsvarn and Laurvig, Norway; at Brevig; near Miask 
 in the Urals ; Kaiserstuhlgebirge in Breisgau (koppite) ; with samarskite in N. Carolina (G-.= 
 4*794, chemical character unknown). 
 
 MICROLITE.* In minute yellow octahedrons in feldspar. G.=5'5. Near pyrochlore, bufc 
 probably containing more tantalum pentoxide. Chesterfield, Mass. 
 
 PYRRHITE. In isometric octahedrons. Color orange-yellow. Chemical character un- 
 known. From Mursinsk in the Ural. A mineral supposed to be similar from the Azores 
 contains essentially, according to Hayes, columbium, zirconium, etc. 
 
 AZOKITE. In minute tetragonal octahedrons resembling zircon. From the Azores in albifcu. 
 Chemical character unknown. 
 
 TANTALITB.* 
 
 Orthorhombic. Observed planes as in 
 O A 14 = 122 3' ; c : I : d = 1-5967 : 1-2247 : 1. A 
 f-i = 117 2', a A 1-2 = 143 6i', 1-2 A 1-2, adj., = 141 
 48', i4 A *'-!== 11 8 33'. Twins: twinning-plane i-l, 
 common. Also massive. 
 
 H.=6-6'5. G.=7-8. Lustre nearly pure metallic, 
 somewhat adamantine. Color iron-black. Streak red- 
 dish-brown to black. Opaque. Brittle. 
 
 the figure. /A7=101 C 35s', 
 
 IT 
 
 Comp., Var A tantalate either (1) of iron, or (2) of iron and 
 manganese, or (3) a stanno- tantalate of these two bases. Formula 
 Fe(Mn)Ta 2 6 . Sn is also often present (as FeSnO 3 . according to Ram- 
 in elsberg\ and some of the tantalum is often replaced by columbium. 
 Analysis. Ramm., Tammela (G.=7'384), Ta 2 O 5 70 '34, Cb 2 O 5 7 '54, 
 SnO* 0'70.FeO 13-90, MnO 1-42=99'90. Other varieties contain much 
 more Cb 2 O 6 , the kinds shade into one another. 
 
 Pyr., etc. B.B. unaltered. With borax slowly dissolved, yielding an iron glass, which, ati 
 a certain point of saturation, gives, when treated in R.F. and subsequently flamed, a gray- 
 ish-white bead ; if completely saturated becomes of itself cloudy on cooling. With salt of 
 phosphorus dissolves slowly, giving an iron glass, which in R.F., if free from tungsten, is 
 pale yellow on cooling ; treated with tin on charcoal it becomes green. If tungsten is present 
 the bead is dark red, and is unchanged in color when treated with tin on charcoal. With 
 soda and nitre gives a greenish-blue manganese reaction. On charcoal, with soda and suffi- 
 cient borax to dissolve the iron, gives in R.F. metallic tin. Decomposed on fusion with 
 
360 
 
 DESCRIPTIVE MINERALOGY. 
 
 potassium bisulphate in the platinum spoon, and gives on treatment with dilute hydrochloric 
 acid a yellow solution and a heavy white powder, which, on addition of metallic zinc, assumes 
 u ^malt-blue color ; on dilution with water the blue color soon disappears (v. Kobell). 
 
 Obs. Tantalite is confined mostly to albite or oligoclase granite, and is usually associated 
 with beryl. Occurs in Finland, at several places ; in Sweden, in Fahlun, at Broddbo and 
 Finbo ; in France, at Chanteloube near Limoges, in pegmatite ; in North Carolina. 
 
 Named Tantalite by Ekeberg, from the mythic Tantalus, in playful allusion to the difficul- 
 ties (tantalizing) he encountered in his attempts to make a solution of the Finland mineral in 
 acids. 
 
 COLUMBITE.* Niobile. Ferroilmenite. 
 
 Orthorhombic. 7 A 7= 101 26', A 14 = 134 53i' ; c:l\d = 
 1-0038 : 1-2225 : 1. A 1-2 = 140 36', A 1-3 = 138 26', i-l A 1-3 = 
 104 30', 1-S A 1-5, adj., = 151, i-3 A i-%, ov. i-t, 135 40', *'-2 A *-2, ov. i-i, 
 = 135 30'. Twins : twinning-plane 2-1 Cleavage : i-l and i-$, the former 
 most distinct. Occurs also rarely massive. 
 
 661 '62 663 
 
 Haddam. Middletown, Conn. Greenland. 
 
 H.=6. G.=5'4-6'5. Lustre submetallic ; a little shin irig. 
 black, brownish-black, grayish-black ; often iridescent 
 black. Opaque. Fracture subconchoidal, uneven. 
 
 Color iron- 
 Streak dark red to 
 Brittle. 
 
 Comp., Var. FeCb 2 (Ta 2 )0 6 , with some manganese replacing part of the iron. The ratio 
 of Cb : Ta generally=3 : 1 (Bodenmais, Haddam), sometimes 4 : 1, 8 : 1, 10 : 1, etc.; in the 
 Greenland columbite the Ta 2 5 is almost entirely absent. 
 
 Analyses, Blomstrand, (1) Haddam ^G.=615), (2) Greenland (G.=5'395). 
 
 Cb 2 5 Ta 2 5 W0 8 SD0 2 ZrO 2 FeO MnO H 2 O 
 
 (1) 51-53 28-55 0-76 0-34 0'34 13-54 497 0-16=100-19 
 
 (2) 77-97 0-13 0-73 013 17*33 3 51 = 99 -80 
 
 Pyr., etc. Like tantalite. Von Kobell states that when decomposed by fusion with 
 caustic potash, and treated with hydrochloric and sulphuric acids, it gives, on the addition of 
 zinc, a blue color much more lasting than with tantalite ; and the variety dianite, when 
 similarly treated, gives, on boiling with tin-foil, and dilution with its volume of water, 
 sapphire-blue fluid, while, with tantalite and ordinary columbite, the metallic acid remains 
 undissolved. The variety from Haddam, Ct., is partially decomposed when the powdered 
 mineral is evaporated to dryness with concentrated sulphuric acid, its color is changed to 
 white, light gray, or yellow, and when boiled with hydrochloric acid and metallic zinc it gives 
 a beautiful blue. The remarkably pure and unaltered columbite from Arksut-fiord in Green- 
 land is also partially decomposed by sulphuric acid, and the product gives the reaction test 
 with zinc, as above. 
 
 Obs. Occurs at Rabenstein, Bavaria ; at Tirschenreuth, Bavaria ; at Tammela in Finland ; 
 at Chanteloube, near Limoges ; near Miask in the Hmen Mts. ; at Hermanskar, near Bjorskar, 
 in Finland ; in Greenland, at Evigtok. 
 
OXYGEN COMPOUNDS. TANTALATES, COLUMBATES. 
 
 361 
 
 In the United States, at Haddam, in a granite vein, and near Middletown, Conn. ; at 
 Chesterfield, Mass. ; Standish, Me. ; Acworth, N. H. ; also Beverly, Mass.; Northfield, Mass, j 
 Plymouth, N. H. ; Greenfield, N. Y. 
 
 The Connecticut crystals are usually rather fragile from partial change ; while those of 
 Greenland and of Maine are very firm and hard. 
 
 HEKMANNOLITE (Shepard). From the columbite locality at Haddam, Ct., and a variety of 
 columbite due to alteration. G. =5 '85. Supposed by Hermann to contain " ilmenium " pent 
 oxide (I1 2 5 ). 
 
 TAPIOLITE. Tetragonal. c=-6464 (rutile c=*6442). FeTa 2 (Cb 2 )O 6 , \\ith Ta : Cb=4 : 1. 
 Tammela, Finland. 
 
 HJELMITE. A stanno-tantalate of iron, uranium and yttrium. Massive. Color black. 
 Near Fahlun, Sweden. 
 
 YTTROTANTALITE. Black Yttrotantalite. 
 
 Orthorhoinbic. 7A 7= 123 10' ; A 2-1 = 103 26'; c : I : d = 2-0934 
 : 1-8482 : 1. Crystals often tabular parallel to i-L 664 
 
 Also massive ; amorphous. 
 
 H.=5-5'5. G.=5'4-5-9. Lustre submetallic to 
 vitreous and greasy. Color black, brown. Streak 
 gray to colorless. Opaque to subtranslucent. Frac- 
 ture small conchoidal to granular. 
 
 Comp. Mostly Jl 2 (Ta,Cb)y0 7 , with two equivalents of water, 
 perhaps from alteration ; R=Fe : Ca : Y(Er,Ce)^l : 2 : 4. Con- 
 taining also W0 3 and Sn0 2 . Analysis (Rainm.), Ytterby, Ta 2 6 
 46-25, Cb 2 O 6 12 32, SnO 2 M2, W0 3 2'36, U0 2 1*61,YO 10 ; 52, ErO 
 6-71, FeO 3-80, CeO 2'22, Ca 5-73, H 2 O 6'31=98'95. 
 
 Pyr., etc. In the closed tube yields water and turns yellow. Ytterby. 
 
 On intense ignition becomes white. B.B. infusible. With salt of , 
 
 phosphorus dissolves with at first a separation of a white skeleton of tantalum pentoxid, 
 which with a strong heat is also dissolved ; the black variety from Ytterby gives a glass faintly 
 tinted rose-red from the presence of tungsten. With soda and borax on charcoal gives traces 
 of metallic tin (Berzelius). Not decomposed by acids. Decomposed on fusion with potas- 
 sium bisulphate, and when the product is boiled with hydry chloric acid, metallic zinc gives a 
 pale blue color to the solution which soon fades. 
 
 Obs. Occurs in Sweden at Ytterby ; at the Korarfvet mine, etc., near Fahlun. 
 
 SAMARSKITE.* Uranotantalite. 
 
 Orthorhombic. 7A7=122 46' 
 1-833 : 1. Crystals often flattened 
 parallel to i-l, also less often to i-l. 
 Also in large irregular masses (N. 
 Carolina). In flattened imbedded 
 grains (Urals). 
 
 H.=5-5-6. G.=5-614-5-75 ; 5-45 
 -5-69, North Carolina. Lustre of 
 surface of fracture shining and sub- 
 metallic. Color velvet-black. Streak 
 dark reddish-brown. Opaque. Frac- 
 ture subconchoidal. 
 
 Comp. Analyses : 1. Allen (priv. 
 trib.) ; 2. Finkener anil Stephaus : 
 
 l-l A l-l = 93 C 
 
 665 
 
 I : d = 0-949 . 
 
 North Carolina. 
 
362 DESCRIPTIVE MINERALOGY. 
 
 CbaOs Ta 2 6 W0 3 Sn0 2 ThOiZrO.UOs MnO FeO CeO* YO CaO H 2 
 
 1. Mitchell 
 
 Co., N. C., 37-20 18.60 0-08 12 46 0*75 10-90 4'25 14'45 0-55 1-12= 
 
 U0 2 100-36 
 
 2. Miask, 47*47 1'36 0'05 6'05 4-35 10-950-96 ll*33f 3-31 12-61 0'73 0-45 
 
 MgO 0-14=99 -76 
 
 * With LaO, DiO. 
 t With 0-JJ5 CuO. 
 
 Pyr., etc. In the closed tube decrepitates, glows like gadolinite, cracks open, and turns 
 black, and is of diminished density. B.B. fuses on the edges to a black glass. With borax 
 in O.F. gives a yellowish-green to red bead, in R.F. a yellow to greenish-black, which on 
 flaming becomes opaque and yellowish-brown. With salt of phosphorus in both flames an 
 emerald -green bead. With soda yields a manganese reaction. Decomposed on fusion with 
 potassium bisulphate, yielding a yellow mass which on treatment with dilute hydrochloric 
 acid separates white tantalic acid, and on boiling with metallic zinc gives a fine blue color. 
 Samarskite in powder is also sufficiently decomposed on boiling with concentrated sulphuric 
 acid to give the blue reduction test when the acid fluid is treated with metallic zinc or tin. 
 
 Obs. Occurs in reddish-brown feldspar, near Miask in the Ural ; the pieces having the 
 size of hazel-nuts. In masses, sometimes weighing 20 Ibs.. in the decomposed feldspar of the 
 mica mines of western North Carolina, especially in Mitchell Co. At both localities it is 
 often intimately associated with columbite ; at Miask the crystals of the latter species are 
 eometimes implanted in parallel position upon those of the samarskite. 
 
 NOHLITE. Xear samarskite, but contains 4 "62 p. c. water. Nohl, Sweden. 
 
 EUXEJNITJB. 
 
 Orthorhombic. Form a rectangular prism with lateral edges replaced, 
 and a pyramid at summit. Cleavage none. Commonly massive. 
 
 11.= 6*5. G.= 4*60-4*99. Lustre brilliant, metallic-vitreous, or some- 
 what greasy. Color brownish-Mack ; in thin splinters a reddish-brown 
 translucence lighter than the streak. Streak-powder yellowish to reddish- 
 brown. Fracture subconchoidal. 
 
 Comp. According to Rammelsberg 2RTi03 + RCb 2 6 +aq ; here R=Y,Fe,U mostly. 
 Analysis, Ramm., Arendal, Cb 2 8 35*09, TiO a 2116, YO27'48, ErO3'40, U0 2 4 -78. CeO 3-17, 
 FeO 1-38, H 2 O 2-63=99*63. 
 
 Obs. Occurs at Jolster in Norway ; near Tvedestrand ; at Alve, island of Tromoen, near 
 Arendal ; at Moretjar, near Naskilen. 
 
 Named by Scheerer from etil-evos, a stranger, in allusion to the rarity of its occurrence. 
 
 -<EscnYNiTE. -Orthorhombic. H. 5-6. G. =4*9-5 '14. Lustre subrnetallic to resinous, 
 nearly dull. Color nearly black. Streak gray. Fracture small subconchoidal. Analysis, 
 Ramm., Cb 2 O 5 28*81, TiO 2 22'64, Sn0 2 018, Th0 2 15*75, FeO 317, CeO 18 '49, LaO(DiO) 
 5'60, YO 1*12, CaO 2'75, H 2 1-07=99*58. In feldspar with mica and zircon. Miask in the 
 Urals. 
 
 POLYMIGNITE. Orthorhombic. In slender crystals. H =6*5. G. 4'77-4-85. Lustre 
 brilliant. Color black. Streak dark brown. Fracture perfect conchoidal. Composition 
 doubtful. Fredericksvarn, Norway. Perhaps identical with aeschynite (Frankenheim). 
 
 POLYCKASE. Orthorhombic. H.=5'5. G.=5*09-5*12. Lustre bright. Color black. 
 Streak grayish-brown. Fracture conchoidal. Analysis, Ramm., Cb 2 5 20*35, Ta 2 O 5 4*00, 
 TiO 2 26*59, YO 23 '32, FeO 2*72, CeO 2 61, U0 3 7 70 H 2 4 '02=98*84. In crystals in granite 
 at Hitteroe, Norway. 
 
 MENGITE. Occurs in short prisms. H. =5-5*5. G. ^=5"48. Color iron-black. Contains 
 zirconium, iron, titanium. In granite veins in the Ilmen Mts. 
 
 RUTHERFORD ITE. Doubtful; contains titanium, cerium, etc. Rutherford Co., N. C. 
 
 FERGUSONTTE.* Yellow Yttrotantalite. Tyrite. Bragite. 
 
 Tetragonal, hemihedral. O A l-i = 124 20' ; c = 1'464. Cleavage : 1, 
 in distinct traces. 
 
OXYGEN COMPOUNDS. TANTALATES, COLTJMBATES. 
 
 H. 5-5-6. G.=5-83S, Allen; 5-800, Turner. Lustre externally dull, 
 on the fracture brilliantly vitreous and submetallic. 
 Color brownish-black; in thin scales pale liver-brown. 
 Streak pale brown. Subtranslucent opaque. Frac- 
 ture imperfect conchoiclal. 
 
 Conap. According to Rammelsberg, essentially R 3 (Cb,Ta) 2 08. 
 Analysis, Ramm., Greenland, Cb 2 O 6 44 '45, Ta 2 O.s 6 "30, Sn0 2 0'47, 
 W0 3 0-15, YO 24-87.Er09-81, Ce07'63 (5 "63 LaO,DiO), UO 2 2-58, 
 Fed 0-74, CaO 0'6 1, H 2 O 1-49 -=99 '10. The amount of water varies 
 from 1 -49-7 p. c. , and is regarded by Rammelsberg as arising from 
 alteration. 
 
 Obs. Fergusonite occurs near Cape Farewell in Greenland, dis- 
 seminated in quartz. Also found at Ytterby, Sweden ; in Silesia. 
 Bragite is from Helle, Alve, and elsewhere in Norway. Tyrite is 
 associated with euxenite at Hampemyr on the island of Tromoe, 
 and Helle on the mainland ; at Naeskul, about ten miles east of 
 Arendal. 
 
 KOCHELITE. Near fergusonite. In yellow square-octahedrons and crusts in granite. 
 Kochelwiesen, near Schreiberhau, Silesia. 
 
 ADELPHOLITE. A columbate of iron and manganese, containing 41'8 p. c. of metallic 
 acids, and 9'7 p. c. of water. Tetragonal. H. =3 -5-4 -5. G.=3'8. Tammela, Finland. 
 
361 
 
 DESCRIPTIVE MINERALOGY. 
 
 3. PHOSPHATES, AESENATES, VANADATES, ETC. 
 
 ANHYDROUS PHOSPHATES, ARSENATES, ETC. 
 XENOTIMB. Ytterspath, Germ. 
 
 Tetragonal. A 1 = 138 45' ; c = 0-6201. 1 A 1, pyram., = 124 26' ; 
 basal, = 82 30'. Cleavage : /, perfect. 
 
 H.=4-5. G. =4-45-4'56. Lustre resinous. 
 Color yellowish-brown, reddish-brown, hair-brown, 
 flesh-red, grayish-white, pale yellow ; streak pale 
 brown, yellowish, or reddish. Opaque. Fracture 
 uneven and splintery. 
 
 Comp. Y 3 P 2 8 =Phosphorus pentoxide (P 2 5 ) 37 '87, yttria 
 62 13 =100. 
 
 Pyr., etc. B.B. infusible. When moistened with sulphuric 
 acid colors the flame bluish-green. Difficultly soluble in salt 
 of phosphorus. Insoluble in acids. 
 Obs. From a granite vein at Hitteroe ; at Ytterby, Sweden ; St. Gothard ; Binnenthal. 
 In the TJ. S., in the gold washings of Clarksville, Georgia; in McDowell Co., N. C.; in the 
 diamond sands of Bahia, Brazil. The wiaeiwe of Kenugott has been shown by Klein to be 
 octahedrite (vide p. 255). 
 
 CRYPTOLITE (PhospJwcerite}. CesPaOs (with some Di), like monazite. Occurs in minute 
 grains imbedded in apatite at Arendal ; Siberia. 
 
 Apatite Group. 
 APATITE.* 
 
 Hexagonal ; often hemihedral. A 1 = 139 41' 38", Kokscharof ; c 
 0*734603. O A 2-2 = 124 14J'. Cleavage : 0, imperfect ; /, more so. Also 
 
 669 
 
 St. Gothard. 
 
 globular and reniform, with a fibrous or imperfectly columnar structure , 
 also massive, sti icture granular. 
 
OXYGEN COMPOUNDS. PHOSPHATES, AKSENATES, ETC. 365 
 
 H.= 5, sometimes 4-5 when massive. G.^2'92-3'25. Lustre vitreous, 
 inclining to subresinous. Streak white. Color usually sea-green, bluish- 
 grceu ; often violet-bine; sometimes white ; occasionally yellow, gray, red, 
 flesh-red, and brown; none bright. Transparent opaque. A ^ bluish 
 opalescence sometimes in the direction of the vertical axis, especially in 
 white varieties. Cross fracture conchoidal and uneven. Brittle. 
 
 Var. 1. Ordinary. Crystallized, or cleavable and granular massive, (a) The asparagus 
 
 stone (originally from Murcia, Spain) and moroxite (from Arendal) are ordinary apatite. The 
 former was yellowish-green, as the name implies ; the latter was in greenish-blue and bluish 
 crystals ; and the names have been used for apatite of the same shades from other places. 
 2. Fibrous, concretionary, stalactitic. The name Phosphorite was used by Kirwan for all apatite, 
 but in his mind it especially included the fibrous concretionary and partly scaly mineral from 
 Estremadura, Spain, and elsewhere. 3. Fluor-cvpatite, Ohlor-apatite. Apatite also varies as 
 to the proportion of fluorine to chlorine, one of these elements sometimes replacing nearly or 
 wholly the other. 
 
 Comp. The formulas of the two varieties are 3Ca 3 P-2O 8 4- CaCl 2 = Phosphorus pentoxide 
 40-92, lime 53-80, chlorine 6 '82 =101 '54; and 3Ca 3 PsO 8 + CaF 2 =Phosphorus pentoxide 42 '26, 
 Lime 55 '55, fluorine 3'77=101 '58. Sometimes both calcium chloride (CaCl 2 ), and calcium 
 fluoride (CaF 3 ), are present. 
 
 Pyr., etc. B.B. in the forceps fuses with difficulty on the edges (F.=4'5-5), coloring the 
 flame reddish-yellow ; moistened with sulphuric acid and heated colors the flame pale bluish- 
 green (phosphoric acid) ; some varieties react for chlorine with salt of phosphorus, when the 
 bead has been previously saturated with copper oxide, while others give fluorine when fused 
 with this salt in an open glass tube. Gives a phosphide with the sodium test 
 
 Dissolves in hydrochloric and nitric acid, yielding with sulphuric acid a copious precipitate 
 of calcium sulphate ; the dilute nitric acid solution gives with lend acetate a white precipi- 
 tate, which B. B. on charcoal fuses, giving a globule with crystalline facets on cooling. Some 
 varieties of apatite phosphoresce on heating. 
 
 Diff. Characterized by its hexagonal form. Distinguished by it^ softness from beryl; 
 does not effervesce with acids like the carbonates ; unlike pyromorphite, yields no lead B.B. 
 
 Obs. Apatite occurs in rocks of various kinds and ages, but is most common in metamor- 
 
 phic crystalline rocks, especially in granular limestone, granitic and many metalliferous veins, 
 particularly those of tin, in gneiss, syenite, hornblendic gneiss, mica schist, beds of iron ore ; 
 occasionally in serpentine, and in igneous or volcanic rocks ; sometimes in ordinary stratified 
 limestone, beds of sandstone or shale of the Silurian, Carboniferous, Jurassic, Cretaceous, or 
 Tertiary formations ; also in microscopic crystals in many igneous rocks, doleryte, etc. It 
 has been observed as the petrifying material of wood. 
 
 Among its prominent localities are Ehrenfriedersdorf in Saxony ; region of St. Gothard 
 in Switzerland; Mussa-Alp in Piedmont; Untersulzbachthal and elsewhere in the Tyrol; 
 Bohemia; in England, in Cornwall, with tin ores; in Cumberland ; in Devonshire ; atWheal 
 Franco (f ran oolite), etc. The variety, moroxite, occurs at Arendal, Snarum, etc., in Norway. 
 The asparagus stone or Spargelstein of Jumilla, in Murcia, Spain, is pale yellowish-green in 
 color ; and a variety from Zillerthal is wine-yellow. The phosphorite, or massive radiated 
 variety, is obtained abundantly near the junction of granite and argillyte, in Estremadura 
 Spain ; at Schlackenwald in Bohemia ; at Krageroe, etc. 
 
 In Mass., at Norwich; at Bolton, and elsewhere. In New York, in St. Lawrence Co., in 
 granular limestone; in Rossie; Sanford mine, Essex Co.; near Edenville, Orange Co. In 
 New Jersey, near Suckasunny, ; Mt. Pleasant mine, near Mt. Teabo ; at Hurdstown, Sussex 
 Co. In Penn., at Leiperville, Delaware Co.; in Chester Co. In Delaware, at Dixon's quarry, 
 Wilmington. In Canada, in North Elmsley, and passing into South Burgess ; similar in 
 Boss ; at the foot of Calumet Falls ; at St. Roch, on the Achigan. 
 
 * Apatite was named by Werner from diroT<o>, to deceive, older mineralogists having referred 
 it to aquamarine, chrysolite, amethyst, fluor, schorl, etc 
 
 OSTEOLITB is massive impure altered apatite. The ordinary compact variety looks like 
 lithographic stone of white to gray color. It also occurs earthy. Hanau. 
 
 GUANO. Guano is bone-phosphate of calcium, or osteolite, mixed with the hydrous phos- 
 phate, brushite, and generally with some carbonate of calcium, and often a little magnesia, 
 alumina, iron, silica, gypsum, and other impurities. It often contains 9 or 10 p. c. of water. 
 It is often granular or oolitic ; also compact through consolidation produced by infiltrating 
 waters, in which case it is frequently lamellar in structure, and also occasionally stalagmitic 
 and stalactitic. Its colors are usually grayish-white, yellowish and dark brown, and some- 
 times reddish, and the lustre of a surface of fracture earthy to resinous. 
 
368 
 
 DESCRIPTIVE MINERALOGY. 
 
 PHOSPHATIC NODULES. COPROLITES. Phosphatic nodules occur in many fossiliferous 
 rocks, which are probably in all cases of organic origin. They sometimes present a spiral 01 
 other interior structure, derived from the animal organization that afforded them, and in 
 such cases their coprolitic origin is unquestionable. In other cases there is no structure to aid 
 in deciding whether they are true coprolites or not. 
 
 FYROMORPHITE* Griinbleierz, Germ. 
 
 Hexagonal. Hemihedral. O A 1 139 38' ; c = 0-7362. Cleavage : 
 1 and 1 in traces. / commonly striated horizontally. Often globular, 
 reniform, and hotryoidal or verruciform, with usually a subcolumnar struc- 
 ture ; also fibrous, and granular. 
 
 H.=3'5-4. G.:=6'5-7-l, mostly when without lime; 5-6*5, when con- 
 taming lime. Lustre resinous. Color green, yellow, and brown, of differ- 
 ent shades; sometimes wax-yellow and fine orange-yellow; also grayish- 
 white to milk-white. Streak white, sometimes yellowish. Subtransparent 
 subtranslucent. Fracture subconchoidal, uneven. Brittle. 
 
 Comp Analogous to apatite, 3Pb 3 P 2 8 +PbCl 2 = Phosphorus pentoxide 1571, lead oxide 
 82 '27, chlorine 2-62=100-60. Some varieties contain arsenic replacing part of the phosphorus, 
 and others calcium replacing the lead. 
 
 Pyr., etc. In the closed tube gives a white sublimate of lead chloride. B.B. in the forceps 
 fuses easily (F.=1'5), coloring the flame bluish-green ; on charcoal fuses without reduction 
 to a globule, which on cooling assumes a crystalline polyhedral form, while the coal is coated 
 white from the chloride, and, nearer the assay, yellow from lead oxide. With soda on charcoal 
 yields metallic lead ; some varieties contain arsenic, and give the odor of garlic in R.F. on 
 charcoal. With salt of phosphorus, previously saturated with copper oxide, gives an azure- 
 blue color to the flame when treated in O.F. (chlorine). Soluble in nitric acid. 
 
 Diflf. Characterized by its high specific gravity, and pyrognostics. 
 
 Leadhills in Scotland ; Wicklow, and elsewhere, Ireland. In the U. S. at Phenixville Penn 
 also in Maine, at Lubec and Lenox ; in Davidson Co., N. C. 
 
 The figures produced by etching (see p. 118) show that pyromorphite is hemihedral like 
 apatite (Baumhauer). 
 
 Named from rip, fire, popf-fi, form, alluding to the crystalline form the globule assumes on 
 cooling. 
 
 Hexagonal, 
 
 
 MIMETITE.* Mimetesite. 
 
 O A 1 = 139 58' ; c = 0-7276. Cleavage : 1, imperfect. 
 H.=3'5. G.=7'0-7'25, mimetite ; 5'4-5'5, hedy- 
 phane. Lustre resinous. Color pale yellow, passing 
 into brown; orange-yellow; white or colorless. Streak 
 white or nearly so. Subtransparent translucent. 
 
 Comp. Formula 3Pb 3 As 2 8 -j-PbCl 2 =Arsemc pentoxide 23-20, 
 lead oxide 74-96, chlorine 2'39=100'55. Generally part of the 
 arsenic is replaced by phosphorus, and often the lead in part by cal- 
 cium. 
 
 Pyr., etc. In the closed tube like pyromorphite. B.B. fuses at 1, 
 and on charcoal gives in R. F. an arsenical odor, and is easily reduced 
 to metallic lead, coating the coal at first with lead chloride, and 
 later with arsenous oxide and lead oxide. Gives the chlorine reac- 
 tions as under pyromorphite. Soluble in nitric acid. 
 
 Obs. Occurs at several of the mines in Cornwall ; in Cumberland. At St. Prix in France T 
 at Johanngeorgenstadt ; at Nertschinsk, Siberia. At the Brookdale mine, Phenixville, Pa. 
 
OXYGEN COMPOUNDS. PHOSPHATES, AESENATES, ETC. 367 
 
 Mimetite is hemihedral like apatite and pyromorphite, as shown by etching (Baumhauer), 
 
 Named from iiiu-nriis, imitator, it closely resembling pyromorphite. 
 
 HEPYpS^.S variety containing much calcium. CAMPYLITE contains much lead phc* 
 
 phate. 
 
 VANADINITE.* 
 
 Hexagonal. In simple hexagonal prisms, and prisms terminating in 
 planes of the pyramids ; 1 A 1, over terminal edge, 142 58', A 1 = 140 
 34/ /A 1 = 130. Usually in implanted globules or incrustations. 
 
 H =2-75-3 G.= 6-6623-7.23. Lustre of surface of fracture resinous. 
 Color light brownish-yellow, straw-yellow, reddish-brown. Streak white or 
 yellowish. Subtranslucent opaque. Fracture uneven, or flat concnoi 
 brittle. 
 
 Comp,-Formula 3Pb 3 V 2 8 +PbCl 2 =Vanadium pentoxide 10-86, lead oxide 7870 chlorine 
 
 P Pvr!, eto^In the closed tube decrepitates and yields a faint white sublimate B.B. fusea 
 easily and on charcoal to a black lustrous mass, which in R. P. yields metallic lead and a cpat- 
 LTof chloride of lead; after completely oxidizing the lead in O.F the black residue give* 
 with salt of phosphorus an emerald-green bead in R.F., which becomes light yellow in O.F. 
 Gives the chlorine reaction with the copper test. Decomposed by hydrochloric acid. 
 
 If nitric acid be dropped on the crystals they become first deep red from the separation of 
 vanadium pentoxide, and then yellow upon its solution. -.T-MM c- ^ O i 
 
 Obs.-This mineral was first discovered at Zimapan in Mexico, by Del Rio. Since obtained 
 at Waniockhead in Dumfriesshire ; also at Beresof in the Ural ; and near Kappel in Carmthia. 
 
 DECBENITE. PbV 2 8 (or with some Zn)= Vanadium pentoxide 451, lead oxide 54 -9-100 
 Massive. Color deep red. Dahn, near Niederschlettenbach, Rhenish Bavaria. 
 
 pentoxide 29'1, lead oxide 70 9=100. Orthorhombic. 
 
 c near brookite in form ( W**fl* Occurs m small 
 
 implanted crystals. Color reddish-brown. In composition a bismuth vanadate, BiVO 4 - 
 Vanadium pentoxide 28-3. bismuth oxide 71 '7. Pucher mine, Schneeberg, Saxony. 
 
 
 
 ROSCOELITE. Occurs in thin micaceous scales, arranged in stellate or fan-shaped &P*' 
 Color dark brownish-green. Soft. G.=2 938 (Genth) ; 2-902 (Roscoe). Analyses : 1. Ros- 
 coe (Proc. Roy. Soc., May 10, 1876); 2. Genth (Am. J. Sci., July, 1876). 
 
 Si0 2 V 2 5 A10 3 Fe0 3 Mn0 3 MgO CaO K 2 O Na.0 
 
 1. |41-25 28-60 14-14 113 115 2*01 0'61 
 
 2. 47-69 2202V 6 On 1410 1-67 FeO 2'00 to. 
 
 The above analyses, made upon material derived from the same source differ widely, 
 especially in regard to the state of oxidation of the vanadium. Genth makes it V.On - 
 2V 2 3 ,V;0, The formula given by Roscoe is 2MV,O. t K,Si 9 O 20 + aq. Found *Bh 
 the porphyry and in cavities in quartz at the gold mine at Granite Creek, El Dorado Uo., 
 Cal. Named by Dr. Blake, who discovered it. See further on p. 435. 
 
368 
 
 DESCRIPTIVE MINERALOGY. 
 
 WAGNERTTB. 
 
 f Monoclimc. C= 71 53', /A 1= 95 25', 6> A l-l = 144 25', B.&M.; 
 c : b : d = O7S654: : 1-045 : 1. Most of the prismatic planes deeply striated. 
 Cleavage : 7, and the orthodiagonal, imperfect ; O in traces. 
 
 H.=5-5'5. Gr.= 3-068, transparent crystal; 2-9S5, untraiisparent, Ram- 
 melsberg. Lustre vitreous. Streak white. Color yellow, of different 
 shades ; often grayish. Translucent. Fracture uneven and splintery acrosa 
 the prism. 
 
 Oomp. Mg 3 P 2 8 +MgF 2 = Phosphorus pentoxide 43 '8, magnesia 371, fluorine 11 '7, mag- 
 nesium 7 '4 =100. 
 
 Pyr., etc. B.B. in the forceps fuses at 4 to a greenish-gray glass ; moistened with sulphu- 
 ric acid colors the flame bluish-green. With borax reacts for iron. On fusion with soda 
 effervesces, but is not completely dissolved ; gives a faint manganese reaction. Fused with 
 salt of phosphorus in an open glass tube reacts for fluorine. Soluble in nitric and hydro- 
 chloric acids. With sulphuric acid evolves fumes of fluohydric acid. 
 
 Obs. Occurs in the valley of Hollgraben, near Werfen, in Salzburg, Austria. 
 
 KJERULFINE (v. Kobell). Stands near wagnerite, but exact nature uncertain. In masses 
 of a pale red color at Bamle, Norway. 
 
 MONAZITE.* 
 
 Monoclinic. C= 76 14', /A 7=93 10', A 14 = 138 8'; c : b : d 
 
 = 0-94715 : 1-0265 : 1. Crys- 
 tals usually flattened parallel" to 
 i-i. Cleavage : very perfect, 
 and brilliant. Twins: twin- 
 ning plane O. 
 
 H. = 5-5-5. G. = 4-9-5-26. 
 Lustre inclining to resinous. 
 Color brownish-hyacinth-red, 
 clove-brown, or yellowish- 
 brown. Subtransparent sub- 
 translucent. Rather brittle. 
 
 Norwich, Ct. 
 
 ii 
 
 Watertown, Ct. 
 
 Comp. According to Rammelsberg, 
 5R 3 P 2 O 8 +Th 2 P.,O 9 , where R=Ce,La, 
 Di. Analysis by Kersten, Slatoust, 
 P 2 5 28-50, Th0 2 17-95, Sn0 2 210, CeO 26'00, LaO 23'40, MnO 1'86, CaO l'b'8, K 2 O and TiO, 
 Jr. =101 -49. 
 
 Pyr., etc. B.B. infusible, turns gray, and when moistened with sulphuric acid colors the 
 flame bluish-green. With borax gives a bead yellow while hot and colorless on cooling ; a 
 saturated bead becomes enamel-white on flaming. Difficultly soluble in hydrochloric acid. 
 
 Diflf. Its brilliant basal cleavage is a prominent character, distinguishing it from tita- 
 nite. 
 
 Obs. Monazite occurs near Slatoust in the Ilmen Mtn. ; also in the Ural ; near Notero in 
 Norway ; at Schreiberhau. In the United States, with sillimanite at Norwich ; at Yorktown, 
 Westchester Co., N.Y.; near Cfowder's Mountain, N. C. 
 
 Named from //omCw, to be solitary, in allusion to its rare occurrence. 
 
 TURNERITE. Identical with monazite, as first suggested by Prof. J. D. Dana. Occurs in 
 minute yellow to brown crystals, rarely twins, at Mt Sorel. Dauphiny ; Santa Brigritta, 
 Tavetsch; Lercheltiny Alp, Binnenthal ; Laacher See (v. Rath.), c : b : d= '921696 : 1 ; 
 0-958444. 01=77 18' (Trechmann). 
 
 KORABPVEITE (Rodominski). A cerium phosphate containing fluorine; near monazite 
 Occurs in large crystalline masses of a yellowish color at Korarfvet, near Fahlun, Sweden. 
 
OXYGEN COMPOUNDS. PHOSPHATES, AKSENATES, ETC. 369 
 
 TRIFHYLITE.* Triphyline. 
 
 Orthorliombic. /A 1= 98, A l-l = 129 33', Tschermak ; c : I : d = 
 1-211 : 1-1504 : 1. Faces of crystals usually uneven. 
 Cleavage : nearly perfect in unaltered crystals. 
 Massive. 
 
 H.=5. G.=3'54-3*6. Subresinous. Color greenish- 
 gray ; also bluish ; often brownish-black externally. 
 Streak grayish-white. Translucent in thin fragments. 
 
 Comp. R 3 P 2 8 , where R=Fe, Mn, (Ca) and Li 2 (K 2 , Na 2 ). Analysis 
 by Oesten, from Bgdenmais, P 2 O 6 44 -19, FeO 38 "21, MnO 5 "63, MgO 
 2-39, CaO 0-76, Li 2 O 7'69, Na 2 O 0'74, K 2 O 0'04, SiO, 40 =100 '05. 
 The analyses vary much, owing to the impure material employed. 
 
 Pyr., etc. In the closed tube sometimes decrepitates, turns to a Norwich, 
 
 dark color, and gives off traces of water. B.B. fuses at 1/5, coloring 
 
 the flame beautiful lithia-red in streaks, with a pale bluish-green on the exterior of the cone 
 of flame. The coloration of the flame is best seen when the pulverized mineral, moistened 
 with sulphuric acid, is treated on a loop of platinum wire. With borax gives an iron bead ; 
 with soda a reaction for manganese. Soluble in hydrochloric acid. 
 
 Ob*. Triphylite occurs at Rabenstein near Zwiesel in Bavaria ; also at Keityo in Finland ; 
 
 Norwich, Mass. 
 
 Named from r/o/f, three-fold, and QvW, family, in allusion to its containing three phos- 
 phates. 
 
 TRIFLITE.* Zwieselite. 
 
 Orthorhombic. Imperfectly crystalline. Cleavage : unequal in three 
 directions perpendicular to each other, one much the most distinct. 
 
 H.=5-5-5. G. = 3'44r-3'8. Lustre resinous, inclining to adamantine. 
 Color brown or blackish-brown to almost black. Streak yellowish- gray or 
 brown. Subtranslucent opaque. Fracture small conchoidal. 
 
 Comp. R 3 P 2 O s -fRF 2 ; R=Fe, Mn(Ca). Analysis, v. Kobell, Schlackenwald, P 2 O 8 33 85, 
 Fe0 3 3-50, FeO 23'38, MnO 30'00, CaO 2 20, MgO 3 05, F=810=104-08. 
 
 Pyr., etc. B.B. fuses easily at 1/5 to a black magnetic globule; moistened with sulphuric 
 acid colors the flame bluish-green. With borax in O.F. gives an amethystine colored glass 
 (manganese) ; in R.F. a strong reaction for iron. With soda reacts for manganese. With 
 eulphuric acid evolves fluohydric acid. Soluble in hydrochloric acid. 
 
 Obs. Found by Alluaud at Limoges in France, with apatite ; at Peilau in Sdesia. 
 
 Zwieselile, a clove-brown variety, was found near Rabenstein, near Zwiesel in Bavaria, m 
 quartz (Gk=3'97, Fuchs). 
 
 SARCOPSIDE. Near triplite. Valley of the Muhlbach, Silesia. 
 
 AMBLYGONTTE.* 
 
 Triclinic. Cleavage : O perfect ; i-l nearly perfect, angle between these 
 cleavages 104 J ; also /imperfect. Usually massive, cleavable ; sometimes 
 columnar. /xlx 
 
 H.=6. G.= 3-3*11. Lustre pearly on face of perfect cleavage (U)\ 
 vitreous on i-l, less perfect cleavage-face ; on cross-fracture a little greasy. 
 Color pale mountain or sea-green, white, grayish, brownish-white, bub- 
 transparent translucent. Fracture uneven. Optical axes very divergent ; 
 plane of axes nearly at right angles toi; bisectrix of the acute angle 
 negative, and parallel to the edge O/i-l; Dead. 
 
370 
 
 DESCRIPTIVE MINERALOGY. 
 
 Oomp. According to Rammelsberg, 2MP 2 Oe+3Li(Na)F. If Na : Li=l : 4, the formula 
 requires : Phosphorus pentoxide 49 '24, alumina 35-58, lithia 6 '24. soda 
 3-23, fluorine 9 "88 = 104 -17. 
 
 Pyr., etc. In the closed tube yields water, which at a high heat is 
 acid and corrodes the glass. B. B. fuses easily at 2, with intumescence, 
 and becomes opaque -white on cooling. Colors the flame yellowish- red 
 with traces of green ; the Hebron variety gives an intense lithia-red ; 
 moistened with sulphuric acid gives a bluish-green to the flame. With 
 cobalt solution assumes a deep blue color (alumina). With borax and 
 salt of phosphorus forms a transparent colorless glass. In fine powdei 
 dissolves easily in sulphuric acid, more slowly in hydrochloric. 
 
 Diff. Distinguished by its easy fusibility ; reaction for fluorine and 
 lithia ; greasy lustre in the mass, etc. 
 
 Obs. Occurs at Chursdorf and Arnsdorf , near Penig in Saxony ; also 
 at Arendal, Norway. In the U. States, in Maine, at Hebron (hebronite), 
 imbedded in a coarse granite with lepidolite, albite,, quartz, red, green, 
 and black tourmaline ; also at Mt. Mica in Paris, 8m. from Hebron, 
 with tourmaline. 
 
 The name is from a///3/\wf, blunt, and y6v\\ angle. 
 HEBRONITE. The mineral from Hebron, Me. (see above), has been 
 shown by DesCloizeaux to diifer in optical character (v > p) from the 
 , Penig amblygonite. On this ground, as well as oh account of a variation 
 in the composition, it has been proposed (v. Kobell) to make it a new species. The sam 
 optical character and composition belong to the mineral from Montebras (called montebrasiti 
 on the basis of an erroneous analysis). Analysis of hebronite, Pisani, P 2 O 3 46'65, :MO< 
 3G-00, Li 2 O 9-75, H 2 4 '20, F 5 '22 =101 -82. 
 
 HERDERITE. Supposed to be an anhydrous aluminum-calcium phosphate, with fluorine. 
 Color yellowish-white. Ehrenfriedersdorf. 
 
 DURANGITE. Monoclinic Cleavage prismatic (110 10'). H.=5. G. =3 '937-4 -07. Coloi 
 bright orange-red. Analysis, Hawes, Arsenic pentoxide 53 '11, alumina 1719, iron sesqui- 
 oxide 9'23, manganese sesquioxide 2 -08, soda 13'0b', lithia 0'05, fluorine 7 -67=102-99. 
 
 Hebronite, Maine. 
 
 Formula HaRAs^Ou (with one-ninth of the oxygen replaced by fluorine), or 
 
 Here R Na : Li^lO : 1 ; ft=Al : Fe : Mn=15 : 5 : 1. Other varieties, having a lighter color, 
 
 have Al : Fe=5 : 1. Occurs with cassiterite, near Durango, Mexico (Brush). 
 
 ANHYDROUS ANTIMONATES. 
 
 MONIMOLITE. Mainly an antimonate of lead. Yellow. G.=5'94. Paisberg, Sweden. 
 
 NADORITE. PbSb >0 4 + PbCl 2 . In yellow translucent crystals. H. =3. G. =7 -02. Djebel 
 Nador, province of Constantino, Algiers. 
 
 ROMEITE. An antimonate (or antimonite) of calcium. Occurs in groups of minute tetra- 
 gonal crystals. Color yellow. St. Marcel, Piedmont. 
 
 RIVOTITE. Contains antimonic oxide, carbon dioxide, and copper. Amorphous. ColoJ 
 yellowish-green. Sierra del Cadi. 
 
 STIBIOFERRITE. Amorphous coating on stibnite, from Santa Clara Co., Cal. Mixture (?). 
 
 HYDROUS PHOSPHATES, ARSENATES, ETC. 
 
 PHARMACOLITB. 
 
 Monoclinic. /A 1= 111 6', i-l A a-2 = 109 26', 1 A 1 = 117 24', 
 Cleavage : ?<4 eminent. One of the faces 1 often obliterated by the exten 
 eion of the other. Surfaces i-i and i-2 usually striated parallel to theii 
 mutual intersection. Rarely in crystals; commonly in delicate silky fibres 
 or acicular crystallizations, in stellated groups. Also botryoidal and stalac- 
 titic, and sometimes massive. 
 
OXYGEN COMPOUNDS. PHOSPHATES, ARSENATES, ETC. 
 
 371 
 
 H.==2-2'5. G. = 2'64r-2'73. Lustre vitreous ; on i-l inclining to pearly 
 Color white or grayish ; frequently tinged red 
 )y arsenate of cobalt. Streak white. Trans- 
 .11 cent opaque. Fracture uneven. 
 USB flexible. 
 
 Thin lam i- 
 
 Comp. 2HCaAs04+5aq= Arsenic pentoxide 51 '1, lime 
 34-9, water 24-0= 100. 
 
 Pyr., etc. In the closed tube yields water and becomes 
 Dpaque. B.B. in O.F. fuses with intumescence to a white 
 anamel, and colors the flame light blue (arsenic). On char- 
 
 3oal in R.F. gives arsenical funus, and fuses to a semi-transparent globule, sometimes tinged 
 >lue from traces of cobalt. The ignited mineral reacts alkaline to test paper. Insoluble in 
 water, but readily soluble in acids. 
 
 Obs. Found with arsenical ores of cobalt and silver at Wittichen, Baden ; at Andreasberg, 
 and at Riechelsdorf and Bieber ; at Joaohimsthal. 
 
 This species was named, in allusion to its containing arsenic, from (pdpnatcov, poison. 
 
 STRUVITE. An ammonium-magnesium phosphate containing 12 equivalents of water. In 
 guano from Saldanha Bay, Africa. 
 
 HAIDINGERITE. HCaAs0 4 +aq.= Arsenic pentoxide 58'1, lime 28'3, water 13 6=100. 
 Foachimsthal (?). 
 
 BRUSHITE. HCaP0 4 (R 3 P.O 8 )-j-2aq=Pho8phorup pentoxide 41-3, lime 32'6, water 61 = 
 [00. Monoclinic. G-.=2 208. On guano at Aves Island and Sombrero. 
 
 METABKUSIIITE. 2HCaP0 4 +3aq. G.=2'35. Sombrero. ORNITHRITE. Probably altered 
 brushite. 
 
 CHUROIIITE. R 3 Pi0 8 +4aq, with R=Ce(Di),Ca. Cornwall. 
 
 WAPPLERITE (Frenzd). Triclinic. In minute crystals and in incrustations. Color white. 
 Composition H,Ca.Mg)As0 4 +7aq=(Ca : Mg=4 : 3) arsenic pentoxide 48'7, lime 13-5, mag- 
 nesia 7'3, water 30 '5 =100. Found with pharmacolite at Joachimsthal. Schrauf states that 
 r&sslerite is a pseudomorph after wapplerite. 
 
 HOERNESITE. Monoclinic. Color snow-white. Composition Mg 3 As 2 8 +8aq. From the 
 Banat. 
 
 PICROPHARMACOLITE. Monoclinic. Ca 3 (Mg 3 )As 2 O 8 -l-Gaq. Riechelsdorf; Freiberg. 
 
 VTVIANITE. 
 
 Monoclinic. O = 75 34', /A 7 = 108 2', 1 A 1 = 120 26', 
 935792 : 1-33369 : 1 ; v. Rath. Surface i-l smooth, others 
 striated. Cleavage : i-l, highly perfect ; i-i and \-i in 
 traces. Often reniform and globular. Structure diver- 
 gent, fibrous, or earthy ; also incrusting. 
 
 II. = 1-5-2. G.=2-58-2-68. Lustre, i-l pearly or me- 
 tallic pearly ; other faces vitreous. Color white or color- 
 less, or nearly so, when unaltered ; often blue to green, 
 deepening on exposure; usually green when seen per- 
 pendicularly to the cleavage-face, and blue transversely ; 
 the two colors mingled, producing the ordinary dirty blue 
 color. Streak colorless to bluish-white, soon changing to 
 indigo-blue; color of the dry powder often liver-brown. 
 Transparent translucent; becoming opaque on expo- 
 sure. Fracture not observable. Thin laminae flexible. 
 Sectile. 
 
 Comp FeP 2 6 -f 8aq= Phosphorus pentoxide 28*3, iron protoxide 43 '0, water 28 '7 =130 
 
 ?&* 
 
372 
 
 DESCRIPTIVE MINERALOGY. 
 
 Pyr., etc. In the closed tube yields neutral water, whitens and exfoliates. B.B. fuses at 
 1*5, coloring the flame bluish- green, to a grayish-black magnetic globule. With the fluxeg 
 reacts for iron. Soluble in hydrochloric acid. 
 
 Diff. Distinguishing characters : deep-blue color ; softness ; solubility in acid. 
 
 Obs Occurs associated with pyrrhotite and pyrite in copper and tin veins ; in beds of 
 
 clay, and sometimes associated with limonite, or bog iron ore; often in cavities of fossils or 
 buried bones. Occurs at Wheal Falmouth, and elsewhere in Cornwall ; in Devonshire, near 
 Tavistock ; at Bodenmais. The earthy variety, called blae iron earth or native Prussian blue 
 occurs in Greenland, Carinthia, Cornwall, etc. At Cransac, Prance. 
 
 In N. America, it occurs in New Jersey, at Allentown ; at Franklin. Also in Delaware, near 
 Middletown ; near Cape flenlopen. In Maryland, in the north part of Somerset and Wor- 
 cester Cos. In Virginia, in Stafford Co. In Canada, with limonite at Vandreuil, abundant. 
 
 LUDLAMITE (Field). Monoclinic. H.=3 4. G.=3-12. Color clear green, from pale to 
 dark. Transparent, brilliant. Composition 2Fe 3 P v ,O 8 + H 2 FeO 2 + 8aq=Phosphorus pentoxide 
 29-88, iron protoxide 53 "06, water 17-06=100. Cornwall. 
 
 ERYTHRITE. Cobalt Bloom. Kobaltbliithe, Germ. 
 
 Monoclinic. C= 70 54', /A 1= 111 16' O A 14 = 146 19'; c : I : d 
 = 0-9747 : 1-3818 : 1. Surfaces i-i and I-i vertically 
 striated. Cleavage : i-\ highly perfect, i-i and \-i indis- 
 tinct. Also in globular and reniform shapes, having a 
 drusy surface and a columnar structure ; sometimes stel- 
 late. Also pulverulent and earthy, incr listing. 
 
 H. 1-5-2-5 ; the lowest on i-i. G.= 2-948. Lustre 
 of i-i pearly ; other faces adamantine, inclining to vitre- 
 ous ; also dull and earthy. Color crimson and peach- 
 red, sometimes pearl- or greenish-gray ; red tints incline 
 to blue, perpendicular to cleavage-face. Streak a little 
 paler than the color ; the dry powder deep lavender- 
 blue. Transparent subtranslucent. Fracture not ob- 
 Schneeberg. servable. Thin laminae flexible in one direction. Sectile, 
 
 Comp. Co 3 As 2 O 8 +8aq= Arsenic pentoxide 38 '40, cobalt oxide 37 '56, water 2404; Co 
 often partly replaced by Fe,Ca, or Ni. 
 
 Pyr., etc. In the closed tube yields water at a gentle heat and turns bluish ; at a highei 
 heat gives off arsenous oxide, which condenses in crystals on the cool glass, and the residue 
 has a dark gray or black color. B. B. in the forceps fuses at 2 to a gray bead, and colors the 
 flame light blue (arsenic). B.B. on charcoal gives an arsenical odor, and fuses to a dark gray 
 arsenide, which with borax gives the deep blue color characteristic of cobalt. Soluble in 
 hydrochloric acid, giving a rose-red solution. 
 
 Obs. Occurs at Schneeberg in Saxony ; at Saalfeld in Thuringia ; Wolfach and Witticher 
 in Baden; Modum in Norway; at Allemont in Dauphiny; in Cornwall, at the Botallack 
 mine, etc. 
 
 Erythrite, when abundant, is valuable for the manufacture of smalt. Named from 3pv6p6s, 
 red. 
 
 ROSELITE.* Triclinic (Schrauf). Usually in complex twin crystals. H.=3'5. G. =3-585 
 -3'738. Color rose-red. Composition R 3 As 2 O 8 +2aq (or 3aq), with R=Ca,Mg, and Co. Ana- 
 lysis, Winkler, As 2 O 6 49'96, CoO 12'45, CaO 23-72, MgO 4 '67, H 2 O 9-69=100 "49. Found at 
 Schneeberg, Saxony ; the crystals from the Daniel Mine have a lighter color than those of the 
 Rappold Mine, the latter containing less cobalt and more calcium. 
 
 WINKLEKITE. Contains As 2 6 ,Cu,eo,Fe,Co,Ni,Ca,H,O,CO 2 , etc. Mixture (?). Pria, 
 Spain. 
 
 KOTTIGITR. Near erythrite, but contains zinc. Schneeberg. 
 
 ANNABERGITE (Nickelbliithe, Germ.}. Ni 3 As 2 O 8 f-8aq= Arsenic pentoxide 38'6, nickel 
 oxide 37 "2, water 24-2=100. Soft, earthy. Color apple-green. Allemont; Annaberg ; 
 Biechelsdorf. 
 
 HUKEAULITE. A hydrous iron-manganese phosphate, O3curing in cavities in triphylit* 
 at Limoges, France. 
 
 CHONDRARSEKITE. Yellow grains in barite ; probably a manganese arsenate. Paisberg, 
 Sweden. 
 
OXYGEN COMPOUNDS. PHOSPHATES, AKSENATES, ETC. 
 
 373 
 
 = 0-7311 
 
 LEBETHENITB. 
 
 Orthorhombic. /A 1= 92 20', O A l-l = 143 50' ; 
 
 1*0410 : 1. Crystals usually octahedral in aspect. 
 
 leavage : diagonal, i-l, i-%, very indistinct. Also globu- 
 ar or reniform, and compact. 
 
 .^4. G.=3'6-3-8. Lustre resinous. Color olive- 
 green, generally dark. Streak olive-green. Translucent. 
 io subtranslucent. Fracture subconchoidal uneven. 
 Brittle. 
 
 Comp. Cu 4 P 2 O 9 -f-aq, or Cu 3 P 2 8 -hH 2 Cu0 2 (Ramm.)= Phosphorus 
 pentoxide 29 '7, copper oxide 66 '5, water 3 '8 =100. 
 
 Pyr., etc. In the closed tube yields water and turns black. B.B. 
 'fuses at 2 and colors the flame emerald-green. On charcoal with soda 
 gives metallic copper, sometimes also an arsenical odor. Fused with 
 metallic lead on charcoal is reduced to metallic copper, with the forma- 
 tion of lead phosphate, which treated in R.F. gives a crystalline polyhedral bead on cooling. 
 With the fluxes reacts for copper. Soluble in nitric acid. 
 
 Obs. Occurs at Libethen, in Hungary ; at Rhembreitenbach and Ehl on the Rhine ; at 
 Nischne Tagilsk in the Ural ; in Bolivia ; Chili 
 
 \ 
 
 = 0-72 : 
 
 680 
 
 if 
 
 OLIVBNITE. 
 
 Orthoi-hombic. /A 1= 92 30', A 14 - 144 14' ; c : 
 1*044:6 : 1. Cleavage: / and 14 in traces. Sometimes aci- 
 cular. Also globular and reuiform, indistinctly fibrous, 
 fibres straight and divergent, rarely promiscuous; also 
 curved lamellar and granular. 
 
 H.=3. Gr.=4-l-4-4. Lustre adamantine vitreous ; of 
 some fibrous varieties pearly. Color various shades of olive- 
 green, passing into leek-, siskin-, pistachio-, and blackish- 
 green ; also liver- and wood- brown ; sometimes straw-yellow 
 and grayish-white. Streak olive-green brown. Subtrans- 
 parent opaque. Fracture, when observable, conchoidal 
 uneven. Brittle. 
 
 Com P .-Cu 4 As 2 O a +aq=Cu 3 As 2 8 +H 2 Cu0 2 (Ramm.)= Arsenic pentoxide 40'66, coppei 
 
 X pyr! etl' Tnlhe closed tube gives water. B.B. fuses at 2, coloring the flame bluish-green, 
 and on cooling the fused mass appears crystalline. B. B. on charcoal fuses with deflagration, 
 gives off arsenical fumes, and yields a metallic arsenide, which, with soda yields a globule 
 copper. With the fluxes reacts for copper. Soluble in nitric acid. . . 
 
 Obs. The crystallized varieties occur in many of the Cornwall mines ; near Tavistock in 
 Devonshire ; also at Alston Moor in Cumberland ; at Camsdorf and Saalf eld in Thunngia ; tJ: 
 Tyrol; the Banat; Siberia; Chili; and other places. oi_inn 
 
 ADAMITE. Zn3AsoO 8 +H 2 ZnO 2 =:Arsenic pentoxide 40'2, zinc oxide 56 '7, water d 
 Color yellow. Chanarcillo, Chili ; Cap Garonne. 
 
 TAGILITE -Cu 4 P 2 O 9 +3aq (=Cu 3 P 2 O8+H 2 CuO.+2aq). Color emerald-green. 
 Tagilsk. ISOCLASITE. Ca 4 P-,0 9 +5aq (=Ca 3 P 2 O 8 + H 2 CaO 2 + 4aq). Colorless to snow-white. 
 
 EucnROirE. Cu 3 AsoO 8 +H 2 CuO 2 -H6aq (Ramm.)= Arsenic pentoxide 34'1, copper oxide 
 47-2. water 18 '7= 100. Color emerald -green. Libethen, Hungary. 
 
 CHLOKOTILE. Cu s As 2 O 8 + 6aq. In capillary crystals. Also fibrous^; massive. Color apple- 
 green. In quartz at Schneeberg and Zinnwald ; Thuringia; Chili (^ re ^ff>- K 
 
 VESZELYITE (Schranf).-A hydrous copper phosphate ; composition 4Cu 3 l 2 O 8 +oaq. 
 clinic. Occurs in crystalline crusts on a garnet-rock at Morawicza in the Banat. 
 
 Tri- 
 
374: DESCRIPTIVE MINER ALOOY. 
 
 LIROCONITE. Linsenerz, Germ. 
 
 Monoclinic. /A 7 -=74 21', DesCl. C = 88 33'. Cleavage lateral, 
 but obtained with difficulty. Rarely granular. 
 
 Ii. 2-2-5. G. = 2'88-2*98. Lustre vitreous, inclining to resinous. 
 Color and streak sky-blue verdigris-green. Fracture imperfectly 'on- 
 choidal, uneven. Imperfectly sectile. 
 
 Comp. Formula Cu 3 (rU) As 2 (P.,)0 8 +H 6 (Cu3.Al)0 6 -l-9aq, with Cu 3 : Al=3 : 2, and As : 
 P=l : 4. This requires arsenic pentoxide 23 *1, phosphorus pentoxide 3 "6, copper oxide 35 '9 
 alumina 10 '3, water 27 '1100. 
 
 Fyr-, etc. In the closed tube gives much water and turns olive-green. B.B. cracks open, 
 out does not decrepitate ; fuses less readily than olivenite to a dark gray slag ; on charcoal 
 cracks open, deflagrates, and gives reactions like olivenite. Soluble in nitric acid. 
 
 Obs. With various ores of copper, pyrite, and quartz, at Wheal Gorland, Wheal Muttrell, 
 etc.. in Cornwall; also in minute crystals at Herrengrund in Hungary ; and in Voigtland. 
 
 PSEUDOMALACHITE Phosphochaltite. Cu 6 P.Oi i +3aq=:Cu 3 P,O 8 +3H 2 Cu0 2 =:P 2 O5 21 1 , 
 CuO 70-9, H 2 O 8*0=100. Triclinic (Schrauf). G.=4'34. Color emerald-green. Related 
 sub-species: EHLITE (Prasine), Cu 3 P-iO 8 + 2H 1 CuO^ + aq (Ramm.) ; DIIIYDKITE, Cu 3 PiO ri + 
 2H 2 CuO 2 . Eh.1, near Liuz, on the Rhine ; Libethen, Hungary ; Nischne Tagilsk ; Cornwall. 
 
 ERINITE. Cu 3 As 2 O8+2H 2 CuO 2 . In mammillated crystalline groups. Color green. Corn- 
 wall. 
 
 CORN WALL ITE. Cu 6 AB 2 Oio+3aq (=Cu 3 As 2 08+2H 2 Cu0 2 + aq). Amorphous. Color green. 
 Cornwall (Church). 
 
 PSITTACINTTE. Occurs in thin crypto-crystalline coatings, sometimes having a botryoidaJ 
 structure ; also pulverulent. Color siskin green to olive-green. Formula 2R 3 V-.'O 8 -I- 3H 2 CuO a 
 +6aq, with R=Pb : Cu=3 : 1. This requires : Vanadium pentoxide 19'32, lead oxide 53*15, 
 copper oxide 18*95, water 8 58=100. Found at the gold mines in Silver Star District, Mon- 
 tana (Genth. Am. J. Sci., III., xii., 35, 1870). 
 
 MOTTKAMITE. Occurs as a thin crystalline incrustation, which is sometimes velvety, con- 
 sisting of minute crystals ; more generally compact H. =3. G. =5 '894. Color black by 
 reflected light, in thin particles yellowish, translucent (crystals) ; purplish-brown, opaque, 
 (compact). Formula (Pb,Cu) 3 V 2 O8 + 2H 2 (Pb,Cu)O_>, which requires vanadium pentoxide 18*74, 
 copper oxide 20 '39, lead oxide 57'18, water 3 '69= 100. Related to dihydrite and srinite. 
 Found in Keuper sandstone at Alderley Edge and Mottram St. Andrew's, in Cheshire, 
 England (Roscoe, Proc. Roy. Soc., xxv./III., 1876). 
 
 VOLBORTHITE. R 4 V 2 O 9 -i-aq, with R^Ca : Cu=2 : 3 (or 3 : 7), Ramm. From the Urals. 
 Kalk-volborthit (Germ.), Friedrichsrode, contains calcium. 
 
 OLINOOLASITE. Strahlerz, Germ. 
 
 Monoclinic. C= 80 30 r , /A/, front, = 56. Cleavage : basal, highly 
 perfect. Also massive, hemispherical, or reniform*; 
 681 structure radiated fibrous. 
 
 H.=2-5-3. G.=4-19-4-36. Lustre: pearly; 
 elsewhere vitreous to resinous. Color internally dark 
 verdigris-green; externally blackish-blue green. Streak 
 bluish-green. Subtranslucent. Not very brittle. 
 
 Comp. Cu3As 2 8 4-3H 2 Cu0 2 :=Arsenic pentoxide 30-2, conpei 
 oxide 62*7, water 7 1-100. 
 
 Fyr., etc. Same as for olivenibe. 
 
 Obs. Occurs in Cornwall, with other ores of copper, at several 
 mines. Also found in the Erzgebirge 
 
 TYROLITE (Kupferschaum). A hydrous arsenate of copper (Ou t 
 containing also calcium carbonate (as an impurity ? ) 
 
 Color pale apple-green. Libethen. Hungary ; Schneeberg, etc. 
 
OXYGEN COMPOUNDS. PHOSPHATES, AiiSENATES, ETC, 375 
 
 CHALCOPHYLLITE (Copper mica; Kupferglimmer, Germ.). Cu 3 As 2 0845H 2 Cu0 2 + 7H 2 O- 
 Arsenic pentoxide 21 '3, copper oxide 58 '7, water 20 "0=100. Copper mines of Cornwall, 
 Hungary ; Moldawa. 
 
 LAZULITE. Blauspath, Germ. 
 
 Monoclinic. C = 88- 15', / A 1 = 91 30', A 14 --= 139 45', Priifer ; 
 c : b : d = 0-86904 : 1-0260 : 1. Twins : twiuning-plane i-i\ also 0. Cleav- 
 age : lateral, indistinct. Also massive. 
 
 683 684 
 
 -2 
 
 H =5-6 G.=3-057, Fuchs. Lustre vitreous. Color azure- bl ue ; com- 
 monly a fine deep blue viewed along one axis, and a pale greenish-blue 
 along another. Streak white. Subtranslucent opaque. Fracture uneven. 
 
 Brittle. 
 
 Comp. 
 
 (Dana) = Phosphorus pentoxide 46 "8, alu- 
 
 RAlP 2 9 +aq=AlP 2 8 +H 2 (Mg,Fe)0 2 
 -!n e the* clirtube"^*! and yields water. B.B. with cobalt solution the 
 
 , in Krieglach, i 
 
 :Sj^ft2^iSB!SsBBM-w 
 
 N C ; and on Graves Mt., Lincoln Co, Ga, 50 m. above Augusta. 
 
 SCORODITE. 
 1 A /= 98 2', 0A1-I 
 
 _ 7 132 20'; d 
 
 Cleavage : i-2 imperfect, i-i and i-l in 
 
 Orthorhombic. 
 1-1511 : 1, Miller, 
 traces. 
 
 jj 3.5-4 G.=3-l-3-3. Lustre vitreous subadaman- 
 tine and subresinous. Color pale leek-green or liver-brown. 
 Streak white. Subtransparent translucent. 
 
 Comp.-FeAs 2 8 +4aq=Arseiiic pentoxide 49'8, iron sesquioxide 
 
 -r Va etl In~the closed tube yields neutral water and turns yellow. 
 BB fuses easily, coloring the flame blue. B.B. on ^ c al fl ^ 
 arsenical fumes, and with soda a black magnetic scona. With the fluxes 
 reacts for iron. Soluble in hydrochloric acid. 
 
376 DESCRIPTIVE MINERALOGY. 
 
 Obs. Found at Schwarzenberg in Saxony ; at Nertschinsk, Siberia ; Dernbach in Nassau ; 
 in the Cornish mines ; at the Minas Geraes, in Brazil ; in Popayan ; at the gold mines of Vic- 
 toria in An; tralia. Occurs in minute crystals and druses, near Edeiiville, N. Y. : in Cabarras 
 Co., N. C. 
 
 WAVELLITE. 
 
 Orthorhombic. /A I 126 25', A 14 = 143 23' ; c : I : & = O7431 
 : 1*494:3 : 1. Cleavage : 1 rather perfect ; also brachydia- 
 686 gonal. Usually in hemispherical or globular concretions, 
 
 having a radiated structure. 
 
 H.=3-25-4. G.=:2-316-2-337. Lustre vitreous, inclin- 
 ing to pearly and resinous. Color white, passing into yel- 
 low, green, gray, brown, and black. Streak white. Trans- 
 lucent. 
 
 Comp Al 3 P 4 O 
 
 ide3516, alumina 38 10, water 26 '74=100; 1 to 2 p. c. fluorine is often 
 present, replacing the oxygen. 
 
 Pyr., etc. In the closed tube gives off much water, the last portions 
 of which react acid and color Brazil-wood paper yellow (fluorine), and 
 also etch the tube. B B. in the forceps swells up and splits frequently into fine acicular 
 particles, which are infusible, but color the flame pale green ; moistened with sulphuric acid 
 the green becomes more intense. Gives a blue with cobalt solution. Some varieties react 
 for iron and manganese with the fluxes. Heated with sulphuric acid gives off fumes of fluo- 
 hydric acid, which etch glass. Soluble in hydrochloric acid, and also in caustic potash. 
 
 Diff. Distinguished from the zeolites and from gibbsite by its giving a phosphorus reac- 
 tion ; it dissolves in acid without gelatinization. 
 
 Obs. Found near Barnstaple, Devonshire ; at Clonmel and Cork, Ireland ; in the Shiant 
 Isles of Scotland ; at Zbirow in Bohemia; Zajecovin Bohemia; at Frankenberg and Langen- 
 striegis, Saxony ; Diensberg, near Giessen, Hesse Darmstadt ; in a manganese mine in Wein- 
 bach, near Weilburg, in Nassau ; at Villa Rica, Minas Geraes, Brazil. In the United States, 
 at the slate quarries of York Co., Pa.; at Washington mine, Davidson Co., N. C.; at White 
 Horse Station, Chester Co., Pa ; Magnet Cove, Ark. 
 
 ZEPIIAROVICHITE. Near wavellite. Composition A1P 2 8 + 6aq (or 5aq, Kamm.). Compact. 
 Color greenish to grayish. Occurs in sandstone at Trenic, Bohemia. 
 
 CCERULEOLACTITE. Crypto-crysta'lline. Color milk-white to light blue. Composition 
 (Petersen) Al 3 P 4 Oi9 + 10aq. Katzenellnbogen. Nassau. Also Chester Co., Penn. (Genth, 
 who regards the copper, 4 p. c., as belonging to the mineral.) 
 
 PHARMACOSIDERITE. Wiirfelerz, Gain. 
 
 Isometric ; tetrahedral. Crystals modified cubes and tetrahedrons. 
 Cleavage: cubic, imperfect. O sometimes striated parallel to its edge of 
 intersection with plane 1 ; planes often curved. Rarely granular. 
 
 H. = 2'5. G.=2'9-3. Lustre adamantine to greasy, not very distinct 
 Color olive-green, passing into yellowish-brown, bordering sometimes upon 
 hyacinth-red and blackish-brown ; also passing into grass-green, emerald- 
 green, and honey -yellow. Streak green brown, yellow, pale. Subtrans- 
 parent subtranslucent. Rather sectile. Fyroelectric. 
 
 Oomp Fe 4 A3 6 027,15aq=3FeAs 2 8 +H 6 Fe0 6 + 12H 2 0- Arsenic pentoxide 43'13, iron 
 esquioxide 40 '00, water 16 '87 =100. 
 
 Pyr., etc. Same as for scorodite. 
 
 Obs.- -Formerly obtained at the mines of Wheal Gorland, Wheal Unity, and Carharrack, 
 in Cornwall ; now found at Burdle Gill in Cumberland ; in minute tetrahedral crystals at 
 Wheal Jane ; also in Australia ; at St. Leonard in I ranee and at Sv oneeberg and Sch war- 
 sen berg in Saxony. 
 
OXYGEN COMPOUNDS. PHOSPHATES, AKSENATE8, ETC. 377 
 
 Named from ^dp/LLaKov, poison (in allusion to the arsenic present), and <r5rj/>ov, iron. Wurfd- 
 erz, of the Germans, means cube-ore. 
 
 RIIAGITE (Wdsbach}. Composition Bi 10 As40 2 5-f 9aq=2BiAsO 4 +3H 3 Bi0 3 :=Arsenic pent- 
 oxide 15'6, bismuth oxide ?8'9, water 5'5=100. Spherical crystalline aggregates. Coloi 
 bright green. Schneeberg, Saxony. 
 
 PLUMBOGUMMITE. Composition uncertain. Contains essentially alumina, lead, water, 
 and phosphorus pentoxide. Huelgoeb ; Cumberland ; Mine la Motte, Mo. 
 
 CHILDRENITE.* 
 
 Orthorhombic. 1 A /= 111 54', A 14 = 136 26' ; c : I : d = 0-9512 
 1-4798 : 1. Plane O sometimes wanting, and the form a double six- 
 eided pyramid, made up of the planes 1, 2-, with i-l small. Cleavage : i-$ 9 
 imperfect. 
 
 H.=4'5-5. G. 3-18-3-24. Lustre vitreous, inclining to resinous. 
 Color yellowish-white and pale yellowish-brown, also brownish-black 
 Streak white, yellowish. Translucent. Fracture uneven. 
 
 Comp. Formula somewhat uncertain. Analysis: Rammelsberg, P 2 O 5 28 92, A10 3 14 '44, 
 FeO 30-68, MnO 9'07, MgO (H4, H. 2 O 16'98=100'23. 
 
 Pyr., etc In the closed tube gives off neutral water. B.B. swells up into ramifications, 
 and fuses on the edges to a black mass, coloring the flame pale green. Heated on charcoal 
 turns black and becomes magnetic. With soda gives a reaction for manganese. With borax 
 and salt of phosphorus reacts for iron and manganese. Soluble in hydrochloric acid. 
 
 Obs. Occurs near Tavistock ; also at Wheal Crebor, in Devonshire ; on slate at Crinnia 
 mine in Cornwall. Hebron, Me. (f. 688.). 
 
 TJRQUOIS. Callaite. Kallait, Kalait, Germ. 
 
 Reniform, stalactitic or incrusting. Cleavage none. 
 
 H.=6. G-.rr 2*6-2-83. Lustre somewhat waxy, feeble. Color sky-blue, 
 bluish-green to apple-green. Streak white or greenish. Feebly subtrans- 
 lucent opaque. Fracture small conchoidal. 
 
 Comp. Hydrous aluminum phosphate, perhaps AlaPsOn+Saq^: Phosphorus pentoxide 
 32'G, alumina 46-9, water 20-5 = 100 
 
 Pyr., etc. In the closed tube decrepitates, yields water, and turns brown or black. B.B. 
 in the forceps becomes brown and assumes a glassy appearance, but does not fuse ; colora 
 the flame green; moistened with hydrochloric acid the color is at first blue (copper chloride). 
 With the sodium test gives phosphuretted hydrogen. With borax and salt of phosphorus gives 
 beads in 0. F. which are yellowish green while hot, and pure green on cooling. With salt of 
 phosphorus and tin on charcoal gives an opaque red bead (copper). Soluble in hydrochloric 
 acid. 
 
 Obs. Occurs in clay slate in a mountainous district in Persia, not far from Nichabour. 
 According to Agaphi, the only naturalist who has visited the locality, turquois occurs only in 
 veins, which traverse the mountain in all directions. An impure variety is found in Silesia, 
 
378 DESCRIPTOR MINERALOGY. 
 
 and at Oelsnitz in Saxony. W. P. Blake refers here to a hard yellowish- to bluish-green stone 
 (which he identifies with the clmlcWmitl of the Mexicans) from the mountains Los Cerillas, 
 20 m. S. E. of Santa Fe. A pale green turquois occurs in the Columbus district, Nevada. 
 
 Turquois receives a good polish, and is highly esteemed as a gem. The Persian king is 
 said to retain for his own use all the larger and finely tinted specimens. 
 
 PEGANITE. Composition AljP 2 Ou -t-6aq= Phosphorus pentoxide 31 1, alumina 31 '1, 
 water 23 7= 100. Striegis, Saxony. 
 
 DUFRENITE. Composition Fe 2 P,O u +3aq (FeP.20,i+H 6 FeO 6 ) = Phosphorus pentoxide 
 27*5, iron sesquioxide 62'0, water 10-5=100. Anglar, Dept. of Haute Vieune ; Hirschberg, 
 Westphalia ; Allentown, N. J. In deposits of nodules 1 to 6 in. thick, in Rockbridge Co., Va 
 
 ANDREWSITE. In globular forms, having a radiated structure. H.=4. G.=3'475. 
 Color dark green. Analysis, Plight. P 2 5 26-09, FeO 3 44-64, A1O 3 0'92, CuO 10 86, FeO 711, 
 MnO 0-60, CaO 0'09, Si0 2 0'49, H 2 8 -79 =99 '59. In a tin lode, West Phenix mine, near 
 Liskeard, Cornwall. 
 
 CHALCOSIDERITE. In bright green crystals (triclinic) on Andrewsite (see above). H. = 
 4-5. G.=3108. Analysis, Flight, P 2 O 5 29 93, As,0 5 0'61, Fe0 3 42 -81, A1O 3 4-45. CuO 8 '14, 
 H,0 15-00, UO 3 tr.=100-94. Also as a coating on dufrenite. Cornwall. Sayn, Westphalia. 
 
 HENWOODITE. In globular forms, with a radiated structure. H.=4-4 5. G. = 2-67. 
 Color turquois-blue to bluish -green. B.B. infusible. Analysis, P& 5 48'94, A10 3 18'24, 
 FeO 3 2-74, CuO 710, CaO 54, H 2 O 1710, SiO 2 1-37, loss 3 '97=100. Occurs on limonite at 
 the West Phenix mine, Cornwall (Collins^ Min. Mag., 1, p. 11). 
 
 CACOXEN IT E. Supposed to be an iron wavellite. Composition FeaP.jOj.+lSaq. In ra- 
 diated tufts. Color yellow. Hrbeck mine, Bohemia. 
 
 ARSENIOSIDERITE. Analysis by Church, As 2 O 6 39*86, Fe0 3 35-75, CaO 15'53, MgO 018, 
 K 2 O 0-47, H,O 7-87=9966. Formula (Eamm.) 2Ca 3 As 2 O 8 +FeAs i 8 + 3H 6 Fe0 6 . Ro- 
 maneche. 
 
 ATELESTITE. Essentially a bismuth arsenate. In minute yellow crystals at Schneeberg. 
 
 TORBERNTTE. Chalcolite. Kupfer-Uranit, Germ. 
 
 Tetragonal. O A 14 = 134: 8' ; c = 1-03069. Forms square tables, with 
 often replaced edges ; rarely suboctahedral. Cleav- 
 age : basal highly perfect, micaceous. Unknown 
 massive or earthy. 
 
 H. = 2-2-5. G.=3-4-3-6. Lustre of O pearly, of 
 other faces subadamantine. Color emerald- and 
 grass green, and sometimes leek-, apple-, and sis- 
 Cornwall, kin-green. Streak somewhat paler than the color. 
 Transparent subtranslncent. Fracture not ob- 
 servable. Sectile. Laminae brittle and not flexible. Optically uniaxial ; 
 double refraction negative. 
 
 Comp. Q. ratio f or R : U : P : O=l : 6 : 5 : 8 ; formula CuU 2 P 2 O 12 + 8aq=2(UOo) 3 P,O 
 + Cu 3 P.,0 8 +24aq. The formula requires: Phosphorus pentoxide 151, uranium tricside 
 61-2, copper oxide 8 '4, water 15 '3 = 100. 
 
 Pyr., etc. In the closed tube yields water. In the forceps fuses at 2 '5 to a blackish mass, 
 and colors the flame green. With salt of phosphorus gives a green bead, which with tin on 
 charcoal becomes on cooling opaque red (< opper). With soda on charcoal gives a globule of 
 copper. Affords a phosphide with the sodium test. Soluble in nitric acid. 
 
 Obs. Grunnis Lake, Tincroft and Wheal Buller, near Redruth, and elsewhere in Cornwall. 
 Found also at Johanngeorgenstadt, Eibenstock, and Schneeberg, in Saxony ; in Bohemia, at 
 Joachimsthal and Zinnwald ; in Belgium, at Vielsalm. 
 
 Both this species and the autunite have gone under the common name of uranite ; the 
 former also as Copper-uranite^ the latter Lime-uranite. 
 
OXYGEN COMPOUNDS. PHOSPHATES, ARSENATES, ETC. 379 
 
 AUTUNITE.* Uranit; Kalk-Uranglimmer, Kalk-Uranit, Germ. 
 
 Orthorhombic ; but form very nearly square, and crystals resembling 
 closely those of torbernite. Cleavage : basal eminent, as in torbernite. 
 
 H. = 2-2'5. Gr.^3'05-3'19. Lustre of pearly ; elsewhere subadaman- 
 tine. Color citron- to sulphur-yellow. Streak yellowish. Translucent. 
 Optically biaxial, DesCl. 
 
 Comp. Q. ratio f or R : U : P : H=l : 6 : 5 : 10. Formula CaU 2 P 2 Oi 2 + 10aq, which may 
 be written 2(U0 2 ) 3 P...O8 + Ca 3 P 2 084-30aq. The formula requires : Phosphorus pentoxide 14 '9, 
 uranium fcrioxide (U0 3 ) 60'4, lime 5 % 9, water 18-8=100. 
 
