-tttKAKY LIBRARY OF THE NIVERSITY OF CALIFORNIA. UNI7ERSIT7 1 OrtUorlioinbir, < ... S Monocltnic Inclined Dispersion 3 Mono cl mi c Hor izo n t a 1 Dispersion Monoelinic C'rossod A TEXT-BOOK OF MINERALOGY WITH AN EXTENDED TREATISE ON CRYSTALLOGRAPHY AND PHYSICAL MINERALOGY. Iff EDWARD SALISBURY DANA, CURATOR OF MINERALOGY, YALE COLLEGE. ON THE PLAN AND WITH THE CO-OPERATION OP PROFESSOR .JAMES D. DANA. UPWARDS OF EIGHT HUNDRED WOODCUTS AND ONE COLORED PLATI. NEWLY REVISED AND ENLARGED* (16TH EDITION.) NEW YORK: JOHN WILEY AND SONS, 53 EAST TENTH STREET, Second door west of Broadway. 1891. EARTH SCIENCES LIBRARY COPYRIGHT BT EDWARD S. DANA 1877. Press of J. J. Little & Co* Astor Place, New York. 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 Xaumann ; 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 species and a complete list of its synonyms ; for an enumeration of ob- served crystalline planes, and their angles ; for all published analyses ; IT PREFACE. for a fuller description of localities and methods of occnrre ace, 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- ever, 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 Miner alcJiemie 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 many points. PKEFACE TO THE REVISED EDITION. IN this Eevised 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. NEW HAVEN, January, 1883. TABLE OF CONTENTS. INTRODUCTION. / F A R T I. PHYSICAL MINERALOGY. Section I. CRYSTALLOGRAPHY. DESCRIPTIVE CRYSTALLOGRAPHY ..1-S3 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 IIL 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 OP CRYSTALS 102 CRYSTALLINE AGGREGATES. Ill PSEUDOMORPHOUS CRYSTALS 1 13 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 19 Cleavage and Fracture 119 Hardness 120 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 u. 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 D. Supplementary Catalogue of American Localities of Minerals ......... 503 APPENDIX E. Tables to be used in the Determination of Minerals .................. 509 GENERAL INDEX . . . 525 j r THE - f UNIVERSITY OF INTRODUCTION. THE Third Kingdom of Nature, the Inorganic, embraces all species nol 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, fouud 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 us 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 aud 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 Minei alogy, which is not here 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, Litholo- ffical geology, or Lithohgy, which treats of minerals as constituents of rooks. 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 paragenesis of minerals ; while the origin of minerals or rocks through alteration, is called metamorpJiism 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. LITEBATUKE. 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. (1874), 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 der theoretischen Krystallographie. L83 pp., 8vo. Leipzig, 1856. Miller. A Treatise on Crystallography. Cambridge, 1839. Grailich. Lehrbuch der Krystallographie von W. H. Miller. 328 pp., Svo. Vienna, 1856. Kopp. Einleitung in die Krystallographie. 348 pp., 8vo. Braunschweig, 1862. Von Lang. Lehrbuch der Krystallographie. 358 pp., 8vo. Vienna, 18(50. Quenstedt. Grundriss der bestiminenden und rechnenden Krystallographie. Tubingen, 1878. Rose-SadebecTc. Elemente der Krystallographie. Eded., vol. i., 181 pp., 8vo. Berlin, 1873. Vol. ii., Angewandte Krystallographie. 284 pp., 8vo. Berlin, 1876. Schrauf. Lehrbuch der Physikaiischen Mineralogie. Vol. i., Krystallographie. 251 pp., 8vo., 1866; vol. ii., Die angewandte Physik der Krystalle. 420 pp. Vienna, 1868. Groth. Physikalische Krystallographie. 527 pp., 8vo. Leipzig, 1876. Klein. Einleitung in die Krystallberechnung. 39:5 pp., Svo. Stuttgart, 1876. Mallard. Traite de Cristallographie geomctrique et physique, vol. i. Paris, 1876. Bauerman. Text-Book of Systematic Mineralogy. Vol. i , 367 pp, 12mo. London, 1881. Liebisch. Geometrische Krystallographie. 464 pp., Svo. Leipzig, 1881. Tschermak. Lehrbuch der Mineralogie. Lief. I., II., pp. l-3o8. Vienna, 1881-82. In PHYSICAL MINERALOGY the works of Schrauf (1868), and Oroth (1870), and Tscherma'k, titles as in the above list. Reference is also made to the works on Physics, mentioned on p. 160. In addition to thes3, on pp. Ill, 122, 160, 167, 171, 190, a few memoirs of especial importance on the different subjects are enumerated. In CHEMICAL MINERALOGY : JRammelsbcrg,.IInrn\b\ich derMineralchemie, 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; Schrauf, Atlas der Krystallforrnen, Lief. I.-V., 1871-1878 ; Groth (Tabellarische Uebersicht der Mincralien, etc.), 2d ed., 1882; v. Kokscharof, Materialien >;ur IS'ineralogie Russ'ands. vol. i., 1865, vol. viii., 1881 ; Des Cloizeauz, vol. i., 1862, vol. ii., Paris, 1874 ; Dana, System of Miner- alogy, 1868, App. I., 1872, App. II., 1874, App. III., 1882; Blum, 4th ed., 1874; Nau> mann-ZirTeel, llth ed., 1881. The following publications are devoted particularly to Minera'ogy : Jahrbuch fiir Mineralogie ; G. Leonhard and II. 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. Zeitschrift fur Krystallographie ; P. Groth Editor ; Leipzig. Commenced 1876. Bulletin de la Societe Mineralogique de France. Commenced 1878. ABBKEVIATIONS. For abbreviations of the names of Mineralogical works, of Journals, publications of Scientific Societies, etc., see System Min., 5th ed., pp. xSxv.-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. Specific Gravity. Q. Ratio. Quantivalent Ratio (p. 198). Germ. German. R.F. Reducing Flame (p. 204). M. Hardness. . Var. Varieties. An asterisk (*), nppende-l to the name of a mineral species in the Descriptive part of th's i >'k, indicates that additional facts in regard to it are mentioned in the Supplementary or, pp. 420 to 440. ix 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 I. 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 ike same species. The crystal o of any species are essentially constant in the angle of inclination betwe'en like planes. The angle between 1 and *, in a given species, is always csser.tially the same, wherever tHe crystal is found, and whether a product o' nature 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, from the merest microscopic point to a yard or more in diame- ter. A single crystal of quartz, now at Milan, is three and a quarter feet long 1 , and five and a half in circumference ; and its weight is estimated at eight hundred and seventy pounds. A single cavity in a vein of quartz near the Tiefen Glacier, in Switzerland, discovered in 1867, has afforded smoky quartz crystals weighing in the aggregate about 20,000 pounds ; a considerable number of the single 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. I), which the ancient philosophers believed to be water congealed by intense cold. Hence the term, from KpiWaAAos, 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 or 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 oftt^ smooth and brilliant. The directions of cleavage are those of least cohesive lorce 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. (o) 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- taineid 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 affords on measurement the angles 74 55' and 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 iJinds of angles may come under consideration, solid, plam, and interfa- 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, 01 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), rhoiphic dodecahedron (f. 19), are similar. In the rhombohedron (f. 16) there arc two sets of similar edges, six being obtuse and six acute. SoU 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, IT), 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. Rhombic Dodecahedron (f. 19). Faces rhombs, with tho plane angles 109 28' 16", 70 31' M". Edges twenty-four, all similar; interfa.cial 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 ot opposite faces ; and the octahedral the apices of the trihedral solid angles. Named from ScoBe/ca^ twelve, and e'8/m, face. 2. Pyramidal dodecahedron, or Quartsoid. (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 lattoi oblique. 3 . 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) four 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 in different species, and longer or shorter than the lateral ; two lateral, equal, at right ano-les 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. 23 24 2. Right 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 () acute at the extremities of the acute edge. Axes rect- angular, unequal ; a vertical ; a longer lateral, the macrodiagonal axis (named from pd/cpos, large), and a shorter lateral, the brachijdiagonal axis (named from fipaxfa, short). 3. Right 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 ; (c) four lateral. Axes con- necting the centres of opposite faces, rectangular, unequal; a vertical, a macrodiagonal, and a brachydiagenal, 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 a, called the clinodlagonal axis ; but &, the orthodiagonal axis, is at right angles to both c and d. Similarly, the axial sections cb, ba are mutually oblique in their inclinations, while ca, cb and ca^ba are at right angles. The clinodiagonal 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 8 CRYSTALLOGRAPHY. other. All these cases will receive further attention in the description oi actual crystalline forms. 28 ^9 The prisms (in f. 21, 24, 26, 28) in which the planes are parallel to the three diametral sections, are sometimes called diametral prisms. This term also evidently includes the cuhe. The planes which form these diametral prisms are often called pinacoids. The terminal plane is the basal pinacoid, or simply base ; also, iri f. 24 the plane (lettered i-l) parallel to the macrodiagonal section is called the macromnacoid. and the plane (i-i) parallel to the brachy diagonal the brachypinacoid. In f. 26 the plane (i-i) parallel the to orthodiagonal section is called the orthopinacoia, and the plane (i-l) parallel to the clinodiagonal section the dinopinacoid. The word pinacoid is from the Greek iriva^ 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, over 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 01 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 assumecTiii 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 arid inclinations ; that is, there are (as has been exemplified in the forms which liave been described), (A) among ortho- metrio 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 clinometric kinds, one or more of the iutersections 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. ORTJIORHOMBIC 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. TRICLINIC SYSTEM. Axes unequal ; three of the axial intersections ob- lique. Ex., oblique rhomboidal prism (f. 27, 28). 0. Axes four. HEXAGONAL SYSTEM. Three lateral axes equal, 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 triclinia 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 tVo9, equal, and /ierpoi/, measure), the axes being all equal; including: I. ISOMETRIC SYSTEM. 2. Isodiametric, the lateral axes or diameters being equal ; including : II. TETRAGONAL SYSTEM ; III. HEXAGONAL SYSTEM. 3. Anisometric (from awcro?, unequal, etc.), the axes being unequal ; in- cluding : IY. ORTHORHOMBIO SYSTEM; V. MONOCLINIO 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. Tessular of Mohs and Haidinger ; Isometric of Hausmann ; Texseral of Nau- maun ; Regular of Weiss and Rose ; Cubic of Dufrenoy, Miller, Des Cloizeaux ; Monometiic of the earlier editions of Dana's System of Mineralogy. 2. TETRAGONAL. Pyramidal of Mohs ; Viergliedriege, or Zwei-und-dnaxige, of Weiss ; Tetragonal of Naumann ; Monodimetric of Hausmann ; Quadratic of von Kobell ; Dimetric of early editions of Dana's SysteTHj, 3. HEXAGONAL. RJwmbohedrd^t Mohs ; Sechsgliedrige, or Drei-und-einaxige of Weiss; Hexagonal of Naumann ; Monotnmetric of Hausmann. 4. ORTIIORHOMIJIC. Prismatic, or Orthotype, of Mohs; Ein-und-einazige of Weiss; Rhombic and Anisometric of Naumann; Trimetric and OrtJiorJiombic of Hausmann; Tnmct- ric of earlier editions of Dana's System. 5. MONOCLINIC. Hemiprismatic ^o^Hemiorthotype of Mohs ; Zwd-iind-tingliederige of Weiss; Monodinohcdral of Naumann ; utyorhombic of v. Kobell, Hausmann, Des Cloizeaux; Augitic, of Haidinger ; Oblique of Miller; Afiftioaynimetrio of Groth. 6. TBICLINIC. Tetarto^prismatic of Mohs ; Eiii-und-dnfjliederigc of Weiss ; TridinoJicdi'al of Naumann ; GlinorJiomboidal of v. Kobell ; Anorthic of Haidinger and Miller ; AnorUdc* 01 Doubly Oblique, of Des Cloizeaux ; Asyqjmefric, of Groth. 10 CR rSTALLOGRAPII Y. 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; secondly, the law of symmetiy. 1. THE LAW OF SIMPLE MATHEMATICAL RATIO. The crystallographic axes afford the means, after the methods o^ 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 A 13 C, 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 0, 5, a, are the lengths of the axes * (strictly speaking semi-axes) for a given species, then the position of the first plane is expressed by 10 : ~Lb : 1# ; that of the second by 2c : \l> : la (if OD=2OC), and still another plane might be 2c : 2b : la, and so on. Consequently the general position of any plane may be expressed by me : no : nz,f or more simply mo : nb : a, as ever}' 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, to 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 ia more convenient. CRYSTALLOGRAPHY. 11 This subject will become clear in, the subsequent study of die different crystalline forms ; in passing, however, reference may be made to f. 32 (zircon) as a single example. The planes lettered 1 and 3 have respectively the positions, \c : \b : 1#, 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 apparellt exceptions, such as occasionally occur, do not at all set aside this rule. The expression nw : nb : a is called the symbol of a plane, as it expresses its exact mathematical position, and the values of m 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 infynty (oo ) ; hence the general expression for a plane parallel to the vertical axis c (as in f. 33) will be c : nb : a, or oo 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 me : oo b : a ; if parallel to the lateral axis a (as in f. 35), me : b : oo a. If a plane is parallel to two axes, b and a, that is, intercepts these axes at an infinite distance, its position is expressed by c : oo b : oo#, as is illus- trated by f. 36 ; again, its position is expressed by oo c : b : oo a, if parallel to c and a ; and by oo c : oo b : #, if parallel to c, b. These may also be written Oc : b : a, etc. The following important principle should be kept in mind. The relative not the absolute position of an} 7 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, tc : b : 2# , and 2c : 2b : a. and c : b : \a are identical, for the ratios of the three axes are the same throughout, the planes being of course parallel. Similarly the symbol \c : $b : $a may be written 3c : b : a, 12 CRYSTALLOGRAPHY. and c : oo b: aoa is the same as Qc : : a. It will be seen that this prin- ciple 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 mvinb: ra to the simpler form me : nb : #, 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 c, &, a adopted for the species. The faces of this octahedron intersect the axes at distances from the centre equal to nc, nb, na (or c : b : a) respectively, and, since the ratio of the coefficients winch 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 ca, making it thus oblique to c while at right angles to >, 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 position? 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 formed, which are conditions not often realized in the crystals furnished by nature. 2. LAW OF 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 awe* 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 be alone similar in ifa planes or modifications. The forms resulting according to the first method are termed holohe- dral forms, from 0X09, all, eSpa, face ; and those according to the second, hem.ihedral, from TJ/LUO-U?, 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 (a) 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 solid 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. Ilemimorphic, 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 tf/unT},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 plan is. Again, as to the relative positions of the sectants containing the planes, tha 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 lik 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, bein^ 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 1 will be ma : na : a, or, since the axes are equal, simply mi nil. 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, oroo. In this way are derived : 1 [m-n] when m and n have both different values greater 1. m 2. m 3. m 4. 1 5. oo 6. oo 7. oo n than unity. 1 \m~rn] when m > 1, n = m. 1 [m~\ when m > 1, n = 1. 1 [1] when in and n ~ 1 . 1 \i-n\ when m = oo , n > 1. when m = oo jn = 1. when m and n ss oo . In lettering- the planes of the several forms only the essential part of the symbol is used: tV cube is H (hexahedron) ; the octahedron 1(=1 : 1 : 1) ; the dodecahedron * (oo : 1 : 1), (t taiids for infinity) ; m is used for the planes m : 1 : 1 ; m*m f or m : m : 1 ; i~n f or oc : : 1 I ISOMETRIC SYSTEM. 15 w-n lor m : n : 1. These symbols are the same as those of Naumann, except that he wiote oo instead of for infinity, and introduced also the letter (octahedron) as the sign of tha system ; oo o> of his system^jH"; 0=1 ; oo 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 QO : 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, modify one anothe as they 38 ier, are exhibited in the following figures : 40 41 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 facea, 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 if 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-octahedron. //A 1=125 15' 52". If the twelve edges of the cube are truncated (for all will be truncated ii Mie is) it affords the form in f. 43 ; then that of f . 44 : then the dodecahe- 16 CRYSTALLOGRAPHY. 1C dron, f. 45 ; tlie axes of the cube becoming, in the transition, the axes con necting the tetrahedral solid angles of the dodecahedron ; H A 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 beinoj 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 apices 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- 48 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 symbol 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 tri'gonal trisoctakedron, and one, having TO=|, is shown in f. 49. It will be found a very valuable practice for the student to construct the figures of th ive crystalline forms in this way, laying off the proper lengths of the several axes and ISOMETRIC SYSTEM. 17 noting- the points where the different planes intersect, crystals will be found in the Appendix. Further remarks on the drawing of The symbol m : m : I 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 r/oW, 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 m : 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- h^dron. If m becomes less than unity, the symbol maybe, for example, : 1 : 1, 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-trisootaJiedron. In this form the solid angles are of two kinds : the trigonal or octahedral, and the octagonal or cubic. The edges are thirty-six in number, twenty-four of one kind, forming the octahedral or trihedral solid angles, and twelve edges meeting at the extremities of the cubic axes. Each of the twenty-four planes is an isosceles triangle. 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 r commonlv occurring examples of this form are 2 (=2 : 1 : 1), also f ( --| : 1 : 1), and 3(3:1: 1). The Tetragonal-trisoclahedron 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 18 CRYSTALLOGRAPHY. the faces of the cube. Figs. 56, 57, 58, 59, 60, 62, also ehow 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 54 55 56 57 59 01 j-| 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 rerpa/a?, four times, e, S'ix, and e'Spa, face, it being a 4xG-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 66 67 68 The tetrahexahedron, in f. 65, lettered *-2, has the symbol oo : 2 : 1 ; and that of f. 66, lettered -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 i-2 rej lace ISOMETRIC SYSTEM. 19 the solid angles of the octahedron by planes inclined on its edges. Its rela- tion to the dodecahedron is presented in f. 68, which is a dodecahedron (planes i being the dodecahedral planes, see f. 45) with the tetrahedral solid angles replaced by four planes inclined each on an i. The tetrahexahedron is called a fluoroid, by Haidinger, the form being common in fluorite. It is the Tetrakishexahedron (or Pyramidenwiirfel) of Naumann. In accordance with considerations already presented it is evident that n, in the symbol i-n, may always be written as a whole number, for the symbol oo : : I is identical with oo ; 1 ; 2. Moreover it is seen that when n is oo ? the form passes into the cube (00:00: 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 planes 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-eight planes. It is hence called a hexakisoctahedron (ea/a?, six times, OKTCI), eight, and eSpa, 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 three differ- ent kinds of edges, and three kinds of solid angles; each of the forty- eight planes is a scalene triangle. When modifying the cube it appears as six planes replacing each of the solid angles, f . TO. 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 dodecahed ron by eight planes, or the eight obtuse by six planes. The hexoctahedron of f. 69, 70, 71 is that whose planes huve the axia ratio 8 : j : 1. Others have the ratio 4 : 2 : 1, 2 : f : 1 (=6 : 4 : 3), 5 : 4 : f 1=15 : 5 : 3), 7 : | : 1 (=21 : 7 : 3), etc. 72 78 Amalgam. Magnetite. ORYST ALLOGRAPH Y. The preceding figures show dodecahedrons variously modiried. In f. 72, /, or *, are faces of the dodecahedron ; Hot 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, 0, and 1 are as i f. 72 ; 3-3 is the trapezohedron of f . 61, 62 ; and 5-|- (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 hexakisocia- hedron of Naumann. JB. 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 ftolohemihedral, in which all the sectants are represented by half the full number of planes, parallel hemihedrons. In the former the sectauts to which this 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 -J(w : n : 1), of the parallel hemihedrona in the form \ [m : n : 1] ; also written *(ra :n:l) and ir(m : n : 1) re- spectively. a. Inclined or Tetrahedral JJemihedrons. 1. Tetrahedron, or H.tmi- 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 78 79 80 occur in alternate octants; thus in two opposite sectants above, and r,hc two diagonally opposite below, as shown by the shaded planes in f. 74. If ISOMETRIC SYSTEM. 21 these four shaded planer are suppressed, while the other four of the octa- hedron are extended, the resulting form is the regular tetrahedron, f. 76. The relation of the octahedron and tetrahedron may be better understood from f. 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 latter pairs intersect in 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 edges. Further 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. 76A. 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 of boracite, where the planes of one tetrahedron are polished while those of the other are without lustre. The plane angles of the tetrahedron are 60 3 , and the interfacial angles 70 31' 44". 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 84 Hemi-trisoctahedrom, \(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 i(2-2). The faces, as will be ob served, re 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 as with the tetrahedrons. Figs. 82, 83, 84 show combinations of -f %(m-m) wJlh the plus tetrahedron, the dodecahedron, and the tetrahexahedron. 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 on tetrahedral Hemi-hexoctaliedron \(m : n : 1). The form 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 86 87 88 number of sectants, produces the solid seen in f . 87. There is here also y 7 plus solid, and a minus solid, corresponding to the + and tetrahedroi/ 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 seWants^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. 89 89A Sphalerite. Sphalerite. Tetrahedrite. In f . 89, the cuproid 3-3 is combined with the faces /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 position essentially with 2-2. Fig. 90 has as its most prominent t of f . 81 , but the position given it is relatively to f . 81 that of thp minus hemihedron ; and there are also the small planes 2-2 about the angles, which are those of the minus hemihedron. //, are planes of th^ cube ; 1, those of the tetrahedron; i, those of the dodecahedron ; i-3 those of a tetrahexahedron (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. b. Parallel or pyritohedral hemihedrons. According to the second 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 hemihedrism obviously produces Distinct forms only in those cases where there is an even number of planes in each octant. Pentagonal, 3)odecafiedron, or Hemi-tetra/iexahedron, -J(oo : n : 1). If of the twenty-four planes of the form -n(oo: n': I), 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[V-2], and Jhe other minus, J [^-2]. These solids are |ery common in the species pyriie, and are hence called pyritohe- 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 anirra- 14- V'B" tional value, viz., L- , see p. 10. 2 In combination with the cube the form -f J[i-2] is seen in f. 94 and f. 95, iind in f. 96, 97, witli the octahedron, and in f. 98, with the cube and octa- hedron. 91 93 Parallel hemi-hexoctahedron, \\m \ n : 1]. When of the forty-eight planes of the form m-n, only half are present, viz., the three ^alternate 99 101 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 Haioinger. It is also called 24 CBY STALLOGRAPH Y. a clyakis-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-tetrahexaheclrons (pentagonal dodecahedrons) &-2, i-\ ; and of two diploids 4-2, 3-J, along with planes of the octahedron, 1, and of the trapezohedron 2-2. In f. 104 the dominant form is the dode- cahedron, /; it has the faces of the cube, H\ of the octahedron, 1 ; of the 103 104 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 .//, 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-, 3 : { : I (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 i-%. (3) The fact that the following are common an- gles in the system 135 (=HAt); 109 28' (angle of octahedron), 70 32' (angle in octahedron and tetrahedron) ; 120 (angle of dodecahedron); 125 16' (=HA1) ; 144 44' (=HA2-2= lA^) ; 153 26' (=HA*-2) ; 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 cubic, octahedral, or dodecahedral / and sometimes two of these kinds, and occasionally the three, occur in the same species, but always with great difference of facility between them. Galenite is an example of easy cubic cleavage ; fluorite of easy octahedral ; sphalerite (blende) of easy dodecahedral. Planes of symmetry. The seven 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 has already been stated, all planes, solid angles, and edgea are equal and similar. The three diametral planes, passing each through two of the axes, ar the chief planes of symmetry, every part of the crystal TETRAGONAL SYSTEM. 25 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. TETRAGONAL SYSTEM. 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 (c). The general geometrical expression for the planes of crystals becomes for this system me : 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 [m-n\ when m >1, n >1. 2 j c : a : a [1] when wi=l, n=l. ' ( me : a : a [m] when m^l, n=l* Q j c : GO a : a [l-i\ when m=i, n=^ me 4. oo c 5. QO c 6. oo c oo a : a m-i~ when ml, h=co Em-i'\ i-n\ na : a \i-n\ when 7/1=00 , n >1. a: a [7] when 771=00, n=l. GO a : a [i-i] when 771=00 , n= GO . Y j (c : oo a : oo a) [ , and the unit Lena is omitted as unnecessary, me : ooa : a=m-i, etc. These are the same as the symbols or Naumann, except that he wrote oo , and added P as the sign of the systems which are not isometric; QP=0 ; oo/ > oo=i-t; P=I\ Pn i-n ; mP&> =m-i ; mP=m ; P 1; and mPn=m-n. A. Holohedral Forms. Basal plane. There are two similar planes corresponding to the sym- bol c : oo 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 (tan occur onlv in combination with other planes. Prisms. The planes having the symbol oo c : GO 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 c : 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 donned. In a crystallographic gense it includes all thf -ianea geometrically possible, never loss than two, which have the same general symbol. 250 CRYSTALLOGRAPHY. and meet the others at equal distances. There are, as in the preceding 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 ihe vertical. There are also in each case eight similar solid angles. 108 n 109 /5J 12 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 Y (f. 109). The regular octagonal prism, with eight similar vertical edges, each angle being 135, is crystallographically impossible. Ill 112 The planes 7 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-2. 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 (7~) 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 axis at variable distances, multiples (denoted by m) of the unit length. The total munber of such planes, for a given value of m, is obviously eight, and TETRAGONAL SYSTEM. 27 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 the four planes above and below coincide with the two basal 115 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 n umber 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. 118 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 771=00 they coincide with the prism /; 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 ID 121, and this too gradually passes into f. 122 and f. 114. CRYSTALLOGRAPHY. The relation of the octahedrons 1 and 1-i (m andra-) 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, I-i truncates the pyramidal edges of the octahe- diDii 1, and, conversely, the edges of the octahedron 2-i are truncated by the octahedron 1 (f. 124). Octagonal pyramids. The form m-n (mo : iia : 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 eectants, as in f. 125, where m=l, n= 2. These sixteen similar planes together form the octagonal pyramid (strictly double pyramid) or zirconoid, f. 126. It has two 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 bevela 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, i-3 ; of zir- jorioids 2-2, 3-3, 5-5, 4-2f-3, the whole num- oer of planes being 154. B. Jlemihedral Forms. Among hemihedral forms there are two divisions, as in the isometric system : 1. Remiholohedral, having the f nil number of planes in half the sectants (a) Vertically-alternate, or sphenoidal forms. The planes occur m two seetants situated in a diagonal line at one extremity, and two in the trim* 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 130 131 f. 106 that the regular tetrahedron has to the cube. Fig. 130 is I\IQ positive sphenoid or +1, and 131 the negative, or 1. The form %(mc : a : a) is similar. Fig. 132 represents the sphenoid in combination with the prism *-i. If the planes of each sectant are the two of the octagonal pyramid %(mc : na : a) (f. 126), the form is a diploid (f. 133). It is in combi nation with the octahedron I-i in f . 134. (b) Vertically-direct, or the planes occnring in two opposite sectants 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. Ilolohemihedral, 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. 135 186 (b) Vertically -alternate. The occurring plane the right above, and that in the alternate zone below, as indicated in f. 137 ; or else the left 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 m-n and the U m-n (in f. 138, on the angles of the prism i^i). so CRYSTALLOGRAPHY. Wernerite. Scheeli^e. 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 planea 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- 140 141 bi nation of the octahedron \-i 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- tahedral kind, rl 3-3 and Ir 3-3. Fig. 142 contains the hemihedral prism I *-J, 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. (d) 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 I (oo 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 :/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 So : 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 ia HEXAGONAL SYSTEM. 31 assumed as fundamental which is of most common occurrer.ee or to which 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 thb ^quare 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 KHOMBOHEDRAL, 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 Rhombohedral 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, & 32 CRYST ALLOGRAPH Y. It is evident, however, that the position of any plane is determined by ir intersections with two of the lateral axes, as its direction with the third follows directly from them. (Compare f. 146.) Consequently, in writing 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 p n mo inaia: (pa) me :Za:a: (Za) mo \ a\a\ (GO a) c:a:a: (coa) ccc:na:a: (pa) \m-n\ when m [?>?,-2] when m when m 00 c : a : a : (cca) Qc : a : a : (a) [m] [1] 10] 1, ii > 1 and < 2. 1,' n = L when m = 1? ^ = 1. when m = CQ , n> 1 and < 2. when in = oo ? ^ = 2. when m = oo , n = 1. when m = 0, n 1. The abridged symbols need no explanation beyond that which has been given on p. 25 : mPn=m-n ; oojp/i 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. 144 145 146 147 Prisms. The form I=aoc : 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=ooc : 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.es with the basal plane form the diametral prism, f. 145. The relations ol the two prisms / and i-2 are shown m f . 146. In f . 147, it will be seen that the one prism truncates the vertical edges of the other. The faces of the i-2 make 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 ^-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 twc planes answering the given conditions in each sectant, and twelve in all Together they form the dihexagonal, or twelve-sided, prism. This prism bevels the edges of the prism ./, 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 i-^ 2-f, etc. Hexagonal pyramids , or Quartzoids. The symbol 1 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 1. 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 the m series, just described, that the prism ?'-2 has to the prism /. They replace the basal edges between i-% and (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 (in] and the second (m-2) series are well shown in f. 150, of apatite. In the first series there are the pyramids J, 1, and 2 ; and in the second series the pyramids 1-2, 2-2, and 4-2. The cor 149 responding prisms /and a-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. Dihexagonal pyram-ids, or Berylloids. The general form moinaia gives the largest number of similar planes possible in this system, which is here obviously twenty-four, that is, two in each of the twelve sectants. These pyramids correspond to the prisms of the i-n series, and form the dihexagonal pyramids, or berylloids, 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 Yj and the basal edges Z 3 34 CRYSTALLOGRAPHY. in the upper pyramid, one of these two planes for each sectant may b distinguished as the right ^ and the other the left, as lettered in f. 152 and the same, 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 I, r, in accordance with the above. In f. 154, of a crystal of beryl, the prism / is combined with the pyramids 1, 2, 2-2, and the berylloid 3-f. B. Hemihedral Forms. I. VERTICALLY DIRECT. The planes of the upper range of sectants being in the same vertical zone severally with those below. (A). Hemiholohedral. Half the sectants having the full number of planes : 1. Trigonal pyramids. The diametral pyramid w-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 at each nxtremity, 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 7J or -&-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- nedral 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. (E\ ILolohemiliedral. All the sectants having half the full number of p.anes: 1. Ilemi-dihexagonal pyramids. Each sectant has one out of the fwo 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 Ir m-n. Examples of the first of these occur in f. 158, representing a crystal of apatite, the planes 0(3-J), and , f ; E, 4 ; having respectively for the vertical axis, Ic, \c, 2c, -Jc, 4c, with c= 0.8543, tlie lat- eral axes being made equal to unity. In f. 169 the rhombohedron "2 (or 27?) is combined with 1 (or /?)> the latter truncating the terminal edges of the former. In relation to the series of -j- and rhombohedrons it is important to note that, since the position of 4 7? is that of the vertical edge of +7?, in combination with it, it truncates these edges. Similarly +J7? truncates the same edges of 7?, and so on. Cinnabar. Calcite. HEXAGONAL SYSTEM. 37 Also +7? truncates the edges of 27?, and R the edges of + %R (f. 169), 27? 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 scalenohedron is a hemihedral dihexagonal pyramid or berylloid. The method of hemihedrism is similar by the suppression of the planes of the alternate sectants, as indicated by the shading in f . 170 (analogous to f. 159) and the extension of those of the other sectants. A scalenohedron ia 170 171 represented in f. 171, a hexagonal double pyramid with a zig-zag basal out- line, and three kinds of edges : the shorter terminal edge JT, 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 m^/ms '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- bohedron are illustrated in the other figures. Fig. 172 repre- sents a rhombohedron (+1 or 7?) with its basal edges bevel- led ; and this bevelment, continued to the obliteration of the planes R, produces the scalenohedron shown by the dotted lines. The scalenohedron in f. 171, 172 has the vertical axis equal to 3#, or three times as long as that of R, 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 , 1 s , combined with the rhombohedrons R (or +1) and + 4. Fig. 174 shows the scalenohedron 1* combined with the rhombohedron 4 (or 47?) ; and 175, the same with the rhombohe- dron 5 (+5K). Other scalenohedrons replace the basal angles of a rhombohedron by two similar planes (f. 1 76) ; or bevel the terminal edges; or replace the terminal solid angles by six planes, two to each terminal edge, or to each CRYSTALLOGRAPHY. rhombohedral face ; a- id they will be relatively + or , according to their position in one or the other set of sectants, as has been explained. Fig. 17'f represents the top view of a crystal of tourmaline. It contains the rhorobo 176 Tourmaline. hedral planes, ^?,f, -y-, J-, J, f, 2, along with the scalenohedrons J 8 , -J 3 , B , 1|, I 2 , and also two others bevelling the terminal edges of the rhombohedron R. The scalenohedrons i 2 , -J 3 , -J 5 , bevel the basal edges of the rhombohedron ; and consequently the lengths of the axes are respectively 2, 3, 5 times that of the rhombohedron ^, and hence, equal le, fe, fc. 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 tihem accordingly aro 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 w-2 or diagonal series occur in many rhombohedral species ; as f. 178 of corundum, which contains f-2(r), 4-2, - 2 /-2 (for 9-2 on the figure read 2-2, Klein), along with the rhombohedron 1, and the basal plane O ; 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- im ' agonal prisms (p. 34) are also 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 -i- 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 +R] of the 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. 39 )(1) Plus soalenohedrons, or planes of the general form +m n . (2) Zone of plus rhombohedrons, +mR. (3) Plus scalenohedrons, or planes of the general form +w n . (4) Zone of diagonal pyramids, m-2. C (5^ Minus scalenohedrons, or planes of the general form m n . II. X (6) Zone of minus rhombohedrons, mR. ( (7) Minus scaleiiohedrons, m". (8) Zone of diagonal pyramids, m-2. !(9) Plus scalenohedrons, +m'. (10) Zone of plus rhombohedrons, +mR. (11) Plus scalenohedrons, +m n . (12) Zone of diagonal pyramids. A.nd so on around, as the figure illustrates. In the lower pyramid the order of succession ii the same ; but the plat planes are directly below the minus of the above view of the uppei pyramid. The plm 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. Holoheinihedral forms, or those in which all the sectants have half the full number of planes (as shown by the shading in f. 180). Q-yroidol, or tmpezohedral forms. Of the planes, in f. 181 there would occur only those lettered /, 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 II 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 II 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. Wiombohedral tetartohedrism. Occurring planes the alternate cf 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 kino consists of six equal planes, equally spaced, and hence, equal in inclina tions, and is therefore, in the completed state, a rhombohedron. It occure in menaccanite or titanic iron, and in quartz (f. 183, planes 13~Jf). 2. Gyroidal or tmpezohedral tetartohedrism. Occurring planes the alternate of those lettered r or I in f . 153, p. 34, that is, the alternate planee r, or alternate Z, of both bases. 183 184 185 Quartz. Quartz. In f. 185, the planes ^, mR, the oo R, may be regarded as the infinite term of either the -\-rnR series, or else the 'same of the mR series; and as this view accords with the tetartohedral character of the mR series in all such crystals, it might be ranked among tetartohedral forms. From the same point of view, the ditrigonal priems in tourmaline and OBTHORHOMBIC 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 van- 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 / and the other i-2. The general characteristiGs 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. IV. ORTHORHOMBIC SYSTEM. In the ORTHORHOMBIO SYSTEM the three axes are unequal , , a ; of these c is the vertical axis, b is made the longer of the two lateral axes, or the macrodiagonal axis, and d the shorter lateral, or brachydiagonal, axis.* The different occurring forms, deduced as before from the general ex- pression, are: me : nb : a [m-n'] (c:nb:a me :b : na [m-nJ] \ oo c : ft : na mo : b : a \ni\ oo c : b : a c :b : a [1] oo c : & : oo # me : oo b : a [m-%] oo c : oo b : a ( mo : b : oo a [m4] Oo : b : a The abridged symbols 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 all cases to the vertical axis (c), and n refers to one of the lateral axes, whether the longer (6) or the shorter (d) is indicated by the sign placed over it, as n or n. When n oo, this ifl indicated by the i hitherto used, and the sign is placed over it, i, or $, with the same signi- fication. These correspond to the symbols used by Naumann, as follows: 0=0 P; t*4= PHi*n\ mPx>=m-l\ mP=m; m-n^mPn^ etc. * For the relation of the axes thus lettered to those of Dana's System of Mineralogy and of other authors, seep. 53. OETSTALLOGEAPHT. 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 (o 1 and Z*), called the macropinacoids, and the next above includes the planes parallel to the vertical and brachy diagonal axes (G and 0), called the brachypinacoids. 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 pahs 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 O and i-l ; and similarly four brachy- diagoual basal edges between and i-l / the eight solid angles are all similar. 188 Prisms. The form GO c : b : a, or /, includes the four planes of the unit prism which, in combination with 0, 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 I. Of the vertical edges there are two pairs, those at the_extremity of the axis a, 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- pin acoids i-l truncate the obtuse vertical edges of the prism /, and the hrachypinacoids i-l truncate the acute vertical edges of /, as shown in f. 189. There are two other series of prisms witli symbols co c : nb : a and x> c : 1) : na. In the latter series the axis 5 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 ~b at their unit lengths, as in f. 187. If, now, the prismatic planes meet the longer lateral axis (&) at a greate* distance, a prism is formed such aa that in f. 190, whose symbol is 2, or co G : 2b : a. This is a macrodiago- nal prism ; and others might have the symbols i-5 (oo c : 3b : a\ i-1 (oo c : 4 : &), 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 isi-} (oo c : %b : 0), 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 G : b : 2a, 01 -s ; ORTHOKHOMBIC SYSTEM. 43 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 prisrn or i-Z. The prisms of the general form i-n, are called brachy diagonal prisms. The prisms i-n bevel the front and rear (obtuse) edges of the prism I, 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 i4 and / (f. 194), while the i-n prisms replace the edges between i-l and / (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. 192 193 194 I n til 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 brachy pin acoid, is shown in f. 195. These planes are called macrodomes (see also f. 196). 