 Pyr., etc. Same as for torbernite, but no reaction for copper. 
 
 Obs. Occurs at Johanngeorgenstadt ; at Lake Onega, Wolf Island, Russia; near Limoges; 
 near Autun ; formerly at South Basset, Wheal Edwards, and near St. Day, England. Occura 
 sparingly at Middletown, Ct. ; also in minute crystals at Chesterfield, Mass. ; at Acworth, 
 N. H. 
 
 TROGERITE. Composition TJ 3 As 2 Oi4 -I- 12aq=(U0 2 ) 3 As 2 O 8 + 12aq. This requires : Arsenic 
 pentoxide 17*6, uranium trioxide 05 "9, water 16 '5= 100. Monoclinic. In thin tabular crys- 
 tals of a lemon-yellow color. Schneebertf, Saxony. 
 
 WALPURGITE. Composition Bi 1 oy 3 As40 3 4 + 12aq=(U0 2 ) 3 As,O 8 -f2BiAs04+8H,Bi03. This 
 requires: Arsenic pentoxide 11 '9, bismuth oxide (>0'0, uranium trioxide 22'4, water 5 '7= 100. 
 Monoclinic. In thin scaly crystals. Color wax-yellow. Schneeberg, Saxony. 
 
 URANOSPINITE. An arsenic autunite. Composition CaU 2 As 2 12 + 8aq3=2(UO,)sAs 2 08 + 
 Ca 3 As 2 8 +24aq=Arsenic pentoxide 22'9, uranium trioxide 57 '2, lime 5'6, water 14'3 = 100. 
 Color green. Schneeberg, Saxony. URANOSPH^RITE. Color yellow. Analysis, Winkler : 
 U 3 50-88, Bi 2 3 44'34, H 2 O 4-75. Schneeberg. 
 
 ZEUNERITE. According to Winkler, an arsenic chalcolite, with which it is isomorphous. 
 Composition CuU 2 As 2 Oi 2 +8aq=2(U0 2 ) 3 As.208 + Cu 3 As 2 8 +24aq=Arsenic pentoxide 22'3, 
 uranium trioxide 56'0, copper oxide 7 '7, water 14'0=100. Color bright green. Schneeberg, 
 Zinnwald, Saxony ; Cornwall. 
 
 PITTICITE. Iron-sinter. Composition uncertain, contains As^Os, Fe0 3 , S0 3 , H 2 0. DlA- 
 DOCHITB is similar, but contains P 2 5 instead of As 2 O 6 . 
 
 HYDROUS ANTIMONATES. 
 
 BINDHEIMITE (Blemiere). Amorphous, reniform, or spheroidal ; also earthy or incrusting. 
 H.:=4. G. 4 '60-4 '76. Color white, gray, brownish, yellowish. Composition uncertain; 
 analysis by Hermann : Sb-O 5 31-71, PbO 61 '83, H 2 O 6'46=100. Results from the decompo- 
 sition of other antimonial ores. From Nertschinsk in Siberia ; Horhausen ; near Endelliou 
 in Cornwall, with jamesonite, from which it is derived. 
 
 NITRATES. 
 
 The nitrates are all soluble, and hence are rarely met with in nature. They inr lude : 
 
 NITRE, potassium nitrate (KNO 3 ). Found generally in crusts on the surface of the soil, on 
 walls, rocks, etc. Also found in numerous caves in the Mississippi Valley. 
 
 SODA NITRE, sodium nitrate (NaNO,). Tarapaca, Chili. 
 
 NITROCALCITE. calcium nitrate (CaN 2 6 ). Occurs in silky efflorescences in limestone 
 caverns. 
 
 NITROMAGNESITE, magnesium nitrate (MgN 2 O a ). From limestone caves. NITBO- 
 OLAUBERITE, nitro- sulphate of sodium. Desert of Atacama, Chili. 
 
380 DESCRIPTIVE MINERALOGY. 
 
 4. EQUATES. 
 
 SASSOLTTE. 
 
 Triclinic. /A/' == 118 30', 6> A 7= 95 3', O A /' = 80 33', B. & M. 
 Twins: composition -face O. Cleavage: basal very perfect. Usually in 
 Binall scales, apparently six-sided tables, and also in stalactitic forms, com- 
 posed of small scales. 
 
 H.:=l. G.= 1*4:8. Lustre pearly. Color white, except when tinged 
 yellow by sulphur; sometimes gray. Feel smooth and unctuous. Taste 
 acidulous, and slightly saline and bitter. 
 
 Comp. H 6 Bi0 6 =Boron trioxide (B 2 3 ) 56 '46, water 43 '54=100. The native stalactitic 
 salt contains, mechanically mixed, various impurities, as sulphate of magnesium and iron, 
 sulphate of calcium, silica, etc. 
 
 Pyr., etc. In the closed tube gives water. B. B. on platinum wire fuses to a clear glass 
 and tinges the flame yellowish-green. Soluble in water and alcohol. 
 
 Obs. First detected in nature by Heifer in the waters of the Tuscan lagoons of Monte 
 Rotondo and Castelnuovo, and afterward in the solid state at Sasso by Mascagni. The hot 
 papers of the lagoons consist largely of it. Exists also in other natural waters, as at Wies- 
 baden ; Aachen; Krankenheil near Folz ; Clear Lake in Lake Co., California; and it has 
 been detected in the waters of the ocean. Occurs also abundantly in the crater of Vulcano, 
 one of the Lipari islands, forming a layer on sulphur and about the fumaroles, where it was 
 iiscovered by Dr. Holland in 1813. 
 
 SUSSEXITE (Brush). 
 
 In fibrous seams or veins. 
 
 H.=3. Gr.= 3*4:2. Lustre silky to pearly. Color white, with a tinge of 
 pink or yellow. Translucent. 
 
 Comp. ILBoOs+aq, with R=rMn : Mg=4 : 8=Boron trioxide 34'3, manganese protoxide 
 J9-9. magnesia 16'9, water 8'9 = 100. 
 
 Pyr., etc. In the closed tube darkens in color and yields neutral water. If turmeric paper 
 B moistened with this water and then with dilute hydrochloric acid it assumes a red color 
 ;boron). Fuses in the flame of a candle, and B.B. in O.F. yields a black crystalline mass 
 ioloring the flame intensely yellowish-green. Reacts for manganese with the fluxes. Soluble 
 n hydrochloric acid. 
 
 Oba Found on Mine Hill, Franklin Furnace, Sussex Co., N. J.; associated with franklin- 
 ,te. zincite, willemite, and other manganese and zinc minerals. 
 
 SZAIPELYITE. A hydrous magnesium borate, Mg 5 B 4 Oi i +3aq (or f aq). Occurs in acicular 
 crystals. Color white. Hungary. 
 
 LUDWIGITE ( Tschennak}. Finely fibrous masses. H. =5. G-. =3'907-4'016. Color black 
 sh-green to black. Composition R 4 FeB 2 O 10 , with R=Fe : Mg^l : 5, or 1 : 3. For the 
 atter the formula requires : Boron trioxide 16 6, iron sesquioxide 37 '9, iron protoxide 17*1, 
 magnesia 28 '4. Occurs in a crystalline limestone with magnetite at Morawicza in the Banat. 
 ilso altered to limonite. 
 
OXYGEJS COMPOUNDS. BORATE8. 381 
 
 BORACITE.* 
 
 Isometric; tetrahedral. Cleavage: octahedral, in traces. Cubic faces 
 sometimes striated parallel to alternate pairs of edges, as in pyrite. 
 
 H. 7, in crystals; 4'5, massive. G.=2'974, Haidinger. Lustre vitre- 
 ous, inclining to adamantine. Color white, inclining 
 to gray, yellow, and green. Streak white. Sub- 69 
 
 transparent translucent. Fracture conchoidal, un- 
 even. Pyroelectric, and polar along the four octa- 
 hedral axes. 
 
 (. rl 
 
 \ 
 
 Comp. Mg 7 Bi 6 CL0 8 o = 2Mg s B 6 Oi6+MgCl 2 = Boron trioxide 
 62 57, magnesia 31 -28, chlorine 7 "93 =101 "78. 
 
 Pyr., etc. The massive variety gives water in the closed tube. 
 B.B. both varieties fuse at 2 with intumescence to a white crys- 
 talline pearl, coloring the flame green ; heated after moistening 
 
 with cobalt solution assumes a deep pink color. Mixed with copper oxide and heated on char- 
 coal colors the flame deep azure-blue (copper chloride). Soluble in hydrochloric acid. Alters 
 very slowly on exposure, owing to the magnesium chloride present, which takes up water. 
 
 Obs. Observed in beds of anhydrite, gypsum, or salt. In crystals at Kalkberg and Schild- 
 stein in Liineberg, Hanover ; at Segeberg, near Kiel, in Holstein ; at Luneville, La Meurthe, 
 France ; massive and crystallized at Stassfurt, Prussia. 
 
 BORAX. Tinkal of India. 
 
 Monoclinic. (7= 73 25', /A 1= 87, A 24 = 132 49' ; t : I : d = 
 0*4:906 : 0-9095 : 1. Cleavage: i-i perfect; /less so; i-l in traces. 
 
 H.=2-2*5. G. = l*716. Lustre vitreous resinous; sometimes earthy. 
 Color white; sometimes grayish, bluish, or greenish. Streak white. 
 Translucent opaque. Fracture conchoidal. Rather brittle. Taste sweet- 
 ish-alkaline, feeble. 
 
 Oomp Na 2 B 4 O 7 +10aq=2(NaBO a -|-HBO.)-h9aq=Boron trioxide 36 '6, soda 16 '2, water 
 47-2. 
 
 Pyr., etc. B.B. puffs up, and afterwards fuses to a transparent globule, called the glass of 
 borax. Soluble in water, yielding a faintly alkaline solution. Boiling water dissolves double 
 its weight of this salt. 
 
 Obs. Borax was originally brought from a salt lake in Thibet. It is announced by Dr. J. 
 A. Veatch as existing in the waters of the sea along the California coast, and in those of 
 many of the mineral springs of California. Occurs in the mud of Borax Lake, near Clear 
 Lake, Cal. Also found in Peru ; at Halberstadt in Transylvania ; in Ceylon. It occurs in 
 solution in the mineral springs of Chambly, St. Ours, etc., Canada East. The waters of Borax 
 Lake, California, contain, according to G. E. Moore, 535*08 grains of crystallized borax to the 
 gallon. 
 
 ULEXITE. Boronatrocalcite. Natronborocalclte. 
 
 In rounded masses, loose in texture, consisting of fine fibres, which aro 
 acicular or capillary crystals. 
 
 H.=l. G.=1'65, N. Scotia, How. Lustre silky within* Color white, 
 Tasteless. 
 
 Oomp NaCaB 6 9 +5aq=Boron trioxide 49 '7, lime 15*9, soda 8'8, water 525'(3=100. 
 Pyr., etc Yields water. B,B. fuses at 1 with intumescence to a clear blebby glass, color 
 
382 DESCRIPTIVE MINERALOGY. 
 
 ing the flame deep yellow. Moistened with sulphuric acid the color of the flame is moment- 
 arily changed to deep green. Not soluble in cold water, and but little so in hot ; the solution 
 alkaline in its reactions. 
 
 Obs Occurs in the dry plains of Iquique, Southern Peru ; in the province of Tarapaca 
 (where it is called liza), in whitish rounded masses, from a hazelnut to a potato in size, which 
 consist of interwoven fibres of the ulexite, with pickeringite, glauberite, halite, gypsum, and 
 other imparities; on the West Africa coast; in Nova Scotia, at Windsor, Brookville, and 
 Newport (H. How), filling narrow cavities, or constituting distinct nodules or mammillattd 
 masses imbedded in white gypsum, and associated at Windsor with glauber salt, the lustre 
 internally silky and the color very white ; in Nevada, in the salt marsh of the Columbus 
 Mining District, forming layers 2-5 in. thick alternating with layers of salt, and in balls 3-4 
 in. through in the salt. 
 
 BECHILITE. (Borocalcite). An incrustation at the Tuscany lagoons. Composition CaB^, 
 + 4aq. Also similar from South America. LARDERELLITE, LAGONITE, rare borates from the 
 Tuscan lagoons. 
 
 PRICEITE (SiUiman). Compact, chalky. Color milk-white. Composition Ca 3 B & Oj 5 + 6aq. 
 This requires : Boron trioxide 49 '8, lime 29 '9, water 20 '3 = 100. Occurs in layers between a bed 
 of slate above and one of steatite below. Near Chetko, Curry Co., Oregon. 
 
 HOWLITE, SiUcoborocalcite. A hydrous calcium borate (like bechilite), with one-sixth of 
 a silicate analogous to danburite. Near Brookville, and elsewhere in Hants Co. , Nova Scotia, 
 in nodules imbedded in anhydrite or gypsum ; these nodules sometimes made up of pearly 
 crystalline scales. WINKWORTHITE. In imbedded crystalline nodules from Winkworth, N. S. 
 In composition between selenite and howlite ; a mixture (?). 
 
 CRYPTOMORPIIITE. Near ulexite in composition. In microscopic rhombic tables. Nova 
 Scotia. 
 
 LUNEBURGIIE. A phospho-borate of magnesium. Flattened masses in gypsiferous marl 
 at Liineburg. 
 
 WARWICKTTE. 
 
 Monoclinic. 7"A/=:91 20', DesCl. Usual in rhombic prisms with 
 obtuse edges truncated, and the acute bevelled, summits generally rounded ; 
 surfaces of larger crystals not polished. Cleavage : macrodiagonal per- 
 fect, affording a surface with vertical striae and traces of oblique cross 
 cleavage. 
 
 H.=3-4. G.=3-19-3*43. Lustre of cleavage surface submetallic-pearly 
 to subvitreous ; often nearly dull. Color dark hair-brown to dull black, 
 sometimes a copper-red tinge on cleavage surface. Streak bluish-black. 
 Fracture uneven. Brittle. 
 
 Comp. Essentially a borotitanate of masfnesium and iron. Analysis, Smith, B 2 3 27 '80, 
 TiO a 23-82, FeO 3 7 02, MgO 36 -80, Si0 2 1-00, A10 3 2 -21 =98 '65. 
 
 Pyr., etc. Yields water. B.B. infusible, but becomes lighter in water ; moistened with 
 sulphuric acid gives a pale green color to the flame. With salt of phosphorus in O.F. a cleat 
 bead, yeilow while hot and colorless on cooling; in R.F. on charcoal with tin a violet color 
 (titanium). With soda a slight manganese reaction. Decomposed by sulphuric acid ; the 
 product, treated with alcohol and ignited, gives a green flame, and boiled with hydrochloric 
 acid and metallic tin gives on evaporation a violet-colored solution. 
 
 Obs. Occurs in granular limestone 2^ m. S. W. of Edenville, N. Y., with spinel, chondro- 
 dite, serpentine, etc. Crystals usually small and slender; sometimes over 2 in. long and in. 
 broad. 
 
OXYGEN COMPOUNDS TUNG STATES. MOLYBDATES, ETC. 
 
 383 
 
 5. TUJSTGSTATES MOLYBDATES, CHEOMATES. 
 
 WOLFRAMITE. 
 
 Monoclinic. C = 89 22', 1 A 1= 100 37', i-i ^%-i = 118 6', * A + f i 
 = 117 6', 14 A 14 = 98 6', DesOloizeaux. Cleavage: i-l perfect, i-i 
 imperfect. Twins: planes of twinning i-i (f. 692), |4, and rarely -J4. 
 Also irregular lamellar; coarse divergent columnar; massive granular, tho 
 particles strongly coherent. 
 
 691 692 693 
 
 H.=5-5'5. G.=7'l-7'55. Lustre submetallic. Color dark grayish or 
 brownish-black. Streak dark reddish-brown to black. Opaque. Sometimes 
 weak magnetic. 
 
 Var. The most important varieties depend on the proportions of the iron and manganese. 
 Those rich in manganese have G. =7 '19-7 54, but generally below 7 '25, and the streak is 
 mostly black. Those rich in iron have G.=r7-2-7'54, and a dark reddish-brown streak, and 
 they are sometimes feebly attractable by the magnet. 
 
 Comp. (Fe,Mn)WO,, Fe : Mn=2 : 3, mostly ; also 4 : 1 and 2 : 1, 3 : 1, 5 : 1, etc. The 
 ratio 2 : 3 corresponds to : Tungsten trioxide 76'47, iron protoxide 9 '49, manganese protoxide 
 14-04=100. 
 
 Pyr., etc B.B. fuses easily (F.=2'5-3) to a globule, which has a crystalline surface and 
 is magnetic. With salt of phosphorus gives a clear reddish-yellow glass while hot, which is 
 paler on cooling; in R.F. becomes dark red ; on charcoal with tin, if not too saturated, the 
 bead assumes on cooling a green color, which continued treatment in R. F. changes to reddish 
 yellow. With soda and nitre on platinum foil fuses to a bluish-green manganate. Decom- 
 posed by aqua regia with separation of tungsten trioxide as a yellow powder, which when 
 treated B.B. reacts as under tungstite (p. 284). Wolfram is sufficiently decomposed by con- 
 centrated sulphuric acid, or even hydrochloric acid, to give a colorless solution, which, 
 treated with metallic zinc, becomes intensely blue, but soon bleaches on dilution. 
 
 Diff. Characterized by its high specific gravity and pyrognostics. 
 
 Obs. Wolfram is often associated with tin ores ; also in o.uartz, with native bismuth, 
 scheelite, pyrite, galenite, blende, etc. ; and in trachyte, as at Felsobanya, in Hungary. It 
 occurs at Schlackenwald ; ScHneeberg ; Freiberg ; Ehrenfriedersdprf ; Zinnwald, and Nert- 
 schinsk ; at Chanteloup, near Limoges, and at Meymac, Correze, in France ; near Redruth 
 and elsewhere in Cornwall ; in Cumberland. Also in S. America, at Oruro in Bolivia. 
 
 In the U. States, occurs at Lane's mine, Monroe, Conn. ; at Trumbull, Conn. ; on Camdage 
 farm, near Blue Hill Bay, Me.; at the Flowe mine, Mecklenburg Co., N. C.; in Missouri, 
 near Mine la Motte, and in St. Francis Co. ; at Mammoth mining district, Nevada. 
 
 HUBNERITE.* A manganese wolframite, MnW0 4 = Tungsten trioxide 76 9, manganese 
 protoxide 23'1 = 100. Mammoth dist., Nevada. 
 
 MEGABASITE. A manganese tungstate, with a little iron. Schlackenwald. 
 
384 
 
 DESCRIPTIVE MINERALOGY. 
 
 SCHEELITE. 
 
 Tetragonal ; hemihedral. O A l-i = 123 3' ; c = 1-5369. Cleavage : 1 
 most distinct, ~L-i interrupted, O traces. Twins; 
 twinning-plane 7; also i-i. Crystals usually octahe- 
 dral in form. Also reniform with columnar struc- 
 ture ; and massive granular. 
 
 H.=4-5-5. G.= 5 -9-6-076. Lustre vitreous, in- 
 clining to adamantine. Color white, yellowish-white, 
 pale yellow, brownish, greenish, reddish ; sometimes 
 almost orange-yellow. Streak white. Transparent 
 translucent. Fracture uneven. Brittle. 
 
 Comp. CaW0 4 = Tungsten trioxide 80'6, lime 19-4=100. A 
 variety from Coquimbo, Chili, contained 6 '2 p. c. vanadium pent- 
 oxide ; another from Traversella contained didymium. 
 
 Pyr., etc. B.B. in the forceps fuses at 5 to a semi-transparent 
 glass. Soluble with borax to a transparent glass, which after- 
 ward becomes opaque and crystalline. With salt of phosphorus 
 forms a glass, colorless in outer flame, in inner green when hot 
 and fine blue cold ; varieties containing iron require to be treated 
 on charcoal with tin before the blue color appears. In hydro 
 chloric or nitric acid decomposed, leaving a yellow powder soluble in ammonia. 
 Diff. Remarkable among non-metallic minerals for its high specific gravity. 
 Obs. Usually associated with crystalline rocks, and commonly found in connection with 
 tin ore, topaz, fluorite, apatite, molybdenite, wolframite, in quartz. Occurs at Schlacken- 
 wald and Zinnwald in Bohemia ; in the Riesengebirge ; at Caldbeck Fell, near Keswick ; 
 Neudorf in the Harz ; Ehreufriedersdorf ; Posing in Hungary ; Traversella in Piedmont, etc. 
 Llamuco, near Chuapa in Chili. In the U. S., at Lane's mine, Monroe, and Huntington, 
 Conn.; at Chesterfield, Mass.; in the Mammoth mining district, Nevada ; at Bangle mine, in 
 Cabarras Co., N. C. ; and Flowe mine. Mecklenburg Co. 
 
 CUPROSCHEELITE. A scheelite containing about 6 p. c. copper oxide. Color bright green. 
 La Paz, Lower California. Llamuco, near Santiago, Chili. 
 
 CUPKOTUNGSTITE. A copper tungstate, CusWOsH-aq. Amorphous. Color yellowish- 
 green. With cuproscheelite at the copper mines of Llamuco, Chili. 
 
 STOLZITE. Pb WO 4 = Tungsten trioxide 51, lead oxide 49=100. Tetragonal. Zinnwald ; 
 Bleiberg; Coquimbo, Chili. 
 
 Schlackenwald. 
 
 WULFENITE.* Gelbbleierz, Gvrm. 
 Tetragonal. Sometimes hemihedral. O A 1-^=123 26'; c = l' 
 
 695 
 
 697 
 
 Przibram. Phenixville. 
 
 In modified square tables and sometimes very thin octahedrons, Cleavage 
 
OXYGEN COMPOUNDS. TUNGSTATES, MOLYBDATES, ETC. 
 
 385 
 
 1 very smooth ; and \ much less distinct. Also granular!}* massive, 
 coarse or fine, firmly cohesive. Often hemihedral in the octagonal prisms, 
 producing thus tables like f. 696, and octahedral forms having the prisma- 
 tic planes similarly oblique. 
 
 H.=2-75-3. Gr.= 6-03-7-01. Lustre resinous or adamantine. Color 
 wax-yellow, passing into orange-yellow; also siskin- and olive-green, yel- 
 lowish-gray, grayish-white, brown; also orange to bright red. Streak 
 white. Subtransparent subtranslucent. Fracture subconchoidal. Brittle. 
 
 Var. 1. Ordinary. Color yellow. 2. Vanadiferom. Color orange to bright red, a variety 
 occurring at Phenixville, Pa. 
 
 Comp. PbMoO, = Molybdenum trioxide 38'5, lead oxide 61 '5 =100. Some varieties 
 contain chromium. 
 
 Pyr., etc. B.B. decrepitates and fuses below 2; with borax in O. F. gives a colorless glass, 
 in R.F. it becomes opaque black or dirty green with black flocks. With salt of phosphorus 
 hi O.F. gives a yellowish-green glass, which in R.F. becomes dark green. With soda on char- 
 coal yields metallic lead. Decomposed on evaporation with hydrochloric acid, with the 
 formation of lead chloride and molybdic oxide ; on moistening the residue with water and 
 adding metallic zinc, it gives an intense blue color, which does not fade on dilution of the 
 liquid. 
 
 Obs. This species occurs in veins with other ores of lead. Found at Bleiberg, etc., in 
 Carinthia ; at Retzbanya ; at Przibram ; Schneeberg and Johanngeorgenstadt ; at Moldava ; 
 in the Kirghis Steppes in Russia ; at Badenweiler in Baden ; in the gold sands of Rio Chico 
 in Antioquia, Columbia, S. A. ; Wheatley's mine, near Phenixville, Pa.; at the Comstocklode 
 in Nevada. In fine specimens from the Empire mine, Lucin District, Box Elder County, 
 Utah ; at Empire mine, Inyo Co., Cal. ; in the Weaver dist., Arizona. 
 
 EOSITE (Schrauf). In minute tetragonal octahedrons. Color deep-red. Probably a vana- 
 dio-molybdate of lead. Leadhills, Scotland. 
 
 ACII HEMATITE. An arsenio-molybdate of lead. Analysis, As 2 5 18 '25, Mo0 3 5'01, Cl 
 215, Pb 6'28, PbO 68'31=100'00. Compact; structure indistinctly crystalline. H.=3-4. 
 Gr. =5 -965, 6-178 (powder). Color liver-brown, translucent ; in minute grains transparent and 
 color yellow. Brittle. Guanacere, State of Chihuahua, Mexico. (Mallet, J. Ch. Soc., xiii., 
 1141, New Series.) 
 
 CROOOITB. Crocoisite. Rothbleierz, Uerm. 
 
 Monoclinic. C= 77 27', /A I = 93 42', O A 14 = 138 10' ; c 
 0-95507 : 1*0414: : 1, Dauber. Cleavage : /toler- 
 ably distinct; O and i-i less so. Surface /streaked 
 longitudinally ; the faces mostly smooth and shin- 
 ing. Also imperfectly columnar and granular. 
 
 II. =2-5-3. G.=: 5-9-6*1. Lustre adamantine 
 vitreous. Color various shades of bright hyacinth- 
 red. Streak orange-yellow. Translucent. Sectile. 
 
 Comp. PbCrO 4 =Lead oxide 69'0, chromium trioxide 31'0= 
 100. 
 
 Fyr., etc. In the closed tube decrepitates, blackens, but re- 
 jovers its original color on cooling. B.B. fuses at 15, and on 
 nharcoal is reduced to metallic lead with deflagration, leaving a 
 residue of chromic oxide, and giving a lead coating. With salt 
 of phosphorus gives an emerald-green bead in both flames. Fused 
 with potassium bisulphate in the platinum spoon forms a dark 
 violet mass, which on solidifying becomes reddish, and when 
 cold greenish-white, thus differing from vanadinite, which on similar treatment- 
 yellow mass (Plattner). 
 
 25 
 
 Ura:s. 
 
386 DESCRIPTIVE MINERALOGY. 
 
 Obs. First found at Beresof in Siberia ; at Mursinsk anl near Nischne Tagilsk in the 
 Ural ; in Brazil; at Retzbanya; Moldawa ; on Luzon, one of the Philippines. 
 
 PHCENICOCHROITE. Melanochroite. 
 
 Orthorhombic (?). Crystals usually tabular, and reticularly interwoven. 
 Cleavage in one direction perfect. Also massive. 
 
 H.=:3-3-5. G.=5'75. Lustre resinous or adamantine, glimmering. 
 Color between cochineal- and hyacinth-red; becomes lemon-yellow on 
 exposure. Streak brick-red. Subtranslucent opaque. 
 
 Comp. Pb 3 Cr 2 O 9 =2PbCrO +PbO= Chromium trioxide 23 '0, lead oxide 77-0=100. 
 
 Pyr., etc. B.B. on charcoal fuses readily to a dark mass, which is crystalline when cold. 
 In B.F. on charcoal gives a coating of lead oxide, with globules of lead and a residue of 
 chromic oxide. Gives the reaction of chrome with fluxes. 
 
 Obs. Occurs in limestone at Beresof in the Ural, with crocoite, vauquelinite, pyromorphite, 
 and galenite. 
 
 VAUQUELINITE. 
 
 Monoclinic. Crystals usually minute, irregularly aggregated. Also 
 reniform or botryoidal, and granular ; amorphous. 
 
 tl.=2'5 3. G.r= 5*5 5*78. Lustre adamantine to resinous, often faint. 
 Color green to brown, apple-green, siskin-green, olive-green, ochre-brown, 
 liver-brown; sometimes pearly black. Streak greenish or brownish. Faintly 
 translucent opaque. Fracture uneven. Rather brittle. 
 
 Comp. Pb a CuCr 2 9 =2BCr0 4 +BO. B=Pb : Cu=2 : 1. The formula requires: Chro- 
 mium trioxide 27'6, lead oxide 61 '5, copper oxide 10'9 100. 
 
 Pyr., etc. B.B. on charcoal slightly intumesces and fuses to a gray submetallic globule, 
 yielding at the same time small globules of metal. With borax or salt of phosphorus affords 
 a green transparent glass in the outer flame, which in the inner after cooling is red to black, 
 according to the amount of mineral in the assay ; the red color is more distinct with tin. 
 Partly soluble in nitric acid. 
 
 Obs. Occurs with crocoite at Beresof in Siberia, generally in mammillated or amorphous 
 masses, or thin crusts ; also at Pont Gibaud in the Puy de Dome ; and with the crocoite of 
 Brazil. In the U. States it has been found at the lead mine near Sing Sing, in green and 
 brownish -green mammillary concretions, and also nearly pulverulent ; and at the Pequa lead 
 mine in Lancaster Co., Pa., in minute crystals and radiated aggregations on quartz and 
 galenite, of a siskin- to appJe-green color, with cerussite. 
 
 LAXMANKITE (phoepJtochrmuW. Near vauquelinite, but held to be a pi oepho-chi ornate. 
 Beresof. 
 
OXYGEN COMPOUNDS. SULPHATES. 
 
 387 
 
 6. SULPHATES. 
 
 ANHYDROUS SULPHATES. 
 
 Barite Group. 
 
 BARITE. Barytes. Heavy Spar. Schwerspath, Germ. 
 Orthorhombic. /A /= 101 40', O A 14 = 121 50' ; c : I : A = 1-6107 
 
 700 
 
 Cheshire. 
 
 : 1-2276 : 1. A 1 = 115 42' ; \-l A 4, top, - 
 102 17' ; 14 A 14, top, = 74 36. Crystals usu- 
 ally tabular, as in figures; sometimes prismatic 
 in the direction of the different axes. Cleavage : 
 basal rather perfect ; /somewhat less so; i4 imperfect. Also in globular 
 forms, fibrous or lamellar, crested ; coarsely laminated, laminae convergent 
 and often curved ; also granular ; colors sometimes banded, as in stalagmite. 
 H.=2'5-3'5. G.=4'3-4'72. Lustre vitreous, inclining to resinous; 
 sometimes pearly. Streak white. Color white ; also inclining to yellow, 
 
 fray, blue, red, or brown, dark brown. Transparent to translucent opaque, 
 ometiines fetid, when rubbed. Optic-axial plane brachy diagonal. 
 
 Comp. BaSO 4 =Sulphur trioxide 34 '3, baryta 65 '7=100. Strontium and sometimes cal- 
 cium replace part of the barium ; also silica, clay, bituminous or carbonaceous substances 
 are often present as impurities. 
 
 Pyr., etc. B.B. decrepitates and fuses at 3, coloring the flame yellowish-green ; the fused 
 mass reacts alkaline with test paper. On charcoal reduced to a sulphide. With soda gives 
 at first a clear pearl, but on continued blowing yields a hepatic mass, which spreads out and 
 soaks into the coal. If a portion of this mass be removed, placed on a clean silver surface, 
 and moistened, it gives a black spot of silver sulphide. Should the barite contain calcium 
 Bulphate, this will not be absorbed by the coal when treated in powder with soda. Insoluble 
 in acids. 
 
 Diff. Distinguishing characters : high specific gravity, higher than celestite or aragonite ; 
 cleavage ; insolubility ; green coloration of the blowpipe flame. 
 
 Obs. Occurs commonly in connection with beds or veins of metallic ores, as part of the 
 gangue of the ore. It is met with in secondary limestone, sometimes forming distinct veins. 
 and often in crystals along with calcite and celestite. At Dufton, in Westmoreland. Eng 
 
388 
 
 DESCRIPTIVE MINERALOGY. 
 
 land ; in Cornwall, near Liskeard, etc., in Cumberland and Lancashire, in Derbyshire, Staf- 
 fordshire, etc.; in Scotland, in Argyleshire, at Strontian. Some of the most important 
 European localities are at Felsobanya and Kremnitz, at Freiberg, Marienberg, Clausthal, 
 Przibram. and at Roya and Roure in Auvergne. 
 
 In the U. S., in Conn., at Cheshire. In N. York, at Pillar Point; at Scoharie ; in St. 
 Lawrence Co.; at Fowler; at Hammond. In Virginia, at Eldridge's gold mine in Buckingham 
 Co.; near Lexington, in Rockbridge Co.; Fauquier Co. In Kentucky, near Paris ; in the W. 
 end of I. Royale, L. Superior, and on Spar Id., N. shore. In Canada, at Landsdown. In 
 fine crystals near Fort Wallace, New Mexico. 
 
 The white varieties of barite are ground up and employed as a white paint, either alone or 
 mixed with white lead. 
 
 CELESTITE. 
 
 Ortborhombic. /A 7= 104 2' (103 30'-104 30'), A 1-5- = 121 
 19J' ; c : I ; a = 1-6432 : 1-2807 : 1. A 1 = 115 38', O A \-l = 127 56', 
 1 A 1, mac., = 112 35', 1 A 1, brack, = 89 26'. Cleavage : O perfect ; 
 1 distinct ; i-l less distinct. Also fibrous and radiated ; sometimes globu- 
 lar; occasionally granular. 
 
 702 
 
 703 
 
 L. Erie. 
 
 H.= 3-3*5. G.=3'92-3*975. Lustre vitreous, sometimes inclining to 
 pearly. Streak white. Color white, often faint bluish, and sometimes red- 
 dish. Transparent subtranslucent. Fracture imperfectly conchoidal 
 uneven. Yery brittle. Trichroism sometimes very distinct. 
 
 Comp. SrSO 4 = Sulphur trioxide 43 '6, strontia 56*4=100. Wittstein finds that the blue 
 color of the celestite of Jena is due to a trace of a phosphate of iron. 
 
 Fyr., etc. B.B. frequently decrepitates, fuses at 3 to a white pearl, coloring the flame 
 strontia-red ; the fused mass reacts alkaline. On charcoal fuses, and in R.F. is converted 
 into a difficultly fusible hepatic mass; this treated with hydrochloric acid and alcohol gives 
 an intensely red flame. With soda on charcoal reacts like barite. Insoluble in acids. 
 
 Diff. Does not effervesce with acids like the carbonates ; specific gravity lower than that 
 of barite ; colors the blowpipe flame red. 
 
 Obs. Celestite is usually associated with limestone or sandstone. Occurs also in beds of 
 gypsum, rock salt, and clay ; and with sulphur in some volcanic regions. Found in Sicily, at 
 Girgenti and elsewhere ; at Bex in Switzerland, and Conil in Spain ; at Dornburg, near Jena ; 
 in the department of the Garonne, France ; in the Tyrol ; Retzbanya ; in rock salt, at Ischl, 
 Austria. Found in the Trenton limestone about Lake Huron, particularly on Strontian 
 Island, and at Kingston in Canada ; Chaumont Bay, Scoharie, and Lockport, N. Y. ; also 
 the Rossie lead mine ; at Bell's Mills, Blair Co. . Penn. 
 
 Named from calestis, celestial, in allusion to the faint shade of blue often presented by the 
 mineral. 
 
 BARYTOCELESTITE. Celestite containing barium sulphate 26 p. c. (Griiner), 20 '4 p. c. 
 (Turner). l- A 1-1=74 544', HA-H=100 J 35', on crystals from Imfeld in the BinnenthaJ 
 (Neminar). Drammond I. , Lake Erie* Norten, Hanover. 
 
OXYGEN COMPOUNDS. SULPHATES, ETC. 389 
 
 ANHYDRITE. 
 
 Orthorhombic. 7A 1= 100 30', A 14 = 127 19' ; c : I : d = 1-3122 
 : 1-2024 : 1. l- A 1-2, top, = 85. Cleavage : ?4 very per- 
 704 feet ; i-i also perfect ; O somewhat less so. Also librous, 
 
 lamellar, granular, and sometimes impalpable. The 
 lamellar and columnar varieties of ten curved or contorted. 
 H.=3-3-5. G.=2-899-2-985. Lustre: i-itiud i-i some- 
 what pearly ; vitreous ; in massive varieties, vitreous 
 inclining to pearly. Color white, sometimes a grayish, 
 bluish, or reddish tinge; also brick-red. Streak grayish- 
 white. Fracture uneven; of finely lamellar and fibrous 
 varieties, splintery. Optic-axial plane parallel to i-i, or 
 Stassfurt. plane of most perfect cleavage; bisectrix normal to 0\ 
 Grailich. 
 
 Var. (a) Crystallized ; cleavable in its three rectangular directions, (b) fibrous ; either 
 parallel, or radiated, or plumose, (c) Fine granular, (d) Scaly granular. Vulpiniteia a scaly 
 granular kind from Vulpino in Lombardy ; it is cut and polished for ornamental purposes. It 
 does not ordinarily contain more silica than common anhydrite. A kind in contorted concre- 
 tionary forms Ls the tripestone (Qekrosslein). 
 
 Oomp CaSO 4 = Sulphur trioxide 58 '8, lime 41 -2=100. 
 
 Pyr., etc. B.B. fuses at 3, coloring the flame reddish-yellow, and yielding an enamel-like 
 bead which reacts alkaline. On charcoal in R. F. reduced to a sulphide ; with soda does not 
 fuse to a clear globule, and is not absorbed by the coal like barite ; it is, however, decomposed, 
 and yields a mass which blackens silver ; with fluorite fuses to a clear pearl, which is 
 enamel- white on cooling, and by long blowing swells up and becomes infusible. Soluble in 
 hydrochloric acid. 
 
 Diff. Characterized by its cleavage in three rectangular directions; harder than gypsum; 
 does not effervesce with acids like the carbonates. 
 
 Obs. Occurs in rocks of various ages, especially in limestone strata, and often the same 
 that contain ordinary gypsum, and also very commonly in beds of rock salt. Occurs near 
 Hall in Tyrol ; at Sulz on the Neckar, in Wiirtemberg ; Bleiberg in Carinthia ; Liineberg, 
 Hanover ; Kapnik in Hungary ; Ischl ; Aussee in Styria ; Berchtesgaden ; Stassfurt, in fine 
 crystals. In the U. States, at Lockport, N. Y. In Nova Scotia. 
 
 ANGLESITB. Bleivitriol, Germ. 
 
 Orthorhombic. 7 A 7=103 43', 0Al-i = 121 20J', Kokscharof; 
 c : I : d = 1-64223 : 1-273634: : 1. O A 1-i = 127 48' ; A 1 = 115 35J' ; 
 \-l A 14, top, = 75 35'. Crystals sometimes tabular ; often oblong pris- 
 matic, and elongated in the direction of either of the axes (as seen in the 
 figures). Cleavage: 7, O, but interrupted. The planes 7 and i-l often 
 vertically striated, and \-~% horizontally. Also massive, granular, or hardly 
 BO. Sometimes stalactitic. 
 
 H.= 2-75-3. G.= 6-12-6-39. Lustre highly adamantine in some speci- 
 mens, in others inclining to resinous and vitreous. Color white, tinged 
 yellow, gray, green, and sometimes blue. Streak uncolored. Transparent 
 paque. Fracture conchoidal. Very brittle. 
 
 Comp. PbSO 4 Sulphur trioxide 26 '4, lead oxide 73 '6 =100. 
 
 Pyr., etc. B.B. decrepitates, fuses in the flame of a candle (P.=1'5). On charcoal in 0. 
 F. fuses to a clear pearl, which on cooling becomes milk-white ; in R. F. is reduced with effer- 
 vescence to metallic lead. With soda on charcoal in R. F. gives metallic lead, and the soda 
 is absorbed by the coal ; when the surface of the coal is removed and placed on bright silvei 
 and moistened with water it tarnishes the metal black. Difficultly soluble in nitric acid. 
 
390 
 
 DESCRIPTIVE MINERALOGY. 
 
 Diff. Does not effervesce with acid like cerussite (lead carbonate) ; listinguished by blow- 
 pipe tests from other resembling species. 
 
 705 
 
 707 
 
 Siegen. 
 
 Anglesea. 
 
 Siegen. 
 
 Obs. This ore of lead was first observed by Monnet as a result of the decomposition of 
 galenite, and it is often found in its cavities. Occurs in crystals at Leadhills ; at Pary's mine 
 in Anglesea ; also at Melanoweth in Cornwall ; in Derbyshire and in Cumberland : Clausthal, 
 Zillerfeld, and Giepenbach in the Harz ; near Siegen in Prussia ; Schapbach in the Black 
 Forest ; in Sardinia ; massive in Siberia. Andalusia, Alston Moor in Cumberland ; in Aus- 
 tralia. In the U. S., in large crystals at Wheatley's mine, Phenixville, Pa. ; in Missouri lead 
 mines ; at the lead mines of Southampton, Mass. ; at Rossie, N. Y. ; at the Walton gold mine, 
 Louisa Co., Va. Compact in Arizona, and Cerro Gordo, Cal. 
 
 DREELITE. Rhombohedral. H.=3'5. G-. 3'2-3'4. Color white. Composition given as 
 CaSO-4-f 3BaS0 4 . Occurs in small crystals at Beaujeau, France; Badenweiler, Baden. 
 
 DOLEROPHANITB (Scacchi). Cu 2 SO 3 . In minute crystals. Monoclimc. Color brown. 
 Vesuvius. 
 
 HYDROCTANITE (Scacchi). Anhydrous copper sulphate, CuS0 4 . Color sky-blue. Very 
 soluble. Vesuvius. 
 
 APHTHIT ALITE, Arcanite. K 2 SO 4 =Potash 54-1, sulphuric acid 45 "9 = 100. Vesuvius. 
 
 THENAKDITE. Sodium sulphate, Na 2 S0 4 . Spain; Vesuvius. 
 
 LEADHILLITE. 
 
 Orthorhombic. I^ 1= 103 16', O A 14 = 120 10' ; c : I : d = 1'7205 
 : 1-2632 : 1. Heinihedral in 1 and some other planes ; hence monoclinic in 
 aspect, or rhombohedral when in compound crystals. Cleavage : i4 verj 
 perfect ; i-l in traces. Twins, f . 712, consisting of three crystals ; twinning 
 plane, l-i (see f . 298, p. 97) ; also parallel with /. 
 
OXYGEN COMPOUNDS. SULPHATES. 
 
 391 
 
 H. = 2*5. G. 6*26-6*4:4. Lustre of i-4 pearly, other parts resinous, some- 
 what adamantine. Color white, 
 
 passing into yellow, green, 711 712 
 
 or gray. Streak uncolored. 
 Transparent translucent. 
 Conchoidal fracture scarcely 
 observable. Rather sectile. 
 
 Comp. Formerly accepted for- T " 
 mula, PbSO 4 +3PbC0 3 =Lead sul- 
 phate 27 '45, lead carbonate 72 '55 = 
 100. Recent investigations by Las- 
 peyres (J. pr., Ch. II., v., 470; vii., 
 127; xiii., 370), and Hintze (Pogg. 
 Ann., clii., 156), though not entirely 
 accordant, give different results, both 
 
 show the presence of some water. Laspeyres writes the formula empirically, 
 
 5H 2 0, and Hintze, Pb 7 C 4 S 2 O i i+2H 2 O. Analyses: 1. Laspeyres; 2, Hintze: 
 
 S0 3 C0 3 PbO H 2 O 
 
 1. 8-14 8-08 81-91 1-87=100, Laspeyres. 
 
 2. 817 918 80-80 2'00=100'15, Hintze. 
 
 Pyr., etc. B.B. intumesces, fuses at 1'5, and turns yellow ; but white on cooling. Easily 
 reduced on charcoal. With soda affords the reaction for sulphuric acid. Effervesces briskly 
 in nitric acid, and leaves white lead sulphate undissolved. 
 
 Obs, This ore has been found at Leadhills with other ores of lead ; also in crystals at Red 
 Gill, Cumberland, and near Taunton in Somersetshire ; at Iglesias, Sardinia (maxite). 
 
 SUSANNITE. Composition as for leadhillite, but form rhornbohedral. Leadhills; Nert- 
 schinsk, Siberia. 
 
 CONNELLITE. Hexagonal. In slender needle-like blue crystals. Contains copper sulphate 
 and copper chloride. Exact c -imposition uncertain. Cornwall. 
 
 CALKDONITE. Monoclinic (Schrauf). H. =2-5-3. G. =6'4. Color bluish-green. R 2 S0 5 
 + aq (Flight), with R=Pb : Cu=7 : 3, or 5PbS0 4 +3H,CuO,+2H.^PbO 2 . This requires : 
 Sulphuric trioxide 19-1, lead oxide 05 '2, copper oxide 11 '4, water 4 3=100. Leadhills, Scot- 
 land ; Red Gill ; Retzbanya ; Mine la Motte, Missouri. 
 
 LANAUKITE. Monoclinic. H. =2-2*5. G. =6-3-6 '4. Color pale yellow, or greenish- 
 white. Transparent. Composition as formerly accepted, PbSO 4 +PbC0 3 . New analyses by 
 Flight, and by Pisani, show the absence of both carbon dioxide and water ; composition 
 accordingly Pb 2 SO 5 =PbS0 4 +PbO, which requires : Lead sulphate 57'6, lead oxide 42'4=100. 
 Leadhills ; Siberia, etc. 
 
 GLAUBERITE. 
 
 7A7=8320', 
 
 Monoclinic. (7=68 16', 
 0-84:54: : 0*8267 : 1. Cleavage : O perfect! 
 
 H.= 2-5-3. G.=2*64r-2-85. Lustre vitreous. Color 
 pale yellow or gray; sometimes brick-red. Streak white. 
 Fracture conchoidal ; brittle. Taste slightly saline. 
 
 Comp. Na 2 CaS 2 B = Sulphur trioxide 57-6, lime 20'1, soda 22 3= 
 100. 
 
 Pyr., etc. B.B. decrepitates, turns white, and fuses at 1'5 to a 
 white enamel, coloring the flame intensely yellow. On charcoal fuses 
 in O.F. to a clear bead ; in R. F. a portion is absorbed by the charcoal, 
 leaving an infusibe hepatic residue. With soda on charcoal gives the 
 reaction for sulphur. Soluble in hydrochloric acid. In water it loses 
 its transparency, is partially dissolved, leaving a residue of calcium 
 sulphate, and in a large excess this is completely dissolved. On long 
 exposure absorbs moisture and falls to pieces. 
 
 Obs. In crystals in rock salt at Villa Rubia in New Castile ; also at 
 Aussee in Upper Austria ; in Bavaria ; at the salt mines of Vic in France ; 
 and at Borax Lake, California; Province of Tarapaca, Peru. 
 
 A 14 = 136 30'; c:l>\a 
 
 713 
 
392 
 
 DESCRIPTIVE MINERALOGY. 
 
 HYDROUS SULPHATES. 
 
 MIRABILITE. Glauber Salt. 
 
 Monoclinic. C = 72 15', /A 1= 86 31', 6> A 14 = 130 19' ; c:b: ,i 
 = 1'10S9 : 0-8962 : 1. Cleavage : i-i perfect. Usually in efflorescent 
 crusts. 
 
 H.= 1*5-2. G.= 1*4:81. Lustre vitreous. Color white. Transparent 
 opaque. Taste cool, then feebly saline and bitter. 
 
 Very 
 Falls 
 
 Comp. Na,S0 4 H-10aq=Sulphur trioxide 24 "8, soda 19 '3, water 55-9=100. 
 
 Pyr., etc. In the closed tube much water ; gives an intense yellow to the flame, 
 soluble in water ; the solution gives with barium salts the reaction for sulphuric acid, 
 to powder on exposure to the air, and becomes anhydrous. 
 
 Obs. Occurs at Ischl and Hallstadt ; also in Hungary ; Switzerland ; Italy ; at Guipuzcoa 
 in Spain, etc. ; at Kailua on Hawaii ; at Windsor, Nova Scotia ; also near Sweetwater Kiver, 
 Rocky Mountains. 
 
 MASCAGNITE, BOUSSINGAULTITE (cerbolite), LECONTITE, and GDANOVULITE are hydrous 
 sulphates containing ammonium. 
 
 GYPSUM. 
 
 Monoclinic. O= 66 14', if the vertical prism / (see f. 716) correspond 
 to the cleavage prism (second cleavage), and the basal plane O to the 
 direction of the third cleavage. /A / = 138 28', \\l\ 14 = 128 31' ; 
 i : b : d = 0-9 : 2-4135 : 1. A 1 = 125 35', O A 24=145 41', 1 A 1 = 
 143 42', 24 A 2-1=111 42'. 
 
 715 
 
 716 
 
 Cleavage : (1) i-l, or clinodiagonal, eminent, affording easily smooth pol- 
 ished folia ; (2) I, imperfect, fibrous, and often apparent in internal rifts or 
 linings, making with O (or the edge 24/24) the angles 66 14', and 113 
 46', corresponding to the obliquity of the fundamental prism ; (3) 6>, or 
 basal, imperfect, but affording a nearly smooth surface. Twins : 1, Twin- 
 ning-plane O common (f. 717) ; also !-&', or edge 1/1. Simple crystals often 
 with warped as well as curved surfaces. Also foliated massive ; lamellar 
 stellate; often granular massive; and sometimes nearly impalpable. 
 
OXYGEN COMPOUNDS. SULPHATES. 393 
 
 fl.= 1-5-2. G.=2-314-2-32S, when pure crystals. Lustre of. i-l pearly 
 and shining, other faces subvitreous. Massive varieties often glistening, 
 sometimes dull earthy. Color usually white ; sometimes gray, flesh-red, 
 honey-yellow, ochre-yellow, blue ; impure varieties often black, brown, red 
 or reddish- brown. Streak white. Transparent opaque. 
 
 Var. 1. Crystallized, or Selenite ; either in distinct crystals or in broad folia, the folia 
 sometimes a yard across and transparent throughout. 2. Fibrous ; coarse or fine, (a) Satin 
 spar, when fine-fibrous a variety which has the pearly opalescence of moonstone ; (b) plumose, 
 when radiately arranged. 3. Massive; Alabaster, a fine-grained variety, either white or 
 delicately shaded ; scaly- granular ; earthy or rock-gypsum, a dull-colored rock, often impure 
 with clay or calcium carbonate, and sometimes with anhydrite. 
 
 Comp CaSO 4 + 2aq= Sulphur trioxide 46 '5, lime 32'tf, water 20-9 = 100. 
 
 Pyr., etc. In the closed tube gives off water and becomes opaque. Fuses at 2 '5-3, color- 
 ing the flame reddish-yellow. For other reactions, see ANHYDRITE, p. 389. Ignited at a 
 temperature not exceeding 260 C., it again combines with water when moistened, and 
 becomes firmly solid. Soluble in hydrochloric acid, and also in 400 to 500 parts of water. 
 
 Diff. Characterized by its softness ; it does not effervesce nor gelatinize with acids. 
 Some varieties resemble heulandite, stilbite, talc, etc.; and in its fibrous forms it is like some 
 calcite. 
 
 Obs. Gypsum often forms extensive beds in connection with various stratified rocks, espe- 
 cially limestone, and marlytes or clay beds. It occurs occasionally in crystalline rocks. Itia 
 also a product of volcanoes ; produced by the decomposition of pyrite when lime is present ; 
 and often about sulphur springs ; also deposited on the evaporation of sea-water and brines, 
 in which it exists in solution. 
 
 Fine specimens are found in the salt mines of Bex in Switzerland ; at Hall in the Tyrol ; 
 in the sulphur mines of Sicily ; in the gypsum formation near Oqana in Spain ; in the clay of 
 Shotover Hill, near Oxford ; at Montmartre, near Paris. A noted locality of alabaster occurs 
 at Castelino, 35 m. from Leghorn. In the U. S. this species occurs in extensive beds in 
 N. York, Ohio, Illinois, Virginia, Tennessee, and Arkansas ; it is usually associated with salt 
 springs. Also in Nova Scotia, Peru, etc. It is characteristic of the so-called triassic, or red 
 beds, of the Rocky Mountain region ; also of the Cretaceous in the west, particularly of the 
 clays of the Fort Pierre group, in which it occurs in the form of transparent plates. 
 
 Handsome selenite and snowy gypsum occur in N. York, near Lockport ; also near Camil- 
 lus, Onoudaga Co. In Maryland, on the St. Mary's, in clay. In Ohio, large transparent 
 crystals have been found at Poland and Cantield, Trumbull Co. In Tenn., selenite and ala- 
 baster in Davidson Co. In Kentucky, in Mammoth Cave, in the form of rosettes, etc. In 
 N. Scotia, in Sussex, King's Co., large crystals, often containing much symmetrically dis- 
 seminated sand (Marsh). 
 
 Plaster of Paris (or gypsum which has been heated and ground up) is used for making 
 moulds, taking casts of statues, medals, etc. ; for producing a hard finish on walls; also in 
 the manufacture of artificial marble, as the scagliola tables of Leghorn, and in the glazing of 
 porcelain. 
 
 FOLYHALITE. 
 
 Monoclinic (?). A prism of 115, with acute edges truncated. Usually iu 
 compact fibrous masses. 
 
 11.= 2-5-3. Gr. 2-7689. Lustre resinous or slightly pearly. Streak 
 red. Color flesh- or brick-red, sometimes yellowish. Translucent opaque 
 Taste bitter and astringent, but very weak. 
 
 Oomp. 2RS0 4 +aq, where R^Ca : Mg : K 2 in the ratio 2:1:1; that is, 
 +2aq=Calcium sulphate 45 '2, magnesium sulphate 19 9, potassium sulphate 28 '9, water 
 6-0=100. 
 
 Pyr., etc. In the closed tube gives water. B.B fuses at 1'5, colors the flame yellow. On 
 charcoal fuses to a reddish globule, which in R.F. becomes white, and on cooling has a saline 
 hepatic taste ; with soda like glauberite. With fluor does not give a clear bead. Partially 
 soluble in water, leaving a residue of calcium sulphate, which dissolves in a large amount of 
 water 
 
394 DESCRIPTIVE MINERALOGY. 
 
 Obs. Occurs at the mines of Ischl, Ebensee, Aussee, Hallstatt, and Hallein in Austria^ 
 with common salt, gypsum, and anhydrite ; at Berchtesgaden in Bavaria ; at Vic in Lorraine. 
 
 The name Polyhalite is derived from H-OA.WS, many, and oAs, salt, in allusion to the numbel 
 of salts in the constitution of the mineral. 
 
 SYNGENITB, v. Zepharovich; Kaluszite, Rumpf. Near polyhalite. Composition RSO 4 + 
 aq, with R=Ca : K 2 = l : 1, that is, K 2 CaSoO8-|-aq=Potassium sulphate 53 '1, calcium sul- 
 phate 41 '4, water 5 -5 = 100. Monoclinic. Occurs in small tabular crystals in cavities in halito 
 at Kalusz, East Galicia. 
 
 KIESERITE. MgSO.,+aq= Sulphur trioxide 58 -0, magnesia 28 -0, water 13 '0=100. Sfcass- 
 furt. 
 
 PICROMERITE is K 2 MgS 2 O 8 +6aq=Sulphur trioxide 39 '8, magnesia 9 '9, potash 23 4, water 
 26-9=100. Vesuvius; Stassfurt. 
 
 BLOEDITE. Composition Na 2 MgSi0 8 + 4aq= Sulphur trioxide 47-9, magnesia 12-0, soda 
 18-6, water 21'5=100. Salt mines of Ischl ; also in the Andes. SIMOKVITE (Txcliermak) is 
 identical. 
 
 LCEWEITE. 2Na 2 MgS 2 O 8 +5aq= Sulphur trioxide 52'1, magnesia 13 0, soda 20 2, water 
 14-7=100. From IschL 
 
 EPSOMITE. Epsom Salt. Bittersalz, Gtrrm. 
 
 Orthorhombic, and generally hemihedral in the octahedral modifications. 
 IM= 90 3', A 1-t = 150 2' ; c:b:& = 0'57t>6 : 1-01 : 1. l-l A l-, 
 basal, = 59 27', 1-t A 14, basal, = 59 56'. Cleavage: brae hy diagonal, 
 perfect. Also in botrj'oidal masses and delicately iibrous crusts. 
 
 II. 2*25. Gr.=l'751 ; 1*685, artificial salt. Lustre vitreous earthy 
 Streak and color white. Transparent translucent. Taste bitter and saline. 
 
 Comp. MgSO 4 +7aq, when pure = Sulphur trioxide 32'5, magucsia 16 '3, water 51-2=100. 
 
 Pyr., etc. Liquifies in its water of crystallization. Gives much water in the closed tube 
 at a high temperature; the water is acid. B.B. on charcoal fuses at first, and finally yields 
 an infusible alkaline mass, which, with cobalt solution, gives a pink color on ignition. Very 
 soluble in water, and has a very bitter taste. 
 
 Obs. Common in mineral waters, and as a delicate fibrous or capillary efflorescence on 
 rocks, in the galleries of mines, and elsewhere. In the former state it exists at Epsom, Eng- 
 land, and at Sedlitz and Saidschutz in Bohemia. At Idria in Carniola it occurs in silky fibres, 
 and is hence called hairsalt by the workmen. Also obtained at the gypsum quarries of Mont- 
 martre, near Paris ; in Aragon and Catalonia in Spain ; in Chili ; found at Vesuvius, etc. 
 
 The floors of the limestone caves of Kentucky, Tennessee, and Indiana, are in many 
 instances covered with epsomite, in minute crystals, mingled with the earth. In the Mam- 
 moth Cave, Ky., it adheres to the roof in loose masses like snowballs. 
 
 FAUSERITE. A hydrous manganese-magnesium sulphate. Hungary. 
 
 Copperas Group. 
 OHALOANTHITE. Blue Vitriol. Kupfervitriol, Germ. 
 
 Triclinic. O A 1= 109 32', O A 1' = 127 40', /A T = 123 10', A 1 
 =125 38', <? A t'-i = 120 50', 0A* = 103 27'. Cleavage: / imper- 
 fect, /' very imperfect. Occurs also amorphous, stalactitic, reniform. 
 
 H.=2-5. G.=2-213. Lustre vitreous. Color Berlin-blue to sky-blue, 
 of different shades ; sometimes a little greenish. Streak uncolored. Sub- 
 transparent translucent. Taste metallic and nauseous. Somewhat brittle. 
 
 Comp. CuS0 4 -f 5aq= Sulphur trioxide 32'1, copper oxide 31-8, water 36*1=100. 
 
 Pyr., etc. In the closed tube yields water, and at a higher temperature sulphuric acid. 
 B.B. with soda on charcoal yields metallic copper. With the fluxes reacts for copper. Solu- 
 ble in water; a drop of the solution placed on a surface of iron coats it with metallic copper. 
 
 Obs. Blue vitriol is found in waters issuing from mines, and in connection with rocks con- 
 taining chalcopyrite, by the alteration of which it is formed. Some of its foreign localities 
 
OXYGEN COMPOUNDS. SULPHATES. 
 
 
 ervrioe-M E TE, iron vitriol; P.SA N ITE, iron-copper vitriol ; GosLAB- 
 
 of crystallization. 
 
 z, ^^.).-^30 12 +18aq=Sulphurtrioxide36-0, aluminal5-4, water 
 
 **. 28 - 
 
 hl SOs 16-64, MO, 7-70, CaO 27-27, H,0 45'82. In hexa- 
 
 gonll needle4ike crystals from the lava at Ettringen, Laacher See. 
 
 Alum and Halotrichite Groups. 
 Here belong: TscHEKMroiTB 
 
 A180 ECEMERITE, and VOLTAITE. 
 
 COPIAPITB. 
 
 Hexagonal (?). Loose aggregation of crystalline scales, or granular massive, 
 the scafes rhmnbic or hexalonal tables. Cleavage: basal, perfect. In- 
 
 G.=2-14, Borcher. Lustre pearly. Color sulphur-yellow, 
 citron-yellow. Translucent. 
 C S 13aq 5^eS + H 6 e0 6 + 36H 2 O = Sulphur trioxide 41'9, iron 
 
 P^^^Sd^steS!8Maw 
 
 " ''TrSSt'of the decomposition of pyrite at the Rammelsberg mine, near 
 ^ras long called misy, and it might well bear now the name 
 ion Fe a S,Oi.+7aq. FIBBOFEBBITE (stypticite). -Composition 
 *1S2S is red iron vitriol, exact composition uncertain. Fahlun, Sweden. BABTHCV 
 %m^^+*^ Occurs as a yellow efflorescence >n graphite from Mugrau, 
 Bohemia (Schrauf). 
 
 ALUMINITE. 
 
 H =1-2 =1-60. Luscre dull, earthy. Color white. Opaque. 
 Fracture earthy. Adheres to the tongue ; meagre to the 
 
396 DESCRIPTIVE MINERALOGY. 
 
 Comp AlSO 6 +9aq= Sulphur trioxide 23'2, alumina 29'8, water 47*0=100. 
 
 Pyr., etc. In the closed tube gives much water, which, at a high temperature, becomes 
 acid from the evolution of sulphurous and sulphuric oxides. B.B. infusible. With cobalt 
 solution a fine blue color. With soda on charcoal a hepatic mass. Soluble in acids. 
 
 Obs. Occurs in connection with beds of clay in the Tertiary and Post- tertiary formations. 
 Found near Halle ; at Newhaven, Sussex ; Epernay, in Lunel Vieil, and Auteuil, in France. 
 
 WERTHEMANITE. ^lS0 6 -f-3aq. G.=2'80. Occurs near Chachapoyas, in Peru. 
 
 ALUNITE, Alaunstein, Oei'm. Composition K 2 Al 3 S 4 0.. 2 + 6aq. Rhombohedral. Also 
 massive, fibrous. Forms seams in trachyte and allied rocks. Tolfa, near Rome ; Tuscany; 
 Hungary ; Mt. Dore, France, etc. 
 
 LOWIQITE. Same composition as alunite, but contains 3 parts more of water. Tabrze, 
 Silesia. 
 
 LINARITE. Bleilasur, Kupferbleispath, Germ. 
 
 Monoclinic. C= 77 27' ; /A I, over i-i, = 61 36', O A 14 = 141 5', 
 c : T> : d = 0*48134 : 0-5819 : 1, Hessenberg. Twins: 
 twin n ing-plane i-i common ; O A O' 154 54'. 
 
 *j Cleavage : i-i very perfect ; O less so. 
 
 J H.r=2'5. G.=5.3-5'45. Lustre vitreous or ada- 
 mantine. Color deep azure-blue. Streak pale blue. 
 Translucent. Fracture conchoidal. Brittle. 
 
 Comp. PbCuS0 5 +aq=(Pb,Cu)S0 4 +H 2 (Pb,Cu)0 :2 Sulphur trioxide 20 0, lead oxide 55 7, 
 copper oxide 19 '8, water 4 '5 =100. 
 
 Pyr., etc, In the closed tube yields water and loses its blue color. B.B. on charcoal fuses 
 easily to a pearl, and in R.F. is reduced to a metallic globule which by continued treatment 
 coats the coal with lead oxide, and if fused boron trioxide is added yields a pure globule of 
 copper. With soda gives the reaction for sulphur. Decomposed with nitric acid, leaving a 
 white residue of lead sulphate. 
 
 Obs. Formerly found at Leadhills. Occurs at Roughten Gill, Red Gill, etc. , in Cumber- 
 laud ; near Schneeberg, rare; in Dillenburg ; atRetzbanya; in Nertschinsk ; and near Beresof 
 in the Ural ; and supposed formerly to be found at Linares in Spain, whence the name. 
 
 BROCHANTITE. 
 
 Monoclinic. O = 89 27i'. 1 A / = 104 6f, O A 14 = 154 12*' ; <! : 
 b : d = 0-61983 : 1-28242 : 1. Schrauf distinguishes four types of forms : 
 I. Brochantite from Retzbanya (two varieties), also from Cornwall and 
 Russia, triclinic ; II. Warringtonite from Cornwall, a third variety from 
 Retzbanya, monoclinic (?) ; III. Brochantite from Nischne-Tagilsk, mono- 
 clinic triclinic ; IY. Konigine from Russia, and a fourth variety from Retz- 
 bauya, monoclinic (or orthorhombic). 
 
 Also in groups of acicular crystals and drusy crusts. Cleavage : i-\ very 
 perfect ; I in traces. Also massive ; reniform with a columnar structure. 
 
 H. 3-5-4. G.= 3-78-3-87, Magnus ; 3-9069, G. Rose. Lustre vitreous; 
 a little pearly on the cleavage-face. Color emerald-green, blackish-green. 
 Streak paler green. Transparent translucent. 
 
 Comp. Cu 4 SO 7 +8H 2 O:=CuS04 + 3H 2 CuO 2 :=Sulphur trioxide 17'7l, copper oxide 70 '34, 
 water 11 "95=100. This formula belongs to type IV., above ; the warringtonite corresponds 
 more nearly to CuSO 4 +3H i2 GuO^^-H ;2 O, and the existence of other varieties has been also 
 assumed. 
 
 Pyr., etc. Yields water, and at a higher temperature sulphuric acid, in the closed tube, 
 and becomes black. B.B. fuses, and on charcoal affords metallic copper. With soda gives 
 the reaction for sulphuric acid. 
 
OXYGEN COMPOUNDS. SULPHATES. 397 
 
 Cbs. Occurs at Gumeschevsk and Nischne-Tagilsk in the Ural ; the Konigine (or Kdnic/ite} 
 was from Gumeschevsk ; near Roughten Gill, in Cumberland ; in Cornwall (in part warring- 
 tonite) ; at Retzbanya ; in Nassau ; at Krisuvig in Iceland (krisumgite) ; in Mexico (brongnar- 
 tine) ; in Chili, at Andacollo ; in Australia. 
 
 Named after Brochant de Villiers. 
 
 LANGJTE. CuS0 4 + 2H;CuO: + 2aq. In crystals and concretionary crusts of a blue color. 
 G.=3'5. Cornwall. 
 
 CYANOTRTCIIITE, Lettsomite. -Kupfersammterz, Germ. In velvety druses. Color blue. 
 A hydrous sulphate of copper and aluminum. Moldava in the Banat. WoODWARDlTE, near 
 the above. 
 
 KUONKITE CuSO 4 + Na 2 S04 + 2aq:= Copper sulphate 47-2, sodium sulphate 42'1, water 
 10 "7 100. In irregular crystalline masses of a coarse fibrous structure, prismatic. Color 
 azure-blue. Moist to the touch. Found in the copper mines near Calama, Bolivia. (Domeyko.} 
 
 PHILMPITE. CuS0 4 +FeSiOi 2 + ^aq. In irregular fibrous masses, not prismatic. Coloi 
 blue. In the cordilleras of Condes, Santiago, Chili. (Domeyko.} 
 
 EXYSITE. Occurs in stalactitic forms in a cave. H. =2-2'4. G. rrl'59. Color bluish- 
 green. B.B. infusible. Analysis: S0 3 8'12, AlOs 29-85, CuO 16'91, CaO 1'35, H O 39'42, 
 SiOo 3-40, C0 2 1-05=100. Near St. Agnes, Cornwall. (Collins, Min Mag., 1. p. 14.) 
 
 URANIUM-SULPHATES. There are included herejohannite, uranochalcite, medjidite, zippeite, 
 wjlianite, uraconite. These are secondary products found with other uranium minerals at 
 JouchimsthaL 
 
 TKLLURATES. 
 
 MONTANITE. 
 
 Incmsting ; without distinct crystalline structure. 
 
 Soft and earthy. Lustre dull to waxy. Color yellowish to white. 
 Opaque. 
 
 Comp. Bi 2 Te0 6 + 2aq=Tellurium trioxide 26-1, bismuth oxide 68'6, water 5'3=100. 
 Pyr., etc. Yields water in a tube when heated. B.B. gives the reactions of bismuth and 
 tellurium. Soluble in dilute hydrochloric acid. 
 
 Obs. Incrusts tetradymite, at Highland, in Montana ; Davidson Co. , N. C. 
 
398 
 
 DESCRIPTIVE MINERALOGY. 
 
 7. CARBONATES. 
 
 ANHYDROUS CARBONATES. 
 
 Calcite Group. 
 
 CALCITE. Calc Spar. Kalkspath, Gsrm. 
 
 Rhombohedral. Rr\B, terminal, = 105 5', <9 A .72 = 135 23'; 
 0-8543. Cleavage: R highly perfect. 
 
 722 
 
 723 
 
 ANGLES OF RHOMBOHEDRONS. 
 
 O 
 
 Term. Edge. 
 156 2' 
 134 57' 
 105 5' 
 
 166 9' 
 153 45' 
 135 23' 
 
 724 
 
 Term. Edge. 0/\R 
 
 - 95 28' 129 2 
 
 2(-2) 78 51' 116 52' 
 
 4(_4) 65 50' 104 17' 
 
 727 
 
 ANGLES OP SCALENOHEDRONS. 
 
 Edge X (f. 724). Y. 
 P 138 J 5' 159 24' 
 J 128 15' 146 10' 
 1 104 38' 
 I 1 109 1' 
 
 Z. EdgeX. T. Z. 
 
 64 54' f 9 130 J 37' 164 1' 67 41' 
 
 90 20' -* 3 107 38' 145 15' 124 39' 
 
 144 24' 132 58' i 8 117 23' 149 43' 102 25 
 
 134 28' 150 44' -2 2 92 9' 153 16' 136 !' 
 
OXYGEN COMPOUNDS. CARBONATES. 
 
 399 
 
 Twins : (1) Twinning-plane basal (or parallel to 0). (2) 7?, the vertical 
 axes of the two forms nearly at right angles. (3) 272. (4) ~i^?, the 
 vertical axes of the two forms inclined to one another 127 34/. (5) Pris- 
 matic plane i-%. (6) plane i (see p. 95). 
 
 Also fibrous, both coarse and fine ; sometimes lamellar ; often granular ; 
 from coarse to impalpable, arid compact to earthy. Also stalactitic, tube- 
 rose, nodular, and other imitative forms. 
 
 H.= 2-5-3-5 ; some earthy kinds (chalk, etc.) 1. G. =2-508-2-778 ; pure 
 crystals, 2-7213-2-7234:, Beud. Lustre vitreous sub vitreous earthy. Color 
 white or colorless ; also various pale shades of gray, red, green, blue, violet, 
 yellow ; also brown and black when impure. Streak white or grayish. 
 Transparent opaque. Fracture usually conchoidal, but obtained with 
 difficulty when the specimen is crystallized. Double refraction strong. 
 
 729 
 
 730 
 
 Alston-Moor. 
 
 Comp., Var. Calcite is calcium carbonate, CaC0 3 =: Carbon dioxide 41, lime 56=100. 
 Part of the calcium is sometimes replaced by magnesium, iron, or manganese, more rarely by 
 strontium, barium, zinc, or lead. 
 
 The varieties are very numerous, and diverse in appearance. They depend mainly on the 
 following points : (1) differences in crystallization; (2) in structural condition, the extremes 
 being perfect crystals and earthy massive forms ; (3) in color, diaphaneity, odor on friction, 
 due to impurities ; (4) in modes of origin. 
 
 1. Crystallized. Crystals and crystallized masses afford easily cleavage rhombohedrons ; and 
 when transparent they are called Iceland Spar, and also Doubly-refracting Spar (Doppels- 
 path, Germ.}. 
 
 The crystals vary in proportions from broad tabular to moderately slender acicular, and 
 take a great diversity of forms. But the extreme kinds so pass into one another through those 
 that are intermediate that no satisfactory classification is possible. Many are stout or short 
 in shape becau-^ normally so. But other forms that are long tapering in their full develop- 
 
403 DESCRIPTIVE MINERALOGY. 
 
 ment occur short and stout because abbreviated by an abrupt termination in a broad o, or an 
 obtuse rhombohedron (as J- or jR), or a low scalenohedron (as 3 ), or a combiuation of these 
 forms ; and thus the crystals having essentially the same combinations of planes vary greatly 
 in shape. The acute scalenohedrons like f. 724, are called dog-tooth spar. 
 
 Fontainebleau limestone. Crystals of the form in f. 719c, from Fontainebleau and Nemours, 
 France, containing a large amount of sand, some 50 to 63 p. c. Similar sandstone crys- 
 tals occur at Sievring, near Vienna, and elsewhere. Pseudomorphous scalenohedrons of sand- 
 stone, after calcite, are found near Heidelberg. 
 
 Satin Spar ; fine fibrous, with a silky lustre. Resembles fibrous gypsum, which is also 
 called satin spar, but is m ich harder and effervesces with acids. Argentine (Schieferspath), 
 a pearly lamellar calcite, the lamellae more or less undulating ; color white, grayish, yellowish, 
 or reddish. Apkr&6, in its harder and more sparry variety (Schaumspath) is a foliated white 
 pearly calcite, near argentine ; in its softer kinds (Schaumerde, Silvery Chalk, Ecume dz Terre 
 H.) it approaches chalk, though lighter, pearly in lustre, silvery- white or yellowish in color, 
 soft and greasy to the touch, and more or less scaly in structure. 
 
 ' 2. Massive Varieties. Granular limestone (S'lCcJiaroidal limestone, so named because like loaf- 
 sugar in fracture). The texture varies from quite coarse to very fine granular, and the latter 
 passes by imperceptible shades into compact limestone. The colors are various, as white, 
 yellow, reddish, green, and usually they are clouded and give a handsome effect when the 
 material is polished. When such limestones are fit for polishing, or for architectural or orna- 
 mental use, they are called marbles. Statuary marble is pure white, fine grained, and firm 
 in texture. Hard compact limestone, varies from nearly pure white, through grayish, drab, 
 buff, yellowish, and reddish shades, to bluish-gray, dark brownish-gray, and black, and is some- 
 times variously veined. The colors dull, excepting ochre-yellow and ochre-red varieties. 
 Many kinds make beautiful marble when polished. 
 
 Shell-marble includes kinds cons sting largely of fossil shells. Ruin-marble is a kind of com- 
 pact calcareous marl, showing, when polished, pictures of fortifications, temples, etc. , in ruins, 
 due to infiltration of oxide of iron. Lithographic stone is a very even grained compact lime- 
 stone, usually of buff or drab color ; as that of Solenhofen. Breccia marble is made of frag 
 ments of limestone cemented together, and is often very beautiful when the fragments are ol 
 different colors, or are imbedded in a base that contrasts well. The colors are very various 
 Pudding stone marble consists of pebbles or rounded stones cemented. It is often called, 
 improperly, breccia marble. 
 
 HydrauUo limestone is an impure limestone. The varieties in the United States contain 2( 
 to 40 p. c. of magnesia, and 12 to 30 p. c. of silica and alumina. 
 
 Soft compact limestone. Chalk is white, grayish -white, or yellowish, and soft enough tc 
 leave a trace on a board. The consolidation into a rock of such softness may be owing to the 
 fact that the material is largely the hollow shells of rhizopods. Calcareous marl (Mergel 
 kalk, Germ. ) is a soft earthy deposit, often hardly at all consolidated, with or without dis 
 tinct fragments of shells ; it generally contains much clay, and graduates into a calcareous 
 clay. 
 
 Concretionarg massive. Oolite ( Rogenstein, Germ.} is a granular limestone, but its grain; 
 are minute rounded concretions, looking somewhat like the roe of a fish, the name coming 
 from 'cjw, egg. It occurs among all the geological formations, from the Lower Silurian t< 
 the most recent, and it is now forming about the coral reefs of Florida. Pisolite (Erbsentein 
 Germ.} consists of concretions as large often as a small pea, or even larger, the concretions 
 having usually a distinct concentric structure. It is formed in large masses in the vicinity o: 
 the Hot Springs at Carlsbad in Bohemia. 
 
 Deposited from calcareous springs, streams, or in caverns, etc. (a) Stalactites are the calcareoui 
 cylinders or cones that hang from the roof's of limestone caverns, and which are formed fron 
 the waters that drip through the roof ; these waters hold some calcium bicarbonate in solu 
 tion, and leave calcium carbonate to form the stalactite when evaporation takes place. Sta 
 lactites vary from transparent to nearly opaque ; from a granular crystalline structure to a 
 radiating fibrous ; from a white color and colorless to yellowish-gray and brown, (b) Stalag 
 mite is the same material covering the floors of caverns, it being made from the waters tha 
 drop from the roofs, or from sources over the bottom or sides ; cones of it sometimes rise f rou 
 the floor to meet the stalactites above. 
 
 (c) Calc-sinter, Travertine, Gale Tufa. Travertine ( Confetto di Tivoli) is of essentially th< 
 same origin with stalagmite, but is distinctively a deposit from springs or rivers, especially 
 where in large deposits, as along the river Anio, at Tivoli, near Rome, where the deposit i 
 scores of feet in thickness. It has a very cavernous and irregularly banded structure, owinj 
 to its mode of formation. 
 
 (d) Agaric mineral; Rock-milk (Bergmilch, Montmilch, Germ.) is a very soft, white material 
 breaking easily in the fingers, deposited sometimes in caverns, or about sources holding Km 
 in solution. 
 
OXYGEN COMPOUNDS. CARBONATES. 401 
 
 (e) Rock-meal (Bergmehl, Germ.) is white and light, like cotton, becoming a powder on the 
 slightest pressure. It is an efflorescence, and is common near Paris, especially at the quarries 
 of Nanterre. 
 
 Pyr., etc. In the closed tube sometimes decrepitates, and, if containing metallic oxides, 
 may change its color. B.B. infusible, but becomes caustic, glows, and colors the flame red 
 after ignition the assay reacts alkaline ; moistened with hydrochloric acid imparts the charac- 
 teristic lime color to the flame. In borax dissolves with effervescence, and if saturated, 
 yields on cooling an opaque, milk-white, crystalline bead. Varieties containing metallic 
 oxides color the borax and salt of phosphorus beads accordingly. With soda on platinum foil 
 fuses to a clear mass ; on charcoal it at first fuses, but later the soda is absorbed by the coal, 
 leaving an infusible and strongly luminous residue of lime. In the solid mass effervesces 
 when moistened with hydrochloric acid, and fragments dissolve with brisk effervescence even 
 iu cold acid. 
 
 Diff. Distinguishing characters : perfect rhombohedral cleavage ; softness, can be scratched 
 with a knife ; effervescence in cold dilute acid ; inf usibility. Less hard and of lower specific 
 gravity than avagonite. 
 
 Obs. Andreasberg in the Harz is one of the best European localities of crystallized calcite ; 
 there are other localities in the Tyrol, Styria, Carinthia, Hungary, Saxony, Hesse Darmstadt 
 (at Auerbach), Hesse Cassel, Norway, France, and in England in Derbyshire, Cumberland, 
 Cornwall ; Scotland ; in Iceland. 
 
 In the U. States prominent localities are : in $". York, in St. Lawrence and Jefferson Cos., 
 especially at the Rossie lead mine ; in Antwerp; dog-tooth spar, in Niagara Co., near Lock- 
 port ; near Booneville, Oneida Co. ; at Anthony's Nose, on the Hudson ; at Watertown, 
 Agaric mineral ; at Schoharie, fine stalactites in many caverns. In Conn. , ab the lead mine, 
 Middletown In N. Jersty, at Bergen. In Virginia, at the celebrated Wier's cave, stalactite* 
 of great beauty; also in the 'large caves of Kentucky. At the Lake Superior copper mines, 
 splendid crystals often containing scales of native copper. At Warsaw, Illinois ; at Quincy, 
 Jtt.; at Hazle Green, Wis. In Nova Scotia, at Partridge L 
 
 DOLOMITE. 
 
 Ehombohedral. 72 A 72 = 106 15', A 72 = 136 ~-8J' ; c = 0-8322. 
 72 A 72 varies between 106 10' and 106 20'. Cleavage : 
 72 perfect. Faces R often curved, and secondary 
 planes usually with horizontal striae. Twins : similar 
 to f . 733. Also in imitative shapes ; also amorphous, 
 granular, coarse or fine, and grains often slightly 
 coherent. 
 
 H.=3-5-4:. G.= 2-8-2-9, true dolomite. Lustre vit- 
 reous, inclining to pearly in some varieties. Color white, reddish, or green- 
 ish-white ; also rose-red, green, brown, gray, and black. Subtransparent to 
 translucent. Brittle. 
 
 Comp., Var (Ca,Mg)C0 3 , the ratio of Ca : Mg in normal or true dolomite is 1 : 1= Cal- 
 cium carbonate 54 '35, magnesium carbonate 45 '65. Some kinds included under the name 
 have other proportions ; but this may arise from their being mixtures of dolomite with calcite 
 or magnesite. Iron, manganese, and more rarely cobalt or zinc are sometimes present. 
 
 The varieties are the following : 
 
 Crystallized. Pearl spar includes rhombohedral crystallizations with curved faces. Colum- 
 nar or fibrous. Granular constitutes many of the kinds of white statuary marble, and white 
 and colored architectural marbles, names of some of which have been mentioned under calcite. 
 
 Compact massive, like ordinary limestone. Many of the limestone strata of the globe are 
 here included, and much hydraulic limestone, noticed under calcite. 
 
 Ferriferous : Brown, spar, in part. Contains iron, and as the proportion increases it gradu- 
 ates into ankerite (q. v.). The color is white to brown, and becomes brownish on exposure 
 through oxidation of the iron. Manganiferous. Colorless to flesh-red. JK A H= 106 23' ' 
 106 10'. Cobaltiferous. Colored reddish ; G. =2921, Gibbs. 
 
 The varieties based on variations in the proportions of the carbonates are the following ; 
 (a) Normal dolomite, ratio of Ca to Mg=l : 1, (b) ratio 1-J : 1=3 : 2 ; ratio=2 : 1 ; ratio 3 : 
 1 ; ratio=5 : 1 ; ratio 1:3. The last (/) may be dolomitic magnesite ; and the others, from 
 
 26 
 
 
402 DESCRIPTIVE MINER ALOr. 
 
 (J). dolomitic calcite, or calcite + dolomite. The manner in which dolomite is ofted mixed 
 with calcite, forming its veins and its fossil shells (see below), shows that this is not improb- 
 able. 
 
 Pyr., etc. B. B. acts like calcite, but does not give a clear mass when fused with soda on 
 platinum foil. Fragments thrown into cold acid are very slowly acted uoon, while in powdei 
 in warm acid the mineral is readily dissolved with effervescence. The ferriferous dolomites 
 become brown on exposure. 
 
 Diff.- -Resembles calcite, but generally to be distinguished in that it does not effervesce 
 readily in the mass in cold acid. 
 
 Obs. Massive dolomite constitutes extensive strata, called limestone strata, in various 
 regions. Crystalline and compact varieties are often associated with serpentine and other 
 magnesian rocks, and with ordinary limestones. Some of the prominent localities are at Salz- 
 burg; the Tyrol; Schemnitz in Hungary; Kapnik in Transylvania; Freiberg in Saxony; 
 the lead mines at Alston in Derbyshire, etc. 
 
 In the TJ. States, in Vermont, at Roxbury. In Rhode Island, at Smithfield. In N. Jersey, 
 at Hoboken. In N. York, at Lockport, Niagara Falls, and Rochester ; also at Glenn's Falls, 
 in Richmond Co., and at the Parish ore bed, St. Lawrence Co.; at Brewster, Putnam Co. 
 
 Named after Dolomieu, who announced some of the marked characteristics of the rock in 
 1791 its not effervescing with acids, while burning like limestone, and its solubility after 
 heating in acids. 
 
 ANKERITE. 
 
 Rhombohedral. .Z? A .ff = 106 7', Zepharovich. Also crystalline mas- 
 sive, coarse or fine granular, and compact. 
 
 H.=3'5-4. G.= 2*95-3' 1. Lustre vitreous to pearly. Color white, gray, 
 reddish. Translucent to subtranslucent. 
 
 Coxnp. CaC0 3 +FeCO 3 +2\'CaMgC 2 6 ). Here, according to Boricky, x may have the values 
 *> 1, f , f , , 2, 3, 4, 5, 10. The varieties having the five higher values of x he calls paran- 
 kerite, while the others are normal ankerite. If a?=l, the formula is equivalent to 2CaCO 3 + 
 MgCO 3 +FeC0 3 , and requires: Calcium carbonate 50, magnesium carbonate 21, iron carbon- 
 ate 29=100. Manganese is also sometimes present. 
 
 Pyr., etc. B.B. like dolomite, but darkens in color, and on charcoal becomes black and 
 magnetic ; with the fluxes reacts for iron and manganese. Soluble with effervescence in the 
 acids. 
 
 Obs. Occurs with siderite at the Styrian mines ; in Bohemia; Siegen ; Schneeberg ; Nova 
 Scotia, etc. 
 
 MAGNESITE. 
 
 Khombohedral. R/\R = 107 29', Of\K = 136 56' ; c = 0-8095. 
 Cleavage: rhombohedral, perfect. Also massive; granular, to very com- 
 pact. 
 
 H.=3'5-4-5. G.=3-3-OS, cryst. ; 2-8, earthy; 3-3 -2, when ferriferous, 
 Lustre vitreous; fibrous varieties sometimes silky. Color white, yellowish 
 or grayish-white, brown. Transparent opaque. Fracture flat conchoid al 
 
 Var. Ferriferous, Breunerite; containing several p. c. of iron protoxide; G. 3-3'2; 
 white, yellowish, brownish, rarely black and bituminous; often becoming brown on exposure 
 and hence called Brown Spar. 
 
 Comp. Magnesium carbonate, MgC0 3 Carbon dioxide 52 '4, magnesia 47 '6 = 100; butiroi 
 often replacing some magnesium. 
 
 Pyr., etc. B. H. resembles calcite and dolomite, and like the latter is but slightly actec 
 upon by cold acids ; in powder is readily dissolved with effervescence in warm hydrochlori< 
 acid. 
 
 Obs. Found in talcose schist, serpentine, and other magnesian rocks ; as veins in serpen 
 tine, or mixed with it so as to form a variety of verd-antique marble (magnesitic ophiolite o 
 
OXYGEN COMPOUNDS. CARBONATES. 403 
 
 ilunt) ; also in Canada, as a rock, more or less pure, associated with steatite, serpentine, and 
 dolomite. 
 
 Occurs at Hrubschiitz in Moravia ; in Styria, and in the Tyrol ; at Frankenstein in Silesia ; 
 Snarum, Norway ; Baudissero and Castellamonte in Piedmont. In America, at Bolton, Mass.; 
 at Barehllls, near Baltimore, Md. ; in Penn., at West G-oshen, Chester Co. ; near Texas, Lan- 
 caster Co. ; California. 
 
 MESITITE and PISTOMESITE come under the general formula (Mg,Fe)C0 3 ; with the formei 
 Mg : Fe=2 : 1 ; with the latter=l : 1. 
 
 SIDERITE. Spathic Iron. Chalybite. Eisenspath, Germ. 
 
 Rhombohedntl. Rf\R= 107, Ol\R = 136 37' ; c = 0-81715. The 
 faces often curved, as below. Cleavage : rhom- 
 bohedral, perfect. Twins : twinning-piane . 735 
 
 Also in botryoidal and globular forms, sub- 
 fibrous within, occasionally silky fibrous. Often 
 cleavable massive, with cleavage planes undu- 
 lating. Coarse or fine granular. 
 
 H. = 3-5-4-5. G. =3-7-3-9. Lustre vitreous, 
 more or less pearly. Streak white. Color ash- 
 gray, yellowish-gray, greenish-gray, also brown 
 and brownish-red, rarely green ; and sometimes 
 white. Translucent subtranslucent. Fracture 
 uneven. Brittle. 
 
 Comp., Var. Iron carbonate, FeC0 3 = Carbon dioxide 37'9, iron protoxide 62'1. But part 
 of the iron usually replaced by manganese, and often by magnesium or calcium. Somo 
 varieties contain 8-10 p. c. MnO. 
 
 The principal varieties are the following : 
 
 (1) Ordinary, (a) Crystallized, (b) Goner etionary = Splier osiderite ; in globular concretions, 
 either solid or concentric scaly, with usually a fibrous structure, (c) Granular to compact mas- 
 sive, (d) Oolitic, like oolitic limestone in structure. (e) Earthy, or stony, impure from 
 mixture with clay or sand, constituting a large part of the clay iron stone of the coal forma- 
 tion and other stratified deposits ; H. =3 to 7, the last from the silica present ; G-. =3'0-3'8, 
 or mostly 3 '15 -3 '65. 
 
 Pyr., etc. In the closed tube decrepitates, evolves carbon oxide and carbon dioxide, 
 blackens and becomes magnetic. B.B. blackens and fuses at 4'5. With the fluxes reacts for 
 iron, and with soda and nitre on platinum foil generally gives a manganese reaction. Only 
 slowly acted upon by cold acid, but dissolves with brisk effervescence in hot hydrochloric acid. 
 
 Diff. Specific gravity higher than that of calcite and dolomite. B.B. becomes magnetic 
 readily. 
 
 Obs. Siderite occurs in many of the rock strata, in gneiss, mica slate, clay slate, and aa 
 clay iron-stone in connection with the Coal formation and many other stratified deposits. It 
 is often associated with metallic ores. At Freiberg it occurs in silver mines. In Cornwall it 
 accompanies tin. It is also found accompanying copper and iron pyrites, galenite, vitreous 
 copper, etc. In New York, according to Beck, it is almost always associated with specular 
 iron. In the region in and about Styria and Carinthia this ore forms extensive tracts in gneiss. 
 At Harzgerode in the Harz, it occurs in fine crystals ; also in Cornwall, Alston-Moor, and 
 Devonshire ; near Glasgow ; also at Mouillar, Magescote, etc., in France, etc. 
 
 In the U. States, in Vermont, at Plymouth. In Mass., at Sterling. In Conn., at Roxbury. 
 In N. York, at the Sterling ore bed in Antwerp, Jefferson Co. ; at the Rossie iron mines, St. 
 Lawrence Co. In N. Carolina, at Fentress and Harlem mines. The argillaceous carbonate, 
 in nodules and beds (clay iron-stone), is abundant in the coal regions of Penn. , Ohio, and manj 
 parts of the country. 
 
 RHODOCHROSITE .* Dialogite. Manganspath, Germ. 
 
 Ehombohedral. Rf\R = 106 51', O f\ R = 136 31i' ; c = 0-8211. 
 Cleavage : R, perfect. Also globular and botryoidal, having a columnai 
 structure, sometimes indistinct. Also granular massive ; occasionally ira 
 palpable; incr listing. 
 
404 DESCRIPTIVE MINERALOGY. 
 
 H. =3-5-4-5. G.= 3-4-3-7. Lustre vitreous, inclining to pearly. Color 
 shades of rose-red, yellowish-gray, fawn-colored, dark red, brown. Streak 
 white. Translucent subtranslucent. Fracture uneven. Brittle. 
 
 Comp MnC0 3 =: Carbon dioxide 38 '3, manganese protoxide 61 '7 ; but part of the man- 
 ganese usually replaced by calcium, and often also by magnesium or iron ; and sometimes by 
 cobalt. 
 
 Pyr., etc. B.B. changes to gray, brown, and black, and decrepitates strongly, but is in- 
 fusible. With salt of phosphorus and borax in O.F. gives an amethystine -colored bead in 
 R.F. becomes colorless. With soda on platinum foil a bluish-green manganate. Dissolve? 
 with effervescence in warm hydrochloric acid. On exposure to the air changes to brown, and 
 pome bright rose-red varieties become paler. 
 
 Obs. Occurs commonly in veins along with ores of silver, lead, and copper, and with other 
 ores of manganese. Found at Schemuitz and Kapnik hi Hungary ; Nagyag in Transylvania ; 
 near Elbingerode in the Harz ; at Freiberg in Saxony. 
 
 Occurs in New Jersey, at Mine Hill, Franklin Furnace. Abundant at the silver mines oi 
 Austin, Nevada ; at Placentia Bay, Newfoundland. 
 
 Named rJwdochrosite f rom /M5oi>, a rose, and xpcStrts, color; and dialogite, from 8(0X07^, doubt, 
 
 SMITHSONITE. Calamine pt. Galmei pt. Zinkspath, Germ. 
 
 Khombohedral. Rf\R= 107 40', 0/\R = 137 3' ; c = 0-8062. E 
 generally curved and rough. Cleavage : R perfect. Also reniform, botry- 
 oidal, or stalactitic, and in crystalline incrustations; also granular, and 
 sometimes impalpable, occasionally earthy and friable. 
 
 H. 5. G.= 4-4-45. Lustre vitreous, inclining to pearly. Streak white, 
 Color white, often grayish, greenish, brownish- white, sometimes green 
 and brown. Subtransparent translucent. Fracture uneven imperfect!}' 
 conchoidal. Brittle. 
 
 Comp., Var.ZnCO 3 = Carbon dioxide 35 "2, zinc oxide 64 '8 =100; but part of the zinc 
 often replaced by iron or manganese, and by traces of calcium and magnesium ; sometimes 
 by cadmium. 
 
 Varieties. (1) Ordinary, (a) Crystallized; (b) botry oidal and stalactitic, common; (c] 
 granular to compact massive; (d) earthy, impure, in nodular and cavernous masses, varying 
 from grayish-white to dark gray, brown, brownish-red, brownish-black, and often with drusj 
 surfaces in the cavities ; " dry-bone " of American miners. 
 
 Pyr., etc. In the closed tube loses carbon dioxide, and, if pure, is yellow while hot and 
 colorless on cooling. B.B. infusible; moistened with cobalt solution and heated in O.F. gives 
 a green color on cooling. With soda on charcoal gives zinc vapors, and coats the coal yellow 
 while hot, becoming white on cooling ; this coating, moistened with cobalt solution, gives a 
 green color after heating in O.F. Cadmiferous varieties, when treated with soda, give at 
 first a deep yellow or brown coating before the zinc coating appears. With the fluxes some 
 varieties react for iron, copper, and manganese. Soluble in hydrochloric acid with efferves- 
 cence. 
 
 Diff. Distinguished from calarnine by its effervescence in acids. 
 
 Obs. Smithsonite is found both in veins and beds, especially in company with galeuite 
 and blende ; also with copper and iron ores. It usually occurs in calcareous rocks, and is 
 generally associated with calamine, and sometimes with limonite. It is often produced by 
 the action of zinc sulphate upon calcium or magnesium carbonate. 
 
 Found at Nertschinsk in Siberia ; at Dognatzka in Hungary ; Bleiberg and Eaibel in Cariu- 
 thia ; Moresnet in Belgium. In England, at Roughten Gill, Alston Moor, near Matlock, in 
 the Mendip Hills, and elsewhere ; in Scotland, at Leadhills; in Ireland, at Donegal. 
 
 In the U. States, in N. Jersey, at Mine Hill, near the Franklin Furnace. In Penn. , at 
 Lancaster abundant ; at the Perkiomen lead mine ; at the Ueberroth mine, near Bethlehem. 
 In Wisconsin, at Mineral Point, Shullsburg, etc. In Minnesota, at Ewing's diggings, N. W. 
 of Dubuque, etc. In Missouri and Arkansas, along with the lead ores in Lower Silurian 
 limestone. 
 
OXYGEN COMPOUNDS. CARBONATES. 
 
 405 
 
 Aragonite Group. 
 
 ARAGONITB. 
 
 Ortliorhombic /A 7 = 116 10', O A 14 = 130 50' ; c : 3 : = 1-1571 
 : 1-6055 : 1. O A 1 = 126 15', A 1-2 = 137 15', 14 A 14, top, := 108 
 26'. Crystals usually having O striated parallel to the shorter diagonal ; 
 often tapering from the presence of acute domes and pyramids, which have 
 unusual indices. Cleavage: I imperfect; i-i distinct; l-# imperfect. 
 Twins : twinning-plane 7, producing often hexagonal forms, f . 738, compare 
 figures on pp. 96, 97. Twinning often many times repeated in the same 
 crystal, producing successive reversed layers, the alternate of which may be 
 exceedingly thin ; often so delicate as to produce by the succession a fine 
 striation of the faces of a prism or of a cleavage plane. Also globular, 
 reniform, and coralloidal shapes; sometimes columnar, composed of 
 Etraight and divergent fibres ; also stalactitic ; incrusting. 
 
 737 
 
 738 
 
 it 
 
 /If 
 
 H.i=3*5-4. G.= 2-931, Haidinger. Lustre vitreous, sometimes inclin- 
 ing to resinous on surfaces of fracture. Color white ; also gray ^yellow, 
 green, and violet ; streak uncolored. 
 subconchoidal. Brittle. 
 
 Transparent translucent. Fracture 
 
 Var. 1. Ordinary, (a] Crystallized in simple or compound crystals, the latter much the 
 most common ; often in radiating groups of acicular crystals, (b) Columnar ; a fine fibrous 
 variety with silky lustre is called Satin spar, (c) Massive. Stalactitic or stalagmitic (either 
 compact or fibrous in structure), as with calcite ; Sprudelstein is stalactitic from Carlsbad. 
 Coralloidal ; in groupings of delicate interlacing and coalescing stems, of a snow-white color, 
 and looking a little like coral. 
 
 Comp CaC0 3 , like calcite, = Carbon dioxide 44, lime 56100. 
 
 Pyr., etc. B. B. whitens and falls to pieces, and sometimes, when containing strontia, im- 
 parts a more intensely red color to the flame than lime ; otherwise reacts like calcite. 
 
 Diflf. See calcite, p. 401. 
 
 Obs. The most common repositories of aragonite are beds of gypsum, beds of iron ore 
 (where it occurs in coralloidal forms, and is denominated flos-ferri, "flower of iron," Eisen- 
 bliithe, Germ.), basalt, and trap rock; occasionally it occurs in lavas. It is often associated 
 with copper and pyrite, galenite, and malachite. 
 
 First discovered in Aragon, Spain (whence its name), at Molina and Valencia. Since 
 found at Bilin in Bohemia ; at Herrengrund in Hungary, f. 738 ; at Baumgarten in Silesia ; 
 
406 
 
 DESCRIPTIVE MINERALOGY. 
 
 at Leogang in Salzburg ; in Waltsch, Bohemia, and many other places. The flosferri variety 
 is found in great perfection in the Styrian mines. In Buckinghamshire, Devonshire, in 
 caverns ; at Leadhills in Lanarkshire. 
 
 Occurs in serpentine at Hoboken, N. J.; at Edenville, N. Y.; at the Parish ore bed, Rossie, 
 N. Y.; at Haddam, Conn.; at New Garden, in Chester Co., Penn.; at Wood's Mine, Lancas- 
 ter Co., Penn.; at Warsaw, 111., lining geodes. 
 
 MANGANOCALCITE. Composition 2MnC0 3 -HCa,Mg)C0 3 , with a little iron replacing part 
 of the manganese. G. =3-037. Color flesh-red to reddish-white. Schemnitz, Hungary. 
 
 WITHERITE. 
 
 Orthorhombic. /A 1= 118 30', A 14 = 128 45' ; c:b:d = 1-246 : 
 1'6808 : 1. Twins : all the annexed figures, com- 
 position parallel to I\ reentering angles some- 
 times observed. Cleavage : / distinct ; also in 
 globular, tuberose, and botryoidal forms; struc- 
 ture either columnar or granular ; also amor- 
 phous. 
 
 H. = 3-3-75. G. 4-29-4-35. Lustre vitreous, 
 inclining to resinous, on surfaces of fracture. 
 Color white, often yellowish, or grayish. Streak 
 white. Subtransparent translucent. Fracture 
 uneven. Brittle. 
 
 Comp. BaCO 3 = Carbon dioxide 22 '3, baryta 77'7-100. 
 Pyr. 3 etc. B.B. fuses at 2 to a bead, coloring the flame yel- 
 lowish-green; after fusion reacts alkaline. B.B. on charcoal 
 with soda fuses easily, and is absorbed by the coal. Soluble 
 
 in dilute hydrochloric acid; this solution, even when very much diluted, gives with sulphuric- 
 acid a white precipitate which is insoluble in acids. 
 
 Diff. Distinguishing characters : high specific gravity ; effervescence with acids ; green 
 coloration of the flame B.B. 
 
 Obs. Occurs at Alston-Moor in Cumberland ; at Fallowfield, near Hexham in Northumber- 
 land ; Tarnowitz in Silesia ; Leogang in Salzburg ; Peggau in Styria ; some places in Sicily ; 
 the mine of Arqueros, near Coquimbo, Chili ; near Lexington, Ky., with barite. 
 
 Witherite is extensively mined at Fallowfield, and is used in chemical works in the manu- 
 facture of plate-glass, and in France in making beet- sugar. 
 
 BHOMLITE.- Formula as for barytocalcite, but orthorhombic in form. 
 
 STRONTIANITE. 
 
 Orthorhombic. I^ 1= 117 19', A 1-t = 130 5' ; c:l:d = MS83 : 
 
 1-6421 : 1. O A 1 = 125 43', O A 1-2 = 144 6', 
 1 A 1, mac., = 130 1', 1 A 1, brack, = 92 IV. 
 Cleavage : 1 nearly perfect, i-l in traces. 
 
 Crys- 
 tals often acicular and in divergent groups. 
 Twins : like those of aragonite. O usually stri- 
 ated parallel to the shorter diagonal. Also in 
 columnar globular forms ; fibrous and granular. 
 H.=3-5-4. G. 3-605-3-713. Lustre vitre- 
 ous ; inclining to resinous on uneven faces of 
 
 fracture. Color pale asparagus-green, apple-green ; also white, gray, yel- 
 low, and yellowish-brown. Streak white. Transparent translucent. 
 Fracture uneven. Brittle. 
 
OXYGEN COMPOUNDS. CARBONATES. 
 
 407 
 
 Comp. SrCO 3 =: Carbon dioxide 297, strontia 70'3 ; but a small part of the strontium 
 often replaced by calcium. 
 
 Pyr., etc. B.B. swells up, throws out minute sprouts, fuses only on the thin edges, and 
 colors the flame strontia-red ; the assay reacts alkaline after ignition. Moistened with hydro- 
 chloric acid and treated either B.B. or in the naked lamp gives an intense red color. With 
 soda on charcoal the pure mineral fuses to a clear glass, and is entirely absorbed by the coal ; 
 if lime or iron be present they are separated and remain on the surface of the coal. Soluble 
 in hydrochloric acid ; the dilute solution when treated with sulphuric acid gives a white pre- 
 cipitate. 
 
 DifT. Differs from related minerals, not carbonates, in effervescing with acids ; lower 
 specific gravity than witherite, and colors the flame red. 
 
 Obs. Occurs at Strontian in Argyleshire ; in Yorkshire, England ; Giant's Causeway, Ire- 
 land ; Clausthal in the Harz ; Briiunsdorf , Saxony ; Leogang in Salzburg. In the U. States 
 it occurs at Schoharie, N. Y., in granular and columnar masses, and also in crystals. At 
 Muscalonge Lake; at Chaumont Bay and Theresa, in Jefferson Co., N. Y. ; MifflinCo., Penn 
 
 CERUSSITE. Weissbleierz, Bleispath, Germ. 
 
 745 
 
 Orthorhombic. /A 1= 117 13', A 14 = 130 9f ; c:t>:d= 1-1852 
 : 1-6388 : 1. O A 1 = 125 
 46', 0Al--& = 144: 8', lAl, 
 mac., = 130, 1 A 1, brach., = 
 92 19'. Cleavage: /often 
 imperfect ; 2-i hardly less so. 
 Crystals usually thin, broad, 
 and brittle ; sometimes stout. 
 Twins : very common ; twin- 
 ning-plane I, producing usu- 
 ally cruciform or stellate 
 forms ; also less commonly, 
 ^winning-plane i-&. Rarely 
 fibrous, often granular mas- 
 sive and compact. Sometimes stalactitic. 
 
 II. = 3-3-5. G. = 6*465-6 '480 ; some earthy varieties as low as 5'4. 
 Lustre adamantine, inclining to vitreous or resinous; sometimes pearly; 
 sometimes sub metallic, if the colors are dark, or from a superficial change. 
 Color white, gray, grayish-black, sometimes tinged blue or green by some 
 of the salts of copper; streak uncolored. Transparent subtranslucent. 
 Fracture conchoidal. Very brittle. 
 
 Comp. PbC0 3 = Carbon dioxide 16 '5, lead oxide 83 '5 =100. 
 
 Pyr., etc. In the closed tube decrepitates, loses carbon dioxide, turns first yellow, and at 
 a higher temperature dark red, but becomes yellow again on cooling. B.B. on charcoal fuses 
 very easily, and in R. F. yields metallic lead. Soluble in dilute nitric acid with effervescence. 
 
 Diff. Unlike anglesite, it effervesces with nitric acid. Characterized by high specific 
 gravity, and yielding lead B.B. 
 
 Obs Occurs in connection with other lead minerals, and is formed from galenite, which, 
 as it passes to a sulphate, may be changed to carbonate by means of solutions of calcium 
 bicarbonate. It is found at Johanngeorgenstadt ; at Nertschinsk and Beresof in Siberia ; at 
 Clausthal in the Harz ; at Bleiberg in Carinthia ; at Mies and Przibram in Bohemia ; at Retz- 
 hanya. Hungary; in England, in Cornwall; near Matlock and Wirksworth, Derbyshire; at 
 Leadhills, Scotland ; in Wicklow, Ireland. 
 
 Found in Penn. , at Phenixville ; at Perkiomen. In N. York, at the Rossie lead mine. In 
 Virginia, at Austin's mines, Wythe Co. In N. Carolina, at King's mine, Davidson Co. , good. 
 In Wisconsin and other lead mines of the northwestern States, rarelv in crystals ; near the 
 Blue Mounds, Wise. , in stalactites. 
 
408 DESCRIPTIVE MINERALOGY. 
 
 BARYTOCALCITE. 
 
 Monoclinie. C = 73 52', I^ 1= 106 54', A 14 = 149 W ; c : I : d =-. 
 0-81035 : 1'295S3 : 1. Cleavage : /, perfect ; O, less perfect ; also massive. 
 
 H.=4:. G. =3-6363-3*66. Lustre vitreous, inclining to resinous. Color 
 white, grayish, greenish, or yellowish. Streak white. Transparent 
 translucent. Fracture uneven. 
 
 Comp (Ba,Ca)C0 3 , where Ba : Ca=l : l=Barium carbonate 66 -3, calcium carbonate 
 33-7=100. 
 
 Pyr., etc. B.B. colors the flame yellowish -green, and at a higher temperature fuses on 
 the thin edges and assumes a pale green color ; the assay reacts alkaline after ignition. With 
 the fluxes reacts for manganese. With soda on charcoal the lime is separated as an infusible 
 mass, while the remainder is absorbed by the coal. Soluble in dilute hydrochloric acid. 
 
 Obs. Occurs at Alston-Moor in Cumberland, in the Subcarboniferous or mountain lime- 
 stone. 
 
 PAKISITE. A carbonate containing cerium (also La,Di), and calcium with 6 p. c. fluorine. 
 Exact composition uncertain. In hexagonal crystals. Color brownish-yellow. Muso valley, 
 New Granada. KISCIITIMITE, from the gold washing of the Barsovska river, Urals, is similar 
 in composition, but contains no calcium. 
 
 BASTNASITE (Hamartite). Composition 2RCO 3 +RF, with R=Ce : La =2 : 3. Analysis, 
 Nordenskiolil, CO, 19'50, LaO 45-77, CeO 28'49, H,O I'Ol, F,0, (5 '23)=100. Found in small 
 masses imbedded between allanite crystals. Riddarhyttan, Sweden. 
 
 PHOSGENITE. Bleihornerz, Germ. 
 
 Tetragonal. 6>Al-a = 132 37'; c = 1-0871. Cleavage: / and i-i 
 bright ; also basal. 
 
 H.=2'75-3. G.=6-6'31. Lustre adamantine. Color white, gray, and 
 yellow. Streak white Transparent translucent. Rather sectile. 
 
 Comp. PbC0 3 +PbCl 2 =Lead carbonate 49, lead chloride 51=100, or lead oxide 81 -9, car- 
 bon dioxide 8-1, chlorine 13'0=102'9. 
 
 Pyr., etc. B.B. melts readily to a yellow globule, which on cooling becomes white and 
 crystalline. On charcoal in R.F. gives metallic lead, with a white coating of lead chloride. 
 With a salt of phosphorus bead previously saturated with copper oxide gives the chlorine 
 reaction. Dissolves with effervescence in nitric acid. 
 
 Obs. At Cromford near Matlock in Derbyshire ; very rare in Cornwall ; in large crystals 
 at Gibbas and Monteponi in Sardinia ; near Bobrek in Upper Silesia. 
 
 HYDEOUS CARBONATE. 
 TRONA. 
 
 Monoclinic. A i-i = 103 15'. Clea\ 7 age : i-i perfect. Often fibrous 
 or columnar massive. 
 
 H.= 2-5-3. G. 2-11. Lustre vitreous, glistening. Color gray or yel- 
 lowish-white. Translucent. Taste alkaline. Not altered by exposure to 
 a dry atmosphere. 
 
 Comp Na 4 C 3 8 +3aq=Carbon dioxide 40-2, soda 37'8, water 22 '0. 
 
 Pyr., etc. In the closed tube yields water and carbon dioxide. B.B. imparts an intensely 
 yellow color to the flame. Soluble in water, and effervesces with acids. Reacts alkaline 
 with moistened test paper. 
 
 Obs. The specimen analyzed by Klaproth came from the province of Suckenna, two days' 
 journey from Fezzen, ica. To this species belongs the urao found at ths bottom of a lake 
 
OXYGEN COMPOUNDS. CARBONATES. 
 
 409 
 
 In Maracaibo, S. A. , a day's journey from Merida. Efflorescences of trona occur near the 
 Sweetwater river, Rocky Mountains, mixed with sodium sulphate and common salt. 
 
 NATRON or Soda (sodium carbonate, Na a CO 3 +10aq). THEKMONATIUTE, Na 2 C0 8 +a(i. 
 TESCIIEMACHERITE, Ammonium carbonate. 
 
 Maracaibo. 
 
 Nevada. 
 
 GAY-LUSSITE. 
 
 Monoclinic. C = 78 27', /A 1= 68 50' and 111 10' 0*14 = 125 
 15' ; c:b:d = 0-96945 : 0-67137 : 1. 
 14 A 14, adj., = 109 30', A i = 110 
 30'. Crystals often lengthened, and 
 prismatic in the direction of 14; also in 
 that of ^ ; also (fr.. Nevada) not elongate, 
 but thin in the direction of the orthodia- 
 gonal, O being very narrow or wanting ; 
 surfaces usually uneven, being formed 
 of minute subordinate planes. Cleav- 
 age : I perfect ; less so, but giving a 
 reflected image in a strong light. 
 
 H.=2-3. G.=l-92-l-99. Lustre vitreous. Color white, yellowish- 
 white. Streak uncolored to grayish. Translucent. Fracture conchoidal. 
 Extremely brittle. Not phosphorescent by friction or heat. 
 
 Comp. Na 2 COs + CaC0 3 + 5aq=: Sodium carbonate 35-9, calcium carbonate 33*8, water 
 30-3 = 100. 
 
 Pyr., etc. Heated in a matrass the crystals decrepitate and become opaque. B B fuses 
 easily to a white enamel, and colors the flame intensely yellow. With the fluxes it behaves 
 like calcium carbonate. Dissolves in acids with a brisk effervescence ; partly soluble in water, 
 and reddens turmeric. 
 
 Obs. Abundant at Lagunilla, near Merida, in Maracaibo, where its crystals are dissemi- 
 nated at the bottom of a small lake, in a bed of clay, covering urao ; the natives call it davos 
 or natts, in allusion to its crystalline form. Also on a small island in Little Salt Lake, near 
 Ragtown, Nevada, about H in. S. of the main emigrant road to Humboldt. The lake is in a 
 crater-shaped basin, and its waters are dense and strongly saline. 
 
 The distorted crystals from Sangerhausen have been long considered pseudomorphs after 
 gay-lussite, though Des Cloizeaux regards them as pseudomorphs after celestite. Groth 
 regards them as perhaps pseudomorphs after anhydrite. See also thinolite, p. 438. 
 
 H Y DROM AGNE SITE. 
 
 Monoclinic. <7=82-83, 7 A 1= 87 52 / -88, O A 24 = 137; 
 : d = (nearly) 0-455 : 1-0973 : 1. Crystals small, usually 
 acicular or bladed, and tufted. Also amorphous ; as 
 chalky or mealy crusts. 
 
 H. of crystals 3-5. G.=2-l 45-2-18, Smith & Brush. 
 Lustre vitreous to silky or subpearly ; also earthy. Color 
 and streak white. Brittle. 
 
 Comp. 3MgCO 3 +H 2 MgO 2 +3aq:= Carbon dioxide 36 '3, magnesia 
 43-9, water 19 -6= 100. 
 
 Pyr., etc. In the closed tube gives off water and carbon dioxide. 
 B.B. infusible, but whitens, and the assay reacts alkaline totuimeric 
 paper. Soluble in acids ; the crystalline compact varieties are but 
 slowly acted upon by cold acid, but dissolves with effervescence in hot 
 acid. 
 
410 DESCRIPTIVE MINERALOGY. 
 
 Obs Occurs at Hrubschitz, in Moravia, in serpentine ; in Negroponte, near Kami ; at 
 Kaiserstuhl, in Baden, impure. In the U. States, near Texas, Lancaster Co., Penn. ; at 
 Hoboken, N. J. 
 
 HYDKODOLOMITE. Composition 3(CaMg)C0 3 -i-aq. From Mt Somma. PKNNITE from 
 Texas, Pa. , is similar. 
 
 PREDAZZITE and PENCATITE are mixtures of calcite and brucite. Tyrol. 
 
 DAWSONITE. In thin-bladed, white, transparent crystals on trachyte. H. =3. G.=2'40- 
 Analysis, Harrington, A10 3 32 84, MgO tr., CaO 5*1)5, Na.O 20'20, K.O 38, H 2 O 11-91, CO, 
 29 '88, Si0 2 '40 = 101*56. Regarded as ' a hydrous carbonate of aluminum, calcium, and 
 aodium ; or perhaps as a hydrate of aluminum with carbonates of calcium and sodium." 
 Montreal, Canada. 
 
 HOVITE. Supposed to be a hydrous carbonate of aluminum and calcium. Soft, white, 
 and friable ; earthy in fracture. From Hove, near Brighton, with colly rite. 
 
 LANTHANITB. 
 
 Orthorhombic. /A 1= 93 30'-94, Blake, 92 46', v. Lang ; /A 1 
 142 36' ; c:l>:d = 0-99898 : 1-0496 : 1, v. Lang. In thin four-sided 
 plates or minute tables, with bevelled edges. Cleavage micaceous. Also 
 hue granular or earthy. 
 
 II. =2-5 3. G.=2'666. Lustre pearly or dull. Color grayish-white, 
 delicate pink, or yellowish. 
 
 Comp. LaCO 3 +3aq=Lanthana 52-6, carbon dioxide 21 '3, water 26*1=100. There is 
 some oxide of didyrnium with the lanthana, according to Smith. 
 
 Pyr., etc. In the closed tube yields water. B.B. infusible ; but whitens and becomes 
 opaque, silvery, and brownish; with borax, a glass, slightly bluish, reddish, or "amethystine, 
 on cooling ; with salt of phosphorus a glass, bluish amethystine while hot, red cold, the 
 bead becoming opaque when but slightly heated, and retaining a pink color. Effervesces in 
 the acids. 
 
 Obs. Found coating cerite at Bastniis, Sweden ; also with the zinc ores of the Saucon 
 valley,. Lehigh Co., Pa. ; at the Sandford iron-ore bed, Moriah, Essex Co., N. Y. 
 
 TENGERITE. Yttrium carbonate. As a coating on gadolinite from Ytterby. 
 
 ZARATITE. Emerald Nickel, tiiUiman. Nickelsmaragd, Germ. Composition Ni 3 CO 5 f- 
 (Jaq, or NiCO 3 + 2H NiO.+4aq. This requires: Carbon dioxide 11*8, nickel oxide 59 3, 
 water 28 '9 = 100. Usually as an emerald-green coating; thus on chromite at Texas, Penn., 
 where it was first noticed ; Swinaness, Shetland ; Cape Ortegal, Spain. 
 
 BEMINGTONITE. A hydrous cobalt carbonate. Finksburg, Md. 
 
 HYDROZINCITE. Zinkbliithe, Germ. 
 
 Massive, earthy or compact. As incrustations, the crusts sometimes con- 
 centric and agate-like. At times reniform, pisolitic, stalactitic. 
 
 IL 2-2-5. G.=3-58-3-8. Lustre dull. Color pure white, grayish or 
 yellowish. Streak shining. Usually earthy or chalk-like. 
 
 Comp. In part ZnC0 3 +2H 2 ZnO, = Carbon dioxide 13'6, zinc oxide 75-3, water 11'1=100. 
 
 Pyr., etc. In the closed tube yields water ; in other respects resembles smithsonite. 
 
 Obs. Occurs at most mines of zinc, and is a result of the alteration of the other ores of 
 this metal. Found in great quantities at the Dolores mine, Udias valley, province of Santan- 
 der, in Spain ; at Bleiberg and Raibel in Carinthia ; near Reimsbeck, in Westphalia 
 
 In the U. States, at Friedensville, Pa.; at Linden, in Wisconsin; in Marion Co., Arkansas 
 (marionite). 
 
 AURICHALCITE. A cupreous hydrozincite. Usually in drusy incrustations. Altai; 
 Matlock, Derbyshire; Spain; Lancaster, Pa. 
 
OXYGEN COMPOUNDS. CAEBONATE8. 411 
 
 MALACHITE. 
 
 Monoclinic. G= 88 32', /A 1= 104 28', i-* A -1-i = 118 15', Zepharo 
 dch ; c : I : d = 0-51155 : 1-2903 : 1. Common form 
 f. 750 ; also same with other terminal planes; also with 
 i-i wanting ; also with i-i, i-l very large, making a rect- 
 angular prism ; also with the vertical prism very short, 
 as in f. 321. Crystals rarely simple. Twins : twinning- 
 plane i-i, f. 750 ; often penetration twins, as in f. 321, 
 322, p. 99. Cleavage : basal, highly perfect ; clino- 
 diagonal less distinct. Usually massive or incrnsting, 
 with surface tuberose, botryoidal, or stalactitic, and struc- 
 ture divergent ; often delicately compact fibrous, and 
 banded in color ; frequently granular or earthy. 
 
 PL 3-5-4. G.=3-7-4-01. Lustre of crystals adaman- 
 tine, inclining to vitreous ; of fibrous varieties more or 
 less silky ; often dull and earthy. Color bright green. Streak paler green. 
 Translucent subtranslucent opaque. Fracture subconchoidal, uneven. 
 
 Comp. Cu 2 C0 4 4-H 2 0=CuC0 3 +H 2 CuO a = Carbon dioxide 19'9, copper oxide 71'9, water 
 8-2=100. 
 
 Pyr., etc. In the closed tube blackens and yields water. B.B. fuses at 2, coloring the 
 flame emerald-green ; on charcoal is reduced to metallic copper ; with the fluxes reacts like 
 tenorite. Soluble in acids with effervescence. 
 
 Diff. Differs from other copper ores of a green color in its effervescence with acids. 
 
 Obs. Green malachite accompanies other ores of copper. Perfect crystals are quite rare. 
 Occurs abundantly in the Urals ; at Chessy in France ; at Schwatz in the Tyrol ; in Cornwall 
 and in Cumberland, England ; Sandlodge copper mine, Scotland ; Limerick, Waterf ord. and 
 elsewhere, Ireland ; at Grimberg, near Siegen in Germany. At the copper mines of Nischne- 
 Tagilsk, belonging to M. Demidoff, a bed of malachite was opened which yielded many tons 
 of malachite. Also in handsome masses at Bembe, on the west coast of Africa ; with the 
 copper ores of Cuba ; Chili ; Australia. 
 
 In N. Jersey, at New Brunswick. In Pennsylvania, near Morgan town, Berks County ; at 
 Cornwall, Lebanon Co. ; at the Perkiomen and Phenixville lead mines. In Wisconsin, at the 
 copper mines of Mineral Point, and elswhere. In California, at Hughes's mine in Calaveras 
 Co. 
 
 Green malachite admits of a high polish, and when in large masses is cut into tables, snuff- 
 boxes, vases, etc. Named from //aAa^, mallows, in allusion to the green color. 
 
 CUPBOCALCITE. Massive. H.=3. G.=3'90. Color vermilion-red. Analysis, Raymondi, 
 Cu 2 50-45, CaO 2016, C0 2 24 '00, H 2 O 3-20, Fe0 3 0'60, A1O 3 0'20, MgO 0'97, SiO a 
 99 '86. Occurs with a ferruginous calcite at the copper mines of Canza in Peru. 
 
 AZURITE. Kupferlasur, Germ. 
 
 Monoclinic. 7= 87 39'; /A/= 99 3 -32', O A 14 = 138 41'; c : t> : d 
 == 1-039 : 1*181 : 1. O usually striated parallel with the clinodiagonal. 
 Cleavage : 2-i rather perfect ; i-i less distinct ; I in traces. Also massive, 
 and presenting imitative shapes, having a columnar composition ; also dull 
 and earthy. 
 
 H. = 3-5-4'25. G.=3'5-3'S31. Lustre vitreous, almost adamantine. 
 Color various shades of azure-blue, passing into Berlin-blue. Streak blue, 
 lighter than the color. Transparent subtranslucent. Fracture conchoidal. 
 Brittle. 
 
412 DESCRIPTIVE MINERALOGY. 
 
 Comp. Cu 3 C 2 O T +H 2 0=2CuCO 3 +H 3 Cu0 3 =Carbon dioxide 25*6, copper oxide 69-2, 
 water 5 '2= 100. 
 
 Pyr., etc. Same as in malachite. 
 
 Obs. Occurs at Chessy, near Lyons, whence its name Chessy Copper. Also in Siberia ; at 
 Moldava in the Banat ; at Wheal Buller, near Redruth in Cornwall also in Devonshire and 
 Derbyshire. 
 
 In Peini. , at the Perkiomen lead mine ; at Phenixville, in crystals ; at Cornwall. In Wif> 
 connn, near Mineral Point In California, Calaveras Co. , at Hughes's mine. 
 
 According to Schrauf, who has given a crystallographic monograph of the species, the f oruc 
 la closely related to that of epidote (Ber. Ak. Wien, July 3, 1871). 
 
 BISMUTITE. Wismuthspath, Germ. 
 
 In implanted acicular crystallizations (pseudomorphons) ; also incrusting 
 or amorphous ; pulverulent. 
 
 H.=4-4:*5. (jr.=6'86-6-909. Lust-re vitreous, when pure; sometimes 
 dull. Color white, mountain-green, and dirty siskin-green ; occasionally 
 &traw-yellow and yellowish-gray. Streak greenish-gray to colorless. Sub- 
 translucent opaque. Brittle. 
 
 Comp. 2Bi e C 3 18 f 9H 2 0, Eamm. (S. Carolina) = Carbon dioxide 6-38, bismuth oxide 
 89-75, water 3-87=100. 
 
 Pyr., etc. In the closed tube decrepitates and gives off water. B.B. fuses readily, and on 
 charcoal is reduced to bismuth, and coats the coal with yellow bismuth oxide. Dissolves in 
 nitric acid, with slight effervescence. Dissolves in hydrochloric acid, affording a deep yellow 
 solution. 
 
 Obs. Bismutite occurs at Schneebarg and Johanngeorgenstadt ; at Joachimsthal ; near 
 Baden ; also in the gold district of Chesterfield, S. C. ; in Gaston Co., N. C., in yellowish- 
 white concretions. 
 
 LIEBIGITE ; VOGLITE (Urankalk, Germ.). Carbonates of uranium and calcium, from the 
 decomposition of uraninite. Exact composition doubtful. SCHROCKINGERITE is an oxycar- 
 bonate of uranium (Schrauf). Orthorhombic. Occurs in six-sided tabular crystals. Joachims- 
 thai. 
 
 WHEWELLITE. An oxalate of calcium. In minute monoclinic crystals on calcite. 
 
 HUMBOLDTITE. A hydrous oxalate of iron, 2FeC a O 4 + 3aq. Compact ; earthy. In' brown - 
 coal of Koloseruk, near Bilin; also in black shales at Kettle Point ; in Bosanquet, Canada. 
 
 MELLITE (Honigstein, Germ.). Tetragonal. In octahedrons ; also massive, honey -yellow, 
 reddish, or brownish, rarely white. Al CiaOn+lSaq^ Alumina 14'36. mellitic acid 40'30, 
 water 45 '34= 100. Arteru, Thuringia; Luschitz, Bohemia ; Walchow, Morav^i ; Nertschinsk, 
 etc. 
 
HYDROCARBON COMPOUNDS. 413 
 
 VI. HYDROCARBON COMPOUNDS 
 
 The Hydrogen-Carbon Compounds include (1) the SIMPLE HYDROCARBONS ; 
 and (2) the OXYGENATED HYDROCARBONS. 
 
 1. The SIMPLE HYDRO CARBONS embrace : 
 
 (a) The Marsh Gas series. General formula CnTI^.^. Here belong the 
 liquid naphthas, the more volatile parts of petroleum ; also the butter-like 
 solids scheererite and chrismatite. 
 
 PETROLEUM. Mineral oil. Kerosene. Bergol, Steinjl, Erdjl, Germ. Petroleum is a thick to 
 thin fluid. Color yellow or brown, or colorless ; translucent to transparent. The specific gravity 
 varies from 0'7 to 0'9. Chemically it consists essentially of carbon and hydrogen ; contain- 
 ing several members of the naphtha group, as also the oils of the ethylene series, and the 
 paraffins. The proportion of the latter constituents increases with the increase of the density 
 or viscidity of the fluid. It grades insensibly into pittasphalt. and that into solid bitumen. 
 
 Occurs in rocks or deposits of nearly all geological ages, from the Lower Silurian to the 
 present epoch. It is associated most abundantly with argillaceous shales and sandstones, but 
 is found also permeating limestones, giving them a bituminous odor, and rendering them 
 sometimes a considerable source of oil. From these oliierous shales and limestones the oil 
 often exudes, and appears floating on the streams or lakes of the region, or rises in oil springs. 
 It also exists collected in subterranean cavities in certain rocks, whence it issues in jets or 
 fountains whenever an outlet is made by boring. These cavities are situated mostly along 
 the course of gentle anticlinals in the rocks of the region ; and it is therefore probable, as has 
 been suggested, that they originated for the most part in the displacements of the strata caused 
 by the slight uplift. The oil which fills the cavities has ordinarily been derived from the 
 subjacent rocks ; for the strata, in which the cavities exist, are frequently barren sandstones. 
 
 Obtained in large quantities from the oil wells of Pennsylvania ; also found in eastern Vir- 
 ginia, Kentucky, Ohio, Illinois, Michigan, and .New York. In Canada, at several places; in 
 southern California ; in Mexico ; Trinidad. 
 
 Some well-known foreign localities are : Rangoon, Burmah ; western shore of the Caspian 
 Sea ; in Parma, Italy ; Sicily ; Galicia ; Tegernsee, Bavaria ; Hanover. 
 
 (b) The defiant or Ethylene series. General formula C n H 2n . Here 
 belong the pittoliuin group of liquids, or pittas phalt 8 (mineral tar), and the 
 marajfins. 
 
 PARAFFIN GROUP. Wax-like in consistence ; white and translucent. Sparingly soluble in 
 alcohol, rather easily in ether, and crystallizing more or less perfectly from the solutions. Gr. 
 about 085-0-98. Melting point for the following species, 33M)0\ The different species 
 varying in the value of n, vary also in boiling point, and other characters. 
 
 Paraffins occur in the Pennsylvania petroleum, a freezing mixture reducing the tempera- 
 ture being sufficient to separate it in crystals. Also in the naphtha of the Caspian, in Ran- 
 goon tar, and many other liquid bitumens. It is a result of the destructive distillation of 
 peat, bituminous coal, lignite, coaly or bituminous shales, most viscid bitumens, wood-tar, 
 and many other substances. 
 
 The name is from the Latin parum, little, and affinis, alluding to the feeble affinity for othei 
 substances, or, in other words, its chemical indifference. 
 
 To the Paraffin Group belong : 
 
 , URPETHITE. Consistency of soft tallow. Melting point 39 C. Soluble in cold ether. 
 Urpeth Colliery. 
 
414 DESCRIPTIVE MINER ALOGi. 
 
 HATCHETTITE. In thin plates or massive. Color yellowish, or greenish- white ; blacken* 
 on exposure. Melting point 46 C. In the coal-measures of Glamorganshire ; Rossitz, 
 Moravia. 
 
 OZOCERITE. Like wax or spermaceti in appearance and consistency. G. =0-85-0 '90. 
 Calorless to white when pure; often leek-green, yellowish, brownish-yellow, brown. Trans 
 lucent. Greasy to the touch. Fusing point 56 to 63 C. Occurs in beds of coal, or associ- 
 ated bituminous deposits ; that of Slanik, Moldavia, beneath a bed of bituminous clay shale ; 
 in masses of sometimes 80 to 100 Ibs., at the foot of the Carpathians, not far from beds oJ 
 coal and salt ; that of Boryslaw in a bituminous clay associated with calciferous beds in the 
 formation of the Carpathians, in masses. The same compound has been obtained from mine 
 ral coal, peat, and petroleum, mineral tar, etc., by destructive distillation. Named from bC,u. 
 smett, and mjpoq , wax, in allusion to the odor. 
 
 ELATERITE. Massive, soft, elastic; of ten like india-rubber, though sometimes hard anc 
 brittle. It is found at Castleton in Derbyshire, in the lead mine of Odin, along with lead or( 
 and calcite, in compact reniform or fungoid masses, and is abundant. Also reported from St 
 Bernard's Well, Edinburgh, etc. 
 
 ZIETRISIKITE and PYROPISSITE belong here. 
 
 (c) The Camphene Series. General Formula CjJ^zn-t- 
 
 FICHTELITK. In white monoclinic crystals. Brittle. Solidifies at 36 C. Soluble in ether 
 The mineral occurs in the form of shining scales, flat crystals, and thin layers between th< 
 rings of growth and throughout the texture of pine wood (identical in species with the moden 
 Pinus sylvestris) from peat beds in the vicinity of Redwitz in the Fichtelgebirge, Nortl 
 Bavaria. In peat near Sobeslau ; in a log of Pinus Australis. 
 
 HARTITE. Resembles fichtelite, but melts at 74-75 C. Found in a. kind of pine, lik< 
 fichtelite. but of a different species, the Pence acerosa Unger, belonging to an earlier geologica 
 epoch. From the brown-coal beds of Oberhart, near Gloggnitz, not far from Vienna. Reportec 
 also from Rosenthal near Koflach in Styria, and Pravali in Carinthia. 
 
 DINITE and IXOLYTE belong here. 
 
 (d) The Benzole Series, General Formula CnH^.g. Including the 
 Benzole liquids and KONLITE from Uznach, and Redwitz. 
 
 (e) The Naphthalin Series. General Formula 
 
 NAPHTHALIN. Occurs in Rangoon tar. IDRIALITE, crystalline in the pure state. Ooloi 
 white. In nature found only impure, being mixed with cinnabar, clay, and some pynte anc 
 gypsum in a brownish -black earthy material, called from its combustibility and the presence 
 of mercury, inflammable cinnabar (Quecksilberbranderz). Idria, Spain. ARAGOTITE, front 
 New Almaden Mine, Cal., is related to idrialite. 
 
 2. The OXYGENATED HYDROCARBONS embrace different groups having 
 ratios of C : H varying from 1 : 2 to 5 : 5, or less. Some of the more 
 important are : 
 
 GEOCERITE. Wax-like. Color white. Melting point near 80 C. ; after fusion solidifies ai 
 a yellowish wax, hard but not very brittle. Soluble in alcohol of 80 p. c. CaeHBeOa^Carboi 
 79'24, hydrogen 13 '21, oxygen 7 '55=100. From the same dark-brown brown coal of Gester 
 witz that afforded the geomyricite, and from the same solution. 
 
 GEOMYRICITE. Wax-like. Obtained in a pulverulent form from a solution, the grains con 
 eisting of acicular crystals. Color white. Melting point 80-83 C. After fusion has th( 
 aspect of a yellowish brittle wax. Soluble easily in hot absolute alcohol and ether, bu1 
 slightly in alcohol of 80 p. c. C 3 4He&0 2 = Carbon 80;59, hydrogen 13*42, oxygen 5 99=100, 
 Burns with a bright flame. Occurs at the Gesterwitz brown coal deposit, in a dark brow* 
 layer. 
 
HYDROCARBON COMPOUNDS*, 415 
 
 SUCCINITE. Amber. Succin, Ambre, Fr. Bernstein, Germ. 
 
 In irregular masses, without cleavage. H. = 2-2*5. G.=1*065-1'081, 
 
 Lustre resinous. Color yellow, sometimes reddish, brownish, and whitish, 
 
 often clouded. Streak white. Transparent translucent. Tasteless. Elec- 
 
 rc on friction. Fuses at 287 C., but without becoming a flowing liquid. 
 
 Comp. Ratio for C : H : O=40 : 64 : 4=Carbon 78*94, hydrogen 10'53, oxygen 10'53= 
 100. But amber is not a simple resin. According to Berzclius, it consists mainly (85 to 90 
 p. c.) of a resin which resists all solvents (properly the species succinite), along with two othex 
 resins soluble in alcohol and ether, an oil, and 2^ to 6 p. c. of succinic acid. Amber is hardly 
 acted on by alcohol. Burns readily with a yellow flame, emitting an agreeable odor, and 
 leaves a black, shining, carbonaceous residue. 
 
 Obs. Occurs abundantly on the Prussian coast of the Baltic ; occurring from Dantzig to 
 Memel ; also on the coast of Denmark and Sweden ; in Galicia, near Lemberg, and at Miszau ; 
 in Poland ; in Moravia, at Boskowitz, etc. ; in the Urals, .Russia ; near Christiania, Norway ; 
 in Switzerland, near Bale; in France, near Paris, in clay. Jn England, near London, and on 
 the coast of Norfolk, Essex, and Suffolk. In various parts of Asia. Also near Catania, on 
 the Sicilian coast. It has been found in various parts of the Green sand formation of the 
 United States, either loosely imbedded in the soil, or engaged in marl or lignite, as at Gay 
 Head or Martha's Vineyard, near Trenton, and also at Camden in New Jersey, and at Cape 
 Sable, near Magothy river in Maryland. In the royal museum at Berlin there is a mass 
 weighing- 18 Ibs. Another in the kingdom of Ava, India, is nearly as large as a child's head, 
 and weighs 2^ Ibs. 
 
 It is now fully ascertained that amber is a vegetable resin altered by fossilization. This 
 is inferred both from its native situation with coal, or fossil wood, arid from the occurrence 
 of insects incased in it. Of these insects, some appear evidently to have struggled after being 
 entangled in the then viscous fluid ; and occasionally a leg or a wing is found some distance 
 from the body, which had been detached in the effort to escape. 
 
 Amber was early known to the ancients, and called rj'/EK-pov^ electrum, whence, on account 
 of its electrical susceptibilities, we have derived the word electricity. It was named by some 
 lyncurium, though this name was applied by Theophrastus also to a stone, probably to zircon or 
 tourmaline, both minerals^f remarkable electrical properties. 
 
 Other related resins are: COPALITE (retinite pt.) from Highgate Hill, near London; 
 KRANTZITE, Nienburg ; WALCHOWITE, Walchow, Moravia ; AMBRITE, N. Zealand ; BATH- 
 VILLITE, occurring in the torbanite, or Boghead coal of Bathviile, Scotland ; torbanite is 
 related to it. SIEQBDRGITE, ^CHRAUFITE, AMBROSINE, DUXITE. 
 
 XYLORETLNITE (hartine). C : H : O=40 : 64 : 4. BOMBI^CITE, C : H : O=13 : 7 : 1, in 
 lignite in the valley of the Arno, Tuscany. LEDCOPETRITE. C : H : 0=50 : 84 : 3. Ges- 
 terwitz, near Weissenf els. EUOSMITE. C : H : O=34 : 29 : 2, from the brown coal at Baiershoi 
 in the Fichtelgebirge. ROSTHORNITE. C : H : O=24 : 40 : 1. In coal at Sonnberg, Carin- 
 thia. The above species are soluble in ether. 
 
 SCLERETINITE. C : H : 0=40 : 64 : 4. Insoluble in ether. Wigan, England. 
 
 PYRORETINITE, JAULINGITE, REUSSINITE, GUYAQUILLITE, WHEELERITE (New Mexico), 
 etc. Ratio of C : H=5 : 7 to 5 : 6*. 
 
 MlDDLETONITE, STANEKITE, ANTHRACOXENITE. Ratio of C : H=5 : 5^ Or less. IttSOlu- 
 
 able in ether or alcohol. 
 
 TASMANITE and DYSODILE are remarkable in containing sulphur, replacing part of the 
 oxygen. 
 
 The ACID OXYGENATED HYDROCARBONS include Butyrellite (Bogbutter), 
 Succinellite, Dopplerite, etc., etc. 
 
416 DESCRIPTIVE MINEKALOGY. 
 
 APPENDIX TO HYDEOCAEBOISrS. 
 
 ASPHALTUM. Bitumen. Asphalt, Mineral Pitch. Bergpech, E -dpech, Oeivn. 
 
 Asphaltum, or mineral pitch, is a mixture of different hydrocarbons, part 
 of which are oxygenated. Its ordinary characters are as follows: 
 
 Amorphous. G. 1-1*8 ; sometimes higher from impurities. Lustre 
 like that of black pitch. Color brownish-black and black. Odor bitumi- 
 nous. Melts ordinarily at 90 to 100 C., and burns with a bright flame. 
 Soluble mostly or wholly in oil of turpentine, and partly or wholly in ether ; 
 commonly partly in alcohol. 
 
 The more solid kinds graduate into the pittasphalts or mineral tar, and 
 through these there is a gradation to petroleum. The fluid kinds change 
 into the solid by the loss of a vaporizable portion on exposure, and also by 
 a process of oxidation, which consists first in a loss of hydrogen, and finally 
 in the oxygenation of a portion of the mass. 
 
 Obs. Asphaltum belongs to rocks of no particular age. The most abundant deposits are 
 superficial. But these are generally, if not always, connected with rock deposits containing 
 some kind of bituminous material or vegetable remains. 
 
 Some of the noted localities of asphaltum are the region of the Dead Sea, or Lake Asphal- 
 tites, on Trinidad ; at various places in S. America, as at Caxitambo, Peru ; at Berengela, 
 Peru, not far from Arica (S.) ; in California, near the coast of St. Barbara. Also in smaller 
 quantities, sometimes disseminated through shale, and sandstone rocks, and occasionally lime- 
 stones, or collected in cavities or seams in these rocks ; near Matlock, Derbyshire ; Poldice 
 mine in Cornwall ; Val de Travers, Neuchatel ; impregnating dolomite on the island of Brazza 
 in Dalmatia ; in the Caucasus ; in gneiss and mica schist in Sweden. 
 
 The following substances are closely related to asphaltum, and, like it, are mixtures of un- 
 determined carbohydrogens. 
 
 GRAHAMITE, Wurte. Resembles the preceding in its pitch-black, lustrous appearance; H. 
 2; G-. = 1'145. Soluble mostly in oil of turpentine ; partly in ether, naphtha, or benzole ; 
 not at all in alcohol ; wholly in chloroform and carbon disulphide. No action with alkalies or 
 hot nitric or hydrochloric acid. Melts only imperfectly, and with a decomposition of the 
 surface ; but in this state the interior may be drawn into long threads. Occurs in W. Vir- 
 ginia, about 20 m. in an air line S. of Parkersburg, filling a fissure (shrinkage fissure) in a 
 sandstone of the Carboniferous formation ; and supposed to be, like the albertite, an inspis- 
 sated and oxygenated petroleum. 
 
 ALBERTITE, Robb. Differs from ordinary asphaltum in being only partially soluble in oil 
 of turpentine, and hi its very imperfect fusion when heated. It has H. =1-2 ; G. =1 '097: 
 lustre brilliant, pitch-like ; color jet-black. Softens a little in boiling water ; in the flame of 
 a candle shows incipient fusion. According to imperfect determinations, only a trace soluble 
 in alcohol ; 4 p. c. in ether ; 30 in oil of turpentine. Occurs filling an irregular fissure in 
 rocks of the Subcarboniferous age (or Lower Carboniferous) in Nova Scotia, and is regarded 
 as an inspissated and oxygenated petroleum. This and the above are very valuable in gas- 
 making. 
 
 PIAUZITE. An asphalt-like substance, remarkable for its high melting point, 315 C. II 
 occurs slaty massive ; color brownish- or greenish-black ; thin splinters colophonite-brown by 
 transmitted light ; streak light brown, amber-brown ; H. = 1'5 ; G.=1'220 ; 1'18G, Kenngott. 
 It comes from a bed of brown coal at Piauze, near Neustadt in Carniola ; on Mt. Chum, neai 
 Tiiffer in Styria 
 
 WOLLONGONGITE, SilUman. Occurs in cubic blocks without lamination. Fracture broad 
 conchoidal. Color greenish- to brownish-black. Lustre resinous. In the tute does nDt melt, 
 but decrepitates and gives off oil and gas ; yields by dry distillation 82 '5 p. c. volatile matter 
 Insoluble in ether or benzole. New South Wales, 
 
HTDKOCARBON COMPOUNDS. 417 
 
 MINERAL COAL 
 
 The distinguishing characters of Mineral Coal are as follows : Compact 
 massive, without crystalline structure or cleavage ; sometimes breaking 
 with a degree of regularity, but from a jointed rather than a cleavage struc- 
 ture. Sometimes laminated ; often faintly and delicately banded, successive 
 layers differing slightly in lustre. 
 
 H.z-05-2-5. Gr.=l-l'80. Lustre dull to' brilliant, and either earthy, 
 resinous, or submetallic. Color black, grayish-black, brownish-black, and 
 occasionally iridescent ; also sometimes dark brown. Opaque. Fracture 
 eonchoidal uneven. Brittle ; rarely somewhat sectile. Without taste, 
 except from impurities present. Insoluble or nearly so in alcohol, ether, 
 naphtha, and benzole. Infusible to snbf usible ; but often becoming a soft, 
 pliant, or paste-like mass when heated. On distillation most kinds afford 
 more or less of oily and tarry substances, which are mixtures of hydrocar- 
 bons and paraffin. 
 
 Mineral coal is made up of different kinds of hydrocarbons, with perhaps 
 In some cases free carbon. 
 
 Var. The variations depend partly (1) on the amount of the volatile ingredients afforded 
 Dn destructive destination ; or (2) on the nature of these volatile compounds, for ingredients 
 Df similar composition may differ widely in volatility, etc. ; (3) on structure, lustre, and other 
 physical characters. 
 
 1. ANTHRACITE. H. =2-2-5. G. =1'32- 1'7, Pennsylvania; 1'81, Rhode Island ; 1-26-1 '36, 
 South Wales. Lustre bright, often submetallic, iron blacK. and frequently iridescent. Frac- 
 bure eonchoidal. Volatile matter after drying 3 to 6 p. c. Burns with a feeble flame of a pale 
 color. The anthracites of Pennsylvania contain ordinarily 85 to 93 pencent. of carbon ; those 
 of South Wales, 88 to 95 ; of France, 80 to 83; of Saxony, 81 ; of southern Russia, some- 
 times 94 per cent. Anthracite graduates into bituminous coal, becoming less hard, and con- 
 baining more volatile matter ; and an intermediate variety is called free-burning anthracite. 
 
 BITUMINOUS COALS (Steinkohie pt. , Germ.}. Under the head of Bituminous Coals, a 
 number of kinds are included which differ strikingly in the action of heat, and which there- 
 fore are of unlike constitution. They have the common characteristic of burning in the fire 
 with a yellow, smoky flame, and giving out on distillation hydrocarbon oils or tar, and hence 
 bhe name bituminous. The ordinary bituminous coals contain from 5 to 15 p. c. (rarely 16 or 
 17) of oxygen (ash excluded) ; while the so-called brown coal or lignite contains from 20 to 
 36 p. c., after the expulsion, at 100 C., of 15 to 36 p. c. of water. The amount of hydrogen 
 in each is from 4 to 7 p. c. Both have usually a bright, pitchy, greasy lustre (whence often 
 called PeohkoJde in German), a firm compact texture, are rather fragile compared with anthra- 
 rite, and have G. 1'14-1'40. The brown coals have often a brownish-black color, whence 
 bhe name, and more oxygen, but in these respects and others they shade into ordinary bitu- 
 minous coals. The ordinary bituminous coal of Pennsylvania has G. =1 '26-1 '37 ; of New- 
 castle, England, 1-27; of Scotland, 1 '27-1 '32; of France, 1 '2-1 '33; of Belgium, 1-27-1 '3. 
 The most prominent kinds are the following: 
 
 2. CAKING C >AL. A bituminous coal which softens and becomes pasty or semi-viscid in 
 bhe fire. This softening takes place at the temperature of incipient decomposition, and is 
 attended with the escape of bubbles of gas. On increasing the heat, the volatile products 
 which result from the ultimate decomposition of the softened mass are driven off, and a 
 coherent, grayish-black, cellular, or fritted mass (coke] is left. Amount of coke left (or part 
 not volatile) varies from GO to 85 p. c. Byerite is from Middle Park, Colorado. 
 
 3. NON-CAKING COAL. Like the preceding in all external characters, and often in ultimate 
 composition ; but burning freely without softening or any appearance of incipient fusion. 
 
 4. CANNEL COAL (Parrot Coal). A variety of bituminous coal, and often caking ; but dii- 
 fering from the preceding in texture, and to some extent in composition, as shown by its 
 products on distillation. It is compact, with little or no lustre, and without any appearance 
 of a banded structure; and it breaks with a eonchoidal fracture and smooth surfaces; coloi 
 dull black or grayish-black. On distillation it affords, after drying, 40 to 66 ol volatile mat- 
 fcr, and the material volatilized includes a large proportion of burning and lubricating oils, 
 
 27 
 
418 DESCRIPTIVE MINERALOGY. 
 
 much larger than the above kinds of bituminous coal ; whence it is extensively used for th( 
 manufacture of such oils. It graduates into oil-producing coaly shales, the more compact o 
 which it much resembles. 
 
 5. TORBANITE. A variety of cannel coal of a dark brown color, yellowish streak, withou 
 lustre, having a subconchoidal fracture; H.=225; G. = 1-17-1 -2. Yields over GO p. c. o; 
 volatile matter, and is used for the production of burning and lubricating oils, paraffin, ilia 
 minating gas. From Torbane Hill, near Bathgate in Linlithgowshire, Scotland. Also calle( 
 Boghead Cannel. 
 
 6. BROWN COAL (Braunkohle Germ.. Pechkohle pt. Germ., Lignite^ The prominen 
 characteristics of brown coal have already been mentioned. They are non-caking, but affon 
 a large proportion of volatile matter They are sometimes pitch-black (whence Pechkohli 
 pt. Germ.}, but often rather dull and brownish-black. G.=l'15-l '3 ; sometimes higner fron 
 impurities. It is occasionally somewhat lamellar in structure. Brown coal is often callec 
 lignite. But this term is sometimes restricted to masses of coal which still retain the form o: 
 the original wood. Jet is a black variety of brown coal, compact in texture, and taking i 
 good polish, whence its use in jewelry. 
 
 7. EARTHY BROWN COAL (E)-dige BraunkoJile) is a brown friable material, sometimes form 
 ing layers in beds of brown coal. But it is in general not a true coal, a considerable part o: 
 it being soluble in ether and benzole, and often even in alcohol ; besides affording largely o: 
 oils and paraffin on distillation. 
 
 Comp. Most mineral coal consists mainly, as the best chemists now hold, of oxygenates 
 hydrocarbons. Besides oxygenated hydrocarbons, there may also be present simple hydrocar 
 bons (that is, containing no oxygen). 
 
 Sulphur is present in nearly all coals. It is supposed to be usually combined with iron, 
 and when the coal affords a red ash on burning, there is reason for believing this true. Bui 
 Percy mentions a coal from New Zealand (anal. 18) which gave a peculiarly white ash 
 although containing 2 to 3 p. c. of sulphur, a fact showing that it is present not as a sulphide 
 of iron, but as a constituent of an organic compound. The discovery by Church of a resir 
 containing sulphur (see TASMANITE, p. 415), gives reason for inferring that it may exist ir 
 this coal in that state, although its presence as a constituent of other organic compounds is 
 quite possible. 
 
 The chemical relations of the different kinds of coals will be understood from the follow- 
 ing analyses: 
 
 Carbon. Hydrogen. Oxygen. Nitrogen. Sulphur. Ash. 
 
 1. Anthracite, S. Wales 92-56 338 2 '53 1-56 
 
 2. Caking Coal, Northumberland 78-69 6 -00 10-07 2 -37 1T>1 1'36 
 
 3. Non-Caking Coal, Zwickau 80'25 4 "01 1098 0'49 2-99 1-51 
 
 4. Cannel Coal, Wigan 80*07 553 8'10 2-12 1 -50 2-7C 
 
 5. Torbanite. Torbane Hill 64-02 8-90 5 "66 0'55 50 20 32 
 
 6. Brown Coal, Meissen, Sax. 58 '90 5-36 21-63 6 "61 7 '50 
 
 Coal occurs in beds, interstratified with shales, sandstones, and conglomerates, and some- 
 times limestones, forming distinct layers, which vary from a fraction of an inch to 30 feet or 
 more in thickness. In the United States, the anthracites occur east of the Alleghany range, 
 in rocks that have undergone great contortions and f racturings, while the bituminous are 
 found farther west, in rocks that have been less disturbed ; and this fact and other observa- 
 tions have led some geologists to the view that the anthracites have lost their bitumen by the 
 action of heat. The origin of coal is mainly vegetable, though animal life has contributed 
 somewhat to the result. The beds were once beds of vegetation, analogous, in most respects, 
 in mode of formation to the paat beds of modern times, yet in mode of burial often of a very 
 different character. This vegetable origin is proved not only by the occurrence of the leaves, 
 stems, and logs of plants in the coal, but also by the presence throughout its texture, in 
 many cases, of the forms of the original fibres; also by the direct observation that peat is 
 a transition state between unaltered vegetable debris and brown coal, being sometimes found 
 passing completely into true brown coal. Peat differs from true coal in want of homo- 
 geneity, it visibly containing vegetable fibres only partially altered ; and wherever changed 
 to a fine-textured homogeneous material, even though hardly consolidated, it may be true 
 brown coal. 
 
 Extensive beds of mineral coal occur in Great Britain, covering 11,859 square miles; in 
 France about 1,719 sq. m. ; in Spain about 3,408 sq. m. ; in Belgium 518 sq. m. ; in Nether- 
 lands, Prussia, Bavaria, Austria, northern Italy, Silesia, Spain, Russia on the south near the 
 Azof, and also in the Altai. It is found in Asia, abundantly in China, etc., etc. 
 
 In the United States there are four separate coal areas. One of these areas, the Appala- 
 chian coal field, commences on the north, in Pennsylvania and southeastern Ohio, and sweep 
 
HYDROCARBON COMPOUNDS. 419 
 
 Ing south over western Virginia and eastern Kentucky and Tennessee to the west of the 
 Appalachians, or partly involved in their ridges, it continues to Alabama, near Tuscaloosa, 
 where a bed of coal has been opened. It has been estimated to cover 60,000 sq. m. A sec- 
 ond coal area (the Illinois) lies adjoining the Mississippi, and covers the larger part of Illinois, 
 though much broken into patches, and a small northwest part of Kentucky. A third covers 
 the central portion of Michigan, not far from 5,000 sq. m. in area. Besides these, there is a 
 smaller coal region (a fourth) in Rhode Island. The total area of workable coal measures in 
 the United States is about 125,000 sq. m. Out of the borders of the United States, on the 
 northeast, commences a fifth coal area, that of Nova Scotia and New Brunswick, which 
 covers, in connection with that of Newfoundland, 18,000 sq. m. 
 
 The mines of western Pennsylvania, those of the States west, and those of Cumberland or 
 Frostburg, Maryland, Richmond or Chesterfield, Va. , and other mines south, are bituminous. 
 Those of eastern Pennsylvania constituting several detached areas one, the SchuylkiU coal 
 field another, the Wyoming coal field those of Rhode Island and Massachusetts, and tome 
 patches in Virginia, are anthracites. Cantel coal is found near Greensburg, Beaver Co., Pa., 
 in Kenawha Co , Va., atPeytona. etc. ; also in Kentucky, Ohio, Illinois, Missouri, and Indiana ; 
 but part of the so-called cannel is a coaly shale. 
 
 Brown coal comes from coal beds more recent than those of the Carboniferous age. But 
 much of this more recent coal is not distinguishable from other bituminous coals. The coal 
 of Richmond, Virginia, is supposed to be of the Liassic or Triassic era ; the coal of Brora, in 
 Sutherland, and of Gristhorpe, Yorkshire, is Oolitic in age. Cretaceous coal occurs on Van- 
 couver Island, and Cretaceous and Tertiary coal in many places over the Rocky Mountains, 
 where a " Lignitic formation" is very widely distributed. 
 
PART III. DESCRIPTIVE MINERALOGY. 
 
 SUPPLEMENTARY CHAPTER.* 
 
 ABRIACHANITE, Heddle. A soft blue clay-like substance, filling seams and cavities in 
 granite. Probably near crocidolite (p. 298) in composition. From the Abriachan district 
 near Loch Ness, Scotland. 
 
 ADAMITE p. 373. Occurs in colorless to deep green crystals, and in mammillary groups, 
 at the ancient mines, recently reopened, at Laurium, Greece. 
 
 AGLAITE. Same as cymatolite ; that is, an alteration product of spodumene, consisting oi' 
 an intimate mixture of albite and muscovite. From Goshen, Mass. 
 
 ALASKAITE, Ko'nig. Massive. G. = 6*878. Lustre metallic. Color whitish lead-gray. 
 Composition probably (Ag 2 ,Cu 2 ,Pb)S + Bi 2 S 3 . Analysis after deducting impurities, S 
 17-63, Bi 56-97, Sb 0'62, Pb 11 79, Ag 8'74, Cu 3'46, Zn 0'79 = 100. From the Alaska 
 mine, Poughkeepsie Gulch, Colorado. SILBERWISMUTHGLANZ of Rainmelsberg, from Moro- 
 cocha, Peru, is pure Ag 2 S -f Bi 2 S 3 . 
 
 ALBITE, p. 323. Has been made artificially, identical in form and composition with natu- 
 ral crystals, by Haute feuille. 
 
 AMBLYGONITE, p. 369. Penfield has analyzed specimens from Penig, Monte bras, Hebron 
 and Auburn, Me., Branchville, Ct. (including "hebronite" and " montebrasite "\ He 
 shows that, while the varieties vary from F 11'26,H 2 1'75 in one sample to F 1'75, H 2 6 '61 , 
 in another, they ail conform to the general formula: Al a P 3 B 4- 2R(F,OH), differing only 
 in the extent to which the hydroxyl replaces the fluorine. 
 
 AMPHIBOLE, p. 296. A variety containing only 0'9 p.c. MgO, has been called lergamas- 
 Tcite by Lucchetti Occurs in a hornblende porphyry. Monte Altino, Bergamo, Italy. 
 
 Phdactinite (Bertels) is a chloritic alteration product from a rock called isenite. Nassau, 
 Germany. 
 
 ANALCITE, p. 343. On the crystalline system, see p. 189. 
 
 Picranalcite, of Bechi, is identical with ordinary analcite, containing only a trace of 
 magnesia, according to Bamberger, 
 
 ANIMIKITE, Wurtz. An impure massive mineral supposed to be a silver antimonide 
 (Sb 11-18, Ag 77-58). Silver Islet, Lake Superior. 
 
 ANNERODITE, Brogger. A rare columbate, almost identical with samarskite in composi- 
 tion, but in form very near columbite. From a pegmatite vein at Annerod, near Moss, 
 Norway. 
 
 APATITE, p. 364. Large deposits of apatite, affording sometimes gigantic crystals, and 
 sometimes mined for commercial purposes, occur in Ottawa County, Quebec, Canada ; also 
 large crystals, with zircon, titanite and amphibole in Renfrew County, Ontario, and else- 
 where ; there are similar deposits at Kjorrestad, Bamle, Norway. A variety from San 
 Roque. Argentine Republic, containing 6'7 p.c. MnO, has been called mangdnapatite by 
 Siewert. Penfield found 10'6 p.c. MnO in a bluish-green specimen from Branchville, Ct. 
 
 Pseudo-hexagonal, Mallard, see p. 187. 
 
 * For fuller descriptions of new species, references to original papers, etc., see Appendix III. (1882), System 
 of Mineralogy. 
 
 420 
 
DESCRIPTIVE MINERALOGY. 421 
 
 APOPHYLLITE, p. 340. Pseudo-tetragonal (monoclinic), according to Mallard and Rumpf, 
 but the correctness of their conclusions is doubtful ; see p. 185 et seq. 
 
 ARAGONITE, p. 405. A variety from the Austin mine, Wythe Co., Va., afforded 7 '29 p.c. 
 PbC0 3 . 
 
 ARCTOLITE, Blomstrand. A doubtful silicate, composition near prehnite, prismatic angle 
 near hornblende. Hvitholm, near Spitzhergen. 
 
 AREQUIPITE, Raimondi. A honey-yellow compact substance, supposed to be a silico-anti- 
 monate of lead, but probably a mixture. Victoria mine, Province of Arequipa, Peru. 
 
 ARFVEDSONITE, p. 298. Occurs with zircon and astrophyllite in El Paso Co., Colorado. 
 
 ARRHENITE, Nordenskiold. A silico-tantalate of yttrium, erbium, etc., resembling feld- 
 spar in appearance. Probably an uncertain decomposition product. Ytterby, Sweden. 
 
 ARSENARGENTITE, Hannay. An uncertain silver arsenide of doubtful source. 
 
 ASMANITE, p. 288. According to Weisbach and v. Lasaulx, identical with tridymite ; 
 observed in the meteoric iron of Rittersgriin, Saxony. 
 
 ASTROPHYLLITE, p. 313. Referred to the triclinic system by Brogger ; properly a mem- 
 ber of the pyroxene group, not one of the true micas. 
 
 Occurs with arfvedsonite and zircon in El Paso Co., Colorado. 
 
 ATELINE (or atelite\ Scacchi. An alteration product of tenorite at Vesuvius ; near ata- 
 camite in composition. 
 
 ATOPITE, Nordenskiold. In isometric octahedrons. H. = 5*5-6, G. = 5 03. Color yellow 
 to brown. Composition essentially Ca 2 Sb a 7 (near romeite). Imbedded in hedyphane at 
 Langban, Sweden. 
 
 AUTUNITE, p. 379. Monoclinic (or triclinic), according to Brezina. 
 
 BALVRATDITE, Heddle. A doubtful substance having a saccharoidal structure, and pale 
 purplish-brown color G. 2'9. An analysis gave, Si0 2 46 04, A1 2 3 20*11, Fe 2 3 2*52, 
 MnO 0-79, MgO 8-30, CaO 13'47, Na 2 2*72, K 2 O 1'36, H 2 4-71 = 1(JO'02. In limestone 
 atBalvraid, Inverness-shire, Scotland. 
 
 BARCENITE, Mallet. An uncertain alteration product of livingstonite, massive, earthy, 
 color dark gray. G. = 5*343. Huitzuco, Guerrero, Mexico. 
 
 BARYLITE, Blomstrand. In groups of prismatic crystals. Two distinct cleavages (84). 
 H. = 7. G. = 4;03. White. BB. infusible. A silicate of aluminum and barium (46 
 p.c. BaO). In limestone at Langban, Sweden. 
 
 BEEGERITE, Konig. In elongated isometric crystals. Cleavage cubic. G. = 7*273. 
 ay. Lustre metallic. Composition, 6Pbb'+ Bi,S 3 = S 14-78, Bi 21 36, Pb 63*84 
 = 100. From the Baltic Lode, Park Co., Colorado. 
 
 Color gray. Lustre 
 
 BERYL, p. 299. Pseudo-hexagonal, according to Mallard, see p. 186. 
 
 A variety in short prismatic to tabular crystals has been called rosterite by Grattarola. 
 Locality, Elba. 
 