195 196 197 if The form me : b : oo a 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 2-, in combination with other forms. (See also f.. 198.) The word dome, used here and above, is derived from So/^, or domus, a house, the form resem- bling the roof of a house. The combination of 14 with 1-1 is shown in f. 199, form ing a rectangular octahedron, and in f. 200 they are shown replacing the solid angles formed by I 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, O. -*, i~$y I, 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-i, and if one is, all must be ; and the other set (lateral) is replaced by the four planes of the form m-t, f. 200. Octahedrons (or Pyram.ids). The sym- bol c : b : a (1) belongs to the unit octahedron (f. 201). It replaces the between the prism 1 and the basal plane (f. 202). It also replaces 201 202 the eight similar solid angles of the diametral pi ism. as in f. 203. This is a special case of the form mo : I : a, in which in 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=oo for /; also. m=l, m=l m= m=, and finally t-0, for the basal plane O. 204 207 The general form m this system, consisting of eight similar planes, may l.e written either me : nb : a (m-n) ormc:b:na (m-n\ The relation be- tween the two is the same as that between the prisms fc and M. Thus, 04 one plane of the octahedron 2c : M : a (2-2) is given, and also one plane ot another octahedron or pyramid, whose symbol is 2c : I : a (2). If n becomes less than unity, as , the plane has the symbox 2c : & : a (2-11 In order to avoid this use of fractions the symbol is written 4c : b: 2% that IB 4-S The plane is shown in f. 205, in its two positions correspond- ing to 2c : \l : a, and 40 : * : 20, the two being crystallographically iden- ORTHORHOMBIC SYSTEM. Thus there are two series of pyramidal planes : a macrodiagonal ( where the shorter axis is taken as the unit, and a br achy diagonal (m-n\ 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 1 lies between the prisms i-n and i-n. The macrodiagonal planes 1-2 and 2-2 are shown in f. 206 and f. 207. 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-$, 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 f nil symbol of the plane 1-3 is c : 1 : 3a, Sulphur. B. Hemihedral Forms. The hemihedral forms that have been observed are of two kinds : 1, The vertically-oblique ( p. 14 ), producing monodinic 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. Ilumite. Calaminc. is illustrated in f. 209, of the species chondrodite (var. humite, type III). Fig. 210 represents the holohedral form of the same ; the planes --4, 14, 24, are of macrodomes ; -f-4, |-, |~, 44, of brachy domes ; and the others of various octahedrons, mostly in two vertical zones, the unit zone (mo : b : a\ and the 1 : 2 zone (ma : 2& : 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 tho 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 chon 4:6 CRYSTALLOGRAPHY. drodite of the second and third types (see p. 327) is not orthoihombk but monodinic, and this must be true also of humite.* Hemimorphic forms characterize the species topaz and calamine. The latter (in f. 211) has only the planes of a hemioctahedron 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 tiit, 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 1-i 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 (b). 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 that 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 different 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 brachydomes ; 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 * Siuce 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 realty monodinit, as suggested above. The figures are allowed to remain, however, since they illus trate the form which this met! od of hemihedrism would produce. MONOCLINIO 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, 3V'. 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. V. MONOCLINIC SYSTEM. In the MONOCLTNIO 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, , make retangular intersections, The same is true of b and d, 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 : ( 77^6' : nb : a \ -\-rnc : nb : a ( me : b : na \ +mc : b : na me i b i a c : b : a + mc : b : a + c : b : a me : b : cca m-n i-m-n m-n + m-h [-TO] [-1] [+f] [+1] [m-ij 214 j me : oo b : a [m-i] \ + mc : oo b : a [+m-i] j oo G : nb : a \ oo c : b : na x> c : b : a [i-n [i-n i oo c : oo b : a 1 ^"'^ oo c : J : oo a Oc : b : a fvV [0] 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 is indicated by an accent placed over it, as w-i, m-n ; but in m-i, and m-n, etc., i and n refer to the orthodiagonal axis. Naumann wrote these mPcc , and mP,\, 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=0c : b : a\ the ortkopinacoid, parallel to the CRYSTALLOGRAPHY. 216 / 1 ' 1 / -\ }-- ortho-axis (b) oo c l J : 0, or i-i ; and the d'mopinacoid, parallel to the in clined axis (a), oo c : 5 : oo &, or ^4. In the solid (f. 216) or diametral prism formed of these three pairs oi planeo, the four vertical edges are similar, and this is also true of the foul edges between O and i-\. 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 seta 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 cli nodi agon al, i-n, bearing the same relation to each other as the macro- and brachy-diagonal prisms in the orthorhombic system, in fact, the 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, frb. Clinodomes. The form m-l (me : b : oo 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, sinee, as has been remarked, the four clino- diagonal edges in f. 215 are similar, and hence are simultaneously replaced by these cliiiodomes. 220 Orthodomes.Oi the general form, me : oo b : a, there are two sets oi planes, two in each (hemi-orthodomes), 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 MONOCLINIO SYSTEM. independently of each other. To distinguish between them, those belonging to the obtuse sectants receive the minus sign ( m-i), and those belonging to the acuta^actants the plus sign (+m4), f. 219. This same point is illus- trated by f . 220, where, as has been remarked, the obtuse edges, above in 221 223 front, and below behind, are similar, and are hence replaced by planes of the m-i series, while the remaining two (f. 221), are also similar, and are replaced by +m-i planes. Hemi-octahedrons. The same distinction of plus and minus belongs to all the pyramidal planes, and the signs are used in the same way. Foi each form there are only four similar planes. The m series is that of the unit octahedrons, properly hemi-octahe- drons, or hemi-pyramids +ra and m. The form made up of +1 and 3 is seen in f. 223, and in f. 222 the same planes are in combination with the three pinacoids. The general form, +ra-n, m-n, and +m-n, m-n, give each four simi- lar planes. They bear exactly the same relation to each other as the m-n and m-n of the orthorhombic system, so that no additional explanation is needed here in regard to them. The figure (f. 217) of datolite may be referred to for illustrations of the different forms which have been named. There are here three different clinodomes -J4, 24, and 44, each comprising four planes ; a minus hemi- orthodome (opposite the obtuse angle), 24, and also a plus orthodome, + 24 (these two planes are quite distinct, though numerically the symbols are the same) ; moreover, of hemi-octahedrons of the unit series, there are 4, |, and +4, +2, +4, + !,+, + $ > a ^ so ^ orthodiagonal pyramids, 4-2, 6-3, also +2-2, and of clinodiagonal planes, 8-S, and +12-f. A careful 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 noticed that all the planes above in front are repeated below behind, and those below in front appear again above behind. More important than this, 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. Hemihedral forms occur of a hemimorphic character, in which the planes about the opposite extremities of the vertical axis are unlike ; thus, the planes of one or more hemi-pyramids may .occur at one extremity, without those corresponding at the other, as in tartaric acid, ammonium tartrate, etc. With many monoclinic crystals the obliquity is obvious at sight ; but with many others'it is slight, and can be determined only by exact measurements. 60 CRYSTALLOGRAPHY. In datolite it is only six minutes. The character of the symmetry exhibits further the obliquity. But, as seen above, both 4- and planes of the same value do occur together, and though they are really distinct yet they may give a monoclinic crystal the aspect of an orthorhombic crystal. On the other hand, true orthorliombic 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 orthodiagpnal 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 in the zone at right angles to the clinopinacoid may be taken as the base (O) and any other 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 of sym- metry, the diametral plane in which the vertical and clinodiagonal 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 geome ' ' ' solid. VI TKICLINIC 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 of symmetry. Only diagonally opposite octants are similar ; there can conse- quently be only two planes of anyone kind. There .are no truncations or bevelments, and no interfacial angles of 90, 135, or 120. The prisms are all hemiprisms, and the octahedrons tetarto-octahedrons. The lateral axes are called the mawodiagonal (&), and the brachy diago- nal (d). In f . 225 the diametral prism (made up of three pairs of different planes) is represented, and in f. 224 the unit prism. To the latter is added (in f. 226) one plane 1 on two diagonally opposite edges, which are two out of the eight of the unit octahedron (f. 227). This octahedron, as will MATHEMATICAL CKfSTALLOGRAPHY. 51 be seen, is made up of four sets of different planes. The different kinda 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 hemiclome and a vertical plane parallel to the brachy diagonal section. The forms, although oblique in every direction, may still be closely Bimilar to monoclinic forms of related species. 229 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 monoclinic feldspar, orthoclase ; in orthoclase, O 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 CEYSTALLOGEAPHY. 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, arid 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 (+); 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 first quadimt (see also f. 232) are all positive (-f); the planes of the second positive (+) with reference to the axes c 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 5, but negative with respect to a. The lower quadrants are respectively similar, except that the vertical axis is always negative. The symbols for each plane of the orthorhombic octahedron (f. 231), taken in the same order, will be as follows . Above, -f c : -fJ : -fa; +c : I : +a; +c : b : a; +c : +J : a. Below, c : + b : + a\ c : b : -fa; e : b : a: c : +b : a. The hexoctahedron (ma : no, : a) may be taken as another example. The general symbol of the form of f . 247, p. 64, is 3-f (3a : 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 of 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). a a 2 = f a : 3a : a 3 = a : 3a 4 =. a : fa 5 = fa : a : 3a 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 ; in 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. c 6 = 3a: 7 = -3a : 8 = -3a : 9 = fa: 10 = -3a : b a a : fa fa : a a : fa 3a : a fa : a, ; and so on . 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. Monuclinic. vert, orthodiag. clinodiug, d Tetrag. (Hexag.) Orthorhombic, Triclinic. vert. lat. vert, macrodiag. brachydiag Common usage This work ( Weiss, Kose.; Miller's School, Mohs, Naumann, Dana (System 1868) 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 Einldtung in dieKrystattberechnung. DETEBMINATION OF PLANES BY ZONES. The subject of zones has been briefly explained on page 4, and various examples have been pointed out. The principle is one or 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. Parallel ism in the combination edges, or mutual intersections of planes, is based upon some common geometrical ratio, and this common ratio ha longs to the symbols of all the planes of the zone. 233 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 i4, a-2, /, a-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 = GO be- longs to them all. Again, in the zone O, l-, 2-#, Acanthite. #, etc. (f. 197, p. 43), the planes are alike in that they are all parallel to the brachydiagonal axis ; in other words, a = is true of all of them. Still again, the pyramidal planes i, 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 *-2, and for them the lateral axes have the ratio 1:2. In the case of an oblique zone, as *-, 3-3, 2-2, 1, etc. (f. 233), this fact is less evident on inspection, but ia 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 comiron 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 me : nb : ra, making parallel intersections with the planes m'c : n'b : r'a and m"c : n"b : r"a is, M N It + -\ -- = 0; in which, m n r M= m'm"(n r r n -n"r'Y, 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 tc that used in Miller's system. (as suggested by Prof. J. P. Cooke). If wo write the parameters in parallel lines, repeating the first two terms, we have n s r m \y /\ m" , n" \ r" /\ m" and it will be seen that the coefficients J/, N, R are found by multiplying together the parameters in the manner winch the scheme indicates. M= m'm" (rir"-r'ri r ). &= n'n" (r'm"m'r"). R = r'r" (m'ri'-rim"). Take, for example, the zone of planes between i-l and 1 (f. 233). For i-l, m' = i, n'=l,r'=i', for 1, m" = 1, n" = 1, r" = 1 ( i = oo ) ; hence the scheme becomes ' and for the several values of the coefficients M=i(l-i)= _. ^=l(i-i)=0. fi = i(i-l) = #. 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 l-i, /, 3-f, 14,^etc., in f. 234. The parameters of the plane / and 14 arranged as above give i 1 1 i 1 1 i 1 1 i and the values of M, N y R are P, -i 2 and +# respectively. Hence the Bone equation becomes 1 1 1 _ __ _ _ i _ =() m n r ' MATHEMATICAL CRYSTALLOGRAPHY. 55 234 and if r = 1, the general formula n = r is derived. Between i : 1 : 1 (/) and 1 : * : 1 (1-&) the values of n are positive, as with the series of planes :l-t:l-; 6ti:%b:a; 5 : : 1; 4 : f : 1 ; 3:f:l; 2:2:1; f : 3 : 1, etc., l:i:l. Between 1 : * : 1 and -J the values of n are negative, that is, are measured on tho back half of the axis b ; as, for example, f:-4:l;f:-3:l;|:-2:l;i: 1:1. As the zone continues on from : 1 : 1 to 1 : 1 : * (!-#), and i: 1 : 1 (7), the unit axis is changed, making n-= 1. The zone equa- tion then becomes r = j, the values of r being positive between -J : 1 : 1 and 1 : 1 : i, and negative between 1 : 1: i and i : 1 : 1. The successive planes are f: 1:2; J: 1:3; th 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 OF THE ZONE-RELATIONS OF DIFFERENT PLANES BY MEANS OF METHODS OF 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. Quenstedtfs method of p?*ojection. 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 f-J. 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 oa, 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 H, H. 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 CEYS I ALLOGRAPH 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 i 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: |, and 1 : | : | s in the first quadrant, and similarly in the other three. 237 The projection of the first of these planes is the line joining the points x. (ex = f of c^)and a 9 ; that of the second plane is the line joining the points a 1 and y (cy = f of 2 , p*. From the section (f. 241), the relation of the vertical axes to the tangents of the basal angles is at once obvious. It will be seen here that a 1 , a 2 , etc., are not only the supplements of the interfacial angles measured on 0, but are also equal to the angles measured on i-i diminished by 90, and this is true in general. It will be also seen that the angles a 1 , a 2 , etc., may be obtained from the angles of the planes measured on each other. Thus, given 1 A# = 180" a 1 and given d 1 A a , obviously a 2 (sup- plement of * 2 A 0) - a + (180 - e l A* 2 ). 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 zircon. 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 : O = the angle between here 90. the basal and vertical diametral sections ; a = the inclination of the vertical edge on the lateral axis. B= the semi-vertical angle of the octahedron (= \K\ h (the hypothenuse) = the plane angle of the octahedral face. A = the "semi-basal angle ( \Z). b = 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 run, 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 parts, 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 = iZ= 42 9' 53", and hence 90 A = 47 50' 7". Then the parts of tbc triangle may be written, commencing with (7, 5(45) 90 (O) (90 - A) (90 - B) (90 _ h). IfB 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, the vertical axis. 62 CRYSTALLOGKAPHY. For convenience, some of the more important formulas for the solution of spherical triangles are here added. In spherical right triangles C = 90. Sin A Cos 4 Tan.1 sin a ~~ sin h tan b sin 5 cos B tan# sin # cos a cos A cot A cot # sin* ~ sin h tan ~~ tan h tana ~~ tan h tan & ~~ sin b _cosB ~ cos b cos h - cos h = sin a cos^l cos a La 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 ; (3) Cot b sin c cos c cos .4 + sin A cot J? ; (4) Cos A -- cos B cos (7 + sin B sin (7 cos , and, as before, tan \B V% = m. See further the following case. are thus : The general equal ions (a) tan \B = m. = 144 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, O= 90 , and 64 CRYSTALLOGRAPHY. each of the other angles equals (= angle v) is obtained, and tan Hence, one of the equal sidea m. () If the angle is given. the triangle 2, in f . 246, is employed .; here one angle is 90, a second = 60, and the third =4(7, half the measured angle of the edge 6* The side of the triangle the angle f) is calculated, and, as in the preced- ing case, f = 144: 44' p, then m+ 1 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 (= 1 : m : m). The general equations for the form m-m are : (a) cos v cot %B ; tan v m. (&) cos p = cot 4<7 V^ ; f = 144 -4A'-p ; tan fV/2 = m + 1. 4. Form m-n, hexoctahedron. The edges of the hexoctahedron are of three kinds, A, J2, (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 4-4? %B, and 45. In this triangle, the side opposite \A (= angle v) is calculated, and from it are obtained the values of ra and n, as follows : cos v = cos \B sin tan sm v = m ; tan v 2 Given A and O. 38 are equal respectively to A, In the oblique-angled triangle II (f. 247), the three , and 60 The side opposite \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 O on the dodecahedral axis ; MATHEMATICAL CRYSTALLOGRAPHY. 65 hence, = 144 44' p. Again, in the right-angled triangle III (f. 247), one angle = i6 y , and the adjacent side =, whence the other side, S (the in- clination of the edge B on the dodecahedral axis), is obtained ; v =135 B, and from this, as above, and from the angle />, are deduced the values oJ n and n. The formulas are : cos p = cos Bini6 r V3 z/ = 135 S; tan v = ?i ; . , ~ = 144 44 p ; tan 8 = sin tan ;r - tan 7/. (c) Given ^ and G. K the right-angled triangle, III (f. 247), the two angles are given, equal respectively to %B and jfi From the triangle is deduced the side opposite $G (= angle 8 denned before), and from it is obtained v, and from v and %B, the values of ra and w, as in the first case. The formulas are : cos B = - -= z> = 135 tan v = tan sn sn v = m. If, instead of m-7^, the form is m , 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 piano at a* will be the supplement of its angle upon the section V, that is, the angle B in the spherical triangle ; similarly, the angle of a cubic plane at a 3 will be the supplement of its angle on the section a 1 a?, 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 respectively, 'and the symbol, hence, J : i : 1, which is equivalent to 1 : f : 3, or m-n = 3-f for the general form. Hemihedral 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 G are the same in both, while B oi the holohedral form differs from B' of the hemihedral. The formulas re- 66 CRYSTALLOGRAPHY. quired to cover these additional cases are given below, they are obtained in a manner similar to those in the preceding pages. Form %(m\ f. 85. Given B'. cos e = 2 cos \B'V\ ; = 35 16'+ e ; tan f VJ = m. Form (ra-ra), f. 81. Given B'. tan Form i(ra-n), f . 87. (a) Given A! and .#'. cos a = cos . Q cos t _ _ ~ sin A' ' ~~ sin J^ 7 ' ^ ~ cot a cot ft ' ' ~ cot a + cot ^. J Given ^' and ^. sin tan (8 + 45) = n-, tan = m. 7i + l p-n], f. 92. Given A". tan ^4"= n. Form [-tt], f. 100. (a) Given J/' and ^ r/ . cos \A" n cos iy4" Given ^ r/ and (7" COS " cos ; cos = sin J4" v 2 tan (45 + <9) = m ; sin (45 + 6) tan J4"= Given ." and 67". 2 cos tf "V/ ^ sin O ; cos 8 = C 8 ^ - cos sn tan (45+ 8) = n; sin (45 +5) tan i^" = m. The various combinations of holoheclral and hemihedral forms whicli may occur are unlimited, and it would be unwise to attempt here to show 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 interfacial 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 tie corresponding edges in related forms : H A H= 90, f . 38 1 A 2-2 = 160 32', f. 58 e-f A a-f, 4= 133 49' H A 1 = 125 16', f. 40, 41 1 A 3-3 = 150 30, f. 57 i-\ A '-f, C\ = 157 23 H A > = 135, f. 43, 45. 1 A I = 169 49 t-2 A *-2, .4,= 143 8, f. C5 #A *-f = 146 19 1 A 2 = 164 12, f. 53 i-2 A i-2, G,= 143 8 H A -2 = 153 26, f . 64 1 A 8 = 158 i-2 A <-2, ov. top, = 126 52 H A -3 = 161 34 1 A 3-f = 157 45 i-2 A t-3 = 171 52 H A H = 133 19 1 A 4-2 = 151 52 i-2 A 2-2 = 155 54 #A $-$ = 136 45 1 A 5-f = 151 25 i-3 A 8, -4,= 154 9. f. 6 //A 2-2 = 144 44, f. 55 < A = 120 f. 45 *-3 A -3, 9 , respectively, on the lateral axis. The tangents of these angles give the values of m and n. The formulas are as follows : = cos a, tan a = mo ; cos "* cos v. tan v = n. sin %Z () Given Y and Z. In a second triangle placed as indicated (2, f. 250), two of the angles are ^^Fand \Z respectively, and the third is 90. The solution of this second triangle gives 8, the inclination of the edge Z on the diagonal axis, from which, in the plane triangle we have v = 135 8, 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 m ; as by the following formulas : cos S,v = 135-S, tan v = n ; tan \Z sin v tun a = me. (o) Given Xand T". A third triangle, numbered 3 in the figure, has two of the angles equal to JXand Y respectively, and the third is 45. Solv- ing this oblique-angled triangle, the angle of the inclination of the edge Y on the vertical axis is obtained, and its complement is the angle e, the in- clination of the edge You the diagonal axis; from e and -J- Y are obtained, by triangle 2, S, and thence, as above, n\ and finally, from Xand v, is obtained a, and from that the value of m. The simplified formulas are as follows : cos cos n\ ; sin a n cot JX, tan a = me. Pyramids of the general symbol 1-ra, 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 eecting at angles of 60, and a fourth vertical axis (c) at right angles to the plane of the others. Taking a = 1, there remains but one unknown quantity in the elements of a crystal, 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. Schrauf 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 : aVs : 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 eclge X is given, then f, the inclination of the edge X upon the adjoining lateral axis, is calculated : sin f = cot \X V3j and tan f = me, 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-2 : 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 i Y = sin Z, and tan \Z = me, or c when m = 1. (b) Given the angle Z. Then simply tan \Z = mo. 3. Form i-n : dihexagonal prism. The vertical edges are of two kinds. axial X, and diagonal JT; 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. (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 ^Tand 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 cos v = -, n i = tan (v - 30) Vf ; tan \Z sin v = mo. (b) Given T and Z. The right-angled spherical triangle has its vertices on the eolges T^and Z and the diagonal axis. If 8 = the inclination of the edge Ztipon this diagonal lateral axis, then : cos 8 = COS ; but n - J = tan (120- 8) also (150 8) = v ; and, as before, tan \Z sin v = me. (c) 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., \X, \Y, and 30, hence : cos cos Further, if f = the angle of inclination of the edge X upon a lateral axis, that is, the complement of the same edge upon tne vertical axis (the side of the spherical triangle opposite the angle sin f = n - - cot \ X, and tan f = me. 2 n m If the pyramid m-n takes the form m- , as determined by its zonal m 1 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 rhombohedron is iJie hemihedral form of the hexagonal pyramid m, and its symbol is writ- 72 CRYSTALLOGRAPHY. ten , or usually mR. The scalenohedron is the corresponding hemihe dral form of the twelve-sided pyramid, and its symbol is written %(m-ri) 01 m'R nl . The latter symbol, proposed by Naumann, has reference to the rhombohedron whose lateral edge corresponds to the edge Z of the given scalenohedron. The formulas given by Naumann for reducing the symbol <(m-n) to tno form m'R nr are as follows : n For the converse, to reduce m'R*' to the form m = m'n' and n = n , ^ 1. Rhombohedrons, mR The methods of calculation are simple, and will be understood from f . 252. The edges are of two kinds, X and 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 ABC,v& f. 252, with its vertices respectively on the edge X, the vertical axis, and the diagonal of the rhoinbohe- dral face. In this triangle A = \X, B = 60, cos A cos ^>X and C = 90. but cos a = - ^ = -r- ^ sm 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 iu the plane triangle abc, where ac = the lateral axis = 1, ab = VJ , hence, tan a V'f = me, or = c, the vertical axis of the rhombohedron, when in = 1. The general formulas are then : cos sin a = , and tan a 4/J = me. Obviously, when the angle of R (or mR) upon the basal plane O 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. Scalenohedrons, ml? 1 . As seen in f. 171, p. 37, the edges are of three kinds, X) Y, Z, and two angles, must in general be measured to allow of n i found from = ; further, sin $Z = -- cos n 1 cosi^T n H 1 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 JTand Y. V( also, cos % =. - r!~ ? and cot % (&) Given X and Z. 2n sin ^-Z tan -JZ (c) Given T^and Z. 2n _ sin-|Z ^ _ tan JZ ^ ,- _ If m, that is the inscribed rhombohedron, is known, one measurement will give the value of n. Z' = basal edge of the inscribed rhombohedron (care must be taken to note whether is obtuse or acute). (d) Given X. sin = 2 cos \X cos JZ r . tan (<- JZ') cot JZ' = n> () Given y. sin = 2 cos IT cos (/ ) Given Z. tan JZ, cot JZ' = n, If 7i is known. From X, we have sin |Z = cos \X ; then, as under (a). From I 7 ", sin JZ = -3L cos J T", and then as above. From Z, n\ cos f ' is obtained as under (a\ and then mc. IY. ORTHORHOMBIC SYSTEM. Of the three rectangular axes in the Orthorhombic system, one is always taken equal to unity, in this work the shortest (a). This leaves two unknown quantities to be determined for each species, namely, the lengths 74 CRYSTALLOGRAPHY. of the axes c and , expressed in terms 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). 8 = the inclination of the edge X to the axis a. 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 : 1) Given a and /S, tan S = c and tan a = 2. 2) Given a and 7, 3 ) Given and 7, tan a = 3, and tan 7 = 4 tan /3 = c, and c cot 7 = I. The angles a. & 7 are often given direct by measurement ; for, obviously (f. 254, 255), a = the semi-prismatic angle /A 1 (over t'4). # = the semi-basal angle of 14 A 14. 7 = the semi-basal angle of 1-iA \-l. Also /A *4 = a + 90 ; 14 A i-l = + 90 ; II A # = 180 , etc. From the octahedron (f. 253), the angles a, /3, 7 are calculated immedi- ately by the following formulas, and from them the length of the axes as above. (a) Given X and Z (spherical triangle I, f . 253), cos a = (b) Given Fand Z (spherical triangle II, f . 253), gna= (c) Given 2Tand T (spherical triangle III, f. 253), sin ft = c ? MATHEMATICAL CRYSTALLOGRAPHY. ' . 75 If any one of the angles a, ft, or 7 is given, as from the measurement of a prism 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 JTand a, sin ft = cot JJTtan a. X and ft, tan a = tan \X sin ft. X and 7, cos ft = cot \X cot 7. (2) Given y and a, sin 7 = cot ^y cot a. y and /3, cos 7 = cot Y cot y3. y and 7, cot a = tan I 7 sin 7. (3) Given Z and a, tan 7 = tan -J- Z cos a. Z and , cos a = cot -J- Z tan 7. Z and 7, sin a = cot Z tan /3. Calculation of the values of m and n. The above formulas cover all the ordinary cases, the only change that is required in them is to write for e, b,a, in equations (1), (2), (3), above, c', b', #', the lengths of the axes for the given form, noting that c' = me, and so on. 1. Prisms, i-n or fan. As remarked, the semi-prismatic angle (over i-l) is the angle a (f. 254X &nd tan a = nb. If the calculated value of n is greater than unity, tne iorm is written oo c : nb : a (i-n) ; if less than unity the form is written at/c:b:na (i-n), b being the unit axis. Thus i- (oo c : %b : a) becomes &-2 (cooib : 2a). 2. Domes, m-i and an-l. No further explanation is needed (f. 255) ; here tan ft me, or I tan Ay = me. 3. Octahedrons, mi. Here the angle a is always known (it being the same as for the unikfoctahedron where tan a = b\ 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 ftjtz me, b tan 7 = me. 4. Forms m^fior m-n. The measurement of the angles X, Y, Z will give the values of a, /3, 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 2c : %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 . 248) ; for m-n A (base) = supplement of the angle %Z ; m-n A iri (macropinacoid) = supplement of the angle -J- 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 iinds a wide application in this system. It applies not only to the main zones O to i-l (macrodomes), CKTSTAXLOGEArHY. O to i-l (brachy domes), i-l to i-l (vertical prisms), and I to O (unit octahe- drons), but also to any z.^ne of octahedrons m-n (or m-#) between O and i fk (or i-ti), and any transverse zone from i-l to m\ and i-l to m-l. V. MONOCLINIO SYSTEM. In the Monoclinic system the number of unknown quantities is three, viz., the lengths of the axes c and J, expressed in terms of the unit clinodiagonal axis , and the oblique angle ft (also called <7), 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 /5 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 _ 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' 6 p'. X f on d by v'. Z on d by <7. For the relation of the axes in terms of these angles we have : (1) In the oblique-angled plane triangle, in the clinodiagonal section a : c = sin a sin 6 sin v , : sin v. or, c = -. when a = L 8111 yL6 tan u, = c a cos /5' a c cos /3' 2 sin u, sin a a sin fi tan u! = -5. c+a cos 6 tan v' = tan 5 = sn a 4- c cos / 2 sin v sin i/ sin (/*- tM') sin (v - v ') ' Further, p + v + /3 = 180 ^' + v '= ft. (2) In the right-angled triangle of the orthodiagonal section, 5 cot p = MATHEMATICAL CRYSTALLOGRAPHY. 77 (3) In the basal section, d tan sin F' sin 2T" cosZ' sin Y cos X _ sin X" tan Y, tan sin Z G" tan / sin Z' 3 ? sin v' sin L t '* tan /JL tan /*' sin p ' = sin p ' _ tan v tan i/ tan Z = -. , tan Z' = . sin cr sin or (g\ Given the prism /and 1 (or -f 1). The angles /A/, 1 A /, 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) = 27, from which the sides ^4Z> = v r + (180 ft) and ^.^ are calculated. Then in the second triangle, ABC, C = 90, AB is known, also A\ ence, CB = o-and 6"J. = 180 are calculated. Thus r' and /A' and ft become known, and the relation of a to A : also from <7 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 ^ v, p, b cot X n = - ii_ - an( j f or v^n n = . Since i-i A i-l = 90, the tangent law can be applied in this zone ad van tageously. If JT 1 , Y^ are the corresponding angles for the unit prism /, then for i-n, and for 3. Forms m-i, hemi-orthodomes. For each form the corresponding values of /t, v (/*', v') are to be obtained by measurement or else calculated, and from them the value of mo obtained from the formulas (1), me = sin v , etc. sin /A 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 w4, Or by the tangent law, X 1 being the corresponding angle for 14, 80 CRYSTALLOGRAPHY. TRICLINIO SYSTEM. The triclinic system is characterized by its entire want of symmetry The inclinations of all the diametral planes, and hence, the inclination oi 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 1) and c, a being made = 1. The axes are lettered as in the orthorhombic system : c = the vertical axis, b = the macrodiagonal axis, and a = the brachydiagonal axis. Let (f. 259) a angle between the axes c and ; 259 /3 = angle between the axes c and a ; 7 = angle between the axes l> and d. Also, let A = angle of inclination of the diame- tral planes meeting in the axis d', J2 = angle of inclination for those intersecting in the axis #, and C 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 (J3) are called +, and those opposite the corre- sponding obtuse angle ; furthermore, the planes in front, to the right (and behind, to the left) are distinguished by an accent, as 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), -2T= inclination of a plane on the brachydiagonal section ; 7 = " macrodiagonal 7. Koool Let the inclination of the edge, Xonc = fjL 9 Yonc = p, X on d = v, Y on 1) TT, Z on a --= tan T = 7 - - tan a = 7 - - -- ^ - . a cos 7 a o cos 7 Also, sin T sin p sin sin , 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 smaller 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- sents a crystal, whose angle, abc< is required. The eye at P, looking at the face of the crystal, 30, observes a reflected * See alco Supplementary Chapter, pp. 115 et seq. 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 dbo^ measures, therefore, the number of degrees through which the crystal must be turned. But dbc, subtracted from 180, 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 foi the sake of greater exactness. The circle, 6 y , is graduated, in this case, to twenty minutes, and by meana 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, 1), 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 t>e accurately adjusted; 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, \7hich 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 t, f. 262, with slight magnifying power. Thig 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 iu 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. V ery often, however, the second telesc6pe 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 Schrauf, the spider-lines of the second telescope may be re- placed by a piece of tin-foil, in which two fine dross 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 (e.g.) 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 is 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 to MATHEMATICAL CRYSTALLOGRAPHY. Si 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, #, 5, moving at right angles to each other ; here they are moved by hand, but in better instruments by tine 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 Knppfer (Preis- schrift uber 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. Tlie 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 J 31' 48", required 70 3 31' 44" ; for the octahedral angle 109 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 in approximate measurement may not be the more accurate because it happens to agree clo&ely with the theoretical angle. For the determination of the symbols of planes, measurement accurate within 30', or even 1, are generally sufficient. When planer are rough and destitute of lustre the angles can best be obtained with th* CRYSTALLOGRAPHY. 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 204 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. 264rA, 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 deducible 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 apparently holohedral form, the axes of the parts revolved remaining parallel. TWIN CRYSTALS. 39 In some cases (e>g,. hexagonal forms), a re volution of 60 would prod ace the twinned form, but in treating of the subject it is better to make the uniform assumption of a revolu tion of iSO, 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 that of 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 laws 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 correspondence between the actual angles and fchose 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 twinning-axis (Zwillingsaxe, Germ.\ 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-plane. 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 plane of twinning have, as always, a definite position, but the composition- face 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 7?, 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 inor 90 CBTSTALLOGBAPHT. frequenf- or fundamental planes. The exceptions occur only in tlie triclinic and monoclinic systems, where the twinning axis is sometimes one of the oblique crystallographic axes, and then the plane of twinning normal to it is obviously not necessarily a crystallographic plane, this is conspicuous in albite. In these cases the composition-face is often of more significance than the t winning-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 i-i, 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 i-% was 70 30' ; the twinning-axis deduced from this may be the normal to the plane a-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, i-3 becomes the twinn ng- plane, and the axis of revolution is normal to it. Hence, either i-' or &-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 (i-$) 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 by 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. Very 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 CKYSTAJ,8. 91 tinct line on some of the faces marks the division between the two 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' 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 nuclea.1 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 paragenic. 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 ' O A i-l. 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. Examples 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 in most cases also the latter coincides 270 Galenite. Sphalerite. Galenite. with the composition-face. Fig. 263 shows this kind as applied to the 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 of * 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 Krystallographie, 284 pp., 8vc, Berlin, 1876). TWIN CRYSTALS. 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. 273 274 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 angle of divergence of the branches is- 60 and 120, the interfacial angles or 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 \4. It is especially characteristic of rutile 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. CK rSTALLOGBAPHY. add four more behind, the last (YIII) 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 ia 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 Rutile. Rutile. is a diagonal axis, and the plane of twinning the prism I. 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. 284 Entile. 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-i (Jahrb. Min., 1873, 113.) TWIN CRYSTALS. 95 HEXAGONAL SYSTEM. In the holohedral division of this system twins are rare. An example is furnished by pyrrhotite, f. 284, where the twinning- plane is the pyramid 1, the vertical axes of the individual crystals being nearly at right angles to each other (O A 1 = 135 8') ; Another example is tridymite * (see p. 288), where the twinning-plane is either the pyramid I orf. 285 Calcite. Calcite. Ghabazite. 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.) Calcite. Calcite. 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., eaoocv. 437 ; clii. 1. 96 CRYSTALLOGRAPHY. ORTHORHOMBIC 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 (winning-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. Prism vertical. The principal examples are aragonite, / A / == 116 10'; cerussite,7A7 = 117 13'; witherite, 7 A I = 118 30'; bromlite, /A 7 = 118 50'; chalcocite,/A 1 = 119 35'; stephanite, 1 1\ 1 = 115 39'; dyscrasite, /A I 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. 291 295 i/ if Aragonite. Aragonite. Aragonite. 2. Prism horizontal ; that is, a macrodome. Examples : arsenopyrite, 14 A 14 = 120 46' ; leadhillite, 14 A 14 = 119 20' ; humite, type 1. 3. Prism horizontal ; that is, a brachydome. Examples : manganite, 14 A 14 = 122 50' (f. 206) ; chrysoberyl, 34 A 34 (f. 300) =120 13' ; columbitc, 24 A 24 = 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 a crystal of leadhillite, in its twinned form of very rhombohedral aspect. Figs. 299 and 300 are both chrysoberyl, where 34 is the twinning-plane ; Bix-rayed twins are very common in this species. The genesis of these forms is further illustrated by the following croes- Manjranite. TWIN CRYSTALS. 97 sections. Fig. 301 shows a cross-section of a cerussite twiii, and f. 302 cne 'vstal c " of the crystal of leadhillite figured above (f. 298). 297 Witherite. Leadhillite. Chrysoberyl. 300 Chrysoberyl. In f . 303, three rhombic prisms, 7, of aragonite, are combined about their acute angles, the dotted lines showing the outlines of the prisms, and the cross lining the direction of the brachy diagonal ; and in f. 304, four are similarly united. In f . 305, three similar prisms, I, are combined about the 301 304 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 CRYSTALLOGRAPHY. tw inning-plane is 307 308 \ , and the corresponding prismatic angle is 109 14' (over i-l, or 70 46' over i-l). Another example is furnished by marcasite, whose prismatic angle is 106 5'. The twins are generally compound, the repetition with the tvvinning- plane sometimes parallel, sometimes oblique, see p. 247 In f. 308 the compound crys- tal consists of five individuals, since five times 73 55' is ap- proximately equal to 360. ( 5. Apatite ; transparent variety. (5.5. Scapolite ; crystalline variety.) 6. Feldspar (orthoclase) ; white cleavable variety. 7. Quartz; transparent. HARDNESS TENACITY. 121 8. Topaz i transparent. 9. Sapphire ; cleavable varieties. 10. Diamond. 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 scale of twelve minerals ; but the scale of Mohs is now universally accepted. Accurate determinations of the hardness of minerals have been made by Frankenheim, 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 gi ven 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 oif 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 haLimer. 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 tc 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- ^ lically identical ; hence he gives as the definition of a crystal, a solid 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 cry stall ographic 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. Frankenheim. De Ciystallorum Cohsesione, 1829 ; also in Baumgartner's Zeitschrift fui Physik, ix.. 94, 194. 1831. Frankenheim. Ueber die Anordnung der Molecule in Krystallen ; Pogg. xcvii., 337. 1856. Sohncke. Ueber die Cohesion des Steinsalzes in krystallographisch verschiedenen Eich- tungen; Pogg. cxxxvii., 177. 1869. Franz. Ueber die Harte der Mineralieu und ein neues Verfahren dieselbe zu messen : Pogg. Ixxx., 37. 1850. Grailich und Ptkdrek. 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, Beusch. Ueber die Kornerprobe am Steinsalz u. Kalkspath. Pogg. cxxxii., 441, 3 867; am zwei-axigen Glimmer, Pogg. Ann. cxxxvi, 430, 632; am krystallirten Gyps, ibid., p. 185. SPECIFIC GKAVITS 123 Raumhauer. Ueber Aetzfiguren und die Erscheinangen des Asteiisrnus an Krystallen ; Pogg. Ann. cxxxviii, 163 ; cxxxix., 349 ; cxL, 271 ; cxlv., 459 ; sliii., 621 ; Ber. Ak. Miinchen, 1875, 169. Daniel 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. Leyddt. Ueber Aetzungen ; Ber. Ak. Wien, xv., 58; xix., 10. Pape. Ueber das Verwitterungs-Ellipsoid wasserhaltiger Krystalle ; Pogg. cxxiv., 339 : axxv., 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 Hence, O= ^7. w w 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 ~r^ 9 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 ifc 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 * See further on p. 173. 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 specific gravity (G) of the mineral as referred to water is determined, as by the formula : w w' " A very convenient form of balance is the spiral balance of Jolly, where the weight is mea- sured 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 specific 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 ar.d weigh it in a little glass bottle (f. 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 ir> a less finely divided state. This increase of density also characterizes, though to a less extent, a mineral in a fine stale 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 gravky 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. LlTERATUKE. SpBCIftD GRAVITY. Beudant. Pogg. Ann., xiv., 474. 1828. Jenzsch. Ueber die Bestimmung der specifischen Gewichte ; Poggr. xcix., 151. 1856. Jolly. Ber. Ak. Munchen. 1864, 162. Gadolin. Eine eini'ache Methode zur Bestimmung des specifischen Gewichtes der Minera- lien; Pog-g., cvi., 213. 1859. G. liose. Ueber die Fehler, welche in der Bestimmung des specifischen Gewichtes del Korper entstehen, wenn man dieselben im Zustande der feinsten Vertheilung wagt ; Pogg. hrciii., Ixxv , 40& 1848. Scheerer. Ueber die Bestimmung des specifischen Gewichtes von Mineralien ; Pogg. Ann. , Ixvii., 120, 1846. Journ. pr. Ch., xxiv., 139. iSchiff. 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 fiir das specifische Gewicht derselben angenommenen and gefundenen Werthen ; 170 pp. Breslau, 1868. III. LIGHT.* t 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 linos 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 AJB 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- * See further on rm 177 et sea. 126 PHYSICAL CHARACTERS OF MINERALS. tion 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 \'me Al? 