 Found (W. E. Hidden) in fine crystals of large size (to 10 inches in length), and emerald 
 color, in Alexander Co., N. C., also in highly modified crystals of pale green color. 
 
 BERZELIITE. This arsenate from Langban, Sweden, is isometric according to Sjfigren ; 
 honey to sulphur yellow, lustre resinous. Lindgren regards the ortho-arsenate of calcium 
 and magnesium, anisotrope, of the same locality, as distinct, and says that earlier descrip- 
 tions of berzeliite belong to it. 
 
422 DESCRIPTIVE MINERALOGY. 
 
 BHRECKITE (or Vreckite), Heddle. A doubtful soft apple-green substance, coating quartz 
 crystals. A hydrous silicate of alumina, iron, magnesia and lime. From the hill Ben 
 Bhreck, Sutherland, Scotland. 
 
 BISMUTOSPH^ERITE, Weisbach. Tn spherical forms, with concentric, fine fibrous radiated 
 structure. Regarded as an anhydrous bismuth carbonate. From Neustadtel, Schneeberg, 
 Saxony. 
 
 BLOMSTRANDITE, Lindstro'm. A columbo-titanate of uranium, allied to samarskite. 
 From Nohl, Sweden. 
 
 BOLIVITE, Domeyko. An alteration product of bismuthinite, probably a mechanical 
 mixture of Bi 2 3 and Bi 2 S 3 . Mines of Tazna, Province of Choroloque, Bolivia. 
 
 BORACITE, p. 381. On the crystalline system, see p. 189. 
 
 BOWLINGITE, Hannay. A soft, soapy, green substance, containing silica, alumina, iron, 
 magnesia, lime, water ; doubtless heterogeneous. Bowling on the Clyde, Scotland. 
 
 BRAVAISITE, Mallard. In fine crystalline fibres, of a grayish color, forming layers in the 
 coal schists at Noyant, Allier Dep't, France. G. = 2-6. Analysis, Si0 2 51 -4, A1 2 3 18*9, 
 Fe 2 3 40, CaO 2-0, MgO 3-3, K 2 6-5, H 2 13 3 = 99'4. 
 
 BROOKITE, p. 277. In Mallard's view, brookite, rutile and octahedrite are all monoclinic, 
 having the same primitive form, but differing in the way in which the individuals are 
 grouped, see p. 186. 
 
 BRUCITE, p. 281. Manganbrucite (Igelstrom) is a manganesian variety of brucite (14'16 
 MnO) from the manganese mines of the Jakobsberg, Wermland, Sweden. In fine granular 
 form with hausmannite in calcite. 
 
 Eisenbrucite, Sandberger. A doubtful substance resulting from the alteration of bru 
 cite. Sieberlehn near Freiberg. 
 
 CABRERITE. Occurs in crystals (isomorphous with erythrite) at the zinc mines of Lau- 
 rium, Greece. An analysis by Damour corresponds to Ni 3 As 2 8 -\-S aq. 
 
 CALAMINE, p. 329. According to Groth, the formula should be written H 2 Zn 2 Si0 5 . 
 
 CALAVERITE, p. 249. Occurs at the Keystone and Mountain Lion mines, Colorado. Com- 
 position (Genth) : (Au,Ag/Te 2 , with Au : Ag = 7 : 1. H. = 2'5. G. = 9'043. 
 
 CANCRINITE, p. 317. An original species (Rauff, Koch), and not an alteration product of 
 nephelite, the carbon dioxide being essential and not due to calcite. 
 
 CARYINITE, Lundstrom. Massive, monoclinic ; two cleavages (130). H. = 3-3-5. G. 
 = 4-25. Color, brown. Composition, R 3 As 2 0, with R = Pb,Mn,Ca,Mg. Occurs with 
 calcite and hausmannite at Langban, Sweden. 
 
 CHABAZITE, p. 344. Triclinic, according to Becke, the crystals being complex twins of 
 several individuals. 
 
 CHALCOMENITE, Des Cloizeaux and Damour. Monoclinic. / A /= 108 20'. A *- - 
 89 9'. G. = 3-76. Color, bright blue. Composition, CuSe0 3 + 2 aq, or a copper sele- 
 nite. From the Cerro de Cacheuta, Mendoza, Argentine Republic. 
 
 CHALCOPYRITE, p. 244. Found well crystallized, often coated with crystals of tetrahe- 
 drite in parallel position, near Central City, Gilpin Co , Colorado. 
 
 CHILDRENITE, p. 377. Formula, as shown by Penfield, R 2 A1 2 P 2 10 + 4H 2 0. or A1 2 P 2 8 + 
 2RH 2 + 2aq, with R = Fe principally, also Mn. This requires: P 3 6 30'80, A10 3 22'31 
 FeO 26-37, Mn04'87, H 2 15-65. 
 
DESCRIPTIVE MINERALOGY. 
 
 423 
 
 A mineral closely related to childrenite has been called eospliorite by Brush and E S. 
 Dana. Orthorhombic. In prismatic crystals (see fig.), near chil- 
 drenite. I/\I= 104 19' ; p /\p (1 A!) = 133 32' (front), = 118 
 58' (side). Here /, and a (i-l) = 2-1 and of childrenite. Also mass- 
 ive, cleavable to compact. Cleavage parallel a (i-l) nearly perfect. 
 H. 5. G. = 3 11-3145. Lustre vitreous to sub-resinous, also 
 greasy. Color rose pink, yellowish, colorless, when compact various 
 shades of white. Streak white. Transparent to translucent. 
 
 (General formula like childrenite (see above), but with much man- 
 ganese and little iron (10 : :j). Percentage composition : P 2 5 
 30-93, A1 2 3 2-2 -35, MnO 23-80, FeO 7'24, H 2 O 15-68 = 100. B. B. in 
 the forceps cracks opens, sprouts and whitens, colors the flame pale 
 green and fuses at 4 to a black magnetic mass. Reacts for manga- 
 nese and iron ; is soluble in acids. Occurs with other manganesian 
 phosphates in a vein of pegmatite at Branchvilie, Conn. 
 
 CHLORALLUMINITE, Scacchi. Hydrous aluminum chloride from Vesuvius. 
 
 CHLOROMAGNESITE, Scacchi. Hydrous magnesium chloride from Vesuvius. Bischofite 
 /Ochscnius and Pfeiffer) from Leopoldshall, Prussia, has the composition MgCl 2 + 6 aq. 
 Crystalline, massive, foliated or fibrous. Color white. Forms thin layers in halite, with 
 kieserite and carnallite. Readily assumes water on exposure. 
 
 CHLOROTHIONITE, Scacchi. Regarded as a compound salt, K 2 S0 4 + CuCl 2 , forming thin 
 mammillary crusts of a blue color. Vesuvius. 
 
 CHONDRODITE, HUMITE, CLINOHUMITE, p. 327. H. SjOgren has described humite, well 
 crystallized, from the Ladu mine, Wermland, Sweden, and chondrodite from Kaveltorp. 
 
 CHROMITE, p. 274. Not opaque, but in thin sections transmits a yellowish red color, 
 Thoulet. Identified in meteoric irons by J. Lawrence Smith. 
 
 CIIRYSOCOLLA, p. 338. Pilarite, from Chili, is an aluminous variety, 16 f 9 p.c. A1 2 3 . 
 
 CHRYSOLITE, p. 300. Neochrysolite (Scacchi) is a manganesian variety from Vesuvius. 
 A variety from Zermatt, containing 6 p.c. Ti0 2 , has been called titanolivine. 
 
 CLEVEITE, Nordenskiold. A mineral closely related to uraninite, but besides uranium 
 (and lead) contains yttrium, erbium, cerium, etc. In isometric crystals. H. 55. G. 
 = 7'49. Color iron black. A decomposition product of a yellow color is called yttro- 
 aummite (analogous to ordinary gummite). Occurs in feldspar at Garta, near Arendal, 
 Norway. 
 
 CLINOCROCITE, Sandberger, Singer. An imperfectly described sulphate of iron, etc., 
 occurring in saffron-yellow microscopic crystals, derived from the decomposition of pyrite 
 at the Bauersberg, near Bischofsheim vor der Rho'n. Clinoph&ite, from the same source, 
 occurs in blackish green microscopic crystals; formula 5RsS0 4 -f [R 2 ]H 6 6 + 5 aq, with 
 [R 2 ] = Fe 2 ,Al 2 , and R 2 = Fe,K 2 ,Na 2 . 
 
 CLINTONITE, p. 358. On the relations of the "clintonite group" of minerals, see Tscher- 
 mak and Sipocz, Z. Kryst., iii., 496. 
 
 COLORADOITE, Genth. Massive, granular. H. 3. G. = 8-627. Lustre metallic. Color 
 iron black. Composition HgTe = tellurium 39, mercury 61 = 100. Occurs with native 
 tellurium, sylvanite, gold, at the Keystone, Mountain Lion, and Smuggler mines in Colorado. 
 
 COLUMBITE, p. 360. Occurs sparingly in small translucent crystals at Branchvilie, Conn., 
 having the composition MnCb 2 + MnTa 2 ; containing 15-58 pc.MnO, and 0-43 FeO. 
 Also the ordinary variety in groups of very large, though rough, crystals, weighing some- 
 times 50 pounds, at the same locality. Found with amazonstone at Pike's Peak, Colorado, 
 
424 
 
 DESCRIPTIVE MINERALOGY. 
 
 and in Yancey Co., N. C. Also with monazite, orthite, etc., in Amelia County, Virginia, 
 allied in composition to the above manganesian variety from Branchville. 
 
 COROXGUITE, Raimondi. An earthy, pulverulent substance of a gray to black color. 
 Containing antimony pentoxide, lead, and silver oxides, water, but of doubtful homogeneity. 
 District of Corongo and elsewhere in Peru. 
 
 CORUNDOPHILITE, p. 358. Amesite of Shepard, from Chester, Mass., is very near corun- 
 dophilite. 
 
 CORUNDUM, p. 267. Monoclinic according to Tschermak (orthorhombic, Mallard) ; often 
 optically biaxial. See p. 18 > et seq. 
 
 Made artificially, with the colors of rubies and sapphires, by Fremy and Feil. 
 
 COSALITE, p. 252. Bjelkite of H. Sjogren is identical with cosalite. From the Bjelke 
 mine, Nordmark, Sweden. 
 
 COSSYRITE, Foerstner. Near amphibole in form, but triclinic, and with I /\ I' = 
 114 5'. Cleavage prismatic. G. = 3 '75. Color black. An analysis gave : Si0 2 43 '55, 
 A1 2 3 4-96, Fe 2 3 7'97, FeO, 32 -87, MnO 1-98. CuO 0'39, MgO 0'86, CaO 2 01, Na 2 5-29, 
 K 2 0'33 = 100*21. In minute crystals weathered out of the ground mass of the liparite 
 lavas of the Island Pantellaria (ancient name Cossyra). 
 
 CBAIGTONITE, Heddle. Doubtful mineral, contains A1 2 3 , Fe 2 3 , MgO, etc. Dendritea 
 in granite at Craigton, Aberdeenshire, Scotland. 
 
 CROCOITE, p. 385. Described by B. Silliman as occurring at the Phenix and other mines 
 in Yavapai Co., Arizona. 
 
 CRYOLITE, p. 264. Observations of Krenner make cryolite monoclinic instead of triclinic. 
 Cryolite and some related fluorides have been found (Cross and Hillebrand) in the Pike's 
 Peak region, El Paso Co., Colorado. 
 
 CUPROCALCITE, p. 411. Mechanical mixture of CaC0 3 and Cu 2 0, Damour. 
 
 ^ CUSPIDINE, Scacchi. In spear-shaped monoclinic crystals ; color pale rose red. A calcium 
 silicate containing fluorine. Vesuvius. 
 
 CYANITE, p. 332. Recently found in well terminated crystals, Bauer, vom Rath. 
 
 CYPRUSITE, Reinsch A supposed anhydrous iron sulphate, occurring in the western 
 part of the island of Cyprus. Soft. Color yellow. Analysis : S0 3 21 '5, Fe 2 O 3 (A1 2 3 tr.) 
 51-5, insol. silica (shells of Radiolaria) 25, H 2 (hygrosc.) 2 = 100. 
 
 DANALITE, p. 302. Occurs at the iron mine of Baitlett, N. H. (Wadsworth). 
 
 DANBURITE, p. 311. Occurs (G. J. Brush and E. S. Dana) well crystallized and abundant 
 at Russell, N. Y. Orthorhombic, homoeomorphous with topaz and like it in habit. I /\1 
 = 122 52' (topaz = 124 17'), w A w = 54 58' (topaz = 55 20'), d /\d = 97 7' (topaz = 96 6'). 
 Common forms as in figures, w = 4-2, d = l-i, l=i-2, n = i-4, r = 2-2. Color pale wine 
 or honey yellow, colorless. Transparent. Composition CaB 2 Si 2 8 , as of Danbury mineral. 
 
 Also from the Skopi, Switzerland, in transparent crystals. 
 
DESCRIPTIVE MINERALOGY. 425 
 
 DAVREUXITE, de Koninck. In aggregates of minute acicular crystals. Color white, 
 with tinge of red. Calculated composition : Si0 2 46 -89, A1 2 3 40'19, MnO 6-93, MgO 1 30, 
 H 2 4'69 = 100. Occurs in quartz veins in the Ardennes schists at Ottre, Belgium. 
 
 DAWSONITE, p. 410. Occurs (C'haper) in the province of Siena, Pian Castagnaio, Tuscany. 
 Analysis gave Friedel : (|) C0 2 29 "09, A1 2 3 3589, Na 2 1913, H 2 O 12-00, MgO l'B9, 
 CaO 0-42. 
 
 DELESSITE, p. 3o6. More or less related to the chloritic delessite are : Subdelessite from 
 the Thiiringer Walcl ; Hullite, Carnmoney Hill, near Belfast, Ireland. 
 
 DESCLOIZITE, p. 367. Occurs in the Sierra de Cordoba, Argentine Republic ; perhaps also 
 in Arizona. Composition of South American mineral (Ramrnelsberg) R 3 V 2 O 8 + RH 2 2 , 
 with R -= Pb (56 p.c.), Zn (17 p.c.) 
 
 Srac-kebuschite from Cordoba, Argentine Republic, occurs in small striated crystals. 
 Color black. Com position perhaps R 3 V 2 8 + H 2 O, with R = Pb : Fe : Mn = 4:1:1. 
 
 DESTINEZITE, Forir and Jorissen. An iron phosphate from Argenteau, Belgium ; occurs 
 in yellowish white earthy masses. 
 
 DIAMOND, p. 228. Has been made artificially, in the form of a fine sand, by J. B. Hannay. 
 
 DICKINSONITE, G. J. Brush and E. S. Dana. Monoclinic, pseudo-rhombohedral, (3= 61 
 30 . c /\a 118 30', c /\p = 118 52', c^s = 97 58' ; c = 0,p =1, s = 2, x 3-^. Com- 
 monly foliated to micaceous. Cleavage basal perfect. H. = 3 '5-4. G. = 3-338-3-343. 
 Lustre vitreous, on c pearly. Color various shades of green. Composition 4R 3 P 2 8 + 3aq. 
 with R = Mn,Fe,< a,Ka 2 , requiring: P,,0 5 40-05, FeO 12-69, MnO 25'04, CaO 11-85, 
 Na 2 6*56, H 2 3-81 = 10 ). Occurs with eosphorite, triploidite, etc., in pegmatite at 
 Branchville, Conn. 
 
 DIETRICHITE, v. Schrockinger. A zinc-iron-manganese alum, related to mendozite, etc. 
 A recent formation at Felsobanya, Transylvania. 
 
 DOPPLERITE, p. 415. A black gelatinous hydrocarbon from a stratum of muck below a 
 peat bed at Scranton, Penn., is called by H. C. Lewis phytocollite ; empirical formula 
 
 DOUGLASITE, Ochsenius, Precht. From Douglasshall, formula, 2KCl,FeCl 2 ,2H 2 0. 
 
 DUMORTIERITE, Damour, Bertrand. In minute prismatic crystals of a cobalt blue color, 
 imbedded in gneiss. Analysis (Damour) : SiO 2 29 -85, A1 2 3 66 02, Fe 2 O 3 I'Ol, MgO 0'45, 
 ign. 2 25 = 99-58 ; near andalusite. From the gneiss at Chaponost, near Lyons, France. 
 
 DUPORTHITE, Collins. An asbestiform mineral filling fissures in serpentine. Color green- 
 ish to brownish gray. Contains silica, alumina, iron, magnesia, and water. Duporth, St. 
 Austell, Cornwall. 
 
 DURFELDTITE, Raimondi. Massive, indistinctly fibrous. Color light gray. Metallic. 
 Composition 3RS + Sb 2 S 3 (if the results of an analysis after deducting 31 p.c. gangue can 
 be trusted), with R = Pb,Ag 2 ,Mn, also Fe,Cu 2 . From the Irismachay mine, Anquimarca, 
 Peru. 
 
 DYSAXALYTE, Knop. The perpfskite of the Kaiserstuhl is, according to Knop, a new 
 columbo-titanate of calcium and iron (with also Ce,Na). 
 
 EGGONITE, Schrauf. In minute, grayish-brown crystals (triclinic) near barite in habit. 
 Supposed to be a cadmium silicate. Occurs with calamine and smithsonite at Altenberg. 
 
 EKDEMITE, Nordenskiold. Massive, coarsely granular, also incrusting. Cleavage basal. 
 H. = 2-5-3. G. 7-14. Color bright yellow to green Composition Pb 5 As. 2 O ft + 2PbCl a 
 = As 2 3 10-59, PbO 59-67, Cl 7*58, Pb 22-16 = 100. Found at L&ngban, Sweden. 
 
426 
 
 DESCRIPTIVE MINERALOGY. 
 
 ELEONORITE, JTies. Monoclinic ; often in druses and in radiated crusts. Cleavage ortho- 
 diagonal. H. = 3-4. Lustre vitreous. Color red brown to dark hyacinth red. Streak 
 yellow. Composition (Streng) 2Fe 2 P 2 O 8 + Fe 2 H 6 6 +5 aq. From the Eleonore mine on the 
 Diinsberg, near Giessen, and the Rothlaufchen mine near Waldgirmes. Perhaps identical 
 with the iron phosphate beraunite from Benigna, Bohemia. 
 
 ELLONITE, Heddle. Impure silicate of magnesia, containing Si0 2 . In gneiss near Ellon, 
 Aberdeenshire, Scotland. 
 
 ELBOQUITE, Shepard. A heterogeneous substance containing silica, alumina, iron oxide, 
 water and (as an impurity; 32 p.c. P 2 5 . Island of Elroque, Caribbean Sea. 
 
 ENYSITE, Collins. A bluish-green stalagmitic substance consisting of aluminum hydrate, 
 basic copper sulphate, calcite, etc. St. Agnes, Cornwall. 
 
 EPISTILBITE, p. 347. Monoclinic, Des Cloizeaux. Parastilbite and reissite are probably 
 
 1 A 1 " 
 
 identical. 
 
 EPSOMITE, p. 394. Reichardtite (Krause) is a massive variety from Stassfurt and Leo- 
 poldshali. 
 
 ERILITE, Lewis. Acicular, wool-like crystals of unknown nature occurring in a cavity 
 in the quartz from HerkimerCo., N. Y. 
 
 ERIOCHALCITE, Scacchi. Copper chloride from Vesuvius. 
 
 ERYTHROZINCITE, Damour. In thin crystalline plates. Color red. Perhaps (Des Cloi- 
 zeaux) a manganesian variety of wurtzite. 
 
 EUCLASE, p. 328. Found in good crystals in the Tyrol, from the Hohe Tauern, perhaps 
 at Kauris. 
 
 EUCRASITE, Paijkull. A mineral from Brevig, Norway, near thorite. 
 
 EUCRYPTITE, G. J. Brush and E. S. Dana. Hexag- 
 onal. In regularly arranged crystals imbedded in 
 albite (like graphic granite, see fig.) both of which have 
 resulted from the alteration of spodumene. G. = 2 '667. 
 Composition Li 2 Al 2 Si 2 8 = Si0 2 47*51, Al,0 3 40 61, 
 Li 2 11 -88 - 100. Branchville, Conn. 
 
 EULYTITE, p. 
 
 to Bertrand. 
 
 5. Pseudo rhombohedral according 
 
 ETJSYNCHITE is (Rammelsberg) 4Pb 3 V 2 8 + 3Zn 3 V 2 8 . 
 Araoxene is 2(Pb,Zn) 3 V 2 8 + (Pb,Zn) 3 As ? 8 . 
 
 Tritochorite (Frenzel) is related, composition R 3 V 2 8 , 
 with R = Pb (54 p.c.), Cu (7 p.c.), Zn (11 p.c.). Lo- 
 cality uncertain. 
 
 FAIRFIELDTTE. G. J. Brush and E. S. Dana. Triclinic. Foliated or lamellar, crystalline; 
 also in radiating masses, curved foliated or fibrous. Cleavage brachydiagonal perfect. 
 Lustre pearly to subadamantine. Color white to pale straw yellow. Transparent. Com- 
 position R 3 P 2 0* + ^aq, with R = Ca : (Mn + Fe) = 2 : 1. This requires : P 2 5 39'30, FeO 
 6-64. MnO 13-10, CaO 30-99, H 2 9-97 = 100. Occurs with other manganesian phosphates 
 at Branchville, Conn. 
 
 Leucomanganite (Sandberger) from Rabenstein, Bavaria, may be identical ; not yet 
 described. 
 
 FELDSPAR GROUP. Schuster has shown that in the series of triclinic feldspars there is 
 
DESCRIPTIVE MINERALOGY. 427 
 
 in optical relations the same gradual transition from the one extreme (albite) to the other 
 (anorthite) as exists in composition. Thus, he finds that the directions of light-extinction, 
 as observed on the basal and clinodiagonal sections, the position of the axes of elasticity, 
 the dispersion of the axes, and the axial angle all fchow this gradual change in the same 
 direction. These results confirm the accepted view of Tschermak that the intermediate 
 triclinic feldspars are to be regarded as isomorphous mixtures of albite and anorthite in 
 varying proportions ; moreover, they explain the apparent difficulties raised by the obser- 
 vations of Des Cloizeaux (p. 319). The angles given on p. 320 are then true only in special 
 cases, since in the varieties varying in composition these values will also vary. The values 
 for angles (given by Schuster) made by the extinction-directions with O and i-i are as 
 follows : 
 
 With With i-i 
 
 Albite -f4 to +3 +18 
 
 Varieties between Albite) 9 o < -,<> 19 o 
 
 and Oligoclase f 
 
 Oligoclase +2 to +1 +3 to +2 
 
 Andesite -1 to -2 -4 to -6 
 
 Labradorite -4 to -5 -17 
 
 Varieties between Labra- 
 
 dorite and Anorthite.... f ~ 16 to 
 Anorthite -38 -40 
 
 FERGTJSONITE, p. 362. New localities : Rockport, Mass. (J. L. Smith) ; Burke Co., N. C. 
 [Hidden) ; Mitchell Co., N. C. (Shepard). 
 
 FEKROTELLURITE, Genth. In delicate radiating crystalline tufts of a yellow color. Per- 
 haps an iron tellurate. Keystone mine, Magnolia District, Colorado. 
 
 FILLOWITE, G. J. Brush and E. S_ Dana. Monoclinic ; pseudo-rhombohedral. Gener- 
 
 it 
 
 70 
 = 100. Occurs with other manganesian phosphates in pegmatite at Branchville, Conn. 
 
 FLUORITE, p. 263. Pseudo-isometric, according to Mallard ; see p. 186. 
 FORESITE, p. 347. Probably identical with stilbite. 
 
 FRANKLANDITE, Reynolds. Near ulexite. Massive. White. G. = 1'65. Composition 
 NTa 4 Ca 2 B 12 22 , 15H 2 0. Tarapaca, Peru. 
 
 FREYALITE, Esmark, Damour. A silicate of cerium, thorium, etc. G. = 4-06-4-17. 
 Color brown. From Brevig, Norway. 
 
 GADOLINITE, p. 309. Contains the new earth ytterbium (Marignac), also scandium (Cleve). 
 
 GALENOBISMUTITE, H. Sj5gren. Massive, compact. H. = 3-4. G. 6'88. Lustre me- 
 tallic. Color tin white. Streak grayish black. Composition PbBi 2 S 4 or PbS + Bi 2 S 3 , 
 requiring, S 16 '95, Bi 55 '62, Pb 27 '43 100. Occurs with bismutite at the Kogrufva, 
 Nordmark, Sweden. 
 
 GANOMALITE, Nordenskiold. Massive. H. = 4. G. = 4'98. Lustre greasy. Colorless 
 to white or whitish gray. Transparent. Composition (Pb,Mn)Si0 3 ; analysis (Lind- 
 strOm : Si0 2 34'55, PbO 34'89, MnO 2001, CaO 4'89, MgO 3'68, alk., ign. 1 S8=99'58. 
 Occurs with tephroite, native lead, etc., at Langban, Sweden. 
 
 GARNET, p. 302. Pseudo-isometric, according to Mallard and Bertrand, see p. 186. 
 Nearly colorless garnets occur at Hull, Canada ; others containing 5p.c. Cr 2 3 at Wakefield, 
 Quebec. Large perfect crystals in mica schist near Fort Wrangell, Alaska. 
 
 GARNIERITE, p. 351. An allied hydrated silicate of magnesium and nickel has been 
 found in Southern Oregon, at Piney Mountain, Cow Creek, Douglas County. 
 
428 DESCRIPTIVE MINERALOGY. 
 
 GINILSITE, Fischer. A doubtful silicate from the Ginilsalp, Graubiinden, Switzerland. 
 GISMONDITE, p. 341. Triclinic, complex twins, according to Schrauf and v. Lasaulx. 
 
 GUANAJUATITE, Fernandez, 1873. The same mineral as that afterward called frenzeli 
 (p. 223). Composition (Mallet), Bi 2 Se 3 , with a little Se replaced by S. Sttaonite is 
 mechanical mixture of this mineral and native bismuth. 
 
 GUNNISONTTE, Clarke and Perry (Am. Chem. Journ., iv., 140). A massive substance, < 
 a deep purple color, mixed with calcite. An analysis, after deducting 12 '75 CaC0 3 , yieldt 
 CaF 2 74-89, CaO 11'44, Si0 2 6'87, A1 2 3 5 '95, Na 2 O'So = 100. Probably an impu 
 fluorite ; perhaps altered ; certainly not a homogeneous mineral. 
 
 GUEJARITE, Cumenge. Orthorhombic ; in prismatic crystals, form near that of chalc< 
 stibite. H. = 3'5. G. = 5 '03. Color steel gray. Composition Cu 2 Sb 4 S 7 or Cu 2 S + 2Sb 2 S 
 From me copper mines in the district of Guejar, Andalusia. 
 
 GUMMITE. This decomposition product of uraninite occurs in considerable masses j 
 the Flat Rock mine, Mitchell Co., N. C. 
 
 GYROLTTE, p. 328. Tobermorite of Heddle, is near gyrolite and okenite. Massive. Col< 
 pinkish white. G. = 2'423. Analysis : Si0 2 46'62, A1 2 3 3'99, F 2 3 0-66, FeO 1-08, Ca 
 33'98, K 2 0-57, Na 2 0'89, H 2 1211 = 99 '81. Filling cavities in rocks near Tobermor 
 Island of Mull. 
 
 HALLOYSITE, p. 352. Indianaite of Cox, is a white porcelain clay, useful in the art 
 occurring in considerable beds in Lawrence Co., Indiana. 
 
 HANNAYITE, vom Rath. In triclinic prismatic crystals. G. = 1*893. Compositic 
 H 4 (NH 4 )Mg 3 P40 16 4- 8 aq. Occurs in guano of the Skipton Caves, Victoria. 
 
 HATCHETTOLITE, J.L. Smith. Isometric, habit octahedral. H. = 5. G. = 4-77-4-90. Lust] 
 resinous. Color yellowish brown. Translucent. Fracture conchoidal. A columbo-tai 
 talate of uranium and calcium, containing 5 p.c. water ; closely related to pyrochlon 
 With samarskite in the mica mines of Mitchell Co., N. C. 
 
 HAYESINE. According toN. H. Barton, this borate occurs sparingly with datolite andca 
 cite at Bergen Hill, N. J. 
 
 HEDYPHANE, p. 367. A variety from Langban contains (Lindstrom) 8 p.c. BaO. Mom 
 clinic (Des Cloizeaux), and perhaps isomorphous with caryinite, p. 422 ; this would sepi 
 rate it from mimetite. 
 
 HELDBURQITE, Liidecke. In minute tetragonal crystals, resembling guarinite. Cok 
 yellow. H. = 6 '5. Composition unknown. In feldspar of the phonolyte of the Heldbur^ 
 near Coburg. 
 
 HELVITE, p. 302. Occurs at the mica mine near Amelia Court House, Amelia Co., Vii 
 ginia. In crystals and crystalline masses, of a sulphur-yellow color, imbedded in orth< 
 clase. 
 
 HENWOODITE. Collins. In botryoidal globular masses, crystalline. H. = 4-4 '5. G 
 = 2 '67. Color turquoise blue. A hydrous phosphate of aluminum and copper (7 p.< 
 CuO). West Phenix mine, Cornwall. 
 
 HERRENGRUNDITE, Brezina (= Urvolgyite, Szabo). In spherical groups of six-sided tabi 
 lar crystals (monoclinic). Cleavage basal perfect. H. = 2 '5. G. = 3 '132. Lustre vitreoui 
 pearly on cleavage face. Color emerald to bluish green. A hydrous basic sulphate < 
 copper, allied to langite. From Herrengrund (= Urvolgy) in Hungary. 
 
DESCRIPTIVE MINERALOGY. 429 
 
 HESSITE, p. 228. Pseudo-isometric (triclinic) according to Becke, but the conclusion is 
 ot beyond question. 
 
 HET^ROLITE (Hetairite), G. E. Moore. In botryoidal coatings, with radiated structure. 
 [. = 5. G. = 4 '933. Stated to be a zinc hausmannite. Occurs with chalcophanite at 
 terling Hill, New Jersey. 
 
 HEUBACHITE, Sandberger. In thin soot-like incrustations, also dendritic. Color black. 
 i hydrous oxide of cobalt and nickel. Heubachthal, near Wittiehen, Baden. 
 
 HEULANDITE, p. 347. Oryzite of Grattarola may be identical with heulMNiite. In 
 ninute white crystals, resembling rice grains (opv^a, rice). Elba. 
 
 HIBBERTITE, Heddle. A lemon-yellow powder in kammererite ; in composition probably 
 i mixture of magnesium hydrate and calcium carbonate. From the chromite quarry in 
 -he island of Unst, Scotland. 
 
 HIERATITE, Cossa (Trans. Acad. Line., III., vi., 14). A potassium fluo-silicate, 2KF + 
 >iF 4 , obtained in octahedral crystals from an aqueous solution of part of stalactitic concre- 
 ions found at the fumarolesof the crater of Vulcano. The concretions have a grayish color, 
 t spongy texture, rarely compact, and consist of hieratite, lamellae of boracic acid, with 
 elensulphur, arsenic sulphide, etc. 
 
 HOMILTTE, Paijkull. Near gadolinite and datolite in angles and habit. H. = 4 '5-5. 
 r. = 3'34. Lustre resinous to vitreous. Color black or blackish brown. Translucent in 
 hin splinters. Composition FeCaB 2 Si 2 Oi , or analogous to datolite. From the Stocko, 
 lear Brevig, Norway. 
 
 HOPEITE. Composition probably Zn 3 P 2 8 + 4 aq. Orthorhombic. Altenberg. 
 
 HUBNERITE, p. 383. Found (Jenney) near Deadwood, Black Hills, Dakota. Also in rho- 
 lochrosite at Adervielle, in the Hautes Pyrenees. 
 
 HUNTILITE, Wurtz. An impure massive mineral from Silver Islet, Lake Superior, re- 
 jarded as a basic silver arsenide. 
 
 HYALOTEKITE, Nordenskiold. Coarsely crystalline, massive. H. = 5-5*5. Gr. = 8*81. 
 Lustre vitreous to greasy. Color white to pearly gray. Analysis (incomplete) : SiO a 39 62, 
 ?bO 25-30, BaO 20 66, CaO 7 '00, ign. 0-82, A1 2 3 K 2 O, etc., tr. From Langban, Sweden. 
 
 HYDROCERUSSITE, NordenskiSld. A hydrous lead carbonate, occurring in white or color- 
 ess crystalline plates on native lead at Langban, Sweden. 
 
 HYDROFRANKLINITE, Rcepper. A hydrous oxide of zinc, manganese and iron, occurring 
 n brilliant regular octahedrons, with perfect octahedral cleavage. Sterling Hill, N. J. 
 Sever completely described. 
 
 HYDROPHILITE, Adam. Calcium chloride ; see chlorocalcite, p. 260. 
 
 HYDRORHODONITE, Engstrom. A hydrous silicate of manganese (MnSi0 3 + aq). Massive, 
 crystalline. Color red brown. Langban, Sweden. 
 
 ILESITE, Wuensch. In loosely adherent crystalline aggregates. Color white. Taste 
 jitter, astringent. Composition (M. W. lies) RSO 4 + 4 aq, with R Mn : Zn : Fe = 5 : 
 L : 1. Occurs in a siliceous gangue in Hall Valley, Park Co., Colorado. 
 
 IOCOBROMITE, v. Lasaulx. Isometric, octahedral. G. = 5'713. Color sulphur yellow, 
 sometimes greenish. Composition 2Ag(Cl,Br) -f- Agl. From the mine "Schone Aus- 
 sicht," Dernbach, Nassau. 
 
 IRON, p 226. The later investigations of the so-called meteoric iron of Ovifak, Disco 
 
430 DESCRIPTIVE MINERALOGY. 
 
 Bay, Greenland, more especially by Tornebohm and J. Lawrence Smith, leave no doubt thai 
 it is in fact terrestrial. 
 
 JAMESONITE, p. 251. Occurs in Sevier Co., Arkansas, with other ores of antimony. 
 
 JAROSITE. Occurs in tabular rhombohedral crystals at the Vulture mine, Arizona 
 (Silliman), and at the Arrow mine, Chaff ee Co., Colorado (Konig). Composition K 2 S0 4 -f 
 Fe 2 S 3 12 + 2Fe 2 H 6 O 6 . 
 
 KENTROLITE, Damour and vom Rath. In minute orthorhombic crystals, grouped ir 
 sheaf -like forms like stilbite. H. = 5. G. 6*19. Color dark reddish brown. Compositior 
 probably Pb 2 Mn 2 Si 2 9 . From Southern Chili. 
 
 KRENNERITE, vom Rath (Bunsenin, Krenner). Orthorhombic ; in vertically striatec 
 prismatic crystals. Color silver white to brass yellow. Lustre metallic, brilliant. A tellu 
 ride of gold, perhaps related to calaverite. Nagyag, Transylvania. 
 
 LAUTITE, Frenzel. Generally massive. H. =3-3 '5. G. = 4*96. Metallic. Color iror 
 black. Formula given CuAsS, but very probably a mixture. Lauta, Marienberg, Saxony. 
 
 LAWEENCITE, Daubree. Iron protochloride occurring in the Greenland native iron, etc, 
 LEADHILLITE, p. 390. Susannite is very probably identical with leadhillite. 
 
 LEIDYITE, Konig. In verruciform incrustations, consisting of fine scales. Color various 
 shades of green. A hydrous silicate of aluminum, iron, magnesium, and calcium. Leiper 
 ville, Delaware Co., Penn. 
 
 LEUCITE, p. 318. Has been made artificially by Fouque and Levy ; also an iron leucit< 
 has been made by Hautef euille ; optical character as of natural crystals. 
 
 LEUCocriALCiTE, Sandbcrger. In slender, nearly white crystals. According to an imper 
 feet description, an arsenical tagilite. Wilhelmine mine in the Spessart. 
 
 LEUCOPHANTTE, p. 300. Monoclinic (Bertrand, Groth), twins analogous to those of har 
 motome. 
 
 LEUCOTILE, Hare. In irregularly grouped silky fibres of a green color. Analysis : SiO 
 28-98, Al a O, 6-99, Fe 9 3 8'16, MgO 29'78, CaO 7 '37, Na 2 1'32, K 2 tr., H 2 17"29 = 99'89. 
 Reichenstein, Silesia. 
 
 LIBETHENITE, p. 373. Pseudo-orthorhombic, monoclinic, according to Schrauf. 
 
 LISKEAEDITE, Maskelyne. Massive, incrusting. Color white. Stated to have the compo- 
 sition Al 6 As 2 14 ,16H 2 0. Not fully described. Liskeard, Cornwall. 
 
 LIVINGSTONITE, p. 232. Composition probably Hg 2 S + 4Sb 2 S 3 . 
 
 LOUISITE, Honey mann. A transparent, glassy, leek-green mineral. H. = 6 -5. G. = 2-41. 
 Analysis (H. Louis) : Si0 2 63'74, A1 2 S 57, FeO 1 25, MnO tr., CaO 17-27, MgO 0'38, 
 K 2 3 38, Na 2 OO-08, H,0 12-96 = 99-63. 
 
 MACFARLANITE, Sibley. A name given to the complex granular silver ore of Silver Islet, 
 Lake Superior, which has yielded the supposed huntilite. 
 
 MAGNOLITE, F. A. Genth. In radiating tufts of minute acicular crystals. Color white. 
 Lustre silky. Composition perhaps Hg 2 TeO 4 . A decomposition product of coloradoite, 
 Keystone mine, Magnolia District, Colorado. 
 
DESCRIPTIVE MINERALOGY. 431 
 
 MALLARDITE, Carnot. In colorless cystalline fibrous masses. Composition MnS0 4 4- 7aq. 
 From the "Lucky Boy" silver mine, Butterfield Canon, near Salt Lake, Utah. 
 
 MANGANOSITE, Blomstrand. Isometric. Cleavage cubic. H. = 5-6. G. = 5'118. 
 Lustre vitreous. Color emerald green on fresh fracture, becoming black on exposure. 
 Composition MnO. From Langban, and from the Mossgrufva, Nordmark, Sweden. 
 
 MARMAIROLITE. Hoist. In fine crystalline needles. H. = 5. G. = 3 07. Color pale 
 yellow. Composition near enstatite, but with 6 p.c.Na 2 and 1-9 p.c. K 2 0. Langban, 
 sweden. 
 
 MATRICITE, Hoist. In crystalline masses. H. = 3-4. G. = 2 '53. Color gray. Feel 
 Creasy. A hydrous silicate of magnesium, near villarsite, but with one molecule H 2 0. 
 ?rom the Krangrufva, Wermland, Sweden. 
 
 MELANOTEKITE, Lindstrom. Massive, cleavable. H. = 65. G. = 5 - 73. Lustre metallic 
 ;o resinous. Color black to blackish gray. Composition Pb 2 Fe 2 Si<.0 9 (analogous to ken- 
 brolite). With magnetite and yeilow garnet at L&ngban, Sweden. 
 
 MELANOTHALLITE, Scacchi. Copper chloride from Vesuvius. 
 
 MELANTERITE, p. 395. Luckite of Carnot is a variety containing 1*9 p.c. MnO. " Lucky 
 Boy " silver mine, Butterfield Canon, near Salt Lake, Utah. 
 
 MELIPHANITE, p. 300. Tetragonal according to Bertrand. 
 
 MENACCANITE, p. 269. Hydroilmenite of Blomstrand is a partially altered variety, con- 
 taining a little water. From Smaland, Sweden. 
 
 MICA GROUP, pp. 311 to 315. Tschermak has shown that all the species of the mica 
 group are monoclinic, an axis of elasticity being inclined a few degrees to the plane of 
 cleavage ; these conclusions are confirmed by Bauer ; and von Kokscharof shows that in 
 angle there is no sensible deviation from the orthorhombic type. 
 
 Tschermak divides the species into two groups as follows : 
 
 I. II. 
 
 Biotites: Anomite. Meroxene, Lepidomelane. 
 
 Phlogopiles : Phlogopite, Zinnwaldite. 
 
 ( Lepidolite, 
 Muscovites : < Muscovite, 
 
 ( Paragonite. 
 Margarites : Margarite. 
 
 In group I. are included all the micas in which the optic axial plane is perpendicular to the 
 plane of symmetry ; and group II. includes those in which it is parallel to the plane of 
 symmetry. Thus, the former species biotite is divided on this principle into anomite 
 (dvojuof, contrary to law) and meroxene (Breithaupt's name for the Vesuvian biotite). For 
 example, the mica occurring with diopside in granular calcite at Lake Baikal is anomite, 
 as also that from Greenwood Furnace, N. Y. Meroxene is represented by the Vesuvian 
 magnesian mica. Muscovite includes also some of the "hydro-micas" to all of which 
 belong the formula (H,K)oAl 2 SinO* ; plien'/ite is a name given to some muscovites approach- 
 ing lepidolite in composition, and thus not conforming to the unisilicate type. For the full 
 discussion of the subject, see the original memoirs of Tschermak and also those of Rammels- 
 berg, etc , referred to in Appendix III. 
 
 Haui'htonit* (Meddle), from Scotch granite, etc., is a variety of biotite, characterized by 
 containing much FeO (to 19 p.c ) and little MgO. Siderophyttite (H. C. Lewis) from Col- 
 orado contains all FeO (25-5 p.c.) and only a trace of magnesia. 
 
 MICROLITE, p. 359 In small brilliant octahedrons, light grayish yellow to blackish brown 
 (Nordenskiold), at Uto, Sweden. G. - 5-25. Composition Ca' 2 Ta 2 7 , with also MnO and 
 MgO. 
 
432 ^ DESCRIPTIVE MINERALOGY. 
 
 Occurs at the mica mines of Amelia Co., Virginia (Dunnington). In modified octa- 
 hedrons, also in large (to 4 Ibs.) imperfect crystals. G. = 5*656. Composition essentially 
 GfcsTftsOi) with also -$ CbOF 3 . Also occurs at Branchville, Conn. (Brush and Dana). 
 
 Haddamite of Shepard, from Haddam, Conn., is related, perhaps identical. 
 
 MILARITE. Orthorhombic, pseudo-hexagonal. Composition HKCa 2 Al 2 Si 2 20 8 o. Origin- 
 ally described from Val Milar, but really (Kuschel) from Val Giuf, Switzerland (giufite). 
 
 MIMETITE, p. 366. According to Bertrand and Jannettaz, crystals of pure lead arsenate 
 are biaxial ; as the amount of lead phosphate increases the angle diminishes and pure lead 
 phosphate (pyromorphite) is uniaxial ; but this may be due to the grouping of uniaxial 
 crystals in positions not quite parallel. Occurs with vanadinite in Yuma Co., Arizona 
 (Silliman, Blake). 
 
 MIXITE, Schrauf. Incrusting, crypto crystalline. Color emerald to bluish green. H. 
 = 3-4. G. = 2*66. A hydrous arsenate of copper and bismuth. Joachimsthal. 
 
 MOLYBDENITE, p. 233. Perhaps orthorhombic (Groth). 
 
 MOLYBDOMENITE, CoBALTOMEXiTE, Bertrand (Bull. Soc. Min., v. 90). Minerals belonging 
 to the same group of selenites as chalcomenite. Molybdomenite is a lead selenite, occur- 
 ring in thin white lamellae, nearly transparent, orthorhombic, two cleavages. Cobaltome- 
 nite is a cobalt selenite in minute* rose-red crystals occurring in the midst of the selenides 
 of lead and cobalt. From Cacheuta, Argentine Republic. 
 
 MONAZITE, p. 363. From Arendal, a normal phosphate (Rammelsberg) of cerium, lan- 
 thanum and didyinium, containing no thorium nor zirconium. Pentield has proved that 
 the thorium sometimes found is due to admixed thorite. Turnerite, according to Pisani, 
 has the same composition. 
 
 Occurs in very brilliant highly modified crystals at Milholland's Mill, Alexander Co., N. 
 C. ; also at other localities in North Carolina (Hidden). In large masses with microlite at 
 the mica mines of Amelia Co., Va. ; also at Portland (near Middletown) Conn. 
 
 MOXETITE, C. U. Shepard and C. U. Shepard, Jr. In irregular aggregates of small tri- 
 clinic crystals. H. 3'5. G. = 2*75. Lustre vitreous. Color pale yellowish white. Semi- 
 transparent. Composition HCaP0 4 , requiring P 2 5 52' 20, CaO 41 '18, H 2 6'62 = 100. 
 Occurs with gypsum and monite at the guano islands, Moneta and Mona, in the West 
 Indies. 
 
 MONITE occurs as a slightly coherent, uncrystalline, snow-white mineral. G. 21. 
 Composition perhaps Ca 3 P 2 8 + H 2 0. 
 
 MORDENITE. Steeleite of How is an altered mordenite from Cape Split, N. S. Mor- 
 denite (How) has the composition Si0 2 68 '40, A1 2 3 12 '77, CaO 3 '46, Na 2 2'35, H 2 
 13-02 = 100. 
 
 NAGYAGITE, p. 249. Perhaps orthorhombic (Schrauf). 
 NATROLITE, p. 342. Monoclinic, according to Ludecke. 
 
 NEOCYANITE, Scacchi. In minute tabular crystals of a blue color. Supposed to be an 
 anhydrous copper silicate. Mt. Vesuvius. 
 
 NEPHRITE, p. 297. The general subject of nephrite and jadeite in their mineralogical 
 and archaeological relations has been exhaustively discussed by Fischer in a special work 
 on that subject. 
 
 NEWBERYITE, vom Rath. In rather large tabular orthorhombic crystals. Composition 
 Mg 2 H a P 2 Os + 6 aq. From the guano of the Skipton Caves, Victoria, 
 
DESCRIPTIVE MINERALOGY. 433 
 
 NITROBARITE. Crystals of native barium nitrate have been obtained from Chili; in 
 apparent octahedrons formed of the two tetrahedrons. 
 
 NOCERINE, Scacchi. In white acicular crystals, perhaps rhombohedral ; regarded as a 
 double fluoride of calcium and magnesium. From the volcanic bombs of Nocera. 
 
 OCTAHEDRITE (Anatase), p. 277. Belongs to the monoclinic system, according to Mal- 
 lard's view (see p. 186). 
 Found in nearly colorless transparent crystals at Brindletown, Burke Co., N. C. (Hidden). 
 
 ONOFRITE. A massive mineral (G. = 7 62 \ from Marysvale, Utah, has the composition 
 Hg(S,Se), with S : Se = 6 : 1. It thus corresponds nearly with Haidinger's onofrite, which 
 has S : Se = 4 : 1. 
 
 ORPIMENT (p. 231) and realgar (p. 231) occur in Iron Co., Utah (Blake). 
 
 ORTHOCLASE, p. 325. Klockmann (Z. Kryst., vi., 493) has described twins of orthoclase 
 from the Scholzenberg, near Warmbrunn, in Silesia, the twinning planes in different cases 
 were i-i, 0, 2-i, 24, /, *'-3. 
 
 ORTHITE, p. 308. Found in imperfect bladed crystals at the mica mines in Amelia Co., 
 Virginia, with inonazite, columbite, etc. 
 
 OTTRELITE, p. 358. A variety of ottrelite from Venasque, in the Pyrenees, has been 
 called venasquite (Damour). 
 
 OXAMMITE. Ammonium oxalate (Shepard) from the Guanape Islands. Also called guana- 
 pile by Raimondi. 
 
 OZOCEEITE. A related mineral wax has been found in large quantities in Utah. 
 PACHNOLITE, p. 265. See thomsenolite, p. 438. 
 
 PECKHAMITE, J. L. Smith. From the Estherville, Emmet Co., Iowa, meteorite. In 
 rounded nodules, with greasy lustre, and light greenish-yellow color. G. = 3 '23. Compo- 
 sition equivalent to two molecules of enstatite and one of chrysolite. 
 
 PECTOLITE, p. 327. Walkerite (Heddle) is a closely related mineral from the Corstor- 
 phine Hill, near Edinburgh, Scotland. 
 
 PELAGITE, Church. A name given to the composite manganese nodules obtained by the 
 " Challenger" from the bottom of the Pacific. 
 
 PENWITHITE, Collins. Described as a hydrated silicate of manganese (MnSi0 8 + 2 aq) 
 from Penwith, Cornwall. 
 
 PEROFSKITE, p. 270. Recent observations refer it to the orthorhombic system, the crys- 
 tals being complex twins. Ben-Saude, however, regards it as isometric and parallel 
 hemihedral, the observed double refraction being due to secondary causes, see p. 190. 
 
 PETALITE, p. 295. Hydrocastorite is an alteration product of castorite from Elba (Grat- 
 fcarola). 
 
 PHARMACOSIDEBITE, p. 376. Pseudo-isometric, according to Bertrand, see p. 186. 
 
 PHENACITE, p. 301. Obtained well crystallized from Switzerland, perhaps from Val 
 Giuf. Also (Cross and Hillebrand) from near Pike's Peak, El Paso Co., Colorado. 
 
 PHILLIPSITE, p. 345. Crystalline system monoclinic (Streng), with a higher degree of 
 pseudo-symmetry due to twinning. 
 28 
 
434 DESCRIPTIVE MINERALOGY. 
 
 PHOSPHURANYLITE, G-enth. As a pulverulent incrustation, of deep lemon-yellow color 
 Composition probably (UO 2 ) 3 P 2 O 8 + 6 an. Occurs with other uranium minerals at thi 
 Flat Rock mine, Mitchell Co., N. C. 
 
 PICITE, Nies. An amorphous, dark brown hydrous iron phosphate from the Eleonon 
 mine and the Rothlaufchen mine, near Giessen'. Of doubtful homogeneity. 
 
 PICKERINGITE, p. 395. Sonomaite (Goldsmith), from the Geysers, California, andpicroal 
 lumogene (Roster), from Elba, are closely related minerals. 
 
 PILOLITE, Heddie. A name suggested for some minerals from Scottish localities of nearl; 
 related composition, which have gone by the names "mountain leather" and ''mountaii 
 cork." 
 
 PLAGIOCITRITE, Sandberger, Singer. A hydrous sulphate of alumina, iron, potassium 
 sodium, etc., occurring in lemon-yellow microscopic crystals, and formed from the decom 
 position of pyrite at the Bauersberg, near Bischofsheim vor der Rhon. 
 
 PLATINUM, p. 223. A nugget weighing 104 grams, and consisting of 46 p.c. platinun 
 and 54 p.c. chromite, was found near Plattsburgh, N. Y. (Collier). 
 
 PLUMBOMANGANITE, Hannay. Described as a sulphide of manganese and lead, but doubt 
 less a mixture. Source unknown. 
 
 PLUMBOSTANNITE, Raimondi. An impure massive mineral, described as a sulph-antimo 
 nite of tin, lead and iron, but of doubtful homogeneity. From the district of Moho, Peru 
 
 POLYDYMITE, Laspeyres. Isometric, octahedral. H. = 4-5. G-. = 4'808-4'816. Com 
 position Ni 4 S 5 . From Grlinau, Westphalia. Laspeyres regards the saynite of von Kobell 
 grunauite of Nicol, as an impure polydymite. 
 
 POLYHALITE, p. 393. Krugite (Precht) is a related mineral from New Stassfurt. Com 
 position, if homogeneous, K 2 S0 4 + MgS0 4 + 4CaSO 4 + 2 aq. 
 
 PRICETTE, p. 382. Pandermite (yom Rath) is a borate from Panderma on the Black Sea 
 near priceite, if not identical with it. 
 
 PSEUDOBKOOKITE, Koch. In thin tabular striated crystals, orthorhombic. H. = 6, 
 G. = 4 -98. Lustre adamantine, on crystalline faces. Color dark brown to black. Con 
 tains principally the oxides of iron and titanium. From the andesite of the Aranyer Berg 
 Transylvania, and Riveau Grand, Monte Dore, also with the asparagus stone of Jumilla 
 Spain '(Lewis). Near brookite. 
 
 PSEUDONATROLITE, Grattarola. In minute acicular crystals. Colorless. A hydroui 
 silicate (62 '6 p.c. Si0 2 ) of aluminum and calcium. From San Piero, Elba. 
 
 PSILOMELANE, p. 282. Calvonigrite (Laspeyres) from Kalteborn is a variety. 
 PYRITE, p. 243. Occurs in highly modified crystals in Gil pin Co., Colorado. 
 PYROLUSITE, p. 278. According to Groth, the prismatic angle is 99 30'. 
 
 PYROPHOSPHORITE, C. U. Shepard, Jr. A massive, earthy, snow-white mineral from th< 
 West Indies. Described as a pyrophosphate of calcium and magnesium. 
 
 PYRRHOTITE, p. 241. Perhaps only pseudo-hexagonal, the apparent form due to twin 
 ning. 
 
 QUARTZ, p. 284. The smoky quartz of Branchville, Conn. , contains very large quanti 
 ties of liquid C0 a (Hawes), also N,H 2 S,S0 2 ,H 8 N,F (A. W. Wright). 
 
DESCRIPTITE MINERALOGY. 435 
 
 RALSTONITE, p. 265. Composition (Brandl) 3(Na 2 ,Mg,Ca)F 2 + 8A1 2 F 6 + 6H 2 0. 
 
 RANDITE, Konig. A canary yellow incrustation on granite at Frankford, near Phila- 
 delphia. Contains calcium and uranium, but composition doubtful. 
 
 REDDINGITE, G. J. Brush and E. S. Dana. Orthorhombic ; habit octahedral ; form near 
 that of scorodite. H. = 3-3'5. G. =3'lO. Lustre vitreous to sub-resinous. Color pale 
 rose pink to yellowish white. Composition Mn 3 P 2 Op + 3 aq, with a varying amount of iron 
 ;5-8 p.c.FeO). With other manganesian phosphates at Branchville, Conn. 
 
 REINITE, K. v. Fritsch, Liidecke. A tetragonal iron tungstate (FeW0 4 ) near scheelite in 
 form, and perhaps a pseudomorph. From Kimbosan, Japan. 
 
 RESIN. The following are names recently given to various hydrocarbon compounds : 
 ajkite, bernardinite, celestialite, duxite, gedanite, hofmannite, huminite, ionite, koflachite, 
 muckite, neudorflte, phytocollite, posepnyte. 
 
 RHABDOPHANE, Lettsom. A cerium phosphate, perhaps the same as phosphocerite. 
 
 RHODOCHROSITE, p. 403. A Hungarian variety, containing 39 p.c. FeC0 3 , has been called 
 maMganosiderit? (Bayer). 
 Occurs at Branchville, Conn., containing 16*76 p.c. FeO (Penficld). 
 
 RHODIZITE. According to Damour, rhodizite of Rose, from the Ural, is an alkaline boro- 
 aluminate. Pseudo-isometric according to Bertrand. 
 
 ROGERSITE, J. L. Smith. A thin mammillary crust, of a white color, on samarskite. A 
 hydrous columbate of yttrium, etc., exact composition undetermined. Mitchell Co., N. C. 
 
 ROSCOELITE, p. 367. A silicate, according to recent analyses by Genth, having the for- 
 mula K(Mg,Fej(Al 2 ,V 2 ) 2 Si 12 32 + 4 aq ; also (Hanks) from Big Red Ravine, near Sutter's 
 Mill, Gal. 
 
 ROSELITE, p. 872. True composition R 3 As 2 8 + 2 aq (Winkler), hence analogous to fair- 
 fieldite, p. 426. 
 
 RUBISLITE, Heddle. An uncertain chloritic substance from the granite of Rubislaw, near 
 Aberdeen, Scotland. 
 
 RUTILE, p. 276. Pseudo-tetragonal according to the view of Mallard (see p. 186). 
 Occurs in splendent crystals in Alexander Co., N. C (Hidden). 
 
 SAMARSKITE, p. 361. The North Carolina mineral has been shown to contain erbium, ter- 
 bium, phillipium, decipium (Delafontaine, Marignac). A supposed new element, mosan- 
 drum. was also announced by Smith. Vietinghofite is a ferruginous variety from Lake 
 Baikal, in the Ural. 
 
 SARAWAKITE, Frenzel. Occurs in minute crystals in the native antimony of Borneo; 
 perhaps senarmontite. 
 
 SCAPOLITE, p. 317. The scapolites have been shown by Adams to contain chlorine (up to 
 2'48 p. c.) when quite unaltered. The analyses of Neminar, Sipocz, and Becke prove the 
 same. 
 
 Ontariolite (Shepard) is a variety occurring in limestone at Galway, Ontario, Canada. 
 
 SOHNEEBERGITE, Brezina. In isometric octahedrons of a honey-yellow color from Schnee- 
 berg, Tyrol. Contains lime and antimony, but exact composition unknown. 
 
 SCHORLOMITE, p. 337. Theso-called schorlomite of the Kaiserstuhl is, according to Knop, 
 either a titaniferous melanite or pyroxene. 
 
436 DESCRIPTIVE MINERALOGY. 
 
 SEMSEYITE, Krenner. Stated to be related to plagionite ; from Felsobanya. Not yet 
 described. 
 
 SENARMONTITE, p. 284. Pseudo-isometric according to Mallard (p. 186). Grosse-Bohle, 
 who has investigated the subject, suggests the same for arsenolite. 
 
 SEPIOLITE, p. 349. Chester has analyzed a fibrous variety from Utah. 
 
 SERPENTINE, p. 350. Schrauf (Z. Kryst., vi., 321) has studied the magnesia silicates from 
 the serpentine region near Budweis, Southern Bohemia. He introduces the following new 
 names : Kelyphite, a serpentinous coating of altered crystals of pyrope ; Enophite. a chloritic 
 variety of serpentine ; Lernilite (wrong orthography for lennilite) in composition near the 
 vermiculite of Lenni (Cooke), hence name ; Siliciophite, a heterogeneous substance high in 
 silica ; Hydrobiotite (same name used by Lewis) a hydrated biotite ; Berlauite, a chloritic 
 substance filling cavities between the granite and serpentine ; Schuchardtite, the so-called 
 chrysopraserde from Glasendorf, Silesia. He also uses the general name parachlorite for 
 substances conforming to wA! 2 Si 3 Oi 2 -f nR 2 Si0 4 + p&q, and protochlorite for those corre- 
 sponding to wAUSiOs 4- n(R 2 Si0 4 ) + paq. 
 
 Totaigite (Heddle) is an uncertain serpentinous mineral, derived from the decomposition 
 of malacolite. From Totaig, Rosshire, Scotland. 
 
 SERPIERTTE, Des Cloizeaux. In minute tabular crystals ; orthorhombic. Color greenish. 
 Stated to be a basic sulphate of copper (Damour). From Laurium, Greece. 
 
 STDERAZOT, Silvestrl Iron nitride, a coating on lava at Etna. 
 
 SIDERONATRITE, Raimondi. Sideronatrite, from Huantajaya, Peru, and urusite (Frenzel) 
 from the island Tschleken, Caspian Sea, are hydrous sulphates of iron and sodium, near 
 each other and related to the doubtful bartholomite. 
 
 SIPYLITE, Mallet. Tetragonal, in octahedrons. Form near that of fergusonite. Cleav- 
 age octahedral ; usually massive, crystalline. H = 6. G. = 4'89. Color brownish black tc 
 brownish orange. Essentially a columbate of erbium, cerium, lanthanum, didymiunx 
 uranium, etc. With allanite on the Little Friar Mt., Amherst Co., Va. 
 
 SMALTITE, p. 245. Occurs near Gothic, Gunnison County, Colorado. 
 
 SPH^EROCOBALTITE, Weisbach. In small spherical masses, concentric, radiated. Coloi 
 within rose-red. H. =4. G. = 4 '02-4 13. Composition CoC0 3 . With roselite al 
 Schneeberg, Saxony. 
 
 SPODIOSITE, Tiberg. In flattened prismatic crystals. A calcium phosphate, and per 
 haps pseudomorphous. From the Krangrufra, Wermland, Sweden. 
 
 SPHALERITE, p. 237. The sphalerite from the Pierrefitte mine, Vallee Argeles, Pyrenees, 
 contains gallium (L. de Boisbaudran), and various American (Cornwall) and Norwegiar 
 (Wleugel) varieties afford indium. 
 
 SPODUMENE, p. 295. The true composition is expressed by the formula Li 2 Al 2 Si 4 Oi 2 , as 
 proved by numerous recent analyses. 
 
 Occurs in small prismatic crystals of a deep emerald green to yellowish green color, witl 
 beryl (emerald), rutile, monazite, etc., in Alexander Co., N. C. This variety, which ha; 
 been extensively introduced as a gem, was called hiddenite by J. L. Smith, after W. E 
 Hidden. 
 
 The alteration products of the spodumene of Chesterfield and Gosh en, Mass., have beer 
 described by A. A. Julien. 
 
 Occurs in immense crystals at Branchville, Conn. (Brush and Dana). The unaltered min 
 eral is of an amethystine purple color and perfectly transparent, but the crystals are mostl] 
 altered. This alteration nas yielded (1) a substance called y^-spodumene, apparently homo 
 geneous, but in fact an intimate mixture of albite and eucryptite (q. v. , p. 420) ; also cymatolite 
 a mixture of albite and muscovite ; also albite alone ; muscovite ; microcline, and killinite 
 
DESCRIPTIVE MINERALOGY. 437 
 
 STAUROLITE, p. 336. Xantholite (Heddle) from near Milltown, Loch Ness, Scotland, is a 
 jlosely related mineral. 
 
 STERNBERGITE, p. 240. Argentopyrile, Argyropyrite and Frieseite are varieties, or at 
 .east closely related minerals. They are essentially identical in form, while Streng shows 
 ;hat the composition of the series may be expressed by the general formula Ag 2 S + 
 
 STIBIANITE, Goldsmith. A doubtful decomposition product of stibnite, near stibiconite. 
 Prom Victoria. 
 
 STIBICONITE. Extensive deposits of an antimony oxide, near stibiconite, occur at Sonora, 
 Mexico. The ore carries silver chloride. 
 
 STIBNITE, p. 232. Occurs with other antimony minerals in Sevier Co., Arkansas. In 
 groups of large splendent crystals on an island in western Japan. 
 
 STILBITE, p. 346. Monoclinic, and isomorphous with harmotome and phillipsite 
 (v. Lasaulx). 
 
 STRENGITE, Nies. Orthorhombic, and isomorphous with scorodite. Generally in spherical 
 md botryoidal aggregates. H. = 3-4. G. = 2 '87. Lustre vitreous. Color various 
 shades of red to colorless. Composition Fe^PsOs + 4 aq. From the Eleonore mine near 
 Seissen, the Rothliiufchen mine near Waldgirmes ; also in cavities in the dufrenite from 
 Rockbridge Co., Va. (Konig). 
 
 STRONTIANITE, p. 406. Occurs at Hamm, Westphalia, sometimes in highly modified 
 pseudo-hexagonal crystals, resembling common forms of aragonite (Laspeyres). 
 
 STUTZITE, Schrauf. A silver telluride, occurring in pseudo-hexagonal crystals of a lead 
 sp-ay color. Named from a single specimen probably from Napyag. 
 
 SZABOITE, Koch. In minute triclinic crystals, near rhodonite in form. H. = 6-7. G. 
 = 3-505. Lustre vitreous ; sometimes tending to metallic and pearly. Color hair brown ; 
 in very thin translucent crystals brownish red. A silicate of calcium and iron (RSi0 2 ) re- 
 lated to babingtonite. Occurs with pseudobrookite in the andesite of the Aranyer Berg, 
 Transylvania; Mt. Calvario, Etna ; Riveau Grand, Monte Dore. 
 
 SZMIKITE, v. Schrockinger. Amorphous, stalactitic. Color whitish to reddish. Com- 
 position MnS0 4 + H 2 0. Felsobanya, Transylvania. 
 
 TALKTRIPLITE (Igelstrom). A phosphate of iron, manganese, magnesium and calcium ; 
 probably a triplite remarkable as containing MgO (17*42 p.c.) and CaO (14-91). From 
 Horrsjoberg in Wermland, Sweden. 
 
 TANTALITE, p. 359. Occurs in North Carolina; in CoosaCo., Ala. 
 
 MangantantoMte (Nordenskiold) is a manganesian variety (9 p c. MnO) from Uto, Sweden. 
 
 TARAPACAITE, Raimondi. A supposed potassium chromate, occurring in bright yellow 
 fragments in the midst of the soda nitre from Tarapaca, Peru. 
 
 TAZNITE, Domeyko. Regarded as an arsenio-antimonate of bismuth, but probably a 
 heterogeneous substance. 
 
 TELLURITE. The tellurium oxide (Te0 2 ) occurs in minute prismatic, yellow to white 
 crystals, imbedded in native tellurium ; also incrusting. Keystone, Smuggler and John 
 Jay mines in Colorado. 
 
 TELLURIUM, p. 227. An impure variety from the Mountain Lion mine, Colorado, has 
 been called LIGNITE. 
 
438 DESCRIPTIVE MINEKALOGY. 
 
 TENNANTITE, p. 256. Fredricite (H. Sjogren) is a variety from Falu, Sweden, con- 
 taining lead (o p.c.), tin (1'4 p.c.) and silver (-3*9 p.c.). 
 
 TENORITE, p. 267. Made triclinic, on optical grounds, by Kalkowsky. 
 
 TEQUESQUITE. A corruption of tequixquitl, a name used in Mexico to designate a mix- 
 ture of different salts. 
 
 TETRAHEDRITE, p. 255. Occurs near Central City, Gilpin Co., Colorado, in crystals 
 coating chalcopyrite in parallel position. Also at Newburyport, Mass.; in Arizona (16*23 
 p.c. Pb). 
 
 Frigidite (D'Achiardi) is a variety with 12*7 p.c. Fe, etc., from the Valle del Frigido, 
 Apuan Alps. 
 
 THAUMASITE, Nordenskiold. Massive, compact. H. 3*5. G. = 1*877. Color white. 
 Lustre greasy, dull. Composition deduced CaSi0 3 + CaC0 3 + CaS0 4 + 14 aq, but it is 
 very doubtful whether the material analyzed was homogeneous. 
 
 THENAEDITE, p. C90. Occurs in large deposits on the Rio Verde, Arizona (Silliman). 
 
 THOMSENOLITE, p. 265. According to Klein and, later, Brandl and Groth, thomsenolite 
 and pachnolite are distinct minerals. Thomsenolite is monoclinic, ft = 89 37', and c 
 (vert.) : b : a = 1'0877 : 1 : 9959, and has the composition (Na + Ca)F 3 + A1 2 F 6 + H 2 0. 
 PaeJinolite is monoclinic,^ = 89 40', c (vert.) : b : a = 1-5320: 1 : 1 626, and has the compo- 
 sition (Na + Ca)F 3 + A1 2 F 6 . Pachnolite is a cryolite with two sodium atoms replaced by 
 one calcium atom, and thomsenolite is the same, with also one molecule of water. 
 
 THOMSONITE, p. 342. Occurs in amygdules in the diabase of Grand Marais, Lake Supe- 
 rior ; also in polished pebbles on the lake shore. The pebbles are sometimes opaque white, 
 like porcelain ; sometimes green in color and granular (variety called lintonite) ; some- 
 times with fibrous radiated structure, of various colors, and of great beauty. The last are 
 valued as ornaments. 
 
 THIXOLITE. Calcium carbonate, forming large tufa-like deposits in Nevada, a shore 
 formation of the former Lake Lahontan. Regarded by King as pseudomorph after gay- 
 lussite, but this is doubtful. 
 
 THORITE, p. 340. A variety of thorite is called uranothorite by Collier ; it contains 
 9-96 U Z 3 . Massive. G. = 4'126. Color dark red-brown. From the Champlain iron 
 region, N. Y. 
 
 TITANITE, p. 335. Occurs, often in enormous crystals or groups of crystals, at Renfrew, 
 Canada, with zircon (twins), apatite andamphibole. 
 
 Alshedite (Blomstrand) is a variety from Smaland, Sweden, containing 2 '8 p.c. YO. 
 
 Titanomorphite is a name given by v. Lasaulx to a part of the white granular aggregates 
 surrounding rutile and menaccanite/and derived from their alteration. It is a calcium tita- 
 nate, according to Bettendorff's analysis, but Cathrein (Z. Kryst.. vi., 244) shows that it is 
 really a variety of titanite. Leucoxene is a name earlier (1374) given by Giimbel for a 
 similar substance of doubtful chemical nature often observed in rocks ; according to 
 Cathrein it is a titanite with or without a mixture of rutile microlites. 
 
 TOPAZ, p. 332. Pseudo-orthorhombic (monoclinic), according to the view of Mallard 
 (see p. 186). 
 Occurs near Pike's Peak, El Paso Co., Colorado, and at Stoneham, Maine. 
 
 TORBANITE, p. 4l8.WoUongongite (p. 416) is referred to torbanite by Liversidge ; it is 
 from Hartley, New South Wales, not Wollongong, so that the name is inappropriate. 
 
 TOURMALINE, p. 329. Pseudo-rhombohedral. according to the view of Mallard (see 
 p. 186). 
 Occurs in white, nearly colorless crystals, at De Kalb, St. Lawrence Co. , N. Y. 
 
DESCRIPTIVE MINERALOGY. 439 
 
 TRIDYMITE. p. 288. Pseudo-hexagonal (triclinic), according to Schuster and also v. 
 Lasaulx. Asmanite is probably identical with it. 
 
 Hautefeuille has made it artificially ; and it has been observed with zinc spinel as a result 
 of the alteration of zinc muffles. 
 
 TRIPHYLITE, p. 369. The composition (Penfield) is LiFePO 4 = Li 3 P0 4 + Fe 3 P 2 8 , with 
 the iron replaced by manganese in part. 
 
 Lithiophilite (Brush and Dana) is a variety almost free from iron (down to 4 p.c.), and 
 corresponding to the formula LiMnP0 4 = Li 3 P0 4 + Mn 3 P 2 8 . Massive, cleavable (0, /, 
 i-V). Color salmon, honey yellow, yellowish brown, light clove brown. Occurs with other 
 manganesian phosphates in pegmatite, at Branch ville, Fairlield Co., Conn. 
 
 TRIPLOIDITE (G. J. Brush and E. S. Dana). Monoclinic, near wagnerite in form. Gen- 
 erally in fibrous crystalline aggregates H. =4-5-5. G. = 8 697. Lustre vitreous to 
 greasy adamantine. Color yellowish to reddish brown, topaz yellow, hyacinth red. Trans- 
 parent. Composition R 3 P 2 8 -+- R(OH) 2 . with R = Mn : Fe =3: 1; hence analogous to 
 triplite, but with (OH) replacing F. With other manganesian phosphates (eosphorite, 
 lithiophilite, etc.) from Branch ville, Conn. 
 
 TRIPPKEITE, Damour and vom Rath. In small brilliant crystals, tetragonal. Color 
 bluish green. Stated to be a hydrous arsenito of copper. \Vith olivenite in cuprite from 
 Copiapo, Chili. 
 
 TYSONITE, Allen and Comstock. Hexagonal. Cleavage basal. H. =4'5-5. G. = 6'13. 
 Lustre vitreous to resinous. Color pale wax yellow. Composition (Ce,La,Di) 2 F 6 . From 
 near Pike's Peak, Colorado. The crystals are mostly altered to baslnasite (also called 
 hamartite), which is a fluo-carbonate, near parisite. 
 
 URANINITE, p 274. Occurs in brilliant black octahedral crystals at Branchville, Conn. 
 G = 9-25. Analysis: U0 3 40'08, UO 2 5451, PbO 427, FeO 0'49, H 2 -88 = 100-23. 
 AJso from Mitchell Co., N. C. ; mostly altered to gummite. 
 
 UKANOCIRCITE, Weisbach. Orthorhombic, like autunite. Cleavage basal perfect. G. = 
 3-53. C'olor yellow green. Composition BaU 2 P 2 J2 + 8 aq. In quartz veins, Saxon 
 Voightland. 
 
 URANOTHALLITE, Schrauf (Z. Kryst., vi., 410). A uranium carbonate from Joachims- 
 thai, originally mentioned by Vogl. Occurs in confused aggregates of orthorhombic crys- 
 tals. Calculated formula UC 2 6 + 2CaC0 3 + 10 aq. 
 
 URANOTILE, p. 341. Occurs in Mitchell Co., N. C. Genth writes the formula, 
 Ca 3 (U0 2 ) 6 Si 21 + 18 aq. 
 
 VANADINITE, p. 367. Occurs in highly modified crystals in the State of Cordoba, Argen- 
 tine Republic. Also in very beautiful ruby-red crystals at the Hamburg and other mines 
 in Yuma Co., Arizona (Silliman; Blake), and in yellow to nearly white crystals at other 
 localities in Arizona. 
 
 VARISCITE. The so-called pcganite from Montgomery Co., Ark., is shown by Chester to 
 be identical with Breithaupt's variscite. Composition A1 2 P 2 8 + 4 aq. 
 
 VENERITE, Hunt. An impure chloritic mineral containing copper ; mined as copper ore 
 at Jones' mine, near Springfield, Berks Co., Penn. 
 
 VERMICTTLITE, p. 355. Protovermiculite (KGnig) and pMladelphite (Lewis) are minerals 
 related to the other " vermiculites," the whole group being decomposition products of other 
 micas. 
 
 VESBINE, Scacchi. Forms thin yellow crusts on lava of 1631, Vesuvius ; supposed to 
 contain a new element, vesbium. 
 
440 DESCRIPTIVE MINERALOGY. 
 
 VESUVIANITE, p. 405. Pseudo-tetragonal, according to the view of Mallard (see p. 186). 
 A variety from Jordansmuhl contains 3 p.c. MnO (manganidocrase). 
 
 VESZELYITE, p. 373. Composition, according to Schrauf, 2(Zn,Cu) 3 As208+9(Zn,Cu)H 2 02 
 + 9 aq, with Cu : Zu = 3 : 2, and As : P = 1 : 1. 
 
 WAD, p. 283. Lepidophceite (Weisbach) is a related mineral from Kamsdorf, Thuringia. 
 Composition stated to be CuMn 6 Oi 2 + 9 aq. 
 
 WAGNERITE, p. 368. Kjerulfine has been shown to be identical with wagnerite in 
 form and composition ; often partially altered. 
 
 WALPURGITE, p. 379. Triclinic (pseudo-monoclinic), according to Weisbach. 
 
 WATTEVILLITE, Singer. In minute acicular snow-white crystals. A hydrous sulphate 
 of calcium, sodium, potassium, etc Formed from the decomposition of pyrite at the 
 Bauersberg, near Bischofsheim vor der Rhon. 
 
 WULFENITE, p. 384. Occurs in fine crystals in the Eureka district, Nevada ; also in 
 Yuma Co., Arizona, sometimes in simple octahedral crystals (Silliman). 
 
 XANTHOPHYLLITE, p. 358. Waluewite (v. Kokscharof) is a well crystallized variety from 
 Achmatovsk, Ural. 
 
 XENOTIME, p. 364. Occurs compounded with zircon in Burke Co., N. C. (Hidden). 
 
 YOUNGITE, Hannay. Described as a sulphide of lead, zinc, iron and manganese, but 
 doubtless a mixture. 
 
 ZINCALUMINITE, Bertrand and Damour. In thin hexagonal plates, minute. H. =2 '5-3. 
 G. =i 2-26. Composition 2ZnS0 4 + 4ZnH 2 2 + 3A1 2 H 6 6 + 5 aq. From the zinc mines of 
 Laurium, Greece. 
 
 ZIRCON, p. 304. Occurs in fine twin crystals (1-t, like rutile and cassiterite) with titanite 
 and apatite, in Renfrew Co., Canada (Hidden). Also with astrophyllite and arfvedsonite in 
 El Paso Co., Colorado. 
 
 Pseudo-tetragonal, according to the view of Mallard (see p. 186). 
 
 Beccarite (Grattarola) is a variety from Ceylon. 
 
APPENDIX A. 
 
 SYNOPSIS OF MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 
 
 THE following pages contain a concise presentation of the System of Crystallography pro- 
 posed by Prof. W. H. Miller in 1839, and now employed by a large proportion of the workers 
 in Mineralogy. The attempt has been made to present the subject briefly, and yet with suffi- 
 cient fulness to enable any one having some previous knowledge of Crystallography not only 
 to understand the System, but also to use it himself. For the full development of the subject, 
 especially of its theoretical side, reference must be made to the works of Miller, Grailich, 
 von Lang, Schrauf and Bauerman (see the Introduction), as also to the admirable Lectures 
 of Prof. Maskelyne, printed in the Chemical News for 1873 (vol. xxxi., 3, 13, 24,63, lUl, 
 111, 121, 153, 200, 232). 
 
 GENERAL PRINCIPLES. 
 
 The indices of Milkr and their relation to those of Naumann.The position of a plane ABC 
 (. 751) is determined when the distances OA, OB, OC are known, which it cuts off in the 
 
 assumed axes X, Y, Z from their point of intersection O. The lengths of these axes for a 
 ningle plane of a crystal being taken as units, thus OA a, OB = b, OC c, it is found that the 
 lengths of the corresponding lines OH, OK, OL for any other plane, IDCL, of the same crys- 
 
442 
 
 APPENDIX. 
 
 tal always bear some simple relation, expressed in whole numbers, to these assumed units 
 This relation may be expressed as follows : 
 
 OH 
 or in the more common form 
 
 _L JL 
 
 h ' OH 
 
 *- 
 
 k OK 
 
 (1) 
 
 The numbers represented by 7*, &, I are called the indices of the plane and determine its 
 position, when the elements of the crystal the lengths and mutual inclinations of the axes 
 are known. When the lines are taken in the opposite direction from O, they are called nega- 
 tive ; the corresponding negative character of the indices is indicated by the minus sign 
 placed over the index, thus, #, &, or /. When the unit, or fundamental form, is appropriately 
 chosen, the numbers representing 7i, &, I seldom exceed six. 
 
 The above relation may also be written in the form : 
 
 OH 
 a 
 
 OK 
 b 
 
 PL 
 
 c 
 
 Here ?', n, m, which are obviously the reciprocals of the indices A, k, I respectively, are 
 itially identical with the symbols of Naumann. For example, if h = 3, k = 2, / 2, 
 then r = , n , m = i, and the symbol (322) of Miller becomes i : $b : & but by Nau- 
 mann' s usage this is so transformed that r = 1, and n > 1 (or sometimes n = 1, and />!), 
 in other words, by multiplying through by 3, in this case, the symbol takes the form a : %b : 
 fc,* or, as abbreviated, $-$ (fPf). The symbol a : $ b : \c properly belongs to the plane MNR 
 (f. 751), which is parallel to, and hence crystallographically identical (p. 11) with the plane 
 HKL. 
 
 Special values of the indices h, k, I. It is obvious that several distinct cases are possible : 
 (1) The three indices ^, &, I are all greater than unity, then including the various pyramidal 
 
 planes. The number of similar planes corresponding to the general form -j hkl I depends 
 
 upon the degree of symmetry of the crystalline system, and upon the special values of h, k, I, 
 e.g., h = k, etc. These cases are considered later in their proper place. 
 
 (2) One of the three indices may be equal to zero, indicating then that the plane is parallel 
 to the axis correspond big to this index. Thus the symbol (MO), = a : nb : oo e, or na : b : oo e 
 (p. 11), belongs to the planes parallel to the vertical axis (', as shown in f. 752. They are 
 called prismatic planes. The symbol (hOl), = a : oo b : me (p. 11) belongs to the planes par- 
 allel to the axis o, as in f. 753. The symbol (Qkl), oo a : b : me, belongs to the planes parallel 
 to the axis , f . 754. 
 
 752 
 
 753 
 
 (3) Two of the indices may be zero, the symbol (hkl} then becomes (001), = CD a : y>b : 5, 
 the basal plane, f. 755 ; (010), = oo a : b : ooc; and (100), a : b : x> c. These are the 
 three diametral or pinacoid planes. 
 