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 b', or pass from the denser medium, water, into the rarer medium, air, at a, 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 of incidence, cam (?'), may be, there is always a constant relation between it and the angle of refraction, gam (?), for two given substances, as here for air and water. This is seen in the figure where (if 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 - = 1.35, 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 Kock-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 sin t In the principle which has been stated, - = n. twc points are to be sinr 128 PHYSICAL CHARACTERS 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 - = 7i, or sin r = - . As n has a fixed value for every substance. sin >' 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 = ^, and r = 48 35' ; for diamond, sin r = , and r = 24 25'. In the example employed above, if the angle bao (r) = 48 35', the line ac will coincide with of, 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 MNP in f. 376, it is possible to determine the value of n, 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- 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. 3T6), 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 + 8 ) > sin -Jar In determining the value of n for different colors, it is desirable to employ rays ofrknown position in the spectrum. Double refraction. Hitherto the existence of only one refracted ray haa been assumed when light passes from one medium to another. But it ia a well-known fact that there are sometimes two refracted rays. The most familiar example of this is furnished by the mineral 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 meet! * See further on p. 177. REFLECTION, DISPERSION AND DIFFRACTION OF LIGHT. 129 it at b, it will, in passing through, be divided into two rays, oo y ou, Similarly a line seen through' a piece of calcite ordi- narily appears double. 877 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, remain? to be enunciated : The rays of incidence, reflection, and refraction in the same plane. Dispersion. Thus far the change in direction which a ray of liglr. on refraction has alone been considered. It is also true that the of refraction differs for the different colors of which ordinary whi, is composed, being greater for blue than for red. In consequence fact, if a ray of ordinary light pass through a prism, as in f. 376, ^ *i 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 more slowly, and hence suffer less refraction than the violet rays, for which the wave-length.- are shorter and the velocity greater. Interference of light ; diffraction. When a ray of monochromatic lighl is made to pass through a narrow slither 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 bande are successive spectra. Diffraction gratings, consisting of a series of ex- tremely fine lines very closely ruled upon 'glass, are employed for the saint purpose as the prism to produce the colored spectrum. The familiaj phenomena of the colors of thin plates and of Newton's rings depend upor the same principle of the interference of the light waves. This subject i: one of the highest importance in its connection with the optical propei tie of crystals, since the phenomena observed when they are viewed, nnde certain circumstances, in polarized light are explained in an aralogon manner. (Compare the colored plate, Frontispiece.) 9 PHYSICAL Cl AKACTERS OF MINERALS. 378 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 ure 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 x>rmer position, the amount of light reflected will be a minimum, the >lanes 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 ', equal in brilliancy to that previously obtained for the position CJ). The same diminution to a minimum will be seen if the revolution is con- tinued 90 fartherf and the reflected ray again becomes as brilliant as before when ;he mirror resumes its flrst position op. In ;he above description it w r as 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 eacii 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, ABU, for this case is called the angle of polar- izatioii, and its value varies for different substances. It was shown further by Brewster that : r he 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- flectioii, is called polarization. In order to give a partial explanation of this phenomenon and to make POLARIZATION OF LIGHT. Hie same subject intelligible as applied to other cases in which polarization 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, AB, 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 whos^ direction is normal to its plane of reflection called tho plane of polari2at^on. 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 .^^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 .#(7 as an axis, no part of the vibrations of the ray BC &re 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 ra} T ca, meeting the surface of the water at #, 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 is 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 tc the plane of polarization. This is the assumption which ia 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 in one direction only, and that parallel to the vertical axis, the other vibrationa 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 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 the 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. Polarisation by means of Nicol prisms. The most convenient method of obtaining polarized light is by means of a Nicol prism of calcite. A POLABIZATION 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 rhombohedral faces opposite each other. In 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 HH (f. 382), the parts then polished and cemented together again with Canada balsam. A ray of light, ab, entering the prism is divided into two rays polarized at right angles to each other. One of these, bo, on IA|gJ)g 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 onlv. 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 ii extinguished by the prism. 134 PHYSICAL CHARACTERS OF MINERALS. Polariscopes* The Nicol prisms, when ready for use, are mounted iu an upright instrument, called a polariscnpe. 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 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 (0) above act as a weak microscope, having a field of vision of 130. The stage (Zand k\ carrying the object, admits of a horizontal revolution. The distance between the two halves of the instrument is adjusted by the screws in arid 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 pa) 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 (o>). 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 UNI ATT AT, 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 o> 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-surface 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 (o>) of the ordinary ray may be (1) greater than that of the extraordinary ray (e), in which case the velocity of the light in the direction of the vertical axis is less than that in any other direction ; or (2) &> may be less than e, and in this case the velocity of pro- pagation for the light has its maximum parallel to the vertical axis. The former 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 w =1*654, e = 1*483, it is hence one. of the class of negative crystals. The former value (&>) 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 axis. Also ma, mb represent the velocity 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 Line, hm. Now let this figure be revolved about the axis ab ; there will be generated 387 PHYSICAL CHARACTERS OF MINERALS. 389 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. $*, 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 fo, which is less refracted, is the extraordinary ray. Positive crystals ; Wave-surface. For quartz CD = 1'54:8, e = 1*558. The index of refraction for the ordinary ray (&>) 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 1'54:8. 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 axw.] 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 ma, mb represent the velocity of the ordin- ary ray, which corresponds to the least re- fractive index (1*54:8), the circle afbe will express the law for this ray, viz., the velocity the same in every direction. Moreover, let md, me 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, there will be generated a sphere, whose surface is the wave-surface of the ordin- ary ray, and within it a prolate ellipsoid whose 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 CBYSTAL8. 139 been observed. Certain crystals of apophyllite are positive for ono 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 prismi 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 Nicols 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 utii- iM.ial 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. 140 PHYSICAL CHARACTERS OF MINERALS. All the rays of light, whose vibrations coincide with the vibration -planet 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 390 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 muFt 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 Been. 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 polari- scope (, , 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 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 TJNIAXIAL CRYSTALS. 141 suffice 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 JSicol 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 ita 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. (5) If the refracting edge or 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 (&> > e or a> ? U^V*^H*- & fw-c ^b^t- /< vtVtl tr* -t/**x/uA iy* U J-riA 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. T\vins 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 -trapezoheclral 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 fc*, or intc sectors of 60. 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 Cloizeau*, from a crystal from the Dept. of the Aude), half of each sector of 60 is 395 R 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 two kinds. These overlapping portions often exhibit the phenomenon of Airy'g spiral. C. BIAXIAL CRYSTALS. General Optical Character. As in the crystalline systems, thus far considered, so also in the anisome- trie 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, and his conclusions have since been fully 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, CU represents the axis (c) of least elasticity, AA' of greatest elaeticity (a), and BB' of mean elasticity (b). A ray passing in the direo- 396 A'. > OPTICAL CHARACTERS OF BIAXIAL CRYSTALS. 145 397 tion CC' vibrates in a plane at right angles, that is, parallel to BB' and AA f . Similarly for the ray BB' the vibrations are parallel to AA' and CC", and for the ray A A' 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 axes BB' and CC' (f. 397). A ray pass- ing in the direction BB' is separated into two sets of vibrations, one paral- lel to AA', corresponding to the greatest elasticity, moving more rapidly than the other set, parallel to CO', 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 (7(7', 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', nm", and mq" are made proportional to these two velocities ; here inn = i same inn", and for a ray in the plane in any other direction there will be one set of vibration* 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 CC' and BB'. The circle nn" shows the constant velocity for all vibrations par- allel to AA', 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 vt-locity 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 AA' (= mn, f . 398), or parallel to BE' (= 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 parallel to AA, the vibrations will be (1) parallel to CO, 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 A A, 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" (= m.q'}. For any intermediate position of the ray in the same plane there will always be one set of vibrations parallel to BB' ), 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 (mn"). 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', tho 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. (mq f = mq", L OPTICAL CHARACTERS OF BIAXIAL CRYSTAL I. 147 ffl 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 CG', f. 399, bisects the acute angle is called the acute bisectrix, or first mean-line (erste Mittellinie, Germ.), and that bisecting the obtuse angle, the obtuse bisectrix, or second mean-line (zweite Mittellinie, Germ.). 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 ; ft is the index for rays propagated perpen- dicularly to bj by vibrations parallel to b ; 7 is the index for rays propagated perpendicularly to c, but vibrating parallel to c. a = > ft = r 7 - If a, /3, and 7 are known, the value of the optic axial angle (2 V) can be calculated from them by the following formula : cos V = 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 JBiaxial 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 ia 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 IN" icols, two black hyper- U>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 iNicul, these being crossed, an unsymmetrieal black cross is observed, and also a series of elliptical curves. Both these figures are well exhibited cm the frontispiece ; the one gradually changes into the other as the crystal-section is revolved in the horizontal plane, the N icols 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 oilers no great difficulties. Figi-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 (ffN). 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 off 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 (oca, f. 402). tt is only the apparent angle, for, owing to the refraction suffered on passing from the section of the crystal to tlio 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 tbat 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 ubtuse bisectrix. E the apparent semi-axial angle in air (f. 402). j H* = the apparent semi-acute angle in oil. \H = " '< " obtuse " " " V a = the real (or interior) semi-acute angle (f. 402). V = " " semi-obtuse " (f. 402). n = index of refraction for the oil. /3 = the mean refractive index for the given crystallized substance. If * See further on p. 180. f Almond oil, which has been decolorized by exposure to the light, is commonly employed. 150 PHYSICAL CHARACTERS OF MINERALS. -5 P sin E = n sin Ha ; sin V a = -5 sin . ; sin V = -5 sin .Z7" These formulas give the true interior angle from the measured apj. arenl angle when the mean refractive index (/?) is known. If, however, it is possible to measure both the acute and obtuse apparent angles, the true angle, and also the value of /3, can be determined from them. For sin V = cos F~ a , hence : sin Ho. sin H a _ sin H _ sin E ' ~ ~~ a. 7-7 ~~~ TT ' YT ~~ * TT sin H sin F cos F a sm F a In measuring this angle, if white light is employed, the colors being separated, the position or 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, /3, 7, for biaxial crystals, may be determined from three prisms cut with their refracting edges parallel respectively to the three axes of elasticity a, b, and r. 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, /3, and 7 with two 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 /3 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, ihe 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 uniaxia] crystals, but its use is not very satisfactory excepting when the axial diver- In this case it can be employecT to advantage, the * See further on pp. 177 et seq. DISTINGUISHING OPTICAL CHARACTERS OF ORTHORHOMBIC 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 thaTone 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 makjng_an_ angle of 45 with the pokijzation-plane of the NicoTprlsmsyihat js^so that^ the'black: liyperbolas 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 Une joining the hyperbolas, of the plate investigated ; and secoiid, 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 x 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, tkon 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. l^or the investigation of the absorption phenomena of biaxial crystals, see p. 165. DISTINGUISHING OPTICAL CHARACTERS OP OBTHOBHOMBIC CRYSTALS. In the Orthorhombic System, in accordance with the symmetry of the crystallization, the three axes of elasticity coincide with th'e three crystallo- ; graphic axes. Further than this, there is no immediate relation between gA the two sets of axes in respect to magnitude, for the reason that, as has been W 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 orthorhombic 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 ahown there is a close analogy between certain 152 PHYSICAL CHARACTERS OF MINERALS. orthorhombic crystals wbose 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 of 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. ScL, Boston, p, 35, 1874). Practical Optical Investigation of OrthorTwmbic 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 (39). 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, 1#, in the colored plate, (frontispiece). lt v is obviously true in this case, from f. 1, as also f . 1J, that the angle for the blue rays is greater than that tor 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 J2 l and ^ 2 ^ 2 , bisect the angles of both red (pOp) and blue (vOv f ) rays. It also needs no further explanation that for a certain relation DISTINGUISHING OITICAL CHARACTERS OF MCNOCLINIC 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 (-f 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. ^STENGUISHTNG 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 rifcht 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. Dispersion 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 DesOloizeaux 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 ortliodiagonal axis b. In other words, the acute- bisectrix and the axis of mean elasticity both lie in the plane of symmetry. 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 vertical 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 , so that the obtuse bisectrix and axis of mean elasticity lie in the plane of symmetry. The dispersion which 154 PHYSICAL CHARACTERS OF MINERALS. results in this case is called by DesCloizeaux crossed (dispersion toumante, or croisee). 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 orthorhornbic crystal (nitre), characterized by the symmetry in the size of the rings, and the distribution of the colors. Figs. 2 or Berlin blue: pure blue; sapphire, cyanite. 6. Smalt-blue: some varie- ties of gypsum. 7. Indigo-blue : blue with black and green ; blue tourma- line. 8. Sky-blue : pale blue with a little green ; it is called mountain blue by painters. E. GREEN. 1. Verdigris-green : green inclining to blue ; some feldspar (ainazon-stone). Celandine-green: green with blue and gray ; some varie- ties of talc and beryl. It is the color of the leaves of the celandine (Cheli- doniiun rnajus). 3. Mountain-green : green with much blue ; beryl. 4. Leek-green: green with some brown; the color of leaves of garlic; dis- tinctly seen in prase, a variety of quartz. 5. Emerald-green : pure deep green ; emerald. 6. Apple-green : light green with some yellow ; chryso- prase. 7. Grass-green : bright green with more yellow ; green diallage. 8. Pistachio-green : yellowish green with some brown ; epidote. 9. Aspa- ragus-green : pale green with much yellow ; asparagus stone (apatite). 10. Blackish-green: serpentine. 11. Olive-green: dark green with much brown and yellow; chrysolite. 12. Oil-green: the color of olive oil; beryl, pitchstone. 13. Siskin-green : light green, much inclining to yellow; uranite. F. YELLOW. 1. Sulphur-yellow: sulphur. 2. Straw-yellow: pale yel- low ; topaz. 3. Wax-yellow : grayish yellow with some brown ; blende, opal. 4. Honey-yellow : yellow with some red and brown ; calcite. 5. Lemon-yellow : sulphur, orpiment. 6. Ochre-yellow : yellow with brown ; yellow ochre. 7. Wine-yellow: topaz and fluorite. 8. Cream-yellow: some varieties of lithomarge. 9. Orange-yellow : orpiment. G. RED. 1. Aurora-red : red with much yellow; some realgar. 2. Hyacinth-red: red with yellow and some brown ; hyacinth garnet. 3. Brick-red: poly halite, some jasper. 4. Scarlet-red: bright red with a tinge of yellow; cinnabar. 5. Blood-red: dark red with some yellow; pyrope. 6. Flesh-red: feldspar. 7. Carmine-red: pure red; ruby sap- phire. 8. Rose-red: rose quartz. 9. Crimson-red: ruby. 10. Peach- blossom-red: red with white and gray; lepidolite. 11. Columbine-red: deep red with some blue; garnet. 12. Cherry-red : dark red with some blue and brown : spinel, some jasper. 13. Brownish-red: jasper, limonite. H. BROWN. 1. Ueddish-brown : garnet, zircon. 2. Clove-brown: brown with red and some blue ; axinite. 3. Hair-brown : wood opal. 4. Broc- coli-brown : brown, with blue, red, and gray ; zircon. 5. Cliestnut-brown : pure brown. 6. Yellowish-brown,: jasper. 7. Pinchbeck-brown: yellow- ish-brown, with a metallic or metallic-pearly lustre; several varieties of talc, bronzite. 8. Wood-brown: color of old wood nearly rotten ; some specimens of asbestus. 9. Liver-brown : brown, with some gray and green ; jasper. 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 succession on turning the mineral. This property belongs in perfection to the diamond ; it is also observed in precious opal, and is most brilliant by candle-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 tin ning 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 lamellae, 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. A.sterism. 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 Volger 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. 16T.) 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 Becquerd, Ann. Ch. Phys., III., lv., 5-119, 1859 ; Faster, Mitth. nat. Ges. Bern, 1867, 62; and Hahn, Zeitsch. Ges. nat. Wiss. Berlin, II., Is., 1,131, 1874. DIAPHANEITY COLOR LUSTRE. 165 By the application of heat, minerals lose their phosphorescent properties. But on passir. 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 ligho Fs 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. PLEOCHBOISM. 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. In uuiaxial 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 right 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 dichroic, 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 di as pore 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, tney 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 6, brown (absorbed). l a, yellow. Vibrations parallel to *, green, ' u i), brown (absorbed). 9 Vibrations parallel to , green. a, yellow. 3. The colors observed by the eye alone are the resultants of the double set ol 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 412 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 apleochroic 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 aro situated side by side, a very slight difference of color is perceptible. LITERATURE. PLEOCHROISM, ASTERISM, ETC. Haidinger. Ueber den Pleochroisinus der Krystalle ; Fogg. Ixv., 1, 1845. Ueber dag Schiliern der KrystaUflachen ; Pogg. bcx., 574, 1847; bcxi., 321; hcxvi., 99, 1849. Reusch. Ueber das Schiliern gewisser Krystalle ; Pogg. cxvi., 392, 1862; cxviii, 256. 1863 ; cxx. , 95, 1863. i). Kobell. Ueber Asterisrnus; Ber. Ak. Miinchen, 1863, 65. Haushofer. Der Asterismus des Calcites ; Ber. Ak. Miinchen, 1869. Vogelsang. Sur le Labradorite colore ; Arch. Neerland., iii., 32, 1868. Sclirauf. Labradorit; Ber. Ak., Wien, lx., 1869. Kosmatm, Ueber das Schiliern und den Dichroismus des Hypersthens ; Jahrb. Min., 1869, 368, 532; 1871, 501. Hose. Ueber den Asterismus der KrystaUen ; 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 produces: 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. Resinous: 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.^ affording 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. Tlio true difference between metallic and vitreous lustre is due to th* 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 u 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 01 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. J5. 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 tri clinic 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, 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 AYininetry 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 maybe 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. ELECTEICITY 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. Functional 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 \\\\& 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 Kiess, 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 + and tetrahedrons often occur, shows by heating the positive electricity for the faces of one tetrahedron and the ueg;Uive 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 cnce supposed, essentially connected with hemihedral development. The num- ber of poles, too, may be more than two, that is, the points at which poai 170 PHYSICAL CHARACTERS OF MINERALS. tive and negative electricity is developed. Thus for prehnite there fs a large series of such poles, distributed over J^ie 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 samo peculiarity belongs also to glaucodot, tetradyinite, 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 franklin ite, alrnandite, and other minerals, containing considerable iron protoxide (FeO). When such minerals in one part attract and in another repel the poles of TASTE AND ODOE. 171 the magnet, they are said to possess polarity. This is true of the variety of magnetite called in popular language loadstone. / LITERATURE. ELECTRICITY.* Hankd. Ueber die Thermo-Electricitat der Krystalle; Pogg., xlix., 493; L, 237, 1840; Ixi., 281. Rose u. Hies. Ueber die Pyro-Electricitat der Mineralien ; Ber. Ak. Berlin, 1843. Ueber den Zusam men hang zwischen der Form uud der elektrisohen Polaritat de KrystaJle ; Ber. Ak. Berlin. 1836. v. Kcbell. Ueber Mineral-Electricitiit ; Pogg., cxviii., 594, 1863. Bunsen. Thermo-Ketten von grosser Wirksamkeit ; Pogg., cxxiii., 505, 1864. FriedeL Sur les proprieties pyro-electrique des Cristaux bons conducteurs de 1'electricite j Ann. Ch. Phys., IV., xvii., 79, 1869. Hose. Ueber den Zusammenhang zwischen hemiedrischer Krystallform und thermo-elek- trischem Verhalten beim Eisenkies und Kobaltglanz ; Pogg., cxlii., 1, 1871. Schraufu. E. 8. Dana. Ueber die th^rmo-elektrischen Eigenschaften von Mineral varie- taten; Ber. Ak. Wien, Ixix., 1874 (Am. J. Sci., III., viii., 255). H'inkd. Ueber die thenno-elektrischen Eigenschaften des Boracites ; Sachs. Ges. Wiss., vi., 151, 1865; ibid., viii., 323, 1866; Topaz, ix., 1870, 359; 10 Abhandlung, 1872, 2i; cal- cite, 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; Ixxvi., 576; Ixxvii., 4i7; Ixxxvi., 1; Grailich u, von Lang, Ber. Ak., Wien, xxxii., 43 ; xxxiii., 439, etc., etc. VI. TASTE AND 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 or common salt. 4. Alkaline taste of soda. 5. Cooling / taste of saltpeter. 6. Bitter" taste of epsom salts. 7. Sour ; taste of sulphuric acid. ODOII. Excepting a few 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 / 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 ser- * See also on p. 190. 172 PHYSICAL CHARACTERS OF MINERALS. pentine and some allied minerals, after moistening them with tho 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 II SUPPLEMENTAEY 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 BAUMHAUER of the etching-figures of lepidolite, tourmaline, topaz, calamrne, Jahrb. Min., 1876, i. ; pyromorphite, mimetite, vanadinite, ib., 1876, 411 ; of adularia, albite, fluorifce, ib., 1876, 602 ; of leucitc, Z. Kryst., i.,257, 1877; quartz, ib., ii., 117, 1878; mica (zinnwaldite), ib., iii., 113, 1878; boracite, 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, linnssitc, biotite, epidote, apatite, gypsum, in Ber. Ak. Munchen, 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 ; BREZI^A, ib., ivi, 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 (L 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 Mgli 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. SONSTADT in 1873 (Chem. News, xxix., 127) ; its application for the above objects was proposed by CHURCH in 1877 (Mill. Mag., i., 237) ; and the method elaborated bv THOULET in 1878 (0. E., Feb. 18, 1878 ; Bull. Soc. Min., ii., 17, 189, 1879), and later by GOLDSCHMIDT (J. Min., Beil.- Bd.,i., 179, 188i). The solution is prepared (Goldschmidt) as follows : The KI and Hg 2 I are taken in the ratio of 1:1-230, 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 descri'ber 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 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 C, 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 = v(D A ) A 1 where v = volume of the solution, D its specific gravity, v l the volume of the water, and A the density desired. H^he 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 ^oes 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 ot" 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, and density of the float alone I V = j andjo, 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 A = or d =Jr - V+ P_ P+p-Kj.. a BEEOK 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, in 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 lias 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, ILCdsBAVeC^ + lG 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 sui'f;ice 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 KEFLECTROMETER. 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 (6) 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 the 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.T?. KOHLRATJSCH 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 telescope. Now the crystal is turned in the opposite direction, and the angle again read off. Half the observed angle (2 at) 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- 12 178 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 7, and if 2E, the appa- rent axial angle in air, is known, then ft, 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. Roy. 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 _ _t_ ~t^d 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 Rosenbusch 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 polariscope for converging and for par- POLARIZATION INSTRUMENTS POLARISCOPE. 179 412c. 412E, allel light, as arranged by Groth and constructed by Fuess, are shown in figs. 384, 385, 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, f, 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 Nicol, 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, i, 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 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 f a point which varies according to the combination of lenses employed. 412r. 180 POLARIZATION INSTRUMENTS. 412G. Stauroscope 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, and is made 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 plate is 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. 412D), and when the arrangements are completed v--" --/ 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. 412n). 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 412K. 182 POLARIZATION INSTRUMENTS. held, there is here an arrangement consisting of two concentric tubes, turn- ing independently, but so as to be clamped at c. The adjustable disk hav- ing a horizontal motion at F, and the spherical segment at H (Petzval support) allow of the section being both centered and adjusted. Polariscope of A dams- 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 o, o, o, 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, arid 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 the hand, the tube sliding freely in the support, p. The fine ad- justment is made by 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 O'OOl 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 vibnit-! on-plane can be fixed. The analyzing prism is placed above the eye-piece in a support, s, which may be removed at POLARIZATION MICEOSCOPE. 183 pleasure ; the edge of this if? 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 (124-J ); 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. COHEX, E. Sammlung von Mikrophotographieen zur Veranschaulichung der mikroskop- ishen Structur von Mineralien und Gesteinen, aufgenommen von J. Grimm in Orenburg, 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, 36 pp. 8vo, Vienna, 1876. FOUQUE, F. and MICHEL-LEVY, A. Mineralogie micrographique, roches eruptives Fran- $aises, 509 pp. 4to, Paris, 1879. RUTLEY, F. The Study of Rocks, 319 pp. 12mo, London, 1879. THOULET. Contributions a Petude 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. iii.\ 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 the 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 stage), 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 J_ 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 asectiou 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 sections a quartz plate (_L vertical axis) is sometimes inserted (ZZ at it in f. 41 SK); 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 l to the vibration plane of the lower prism (rr, in f. 412n). 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. 412K) and one above, strongly converging light is obtained. In many cases wh p 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 J -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- trand, Bull. Soc. Min., 1878, 27 ; Klein, Nachr. Ges. Wiss. Gottingen, 1878, 461 ; Laspcyres, Z. Kryst., iv., 460. (7) For a description of the various inclosures often, observed in sections of minerals, and the n^etbod 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 C0 2 ) the air bath (f. 41 2L) heated by the lamp, L, arid 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 mineralogical 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 hy a rack and pinion movement, and is measured hy a scale and vernier; the latter is mado 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 Cloizeaux, 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 184.1 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 lamella, which exerted on transmitted light an effect analogous to that of a bundle of parallel glass plates. VOLGEE (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 m 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 soon (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, penninite, ripidolite, tourma- line ; pseudo-ortliorJiombic species: harmotome, topaz; pseudo-monoclinic : orthoclase. Many observations similar to those of Mallard have been made by BER- TRAND (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 species, 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-refracting 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 (DelP 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, aragonito ; 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., 6b7, 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 Eeusch, 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 si.ii sectors by radial lines passing from the angles to the centre ; thedirectionsol 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 diiferent 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 plane- perpendicular to the edge. The behavior of each field in a section of apophyllite consequently is (optically -f, sue 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 JANKETTAZ, 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 KLEIST (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 whose 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 (N"achr. 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. BEN^ 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 Preisschrif t der Universitat Gottingen, 1882) from the same standpoint, with reference to the etching- figures and optical phenomena. He 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 Brechungsexponenten der natiirlichen Sulfate des Baryum, Strontium und Blei, Zeitsch. Kryst. , i., 165, 1877. J. Beckenkamp. Ueber die Ausdehnung monosymmetrischer und asymmetrischer 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., p. 264; iii., 499; iv., 1, 553 ; ix. ; Sur un appareil a conductibiiite thermique, Bull. Soc. Min., i., 119. Joubert. Sur le pouvoir rotatoire du Quartz et sa variation avec la temperature, C. R., Ixxxvii., 497, 1878. V. von Ltmg. Ueber die Abhangigkeit der circularpolarization des Quarzes von der Temperatur, Ber. Ak. Wien., Ixxi., 707, 1875. Grosse und Lage der optischen Elasiicitat- saxen beim 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. Pape. 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. Deyeloppement par compression de Felectricite polaire dans les cristaux hemiedres a faces inclinees, C. R., xci., 294. 383, 1880; Lois du degagement de 1'electricite par pression dans la tourmaline, ib., xcii., 186, 1881 ; Sur les phenomenes elec- triques de la tourmaline et des cristaux hemiedres a faces inclinees, ib., xcii., ;i50; 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. W. Gr. Hankel. Elektrische Untersuchungen (I. Thermoelektricitat, II. Aktinolektrici- tat, III. Piezoelectricitat), Abhandl. K. Sachs Ges. Wiss., xii., 459, 1881. Ueber eine direcie Umwandlung der 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. T 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 fixed gases ; chlorine and fluorine are generally gases, but may be condensed to the liquid state ; bromine 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 the 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 uiii- * 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, BO 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 35-5 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 2 O,, Di a O 3 , La 2 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 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 Eo 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 82 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 '1 Zinc Zn 65 Zirconium Zr 90 Atomicity / Quantivalence. The combining power of each element ia 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 (I 2 O), two atoms of hydrogen combine with one of oxygen ; in ammonia (II 8 N), three atoms of hydrogen combine with one of nitrogen ; and in marsh gas (H^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 quanti valence, are called monads / those which require two of hydrogen, or two other monad atoms, in forming the compound, are called dyads / those unitina with three atoms of hydrogen are called triads / and similarly 'tetrads, pemads, hexads, and heptads. The adjective terms univalent, bivalent , trivalent, quadrivalent, etc., are also employed with similar meaning. Atoms having the same degree 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 [FeJO, it is sexivalent (for the double atom). Perissads ; Artiads. Those elements whose atoms have an odd qu anti- valence (I, III, Y, or YII), are called perissads ; those whose quantivalence is even (II, IY, YI) are called artiads. These terms, perissad and artiad, are derived from Trepicra-os and apnos, 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 : - - i94 CHEMICAL MINERALOGY. PERISSADS. Monads : Hydrogen. Fluorine. Chlorine, T, III. V, VII. Bromine, I, III, V, VII. Iodine, I, III, V, VIL ARTIADS. Lithium. Sodium, Potassium, Rubidium. Caesium. Silver, Thallium, I, III. i, in, v. i, in. I, HI. 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, III, V. Dtfads : Oxygen. Sulphur, II, IV, VI. Selenium, II, IV, VI. Tellurium, H, IV, VI. Calcium, II, IV. Strontium, II, IV. Barium, H, IV. Magnesium. Zinc. Cadmium. Glucinum. Yttrium. Cerium. Lanthanum. Didymium. Erbium. Mercury [Hg 3 ] ri , II. Copper [Cu a ] n , II. Tetrads : Carbon, II, IV. Silicon. Titanium, II, IV. Tin, II, IV. Thorium, Zirconium. Platinum, Palladium, Lead, Indium. II, IV. II, IV. H, IV. Hexads : Molybdenum, II, TV, VI, Tungsten, IV, VI. Euthenium, II, IV, VI. Rhodium, II, IV, VI. Indium, II, IV, VI. Osmium, II, IV, VI. Aluminum, IV, [A1,] 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 IIC1, 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 f (1) The Native Elements ; (2) Binary compounds, including the sulphides, oxides, chlorides, iodides, fluorides ; (3) Ternary compounds, including sulph-arsenites, etc., hydrates (hydrated oxides), silicates, mostly salts of the acids II 4 SiO 4 and H 2 SiO 8 , tantalates, colurnbates, phosphates, arsenates, sulphates, chrornates, 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 iu 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. Tt 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 + 4II 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 : H 2 a 4 P 2 O 8 4-24aq. 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 ftfivnulas simply state in the briefest form the result of the analysis, giving the number of atoms of each element present without any theoretica 1 "Considerations. For example, the empirical formula of epidote is Si^CXHAs. 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 dnalistic 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 3 , instead of BiO 3 , 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, Na^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 quantivalence. 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 = [A1J. 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 EO E 2 O 3 EO 2 E 2 O 5 EO 3 E 2 O 7 EO 4 B EO E*O E*O E*O E*O E?O EO C E E* E* E* E* K* E* According to the above law the &, E 1 , E*, 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 8 O 8 , (3) FeS 2 , (4) FeO 3 , containing this metal in four Btates Fe, Fe 1 , Fe*, Fe*. The use of the fractions can be avoided by multiplying, instead of divid- ing, thus, Fe* of Fe 2 O 3 replaces Fe of FeO, we might have said, 2Fe of Fe 2 O 3 replaces 3Fe of FeO (Fe 2 O 3 , Fe 3 O 3 ), 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, /?, etc., thus avoiding all confusion. The above lines A, B, C then become A aRO 3/3RO 2yRO 5SRO 3eRO 7?RO K aRO /3RO yRO SRO eRO ?RO 7?RO aR /3R 7 R SR eR R ^R By means of this system all the different oxides may be reduced to tho common protoxide form, and thus the true relations of the silicates may bo 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. An 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 : **8* _ . 2 o7 - 13 ' 06 - .906 - 24 ' 34 - -217 19 ' 76 207 ' T ' 63T W "32" The atomic ratio is hence: Pb : Cu : Sb : S = -207 v206 : -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 2 A1O 3 FeO 3 FeO CaO H 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, Pe 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 12-06 28 for Si, ^^ = 0-22 for Al (= A1 2 ), etc. Or, the percentage amounts of each oxide may be divided by its molecular weight, and the result will be the same ; 07.09 for SiO 2 , the molecular weight is 60 (28 + 2x16), hence, -^- = -630 as 22*63 before ; also for Al, 103 (= 2 x 27'5 + 3 x 16), and -j^- = 0-22, etc. Thi atomic proportions thus obtained are : 198 CHEMICAL MINER A.LOGY. Si Al Fe Fe Ca H O 0-630 0-220 0-094: 0-013 0-415 0-230 2*727, 01 simply 0-428 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^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 quantiva- 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 " owy gen- 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 IP 3R, K, 3Si = 3RO, RO 3 , SSiOgj an( i the oxygen ratio for II : fi : Si = 1 : 1 : 2, or for bases to silica, 1 : 1. Here R may be either Ca, Mg, Fe, Mn, or Or, and S either atl, 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 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 x II : VI : 3 x IV, or, Q. ratio for R : R : Sif = 6 : 6 : 12, that is, 1 : 1 : 2. The same ratio for (R+R) : 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 Mineralogy, 1868. Prof. Cooke has discussed the same subject (Am. J. Sci., II., xlvii., 386, 1869), he calls the ratio, the Atomic Ratio ; the latter term, however, is generally used in a different sense, hence the expression Quantivalent Ratio employed here. f Throughout this work the letter R, unless otherwise indicated, represents a bivalent metal, Jtod R either Fe, Al, Or, Mn, where the quantivalence of the double atom is six. In A few cases, to indicate further relations, the Bign of the quantivalence is sometimes emrjloved 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 Ifc replaces 3R (as in spodumerie 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 homoeo- morphous). This phenomenon is called ISOMORPHISM. An example of pleomorphism is given by the compound calcium carbon- ate (CaCO 3 ), which is trimorphous : 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 (2- 7). Again, as baryto-calcite^ calcium carbohate crystal- lizes in a rnonoclinic 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 C., it takes the form of aragonite. Moreover, he found that aragonite on heating fell to powder, and though no loss of weight took place, the specific gravity (i4'9) became that of calcite (2'7). Many other examples of pleomorphism may be given : Silica (SiO 2 ) is trimorphous ; appearing as quartz, rhombohedral, Gr = 2*66; as tridymiie. 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 (o -64:42), G = 4-25 ; octahedrite (c = 1'778), G = 3-9 ; and broo&ite, orthorhombic or monoclinic, G = 4'15. Carbon appears in two forms, in diamond and graphite. Other familiar examples are pyrite and marcasite (FeS 2 ) ; acanthite and argentite (Ag 2 S) ; sphalerite and wiirtzite (ZnS) ; sulphur natural, orthorhombic, if artificial and crystallizing from a molten condition, monoclinic. 