 The symbol (010) represents the clinopinacoid (i-l)ot the Monoclinic system, and (following 
 Groth) the brachypinacoid (i-%) of the Orthorhombic. Similarly (MM) belongs to the orlho- 
 
 * The symbol is written here in this order to correspond with the (7i k I) of Miller ; on 
 page 10, and subsequently, the reverse order \c : %b : a was adopted for the sake of uni- 
 formity with Naumann' s abbreviated symbols. 
 
MILLER S SYSTEM OF CRYSTALLOGRAPHY. 
 
 443 
 
 domes of the Monoclimc, and the macrodomes of the Orthorhombic system ; also (0# 
 belongs to the clinodomes of the former, and the brachydomes of the latter. See also p. 457. 
 
 Spherical Projection. If the centre of a crystal, that is, the point of intersection of the 
 three axes, be taken as the centre of a 
 sphere, and normals be drawn from it to 
 the successive planes of the crystals, the 
 points, where they meet the surface of the 
 sphere, will be the polos of the respective 
 planes. For example, in f. 756 the com- 
 mon centre of the crystal and sphere is at O, 
 the normal to the plane b meets the surface 
 of the sphere at B, of b' at B', of d and e 
 at D and E respectively, and so on. These 
 poles evidently determine the position of 
 the plane in each case. 
 
 It is obvious that the pole of the plane b' 
 (010) opposite b (010), will be at the oppo- 
 site extremity of the diameter of the sphere, 
 and so in general, (120) and (120), etc. It is 
 seen also that all the poles, or normal points, 
 of planes in the same zone, that is, planes 
 whose intersection-lines are parallel, are in 
 the same great circle, for instance the 
 planes b (010), d (110), a (100), c (110), and 
 so on. 
 
 It is customary* in the use of the sphere 
 to regard it as projected upon a horizontal 
 plane, usually that normal to the prismatic 
 zone, so that, as in f. 759, the prismatic planes lie in the circumference of the circle, and the 
 other planes within it. The eye being supposed to bt- situated at the opposite extremity of 
 the diameter of the sphere normal to this plane, the great circles then appear either as arcs 
 of circles, or as straight lines, i. e. , diameters. 
 
 It will be further obvious from f. 756 that the arc BD, between the poles of b and d, mea- 
 sures an angle at the centre (BOD), which is the supplement of the actual interior angle bnd 
 between the two planes. This fact, that the arc of a great circle intercepted between the 
 poles of two planes always gives the supplement of the actual angle between the planes them- 
 selves, is most important, and does much to facilitate the ease of calculation. In consequence 
 of this, it is customary with many cry stall ographers to give for the angle between two planes, 
 not the interfacial angle, but that between their normals. 
 
 It is one of the great advantages of this method of projection that it may be employed to 
 show not only the relative positions of the planes, but also those of the optic axes, and the 
 axes of elasticity. 
 
 Relation between the indices of a plane and the angle made by it with the axes. When the 
 assumed axes are at right angles to each other they coincide 
 with the normals to the piuacoid planes (001, 010, 100). and 757 
 
 consequently meet the spherical surface at their poles. When 
 the axial angles are not 90, this is no longer true. In all 
 cases, however, the following relation holds good between 
 the cosines of the angles made by a plane with the axes : 
 
 op 
 OK 
 
 = cos PY 
 
 But from the equation (1) before given, by the introduction 
 of the values of OH, OK, OL, we obtain : 
 
 -f cos PX = -|- cos PY = 4- cos PZ. . (2) 
 
 II K I 
 
 This equation is fundamental, and many of the relations given beyond are deduced from it. 
 It will be seen that in the case of the orthometric systems the angles PX. PY, PZ are the 
 supplement-angles between any plane (hkl) and the pinacoids (001), (010), (100). 
 
 llelations between planes in the same zone. By the use of the equation (2), it may be shown 
 
 * On the construction of the spherical projection, see p. 58. 
 
444 
 
 APPENDIX. 
 
 that if two planes (hJd) and ( pgr) lie in the same zone, that the following equation must hold 
 good : 
 
 n<r cos XQ + vb cos YQ + we cos ZQ = 0. 
 
 where 
 
 u = kr 
 
 v = Ip hr, w = hq kp. 
 
 The letters u, v, w are called the symbol of the zone or great circle PR. Every plane 
 of this zone must satisfy the equation : 
 
 = 
 
 (3) 
 
 If now (uvw) be the symbol of one zone, and (efg) of another intersecting it, then the point 
 of intersection will be the pole of a plane lying in both zones, whose indices (hkl) must satisfy 
 two equations similar to (3). These indices are equal to : 
 
 h = gv f w 
 
 k = ew gu 
 
 = f u - ev. 
 
 The application of this principle is extremely simple, and its importance cannot be over- 
 ettimated. Some examples are added here, showing the method of use. 
 
 Example* of the meifwda of calculation by zones. (1) For the zone of planes between (100) 
 and (001), the zone indices are u = 0, v = 1, w = 0. They are obtained by multiplication 
 in the manner indicated in the following scheme : 
 
 In general 
 
 k I h k 
 
 XXX 
 
 q r p g 
 
 In this case 
 
 
 
 
 
 u = kr lq ; v = Ip hr ; w = hq 
 
 u = 0; v = l; w =0. 
 
 Consequently every plane (hkl) in the zone named must answer the condition : vJi + v/c 
 -4- wl = 0, that is, in this case k = 0. The general symbol is consequently (hQl). Compare 
 f. 759. 
 
 00100 
 
 (2) For the zone (001), (010), in a similar manner: ^ 
 
 0100 
 
 u = 1, v = 0, w = 0, and the equation of condition becomes U = 0, and the general sym- 
 bol is (QM). Compare f. 759. 
 
 (3) For the prismatic zone between (100) and (010), the general symbol will be found to be 
 
 (MO). Compare f. 759. 
 (4) For the pyramidal zone between the basal plane (001) and 
 
 00100 
 
 XXX 
 
 11011 
 
 Hence u=l, v = l,w = 0, and the equation of condition be- 
 comes h = k, and hence the general symbol is Ml for the unit pyra- 
 mids. 
 
 For a plane lying at once in two zones, for instance the plane 
 lettered 2-2 in f. 758, lying in the zone 7, 2-2, 1-f, and in the zone 
 i-l, 3-, 2-2, 1, l-l. The indices, uvw, for the first zone l-l (Oil), 
 / (110), are, obtained as above, u = 1, v = 1, w = 1. Again, for 
 the zone between i-l (010), l-l (101), the zone indices, efg, are, 
 e = I, f = 0, g = 1. The indices (hkl), for the plane (2-j lying in 
 both these zones, and hence answering to two equations of con- 
 dition, are obtained by multiplication in a scheme exactly like that 
 already given, viz. : 
 
 the unit prism (110), we have the scheme : 
 
 In general uvw 
 
 In this case 
 
 XXX 
 
 e f g e f 
 h = gv f w ; k = ew gu ; I = f u ev. 
 The plane has consequently the symbol (211). 
 
MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 
 
 445 
 
 759 
 
 For the zone of planes, lettered on the figure (f. 758) i-l y 3-3, 2-2, etc., the indices, as 
 already shown, are e 1, f = 0, g=\t 
 and consequently the equation of condi- 
 tion reduces to h=l, and the general 
 symbol is hkh. This zone is shown on 
 the spherical projection, f. 759, and in- 
 cludes the planes 010 (i-t), 131 (3-3), 121 
 (2-2), 111 (1), 101 (1-f), and so on. 
 
 A second examp e of the above method 
 is afforded by the plane lettered 2-2 in 
 f. 758. It lies in the zone i-l (100) to 1-fc 
 (Oil), whose indices, uvw, obtained as be- 
 fore, are, u = 0, v = 1, w = 1. It is also 
 in the zone between 7(110) and l-l (101), 
 whose indices, efg, are, e = 1, f = 1, g = 1. 
 Its own symbol (tiki) is deduced as above : 
 
 o 1 i o i 
 
 l 1 
 A = 2; fc = l; 1 = 1. 
 
 The symbol is consequently (211). The 
 position of this piano is shown on the 
 spherical projection, f. 750, as also that of the zone first mentioned above, whese indices 
 were u = 0, v=l, w = l, and for which the equation (3) consequently reduces to k = I ; 
 the general symbol is then (hkk\ the planes 100 (**), 211 (2-2), 111 (1), Oil (14), etc., belong 
 in this zone. 
 
 The example employed here serves to show the extensive application of this principle of 
 zones. Supposing that in this crystal, f. 758, 7(110), and 1-2 (Oil) have been assumed as 
 fundamental planes in their respective zones, the symbols of all the others may be obtained 
 in this way, without the necessity of a single measurement ; the reflecting goniometer would 
 indicate the presence of the few necessary zones not shown by the parallel intersections. 
 
 Methods of Calculation. In consequence of the wide application of this method of deter- 
 mining the symbols of a plane by the zones in which it lies, actual trigonometrical calcula- 
 tions are not very frequently required. The methods employed are always those of spherical 
 trigonometry, and in most cases no formulas are needed, the problems arising requiring 
 nothing but the solution of the triangles, mostly right-angled, seen on the spherical projection. 
 It is to be remembered that an arc of a great circle, between two poles, shown in the projec- 
 tion, is always the supplement of the actual interfacial angle between the planes themselves. 
 
 Some of the more commonly used formulas for the solution of spherical triangles, which 
 have been already given on p. 62, are, for the sake of convenience, repeated here. 
 In right-angled spherical triangles C = 90, h the hypothenuse. 
 
 Sin A = 
 
 CosA = 
 
 TanA = 
 
 sin a 
 sin h 
 tan b 
 
 tan/i 
 
 tana 
 sin b 
 
 sin B = 
 
 cos B = 
 
 tan B 
 
 cos B 
 Sin A = - 
 
 cos b 
 
 ain B = 
 
 sin b 
 sin h 
 tan a 
 tan h 
 tan b 
 sin a 
 cos A 
 cos a 
 
 cos h = cos a cos b 
 cos h = cot A cot B 
 
 n oblique-angled spherical triangles : 
 
 (1) Sin A : sin B = sin a : sin b ; 
 
 (2) Cos a cos b cos c + sin b sin c cos A 5 
 
 (3) Cot b sin c cos c cos A + sin A cot B ; 
 
 (4) Cos A = cos B cos C -f- sin B sin C <we fl. 
 
446 APPENDIX. 
 
 In calculation it is often more convenient to use, instead of the latter formulas, those 
 especially arranged for logarithms, which will be found in any of the many books devoted 
 to mathematical formulas. 
 
 In addition to the mere solution of triangles on the spherical projection, it is also necessary 
 to connect by equations the actually measured angles with the lengths and inclinations of 
 axes of the crystals themselves. These equations are given in connection with the different 
 systems. 
 
 The following relation between the planes in the same zone is also of very wide appli- 
 cation : 
 
 Let P, Q, S, R be the poles of four planes in a zone (f. 760), having the following indices, 
 viz. : P (#), Q = (pqr), R = (uvw), S (xyz). The folowing relation may 
 760 be deduced between them, on the supposition that PQ < PR. 
 
 cot PS -cot PR _ (P.Q) (S.R) 
 cot PQ - cot PR ' tQ.~R) * (P.S) ' 
 
 H r (P.Q) _ kr lq _ Ip 7tr _ Jig kp 
 
 (Q.R) ~ qw rv ~ ru pw ~ pv qu" 1 
 
 (S.R) _ icy zv _ zu xw _ xo yu 
 (P.S) ~ kz-ly ~ Ix-hz ky^kx ' 
 
 By means of the above equation it is possible to deduce the indices or angle of a fourth 
 plane, when those of the three others are given. In the application of this principle it is 
 essential that the planes should be taken in the proper order, as shown above ; to accomplish 
 this it is of ten necessary to use the indices and corresponding angles, not of (hkl), but its 
 opposite plane (hkl], etc. 
 
 In the orthometric systems this relation admits of being much simplified. 
 
 If one of the above four planes coincides with a pinacoid plane (100), (010), or (001), and 
 another with a plane in a zone with a second pinacoid 90 from the first, then the following 
 relations hold good for two planes F(AQ, and Q(pqr) in this zone : 
 
 h ten_PA = *_f 
 
 p ' tan QA ~ q ~ r ' 
 
 h_ k tan PB _ I 
 p "~ q ' tanQB ~~ P 
 
 h_k_l_ tan PC 
 p ~~ q ~ r ' tan QC' 
 
 As a further simplification of the above equation for the case of a prismatic plane (MO), 01 
 a dome (hQl) or (0-W), between two pinacoid planes 90 from another, we have : 
 
 h _ tan (100) (110) t h _ tan (001) (JtOZ) t k _ tan (001) (O&g) 
 k ~ tan (100) (hkti)' I ~ tan (001) (101) ' I ~ tan (001) (Oil)' 
 
 These equations are the ones ordinarily employed to determine the symbol of any prismatic 
 plane or dome. It will be seen at once that all the above relations for rectangular zones are 
 essentially identical with those given on p. 59, though here expressed in a clearer and more 
 concise form. 
 
 SYSTEMS OF CRYSTALLIZATION. 
 
 All crystals are divided into six classes, according to the degree of symmetry which charac- 
 terizes them. This symmetry, as well as the relations of the different planes of a crystal, is 
 shown in the lengths and position of the axes which are taken for each. With reference to 
 their axial relations crystals are divided into the following six systems : 
 
 I. Isometric System. Three equal axes (a, a, a) at right angles to one another. 
 
 II. Tetragonal System. Two equal lateral axes (a, a), and a third vertical axis (c) of on 
 equal length ; all at right angles. 
 
MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 
 
 447 
 
 III. Hexagonal System. Three equal lateral axes (, a, a) crossing- at angles of 60, and a 
 fourth vertical axis (c) of unequal length, perpendicular to the plane of the others. 
 
 IV. Ortliorlwmbin System. Three unequal axes (c, , a) at right angles to each other. 
 
 V. Monodinic System Three unequal axes (c, 6, d) ; the angle between c and 6, and 
 between b and d = 90, but the angle between c and d greater and less than 90. 
 
 VI. Tridinic System. Three unequal axes (c, , a) ; the axial angles all oblique. 
 
 I. ISOMETRIC SYSTEM. 
 
 The symbol [Ji.kl] embraces all the forms possible under each system in the most general 
 case. Since in the Isometric System all the axes are of equal value, it obviously follows 
 from the symmetry of the system that each one of the indices may be exchanged for each of 
 the others, so that the total number of planes possible will be given by all the arrangements 
 of the indices A, &, Z, or as follows: 
 
 Tiki 
 Ml 
 Tiki 
 hkl 
 hkl 
 
 hki 
 
 hkl 
 
 hlk 
 
 hik 
 
 hlk 
 hlk 
 hlk 
 
 hik 
 hik 
 hik 
 
 klil 
 khl 
 
 kill 
 khi 
 
 khl 
 
 hhl 
 
 khl 
 khl 
 
 kill 
 klh 
 klh 
 klh 
 klh 
 klh 
 klh 
 klh 
 
 Ihk 
 Ihk 
 Uik 
 Ihk 
 Ihk 
 
 ihk 
 ihh 
 ihk 
 
 Ikh 
 
 ikh 
 ikh 
 
 ikh 
 ikh 
 ikh 
 
 A. Holohedral Forms. 
 
 There are seven cases possible among the holohedral forms of this system, according to the 
 valued of h, k, I. These are shown in the list below, to which are added the symbols, aftei 
 Naumann, given on p. 14, though, as already explained, written in the inverse order. In the 
 most general case [hkl]* the form includes forty eight similar planes, and in the most 
 special case 1100J, there are included six similar planes. 
 
 MILLER. 
 
 1. [hkl]: h>k>l. 
 
 2. [hkk] 
 
 3. [hkk] 
 
 4. [Ill] 
 
 5. [MA] 
 
 6. [110] 
 
 NAUMANN. 
 
 a ma : ma 
 
 h>k. 
 
 .k = \ I = 0. 
 
 a 
 
 a : ma 
 
 a 
 
 a : a 
 
 a 
 
 na : <x>a 
 
 a 
 
 a : ooa 
 
 7. [100] ; h ^ 1, k = I = 0. 
 
 a <x>a : <x>a 
 
 [m-n], 
 
 [m-m]. 
 
 [m].' 
 
 [I]. 
 
 [*']. 
 
 
 
 The seven distinct forms corresponding to these symbols are as follows, taken in the same 
 order as on pp. 14-20, where the forms are described : 
 
 Cube (f. 761). Symbol [100], including the six planes (100), (010), (100), (010), (001), 
 (001). See also the spherical projection (f. 766). 
 
 761 762 763 704 765 
 
 [100] 
 
 [111] 
 
 [HO] 
 
 [100] [111] 
 
 [100] [110] [111] 
 
 Octahedron _(f. 762X Symbol [11 l],_including the eight planes taken in order shown in 
 f. 762, (111), (111), (111), (111), (111), (111), (lilj, (111). 
 
 *In general the indices of any individual plane are written (hkt), whereas the general 
 symbol [hkl] indicates all the planes belonging to the form, varying in number in the different 
 systems ; thus, in this system, [100] is the general symbol for the six similar planes of the 
 cube. 
 
448 
 
 APPENDIX. 
 
 iJodewhedron (f. 763). Symbol [110], including the twelve planes, (110), (110), (110) 
 (110), (101), (Oil), (101), (Oil), (101), (Oil), (101), (Oil). 
 The relations between these three forms are given in full on pp. 15, 16, and need not be 
 
 and (111), 109 28'. 
 
 766 
 
 Tetragonal trisoGtahedron (f. 767, 768). Symbol [kkk], with h>lc, comprising twenty-foui 
 similar planes. 
 
 Trigonal trisoctahedron (f. 769). Symbol [M/fc], with h >&, also embracing twenty-four like 
 planes. 
 
 [321] 
 
 [210] 
 
 [310] 
 
 [321] 
 
 Tetrakexahedron (f. 770. 771). Symbol [/i&Ol including twenty-four like planes. As seen on 
 the spherical projection (f. 766), the planes of the form [MOJ lie in a zone with the dodeca- 
 hedral planes, between two pinacoid planes. 
 
 Hexoctahedron (f. 772), [hJd] . This is the most general form in the system, including the 
 forty-eight planes enumerated on p. 447. Their position (h = 8, k = 2, I = 1) is shown on 
 the spherical projection (f. 766). 
 
 B. ffemihedral Forms* 
 
 There are two kinds of hemihedral forms observed, as shown on p. 20: (1) tbehemiholo. 
 liedral, where half the quadrants have the whole number of planes ; and (2) the holohemihedral 
 where all the quadrants have half the full number of planes. The first kind produces inclined 
 hemihedrons, indicated by the symbol K\hJd], and the second kind produces parnUd hemihe- 
 drone, indicated by the symbol K[hkt\. The resulting forms in the several oases are as follows 
 
MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 
 
 449 
 
 INCLINED HEMIHEDRISM. Tetrahedron^ (1). _ 
 (f. 773) includes the four planes (111), (111), (111), (111), 
 includes the planes (111), (111), (111), (111). 
 
 Symbol [111]. The plus tetrahedron 
 The minus tetrahedon (f . 774) 
 
 773 
 
 774 
 
 [121] 
 
 /c[321] 
 
 Hemi-fr'isoctahedrons. The symbol K[7tkk] denotes the solid shown in f. 775, and K\hM\ 
 the solid shown in f . 776. They are the hemihedral forms of the tetragonal and trigonal 
 trisoctahedrona respectively. 
 
 Hemi-hexoctahedron. The same kind of hemihedrism applied to the hexoctahedron pro- 
 duces the form shown in f. 777, having the general symbol n[hkl\. 
 
 Inclined hemihedrism as applied to the three other solids of this system produces forms 
 in no way different, in outward appearance, from the holohedral forms. 
 
 PARALLEL HEMIHEDRISM produces distinct, independent, forms only in the case of the 
 tetrahexahedron and the hexoctahedron. The symbol of the former is v [MO], and of the 
 latter, ir[hkf\ ; they are shown in f. 778-782. 
 
 778 
 
 779 
 
 780 
 
 781 
 
 7T[210] 
 
 7T[210] 
 
 7T[120] 
 
 [210] [100] 
 
 77 [321] 
 
 Tetartohedral forms of several kinds are possible in this system, but they are of small 
 practical interest. 
 
 MatJiematical Relations of the Isometric System. 
 
 (1) The distance of the pole of any plane P(hkl) from the cubic (or pinacoid) planes is given 
 by the following equations. These are derived from equation (2), p. 443. Here PX(=PA) 
 is the distance between (hkl) and (100) ; PY(=PB) is the distance between (hkl) and (010) ; 
 ar.d PZ(:=PC) that between (hkl) and (001). 
 
 The following equations admit of much simplification in special cases, for (MO), (hhk), etc. 
 
 cos 3 PA = 
 
 + I* ' 
 
 cos 2 PB = 
 
 /j2 4. 2 + 1-2 ' 
 
 cos 2 PC = 
 
 (2) The distance between the poles of any two planes (hkl) and (pqr) is given by the fol- 
 lowing equation, which in special cases may also be more or less simplified : 
 
 ty + kq+lr 
 
 cosPQ- 
 
 (3) Calculation of the values of h, k, I, for the several forms. (a) Tetragonal trisoctdh* 
 dron (f. 767). B and are the supplement angles of the edges as lettered in the figure. 
 
 cosB=: 
 
 cosC = 
 
 2hk + 
 
 29 
 
450 APPENDIX. 
 
 For the hemihedral form (f . 775), cos B = ~ 
 
 fit ~7~ &K 
 
 (b) Trigonal trisoctaJiedron. The angles A and C are, as before, the supplements of the 
 iiiterf acial angles of the edges lettered as in f . 769. 
 
 W + 2hk 27i 8 - k 3 
 
 For the hemihedral form (f. 776), cos B = L 
 
 TetrdhexaTiedron (L 770), 
 
 A* 2hk 
 
 For the hemihedral form (f. 778), cos A* = 
 
 Eexoctcihedron (f. 772). 
 
 A - 
 
 - A = 08 B = 8 c = 
 
 For the hemihedral fonn /t[A] (f. 777), cos B' = 
 
 
 n,,, m+m 
 
 For ^[A*q, cos A =. .i cos C = 
 
 For planes lying in the same zone the methods of calculation given on p. 444 and p. 440 
 are made use of. In many cases, however, the simplest method of solution of a given prob- 
 lem is by means of the spherical triangles on the projection (f. 766). 
 
 IL TETRAGONAL SYSTEM. 
 
 In the Tetragonal System, since the vertical axis c has a different length from the two 
 equal lateral axes, the index , referring to it, is never exchangeable for the other indices, h and k. 
 The general form [hkl] consequently embraces all the planes which have as their symbols 
 the different arrangements of A, k, 1, in which I always holds the Last place. We 
 thus obtain ! 
 
 jiu iiU m hki m m m km 
 m m m m m m m w 
 
 A. Hohhedral Forms. 
 
 According to the values of #, ^, and I in this general form (h = 0, k =h, etc.), different 
 cases may arise. By this means we obtain a list of all the possible distinct holohedral forma 
 in this system. They are analogous to those of the Isometric System. 
 
 MILLER. NAUMANN. 
 
 1. [hkl\\ h>k. a 
 
 2. \m\ ; h = k. a 
 
 3. [hOl] ; h or k = 0. a 
 
 4. [MO]; h>k, 1 = 0. a 
 
 5. [110]; h = k = l, 1 = 0. a 
 
 6. [100] ; k = 0, I = 0. a 
 
 7. [001] ; h = k = 0. 
 
 na : me [m-n] 
 
 a : mo [m]. 
 
 co a : mo [m-i]. 
 
 na:ccc 
 
 a : <x>c [/]. 
 ooarooc [*-]. 
 
MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 
 
 451 
 
 The forms answering to these general symbols (compare f . 790) are as follows : 
 Based planes, Symbol [001], including the planes (001) and (001). 
 Prisms. (a) Diametral prism, or_that of the second series (f. 783). Symbol [100], in 
 sluding the four planes (100), (010), (100), (010). 
 
 (b) Unit prism, or prism of the first series (f. 784). Symbol [110], embracing the foui 
 planes (110). (110), (110), (110). The relation of these two prisms is shown on p. 26. 
 
 (c) Octagonal prism (f. 785). Symbol [hkQ], including the eight planes (MO), (MO), (AO). 
 (MO), (MO), (MO), (MO), (MO). 
 
 Octahedrons or Pyramids. There are two series of octahedral planes, corresponding to the 
 two square prisms, (a) Octahedrons of the second, or diametral series. Symbol [hQl] , in- 
 cluding eight similar planes. The form [101] is shown in f. 786. 
 
 (b) Octahedrons of the first, or unit series. Symbol [MZ], embracing eight similar planes. 
 The form [111] is shown in f. 787. 
 
 784 
 
 785 
 
 T ^* 
 
 12 
 
 ^ 
 
 1/2 
 
 i i 
 
 T ; 
 
 |/2 | 
 
 ^^ 
 
 i-- 
 
 1 i 
 .. "* 
 
 [100] [001] 
 
 [110] 
 
 [210] 
 
 [101] 
 
 [111] 
 
 Octagonal Pyramids. The general symbol [hkl] embraces, as already shown, sixteen 
 like planes, whioh together form the octagonal pyramid shown in f . 788. 
 
 788 
 
 789 
 
 Meionite. 
 
 The relations of the various tetragonal forms will be understood by reference to f. 790, 
 showing the projection for the crystal represented in f. 789. 
 
 B. Hemihedral Forms. 
 
 Among the hemihedral forms there are to be distinguished three classes, 
 us shown on p. 28 et seq. .1. Sphenoidal hemihedrons, corresponding to the 
 inclined hemihedrons of the isometric system. They are indicated by the 
 symbol ^[hkl]. The sphenoid 7r[lll] is shown in f. 791. 
 
 2. Pyramidal hemihedrons, that is, those which are hemiholohedral, and 
 vertically direct. These are indicated by the symbol x\kkX\. 
 
 3. Trapezoidal hemihedrons, hemiholohedral like those just mentioned, 
 but' vertically alternate. They have the symbol " 
 
 791 
 
452 APPENDIX. 
 
 Mathematical Relations of the Tetragonal System. 
 
 (1) The distances of the pole of any plane P(hkl) from the pinacoid planes 100 (= PA), 010 
 = PB), 001 (= PC) are given by the following equations: 
 
 c08 ' PA = AV+W+W ; cos ' PB = ; 08 ' PC = 
 
 These may also be expressed in the form : 
 
 (2) For the distance between the poles of any two planes (hkl), (pqr), we have in general : 
 
 cosPQ= hpc* + kqc? + lra* 
 
 The above equations take a simpler form for special cases often occurring. 
 
 (3) Planes in the same zone. For the general case of planes (hkl) and (pqr) the re 
 lation given in equation 4 (p. 446) is made use of. In the special cases, practically of the 
 most importance, where the planes lie in a zone with a pinacoid plane, the simplified formula* 
 are employed. 
 
 For the octagonal prism this relation becomes : 
 
 tan (100) (MO) = cot (010) (7*&0) = -|. 
 
 Determination of the axis c. This follows from equation (1), p. 446, which, for this case , 
 becomes : 
 
 \ cos PA = -. cos PC, (a = 1). 
 
 fl L 
 
 For an octahedron (hW) in the diametral series, we have : 
 
 tan (Ml) (001) = y. 
 
 For the unit octahedron (111), we have : 
 
 tan (111) (001). cos 45 = c. 
 
 ILL HEXAGONAL SYSTEM. 
 
 The Hexagonal System and its hemihedral, or rhombohedral, division are both included by 
 Miller in his RHOMBOHEDRAL SYSTEM (see p. 462). All hexagonal and rhombohedral forma 
 are referred by him to three equal axes, oblique to one another, and normal to the faces of 
 the unit rhombohedron. This method has the great disadvantage of failing to exhibit the 
 hexagonal symmetry existing in the holohedral forms, since in this way the similar planes of a 
 hexagonal pyramid receive two different sets of symbols, having no apparent connection with 
 each other. It, moreover, hides the relation between this system and the tetragonal system, 
 which, optically, are identical, since they possess alike one axis of optical symmetry. 
 
 The latter difficulty was avoided by Schrauf, who introduced the ORTHOHEXAGONAL SYS- 
 TEM. In this the optical axis was made the crystallographical vertical axis, and otherwise 
 two lateral axes, at right angles to each other, were assumed, a and a V3. This method, how- 
 ever, does not overcome the other objection named above. 
 
 In the method of Weiss and Naumann a vertical axis, coinciding with the optical axis, was 
 adopted, and three lateral axes in a plane at right angles to it, they intersecting at angles of 
 60, corresponding to the planes of symmetry in the holohedral forms (see p. 462). In this 
 way only can the symmetry of the hexagonal forms be clearly brought out, and at the same 
 
MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 
 
 453 
 
 792 
 
 time the relation between the hexagonal and tetragonal systems exhibited. Recently Groth 
 (Tsch. Min. Mitth., 1874, 223, and Phys. Kryst., 1876, p. 252) has shown that the complete 
 symbols of Weiss and Naumann could be translated into a reciprocal, integral form after 
 the manner of Miller. The symbols then obtained, as was also shown, admit of a like con- 
 venient use in calculation. Essentially the same method was proposed in 1800 by Bravais, 
 and his suggestion is followed here; the more important equations, expressing the relations 
 between the poles of the planes, their indices, and the axes of the crystal are also added. 
 They are given somewhat in detail, since they are not included in any of the works on Miller's 
 System before referred to. 
 
 All hexagonal forms are referred to a vertical axis, e, and three equal lateral axes in a 
 plane at right angles to it, intersecting at angles of 60 
 and 120 (f. 792). The general symbol for a plane in this 
 system is (hkli), where it is always true that the alge- 
 braic sum of h, k, I is zero, that is, h + k + I = 0. The 
 indices here are the reciprocals of those of Naumann, 
 except that the index I has the opposite sign, and the 
 order of two of the indices is inverted. According to 
 him the general symbol of any plane is m-n (=mPri), 
 
 or, in full, - a : a : na : me. Thus the plane 3-| (3P|) 
 
 has the full symbol, 3a : a : \a : 3c, or to correspond 
 with the other symbols it must be written, '3a : \a : a : 3c. 
 The reciprocals of the latter indices are : f : 1 : , or, 
 reduced to integers (and changing the sign of I) (1231), 
 which is the symbol according to the plan here fol- 
 lowed. Similarly the plane (2243) gives, on taking the 
 reciprocals, \a : \a, : %a : $c, which is equivalent to 2a : 2a 
 : a : ^c, or in Naumann's abbreviated form f { -2 (=^P2). 
 
 It is the great advantage of this method that it makes it possible to change the almost uni- 
 versally adopted symbols of Weiss and 
 Naumann into a form which allow of all 
 the readiness of calculation and the appli- 
 cation to the spherical projection which 
 are the characteristics of Miller's System. 
 
 In calculations, both by zone equations 
 and other methods, only two of the indices 
 h, k, or I of the form (hkli) need be 
 employed, with the remaining index i (re- 
 ferring to the vertical axis). This is ob- 
 viously true, since the three indices named 
 are connected by the equation h + k + I 
 0. Disregarding, then, in calculation 
 the third index I, as shown beyond, the 
 planes are referred to two equal lateral 
 axes, intersecting at an angle of 120, 
 and a third vertical axis c. 
 
 The symbol [hkli] in its more gen- 
 eral form embraces twenty-four planes, 
 as is evident from an inspection of the 
 spherical projection, f. 793. Here h, k y I 
 are of equal value and mutually exchange- 
 able, with the condition, however, that 
 their algebraic sum shall always equal 
 zero. Of the twenty -four planes of the 
 
 dihexagonal pyramid, the following are those of the upper quadrants mentioned in order 
 from left to right around the circle (f . 793). Those below have the same symbols, except that 
 the index i in each case is minus : 
 
 on 
 
 (hkli) 
 
 (hkli) 
 
 (Wei) 
 (hlki) 
 
 (klU) 
 (klhi) 
 
 (Ikhi) 
 (Ikhi) 
 
 (Ihki) 
 
 (khli) 
 (khh) 
 
 In this general form [hkli] the following special cases are possible, each one giving rise 
 to an independent form or group of forms, as seen below : 
 
454: 
 
 APPENDIX. 
 
 BRAVAIS-MILLEB. 
 
 NAUMANN.' 
 
 [hkli] 
 
 [7ih2h2i] 
 [1122] ; 
 [Ohhi] : 
 [0111] ; 
 
 [1120] ; 
 [0110] ; 
 [0001] ; 
 
 a = 0, 7i = k = l.\ 1=2 
 
 = 0, k = 0, h = 1 .-. J =1 
 h = k = I = 0. 
 
 -- : na : a : mo 
 n-l 
 
 [m-n] 
 
 2a :2a : a :mc 
 
 [m-2] 
 
 2a :2a : a : c 
 
 [1-2] 
 
 oo a : a : a : mo 
 
 [m] 
 
 ooa : a : a : c 
 
 [1] 
 
 n 
 
 
 r a : na : a : oo c 
 
 r-7fci 
 
 n-l 
 
 
 2a :2a a : oo c 
 
 [*] 
 
 aa : a : a : ccc 
 
 M 
 
 a : oo a : oo a : o 
 
 [0] 
 
 A. HoloJiedral Forms. 
 
 The forms to which these symbols belong have been already mentioned on pp. 32-34. 
 They may be briefly recapitulated here. They are taken in the reverse order from that given 
 in the table. 
 
 Basal virtues. Symbol (0001) and (0001). 
 
 Prisms. -,a) The unit prism (/). General symbol [0110], including (sf j e f. 793. 794) the 
 six planes with the following symbols: (0110), (1100), (1010), (0110), (1100), (1010). 
 
 (b) The diagonal prism (i-2). General symbol [1120], including (f. 793, 795) the follow- 
 ing six planes : (1120), (1210), (2110), (1120), (1210), (2110). 
 
 (c) The dihexagonal prism (i-n). General symbol [AHO], embracing the following twelve 
 planes mentioned in order : 
 
 (ftH, (MO), (MO), (77^0), (ZfcfcO), (MZO), (ABO), (7tM), (*Z&0), (ZMO), (ZMO), (MJO). 
 
 Hexagonal pyramids, or Quartzoids. (a) The pyramids of the first or unit series. General 
 symbol [Qhhi] embracing twelve_ similar planes. All the pyramids of this series lie in a 
 zone between the unit prism [0110] and the base [0001]. A special case of this is when 
 A = k = i = 1. The planes of this form (f. 796) are shown on the projection, f. 793. 
 
 794 
 
 795 
 
 [0110] 
 
 [1120] 
 
 [0111] 
 
 [AtiQ 
 
 (b) Pyramids of the second, or diagonal series. General symbol [h7i2h2i], including twel ye 
 planes, analogous to those of the pyramid unit series. All the pyramids of this series lie in 
 a zone between the diagonal prism, whose general symbol is [1120], and the basal plane 
 [0001]. 
 
 Twelve-sided pyramids, or Berylloids (f. 797). General symbol [hkli\, including the twenty- 
 four planes enumerated on p. 453. 
 
 * The order of the terms in the symbols below is made to correspond to that of the indices 
 
MILLER S SYSTEM OF CRYSTALLOGRAPHY. 
 
 455 
 
 798 
 
 B. Hemihedral Farms. 
 
 The most important of the hemihedral forms in this system are as follows : 
 
 1. PYRAMIDAL hemihedrism. This comes under the head of holohemihedral forms, which 
 are vertically direct (see pp. 34, 35). It is indicated like 
 
 the corresponding hemihedrism in the tetragonal system 
 v[hkli\. It is common on apatite. 
 
 2. RHOMBOKEDRAL hemihedrism. These included 
 here are hemiholohedral, and vertically alternate. They 
 are indicated in general by K\Jikli\. This class is import- 
 ant, since it embraces the RHOMBOHEDRAL DIVISION. 
 
 (a) Rhoiribohedrom. Symbol x[Qhhi\ ; the unit, or 
 fundamental rhombohedron (+-K, f. 798) has the symbol 
 K[0111], including^ the six planes: (0)11), (1011), 
 (1101), (1011), (1101), (0111). The negative rhombohe- 
 dron ( 7?, f . 799) includes the planes: (1101), (0111), 
 (lOli), (0111), (1011), (.1101). 
 
 (b) Scalenoltedrons (f. 800). Symbol K\hkU\. 
 
 3. GYROIDAL, or trapezohedral hemihedrism. The 
 forms here included are holohemihedral, and vertically 
 alternate. They are indicated by K" [hkli] . see p. 39. 
 
 4. TETRATOHEDRISM. This may be (1) rJiombohedral, 
 
 indicated by mr[hkli] \ or (2) traptzohedral (sryroidal), as common on quartz, having the gen* 
 eral symbol 
 
 Mathematical Relations of the Hexagonal System. 
 
 In the Hexagonal System, as has been explained, the symbol in general has the form 
 [hkli] . where the algebraic sum of li , h, and I is zero. This general symbol has four in- 
 dices, referring respectively to the three equal lateral axes and the vertical axis, as shown 
 in f. 792, thus showing the fundamental hexagonal symmetry of the forms. Since, however, 
 the position of a plane is known by its intersection with three axes aione, two of the three 
 indices 7i, &, I are all that are needed in calculation, the third, , being a function, as given 
 above, of h and k. The mathematical relations of the planes in this system are brought out by 
 referring them to three axes, viz., two equal lateral axes //, K, (= a = \) oblique (120 and 
 60) to one another, and a third axis (c) of unequal length perpendicular to their plane. 
 
 This applies also to the calculation by zonal equations. The indices (u, v, w) of the zone 
 in which the planes (hldi), (pqrt) lie, are given by the scheme : 
 
 h k i h k 
 
 XXX 
 
 p q t p q 
 u = let qi v = ip ht w = hq kp. 
 
 (1) The distances (see f . 793) of the pole of any plane (hkli) from the poles of the plane* 
 (1010), (0110), (1100), and (0001) are given by the following equations: 
 
 cos PA = cos 
 
 (1010) = 
 
 hk)' 
 
 cos PB = ooa 
 
 (OtlO) = 
 
 oo. PC = ooa (UK) (0001) = 
 
456 APPENDIX. 
 
 (2) The distance (PQ) between the poles of any two planes (hkli) and (pqrt) is giveu by tht 
 equation : 
 
 cos po = 8ft + 2?(hq + pk + 2hp + 2kq} 
 
 4#(A a + k* + hkj\ [3 a + 4c 2 (p a + q* + pq)}' 
 
 (3) For special cases the above formula becomes simplified ; it serves to give the value oi 
 the normal angles for the several forms in the system. They are as follows : 
 (a) Hexagonal Pyramid [0/i/w], f. 790, 
 
 Si 2 + 2/A;* 47*^* - S* 2 
 
 cos X (terminal) = ^ + ^ J cos Z < basal ) = w 
 
 For the hexagonal pyramids of the second series [Qh2h2l] the angles have the same value. 
 (&) Dihexagonal Pyramid \hkli], 
 
 cos X fsee f 7W - 
 cos X (see f. 797) _ 
 
 cos Y (see f . 797) = 
 
 4c(A a + ** 
 cos Z (basal) = 
 
 (f) Dihexagonal Prism [A*20], 
 
 A 8 + A ! + 4A* 
 oosX(ax la l) = - 
 
 cos Y 
 Rhombohedron 
 
 () Scalenohedron K[7Mi\, 
 
 St 8 + W(2k* + 27ik - ?*) 
 cos Y (see f . 800; = -^77 - . ,, /7 . - j-. - rrr. 
 Si- + 4c*(A s + k 2 + hk) 
 
 r, n. n 
 
 cos Z (basal) = 
 
 (4) Relations of planes in a zone. The general equation (3, p. 446) is to be employed. 
 For the pyramidal zones passing through the pole (0001) it takes a simpler form, viz. : 
 
 h L __k = i tan PC 
 p ~ q~ t 'tan QC* 
 If Q = (0111), then : 
 
 tan_PC_,& 
 tanQC" ' 
 
 Determination of the axis c. The value of c may be determined from any one of the 
 equations which have beer: given. The following are simple cases : 
 
 tan (Mi 27i 2i) (0001) = ^. 
 Also tan (QhJii) (0001) . sin 60 = ^, or tan (0111) (0001) . sin 60 = i. 
 
MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 
 
 457 
 
 IV. ORTHORHOMBIC SYSTEM. 
 
 The Orthorhombic System is characterized by three unequal rectangular axes c I tL* 
 hP indices h k I may be either plus or minus, in the general form [hkl], but they are not 
 
 JShJ^ftblo; B^fcey refer to axes of different lengths. This general symbol then embraces 
 
 .he following planes : 
 
 (hkl) 
 (hkl) 
 
 (Ml) 
 
 (Ml) 
 hkl 
 
 As different values are given to h, k, I, this general form becomes more or less specialized. 
 The possible forms are as follows : 
 
 1. 
 
 2. 
 3. 
 
 4. 
 
 5. 
 6. 
 
 7. 
 
 ( [hM] ; 
 \ \kM] ; 
 ( [hhl] ; 
 [hW] ; 
 
 ([hkQ]', 
 UMOJ; 
 (lllO] ; 
 [100] ; 
 [010] ; 
 [001] ; 
 
 h 
 
 h 
 
 h 
 I 
 I 
 h 
 k 
 h 
 
 > 
 
 k. 
 
 0. 
 0, 
 0, 
 k 
 I 
 
 h>Jc. 
 h > k. 
 = 1, 1 = 0. 
 
 = 0. 
 = 0. 
 
 & : nb 
 nd:_b: 
 & \ b 11 
 & : oo5 
 
 me 
 me 
 
 1C 
 
 me 
 
 ooc 
 : ooc 
 
 d:nb 
 nti'^l 
 A : b :_ooc 
 (t : ccb : ooc 
 00$ : b : ooc 
 cod : oo& : c 
 
 [w-w] 
 
 [m-n 
 
 [m]. 
 
 [m-l]. 
 
 [m-*]. 
 
 [ill 
 
 [a]. 
 
 [0]. 
 
 These symbols belong to the various distinct forms of this system, as follows : 
 Pinactids (a) Basal plane. Symbol [001], including the two planes (001) and 001). (b) 
 
 Macropinaeoid. Symbol [100], including the plane [100], and [100] opposite to it. (c) 
 
 Srachypinacoid. Symbol [010], including the planes [010] and [010]. 
 Prisms,-(a) Unit prism (/). Symbol 110, including four planes, (110), (110), (HO), (110). 
 
 (b) Macrodiagonal and brachydiagonal 
 
 prisms, having respectively the symbols 
 
 [JM] and [MO], if h is greater than k. 
 
 Thus the symbol i-2 corresponds to [210], 
 
 and i-2 to [120]. 
 
 Domes. (a) Macrodiagonal, or macro- 
 domes, having the symbol [hW] ; and (b) 
 brachydiagonal, or brachydomes, with the 
 symbol [Qkl]. In each case the symbol 
 embraces four similar planes. 
 
 Octahedrons or Pyramids. Tine sym- 
 bol [hhl] belongs to the eight planes of the 
 unit pyramids, all lying in the zone be- 
 tween the unit prism [110], and the base 
 [001]. If h = I the form is then [111], 
 and the eight planes are : (111), (111), 
 
 (111), (111), (111), (HI), (HI), (111)- 
 
 Of the general pyramids two cases are 
 possible, either [hkl] or [khl], when h>k, 
 these correspond respectively to the 
 prisms [hkO] and [MO]. They are the 
 macrodiagonal and brachydiagonal pyra- 
 mids of Naumann ; thus 2-2 (= ft: 26 : 2c) 
 is [211], according to Miller, and 2-2 (= 2df : b : 2b) is [121]. 
 
 * The same lettering is employed here as in the early part of this work ; it differs from 
 that of Miller in that with him a is the macrodiagonal, and b the brachydiagonal axis 
 Following Groth, and later writers (Bauerman, etc.), the macropmacoid has the symbol 
 (100\ and the brachypinacoid the symbol (010) ; similarly the macrodomes are m general 
 ()l)', wod the brachydomes (Qkl). 
 
 110 
 
458 APPENDIX. 
 
 For the figures of the above-mentioned forms see pp. 42-44. Their relations will be under- 
 stood from an examination of f. 801, showing the projection of the crystals in f . 758, p. 444. 
 It will be seen that all the macrodiagonal planes lie between the zonal circles (diameters) 
 (110) (001), and (100) (001), and the brachydiagonal planes between (110) (001; and (010) (001). 
 
 Mathematical Relations of the Orthorhomlic System. 
 
 (1) For the distance between the pole of any plane P (Ml) and the pinacoid planes we 
 have in general : 
 
 cos' PA = 
 
 cos' PB = cos' (W) (010) = >w + 
 cos* PC = cos' (Ml) (001) = 
 
 (2) For the distance (PQ) between the poles of any two planes (hkl) and (pqr) : 
 cosPQ= 
 
 (3) For planes lying in a zone, the general relation (p. 446) is to be employed. For the 
 
 " 5 simplified equations which follow a 
 general equation may be employed : 
 
 \vj A'ui jjiiiic -ijiug iii a. ziuiie, ilia general reiaiiiuji 
 
 special cases, practically of most importance, the simplified equations which follow are used, 
 (4) To determine the lengths of the axes, the genera' 
 
 ~ cos PA = 4 cos PB = 4 cos PC. 
 h lc I 
 
 Here PA, PB, PC are the distances from the pole of any plane (hJcl) to the pinacoid planes 
 (100), (010), (001) respectively. The brachydiagonal axis* a, is made the unit. 
 
 If the angle between any dome or prism and the adjoining pinacoid plane is given, the 
 relations follow immediately : 
 
 tan PA = tan (MO) (100) = ~ 
 oh 
 
 tan PB = tan (OJcl) (010) = ^ 
 
 CK 
 
 tan PC = tan (hQl) (001) = 
 
 V. MONOCLINIC SYSTEM. 
 
 In the Monoclinic System there are three unequal axes, and one of these makes an oblique 
 angle with a second. The axes are lettered as uhown in f. 802, 
 QQO c is vertical, b the orthodiagonal axis, and d the clinodiagonal 
 
 axis oblique to , but at right angles to b. The symbol [h/d,] 
 embraces only four similar planes in the most general case, for 
 ^90 i n consequence of the obliquity of one of the axes, the quajranta 
 
 above in front correspond alone to those below and behind, and 
 those above behind correspond to those below in front. This is 
 / $ seen clearly in the projection of f. 803. For h, k, 1 the 
 
 symbol [hid} includes two distinct forms, viz. : 
 
 (1) (hkf) (Wei) (hkl) (7wB) 
 
 and (2) (hkl) (hkl} (hkf) (JM, 
 
 The various forms are as follows : 
 
MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 
 
 459 
 
 Pinacoids. Base [001]. Orthopinacoid [100]. Clinopinacoid [010]. Each symbol, of 
 xmrse, comprehending two planes only. 
 
 80i 
 
 Crocoite. 
 
 Prisms.-(a) Unit prism [110], = d : b : oo c (I) of Naumann. This symbol embraces four 
 similar prismatic planes, (b) Orthodiagonal prisms &*>}<"*** h f >*' ^ThW^es^nd 
 prisms fall on the prismatic zonal circle between 100 and 110 (see f 803). Th ^*f. d 
 to the prisms i-n = d : nb : *c) of Naumann. (c) Clinodiagonal prisms. ^ol [MO], 
 h > k lyimr between (110) and (010). They correspond to i-n (= nd : b: oo c) of ISaumann. 
 
 Lorn is -(a) Hemi-orthodomes, including two cases, (101) _and (10h|, the minus *?\* 
 Naumann (opposite the obtuse angle) ; and also (101) and (101)), the plus domes of Naumann 
 (opposite thfacute angle ft), (b) Clinodomes. Symbol [OAQ. e mbracmg our sim lar pi anes 
 \0kl) (OH), (0/W), (OH). The clinodome [Oil], equivalent to 1-* (=00 d : b : me}, is ox 
 
 pa:-The pyramids are all hemi-pyramids. (a) The symbol [^includes theunit 
 pyf/mids in a zone between [110] and [001]. (b) The symbol [M*\ includes two sets of hemi- 
 pyramids, whose indices have been given on p. 416, corresponding respectively to - 
 
 + ff h i^SteTthan k these are orthodiagonal pyramids, corresponding to (d: J 1 ^^ 
 Naumann. The symbol [Ml] on the same supposition includes two sets of planes, like those 
 of p. 458, and differing only in being ^^^JJ?^^* % ( ^ ^0^ whL the^Hno- 
 The orthodiagonal planes lie between the zone (100), (001) and (110), (^>JJJf !?VPS tha 
 diagonal are between the latter zone and (010) (001), as is seen on f. 803, which gives 
 projection for f. 804. 
 
 Mathematical Relations for the Mbnoclinic System. 
 
 (1) The distances of the pole of any plane (hM) from the pinacoid planes are given by the 
 ing equations : 
 
 Tile + lab cos )8 __ t 
 
 following equations : 
 
 cos PA = cos (AM) (100) = 
 
 o cos 
 
 cos PB = cos (hid) (010) = 
 cos PC = coa (hkl) (001^ = 
 
 27 
 
 kac sin )3 
 
 lab + hbc cos 3 
 
 ____ 
 + 2hlaVc cos/3 * 
 
460 APPENDIX. 
 
 (2) The distance between any two planes may be expressed ia general form, but in all 
 practically arising cases the end can be attained by the solution of one or more spherical tri- 
 angles on the projection. 
 
 (3) For the relation between the planes in a zone the general equation before given holds 
 good: 
 
 cot PS -cot PR _ (PQ) . (SB) 
 cot PQ - cot PR (QR) . (PS)* 
 
 (4) For all zones passing through the clinopinacoid (010), the value of PR may be taken aa 
 90, and the above equation consequently simplified : 
 
 tanPB l 
 
 p q tan QB r 
 
 This equation is especially valuable for determining the indices of planes in the prismatic 
 and clinodome series. 
 
 (5) To determine the axial relations the general equation admits of being transformed so aa 
 to read : 
 
 h sin PYA _ p sin QYA _ a 
 T* sin PYC ~ 7" ' sinQYC~T' 
 
 *_ sinpYA _ 9_ s 
 
 I ' cotPY ~ r ' cotQY " c' 
 
 The angles PYA, PYC are angles which may be calculated directly by spherical triangles 
 from the measured angles. Similarly for QYA, QYC. PY and QY are the angles betweer 
 the given plane P or Q with the clinopinacoid. 
 
 VL TRICLINIC SYSTEM. 
 
 In the Triclinic System, since the axes are unequal and all mutually oblique, there can be 
 no plane of symmetry, and there can in no case be more than two planes included in a single 
 form. The three axes are distinguished as a vertical, c, a longer lateral, or macrodiagonal 
 axis, b, and a shorter lateral, or brachydiagonal axis, a. The position assumed for the axea 
 is shown in f. 259, p. 80. 
 
 The general symbol \hJd\ , which includes eight similar planes in the orthorhombic system, 
 is here resolved into four independent forms, embracing two opposite planes only. They 
 are thus : 
 
 i9\ W (^ (**$ (A.\ 
 
 (2) (Tiki) < 3) (MO (4) 
 
 These correspond respectively to rri?'n (1), m'Pn (2), mP,n (3), m,Pn (4) of Naumann, 01 
 m-ri, m-n, m-n! , m-n! , as the abbreviated symbols are written in the earlier part of this 
 work. 
 
 Contrary to the usage in the orthorhombic system, it is customary to make [100] the 
 macropinacoid (i-l = a : oo b : oo c), and [010] the brachypinacoid (i-l = oo a : b : occ >. Planes 
 having the symbol [7iOf] are then macrodoines ; and those of the symbol [Qkl] are brachy- 
 domes. Similarly then pyramids (h > k) of the form [hkl] are macrodiagonal planes, and 
 those of the form (Jtkl) are brachydiagonal planes. The unit prism consists of two independent 
 forms (110), (110) (I'=ooP/), and (110), (110) (I =00 ',P). 
 
 Mathematical Relation* of the Triclinic System. 
 
 In consequence of the obliquity of the axes in the Triclinic System the mathematical rela- 
 tions are less simple, and the general equations deduced as before become so complicated as 
 to be seldom of much practical value. Most problems which arise may be solved by the zonal 
 relations, or by the solution of the spherical triangles in the projection. Some of the most 
 important relations (given by Schrauf ) are as follows : 
 
MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 
 
 461 
 
 If the angle between the axes X and Z = rj, between X and Y = , and between Y and Z 
 = | (see f. 757) ; if also a, j8, y are the corresponding angles between the pinacoid planes 
 hen 
 
 cos $ cos 7 cos a cos 7 cos a cos 
 . COS t\ = : 
 
 sin sin 7 sin 7 sin a 
 
 COS COS a 
 
 COS ) 
 
 -- 
 
 where 
 
 Also 
 
 AW A! 
 
 and cos- PX - 
 
 cos 9 PY = 
 
 cos 2 PZ = 
 
 Mi MI 
 
 AI = [1 + 2 cos a cos cos 7 (cos 2 a 4- cos 2 + cos 9 7)]. 
 
 Mi = Ji-o-e 12 sin 2 a 4- &Vc 9 sin 2 + 1-aW sin 2 7 + 2rcfte (Jilb cos sin a sin 7 
 + 7ic cos 7 sin a sin + kla cos a sin sin 7). 
 
 cos 9 AX = 
 
 cos BY = 
 
 A, 
 
 cos CZ = 
 
 When PX, PY, PZ have been found by calculation, then the following equation gives th* 
 relation of the axes : 
 
 2- cos PX = ~ cos PY = 4- cos PZ. 
 h k I 
 
 As seen in f . 805. 
 
 cos PX = sin PBC sin PB = sin PCB sin PC ; 
 cos PY = sin PGA sin PC = sin PAC sin PA ; 
 cos PZ sin PAB sin PA = sin PBA sin PB ; 
 and also from these it follows that 
 
 4- sin PAC = -f sin PAB ; 
 
 /C I 
 
 sin PBA = sin PBC ; 
 
 sin PCB = - sin PGA. 
 h h 
 
 - 180 - CAB ; 
 
 7, = 180 - ABC ; 
 
 = 180 - ACB. 
 
 RELATIONS OF THE Six CRYSTALLINE SYSTEMS IN RESPECT TO SYMMETRY. 
 
 From a careful study of the spherical projections for the successive systems a very clear 
 idea may be obtained of the degree of symmetry which characterizes each. It is well under- 
 stood that in the Isometric System there are nine planes of symmetry ; in the Tetragonal, 
 five ; in the Hexagonal, seven ; in the Orthorhombic, three ; and in the Monoclinic only one. 
 These relations are shown on the projections by the symmetrical distribution of the poles about 
 the respective great circles. These zone-circles of symmetry are as follows : 
 
 Isometric System (f . 766) : 1st, the three diametral zones 
 
 1. (100), (010), (TOO). 
 Also the diagonal zones : 
 
 4. (110), (001), (110). 
 
 5. (110), (001), (110). 
 
 Tetragonal System (f . 790) 
 1. (100), (010), (100). 
 
 2. (100), (001), (100). 
 
 6. (100), (Oil), (100). 
 
 7. (100), (Oil), (100). 
 
 3. (010), (001), (010). 
 
 8. (010), (101), (010). 
 0. (010), (101), (010). 
 
 2. (100), (001), (100). 
 
 3. (010), (001), (010^ 
 
 Also: 
 
 4. (110), (001), (110). 
 
 5. (110), (001), (110). 
 
462 APPENDIX. 
 
 Hexagonal System (f. 793) : 
 
 1. (1010), (0001), (1010). 
 4. (1120), (0001), (1120). 
 
 Orttiorhombic System (f. 801) : 
 
 1. (100), (010), (100). 
 Monodinic System (f. 804) : 
 
 1. (100), (001), (100). 
 In the Triclinic System there is no plane of symmetry. 
 
 2. (0110), (0001), (0110). 
 5. (1210), (0001) (1210). 
 7. (1010), (0110), (1100). 
 
 3. (1100), (0001), (1100). 
 6. (2110), (0001), (2110). 
 
 
 2. (100), (001), (100). 3. (010), (001), (010). 
 
 51 
 
 THE BHOMBOHEDRAL DIVISION OF MILLER. 
 
 The following projection (f. 806) is added in order to show the relation of the forms in the 
 
 Hexagonal and Rhombohedral Systems a 
 referred to the three equal oblique axes of 
 Miller. The forms are as follows : 
 
 The planes having the indices (100), 
 (010), (001) are those of the (plus) funda- 
 mental rhombohedron, while the plane 
 (111) is the base. The planes (221), (121), 
 (122) are those of the minus fundamental 
 rhombohedron; with the planes (100), 
 (010), (001) they form the unit hexagonal 
 pyramid. 
 
 The hexagonal unit prism (1= [0110]) 
 has the symbols : (2J1), (121), (112), (211), 
 (121), (112). The second, or diagonal hexa- 
 gonal prism (i-2_= [1120]) has the symbols : 
 (101), (110), (Oil), (101), (110), (Oil). 
 
 The dihexagonal pyramid embraces, 
 like the simple hexagonal pyramid, two 
 forms, [hkl] and [efg] ; the symbol [hfd] 
 hence belongs to the plus scatenohedron, 
 and [tfff] to the minus. In this as in other 
 cases it is true that : e = h + 2k + 2L 
 f = 2h-k + 2l,g = 27* + 2k - I. 
 
 The dihexagonal prism includes the six 
 
 ing six of the form [efO]. ^^ ** f0rm C ** ] and the remain ' 
 
 Most of the problems arising under this system can be solved by the zone equations, or 
 by the working out of the spherical triangles on the sphere of projection. 
 
APPENDIX B. 
 
 ON THE DRAWING OF FIGURES OF CRYSTALS. 
 
 IN the projection of crystals, the eye is supposed to be at an infinite distance i 
 avs of light fall from it on the crystal in parallel lines. The plane on which the crystal is 
 Ejected is termed the plane of projection. This plane may be at ^Mangles to the ver 
 ical axis may pass through the vertical axis, or may intersect it at an oblique angle. These 
 Uffer^t potions give rise, respectively, to the HORIZONTAL, VERTICAL, and OBLIQUE pro- 
 ections The rays of light may fall perpendicularly on the plane of projection, or may be 
 obliquely inclined to it; in the former case the projection is termed ORTHOGRAPH ^, m wie 
 second CLINOGRAPHIC In the horizontal position of the plane of projection, the projection 
 L always orthographic. In the other positions, it may be either o rtho ^. a P hl ^ o %f ft ^ o f^ P ^ s 
 It is generally preferable to employ the vertical position and clmographic projection, and 1 
 method is elucidated in the following pages. 
 
 PROJECTION OF THE AXES. 
 
 The projection of the axes of a crystal is the first step preliminary to the projection of the 
 form of P the costal itself. The projection of the axes in the isometric svstem, which are 
 equal and intersect at right angles, is here first given. The projection ot ------, 
 
 systems, with the exception of the hexagonal, may be obtained by varying the lengths 
 projected isometric axes, and also, when oblique, their inclinations as shown beyond 
 
 Isometric ^m.-When the eye is directly in front of a face of a cube, neither the sidee 
 nor top of the crystal are visible, nor the planes that may be 
 situated on the intermediate edges. On turning the crystal 
 a few degrees from right to left, a side lateral plane is brought 
 in view, and by elevating the eye slightly, the terminal plane 
 becomes apparent. In the following demonstration, the 
 angle of revolution is designated 5, andr the angle of the ele- 
 vation of the eye, e. Fig. 807 represents the normal position 
 of the horizontal axes, supposing the eye to be in the direc- 
 tion of the axis BB ; BB is seen as a mere point, while CO 
 appears of its actual length. On revolving the whole through 
 a number of degrees equal to BMB' (8) the axes have the 
 position exhibited in the dotted lines. The projection of the 
 semiaxis MB is now lengthened to MN, and that of the semi- 
 axis MO is shortened to MH. 
 
 If the eye be elevated (at any angle, e), the lines B N, BM, 
 and C'H will be projected respectively below N, M, and H, 
 
 and the lengths of these projections (which we may designate b N, ftM, and c H) will be di- 
 rpot.lv nronortional to the lengths of the lines B N, BM, and C'H. 
 
 It is P uSo^dopt such a Evolution and such an elevation of the eye as may be expressed 
 by a simple ratio between the projected axes. The ratio Between the two axes MN: Mil, 
 as projected after the revolution, is designated by 1 : r ; and the ratio of b N to MN by 1 . 
 Suppose r to equal 3 and a to equal 2, then proceed as follows : 
 
464 
 
 APPENDIX. 
 
 Draw two lines AA', H'H (f. 808), intersecting one another at right angles. Make MH = 
 
 MH' = b. Divide HH' into 8 (r) parts, and through the 
 points, N, N', thus determined, draw perpendiculars to 
 HH'. On the left hand vertical, set off, below H', a 
 
 part H'R, equal to b = H M ; and from R draw RM, 
 
 and extend the same to the vertical N'. B B is the pro- 
 jection of the front horizontal axis. 
 
 Draw BS parallel with MH' and connect SM. From 
 the point T in which SM intersects BN, draw TO par- 
 allel with MH. A line (CO") drawn from C through M, 
 and extended to the left vertical, is the projection of the 
 side horizontal axis. 
 
 Lay off on the right vertical, a part HQ equal tc 
 
 ^MH, and make MA = MA'= MQ ; A A' is the vertical 
 o 
 
 axis. If, as here, r 3, and s = 2, then 8 = 18 26', 
 and e = 9 28', for cot 5 = r, and cot e = rs. 
 Tetragonal and OrthorJiombic Systems. The axes AA', CO', BB, constructed in the mannei 
 described, are equal and at right angles to each other. The projection of the axes of a tetra- 
 gonal crystal is obtained by simply laying off, with a scale of proportional parts, on MA and 
 MA' taken as units, the value of the vertical axis (c) for the given species. Thus for zircon, 
 where c = "04, we must lay off '64 of MA above M and the same length below. 
 
 For an orthorhombic crystal, where the three axes are unequal, the length of c must as 
 before be laid off above and below from M, and that of b to the right and left of M, on CC , 
 MC being taken as the unit. It is usual to make the front axis MB = a = 1. 
 Monodinic System. The axes c and a in the monoclinic system are inclined to one another 
 
 at an obliqe angle = . To project this inclination, and 
 thus adapt the isometric axes to a monoclinic form, lay 
 off (f . 809) on the axis MA, M = MA cos 0, and on the 
 axis BB' (before or behind M, according as the inclination 
 of a on c, in front, is acute or obtuse) M6 = MB x sin /8. 
 From the points b and , draw lines parallel respectively 
 with the axes AA' and BB', and from their intersection 
 D , draw through M, D'D, making MD = MD'. The line 
 DD' is the clinodiagonal, and the lines AA, CO, DD' re- 
 present the axes in a monoclinic solid in which a = b = c 
 = 1. The points a and b and the position of the axis 
 DD' will vary with the angle 0. The relative values of 
 the axes may be given them as above explained ; that is, 
 if d 1, lay off in the direction of MA and MA' a line 
 equal to c, and in the direction of MC and MC' a line 
 equal to 6, etc. 
 
 T-nclinio System. The vertical sections through the 
 horizontal axes in the triclinic system are obliquely in- 
 clined ; also the inclination of the axis a to each axis b 
 In the adaptation of the isometric axes to the triclinic forms, it is there- 
 fore necessary, in the first place, to give the requisite 
 obliquity to the mutual inclination of the vertical sec- 
 tions, and afterwards to adapt the horizontal axes. The 
 inclination of these sections we may designate A, and as 
 heretofore, the angle between a and 6, 7, and a and c, 0. 
 BB' is the analogue of the brachydiagonal, and GC of the 
 macrodiagonal. An oblique inclination may be given the 
 vertical sections, by varying the position of either of 
 these sections. Permitting the brachydiagonal section 
 ABA'B' to remain unaltered, we may vary the other sec- 
 tion as follows : 
 
 Lay off (f. 810) on MB, W)'= MB x cos A, and on the 
 axis C C (to the right or left of M, according as the 
 acute angle A is to the right or left), Me = MC x sin A ; 
 completing the parallelogram M6' DC, and drawing the 
 diagonal MD, extending the same to D' so as to make 
 MD' MD, we obtain the line DD' , the vertical station 
 
 and c, is oblique. 
 
 810 
 A 
 
ON THE DRAWING OF FIGTJKES OF CRYSTALS. 
 
 465 
 
 passing through this line is the correct macrodiagonal section. The inclination of a to the 
 new macrodiagonal DD' is still a right angle ; as also the inclination of a to 5, their oblique 
 inclinations may be given them as follows : Lay off on MA (f. 810), Ma = MA x cos , and 
 on the axis BB' (brachy diagonal), M# MB' x sin #. By completing the parallelogram Ma, 
 K'J, the point E' is determined. Make ME = ME ; EE is the projected brachy diagonal. 
 Again lay off on MA, Ma'= MA x cos o, and on MD', to the left. Mrf =. MD' x sin o. Dra\ 
 lines from a! and d parallel to MD and MA ; F', the intersection of these lines, is one extremity 
 of the macrodiagonal; and the line FF', in which MF = MF', is the macrodiagonal. The 
 vertical axis AA' and the horizontal axes EE' (brachy diagonal) and FF' (macrodiagonal) thus 
 obtained, are the axes in a triclinic form, in which a = b = c = 1. Different values may be 
 given these axes, according to the method heretofore illustrated. 
 
 Hexagonal System. In this system there are three equal horizontal axes, at right angles to 
 the vertical axis. The normal position of the horizontal 
 axes is represented in f. 811. The eye, placed in the 
 line of the axis YY, observes two of the semiaxes, MZ 
 and MU, projected in the same straight line, while the 
 third, MY, appears a mere point. To give the axes a 
 more eligible position for a representation of the various 
 planes on the solid, we revolve them from right to left 
 through a certain number of degrees 8, and elevate the 
 eye at an angle e. The dotted lines in the figure repre- 
 sent the axes in their new situation, resulting from a 
 revolution through a number of degrees equal to 5 = 
 YMY'. In this position the axis MY is projected upon 
 MP, MU' upon MN, and MZ on MH. Des gnating the 
 intermediate axis I, that to the right II, that to the left 
 III, if the revolution is such as to give the projections 
 of I and II the ratio of 1 : 2, the relations of the three 
 projections will be as follows : I : II : III = 1 : 2 : 3. 
 
 Let us take r ( = PM : HM) equal to 3, and * (= b'P : 
 PM) equal to 2, these being the most convenient ratios for 
 
 representing the hexagonal crystalline forms. The following will be the mode of construc- 
 tion : 
 
 1. Draw the lines AA, HH (f. 812) at right angles with, and bisecting, each other. Let 
 HM = , or HH 2b Divide HH into six parts by vertical lines. These lines, including 
 the left-' and right-hand verticals, may be numbered from one to six, as in the figure. In the 
 first vertical, below H, lay off HS = -6, and from S draw a line through M to the fourth 
 vertical. YY' is the projection of the axis I. 
 
 2. From Y draw a line to the sixth vertical and parallel with HH. From T, the extremity 
 of this line, draw a line to N in the second vertical. 
 
 Then from the point U, in which TN intersects the 
 fifth vertical, draw a line through M to the second 
 vertical ; TJU' is the projection of the axis II. 
 
 3. From R, where TN intersects the third verti- 
 cal, draw RZ to the first vertical parallel with HH. 
 Then from Z draw a line through M to the sixth 
 vertical : this line ZZ' is the projection of the axis 
 III. 
 
 4. For the vertical axis, lay off from N on the sec- 
 ond vertical (f. 812) a line of any length, and con- 
 struct upon this line an equilateral triangle ; one side 
 (NQ) of this triangle will intersect the first vertical 
 at a distance, HV, from H, corresponding to Z H in 
 f. 811 ; for in the triangle NHV, the angle HNV is 
 an angle of 30, and HN = |MH. MV is therefore 
 the radius of the circle (f. 811). Make therefore 
 MA = MA' MV ; AA' is the vertical axis, and YY', 
 
 riU , ZZ' are the projected horizontal axes. , . 
 
 The vertical axis has been constructed equal to the horizontal axes. Its actual 1< 
 different hexagonal or rhombohedral forms may be laid off according to the method sut 
 
 The projection of the isometric and hexagonal axes, having been once accurately made, and 
 that on a conveniently large scale, may be kept on a piece of cardboard, and will 
 all subsequent requirements. Whenever needed for use, these axes may be transferred 
 sheet of paper, and then adapted in length, or inclination, or both, to the case 11 
 
 30 
 
466 
 
 APPENDIX. 
 
 PROJECTION OF THE FORMS OP CRYSTALS. 
 
 
 ' , Simple forms. When the axial cross has been constructed for the given species, the anil 
 
 octahedron is obtained at once by joining the 
 extremities of the axes, AA', BB', CO', as in 
 f. 813. Here as in all cases the lines which 
 fall in front are drawn strongly, while those 
 behind are simply dotted. 
 
 For the diametral prisms draw through B, 
 B', C, C', of the projected axes of any species, 
 lines parallel to the axes BB', CC', until they 
 meet; they make the parallelogram, abed, 
 which is a transverse section of the prism, par- 
 allel to the base. Through a, 6, c, d draw 
 lines parallel and equal to the vertical axis, 
 making the parts above and below these points 
 equal to the vertical semiaxis. Then, connect 
 the extremities of these lines by lines parallel 
 to ab, be, cd, da, and the figure will be that ol 
 the diametral prism, corresponding to the axes 
 projected. 
 
 In the case of the isometric system this dia- 
 metral prism is the cube, whose faces are represented by the letter H; in the tetragonal 
 system it is the prism 0, i-i ; in the orthorhombic, the prism 0, i-i, i-i ; in the monoclinic, the 
 prism 0, i-i* i-i ; in the triclinic, 0, i-1, i-l. 
 
 The unit vertical prism in the tetragonal, orthorhombic, and clinometnc systems may be 
 projected by drawing lines parallel to the vertical axis AA' through B, C, B', C , making the 
 parts above and below these points equal to the vertical semiaxis ; and then connecting the 
 extremities of these lines by lines parallel to BC, CB', B'C , C B. The plane BOB C is a 
 transverse section of such a prism parallel to its base. It is the prism 0, /, in each of the 
 systems excepting the triclinic, and in that 0, /, /' ; a square prism in the tetragonal system ; 
 a right rhombic in the orthorhombic ; an oblique rhombic in the monoclinic ; an oblique rhom- 
 boidal in the triclinic. 
 
 Other simple forms under the different systems are constructed in essentially the same way. 
 It is only necessary to lay down upon the axes each plane of the form, in lightly drawn lines, 
 
 note the points where it intersects the adjoining planes, and draw these in more strongly. 
 When the process is complete the construction lines may be erased. The process will be 
 illustrated by f . 814 and f. 815. In the former case it is required to draw the trigonal trisoo 
 tahedron, whose symbol is 2 
 
ON THE DRAWING OF FIGURES OF CRYSTALfl. 467 
 
 In f. 814 the three planes of the first octant are represented, they are 2 : 1 : 1, 1 : 2 : 1, 
 and 1:1: 2. It will be seen here, what is always true, that the two points of intersection 
 required to determine the line of intersection, lie in ike axial planes. These lines of intersec- 
 tion are represen'ed by the dotted lines in f. 814. If the same process be performed for the 
 other octants, the complete form, as in f. 816, will be obtained. 
 
 Similarly in f. 815, the octagonal pyramid 1-2 is constructed; the figure shows the planes 
 of one octant only, c : 2a : a, and c : a : 2a, and the dotted line gives their line of intersec- 
 tion. Carry out the same plane of construction in the other octants, and the form of f. 817 
 will result. 
 
 The construction of the various crystalline forms, by this method, especially those of the 
 isometric system, will be found an interesting and instructive process, and will lead to a clear 
 understanding of the forms themselves and their relations to each other. Another and quicker, 
 though more mechanical method of constructing the isometric forms may also be given. 
 
 Projection of Simple Isometric Forms. This method depends upon the principle that in the 
 different isometric forms the vertices of the solid angles are occupied by one or more of the 
 interaxes (p. 16). If, therefore, these points (the extremities of the interaxes), can be deter- 
 mined in the several crystalline forms, it is only necessary to connect them in order to obtain 
 the projection of the solid itself. 
 
 As a preparation for the construction of figures of isometric crystals, it is desirable to have 
 at hand the figure of a cube projected on a large scale, with its axes, and its trigonal (octahe- 
 dral), and rhombic (dodecahedral) interaxes. 
 
 The values of the interaxes t and r, for a given form, are obtained by adding to their nor- 
 mal length the values of t' and r' respectively given by the following equations ; those of th 
 octahedron being taken as a unit : 
 
 2mn (m + ri) , n \ 
 mn + (m + n) ~ n + 1 * 
 
 The proportion to be added to the interaxes for some of the common forms is as follows; 
 
 t r t r 
 
 2 i t-3 1 * 
 
 i i i-3 
 
 8-| i 3-3 j * 
 
 4-2 f i 3-3 f i 
 
 To construct the form 4-2, the octahedron is first to be projected, and its axes and inter- 
 axes drawn. Then add to each half of each trigonal interaxis, five-sevenths of its length ; 
 and to each half of each rhombic interaxis, one-third of its length. The extremities of the 
 lines thus extended are situated in the vertices of the solid angles of the hexoctahedron 4-2, 
 and by connecting them, the projection of this form is completed. 
 
 In the inclined hemihedral isometric forms (p, 20), the rhombic interaxes do not terminate 
 In the vertices of the solid angles, and may therefore be thrown out of view in the projection 
 of these solids. The two halves of each trigonal interaxis terminate in the vertices of dis- 
 similar angles, and are of unequal lengths. One is identical with the corresponding interaxis 
 in the holohedral forms, and is called the holohedral portion of the interaxis ; the other is the 
 hemihedral portion. The length of the latter may be determined by adding to the half of 
 the octahedral interaxis that portion of the same indicated in the formula : 
 
 2mn (m n) 
 mn + (m n) ' 
 
 If the different halves of the trigonal interaxes be assumed at one time, as the holohedral, 
 and again as the hemihedral portion, the reverse forms -^~ and ^^ may be projected. 
 
 The following table contains the values cf the above fraction for several of the inclined 
 hemihedral forms, and also the corresponding values for the holohedral portion of the inter- 
 
 Axis : 
 
 Hoi. interax. Hem. interax. Hoi. interax. Hem. interax, 
 
 ( -^- (f. 76, p. 20) 02^- (f. 85) i 1 
 9181) * 2 <>(f.87) i * 
 
 2 
 
468 
 
 APPENDIX. 
 
 
 The parallel hemihedrons (for example, the pentagonal dodecahedron, or hemi-tetrahexahe- 
 dron) contain a solid angle, situated in a line between the extremities of each pair of semiaxes, 
 which is called an unsymmetrical solid angle. The vertices of these angles are at unequal 
 distances from the two adjacent axes, and therefore are not in the line of the rhombic inter- 
 axes. The co-ordinates of this solid angle for any form, as - , may be found by the for- 
 mulas p and - Y . By means of these formulas, the situation of two points, a 
 
 and 5 (f. 818), in each of the axes may be determined : and if lines are drawn through a and 
 b in each semiaxis parallel to the other axes, the intersections c, c', of these lines will be the 
 
 vertices of the unsymmetrical solid angles, those marked c of the form and those marked 
 f of the form _^. 
 
 The trigonal interaxes are of the same length as in the holohedral forms. The values of 
 these interaxes, and of the coordinates of the unsymmetrical solid angle for different parallel 
 hemihedrons, are contained in the following table : 
 
 Trigonal 
 interaxis. 
 
 Coord, of the 
 unsym. S. A. 
 
 Trigonal 
 interaxis. 
 
 (sim. f. 92) 
 
 Coord, of the 
 unsym. S. A. 
 
 ^ * * f -BJU*, i i 
 
 * 5s 
 
 Projection of a Rhombohedron. To construct a rhombohedron, lay off verticals through the 
 extremities of the horizontal axes, and make the parts both above and below these extremities 
 equal to the third of the vertical semiaxis (f. 819). The points E, E, E', E', etc., are thus 
 determined ; and if the extremities of the vertical axis be connected with the points E or E , 
 rhombohedrons in different positions, wR, or raR, will be constructed. 
 
 Scalenohedron. The scalenohedron m n admits of a similar construction with the rhombohe 
 dron raR. The only variation required, is to multiply the vertical axis by the number of 
 units in n, after the points E and E' in the rhombohedron raR have been determined ; then 
 connect the points E, or the points E', with one another and with the extremities of the ver- 
 tical axis. 
 
 2. Complex Forms. When it is required to figure not only the planes of one form, that 
 is, those embraced in one symbol, but also those of a number modifying one another, a some- 
 what different process is found desirable. It is possible indeed to construct a complex form 
 in the way mentioned on p. 466, each plane being laid off on the given axes, and its intersec- 
 tion-edges with adjoining planes determined by two points, always in the axial sections, which 
 it has in common with each. In this way, however, the figure will soon become so complex 
 as to be extremely perplexing, and thus lead to error and consequent loss of time. 
 
 This difficulty is in part avoided by the use of one projection of the axes on a larger scale, 
 apon which the directions of the intersection-lines are determined, while a second smaller one, 
 
ON THE DRAWING OF FIGURES OF CRYSTALS. 
 
 469 
 
 placed below and parallel to it on the same sheet of paper, is used for the actual drawing of 
 the crystal. In most cases, however, the crystal may be drawn as conveniently without the 
 use of the second set of axes. The size of the figure may be either that which is to be finally 
 required, or, more advantageously, it maybe drawn two or three times larger and then reduced 
 by photography. This method is especially to be recommended when the figures are finally 
 to be engraved on wood, since from the enlarged drawing they may be photographed directly 
 upon the wood of any required size, and thus a very high degree of accuracy attained. 
 
 Application of Quenstedfs Projection. The process of determining the direction of the 
 intersection-edges is much simplified if the principles of Quenstedt's Projection (p. 55) are 
 made use of. In other words, the symbol of every plane is so transformed that for it the 
 length of the vertical axis is -unity. This extremity of the vertical axis is then one point of 
 intersection for all planes whatsoever, and the second point will always lie in the horizontal 
 plane, that of the lateral axes. The change in the symbol requires nothing but that the 
 symbol, expressed in full, should be divided by the coefficient of the vertical axis. The direc- 
 tion of each intersection-edge, when determined, is transferred to the figure in process of 
 construction by means of a small triangle sliding against a ruler some 8 inches in length. It 
 will be found in practice that, especially when this method is employed, it is not necessary 
 to actually draw all the lines representing each plane, but to note simply the required points 
 of intersection. This method and its advantages (see Klein, Einleitung in die Krystallberech- 
 nun, II., p. 387) will be made clear by an example. 
 
 It is required to project a crystal of andalusite of prismatic habit, showing also the planes 
 '-, t4, !*, 1,2-2, 1-i, and 0. 
 
 It is evident that an indefinite number of figures may be made, including the planes men- 
 tioned, and yet of very different appearance according to the relative size of ea.ch. It is 
 usually desirable, however, to represent the actual appearance of the crystal in nature, only 
 in ideal symmetry, hence it is very important in all cases to have a sketch of the crystal to 
 be represented, showing the relative development of the different planes. If this sketch is 
 made with a little care, so as to show also the parallelism of the intersection-edges in the 
 occurring zones, it will give material aid. The zones, it is to be noted, are a great help in 
 drawing figures of crystals, and they should be carefully studied, since the common direction 
 of the intersection-edge once determined for any two planes in it, will answer for all others. 
 
 The first step is to take the projection of the isometric axes already made once for all on 
 a conveniently large scale, and which, as before suggested, is kept on a card of large size, 
 and ready to be pierced through on to the paper employed. These axes, now of equal 'engtn, 
 must be adapted to the species in hand. For andalusite the axial ratio is \ e : b :a- u i 
 1-014 : 1 : hence the vertical axis e must have a length -71 of what it now has, and the late! 
 axis one I'Ol : these required lengths are determined in a moment with a scale otequa 
 
 The nexb step is to draw the predominating form, the prism /. Obviously its intersection, 
 edges are parallel to the vertical axis, and its basal edges, intersecting are paral 
 tq in the projection (f . 820). The planes i-l, and * 2 are now to be added, whose intersections 
 with each other and with 1 are parallel to c. The position of one edge, //M. having ^ beei 
 taken, that of the other on the other side is determined by the point where a line paraiie 
 
470 
 
 APPENDIX. 
 