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 fi may be Ca, Mg, Fe, Mu, 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. CaC0 8 1 2C0 3 MgC0 8 MnCO 3 , FeCO 3 ZnCO 3 105 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 JSOMORPIIOUS. Some of the more important isomorphous groups are mentioned below, for the description of the different species reference must be made to Fart 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, gahni-te. etc. (2) The ALUM group, for example, potash-alum K 2 A1S 4 O 15 4- 24aq, etc. (3) The GARNET group, having the general formula Tetragonal system. RUTILE group, RO 2 ; including rutile TiO 2 , and cas- diterite SnO 2 . The SCIIEELITE group ; including scheelite CaWO 4 , stolzite PbWO 4 , wulfenite FbMO 4 . Hexagonal system. APATITE group ; apatite 3Ca 3 P 2 O 8 + Ca(Cl, F) 2 , pyro- saorphite 3Pb 3 P 2 O 8 -l-FbCl 2 , mimetite 3Pb 3 As 2 O 8 +PbCl 2 , and vanadinite 3Pb 3 Y 2 O 8 -fPbCl 2 . COKUNDCIM group, fK) 3 ; corundum A1O 3 , hematite FeO 3 , menaccanite. Rhovtibohedral system. CALCITE group, RCO 3 , already mentioned. Orthorhombic system. ARAGONITE group, RCO 8 ; aragonite CaCO 8 , witherite BaCO 3 , strontianite SrCO 8 , cerussite PbCO 8 . JBAEITE 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 + 7aq ; biebcrite CoSO 4 -r7aq, etc. Pyroxene group, RSiO 3 , etc. Mono clinic and Tridinic. feldspar group. The above enumeration includes only the more prominent amcng the isomorphous groups. In many other cases a close relationship exists among species, 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 rhornbohedral carbonates : calcite has the composition CaCO 3 , 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 (|Ca+-|-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 whick Ca, Mg, Fe (Mn), all enter, and in different proportions. Boricky has shown that the composition of the ankerite group of compounds is expressed by the formula : CaCO 3 + FeCO 3 -f #(CaMgC 2 O 6 ), where x may be , 1, , 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 quautivalence, 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 (3B, = fi). So, too, menac- II IV cauite was included in the corundum group, since here RRO 3 is isomor- phous with iftO 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 ; anti they are then described as isodimorphous. 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 isodimorphism. There are also cases of isotrimorphism. Thus there are the following related groups ; the angle of the rhombohedral forms here given is It : 12 of the orthorhornbic and monoclinic 1 : /(for baryto-calcite 2-fc on 2-fc): Rhomboliedral. Orthorhombie. Monodinic. RCO. Calcite, 105 5'. Aragonibe, 110 10'. Barytocalcite, 95 8'. RS0 4 Dreelite, 93-94. Anglesite, 103 38'. Glauberite, 83-83 30*. BSO 4 +nRCO, Susannite, 94. Leadhillite, 103 16'. Lanarkite, 84. 202 CHEMICAL MINERALOGY. . Gal cite, aragonite, and barytocalcite form an undoubted case of trimor phis7n, 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 sulphate-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 laboi, 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 an 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, nitric 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- Ehuretted hydrogen (HgS) is evolved by some sulphides, when dissolved in ydrochloric 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 MINERALS, 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 arid, 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, aro 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, chrornite, diaspore, rutile, cassiterite, quartz; also cerargyrite ; many silicates, titanates, tantalates, and columbates ; also the sulphates (barite, celestite, angiesite); many phosphates (xenotime, laztilite, children ite, 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 uninter- 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. Of LJ A similar 204 CHEMICAL MINERALOGY. 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 side 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 \\^ 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 pp ; other forms open by the spring of the wire in the handle. Care must be 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 J to 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-tubes, etc., used in the laboratory. Chemical reagents. The commonest reagents employed are the fluxes* viz., soda (sodium carbonate) ; salt of phosphorus (sodium-ammonium phosphate) ; and borax (sodium biborate). The method of using them ia 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 fiame, 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 othei 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) Eeaminat'ion 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 heafc must be applied slowly, or, if this does not prevent it, the mineral may be powdered and u 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. Ill connection with the trial of fusibility, the following phenomena may be observed : (a) a coloration of the fkme ; (b) a swelling up (stilbite), or an exfoliation of the mineral (vermiculite) ; or (.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. ; antirnonial 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 (SbaOg). 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 al] 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, ana fused on charcoal, a beauti- ful red sublimate of bismuth iodide is obtained. Boracic acid. Borates. B.B. ; many compound** tinge the flame intense yellowish-green, especially if moistened with su^huric acid. For silicate* 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 bisulphate. The mixture is moistened and placed on platinum wire. At the moment of fusion the green color 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. 13. 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. JB.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 ; R.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. L^ad. 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. Ill solutions containing lime salts, even when dilute, ammonium oxalato throws down a white precipitate of calcium oxalate. Lithia. B.B. ; lithia gives an intense red to the outer flame ; in \ery 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.P.) 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. Merciric 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; (K.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, phosplinretted hydrogen is 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 ac: d 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 of 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 MINERALOGT. 213 in acid or water, but entirely so in ammonia. It changes color on exposure to the light. Soda. B.B. ; 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 (K.F.). Fused and treated as titanic acid (see above) with the addition of zinc instead of tin, gives a n'ne blue color. Uranium. B.B. ; salt of phosphorus bead, in O.F., a greenish-yellow bead when cool. In K.F. a nne 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 fine green (p. 207). Ziroonia. 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. II. 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 depends 214 CHEMICAL MINERALOGY. mostly upon chemical tests. But crystallographic and all physical chaiactcra have also to be used. There is but one satisfactory way in which the identity of an unknown mineral may in all cases be lixed 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 fiame, 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 fc!3) with reagents, and before the blowpipe. If the results of such a preliminary examination are sufficiently definite to suggest that the mineral in hand is one of a small number o:l species, reference may be made to their full description in Part III. of this work for the final decision. A number of minor table?, 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 iu 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 moro 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. IRON 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. ; Ttereury 5 amalgam, AgH to 16 p. c. of silver. Color varying, accordingly, from deep gold-yellow to pale yellow; Gr.= 19-15*5. 2. Argentiferous; Plectrum. 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 -Op. 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 925. 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.) Pyrognostic and other Chemical Characters. B.B. fuses easily. Not acted on by fluxes. Insoluble in any single acid ; soluble in nitro-hydrochloric acid (aqua-regia). D ff . Readily recognized by its malleability and specific gravity. Distinguished by its insolubility ia nitric acid from pyrite and chalcopyrite. Observations. Native gold is found, when in situ, 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 quart/yte, called itacolumyte, is common in many gold regions, as those of Brazil and North Carolina, and sometimes specular schists, or slaty rocks containing much foliated specular iron (hematite), or magnetite in grains. The gold occurs in the quartz in strings, scales, plates, and in masses which are sometimes 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 to the assayer. It is always very irregularly distributed, and never in continuous pure bands of *netal, 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, sphalerite, arsenopyrite, each frequently auriferous ; often tetradymite and other tellurium ores, native bismuth, stab- nite, magnetite, hematite ; sometimes barite, apatite, fluorite, siderite, chrysocolla. The gold of the world has been mostly gathered, not directly from the quartz veins, but 222 DESCRIPTIVE MINERALOGY. from the gravel or sands of rivers or valleys in auriferous regions, or the slopes of mountaina or hills, whose rocks contain in some part, and generally not far distant, auriferous veins , such mines are often called alluvial washings ; in California placer-digqings. 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 assort ng process ; the 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 elopes or bottom of a valley, or a place where the waters may have eddied, generally proves hi 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 monazite, 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. Ilmen (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, Uorneo, 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 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, and 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. Alsp 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 uhey 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. ; "Rridgewater, 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 much superior in the purity of the metal, the principal gold mines occur along the streams in the mountains ot N. S. Wales (S. E. Australia), and along the continuation of the same range in Victoria IS. Australia). NATIVE ELEMENTS. 223 SILVER. Isometric. Cleavage none. Twins : t winning-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. 10-1-11-1, 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. Cuprifei'ous. Contains sometimes 10 p. c. of copper. Pyr., 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, g-alenite, 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 has 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 " 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 dia* 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, indium, 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 Hue dust, when reactions for iron and copper may be obtained. Soluble only in heated nitro* hydrochloric aoid. 224 DESCRIPTIVE MINERALOGr. 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 nearJy 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. 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 ; also 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.==6-7. 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. Newjanskite, Haid. ; H.=7; G.=18'8-19-5. In flat scales; color tin- white. Over 40 p. c. of Iridium. Probably IrOs. 2. Sisserskile, 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 Berzehus .IrOs 4 =:Iridium 19-9, osmium 801 = 100 ; G.=21'118. Another corresponded to the formula IrOs 3 . 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 tla gold-washings on the rivers du Loup and des Plantes, Canada. * MERCURY. Quicksilver. Gediegeu Quecksilber, Germ. Isometric. Occurs in small fluid globules scattered through its gangua 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 Carniola, and Almaden in Spain. It is 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. Comp. Both Ag Hg (=Silver 35-1, mercury, 64-9), and Ag,Hg 3 (=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. Chill KONQS- BERGITE, Agi 8 Hg (?) Kongsberg, Norway. COPPER. Isometric. Cleavage none. Twins : twinning-plane octahedral, very common. Often filiform and arborescent; the latter with the bra?iches 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. Comp Pure copper, but often containing some silver, bismuth, etc. Pyr,, etc. B.B., fusee 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 NCM 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 oi immense size have been obtained. It is associated with prehnite, d uolite, 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 rivej in Arizona ; in large drift masses in Alaska. 15 220 DESCRIPTIVE MINERALOGY. IRON.* y^ Isometric. Cleavage octahedral. H. 4-5. G. T'3-7'8. Lustre metallic. Color iron-gray. Streak shin ing. Fracture hackly. Malleable. Acts strongly on the magnet. Obs, The occurrence of masses of native iron of terrestrial origin has been several times reported, but it is not yet placed beyond doubt. The presence of metallic iron in grains in 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 axithors to be terrestrial. Meteoric iron usually contains 1 to 20 per cent, of nickel, besides a small percentage oi 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 m-eteorite, in the Yale College cabinet, weighs 1,085 Ibs. ; it was brought from Bed 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. ZINC.- -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. R A R = 85 41', A R = 122 9', c = 1-3779, Miller. Cleavage : basal, imperfect. Often granular massive ; sometimes reticu- lated, reniform, and stalactitic. Structure rarely columnar. H.=3-5. Gr.:=5'93. Lustre nearly metallic. Color and streak tin-white, tainishing soon to dark-gray. Fracture uneven and line granular. Comp. Arsenic, often with some antimony, and traces of iron, silver, gold, or bismuth. Py r. B. B. , on charcoal volatilizes without fusing, coats the coal with white arsenous oxide, and affords the odor of garlic ; the coating treated in B. 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 Haverhill and Jackson, N. H., at Greenwood, Me. ANTIMONY. Ehombohedral. R/\R = ST 35', Kose ; 6> A 7? = 123 32' ; c = 1-3068. 2 A 2 = 89 25'. Cleavage : basal, highly perfect ; J distinct. Generally massive, lamellar ; sometimes botryoidal or reniform 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 TL 3-3-5. G.= 6 '64:6-6-72. Lustre metallic. Color and streak tin- white. Yery brittle. Comp, Antimony, containing sometimes silver, iron, or arsenic. Pyr, B.B., on charcoal fuses, gives a white coating in both O. and R.F. ; if the bloving be intermitted, the globule continues to glow, giving off white fumes, until it is finally crusted ovor with prismatic crystals of aatimonous oxide. The white coating tinges the B.F. bluish- green. 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, SbA.s 3 . Color tin- white or reddish-gray. Occurs at Allemont ; in Bohemia ; the Harz. BISMUTH. Gediegen Wismuth, Germ. Hexagonal. R A R = 87 40', G. Rose ; O A R = 123 36' ; c = 1-3035. Cleavage : basal, perfect ; 2, 2, less so. Also in reticulated and arbores- cent shapes ; foliated and granular. II. =2-2-5. Gr.=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. Comp., Var. Pure bismuth, with occasional traces of arsenic, sulphur, tellurium. Pyr,, 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 causes R white precipitate. Crystallizes readily from fusion. Diff Distinguished by its reddish color, and high specific gravity, from the other brittle metals. Obs, 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 found in Norway, and at Fahlun in Sweden. At Wheal Sparnon, and elsewhere in Cornwall, and at Carrack Fell in Cumberland ; at the Atlas mine, Devonshire ; at Meymac, Correze ; at San Antonio, Chili ; Mt. Illampa (Sorata), in Bolivia ; in Victoria. At Lane's mine in Monroe, and near Seymour, Conn., in quartz ; occurs also at Brewer'g mine, Chesterfield district, South Carolina ; in Colorado. TELLURIUM.* Hexagonal, R A R = 86 57', G. Kose ; A R = 123 4', c = 1-3302. 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 tin-white. Brittle. Oomp. According to Klaproth, Tellurium 92 '55, iron 7*20. and gold 0'25. Pyr In the open tube fuses, giving a white sublimate of tellurous oxide, which B.B. fuses to colorless transparent drops. On charcoal fuses, volatilizes almost entirely, tinges the flame green, and gives a white coating of telluroua oxide. Obs. Native tellurium occurs in Transylvania (whence the name Sylvanite) ; also at the Red Cloud mine, near Gold Hill, Boulder Co., Colorado. 228 DESCRIPTIVE MINERALOGY. NATIVE SULPHUR. Orthorhombic. iKl = 101 46', A 14 == 113 6'; c : I : A 1-i = 117 41' ; O A i = 108 19'. Cleavage: /, and 1, imperfect. Twins, 417 . composition-face, /, sometimes producing cruci- form crystals. Also massive, sometimes con sisting of concentric coats. II.=l-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. Sectile. Comp. Pure sulphur ; but often contaminated with clay or bitumen. Pyr., etc. Burns at a low temperature with a bluish name, 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 Frank enheim). 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 Conil, 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 Bsmeralda Cos., etc. The sulphur mines of Sicily, the crater of Vulcano, the Solfatara near Naples, and the beds of California, afford large quantities of sulphur for commerce. X\ 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. H.. 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 conchoidal. Index of refraction 2'4. Exhibits vitreous electricity when rubbed. Comp. Pure carbon, isometric in crystallization. Var. 1 . 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. Antkracitic. 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. Fyr. ; ets. Burns, and is wholly consumed at a high temperature, producing carbonic dioxide. It is not acted on by acids or alkalies. Diflf. Distinguished by its extreme hardness, brilliancy of reflection, and adamantine lustre. Ob 3 The diamond often occurs in regions that afford a laminated granular quartz roo-k, 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 been 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 srold, and also at other places. In India the diamond is met with at Purteal, between Hyderabad and Masulipatam, where the famous Kohinoor was found. The locality on Borneo is at Pontiana, 011 the west side of the Ratoos mountain. Also found in Australia. The diamond region of South Africa, discovered in 1857, 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 th3 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 Cape is very large, and some of them are of considerable size. It has been estimated that the value of those obtained from March, 1867, to November, 1873, exceeded sixty millions of dollars. As a consequence of this production the market value of the stones has been much dimin- ished. In the United States a few crystals have been met with in Rutherford Co., N. C., and Hall Co., dia. ; 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 Tavernier as in 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 130'25 carats, or 419^- grains ; but is of unblemished transparency and color. It is cut in the form of a bril- liant, and Its value is estimated at 125.000. The Kohinoor measured, on its arrival in Eng- land, about 1 1 inches in its greatest diameter, over of an inch in thickness, and weighed 186-/Y carats, and was cut with many facets. It has since been recut, and reduced to a dia- meter of l-, 1 ^ by If nearly, and thus diminished over one-third in weight. It is supposed by Rlr. 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 dode- cahedron. Tavernier gives the original weight at 787^ carats. The Rajah of Mattan has in hia possession a diamond from Borneo, weighing 367 carats. The mines of Brazil were not know n to afford diamonds till the commencement of the eighteenth century. 230 DESCRIPTIVE MINERALOGY. GRAPHITE. Plumbago. Hexagonal. In flat six-sided tables. The basal planes ((7) 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 ; (<a>, to write. Nordenskiold makes the graphite of Ersby and Storgard numodinic. IT. SULPHIDES, TELLURIDES, SELENIDES, ARSEN- IDES, BISMUTHIDES. 1. BINARY COMPOUNDS. SULPHIDES AND TELLURIDES OF THE METALS OF THE SULPHUR AND ARSENIC GROUPS. REALGAR,* Monoclinic. C = 66 5', /A 7 = 74 26', Marignac, Scacchi, A 14 = 138 21' ; e: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 charcoal burns with a blue flame, emitting arsenical and sulphurous odors. Soluble in caustic alkalies. Obs. Occurs with ores of silver and lead, in Upper Hungary ; in Transylvania ; at Joachims- thai ; Schneeberg ; Andreasberg ; in the Binnenthal, Switzerland, in dolomite ; at Wiesloch in Baden ; near Julamerk in Koordistan ; in Vesuvian lavas, in minute crystals. ORPIMENT.* Orthorhombic. 1 A 1 = 100 40', OM-l = 126^30', Mohs. I : 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 reni-' form. H. = l'5-2. G. = 3'48, Haidinger. Lustre pearly upon the faces of per- fect cleavage ; elsewhere resinous. Color several shades of lemon-yellow. Streak yellow, commonly a little paler than the color. Subtransparent Bubtranslucent. Sub-senile. Thin laminae obtained by cleavage flexible but not elastic. Comp. As 2 S 3 = Sulphur 39, arsenic 61=100. Pyr., etc. In the closed tube, fuses, volatilizes, and gives a dark yellow sublimate ; other reactions the same as under realgar. Dissolves in nitre-hydrochloric acid and caustic alkalies. Obs Orpiment in small crystals is imbedded in clay at Tajowa, in Upper Hungary. It is usually in foliated and fibrous masses, and in this form is found at Kapnik, at Moldawa, and at Felsbbanya ; at. Hall in the Tyrol it is found in gypsum ; at St. Gothard in dolomite ; at 232 DESCRIPTIVE MINERALOGY. the Solfatara near Naples. Near Julamerk in Koordistan. Occurs also at Acobambillo, Peru. 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 Scacchi may be, according to Kenngott, a variety of orpiment. STIBNITB, Antimonite. Gray Antimony. Antimony Glance. Antimonglanz, Orthorhombic. /A / = 90 54', O A l-l = 134 16', Krenner ; c\b\d = 1-0259 : 1-0158 : 1. O A 1 = 124 423 45'; O A 1-2 = 134 Lateral planes deeply striated longitudinally. Cleavage : i-l highly perfect. Often columnar, coarse or line ; 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 1 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 Fereta, 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 '" 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. LIVINGSTONITE (Barcend). 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 Orth Drhombic. /A / = 91 30', Haidinger. perfect ; macrodiagonal less so ; basal perfect, massive, with a foliated or fibrous structure. IL=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, TELLTJRIDES, SELENIDES, ETC. 233 Comp. BioS 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. fusea 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, Carrock Fells, in Cumberland ; near Redruth ; at Botallack near Land's End ; at Herland 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 ; X'remdite. Fernandez, 1873 ; Castillo, 1873 ; Frenzel, 1874. A bismuth selenide, Bi 2 Se 3 ; sometimes with part of the selenium replaced by sulphur^Jiat is, Bi 2 (Se,S) 3 , with Se : S=3 : 2, which requires Selenium 23*8, sulphur 6 '5, bismuth 6^7=100. Isomor- phous with stibnite and bismuthinite (Schrauf). Guanajuato, Mexico. SlLAONlTE from Guanajuato is Bi 3 Se (Fernandez). See p. 428. TETRADYMITE, Tellurwiamuth, Germ. Hexagonal. Ol\R = 118 38', R A E = 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. !N"ot very sectile. Laminae flexible. Soils paper. Comp., Var. Consists of bismuth and tellurium, with sometimes sulphur and selenium. It sulphur, when present, replaces part of the tellurium, the analyses for the most part afford the general formula Bi 2 (Te, S) 3 . Var. 1. Free from sulphur. Bi 2 Te 3 = Tellurium 48'1, bismuth 51 D ; Gr.=7'868, from Dahlonega, Jackson; 7*642, id., Balch. 2. Sulphurous. Containing 4 or 5 p. c. sulphur. &. 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. Diff. 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 selenium ; Brazil. WEHKLITE. 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. Sectile, and almost malleable. .Bluish-gray trace on paper. 234 DESCRIPTIVE MINERALOGY. Comp MoS 2 = 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 flame ; 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 (molybdic 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 Chestei Creek ; near Concord, Cabarrus Co., N. C. In California, at Excelsior gold mine, in Excel- sior district. In Canada, at several places. 2. BINARY COMPOUNDS. SULPHIDES, TELLTJKIDES, ETC., OF METALS OF THE GOLD, IKON, AND TIN GROUPS. A. BASIC DIVISION. DYSCRASITB. Antimonial Silver. Antimon-Silber, Germ. Orthorhornbic. /A 7 = 119 59' ; A 1-* 130 41' ; c:l: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. II. =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 Allemont in Daupbine, Casalla in Spain, and in Bolivia, S. A. DOMEYKITE. Arsenikkupfer, Germ. Reniform and botryoidal ; also massive and disseminated. II. ~3-3-5. G. =f-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. SULPHIDES, TELLUKIDES, 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 arsenous 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. Wn ITNEUTE. Cu 9 As=Arsenic 11 '6, copper 88 '4= 100. Houghton, Mich., also California, Arizona. B. PHOTO DIVISION. (a) Galenite Group. Isometric ; holohedral. ARGENTITB. Silver Glance. Vitreous Silver. Silberglanz, Germ. Isometric. Cleavage : dodecahedral in traces. Also reticulated, arbores- cent, and filiform ; also amorphous. H. = 22-& G.= 7-196-7-365. Lustre metallic. Streak and color black- ish lead-gray ; streak shining. Opaque. Fracture small sub-conchoidal, uneven. 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. Dlff. 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 seienide, containing also some lead. Color iron-black. From the Harz. EUCAIRITE. A silver-copper seienide, (Cu, Ag) 2 Se. Color silver- white to gray. Sweden; Chili. CROOKESITE, Massive, compact ; no trace of crystallization. H.= 2-5-3. G.=6-90. Lustre metallic. Color lead-gray. Brittle. Comp. (Cu 2 ,Tl,Ag) Se=Seleniuin 33 -28, copper 45-76, thallium 17-25, silver 37110C. 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 seienide of copper or berzelianite. GALENITE. Galena. Bleiglanz, Germ. Isometric ; habit cubic (see f. 38, 39, etc., p. 15). Cleavage, cubic, per- fect ; octahedral in traces. Twins: t winning-plane, the octahedral plane, f . 4.25 (f. 263, p. 88) ; the same kind of composition repeated, f. 426, and 236 DESCRIPTIVE MINERALOGY,. flattened parallel to 1. Also reticulated, tabular ; coarse or fine granular ; sometimes impalpable ; occasion ally fibrous. 434 426 H.=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- chonckoidal, or even. Frangible. Comp., Var PbS=Sulpbur 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, Sula 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 Wy the 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. CLAUSTHALITE. Selenblei, Germ. Isometric. Occurs commonly in fine granular masses ; some specimens foliated. Cleavage cubic. H.= 2*5-3. G. 7'6-8-S. 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 arrangsd as distinct species, whioh contain cobalt, copper, or mercury in place of part of the lead, and sometimes a little silver or iron. SULPHIDES, TKLLUKIDES, 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 Clausthal, Tilkerode, Zorge, Lehrbach, etc., in the Harz ; at Reiusberg in Sax- ony ; at the Rio Tinto mines, Spain ; Cacheuta mine, Mendoza, S. A. ZORGITE and LEHRBACIIITE occur with clausthalite in the Harz. Zorgite is a lead-copper aelenide. Lehrbachite is a lead-mercury selenide. BERZELIANITE. 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. BORNITB. 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. Comp. 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 a , 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, Collier, from Bristol, Ct. Sulphur 25-83, copper 61 '79, iron 11 '77, silver tr. =99*39 (R : S=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, und 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 Ross 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. GRUNAUITE. A sulphide containing nickel, bismuth, iron, cobalt, copper. From Griinau. (b) Blende Group. Isometric ; tetrahedraL ^ SPHALERITE or ZINC BLENDE. Black-Jack, Engl Miners. Ipometric: 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 MTNEKALOGY. when pure. Streak white reddish-brown. Transparent transit cent Fracture conchoidal. Brittle. Comp., Var ZnS Sulphur 33, zinc 67=100. Bufc often having 1 part of the zinc replaced by iron, and sometimes by cadmium ; also containing in minute quantities, thallium, indium, and gallium. Var. 1. Ordinary. Containing 1 little or no iron ; colors white to yellowish- brown, sometimes black ; G. =3 9-4'l. 2. Ferriferous; Marmatite. Containing 1 10 p. c. 01 more of iron; dark-brown to black ; G.=3*9-4'2. The proportion of iron sulphide to zinc sulphide varies from 1 : 5 to 1 : 2. 3. Cadmiferous ; 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 ?ive 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.F. 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. Dissolve? in hydrochloric acid, during which sulphuretted hydrogen is disengaged. Some Bpecimens 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. Occuis 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 JV. 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 W'iscomin, at Mineral Point. In Tennessee, at Haysboro', near Nashville. Named blende because, while often resembling galena, it yielded no lead, the word in Ger man meaning blind or deceiving. Sphalerite is from o-^oAepos, treacherous. (c) Ckalcocite Group. Orthorhombic. HESSITE * Tellursilber, Germ. Orthorhombic, and resembling chalcocite. Cleavage indistinct. Mas eive ; compact or fine grained ; rarely coarse-granular. SULPHIDES, TELLUKIDES, 8ELENIDES, ETC. 239 H.=2-3-5. G.=8'3-8'6. Lustre metallic. Color between lead-gray and steel-gray. Sectile. Fracture even. Coinp Ag 2 Te= Tellurium 37 '2, silver 62*8=100. Silver sometimes replaced in part bjr gold. Pyr. In the open tube a faint white sublimate of tellurous oxide, which B.B. fuses tu 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.= S72-8-83, 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 41-80, 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 1 = 110 54' ; A l-l = 124 42', Dauber ; i : I : d = 1-4442:1-4523:1. O A 1-2 = 135 10'; 6>Al = 119 42'. Twins: parallel to 1-t. Crystals usually slender-pointed prisms. Cleavage indis- II. =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. Fyr. Same as for argentite, p. 235. Obs. Found at Joachimsthal ; also near Freiberg in Saxony. CHALCOCITE. Chalcosine. Vitreous Copper. Copper Glance. Kupferglanz, Germ. x 'Orthorhombic. /A 1= 119 35', O A 14 = 120 57'; c, : I : a, = 1-6676 : 1-7176:1; <9 A 1 = 117 24' ; A l-l 135 52'. Cleavage : 7, indistinct. Twins : t winning-plane, /, producing hexagonal, or stellate forms (left half 430 431 432 433 \ of f. 432) ; also Bristol, Ct Bristol, Ct. Bristol, Ct. , a cruciform twin (f. 432), crossing at angles of 111 and 69 ; f. 433, a cruciform twin, having O and / of one crystal parallel respectively to i-l and O of She other. or compact and impalpable Also massive, structure granular s 240 DB8CEIPTIVE 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 79-8100. 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 Banat, 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, Genth). STROMEYERITE, Silberkupferglanz, Germ. Orthorhorabie : isomorphous with chalcocite. /A/=119 35'. Also massive, compact. H.= 2-5-3. G.= 6-2-6-3. Lustre metallic. Color dark steel-gray. Streak shining. Fracture subconchoidal. Comp, AgCuS=Ag2S+Cu 2 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 Corn- bavalla in Peru ; at Heintzelman mine in Arizona. STERNBERGITE.* An iron-silver sulphide, AgFe 2 S 3 . Johanngeorgenstadt and Joachimsthal. (d) Pyrrhotite Group. Hexagonal. CINNABAR. Zinnober, Germ. Ehombohedral. E A E = 92 36', E A O = 127 6' ; c = 1-1448. Ac- cording to DesCloizeaux, tetartohedral, like quartz. 434 Also granular, massive ; sometimes forming super- ficial coatings. Cleavage: /, very perfect. Twins: twinning- plane O. . 11=2-2-5. G=8-99S, a cleavable variety from Neumarktei. Lustre adamantine, inclining to metal- lic when dark-colored, and to dull in friable varieties. Color cochineal-red, often im-.lining to brownish-red and lead-gray. Streak scarlet, sub- transparent, opaoue. Fracture subconchoidal, un v even. Sectile. .Polarization circular. Oomp. HgS (or Hg 3 S 3 )= Sulphur 13-8, mercury 86 '2= 100. Sometimes impur< from clay, iron sesquioxide, bitumen. SULPHIDES, TELLUEIDE8, SELENIDES, ETC. 241 Pyr. In the closed tube a black sublimate. Carefully heated in the open tube gives sul phurous fumes and metallic mercury, condensing in minute globules on the cold walls of the tube. 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; |n 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). Barely crystallized II. =3. Gr. 7 '75. Lustre metallic. Redington mine, Lake Co., Cal. OUADALCAZARITE. Essentially HgS, with part (fa) of the sulphur replaced by selenium, and part of the mercury replaced by zinc (Hg : Zn=6 : 1, Petertsen ; 12 : 1, Ramm.). Massive. Color deep black. Guadalcazar, Mexico. LEVIGLIANITE is a ferruginous variety from Levigliani, Italy. MILLERITE.* Capillary Pyrites. Haarkies ; Mckelkies, Germ. Ehombohedral. It AT? = 144 8', Miller. c = 0-32955. 0A# = 15910'. Cleavage : rhombohedral, perfect. Usual in capillary crystals. Also in columnar tufted coatings, partly semi-globular and radiated. H. = 3-3'5. G.=4*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 O.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. BKYBICHITE (Liele). Formula Ni 5 S 7 = Sulphur 43 -G, nickel 56'4=100. Color lead-gray. Occurs in radiated groups with millerite in the Westerwald. V^ PYRRHOTITE. Magnetic Pyrites. Magneikies, Germ. Hexagonal. O A 1 135 8'; c 0-862. Twins: twhming-plane I (f . 435). Cleavage : O, perfect ; I, less so. Commonly 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 Fe 7 S 8 Sulphur 39-5, iron 60-5=100 ; but varying to Fe 8 S 9 ,Fe 9 S JO and Fc, S, ,. 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 tuhe gives sulphurous oxide. On 16 242 DESCRIPTIVE MINERALOGY. charcoal in R.F. fuses to a black magnetic mass ; in O.F. is converted into iron 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. Difi. 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. , niccoliferous. In Tennes- see, at Ducktown mines. In Canada, at St. Jerome ; Elizabethtown, Ontario (f. 435), etc. The niccoliferous pyrrhotite is the ore that affords the most of the nickel of commerce. TROILITE. According to the latest investigations of J. Lawrence Smith, composition FeS, iron proto- sulphide ; that is, iron 63 '6, sulphur 86*4=100. Occurs only in iron meteor- ites: DAUBKEELITE (Smith). Composition Cr 2 S 3 . Observed in the meteoric iron of Northern Mexico ; occurring on the borders of troilite nodules. Similar to shepardite, Haidingei (=schrdbersite, Shepard), described by Shepard (1846) as occurring in the Bishopville, S. C., meteoric iron. SCHKEIBERSITE 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. Ii.=: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. Gomp. 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 R.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 at Granby, Mo. NICCOLITE. Copper Nickel. Kupfernickel, Kothnickelkies, 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. EL. =5-5 -5. G. T-33-7'671. Lustre metallic. Color pale copper-red, with a gray to blackish tarnish. Streak pale brownish-black. Opaque, Fracture uneven. Brittle. Comp MAs (or M 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 mtro-hydrochloric acid. . Diff. Distinguished by its color from other similar sulphides, as also by its pyrognostics. SULPHIDES, TELLTJRIDES, 8ELENIDES, ETC. 243 Obs. Occurs at several Saxon mines, also in Thuringia, Hesse, and Styria, and at Alle oiont in Dauphiny ; occasionally in Cornwall ; Chili ; abundant at Mina de la Kioja, in the Argentine Provinces. Found at Chatham, Conn., in gneiss, associated with smaltite. BREITHAUPTITE. Composition NiSb= Antimony 07 '8, iiickel 32 '2= 100. Color light coppor-red. Andreasberg. AIUTE Ac. antimoniferous niccolite, containing 28 p. c. Sb. Basses-Pyrenees ; Wolfacb, Baden. C. DEUTO OR PYKITE DIVISION.' (a) Pyrite Group. X FYRITE.* Iron Pyrites. Schwefelkies, Eisenkies, Germ. Isometric ; pyritohedral. The cube the most common form ; the pyrito 'iedron, 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 O and i-2. Crystals sometimes acicular through elongation of cubic and other forms. Cleavage : cubic and octahedral, more or less distinct. Twins: twining-plane 7, f. 276, p. 93. Also reniform, globular, stalactitic, with a / crystalline surface ; sometimes radiated subfibrous. Massive. 436 438 IT. = 6-6-5. G.= 4-83-5-2. Lustre metallic, splendent to glistening. Color a pale brass-yelloWjjiearly 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. B.B. on charcoal gives off sulphur, burning with a blue flame, leaving a residue which reacts like pyrrhotite. Insoluble in hydrochloric acid, but decomposed by nitric acid. Diff. Distinguished from chal copy rite by its greater hardness, since it cannot be out with a knife ; as also by its pale color ; from marcaeite by its specific gravity and color. Not malleable like gold Obs. Pyrite occurs abundantly in rocks of all ages, from the oldest crystalline rocks to the 244 DESCRIPTIVE 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, Traverselia 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 ; in Orange Co. , at Warwick and Deerpark, and many other places. 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 pyrite is derived from vvp, fire, and alludes to the sparks from friction. HAUEMTE. Composition MnS 2 = Sulphur 53-7, manganese 46 '3 =100. Isometric. Color reddish-brown. Kalinka, Hungary. -a CHALCOPYRITE.* Copper Pyrites. Kupferkies, Germ. Tetragonal ; tetrahedral. O A l-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 ; the plane 1 (see p. 94). Often massive. 440 EL =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 otbei proportioiis ; 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 sxilphur 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, TELLTJKIDES, SELENIDES, ETC. 245 Oba. Chalcopyrite 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 tine crystals at Cerro Blanco, Chili. A common mineral in America, some localities are : Stafford, Vt. ; Rossie, Ellenville, N. Y.; Phenixville, 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 Nortt 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 x a ^ K " s -! brass, and pyrites, by Henckel, who observes in his Pyritology (1725) thnt chalcopyrite is a good distinctive name for the ore. Cur.ANiTE is CuFe 2 S 4 , or CuFe 2 S 3 (Scheidhauer). Occurs massive at Barracanao, Cuba; Tuna berg, Sweden. BAKNIIAIIDTITE, from North Carolina. Composition uncertain, perhaps Cu,Fe 2 S 5 . It may be partly altered from chalcopyrite. STANNITE (Zinnkies, Germ.). A sulphide containing 1 26 p. c. tin ; also copper, iron, and Trine. Massive. Color steel-gray. Chiefly from Cornwall, also Zinnwald. LINN2SITE. KobaltnickeUdes, Germ. Isometric. Cleavage: cubic, imperfect. Twins: twinning-plane octa- hedral. Also massive, granular to compact. H.=5'5. G.=4-8-5. Lustre metallic. Color pale steel-gray, tarnishing copper-red. Streak blackish-gray. Fracture uneven or subconchoidal. Comp Co s 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 Musen ore (siegenite) contains 80-40 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. Oba, In gneiss, at Bastnaes, Sweden; at Miisen, near Siegen, in Prussia; at Sicgeu (sicgenite), in octahedrons; at Mine la Motte, in Missouri, mostly massive, also crystalline and at Mineral Hill, in Maryland. SMALTTTE.* Speiskobalt, Germ. Isometric. Cleavage : octahedral, distinct ; cubic, in traces. Also mas- sive and in reticulated and other imitative shapes. II. =5*5-6. G. 6'4to7'2. 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 9 '4, nickel 9 '5, iron 9*0=100. It is probable that nickel is nevei wholly absent, although not detected in some of the earlier analyses ; and in some kinds it ia 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=99'88 Hofmann 2. Allemont(cflfoaw*7ite)7I-ll 1871 0-82 S 2-29=98'93 Raminelsberg. b, Kiechelsdorf 6042 10'80 25'87 0'80 8211=100. 4. Schneeberg 7480 3'79 12'86 7'33 S -85=99 f>3 Karstedt. 246 DESCRIPTIVE MINERALOGY. Pyr., etc. In the close tube gives a sublimate of metallic arsenic ; in the open tube s 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 silver 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. Also in crystals at Mine La Motte, Missouri. At Chatham, Conn. , the chloanthite (chathamite) occurs in mica slate, associated generally with arsenopyrite and sometimes with niccolite. SPATHIOPYRITB is closely allied to smaltite, with which it occurs at Bieber in Hessen. SKUTTERUDITE (Tesseralkies, Germ.*).GoA.a a = Arsenic 79 '2, cobalt 20 '8=100. Isometric. Skutterud, Norway. COBALTITE. Glance Cobalfc. Kobaltglanz, Germ. Isometric ; pyritohedral. Commonly in pyritohedrons (f. 92, 95, etc., p. 23). Cleavage : cubic, perfect. Planes O striated. Also massive, granular or compact. H. 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 2 +CoAs 2 )=: 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. Diff. Distinguished by its reddish-white color ; also by its pyritohedral form. Obs. 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 smaltito afford the greater part of the smalt of commerce. It is also employed in porcelain painting. GERSDORFFITE. Nickelarsenikkies, Arseniknickelglanz, Oerm. 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. Fyr., etc. In the closed tube decrepitates, and gives a yellowish-brown sublimate oi arsenic sulphide. In 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 i Lower Thuringia ; Haueisen, Voigtland ; near Ems. Also found as an incrustation af Phenixville, Pa. SULPHIDES, TELLTTKIDES, SELENIDES, ETC. 247 ULLMANNITE. NiSbS (NiS 2 +NiSb 2 ) = Antimony 57'2, sulphur 151, nickel 27 '7=100 Generally contains also some arsenic. Color steel-gray. Siegen, Harzgerode, etc. CORYNITE. Ni(As,Sb)S, but the arsenic (38 p. c.) in excess of the antimony. Olsa, Corin- thia. WoLFAcniTE (Petersen), from Wolfach, Baden, is similar in composition, but is orthorhombic in form. LAURITE. An osmium-ruthenium sulphide. Analysis (Wohler) Sulphur 31 '79 [Osmiam 3 -03], Ruthenium 05.18=100. Occurs in minute octahedrons from the platinum-washings of Borneo ; as also those in Oregon. Marcasite Group. Orthorhombic. MARCASITE, White Iron Pyrites. Strahlkies, etc., Germ. Orthorhombic. /A I 106 5', O A 14 = 122 26', Miller ; c : I : d = 1-5737 : 1-3287 : 1. O A 1 = 116 55' ; O A \-l = 130 10'. Cleavage: /rather perfect; \4 in traces. Twins : twinning-plane 7, sometimes consisting of five individuals (see f. 308, p. 98) ; also \-\. Also globular, reniform, and other imitative shapes structure straight columnar ; often massive, columnar, or granular. II. 6-6 5. Gk=4*678-4-B47. Lustre metallic. Color pale bronze-yel- low, sometimes inclined to green or gray. Streak grayish- or brownish- black. Fracture uneven. Brittle. Oomp., Var. FeS a , like pyrite = Sulphur 53 '3, iron 46'7=100. The varieties that have been recognized depend mainly on state of crystallization ; as the Radiated (Siraldkies) : Radiated ; also the simple crystals. Cockscomb (Kammkies) : 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 pyrite. 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. Obs. 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 Ecgland, particularly at Cummington, Mass. Occurs at Lane's mire, in Monroe, Conn. ; in Trumbull ; at East Haddam ; at Haverhill, N. H. ; Galena, III , in stalactites. In Canada in Neebing. Marcasite is employed in the manufacture of sulphur, sulphuric acid, and iron sulphate, though less frequently than pyrite. ARSENOPYRTTB, or MISPICKEL. Arsenical Pyrites. ArsenikMes, Germ. Orthorhombic. 1 A 7= 111 53', O A 14 = 119 37' ; c : I : a = 1-7588 : 1-4793 : 1. O A 1 = 115 12', A \-l = 130 4'. Cleavage : I rather distinct ; 0, faint traces. Twins : twinning-plane /, and 1 -I. Also colum- nar, straight and divergent ; granular, or compact. H.=5-5-6. G.=6'd-6-4; 6-269, Franconia, Kenngott. Lustre 248 DESCRIPTIVE MINERALOGY. Color silver-white, inclining to steel-gray. Streak dark grayish-black. Frac ture uneven. Brittle. 443 445 Franconia, N. H. Franconia, N. H., and Kent, N. Y. Danaite. Comp., Var. FeAsS=FeS a +FeAs 2 = Arsenic 46-0, sulphur 19'G, iron 34 '4=100. Part of 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 ; Andrea sberg ; Joachims- thai ; at Tunaberg in Sweden ; at Skutterud in Norway ; in Cornwall ; in Devonshire at the Tarnar mines. In New Hampsliwe, 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.York, 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 ', iron 33 -2). They are both like arsenopyrite in f orm. 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 nrsenopy rite. Huasco, Chili ; Hakansbo, Sweden. ALLOCLASITE R 4 (As,Bi) 7 S c , with R=Bi,Co,Ni,Fe,Zn. Orawicza, Hungary. SYLVANTTE. Graphic Tellurium. Schrifterz, Schrift-TeUur, Germ. Monoclinic. O= 55 21 J', /A 1= 94 26', <9 A 14 = 121 21' ; c : * : = 1-7732 : 0-889 : 1, Kokscharof. Cleavage : i4 distinct. Also massive ; imperfectly columnar to granular. H.=1'5 2. Gr. = 7'99-8'33. Lustre metallic. Streak and color pure steel- gray to silver- white, and sometimes nearly brass-yellow. Fracture uneven, Comp., Var (Ag,Au)Te a =(if Ag : Au=l : 1) Tellurium 55'8, gold 28'5, silver 15 7= 100 Antimony sometimes replaces part of the tellurium, and lead part of the other metals. 8ULPHABSENITES, SULPHANTlMONITES, 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 nt lead and antimony on charcoal. Obs. Occurs at Offenbanya and Nagyag in Transylvania. In California, Calaveras Co., at the Melones and Stanislaus mines ; Red Cloud mine, Colorado. Named from Transylvania, the country in which it occurs, and in allusion to sylvanium, 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 orttwrhombic. CALAVERTTE (Genth.) has the composition AuTe 4 = Tellurium 55 5, gold 44-5=100. Mas- give. Color bronze-yellow. Stanislaus mine, Cal ; Red Cloud mine, Colorado. NAGYAGITE.* Blattererz, Blatterteliur, Germ. Tetragonal. A \4 = 127 37' ; c = 1-298. O A 1 = 118 ST. Cleav- age: basal. Also granularly massive, particles of various sizes ; generally foliated. H.=l-l-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 R(S,Te) 2 , 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 tellui ate, with perhaps some sulphate of lead ; farther up the tube the sublimate consists of antimonous 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 c ryptalline plates. . COVBLLITB (Kupferindig, Germ.). Composition CuS= Sulphur 33 -5, copper 66 -5=100. Hexagonal. Commonly massive. Color indigo-blue. Mansfeld, etc. ; Vesuvius, on lava ; Chili. MELONITE (Genth.). A nickel telluride, formula probably Ni 2 Te 8 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. TERNARY COMPOUNDS. SULPHARSENITES, SULPHANTIMONITES, SULPHOBISMUTHITES.* (a) GROUP I. Formula R(As,Sb) 2 S 4 =RS + (As,Sb) 2 S 8 . MIARGYRITE. Monoclinic. C= 48 14'; /A 1= 106 31', O A 14 = 136 8' ; c : I : d = 1-2883 : 0-9991 : 1, Naumann. Crystals thick tabular, or stout, or short prismatic, pyramidal. Lateral planes deeply striated. Cleavage : \-i, \-i imperfect. * The species of this group contain as bases chiefly copper, lead, and silver. They can be most readily distinguished by their behavior before the blowpipe. Attention may be called to the group of lead sulphantimonites, zinkentte, plagionite, (jamesonite) boulangerite, mene- 'jhinite, geocroni'.e, for which the pyrognostics are nearly similar, and which are most surely by their specific gravity. 250 DESCEIPnVE MINERALOGY. H.=2-2-5. G.=5'2-5-4. Lustre snbmetallic-adamantine. Color iron black. Streak dark cherry-red. Opaque, except in thin splinters, w aich, by transmitted light, are deep blood-red. Fracture subconchoidal. Comp. AgSbS 2 (or Ag 2 S+Sb 2 S 3 )= Sulphur 21 '8, antimony 41*5, silver 36 '7=100. Fyr., 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 copper when fused with tin in R. 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 (hypargyrite} ; Guadalajara in Spain ; at Parenos, and the mine Sta, M. de Catorce, near Potosi ; also at Molinares, Mexico. SARTORITE. SCLEKOCLASE. Orthorhombic. 7 A 1= 123 21', O A 14 = 131 3' ; c : I : & = 1-1483 : 1*8553 : 1. Crystals slender. Cleavage : 447 O quite distinct. H.=3. G.=5-393. Lustre metallic. Color dark lead-gray. Streak reddish-^ brown. Opaque. Brittle. Oomp PbAs 2 S 4 (PbS+As 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 Hnnite of Heusser. yCi ZINKENITE. Orthorhombic. /A /= 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+Sb 2 S 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 Sb 2 S 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 a (or CUiS-i-BiaSg) Sul- phur 19'1, bismuth 62'0, copper 18-9=100. Color grayish to tin-white. Schwa rzenberg, Scxony; Copiapo, Chili. 8ULPHARSENITES, SULPHANTTMONITES, ETC. 251 BERTHIEKITE. Composition approximately FeSb 2 S 4 (orFeS+Sb 2 S 3 )=Stilplnir30*0, anti- mony 57*0, iron 13-0=100. Color dark steel-gray. Auvergne ; Braunsdorf, Saxony; Corn- wall, etc. ; San Antonio, Cal. (b) SUB-GROUP. Formula K 3 ( A ,s,Sb,Bi) 4 S 9 =3ES + 2(As J Sb,Bi PLAGIONITE. Composition (Rose) Pb 4 Sb 6 Si 3 (or 4PbS-j-3Sb 2 S 3 )=Sulphur 21-1, antimonj 37-0, lead 41 '9. Monoclinic. G. =5 '4. Found at Wolfsberg in the Harz. JORDANITE (v. Rath). Composition Pb 3 As 4 S9 (or 3PbS-j-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. BiNNiTii. 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 ol v. Walter shausen). KLAPROTIIOLITE (Petersen). Composition Cu 6 Bi 4 Sb 9 (or 3Cu a S+2Bi 2 S 3 ). Orthorhombio. Cleavage i-\ distinct. Color steel-gray. G.=4'6. Wittichen, Baden. SCHIKMERITE ( Genffi).- Composition R 3 Bi 4 S 9 (or 3RS + 2Bi 2 S 3 ), with R=Ag a : 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. (0) GKOUP II. Formula * S\ JAMESONITE. Federerz, Germ. Orthorhombic. /A I 101 20' and 78 40'. Cleavage basal, highly perfect; I an d i-% less perfect. Usually in acicular 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. SmaU quantities of zinc, bis- muth, silver, and copper are also sometimes present. Pyr. 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 Claus- thal ; at Freiberg and Schemnitz ; at Pfaffenberg and Meiseberg ; in Tuscany, near Bottino ; at Chonta in Peru, DUFRENOYSITE. Orthorhombic. /A 1= 93 39', A 14 = 121 30', c : b : d = 1'6318 : 1-0658 : 1. Usual in thick rectan- gular tables. Cleavage: O perfect. 448 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 8 (or 2PbS+2As a S,)=Sul- phur 22-10, arsenic 20-72, lead 57-18=100. Pyr., etc. Easily fuses and gives a subli- mate of sulphur and arsenous sulphide ; in the open tube a smfill of sulphur only, with a sublimate of sulphur in upper part of tube, and 252 DESCRIPTIVE MINERALOGY. of arsenous oxide below. On chareoa; decrepitates, melts, yields fumes of arsenic and & 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 ditfrenoysite. 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 arsenomelan and gderodase, 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 1 s dufrenoysite; another he makes sclerodase of von Waltershausen (sartorite, p. 250) ; and the other he names jordanite (p. 251). The isometric mineral was called binnite by DesCloizeaux. FREIESLEBENITB. Schilfglaserz, Germ. Monoclinic. C = 87 46', /A 1= 119 12', A 14 = 137 10' (B. & M.) ; c:t>:d = 1-5802 : 1-7032 : 1. O A \4 = 123 55'. Prisms longitudinally striated. Cleavage : / perfect. II. = 2-2 : 5. G. = 6-0-4. 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. Oomp. PbaAgsSbsSg, 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 antimonoiis oxide, and near the assay yellow, from oxide of lead ; continued blowing leaves a globule of silver. Obs. Occurs at Freiberg in Saxony and Kapnik in Transylvania; at Ratieborzitz ; atPrzibram ; at Felsbbanya; atHieudelencinainSpain. 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 orthorhombic form. It is called by him DIAPIIOTIITE. BRONGNIARDITE. Composition Ag 2 PbSb 2 S 5 (or PbS+Ag 2 S + Sb 2 S 3 )=: Sulphur 19 '4, anti- mony 29-5, silver 2(5'1, lead 25'0=100. Isometric ; in octahedrons, also massive. Color gray- ish-black. Mexico. COSALITE (Oenth). 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 02 "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. A (d) GROUP III. Formula E^( As,Sb)j3 6 = 3KS 4- (As,Sb) 2 S 3 . P3TRARGYRITB. Ruby Silver. Dark Red Silver Ore. Dunkles Rothgiiltigerz, Germ. Rhombohedral. Opposite extremities of crystals often unlike. R A R = 108 42' (B. & M.) ; O Mt = 137 42' ; c = 0-788. O A 1 s = 112 33 7 , 14/, #Ai = 144 21'. Cleavage: R rather imperfect RULPHABSENITES, SULPHANTIMONITES, ETC. 253 450 451 Twins: composition-face^; O or basal plane, as in f. 290, p. 95; also It and /. Also massive, structure granular, sometimes impalpable. H.=:2-2-5. G.=5-7-5-9. Lustre metallic-adamantine. Color black, sometimes approaching cochineal- red. Streak cochineal-red. Translucent opaque. Fracture conchoidal. Ocmp. Ag 3 SbS 3 (or 3Ag a S+Sb 2 S 8 )=Sul- phnr 17-7, antimony 22'5, silver 59-8100. Pyr., elc. 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 R.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 Washoe in Daney Mine ; abundant about Austin, Reese river ; at Poor Man lode, Idaho. PROUSTITE. Light Red Silver Ore. Lichtes Rothgiiltigerz, Germ. 9' c = 0-78506. Khombohedral. R A E = 107 48', Also granular massive. II. 2-2-5. G.=5-422-5-56. Lustre adamantine. Color cochineal-red. Streak cochineal-red, sometimes inclined to aurora-red. Subtransparent- subtranslucent. Fracture conchoidal uneven. Comp.-Ag 3 AsS 3 (or 3Ag, S+ As, S,)= Sulphur 19'4, arsenic 15'1, silver 65 "5=100. Pyr., ete. In the closed tube fuses easily, and gives a faint sublimate of arsecous 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., 01 with soda 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 in Baden ; Chalanches in Dauphine; 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. /A / = 93 40', O A 14 = 136 IT (Miller; ; c l> : a = 0-95618 : 1-0662 _: 1. 0A1-S = 133 26', OM = 127 20', CMW= 138 ti'. Cleavage : i-i imperfect ; i-l and O less distinct. Twins : twinning- plane face 7 / crystals often cruciform (f. 453), crossing at angles of 93 44V and 86 20' ; hence, also, cog-wheel shaped. Also massive ; granular, compact. DESCEIPTIVE MINERALOGY. H.= 2-5-3. G.=5-T-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., Van CuPbSbS 3 Ramm. (or 3RS+Sb 2 S 3 , with 3RS=2PbS+Cu 2 S)= Sulphur 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 2oal 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 my 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 Machacarnarca 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 8 (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 ISTasaf 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 2 S + Bi 2 S 3 )- Sulphur 19'4, bismuth 42.1, 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 36-2, lead 30 -0, copper 111 100. In acicular crystals, also massive. Color blackish lead gray. Beresof, Urals ; Gold Hill, North Carolina. SULPHAESENITE8, SULPHANTIMONITES, ETC. 255 toETRAH (e) GEOUP IY. Formula EDRITE.* Gray Copper Ore. Fahlerz ; Antimon- and Quecksilberfahlerz, 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 G.=4:-5-5-56. Lustre metallic. Color between light flint- gray and iron-black. Streak generally same as the color ; sometimes inclined to brown and cherry-red.' Opaque ; sometimes subtranslucent in Vrery thin splinters, transmitted color cherry-red. Fracture subconchoidal uneven. Rather brittle. Comp. ; Var.-CugSb.jS7 (or 4Cu 2 S + Sb 2 S 3 ), with part of the copper (Cu a ) 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. Ratio Ag 2 +Cu a : Zn+Fe generally 2:1. There are thus : A. An antimonial series ; B. An arsenio-antimonial series ; C. A bismuthio arsenio-anti- monial; 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 : 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 0'87 Zn Ag 3'50 0-60NiCol-64=98-59Rammelsberg. 3 '39 10.48 Pb '78 =100 '00 0'69 - Hg 17'27, Pb 021 Bi 081=100 v. Rath. Pyr., etc. Differ in the different varieties. In the closed tube all fuse and givo a dark- red sublimate of antimonous sulphide ; when containing mercury, a faint dark-gray sublimate appears at a low red heat ; and if much arsenic, a sublimate of arsenous sulphide first forms. In the open tube fuses, gives sulphurous fumes and a white sublimate of antimony ; if arsenic is present a crystalline volatile sublimate condenses with the antimony ; if the ore contains mercury it condenses in the tube in minute metallic globules. B.B. on charcoal fuses, gives a coating of antimonous oxide and sometimes arsenous acid, zinc oxide, and lead oxide ; the arsenic may be detected by the odor wh*en the coating is treated in R.F. ; the zinc oxide assumes a green color when heated with cobalt solution. The roasted mineral gives with the fluxes reactions for iron and copper ; with soda yields a globule of metallic copper. To determine the presence of a trace of arsenic by the odor, it is best to fuse the mineral on charcoal with soda. The presence of mercury is best ascertained by fusing the 256 DESCRIPTIVE MINERALOGY. 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 Schm3lnitz, 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 Bolivia ; 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 1-J p. c. of silver ; at the Sana Rita mine. HIONITE (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 Bocuay, Peru. (5th Append. Min. Chili.) TENNANTITE.* Graukupfererz, Germ. Isometric ; holohedral, Phillips. Cleavage : dodecaliedral imperfect. Twins as in tetrahedrite. Massive forms unknown. H.r=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 b As 2 S 7 (or 4Cu 2 S+As 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. Pyr. In the closed tube gives a sublimate of arsenous sulphide. In the open tube gives 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. JULIAN ITE (Websky) is near tennantite. G.=5-12. Rudelstadt, Silesia. MF.NEGIIINITE has the composition Pb 4 Sb.2S7(4PbS + Sb2S 3 )=Sulphur 17'3, antimony 16'S, lead 63-9=100. Resembles boulangerite. Bottino, Tuscany ; Schwarzenberg, Saxony. (/) GROUP Y. Formula E 5 (As,Sb) 2 S 8 =5ES-f-(As 3 Sb) 2 S 3 . STEPHANITE. Sprodglaserz, Germ. Orthorliorabic. 7 A 7 = 115 39', O A 14 = 132 32J' ; c\l'.d = l-089'i : 1-5844:1. OM = 127 51', 0*1-1 = 145 34; Cleav- age : 2-^ and i-l imperfect. Twins: twinning-plane // forms like those of aragonite frequent. Also massive, compact, and disseminated. IL 2-2-5. G.= 6-269, Przibram. Lustre metallic. Color and streak iron-black. Fracture uneven. 2* Comp. Ag 6 SbS 4 (or 5 Ag 2 S+Sb 2 S,)= Sulphur 16'2, antimony IS'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 antimonlal fumes and sulphurous oxide. B.B. on charcoal fuses with projection of small particles, coats the coal with antimonoua 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. 8ULPHARSENITES, STJLPHANTIMONITE8, ETC. 257 Obs. At Freiberg and elsewhere in Saxony ; at Przibram in Bohemia ; in Hungary ; at Andreasberg ; at Zacatecas in Mexico ; and in Peru. In Nevada, an abundant silver ore in the Comstock lode ; at Ophir and Mexican mines in fine crystals ; in the Reese river and Humboldt and other regions. In Idaho, at the silver mines. GEOCRONITE. Composition Pb 5 Sb,Se (or 5PbS+Sb 2 S 3 ) = Sulphur 167, antimony 15'9, lead 67 '4=: 100 (also contains a little arsenic). Color light lead-gray. Sala, Sweden; Merido, Soain ; Val di Castello, Tuscany. POLYBASITB. Orthorhombic, DesCl. /A I nearly 120, O 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. Agt,SbS 8 (or 9Ag 2 S+Sb a 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 Puntos, 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 S4-Sb a S,. Wol- fach, Baden. y ENARGITB. Orthorhombic. /A / = 97 53', O A 14 = 136 37' (Dauber) ; c : I : d = 0-94510 : 1-1480 : 1. OM-l=\ 40 20', O A 1 = 128 35'. Cleavage : I perfect ; i4, 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 AsS 4 Sulphur 82 '5, arsenic 19 '1, copper 48*4=100, usually containing also a little antimony, and zinc, and sometimes silver. Pyr. In the close- 1 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 antimonous 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 Mis.. 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 ; southern Utah ; Morning Star mine, Cal. FAMATINITE (titelzner). An antimonial enargite. 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. CLAIUTE (Sandberger}. Also similar to enargite in composition, but in form monoclinic, and having a perfect cleavage parallel to the clinopinacoid. Schapbach, Black Forest. EriGENiTE. Composition S 32-24, As 12-78, Cu 4068, Fe 14 '20=100. Orthorhombio, Color steel-gray. Neugliick mine, Wittichen, COMPOUNDS OF CHLORINE, B&OMINE, IODINE. 259 III. COMPOUNDS OF CHLORINE, BROMINE, IODINE 1. ANHYDROUS CHLORIDES, ETC. 458 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-l-2-257. Lustre vitreous. Streak white. Color white, also sometimes yellowish, red- dish, bluish, purplish ; often colorless. Transparent translucent. Fracture conchoidal. Rather brittle. Soluble ; taste purely saline. Oomp. NaCl= Chlorine GO '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. Diflf. 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 salt springs. The principal 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, Galicia, 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 \Igeria ; in Abyssinia ; in India in the province of Lahore, and in the valley of Cashmere ; in 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- ington Co. ; in the Salmon River Mts. of Oregon ; in Louisiana. Brine springs are very numerous in the Middle and Western States. These springs are worked at Salina and Syra- cuse, X. Y. ; in the Kanawha Valley, Va. ; Muskingum, Ohio ; Michigan, at Saginaw 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 20NaCl + AgCl. Occurs in white cubes in the mine of San Simon, Cerro de Huantajaya, Peru. 260 DESCRIPTIVE MINERALOGY. SYLVITE. 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. \, CERARGYRTTE. Kerargyrite. Horn Silver. Silberhornerz, Germ. Isometric. Cleavage none. Twins : twinning-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 couchoidal. Sectile. Comp. AgCl= Chlorine 24 '7, 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 Oohanngeorgenstadt 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 nspac, horn, and apyvpoc, silver. CALOMEL (Quecksilberhornerz, Germ.). Composition HgCl= Chlorine 15-1, mercury 84 '9 erlOO. 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, Cnili. 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. BROMYRITE, Bromargyrite (Bromsilber, Germ.). Silver bromide, AgBr=Bromine 42 6, silver 57*4=100. Color when pure bright yellow, slightly greenish. Chili ; Mexico. IODTRITE, 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 Agl+Hgl. Amorphous. Color pale yellow. Chanarcillo, Chili. CHLOROCALCITE (Scacchi). From Vesuvius, contained 58 '76 p. c. Cad* ; with also KC'l, NaCl,MgCl 2 . CHLORALLUMINITE, CIILORMAGNESITE, and CHLOHOTHIONITE are also frcm Vesuvius. COMPOUNDS OF CHLORINE, BKOMTNE, IODINE. 261 COTUNNITE. Lead chloride, PbCl 2 = Chlorine 25 '5, lead 74 '5 =100. Soft. White. Veau HUB. PSEUDOCOTUNNITE (Scacchi), Vesuvius. MOLYSITE. Composition FeCl 6 = Chlorine 65-5, iron 34-5=100. Vesuvius 2. HYDKOUS CHLOEIDES. OARNALLTTE. 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+MgCla + 6aq=Magnesium chloride 34-2, potassium chloride 20 '9, water 88 = 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 J C. taking up 61-5 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. TACIIIIYDHITE. Composition CaMg 2 Cl e + 12aq=CaCl 2 +2MgCl 2 + 12aq (Ramm.)= Chlorine 40'3, magnesium 9'5, calcium 7'5, water 42'7=100. Color yellowish. Deliquescent. Stas- furt. K.REMERSITE. Probably 2NH 4 Cl-f-2KCl+FeCl 8 +3aq. Vesuvius. ERYTHROSIDKRITE, also from Vesuvius, is 2KCl+FeCle+2aq. 3. OXYCHLOEIDES. ATACAMTTE. Orthorhombic. 1 A /= 112 20', O A 14 = 131 29' ; c : I : d = M31 : 1*492 : 1. Usually in modified rectangular prisms, vertically striated ; also in rectangular octahedrons. Twins : twinning-plane I\ consisting of three individuals. Cleavage: i-l perfect, 1-1 imperfect. Occurs also mas- sive lamellar. H.= 3-3-5. G.= 3-761 (Klein), 3-898 (Zepharovich). Lustre adamantine- vitreous. Color various shades of bright green, rather darker than emerald, sometimes blackish-green. Streak apple-green. Translucent subtrans- lucent. 262 DESCRIPTIVE MINERALOGY. Comp. CuCl 2 +3H 2 O^O8= 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. OE 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 acids easily soluble. Obs. Occurs in different parts of Chili ; in the district of Tarapaca, Bolivia ; at Tocopitta in Bolivia ; with malachite in South Australia ; Serro do Bembe, near Arabriz, on the west coast of Africa ; at the Estrella mine in southern Spain ; at St. Just in Cornwall. TALLINGITE. Composition CuCl 2 +4H 2 Cu0 2 +4aq. In thin crusts. Color blue. Botal- lack mine, Cornwall. ATELITE. Composition CuGh-f-SHaCuOa + aq. Formed from tenorite. Vesuvius. PERCYLITE. An oxychloride of lead and copper. Occurs in minute sky-blue cubes. Sonora, Mexico ; So. Africa. MATLOCKITE. Composition P bCl a +PbO= Lead chloride 55-5, lead oxide 44 '5=100. Crom- ford, near Matlock, Derbyshire. MENDIPITE. Composition PlCl 2 +2PbO=Lead chloride 38'4, lead oxide 61 '6=100. In columnar masses, often radiated. Color white. Mendip Hills, Somersetshire; Brillon, Westphalia. SCHWAUTZEMBERGITE. Composition Pb(I,Cl) 3 +2PbO. Color yellow. Desert of Ata- cama. DAUBREITE. Composition (Bi 2 O 3 )4BiCl 3 =Bi 2 Os 76-16, BiCl 3 23-84=100. Amorphous. Structure earthy, sometimes fibrous. Color yellowish-gray. H.=2'5. G. =6 '4-6 '5. From the mine Conetancia, Cerro de Tatiza, Bolivia (Domeyko). FLUOBINE COMPOUNDS. 263 IV. FLUORINE COMPOUNDS. 1. ANHYDROUS FLUORIDES. ' FLUORITE or FLUOR SPAR* Flusspath, Germ. Isometric; forms usually cubic (see f. 39, 40, 41, 52, 55, etc., pp. 10 to 19). Cleavage : octahedral, perfect. Twins : twinmng-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 cavities. fi.= 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-bine, most common ; red, rare. Streak white. Trans- parent sub translucent. 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 culled, 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 chlorophane. Pyr., etc. In the closed tube decrepitates and phosphoresces. B.B. in the forceps and 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. Pho 264 DESCRIPTIVE MINERALOGY. phorescence is obtained from the coarsely powdered spar below a red heat. At a high tenv perature it ceases, but is partially restored by an electric discharge. Diff. Recognized by its octahedral cleavage, its etching power when heated in the glasi 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- eon Co., N.Y., in gigantic cubes ; Kossie, St. Lawrence Co. ; near the Franklin 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. YTTBOCEKITE. Composition 2(9CaF 2 +2YF 2 +CeF2)4-3aq (Ramm.). Color violet-blue, white. Near Fahlun, Sweden ; Amity, N. Y. ; Paris, Me. ; etc. FLUOCERITE. Contains (Berzelius) -GeOa 82-64, YO 1'12. Sweden. FLUELLITE. Contains (Wollaston) fluorine and aluminum. Cornwall. CRYPTOIIALITE. 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 (7) = 90 2', P(0] A M(l') = 90 24', M A T(If\ 1') = 91 57' ; also I (141 A J/ (/') = 124 30', I (!-') A r(7) = 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. G.= 2-9-3-077. Lustre 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. Oomp. NaAlF 12 (or 6NaF+AlF )=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 remains, 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. Oba, Occurs in a bay in Arksut-fiord, in West Greenland, at Evigtok, where it constitutes ft 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 3NaF4-AlF 6 ). CHODNEFPITE. G.=3-01. Na^Al P, (or4NaF + AlF 6 ) Ramm. The two minerals are alike in physical characters, occurring In minute tetragonal pyramids ; both from Miask. FLUORINE COMPOUNDS. 265 2. HYDROUS FLUORIDES. PACHNOLITB. Thomsenolite.* Monoclinic, with the lateral axes equal (" clino-quadratic " Nordens kiold). c:b:d = 1-044 : 1 : 1 ; G = 92 30'. Prisms slender, a little tapering ; I horizontally striated. Cleavage : basal very perfect. Also massive, opal or chalcedony-like. fL=2'5-4. G.= 2-929-3-008, of crystals. Lust re vitreous, of a cleavage-face a little pearly, of massive waxy. Color white, or with a reddish tinge. Transparent to translucent. 460A Comp Na 2 Ca 2 AlFi 2 + 2aq, or 2XaF + 2CaF 2 + A1F 6 -f- 2aq Fluorine 51.28, aluminum 12*28, calcium 17'99, sodium 10'35. water 8-10=100. Pyr., 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 the appearance of cryolite The mineral was first described by Knop, and though his descriptic 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 (dimetric pachnolite thomsenolite), Wohler (pyroconite) and Kcenig, as urg^d 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, intersecting at angles of approximately 90. These cleavage planes seemed to be con- tinued on into the mass of the cryolite on which the crystals were implanted. The second variety, B, was in small brilliant crystals, of prismatic form, grouped together often in par- idlel position upon the cryolite (hence the name, from iraxviit frost). The identity of the two varieties chemically was shown by the analyses of Knop and Wohler. The crystals of variety B, according to Knop, had /A /= 81 24', etc. Knop has recently (Jahrb. Min., 1876, 849) suggested the possibility that the crystals of " cryolite," upon which Websky obtained the angles quoted on the preceding page, were really identical with variety A of pachnolite. The crystallographio relation of the two species is not yet clearly made out. AUKSUTITE, HAGEMANNITE, GEARKSUTITE, all from Greenland ; and PHOSOPITE, from Altenberg. Fluorine minerals, related to those which precede, but whose exact nature 'is not yet known. RALSTON ITS (Brmh). An hydrous aluminum fluoride, containing also a little magnesium and sodium. Occurs in minute regular octahedrons on the cryolite from Greenland. 266 DESCEIPTIVE MINERALOGY. V. OXYGEN COMPOUNDS. 1. OXIDES OF METALS OF THE GOLD, IKON, OR TIN A. ANHYDKOUS OXIDES, (a) PROTOXIDES, RO(or R 2 O). V CUPRITE. Red Copper Ore. Bothkupfererz, Germ. Isometric (see figures on p. 17). Cleavage: octahedral. Sometimes cubes lengthened into capillary forms. Also 461 massive, granular ; sometimes earthy. 11.= 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 subtranslucent. Frac- ture conchoidal, uneven. Brittle. Comp., Var. Cu 2 0=Oxygenll-2, copper 88 '8 =100 Sometimes affords traces of selenium. ChakotncJiiti 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. Pyr., 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 lithomarg-e, 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. HYDKOCUPIUTE (Genth). A hydrous cuprite. Occurs in orange-yellow coatings on nrgnetite. Cornwall, Lebanon Co., Pa. \_- ZINCITE. Eed Zinc Ore. Rothzinkerz, Germ. Hexagonal O A 1 = 118 T ; c = 1*6208. In qnartzoids 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. Gr.=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. infusib.e ; with the fluxes, on the platinum wire, gives reactions for manganese, and OB 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 f ranklinite 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. Schwarzktipfererz (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)O, where Mg : Fe=20 : 1, or 30 : 1. Mt. Somma. BtTNSENlTE. NiO. Found at Johanugeorgenstadt. 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. Badenweiler, Baden. Mexico. Austin's mines, Va. HYDRARGYRITE. HgO ; with BORDOSITE, AgCl + HgCl, at Los Bordos, Chili SESQFIOXIDES. GENERAL FORMULA >S CORUNDUM.* Khombohedral. E A R = 86 4', A 1(72) = 122 26' ; (122 scharof) ; 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 J?. Also massive granular or impalpable ; often in layers from composition parallel to /?. 11.= 9. G.= 3-909-4-16. Lustre vitreous; sometimes pearly on the basal planes, and occa- sionally exhibiting a bright opalescent star of six rays in the direction o the axis. Color blue, -ed, yellow, brown, gray, and nearly wHte; streak uncolored. Transparent translucent. Fracture conchoidal uneven. Exceedingly tough when compact. 462 Comp., Var. Pure alumina AlO s =Oxygen 46*8, aluminum 53-2=100. There are three 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. VAK. 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 ; Topc^ 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 that 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 inf usability 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' Hiver in Montana. HEMATITE. Specular Iron. Eisenglanz, Rotheisenerz, Germ. Khombohedral. 72 A 72 = 86 10', O A R = 122 30'; c = 1-3591. O A f 2 = 118 53', A I 3 = 103 32, R A f 2 = 154 2'. Cleavage : par- allel to R and 0; often indistinct. Twins: twiiming-plane R ; also 4C5 466 X 468 469 Vesuvius. Elba. Elba. (f. 267, p. 91). Also columnar granular, botryoidal, and stalactitic shape* , also lamellar, laminae joined parallel to O, and variously bent, thick \>* thin ; also granular, friable or compact. OXYGEN COMPOUNDS ANHYI/BOUS 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 magnetipolar. 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. 8. Red Ochreous. Red and earthy. Often specimens of the preceding are red ochreous on some parts. Reddle and rtd chalk are red ochre, mixed with more or less clay. 4. Clay 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 011 cooling ; in R.F. gives a bottle-green color, and if treated on 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, a at Vesuvius. Traversella in Piedmont ; the island of Elba, afford fine specimens ; also St. Gothard, often in the form of rosettes (Eisenrose , and Cavradi in Tavetsch ; and near Limoges, France. At Etna and Vesuvius it is the result of volcanic action. Arendal in Norway, Long- ban in Sweden, Framont in Lorraine, Dauphiuy, also Cleator Moor in Cumberland, are other localities. In N. America, widely distributed, and sometimes in beds of vast thickness in rocks of the Archaean 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. Red 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 conchoidal. Not magnetic, or only fecbry 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, neai Bchonberg, in granite. \^ MENAOCANITE.* ILMENITE. Titanic Iron Ore. Titaneisen, Germ. Rhombohedral ; tetartohedral to the hexagonal type. R A R = 85 3CX 270 DESCRIPTIVE MINERALOGY. 470 56 f/ (Koksch.), c 1-38458. Angles nearly as in hematite. Often a cleavage parallel with the terminal plane, but probably due to planes of composition. Crystals usually tabular. Twins : twinn ing-plane O ; sometimes producing, when repeated, a form resembling f. 468. Often in thin plates or laminae ; massive ; in loose grains as sand. H.=:5-6. Gr.= 4-5-5. 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 : Ti0 2 to be alwaya 1:1, and that in addition variable amounts of FeO 3 are present in the different varieties. The extensive investigations of Eamrnelsberg have led him to write the formula like Mosan- der (FeO,Ti0 2 )+nFeO 3 (notice here that FeO,TiO 2 =fK) 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 O 3 . Friedel and G-uerin 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 : FeO MnO MgO 37-86 273 1-14=99 '39, Mosander. 10-02 77-17 8-52 1'33, A1O 3 1-46 =98 '50, Eamm. 57-71 26-82 0'90 13-71=99'14, Eamm. Pyr., etc. B.B. infusible in O.F. although slightly rounded on the edges in E. 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 E.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. Eesembles hematite, but has a submetallic, nearly black, streak. Obs, Some of the principal European localities of this species are : Krageroe, Egersund, Arendal, Norway; Uddewalla, Sweden; Ilmen Mts. (ilmenite) ; Iserwiese, Eiesengebirge (iser- ine) ; Aschaffenburg ; Eisenach ; St. Cristophe (crichtonite). Occurs in Warwick, Amity, and Monroe, Orange Co., N. Y. ; also near Edenville ; at Ches- ter and South Eoyalston, Mass. ; at Bay St. Paul in Canada; also with labradorite at Chateau Richer. Grains are found in the gold sands of California. Ti0 2 1. 2. Snarum 3. Warwick, N. Y. Fe0 3 10'74 77' 17 PEROFSKITE.* 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. II. 5-5. G.=4'02-4:'04:. Lustre metallic adamantine. Color pale yeilow, 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 Comp.~-(Ca+Ti)0 8 =RO3=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 aolves easily, giving a bead greenish while hot, which becomes colorless on cooling; in B.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 Wildkreuzrjoch 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. 17G). HYDROTITANITE. A decomposition-product of perofskite crystals from Magnet Cove, Arkansas. Form retained but color changed to yellowish-gray (Kosnig). (c) COMPOUNDS OP PROTOXIDES AND SESQUIOXIDES,* KHO 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. Oomp., Var. The spin els proper have the formula MgAlO 4 (= -t-A-lO 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. MgA104= Alumina 72, magnesia 28=100. Var. 1. Ruby, or Magnesia Spinel. Clear red or reddish; transparent to translucent; sometimes subtranslucent. Q-. =3 '52-3 '58. Composition MgA-10 4 , with little or no Fe, and sometimes chromium as a source of the red color. 2. Ceylonite, or Iron-Magnesia Spinel. Color dark-green, brown to black, mostly opaque or nearly so. G, 3*5-3 - 6. Composition MgrtlO 4 -f-FeA:104. Sometimes the A-l is replaced in part by Fe. 3. Pic-olite. Contains over 7 p. c. of chromium oxide. Color black. Lustre brilliant. G. =4/08. The original wan 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. HatlOi, that is, as aluminates, ferrates, etc. 272 DESCRIPTIVE MINERALOGY. cooling. The black varieties give reactions for iron with the fluxes. Soluble with difficult? in concentrated sulphuric acid. Decomposed by fusion with sodium or potassium bisulphate. Diff. Distinguished by its octahedral form, hardness, and infusibility ; magnetite u attracted by the magnet, 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 granulai 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 Oo., N. Y. ; at Bolton and elsewhere in Mass. HEKCYNITE. FeA10 4 (or FeO+2^10 3 ). Color black. Massive. Bohemia. JACOBSITE (Damour). RBO 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. ZnA10 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. Automolite, or Zinc QaJmite; 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 Gahnite. Composition ^Zn, Fe,MgX^l,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, 472 474 475 Achmatovsk. Had dam. Fig. 475 is a distorted dodecahedron. Cleavage : octahedral, perfect to OXYGEN COMPOTJNDS. ANHYDROUS OXIDES. 273 imperfect. Dodecahedral faces commonly striated parallel to the longer diagonal. Twins : twi^ ng-plane, 1 ; also in dendrites, branching at angles of 60 (f. 277, p. 5*3;. Massive, structure granular particles of various sizes, sometimes impalpable. H.= 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 O 4 )=FeO+FeOs=Oxygen27-6, 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 FeO 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. Dlff. 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 Archa3an 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 ^ T orthem N. York ; also in Canada ; at Cornwall iu Pennsylvania, and at Magnet Cove, Arkansas. Also, found in Putnam Co. (Tilly Foster Mine), N. Y., etc. In Conn., at Haddam. In Petm., at Chester Co. in mica at Pennsbury. In California, in Sierra Co. ; in Plumas Co., and elsewhere. In N. Scotia, Digby Co., Nichol's Mt. MAGNESIOPERRITK (magnoferrite). MgFe0 4 . In octahedrons; resembling magnetite. Vesuvius. FRANK UNITE. Isometric. Habit octahedral. Cleavage : octahedral, indistinct. Also massive, coarse or fine granular to compact. IL=5-5-6-5. G.=:5-069. Lustre metallic. Color iron-black. Streak dark reddish-brown. Opaque. Fracture conchoidal. Brittle. Acts slight]} on the magnet. Comp. (Fe,Zn,Mn) (Fe,Mn)0 4 , or corresponding to the general formula of the spiuw group, though varying much in relative amounts of iron, zinc, and manganese. Analysis, Sterling Hill, N. J., t FeO 3 (57-42, A1O 3 0'65, FeO 15 '(35, ZnO 6-78, MnO 9'53=100'12, Seyms Q. ratio for R : K=l : 1 nearly. In a crystal from Mine Hill, N. J., Seyms found 4'44 p. c. Mn0 3 . The evolution of chlorine in the treatment of the mineral is attributed by v. Kobell to the presence of a little MnO 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 small amount of chlorine. Diff. Resembles magnetite, but is only slightly attracted by the magnet; it a] so leactt for zinc on charcoal B.B. 18 ** OF T tTH 274 DESOBIPTTVE 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. Fe^r0 4 , or (Fe,Mg,Cr) (Al,Fe,^r)O 4 . FerO 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. inO.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 only a reaction for iron, biit 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 i'usicn with potassium or sodium bisulphate. Ditf. 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 Zealaud. URANINITE* (Pitchblende ; Uranpecherz, Qerm.\ U 3 6 (UO a +2U0 8 ). Massive. Black. Saxony, etc. CHRYSOBBRYL. Orthorhombic. /A I 129 38', A 14 = 129 1' ; c : I : d = 1-2285 : 2-1267:1. i-lM = 13652',*4A 473 47? 2-2 = 128 52', i4 A 14 = 120 7'. Plane i-l vertically striated ; and sometimes also i-l, and other verti- cal planes. Cleavage : 1-i 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.=S-5. G.=3 : 5-3*84:. Lustre vitreous. Color asparagus-green, Norway, Me. AlexTndrite. grass-green, emerald-green green. ish-wlnte, and yellowish-green, iometimes raspberry or columbine-red by transmitted light. Streak uncol- ored. Transparent translucent. Sometimes a bluish opalescence inter- nally. Fracture conchoidal, uneven. 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 BeiVlO 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. Distinguished 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 Mourna 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, Hutile Group. Tetragonal. CASSITERITE. Tin Stone. Zinnstein, Zinnerz, Germ. J^ Tetragonal. O A l-i = 14*6 5' ; c = 0-6724. 1 A 1, pyr.; = 121 40' ; /Al = 133 34'; l-i A l-i, pyr., = 133 31'. Cleavage: 1 and i-i hardly distinct. Twins: f. 478, twin n ing-plane I-i; producing often complex forms through the many modifying planes ; sometimes repeated parallel to all the eight planes l-i; also f. 480, a metagenic twin. Often in reniform shapes, structure fibrous divergent ; also massive, granular or impalpable. H.=6-7. G.=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 Bubconchoidal, uneven. Brittle. Var. 1. Ordinary, Tin-stone. In crystals and massive. G. of ordinary cryst. 6 '96; of colorless, from Tipuaui R., Bolivia, 6 '832, Forbes. 2. Wood Tin (Holz-Zinn, Germ.). In botrvoidal 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. SnO a = 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 fcin B.B. from some varieties of garnet, sphalerite, and black tourmaline, to which it has ome resemblance. Specific gravity (0'5) higher than that of ruiile (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 Galicia ; 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 N. Hamp., at Lyme ; in California, in San Bernardino Co. ; in Idaho, near Boonville. X RUTILE.* Tetragonal. O A \4 = 147 12J', c = 0*6442. 1 A 1, pyr., = 123 7*', /A 1 = 132 20'. Cleavage: 7 and i-i, distinct; 1, in traces. Vertical planes usual ly striated. Crystals often acicular. Twins : (1) twinning-plane 1-t (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, Hessen- berg). Occasionally compact, massive. 481 482 483 t3 i3 H/l Graves Mtuu , H.=6-6'5. G. =4-18-4-25. Lustre metallic-adamantine. Color ><-d dish-brown, passing into red; sometimes yellowish, bluish, \io,et, black ; rarely grass-green. Streak pale brown. Subtransparent opaque. 1 rac- ture subconchoidal, uneven. Brittle. Comp., Var. Titanic oxide, TiO 2 = Oxygen 39, titanium 61 = 100. Sometimes a lit cle 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 brownie,h-yello\v or red bead in R.F.. the violet only appearing after treatment of the bead with metallic tiu 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 nolet-color when concentrated. OXYGEN COMPOUNDS. ANHYDKOUS OXIDES. 277 Diff. Characterized by its peculiar sub-adamantine lustre, and brownish-red color. Differ* horn \ armaline, vesuvianite, augite in being entirely unaltered when heated alone B.B. SpecJfx gravity about 4, cassiterite 6*5. O'o black, opaque, and submetallic (arkaneite). Streak tmcolored grayish, yellowish. Brittle. 487 488 12 Arkansas. EUenville, N. Y. Miask, Ural. 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 (arkanaite f. 486) at Magnet Cove, Arkansas, sometimes altered to rutile by paramorphism ; at EUenville, Ulster Co., N. Y. ; at Paris, Maine. Schrauf has announced (Atlas Min., Reich. IV.) that he has found brookite to be monodinif, (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 orthorJwinbic. EUMANITE. From Chesterfield, Mass., may be identical with brookite. PYROLUSITE.* Polianite. Orthorhombic. /A/ = 93 40', O A 14 = 142 11' ; c : I : a = 0-776 : 1*066 : 1. Cleavage /and i-l. Also columnar, often divergent ; also granular massive, and frequently in reniform 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. Diff. 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 Flatten in Bohemia, and elsewhere. Occurs in the United States in Vermont, at Brandon, etc. ; at Conway, 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 7ri)p, fire, and Aww, to wash. CRBDHEBITE. Cu 8 Mn 2 9 , or 3CuO4-2MnO a . Foliated. Color black. Thuringia. OXYGEN COMPOUNDS. HYDKOCS OXIDES. 279 B. HYDROUS OXIDES. TURGITE. \ Compact fibrous and divergent, to massive; often botryoidal and sta- lactitic like limonite. Also earthy, as red ochre. i 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 limonite. Opaque. Comp. H,Fe 2 O 7 = Iron sesquioxide 947, water 5 -3=100. Pyr., etc. Seated 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 TJ. S. it occurs at Salisbury, Ct. DIASPORE. Orthorhombic. /A /= 93 42f ', O A 14 = 147 0-64425 : 1-067 : 1. v4 A l-l = 121 ?i', i-l A 1-5 = 104 14J', -&Al = 116 54'. Crystals usually thin, flattened parallel to i-l\ sometimes acicular; commonly implanted. Cleavage: i-l eminent; i-& 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-gray, 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. Oomp. H 2 A10 4 =Alumina 85'1, water 14'9=100 ; a little phosphorus pentoxide is often present. Pyr.j 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. Ob.s. Commonly found with corundum or emery. Occurs in the Ural; at Scbemnitz; at Broddbo near Fahlun; in Switzerland ; in Asia Minor, and the Grecian islands ; in Chestei Co., Pa. ; at the emery mines of Chester, Mass. ; IS". Carolina. Diaspore was named by Hauy from diaaTrtipu^ to scatter, alluding to the -asual decrepitation before the blowpipe, 280 DESCRIPTIVE MINERALOGY. GOTHITE. OrthorhomVc. /A 1= 94 52' (B. & M.) ; O A 1-t = 146 33' ; c : 15 : a = 0*66 : 1*089 : 1. In prisms longitudinally striated, and often flattened into scales or tables parallel to the shorter diagonal. Cleavage : braehydiagonal, very perfect. Also fibrous; foliated or in scales; massive; reniform; stalac- titic. iz i ii H.=5-5'5. G.=r 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 (NaddeUenstein}. It passes into (b) a variety with a velvety surface : the Przibramite (Sammelbiende) of Przibram is of this kind. Other varieties are columnar or fibrous, scaly-fibrous, or feathery columnar; compact massive, with a flat con- ch oidal fracture ; and sometimes reniforrn or stalactitic. Comp. H,Fe0 4 =H 6 FeO 6 + 2Fe0 3 Iron sesquioxide 89D, water 1(H=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 PyrrJiosiderite from rri-ppof, fire-red, and aidqpog, iron. "j MANGANITE. Orthorhombic. /A 1= 99 40', A l-l = 147 9f ; c : t> : a = 0-6455 : 1-185 : 1. Twins : twinning-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. JBL=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 6 MnO 6 + 2Mn0 3 =Manganese sesquioxide 89 '8 (=Mn 62 -5, 27 '3), water 10 '2=100. Pyr., etc. In the closed tube yields water ; otherwise like braunite. Obs. Occurs in veins traversing porphyry, at Ilefeld in the Harz ; in Thuringia ; Undenaes in Sweden; Christiansand in Norway; Cornwall, at various places; also in Cumberland, Devonshire, etc. 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 submetallic ; 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) Ochreous 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, Germ.)] or (b) oolitic. Comp. HaFe.Og^HeFeOe-f-FeOs^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. Pyr., 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 ; alsu 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 metnllic buttons, etc. MELANOSIDERITE. Near limonite, but containing 7 '39 p. c. Si0 2 , perhaps as an impurity. Cooke regards it as a very basic silicate of iron. G. =3'3Q. Westchester, Penn. XANTHOSIDSRTTE. H 4 Fe0 6 =Fe0 3 81*6, H 2 18-4=100; or H e FeO a (Ramm.). In fine needles. Color yellow, brown. Ilmenau ; the Harz. BEATJXITE. Occurs in concretionary grains. Color whitish to brown. Composition doubt- ful, perhaps Al(Fe)0 3 +2aq. Beaux, near Aries, France; near LakeWochein, Styria (wochei- nite) ; French Guiana. BRUCITE.* Ehombohedral. R/\E ^ Q 22', 6>Aj = 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. 282 DESCKIPTIVE 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 subtranslucent. Sectile. Thin laminae flexible. Comp. H 2 Mg0 3 =: 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 TJnst, 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. Monoclinic (DesCL). In small hexagonal crystals wi';h replaced lateral edges. Planes vertically striated. Cleavage : basal or eminent. Occa- sionally in lamello-radiate spheroidal concretions. Usually stalactitic, or small mammillary 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 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 hydrar^Ute. 2. Stalactitic ; gibbsite. Comp. H 6 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 Ural ; 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. PYROCimoiTE.H 2 Mn0 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.=5-6. G.=3'7-4'T. Lustre submetallic. Streak brownish-black, shining. Color iron-black, passing into dark steel-gray. Opaque. OXYGEN COMPOUNDS. HYDROUS OXIDES. 283 Gomp. Somewhat doubtful. Contains manganese oxide, with varying amounts of baryta, and potash (lithia), and also water. General formula, according to Rammelsberg, R 6 O 9 =RG +4MnO 2 , where R is Ka 2 , Ba or Mn. Analyses: O MnO BaO K 2 O H 2 O 1. Thuringen 11-43 65'76 16 '59 5-25 CuO 0-59, CoO 0'79, CaO 0'51 = 100'7S Olschewsky. 2. limenau 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. Obi 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 HaMnaOe^MnOa+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 ten silica, alumina, baryta. B. ASBOLITE, or Earthy Cobalt, is wad containing cobalt oxide, which sometimes amount* to 82 p. c. lAthiopJiorite, heterogenite, and rabdionile 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). Gr. =3' 1-3*2. Pyr.j etc. Wad reacts like psilornelane. 