 , 
 
 nn. 
 
 the axis b meets the basal edge of the pri?m. Similarly the position of the same prismat 
 edges behind are given by the intersection of lines from front to rear parallel to the axis . 
 
 The prisms drawn, it remains to add the terminal planes, and as they thus modify one an- 
 other's position, they are drawn together. The required intersection-lines are easily obtained. 
 The macrodome 14 is the plane passing through the point c and intersecting the horizontal 
 plane in the line paq ; this line is obviously the direction of its intersection-edge with i-1 and 
 with 0. The prism i-'2 appears (f. 820) as the two lines mm', nri ; the line mm produced 
 beyond m meets paq at 2, this will be one common point for the two planes 14 and i-2 ; the 
 second common point is, as always, the point c, hence the line joining these two points, trans- 
 ferred to the crystal in the way described, gives the required intersection- edge for -2 and 14. 
 Similarly for i-2 on the right, the two points of intersection are c, and the point where n'n 
 and qap, produced, meet, and this gives the second intersection-edge. The planes 14 and 1 
 (right) meet at d and c ; hence the line cd gives the direction of their intersection- edge, which 
 is also the direction of that of 14 and 1 (left), and of 1 and 2-2, right and left on both sides. 
 Still again, the plane 2-2 has the full symbol 2J : b : 2 2, or c : \b : d ; and hence intersects the 
 horizontal plane (f. 820) in the lines as (right), at (left), and a'q, a'p (behind). Hence the 
 intersection-edge of 7, 2-2, 1-2 has the direction of the line joining the points c, and s (right), 
 and similarly to the left and behind. The intersection- edge of 2-2 front, and 2-2 behind, has 
 the direction of the line joining the points c and x (right) and c and y (left). 
 
 The method of obtaining the intersection-edges of the planes will be clear from this ex- 
 ample. Practical facility in drawing figures by this or any other 
 method is only to be obtained by practice. 
 
 It will be found that at almost every step there is an opportunity 
 to test the accuracy of the work thus every point of intersection 
 on the basal plane behind must lie on a line drawn from the cor- 
 responding point in front on the basal plane, in the direction of the 
 axis a; so, too, the point of intersection of 2-2 and 1 (front), 2-2 
 and 7 (behind), on one side, must be in the line of the horizontal 
 axis (b) with that on the other side, and similarly in other cases. 
 
 If it were required, as is generally necessary, to complete the 
 form (f . 821) below, it is unnecessary to obtain any new intersec- 
 tion lines, since every line above has its corresponding line oppo- 
 site and parallel to it below. Moreover, in an orthorhombic crys- 
 tal every point above has a corresponding point below on a line 
 parallel to the vertical axis. This, as above, will serve as a control 
 of the accuracy of the work. 
 
 There is another method of drawing complex crystalline forms 
 which has many advantages and is sometimes to be preferred to 
 any other ; it can be explained in a very few words. After the 
 axes have been obtained the diametral prism is constructed upon them. Upon the solid 
 angles of this each plane of the required form is laid off, the edges being taken instead of the 
 
 822 
 
 824 
 
 6 P 
 
 M 
 
 :M 
 
 axes. Suppose that f. 822 repre_sents the diametral prism of an orthorhombic crystal. Here 
 obviously the edge e = 2c, e = 2b, e = 21. The plane 1 (c : b : a) may be laid off on it by 
 taking from the angle a equal portions of the edges , e, e, for instance, conveniently one 
 
ON THE DRAWING OF FIGUEES OF CRYSTALS. 
 
 471 
 
 ialf of each, hence the plane appears as mno. Again the plane 2 (2c : b : a) is laid off by taking 
 :he unit lengths of the edges e (b), and e (a) and twice the unit length of e (c), the plane is 
 then mnb. Again, the plane 4-2 (4 : b : 21) takes the position npb, since ap = 2c, ap = 2 b, 
 and an = a, the ratio of the edges (axes) being the same as in the symbol. So also the plane 
 2-2 (2c : 2b : a) has the position rmo, since ao = c, am = 5, and ar = J, here, too, the 
 ratio of the axes being preserved. By plotting the successive planes of the crystal in this 
 way, each solid angle corresponding to an octant, the direction of the intersection-edges 
 :'or the given f orm are at once obtained. For example, the intersection- edge for 1, and the basal 
 slane, as also for 1 and 2, it is the line mn ; for 1 and 4-2 it is the dotted line joining the common 
 joints )i and a ; for 1 and 2-2 it is the line mo ; for 2 and 4-2, also for 2 and 2-2, it is the line 
 joining the common points a. 
 
 The direction of the required intersection- edges being obtained in this way, they are used 
 ;o construct the crystal itself, being transferred to it in the usual way. In f. 823 they have 
 aeen placed upon the diametral prism, and when this process has been completed for the 
 other angles, and, too, the domes e i', e\ are added, the form in f. 824 results. 
 
 ON THE DRAWING OF TWIN CRYSTALS. 
 
 In order to project a compound or twinned crystal it is generally necessary to obtain first 
 ihe axes of the second individual, or semi -individual, in the position in which they are brought 
 Dy the re volution of 180. This is accomplished in the following manner. In f. 825 a com- 
 pound crystal of staurolite is represented, in which twinning has taken place (1) on an axis 
 normal to f -, and (2) on an axis normal to f-if-. The second, being the more general case, is 
 of the greater importance for the sake of example. In f. 825, cc', bb', aa' represent the rect- 
 angular axes of staurolite (c = 1 '441, b 2'112, d = 1). The twinning-plane f-| (fc : b : $a) 
 
 825 
 
 has the position MNR. It is first necessary to construct a normal from the centre to this 
 plane. If perpendiculars be drawn from the centre to the lines MN, NB, MR, they will meei 
 them at the points x, y< z, dividing eachline into segments proportional to the squares 
 adjacent axes ;* or N* : Ma = ON 2 : OM 2 . In this way the points a?, y, z are fixed, and linei 
 
 * This is true since the axial angles are right angles. In the Monoclinic System two of 
 ihe axial intersections are perpendicular, and they are sufficient to allow of the < 
 tion of the point T, as above. In the Triclinic System the method needs to b< 
 modified. 
 
472 
 
 APPENDIX. 
 
 
 827 
 
 drawn from any two of them to the opposite angles R, N, or M will fix the point T. A line 
 joining T and O is normal to the plane (MNR = f-|). Furthermore, it is obvious that if a 
 revolution of 180 about TO take place, that every point in the plane MNR will remain 
 equally distant from T. Thus, the point M will take the place /*(MT = T^u), the point b the 
 place ft' (NT T'), and so on. The lines joining these points /it, ', #, and the common 
 centre O will be the new axes corresponding to MO, NO, RO. In order 
 to obtain the unit axes corresponding to c, b, a it is merely necessary to 
 draw through c a line parallel to MT,u, meeting /*O at 7, then 707' is the 
 new vertical axis corresponding to cOe , also &Q&' corresponds to bOb', 
 and aOa' corresponds to aOa'. These three axes then are the axes for 
 the second individual in its twinned position ; upon them, in the usual way, 
 the new figure may be constructed and then transferred to its proper 
 position with reference to the normal crystal. 
 
 For the second method of twinning, when the axis is normal to f-2, the 
 construction is more simple. It is obvious the axis is the line O#, and 
 using this, as before, the new axes are found ; /cO/c' corresponds to cOc 
 (sensibly coinciding with bb), since (Mf- 134 21', and so on. 
 
 In many cases the simplest method is to construct first the normal 
 crystal, then draw through its centre the twinning-plane and the axis of 
 revolution, and determine the angular points of the reversed crystal in 
 the principle alluded to above : that by the revolution every point 
 remains at the same distance from the axis, measured in a plane at right 
 angle to the axis. 
 
 Calcite. 
 
 Thus in f. 827 when the scalenohedron has been drawn, since the twinning-plane is the 
 basal plane, each angular point, by the revolution of 180, obtains a position equidistant from 
 this plane and directly below it. In this way each angular point is determined, and the com- 
 pound crystal is completed in a moment. 
 
APPENDIX C. 
 
 CATALOGUE OF AMERICAN LOCALITIES OF MINERALS. 
 
 The following catalogue * may aid the mineralogical tourist in selecting his routes and 
 arranging the plan of his journeys. Only important localities, which have afforded cabinet 
 specimens, are in general included ; and the names of those minerals which have been 
 obtained in good specimens are distinguished by italics, the addition of an exclamation 
 mark (!), or of two (!!), indicates the degree of excellence of the specimens. Many of the 
 localities mentioned have been exhausted, others will now yield good specimens only when 
 further explored with blasting, etc. In general, only those of the localities mentioned can 
 be relied upon as likely to reward the visitor liberally where active work is being continually 
 carried on. 
 
 MAINE. 
 
 ALBANY. Beryl! green and black tourmaline, feldspar, rose quartz, rutile. 
 
 AROOSTOOK. Red hematite. 
 
 AUBURN. Lepidolite, amblygonite (hebronite), green tourmaline. 
 
 BATH. Vesuvianite, garnet* magnetite, graphite. 
 
 BETHEL. Cinnamon garnet, calcite, sphene, beryl, pyroxene, hornblende, epidote, 
 graphite, talc, pyrite, arsenopyrite, magnetite, wad. 
 
 BINGHAM. Massive pyrite, galenite, blende, andalusite. 
 
 BLUE HILL BAY. Arsenical iron, molybdenite! galenite, apatite! fiuorite! black tourma- 
 line (Long Cove), black oxide of manganese (Osgood's farm), rhodonite, bog manganese, 
 wolframite. 
 
 BOWDOIN. Rose quartz. 
 
 BOWUOINUAM. Beryl, molybdenite. 
 
 BRUNSWICK. Green, mica, garnet/ black tourmaline/ molybdenite, epidote, cakite, mua 
 covite, feldspar, beryl. 
 
 BUCKFIELD. Garnet (estates of Waterman and Lowe), iron ore, muscovite! tourmaline! 
 magnetite. 
 
 CAMDAGE FARM. (Near the tide mills), molybdenite, wolframite 
 
 CAMDEN. Made, galenite, epidote, black tourmaline, pyrite, talc, magnetite. 
 
 CARMEL (Penobscot Co.). Stibnite, pyrite, made. 
 
 CORINNA. Pyrite, arsenopyrite. 
 
 DEER ISLE. Serpentine, verd- antique, asbestus, diallage, magnetite. 
 
 DEXTER. Galenite, pyrite, blende, chalcopyrite, green talc. 
 
 DIXFIELD. Native copperas, graphite. 
 
 EAST WOODSTOCK. Muscovite. 
 
 FARMINGTON. (Norton's ledge), pyrite, graphite, bog ore, garnet, staurolite. 
 
 FBEEPORT. Rose quartz, garnet, feldspar, scapolite, graphite, muscomte. 
 
 FRYEBURG. Garnet, beryl. 
 
 GEORGETOWN. (Parker's island), beryl! black tourmaline. 
 
 GREENWOOD. Graphite, black manganese, beryl! arsenopyrite, cassiterite, mica, rose 
 quartz, garnet, corundum, albite, zircon, molybdenite, magnetite, copperas. 
 
 * The catalogue is essentially the same as that published in the 5th Edition of Dana's Sys 
 tern of Mineralogy, 18G8. The names of a considerable number of new localities have been 
 added, however, which have been derived from various printed sources, and also from private 
 contributions from Prof. G. J. Brush, Mr. G. W. Hawes, Mr. J. Willcox, and others. 
 
 See further on pp. 503 to 508. 
 
474 APPENDIX. 
 
 HEBRON. Cassiterite, arsenppyrite, idocrase, lepidolite, amblygonite (Jtebron'te)^ rubettite! 
 indicolite, green tourmaline, mica, beryl, apatite, albite, childrenite, cookeite. 
 
 JEWELL'S ISLAND. -Pyrite. 
 
 KATAHDIN IRON WORKS. Bog-iron ore, pyrite, magnetite, quartz. 
 
 LETTER E, Oxford Co. Staurolite, made, copperas. 
 
 LINN/EUS. Hematite, limonite, pyrite, bog-iron ore. 
 
 LITCHFIELD. Sodalit.e, cancrinite, elceolite, zircon, spodumene, muscovite, pyrrhotite. 
 
 LUBEC LEAD MINES. Galenite, chalc(/pyrite, blende. 
 
 MACHIASPORT. Jaspei\ epidote, laumontite. 
 
 MADAWASKA SETTLEMENTS. Vivianite. 
 
 MINOT. Beryl smoky quartz. 
 
 MONMOUTH. Actinolite, apatite, elceolite, zircon, staurolite, plumose mica, beryl, rutile. 
 
 MT. ABRAHAM. Andalusite, staurolite. 
 
 NORWAY. Chrysoberyl! molybdenite, beryl, rose quartz, orthodase, cinnamon garnet. 
 
 ORR'S ISLAND. Steatite, garnet andalusite. 
 
 OXFORD. Garnet, beryl, apatite, wad, zircon, muscovite, orthoclase. 
 
 PARIS. Green! red! black, and blue tourmaline! mica! lepidolite! feldspar, albite, quartz 
 crystals ! rose quartz, cassiterite, amblygonite, zircon, brookite, beryl, smoky quartz, spodu- 
 mene, cookcite, leucopyrite. 
 
 PARSONSFIELD. Vesucianite ! yellow garnet, par gasite, adularia, scapolite, galenite, blende, 
 chalcopyrite. 
 
 PERU Crystallized pynte. 
 
 PHIPPSBURG. Yellow garnet ! manganesian garjiet, vesuvianite, pargasile, axinite, laumon- 
 tite ! chabazite, an ore of cerium ? 
 
 POLAND. Vesuvianite, smoky quartz, cinnamon garnet. 
 
 PORTLAND. Prehnite, actinolite, garnet, epidote, amethyst, calcite. 
 
 POWNAL. Black tourmaline, feldspar, scapolite, pyrite. actinolite, apatite, rose quartz. 
 
 RAYMOND. Magnetite, scapolite, pyroxene, lepidolite, tremolite, hornblende, epidote, ortho- 
 clase, yellow garnet, pyrite, vesuvianite. 
 
 ROCKLAND. Hematite, tremolite, quartz, wad, talc. 
 
 RUMFORD. Yellow garnet, vesuvianite, pyroxene, apatite, scapolite, graphite. 
 
 RUTLAND. Allanite. 
 
 SANDY RIVER. Auriferous sand. 
 
 SANFORD, York Co. Vesuvianite! albite, calcite, molybdenite, epidote, black tourmaline, 
 labradorite. 
 
 SEARSMONT. Andalusite, tourmaline. 
 
 SOUTH BERWICK. Made. 
 
 STANDISII. Columbite ! 
 
 STREAKED MOUNTAIN. Beryl! black tourmaline, mica, garnet. 
 
 THOMASTON. Calcite, tremolite, hornblende, sphene, arsenical iron (Owl's head), black 
 manganese (Dodge's mountain), thomsonite, talc, blende, pyrite, galenite. 
 
 TOPSHAM. Quartz, galenite, blende, tungstite ? beryl, apatite, molybdenite, columbite. 
 
 UNION. Magnetite, bog-iron ore. 
 
 WALES. Axinite in boulder, alum, copperas. 
 
 WATERVILLE Crystallized pynte. 
 
 WINDHAM (near the bridge).' Slaurolite, spodumene, garnet, beryl, amethyst, cyanite, 
 tourmaline. 
 
 WIN SLOW. Cassiterite. 
 
 WINTHROP. Staurolite, pyrite, hornblende, garnet, copperas. 
 
 WOODSTOCK. Graphite, hematite, prehnite, epidote, calcite. 
 
 YORK. Beryl, vivianite,, oxide of manganese. 
 
 NEW HAMPSHIRE. 
 
 ACWORTH. Beryl!! mica! tourmaline, feldspar, albite, rose quartz, columbite! cyanite, 
 autunite. 
 
 ALSTEAD. Mica! ! albite, black tourmaline, molybdenite, andalusite, staurolite. 
 
 AMHERST. Vesuvianite, yellow garnet, pargasite, calcite, amethyst, magnetite. 
 
 BARTLETT. Magnetite, hematite, brown iron ore in large veins near Jackson (on tl Bald 
 face mountain "), quartz crystals, smoky quartz. 
 
 BATH. Galenite, chalcopyrite. 
 
 BEDFORD. Tremolite, epidote, graphite, mica, tourmaline, alum, quartz. 
 
 BELLOWS FALLS. Cyanite, staurolite, wavellite. 
 
 BBISTOL. Graphite. 
 
AMERICAN LOCALITIES. 475 
 
 C AMPTON. Beryl ! 
 
 CANAAN. Gold in pyrites, garnet. 
 
 CHARLESTON. Staurolite made, andalusite made, bog-iron ore, prehnite, cyanite. 
 
 CORNISH. Stibnite, tetrahedrite, rutile in quartz! (rare), staurolite. 
 
 CROYDEN. lolite ! chalcopyrite, pyrite, pyrrhotite, blonde. 
 
 ENFIELD. Gold, galenite, staurolite, greeu quartz. 
 
 FRANCESTON. Soapstotie, arsenopyrite, quartz crystals. 
 
 FRANCONIA. Hornblende, staurolite ! epidote ! zoisite, hematite, magnetite, black and red 
 manganesian gnrnets, arsenopyrite (danaite], chalcopyrite, molybdenite, prehnite, green 
 quartz, malachite, azurite. 
 
 GILFORD (Gunstock Mt.). Magnetic iron ore, native "loadstone." 
 
 GOSHEN. Graphite, black tourmaline. 
 
 GILMANTOWN. Tremolite, epidote, muscovite, tourmaline, limonite, red and yellow 
 quartz crystals. 
 
 GRAFTON. Mica ! (extensively quarried at Glass Hill, 2m. S. of Orange Summit), albite ' 
 blue, green, and yellow beryls! (1 in. S. of O. Summit), tourmaline, garnets, triphylite, apa- 
 tite, fluorite. 
 
 GRANTHAM. Gray staurolite! 
 
 GROTON. Arsenopyrite, blue beryl, muscovite crystals. 
 
 HANOVER. Garnet, a boulder of quirtz containing rutilc ! black tourmaline, quartz, cya- 
 nite, labradorite, epidote. 
 
 HAVERIIILL. Garnet! arsenopyrite, native arsenic, galenite, blende, pyrite, chalcopy- 
 rite, magnetite, marcasite, steatite. 
 
 HILLSBORO' (Campbel.'s mountain). Graphite. 
 
 HINSDALE. RJiodonite, black oxide of manganese, molybdenite, indicolite, black tour- 
 maline. 
 
 JACKSON. Drusy quartz, tin ore, arsenopyrite, native arsenic, fluorite, apatite, magnetite, 
 molybdenite, wolframite, chalcopyrite, arsenate of iron. 
 
 JAFFREY (Monadnock Mb.). Cyanite, limonite. 
 
 KEENE. Graphite, soapstone, milky quartz, rose quartz. 
 
 LANDAFF. Molybdenite, lead and iron ores. 
 
 LEBANON. Bog-iron ore, arsenopyrite, galenite, magnetite, pyrite. 
 
 LISBON. Staurolite, black and red garnets, granular magnetite, hornblende, epidote, zoisit^ 
 hematite, arsenopyrite, galenite, gold, ankerite. 
 
 LITTLETON. Ankerite, gold, bornite, chalcopyrite. malachite, menaccanite, chlorite. 
 
 LYMAN. Gold, arsenopyrite, ankerite, dolomite, galenite, pyrite, copper, pyrrhotite. 
 
 LYME. Cyanite (N. W. part), black tourmaline, rutile, pyrite, chalcopyrite (E. of E. vil- 
 lage), stibnite, molybdenite, cassiterite. 
 
 MADISON. Galenite, blende, chalcopyrite, limonite. 
 
 MERKTMACK. Rutile! (in gneiss nodules in granite vein). 
 
 MlDDLETOWN. Rutile. 
 
 MONADNOCK MOUNTAIN. Andalusite, hornblende, garnet, graphite, tourmaline, ortho- 
 clase. 
 
 MOOSILAUKE MT. Tourmaline. 
 
 MOULTONBOROUGH (Red Hill). Hornbende, bog ore, pyrite, tourmaline. 
 
 NEWINGTON. Garnet, tourmaline. 
 
 NEW LONDON. Beryl, molybdenite, muscovite crystals. 
 
 NEWPORT. Molybdenite. 
 
 ORANGE. Blue beryl*! Orange Summit, chrysoberyl, mica (W. side of mountain), apatite, 
 galenite, limonite. 
 
 ORFORD. Brown tourmaline (now obtained with difficulty), steatite, rutile, cyanite, brown 
 iron ore, native copper, malachite, galenite, garnet, graphite, molybdenite, pyrrhotite, mela- 
 conite, chalcocite, ripidolite. 
 
 P E LII AM . Steatite. 
 
 PIERMONT. Micaceous iron, barite, green, white, and brown mica, apatite, titanic iron. 
 
 PLYMOUTH. Columbite, beryl. 
 
 RICHMOND. lolite! rutile, steatite, pyrite, anthophyllite, talc. 
 
 RYE. Chiastolite. 
 
 SADDLEBACK MT. Black tourmaline, garnet, spinel. 
 
 SHELBURNE. Galenite, black blende, chalcopyrite, pyrite, pyrolusite. 
 
 SPRINGFIELD. Beryls (very large, eight inches diameter), manganesian garnets! otOM 
 tourmaline ! in mica slate, albite, mica. 
 
 SULLIVAN. Tourmaline (black), in quartz, beryl. 
 
 SURREY. Amethyst, calcite, galenite, limonite, tourmaline. 
 
 SWANZEY (near Keene). Magnetic iron (in masses in granite). 
 
476 
 
 APPENDIX. 
 
 TAMWORTH (near White Pond). Galenite. 
 
 JrfS ( f/ tate f J . aD ?v 3 ^V'-CoPper an d *> Pities, cJforophyttite, green, mica, rod* 
 ated actinohte, garnet, titamferous iron ore, magnetite, tourmaline 
 
 WALPOLE (near BeUows Falls). Made, staurolite, mica, graphite 
 
 WARE. Graphite. 
 
 WAXnHK.Chai&>pyrite, blende, epidote, quartz, pyrite, tremolite, galenite, rutile, talc 
 molybdenite, cinnamon stone ! pyroxene, hornblende, beryl, cyanite, tourmaline (massive) 
 
 W ATERVILLE Labradorite, chrysolite. 
 
 WESTMORELAND (south part). Molybdenite! apatite! blue feldspar, bog manganese (north 
 village), quartz, fiuorite, chalcopyrite, oxide of molybdenum and uranium 
 
 WHITE MTS. (Notch near the " Crawford House"). Green octahedral fluorite quarts 
 crystals, black tourmaline, chiastolite, beryl, calcite, amethyst, ainazonstone. 
 
 W I Li MOT. 
 
 WINCHESTER. Pyrolusite, rhodochrosite, psilomelane, magnetite, granular quartz, spodu- 
 
 VERMONT. 
 
 ADDISON. Iron sand, pyrite. 
 
 ALBURGH. Quartz crystals on calcite, pyrite. 
 
 ATHENS. Steatite, rhomb spar, actinolite, garnet. 
 
 BALTIMORE. Serpentine, pyrite! 
 
 BARNET. Graphite. 
 
 BELVIDERE. --Steatite, chlorite. 
 
 BENNINGTON. Pyrolusite, brown iron ore, pipe clay, yellow ochre 
 
 BERKSHIRE. Epidole, hematite, magnetite. 
 
 BETHEL. ActinoUte! talc, chlorite, octahedral iron, rutile, brown spar in steatite. 
 
 RANDON. Braunite, pyrolusite, psilomelane, limonite, lignite, white clay, statuary 
 marble ; fossil fruits in the lignite, graphite, chalcopyrite. 
 
 BRATTLEBOROUGH. Black tourmaline in quartz, mica, zoisite, rutile, actinolite sea polite 
 spodumene, roofing slate. 
 
 BRIDGEWATER. -Tate, dolomite, magnetite, steatite, chlorite, gold, native copper, blende 
 galenite, blue spinel, chalcopyrite. 
 
 BRISTOL. RutUe, limonite, manganese ores, magnetite. 
 
 BROOKFIELD. Arsenopyrite, pyrite. 
 
 CABOT. Garnet, staurolite, hornblende, albite. 
 
 CASTLETON. Roofing slate, jasper, manganese ores, chlorite. 
 
 CAVENDISH. Garnet, serpentine, talc, steatite, tourmaline, asbestus, tremolite. 
 
 CHESTER. Asbestus, feldspar, chlorite, quartz. 
 f CHITTENDEN. Psilomelane, pyrolusite, brown iron ore, hematite and magnetite, galenite, 
 
 lOlluG. 
 
 COLCHESTER. Brown iron ore, iron sand, jasper, alum. 
 
 CORINTH. Chalcopyrite (has been mined), pyrrhotite, pyrite, rutile, quartz. 
 
 COVENTRY. Rhodonite. 
 
 CRAPTSBURY. Mica in concentric balls, calcite, rutile. 
 
 DERBY. Mica (adamsite). 
 
 DUMMERSTON. Rutile, roofing slate. 
 
 FAIR HAVEN. Roofing slate, pyrite. ' 
 
 FLETCHER. Pyrite, magnetite, acicular tourmaline. 
 
 GRAFTON. The steatite quarry referred to Graf ton is properly in Athens ; quartz, acti- 
 
 GUILFORD. Scapolite, rutile, roofing slate. 
 
 HARTFORD. Calcite, pyrite! cyanite in mica slate, quartz, tourmaline. 
 
 IR ASBURGH . Rhodonite, psilomelane. 
 
 JAY. Chromic iron, serpentine, amianthus, dolomite. 
 
 LOWELL. Picrosmine, amianthus, serpentine, cerolite, talc, chlorite. 
 
 MARLBORO'. Rhomb spar, steatite, garnet, magnetite, chlorite. 
 
 MENDON. Magnetic iron ore. 
 
 MIDDLEBURY. Zircon. 
 
 MIDDLESEX. Rutile ! (exhausted). 
 
 MONKTON. Pyrolusite, brown iron ore, pipe clay, feldspar.. 
 
 MORF-TOWN. Smoky quartz! steatite, talc, wad, rutile, serpentine. 
 
 MORRISTOWN. Galenite. 
 
 MOUNT HOLLY. Asbestus, chlorite. 
 
 NEW FANE. Glassy and axbextiform actinolite, steatite, green quartz (called chrysoprase 
 
AMERICAN LOCALITIES. 477 
 
 t the locality), chalcedony, drusy quartz, garnet, chromic and titanic iron, rhomb par, 
 
 o^nc^- Actinolite. feldspar, brown spar in talc, cyanite, zoisite, chalcopyrite, pyrite. 
 PiTTSFOiiD.- Brown iron ore, manganese ores. 
 PLYMOUTH. Siderite, magnetite, hematite, gold, galemte. 
 PLYMPTON. Massive hornblende. 
 
 PUTNEY. Fluorite, brawn iron ore, rutile, and zoisite, in boulders, staurohte. 
 READING. Glassy 'actinolite in talc. _ 
 READSBORO'. Ulassy actinolite, steatite, hematite 
 RIPTON Brown iron ore, augite in boulders, octahedral pyrite. 
 ROCHESTER. ttutile, hematite cryst., magnetite in chlorite slate. 
 ROCKINGHAM (Bellows Falls). Cyanite, indicolite, feldspar, tourmaline, fluorite, caloite, 
 
 torehuite, staurolite. 
 
 ROXBURY. Dolomite, talc, serpentine, asbestus, quartz. 
 RUTLAND. Magnetite, white marble, hematite, serpentine, pipe clay. 
 SALISBURY. Brown iron ore. 
 SHARON. Quartz crystals, cyanite. 
 SHOREHAM. Pyrite, black marble, calcite. 
 SHREWSBURY. Magnetite and chalcopyrite. 
 STARKSBORO'. Brown iron ore. 
 STIRLING. Chalcopyrite, talc, serpentine. 
 STOCKBRIDGE Arsenopyrite, magnetite. 
 STRAPFORD. -Magnetite and chalcopyrite (has been worked), native copper, hornblende, 
 
 ^HETFORD.-Blende, galenite, cyanite, chrysolite in basalt, pyrrhotite, feldspar, roofing 
 
 TOWNSHENIX ^Actinolite, black mica, talc, steatite, feldspar. 
 
 TR ? -Magnetite, talc, serpentine, picrosmine, amianthus steatite, one mile southeast of 
 village of South Troy, on the farm of Mr. Pierce, east side of Missisco, chromite, zaratite. 
 VERSHIRE Pyrite, chalcopyrite, tourmaline, arsenopyrite, quartz. 
 \V\RDSBOKO'. Zowte, tourmaline, tremohte, hematite. 
 WARREN. Actinolite, magnetite, wad, serpentine. 
 WATERBURY. -Arsenopyrite, chalcopyrite, rutile, quartz, serpentine. 
 WATERVILLE Steatite, actinolite, talc. 
 WEATHERSFIELD. -Steatite, hematite, pyrite, tremohte. 
 WELLS' RIVER. Graphite. 
 WESTFIELD. Steatite, chromite, serpentine. 
 WESTMINSTER. Zoisite in boulders. 
 WINDHAM. lassy actinolite, steatite, garnet, serpentine. 
 WOODBURY. Massive pyrite. 
 WOODSTOCK. Quartz crystals, garnet, zoisite. 
 
 MASSACHUSETTS. 
 
 ALPORD. Galenite, pyrite. 
 
 ATliois.Allanite, fibrolite (?), epidote! babmgtomte ? 
 
 AUBURN. Masonite. 
 
 BARRE. Entile! mica, pyrite, beryl, feldspar, garnet. 
 
 GREAT BARRINGTON. Tremolite. 
 
 BEDFORD. Garnet. 
 
 BELCHERTON. Allanite. 
 
 BERNARDSTON. Magnetite. 
 
 o.- jrtdto, .*, , 
 
 nesite rhomb spar, alianite, yttroceriU! cerium ochre? (on the scapo 
 BoxBOROUen. Scapolite, spinel, garnet, augite, actinolite, apat 
 
 to Warren). lolite, adularia, molybdenite, mica, garnet. 
 garnet/ scapolite, actinoh'te. , Q i TinlifA 
 
 e, laumontite, stilbite, chabazite, quartz crystals, ^elanolite. 
 
 (chelmsfordite), chmdrodite, blu* spinel, amianU 
 quartz. 
 
478 APPENDIX. 
 
 CHESTER. Hornblende, scapolite, zoisite, spodumene, indicolite, apatite, magnetite, chro 
 mite, stilbite, heulandite, analcits and chabazite. At the Emery Mine, Chester Factories. 
 Corundum, margarite, diaspore, epidote, corundophilite, chloritoid, tourmaline, menaccan* 
 ite ! rutile, biotite, indianite ? andesite ? cyanite, amesite. 
 
 CHEST KRFIELD. Blue, green, and red tourmaline, cleavelandite (albite), lepidolite, smofo, 
 quartz, microlite, spodumene, cyanite, apatite, rose beryl, garnet, quartz crystals, stanrolite> 
 cassiterite, columbite, zoisite, uranite, brookite (eumanite), scheelite, anthophyllite, bornite, 
 
 CONWAY. -Pyrolusite, fluorite, zoisite, rutile! ! native alum, galenite. 
 
 CUMMIN GTON. Rhodonite! cummingtonite (hornblende), marcasite, garnet. 
 
 DEDHAM. Asbestus, galeiiite. 
 
 DEERFIELD. Chabazite, heulandite, stilbite, amethyst, carnelian, chalcedony, agate. 
 
 FITCHBDHG (Pearl Hill). Beryl, staurolite! garnets, molybdenite. 
 
 FOXBOROUGH. Pyrite, anthracite. 
 
 FRANKLIN. Amethyst. 
 
 GOSHEN. Mica, albite, spodumene! blue and green tourmaline, beryl, zoisite, smoky quartz, 
 columbite, tin ore, galenite, beryl (goshenite), pihlite (cymatolite). 
 
 GREENFIELD (in sandstone quarry, half mile east of village). Allophane, white and 
 greenish. 
 
 HATFIELD. Barite, yellow quartz crystals, galenite, blende, chalcopyrite. 
 
 HAWLEY. Micaceous iron,, massive pyrite, magnetite, zoisite. 
 
 HEATH. Pyrite, zoisite. 
 
 HINSDALE. Brown iron ore, apatite, zoisite. 
 
 HUBBARDSTON. Massive pyrite. 
 
 LANCASTER. Cyanite, chiastolite! apatite, staurolite, pinite, andalusite. 
 
 LEE. Tremolite! sphene! (east part). 
 
 LENOX. Brown hematite, gibbsite(?) 
 
 LEVERETT. Barite, galenite, blende, chalcopyrite. 
 
 LEYDEN. Zoisite, rutile. 
 
 LITTLEFIELD. Spinel, scapolite, apatite. 
 
 LYNNFIELD. Magnesite on serpentine. 
 
 MARTHA'S VINEYARD. Brown iron ore, amber, selenite, radiated pyrite. 
 
 MENDON. Mica ! chlorite. 
 
 MIDDLEFIELD. Olassy actinolite, rhomb spar, steatite, serpentine, feldspar, drusy quartz, 
 apatite, zoisite, nacrite, chalcedony, talc/ deweylite. 
 
 MILUURY. Vermicidite. 
 
 MONTAGUE. Hematite. 
 
 NEWBURY. Serpentine, chrysotile, epidote, massive garnet, siderite. 
 
 NEWBURYPORT. Serpentine, nemalite, uranite. Argentiferous galenite, tetrahedrite, 
 chalcopyrite, pyrargyrite, etc. 
 
 NEW BRAINTREE. Black tourmaline. 
 
 NORWICH. Apatite! black tourmaline, beryl, spodumene! triphylite (altered), blende, 
 quartz crystals, cassiterite. 
 
 NORTHFIELD. Columbite, fibrolite, cyanite. 
 
 PALMER (Three Rivers). Feldspar, prehnite, calc spar. 
 
 PELHAM. Asbestus, serpentine, quartz crystals, beryl, molybdenite, green hornstone, epidote, 
 amethvst, corundum, vermiculite (pelhamite). 
 
 PLAINFIELD. Cummingtonite,, pyrolutite, rhodonite. 
 
 RICHMOND. Brown iron ore, gibbsite! allophane. 
 
 ROCKPORT. Danalite, cryophyllite,. annite, cyrtoUte (altered zircon), green and white ortJio- 
 dase. 
 
 ROWE. Epidote, talc. 
 
 SOUTH ROYALSTON. Beryl ff (now obtained with great difficulty), mica/ f feldspar/ 
 allanite. Four miles beyond old loc., on farm of Solomon Hey wood, mica / beryl / j eldspar! 
 menaccanite. 
 
 RUSSEL. Schiller spar (diallage ?), mica, serpentine, beryl, galenite, chalcopyrite. 
 
 SALEM. In a boulder, cancrinite, sodalite, elaeolite. 
 
 SAUGUS. Porphyry, jasper. 
 
 SHEFFIELD. Asbestus, pyrite, native alum, pyrolusite, rutile. 
 
 SHELBURNE. Rutile. 
 
 SHUTESBURY (east of Locke's Pond). Molybdenite. 
 
 SOUTHAMPTON. Galenite, cerussite, anglesite, wulfenite, fluorite, barite, pyrite, chalcopy- 
 rite, blende, corneous lead, pyromorphite, stolzite, chrysocolla. 
 
 STERLING. Spodumene, chiastolite, siderite, arsenopyrite, blende, galenite, chalcopyrite. 
 pyrite, sterlingite (damourite). 
 
 STONEHAM. Nephrite. 
 
AMERICAN LOCALITIES. 
 
 STURBRIDGE. Graphite, garnet, apatite, bog ore. 
 
 SWAMPSCOT. Orthite, feldspar. 
 
 TAUNTON (one mile south). Paracolumbite (titanic iron). 
 
 TURNER'S FALLS (Conn. River). Chalcopyrite, prehnite, chlorite, chtorojhaite siderite 
 raalachite, magnetic iron sand, anthracite. 
 
 TYRINGHAM. Pyroxene, scapolite. 
 
 UXBRIDGE. Galenite. 
 
 WARWICK. Massive garnet, radiated black tourmaline, magnetite, beryl, epidote. 
 
 WASHINGTON. Graphite. 
 
 WESTFIELD. Schiller spar (diailage), serpentine, steatite, cyanite, scapolite, actinolite. 
 
 WESTPORD. Andalusite ! 
 
 WEST HAMPTON. Galenite, argentine, pseudomorpJwus quartz. 
 
 WEST SPRINGFIELD. Prehnite, ankerite, satin spar, celestite, bituminous coal. 
 
 WEST STOCKBRIDGE. Hematite, fibrous pyrolusite, siderite. 
 
 WHATELY. Native copper, galenite. 
 
 WILLIAMSBURG. Zoisite, pseudomorphous quartz, apatite, rose and smoky quartz, galeaite 
 pyrolusite, chalcopyrite. 
 
 WILLIAMSTOWN. Cryst. quartz. 
 
 WINDSOR. Zoisite, actinolite, rutile! 
 
 WORCESTER. Arsenopyrite, idocrase, pyroxene, garnet, amianthus, bucholzite, siderite, 
 galenite. 
 
 WORTHTNGTON. Cyanite. 
 
 ZOAR. Bitter spar, talc. 
 
 RHODE ISLAND. 
 
 BRISTOL. Amethyst. 
 
 COVENTRY. Mica, tourmaline. 
 
 CRANSTON. Actinolite in talc, graphite, cyanite, mica, melanterite, bog iron. 
 
 CUMBERLAND. Manganese, epidote, actinolite, garnet, titaniferous iron, magnetite, red 
 hematite, chalcopyrite, bornite, malachite, azurite, calcite, apatite, feldspar, zoisite, mica, 
 quartz crystals, ilvaite. 
 
 DIAMOND HILL. Quartz crystals, hematite. 
 
 FOSTER. Cyanite, hematite. 
 
 GLOUCESTER. Magnetite in chlorite slate, feldspar. 
 
 JOHNSTON. Talc, brown spar, calcite, garnet, epidote, pyrite, hematite, magnetite, chal- 
 copyrite, malachite, azurite. 
 
 LIME ROCK. Calcite crystals, quartz pyrite. 
 
 LINCOLN. Calcite dolomite. 
 
 NATIC. See WARWICK. 
 
 NEWPORT. Serpentine, quartz crystals. 
 
 PORTSMOUTH Anthracite, graphite, asbestus, pyrite, chalcopyrite. 
 
 SMITHFIELD. Dolomite, calcite, bitter spar, siderite, nacrite, serpentine (bowenite), tremo- 
 lite, asbestus, quartz, magnetic iron in chlorite slate, talc! octahedrite, feldspar, beryl. 
 
 VALLEY FALLS. Graphite, pyrite, hematite. 
 
 WARWICK (Natic village). Masonite, garnet, graphite, bog iron ore. 
 
 WESTERLY. Menaccanite. 
 
 Woo NSOCKET. Cyanite . 
 
 CONNECTICUT. 
 
 BEKLIN. Barite, datolite, blende, quartz crystals. 
 
 BOLTON. Staurolite, chaloopyrite . 
 
 BRADLEYVILLE (Litchfield). Laumontite. 
 
 BRISTOL. Chalcocite! chakopyrite, barite, bornite, talc, attophane, pyromorphite, calcify 
 malachite, galenite, quartz. 
 
 BROOKFIELD. Galenite, calamine, blende, spodumene, pyrrhotite. 
 
 CANAAN. Tremolite and white augite! in dolomite, canaanite (massive pyroxene). 
 
 CHATHAM. Arsenopyrite, smaltite, chloanthite (ehathamite), scorodite, niccolite, ueryt, 
 erythrite. 
 
 CHESHIRE. Barite, chalcocite, bornite cryst>, malachite, kaolin, natrclite, prehnite, cba 
 isite, datolite. 
 
 CHESTER. Sillimanite/ zircon, epidote. 
 
480 APPENDIX. 
 
 CORNWALL. Graphite, pyroxene, actinolite, sphene, scapolite. 
 
 D ANBURY. Danburite, oligodase, moonstone, brown tourmaline, orthoclase, pyroxene, 
 parathorite. 
 
 FARMINGTON. Prehnite, chabazite, agate, native copper ; in trap, diabantite. 
 
 GRANBY. Green malachite. 
 
 GREENWICH. Black tourmaline. 
 
 HADDAM. Chrysoberyl ! beryl! epidote! tourmaline! feldspar, garnet! iolite! oligoctage, 
 thlorophyttite ! automolite, magnetite, adularia, apatite, columbite ! (hermannolite), zircon 
 (calyptolite), mica, pyrite, marcasite, molybdenite, allanite, bismuth, bismuth ochre, bismn- 
 tite. 
 
 HADLYME. Chabazite and stilbite in gneiss, with epidote and garnet. 
 
 HARTFORD. Datolite (Rocky Hill quarry). 
 
 KENT. Brown iron ore, pyrolusite, ochrey iron ore. 
 
 LITCHFIELD. Cyanite with corundum, apatite, and andalusite, menaccanite (Washington- 
 ite), chalcopyrite, diaspore, niccoliferous pyrrhotite, margarodite. 
 
 LYME. Garnet, sunstone. 
 
 MERIDEN. Datolite. 
 
 MIDDLEFIELD FALLS. Datolite, chlorite, etc., in amygdaloid. 
 
 MIDDLETOWN. Mica, lepidolitt with green and red tourmaline, albite, feldspar, columbite! 
 prehnite, garnet (sometimes octahedral), beryl, topaz, uranite, apatite, pitchblende ; at lead 
 mine, galenite, chalcopyrite, blende, quartz, calcite, fluorite, pyrite, sometimes capillary. 
 
 MILFORD. Sahlite, pyroxene, asbestus, zoisite, verd-antique, marble, pyrite. 
 
 NEW HAVEN. Serpentine, asbestus, chromic iron, sahlite, stilbite, prehnite, chabazite, 
 gmelinite, apophyllite, topazalite. 
 
 NEWTOWN. Cyanite, diaspore, rutile, damourite, cinnabar. 
 
 NORWICH. Sittimanite, monazite ! zircon, iolite, corundum, feldspar. 
 
 OXFORD, near Humphreys ville. Cyanite, chalcopyrite. 
 
 PLYMOUTH. Galenite, heulandite, fluorite, chlorophyUite ! garnet. 
 
 READING (near the line of Danbury). Pyroxene, garnet. 
 
 ROARING BROOK (Cheshire). Datolite ! calcite, prehnite, saponite. 
 
 ROXBURY. Siderite, blende, pyrite! ! galenite. quartz, chalcopyrite, arsenopyrite, limon- 
 le. 
 
 SALISBURY. Brown iron ore, ochrey iron, pyrolusite, triplite, turgite. 
 
 SAYBKOOK. Molybdenite, stilbite, plumbago. 
 
 SEYMOUR. Native bismuth, arsenopyrite, pyrite. 
 
 STMSBURY. Copper glance, green malachite. 
 
 SOUTHBURY. Rose quartz, laumontite, prehnite, calcite, barite. 
 
 SOUTHINGTON. Barite, datolite, asteriated quartz crystals. 
 
 STAFFORD. Massive pyrites, alum, copperas. 
 
 STONINGTON. Stilbite and chabazite on gneiss. 
 
 TARIFFVILLE. Datolite. 
 
 THATCHERSVILLE (near Bridgeport). Stilbite on gneiss, babingtonite ? 
 
 TOLLAND. Staurolite, massive pyrites. 
 
 TRUMBULL and MONROE. Chlorophane, topaz, beryl, diaspore, pyrrhotite, pyrite, nicco- 
 lite, scheelite, wolframite (pseudomorph of scheelite), rutile, native bismuth, tungstic acid, 
 siderite, mispickel, argentiferous galenite, blende, scapolite, tourmaline, garnet, albite, 
 augite, graphic tellurium (?), margarodite. 
 
 WASHINGTON. Triplite, menaccanite! (washingtonite of Shepard), rhodochrosite, natro- 
 lite, andalusite (New Preston), cyanite. 
 
 WATERTOWN, near the Naugatuck. White sahlite, monazite. 
 
 WEST FARMS. Asbestus. 
 
 WILLIMANTIC. Topaz, monazite, ripidolite. 
 
 WINCHESTER and WILTON. Asbestus, garnet. 
 
 NEW YORK. 
 
 ALBANY CO. BETHLEHEM. Calcite, stalactite, stalagmite, calcareous sinter, snowy 
 gypsum. 
 
 COEYMAN'S LANDING, Gypsum, epsom salt, quartz crystals at Crystal Hill, three milea 
 outh of Albany. 
 
 QUILDERLAND. Petroleum, anthracite, and calcite, on the banks of the Norman's Kill ; 
 two miles south of Albany. 
 
 WATERVLIKT. Quarto crystals^ yellow dnisy quarto. 
 
AMERICAN LOCALITIES. 481 
 
 ULLEGHANY CO. CUBA. Calcareous tula, petroleum, 3* miles from the village. 
 CATT ARAUGUS CO. FREEDOM. Petroleum. 
 
 CAYUGA CO. AUBURN. Celestite, calcite, fluorspar, epsomite. 
 
 CAYUGA LAKE. Sulphur. 
 
 LUDLOWVILLE. Epsomite. 
 
 UNION SPRINGS. Selenite, gypsum. 
 
 SpRWGPORT.-At Thompson's plaster beds, sulphur! selemte. 
 
 SPRINGVILLE. Nitrogen springs. 
 
 CLINTON CO ARNOLD IRON MINE. Magnetite, epidote, molybdenite. 
 FINCH ORE BED.-C&Wfc, green and purple fluor. 
 
 CHATAUQUE CO. FREDONIA. Petroleum, carburetted hydrogen. 
 L AON A. Petroleum. 
 SHERIDAN. Alum. 
 
 COLUMBIA CO. AuOTERLiTE.-2Rir% manganese, wnlfenite, chalcocite ; Livingstor 
 
 m cubic crystals in slate (Hillsdale). 
 . Chalcocite, chalcopyrite. 
 
 eps'om salt, brown spar, wad. 
 DUTCHESS CO AMENIA. Dolomite, Umonite, turgite. 
 
 =:H!^ 
 
 lite hydrous anthophyllite, Umonite. 
 
 NORTH EAST. -Chalcocite, chalcopyrite, galemte, blende. 
 
 H.-', green feldspar, epidote, tourmaline. 
 UNION VALE. At the Clove mine, gibbsite, limomte. 
 
 Sgj^SS|3Sft^^^^ 
 
 epidote, mica. 
 
 , garnet, taMMU, ******, aotinoUte; too miles 
 , **,// ^, magnetite, * 
 
 ; in the toWD 
 
 OT albit; in the toWD 
 
 of Moriah, magnetite, 6tecfc m^a ; Barton Hil Ore Bed atoto. 
 
 Xvwco*LV.-Labr<Mte, feldspar, magnetite, JWfSifiM orawand black pyroxene, 
 -rnef 
 
 . 
 
 PORT HW1.-Brow*1wr^ne,f^, ^^UeJ atCheeve, 
 honiblende, sryst.pyrite, graphite, wollastomte, pyrrhotite, 
 
 , ooccolite. 
 
 W^?' ** k * 
 
 h muende - 
 
 EE1E CO ELLTCOTT'S MILLS. Calcareous tufas. 
 31 
 
482 APPENDIX. 
 
 FRANKLIN CO. CHATEAUGAY. Nitrogen springs, calcareous tufas. 
 MALONE. Massive pyrite, magnetite. 
 
 GENESEE CO. Acid springs containing sulphuric acid. 
 
 GREENE CO. CATSKILL. Calcite. 
 DIAMOND HILL. Quartz crystals. 
 
 HERKIMER CO. F AIRFIELD. --Quart z crystals, fetid barite. 
 
 LITTLE FALLS. Quartz crystals f barite, calcite, anthracite, pearl spar, smoky quarto t 
 >ne mile south of Little Falls, calcite. brown spar, feldspar. 
 MIDDLE VILTK. Quartz crystals! r.alcite, brown and pearl spar, anthracite. 
 NEWPORT. Quartz crystals. 
 
 SALISBURY. Quartz crystals f blende, galenite, pyrite, chalcopyrite. 
 STARK. Fibrous celestite, gypsum. 
 
 HAM [LTON CO. LONG LAKE. Blue calcite. 
 
 JEFFERSON CO. ADAMS. Fluor, calc tufa, barite. 
 
 ALEXANDRIA. On the S.E. bank of Muscolonge Lake, fluorite, phlogopite, chalcopyrite, 
 apatite; on High Island, in the St. Lawrence River, feldspar, tourmaline, hornblende, ortho- 
 clase. celestite. 
 
 ANTWERP. Stirling iron mine, hematite, chalcodite, siderite, miUerite, red hematite, crys 
 taJiized quartz, yellow aragonite, niccolit'erous pyrite, quartz crystals, pyrite ; at Oxbow, col- 
 cite ! porous coralloidal heavy spar ; near Vrooman's lake, calcite ! vesuvianite, phtoffvpite ! 
 pyroxene, sphene, fluorite, pyrite, chalcopyrite ; also feldspar, bog-iron ore, scapolite (farm ol 
 David Eggleson), serpentine, tourmaline (yellow, rare). 
 
 BROWNSVILLE. Celestite in slender crystals, calcite (four miles from Watertown). 
 
 NATURAL BRIDGE. Feldspar, gieseckite! steatite pseudomoj-phous after pyroxene, apatite. 
 
 NEW CONNECTICUT. Sphene, brown phlogopite. 
 
 OMAR. Beryl, feldspar, hematite. 
 
 PHILADELPHIA. Garnets on Indian river, in the village. 
 
 PAMELIA. Agaric mineral, calc tufa. 
 
 PIERREPONT. Tourmaline, sphene, scapolite, hornblende. 
 
 PILLAR POINT. Massice barite (exhausted). 
 
 THERESA. Fluorite, calcite, hematite, hornblende, quartz crystals, serpentine (associated 
 with hematite), celestite, strontianite ; the Muscolonge Lake locality of fluoris exhausted. 
 
 WATERTOWN. Tremolite, agaric mineral, calc tufa, celestite. 
 
 WILNA. One mile north of Natural Bridge, calcite. 
 
 LEWIS CO. DIANA (localities mostly near junction of crystalline and sedimentary rocks, 
 and within two miles of Natural Bridge). Scapolite! wollastonite, green coccolite, feldspar, 
 tremolite, pyroxene ! sphene.! ! mica, quartz crystals, drusy quartz, cryst. pyrite, pyrrhotite. 
 blue calcite, serpentine, renssefaerite, zircon, graphite, chlorite, hematite, bog-iron ore, iron 
 Band, apatite. 
 
 GREIG. Magnetite, pyrite. 
 
 LOWVILLE. Calcite, fluorite, pyrite, galenito, blende, calc tufa. 
 
 MARTINSBIJRGH. Wad, galenite, etc., but mine not now opened, calcite. 
 
 WATSON, BREMEN. Bog-iron ore. 
 
 MONROE CO. ROCHESTER. Pearl spar, calcite, snowy gypsum, fluor, celestite, galenite, 
 blende, barite, hornstone. 
 
 MONTGOMERY CO. CAN A JOH ABIE. Anthracite. 
 
 PALATINE. Quartz crystals, drusy quartz, anthracite, hornstone, agate, garnet. 
 
 ROOT. Drusy quartz, blende, barite, stalactite, stalagmite, galenite, pyrite. 
 
 NEW YORK CO. CORLEAR'S HOOK. Apatite, brown and yellow feldspar, sphene. 
 
 KINGSBRIDGE. Tremolite, pyroxene, mica, tourmaline, pyrites, rutile, dolomite. 
 
 HARLKM. Epidote, apophyilite, stilbite, tourmaline, vivianite, lamellar feldspar, mica. 
 
 NEW YORK. Serpentine, amianthus, actinolite, pyroxene, hydrous anthophyllite, garnet, 
 staurolite, molybdenite, graphite, chlorite, jasper, necronite, feldspar. In the excavations foi 
 tlio 4th Avenue tunnel, 1875, harmotome, stilbite, chabazite, heulandite, etc. 
 
AMERICAN LOCALITIES. 483 
 
 NIAGARA CO. LEWISTON. Epsomite. 
 
 LOCKPORT. Celestite, calcite, selenite, anhydrite, fluonte, dolomite, blende. 
 
 NIAGARA FALLS.- -Calcite, fluorite, blende, dolomite. 
 
 ONEIDA CO. BOONVILLE. Calcite-. wollastonite, coccoUte. 
 
 CLINTON. Blende, lenticular argillaceous iron ore ; in rocks of the Clinton Group, Btronti 
 
 anite, celestite, the former covering the latter. 
 
 OXOXDAGA CO CAMILLUS. Selenite and fibrous gypsum. 
 
 COLD SPRING. Axinite. 
 
 MAN LI us. Gypsum and fluor. 
 
 SYRACUSE. Serpentine, celestite, selenite, bante. 
 
 ORAXGE CO. CORNWALL. Zircon, chondrodite, Jwrnblende, spind, massive feldspar, 
 fibrous epidote, hudsonite, menaccanite, serpentine, coccolite. 
 
 DEER PARK. Cryst. pyrite, galenite. 
 
 MONROE. Mica! sphene ! garnet, colophonite, epidote, chondrodite, allanite, bucholzite, 
 brown spar, spinel, hornblende, talc, menaccanite, pyrrlwtite, pyrite, chromite, graphite, raa- 
 tolyte, moronolite. 
 
 At WILKS and O'NEIL Mine in Monroe. Aragomte, magnetite, dimagnetite (pseud. ?), jen 
 kinsite, asbestus, serpentine, mica, hortonolite. 
 
 At Two PONDS in Monroe. Pyroxene! chondrodite, Jwrnblende, scapohte ! zircon, sphene, 
 
 At GREENWOOD FURNACE in Monroe. Chondrodite, pyroxene ! mica, hornblende, spinel, 
 scapolite, biotite! menaccanite. 
 
 At FOREST OF DEAN. Puroxene, spinel, zircon, scapohte, hornblende. 
 
 TOWN OF WARWICK, WARWICK VILLAGE. Spinel! zircon, serpentine! brown spar, pyrox- 
 ene ' hornblende! pseudomorphous steatite, feldspar ! (Rock Hill), menaccanite, dintomte, 
 tourmaline (R. H.), rutile, sphene, molybdenite, arsenopyrite, marcasite, pyrite, yellow 11 
 uartz iasper, mica, coccolite. 
 
 ' Spinel f garnet, scapolite, hornblende, vesuvianite, epidote! dintomte! magnetite, 
 tourmaline warwickite, apatite, chondrodite, talc! pyroxene! rutile, menaccanite, zircon, 
 corundum, 'feldspar, sphene, calcite, serpentine, schiller spar (?) silvery mica. 
 
 E3ENVILLE Apatite, chondrodite! hair-brown hornblende ! tremolite, spinel, tourmaline, 
 wancickite, pyroxene, sphene, mica, feldspar, mispickel, orpiment, rutile, menaccanite, sc 
 dite, chalcopyrite, leucopyrite (or lollingite), allanite 
 
 WEST POINT. Feldspar, mica, scapolite, sphene, hornblende, allanite. 
 
 PUTXAM CO BREWSTER. Tilly Foster Iron Mine. Ghondrodite! (also humite and olino- 
 humite) crystals very rare, magnetite, dolomite, serpentine pseudomorphs, brucite, enstatite, 
 ripidolite, biotite, actinolite, apatite, pyrrhotite, fluorite, albite, epidote sphene. 
 
 CAHMEL (Brown's quarry ).-Anthophyllite, schiller spar (?), orpiment, arsenopyrite, ept- 
 
 dote. 
 
 COLD SPRING. Chabazite, mica, sphene, epidote. . 
 
 PATTERSON. W/tite pyroxene f calcite, asbestm, trenwlite, dolomite massive pyrite 
 
 PIIILLIPSTOWN Treinolite, amianthm, serpentine, sphene, diopside, green coccohte, n< 
 blende, scapolite, stilbite, mica, laumontite, gurhofite, calcite, magnetite, chroi 
 
 PHILLIPS Ore Bed. Hyalite, actinolite, massive pyrite. 
 
 REXSSELAER CO. Hoosic. Xitrogen springs. 
 LANSINGP.URGH. Epsomite. quartz crystals, pyrite. 
 TROY. Quartz crystals, pyrite, selenite. 
 
 RICHMOND CO. ROSSVILLE. Lignite, cryst. pyrite. 
 QUARANTINE. Asbestus, amianthus, aragonite, dolomite, gurlwjite, 
 ttilc, magnesite. 
 
 ROCKLAND CO. CALDWELL. Calcite. 
 GRASSY POINT. Serpentine, actinolite. 
 , HAVERSTRAW. Hornblende, barite. 
 
 LADENTOWN. Zircon, malachite, cuprite. .iitfl r.yia.bftaite 
 
 PiERMONT.-Datolite, stilbite, apophyllite, strllite, prehmte, thomsomte ; ca ite, CB 
 STONY POINT. Cerolite, lamellar hornblende, asbestus. 
 
484 APPENDIX. 
 
 ST. LAWRENCE CO. CANTON. Massiv . pyrite, calcite, brown tourmaline, sphene, ser- 
 pentine, talc, rensselaerite, pyroxene, hematite, chalcopyrite. 
 
 DEKALB. Hornblende, barite, fluorite, tremolite, tourmaline, blende, graphite, pyroxene, 
 quartz (spongy), serpentine. 
 
 EDWARDS. Brown and silvery mica ! scapolite, apatite, quartz crystals, actinolite, treno- 
 lite! hematite, serpentine, magnetite. 
 
 FINE. Black mica, hornblende. 
 
 FOWLER. Barite, quartz crystals! hematite, blende, galenite, tremolite, chalcedony, bog 
 ore, satin spar (assoc. with serpentine), pyrite, chalcopyrite, actinolite, rensselaerite (neai 
 Somerville). 
 
 GOUVERNEUR. Calcite ! serpentine! hornblende! scapolite! orthockise, tourmaline! ido- 
 crase (one mile south of G-.), pyroxene, malacolite, apatite, rensselaerite, serpentine, sphene, 
 fluorite, barite (farm of Judge Dodge), black mica, phlogopite, tremolite ! asbestus, hematite, 
 graphite, vesuvianite (near Somerville in serpentine), spinel, houghite, scapolite, phlogopite, 
 dolomite ; three-quarters of a mile west of Somerville, chondrodite, spinel ; two miles north 
 of Somerville, apatite, pyrite, brown tourmaline! ! 
 
 HAMMOND. Apatite! zircon! (farm of Mr. Hardy), ortfioclase (loxocase), pargasite, barite, 
 pyrite, purple fluorite, dolomite. 
 
 HERMON. Quartz crystals, hematite, siderite, pargasite, pyroxene, serpentine, tourma- 
 line, bog- iron ore. 
 
 MACOMB. Blende, mica, galenite (on land of James Averil), sphene. 
 
 MINERAL POINT, Morristown. Fluorite, blende, galenite, phlogojMe (Pope's Mills), barite. 
 
 OGDENSBURG. Labradorite. 
 
 PITCAIRN. Satin spar, associated with serpentine. 
 
 POTSDAM. Hornblende! eight miles from Potsdam, on road to Pierrepont, feldspar, 
 i/mrmaline, black mica, hornblende. 
 
 ROSSIE (Iron Mines). Barite, hematite, coralloidal aragonite in mines near Somerville, 
 limonite, quartz (sometimes stalactitic at Parish iron mine), pyrite, pearl spar. 
 
 ROSSIE Lead Mine. Galcite! galenite! pyrite, celestite, chalcopyrite, hematite, cerussite, 
 anglesite, octahedral ' fluor, black phlogopite. 
 
 Elsewhere in ROSSTE. Calcite, barite, quartz crystals, chondrodite (near Yellow Lake), 
 feldspar ! pargasite ! apatite, pyroxene, hornblende, sphene, zircon, mica, fluorite, serpen- 
 tine, automolite, pearl spar, graphite. 
 
 RUSSEL. Pargasite, specular iron, quartz (dodec.), calcite, serpentine, rensselaerite, 
 magnetite. 
 
 SARATOGA CO. GREENFIELD. Chrysoberyl! garnet! tourmaline! mica, feldspar l 
 apatite, graphite, aragonite (in iron mines). 
 
 SCHOHARIE- CO. BALL'S CAVE, and others. Calcite, stalactites. 
 
 CARLISLE. Fibrous barite, cryst. and fib. calcite. 
 
 MIDDLEBURY. Anthracite, calcite. 
 
 SHARON. Calcareous tufa. 
 
 SCHOHARIE. Fibrous celestite, strontianite ! cryst. pyrite! 
 
 SENECA CO. CANOQA. Nitrogen springs. 
 
 SULLIVAN CO. WURTZBORO'. Galenite, blende, pyrite, chalcopyrite. 
 
 TOMPKINS CO ITHACA. Calcareous tufa. 
 
 ULSTER CO. ELLENVILLE. Galenite, blende, chalcopyrite ! quartz, brookite. 
 MARBLETOWN. Pyrite. 
 
 WARREN CO. CALDWELL. Massive feldspar. 
 
 CHESTER. Pyrite, tourmaline, rutile, chalcopyrite. 
 
 DIAMOND ISLE (Lake George). Galcite, quartz crystals. 
 
 GLENN'S FALLS. Rhomb spar. 
 
 JOHNSBURG. Fluorite! zircon! ! graphite, serpentine, pyrite. 
 
 WASHINGTON CO. FORT ANN. Graphite, serpentine. 
 GRANVILLE. LameUar pyroxene, massive feldspar, epidute. 
 
 WAYNE CO. WOLCOTT. Barite. 
 
AMERICAN LOCALITIES. 485 
 
 WESTCHESTFR CO. ANTHONY'S NOSE. Apatite, pyrite, calcite! in very large tabulai 
 crystals, grouped, and sometimes incrusted with drusy quartz. 
 
 DAVENPORT'S NECK. Serpentine, garnet, sphene. 
 
 E A STCIIESTER.- Blende, pyrite, chalcopyrite, dolomite. 
 
 HASTINGS. Tremolite, white pyroxene. 
 
 NEW ROCIIELLE. Serpentine, brucite, quaitz, mica, tremolite, garnet, magnesite. 
 
 PEEKSKILL. Mica, feldspar, hornblende, stilbite, sphene; three miles south, emery. 
 
 R YE Serpentine, chlorite, black tourmaline, tremolite. 
 
 SINGSING. Pyroxene, tremolite, pyrite. beryl, azurite, green malachite, cerussite, pyromor 
 phite, anglesite, vauquelinite, gaJenite, native silver, chalcopyrite. 
 
 WEST FARMS. Apatite, tremolite, garnet, stilbite, heulandite, chabazite, epidote, sphene 
 
 YONKERS Tremolite, apatite, calcite, analcite, pyrite, tourmaline. 
 
 YORKTOWN. Sitttmamte, monazile, magnetite. 
 
 NEW JERSEY. 
 
 ANDOVER IRON MINE (Sussex Co.). Willemite, brown garnet. 
 
 ALLEN TOWN (Monmouth Co.). Vivianite, dufrenite. 
 
 BELVILLE. Copper mines. 
 
 BERGEN. Calcite! datolite! pectolite (called stellite) ! analcite, apophyllite! gmelimte, 
 prehnite, sphene, stilbite, natrolite, heulandite, laumontite, chabazite, pyrite, pseudomorphons 
 steatite, imitative of apophyllite, diabantite. 
 
 BRUNSWICK. Copper mines; native copper, malachite, mountain leather. 
 
 BRYAM. Chondrodite, spinel, at Roseville, epidote. 
 
 CANTWELL'S BRIDGE (Newcastle Co.), three miles west. Vivian ite. 
 
 DANVILLE (Jemmy Jump Ridge). Graphite, chondrodite, augite, mica. 
 
 FLEMINGTON. Copper mines. 
 
 FRANKFORT. Serpentine. v. 
 
 FRANKLIN and STERLING. Spinel! garnet! rhodonite f willemite! frankhnite! zincite! 
 dwluite >' hornblende, tremolite. chondrodite, white scapolite, black tourmaline, epidote, pink 
 calcite 'mica, actinolite, augite, sahlite, coccolite, asbestus, jeffersonite (augite), ealamine, 
 srraphite fluorite, beryl, galenite, serpentine, honey-colored sphene, quartz, chalcedony 
 amethyst zircon, molybdenite, vivianite, tephroite, rhodochrosite, aragonite, sussexite, chal 
 cophanite, roepperite, calcozincite, vanuxemite, gahnite. Also algerite in gran, limestone. 
 
 FRANKLIN and WARWICK MTS. Pyrite. 
 
 GREENBROOK. Copper mines. 
 
 GRIGGSTOWN. Copper mines. 
 
 HAMBURGH One mile north, spinel/ tourmaline, phlogopite, hornblende, hmonite, hematite. 
 
 HOBOKEN. Serpentine (marmolite), brucite, nemalite (or fibrous brucite), aragonite, dol 
 
 mite. 
 
 HURDSTOWN. Apatite, pyrrhotite, magnetite. 
 
 IMLEYTOWN. Vivianite. 
 
 LOCKWOOD. Graphite, chondrodite, talc, augitt, quartz, green spinel. 
 
 MONTVILLE (Morris Co.). Serpentine, chrysotile. 
 
 MULLICA HILL (Gloucester Co. }, Vivianite lining belemnites and other iossils 
 
 NEWTON. Spinel, blue, pink, and white corundum, mica, vesuviamte, hornblende,^ 
 line, scapolite, rutile, pyrite, talc, calcite, barite, pseudomorplwus steatite. 
 
 PATERSON. Datolite. 
 
 VERNON. Serpentine, spinel, hydrotalcite. 
 
 PENNSYLVANIA.* 
 ADAMS CO. GETTYSBURG. Epidote, fibrous and massive. 
 
 BERKS CO -MoRGANTOWN.-At Jones's mines, one mile east of 
 molaMe, native copper, chrytocolla, magnetite, allophane pyrite ^ ch 
 apatite, talc; two miles N.E. from Jones's mine, graphite, sphene; at 
 mile N.W. from St. Mary's. Chester Co., magnetite, micaceous ^on, coccolite brown garnet. 
 
 READiNG.-^/n^^/ quartz crystals, zircon, stilbite, iron ore, near Prv cetown , nw ^ ai a 
 ite, epidote; at Eckhardt's Furnace, allanite with zircon ; at Zion s Church, molybc 
 
 ~* See also the Report on the Mineralogy of Pennsylvania, by Dr. F A. Genth, 187o. 
 
486 APPENDIX. 
 
 near Kutztown, in the Crystal Cave, stalactites ; at Fritz Island, apophyttite, thomsonite, chaba 
 \ite, calcite, azurite, malachite, magnetite, chalcopyrite, stibnite, prochlorite, precious ser 
 pentine. 
 
 BUCKS CO. BUCKINGHAM TOWNSHIP. Crystallized quartz; near New Hope, vesuvian 
 ite, epidote, barite. 
 
 SOUTHAMPTON. Near the village of Feasterville, in the quarry of George Van Arsdale 
 graphite, pyroxene, sahlite, eoccolite, sphcne, green mica, calcite, wollastonite, glassy feid 
 spar sometimes opalescent, phlogopite, blue quartz, garnet, zircon, pyrite. moroxite, scapolite 
 
 NEW BRITAIN. Dolomite, galenite, blende, malachite. 
 
 CARBON CO. SUMMIT HILL, in coal mines. Kaolinite. 
 CHESTER CO. AVONDALE. Asbestus, tremolite, garnet, opal. 
 
 BIRMINGHAM TOWNSHIP. Amethyst, smoky quartz, serpentine, beryl ; in Ab'm Darling 
 ton's lime quarry, calcite. 
 
 EAST BRADFORD. Near Buffington's bridge, on the Brandywine, green, blue, and gra; 
 cyanite, the gray cyanite is found loose in the soil, in crystals ; on the farms of Dr. Elwyn 
 Mrs. Foulke, Wm. Gibbons, and Saml. Entrikin, amethyst. At Strode's mill, asbestus. mag 
 nesite, anthophyllite, epidote, aquacrepitite, oligoclase, drusy quartz, collyritef on Os 
 borne's Hill, wad, manganesian garnet (massive), sphene, schorl ; at Caleb Cope's lime quarry 
 fetid dolomite, necronite, garnets, blue cyanite, yellow actinolite in talc; near the Blacl 
 Horse Inn, indurated talc, rutile ; on Amor Davis' farm, orthite! massive, from a grain t 
 lumps of one pound weight ; near the paper-mill on the Braudywine, zircon, associated wit] 
 titaniferous iron in blue quartz. 
 
 WEST BRADFORD. Near the village of Marshalton, green cyanite, rutile, scapolite, pyrite 
 Btaurolite ; at the Chester County Poor-house limestone quarry, chesterlite ! in crystals ira 
 planted on dolomite, rutile ! in brilliant acicular crystals, which are finely terminated, cal 
 cite in scalenohedrons, zoisite, damouritef in radiated groups of crystals on dolomite, quart 
 crystals ; on Smith & McMullin's farm, epidote. 
 
 CHARLESTOWN. Pyromorphite, wrussite, galenite, quartz. 
 
 COVENTRY. Allanite, near Pughtown. 
 
 SOUTH COVENTRY. In Chrisman's limestone quarry, near Coventry village, augiu 
 sphene, graphite, zircon in iron ore (about half a mile from the village). 
 
 EAST FALLOWFIELD. Soapstone. 
 
 EAST GOSHEN. Serpentine, asbtxtus, magnetite (loadstone), garnet. 
 
 ELK. Menaccanite with muscovite, chromite ; at Lewisville, black tourmaline. 
 
 WEST GOSHEN. On the Barrens, one mile north of West Chester, amianthus, serpentine 
 cellular quartz, jasper, chalcedony, drusy quartz, chlorite, marmolite. indurated talc, mag 
 nesite in radiated crystals on serpentine, hematite, asbestus ; near R. Taylor's mill, chromit 
 in octahedral crystals, deweylite, radiated mag nesite, aragonite, staurolite, garnet, asbestua 
 epidote; zoisite on hornblende at West Chester water- works (not accessible at present). 
 
 NEW GARDEN. At Nivin's limestone quarry, brown tourmaline, necronite, scapolite, apa 
 tite, brown and green mica, rutile, aragonite, fibrolite, kaolinite, tremolite. 
 
 KENNETT. Actinolite, brown tourmaline, browu mica, epidote, tremolite, scapolite, ara 
 gonite ; on Wm. Cloud's farm, sunstone! ! ehabazite, spheue. At Pearce's old-mill, zoisite 
 epidote, sunstone ; sunstone occurs in good specimens at various places in the range of horn 
 blende rocks running through this township from N E. to S.W. 
 
 LOWER OXFORD. Garnets, pyrite in cubic crystals. 
 
 LONDON GROVE. Rutile, jasper, chalcedony (botryoidal), large and rough quartz crystals 
 epidote ; on Wm. Jackson's farm, yellow and black tourmaline, tremolite, rutile, green mica 
 apatite, at Pusey's quarry, rutile, tremolite. 
 
 EAST MARLBORO UGH. On the farm of Baily & Brothers, one mile south of Union ville 
 bright yellow and nearly white tourmaline, chesterlite, albite, pyrite ; near Maryborough meet 
 ing-house, epidote, serpentine, acicular black tourmaline in white quartz; zircon in smal 
 perfect crystals, loose in the soil at Pusey's saw-mill, two miles S.W. of Unionville. 
 
 WEST MARLBOROUGH. Near Logan's quarry, staurolite, cyanite, yellow tourmaline, rutik 
 garnets ; near Doe Run village, hemati'e, scapolite, tremolite ; in R. Baily's limestone quarry 
 two and a half miles S.W. of Unionville, fibrous tremolite, cyanite, scapolite. 
 
 NEWLIN. On the serpentine barrens, one and a half mile N.E. of Unionville, corundum 
 massive and crystallized, also in crystals in albite, often in loose crystals covered with a thi 
 coating of steatite, spinel (black), talc, picrolite, brucite, green tourmaline with flat pyram 
 idol terminations in albite, unionite (rare) euphyUite* mica in hexagonal crystals, fddspat 
 
AMERICAN LOCALITIES. 
 
 487 
 
 beryl! in hexagonal crystals, one of which weighs 51 Ibs., pyrite in c,-bic crystals, chromic 
 iron, drusy quartz, green quartz, actinolite, emerylite, chloritoid, diallage, oligoclitse ou 
 Johnson Patterson's farm, massive corundum, titaniferous iron, clinochlore, emerylitf 
 
 crystals in the euphyllite, orthoclase; two miles N. of Unionville, magnetite in octahedral 
 crystals; one mile E. of Unionville, hematite; in Edwards's old limestone quarry, purple 
 fluorite, rutile. 
 
 EAST NOTTINGHAM. Sand chrome, asbestus, chromite in octahedral crystals, hallite, beryl. 
 
 WEST NOTTINGHAM. At Scott's chrome mine, chromite, foliated talc, marmolite, serpeu 
 tine, chalcedony, rJwdochrome ; near Moro Phillip's chrome mine, asbextus ; at the magnesia 
 quarry, detceylite, marmolite, magnesite, leelite, serpentine, sand chrome; near Fremont 
 P.O., corundum. 
 
 EAST PIKELAND. Iron ore. 
 
 WEST PIKELAND. In the iron mines near Chester Springs, gitjbsite, zircon, turgite, hesna 
 tite (stalactitical and in geodes), gothite. 
 
 PENN. Garnets, agalmatolite. 
 
 PENNSBURY. On John Craig's farm, brown garnets, mica; on J. Dil worth's farm, near 
 Fairville, Muscovite! in hexagonal prisms from one-quarter to seven inches in diameter ; in 
 the village of Fairville, sunstone ; near Brinton's ford, on the Brandy wine, chondroditf, sphene t 
 diopside. aufjite. coccolite ; at MendenhalTs old limestone quarry, fetid quartz, sunstone ; at 
 Swain's quarry, crystals of orthoclase. 
 
 POCOPSON. On the farms of John Entrikin and Jos. B. Darlington, amethyst. 
 
 SADSBURY. Rutile! ! splendid geniculated crystals are found loose in the soil for seven 
 miles along the valley, and particularly near the village of Parkesburg, where they sometimes 
 occur weighing one pound, doubly geniculated arid of a deep red color; near Sadsbury village, 
 amethyst, tourmaline, epidote, milk quartz. 
 
 SCHUYLKILL. In the railroad tunnel at PIIOZNIXVILLE, dolomite! sometimes coated with 
 pyrite, quartz crystals, yellow blende, bro>Aite, calcite in hexagonal crystals enclosing pyrile ; 
 at the WHEATLEY, BROOKDALE, and CHESTER COUNTY LEAD MINKS, one and a half mile 
 S. of Phcenixville, pyromorphite! cerussite! galenite, angleite! ! quartz crystals, chalcopy- 
 rite, barite, fluorite (white), stolzite, wulfenite! calcimine, vanadinite, blende! mimetite! 
 descloizite, gothite, chrysocolla, native copper, malachite, azurite, limonite, calcite, sulphur, 
 pyrite, melaconite, pseudomalachite, gersdorffite, chalcocite? covellite. 
 
 THORNBDRY. On Jos. H. Brinton's farm, muscovite containing acicular crystals of tour- 
 maline, rutile, titaniferous iron. 
 
 TREDYFFRIN. Pyrite in cubic crystals loose in the soil. 
 
 UwcnLAN. Massive blue quartz, graphite. 
 
 WARREN. Melanite, feldspar. 
 
 WEST G-OSHEN (one mile from West Chester). Chromite. 
 
 WILLISTOWN. Magnetite, chromite, actinolite, asbestus. 
 
 WEST-TOWN. On the serpentine rocks, 3 miles S. of West Chester, clinocJilore ! jeffermte! 
 mica, asbestus, actinolite, magnesite, talc, titaniferous iron, magnetite and massive tourma- 
 line. 
 
 EAST WHITELAND. Pyrite, in very perfect cubic crystals, is found on nearly every farm 
 in this township, quartz crystals found loose in the soil. 
 
 WEST WHITELAND. At Gen. Trimble's iron mine (south-east), stalactitic hematite! 
 wavellite ! ! in radiated stalactites, gibbsite, coeruleolactile. 
 
 WARWICK. At the Elizabeth mine and Keim's old iron mine adjoining, one mile JN. ol 
 Knauertown, aplome garnet! in brilliant dodecahedrons. Jto*fcrri, pyroxene, micaceous liemo- 
 tite, pyrite in bright octahedral crystals in calcite, chrysocolla, chalcopyrite massive 
 single tetrahedral crystals, magnetite, fasciailar hornblende! bornite, malachite, brown 9 ( "'^ 
 calcite, byssolite! serpentine; near the village of St. Mary's, magnetite in dodecahedra 
 crystals, melanite, garnet, actinolite in small radiated nodulea ; at the Hopewell iron n me, 
 one mile N.W. of St. Mary's, magnetite in octahedral crystals. 
 
 COLUMBIA CO. At Webb's mine, yellow blende in calcite ; near Bloomburg, cryst. mag 
 netite. 
 
 DAUPHIN CO. NEAR HUMMERSTOWN. Green garnets, cryst. smoky quartz, feldspar. 
 
 DELAWARE CO. ASTON TOWNSHIP. Amethyst, corundum, emerylite 
 lite, black tourmaline, margarite, sunstone, asbestus, anthophyllite, steatite- 
 mill, garnet, staurolite ; at Peter's mill-dam in the creek, pyrope garnet. 
 
488 APPENDIX. 
 
 BIRMINGHAM. Fibrolite, kaolin (abundant), crystals of rutile, amethyst; at Bullock's old 
 quarry, zircon, bucJwlzite, nacrite, yellow crystallized quartz, feldspar. 
 
 BLUE HILL. Green quartz crystals, spinel. 
 
 CHESTER. Amethyst , black tourmaline, beryl, crystals of feldspar, garnet, cryst. pyrite, 
 molybdenite, molybdite, chalcopyrite, kaolin, uraninite, muscocite, orthoclase, bismutite. 
 
 CHICIIESTER. Near Trainer's mill-dam, beryl, tourmaline, crystals of feldspar, kaolin; on 
 Wm. Eyre's farm, tourmaline. 
 
 CONCORD. Crystals of mica, crystals of feldspar, kaolin abundant, drusy quartz of a bluf 
 and green color, meerschaum, stellated tremolite, some of the rays 6| in. diameter, antho- 
 phyttite, fibrolite, acicular crystals of rutile, pyrope in quartz, amethyst, actinolite, mangane- 
 sian garnet, be>yl : in Green's creek, pyrope ganiet. 
 
 DARBY. Blue and gray cyanite, garnet, staurolite, zoisite, quartz, beryl, chlorite, mica, 
 limonite. 
 
 EDGEMONT. Amethyst, oxide of manganese, crystals of feldspar ; one mile east of Edge 
 mont Hall, rutile in quartz. 
 
 ( GREEN'S CREEK. Garnet (so-called pyrope). 
 
 HAVERPORD. Staurolite with garnet. 
 
 MAUPLE. Tourmaline, andalusite, amethyst, actinolite, antJiophyllite, talc, radiated actin- 
 olite in talc, chromite, drusy quartz, beryl, cryst. pyrite, menac&aniie in quartz, chlorite. 
 
 MIDDLETOWN. Amethyst, beryl, black mica, mica with reticulated magnetite between the 
 plates, manganesian garnets ! large trapezohedral crysials, some 3 in. in diameter, indurated 
 talc, hexagonal crystals of rutile, crystals of mica, green quartz! anthophylhte, radiated tour- 
 maline, staurolite, titanic iron, fibrolite, serpentine ; at Lenni, chlorite, gieen and bronze 
 vermiculite ! green feldspar ; at Mineral Hill, fine crystals of corundum, one of which weighs 
 1 lb., actinolite in great variety, bronzite, green feldspar, moonstone, sunstone, graphic 
 granite, magnesite, octahedral crystals of chromite in great quantity, beryl, chalcedony, 
 asbestus, fibrous Jiornblende, rutile, staurolite, melanosiderite, hallite ; at Painter's Farm, 
 near Dismal Run, zircon wiih oligoclase, tremolite^ tourmaline ; at the Black Horse, near 
 Media, corundum ; at Hibbard's Farm and at Fairlamb's Hill, chromite in brilliant octahe- 
 drons. 
 
 NEWTOWN. Serpentine, hematite, enstatite, tremolite. 
 
 UPPER PROVIDENCE. AnthophyUite, tremolite, radiated asbe.stus, rad>ated actinolite, tour- 
 maline, beryl, green feldspar, amethyst (one found on Morgan Hunter's farm weighing over 7 
 Ibs.), andalusite ! (one terminated crystal found on the farm of Jas. Worrall weighs 7.? Ibs.) ; 
 at Blue Hill, very fine crystals of blue quartz in chlorite, amianthus in serpentine, zircon. 
 
 LOWER PROVIDENCE. Amethyst, green mica, garnet, large crystals of feldspar/ (some 
 over 100 Ibs. in weight). 
 
 RADNOR. Garnet, marmolite, deweylite, chromite, asbestus, magnesite, talc, blue quartz, 
 picrolite, limonite, magnetite. 
 
 SPRINGFIELD. Andalusite, tourmaline, beryl, titanic iron, garnet; on Fell's Laurel Hill, 
 beryl, garnet ; near Beattie's mill, staurolite, apatite ; near Lewis's paper-mill, tourmaline, 
 mica. 
 
 THORNBURY. Amethyst. 
 
 HUNTINGDON CO. NEAR FRANKSTOWN. In the bed of a stream and on the side of a 
 hill, fibrous celeslite (abundant), quartz crystals. 
 
 LANCASTER CO. DRUMORE TOWNSHIP Quartz crystals. 
 
 FULTON. At Wood's chrome mine, near the village of Texas, brucite ! ! zaratite (emerald 
 nickel), pennite! ripidolitc! kdmmererite! baltimorite, chromic iron, williamsite, chrysolite! 
 marmolite, picrolite, hydromagnesite, dolomite, magnesite, arayonite, calcite, serpentine, 
 hematite, menaccanite, genthite, chrome-garnet, bronzite, millerite ; at Low's mine, hydro- 
 ma.gnesite, brucite (lancasterite), picrolite, magnesite, williamsite, chromic iron, ta'c, zaratite, 
 baltimorite, serpentine, hematite ; on M. Boice's farm, one mile N.W. of the village, pyritt 
 in cubes and various modifications, anthophyllite ; near Rock Springs, chalcedony, carnelian, 
 m<>ss agate, green tourmaline in talc, titanic iron, chromite, octahedral magnetite in chlorite ; 
 at Reynolds's old mine, calcite, talc, picrolite, cliromite. ; at Carter's chrome mine, brookite. 
 
 GAP MINES. Chalcopyrite, pyrrhotite (niccoliferous), millerite in botryoidal radiations, 
 vfciartiff f (rare), actinolite, siderite, hisingerite, pyrite. 
 
 PEQUEA VALLEY. Eight miles south of Lancaster, argentiferous galenite (said to contain 
 250 to oOO ounces of silver to the ton ?), vauqueliriile, rutile at Pequea mine ; four miles N.W. 
 of Lancaster, on the Lancaster and Harrissburg Railroa^, calimite, galenite, blende ; pyrite in 
 cubic crystals is found in great abundance near the city of Lancaster ; at the Lancaster zinc 
 mines, calamine, blende, tennantite? sriithsonite (pseud, of dolomite), aurichalcite. 
 
AMERICAN LOCALITIES. 489 
 
 LEBANON CO. CORNWALL. Magnetite, pyrite (cobaltiferous), chalcopyrite, native cop- 
 ver azurite malachite, chrysocolla, cuprite (hydrocuprite), attophane, brochantite, serpentine, 
 quartz pseudomorphs ; galenite (with octahedral cleavage), fluorite, covellite, hema:ite (mi 
 caceous), opal, asbestus. 
 
 LEHIGH CO _ FRIEDENSVILLE. At the zinc mines, salamine, smithsonite, hydrozincite, 
 massive blende greenockite, quartz, allophane, zinciferous clay, mountain leather, aragonite, 
 sauconite near Allentown, magnetite, pipe-iron ore ; near Bethlehem, on S. Mountain, 
 alianite, with zircon and altered sphene in a single isolated mass of syenite, magnetite, mar- 
 tite, black spinel, tourmaline, chalcocite. 
 
 MIFFLIN CO. Strontianite. 
 
 MONROE CO. In CHERRY VALLEY. Calcite, chalcedony, quartz; in Poconac Valley, 
 near Judge Mervine's, cryst. quartz. 
 
 MONTGOMERY CO. CONSIIOIIOCKEN. Fibrous tourmaline, menaccanite, aventurine 
 auartz phyllite- in the quarry of Geo. Bullock, calcite in hexagonal prisms, aragonite. 
 
 LOWER PROVIDENCE. At the Perkiomen lead and copper mines, near the village of 
 Shannonville, azurite, blende, gaknite, pyromorphite, cerussite, wulfenite, anglesite bante, 
 calamine chalcopyrite, malachite, chrysocolla, brown spar, cuprite, covellite (rare), m 
 
 iron mine, five and a half miles from Spnng Mills 
 limonite in geodes and stalactites, gdthite, pyrolusite, wad lepidocro cite ; at Edge Hill IS reet 
 North Pennsylvania Railroad, titanic iron, braumte, pyrolusite; one mile b.W. ot Hitnera 
 Son mine Umonite, velvety, stalactitic, and fibrous, fibres three inches long, turgite </^to, 
 pyrolusite velvet manganese, wad ; near Marble Hall, at Hitner's marble quarry, white mar- 
 We granular barite, resembling marble; at Spring Mills, limonite, pyrolusite, guthite , ; at 
 Flat Rock Tunnel, opposite Manayunk, stilbite, heulandite, chabasite, ilvaite, beryl, feldspar, 
 
 "" 
 
 "LAFAYETTE, at the Soapstone quarries.-Talc, jefferisite, garnet, albite 
 etaurolite, chalcopyrite ; at Rose's Serpentine quarry, opposite Lafayette, enste ite, serper 
 tine. 
 
 NORTHUMBERLAND CO. Opposite SELIM'S GROVE. Calamine. 
 
 NORTHAMPTON CO.-BusHKiLL TOWNSHIP. -Crystal Spring on Blue Mountain, quart* 
 / (exhausted), nephrite, coccolite, tremolite, pyroxene, sahlite, 
 in geodes in limonite beds, gothite (lepidocrocite) at 
 
 Glendon. 
 
 PHILADELPHIA CO.-FRANKPORD.-Titanite i 
 Trenton and Connecting Railroad, busanite ; ab the ^quarries on 
 molybdenite, hornblende ; on the Connecting Railroad, wad, earthy cobalt , at 
 magnetite, green mica, chalcopyrite, fluorite - W n 
 
 FAIRMOUNT WATER WORKS. -In the quarnes opposite ^^ 
 crystals otfddpar, beryl, pseudomorphs after bery , tourma line, 
 
 GORGAS' and CREASE'S Lane. -Tourmaline cyanite staurohte, horasto^. tourmaline) 
 
 Near GERMANTOWN. Slack tourmaline, laumontite, apatite, i 
 
 HESTONVILLE. Alunogen, iron alum, orthoclase. 
 
 HEFT'S MILL. -Alunogen, tourmaline, cyanite titamte chlorite, vermicu- 
 
 MANAYDNK.-At the soapstone quarries above Manayunk o,Wi"^ 
 lite, anthophyllite, staurolite, dolomite, apatite, Asbestus, brown -*^W*^ mica , ir0 n gar- 
 
 MEAGARGEE'S Paper-mill. Staurolite, titanic iron, hyalite, apat 
 nets in great abundance. . ^.fij^ff natroltte, heulan- 
 
 McKiNNEY's Quarry, on Rittenhouse Lane. -Feldspar, apatite, stit 
 dite, epidote, hornblende, erubescite, malachite. muscovite, tourmaline, pro- 
 
 SCIIUYLKILL FALLS. Chabazite, titamte, fluorite, epidote, n 
 
 SCHUYLKILL CO. TAMAQUA, near POTTSVILLE, in coal raiaea.Kaokwte. 
 YORK CO. Bornite, rutile in slender prisms in granular quartz, calcite. 
 
490 APPENDIX. 
 
 DELAWARE. 
 
 NEWCASTLE CO. BRANDYWINE SPRINGS. Bacholzite, fibrolite abundant, sahlite, pyrox 
 ene ; Brandy wine Hundred, muscovite, enclosing reticulated magnetite. 
 
 DIXON'S FELDSPAR QUARRIES, six miles N. W. of Wilmington (these quarries have beer 
 worked for the manufacture of porcelain). Adularia, albite, oligodase, beryl, apatite, cinna- 
 mon-Atone! ! (both granular like that from Ceylon, and crystallized, rare), mugnesite, serpen- 
 tine, asbestus, black tourmaline! (rare), indicolite! (rare), sphene in pyroxene, cyanite. 
 
 DUPONT'S POWDER MILLS. " Hypersthene. " 
 
 EASTBURN'S LIMESTONE QUARRIES, near the Pennsylvania line. Tremolite, bronzite. 
 
 QUARRYVILLE. Garnet, spoduaiene, fibrolite. 
 
 Near NEWARK, on the railroad. Sphaerosiderite on drusy quartz, jasper (ferruginous opal), 
 cryst. spathic iron in the cavities of cellular quartz. 
 
 WAY'S QUARRY, two miles south of Centreville. Feldspar in fine cleavage masses, apatite, 
 mica, deweylite, granular quartz. 
 
 WILMINGTON. In Christiana quarries, metattoidal diallage. 
 
 KENNETT TURNPIKE, near Centreville. Cyanite and garnet. 
 
 HARFORD CO. Cerolite. 
 
 KENT CO. Near MIDDLETOWN, in Wm. Folk's marl pits. Vivianite! 
 On CHESAPEAKE AND DELAWARE CANAL. Retinasphalt, pyrite, amber. 
 
 SUSSEX CO. Near CAPE HENLOPEN Vivianite. 
 
 MARYLAND. 
 
 BALTIMORE (Jones's Falls, If mile from B.). Chabazite (haydenite), heulai dite (beau 
 montite of Levy), pyrite, lenticular carbonate of iron, mica, stilbite. 
 
 Sixteen miles from Baltimore, on the Gunpowder. Graphite. 
 
 Twenty-three miles from B., on the Gunpowder. Talc. 
 
 Twenty -five miles from B., on the Gunpowder. Magnetite, sphene, pycnite. 
 
 Thirty miles from B. , in Montgomery Co., on farm of S. Eliot. Gold in quartz. 
 
 Eight to twenty miles north of B., in limestone. Tremolite, augite, pyrite, brown and yel 
 low tourmaline. 
 
 Fifteen miles north of B. Sky-blue chalcedony in granular limestone. 
 
 Eighteen miles north of B., at Scott's mills. Magnetite, cyanite. 
 
 BARE HILLS. Chromite. asbestus, tremolite, talc, hornblende, serpentine, chalcedony, 
 meerschaum, baltimorite, chalcopyrite, magnetite. 
 
 CAPE SABLE, near Magothy R. Amber, pyrite, alum slate. 
 
 CARROLL Co. Near Sykesville, Liberty Mines, gold, magnetite, pyrite (octahedrons), chal- 
 copyrite, linnaeite (carrollite) ; at Patapsco Mines, near Finksburg. bornite, malachite, siegen- 
 ite, linnceite. remingtonite, magnetite, chalcopyrite ; at Mineral Hill mine, bornite, chalcopy- 
 rite, ore of nickel (see above), gold, magnetite. 
 
 CECIL Co., north part. Chromite in serpentine. 
 
 COOPTOWN. Harford Co. Olive -colored tourmaline, diallage, talc of green, blue, and rose 
 colors, ligniform asbextus, chromite, serpentine. 
 
 DEER CREEK. Magnetite! in chlorite slate. 
 
 FREDERICK Co. Old Liberty mine, near Liberty Town, black copper, malachite, chalco- 
 cite, specular iron ; at Dollyhyde mine, bornite, chalcopyrite, pyrite, argentiferous galeuite iu 
 dolomite. 
 
 MONTGOMERY Co. Oxide of manganese. 
 
 SOMERSET and WORCESTER Cos., north part. Bog-iron ore, mvianite. 
 
 ST. MARY'S RIVER. Gypsum! in clay. 
 
 PVLESVILLE, Harford Co. Asbestus mine. 
 
 VIRGINIA AND DISTRICT OF COLUMBIA. 
 
 ALBEMARLE Co., a little west of the Green Mts. Steatite, graphite, galenite. 
 AMUERST Co., along the west base of Buffalo ridge. Copper ores, allanite. etc. 
 AUGUSTA Co. At Weyer's (or Weir's) cave, sixteen railes northeast of Staunton, aotf 
 eighty-one miles northwest of Richmond, calcite, stalactites. 
 
AMERICAN LOCALITIES 
 
 BUCKINGHAM Co. Gold at Garnett and Moseley mines, also, pyrite, pyrrhotite calcite 
 garnet ; at Eldridge mine (now London and Virginia mines) near by, and the Buckingham' 
 mines near Maysville, gold, auriferous pyrite, chalcopyrite, tennantite, barite; cyanite* 'tour- 
 maline, actinolite. 
 
 CHESTERFIELD Co. Near this and Richmond Co. bituminous coal native coke 
 
 CULPEPPER Co., on Rapidan river. Gold, pyrite. 
 
 FRANKLIN Co. Grayish steatite. 
 
 FAUQUIER Co., Barnett's mills. Asbestus, gold mines, barite, calcite. 
 
 FLUVANNA Co. Gold at Stockton's mine ; also tetradymite at " Tellurium mine." 
 
 PHENIX Copper mines. Chalcopyrite, etc. 
 
 GEORGETOWN, D. C. Rutile. 
 
 GOOCHLAND Co. Gold mines (Moss and Busby's). 
 
 HARPER'S FERRY, on both sides of the Potomac. Thuringite (owenite) with quartz. 
 
 JEFFERSON Co., at Shepherdstown. - Fluor. 
 
 KENAWHA Co. At Kenawha, petroleum, brine springs, cannel coal. 
 
 LOUDON Co. Tabular quartz, drase, pyrite. talc, chlorite, soapstone, asbestus, chromite, 
 actinolite, quartz crystals ; micaceous iron, bornite, malachite, epidote, near Leesburg (Poto- 
 mac mine). 
 
 LOUISA Co. Walton gold mine, gold, pyrite, chalcopyrite, argentiferous galenite, siderite, 
 blende, anglesite ; boulangerite, blende (at Tinder's mine). 
 
 NELSON Co. Galeuite, chalcopyrite, malachite. 
 
 ORANGE Co. Western part, Blue Ridge, specular iron; gold at the Orange Grove and 
 Vaucluse gold mines, worked by the " Freehold" and u Liberty" Mining Companies. 
 
 ROCKBRIDGE Co. , three miles southwest of Lexington. Barite. 
 
 SHENANDOAH Co., near Woodstock. Fluorite. 
 
 MT. ALTO, Blua Ridge. Argillaceous iron ore. 
 
 SPOTTSYLVANIA Co., two miles northeast of Chancellorville. Cyanite ; gold mines at the 
 junction of the Rappahannock and Rapidan ; on the Rappahannock (Marshall mine) ; White- 
 hall mine, affording also tetradymite. 
 
 STAFFORD Co. , eight or ten miles from Falmouth Micaceous iron, gold, tetradymite, sil- 
 ver, galenite, vivianite. 
 
 WASHINGTON Co., eighteen miles from Abington. Rock salt with gypsum. 
 
 WYTHE Co. (Austin's mines). Cerussite, minium, plumbic ochre, blende, calamine, galenite, 
 graphite. 
 
 On the Potomac, twenty-five miles north of Washington city. Native sulphur in gray 
 compact limestone. 
 
 NORTH CAROLINA. 
 
 ASHE Co. Malachite, chalcopyrite. 
 
 BUNCOMBE Co., (now called Madison Co). Corundum (from a boulder), margarite, coran- 
 dophilite, garnet, chromite, barite, fl uo rite, rutile, iron ores, manganese, zircon; at Swan- 
 nanoa Gap, cyanite. 
 
 BURKE Co. Gold, monazite, zircon, beryl, corundum, garnet, sphene, graphite, iron ores, 
 tetradymite, montanite. 
 
 CABARRUS Co. Phenix Mine, gold, barite. cfialcopyrite, auriferous pyrite, quartz, pseudo- 
 morph after barite, tetradymite, montanite ; Pioneer mines, gold, limonite, pyrolusite, barn,- 
 hardite, wolfram, ^cheelite, cuprotungstite, tungstite, diamond, chrysocolla, chalcocite, molyb- 
 denite, chalcopyrite, pyrite ; White mine, needle ore, chalcopyrite. barite ; Long and Muse's 
 mine, argentiferous galenite, pyrite, chalcopyrite, limonite; Boger mine, tetradymite; Fink 
 mine, valuable copper ores ; Mt. Makins, tetrahedrite, magnetite, talc, blende, pyrite, proup 
 tite, galenite ; Bangle mine, scheelite. 
 
 CALDWELL Co. Chromite. 
 
 CHATHAM Co. Mineral coal, pyrite, chloritoid. 
 
 CHEROKEE Co. Iron ores, gold, galenite, corundum, rutile, cyanite, damonite. 
 
 CLEVELAND Co. White Plaius, quartz, crystals, smoky quartz, tourmaline, rutile in quartz. 
 
 CLAY Co. At the Cullakenee Mine and elsewhere, corundum (pink), zoisite, tourmaline, 
 margarite, willcoxite, dudleyite. 
 
 DAVIDSON Co. King's, now Washington mine, native, silver, cerussite, anglesite, scheel 
 j.yromorphite, galenite, blende, malachite, black copper, wavelUte, garnet, stilbite ; five mile 
 from Washington mine, on Faust's farm, gold, tetradymite, oxide of bismuth and tellurium, 
 montanite, chalcopyrite, limonite, spathic iron, epidote ; near Squire Ward's, golc 
 tals, electrum. 
 
 FRANKLIN Co. At Partiss mine, diamonds. 
 
 GASTON Co. Iron ores, corundum, margarite ; near Crowder's Mountain (in what was 
 
492 APPENDIX. 
 
 formerly Lincoln Co.), lazuUte, cyanite, garnet, graphite ; also twenty miles northeast, ueai 
 south end of Clubb's Mtn., lazulite, cyanite, talc, rutile, topaz, pyrophyllite ; King's Moun- 
 tain (or Briggs; Mine, native tellurium, altaite, tedradymite, montanite. 
 
 GUILFORD Co. McCulloch copper and gold mine, twelve miles from Greensboro', gold, 
 pyrite, dial copy rite (worked for copper), quartz, siderite. The North Carolina Copper Co. are 
 working the copper ore at the old Fentress mine ; at Deep River, compact pyrophyllitt 
 (worked for slate-pencils). 
 
 HAYWOOD Co. Corundum, margarite, damourite. 
 
 HENDERSON Co. Zircon, sphene (xanthitane). 
 
 JACKSON Co. Alunogen? at Smoky Mt.; at Webster, serpentine, chromite, genthite, 
 Chrysolite, talc; Hoghalt Mt., pink corundum, margarite, tourmaline. 
 
 LINCOLN Co. Diamond ; at Randleman's, amethyst, rose quartz. 
 
 MACON Co. Franklin, Culsagee Mine, corundum* spinel, diaspore, tourmaline, damourite, 
 prochlorite, culsageeite, kerrite, maconite. 
 
 MCDOWELL Co. Brookite, monazite. corundum in small crystals red and white, zircons, 
 garnet, beryl, sphene, xenotime, rutile, elastic sandstone, iron ores, pyrornelane, tetrady- 
 mite, montanite. 
 
 MADISON Co. 20 miles from Asheville, corundum, margarite, chlorite. 
 
 MECKLENBURG Co. Near Charlotte (Rhea and Cathay mines) and elsewhere, chalcopyrite, 
 gold; chalcotrichite at McGinn's mine; barnhardtite near Charlotte; pyrophyllite in Cot- 
 ton Stone Mountain, diamond; Flowe mine, scheelite, wolframite; Todd's Branch, mona- 
 zite. 
 
 MITCHELL Co. Sama.rskite, pyrochlore (?) , euxenite, columbite, muscomte. 
 
 MONTGOMERY Co. Steele's mine, ripidolite, albite. 
 
 MOORE Co. Carbonton, compact pyrophyllite. 
 
 ROWAN Co. Gold Hill Mines, thirty-eight miles northeast of Charlotte, and fourteen 
 from Salisbury, gold, auriferous pyrite ; ten miles from Salisbury, feldspar in crystals, bis- 
 muthinite. 
 
 RANDOLPH Co. Pyrophyllite. 
 
 RUTHERFORD Co. Gold, graphite, bismuthic gold, diamond, euclase, pseudomorphovs 
 yuartzf, chalcedony, corundum in small crystals, epidote, pyrope, brookite, zircon, monazite, 
 mtherfordite, samarskite, quartz crystals, itacolumyte ; on the road to Cooper's Gap, 
 cyanite. 
 
 STOKES AND SURIIY Cos. Iron ores, graphite. 
 
 UNION Co. Lemmond gold mine, eighteen miles from Concord (at Stewart's and Moore's 
 mine), gold, quartz, blende, argentiferous galenite (containing 29-4 oz. of gold and 86 o oz. 
 of silver to the ton, Genth), pyrite, some chalcopyrite. 
 
 YANCEY Co. Iron ores, amianthus, chromite, garnet (spessartite), samarskite. 
 
 SOUTH CAROLINA. 
 
 ABBEVILLE. DIST. Oakland Grove, gold (Dorn mine), galenite, pyromorphite, amethyst, 
 garnet. 
 
 ANDERSON DIST. At Pendleton, actinolite, galenite. kaolin, tourmaline. 
 
 CHARLESTON. Selenite. 
 
 CHKOWEE VALLEY. Galenite, tourmaline, gold. 
 
 CHESTERFIELD DIST. Gold (Brewer's mine), talc, chlorite, pyrophyllite, pyrite, native 
 bismuth, carbonate of bismuth, red and yellow ochre, whetstone, enargite. 
 
 DARLINGTON. Kaolin. 
 
 EDGEFTELD DIST. Psilomelane. 
 
 GREENVILLE DIST. Galenite, pyromorphite, kaolin, chalcedony in buhrstone, beryl, 
 plumbago, epidote, tourmaline. 
 
 KERSHAW DIST. Rutile. 
 
 LANCASTER DIST. Gold (Hale's mine), talc, chlorite, cyanite, elastic sandstone, pyrite; 
 gold also at Blackman's mine, Massey's mine, EzelTs mine. 
 
 LAURENS DIST. Corundum, damourite. 
 
 NEWBERRY DIST. Leadhillite. 
 
 PICKEN'S DIST. Gold, manganese ores, kaolin. 
 
 RICHLAND DIST. Chiastolite, novaculite. 
 
 SPARTANBURG DIST. Magnetite, chalcedony, k>matite ; at the Cowpens, limonite, graphite 
 limestone, copperas ; Morgan mine, leadhillite, pyromorphite, cerussite. 
 
 SUMTER DIST. Agate. 
 
 UNION DIST. Fairforest gold mines, pyrite, chalcopyrite. 
 
 YORK DIST. Limestones, whetstones, witherite, barite, tetradymite. 
 
AMERICAN LOCALITIES. 493 
 
 GEORGIA. 
 
 BtJRKE AND SCRIVEN Cos. Hyalite. 
 
 CHEROKEE Co. At Canton Mine, chalcopyrite, galenite, clausthalite, plumbogummite 
 aitchoockite, arsenopyrite, lantbanite, harrisite, c<mtonite, pyromorphite, automolite. zinc' 
 ataurolite. cyanite ; at Ball-Ground, spodumene. 
 
 CLARK Co., near Clarksville. Gold, xenotime, zircon, rutile, cyanite, hematite, nrnofc 
 juartz. 
 
 DADE Co. Halloysite, near Rising Fawn. 
 
 FANNIN Co. Staurolite! chalcopyrite. 
 
 HABERSIIAM Co. GW, pyiite, chalcopyrite, galenite, hornblende, garnet, quartz, kaolinite 
 capstone, chlorite, rutile, iron ores, tourmaline, staurol'ite, zircon. 
 
 HALL Co. Gold, quartz, kaolin, diamond. 
 
 HANCOCK Co. Agate, chalcedony. 
 
 HEARD Co. Molybdite, quartz. 
 
 LINCOLN Co. Lazulite! ! rutile! ! hematite, cyanite. menaccanite, pyrophyllite, gold, 
 itacolumyte rock. 
 
 LOWNS Co. Corundum. 
 
 LUMPKIN Co. At Field's gold mine, near Dahlonega, gold, Utradymite, pyrrhotifce, chlorite, 
 menaccanite, allanite, apatite. 
 
 RABUN Co. Gold, chalcopyrite. 
 
 SPAULDING Co. Tetradymite. 
 
 WASHINGTON Co. , near Saundersville. WaveUite, fire opal. 
 
 ALABAMA. 
 
 BIBB Co., Centreville. Iron ores, marble, barite, coal, cobalt. 
 
 TUSCALOOSA Co. Coal, galenite, pyrite, vivianite, limonite, calcite, dolomite, cyanite, 
 steatite, quartz crystals, manganese ores. 
 
 BENTON Co. Antimonial lead ore (boulangerite ?) 
 
 TALLAPOOSA Co., at Dudley ville. Corundum, spinel, tourmaline. 
 
 FLORIDA. 
 
 NEAR TAMPA BAY. Limestone, sulphur springs, chalcedony, carnelian, agate, silicified 
 shells and corals. 
 
 KENTUCKY. 
 
 ANDERSON Co. Galenite, barite. 
 CLINTON Co. Geodes of quartz. 
 CRITTENDEN Co. Galenite, fluorite, calcite. 
 
 CUMBERLAND Co. At mammoth Cave, gypsum rosettes! calcite, stalactites, nitre, ep- 
 somite. 
 
 FAYETTE Co. Six miles N.E. of Lexington, galenite, barite, witherite, blende. 
 LIVINGSTONE Co., near the line of Union Co. Galenite, chalcopyrite, large vein of fluorite. 
 MERCER Co. At McAfee, fluorite, pyrite, oalcite, barite, oelestite. 
 OWEN Co. Galenite, barite. 
 
 TENNESSEE. 
 
 BROWN'S CREEK. Galenite, blende, barite, celestite. 
 
 CARTER'S Co., foot of Roan Mt. Sahtite,, magnetite. 
 
 CLAIBORNE Co.Galamme, galenite, smithsonite, chlorite, steatite, magnetite, 
 
 COCKE Co., near Brush Creek. Cacoxene ? kraurite, iron sinter, stilpnosidente, brown 
 hematite. 
 
 DAVIDSON Co. Selenite, with granular and snowy gr.psum, or alabaster, crystallized and 
 compact anhydrite, fluorite in crystals? caldte in crystals. Near Nashville, blue tftetfttt, 
 (crystallized, fibrous, and radiated), with barite in limeBtone. Hayaboro', galenite, Wendo, 
 with barite as the gangue of the ore. 
 
 DICKSON Co. Manganite. 
 
494 APPENDIX. 
 
 JEFFERSON Co. Calamine, galenite, fetid barite. 
 
 KNOX Co. Magnesian limestone, native iron, variegated marbles/ 
 
 MAUBY Co. Wavellite in limestone. 
 
 MORGAN Co. Epsom salt, nitrate of lime. 
 
 POLK Co., Ducktown mines, southeast corner of State. Melaconite, chalcopyrite, pyrite, 
 native copper, bornite, rutile, zoisite, galenite, harrisiLe, alisonite, blende, pyroxene, tremoliie, 
 sulphate* of copp a r and iron in stalactites, allophane, rahtite, chalcocite (ducktownite), chal- 
 cotrichite, azurite, malachite, pyrrhotite, limonite. 
 
 ROAN Co., eastern declivity of Cumberland Mts. Wavellite in limestone. 
 
 SEVIER Co., in caverns. Epsom salt, soda alum, saltpetre, nitrate of lime, breccia marble. 
 
 SMITH Co. Fluorite. 
 
 SMOKY MT., on declivity. Hornblende, garnet, staurolite. 
 
 WHITE Go. Nitre. 
 
 OHIO. 
 
 BAINBRIDGE (Copperas Mt., a few miles east of B.). Calcite, barite, pyrite. copperas, 
 alum. 
 
 CANFIELD. Gypsum ! 
 DUCK CREEK, Monroe Co. Petroleum. 
 
 LAKE ERIE. Strontian Island, celestite! Put-in Bay Island, cekstite! sulphur! calcite. 
 LIVERPOOL. Petroleum. 
 
 MARIETTA. Argillaceous iron ore ; iron ore abundant also in Scioto and Lawrence Cos. 
 OTTAWA Co. Gypsum. 
 POLAND. Gypsum ! 
 
 MICHIGAN. 
 
 BREST (Monroe Co.). Calcite, amethystine quartz, apatite, celestite. 
 
 GRAND RAPIDS. Selenite, fib. and granular gypsum, calcite, dolomite, anhydrite. 
 
 *LAKE SUPERIOR MINING REGION. The four principal regions are Keweenaw Point, Isle 
 Royale, the Ontonagon, and Portage Lake. The mines of Keweenaw Point are along two 
 ranges of elevation, one known as the Greenstone Range, and the other as the Southern or 
 Bohemian Range (Whitney) . The copper occurs in the trap or amygdaloid, and in the asso- 
 ciated conglomerate. Native copper ! native silver ! chalcopyrite, horn silver, tetrahedrite, 
 manganese ores, epidote, prehnite, laumontite, datolite, heulandite, orthoclase, analcite, cha- 
 bazite, compact datolite, chrysocolla, mesotype (Copper Falls mine), leonhardite(ib.), analcitt 
 (ib.), apophyllite (at Cliff mine), wollastonite (ib. ), calcite, quartz (in crystals at Minnesota 
 mine), compact datolite, orthoclase (Superior mine), saponite, melaconite (near Copper Har- 
 bor, but exhausted), chrysocolla ; on Chocolate River, galenite and sulphide of copper ; chal- 
 copyrite and native copper at Presq' Isle ; at Albion mine, domeykite ; at Prince Vein, barite, 
 ca'cite, amethyst; at Michipiooten Ids., copper nickel, stilbite, anal cite ; at Albany and Bos- 
 ton mine, Portage Lake, prehnite, analcite, orthoclase, cuprite ; at Sheldon location, domey- 
 kite, whitneyite, algodonite ; Isle Royale mine, Portage Lake, compact datolite ; Quincy mine, 
 calcite, compact datolite. At the Spurr Mountain Iron mine (magnetite), chlorite pseudo- 
 morph after garnet. 
 
 MARQUETTE. Manganite. galenite; twelve miles west at Jackson Mt. . and other mines, 
 hematite, limonite, gothite! magnetite, jasper. 
 
 MONROE. Aragonite, apatite. 
 
 POINT AUX PEAUX (Monroe Co.). Amethystine quartz, apatite, celestite, calcite. 
 
 SAGINAW BAY. At Alabaster, gypsum. 
 
 STONY POINT (Monroe Co.). Apatite, amethystine quartz, celestite, calcite. 
 
 ILLINOIS. 
 
 GALLATIN Co., on a branch of Grand Pierre Creek, sixteen to thirty miles from Shawnee- 
 town, down the Ohio, and from half to eight miles from this river. Violet fluorite ! in car- 
 boniferous limestone, barite, galenite, blende, brown iron ore. 
 
 HANCOCK Co. At Warsaw, quartz geodes ! containing calcite ! chalcedony, dolomite, blende t 
 brown spar, pyrite, aragonite, gypsum, bitumen. 
 
 * See also Pumpelly ; on the Paragenesis of copper and its associate minerals on Lak< 
 Superior Am. J. Sci, III., x, 17. 
 
AMERICAN LOCALITIES. 495 
 
 HARDIN Co -Near Rosiclaie, calcite, galenite, blende ; five miles back from Elizabeth 
 town to-iron one mile north of the river, between Elizabethtown and Rosiclare, mtre 
 
 TO'DAVIES Co -At Galena, galenite, calcite, pyrite, blende; at Marsden's diggings, gate* 
 ite ! blende, cerussite, marcasite in stalactitic forms, pynte. 
 
 JOLIET. Marble. 
 
 Q UINC Y . Calcite ! py rite. 
 
 SCALES MOUND. Barite., pyrite. 
 
 INDIANA. 
 
 * 
 
 top of the blue limestone formation, brown spar, calcite. 
 LAWRENCE Co. -Spice Valle, kaolinite (=indianaite). 
 
 MINNESOTA. 
 
 TRAP RA E .-Epidote, nail-head calcibe, amethystine quarts, oaloite, 
 undetermined zeolites, saponite. 
 
 WISCONSIN. 
 
 Bio BULL FALLS (near). Bog iron. 
 BLUE MOUNDS. Cerussite. 
 . Calcite. 
 
 , chaste, native copper, red ooppe, 
 
 , 
 
 ore, earthy malachite, epidote, chlorite ? quartz crystals. 
 
 LINDEN. Galenite, smitteomte, hydrozincite piwvsocolla azuritef chalcopyrite, 
 
 MINERAL POINT and vicinity. -Copper and lead ores, ^^^ ^ rc(l9ite 8m ithsoniU / 
 
 malachite, galenite, cerussite, anglesite, blende, pynte, bante, co 
 
 ^^ONTREALRIVER PORT AGE. -Galenite in gneissoid granite. 
 
 SANK CoHematite, malachite ch&lc ?W* li *'rmmrtB digging, galenite and pyrite. 
 SHULLSBURG. Galenite! blende, pyrite ; at Emmet s digging, y 
 
 IOWA. 
 
 
 Du BUQUE LEAD MmES, an 
 
 at Ewing's and Sherard's diggings, 
 
 iron ore, spathic iron ; copperas in crystals on the 
 and elsewhere, pyrite, blende. 
 
 FORT DODGE. Celestite. 
 
 MAKOQUETA. Hematite. 
 
 NEW GALENA. Octahedral galenite, anglesite. 
 
496 APPENDIX. 
 
 MISSOURI. 
 
 BIRMINGHAM. Limonite. 
 
 GRANBY. Sphalerite, galenite, calamine, greenockite. as a coating on sphalerite. 
 
 JEFFERSON Co., at Valle's diggings. Galenite, cerussite, anglesite, calamine. chalcopy 
 rite malachite, azurite, witherite. 
 
 MINE & BURTON. Galenite, cerussite, anglesite, barite, calcite. 
 
 DEEP DIGGINGS. Malachite, cerussite in crystals and manganese ore. 
 
 MADISON Co. Wolframite. 
 
 MINE LA MOTTE. Galenite ! malachite, earthy cobalt and nickel, bog manganese, sulph- 
 ide of iron and nickel, cerussite, caledonite, plumbogummite, wolframite, siegenite, sinaltite, 
 aragonite. 
 
 ST. Louis. Millerite, calcite, dolomite, earthy barite, fluorite. 
 
 ST. FRANCIS RIVER. Wolframite. 
 
 PERRY'S DIGGINGS, and elsewhere. Galenite, etc. 
 
 Forty miles west of the Mississippi and ninety south of St. Louis, the iron mountains, 
 specular iron, limonite ; 10 m. east of Ironton, wolframite, tungstite. 
 
 ARKANSAS. 
 
 BATESVILLE. In bed of White R., some miles above Batesville, gold. 
 
 GREEN Co. Near Gainesville, lignite. 
 
 HOT SPRINGS Co. At Hot Springs, wavellite, thuringite ; Magnet Cove, brookite! schor- 
 famite, elceolite, magnetite, quartz, green coccolite, garnet, apatite, perofskite (hydrotitanite), 
 rutile, ripidolite, thomsonite (ozarkite), microcline, segirite. 
 
 INDEPENDENCE Co. Lafferay Creek, psilomelane. 
 
 LAWRENCE Co. Hoppe, Bath, and Koch mines, smithsonite, dolomite, galenite; nitre. 
 
 MARION Co. Wood's mine, smithsonite, hydrozincite (marionite), galenite ; Poke bayou, 
 braunitef 
 
 OOACHITA SPRINGS. Quartz? whetstones. 
 
 PULASKI Co. Kellogg mine, 10 m. north of Little Rock, tetrahedrite, tennantite, nacrite 
 grtleuite, blende, quartz. 
 
 CALIFORNIA. 
 
 The principal gold mines of California are in Tulare, Fresno, Maripos.i, Tuolumne. Cala- 
 vevas, El Dorado, Placer, Nevada, Yuba, Sierra. Butte, Plumas, Shasta, Siskiyou. and Del 
 Norte counties, although gold is found in almost every county of the State. The gold occurs 
 in quartz, associated with sulphides of iron, copper, zinc, and lead ; in Calaveras and Tuo- 
 lomne counties, at the Mellones, Stanislaus, Golden Rule, and Rawhide mines, associated 
 with tellurides of gold and silver ; it is also largely obtained from placer diggings, and further 
 it is found in beach washings in Del Norte and Klamath counties. 
 
 The copper mines are principally at or near Copperopolis, in Calveras county ; near Genesee 
 Valley, in Plumas county ; near Low Divide, in Del Norte county ; on the north fork of 
 Smith's River ; at Soledad, in Los Angeles county. 
 
 The mercury mines are at or near New Almaden and North Almaden, in Santa Clara county; 
 at New Idria and San Carlos, Monterey county ; in San Luis Obispo county ; at Pioneer 
 mine, and other localities in Lake county ; in Santa Barbara county. 
 
 ALPINE Co. Morning Star mine, enargite, stephanite, polybasite, barite, quartz, pyrite, 
 tetrahedite. 
 
 AMADOR Co. At Volcano, chalcedony, hyalite. 
 
 ALAMEDA Co. Diabolo Range, magnesite. 
 
 BUTTE Co. Cherokee Flat, diamond, platinum, iridosmine. 
 
 CALAVERAS Co. Copperopolis, cha'copyrite. malachite, azurite, serpentine, picrolite, native 
 copper, near Murphy's, jasper, opal ; albite, with gold and pyrite ; Mellones mine, calaverit?, 
 petzite. 
 
 CoNTRA-CosTA Co San Antonio, chalcedony. 
 
 DEL NORTE Co. Crescent City, agate, carnelian ; Low Divide, chalcopyrite, bornite, 
 malachite ; on the coast, iridosmine, plaVnun?. 
 
 EL DORADO Co. Pilot Hill, chaloopyritb , near Georgetown, hessite, from placer dig- 
 gings ; Roger's Claim, Hope Valley, grossular garnet, in copper ore ; Coloma, chromite , 
 Spanish Dry Diggings, gold; Granite Creek, roscoelite, gold. 
 
AMERICAN LOCALITIES. 497 
 
 JPKKBAU Co. Chowchillas, andalusite. 
 
 ii HA/TROT r>T Co Crvptomorphite. 
 
 INGO Co. Ingo district, galenite, cerussite, anglesite, barite, atacamite, calcite, giossulai 
 
 K*AKE Co Borax Lake, borax' sassolite, glauberite ; Pioneer mine, cinnabar, native mer- 
 ury, selenide of mercury ; near the Geysers, sulphur, hyalite ; Redington mine, metacinna- 
 
 ANGELES Co -Near Santa Anna 'River, anhydrite ; Williams Pass, chalcedony ; 
 mines, chalcopyrite, garnet., gypsum; Mountain Meadows, garnet, m cooper ore 
 >A Co -Chalcopyrite, itacolumyte ; Centreville, cinnabar; Pine Tree Mine, tet 
 , ,- .***.*. (\^^ f^i^v, rvirrhvnii-,fi La Victoria mine, azuntef n 
 
 PA Co -Chalcopyrite, itacoumye ; enreve, cinna , tetra- 
 
 Burn! fcreek lim^nite; Geyer Gulch, pyrophyllite ; La Victoria mine., azuntef neai 
 CJoulterville. cinnabar, gold. 
 
 MoN?EKE7co"-Atisal Mine, arsenic; near Paneches, chalcedony; New Idria mine cm- 
 aabar near New Idria, chromite, zaratite, chrome garnet; near Pacheco's Pas stibnite 
 
 NEVADA Co -Grass Valley gold! in quartz veins, with pyrite, chalcopyrite, blende, 
 .rsenopyrfte, galenite g^r^fbiotite ; near Truckee Pass gypsum ; Excelsior Mine, molyb- 
 denite, with molybdenite and gold ; Sweet Land, pyrolusite. 
 
 PLACEH Co. -Miner's Ravine, epidote! with quartz, gold. 
 
 AT c A co- N e W , , 
 
 quartz arfgotSe; Nort^ TlTmaden, ctaomite; Ml. Diabolo Range, magues.te, datohte, wit. 
 
 OAJ-X JLJJ^Afc-l.^ /ii^JL^J-J.^ V/- W^. ' 
 
 trict galenite, cerussite ; Francis mine, cerargyrite. 
 
 SHASTA Co .-Near Shasta City, hematite, in large masses. 
 SISKIYOU Co. Surprise Valley, selenite, in large slabs. 
 SONOMA Co. Actinolite, garnets. 
 
 Co. Cassiterite, a single specimen found. 
 
 LOWER CALIFORNIA. 
 LA PAZ.-Cuproscheelite. LoRETTO.-Natrolite, siderite, selenite. 
 
 UTAH. 
 
 BEAVER Co Bismuthinite, bismite, bismutite Mammoth velu, 
 
 TINTIC DISTRICT. At the Shoebridge mine, the Dragon m 
 enargite with pyrite. 
 
 Box ELDER Co. -Empire mine, wulfenite! a - tpTurive m ines especially of ores of 
 
 In the Wahsatch and OquiiTh mountains there are ext< ve mi , ce usgi wu if e nite ; 
 lead rich in silver. At the Emma mine occur W*"^*^,^ ' arg entite, stephanite, 
 azurite, malachite, calamine, anglesite, linante, spha^rite, pyme, 
 etc. At the Lucky Boy mine, Butterfield Canon.. . orp naenV ** .^^ found in color 
 
 One hundred and twenty miles south-west of bait Lake i/ity, ^ 
 less crystals. 
 
 NEVADA. 
 
498 APPENDIX. 
 
 ESMERALDA Co. Alum, 12 m. north of Silver Creek ; at Aurora, fluorite, stibnite nea 
 Mono Lake, native copper and cuprite, obsidian ; Columbus district, ulexite ; Walker Lake 
 gypsum, hematite ; Silver Peak, salt, saltpetre, sulphur, silver ores. 
 
 _ HUMBOLDT DISTRICT. Sheba mine, native silver, jamexotiite, stibnite, tetraJiedrite, proua 
 tite. blende, cernssite, calcite, bournonite, pyrite, galenite, malachite, xanthocone (?) 
 
 MAMMOTH DISTRICT. Orthoclase, turquois, Jiubnerite, scheelite. 
 
 REESE RIVKR DISTRICT. Native silver, proustite, pyravgyrite, stephanite, blende poly! 
 basite, rhodochrosite, embolite, teti ahedrite ! cerargyrite, embolite. 
 
 SAN ANTONIA. Belmont mine, stetefeldtite. 
 
 Six MILE CANON. tielenite. 
 
 ORMSBY Co. W. of Carson, epidote. 
 
 STOREY Co. Alum, natrolite, scolezite. 
 
 ARIZONA. 
 
 On and near the Colorado, gold, silver, and copper mines ; at Bill Williams' Fork, chry- 
 socolla. malachite, atacamite, brochantite ; Dayton Lode, gold, fluorite, cerargyrite Skinnei 
 Lode, octahedral fluorite ; at various places in the southern part of the territory, silver and 
 copper mines ; Heintzelmann mine, stromeyerite, chalcocite, tetraheclrite, atacamite. Mont- 
 gomery mine, Harsayampa Dist., tetradymite. Whitneyite, in Southern Arizona. 
 
 OREGON. 
 
 Gold is obtained from beach washings on the southern coast ; quartz mines and placei 
 mines in the Josephine district ; also on the Powder, Burnt, and John Day's rivers, and othei 
 places in eastern Oregon ; platinum, iridosmine, laurite, on the Rogue River, at Port Oxford 
 and Cape Blanco. In Curry Co. , priceite. 
 
 IDAHO. 
 
 In the Owyhee, Boise, and Flint districts, gold, also extensive silver mines ; Poor Man Lode 
 eerargynte! prouatite, pyrargyrite! native silver, gold, pyromorphite, quartz, malachite- 
 polybasite; on Jordan Creek, stream tin; Rising Star mine, stephanite, argentite, pyrargy 
 rite. 
 
 MONTANA. 
 
 Many mines of gold, etc., west of the Missouri R. HIGHLAND DISTRICT. Tetradymitc 
 SILVER STAR DIST. Psittacinite. 
 
 In the Yellowstone Park, in Montana and Wyoming Territories. Geysente. Amethyst 
 chalcedony, quartz crystals, quartz on calcite, etc. 
 
 COLORADO.* 
 
 The principal gold mines of Colorado are in Boulder, Gilpin, Clear Creek, and Jefferson 
 Cos., on a line of country a few miles W. of Denver, extending from Long's Peak to Pike's 
 Peak. A large portion of the gold is associated with veins of pyrite and chalcopyrite ; silver 
 and lead mines are at and near Georgetown, Clear Creek Co., and to the westward in Sum- 
 mit Co., on Snake and Swan rivers. 
 
 At the GEORGETOWN mines are found : -native silver, pyrargyrite, argentite, tetrahedrite, 
 pyromorphite, galenite, sphalerite, azurite, aragonite, barite, fluorite, mica. 
 
 TRAIL CREEK. Garnet, epidote, hornblende, chlorite; at the Freeland Lode, tetrahedrite, 
 tennantite, anglesite. caledonite, cerussite, tenorite, siderite, azurite, minium ; at the Cham- 
 pion Lode, tonorite, azurite, chrysocolla, malachite; at the Gold Belt Lode, vivianite; at 
 the Kelly Lode, tenorite ; at the Coyote Lode, malachite, cyanotrichite. 
 
 Near JJLACK HAWK. At Willis Gulch, enargite, fluorite, pyrite ; at the Gilpin County 
 Lode, cerargyrite ; on Gregory Hill, feldspar; North Clear Creek, iievrite. Galenite! 
 
 * See the Catalogue of Minerals of Colorado by J. Alden Smith. 
 
AMERICAN LOCALITIES. 499 
 
 BEAK CREEK. Fluorite, beryl; near the Malachite Lode, malachite, cuprite, vesurianite, 
 topazolite ; Liberty Lode, chalcocite. 
 SNAKE RIVER. Penn District, embolite ; at several lodes, pyrargyrite, native silver. 
 
 RUSSELL DISTRICT. Delaware Lode, cliakopyrite, crystallized galenite. Epidote, pyrite 
 
 VIRGINIA CANON. Epidote, fluorite ; at the Crystal Lode, native silver, spinel. 
 
 SUGAR LOAF DISTRICT. Chalcocite, pyrrhotite, garnet (manganesian). 
 
 CENTRAL CITY. Garnet, terorite ; at Leavitt Lode, molybdenite; on Gunnell till, mag 
 netite ; at the Pleasantview mine, cerussite. 
 
 GOLDEN CITY. Aragonite. 
 
 BERGEN'S RANCHE. Garnet, actinolite, calcite. 
 
 BOULDER Co., Red Cloud Mine. Native tellurium, altaite, hessite (petzite), sylvamte, 
 calaverite, schirmerite. 
 
 LAKK CITY, at the Hotchkiss Lode. Petzite, calaverite (?), etc 
 
 PIKE'S PEAK, on Elk Creek. Amazon tone! ! smoky quartz! aventunne felspar, ame 
 thyst, albite, fluorite, hematite, anhydrite (rare), columbite. 
 
 CANADA. 
 
 CANADA EAST. 
 
 ABERCROMBIE. Labradorite. 
 
 BAY ST. PAm.-M&wnwtnite! apatite, allamte, rutile (or brookite ?) 
 
 AUBERT. - Gold, iridosmine, platinum. 
 
 BOLTON - Chromite, magnesite, serpentine, picrolite, steatite, bitter spar, wad. 
 
 menaccanite, phyllite, sodalite, cancrinite, 
 
 .-, chabazite and calcite in trachyte, menaccanite. 
 CHATEAU RICHER. Labradorite, hypertthene, andesite. 
 
 oalcite ' pyroxene ' 8teatite 
 
 etibnite. 
 
 INVERNESS. Variegated copper. 
 LAKE ST. FRANCIS. Andalusite in mica slate. 
 LANDSDO WN. Barite. 
 
 LEEDS Dolomite, chalcopyrite, gold, ehlontoid. 
 
 MILLE IsmiLabradorfot menaccanite, hypersthene, andesite, i f rc0 ^ 
 MoNTHEAi,-(7 <t fct^, augite, spheiie in trap, chrysolite, natrohte, dawsomte. 
 MORIN Sjiheue, apatite, labradoj-ite. 
 
 ORFORD. White garnet, chrome garnet, millerite, serpentine. 
 OTTAWA. Pyroxene. 
 POLTON __ Chromite, steatite, serpentine, amiantnus. 
 
 **.! native silver, a^ntite, chdoopy^, ble^d, 
 
 - 
 i moiybdenitei 
 
 pyrrhotite. 
 
 ST. NORBERT. Amethyst in greenstone. 
 
 . . 
 
 STUKELEY. Serpentine, verd-antique f schiller spar maanesite, chromiferoufi 
 
 SUTTON. Magnetite in fine crystals, hematite, ruttie, dolomite, mag 
 
 talc, bitter spar, steatite. 
 
 UPTON. Chalcopyrite, malachite, calcite. 
 VAUDREUIL. Limonite, vivianite. 
 YA.MASKA. Sphene in trap. 
 
 CANADA WEST. 
 
 -, scapolite quartz, P/^^^'P^ acid ^ 1000). 
 
 BRANTFORD. -Sulphuric acid spring (4-2 parts of l"2^SiSSl 'albite), bytvsntts, 
 BATHURST. Barite, black tourmaline, pcrthtte (orthoclase), per 
 pyroxene, wilsonite, scapolite, apatite, titanite. 
 
500 APPENDIX. 
 
 BROCKVILLE. Pyrite. 
 
 BROME. Magnetite. 
 
 BRUCE MIKES. Calcite, dolomite, quartz, chalcopyrite. 
 
 BURGE?S. Pyroxene, albite, mica, xappkire, sphene, chalcopyrite, ipatite, black spin**. 
 spodumene <in a boulder), serpentine, biotite. 
 
 BYTOWN. Colette, bytownite. chondrodite, spinel 
 
 CAPE IPPERWASH, Lake Huron. Oxalite in shales. 
 
 CLARENDON. Venmnnite. 
 
 DALHOUSIE. Hornblende, dolomite. 
 
 DRUMMUND. Labradorite. 
 
 ELIZABETHTOWN. Pyrrhotite, pyrite, calcite, magnetite, talc, phlogopit*. siderite, apa- 
 tite, cacoxenite. 
 
 ELMSEY. Pyroxene, sphene, feldspar, tourmaline, apatite, biotite, zircon, red spinel 
 uhondrodite. 
 
 FITZROY. Amber, brown tourmaline, in quartz. 
 
 GkETlNEAU RIVER, Blasdell's Mills. Calcite. apatite, tourmaline, hornblende, pyroxene. 
 
 GRAND CALUMET ISLAND. Apatite, pMogojrite ! pyroxene ! sphene, retumanite 1 1 serpen 
 tine, tremolite, tcapolite. brown and black tourmaline ! pyrite, loganite. 
 
 HIGH FALLS OP THE MADAWASKA. Pyroxene! hornblende. 
 
 HULL. Magnetite, garnet, graphite. 
 
 HUNTERSTOWN. Scfipolite, ftphene, vesuvianite, garnet, brown tourmaline! 
 
 H UNTINGTON. Calcite ! 
 
 INNISKILLEN. Petroleum. 
 
 KINGSTON. CeJestite. 
 
 LAC DBS CHATS, Island Portage. Brown tourmaline! pyrite, calcite, quartz. 
 
 LANARK. Raphilite (hornblende), serpentine, asbestus. 
 
 LANDSTOWN. Barite! vein 27 in. wide, and fine crystals. 
 
 M ADOC. Magnetite. 
 
 MAMORA. Magnetite, chalcolite, garnet, epsomite, specular iron. 
 
 MAIM AKSE. Pitchblende (coracite). 
 
 McNAB. Hematite, barite. 
 
 MICIIIPICOTEN ISLAND, Lake Superior. Domeykite, niecolite, genthite. 
 
 XEWBORO UGH. Chondrodite, graphite. 
 
 PACKENHAM.- Hornblende. 
 
 PERTH. Apatite in large beds, phlogopite. 
 
 SOUTH CROSBY. Chondrodite in limestone, magnetite. 
 
 ST. ADKLE. Chondrodite in limestone. 
 
 ST. IGNACE ISLAND. Calcite, native copper. 
 
 SYDENHAM. Celestite. 
 
 TERRACE COVE, Lake Superior. Molybdenite. 
 
 WALLACE MINE, Lake Huron. Hematite, nickel ore, nickel vitriol. 
 
 NEW BRUNSWICK.* 
 
 ALBERT Co. Hopewell, gypsum ; Albert mines, coal (albertite) ; Shepody Mountain, 
 alunite in clay, calcite, iron pyrites, manganite, peilomelane, pyrolusite. 
 
 CARLETON Co. Woodstock, chalcopyrite, hematite, limonite, wad. 
 
 CHARLOTTE Co. Campobello, at Welchpool, blende, chalcopyrite, bornite, galenite. 
 pyrite; at head of Harbor de Lute, galenite ; Deer Island, on west side, calcite, magnetite, 
 quartz crystals; Digdignash River on west side of entrance, calcite! (in conglomerate . 
 chalcedony ; at Rolling Dam, graphite ; Grandmanan. between Northern Head and Dark 
 Harbor, agate, amethyst, apnpJiyllite, calcite, hematite, heulandite, jasper, magnetite, natro- 
 lite, si'dbite ; at Whale Cove, calcite ! heulandite, laumontite. stilbite, semi-opal! Wagagua- 
 davic River, at entrance, aznrite. chalcopyrite in veins, malachite. 
 
 GLOUCESTER Co. Tete-a-Gouche River, eight miles from Bathurst, chalcopyrite 'mined), 
 oxide of manganese ! ! formerly mined. 
 
 KINGS Co. Sussex, near Cloat's mills, on road to Belleisle, argentiferous galenite ; one 
 mile north of Baxter's Inn, specular iron in crystals, limonite ; on Capt. McCready's farm, 
 
 RESTIGOTJCITE Co. Belledune Point, calcite! serpentine, terd-antique ; Dalhousie. agate, 
 camelian. 
 
 * For a more complete list of localities in New Brunswick, Nova Scotia, and Newfound 
 land, see catalogue by 0. C. Marsh, Am, J. Sci., II. xxxv. 210, 1863 
 
AMERICAN LOCALITIES. 5Q1 
 
 OHN Co Black River, on coast, calcite, chlorite, chalcopyrite, Jtematite ! Brandj 
 BrpdoS l^nVende, quartz crystals; Carleton near Falls, calcite ; Chance Harbor. 
 SS-Vin quartz veins, chlorite in argillaceous and talcose slate; Little Dipper Harbor on 
 S side in greenstone, amethyst, barite, quartz crystals ; Moosepath, feldspar, hornblende. 
 nmiovite black tourmaline ; Musquash, on east side harbor, copperas, graphite, pyrite ; at 
 on's' chrvsolite serpentine; east side of Musquash, quarto crystal*!; Portland at 
 the FaHs ^aph^rat iSrf Howe Hill, calcite. graphite ; Crow'. Nest, asbestus, chry^ite 
 petite wwtne. steatite; Lily Lake, white augite? chrysolite, graphite^ serpentine 
 Ste talc How's Road, two miles out, epidote (in syenite), steatite in hmestone, tremo 
 Drnry^'Cove graphite, pyrite, pyrallolite ? indurated talc ; Quaco, at Lighthouse Point, 
 ^e bed oxyd of manganese; Sheldon's Point, actinolite, asbestus excite, tpidtto, mala- 
 uecuLr kon- Cape Spenser, asbestus. calcite, chlorite, specular (m crystals ; 
 S\> tb "ach at e^t end, on Evans' farm, chlorite, talc, qwrtz cryital* ; half a mile west, 
 chalcop^rk, rnagnesite vein,, magnetite ; Point Wolf and Salmon River, asbestus, 
 
 iasper; at mouth south side galenit* ;; 
 at mouS "of Wapskanegln. gypsum, salt spring ; three miles above, stalactites (abundant); 
 
 Ta ^ s farm ' Tf e -v 
 
 irrlt ne on \v?es's farm, asphaltum, petroleum spring; Grandlance apatite, selenite (in 
 tin py rite*? in granite (rare). 
 
 NOVA SCOTIA. 
 
 
 p 
 
 Bro 
 
 SS^O^K^Si, East River, to*;/ -^-^^^^"dt' 
 
 River, barite in limestone). o anf jidte apophyUite ! ! chaba- 
 
 CLMBEHLAND Co.-Cape Cbiegnecto, ^^^^^^^ obsidian, red copper 
 tite, fardelite, laumontite, m/*fe, malachite ^^ o f Ca ^^Or analcite, calcite, stilbite; 
 (rare), vivianite (rare) ; Horse-shoe Cove east side of Cape D Or. an^ ^ meftoiite ^ 
 Isle Haute, south side, ana cite a^phyllt^ // toto^ ^^ te at Seaman's Brook: 
 Wrt/ Joggins, coal, hematite, limonrte; ^^^^TS^^ < rare ^' ?****" 
 Partridge Island, analcite, a^ophylhtef (rare) ' l ^; m a ^; mat i?e, /wtondfl / magne- 
 chabazite (acadialite). chalcedony cat s^ye ^^^^^a^m heulandite, pyrite : 
 tite,*^^/// 8w ^lS?*lfS^^Sfa// M0Dh*mu! (T*Te},calctte.ch'A<izUe.. 
 
 , * -cintv to/W. 
 
 evt side, at Wasson's Bluff and viranity. "^ tte : ] :"^J ui1 . I . Two Islands, mosB agate, 
 
 Co.-Bne r Iriand, native copper 
 /%*t, ', 6*, * . Co ametbyrt. ^. 
 
 tti a^JiirP ai/ir wiuianl8 
 
 D eaf soSce. ^^^ (green), heulandite, 
 
 Dear source, cmjums^^> \i=^**7i ~~ ' . 
 
 GUYSBORO' Co. Cape Canseau, andalimU. artn . hwegfc of HaUfax. garnet, rtaurolite, 
 
 HALIFAX Co. -Gay's river, galemte in limestone ,^ ^??te ^ociated with auriferous pyrites, 
 
 tourmaline : Tangier, go'd! m quartz veins in claj ^*. foand * the same form* 
 
 t!HSS.S:E-o'iT^r- -" - 
 
502 APPENDIX. 
 
 HANTS Co. Cheverie, oxide of manganese (in limestone) ; Petite River, gypsum, oxide of 
 manganese ; Windsor, calcite, cryptomorphite (boronatrocalcite), howlite, glauber riiilt. The 
 last three minerals are found in beds of gypsum. 
 
 KINGS Co. Black Rock, centrallassite, cerinite ; cyanolite ; a few miles east of Black 
 Rock, prehnite ? stilbite ! ; Cape Blomidon, on the coast between the cape and Cape Split, 
 the following minerals occur in many places (some of the best localities are nearly opposite 
 Cape Sharp): analcite! ! agate, amethyst! apophyllite! calcite, chalcedony, chabazite, gme- 
 Unite (ledererite), hematite, heulandite ! laumontite, magnetite, malachite, mesolite, native 
 copper (rare), natrolite ! psilomelane, stilbite ! thomsonite, faroelite, quartz; North Moun- 
 tains, amethyst, bloodstone (rare), ferruginous quartz, mesolite (in soil) ; Long Point, five 
 miles west of Black Rock, heulandite, laumontite! ! stilbite! !; Morden, apophyllite, mor- 
 denite ; Scot's Bay, agate, amethyst, chalcedony, mesolite, natrolite ; Woodworth's Cove, a 
 few miles west of Scot's Bay, agate ! chalcedony ! jasper. 
 
 LUNKNBURG Co. Chester, Gold River, gold in quartz, pyrite, mispickel ; Cape la Have, 
 pyrite ; The u Ovens," gold, pyrite, arsenopyrite ; Petite River, gold in slate. 
 
 PICTOU Co. Pictou, jet, oxide of manganese, limonite ; at Roder's Hill, six miles west of 
 Pictou, barite ; on Carribou River, gray copper and malachite in lignite ; at Albion mines, 
 coal, limonite ; East River, limonite. 
 
 QUEENS Co. Westfield, gold in quartz, pyrite, arsenopyrite ; Five Rivers, near Big Fall, 
 gold in quartz, pyrite, arsenopyrite, limonite. 
 
 RICHMOND Co. West of Plaister Cove, barite and calcite in sandstone ; nearer the Cove, 
 calcite, fluorite (blue), siderite. 
 
 SHELBURNE Co. Shelburne, near mouth of harbor, garnets (in gneiss); near the town, 
 rose quartz ; at Jordan and Sable River, staurolite (abundant), schiller spar. 
 
 SYDNEY Co. Hills east of Lochaber Lake, pyrite, chalcopyrite, sideride, hematite ; Mor- 
 ristown, epidote in trap, gypsum. 
 
 YARMOUTH Co. Cream Pot, above Cranberry Hill, gold in quartz, pyrite; Cat Rock, 
 Fouchu Point, asbestus, calcite. 
 
 NEWFOUNDLAND. 
 
 ANTONY'S ISLAND. Pyrite. 
 
 CATALINA HARBOR. On the shore, pyrite ! 
 
 CHALKY HILL. Feldspar. 
 
 COPPER ISLAND, one of the Wadham group. Chalcopynte. 
 
 CONCEPTION BAY. On the shore south of Brigus, bornite and gray copper in trap. 
 
 BAY OF ISLANDS. Southern shore, pyrite in slate. 
 
 LAWN. Galenite, cerargyrite, proustite, argentite. 
 
 PLACENTIA BAY. AtLaManche, two miles eastward of Little Southern Harbor, g 'lenite! ; 
 on the opposite side of the isthmus from Placentia Bay, barite, in a large vein, occasions llj 
 accompanied by chalcopyrite. 
 
 SHOAL BAY. South of St. John's, chalcopyrite. 
 
 TRINITY BAY. Western extremity, barite. 
 
 HARBOR GREAT ST. LAWRENCE. West side, fluo ide, galenite. 
 
APPENDIX D. 
 
 SUPPLEMENTARY CATALOGUE OP AMERICAN LOCALITIES 
 
 OF MINERALS. 
 
 MAINE. 
 
 NORWAY. Triphylite (lithiophilite), chrysoberyl, cookeite. 
 
 PARIS. Columbite, mica, triphyhte. 
 
 PARSONFIELD. Labradorite, crystallized 
 
 PERU -Triphylite (crystallized), columbite, beryl, spodumene. 
 
 STONEUAM. Triplite, columbite, topaz, curved 
 
 NEW HAMPSHIRE. 
 BARTLETT. At the iron mine, danalite. 
 
 MASSACHUSETTS. 
 
 phteite, kaolin, pyrite, malachite, limomte, wad. 
 ROOKPORT. Fergusonite. 
 
 CONNECTICUT. 
 
 BRANCHVILLE. -In a large vein of pegmatite in gneiss mica (curved ^^^^ 
 albite' (also crystallized), quartz (inclosing liqu id ^X^pod^ a ( lso mangana patite), 
 products (eucryptite, cymatohte ki Imite^ f S,)' c Xkms'onT reddiugite, fairfieldite, 
 Lblygonite, lithiophilite, eosphonte, ^^^^^^^ phosphates, 
 fillowite, rhodochrosite, urammte (crystals\ cyrolite, i 
 chabazite, stilbite, heulandite and other species. 
 
 LITCHFIELD. Staurolite in mica schist. sandstone, garnet (topazolite) ; 
 
 NEW HAVEN.-At Mill Rock, contact surface of ,^ a P ^ S ^ n etitef pyroxene, apatite, 
 at East Rock, on columnar surfaces of trap, garnet (mete 
 
 Ca pTLAND. At Pelton's feldspar quarry, monazite. 
 
 NEW YORK. 
 
 I 
 
 CLINTON CO.-PLATTSBURG, nugget of P^^^ O rthoclase; Champlain iron 
 ESSEX CO. PORT HENRY, black tourmaline < 
 
 re ST?'LAWRENCE CO.-DEKALB, white tourmaline. 
 
 PICTAIRN. Titanite. ^.vUp with Dvroxene, titanite, black mica. 
 
 RUSSELL. -In veins in a granitic rock, danbunte wit 
 
 NEW JERSEY. 
 PSSSSS and STERL^-Chalcophanite, het.rolite, pyrochroit, ^ 
 
504 APPENDIX. 
 
 PENNSYLVANIA. 
 
 BEDFORD CO. BRIDGEPORT, barite. 
 
 BERKS CO. Jones's mine, aurichalcite, melaconite, byssolite. 
 BUCKS CO. PHENIXVILLE, ankerite. 
 BRIDGEWATER STATION. Titanite. 
 CHESTER CO. YELLOW SPRINGS, allanite. 
 
 DELAWARE CO. WATERVILLE, near Chester, and Upland, chabazite. 
 MINERAL HILL, columbitc. 
 
 LEIPERVILLE, garnet, zoisitc, heulandite, leidyite. 
 FRANKLIN CO. LANCASTER STATION, barite. 
 HUNTING TON CO. BROAD TOP MOUNTAIN, barite. 
 LEH1GH CO. SHIMERVILLE, corundum. 
 
 LUZERNE CO. SCRANTON, under a peat-bed, phytocollite (dopplerite). 
 DRIFTON, pyrophyllite. 
 MIFFLIN 'CO. Strontianite. 
 
 MONTGOMERY CO.- -Upper Salford mine, azurite. 
 NORTHAMPTON CO. BETHLEHEM, axinite. 
 PHILADELPHIA CO. GERMANTOWN, fahlunite. 
 
 SCHUYLKILL CO., near MAHANOY CITY, pyrophyllite, alunogen, copiapite, in coal 
 mines. 
 
 DELAWARE. 
 
 DIXON'S QUARRY. Columbite. 
 
 NEWARK. Quartz crystals, doubly terminated, loose in soil. 
 
 VIRGINIA. 
 
 AMELIA CO. From a granite vein (mica mine) in gneiss near Amelia Court House, mica 
 in large sheets, quartz, orthoclase, microlite, monazite, columbite, orthite, helvite with 
 topazolite, beryl, fluorite, amethyst, apatite (rare). 
 
 AMHERST CO. From a feldspar vein in a gneissoid rock on the northwest slope of 
 Little Friar Mt., allanite, sipylite, magnetite, zircon. 
 
 ROCKBRIDGE CO. Underlying limonite, dufrenite in an irregular bed ten inches 
 deep, strengite in cavities in dufrenite. 
 
 WYTHE CO. Austin mine, aragonite (7 p. c. PbC0 3 ). 
 
 NORTH CAROLINA.* 
 
 ALEXANDER Co. Near Stony Point, in narrow veins or pockets in a gneissoid rock (in 
 part also loose in overlying soil), spodumene (hiddenite), beryl (emerald), rutile, monazite, 
 allanite, quartz. 
 
 At White Plains, quartz crystals, spodumene (hiddenite), beryl, rutile, scorodite, 
 columbite, tourmaline. 
 
 At Milholland's mill, rutile, monazite, muscovite, quartz. 
 
 BURKE Co. In the auriferous gravels at Brindletown, cctahedrite (transparent), brookite, 
 zircon, fergusonite, monazite, xenotime (compounded with zircon), garnet, tourmaline, 
 magnetite and other species. 
 
 MITCHELL Co. At the mica mines, muscovite in large quantities, orthoclase, albite, 
 samarskite, columbite, hatchettolite, rogersite, fergusonite, monazite, uraninite, gummite, 
 phosphuranvlite, uranotile, allanite, beryl, zoisite, garnet, menaccanite. 
 
 YANCEY Co. At the Ray mica mine, muscovite, tantalite (columbite), monazite, beryl, 
 garnet, zircon, rutile, etc. 
 
 At Hampton's, chromite, epidote, enstatite, tr^molite, chrysolite, serpentine, talc, 
 magnesite, etc. 
 
 ALABAMA. 
 COOS A CO. Cassiterite, tantalite. 
 
 * For a complete list of the minerals and mineral localities of North Carolina, see Geology 
 of North Carolina, vol. II., chap. I.. Mineralogy by F. A. Genth and W. C. Kerr, with 
 notes by W. E. Hidden; 122 pp., 8vo, Raleigh, 1881. 
 
AMERICAN LOCALITIES. 505 
 
 MICHIGAN. 
 
 NEGAUNEE. Manganite, gftthite, hematite, barite, kaolinite. 
 GRAND MARAIS. Thomsonite (lintonite). 
 
 MISSOURI.* 
 
 AD AIR CO. Gothite with calcite in concretionary masses of clay iron-stone. 
 
 BAitTON CO. McCarrow's coal bank, pickeringite, as a white efflorescence on sandy 
 shales of coal measures. 
 
 BENTON CO Limonite. 
 
 BOLLINurER CO. Limonite, bog manganese, psilomelane. 
 
 CALLAWAY CO. Hematite, clay iron ore. 
 
 CHARiTON CO Selenite. 
 
 COLE CO Barite. At the Eureka mines, galenite, smithsonite. 
 
 COOPEli CO. Collins mine, malachite, azurite, chalcopyrite, smithsonite, galenite 
 sphalerite, limonite. 
 
 CRAWFORD CO. Scotia iron banks, hematite, quartz, jasper, amethyst, gothite, 
 malachite. 
 
 DADB CO. Smithsonite. 
 
 DENT CO. Simmon's Mountain, hematite. 
 
 FRANKLIN CO. Cove mines, galenite, cerussite, anglesite, barite. 
 
 Mine-a-Burton, galenite, cerussite, anglesite. 
 
 Moselle, limonite. 
 
 Mount Hope mine, galenite, sphalerite, calamine, smithsonite. 
 
 Stanton Copper mines, native copper, chalcotrichite, malachite, azurite, chalcopyrite. 
 
 Virginia mines, galenite, anglesite, cerussite, minium. 
 
 IRON CO. PILOT KNOB, hematite, serpentine, magnetite, quartz, manganese ore. 
 
 JASPER CO. Joplin mines, galenite, sphalerite, pyrite. marcasite, cerussite, bitumen. 
 
 OROXOGO. Galenite, sphalerite, cerussite, smithsonite, anglesite. 
 
 WEBB CITY. Galenite, sphalerite. 
 
 JEFFERSON CO. Palmer mines, galenite, cerussite, plumbogummite. 
 
 Valle mines, galenite, cerussite, anglesite, calamine, smithsonite, hydrozincite, mala- 
 chite, azurite. 
 
 MADISON CO. Enistein silver mine, galenite, sphalerite, wolframite, pyrite, quartz, 
 muscovite, actinolite, fiuorite. 
 
 MINE-LA-MOTTE. Galenite, linnaeite (siegenite\ cerussite, anglesite, pyrrhotite, earthy 
 cobalt, bog manganese, plumbogummite, chalcopyrite, annabergite. 
 
 In granites, porphyries, etc., quartz, agate, hornblende, asbestos, serpentine, chlorite, 
 epidote, feldspar. 
 
 MONLTEAU CO Sampson's coal mine, galenite and sphalerite in cannel coal. 
 
 MORGAN CO. Buffalo mines, galenite. 
 
 Humes Hill, barite. 
 
 NEWTON CO. Granby mines, galenite, cerussite, pyromorphite, calamine, greeno- 
 chite. sphalerite, smithsonite, hydrozincite, buratite, dolomite, calcite. 
 
 PHELPS CO Hematite, siderite, limonite, ankerite. 
 
 ST. FRANCOIS CO. Iron mountain, hematite, apatite, tungstite, wolframite, magne- 
 tite, menaccanite. 
 
 ST. GENEVIEVE CO. St. Genevieve copper mines, chalcopyrite, cuprite, malachite, 
 azurite, covellite, chalcocite, bornite, melaconite, chalcanthite. 
 
 ST. LOUIS CO. ST. Louis. In cavities in limestone, millerite, dolomite, calcite, 
 fiuorite, anhydite, gypsum, strontianite. 
 
 SALINE CO. Halite in incrustations. 
 
 WAYNE CO. Limonite. 
 
 KANSAS. 
 BROWN CO. Celestite. 
 
 ARKANSAS. 
 
 SEVIER Co. Stibnite, stibiconite, bindheimite, jamesonite. 
 HOT SPRINGS Co. Rutile in eightlings, variscite. 
 
 *See Notes on the Mineralogy of Missouri, by Alexander V. Leonhard, St. Louis, 1882. 
 
506 APPENDIX. 
 
 COLORADO. 
 
 BOULDER Co Magnolia district (especially the Keystone, Mountain Lion and Smuggler 
 mines), native tellurium, coloradoite, calaverite, tellurite, magnolite, ferrotellurite, 
 sylvanite. 
 
 CHAFFEE Co. Arrow mine, jarosite with turgite. 
 
 CUSTER Co. Silver cliff, niecolite. 
 
 EL PASO COUNTY. Near Pike's Peak, arfvedsonite, astro phyl lite, zircon; siderophyllite, 
 topaz, phenacite, cryolite, thomsenolite (and other tluorides), tysonite, bastnasite. 
 
 GILPIN Co Near Central City, pyrite in moailied crystals, "chalcopyrite oiten coated by 
 tetrahedrite in parallel position, crystallized gold on pyrite, 
 
 GUNNISON Co. Near Gothic, smaltite. 
 
 JEFFERSON Co. Near Golden, in basalt of Table Mountain, chabazite, thomsonite, 
 analcite, apophyllite, calcite, mesolite, laumontite. 
 
 LA PLATA Co. Poughkeepsie Gulch, Alaska mine, alaskaite with tetrahedite, chalco- 
 pyrite, barite. 
 
 LAKE Co. Leadville, cerussite carrying silver, anglesite, pyromorphite, sphalerite, 
 calamine, minium, dechenite (?), rhodochrosite with galenite, chalcopyrite. 
 
 Golden Queen mine, scheelite with gold. Ute and Ule silver mine, stephanite, galenite, 
 sphalerite, chalcocite. 
 
 PARK Co. Grant P. 0., Baltic lode, beegerite. Hall Valley, ilesite. 
 
 CALIFORNIA. 
 
 INTO Co. San Carlos, datolite with grossular garnet and vesuvianite. 
 Los ANGELES Co. Brea Ranch, vivianite in nodules with asphaltum. 
 
 OREGON. 
 
 DOUGLAS Co. Cow Creek, Pkiey Mountain, considerable deposits of a hydrous nickel 
 silicate, allied to garnierite. 
 GRANT Co. Canyon City, cinnabar with calcite. 
 
 UTAH. 
 
 IRON Co. Coyote District, orpiment and realgar in a thin bed in the horizontal sediment- 
 ary formations underlying lava. 
 PIUTE Co. Marysvale, onofrite. 
 
 SALT LAKE Co. Butterfield Canon, mallardite, luckite. 
 Wahsatch Range, head waters of Spanish Fork, ozocerite in considerable beds. 
 
 NEVADA. 
 
 ELKO Co. Emma mine, chrysocolla; Blue Hill mine, azurite, malachite. 
 
 LANDER Co. Austin, polybasite, chalcopyrite, azurite, whitneyite. 
 
 LINCOLN Co. Halite, cerargyrite. 
 
 NYE Co. Anglesite, stetefeldtite, azurite. cerussite, silver ore, cerargyrite. 
 
 WHITE PINE Co. Eberhardt mine, cerargyrite; Paymaster mine, freieslebenite. 
 
 NEW MEXICO.* 
 
 DONA ANA Co. Lake Valley, cerargyrite in the Sierra mines in large masses, rarely 
 crystallized, associated with embolite, cerussite. galenite, vanadinite in small canary-yellow 
 crystals, native silver, pyrolusite, manganite, fluorite, ankerite, apatite, chert. Victoria 
 mine, 40 miles below Nutt, massive anglesite. Kingston, in Black Range, argentite in 
 large masses. 
 
 SOCORRO Co.- Socorro Mt., 3 miles from town of Socorro, large veins of barite carrying 
 cerargyrite, vanadiferous mimetite, vanadinite in barrel-shaped crystals resembling pyromor- 
 phite. Magdalena Mountains, 27 miles west of Socorro, cerussite in heavy veins with 
 galenite, sphalerite, etc. Green and blue calamine on the Kelly location. Sophia mine, 
 stromeyerite? Grafton, on a large quartz vein, Ivanhoe mine, gold in black cerussite, 
 chalcocite, bornite, malachite, azurite, chalcopyrite, cerargyrite, amethystine quartz. New 
 Elk Mountain, 100 miles south of Socorro, cerussite carrying silver. 
 
 * The author is indebted for the following notes, as also for others under Arizona and 
 Montana, to Prof. B. Silliman. 
 
AMERICAN LOCALITIES. 507 
 
 GRANT Co. Silver City, Bremen's mine, argentite, cerargyrite, argentite pseudomorph 
 >f mollusca, barite with cerargyrite, native silver in filagree and dendrites on slate; Santa 
 Sita copper' mines, native copper, tenorite. Mogollon and Burro mountains, Coony mining 
 listrict, Dry Creek; in Mundo mine, melaconite; Silver Twigg mine, bornite, copper; Alba- 
 ross mine, bornite, malachite; Cooney mine, chalcopyrite, azurite, bornite; Clifton mine, 
 mtive copper, cuprite, azurite, malachite, wulfenite. Georgetown, Naiad Queen mine, 
 irffentite pseudomorph of mollusca. cerargyrite, native silver in dendritic form on slate. 
 
 SAN MIGUEL Co. Cerillos, Mt. Chalchuitl, turquoise in tuff. In the Cerillos district are 
 lumerous mineral veins, carrying silver lead and salts of lead, rarely wulfenite and 
 vanadinite, azurite, malachite, sphalerite, etc. 
 
 ARIZONA. 
 
 In the Silver District, YUMA Co., at the Hamburg, Princess and Red Cloud mines, in 
 connection with quartz veins carrying argentiferous galena, fine ruby-red _ vanadmite, 
 red wulfenite massive anglesite. Silent District, Black Rock mine, vanadmite. At the 
 Castle Dome 'mines, vanadinite, mimetite, wulfenite, cerussite, galenite, fluorite. Also 
 wulfenite at the Melissa mine and Rover mine. 
 
 In the Vulture District (also called White Picacho District, YAVAPAI and MARICOPA 
 Cos numerous veins of gold-bearing quartz, carrying lead. Vulture mine, cryst gold, 
 iarosite, wulfenite. Hunter's Rest mine, gold in tourmaline rock Farley s Collateral 
 mine and the Phenix mine, 20 miles north-east of Vulture, yellow vanadmite with 
 calcite, wulfenite, cerussite, descloizite (?), volborthite (?) crocoite, vauquelmite, phoem- 
 cochroite Montezuma mine, vanadinite, cerussite. Sante Domingo mine, mimetite, 
 argentite' Silver Star mine, native silver, cerussite, argentite, crocoite, vanadmite. 
 Tiger mine, native silver, cerargyrite. Tip Top mine, native silver, sphalerite, argentite, 
 pvrargyrite. 
 