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, N. Y. There are large deposits of bog manganese at Blue Hill Bay, Dover, and other places in Maine. Earthy cobalt occurs at Riechelsdorf 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, 0'25, H a O 11 '58= 1 Var. ^Crystallized (pheuocrystalline), vitreous in lustre. 2. Flint-like, massive, or cryp- tocrystalline.j7 The first division includes all ordinary vitreous quartz, whether having crys- talline faces-fSrnot. 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. PHENOCBYSTALLINE OB VITJIEOUS VABIETIES. S 1. Ordinary Crystallized ; Rock Crystal. Coloitess quartz, or nearly so, whether in dis- tinct crystals or not. ,*-% Asteriated; Star quartz (Sternquartz, 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 be due to manganese. ^ 4. Rose. 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 corne in part from manganese. * 5. Yellow ; 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 oftfn 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. Cafs Eye (Katzenauge, Germ.). Exhibiting opalescence, but without prismatic colors, an effect due to fibres of asbestus. j, 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) chlcritic, 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. CBYPTOCRYSTALLINE VARIETIES. ^1. CJialcedony. Having the lustre nearly of wax, and either transparent or translucenu 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. Carnelifin. 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 irpaaov, 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 eubtranslucent or feebly translucent; sometimes dotted with white. Heliotrope, or ISaGd-bione, is the same stone essentially, with small spots of red jaspf-r, 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 rooks, and OAYGEN COMPOUNDS SILICA. 287 deriving their concentric waving courses from the irregularities of the walls of the cavity Owing also to the unequal porosity, agates may be varied in color by artificial means, ft. IT regularly clouded.. The colors various, as in banded agate. y. Colors due to visible impurities, including Moss-agate, filled with brown moss-like or dendritic forms distributed through the mass ; Dendritic, Agate, containing brown or black dendritic markings. There is also Agalized wood : v/ood 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 cufc 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. s 8. Sardonyx. Like onyx in structure, but includes layers of camelian (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, (e) 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 porpJiyry, 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. 13. Jfornstone (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 an I 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. Diff. Quartz is distinguished by its hardness scratching glass with facility ; infusibilitg not fusing before the blowpipe ; insolubility not attacked by water or the acids ; undeava- 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 relate J. 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, Piedtnont, 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 1 s eye, in Ceylon, the coast of Malauar, and also in the Harz and Bavaria. Heliotrope^ in Bucharia, Ta tary, Siberia. 288 DESCEIPTIVE iMINEKALOGY. In New York, quartz crystals are abundant in Herkimer Co. Fine dodecahedral crystala, 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. II., Sharon, Vt., Meadow Mount, Md., and Hot Springs, Ark., are othei localities of quartz crystal. For other localities, see the catalogue of localities in the lattet part of this volume. Hose quartz, at Albany and Paris, Me., Acworth, 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 Ellenville, 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. , Cal. Heliotrope occupies veins in slate at Bloomingrove, Orange Co. , N. Y. Several varieties of this species have long been employed in jewelry. The amttJiyst has 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 severa] 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. Bath). Cleavage O, imperfect. Crys- tals minute, commonly tabular (f. 507), formed by the prism and basal plane ; also frequently iu twins and trillings with (1) -J-, and (2) f 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 cou- choidal. Comp. Pure silica, or SiO 2 , like quartz. Pyr. B.B. infusible. Fuses in soda with effervescence, forming a colorless glass. Soluble ii a boiling saturated solution of sodium carbonate. Obs. First found in cavities in the trachyte from Cerro St. Cristoval, near Pachucft, Mexico. Also in the trachyte of the Siebengebirge, and in related rocks from many looalitiea. 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 (Ma*kelyne). 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 reuifonn. stalactitic, or large tuberose. Also earthy. H. 5-5-6-5. G.=l'9-2'3. Lustre vitreous, frequently subvitreous : often inclining to resinous, 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 or colors, or different colors by refracted and reflected light. Streak white. Transparent to nearly opaque. Comp. Silica, Si0 2 , as for quartz, the opal condition being one of lower degrees of hard- aess and specific gravity. Water is usually present, but it is regarded as unessential. It varies in amount from 2 to 21 p. c. ; or, moscly, from 3-9 p. c. Var. 1. Precious Opal. Exhibits a play of delicate colors, or, as Pliny says, presents various 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. Giraaol. Bluish-white, translucent, with reddish reflections in a bright light. 4. Common Opal. In part translucent ; (a) milk-white to greenish, yellowish, bluish; (b) Hesin-opal (Wachsopal, Pechopal, Germ.), wax-, honey- to ochre-yellow, with a resinoua 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, reniform, botryoidal, or stalactitic surface ; also passing into translucent, and whitish. 10. Fiotite, 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. Geyxerite 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-massive; 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. Tripotite. 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. Infusoi ial 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 Zimapan 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 (LasaulX). Occurs in minute, colorless, cubes coating sulphur crystal! from Girgenti, Sicily. Contains SiO 2 85 '3 p. c., S0 3 7 '2, H 2 O 2 '9 ; chemical nature doubt* t'ul. Turns black upon ignition, hence the name. 19 290 DESCEIPTIVE MINERALOGY. JL TERNARY OXYGEN COMPOUNDS. SILICATES. A. ANHYIE,OUS SILICATES. a. BISILICATES. GENEKAL FORMULA RSi(X (a) Amphibole Group. Pyroxene Section. ' ^~-~~^' ENSTATITE. BKONZITB. P*otob*stite. Ortliorhombic. 508 Bainle Norway 1 A I 88 16' and 91 44' (Breitenbach meteorite, v. Lang);c :b_:d = 0-58853 : 1-03086 :^ 1. Cleavage: I, easy ; i-l, 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 un- colored, grayish. Double refraction positive ; optic- axial plane brachy diagonal ; axes very, divergent, Comp., Var.MgSi0 3 =SOica 60, magnesia 40 -100; also(Mg,Fe) Si0 3 . Var. 1. WitJi little or no iron; Enstatite. 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} t 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 submetallic 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, ittOj, 0'28, FeO 5-77, MgO 35 '59, H 2 O -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 Eif el ; 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 denned the limits of this species, as here laid down. Named from 'ej/orraTTjs, an opponent, because so refractory. The name bronzite has priority, but a bronze lustre is not essential, and is far from universal. HYPERSTHENB. Qrthorhombic, /A 7=91 32, DesCloizeaux (Mt. I)ore) ; 01 40' T. Rath (amblystegite). Cleavage : l-l perfect, / and i-l distinct but inter rupted. Usually foliated massive. II. 5-6. G. 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 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 509 Si-ayish, brownish-gray. Translucent to nearly opaque, rittle. Optic-axial plane brachydiagonal ; axes very divergent; bisectrix negative. ff if Mt. Dore. Comp. (Mg,Fe}Si0 3 with Fe : Mg 1 : 5, 1:3, etc. If Fe to Mg=l : 2 the formula requires Si0 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 ; Eonsberg in Bohemia ; the Tyrol ; Elfdalen in Sweden ; Laacher See (amMytiegiU] 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 for hypersthene. DIACLASITE. Near bronzite ; differs in optical characters. (Mg,Fe,Ca)Si0 3 . Harzburg; Ouadarrama, Spain. WOLLASTON1TE. Tabular Spar. Tafelspath, Germ. Monoclinic. O = 69 48', /A 1 = 87 28', Oj\2-i = 137 48' ; c : ~b : d = 0-4338 : 0-89789 : 1. Fig. 510 in the pyroxene or normal position, but wi^ 1 the edge O/i-i the obtuse edge ; f. 511 in the position given the crys- tals u\ authors who make i-i the plane O, and 2-i the plane /. O A l- r= 160 30', O A l-i = 154 25', i-i A 2 = 132 54', i-i A 2 = 93 52'. Rarely in distinct tabular crystals. Cleavage : O most distinct ; i-i less so ; \.-i and \-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. Gr.^2'78-2'9. Lustre vitreous, inclining to pearly upon tlie 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-\ ; 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, DesCL 292 DESCRIPTIVE MINERALOGY. Comp. CaSiO s =: Silica 51*7, lime 48-3=100. Pyr., etc. Iii 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 Gorkum in Sweden ; in the Harz ; at Auerbach, in granular limestone ; at Vesuvius. In the U. S., in N. 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. ilica 4839, lime 22 '18, iron protoxide 29-43 = 100. Asteroite is a similar pyroxene con- taining also Mn (Igelstrom), Sweden. 4. Lime-Iron- Manganese- Zinc Pyroxene ; JEFFERSONITE. 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, 45-95, A10 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 2 51*50, A10 3 6-15, FeO 3 35, MgO 17'09, CaO 23*80 H,O 1*10=100*59. Looks like diopside. H.=6-5. G.=319. Hunt. Named from Aeivco;, white. Xf Aluminous tyme- 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, Si0 2 49-40, A1O 3 G'70, dfeO 3 7*83, MgO 13-06, CaO 21*88, Na,,O 0*74. H,O 0-50=100-11. a. J^assaitt! (or Pyrgom). Includes the green kinds found in metamorphic rocks. Named from tmelocality at Fassain Piedmont, which affords deep-green crystals, sometimes pistachio* grnen, 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 avyij, 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 diallajre 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 (diopside), Traversella, Ala in Piedmont; Sala, Tunaberg. Sweden ; Pargas ; Achmatovsk ; etc. Sahlite, Sala; Arendal; Degerde ; Schwarzen- berg; etc. Hedenbergite, Tunaberg ; Arendal. Augite, Fassathal ; Vesuvius; etc. in most dolerytic igneous rocks. In N. America common (see list of localities at the close of the volume).. Some localities are : In Mass. , at the Bolton quarries. In Conn. , at Canaan. In N. York, at Warwick, Mon- roe, Edenville, Diana. In N. Jersey, in Franklin. In Penn., 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. RSi0 3 ,R=:Nao,Fe, or Fe(Fe=3R); analysis by Rammelsberg. SiO 9 51-66, FeO 3 28'28, FeO 5'23, MnO 0-69, Na 2 12'46, K- 2 O 0'43, TiO I'll, ign 0-39=100'25 Kongsberg, Norway. ^GIRITE. 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, SiCK 50 '25, AlOj 1-22, Fe0 8 22-07, FeO 8-80, MnO 1'40, CaO 5 '47. MgO 1-28, Na.O 9 29, K 2 94 =100 "72. Also from Magnet Cove, Arkansas. RHODONITE. Triclinie, but approximately isomorphous with pyroxene. Cleavage : 1 perfect ; O less perfect. Usually massive. H.=5-5-6-5. G.=: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. Oomp., Var. MnSi0 3 = Silica 45'9, manganese protoxide 541= 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. Galciferous ; 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 ; FOWLEKITE. In crystals and foliated, the latter looking much like cleavable red feldspar ; the crystals sometimes half an inch to an inch through. /A 7=86 30', Torrey. G.= 3 '44, Thomson. Pyr., etc. B.B. blackens and fuses with slight intumescence at 2*5 ; with the fluxes gives 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 uoluble part becomes of a white color. Darkens on exposure to the air, and sometimes becomes nearly black. Obs. Occurs at Lougban, near Philipstadt in Sweden ; also in the Ilarz ; in the district of OXYGEN COMPOUNDS ANHYDROUS SILICATES. 295 FTatherinenberg- 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 p6$ov, a rose, in allusion to the color. BABINGTONITE. Triclinic. 9RSi0 3 +FeSi 8 O 9 , with R=Fe(Mn) : Ca(Mg)-2 : 3 (Ramm.). Analysis, Rammelsberg, Si0 2 51 '22, Fe0 3 11 '00, FeO 10 '26, MnO 7 '91, MgO 0'77, CaO 19*32, ign=0'44=100-92. Color greenish-black. Arendal; Nassau; Devonshire; Baveno. SPODUMENE.* Monoclinic. O= 69 40' /A/= 87, O A 24 = 130 30'. large. Cleavage: i-i very perfect; / also perfect; 1-i in traces ; in striae on i-l. 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 uncolored. Translucent subtranslucent. Frac- Crystal* ture uneven. Comp. 3RSi0 3 +4AlSi 3 9 ; R=Li a 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. Diff. 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 Uto, 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, Mast?. ; at Windham, Maine ; at Winchester, N. H. ; at Brookfield, Ct. PETALITE. 3Li 2 Si2O6+4A]Si 6 16 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=l : 4. H.=6-6'5. a *=2'5. Colorless; white. Uto, Sweden, Elba (castoritc) ; Bolton, Mass. Norwich, Mass. Am/phibole Section. ^L ANTHOPHYLLITB. / Orthorhombic. /A/= 125 to 125 3 25'. Cleavage: i-l perfect, 1 less so, i-l difficult. Commonly lamellar, or fibrous massive ; fibres often very Blender. H.=5'5. G.=3*l-3'2. Lustre somewhat pearly upon a cleavage sur- face. Color brownish-gray, yellowish-brown, brownish-green, sometimes Bubmetallic. Streak uncolored or grayish. Translucent to subtranslucent. Brittle. Double refraction positive; optical axes in the brachydiagonal section. 296 DESCRIPTIVE JVHNERALOGY. Comp (Fe,Mg)SiO 3 , Fe : Mg=l : 3=Silica 55 '5, magnesia 27*8, iron protoxide 16'7- 100. Pyr., etc B.B. fuses with great difficulty to a black magnetic enamel; with the fluxe gives reactions for iron ; unacted upon by acids. Obs. Occurs near Kongsberg in Norway, and near Modum. Also at Hermannschlag, Moravia. Anthophyllite Itears the same relation to the Amphibole Group that enstatite and hyper- sthene do to the Pyroxene Group. KUPFFERITE. Probably MgSiO 3 , with a little Fe. 1 A 7=124 30', hence an enstatite-Tiorn- Wtnde. Color emerald-green (chrome). Tunkinsk Mts. , Miask. Analysis of a similar min- eral from Perth, Canada, Thomson, SiO 2 57-60, A10 3 3'20, FeO 210, MgO 29'30, CaO 3'55. ign. 3-55=99 30. AMPHIBOLE.* HORNBLENDE. Monoclinic. C = 75 2', I^ 1= 124 30', O A 14 = 164 10', 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: twinning-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. 524 528 530 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 , Ho ; and R 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 j and they lead in general to similar subdivisions OXYGEN COMPOUNDS ANHYDKOUS SILICATES. 297 T. CONTAINING LITTLE OB NO ALUMINA. Magnesia- Isime Amphibole; TREMOLITE Grammatite. Colors white to dark-gray. In distiuct crystals, either longblacTecl of sEort and stout; long and thin columnar, or fibrous; also compact granular massive. 7A/=124 30'. H. =5 '0-6 '5. G. =2 9-3-1. 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 Tremolitety Pini, from the locality at Tremola in Switzerland. NEPHRITE. In part a tough, compact, fine grained tremolite, having a tinge of green 01 blue, and breaking with a splintery fracture and glistening lustre. H. =6-6 '5. G.=2 96-3'l. Named from a supposed efficacy in diseases of the kidney, from ve^pdc, kidney. It occuri 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, B. I., having the hardness 5 '5 is serpentine in composition. The jade of de Saussure is the sanssurite (see under ZOISITE) of the younger de Saussure. Another aluminous jade has been called jadeite (q. v.) by Darnour. Magnesia- Lime -Iron Amphibole; ACTINOLITE,. Strahlstein, Germ. Color bright-green and grayish -green. In crystals, either"~sTT6rT 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 asbcstiform actinolite and radiated actinolite. Actinolite owes its green color to the iron present. Iron- Magnesia Amphibole ; CDMMINGTONITE. 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)Si0 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, tine, 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 chrysotile, 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, Ramm. Resembles, anthophyllite 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) SMARAGUITE 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-iime 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 greenish saussurite, a rock. Aluminous Magnesia- Lime- Iron Ampldbole. (a) PARGASITE ; (b) HORNBLENDE. Colora bright, dark, green, and bluish-green to grayish-black and black. /A /=124 1-124 20'; G. =3 05-3 '47. Pargasite is usually made to include green and bluish-green kinds, occurring in stout lustrous crystals, or granular; and Hornblende 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 2 Os Fe0 3 FeO MnO MgO CaO NaoO K 2 H 2 0(ign) (1) 51-67 5 75 2-86 23-37 12-42 0-75 0-84 0-46=9812 (2) 41-98 14 31 5-81 718 14-06 12-55 1-64 1-54 0-26=9910 43-28* 6 31 6-62 21-72 113 3-62 9-68 314 2-65 0-48=98-63 * With 1-01 TiO a . Pyr., etc. The observations under pyroxene apply also to this species, it being impossible to distinguish the varieties by blowpipe characters alone. Diff, 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, lamellai 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 i-2 of pyroxene. Calculating from the angle /A /in pyroxene, 87 5', the angle of i-2 is precisely 124 30 , or the angle /A Jin 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 forms, 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. Aussig and Teplitz in Bohemia, Tunaberg in Sweden, and Pargas 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 Corsica. Some localities in the U. S. are : Carlisle, Pelhana, 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 Edenviile; near Amity ; in Rossie ; the variety pargaaite 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 ; asbestus 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. ABFVEDSONITE.^ Near hornblende, but contains alkalies. Analysis, Ramm., Greenland. SiO 2 51-22, 7ttO 3 tr.. Fe0 8 23 -75, FeO 7 '80, MnO 112, CaO 2'08, MgO 0-90, Na.O 10'58, K 8 O 0'68, ign 0-16=98-29. Greenland ; Brevig ; Arendal. CROCIDOLITE. Composition uncertain, near arfvedsonite. Analysis, Stromeyer, SiOj 61-22, FeO 34-08, MnO 010, MgO 2*48, CaO 0'03, Na- 2 7'07, H.O 4'80=99'78. Fibrous, asbestus-like. Sometimes altered to " Faserquarz." Color lavender-blue or leek-green. Orange river, So. Africa. Vosges Mts. GASTALDTTE. Monoclinic. Cleavage prismatic, 7 A 7 = 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 : formula R 8 AloSiOa7, with R = Fe,Mg,Ca.Na 2 . Analysis, Striiver, SiO, 5S'5o, A1O S 21-40, FeO 9'04, MgO 3'92, CaO 2 03, Na.O 4-77, K 2 tr=99'71. Occurs in chlorite late in the valleys of Aosta and Looano. GLAUCOPHANE. Monoclinic. Cleavage prismatic, l/\ 1 124 51'. H.=65. G. -3-0907 OXYGEN COMPOUNDS ANHYDEOUS SILICATES. 299 Color blue, bluish-black. Q. ratio for bases to silicon 1 : 2. Analysis from Zermatt. by Bodewig, SiO a 57-81, A10 3 12'03, FeO 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. O A 1 = 150 3' ; c = 0-499. Habit prismatic, the prisrn 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 kinds are called aquamarine; also apple -gree n ; greenish-yellow to iron-yel- low and honey -yellow. Davidsonite is nothing but greenish-yellow beryl from near Aberdeen ; and goxhenite is a colorless or white variety froin Goshen, Mass. Gomp Be 8 MSi a Oi8=Silica 66-8, alumina 191, 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. Berylp of gigantic dimensions have been found in the United States, in W. Hamp., at Acworth and Grat'ton, and in Mass., at Royalston ; but they are mostly poor in quality. A crystal from Graf ton, according to Prof. Hubbard, measures 45 in. by 24 in its diameter, and a single foot in length by calculation weighs 1,076 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, Si0 2 50'38, Zr0 2 15-60, Ta 2 O 6 0'35, FeO 6'37, MnO 1-61, OuO 9 23, Na 2 O 13-10, 01 1-48, H.O 1-25 =09 -37. West Greenland. EUCOLITE is similar, but contains also some of the cerium metals. Norway. POLLUCITE.* 3R,AlSi 4 O, a +2aq with R = mostly Cs(Na,Li). If Na : Cs=l : 2, then Si0 2 42-6, A1O, 18-2, Cs^O 33 4, Na 2 3-7, H 2 O 2-1=100. Isometric. Colorless. . Island of Elba with castcrite. 300 DESCRIPTIVE MINERALOGY. UNISILICATES. GENERAL 'FORMULA E-jSiO Orthorhombic. 533 534 Chrysolite Group. CHRYSOLITE.* Olivine. Peridot. = 94 2' ; O A \-l =128 28' ; c\l\a--= 1-2588 : 1-0729 : 1. O A 1-i = 130 26f. is A i-2, ov. i-l, = 130 2'. Cleavage : i-l rather distinct. Mas&ive 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 conchoid al. 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 jive 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, N. H. (hyalosiderite) ; in London Co., Va. ; in Lancaster Co., Pa., at Wood's Mine. The following are members of the Chrysolite Group : FORSTERITE. Mg 2 Si0 4 . Like chrysolite in physical characters. Vesuvius. BOLTONITE, essentially the same. Bolton, Mass. MONTICELLITE, from Mt. Somma, and BATRACHITE, from the Tyrol, are (Ca,Mg) 2 Si0 4 , with Ca : Mg=l : 1. H. =5-5 "5. G-. =3 '03-3 -25. Monticellibe also occurs in large quantities (v. Rath) on the Pesmeda Alp, Tyrol, altered to serpentine and fassaite. FAYALITE. Fe 2 Si0 4 . G. =4-4'14. Color black. In volcanic rocks at Fayal, Azores ; Mourne Mts., Ireland. HORTONOLITE. (Fe,Mg) 2 Si0 4 , with Fe : Mg 3 : 2. O'Neil mine, Orange Co., N. Y. TEPHROITE- Mn,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.) Si0 2 47-03, A1O 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 (Ramm.) Si0 2 43'66, AlO 3 (Fe0 3 ) 1-57, BeO 11'74, CaO 28-74, 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, Norway. WOIILERITE. Composition given by the analysis (Ramm. ) SiO 2 28-43, Cb 2 O B 14-41, ZrO| 19-63, CaO 26-18, FeO(MnO; 2'50, Na 2 O 7'78=98'93. Monoclinic. G.=3'41. Color light- yellow. Near Brevig. Norway. OXYGEN COMPOUNDS ANHYDROUS SILICATES. 301 Willemite Group. WILLEMITE. Rhombohedral. Rf\R = 116 1', 0/\R = 142 IT ; c = 0-C7378. Cleav- age: t-2 easy in IS". Jersey crystals; 6> easy in those of Moresnet. Also massive and in disseminated grains. Sometimes fibrous. II. = 5-5. G. = 3'89-4*18 ; 4'27, transparent crystals (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 ^fraction 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 trooatite ; 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 0. F., 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 ziucite 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). \ DIOPTASB. Emerald-Copper. Khombohedral; tetartohedral. It A 72=126 24'; O/\=l8 38' c = 05281. Cleavage: It perfect. Twins: twinning- plane R. Also massive. 536 H.=5.. G.=3-278-3-348. Lustre vitreous. Color emerald-green. Streak green. Transparent subtrans- lucent. Fracture conchoidal, uneven. Brittle. Double //r\ -2 refraction strong, positive. Comp. Q. ratio for Cu : Si : H=l : 2 : 1 ; formula H 2 CuSi04 (Ramm.)r= Silica 381, 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 ; Durango, Mexico. 302 DESCRIPTIVE MINERALOGY. FBIEDELITE. Ehombohedral. A 72=147; J?A.Z?=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 7*87=100 This corresponds to the formula Mn 4 Si 3 O 10 +2HoO. 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 Oii= R>Si0 4 . This requires Si0 2 36'00, MnO 56'80, H 2 7'20=100. Occurs with diallogite and alabandite at the manganese mine of Adervielle, Hautes-Pyrenees. (Bertrand, C. R. , May, 1876.) HELVITE.* Isometric : tetraliedral. Cleavage : octahedral, in traces. H.= 6-6-5. G.= 3-1-3-3. 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, Si0 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. II. =z 5-5-6. G.= 3*427. Lustre vitreo-resinous. Color flesh-red to gray. Streak similar, but lighter. Translucent. Fracture subconchoidal, uneven. Brittle. Comp 8(Be,Fe,Mn 1 Zn)^iO4^-CFe,Mii,Zn)S. Analysis : J. P. Cooke, Rockport, SiO 2 81-73, FeO 27 '40, MnO 6 28, 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. EULYTITE (Kieselwismuth, Germ.). Isometric, tetrahedral; in minute crystals often aggregated together. H. =4-5-5. G. =6-106. Color grayish-white to brown. Comp. A uni- eilicate 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). BISMUTOFERKITE. Cryptocrystalline; generally massive. H.=35. G.=4-47. Colo* alive-green. Analysis (Frenzel) Si0 2 24 '05, FeO 3 33-12, Bi 2 O 3 42 "83 =100. Schneeberg. Hypochlorite is hornstone mixed with the above mineral and other impurities. Garnet Group. >J A GARNET.* Granat, Germ. j Isometric; dodecahedron, f. 537, and the trapezohedron 2-2, f. 538, the most common forms; octahedral form very rare. Distorted forma OXYGEN COMPOUNDS ANHYUKOUS SILICATES. 303 shown in f. 345-352, pp. 105, 106. Cleavage: dodecahedral, sometimes quite distinct. Twins: twiiming-plane octahedral. Also massive; granular, coarse, or fine, and sometimes friable ; lamellar, lamellae thick and bent. Also very compact, crypto-crystalline like sausstirite. 538 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 Oi 2 . There are three prominent groups, based on the nature of the predominating sesquioxide. I. ALUMINA GARNET, in which aluminum (Al) predominates. II. IKON GABNET, in which iron (Fe) predominates, usually with some aluminum. III. CniiOME GARNET in which chromium (r) is most prominent. There are the following varieties or subspecies, based on the predominance of one or anothei of the protoxides : A. GROSSULARITE, or Lime-Alumina garnet. B. PYROPE, or Magnesia- Alumina garnet. C. ALMANDITE, or Iron- Alumina garnet. D. SPESSAIITITE, or Manganexe- Alumina (tar net. E. ANDRADITE, or Lime-Iron garnet, including 1, ordinary; 2, manganesian, or Rvihojfite ; 8, yttriferous, or Ttter-garnet. F. BREDBERGITE, or Lime- Magnesia- Iron garnet. G. OOVAROVITE, or Lime- Chrome garnet. 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 CaaAlSisOio^ 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 hi other garnets, or absent. Formula (M^Ca.Fe^n^AlSiaOia. The original pyrope is the kind containing chromium. In the analysis of the Arendal magnesia -garnet, Mg : Ca : Fe+Mn=3 : 1 : 2; Si0 2 42'45, A10 3 22 '47, FeO 9 29, MnO (5'27. MgO 13 "43, CaO G'53= 100 -44 Wachlj. G. =3*157. The name pyrope is from TTI^WT^;, fire-like. C. Iron- Alumina garnet; ALMANDITE. A silicate mainly of aluminum and iron ^Fe); formula Fe 3 7V:lSi3Oi2 = 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, gcvrnet belongs to the AndracKU group, or is iron garnet. 304 DESCRIPTIVE MINERALOGY. D. Manganese- Alumina garnet; SPESSAKTITE. Color dark hyacinth-red (fr. Spessart), sometimes with a shade of violet, to brownish-red. G. =3*7-4 '4. Analysis, Haddam Ct SiO 2 36-16, A1 2 O 3 19-76, FeO 11 '10, MnO 3218, MgO 0'23, CaO 0'58=:100, Ramm. E. Lime- Iron garnet ; ANDRADITE^ Aplome. Color various, including wine-, topaz-, and greenish-yellow (topazolrEeT, apple-green, brownish -red, brownish -yellow, grayish -green, dark green, brown, grayish -black, black. G. =3. 64-4. Comp. CaaFeSisOis, this includes : (a) Topazolite, having the color and transparency oi topaz, and also sometimes green ; although resembling essonite, Dam our has shown that it belongs here, (b) Colophonite, a coarse, granular kind, brownish-yellow to dark reddish- Vrown in color, resinous in lustre, and usually with iridescent hues ; named after the resin colophony, (c) Melanite (named from p&as, black), black, either dull or lustrous; but al] black garnet is not here included. Pyreneite is grayish-black melanite ; the original afforded Vauqueliu 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^FeSisOia^Silica 37 2, iron sesquioxide 33'1, magnesia 12-4, lime 17-3 = 100. It corresponds \mder Iron garnet nearly to aplome under Alumina garnet. K Lime- Chrome garnet ; OUVAROVITE. A silicate of calcium and chromium. Formula Ca 3 6rSi 3 Oi 2 . In the Ural variety, a fourth of the chromium oxide is replaced by aluminum oxide; that is, Al : r=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 '5 in pyrope ; but ouvarovite is almost infusible, F.=6. Allochroite and almandite fuse to a magnetic globule. Reactions with the iluxes 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 fupe less readily than vesuvianite ; the vitreous lustre, absence of prismatic structure, and usually the form, are characteristic ; it has a higher specific gravity tl an tourmaline. Obs. Garnet crystals are very common in mica schist, gneiss, 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 (Exxonite), Ceylon; Mussa-Alp in Piedmont. Grossularite, Siberia; Tellemark, Norway; Ural. Almandite, Ceylon, Pegu, Brazil, and Greenland. Common garnet in large dodecahedrons, Sweden ; Arendal and Kongsberg in Norway, and the Zillerthal. Mtkmite at Vesuvius and in the Hautes-Pyrenees (Pyreneite}. Aplome at Schwarzeuberg in Saxony. Spessartite at Spessart in Bavaria, Elba, at St. Marcel, Piedmont. Pyrope in Bohemia, also at Zoblitz in Saxony. Ouvarovite in the Urals. In N. America in Maine, Phippsburg, Rumford, Windham, at Brunswick, etc. In N. IIamp., Warren. In Mass. , at Carlisle ; massive at Newbury ; at Chesterfield. In Conn. , trapezo- hedrons, -! 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 Keirns' 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 gems 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 ia sometimes employed as a substitute for emery. Vesuvianite Group. ZIRCON* Tetragonal. O A 1-i = 147 22' ; c = 0-640373, Haidinger. /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. JStreak un colored. Transparent to subtransluceut and opaque. Fracture conchoidal brilliant. Double refraction strong, positive. 545 546 Saualpe. McDowell Co., N. C. Var. The colorless and yellowish or smoky zircons of Ceylon have there been long 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. Coinp. 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 Fredericksviirn, 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. 0Al-t = 151 45'; c = 0-537199 (v. Kokscharof). 0Al = 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 plane O ; rarely in a pyramid or zirconoid ; sometimes the prism nearly wanting, and the form short pyramidal with truncated summit and edges. 306 DESCRIPTIVE MINERALOGY. IL = 047 i-5. G.= 3 '34:9-3 '4:5. 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 snbtranslucent. Fracture subconchoidal uneven. Double refraction feeble, axis negative. Sandford, Me. Comp., 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 3 ); ft= Al and also Fe. If we neglect the water the empirical for- mula is RsRjSivO^s, where the quantivalent ratio of bases to silicon is 1 : 1. The ratio of R : ft 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 37-32 38-40 16-08 13-72 FeO 3 3-75 5-54 FeO 2-91 MgO 2-11 6-88 CaO 35-34 35-04 Na. 0(K,O) 16 0-66 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. Ywk, at Amity. In N. Jersey, at Newton. In Canada, at Calumet Falls ; at Grenville. MELILITE from Capo di Bove, and HUMBOLDTILTTE from Mt. Somma, are similar in com- position. Analysis of the melilite by Damour. SiO , 38 '34, rUO 3 8 61, Fe0 3 10 '02, CaO 32 '05, MgO 6-71, Na 2 O 212, 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:; anieoinetric crystallization, and therefore biaxial polarization ; the dominant prismatic angle 112 to 117 ; fibrous forms, when they occur, always brittle ; colors white, gray, brown^ yellowish-green, and deep green to black, and some- times reddish. The prismatic angle in zoisite and other orthorhombic species is /A /; but in epidote it is the angle over a horizontal edge between the planes and t-, the orthodiagonal of epidot* corresponding to the vertical axis of zoisite, as explained under the latter species. OXYGEN COMPOUNDS ANHYDROUS k. ILJOATE8. 307 EPIDOTE, Pistazite. Monoclinic. O= 89 27' ; i-2 A 2 = 63 8', 6> A 14 = 122 C 23'; c : I : a = 0-43436 : 0-30719 : 1. O A 1-i = 154 3', 6> A -l-i = 154 15', t-i 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; \-i less so. Twins: twinning-plane 1-* ; also i-i. Also fibrous, divergent, or parallel ; also granular, particles of various sizes, sometimes fine granular, and forming rock-masses. 552 553 554 -If ft -k- 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 nncolored, grayish. Stibtransparent opaque ; generally subtranslucent. Fracture uneven. Brittle. Var. Epidote lias 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 speoies 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 Cerium-epidote. Comp. Quantivalent ratio for Ca : R : Si- 4 : 9 : 12, and H : Ca=l : 4. The formula is then H.Ca4ft 3 Si 6 O>o. R is Fe or Al, the ratio varying from 1 : 2 to 1 : 6. Analysis, Unter- Bulzbach, Tyrol, by Ludwig : SiO, 37 '83, A-1O 3 22-63, FeO 3 15 '05, FeO 0'93, CaO 23 '27, H 2 2 '05 = 100 '76. As first shown by Ludwig, epidote contains about 2 p. c. water, which ia 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 33 '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 tremolite. 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-roi-ks 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 , Zermatt 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 Ha^dam. DESCRIPTIVE MINERALOGY. In JN~. 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 St, Joseph. PIEDMONTITE (Manganepidot, Germ.). A manganese epidote ; formula, H.Ca t ft 3 Si e p 2 6, with R principally Mil (also Al,Fe). Color reddish-brown. St. Marcel, Aosta valley, Pied- mont. ALLANITE. Monoclinic, isomorphous with epidote. C 89 1' ; A 14 = 1 22 50J', i-2 A i-2 = 63 58' ; c : ~b : d = 555 0-483755 : 0-312187 : 1. Crystals either short, flat tabular, or long and slender, sometimes acicular. Twins like those of epidote. Cleav- age : i-i in traces. Also massive, and in angular or rounded grains. H. = 5-5-6. G-.=3-0-4-2. Lustre submetallic, 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. Var. 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 6p66$, 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,Na9,K 2 , etc.; ft=AlorFe. Analysis, allanite (Ramm.), Fredrikshaab, Si0 2 33 "78, A1O 3 14 '03, FeO 3 6 -36, FeO 13 "63, CeO 12-63, LaO(DiO) 5 "67, CaO 1212, H,0 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 galatinize with hydrochloric acid, but if previously ignited are not decomposed by acid. Obs. Occurs in albitic and common feldspathic granite, syenite, zircon- syenite, porphyry, 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 Thuringerwald. 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 N. 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. ZOISITB, Orthorhombic. /A 1 = 116 40', O A 14 = 131 If ; c:l:a = 1-1493 ; .l.'62125 : 1. Crystals lengthened in the direction of the vertical axis, and OXYGEN COMPOUNDS ANHYDROUS SILICATES. 309 Com rertieally deeply striated or furrowed. Cleavage: i-4 very perfect, monly in crystalline masses longitudinally furrowed. Also compact massive. H.=6-6-5. G.=3-ll-3-3S. Lustre pearly on *-* ; vitreous on surface of fracture. Color grayish- white, gray, yellowish, brown, greenish-gray, apple-green; also peach-blossom-red to rose-red. Streak uncolored. Transparent to subtrarisluecnt. Double refraction feeble, optic-axial plane i-i ; bisectrix positive, normal to i-l ; DesCl. Var. LIME-ZOISITE. 1. Ordinary. Colors gray to white and brown. 2. Hose-red, or Thulite. G. =3'124 ; fragile; dichro- ism strong-, especially in th.3 direction of the vertical axis ; in this direction reddish, transversely colorless ; from Norway, Piedmont. Sav&surite, which forms with smaragdite the euphotide of the Alps, is a lime-soda zoisite. Comp. A lime-epidote, with little or no iron, and thus differing from epidote. Q. ratu. as in epidote, H : Ca=l : 4, and Ca : ft : Si=4 : 9 : 12, whence the formula HoCa 4 R 3 Si 6 O26 Analysis, Ramm., Goshen (G.=3'341) SiO 2 4Q-06,7\10 3 3067, FeO 3 2'45, CaO 23'91, MgO 49, H 2 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.j 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 Fichtelgebm>e ; 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 ( Uniomte). 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 fdtsui ia perhaps the most prized 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. ILVAITE. Lievrite. Yenite. Orthorhombic. 1 A I -112 38', OM-l = 146 24' ; c : b : & = 0-66608 L'5004 : 1. O A 1 = 141 24', <9 A 2- = 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 Biibmetallic. 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 Ca2Fe 4 FeSi4Oi8. 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. Ram aiplsberg considered the water as due to alteration. 310 DESCRIPTIVE MINERALOGY Fyr., 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 acid. Obs. Found in Elba, and at the mine of Temperino in Tuscany. Also at Fossum and at Skeeu 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, Scmerville AIIDENNITE (Dewalquite). Near ilvaite in form. Habit prismatic; vertically striated. Composition given by the analyses, Lasaulx and Bettendorf, Si0 2 29 '60, A10 3 23 '50, MnO 25-88, Fe0 3 l'8, CaO 1'81, MgO 3"38, V^ 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, O 5 ) 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 in the Ardennes, Belgium. ROSCOELITE (p. 367) is another silicate containing vanadium. AXINITE. Triclinic. Crystals usually broad, and acute-edged. Making m = =98'94. Pyr., etc. In the closed tube gives water and reaction for fluorine. B.B. fuses with in- tumescence at 2-2*0 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 /*-/?, scale, after the earlier German name Schuppenstein, alluding to the scaly structure of the massive variety of Rozena. CRYOPIIYLLITE (Cooke). Q. ratio R : ft : Si=3 : 4 : 14, with R=Fe,K 2 ,Li,(Na,Rb,Cs,)> and R=A1. Orthorhonibic. In scales like the micas. Color by transmitted light emerald green. Cape Ann, Mass. Sea/polite Group. In the species of the Scapolite group, the quantivalent ratio varies from 1:1:2, 1:2:3, 1 : 3 : 4, to 1:2:4 and 1 : 2 : 6, but the species are 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. Gr.^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 g(57 and / rather perfect, but often interrupted. H. =5-5-6. G.=2'6-2-74r. Lustre vitreous. Colorless to white. Transparent to translucent ; often much cracked within. Comp. Q. ratio f or R : ft : Si=l : 2 : 3 ; formula R 6 R 4 Si 9 03e. If R= Ca : Na 2 = 10 : 1, and R=:A1 ; thid is equivalent to Silica 41 '6, alumina 81 '7, lime 24 !, soda 2-0 = 100. Neminar has found that meionite loses 1 p. c. water at a very high temperature, so that R must be also replaced by SL> ; his analysis gives approximately the ratio 1 : 2 : 3. Pyr., etc. B.B. fuses with intumescence at 3 to a white blebby glass. Pecoraposed by acid withouo gelatinizing (v. Rath). Obs. Occurs in small crystals in geodes, usually in limestone blocks, on Monte Comma, near Naples. 316 DESCRIPTIVE MINERALOGY. Tetragonal : WERNERITE.* Scapolite. = 156 UJ'; c = 0-4398. 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, H.=5-6. Gr.=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- con choidal. Brittle. Comp Q. ratio for R : R : Si 1 : 3 : 4 (R+R : Si 1 : 1); formula RRSi 2 O 8 =Ca(Na*)AlSi 2 O 8 . Analysis, v. Rath. Pargas, Si0 2 45 '46, A10, 30'96, CaO 17-22, Na 2 O 2-29, K 2 O T31, 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 metamorphic rocks ; sometimes ia beds of magnetite accompanying lime- stone. Some localities are : Arendal, Norway ; Wermland ; Pargas, Finland ; L. Baikal, etc. In the following those of ths wernerite and ekebergite are not yet distinguished. In Mass., 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 G. Calumet Id. ; at Huntersfcown ; Grenville. The following are other members of the scapolite group : SARCOLITE. 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 : 44, containing 6-8 p. o. soda. MIZZONITE. Q. ratio=l : 2 : 5, containing 10 p. c. soda. In crystals at Mb. Somma, DIPYRE. Q. ratio=l : 2 : 6, and for Ca : Na 2 =l : 1. MARIALITE. Q. ratio 1 {2:6, and for Ca : Na 2 =l : 2. NepJielite Group. NEPHELITE. Nepheline. Hexagonal. 569 0/\l = 135 55'; c = 0-839. Usual forms six-sided aiut 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. 11.1=55-6, 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. Var. 1. Glassy, or Sommite. Usually in small crystals 01 Vesuvius. grains, with vitreous lustre, first found on Mt. Somma, in thti region of Vesuvius. Davyne and cavolinite belong here. 3. Elceolile. In large coarse crystals, or massive, with a greasy lustre. I OXYGEN COMPOUNDS. - ANHYDROUS SILICATES. 317 Comp. Somewhat uncertain, as all analyses give a little excess of silica beyond what is 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 AlSio0 8 (Ramm.); some of the Na 2 being replaced by Ca. Analysis, Scheerer, Vesuvius, SiO, 44'03, A\0 3 33 -28, Fe0 3 (MnO 3 ) 0'65, CaO 177. Na.O 15'44, K 2 4'94, H 2 0-21 = 100-32. The variety Eiaolite has the same composition, Pyr., etc. B.B. fuses quietly at 3 '5 to a colorless glass. Gelatinizes with acidk 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 metamorphio rocks allied to granite and gneiss, the former mostly in glassy crystals or grains' (sommite), the latter massive or in stout crystals (dceolite). Nephelite occurs in crystals in the older lavas of Somma ; at Capo di Bove, near Rome ; in doleryte of Katzenbuckel, near Heidelberg, etc. Elseolite is found in Norway ; in the Ilmen Mts. ; Urals ; at Litchfield, Me. in the Ozark Mts. , Arkansas. Named nepheline by Haiiy (1801), from ve^e/lv, a doud, in allusion to its becoming cloudy when immersed in strong acid; elceolite (by Klaproth), from. EMIIOV, oil, in allusion to its greasy lustre. GIESECKITE is shown by Blum to be a pseudomorph after this species (see p. 330). .^ 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, grtiy, yellow, green, blue, reddish ; streak uncolored. Lustre subvitreous, or a little pearly 01 greasy. Transparent to translucent. COMP. Same as for nephelite, with some RC0 3 and water. Analysis, Whitney, Litchfield, Me., SiO a 3742, A1O 3 27'70, CaO 3'91, Na 2 O 20'98, K 2 O 0'Q7, C0 2 5-95. H,02'82, FeO, (Mn0 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.=r5-5-6. G.= 2 -136-2-4:01. Lustre vitreous, sontetimes inclining to greasy. Color gray, greenish, yellowish, white ; sometimes blue, lavender- blue, light red. JSubtransparent translucent Streak uncolored. frac- ture conchoidal uneven. Comp. 3Na 2 AlSi z 8 --2NaCl= Silica 371, alumina 31 '71, soda 25 '55, chlorine 7'31=101 65. Borne varieties contain considerably less chlorine. Pyr., etc. In the closed tube the blue varieties become white and opaque. B.B. f rises with intumescence, at 3 '5-4, to a colorlea# glass. Decomposed by hydrochloric acid, with separation of gelatinous silica. Obs. Occurs in mica slate, granite, syenite, trap, basalt, and volcanic rocks, and is often associated with nephelite (or elaeolite) and eudialyte. Found in West Q-reenland ; on Monte Somma; in Sicily; at Miask, in the Ural; near BreAig, Norway. A blue variety occuri 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. Sub transparent to translucent. Fracture flat conchoi- dal to uneven. f Gk v/ ri Comp. 2Na 2 (Ca)AlSi a 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 29'18, lime 10*62, soda 14-09, sulphui trioxide 11 '38, =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 "t at Niedermendig and Mayen, L. Laach, etc. NOSITE (Nosean). A sorfa-hauynite ; 2Na 2 AlSi 2 084-Na2S04, 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 " 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. Eath. c = O52637. Usual form as in f. 570, closely resembling a trapezohedron. Twins : twinning-plane 2-i ; crystals often very complex, con- sisting of twhined lamellae, as indicated by the stria- tions on the planes. Often disseminated ingrains; rarely massive granular. H.=5-5-6. G.=2-44-2-56. Lustre vitreous. Color white, ash-gray or smoke-gray. Streak 1111 colored. Translucent opaque. Fracture conchoidal. Brittle. Optically uniaxial ; double refraction weak, negative (from Aquacetosa), positive (from Frascati). Comp. Formula K. 2 AlSi 4 1 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. Fyr., etc. B.B. infusible ; with cobalt solution gives a blue cclor (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 tV 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 nd 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 re imbedded, are as clearly uometric, 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 ridered as entirely decided. OXYGEN COMPOUNDS. ANHYDROUS SILICATES. 319 Feldspar Group* The feldspars are characterized by specific gravity below 2*85 ; hardness 6 to 7 , fusibility 3 to 5 ; oblique or clinohedral crystallization ; prismatic angle near 120 ; two easy cleavages, one basal, the other brachydiagonal, 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 R : 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 tho alkali metals, and becoming greatest when alkalies are the only protoxides. The included species are as follows : Crystallization. Appro*. Q. ratio B,R,"SL ANORTHITB Lime feldspar Triclinic LABHADORITE Lime-soda feldspar l * 1 HYALOPIIANK Baryta-potash feldspar Monoclinic 1 ANDESITE Soda-lime feldspar Triclinic 1 OLIGOCLASE ** *' 1 ALBITE Soda feldspar " 1 ORTHOCLASE Potash feldspar Monoclinic 1 4 8 8 9 12 12 To the above list should be added, according to DesCloizeaux, the triclinic, 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 alkali ; 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/lit^ p 326, and the description of microdine, p. 326). The unisilicate ratio of 1 : 1 for bases and silicon is found in anorthite only, as shown above. With Ca alone, as in this species, the Q. ratio for Al and Si is 3 : 4 ; with Na 2 alone, 3 : 12; and for kinds containing combinations of the two, exact combinations of these ratios, nCa, 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 triclinia feldspars is assumed: anorthite CaAlSi 2 Oi), and albite Na 2 AlSi 6 Oi , and the other species (sometimes embraced under the general term PLAGIOCLASE) are regarded as due to isomor- phous mixtures of these two members in different proportions. They have thtn the general formula j ^(Naa^SieOi',,)' Forlabradc -' ite the ratio of m * n ia 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 -M : Si= 1 : 2-303 ; for Ca : Na=3 : 1, Al : Si=l : 1 '257 ; for Ca : Na=l : 1, Al : Si=l : 3'33 ; foi Ca : Na=l : 3, Al : Si=l : 4'4 ; for Ca : Na=i : 6, Al : Si=l : 5. This method of viewing the feldspar species has the advantage of explaining the wide varia- tion in their composition, and is generally accepted among German mineralogists. DesCloi- zeaiix regards his observations upon the optical characters of the feldspars (see p. 298) at showing that they are in fact distinct species, and not inde terminate isomorphous mixtures. 320 DESCRIPTIVE MINERALOGY. Optical properties of the triclinic feldspars. The following table contains the mole import- ant optical properties of the feldspar species as determined by DesCloizeaux (C. R., Feb. 8. 1875, and April 17, 1876). Bx=Bisectrix. , Acute bisectrix ANOBTHITE. always Position of the Bx. has no simple relation to the planes observed on the crys- tals. p < 0(-Bx.) Inclined. 84 58' 85 59' (Somma) LABEADOEITE. always 4- 30 40' 56 27-28 3725'-36 n 25' p > ;(+Bx.) Crossed; also slight in- dined. 88 15' 87 48' (Labrador) OLIGOCLASE. generally sometimes + 18 10' 68 Line parallel to the edge 0\i-i. u u p < (+Bx.) Crossed; also slight in- clined. 89 35' 88 C 31' (Sunstone, Tvedestrand) ALBITE. always + 15 78 35' 20 96 28' (front) p < r(+Bx.) Inclined ; probably also slight hori- zontal. 80 39' 81 59' (Roc tourne) MICHOCLINE. always 15 26' 5 6' P < 0(+Bx.) Horizontal (-Bx.) also inclined (+BX.) 87 54' Amazonst'ne, Mursinsk. Angle made by the+Bx. with a normal to i-i (g) Same, with normal to 0(p} Angle made by the line in which the plane of the optic-axes cuts*-*, with edge i-l/0(g' /p). Same, with edge i-l I Ordinary dispersion Parallel or perpendicular to plane of polariza- tion. Optic-axial angle (in air) for red rays, . . . for blue rays 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.) is 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 aibite, 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-i) ; for orthoclase and microline in simple cry state, 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 microcliue 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 macle (micro- cline in bands), or at 15 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 lamellaB. It follows from this that a plane normal to the plane of the axes cuts the base along a line making with the edge O/t-t the following angles : in orthoclase, 15 27' in microcline, 3 !()' in albite, 5* 12' in labradorite. A variation of one ot two degrees from the above mean angles was observed in somi peoimens. See further on p. 426. OXYGEN COMPOUNDS ANHYDROUS SILICATES. 321 Diff. The feldspars are distinguished from other species by the characters already stated, prominent among which are : cleavage in two directions, nearly or quite at right angles tt each other ; also hardness, etc. The triclinic feldspars can in most cases be distinguished from orthoclase by the fine stria- tion 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 sr&tion in polarized light, the alternate bands of color showing the same fact. The separation of the different triclinic 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. c:l:& = 0-86663 : 1-57548 : 1. /A 1' = 120 31', O A *, (over 2-2)=94 10', Ol\I' = 114 6$', O f\ I = 110 40', A 24 = 98 46' ; a = 93 13V, ft - 115 35$', y = 91 114' Cleavage : 0, i-l perfect, the latter least so. Twins similar to those of albite. Also mas- sive. Structure granular, or coarse lamellar. H. .6-7. G.=2-6G-2-78. Lustre of cleavage planes inclining to pearly ; of other faces vitreous. Color white, grayish, reddish. Streak uricolored. 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. Comp. Q. ratio for R : Al : Si=l : 3 : 4. Formula CaAlSi 2 O 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. By town, Canada. LABRADORITE. Triclinic. 1/\I = 121 37', r^i-l = 93 20', 6>A /= 110 50', OM = 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 cryptocrystaliine 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 un colored. Translucent sub trans- lucent. Comp., Var. Q. ratio for R : Al : Si 1 : 3 : 6, but varying somewhat (see p. 319). Formula RMSi 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. Play of colors either -wanting, an SQL 322 DESCRIPTIVE MINEJRALOGT. 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 striag, 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 (Remch). The various forms of minerals (microplukites, 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 ccloiiess glass. Decomposed with difficulty by hydrochloric acid generally leaving a portion of undecomposed mineral. Ob.3. 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 formations 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 probably of the Vosges. Being a feldspar containing comparatively little silica, it occurs mainly in rocks which include little or no quartz (free silica). Kiew has furnished fine specimens ; also Labrador. It is met with in many places in Canada East. Occurs at Essex Co., N. Y. ; also in St. Lawrence, Warren, Scoharie, and Green 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 (Labradorstein), and also chatoyant, opaline, or Labrador feldspar. Labradorite receives a fine polish, and owing to the chatoyant reflections, the specimens are often highly beaiitiful. 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-t, left, 87-88, O A /= 1H-112, O A /' = 115, If\i-i = 119-120, I' /\i-l =120, 6>A2-i = 101 -102 . Twins: resembling those of albite. Sel- dom in crystals. Cleavage more uneven than in albite. Also granular massive. ll.=5-6. G.= 2-61-274:. Color white, gray, greenish, yellowish, flesh- red. Lustre subvitreous, inclining to pearly. Oomp, Q. ratio 1:3:8, but varying to 1 : 3 : 7. General formula RAlSi 4 Oi 2 ; R=Nas 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 1'Esterel, 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 analyses point to a feldspar having the composition given above. HYALOPHANE. Monoclinic, like orthoclase, and angles nearly the same. 6 r =64r16', f A / = 118 41', A l-i => 130 55Y Cleavage : O perfect, i-l somewhat less so. In small crystals, single, or in groups of two or three. OXYGEN COMPOUNDS ANHYDROUS SILICATES. 323 H.--6-6'5. G.=2'80, transparent; 2-905, translucent. Lustre vitreous, or like that of adularia. Color white, or colorless ; also flesh-red. Trans- parent to translucent. Comp. Q. ratio for R : R : Si=l : 3 : 8. Formula (Ba,Ko)AlSi 4 Oi 2 . Analysis of hyalo- phane from the Binnenthal by Stockar-Escher, SiO 2 52'67, A10 3 21-12, MgO 0'04, CaO 0-46, BaO 15-05, Na 2 2-14, K 2 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 at Jakobsberg in Sweden. OLIGOOLASE. Triclinic. /A T = 120 42', A M, ov. 2-i' = 93 50', A /= 110 55', A I = 114 40'. Cleavage : O, i4 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 aventurine. Transparent, subtranslucent. Fracture conchoidal to uneven. Comp., Var Q. ratio for E : Al : Si=l : 3 : 9, though with some variations (see p. 297). Formula RMSiOi 4 , with R=Na2(K 2 ),Ca The ratio of 3 : 1 for Na : Ca corresponds in this formula to Silica 61 -9, alumina 241, lime 5'2, soda 8-8=100. Var. 1. Cleavable; in crystals or massive. 2. Compact massive ; oUgoclase-felsite; includes part, at least, of the so-called compact feldspar or fdsite, consisting of the feldspar in acorn- pact, either fine granular or flint-like state. 3. Aventurine oligoclase, 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 35 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 granite-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 Mb. Somma ; as sunstone at Tvedestrand, Norway; in Iceland, colorless, at Hafnefjord (hufnefiordite). 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 o/uj'% little, and /c/ldw, to cleave. TSCHERMAKITE (v. Kobell). Supposed to be a magnesia-feldspar, but the conclusion was probably ftased on the analysis of impure material. Later investigations (Hawes, Pisani) make it an oligoclase. Occurs with kjerulfine from Bamle, Norway. ALBITE.* Triclinic. 1 A T = 120 47', O A i-i = 93 36', A /' = 114 42', <9 A / = 110 50', A 2-$' =136 50', A 24 = 133 14'. Cleavage: O, i-l perfect, the first most so ; 14 sometimes distinct. Twins: twimi ing-plane i-i, axis of revolution normal to i-l 9 this is the most common method, and its repetition gives rise to the fine striations (p. 91) upon the plane O, which are so characteristic of the triclinic feldspars ; t winning-plane, 2-i (f. 578) 324 DESCRIPTIVE MINERALOGY. analogous to the Baveno twins of orthoclase; also twinning-axis, the vertical axis (f. 575) ; twinning-axis, the macrodiagonal axis* (&), ihepericli?ie twins. Double twins not uncommon. True simple crystals very rare. Also mas-, sive, either lamellar or granular ; the laminae sometimes divergent ; granulai varieties occasionally quite fine to impalpable. 573 574 575 579 Pericline. Middletown, Ct. H.==6-7. G.s=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 a :A:lSi 6 0, 6 =SilicaG8-G, alumina )-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 1 '. (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 G. =2 '(526 ; 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. LameUar ; 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 gems, including beryl, tourmaline, allanite, columbite, etc. It occurs also in some \rachyte, in phonolyte, in granular limestone in disseminated crystals, as near Modane in feavoy. 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. Tork, 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 species by Gahn and Ber/elius 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. Jfontclinic. O= 63 53', /A 7 = 118 48', O A 14 = 153 28'; b : I : d = 0-844 : 1-51S3 : 1. O A 1-i = 129 41', A 2-a = 99 38', O A 2 == 98 4'. Cleavage : (9 perfect; i-l less distinct; 2-2 faint; also imperfect in the direction of one of the faces 7. Twins: twinning-plane, i-i (Carlsbad twins) f. 582, but the clinopinacoid (i-l) the composition -face (see p. 98) ; twinning-plane the base (O) L 583; also the clinodorne, 24 (Baveno twins), as in f. 588, in which the prism is made up of two adjoining rjlanes O and two i-l, and is nearly square, because O A i-l = 90, and O A 24 = 135 3'; It\ 1= 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 cry pto-cry stall in e, 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 un colored. 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. Comp., Var. Q. ratio for K : Al : Si=l : 3 : 12. Formula K 2 A1 Si 6 18 = Silica 647, 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 crystallization is normally monocJinio, 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, deavable, 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 albite and oligoclase. Sunstone, or aventurine feldspar : In part orthoclase, rest albite or oligoclase (q. v ). Amazonstone: Bright verdigris/green, and cleavable, mostly mixtures of orthoclase and microcline (Dx.). Kcenig concludes that the coloring matter of the Pike's Peak amazon- stone is an organic compound of iron, which has been infiltrated into the mass. Sanidin of Nose, or glassy feldspar (including much of 1*16 Ice-spar, part of which is anor 326 DESCRIPTIVE MINERALOGY. Ihite). Occurs in transparent glassy crystals, mostly tabular (whence the name from board), in lava, pumice, trachyte, phonolite, etc. Proportion of soda to potash varies from 1 : 20 to 2 : 1. tihyacoliteis the same ; the name was applied to glassy crystals from Mt Romma (Eisspath, *Wern.). Chesterlite. 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 microdine (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 2=112' 80', 0A/'=112 50', lAl' = 120* 20', /\i-l (deavage angle) =90, 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 \o<^, transverse, a?fd K\dca, I 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 inteiiaminated albite and orthoclase, as shown by Breithaupt. From Perth, Canada East. COMPACT ORTHOCLASK or ORTHOCLASE-FELSITE. This crypto- crystalline variety is com- mon and occurs of various colors, from white and brown to deep red. There are two kinds (a) the 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 Drachenfels on the Rhine. In the IT. States, orthoclase is found in N. Hamp, , at Ac worth. In Conn. , at Haddam and Middletown. In N. York, at Rossi e ; 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 Amazoustone 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 tridinic. Form generally like that of orthoclase. Cleavage basal and clinodiagonal, and also easy parallel to both prismatic faces (2 and 2') ; for the optical properties see p. 298. Often asso- ciated with orthoclase in regular parallel bands, especially in the amazonstone ; albite is also sometimes present, though irregularly. Analysis of a " pure microclina " from Magnet Cove by Pisani. Gr.=2-54. Si0 2 A1O 3 FeO s K 2 Na 2 O 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 Mta.; 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, Ark. ; it enclosed crystals of aegirite, and was not mixed with orthoclase. STJBSILIOATES.. Humite or Chondrodite Group, including three sub-species: I. Humite; II. Chondrodite; III. Clinohumite. The existence of three types of forms among the crystals of humite (Vesuvius) w), 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 thf- Swedish crystals (type II.) ; he, moreover, proved the orthorhombic character of the crystal*) of type I., Vesuvius. In accordance with these facts DesCloizeaux has proposed that the thre< types be regarded as distinct species, with the names given above. I. HUMITE.* Including type L, Scacchi, Vesuvius. Also rare crystals from Brewster, N. Y, The latter large, coarse, and having suffered more or less alteration. Holohedral. i-z (o 2 ) A i 2 = 130 19' ; O (A) A 3-1 (?) = = 124 16'; O A 3-2 (= Twins : twinning plane \-i (?) and f-^ (?), (both having a prismatic angle nearly 120) ; also the basal plane O (Brewster, K Y., f. 593). Optic-axial plane makes an angle of 26 with the base ; acute bis bisectrix DESCRIPTIVE MINERALOGY. positive, normal to the clinopinacoid (C). 2Ha 88 48' for red rays, Breweter, 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 rectangular DesCloizeaux makes the plane e*'=i-i, and r 4 /, r 2 1, r' A = 1. 593 594 Brewster. Brewster. Vesuvius. III. CLINOHUMITE. Including type III. of Scacchi, Vesuvius ; also rare finely polished red crystals from Brewster, N. Y. Monoclinic. A A A -2-*' = 135 13', 6> A 1 = 149 33', /A /front = 115 3', 2-1 A 24, ov. 0, = 115 21', fc A a-*, ov. -*, = 76 18', 44 A 44, ov. O, = 76 88. Cleavage : O distinct. Also botry- oidal and globular, having a columnar structure ; also divergent and radi- ating ; also massive, granular to compact. 612 613 614 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 iA\ 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 Compact OXYGEN COMPOUNDS ANHYDROUS SILICATES. 335 massive. White opaque, breaking with the surface of porcelain or Wedgewood ware. From the L. Superior region. 3. Botryoidal ; Botryoliie. 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 for H : Ca : B : Si=l : 2 : 3 : 4, like euclase: formula H,Ca 2 B a Si a Oio = 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 ts 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 Hill ; in the Lake Superior region, and on Isle Royale. San Carlos, Inyo Co., Cal., with garnet and vesuvianite. TITANITE.* SPHENK. Monoclinic. G = 60 17' = A i-i ; IM 113 31', A 14 = 159 39''; c : 5 : a = 0-56586 : 1*3251 : 1. Cleavage: 7 sometimes nearly per- fect ; i-i and 1 much less so ; rarely (m 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. 023 Ledbiite. Spinthere. Schwa rzenstein. II. 5-5*5. G.=3*4 3*56. Lustre adamantine resinous. Coloi 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 yery closely normal to 1-?* (x) ; double refraction strong ; axial divergence 53-56 for the red rays, 46-45 for the blue ; DesCl. " Comp,, Var. Q. ratio for Ca : Ti : Si=l : 2 : 2, or making the Ti basic (Ti=2R), R : Si s=3 : 2 ; formula (equivalent to RSi0 6 ) CaTiSi0 6 = Silica 30'61, titanic oxide 40'82, lime 28 -57 =100. Vur. Ordinary, (a) Titanite ; brown to black, the original being thus colored, also opaque or sub translucent, (b) SpJiene (named from ff^v, a wedge) ; of light shades, as yellow, green- ish, etc. , and often translucent ; the original was yellow. Manganesian ; Greenovite. 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 (pictite, Saus.); at Ala, Piedmont (ligurile) 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 Greuville, 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., 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. Urnen Mts. STAUROLITE. Orthorhombic. If\2= 129 20', A l-l = 124 46' ; c : I : & = 1-4406 : 211233 : 1. Cleavage : i-l distinct, but interrupted ; 1 in traces. Twins 627 cruciform: twinning-plane *-f (f. 628) ; %4 (f. 629); and f-f (f. 630). Fig, OXYGEN COMPOUNDS HYDROUS SILICATES. 339 Oomp. Composition varies much through impurities, as with other amorphous Bubstances, resulting from alteration. As the silica has been derived from the decomposition of othei silicates, it is natural that an excess should appear in many analyses. True chrysocolla cor- responds to the Q ratio for Cu : Si : H, 1:2: 2=CuSiO a +2aq= Silica 34-2, copper oxide 45'3, water 20 '5 = 100. But some analyses afford 1:2:3, and 1:2:4. Impure chrysocolla may contain, besides free silica, various other impurities, the color varying from bluish-green to 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 flame emerald groen, but is infusible. With the fluxes gives the reactions for copper. With soda 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 acids. 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 Schwatz in the Tyrol ; in Siberia ; the Bannat ; Thuringia ; Schneeberg, Saxony ; Kupfer- berg, Bavaria; South Australia ; Chili, etc. In Somerville and Schuyler's mines, New Jersey; at Morgantowu, Pa. ; at Cornwall, Lebanon Co. ; Nova Scotia, at the Basin of Mines ; also in Wisconsin and Michigan. DEMIDOFFITE ; CYANOCHALCITE ; RESANITE ; near chrysocolla. CAT APLEIITE. Analysis (Ramm.), SiO 2 39'78, Zr0 2 40'12, CaO 3'45, Na 2 7-59, H 3 O 9-24 =100 '18. Hexagonal. Color yellowish-brown, Lamoe, near Brevig, Norway. B. UNISILICATES. 13', A 14 = CALAMINE. Galmei; Kiesclzinkerz, Germ. Orthorhombic ; hemimorphic-hemihedral. /A /= 104 148 31', Daubar ; c : I : d = 6124 : 1-2850 : 1. Cleav- age : 7, perfect ; 0, 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. 1 : -J ; Zn 2 Si0 4 +aq=Silica 25 0, Oomp. Q. ratio for R : Si : H= zinc oxide 67 '5, water 7 '5 =100. Pyr., etc In the closed tube decrepitates, whitens, and gives off water. B.B. almost infusible (F.=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 f or 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 in Carinthia ; Retzbanya ; Schemnitz. At Roughten Gill in Cumberland ; at Alston Moor ; 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;l:&= 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.=2-8~2-953. 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 for R : R : Si : H=2 : 3 : 6 : 1, whence, if the water is basic, for bases and silicon, 1:1; formula H 2 Ca 3 AlSi 3 O 12 or Ca a AlSi 3 11 H-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. Coupholite, 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 ; JEdelf ors 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 take Superior copper region. CHLORASTROLITE and ZONOCHLORITE from Lake Superior are mixtures, as shown by Hawes. VILLARSITE. Probably an altered chrysolite. Formula R 2 Si0 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, Si0 3 34*66, FeO 27-05, MnO 25-60, CaO 0-52, MgO 0-93, H 2 8-31, Cl 4-88=101-85. In hexagonal tables. Color blackish-green. Nya-Koppai- berg, etc. , Sweden. AFOPHYLLITE.* 635 637 Tetragonal. O A \4 128 38'; c = 1-2515. Crystals sometimes nearly cylindrical or barrel- shaped. Twins : twin- ning-plane the octahe- dron 1. Cleavage : highly perfect ; I less so. Also massive and lamellar. H. = 4-5-5. G.=2-3- 2'4. Lustre of $, pearly; of the other faces vitre- ous. Color white, or grayish ; occasionally with a greenish, yellow- ish, or rose- red tint, flesh red. Streak uncolored./ Transparent; rarely opaque. Brittle. OXYGEN COMPOUNDS HYDROUS SILICATES. 341 Oomp. Q ratio for II : Si : H usually taken as 1 : 4 : 2, part of the oxygen replaced by fctiorine (F 2 ). According to Rammelsberg the ratio is 9 : 32 : 16 ; he writes the formula 4(H 2 CaSi 2 O 6 -faq)+KF. This requires: Silica 52 "97, lime 24-72, potash 5 '20, water 15'90, fluorine 2 < 10=100 "89. It maybe taken as a unisilicate if part of the silica is considered accessory. Pyr,, etc. In the closed tube exfoliates, whitens, and yields water, which reacts acid. ly the open tube, when fused with salt of phosphorus, gives a fluorine reaction. B.B. exfoliates, colors the flame violet (potash), and fuses to a white vesicular enamel. F. =1'5. Decom- posed by hydrochloric acid, with separation of slimy silica. Diff. Distinguishing characters : its occurrence in square prisms ; its perfect basal cleav- age, and pearly lustre on the base. Obs Occurs commonly in amygdaloid and related rocks, with various zeolites ; also occa- sionally in cavities in granite, gneiss, etc. Greenland, Iceland, the Faroe Islands, Andreas- berg, the Syhadree Mountains in Bombay, afford fine specimens. In America, found in Nova Scotia ; Bergen Hill, N. J.; the Cliff mine, Lake Superior region. CHALCOMORPIIITE (v. Rath}, from limestone inclosures in the lava of Niedermendig. Hexagonal. Essentially an hydrous calcium silicate. EDINGTONITE. Analysis by Heddle, SiO 3 36 -98, A1O 3 22'63, BaO 26 '84, CaO tr, Na 2 tr., H 2 12-46=98-91. Tetragonal. Dumbarton, Scotland. GISMONDITE. Analysis, Marignac, Si0 2 35 '38, A10 3 27'23, CaO 13 12, K 3 O2'85, H 2 O21'10 =100-18. Capo di Bove, near Rome ; Baumgarten, near Giessen, etc. CABPHOLITE. In radiated tufts in the tin mines of Schlackenwald ; Wippra in the Harz, Bases mostly in sesquioxide state (Al,Mn,iFe). SUBSILICATES. ALLOPHANE. Amorphous. In incrustations, usually thin, with a mammillary surface, and hyalite-like ; sometimes stalactitic. Occasionally almost pulverulent. H.=3. G.=1'85-1'89. Lustre vitreous to subresinous ; bright and waxy internally. Color pale sky-blue, sometimes greenish to deep green, brown, yellow, or colorless. Streak nncolored. Translucent. Fracture imperfectly conchoidal and shining, to earthy. Yery brittle. Oomp Q. ratio f or Al : Si : H, mostly 3 : 2 : 6 (or 5) ; zArlSi0 6 +6aq, or AlSiO 5 +5aq= Silica 23*75, alumina 40 '62, water 35 '63 = 100. Plumb attophane, from Sardinia, contains a little lead. The coloring matter of the blue variety is due to traces of chrysocolla, the green to mala- chite, and that of the yellowish and brown to iron. Pyr., etc. Yields much water in the closed tube. B.B. crumbles, but is infusible. Gives a blae color with cobalt solution. Gelatinizes with hydrochloric acid. Obs. Allophane is regarded as a result of the decomposition of some aluminous silicate (feldspar, etc.) ; and it often occurs incrusting fissures or cavities in mines, especially those of copper and limonite, and even in beds of coal. Found at Schneeberg in Saxony ; at Gers- bach ; at the Chessy copper mine, near Lyons; near Woolwich, in Kent, England. In the U. S. it occurs at Richmond, Mass. ; at the Friedensville zinc mines, Pa. , etc. COLT.YRITE A hydrous silicate of aluminum. Clay -like in structure, white. Hove, England ; Schemnitz. URANOPHANE, from Silesia, and UBANOTILE , from Wolsendorf, Bavaria, are silicates con taiiiing uranium. 342 DESCKIPTIVE MINERALOGY. II. ZEOLITE SECTION. Orthorhombic. THOMSONITE. Comptonvze. /A 1= 90 40' ; O A 14 = 144 X ; c : I : d =0-7225 : 1-0117 : 1. Cleavage: i-l easily obtained ; i-l 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. Vitreous, more or less pearly. Snow-white; impure varieties brown. Streak uncolored. Transparent translucent. Fracture uneven. Brittle. Pyroelectric. Double refraction weak ; optic- axial plane parallel to O\ bisectrix positive, normal to i-i ; divergence 82-82i for red rays, from Dumbarton ; DesCl. Var Ordinary, (a) In regular crystals, usually more or less rectangular in outline, (b) Tn slender prisms, often vesicular to radiated, (c) Radiated fibrous, (d) Spherical concre- tions, 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 2 ) : R(A1) : Si : H=} : 3 : 4 : 2-, Ca : Na 2 =2 : 1, or 3 : 1 ; formula 2(Ca,Na 2 )AlSi 2 O b -)-5aq. Analysis, Rammelsberg, Dumbarton, SiO 2 38'09, A1O 3 31-62, CaO 12-60, Na 2 O 4'62, H 2 13-40=100-20. Pyr., etc. At a red heat loses 13 '3 p. c. of water, and the mineral becomes fused to a white enamel. B. B. fuses with intumescence at 2 to a white enamel. Gelatinizes with hydrochloric acid. Obs. Found in cavities in lava and other igneous rocks ; and also in some metamorphic rocks, with elaeolite. Occurs near Kilpatrick, Scotland ; in the lavas of Soinma (comptonitf) ; in Bohemia ; in Sicily ; in Faroe ; the Tyrol, at Theiss ; at Monzoni, Fassathal ; at Peter's Point, Nova Scotia ; at Magnet Cove, Arkansas (ozarkite). Orthorhombic. 640 NATROLITE. Mesotype. Nadelzeolith, Germ. 1 A 7=91, O A 1-1 = 144 23'; c : : d = 0-35825 : 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-l; bisectrix positive, parallel to edge i< '.p. 94-9f> rprl ra.va fnr A nvpvo-iiP If I\ axial divergence crystals ; 95 12' for brevicite red rays, for Ativergn DesCl. Comp. Q. ratio for R : R : Si : H 1 : 3 : 6 : 2 ; and for R : Si^ 2 : 3(R=:N'a 2 ,3Rr=R-) ; formula N"a 2 AlSi 3 10 +2aq Silica 47'29, alumina 26 -6, soda lO'SO, 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 ^ame of an ordinary stearine or wax candle. Gela feiuizes with acids. OXYGEN COMPOUNDS HYDROUS SILICATES. 343 Ditf, Some varieties resemble pectolite, thoinsonite, 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. O= 89 6', /A 1= 91 36', A 14 = 161 16J' ; = 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. H. =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 antilogue pole. Double refraction weak ; optic-axial plane normal to i-l ; divergence 53 41', for the red rays ; bisectrix negative, parallel to i-l ; plane of the axis of the red rays and their bisectrix inclined about 17 8' to i-i, and 93 3' to l-i. Comp. Q. ratio f or R : R : Si : H=l : 3 : 6 : 3 ; forR(3R=R) : Si=2 : 3, as in natrolite ; R=Ca,R-=Al; formula CaAJSi 3 Oio+3aq= Silica 45'8o, alumina 26'13, lime 14-26, water 13-76= 100. Pyr., etc. B.B. sometimes curls up like a worm (whence the name from o7ew\7j, a worm, which gives scolecite, and not scoJ^site 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 Staff a ; in Skye, at Talisker ; near Poonah, liindostan (Poonahlite) ; in Greenland ; at Pargas, Finland, etc. MESOLITE. (Ca,Na 2 )AlSi 3 Oi +3aq (5 p. c. Na 2 0). Near scolecite. Iceland ; Nova Scotia. LEVYNITE. Rhombohedral. Q. ratio forR : R : Si : H=l : 3 : 6 : 4. Analysis, Damour, Iceland, SiO a 45'76, A10 3 23'56, CaO 10 57, Na a O 1'36, K 2 O 1-64, H a O 17 "33 =100-22. Ire- land ; Faroe ; Iceland. ANALCITE.* Isometric (?). Usually in trapezohedrons (f. 54, p. 18). Cleavage, cubic, in traces. Also massive granular. II.=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. Comp. Q. ratio f or R : R- : Si : H=l : 3 : 8 : 2, R=Na 2 , R=A1=3R ; R : St=l : 2. For mula Na a AlSi 4 Oi9 + 2aq=Silica 54 -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. Gelati- nizes with hydrochloric acid. Diff. Distinguishing characters : crystalline form ; absence of cleavage ; fusion B.B. with- out intumescence to a clear glass (unlike chabazite). Obs. Some localities are : the Tyrol ; the Kilpatnck 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 ol rrieueck, Bohemia, is properly tetragonal; th implest crystals showing evidence of repeated twinning. DESCRIPTIVE MINERALOGY. FAUJASITE. An octahedral zeolite from the Kaiserstuhlgebirge. Analysis, Damour SiOi 16-12, AlO a 16-81, CaO 4"79, Na 2 5 "09, H 2 O 27'02=99'83. EUDNOPHITE. Near analcite. In syenite near Brevig, Norway. PILINITE. In slender needles (orthorhombio) ; white ; lustre silky. Analysis Si0 2 55*70. AlO 3 (FeO 3 ) 18-64, CaO 19.51, Li 2 (1-18), H 2 O 4 "97=100. In granite of Striegau, Silesia (Laaaulx). CHABAZITE.- Rhombohedral. R A R = 94 46', O/\R = 129 15' ; c = 1-06. Twins : twinning-plane O, very common, and usually in compound twins, as in f. 6M ; 'also It, rare. Cleavage rhombohedral, rather distinct. 642 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 Aridreasberg) 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. Acadialile, 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 lean} ; the original was from Leipa in Bohemia; Rf\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 (H,K) 2 CaAlSi 5 O 15 +6aq, where the Q. ratio for R : R : Si=2 : 3 : 10, R = H,,Na 2 , Ca; or (3R=R), 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 offervesce 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 acadialite}, 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 pkacolite ; and he suggests the same may be true of HEBSCHELITE, from Act Castello, Sicily. OXYGEN COMPOUNDS HYDROUS SILICATES. 345 GMELINITE. Hhombohedral. 0'7254. Crystals usually hexagonal in aspect ; some- times habit rhombohedral ; i often horizontally stri- ated. Cleavage: $ perfect. Observed only in crystals, and never as twins. H.=4-5. GL=2<04-2-17. Lustre vitreous. Colorless, yellowish-white, greenish- white, reddish-white flesh- red. Transparent to trans- lucent. Brittle. = 112 26', 645 O A-l =140 3'; 6 646 C. Blomidon, etc. C. Blomidon. Comp. Q. ratio f or R : B : Si : H=l : 3 : 8 : 6, R=Ca(Na 2 ,K 2 ), B=A1. Formula (Ca,Na 2 ) MSi 4 12 +6aq. Analysis by Howe, Bergen Hill, SiO 2 48'67, iU0 3 18-72, Fe0 3 010, CaO 2-60, Na 2 O 9-14, H,O 21 -35=100-58 (Am. J. Sci., III., xii., 270, 1876). Pyr.j 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 habit at the Bergen Hill tunnel of 1876. FHULLIFSITE.* 647 Orthorhombic. /A 7= 91 12' ; 1 A 1 = 121 20', 120 44', and 88 40' 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. li. =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 2 (Na 2 ) ; Ca : K 2 =3 : 1, 2 : 3, etc. Fonnula Rr J tlSi 4 Oi 2 +4aq. Analysis by Ettling, Nidda. Hessen, Si0 2 4813, &1O 8 21-41, CaO 8-21, K 2 5 "20, Na 2 0'70, H 2 16 '78= 100-48. Pyr., etc. B.B. crumbles and fuses at 3 to a white enamel. Gelatinizes with hydrochloric acid. Diff. 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. Streng (Jahrb. Min., 1876, 585) shows that the forms are exactly analogous to those of harmotome, and suggests that it may be also monoclinic. C. di Bove. 346 DESCKIPTIVE MINERALOGY. HARMOTOME. Monoclinic (DesCloizeaux). Cleavage I, O, easy. Simple crystals un- known. Occurring in peiietra* 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. "x^ "Xy/// ^/ ~^** ^ r x j^ / / vi/X ^^^^ Comp. Q. ratio for R : R : Si : H Qf 7T . , =1:3:10:5; here R=Ba mostly, Andreasberg. algo ^ . R= ^ Formu i a BUBM)" +5aq. If one -fifth of the water is chemically combined (Rammelsberg), then the formula corresponds to HoRAlSi 5 Oi 6 +4aq. Both formulas give Silica 45-91, alumina 1570, 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. Diflf. Characterized by its crystallization in twins ; the presence of barium separates it from other species. Obs. Harmotome 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 Giessen, etc. ; Oberstein ; in the gneiss of upper New York City. DesCloizeaux, who has shown the monoclinic character of the species by optical means, hai adopted a different position for the crystals (1=1, etc.). STILBITE.* Desmine. Orthorhombic. /A 2 = 94 16', 1 A 1, front, = 119 16', side, 114 0'. Cleavage : i4 perfect, i-l less so. Forms as in f . 650 ; more common with the prism flattened parallel to i-k or the cleavage-face, and pointed at the extremities. Twins : cruciform, twinning-plane. 14, rare. Common in sheaf -like aggregations ; divergent or radiated ; some times globular and thin lamellar-columnar. H.^3'5-4. G. = 2-094-2-205. Lustre of M pearly; of other faces vitreous. Color white ; occasionally yellow, brown, or red, to brick-red. Streak uncolored. Transparent translucent. Fracture uneven. Brittle. Var. 1. Ordinary. Either (a) in crystals, flattened and pearly parallel to the plane of cleavage, or sheaf -like, or divergent groups ; or (b) in radiated stars or hemispheres, with the radiating individual* showing a pearly cleavage surface. Splicer ostilbite, Beud, is in spheres, radiated within with a pearly fracture, rather soft externally. Comp Q. ratio for R : R : Si : H=l : 3 : 12 : 6 ; R=Ca(Na 2 ),R=Al. Formula RAlSi 6 0,, -f-6aq. If two parts of water are basic (Ramm.) the ratio becomes (R=Ca,H 2 ,Na 2 ) 3 : 3 : 13 : 4, or R : Si=l : 2, and the formula is H,RA-lSi 6 Oi 8 +4aq. Analysis, Petersen, Seieser Alp, SiO 2 55-61, A10 3 15-62, CaO7'33, Na 2 O 2'01, K 2 O 0'47, H 2 O 18-19=99-23. Pyr., etc. B.B. exfoliates, swells up, curves into fan-like or vermicular forms, and fusee OXYGEN COMPOUNDS HYDEOUS SILICATES. 347 to a white enamel. F. 2-2'5. Decomposed by hydrochloric acid, without gelatinizing. The gphcerostilbite 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 rectangulai tabular crystals ; lustre 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 ; nearFahlun, in Sweden. In North America, at Bergen Hill, New Jersey ; at the Michipicoten Islands, Lake Superior ; Nova Scotia, etc. The name stilbite is from ar/A/fy, lustre ; and desmine from t'taiiri, a bundle. The speciea ebilbite, as adopted by Haiiy, included Strahlzeolith Wern. (radiated zeolite, or the above), and Blatterzeolith Wern. (foliated zeolite, or the species heulaiidite beyond). The former waf 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, Breithaupt separated the two zeolites, and called the former desmine and the latter euzeolite, thus throwing aside entirely, contrary to rule and propriety, Hauy'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 heulandit*. In this he has been followed by the French and English mineralogists, while the Germans have unfortunately followed Breithaupt. EPISTILBFTE (Rdxsite). Composition like heulandite, but form orthorhornbic. Iceland; Faroe ; Poonah, India, etc. ; Bergen Hill, N. J. FOIIESITE. Resembles stilbite inform. Q. ratio for R : ft : Si : H 1 : 6 : 12 : 6. Formula RAl 2 Si 6 Oi9+6aq. (R=Na 2 : Ca=l : 3). Occurs in crystalline crusts on tourmaline, in cavities in granite. Island of Elba. HEULANDITE. Stilbit, Germ. Monoclinic. C = 88 35', /A 1= 136 4', A 14 = 156 45' ; c : I : d = 1'065 : 2-4TS5 : 1. Cleavage : clinodiagonal (i4) emi- nent. Also in globular forms ; also granular. 651 H. 3'5-4. Gr.=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 : ft : Si : H=l : 3 : 12 : 5 ; R=Ca(Na 2 ). Formula CaA:lSi 6 Oi 6 -r-5aq, 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 Oi8+3aq. Both require Silica 59-06, alumina 16 '83, lime 7 '88, soda 1-46, water 14' 77 =100. Fyr. B.B. same as with stilbite. 3DiflF. 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. BREWSTEBITE. Q. ratio same as for heulandite, but R is here Ba or Sr (Ca). Formula requires SiO 3 53 -5, A10 3 15 '3, BaO 7-6, SrO 10 '2, H a O 13 '4=100. Monoclinic. Strontian in Argyleshire, etc. 348 DESCRIPTIVE MINERALOGY. III. MAEGAROPHYLLITE 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. 7"A/==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.=1-1'5. G.= 2*565-2-8. Lustre pearly. Color apple-gj^en 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 reddish when impure. Streak usually white; of dark green varieties, lighter than the color. Subtransparent subtranslucent. Sectile. Thin laminae 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. G. =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 ctialk (Craie de Brianqon], which is milk-white, with a pearly lustre. Comp. Q. ratio for Mg : 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 R : Si=l : 2, (R=Mg(Fe) and H 2 ), and the formula is H 2 Mg 3 Si 4 Oi 2 (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 DO magnesia, most frequently change to pinite-like pseudomorphs. Eensstlaerite and Vl*alb^lite are pseudornorphous varieties. Apple-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 Bridge water; Graf ton, etc. In New Hampshire^ at Pelham, etc. In R. Island, 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 X PYROPHYLLITE. Agalmatolite or Pagodite pt. Orthorliombic. Not observed in distinct crystals. Cleavage: basal eminent. Foliated, radiated lamellar ; also granular, to compact or crypto- crystalline ; the latter sometimes slaty. H. 1-2. G.=2-75-2-92. Lustre" of 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 (1) 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 (Ramm.). Analysis, Chesterfield, S. C., by Genth, Si0 2 64 -82, A1O 3 28'48, FeO, 0-96, MgO 0-33, CaO 0'55, H 2 O 5 -25=100-39. 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 blue 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 Ottre2 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 O 8 + 2aq; OT, if half the water is basic, 1:2: i=H 2 Mg 2 Si 3 O 8 +aq= Silica 60-8, magnesia 271, water 121=100. TJhe 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 ; also found in Greece ; at Hrubschitz 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 orjTua, cuttle-fish, the bone of which is light and porous, and also a pro- duction of the sea. APHRODITE. 4MgSiOa+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. GLA.DCONITE. Green earth pt. A hydrous silicate of iron and potassium, but alwaya impure. Constitutes the green sand of the chalk and other formations (e.g.. in New Jersey). BTILPNOMELANK. In foliated plates, or as a velvety coating. Essentially a hydrous iron 350 DESCRIPTIVE MINERALOGY. (Fe) ailicate. Color black to yellowish-bronze. Silesia; Weilburg; Nassau; Sterling iron mine ; Antwerp, N. Y. (chalcodite}. CULOROPAL. Compact, earthy. Color greenish -yellow. A hydrate d iron silicate. Formula FeSi 3 9 +5aq. Andreasberg ; Steinberg near Gottingen ; Nontron (nontronite), France, eto. AERIKITE. Perhaps related to chloropal (Lasaulx). Color blue. Spain. UNISILICATES. Serpentine Group. SERPENTINE.* Orthorhombic (?). In distinct crystals, but only as pseudomorphs. 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. G.=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. (I) Ordinary massive, (a) Precious or Noble /Serpentine (Edler 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. BowenitA (Smithfield, R. I.), is a jade-like variety with the hardness 5 '5. FOLIATED. Marmdite is thin foliated ; the laminae 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. CJirysotile 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 '2 19. Often constitutes seams in serpentine. It includes most of the silky amianthut of serpentine rocks. The original chrysotile was from Reichenstein. 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 Si 2 O 7 -l-2aq= Silica 43*48, magnesia 4o'48, water 18 '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, 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 O 8 -|-aq. The rela- tion in ratio to kaolinite and pinite corresponds with this view of the formula. Pyr., 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- Botile 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 Fasso valley, Tyrol ; near Miask ; Katharinenberg, and elsewhere ; in Norway, OXYGEN COMPOUNDS HYDROUS SILICATES. 351 at bnarum, etc. Precious serpentines come 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 N. York, at Brewster, Putnam Co. ; at Antwerp, Jefferson Co. ; in Gouver- neur, St. Lawrence Co. ; in Orange Co. ; Richmond Co. In N. Jersey, at Hoboken. In Penn., at Texas, Lancaster Co. ; also in Chester Co. ; in Delaware Co. In Maryland, at Bare Hills ; at Cooptown, Harford Co. The following are varieties of serpentine : retinalite, G-renville, C. W. ; wrhausente, Tyrol ; porcellophite ; bowenite, Smithfield, R. I. ; antigorite, Piedmont ; wittiamsite, Texas, Pa. ; marmolite, 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). H 4 Mg4Si30i 2 +4aq. Occurs with serpentine at Middlefield and Texas, Penn. HYDROPHITE (Jenkinsite), near deweylite, but Mg replaced in part by Pe. CEROUTE. HaMgaSiaOv+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. Oomp. 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., SiO* 35 "36, NiO 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. ALIPITE and PIMELITE, an apple-green silicates containing some nickel. GARNIERITR and NOUMEITE, from New Caledonia are similar, and have been shown by Liversidge to be mixtures. Kaolinite Group. KAOLINITE. Orthorhombic. /A /= 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.^S'^-S'GS. Lustre of plates pearly ; of mass, pearly to dull earthy. Color white, grayish-white, yellowish, sometimeo brownish, bluish, or reddish. Scales transparent to translucent. Scales flexible, inelastic ; usually unctuous and plastic. Var 1. Argitliform. Soft, clay-like ; ordinary kaolmite ; under the microscope, if no* 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 aug-ilai scales. 3. Indurated; LitJiomarge (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 AlSi 2 7 +2aq, or making part of the water basic, H 2 AlSi 2 8 +aq=Silica 46-4, alumina 397, water 13-9=100. Pyr., etc Yields water. B.B. infusible. Gives a blue color with, cobalt solution. Insol- v ble 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 these 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 of 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 porcelain manufactory. In the U. States, kaolin occurs at Newcastle and Wilmington, Del.; at various localities in the limonite region of Vermont (at Branford, etc.) ; Massachusetts ; Pennsylvania ; Jackson- ville, Ala.; Edgefield, S. C.; near Augusta, Ga. PHOLERITE, HALLOYSITE, clays allied to kaolinite. SAPONITB. A soft magnesian silicate ; occurs in cavities in trap. Pinite Group. FINITE. Amorphous ; granular to cryptocrystalline ; usually the latter. Also in crystals, and sometimes with cleavage, but only because pseudomorphs, the 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 ; DesOl. Comp., Var. Finite is essentially a hydrous alkaline silicate. Being a result of alteration, and amorphous, the mineral varies much in composition, and numerous species have been 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.) HcKsALjSiaOao. 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, tulcose schtet, and still more closely related to pyrophyllite schist). Some prominent varieties are : FINITE. Speckstein [fr. the Pini mine at Aue, near Schneeberg]. Occurs in granite, and is supposed to be pseudomorphous after iolite. GIESECKITE. In 6-sided prisms, probably pseudomorphous after nephelite. H=3 5. G. =2 -78-2-85. Color grayish-green, olive-green, to brownish. Brought by Giesecke from Greenland. Also of similar characters from Diana, X. 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 ayaA/xo, an image, SOL& payodite fiom pagoda, the Chinese carving the soft stone into miniature pagodae OXYGEN COMPOUNDS HYDROUS SILICATES. 353 Images, etc. Part of the so-called agalmatolite of China is true pinite in compo&ilion, 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 ; kittinite ; gigantoHte ; hygropJiilite ; gumbeUte restmmeltte. Also cataspilite ; biharite ; palagonite. Hydro-mica Group. FAHLUNITE. In six- or twelve-sided prisms, but derived from pseudomorphism after 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 f or R : R : Si : H=l : 3 : 5 : 1 ; whence the formula I^RaRaSisOao, 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, A1O 8 30-10, FeO 3-86, MnO 2 24, MgO 6 '75, CaO 1-35, K 2 O 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 tridaaite) from Fahlun, Sweden. The following are identical, or nearly so : Esmarkite and praseolite, Brevig ; raumite, Raumo, Finland ; cldorophyUite, Unity, Me. ; pyrargillite, Helsingfors ; polychroilite, Krageroe, and aspasiolite, Norway ; huronite, Lako 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 : ft : Si : H mostly 1:6:9:2; whence the formula H e R 2 Al 4 Si 9 O3, 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., SiO a 44'GO, A1 2 3 36-23,Fe 2 3 l-34,MffO 0'37, CaO 0'50, Na 2 O4-10, K 2 620, H 2 5-26, F tr.=.-100-60. For pyrognostics and localities, see muscovite, p. 313. GILBEKTITE. Essentially identical with margarodite ; tin mines, Saxony. DAMOURITE. An aggregate of fine scales, mica-like in structure. H.=2-3. Gr.=2'792. Lustre pearly. Color yellow or yellowish- whita Optic-axial divergence 10 to 12 degrees ; for sterlingite 70. Comp. A hydrous potash-mica, like margarodite, to which it is closely related. Q. ratio 23 354 DESCRIPTIVE MINERALOGY. for R : 31 : Si : H=l : 9 : 12 : 2, or 1 : 1 for bases to silicon, if the water is basic. Formula H 4 K 2 Al 8 Si B O 24 . Analysis, Monroe, from Sterling, Mass, (sterlingite) , SiO 2 43'87, A10 3 30 '45. Fe0 3 3-36, K 2 10 86, H 2 519=99-73. It is the gangue of cyanite at Pontivy in Brittany; and the same at Horrsjoberg, Werrn- land. Associated with corundum in North Carolina ; with spodumene, at Sterling, Mass. PARAGONITE. 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. Gr.= 2-779, paragonite ; 2*895, pregrattite, (Ellacher. Lustre strong pearly. Color yellowish, grayish, grayish-white, greenish, light apple- green. Translucent ; single scales transparent. i C.omp. A hydrous sodium mica. Q. ratio for R : R : Si : H=l : 9 : 12 : 2, or 1 : 1 for bases and silicon, if the water be made basic. Formula EUNasAlaSieOaUK : Na=l : 6) = Silica 46-60, alumina 39-96, soda 6 90, potash 174, 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 ; coasaite, 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 : ft : 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. EPIIESITE, LESLEYITE. Hydro- micas, perhaps identical with damourite. Occur with corundum, and impure from admixture with it. (ELLACIIEIUTE. 