 From the Rio Verde, MARICOPA Co., thenardite in large deposits. 
 
 MOHAVE Co Moss lode, gold in crystalline plates; fluorite a frequent gangue material. 
 
 FINAL Co. Mule Pass, Bisbey, Copper Queen mine, native copper, copper oxide, m 
 
 mine, Pioneer District, FINAL Co. -Fine crystallized native silver, 
 areentite sphalerite, pyrite. Stonewall Jackson mine, cryst. silver, argentite. 
 f rom the P Bon Ton mines, Chase Creek, near Clifton, dioptase with cuprite and hmomte. 
 
 MONTANA. 
 
 BUTTE Co.-Butte Citv, Alice silver mine, rhodonite, a common gangue of 
 and other silver ores, rhodochrosite. Same in Magna ^^^1 
 Bell, and other copper veins yield various copper salts and arsenical coe 
 
 Sil Original Butte mine," wurtzite with pyrite. Clear Grit mine native silver, argentite, 
 chalcopyrite, sphalerite, calcite, rhodochrosite. Colusa mine, chalcc 
 
 ALASKA. 
 
 Ft. Wrangell at mouth ol the Stickeen River, fine garnets in mica schist. 
 
 CANADA PROVINCE OF QUEBEC. 
 
 MONTREAL. Analcite, sodalite, nephelite (in nephelite-syenite). 
 
 OTTAWA Co.- Veins carrying apatite and pyroxene in large ^uant ^ s 
 Buckingham, Burgess, Templeton, and other townships, y^f^fS 
 scapolite, garnet, tourmaline, titanite, zircon, ortlioclase, phlogopiti 
 
 Templeton, vesuvianite, garnet (cinnamonstone), pyroxene. 
 
 Hull, colorless garnets, vesuvianite, white pyroxene. 
 
 Wakefield, chrome garnet. 
 
 CANADA PROVINCE OF OTTAWA. 
 
 FRONTENAC Co. Scapolite, apatite. fitnnitp zircon (also twins), 
 
 RENFREW Co.-Eganville, large crystals of apatite, titanite, , 
 
 amphibole. 
 
APPENDIX. 
 
 NOVA SCOTIA. 
 CUMBERLAND Co. Alunogen. 
 COLCHESTER Co. New Annan, covellite. 
 KINGS Co. Black Rock, in trap with stilbite, ulexite, heulandite. 
 
 CANADA KEEWATIN DISTRICT. 
 
 CHURCHILL RIVER. Lazulite. 
 
 KNEE LAKE. Magnetite Island, magnetite. 
 
 CANADA BRITISH COLUMBIA. 
 CARIBOO DISTRICT. Native gold, galenite 
 
 Th^mpfon A lSver R c7a R niTe GOld ' argentiferous ^rahedrite, cerargyrite, cinnabar. North 
 HOWE SOUND. Bornite, chalcopyrite, molybdenite, mica. 
 OMINICA DISTRICT. Gold, galenite, silver, silver amalgam 
 CASSIAR DISTRICT. Gold. 
 TEXADA ISLAND. Magnetite. 
 QUEEN CHARLOTTE ISLANDS. -Skincuttle Inlet, Harriet Harbor, magnetite, chalcopyrite. 
 
GENERAL INDEX TO MINERAL SPECIES 
 
 Abriachanite, 420. 
 Acadialite, 344. 
 Acanthite, 239. 
 Achrematite, 385. 
 Achroitc, 330. 
 Acmitc, 294. 
 Actinclite, 297. 
 Adamine, Adamite, 373; 420. 
 Adelpholite, 363. 
 Adular, Adularia, 325. 
 ^Egirine, ^Erite, 294. 
 
 Aerinite, M50. 
 BSschynite, 362. 
 Agalmatolite, 349, 352. 
 
 Agaric mineral, 400. 
 Agate, 286. 
 Aglaite, 420. 
 Agricolite, 302. 
 Aikinite, 254. 
 Ajkite, 4:J5. 
 
 Akanthit, v. Acanthite. 
 Akmit, v. Acmite. 
 Alabandite, '^37. 
 Alabaster, 393. 
 Alalite, 293. 
 Alaskaite, 420. 
 Alaun v. Alum. 
 Alaunstein, 396. 
 Albertite, 416. 
 Albite 323; 420. 
 Alexandrite, 275. 
 Algodonite, 235. 
 Alipite, 351. 
 
 Allanite, 308. 
 
 Allemontite, 227. 
 
 Allochroite, v. Andradite. 
 
 Alloclasite, 248. 
 
 Allophane, 341. 
 
 Allophite, 806 
 
 Almandin, Almandite, 303. 
 
 Alshedite, 438. 
 
 Alstonite. D. Bromlite. 
 
 Altaite, 237. 
 
 Alum, Native, 895. 
 
 Alumina = Aluminum oxide 
 
 Aluminum carbonate, 410. 
 chloride, 260. 
 fluoride, 264, 265 
 fluo-silicate, 332 
 
 Uuminum hydrate, 279, 282. 
 hydro - sulphate, 
 
 395. 
 
 mellate, 412. 
 oxide (Alumina), 
 
 267. 
 
 phosphate, 875, 
 376, 377, 378, 
 431). 
 silicate, 831, 332, 
 
 341, 349, 351. 
 sulphate, 395, 396. 
 Aluminite, 395. 
 Alunite, 396. 
 Alunogen, 895. 
 Amalgam, 225. 
 Amazonstone, 325. 
 Amber, 415. 
 Amblygonite, 369; 420. 
 Amblystegite, 290. 
 Ambrite, 415. 
 Ambrosine, 415. 
 Amesite, 424. 
 Amethyst, 286. 
 Amianthus, 297, 350. 
 Ammonia, v. Ammonium. 
 Ammonium chloride, 260. 
 oxalate, 433. 
 phosphate, 371. 
 sulphate, 39.2. 
 Amphibole, 293; 420. 
 Analcite, Analcime, 343. 
 Anatase, 277. 
 Andalusite, 331. 
 Andesine, Andesite, 322, 
 Andradite, 304. 
 Andrewsite, 878. 
 Anglesite, 389. 
 Anhydrite, 389. 
 Animikite, 420. 
 Ankerite, 402. 
 Annabergite, 372. 
 Innerodite, 423. 
 Annite, 313. 
 Anomite, 431 . 
 Anorthite, 321. 
 Antholite, v. Anthophyllite, 
 Anthophyllite, 295. 
 Anthracite, 417. 
 
 Lnthracoxenite, 415. 
 intigorite. 351. 
 intillite, 351. 
 \ntimonblende, 284. 
 \ntimonbluthe, . Valentin- 
 
 ite. 
 
 Antimonglanz, 232. 
 Antimonite, 232. 
 Antimonsilber, 234. 
 Antimony, Arsenical, 227. 
 Gray, 232. 
 Native, 226. 
 Red Kermesite, 
 
 284. 
 White -Valentin- 
 
 ite, 284. 
 Antimony blende, 284. 
 bloom, 284. 
 glance, 282. 
 ochre, 437. 
 oxide, 284, 437. 
 sulphide, 232. 
 Apatite, 364; 420. 
 Aphanesite . Clinoclasite. 
 Aphrite, 400. 
 Aphrizite, 330. 
 Aphrodite, 349. 
 Aphrosiderite, 356. 
 Aphthalose,Aphthitahte,390. 
 
 Apjohnite, 395. 
 Aplome, 304. 
 Apophyllite, 340; 421. 
 Aquacreptite, 851. 
 Aquamarine, 299. 
 Arseoxene, 426. 
 Aragonite, 405; 421. 
 Aragotite, 414. 
 Arcanite, 390. 
 Arctolite, 421. 
 Ardennite, 310. 
 Arequipite, 421, 
 Arfvedsonite, 298; 421. 
 Argentine, 4 0. 
 Argentite, 235, 
 Argentopyrite, 437. 
 Argyropyrite, 437. 
 Arite, 243. 
 Arkansite, 278. 
 Arksutite, 265. 
 
 509 
 
510 
 
 GENERAL INDEX. 
 
 Arquerite, 225. 
 Arragonite, 405. 
 Arrhenite, 421. 
 Arsenargentite, 421. 
 Arseneisen, v. Leucopyrite. 
 Arseneisensinter, v. Pitticite. 
 Arsenic, Antimonial, 227. 
 
 Native, 226. 
 
 Red, 284. 
 
 Yellow, 284. 
 
 White, 284. 
 Arsenic oxide, 284. 
 
 sulphide, 231. 
 Arsenical Antimony, 227. 
 Arsenikkics, 247. 
 Arsenikkupfer, 234. 
 Arsennickelglanz, 246. 
 Arseniosiderite, 378. 
 Arsenite, v. Arsenolite. 
 Arsenolite, 284. 
 Arsenopyrite, 247. 
 Asbestus, 297. 
 
 Blue,t>. Crocidolite. 
 Asbolan, Asbolite, 283. 
 Asraanite, 288; 421. 
 Asparagus-stone, 365. 
 Aspasiolite, 353. 
 Asphaltum, 416. 
 Aspidolite, 312. 
 Astrakanite, v. BISdite. 
 Astrophyllite, 313; 421. 
 Atacamite, 261. 
 Atelestite, 378. 
 Ateline, Atelite, 262; 421. 
 Atopite, 421. 
 Augite, 29:j. 
 Aurichalcite, 410. 
 Auriferous pyrite, 220. 
 Auripigmentum, 232. 
 Automolite, 272. 
 Autunite, M79; 421. 
 Aventurine quartz, 286. 
 
 feldspar, 322, 323, 
 
 3J5. 
 
 Axinite, 310. 
 Azorite, 859. 
 Azurite, 411. 
 
 Babingtonite, 295. 
 Bagrationite, v. Allanite. 
 Baikalite, v. Sahlite. 
 Balvraidite, 421. 
 Barcenite, 421. 
 Barnhardtite, 245. 
 Barite, 387. 
 Barium carbonate, 406, 408. 
 
 nitrate, 433. 
 
 (and uranium) phos- 
 phate, 439. 
 
 silicate, 322, 346, 420. 
 
 sulphate, 387. 
 Bartholomite, 395. 
 Barylite, 421. 
 Baryt, Barytes, 387. 
 
 Baryta Barium oxide. 
 
 Barytocalcite, 408. 
 
 Barytocelestite, 388. 
 
 Basanite, 287. 
 
 Bastite, 151. 
 
 Bastmisite, 408, 438. 
 
 Bathvillite, 415. 
 
 Batrachite, 300. 
 
 Beaumontite, 347. 
 
 Beauxite, 281. 
 
 Beccarite, 440. 
 
 Bechilite, 382. 
 
 Beegerite, 421. 
 
 Beilstein, v. Nephrite. 
 
 Bell metal ore = Stannite, 
 
 245. 
 
 Belonite, 110. 
 Benzole, 414. 
 Beraunite, v. Vivianite. 
 Bergamaskite, 420. 
 Bergholz, 297. 
 Bergkrystall, v. Quartz. 
 Bergmehl, 401. 
 Bergmilch, 400. 
 Bergol, 413. 
 Bergpech, 416. 
 Bergseife, v. Halloysite. 
 Bergtheer, V. Pittasphalt. 
 Berlauite, 436. 
 Bernardinite, 435. 
 Bernstein, 415. 
 Beryl, 299; 421. 
 Beryllium aluminate, 274. 
 
 silicate, 299, 300, 
 
 801, 302, 333. 
 Berthierite, ',51. 
 Berzelianite, 237. 
 Berzeliite, 421. 
 Beyrichite, 241. 
 Bhreckite, 4^2. 
 Bieberite, 395. 
 Biharite, 353. 
 Bimsstein, t>. Pumice. 
 Bindheimite, 379. 
 Binnite, 251; 250. 
 Biotite, 31-2. 
 Bischofite, 423. 
 Bismite, 284. 
 Bismuth, Acicular (aikinite), 
 
 254. 
 
 Native, 227. 
 Telluric, 2 S3. 
 Bismuth arsenate, 377, 379. 
 
 blende(eulytite),302. 
 
 carbonate, *412, 422. 
 
 chloride. 262. 
 
 glance, 232. 
 
 nickel (griinauite), 
 237. 
 
 ochre, 284. 
 
 oxide, 284. 
 
 selenide, 233. 
 
 silicate, 302. 
 
 silver, 420. 
 
 Bismuth sulphide, 232. 
 tellurate, 397. 
 telluride, 233. 
 Bismuthinite, 232. 
 Bismutite, 412. 
 Bismutoferrite, 302. 
 Bismutosphaerite, 422. 
 Bittersalz, 394. 
 Bitter spar, Bitterspath, 1 
 
 Dolomite. 
 Bitumen, 416. 
 Bituminous coal, 417. 
 Bjelkite, 424. 
 Black jack, 237. 
 Blattererz, Blattertellur, 24! 
 Bliitterzeoiith, t. Heulanditi 
 Blaueisenerz. v. Vivianite. 
 Blaueisenstein, v. Crocidolit 
 Blauspath, ii75. 
 Blei, Gediegen, 226. 
 Bleiglanz, 235. 
 Bleiglatte, 267. 
 Bleigumme, v. Plumbogun 
 
 mite. 
 
 Bleilasur, 396. 
 Bleihornerz, 4C8. 
 Bleiniere, 379. 
 Bleinierite, v. Bindheimite. 
 Bleispath, 407. 
 Blei vitriol, 389. 
 Blende, 237. 
 Blodite, 394. 
 Blomstrandite, 422. 
 Bloodstone, 286. 
 Blue vitriol, 394. 
 Bodenite, 308. 
 Bog-butter, 415. 
 Bog-iron ore, 281. 
 
 manganese, 283. 
 Bole, Bolus - Halloysite. 
 Bolivite, 422. 
 Boltonite, 300. 
 Bombiccite, 415. 
 Boracic acid. 380. 
 Boracite, 381 ; 422. 
 Borax, 381. 
 Bordosite, 267. 
 Bornite, 237. 
 Borocalcite, 382. 
 Boron trioxide, 380. 
 Boronatrocalcite, 381. 
 Bort, 2", 9. 
 Bosjemanite, 395. 
 Botallackite, #. Atacamite. 
 Botryogen, b95. 
 Botryolite, 325. 
 Boulangerite, 254. 
 Bournonite, 253. 
 Boussingaultite, 392. 
 Bowenite, 297, 350. 
 Bowlingite, 422. 
 Brackebuschite, 425. 
 Bragite, 362. 
 Branderz, v. Idrialite. 
 
GENERAL INDEX. 
 
 511 
 
 Brandisite, 358. 
 Brauneisenstein, 280. 
 Braunite, 277. 
 Braunkohle, 418. 
 Braunspath, 401. 
 Bra vai site, 422. 
 Bredbergite, 304. 
 Breislakite, D. Pyroxene. 
 Breithauptite, 243. 
 Breunerite, 402. 
 Brewstcrite, ;-47. 
 Brittle silver ore, v. Stephan- 
 
 ite. 
 
 Brochantite, 396. 
 Bromargyrite, 260. 
 Bromlite, 406. 
 Bromsilber, 260. 
 Bromyrite, 260. 
 Brogniardite, 252. 
 Brongnartine, 397. 
 Bronzite, 290. 
 Brookite, 277; 422. 
 Brown coal, 418. 
 
 iron ore, 280. 
 
 spar, 401, 402. 
 Brucite, 2*1 ; 422. 
 Brushite, 371. 
 Bucholzite, 331. 
 Bucklandite, 308. 
 Bunsenin, 430. 
 Bunsenite, 207. 
 Buntkupfererz, 237. 
 Bnstamite, '294. 
 Butyrellite, 415. 
 Byerite, 417. 
 Bytownite, 321. 
 
 Cabrerite, 422. 
 Cacholong, 289. 
 Cacoxenite, Cacoxene, 378. 
 Cadmium sulphide, 242. 
 Cairngorm stone, 286. 
 Calaite, v. Callaite. 
 Calaminc, 339, 422; 404. 
 Calaverite, 249; 422. 
 Calcareous spar, tufa, 398 ; 
 
 400. 
 
 Calcite, 398. 
 Calcium arsenate, 370, 371. 
 
 antimonate, 370, 421. 
 
 borate, 382. 
 
 boro-silicate, 334. 
 
 carbonate, 398, 405. 
 
 chloride, 2(50. 
 
 fluoride, 26H. 
 
 nitrate, 379. 
 
 oxalate, 412. 
 
 phosphate, 364, 371, 
 426, 432. 
 
 silicate, 291, 338; 
 321. 
 
 sulphate, 389, 392; 
 891. 
 
 sulphide, 235. 
 
 Calcium tantalate, 359, 431. 
 titanate, 270. 
 tungstate, 384. 
 Calcozincite, 267. 
 Calc-sinter, 400. 
 Caledonite, 391. 
 Callais, Callaite, 377. 
 Calomel, 260. 
 3alvonigrite, 434. 
 Campy lite, 367. 
 Canaanite = White Pyroxene 
 Cancrinite, 317; 422. 
 Cannel Coal, 417. 
 Capillary pyrites, 241. 
 Caporcianite, 338. 
 Carbonado, 229. 
 Carbon diamantaire, 229. 
 Carnallite, 261. 
 Darnelian, 2s6. 
 Carpholite, 341. 
 Caryinite, 422. 
 Cassiterite, 275. 
 Castor, Castorite, 295. 
 Catapleiite, 339. 
 Cataspilite, 353. 
 Cat's eye, 2 6. 
 Cavolinite, 316. 
 Celadonite, 349. 
 Celestialite, 435. 
 Celestite, Celestine, 388. 
 Centrallassite, 338. 
 Cerargyrite, 260. 
 
 Cerbolite, 392. 
 
 Cerine, 8u8. 
 
 Cerite, 340. 
 
 Cerium carbonate, 408. 
 fluoride, 439. 
 phosphate, 364, 368. 
 silicates, 308, 330. 
 
 Cerolite, 351. 
 
 Cerussite, 407. 
 
 Cervantite, 284. 
 
 Ceylanite, Ceylonite, 271. 
 
 Chabazite, 344; 422. 
 
 Chalcanthite, 394. 
 
 Chalcedony, 286. 
 
 Chalcocite, 2H9. 
 
 Chalcodite, 350. 
 
 Chalcolite, 378. 
 
 Chalcomenite, 422. 
 
 Chalcomorphite, 351. 
 
 Chalcophanite, 283. 
 
 Chalcophyllite, 375. 
 
 Chalcopyrite, 244; 422. 
 
 Chalcosiderite, 378. 
 
 Chalcosine, 239. 
 
 Chalcostibite, 250. 
 
 Chalcotrichite, 266, 
 
 Chalk, 400. 
 
 Chalybite, 403. 
 
 Chathamite, 246. 
 
 Chert, 287. 
 
 Chester! ite, 326. [41 
 
 Chessy Copper, Chessylit 
 
 hiastolitc, 831. 
 
 hiidrenite, 377; 422. 
 
 hiolite, 264. 
 
 hladnite, 290. 
 
 hloanthite, 245. 
 
 hloralluminite, 260. 
 
 hlor-apatite, 365. 
 
 hlorastrolite, 340. 
 
 hlorite Group. 355. 
 
 hloritoid. 358. 
 
 hloritspath, 358. 
 
 hlormagnesite, 260; 423. 
 
 hlorocalcite, 260. 
 
 hloropal, 350. 
 
 hlorophaeite, 356. 
 
 hlorophane, 263. 
 
 hlorophyllite, 353. 
 Chlorothionite, 2CO. 
 Chloroti'e, 373. 
 Chodneffitc, 264. 
 Chondrarsenite, 372. 
 Chondrodite, 327; 423. 
 Chonicrite, 355. 
 Chrismatite, 413. 
 Chromeisenstein, 274. 
 Chrom glimmer, v. Fuch- 
 
 site. 
 
 Chromic iron, 274. 
 Chromite, 27 \ ; 423. 
 Chroinpicotite, 274. 
 Chromium oxide, 274. 
 
 sulphide, 242. 
 Chrysoberyl, 274. 
 Chrysocolla, 838; 423. 
 
 Chrysolite, 800; 423. 
 
 Chrysoprase, '286. 
 
 Chrysotile, ; 50. 
 
 Churchite, 371. 
 
 Cinnabar, 240. 
 
 Cinnamon stone, 303. 
 
 Clarite, 258. 
 
 Claucletite 284. 
 
 Clausthalite, 236. 
 
 Clay, 351, et seq. 
 
 Cleavelandite, 324. 
 
 Cleveite, 423. 
 
 Clingmanite, 358. 
 
 Clinoclase, Clinoclosite, 3<4. 
 
 Clinochlore, 356. 
 
 Clinocrocite, 423. 
 
 Clinohumite, 328. 
 
 Clinophaeite, 423. 
 
 Clintonite, 358; 423. 
 
 Cloanthite, 245. 
 
 Coal, Mineral, 417. 
 Boghead, 48. 
 Brown, 418. 
 Cannel, 417. 
 
 Cobalt, Arsenical 245 246 
 
 Black (asbohte), 283. 
 Earthy, 283. 
 Gray (smaltite), 245. 
 Red(erythrite), 372. 
 White (cobaltite), 246. 
 
512 
 
 GENERAL INDEX. 
 
 Cobalt bloom, 372. 
 glance, 246. 
 arsenate, 372. 
 arsenide, 246 ; 248. 
 carbonate, 436. 
 oxide, 283. 
 selenite, 432. 
 sulphate, 394. 
 sulphide, 245. 
 Cobaltine, Cobaltite, 246. 
 Cobaltomenite, 432. 
 Coccolite, 293. 
 Coke, 417. 
 
 Colestine, <o. Celestite. 
 Cceruleolactite, 376. 
 Collyrite, 341. 
 Colophonite, 304. 
 Coloradoite, 423. 
 Columbite, 360; 423. 
 Comptonite, 342. 
 Connellite, 391. 
 Cookeite, 354. 
 Copal, Fossil, 415. 
 Copaline, Copalite, 415. 
 Copiapite, 395. 
 Copper, Antimonial (chalco- 
 
 stibite), 250. 
 Arsenical, 234. 
 Black (me 1 aconite), 
 
 267. 
 
 Blue, 411. 
 Emerald (dioptase), 
 
 301. 
 
 Gray, 255. 
 * Indigo, 249. 
 Native, 225. 
 Purple, 237. 
 Eed, 266. 
 Variegated, 237. 
 Vitreous, 239. 
 
 Copper arsenate, 373, 374, 375. 
 arsenide, 234. 
 arsenite (?), 439. 
 carbonate, 411. 
 chloride, 200. 
 chromate, 386. 
 glance, 829. 
 mica, 375. 
 nickel, 242. 
 oxide, 266, 267, 
 oxychloride, 261, 262. 
 phosphate, 373, 374. 
 pyrites, 244. 
 selenide, 237. 
 selenite, 422. 
 silicate, 301, 338. 
 sulph-antimonite, 250, 
 
 254, 255, 257, 4J8. 
 sulph - arsenite, 251, 
 
 256, 257, 25^. 
 sulphate, 890, 394, 
 
 396, 397, 428. 
 sulphide, 239, 249; 
 237, 244. 
 
 Copper s u 1 p h o - bismuthite, 
 250, 251, 254. 
 
 tungstate, 384. 
 
 vanadate, 374. 
 
 vitriol, v. Chalcan- 
 
 thite. 
 Copper ore, Red, 266. 
 
 Yellow, 244. 
 Copperas, 394. 
 Coprolites, 366. 
 Coquimbite. 395. 
 Cordierite, 311. 
 Cornwallite, 374. 
 Coronguite, 424. 
 Corundellite, 358. 
 Corundophilite, 358; 424. 
 Corundum, 267; 424. 
 Corynite, 247. 
 Cosalitc, 252; 424. 
 Cossaito, 354. 
 Cossyrite, 4'24 
 Cotunnite, 261. 
 Covelline, Covellite, 249. 
 Craigtonite, 424. 
 Crednerite, 278. 
 Crichtonite, 270. 
 Crocidolite, 298. 
 Crocoite, Crocoisite, 385; 424. 
 Cronstedtite, 357. 
 Crookesite, 235. 
 Cryolite, 264; 424. 
 Cryophyllite, 315. 
 Cryptohalite, 264. 
 Cryptolite, 3<>4. 
 Cryptomorphite, 382. 
 Cuban, Cubanite, 245. 
 Culsageeite, 355. 
 Cummingtonite, 297. 
 Cuprocalcite, 411; 424. 
 Cuprite, ^66. 
 Cupromagnesite, 395. 
 Cuproscheelite, 384. 
 Cuprotungstite, 384. 
 Cuspidine, 424. 
 Cyanite, 332; 424. 
 Cyanochalcite, 339. 
 Cyanotrichite, 397. 
 Cymatolite, 349, 436. 
 Cyprusite, 424. 
 
 Damourite, 353. 
 Danaite, 248. 
 Danalite, 302; 424. 
 Danburite, 311 ; 424. 
 Datholite, Datolite, 334. 
 Daubreelite, 242. 
 Daubreite, 262. 
 Davids >nite, 299. 
 Davreuxite, 425. 
 Davyne, Davina, 316. 
 Dawsonite, 410; 425. 
 Dechenite, 367. 
 Degeroite, 354. 
 Delessite, 356; 425. 
 
 Delvauxite, v. Dufrenite. 
 
 Demidoffite, 339. 
 
 Derbyshire spar, . Fluorite 
 
 Descloizite, 367; 425. 
 
 Desmine, 346. 
 
 Destinezite, 425. 
 
 Dewalquite, 310. 
 | Deweylite, 351. 
 
 Diabantachronnyn, 355. 
 
 Diabantite, 355.' 
 
 Diaclasite, 291. 
 
 Diaclochite, 379. 
 ; Diallage, Green, 293. 
 | Diallogite, Dialogite, 403, 
 , Diamond, 228; 425. 
 i Dianite, v. Columbite. 
 ! Diaphorite, 252. 
 
 Diaspore, 279. 
 
 Dichroite, 311. 
 
 Dickinsonite, 425. 
 
 Dietrichite, 425. 
 
 Dihydrite, 874. 
 
 Dimorphite, 232. 
 
 Dinite, 414. 
 
 Diopside, 293. 
 
 Dioptase, 301. 
 
 Dipyre, 816. 
 
 Discrasite, v. Dyscrasite. 
 
 Disterrite = Brandisite. 
 
 Disthene, 332. 
 
 Ditrovte, 317. 
 
 Dog-T ooth Spar, 400. 
 
 Dolerophanite, 390. 
 
 Dolomite, 401. 
 
 Domeykite, 234. 
 
 Doppelspath, 899. 
 
 Dopplerite, 415; 425. 
 
 Douglasite, 425. 
 
 Dreelite, 890. 
 
 Dry-bone, 404. 
 
 Dudleyite, 358. 
 
 Dufrenite, 378. 
 
 Dufrenoysite, 251. 
 
 Dumortierite, 425. 
 
 Duporthite, 425. 
 
 Durangite, 370. 
 
 Durfeldtite, 425. 
 
 Duxite, 415. 
 
 Dysanalyte, 425. 
 
 Dyscrasite, 234. 
 
 Dysluite, 272. 
 
 Dysodile, 415. 
 
 Dysyntribite, 353. 
 
 Earthy Cobalt, 283. 
 Edenite, 297. 
 Edingtonite, 341. 
 Edwardsite, v. Monazite, 
 Eggonite, 425. 
 Ehlite, 374. 
 Eisenbliithe, 405. 
 Eisenbrucite, 422. 
 Eisenglanz, 268. 
 Eisenglimmer, 269. 
 

 Eisenkies, 243. 
 Eisenkiesel, v. Quartz. 
 Eisenrpse, 269. 
 Eisensinter, v. Pitticite. 
 Eisenspath, 403. 
 Eisspath, 326. 
 Ekdeinite, 4'25. 
 Ekebergitc. 3.6. 
 Ekmannite, 354. 
 Eljcolite, 316. 
 Elaterite, 414. 
 Elcctruin, 221. 
 Eleonorite, 423. 
 Elroquite, 423. 
 Embolite, 260. 
 
 Embrithitc, v. Boulangerite. 
 Emerald, ^90. 
 Emerald nickel, 410. 
 Emery, 268. 
 Emplectite, 250. 
 Enargite, 257. 
 Enceladite, v. Warwickite. 
 Enophite, 433. 
 Enstatite, 2;;0. 
 Enysite, 3D7. 
 Eosite, 885. 
 Eosphorite, 423. 
 Ephesite, 35 k 
 Epiboulangerite, 254. 
 Epidote, 307. 
 Epigenite, 253. 
 Epistilbite, 347; 426. 
 Epsom Salt, Epsomite, 394; 
 
 423. 
 
 Erbsenstein, 400. 
 Erdkoba.lt, 283. 
 Erdol, 416. 
 Erdpech, 416. 
 Eremite, v. Monazite. 
 Erilite, 426. 
 Erinite, 374. 
 Eriochalcite, 426. 
 Erubescite, 2 ,7. 
 Erythrite, 37 .. 
 Erythrosiderite, 261. 
 Erythrozincite, 4^6. 
 Esmarkite 353. 
 Essonite. 304. 
 Ettringite, 395. 
 Eucairite, 235. 
 Euchroite, 373. 
 Euclase. 333, 426. 
 Eucolite, 299. 
 Eucrasite, 426. 
 Eucryptite. 426. 
 Eudialyte, Eudyalite, 299. 
 Eudnophite, 344. 
 Eugeng'anz, v Polybasite. 
 Eukairite, v. Eucairite, 
 Euklas, 8-3. 
 
 Eulytine, Eulytite, 302; 426. 
 Eumanite, 276. 
 Euosmite, 415. 
 Euphyliite, 354. 
 
 GENERAL INDEX. 
 
 Eusynchite, 426. 
 Euxenite, 362. 
 
 Fahlerz, 255. 
 
 Fahlunite, 808. 
 
 Fairfieldite, 426. 
 
 Famatinite, 258. 
 
 Faserquarz, 298. 
 
 Fassaite, 29-5. 
 
 Faujasite, 344. 
 
 Fauserite, ;, 9k 
 
 Fayalite, 300. 
 
 Feather ore. 251. 
 
 Federerz, 251. 
 
 Feitsui, 309. 
 
 Feldspar Group, 319; 426. 
 
 Felsite, 323, 326. 
 
 Feldspath, v. Feldspar. 
 
 Fergusonite, 362; 4.7. 
 
 Ferroilmenite, 860. 
 
 Ferrotellurite. 427. 
 
 Feuerblende, 252. 
 
 Feuerstein, 287. 
 
 Fibroferrite, 395. 
 
 Fibrolite, 331. 
 
 Fichtelitc, 41 k 
 
 Fillowite, 4\!7. 
 
 Fiorite, 289. 
 
 Fireblende, 252. 
 
 Flint, 287. 
 
 Float-stone, 2 C 9. 
 
 Flos ferri, 405. 
 
 Fluellitc, 2o4. 
 
 Fluocerite, 204 
 
 Fluor-apatite. 865. 
 
 Fluor, Fluorite, 203; 427. 
 
 Fluor Spar, 2(53. 
 
 Flussspath, 203. 
 
 Foliated tellurium, u. Nagya- 
 
 gite. 
 
 Fontaincbleau limestone, 400. 
 Foresite, 347; 4.7- 
 Forsterite, 300. 
 Fovvlerite, 294 
 Francolite, 365. 
 Franklandite. 4" 7. 
 Frank inite, 273. 
 Fredricite 438. 
 Freibergite. 255. 
 Freieslebenite. 252. 
 Frenzelite, 233. 
 Freyalite, 427. 
 Friedelite, 302. 
 Frieseite, 437. 
 Frigidite, 438. 
 Fuchsite, 314. 
 
 GadoMn, Gadol inite, 309; 427. 
 Gahnite, 272. 
 Galena, Galenite, 235. 
 Galenobismutite, 427. 
 Galmei. 339, 40k 
 Ganomalite, 427. 
 Garnet, 302; 427. 
 
 513 
 
 1 Garnierite, 351 ; 427. 
 j Gastaldite, 298. 
 
 Guanovulite, 392. 
 
 Gay-Lussite, 400. 
 
 Gearksutite, 265. 
 
 Gedanite, 435. 
 
 Gehlenite, 331. 
 
 Geierite, v. Geyerite. 
 
 Gekrosstein, 389. 
 
 Gelbbleierz.384. 
 
 Genthite, 351. 
 
 Geoccrite, 414. 
 
 Geocronite, 257. 
 
 Geomyricite, 414. 
 
 Gersdorffite, 240. 
 
 Geyerite, 248. 
 
 Geyserite, 28D. 
 
 Gibbsite, 282. 
 
 Gieseckite, 352; 317. 
 
 Gigantolite, 353. 
 
 Gilbertite, 353. 
 
 Gillingite, 354. 
 
 Ginilsite, 428. 
 
 Girasol, 289. 
 
 Gismondinc, Gismondite, 341 ; 
 428. 
 
 Giufite, 432. 
 
 Glaazkobalt, -c. Cobaltite. 
 
 Glaseritc, v. Arcanite. 
 
 Glaserz, Glanzerz, v. Argen- 
 tite. 
 
 Glauber salt, 392. 
 
 Glauberite, 391. 
 
 Glaucodot, 248. 
 
 Glauconite, 349. 
 
 Glaucophane, 298. 
 
 Glimmer, v. Mica. 
 
 Globulites, 110. 
 
 Gmelinite, 345. 
 
 Gold, 221. 
 
 Gold telluride, 248, 249, 430. 
 
 Goldtellur, . Sylvanite. 
 
 Goshenite, 299. 
 
 Goslarite. 395. 
 
 Gothite, 280. 
 
 Grahamite, 416. 
 
 Grammatite, 2y7. 
 
 Granat, 302. 
 
 Graphic tellurium, 248. 
 
 Graphite, 280. 
 
 Graukupfererz, v. Tennantite. 
 
 Gray antimony, 232. 
 copper, .255. 
 
 Greenockite, 2 :2. 
 
 Greenovite, 335. 
 
 Grenat, v. Garnet. 
 
 Grochauite, 357. 
 
 Grossularite, 803. 
 
 Griinauite, 237. 
 
 Grunbleierz, 366. 
 
 Guadalcazarite. 241. 
 
 Guanajuatite. 2-i3; 428. 
 
 Guanipite. 433. 
 
 Guano, 365. 
 
514 
 
 GENERAL INDEX. 
 
 Guarinite, 336. 
 Guejarite, 428. 
 Giimbelite, 353. 
 Gummite, 428. 
 Gunnisonite, 428. 
 Guyaquillite, 415. 
 Gymmte, 351. 
 Gyps, v. Gypsum. 
 Gypsum, 392. 
 Gyrolite, 338; 428. 
 
 Haarkies, 241 ; 247. 
 Haarsalz, 395. 
 Haddamite, 433. 
 Hafnefiordite, :,23. 
 Hagemannite, 2G5. 
 Haidingerite, 371. 
 Halite, 2r>9. 
 Hallite, 355. 
 Halloysite, 352; 428. 
 Halotrichite, 385. 
 Hamartite, 408, 438. 
 Hannayite, 428. 
 Harmotome, 346. 
 Harrisite, 240. 
 Hartite, 4U. 
 
 Hatchettite, Hatchettine, 414. 
 Hatchettolite, 428. 
 Hauerite, 244 
 Haughtonite, 431. 
 Hausmannite, 277. 
 Haiiyne, Haiiynite, 318. 
 Haydenite, 34 i. 
 Hayesine, 428. 
 Haytorite, 335. 
 Heavy spar, :-!87. 
 Hebronite, 370; 420. 
 Hedenbergite. 293. 
 Hedyphane, 367; 428. 
 Heldburgite, 42S. 
 Heliotrope, 286. 
 Kelvin, Helvite, 302; 428. 
 Hematite, 26 <. 
 
 Brown, 280. 
 Henwoodite, 378. 
 Hercynite, 272. 
 Herderite, 370. 
 Hermannolite, 361. 
 Herrengnmdite, 423. 
 Herschelite, 844. 
 Hessite, 238; 429. 
 Hessonite, v. Essonite. 
 Hetaerolite, Hetairite, 429. 
 Heteromorphite, v. Jameson- 
 
 ite. 
 
 Heubachite, 4C9. 
 Heulandite, 347; 429. 
 Hexagonite. 298. 
 Hibbertite, 42D. 
 Hiddenite, 436. 
 Hielmite, 361. 
 Hieratite. 429. 
 Highgate resin, 415. 
 Hisingerite, 354. 
 
 Hoernesite, 371. 
 Hofmannite, 485. 
 Holzopal, v. Wood Opal. 
 Holz Zinn, 275. 
 Homilite, 429. 
 
 Honey-stone, Honigstein,412. 
 Hopeite, 429. 
 Horbachite. 241. 
 Hornblende, 296. 
 Horn silver, 2GO. 
 Hornstone, 287. 
 Horse-flesh ore, v. Bornite 
 Hortonolite. 300. 
 Houghite, 282. 
 Hovite, 410. 
 Howlite, 382. 
 Huantajayite, 259. 
 Hiibnerite, 383; 429. 
 Huilite, 425. 
 Humboldtine, 412. 
 Hum bo dtilite, 306. 
 Humboldtite, 334. 
 Hurainite, 4 5. 
 Humite, 327, 328, 423. 
 Huntilite. 420. 
 Bureau 1 . ite, 372. 
 Huronite, 353. 
 Hyacinth, 304, 305. 
 Hyalite, 289. 
 Hyalophane, 322. 
 Hyalosiderite, 3 0. 
 Hyalotekite, 429. 
 Hydrargiilite, 282. 
 Hydrargyrite, 267. 
 Hydraulic limestone, 400. 
 Hydrobiotite. 436. 
 Hydrocastorite, 433. 
 Hydrocerussits, 429. 
 Hydrocuprite, 266. 
 Hydrocyanite, 390. 
 Hydrodolomite, 410. 
 Hydrofluorite, 264. 
 Hydrofranklinite, 429. 
 HydroiJmenite. 481. 
 Hydromagnesite, 409. 
 Hydro-mica Group, 353. 
 Hydrophilite, 429. 
 Hydrophite, 351. 
 Hydrorhodonite, 429. . 
 Hydrotalcite. 282. 
 Hydrotitanite, 271. 
 Hytlrozincite, 410. 
 Hygrophilite, 353. 
 Hypargyrite, 250. 
 Hypersthene, 290. 
 Hypochlorite, 802. 
 
 Ice spar, 3?5. 
 Iceland spar, 399. 
 Idocrase, '205. 
 Idrialine, Idrialite, 314. 
 Ihleite, 395. 
 Ilesite, 429. 
 Ilmenite, 269. 
 
 Ilsemannite, 284. 
 i llvaite, 309. 
 j Indianaite, 428. 
 Indianite, 321. 
 Indicolite, 330. 
 lodargyrite, 2 -0. 
 lodobromite, 429. 
 lodsilber, 260. 
 lodyrite, '260. 
 lolite, 311. 
 lonite, 485. 
 Iridosmine, 224. 
 Iron, Arsenical, 247. 
 
 Magnetic, 241, 272. 
 
 Meteoric, 226. 
 
 Native, 226, 429. 
 
 Oligist (hematite), 268. 
 Iron aluminate, 272. 
 
 arsenate, 375, 376. 
 
 arsenide, 247, 248. 
 
 borate, 380. 
 
 boro-silicate, 429. 
 
 carbonate, 403. 
 
 chloride, 261. 
 
 columbate, 360. 
 
 oxalate, 412. 
 
 oxide, 268, 272, 279, 
 280. 
 
 phosphate, 369, 371, 372, 
 378, 426, 437. 
 
 silicate, 300, 334 
 
 sulphate, 895. 
 
 sulphide, 2; 1, 243,247. 
 
 sulph-antimonite, 251. 
 
 tantalate, 359. 
 
 tellurate(?)4.7. 
 
 tungstate, 388. 
 Iron pyrites, 243. 
 
 White, 247. 
 Ironstone, Clay, 269, 281, 
 
 403. 
 
 Iserine, Iserite, 270. 
 Isoclasite, 373. 
 Itacolumyte, 229. 
 Ivigtite, 354. 
 Ixolyte, 414. 
 
 Jacobsite, 272. 
 Jade, Common, 297. 
 Jadeite, 409. 
 Jamesonite, 251; 430. 
 Jargon, 3('5. 
 Jarosite, 430. 
 Jasper, 287. 
 Jaulingite, 415. 
 Jefferisite, 355. 
 Jeffersonite, 293. 
 Jenkinsite, 351. 
 Jet, 418. 
 Johannite, 397. 
 Jollyte, 354. 
 Jordanite, '251. 
 Joseite, 233. 
 Julianite, 256. 
 
GENERAL INDEX. 
 
 515 
 
 N. B. Many names spelt with an 
 initial K in German, begin with C 
 in English. 
 
 Kalait, 377. 
 Kaliglimmer, 313. 
 Kalinite, 395. 
 Kalk-Harmotome, v. Phillips- 
 
 ite. 
 
 Kalk-uranit, 379. 
 Kalkspath, 398. 
 Kalk-volborthit, 374. 
 Kallait, 77. 
 Kaluszite. 394. 
 Kammererite, 355. 
 Kammkies, 247. 
 Kaolin. Kaolinite, 351. 
 Karelinite, v84. 
 Karyinite, 422. 
 Katzenauge, 286. 
 Keatingine, 295. 
 Keilhauite, 333. 
 Kelyphitc. 433. 
 Kenngottite, 250. 
 Kentrolite, 430. 
 Kerargyrite. 260. 
 Kermes Kerraesite, 284. 
 Kerolith, t>. Cerolite. 
 Kerrite, 355. 
 Kiesel, v. Quartz. 
 Kieselkupfer, 338. 
 Kieselwismuth, 302. 
 Kieselzinkerz, 339. 
 Kieserite, 394. 
 Killinite, 353, 436. 
 Kischtimite, 408. 
 Kjerulflne, 36 S. 
 Klaprotholite, 251. 
 Klinochlor, 353. 
 Knebelita, 300. 
 Kobaltbliithe, 372. 
 Kobaltglanz, 246. 
 Kobaltkics. v. LinnaBite 
 Kobaltnickelkies, 245. 
 Kobellite, 254. 
 Kochelite, 363. 
 Kochsalz, 259. 
 Koflachite. 435. 
 Kohle, v. Coal. 
 Kokkolit V. Coccolite. 
 Kongsbergite, 225. 
 Konigine, 396. 
 Konlite, 414. 
 Koppite, 339. 
 Korarfveite, 368. 
 K6ttigite, 372. 
 Korund, v. Corundum. 
 Kotschubeite, 357. 
 Koupholite, 340. 
 Krantzit3, 415. 
 Kreittonite, 272. 
 Kremersite, 261. 
 Krennerile, 430. 
 Krisuvigite, 397. 
 
 Kronkite, 397. 
 Krugite, 434. 
 Kupferantimonglanz, 250. 
 Kupferbleispatti, 396. 
 Kupferglanz, 239. 
 Kupferglimmer, 375. 
 Kupferindig, 249. 
 Kupferkies, 244. 
 Kupferlasur, 411. 
 Kupfernickel. 243. 
 Kupfersammterz, 397. 
 Kupferschaum, 374. 
 Kupferschwiirze, ^67. 
 Kupfferite, 29(>. 
 Kupfer-uranit, 378. 
 Kupfer-vitriol, 394. 
 Kupferwismuthglanz, 250. 
 Kyanite, 3-J2. 
 
 Labradorite, 321. 
 Labrador feldspar, 321. 
 Lagonite, 382. 
 Lampadite, 283. 
 Lanarkite, 391. 
 Langite, 397. 
 Lanthanite, 410. 
 Lapis-lazuli, 418. 
 Larderellite, 383. 
 Lasurstein, 418. 
 Latrobite, v. Anorthite. 
 Laumonite, Laumontite, 338. 
 Laurite, 247. 
 Lautite, 43J. 
 Lavvrencite, 430. 
 Laxmannite, 386. 
 Lazulite, 375. 
 Lead, Argentiferous, 2C3. 
 Black (graphite), 230. 
 Corneous (phosgeriite), 
 
 408. 
 
 Native, 226. 
 Leadantimonate, 370, 379. 
 
 arsenate, 3(50. 
 
 arsenio-molybdate, 385. 
 
 carbonate, 407. 
 
 chloride, ~61. 
 
 chloro-carbonate, 408. 
 
 chromate, 3s5, 386. 
 
 molybdate 384. 
 
 oxichloride, 262. 
 
 oxide. 267, 277. 
 
 phosphate, 366. 
 
 selenide. 236. 
 
 selenite, 432. 
 
 silicate, 427, 429, 430, 
 431. 
 
 sulphate. 389, 390, 391. 
 
 sulphate-carbonate, 3Jl. 
 
 sulphide, 235. 
 
 sulpharsenite, 250, 251. 
 
 sulphantimonite, 250, 
 251, 253, 254. 
 
 sulpho-bismuthite, 252, 
 431,427. 
 
 Lead telluride, 237, 249. 
 tungstate, 38k 
 vanadate, 367 ; 374, 426 
 
 Leadhillite, 390; 430. 
 
 Leberkies, . Marcasite. 
 
 Lecontite, 392. 
 
 Ledererite. 345 
 
 Lederite. 336. 
 
 Lehrbachite, 237. 
 
 Leidyite, 430. 
 
 Lennilite, 436. 
 
 Leopoldite, 260. 
 
 Lepidolite, 314. 
 
 Lepidomelane, 313. 
 
 Lepidophaeite, 440. 
 
 Lernilite, 436. 
 
 Lesleyite, 354. 
 
 Lettsomite, 397. 
 
 Leucaugite, 293. 
 
 Leuchtenbergite, 357. 
 
 Leucite, 318; 430. 
 
 Leucochalcite, 430. 
 
 Leucomanganite, 426. 
 
 Leucopetrite, 315. 
 
 Leucophanite, 300; 430. 
 
 Leucopyrite, 248. 
 
 Leucotile, 430. 
 
 Leviglianite, 241. 
 
 Levyne, Levynite, 343. 
 
 Lherzolyte, 271. 
 
 Libethenite, 373; 430. 
 'Liebigite, 412. 
 
 Lievrite, 309. 
 
 Lignite, 418. 
 
 Ligurite, 336. 
 
 Limbachite, 351. 
 
 Lime = Calcium oxide, v. 
 
 Calcium. 
 
 Limestone, 400, 401 
 Limonite, 280. 
 
 Linarite, 396. 
 LinnaBite, 245. 
 Linsenerz, 374. 
 Lintonite, 438. 
 Lionite, 437. 
 Liroconite, 374. 
 Liskeardite, 430. 
 Lithionglimmer, 314. 
 Lithiophilite, 438. 
 Lithographic Stone, 400. 
 Lithomarge, 352. 
 Livingstonite, 232; 430. 
 Loganite, 358. 
 Loliingite, 248. 
 Louisite, 430. 
 Loweite, 394. 
 Lowigite, 396. 
 Loxoclase, 326. 
 Luckite, 431. 
 Ludlamite, 372. 
 Ludwigite, 38". 
 Luneburgite, 382. 
 Luzonite, 258. 
 Lydian stone, 287. 
 
516 
 
 GENERAL INDEX. 
 
 Macfarlanite, 430. 
 Made, 331. 
 Maconite, 355. 
 
 Magnesia = Magnesium ox- 
 ide, v. Magnesium. 
 Magnesioferrite, 273. 
 Magnesite, 402. 
 Magnesium aluminate, 271. 
 arsenate, 371. 
 borate, 380, 381. 
 carbonate, 402, 
 
 409. 
 chloride, 2GO,261, 
 
 423. 
 
 fluoride, 264. 
 fluo - phosphate, 
 
 368. 
 
 fluo-silicate, 327. 
 hydrate, 281. 
 nitrate, 379. 
 oxide, 267. 
 phosphate, 368, 
 
 432. 
 silicate, 290, 300, 
 
 348, 349, 350. 
 sulphate, 394. 
 Magneteisenstem, 272. 
 Magnetic iron ore, 272. 
 Magnetic pyrites, 241. 
 Magnetite, 212. 
 Magnetkies, 241. 
 Magnoferrite, 273. 
 Magnolite, 430. 
 Malachite, Blue, 411. 
 
 Green, 411. 
 Malacolite, 293. 
 Maldonite, 221. 
 ' Malinovvskite, 256. 
 Mallardite, 431. 
 Manganapatite, 420. 
 Manganblende, v. Alabandite. 
 Manganbrucite, 422. 
 Manganepidot, 308. 
 Manganese borate, 380. 
 
 carbonate, 403. 
 columbate, 423. 
 oxide, 277, 278, 
 280, 282, 283, 
 431. 
 phosphate, 369, 
 
 435, 439. 
 silicate, 294, 300, 
 
 SOI. 
 
 sulphide, 237, 244. 
 sulphate, 431, 437. 
 tantalate, 359, 
 
 437. 
 
 tungstate, 883. 
 Manganglanz, 237. 
 Manganite, 280. 
 Manganocalcite, 406. 
 Manganophyllite, 312. 
 Manganosiderite, 435. 
 Manganosite, 431. 
 
 Manganspath, 403. 
 Mangantantalite, 437. 
 Marble, 400. 
 
 Verd-antique, 350. 
 Marcasite, 247. 
 Margarite, 357. 
 Margarites, 110. 
 Margarodite, 353; 314. 
 Margarophyllites, 348, et seq. 
 Marialite, 316. 
 Marionite. 410. 
 Marmairolite, 431. 
 Mannatite, 238. 
 Marmolite, 350. 
 Martite, 269. 
 
 Mascagnine. Mascagnite, 392. 
 Maskelynite, 322. 
 Masonite, 358. 
 Massicot, 267. 
 Matlockite, 262. 
 Matricite, 431. 
 Maxite, 391. 
 Medjidite, 397. 
 Meerschaum, 349. 
 Megabasite, :-.88. 
 Meionite, 315. 
 Melaconite, 267. 
 Melanglanz, v. Stephanite. 
 Melanite, 304. 
 Melanochroite, 386. 
 Melanophlogite, 289. 
 Melanosiderite, 281. 
 Melanotekite, 431. 
 Melunothallite, 431. 
 Melanterite, 395; 431. 
 Melilite, Mellilite, 306. 
 Melinophane, 300. 
 Meliphanite, 300; 431. 
 Mellite, 412. 
 Meionite, 2^9. 
 Menaccanite, 269, 431. 
 Mendipite, 262. 
 Mendozite, 395. 
 Meneghinite, 256. 
 Mengite, 36->. 
 Mennige, 277. 
 Meroxene, 431. 
 Mercury, Native, 224. 
 Mercury chloride, 260. 
 
 iodide, 260. 
 
 selenide, 237. 
 
 sulphide, 240, 241. 
 
 telluride, 423. 
 
 tellurate, 430. 
 
 sulph -antimonite, 
 
 232. 
 
 Mesitine, Mesitite, 403. 
 Mesolite, 343. 
 Mesotype, 342. 
 Metabrushite, 371. 
 Metacinnabarite, 241. 
 Metaxite, 351. 
 Meymacite, 234. 
 Miargyrite, 249. 
 
 Mica Group, 301; 431. 
 Michaelsonite, 308. 
 Microcline, 326. 
 Wicrolite, 359; 431. 
 Microphyllites,Microplakites, 
 
 322. 
 
 Microsommite, 317. 
 Middletonite, 415. 
 Mikroklin, v. Microcline. 
 Milarite, 432. 
 Millerite, 241. 
 
 Mimetene, Mimetite, 366 ; 432. 
 Mimetese, Mimetesite, 366. 
 Mineral coal, 417. 
 
 oil, 413. 
 
 pitch, 416. 
 
 tar, 413. 
 Minium, 277. 
 Mirabilite, 392. 
 Mispickel, 247. 
 Misy, 395. 
 Mixite, 432. 
 Mizzonite, 316. 
 Molybdanglanz, 283. 
 Molybdanocker, 284. 
 Molybdenite, 233; 432. 
 Molybdenum oxide, 284. 
 
 sulphide, 233. 
 Molybdite, 284. 
 Molybdomenite, 432. 
 Molysite, 261. 
 Monazite, 368: 432. 
 Mondstein, v. Moonstone. 
 Monetite, 432. 
 Monimolite, 370. 
 Monite, 4:i2. 
 Monrolite, 332. 
 Montanite, 397. 
 Montebrasite, 370; 420. 
 Monticellite, 300. 
 Montmartite, v. Gypsum. 
 Montmorillonite, 349.. 
 Moonstone, 323, 324, 825. 
 Mordenite, 432. 
 Morenosite, 895. 
 Moroxite, 365. 
 Mosandrite, 309. 
 Mottramite, 374. 
 Mountain cork, 297. 
 
 leather, 297. 
 Muckite, 435. 
 Muromontite, 308. 
 Muscovite, 313. 
 Musenite, v. Siegenite. 
 
 Nadeleisenstein, 280. 
 Nadelerz, 254. 
 Nadelzeolith, 342. 
 Nadorite, 370. 
 Nagyagite, 249; 432. 
 Namaqualite, 282. 
 Nantokite, 2GO. 
 Naphtha. 413. 
 Naphthaline, 414. 
 
GENERAL INDEX. 
 
 517 
 
 Natrolite, 342; 432. 
 Natron, 409. 
 Natronborocalcite, 381. 
 Naumannite, 235. 
 Needle ore, v. Aikinite. 
 Nemalite, 282. 
 Neochrysolite, 423. 
 Neocyanite, 432. 
 Neotocite, 354. 
 Nepheline, Nephelite, 316. 
 Nephrite, 297, 432. 
 Neudorfite, 435. 
 Newberyite, 432. 
 Newjanskite, 224. 
 Newport! te, 358. 
 Niccolite, 242. 
 Nickel antimonide, 243, 247. 
 
 arsenate, 372. 
 
 arsenide, 242 ; 246. 
 
 carbonate, 410. 
 
 oxide, 267. 
 
 silicate, 351, 427. 
 
 sulphate, 395. 
 
 sulphide, 241. 
 
 telluride, 249. 
 
 Nickel glance, v. Gersdorffite. 
 Nickelarsenikglanz, 246. 
 Nickelarsenikkies, 246. 
 Nickelbliithe, 372. 
 Nickel-Gymnite, 351. 
 Nickelkies, 241. 
 Nickelsmaragd, 410. 
 Niobife, 860. 
 Nitre, 379. 
 Nitrobarite, 433. 
 Nitrocalcite, 379. 
 Nitroglauberite, 379. 
 Nitromagnesite, 379. 
 Nocerine, Nocerite, 433. 
 Nohlite, S62. 
 Nontronite, 350. 
 Nosean. Nosite, 318. 
 Noumeaite, Noumeite, 351. 
 Nuttalite, v. Wernerite. 
 
 Ochre, red, 269. 
 Octahedrite, 277; 433. 
 CEllacherite, 854. 
 Okenite, 338. 
 Oldhamite, 235. 
 Oligoclase, 323. 
 Olivenite, 373. 
 Olivine, 300. 
 Onofrite, 433. 
 Ontariolite, 435. 
 Onyx, 287. 
 Oolite, 400. 
 Opal, 288. 
 Ophiolite, 350, 402. 
 Orangite, 340. 
 Orpiment, 231 ; 433. 
 Orthite, 308; 433. 
 Orthoclase, 325; 433. 
 Oryzite, 429. 
 
 Osmiridium, 224. 
 
 Osteolite, 365. 
 
 Ottrelite, 358; 433. 
 
 Ouvarovite, 304. 
 
 Owenite, 358. 
 
 Oxammite, 433. 
 
 Ozarkite, 342. 
 
 Ozocerite, Ozokerit, 414; 433. 
 
 Pachnolite, 205; 438. 
 Pagodite, 349, 352. 
 Paisbergite, 294. 
 Palagonite, 353. 
 Palladium, Native, 224. 
 Pandermite, 434. 
 Parachlorite, 436. 
 Paraffin, 413. 
 Paragonite, 354. 
 Parankerite, 402. 
 Paranthite, 316. 
 Parasite, v. Boracite. 
 Parastilbite, 426. 
 Parathorite, 340. 
 Pargasite, 297. 
 Parisite, 408. 
 Parophite, 353. 
 Pattersonite, 358. 
 Pealite, 289. 
 
 Pearl -mica, v. Margarite. 
 Pearl-spar, 401. 
 Pechkohle, 417. 
 Pechopal, 289. 
 Peckhamite, 433. 
 Pectolite, 337; 433. 
 Peganite, 378. 
 Pegmatolite, v. Orthoclase. 
 Pelagite, 433. 
 Pelhamite, 355. 
 Pencatite, 410. 
 Pennine, Penninite, 55. 
 Penwithite, 433. 
 Percylite, 262. 
 Periclase. Periclasite, 267. 
 Peridot, 300, 830. 
 Perikline, Periklin, 324. 
 Peristerite, 324. 
 Perlglimmer, 357. 
 Perthite, 326. 
 Perofskite, 270; 433. 
 Perowskit, 270. 
 Petalite, 295; 433. 
 Petroleum, 413. 
 Petzite, 2- 9. 
 Phacolite, 344. 
 Phamctinite, 420. 
 Pharmacolite, 870. 
 Pharmacosiderite, 376; 433. 
 Phenacite, Phenakit; 301 
 
 433. 
 
 Phengite, 431. 
 Philadelphia, 439. 
 Phillipite, 397. 
 Phillipsite, 345; 433. 
 Phlogopite, 312. 
 
 Phcenicochroite, 386. 
 Pholerite, 352. 
 Phosgenite, 408. 
 Phosphocerite, 364. 
 Phosphochalcite, 374. 
 Phosphochromite, 386. 
 Phosphorite, 365. 
 Phosphuranylite, 434. 
 Phyllite, 358. 
 Physalite, 333. 
 Phytocollite, 425. 
 Piauzite, 416. 
 Picite, 431. 
 
 Pickeringite, 395; 434. 
 Picotite, 271. 
 Picranalcite, 420. 
 Picroallumogene, 434. 
 Picrolite, 351. 
 Picromerite, 394. 
 Picropharmacolite, 371. 
 Pictite, 336. 
 Piedmontitc, COS. 
 Pihlite, 349. 
 Pilarite, 423. 
 Pilinite, 344. 
 Pilolite, 434. 
 Pimelite, 351. 
 Finite, 352. 
 Pisanite, 395. 
 Pisolite, 400. 
 Pistacite, Pistazit, 307. 
 Pistomesite, 403. 
 Pitchblende, 274. 
 Pittasphalt, 413. 
 Pitticite, Pittizit, 379. 
 Plagiocitrite, 484. 
 Plagioclase, 319. 
 Plagionite, 251. 
 Plasma, 286. 
 Plaster of Paris, 393. 
 Platinum, Native, 223; 434. 
 Platiniridium, 224. 
 Pleonaste, v. Spinel. 
 Plumbago, 230. 
 Plumballophane, 341. 
 Plumbogummite, 377. 
 Plumbomanganite, 484. 
 Plumbostannite. 434. 
 Plumbostib, v. Boulangerite. 
 Polianite, 278. 
 Pollucite, Pollux, 299. 
 Polyargite, 353. 
 Polyargyrite, 257. 
 Polybasite, 257. 
 Polycrase, 362. 
 Polychroilite, 353. 
 Pol vdy mite, 434. 
 Polyhalite, 393; 434. 
 Polym ignite, 302. 
 Poonahlite,343. 
 Porcellophite, 851. 
 Posepnyte, 435. 
 Potassium chloride, 260. 
 
 chromate (?), 437. 
 
518 
 
 GENERAL INDEX. 
 
 Potassium nitrate, 379. 
 
 silicate, 313, 325. 
 sulphate, 390. 
 Potash = Potassium oxide, 
 
 v. Potassium. 
 Prase, 286. 
 Prasine, 374. 
 Praseolite, 353. 
 Predazzite, 410. 
 Pregattite, 354. 
 Prehnite, 340. 
 Priceite, 382; 434. 
 Prochlorite, 357. 
 Proidonite, 264. 
 Prosopite, 265. 
 Protobastite, 290. 
 Protochlorite, 436. 
 Protovermiculite, 439. 
 Proustite, 25:5. 
 Prussian blue, Native, 372. 
 Przibramite, 218, 280. 
 Pseudobrookite, 434. 
 Pseudocotunnite, 261. 
 Pseudomalachite, 374. 
 Pseudonatrolite, 434. 
 Pseudophite, 356. 
 Psilomelane, 282 ; 434. 
 Psittacinite, 374. 
 Pucherite, 367. 
 Purple copper, 237. 
 Pycnite, v. Topaz. 
 PyraUolite, 348. 
 Pyrargillite, 353. 
 Pyragyrite, 252. 
 Pyreneite, 304. 
 Pyrgom, 293; 434. 
 Pyrite, 243. 
 Pyrites, Arsenical, 247. 
 
 Auriferous, 220. 
 
 Capillary, 241. 
 
 Cockscomb, 247. 
 
 Copper, 244. 
 
 Iron, 243. 
 
 Magnetic, 241. 
 
 Radiated, 247. 
 
 Spear, 247. 
 
 White iron, 247. 
 Pyrochlore, 359. 
 Pyroehroite, 282. 
 Pyroconite, 265. 
 Pyrolusite, 278; 434. 
 Pyromorphite, 366. 
 Pyrope, 303. 
 Pyrophosphorite, 434. 
 Pyrophyllite, 349. 
 Pyropissite, 414. 
 Pyroretinite, 415. 
 Pyrosclerite, 355. 
 Pyrosmalite, 340. 
 Pyrostilpnite, 252. 
 Pyroxene, 292. 
 Pyrrhite, 359. 
 Pyrrhosiderite, 280. 
 Pyrrhotite, 241; 434. 
 
 Quartz, 284; 434. 
 Quecksilberbranderz, 414. 
 Quecksil berhornerz, 260. 
 Quicksilver, 224. 
 
 Radelerz, 253. 
 Radiated Pyrites, 247. 
 Raimondite, 395. 
 Ralstonite, 265, 435. 
 Randite, 43"). 
 Ratofkite, 263. 
 Rauite, 342. 
 Raumite, 353. 
 Realgar, 231. 
 Red copper ore, 266. 
 
 hematite, 209. 
 
 iron ore, 269 . 
 
 ochre, 269. 
 
 silver ore, 252, 253. 
 
 zinc ore, 266. 
 Reddingite, 435. 
 Refdanskite, 851. 
 Reichardtite, 426. 
 Reinite, 4 5. 
 Reissite, 426. 
 Remingtonite, 410. 
 Rensselaerite, 348. 
 Resanite, 339. 
 Resin, Mineral, 415, 435. 
 Restorm elite, 353. 
 Retinalite, 351. 
 Retinite, 415. 
 Reussinite, 415. 
 Rhabdophane, 435. 
 Rhsetizite, 332. 
 Rhagite, 377. 
 Rhodizite, 435. 
 Rhodochrosite, 403; 435. 
 Rhodonite, 294. 
 Rhomb-spar, 401. 
 Rhyacolite, 326. 
 Rionite, 256. 
 Ripidolite, 356. 
 Rittingerite, 252. 
 Rivotite, 370. 
 Rock cork, v. Hornblende, 
 crystal, 286. 
 meal, 401. 
 milk, 400. 
 salt, 259. 
 Roemerite, 395. 
 Roapperite, 300. 
 Rcesslerite, 371. 
 Rogenstein, 400. 
 Rogersite, 435. 
 Romeine, Ifomeite, 370. 
 Roscoelite, 367; 435 
 Rose quartz, 286. 
 Roselite, 372; 435. 
 Rosterite, 420. 
 Rosthornite, 415. 
 Rosite, 353. 
 Rothbleierz, 385. 
 Rotheisenerz, 268. 
 
 Rothgiiltigerz, 252, 253. 
 Rothkupiererz, 266. 
 Rothnickelkies, 242. 
 Rothoffite, 303. 
 Rothzinkerz, 266. 
 Rubellite, 330. 
 Rubislite, 435. 
 Ruby, Spinel, Almandine,271. 
 
 Oriental, ^68. 
 
 Ruby-blende, v. Pyrargyrite. 
 Ruby silver 25 - J . 253. 
 Rutherfordite, 362. 
 Rutile. 276; 435. 
 Ryacolite, v. Rhyacolite. 
 
 Sahlite, 293. 
 Sal ammoniac, 260. 
 Salmiak. 2(iO. 
 Salt, Common, 259. 
 Samarskite, 301 ; 435. 
 Sammetblende, 280. 
 Sanidin, 325. 
 Saponite, 352. 
 Sapphire 3r>8; 330. 
 Sarawakite, 435. 
 Sarcolite, 316. 
 Sarcopside, 369. 
 Sard, 287. 
 Sardonyx, 287. 
 Sartorite, 250. 
 Sassolite, Sassolin, 380. 
 Satin-spar, 398, 400, 405. 
 Saussurite, 309. 
 Savite, v. Natrolite. 
 Scapolite Group, 315; 435. 
 Schaumspath, 4(JO. 
 Scheelite, 384. 
 Scheereite, 413. 
 Schieferspath, 400. 
 Schilfglaserz, 252. 
 Schiller-spar, 351. 
 Schirmerite, 251. 
 Schmirgel, 2' 8. 
 Schneebergite, 431. 
 Schorlomite, 337; 435. 
 Schraufite. 415. 
 Schreibersite, 242. 
 Schrifterz, Schrift-tellur, 248. 
 Schrockingerite, 412. 
 Schuchardtite, 436. 
 Schuppenstein, 415. 
 Schwartzembergite, 262. 
 Schwarzkupfererz, 267. 
 Schwatzite, 255. 
 Schwefelkies, 243. 
 Schwerspath, 387. 
 Scleretinite, 415. 
 Scleroclase, 250. 
 Scolecite, Scolezite, 343. 
 Scorodite, 375. 
 Seebachite, 344. 
 Selenblei, 236. 
 Selenite, 393. 
 Selenquecksilber, 237. 
 
GENERAL INDEX. 
 
 519 
 
 Sellaite, 264. 
 Semeline, 335. 
 Semseyite, 436. 
 Senarmontite, 284; 436. 
 Sepiolite, 349; 436. 
 Serpentine, 350 ; 436. 
 Serpierite, 436. 
 Seybertite, 358. 
 Shepardite, 242. 
 Siderazot, 436. 
 Siderite, 403. 
 Sideronatrite, 436. 
 Siderophyllite, 431. 
 Siegburgite, 415. 
 Siegenite. 24o. 
 Silaonitc, 233: 428. 
 Silberamalgam, 225. 
 Silberglanz, 2 : >5. 
 Silberhorncrz, 260. 
 Silberkupt'erglanz, 240. 
 Silberwismuthglanz, 420. 
 Silex. v. Quartz. 
 Silicified wood, 286. 
 Siliceous sinter, 287, 289. 
 Siliciophite, 4:!6. 
 Silicoborocalcite, 382. 
 Sillimanite, 331. 
 Silver, 223. 
 
 Antimonial. 234. 
 Bismuth, 420. 
 Horn, 260. 
 Native, 223. 
 Ruby, 252, 253. 
 Vitreous, 2^5. 
 Silver antimonide, 234. 
 
 chloride, 260. 
 
 bromide, 260. 
 
 iodide, 260. 
 
 selenide, 235. 
 
 sulph-antimonite, 250, 
 252, 256, 257. 
 
 sulph-arsenite, 253. 
 
 sulphide, 235, 239. 
 
 sulpho-bismuthite,420. 
 
 telluride, 238; 248, 437 
 Silver glance, 235. 
 Simonyite, 394. 
 Sinter, Siliceous, 287, 289. 
 Sipylite, 436. 
 Sismondine, 358. 
 Sisserskite, 224. 
 Skapolith, v. Scapolite. 
 Skleroklas, v. Sartorite. 
 Skolezit, v. Scolecite. 
 Skutterudite, 246. 
 Smaltine, Smaltite, 245; 436. 
 Smaragdite, 297. 
 Smectite, 349. 
 Smithsonite, 404. 
 Soapstone, 348. 
 Soda = Sodium oxide, v. So- 
 dium. 
 
 Soda nitre, 381. 
 Sodalite, 317. 
 
 Sodium borate, 381. 
 
 carbonate, 408, 409. 
 
 chloride, 259. 
 
 fluoride, 264. 
 
 nitrate, 379. 
 
 silicate, 323, 342. 
 
 sulphate, 390, 391, 
 
 892. 
 
 Sommite, 316. 
 Sonnenstein, v. Sunstone. 
 Sonomaite, 434. 
 Spargelstein, 365. 
 Spathic iron, 403. 
 Spathiopyrite, 246. 
 Spear pyrites, 247. 
 Speckstein. 348, 352. 
 Specular iron, ^68. 
 Speerkies, 247. 
 Spessartite, 304. 
 Speiskobalt, 245. 
 Sphaerocobaltite, 436. 
 Sphaerosiderite, 403. 
 Sphaerostilbite, 340. 
 Sphalerite, 237; 436. 
 Sphene, 335. 
 Spiauterite, 242. 
 Spinel. 271. 
 Spinthere, 335. 
 Spodiosite, 430. 
 Spodumene. 295; 436. 
 Sprodglascrz, 256. 
 Sprudelstein, 405. 
 Staffelite, v. Phosphorite. 
 Stalactite, 400. 
 Stalagmite, 400. 
 Stanekite, 415. 
 Stannite, 245. 
 Staurolite, Staurotide, 336; 
 
 437. 
 
 Steatite, 348. 
 Steeleite, 432. 
 Steinkohle, 417. 
 Steinmark, 352. 
 Steinol, 413. 
 Steinsalz, 259. 
 Stephanite, 256. 
 Sterlingite, 354. 
 Sternbergite. 240; 437. 
 Stibianite, 437. 
 Stibiconite, 437. 
 Stibioferrite, 370. 
 Stibnite, 232; 437. 
 Stilbite. 346,437; 347. 
 Stilpnomelane, 349. 
 Stolzite, 384. 
 Strahlerz, 374. 
 Strahlkies, 247. 
 Strahlstein. 297. 
 Strahlzeolith, v. Stilbite. 
 Strengite, 437. 
 Strigovite, 357. 
 Stromeyerite, 240. 
 Strontianite, 406; 437. 
 Strontium carbonate, 406. 
 
 Strontium sulphate, 388. 
 Struvite, 371. 
 Stiizite, 437. 
 
 Stylotyp, Stylotypite, 254. 
 Subdelessite, 425. 
 Succinellite, 415. 
 Succinite. 415. 
 Sulphur, Native, 228. 
 Sunstone, 3-'3, 325. 
 Susannite, 391. 
 Sussexite, 380. 
 Sylvanite, 248. 
 Sylvine, Sylvite, 260. 
 Syngenite, 394. 
 Szaboite, 437. 
 Szaibelyite, 380. 
 Szmikite, 437. 
 
 Tabergite, 356. 
 Tabular spar, 291. 
 Tachhydrite, 261. 
 Tafelspath, 291. 
 Tagilite, 873. 
 Talc, :i48. 
 Talktriplite, 437. 
 Tallingite, 262. 
 Tantalite, 359; 437. 
 Tapalpite, 239. 
 Tapiolite, 361. 
 Tarapacaite, 437. 
 Tasmanite, 415. 
 Taznite, 437. 
 Tellur, Gediegen, 227. 
 Tellurite, 437. 
 Tellurium, Bismuthic, 233. 
 Foliated, 249. 
 Graphic, 24$. 
 Native, 22 7; 437. 
 Tellurium oxide, 437. 
 Tellursilber, 238. 
 Tellurwismuth, 233. 
 Tengerite. 410. 
 Tennantite, 256; 438. 
 Tenorite, 207; 438. 
 Tephroite, 300. 
 Tequesquite, 438. 
 Tequixquitl, 438. 
 Tesseralkies, 246. 
 Tetradymite, 233. 
 Tetrahedrite, 255; 438. 
 Thaumasite, 438. 
 Thenardite, 390; 438. 
 Thinolite, 438. 
 Thomsenolite, 205; 438. 
 Thomsonite, 342; 438. 
 Thorite, 340; 438. 
 Thulite, 309. 
 Thuringite, 358. 
 Tiemannite, 237. 
 Tile ore, 2(56. 
 Tin, Native, 220. 
 Tin ore, Tin stone, 275. 
 
 oxide, 275. 
 
 pyrites, v. Stannite. 
 
520 
 
 GENERAL INDEX. 
 
 Tin sulphide, 245. 
 Tinkal, 381. 
 Titaneisen, 269. 
 Titanic iron, 269. 
 Titanite, 335; 438. 
 Titanium oxide, 270; 276, 277. 
 Titanolivine, 423. 
 Titanomorphite, 438. 
 Tiza, 0. Ulexite. 
 Tobermorite, 428. 
 Tocornalite, 260. 
 Topaz, 332 ; 438. 
 
 False. 286. 
 Topazolite, 304. 
 Torbanite. 415, 418; 438. 
 Torbernite, Torberite, 378. 
 Totaigite. 436. 
 Tourmaline, 329, 438. 
 Travertine, 400. 
 Tremolite, 297. 
 Trichite, 110. 
 Triclasite, J353. 
 Tridymite, 288; 439. 
 Triphylite, Triphyline, 369; 
 
 439. 
 
 Triplite, 369. 
 Triploidite, 439. 
 Tripolite, 289. 
 Trippkeite. 439. 
 Tritochorite, 426. 
 Tritomite, 340. 
 Trogerite, 379. 
 Troilite, 242. 
 Trona. 408. 
 Troostite, 301. 
 Tscheffkinite, 336. 
 Tschermakite, 323. 
 Tschermigite, 395. 
 Tufa, Calcareous, 400. 
 Tungsten oxide, 284. 
 Tungstite, 284. 
 Turgite, 279. 
 Turmalin, 3?9. 
 Turnerite, 368, 432. 
 Turquois, 377. 
 Tyrite, 362. 
 Tyrolite, 374. 
 Tysonite, 439. 
 
 Ulexite, 381. 
 Ullmannite, 247. 
 Ultramarine, 318. 
 Unionite, 309. 
 Uraconise, Uraconite, 397. 
 Uranglimmer, 378, 379; 439. 
 Uranin, Uraninite, 272. 
 Uranite, 378, 379. 
 Uranium arsenate. 379. 
 
 carbonate, 412,439. 
 
 oxide, 274. 
 
 phosphate, 378, 379, 
 434. 
 
 silicate, 341. 
 
 sulphate, 397. 
 
 Urankalk, 412. 
 Uranmica. 378, 379. 
 Uranochalcite, 397. 
 Uranocircite, 439. 
 Uranophane, 341. 
 Uranospinite, 379. 
 Uranotantalite, 361. 
 Uranothallite, 439. 
 Uranothorite, 438. 
 Uranotile, 341; 439. 
 Uranpecherz, 274. 
 Urao, 409. 
 Urpethite, 413. 
 Urusite, 436. 
 Urvolgyite, 428. 
 Uwarowit, 304. 
 
 Vaalite, 355. 
 Valentinite, 284. 
 Vanadinite, 367; 439. 
 Variscite, 439. 
 Vauqueline, Vauquelinite, 
 
 386. 
 
 Venasquite, 433. 
 Venerite, 439. 
 Verd-antique, 350. 
 Vermiculite, 355 ; 439. 
 Vesbine, 439. 
 Vesuvianite, 305, 440. 
 Veszelyite, 373, 440. 
 Victorite, 290. 
 Vietinghofite. 435. 
 Villarsite, 340. 
 Vitreous copper, 239. 
 
 silver, 235. 
 Vitriol. Blue, 394. 
 Vivianite, 371. 
 Voglianite. 397. 
 Voglite, 412. 
 Volknerite, 282. 
 Volborthite, 374. 
 Voltaite, 895. 
 Vorhauserite, 351. 
 Vreckite, 422. 
 Vulpinite, 389. 
 
 Wad, 283, 440. 
 Wagnerite, 368; 440. 
 Walchowite, 415. 
 Walkerite, 433. 
 Walpurgite, 379, 440. 
 Waluewite, 440. 
 Wapplerite, 371. 
 Warringtonite, 396. 
 Warwickite, 382. 
 Wattevillite, 440. 
 Wavellite, 376. 
 Websterite. v. Aluminite. 
 Wehr'ite, 233. 
 Weissbleierz, 407. 
 Weissite, 353. 
 Weisspiessglaserz, 284. 
 Wernerite, 316. 
 
 Werthemanite. 396. 
 Westanite, ;i32. 
 Wheelerite, 415. 
 Wheel-ore, 253. 
 Whewellite, 412. 
 Whitneyite, '235. 
 Wichtine, Wichtisite, 299. 
 Willcoxite, 358. 
 Willemite. 301. 
 Williamsite, 351. 
 Wilsonite, 353. 
 Winklerite, 372. 
 Winkworthite, 382. 
 Wiserine, 277, 364. 
 Wismuth, Gediegen, 227. 
 Wismuthglanz, 232. 
 Wismuthocker, 284. 
 Wismuthspath, 412. 
 Witherite, 406. 
 Wittichenite, 254. 
 Wocheinite, 281. 
 Wohlerite, 300. 
 Wolfachite, 247. 
 Wolfram, 383. 
 Wolframite, 383. 
 Wollastonite. 291. 
 Wollongongite, 416; 438. 
 Wood-opal, 289. 
 Wood tin, 275. 
 Woodwardite, 397. 
 Worthite 332. 
 Wulfenite, 384; 440. 
 Wurfelerz, 376. 
 Wurtzite, 242, 426. 
 
 Xantholite, 437. 
 Xanthophyllite, 358; 440. 
 Xanthosiderite, 281. 
 Xenotime, 364; 440. 
 Xyloretinite, 415. 
 
 Yenite, 309. 
 Youngite, 440. 
 Yttergranat, 303. 
 Ytterspath, 364. 
 Yttrium phosphate, 364. 
 Yttrocerite, 264. 
 Yttrogummite, 423. 
 Yttrotantalite, 361, 362. 
 Yttrotitanite, 336. 
 
 Zaratite, 410. 
 Zeolite section. 342. 
 Zepharovichite, 376. 
 Zeunerite, 379. 
 Ziegelerz, 266. 
 Zietrisikite, 414. 
 Zinc, Native, 226. 
 Zinc aluminate 272. 
 
 arsenate, 373. 
 
 blende, 237. 
 
 bloom, v. Hydrozincite, 
 
 carbonate, 404, 410. 
 

 Zinc ore, Red, 266. 
 
 oxide, 266, 273. 
 
 silicate, 801, 339. 
 
 sulphate, 395, 440. 
 
 sulphide, 237, 242. 
 Zincaluminite, 440. 
 Zincite, 266. 
 
 GENERAL INDEX. 
 
 Zinkbl lithe, 410. 
 Zinkenite, 250. 
 Zinkspath, 404. 
 Zinnerz, Zirmstein, 275. 
 Zinnkies, 245. 
 Zinnober, 240. 
 Zinnwaldite, v. Lepidolite. 
 
 521 
 
 I Zippeite, 397. 
 ] Zircon, 304; 440. 
 
 Zoisite, 308. 
 i Zoblitzite, 351. 
 ! Zonochlorite, 340. 
 
 Zorgite, 237. 
 
 Zwieselite, 369. 
 
 
UNIVERSITY OF CALIFORNIA 
 
 I.BRARY 
 
 3*1 LeConte Hall 
 
 LIBRARY OF THE UNIVERSITY OF CALIFORNIA L 
 
 642-312! 
 
 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS 
 Overdue books are subject to replacemei 
 
 "rniTAS STAMPED BELOVV 
 
 FORM NO. DD 25 
 
 UNIVERSITY OF CALIFORNIA, BERKELEY 
 BERKELEY, CA 94720 
 
" 
 
 iiaet 
 
 WMMU* 
 
 LIBRARY 
 
 ~ V 
 
 1SITY OF CALIFORNIA LIBRARY OF THE UNIVERSITY OF CALIFORNIA LIBRARY ( 
 
 "* 
 
 RSITY OF CALIFORNIA LIBRARY OF THE U 
 
 /TO ^ 
 
 LIBRARY