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 rubellite. HISINQERTTE. Amorphous, compact, without cleavage. H.=3. G. 3-04:5. Lustre greasy, inclining to vitreous. Color black to brownisli-black. Streak yellowish-brown. Fracture conchoidal. Comp. Q. ratio for R+ft : Si : H 2 : 3 : 3 ; formula R 6 J R 2 Si 3 O 18 +4aq (with one-third of the water basic). R=Fe,H 2 ; ft Fe. Analysis, Cleve, from Solberg, Norway, SiO 2 35'33, FeO 3 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 (deyeroite), neai llelsingfors, Finland. EKMANNITE. Foliated, also radiated. Color green, resembles chlorite. Analysis, Igel- strom, SiO 2 34'bO, Fe0 3 4'97, FeO 35'7S, MiiO 11 "45, MgO 2-99, H 2 O 10'51 = 100. With magnetite at Grythyttan. Sweden. NEOTOCITE. Uncertain alteration-products of rhodonite; amorphous, uon tains 20-30 p. c. MnO. Paisberg, near Filipstadt, Sweden ; Finland, etc. GILLINGJTE ; Sweden. JOLLYTE ; Bodenmais, Bavaria. OXYGEN COMPOUNDS HYDKOUS SILICATES. 355 Vermiculite Group* The VEEMICULITES have a micaceous structure. They are all unisilicates, having the general quantivalent ratio K-t-R : Si : H.=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.=1'5. 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 ; DesCl. Comp. Q. ratio f or R : ft : Si : H=2 : 3 : 5 : 2, and R 4-R : Si : H=2 : 2 : 1 ; whence R 4 ftoSi 5 Ooo+5aq. Analysis: Brush, Westchester, SiO* 37'10, A10 3 17'57, Fe0 3 10'54, FeO 1-26, MgO 19-65, CaO 0'56, Na.O tr., K 2 O 0'43, H 2 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 dars 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. PYROSCLEIUTE. -Q. ratio f or R : ft : Si : H=4 : 2 : 6 : 3. and for R+ft : Si : H=2 : 2 : 1. Silica 38-9, alumina 14-8, magnesia 346, 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. CULSAGEEITB. Q. ratio R : ft : 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 ft=Al 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, Unices (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., SiO 2 33 '68, A1O 10-84, FeOs 2-86, FeO 24-33, MnO 0'38, CaO 073, MgO 16'52, Na 2 O 0-33, H a O 10'02=99-69. SUBSILICATES. Chlorite Group. PENNINTTE. Kammererite. Khombohedral. R A R = 65 36', O A E = 103 55 ; c = 34951? 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 1, 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 snbtranslucent. Laminae flexible, not elastic. Double refraction feeble ; axis either negative or positive, and sometimes positive and negative in different laminae of the same plate or crystal. Comp. Q. ratio for bases and silicon 4 : 3, but varying 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 O 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 Unst, 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 : tdbergite ; pseudopJiite, compact, massive (allopJiite) ; loganite, Ddessite, euralite, apJirosiderite, cldoropliceile are chloritic minerals, occurring under simi- lar conditions, in amygdaloid, etc. RIPIDOLITE. Clinochlore. Klinochlor, Germ. Monoclinic. O= 62 51/ '= O ^^-i, 1 A / = 125 37', O A 44 = 108 14' : c : I : d = 1-47756 : 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 tine granular and earthy. IL = 2-2 5. G.=2-65-2-78. Lu&tre 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 HYDROUS SILICATES. 357 657 "Westchester. i f Texas. Oomp. Q. ratio for R : R : Si : H=5 : 3 : 6 : 4 ; corresponding to Silica 32-5, 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 (koUchubdte) 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 ripidolite from pnrtg, a fan, in allusion to a common mode of grouping of the crys tills. 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. G.=2-78-2'96. Translucent to opaque; transparent only in very thin folia. Lustre or cleavage surface feebly pearly. Color green, grass-green, olive-green, blackish-green ; across the axis by transmitted light sometimes red. Streak uncolored 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 f or R : R : Si : H=12 : 9 : 14 : 9J- ; for bases and silicon 3 : 2. Average compositi on = Silica 26 -8, alumina 197, 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. G-othard, 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 : R : Si : H=3 : 3 : 4 : 3. Przibram; Cornwall. STRIGOVITE. Q. ratio=3 : 2 : 4 : 2. In granite of Striegan, Silesia. GKOCHAUITB locality. MARGARITE. Perlglimmer, Germ. Orthorhombic (?) ; hemihedral, with a monoclinic 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. G.=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 tlie longer diagonal ; dispersion feeble. Comp. Q. ratio f or R : B : Si : H=l : 6 : 4 : 1 ; whence, if the water be basic, for baseH andsilicon=2 : 1, formula RRSiOe ; that is, H 2 CaAl 2 Si 2 O 12 . Analysis, Smith, Chester, Mass., SiO a 32-21, A10 3 48-87, FeO 3 2-50, MgO 0'32, CaO 10'02, Na 2 O(K 2 O) 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 G-reiner 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. (cling- manite}, and elsewhere in North Carolina ; at the emery mines of Chester, Mass. OHLORITOID. Monoclinic, or triclinic. /A I' about 100 ; O (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 diehroic. Streak un colored, 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 Sismondine, from St. Marcel. 3. Masonite, from Natic, R. I., in very broad 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 : B : Si : H=l : 3 : 2 : 1, for most analyses. Analysis by v. Kobell, Bregratten, Si0 2 2619, ^rl0 3 38*30, Fe0 3 6 '00, FeO 2111, MgO 3'30, H 2 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. Phyllite (and 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. /Aj=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, SiO 2 20-24, AK),39-18, FeO* 3'27, Mg020'84, CaO 13'69, H 2 1'04, Na 2 0(K 2 O) 1'43, Zr0 3 0'7o= 100*39. Amity, N. Y. (clintonite) ; Fassathal (brandisite] \ Slatoust (xanthophyttite). CORUNDOFHILITE. A chlorite with the Q. ratio=l : 1 : 1 : f . Occurs with ccrundum at Asheville. N. C.; Chester, Mass. DTTDLE'YITE. Alteration product of margarite. Clay Co., N. C. ; Dudley ville, Ala. WILLCOXITE. Near margarite. Decomposition product of corundum. Q. ratio f or B : R r Si : H=3 : 6 : 5 : 1. THUBINGITE. Q. ratio 2:3:3:2. Contains principally iron (Fe and Fe). Hot Springy Arkansas; Harper's Ferry (owenite). Pattersonite from Unionville, Pa., near thuringite. OXYGEN COMPOUNDS. TANTALATES. COLUMBATES. 359 2. TANTALATES, COLUMBATES. FYROCHLORE.* 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-brow/i. Subtranslucent opaque. Fracture conchoidal. Comp. A columbate of calcium, cerium, and other bases in varying- amounts. Analysis, by Rammelsberg. Brevig, Cb 2 6 58 '27, TiO, 5 '38, Th0 2 4 '96, CeO 5 "50, CaO 10 "93, FeOfUCU 5-53, Na 2 5 "31, F 3 "75, H 2 O 1 -53 = 101-16. Obs. Occurs in syenite at Friederichsvarn and Laurvig, Norway ; at Brevig ; near Miask in tbe 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, but probably containing more tantalum pentoxide. Chesterfield, Mass. PYBRHITE. 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. AZOEITE. In minute tetragonal octahedrons resembling zircon. From the Azores in albite. Chemical character unknown. TANTALITE.* Orthorhombic. Observed planes as in the figure. /A 1 101 32'. 6>A14 = 122 3i'; c : I : & = 1-5967 : 1-2247 : 1. O A H = 117 2', i-i A 1-2 = 143 6i', 1-2 A 1-2, adj., = 141 48', i-i/\i-$ =. 118 33'. Twins: twinning-plane t-J, 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. 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 Fc(Mn)Ta 2 O 6 . Sn is also often present (as FeSnO 3 . according to Ram- melsberg), and some of the tantalum is often replaced by columbium. Analysis, Ramm., Tammela (G. =7-384), Ta 2 O 5 76 '34, Cb 2 O 5 7'54, SnO a 0'70.FeO 13-90, MnO 1*43=99 '90. Other varieties contain much more Cb a 5 , the kinds shade into one another. Pyr., etc. B.B. unaltered. With borax slowly dissolved, yielding an iron glass, which, an 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 oda 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 a umalt-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.* Niobite. Ferroilmenite. Orthorhombic. I A 1= 101 26', A 14=134 53V- c I d = 1-0038 : 1-2225 : 1. O A 1-1 = 140 36', A 1-3 =: 138 26'' i-i A 1-3 = 104 30', 1-3 A 1-3, adj., = 151, i* A i-i, ov. U, = 135 40', i-z A i-z, ov. i-\ = 135 30'. Twins : twinning-plane 2-. Cleavage : i-l and i4, the forme* inost distinct. Occurs also rarely massive. 661 ,02 Haddam. Middletown, Conn. Greenland. Lustre submetallic ; a little shining. Color iron- * ^^* "^ *** ^.UK*W uiii'in vi (tin^ , ft, n\ji,i.^j oinii 111^. v^oiur iron- black, brownish-black, grayish-black ; often iridescent. Streak dark red to black. Opaque. Fracture subconchoidal, uneven. Brittle. of Cb Tprit Cb 4 (T i a2 m 6 ^ Witb - On i? ^8*** 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 O 5 is almost entirely absent. Analyses. Blomstrand, (1) Haddam ^G.=615), (2) Greenland (G.=5'895). W 3 SD 2 Zr 3 Fe Mn O H 2 o 272 0<34 ' 34 13>54 497 O-IG^IOO-IO (2) 7797 - 0-13 073 013 17'33 351 __ = 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 additioTof \ Ue T7 Ch n \ or ? 1 > tin S than with tantalite; and thl variety dianite, when treated, gives on boiling with tin-foil, and dilution with its volume of water Ue Th ' ^ f ^^^ * Ordinary columbifce ' the m ^allic acid remains ln?^?f y ? m Hadd . a u ra ' Ct - i8 partially de ^Psed when the powdered P if yne8S Wlth concen *rated sulphuric acid, its color is changed to hnf hf ay ' ' y ellow ' ^nd when boiled with hydrochloric acid and metallic Z inc if gives beautiful blue The remarkably pure and unaltered columbite from Arksut-fiord in Green- witt Snc as abfvf * decom P O8ed ^ sulphuric acid, and the product gives the reaction test Bavaria; at Tirschenreuth, Bavaria; atTammelain Finland: OXYGEN COMPOUNDS. TANTALATES, COLUMBATE8. 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. ; 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. HERMANNOLITE (Shepard). From the columbite locality at Haddam, Ct., and a variety of columbite due to alteration. G. =5 '35. Supposed by Hermann to contain " ilmenium " pent- oxide (Ila0 6 ). TAPIOLITE. Tetragonal. c=-6464 (rutile c=-6442). FeTa 2 (Cb. 2 )O e , *ith Ta : Cb=4 z 1. Tammela, Finland. HJELMITE. A stanno-tantalate of iron, uranium and yttrium. Massive. Color black. Near Fahlun, Sweden. YTTROTANTALITE. Black Yttrotantalite. Orthorhombic. /A /= 123 10' ; A 24 = 103 26'; c : I : a = 2-0934 : 1-8482 : 1. Crystals often tabular parallel to i-L Also massive; amorphous. H.=5-5*o. 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. 12 It it Comp. Mostly Jl 2 (Ta,Cb).iO7, with two equivalents of water, perhaps from alteration ; R=Fe : Ca : Y(Er,Ce)^l : 2 : 4. Con- taining also W0 3 and SnO 2 . Analysis (Ramm.), Ytterby, Ta 2 O 6 46-25, Cb 2 6 12-32, SnO 2 M2, WO 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 'wnite skeleton of tantalum pentoxide, 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 hydrychloric 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. /A 7= 122 46' ; 14 A 14 = 93 ; c : I : & 0-949 1-833 : 1. Crystals often flattened parallel to i-i, also less often to i-l. Also in large irregular masses (N. Carolina). In flattened imbedded grains (Urals). II.=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 Stephana : con- North Carolina. 362 DESCRIPTIVE MINERALOGY. Cb 2 6 Ta 2 6 WO 3 Sn0 2 Th0 2 Zr0 2 UO s MnO FeO CeO* TO CaO n 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 10-95 "96 ll'SSf 3'31 12'61 0'73 0-45 MgO 0-14=99 -76 * With LaO, DiO. tWithO-25CuO. Pyr., etc. In the closed tube decrepitates, glows like gadolinite, cracks open, and turna 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 names 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 sometimes implanted in parallel position upon those of the samarskite. NOHLITE, Near samarskite, but contains 4 '62 p. c. water. Nohl, Sweden. EUXENFTE. Orthorhombie. Form a rectangular prism with lateral edges replaced, and a pyramid at summit. Cleavage none. Commonly massive. H.=6'5. G.=4'60-4*99. Lustre brilliant, metallic-vitreous, or some- what greasy. Color brownish- black ; in thin splinters a reddish-brown translucence lighter than the streak. Streak-powder yellowish to reddish- brown. Fracture subconchoidal. Comp According to Rammelsberg 2RTi0 3 +RCb 2 6 +aq ; here R=Y,Fe,U mostly. Analysis, Ramm., Arendal, Cb 2 6 35 '09, Ti0 2 21-16, YO 27 '48, ErO 3 '40, U0 2 4'78, CeO 3-17, FeO 1-38, H 2 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 e#|eyoy, a stranger, in allusion to the rarity of its occurrence. -flSsCHYNiTE. Orthorhombie. H. 5-6. G-.=4'9-5-14. Lustre submetallic to resinous, nearly dull. Color nearly black. Streak gray. Fracture small subconchoidal. Analysis, Ramm., Cb 2 5 28'81, Ti0 2 22'64, Sn0 2 018, ThO 2 15-75, FeO 3'17, CeO 18 '49, LaO(DiO) 5-60, YO 1-12, CaO 2'75, H 2 O 1 -07=99'58. In feldspar with mica and zircon. Miask in the Urals. POLYMIGNITE. Orthorhombio. In slender crystals. H.=6'5. G.=4'77-4-85. Lustre brilliant. Color black. Streak dark brown. Fracture perfect conchoidal. Comppsition doubtful. Fredericksvarn, Norway. Perhaps identical with seschynite (Frankenheim). POLYCKASE. Orthorhombie. H.=:55. G. =5 '09-5-12. Lustre bright. Color black. Streak grayish-brown. Fracture conchoidal. Analysis, Ramm., Cb 2 5 20*35, Ta 2 O 8 4' 00, Ti0 2 26-59, YO 23'32, FeO 2-72, CeO 2 61, U0 a 7 70 H 2 04 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. BUTHERFOBDITE. Doubtful ; contains titanium, cerium, etc. Rutherford Co. , N. C. FERGUSONTTE.* Yellow Yttrotantalite. Tyrite. Bragite. Tetragonal, hemihedral. A l-i = 124 20' ; c = l'464r. Cleavage : 1 in distinct traces. OXYGEN COMPOUNDS. TANTALATES, COLUMBATES. 363 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 conchoidal. Comp. According to Rammelsberg, essentially R 3 (Cb,Ta) 2 O8. Analysis, Ramm., Greenland, Cb,O 5 44 '45, Ta 2 s 6 '30, Sn0 2 0'47, W0 3 0-15, YO 24-87.Er09'81, CeO7'63 (5 -63 LaO.DiO), U0 2 2-58, FeO 0-74, CaO 0'61, H,O 1 -49-~99 '10. The amount of water varies from 1*49-7 p. c., and is regarded by Ramm elsberg 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 Nseskul, 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. GK=3'8. Tammela, Finland. 364 DRSCEIPTIVE MINERALOGY. 3. PHOSPHATES, AKSENATES, YAKADATES, ETC. ANHYDROUS PHOSPHATES, ARSENATES, ETC. XENOTIME. Ytterspath, Germ. Tetragonal. A 1 = 138 45' ; c = 0-6201. 1 A 1, pyram., = 124 26' ; basal, = 82 30'. Cleavage : 7, 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 O 8 =Phosphorus pentoxide (P 2 O 6 ) 37 '87, yttria 6213=100. Fyr., 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 U. S., in the gold washings of Clarksville, Georgia ; in McDowell Co., N. C.; in the diamond sands of Bahia, Brazil. The wiserine of Kenugott has been shown by Klein to be octahedrite (vide p. 255). CRYPTOLITE (Phosplwcerite). CeaPaOs (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 ; i =s 0-734603. A 2-2 = 124 14'. Cleavage : O, imperfect ; 7, more so. Also St. Gothard. globular and reniform, with a fibrous or imperfectly columnar structure , also inasei ve, sti 'icture granular. OXYGEN COMPOUNDS. PHOSPHATES, AKSENATES, ETO. 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- greeu ; often violet-blue ; 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 P/to&phorifa was used by Kir wan for all apatite, but in his mind it especially included the fibrous concretionary and partly scaly mineral from Estremadura, Spain, and elsewhere. 3. Fluor-apatite, Cldoi'-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 2 08 + CaCl 2 =: Phosphorus pentoxide 40-92, lime 53 '80, chlorine 6 -82 =101 '54 ; and 8Ca,P 2 O 8 +CaF a =Phosphorua pentoxide 42 -2b', lime 55 "55, fluorine 3'77=1C1'58. Sometimes both calcium chloride (CaCL), and calcium fluoride (CaF. 2 ), 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 lead 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 its 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 mobt 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 Ehrent'riedersdorf 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 ; at Wheal 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 Perm., 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 aTrardoo, to deceive, older mineralogists having referred it to aquamarine, chrysolite, amethyst, fluor, schorl, etc OSTEOLITE 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 stalagmitio 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. 366 DESCRIPTIVE MINERALOGY. PHOSPHATIC NODULES. COPROLITES. Phosphatic nodules occur in many foasiliferous rocks, which are probably in all cases of organic origin. They sometimes present a spiral or other interior structure, derived from the animal organization that afforded them, and in such cases their coprolitio origin is unquestionable. In other cases there is no structure to aid in deciding whether they are true coprolites or not. FYROMORFHITE* Griinbleierz, Germ. Hexagonal. Hemihedral. A 1 = 139 38' ; c = 0-7362. Cleavage : 1 and 1 in traces. 1 commonly striated horizontally. Often globular, reniform, and botryoidal or verruciform, with usually a subcolumnar strucj- ture ; also fibrous, and granular. H.=3'5-4r. G.=6'5-7*l, mostly when without lime; 5-6*5, when con- taining 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 O 8 +PbCl2= Phosphorus pentoxide 15-71, lead oxide 82'27, chlorine 2'62=100 > 60. Some varieties contain arsenic replacing part of me 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. Diff. Characterized by its high specific gravity, and pyrognostics. Obs. Pyromorphite occurs principally in veins, and acconipanies other ores of lead. Occurs in Saxony ; at Przibram, Mies, and Bleistadt, in Bohemia ; near Freiberg ; Clausthal in the Harz ; at Nassau ; Beresof in Siberia ; Cornwall, Derbyshire, and Cumberland, in England ; 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 irvp, fire, pop^i], form, alluding to the crystalline form the globule assumes on cooling. MIMETITE.* Mimeteeite. Hexagonal. 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 4-PbCl 2 =Arsenic 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.j 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 Johanngeorgenstadt ; at Nertschinsk, Siberia. At the Brookdale mine, Phenixville, Pa. OXYGEN COMPOUNDS. - PHOSPHATES, AESENATE8, ETC. 367 Mimetite is hemihedral like apatite and pyromorphite, as shown by etohinj (Baumhauer). Named from ^ut^T^s, imitator, it closely resembling pyromorphite. HEDYPHANE.^-A variety containing much calcium. CAMPYUTE contains much lead phoe- phate. VANADINITE. I. In simple hexagonal prisms, and prisms terminating in s pyramids ; 1 A 1, over terminal edge, 142 58', O A 1 = 140 Hexagonal, planes of the A 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 conchoidal. Brittle. Oomp, Formula 3Pb 3 V 2 O 8 4-PbCl2=: Vanadium pentoxide 19 '36, lead oxide 78 '70 chlorine 2-50=100-56. Pyr., etc. 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 B. F. yields metallic lead and a coat- ing of chloride of lead; after completely oxidizing the lead in O.F the black residue gives 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. 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 Gnrinthia. DECB&NITE. PbVaOe (or with some Zn) = Vanadium pentoxide 451, lead oxide 54 -9100, Massive. Color deep red. Dahn, near Niederschlettenbach, Rhenish Bavaria. Freiberg in Breisgau (eusynchite). DESCLOIZITE.* Pb 2 V 2 7 = Vanadmm pentoxide 29 1, lead oxide 70 9 =100. Orthorhombic. South America. Wheatley Mine, Penn. PUCIIERITE (Frenzel). Orthorhombic, near brookite in form (Websky). Occurs in 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 groups. 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. ScL, July, 1876). Si0 2 V 2 O 5 A10 3 Fe0 3 Mn0 8 MgO CaO K-,0 Na 2 O H.O 1. |41-25 28-60 14-14 113 115 2'01 0'61 8 '56 0'82 1'08 moisture 2-27=101-62 2. 47-69 22-02 V 6 O U 1410 1-67 FeO 2'00 ti. 7"59 019ign.4-98 0-85 gangue=100-23 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 6 0n = 2V 2 O 3 ,V 2 O ft . The formula given by Roscoe is 2MV 2 O 8 + K 4 Si 9 O 20 4- aq. Found in fissures in the porphyry, and in cavities in quartz at the gold mine at Granite Creek, El Dorado Co, , Cal. Named by Dr. Blake, who discovered it. See further on p. 435. 368 DESCRIPTIVE MINEEALOOT. WAGNERTTE. Monocliiiic. C = 71 53', IM= 95 25', O A 14 = 144 25', B. & M. ; c : b : d = 0*78654 : 1-045 : 1. Most of the prismatic planes deeply striated. Cleavage : 1^ and the orthodiagonal, imperfect ; O in traces. H.=5-5'5. G-.=3'068, transparent crystal; 2*985, untransparent, Kam- melsberg. Lustre vitreous. Streak white. Color yellow, of different shades ; often grayish. Translucent. Fracture uneven and splintery across the prism. Comp. Mg3P 2 8 4-MgF 2 =Pho8phorus 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. KJEBULFINE (o. Kobell). Stands near wagnerite, but exact nature uncertain. In masses of a pale red color at Bamle, Norway. MONAZITE.* Monoclinic. O = 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. Oomp. According to Rammelsberg, 5R 3 P 2 O s + Th 2 P.,O 9 , where R-Ce,La, Di. Analysis by Kersten, Slatoust, P 2 6 28-50, Th0 2 17-95, Sn0 2 210, CeO 26'00, LaO 23'4C, MnO 1'86, CaO 1'68, K,0 and Ti0 8 tr.=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. Diff. 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 Crowder's Mountain, N. C. Named from [wvd(,u, 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 B.rigritta, Tavetsch; Lercheltiny Alp, Binnenthal; Laacher See (v. Rath.), c : b : d= '921696 : 1 ; 0-958444. (7. =77 18' (Trechmann). KORABFVEITE (Eadominski) . A cerium phosphate containing fluorine; near monazite Occurs in large crystalline masses of a yellowish color at Korarfvet, near Fahlun, Sweden. OXYGEN COMPOUNDS. PHOSPHATES, ARSENATES, ETC. 369 674 TRIPHYLITE.* Triphyline. Orthorhombic. /A 1= 98, A l-l = 129 33', Tschermak ; c : I : p) from the Penig amblygonite. On this ground, as well as on account of a variation in the composition, it has been proposed (v. Kobell) to make it a new species. The same optical character and composition belong to the mineral from Montebras (called montebrasite on the basis of an erroneous analysis). Analysis of hebronite, Pisani, P 2 O 5 46'65, A1O S 36-00, 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. Color bright orange-red. Analysis, Hawes, Arsenic pentoxide 53 '11, alumina 1719, iron sesqui- oxide 9'23, manganese sesquioxide 2 "08, soda 13'06, lithia 0'65, fluorine 7'67=102'99. Formula R 2 RAs 2 O (with one-ninth of the oxygen replaced by fluorine), or RAso0 8 -f 2RF. Here R=Na : Li~10 : 1; ft=Al : Fe : Mn=15 : 5 : 1. Other varieties, having a lighter color, have 3^1 : Fe=5 : 1. Occurs with cassiterite, near Durango, Mexico (Brush). Hebronite, Maine. ANHYDROUS ANTIMONATES. MONIMOLITE. Mainly an an tim on ate of lead. Yellow. G.=5'94. Paisberg, Sweden. NADORITE. PbSb,O 4 + PbCl 2 . In yellow translucent crystals. H.=3. G.=7'02. Djebel- Nador, province of Constantine, 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. Coloi yellowish-green. Sierra del Cadi. STIBIOFERRITE. Amorphous coating on stibnite, from Santa Clara Co. , Cal. Mixture (?). HYDROUS PHOSPHATES, ARSENATES, ETC. PHARMACOLITE. Monoclinic. /A 1 =111 6', i-l A *-2 = 109 26', 1 A 1 = 117 24'. Cleavage : i4 eminent. One of the faces 1 often obliterated by the exten sion of the other. Surfaces i-i and i-% usually striated parallel to theii mutual intersection. Karely in crystals ; commonly in delicate silky fibre? or acicular crystallizations, in stellated groups. Also botryoidal and stalac titic, and sometimes massive. OXYGEN COMPOUNDS. PHOSPHATES, ARSENATE8, ETC. 371 H =:2-2'5. G. = 2'64-2'73* Lustre vitreous ; on i-l inclining to pearly Color white or grayish ; frequently tinged red by arsenate of cobalt. Streak white. Trans- lucent opaque. Fracture uneven. Thin lami- ii83 flexible. Comp. 2HCaAs04+5aq= Arsenic pentoxide 51*1, litne 24'9, water 24-0=100. Pyr., etc. In the closed tube yields water and becomes opaque. B.B. in O.F. fuses with intumescence to a white enamel, arid colors the flame light blue (arsenic). On char- coal in R.F. gives arsenical fumes, and fuses to a semi-transparent globule, sometimes tinged blue 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 Joachimsthal. This species was named, in allusion to its containing arsenic, from (fcap/ua/cop, poison. STRUVITE. An ammonium-magnesium phosphate containing 12 equivalents of water. In guano from Saldanha Bay, Africa. HAIDINGERITE. HCaAsO 4 +aq.=Arsenic pentoxide 58' 1, lime 28'3, water 13 6=100. Joachimsthal (?). BRUSHITE. HCaPO^RsPsOiO+Saq^Phosphorus pentoxide 41-3, lime 32'6, water 6'1= 100. Monoclinic. Gr.=2 208. On guano at Avea Island and Sombrero. METABUUSHITE. 2HCaP0 4 +3aq. G.=2'35. Sombrero. ORNITHRITE. Probably altered brushite. CHTTRCHITE. R 3 P 2 8 +4aq, with R=Ce(Di),Ca. Cornwall. WAPPLERITE (Frenzd). Triclinic. In minute crystals and in incrustations. Color white. Composition H(Ca,Mg)AsO 4 +7aq=:(Ca : Mg=4 : 3) arsenic pentoxide 487, lime 13-5, mag- nesia 7*3, water 30 5 100. Found with pharmacolibe at Joachimsthal. Schrauf states thai rZnO 2 =: Arsenic pentoxide 40'2, zinc oxide 56 '7, water 31=100. Color yellow. Chanarcillo, Chili ; Cap Garonne. TAQILITE Cu 1 P 2 O 9 + 3aq (=Cu 3 P 2 O8+HoCuO,+2aq). Color emerald-green. Mschne- Tagilsk. ISOCLASITE. Ca 4 P 2 O 9 +5aq (=Ca 3 P 2 O 8 + H 2 Ca0 2 -|-4aq). Colorless to snow-white. Joachimsthal. EUCHROITE. Cu 3 As20 8 -f-H.,CuO 2 -f6aq (Ramm.)= Arsenic pentoxide 341, copper oxide 47*2, crater 18 '7=100. Color emerald-green. Libethen, Hungary. CHLOROTILE. Cu 3 As 2 O 8 +6aq. In capillary crystals. Also fibrous ; massive. Color apple- green. In quartz at Schneeberg and Zinnwald ; Thuringia ; t Chili (Frenzel). VEK>ZELYITE (ScJirauf). A hydrous copper phosphate ; composition 4Cu 3 P 2 O 8 +5aq. clinic. Occurs in crystalline crusts on a garnet-rock at Morawicza in the Banat. Tri> 374 DESCRIPTIVE MINERALOGY. LIROCONITE. Linsenerz, Germ. Monoclinic. /A 7=74 21', DesCl. C =88 33'. Cleavage lateral, but obtained with difficulty. Rarely granular. H. = 2-2'5. G.=2'8S-2 a 98. Lustre vitreous, inclining to resinous. Color and streak sky-bine verdigris-green. Fracture imperfectly con- choidal, uneven. Imperfectly sectile. Comp Formula Cu s (Al) As a (P 2 )0 8 +H 6 (Cu3, Al)0 6 -l-9aq, with Cu s : Al=3 : 2, and As : P=l : 4. This requires arsenic pentoxide 231, phosphorus pentoxide 3 '6, copper oxide 35 '9, alumina 10 "3, water 27 "1=1 00. Pyr., etc. In the closed tube gives much water and turns olive-green. B.B. cracks open, but 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 Plwspliochaltite. CuePiOu +3aq=Cu 3 P,O t ,+3H 2 CuO 2 = P 2 O b 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 2 O 8 +2H J Cu0 2 + aq (Ramm.) ; DIIIYDRITE, CusPsOs-f 2H 3 CuO 2 . Ebl, near Liuz, on the Rhine ; Libethen, Hungary ; Nischne Tagilsk ; Cornwall. ERINITE. Cu 3 As2O 8 4-2H2CuCv In mammillated crystalline groups. Color green. Corn- wall. CORNWALLITE. Cu 6 As20i +3aq (=Cu3A8 2 O 8 +2H 2 Cu0 2 -t-aq). Amorphous. Color green. Cornwall (Church). PsiTTAClNTTE. Occurs in thin crypto-crystalline coatings, sometimes having a bntryoidal structure ; also pulverulent. Color siskin green to olive-green. Formula 2R 3 V 2 8 + 3H 2 CuO a -f 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). MOTTHAMITE. 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 y 2 8 + 2H 2 (Pb,Cu)0. 2 , 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^aO-.+aq, with R Ca : Cu=2 : 3 (or 3 : 7), Ramm. From the Urals, Kalk-volborthit (Germ,), Friedrichsrode, contains calcium. Monoclinic. 681 OLINOOLASITE. Strahlerz, Germ. C= 80 30', /A/, front, = 56. Cleavage : basal, highly perfect. -Also massive, hemispherical, or renifornT; struct ure\ad!ated fibrous. H. = 2-5T3. G.=4-19-4'36. Lustre: O pearly; elsewhere vitreous to resinous. Color internally dark verdigris-green; externally blackish-bine green. Streak bluish-green. Subtranslucent. Not very brittle. pentoxide 30 '2, coppei Color pale apple-green. Comp. Cu 3 As 2 O4-3H 2 Cu0 2 = Arsenic oxide 62-7, water 7 1 = 100. Fyr., etc. Same as for oliveuite. 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 As.Oio+Maq), containing also calcium carbonate (as an impurity ? ) Libelhen. Hungary ; Schneeberg, etc. OXYGEN COMPOUNDS. - PHOSPHATES, AJBSENATES, ETC, CHALCOPHYLLITE (Copper mica ; Kupferglimmer, #m?&.). Cu 3 A8 2 8 +5H 2 Cu0 2 Arsenic pentoxide 21 '3, copper oxide 58 '7, water 20'0=100. Copper mines of Cornwall, Hungary; Moldawa. V-LAZULITE. Blauspath, Germ. Monoclinic. C = 88 15', 1 A 1 = 91 30', A l-l = 139 45', Priifer j c : b : d = 0-86904 : 1-0260 : 1. Twins: twinning-plane iri\ also 0. Cleav- age : lateral, indistinct. Also massive. 684 -2 H.=5- monly a fine deep blue G-. =3-057, Fuchsi$ ^Lustre vitreous. Color azure-blue; corn- viewed along one axis, and a pale greenish-blue along another. Streak white." Subtranslucent opaque. Fracture uneven* Brittle. Comp. RAlP 2 9 +aq=rVlP 2 O 8 +H 2 (Mg,Fe)O 2 (Dana) = Phosphorus pentoxide 46 '8, alu- mina 34-0, magnesia 13 -3, water 6 '0=100. ^ Pyr., etc. In the closed tube whitens and fields water. B.B. with cobalt solution the blue color of the mineral is restored. In the forceps whitens, cracks open, swells up, and without fusion falls to pieces, coloring the flame bluish- green.. The green color is made more intense by moistening the assay with sulphiirjc acid. With the fluxes gives an iron glass'; with soda on charcoal an infusible mass. Unacted upon by acids, retaining perfectly its blue color. Diff. Characterized by its fine blue color; blue flame B.B. Obs. Occurs near Werfen in Salzburg; in Gratz, near Vorau ; in Krieglach, in Styria; at Hochthaligrat, at the G-orner glacier, in Switzerland ; in 'Horrsjoberg, Wermland ; Westana, Sweden; also at Tijuco in Minas Geraes, Brazil. Abundant at Crowder's Mt., Lincoln Co., N. C.; and on Graves Mt., Lincoln Co., Ga., 50 m. above Augusta. SCORODITE. 7 A 7= 98 2', A l-l * 132 20' ; i Cleavage : i-2 imperfect, i-l and i-l in Orthorhombic. 1*1511 : 1, Miller. traces. H. = 3-5-4. G.=3'l-3 > 3. Lustre vitreous snbadaman- tine and subresinous. Color pale leek-green or liver-brown. Streak white. Subtransparent translucent. Fracture uneven. Comp. FeAs 2 O 8 +4aq=Arsenic pentoxide 49'8, iron sesquioxide 84-6, water 15 -6 =100. Pyr., etc. In the closed tube yields neutral water and turns yellow. B.B fuses easily, coloring the flame blue. B.B. on charcoal gives arsenical fumes, and with soda a black magnetic scoria. With the fluxes reacts for iron. Soluble in hydrochloric acid. l:& = 1-0977 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 AUJ bralia. Occurs in minute crystals and druses, near Edenville, N. Y. ; in Cabarraa Co., N. C. WAVELLTTB. Orthorhombic. /A 1= 126 25', A 14 = 143 23' ; c:t>:d = 0-7431 : 1 '494:3 : 1. Cleavage : 1 rather perfect ; also brachydia- 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 Oi9,12aq=:2AlPi208 + HflAlO6+9aq Phosphorus pentox- 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; Zajecov in 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. ZEPHAROVICHITE. Near wavellite. Composition A1P 2 8 + 6aq (or 5aq, Ramm.). Compact. Color greenish to grayish. Occurs in sandstone at Trenic, Bohemia. CCEKULEOLACTITE. Crypto-crystalline. Color milk-white to light blue. Composition (Petersen) 2^1 3 P 4 Oi 9 + 10aq. Katzenellnbogen. Nassau. Also Chester Co., Penn. (Genthj who regards the copper, 4 p. c., as belonging to the mineral.) PHARMACOSIDERITE. Wiirfelerz, Gei-m. 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. Subtraus- parent subtranslucent. Rather sectile. Pyroelectric. Comp Fe 4 As6O27,15aq=3FeAs 2 8 +H 6 FeOe + 12H 2 0=Arsenic pentoxide 4313, iron tesquioxide 40 '00, water 16 "87 =100. Pyr., etc. Same as for scorodite. ObSr- -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 France and at Swoneeberg and Schwar* eenbcrg in Saxony. OXYGEN COMPOUNDS. PHOSPHATES, AftSENATES, ETC. 377 Named from a.p/j.aitov, poison (in allusion to the arsenic present), and (n'Srjpos, iron. erz, of the Germans, means cube-ore. RHAGITE (Weisbach] . Composition BiioAs4O25-t-9aq=2BiAs044-3HaBi0 3 :=:Arsenic pent- oxide 15 - 6, bismuth oxide 78-9, water 5-5=100. Spherical crystalline aggregates. Colo* bright green. Schneeberg, Saxony. PLUMBOGUMMITE. Composition uncertain. Contains essentially alumina, lead, water, and phosphorus pentoxide. Huelgoet ; Cumberland ; Mine la Motte, Mo. OHILDRENITE.* Orthorhombic. 1 A /= 111 54', A 14 = 136 26' ; c : I : d = 0-9512 1-4798 : 1. Plane sometimes wanting, and the form a double six- Bid ed pyramid, made up of the planes 1, 2-, with 14 small. Cleavage : i4^ imperfect. H. =4-5-5. G. 3'18-3'24. Lustre vitreous, inclining to resinous. Color yellowish-white and pale yellowish-brown, also brownish-biack. Streak white, yellowish. Translucent. Fracture uneven. Comp. Formula somewhat uncertain. Analysis: Rammelsberg, P 2 O 6 28 '92, A10 3 14 '44, FeO 30-68, MnO 9 "07, MgO 0'14, H 2 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 hi hydrochloric acid. Obs.- Occurs near Tavistock ; also at Wheal Crebor, in Devonshire ; on slate at Crinnia mine in Cornwall. Hebron, Me. (f. 688.). TCJRQUOIS. Callaite. KaUait, Kalait, Germ. Reniform, stalactitic or incrusting. Cleavage none. H.=6. G-.=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 :A:l 2 P 2 Oii+5aq=: Phosphorus pentoxide 32-6, 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 ; colors 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 DESCRIPTIVE MINERALOGY. and at Oelsnitz in Saxony. W. P. Blake refers here to a hard yellowish- to bluish -green stem (which he identifies with the chalchihuitl 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 Baid to retain for his own use all the larger and finely tinted specimens. PEGANITE. Composition Al;,P 2 Oii4-6aq=: Phosphorus pentoxide 31 1, alumina 31*1, water 23 7 = 100. Striegis, Saxo'ny. DUPRENITE. Composition Fe 2 P,On-f-3aq (FeP 2 Oii+H 6 FeO 6 ) = Phosphorus pentoxida 27 '5, iron sesquioxide 62*0, water 10-5=100. Anglar, Dept. of Haute Vienne ; Hirschberg, Westphalia ; Allentown, N. J. In deposits of nodules 1 to 6 in. thick, in Rockbridge Co., Va ANDHEWSITE. In globular forms, having a radiated structure. H. 4. G.=3'475. Color dark green. Analysis, Flight, P 2 O 6 26-09, FeO s 44-64, A10 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,0 5 29'93, As,O 5 0'61, Fe0 3 42'81, A10 3 4-45. CuO 814, H 2 O 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 2 5 48 '94, iV!O 3 18 '24. FeO 3 2-74, CuO 710, CaO 0'54, H 2 O 17*10, Si0 2 1-37, loss 3'97=100. Occurs on limonite at the West Phenix mine, Cornwall (Collins, Min. Mag., 1, p. 11). CACOXENITE. Supposed to be an iron wavellite. Composition Fe 2 P 2 Oji + 12aq. In ra- diated tufts. Color yellow. Hrbeck mine, Bohemia. ARSENIOSIDERITE. Analysis by Church, As 2 6 39 -86, FeO 3 35-75, CaO 15'53, MgO 018 K 2 O 0-47, H,O 7-87=9966. Formula (Kamm.) 2Ca 3 As 2 O8+FeAs,O8 + 3H 6 Fe0 6 . Ko- maneche. ATELESTITE. Essentially a bismuth arsenate. In minute yellow crystals at Schneeberg. TORBERNITE. Chalcolite. Kupfer-Uranit, Germ. Tetragonal. O A l-l = 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 subtranslucent. Fracture not ob- Bervable. Sectile. Lamina) 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(UO 2 ) s P,O s -fCu 3 P.20 8 +24aq. The formula requires: Phosphorus pentoxide 151, uranium trioride 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 (copper). With soda on charcoal gives a globule of copper. Affords a phosphide with the sodium test. Soluble in nitric acid. Obs. G-unnis Lake, Tincroft and Wheal Duller, near Redrutb, 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 ; th former also as Copper-uranite, the latter Lime-uranite. OXYGEN COMPOlJNl/8. PHOSPHATES, ARSENATES, ETO. 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. GK 3'05-3*19. Lustre of O pearly ; elsewhere subadaman- tine. Color citron- to sulphur-yellow. Streak yellowish. Translucent Optically biaxial, DesCl. Comp. Q. ratio f or B : U : P : H=l : 6 : 5 : 10. Formula CaU 2 P 2 Oi 2 + 10aq, which may be written 2(U0 2 ) 3 P.,O 8 4- Ca 3 P 2 8 +30aq. The formula requires : Phosphorus pentoxide 14'9, uranium brioxide (UO 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. Occurs sparingly at Middletown, Ct. ; also in minute crystals at Chesterfield, Mass. ; at Acworth, N. H. TROGERITE. Composition U 3 As 2 Oi4-i-12aq=(U0 2 ) 3 As 2 08 + 12aq. This requires : Arsenic pentoxide 17-6, uranium trioxide 65 9, water 16 '5= 100. Monoclinic. In thin tabular crys- tals of a lemon -yellow color. Schneeberg, Saxony. WALPURGITE. Composition Bi 10 y 3 As4034+12aq=(UO; ! ) 3 As,O8+2BiAs04+8H a BiO: ) . This requires: Arsenic pentoxide 11 '9, bismuth oxide 60'0, uranium trioxide 22*4, waterS 7=100. Monoclinic. In thin scaly crystals. Color wax-yellow. Schneeberg, Saxony. URANOSPINITE. An arsenic autunite. Composition CaU 2 As^On + 8aq 2(UOj).As 2 O8 + Ca 3 As2O 8 -{-24aq=Arsenic pentoxide 22'9, uranium trioxide 57*2, lime 5 '6, water 14 '3 =100. Color green. Schneeberg, Saxony. URANOSPH^KITE. Color yellow. Analysis, Winkler : U 3 50-88, Bi 2 3 44'34, H,0 4-75. Schneeberg. ZEUNERITE. According to Winkler, an arsenic chalcolite, with which it is isomorphoua. Composition CuUoAs 2 Oi 2 +8aq=2(UO 2 )sA8 2 O8 + Cu 3 As208+24aq=Arsenic pentoxide 22"3, uranium trioxide 50 '0, copper oxide 7'7, water 14'0=100. Color bright green. Schneeberg, Zinnwald, Saxony; Cornwall. PITTICITE. Iron-sinter. Composition uncertain, contains ASiOe, Fe0 3 , S0 3 , H-jO. DIA- DOCHITE is similar, but contains P a 6 instead of As a 6 . HYDROUS ANTIMONATES. BINDHEIMITE (Bleiniere). 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 2 6 81-71, PbO 61 '83, H 2 6 '46=100. Results from the decompo- sition of other antimonial ores. From Nertschinsk in Siberia ; Horhausen ; near Endellion in Cornwall, with jamesonite, from which it is derived. KlTJBATKS. The nitrates are all soluble, and hence are rarely met with in nature. They ir.r lude : NITRE, potassium nitrate (KN0 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. NITROMAQNESITE, magnesium nitrate (MgN 2 O 6 ). From limestone caves. GLAUBISRITE, nitro -sulphate of sodium. Desert of Atacama, Chili. 380 DESCRIPTIVE MINERALOGY. EQUATES. SASSOLTTE. Triclinic. 1/\T - 118 30', O A 1= 95 3', A /' = 80 a.r , Jb & M, Twins: composition-face 0. Cleavage: basal very perfect. Ubatlly in Biaall scales, apparently six-sided tables, and also in stalactiti'i forms, com- posed of small scales. H.=l. G. =1*4:8. Lustre pearly. Color white, except when tinged yellow by sulphnr; sometimes gray. Feel smooth and unctuous. Taste acidulous, and slightly saline and bitter. Oomp H 6 B 2 6 =Boron trioxide (B 2 O 3 ) 56 '46, water 43 '54=100. The rmtive stalactitio salt contains, mechanically mixed, various impurities, as sulphate of mag^tsium 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 Hofer in the waters of the Tuscan lagoons of Monte Botondo and Castelnuovo, and afterward in the solid state at Sasso by Mascagni. The hot vapors 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 discovered by Dr. Holland in 1813. SUSSEXITE (Brush). In fibrous seams or veins. H.=3. G.=3'42. Lustre silky to pearly. Color white, with a tinge of pink or yellow. Translucent. Comp. RaBjOs+aq, with R=Mn : Mg=4 : 3=Boron trioxide 34'3, manganese protoxide 39'9, magnesia 16 '9, water 8 '9 =100. Pyr., etc. In the closed tube darkens in color and yields neutral water. If turmeric paper js 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 coloring the flame intensely yellowish-green. Reacts for manganese with the fluxes. Soluble in hydrochloric acid. Obs. Found on Mine Hill, Franklin Furnace, Sussex Co., N. J.; associated with franklin- ite, zincite, willemite, and other manganese and zinc minerals. SZAIBELYITE. A hydrous magnesium borate, Mg 6 B 4 On+3aq (or faq). Occurs in acicular crystals. Color white. Hungary. LUDWIGITE (Tschermak). Finely fibrous masses. H. =5. G.=3'907-4'016. Color black ish-green to black. Composition R 4 FeB 2 O 10 , with R=Fe : Mg=l : 5, or 1 : 3. For the latter the formula requires : Boron trioxide 16 '6, iron sesquioxide 37 9, iron protoxide 17'!, magnesia 28 '4. Occurs in a crystalline limestone with magnetite at Morawicza in the Banat. also altered to limonite. OXYGEK COMPOUNDS. BORATES. 381 BORACITE.* Isometric; tetrahedral. Cleavage: octahedral, in traces. Cubic faces Bometimes 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- transparent translucent. Fracture conchoidal, un- even. Pyroelectric, and polar along the four octa- hedral axes. Comp. Mg 7 Bi 6 Cl 2 3 o = 2Mg s B 8 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. Altera 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- Btein in Liineberg, Hanover; at Segeberg, near Kiel, in Holstein ; at Luneville, La Meurthe, France ; massive and crystallized ab Stassfurt, Prussia. BORAX. Tinkal of India. Monoclinic. C= 73 25', /A 1= 87, A 24 = 132 49' ; c : b : a = 0'4906 : 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. Comp Na a B 4 07+10aq=2(NaB0 2 +HBO 2 )+9aq=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. Natronborocalcite. In rounded masses, loose in texture, consisting of fine fibres, which are acicular or capillary crystals. H.=l. Gr.=r65, N. Scotia, How. Lustre silky within. Color white. Tasteless. Comp NaCaB 6 O+5aq=Boron trioxide 49*7, lime 15'9, soda 8'8, water 25 '6=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 flan e 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 impurities; 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. BECIIILITE. (Borocalcite). An incrustation at the Tuscany lagoons. Composition CaB 4 Oi + 4aq. Also similar from South America. LARDERELLITE, LAGONITE, rare borates from the Tuscan lagoons. PRICEITE (SiUimari). Compact, chalky. Color milk-white. Composition Ca s B 8 Oi6 + 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, SiliGoborocaltite, 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 (?). CRYPTOMORPHITE. Near ulexite in composition. Ir microscopic rhombic tables. Nova Scotia. LUNEBURGITE. A phospho-borate of magnesium. Flattened masses in gypsiferous marl at Liineburg. WARWIOKITE. Monoclinic. I/\ 7=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.=3-4r. 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 magnesium and iron. Analysis, Smith, B 2 O 3 27 '80. Ti0 2 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 clear bead, yellow while hot and colorless on cooling ; in R. F. on charcoal with tin a violet colqr (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 | ia. broad. OXYGEN COMPOUNDS TUNGSTATES. MOLYBDATES. ETC. 383 5. TUKGSTATES MOLYBDATES, CHKOMATES. WOLFRAMITE. Monoclinic. C = 89 22', l/\ 1= 100 37', +4 A H = 118 6', i-i A = 117 6', 14 A 14 = 98 6', DesOloizeaux. Cleavage: ^4 perfect, i-i imperfect. Twins: planes of twinning i-i (f. 692), |4, and rarely 4. Also irregular lamellar; coarse divergent columnar; massive granular, the particles strongly coherent. 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. =719-7 54, but generally below 7*25, and the streak is mostly black. Those rich in iron have G. =7'2-7'54, 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 ia paler on cooling; in B.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 quartz, 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. A l-i = 123 3' ; c = 1-5369. Cleavage : 1 most distinct, ~L-i interrupted, O traces. Twins: twinning-plane /; 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 CaWO 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 caloric 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 ; Ehrenfriedersdorf ; 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 Flo we mine, Mecklenburg Co. CUPROSCHEELITE. A scheelite containing about 6 p. c. copper oxide. Color bright green. La Paz, Lower California. Llamuco, near Santiago, Chili. CUPBOTUNGSTITE. A copper tungstate, Cu 2 W0 6 +aq. Amorphous. Color yellowish- green. With cuproscheelite at the copper mines of Llamuco, Chili. STOLZITE. PbW0 4 Tungsten trioxide 51, lead oxide 49=100. Tetragonal. Zinnwald ; Bleiberg; Coquimbo, Chili. Schlackenwald. WULPENITE.* Gelbbleierz, Germ. Tetragonal. Sometimes hemihedral. A l-i = 123 26' ; c = 1 -574. 695 696 697 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 granularly 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. G.= 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. Vanadiferous. 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 Cornstock lode 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 (Sdirauf ).1x. minute tetragonal octahedrons. Color deep-red. Probably a vana- dio-molybdate of lead. Leadhills, Scotland. ACIIKEMATITE. An arsenio-molybdate of lead. Analysis, As,0 5 1825, Mo0 3 5 '01, 01 215, Pb 628, PbO 68-31=100-00. Compact; structure indistinctly crystalline. H.=3-4. G. =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.) CROCOITE. Crocoisite. Rothbleierz, Germ. 698 Moiioclinic. O= 77 27', /A I = 93 42', O A 14 = 138 10' ; I : I : a = 0-95507 : 1-0414 : 1, Dauber. Cleavage : /toler- ably distinct ; and i-i less so. Surface /streaked longitudinally ; the faces mostly smooth and shin- ing. Also imperfectly columnar and granular. H.=2-5-3. G.=5-9-6-l. Lustre adamantine- vitreous. Color various shades of bright hyacinth- red. Streak orange-yellow. Translucent. Sectile. Oomp. PbCr0 4 =Lead oxide 69*0, chromium trioxide 31'0 100. Pyr., etc. In the closed tube decrepitates, blackens, but re- sovers its original color on cooling. B.B. f uses at 1 "5, and on charcoal 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 Urals. Brazil violet mass, which on solidifying becomes reddish, and when cold greenish-white, thus differing from vanadinite, which on similar treatment gives a yellow mass (PlattnerX 25 386 DESCRIPTIVE MINERALOGY. Obs. First found at Beresof in Siberia ; at Mursinsk anJ near Nischne Tagilsk in the Ural; in Brazil; at Retzbanya; Moldawa; on Luzon, one of the Philippines. FHCENICOCHROITE. 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. Oomp. 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. A Iso reniform or botryoidal, and granular ; amorphous. H.=2'5-3. G. =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 B =2BCr0 4 +B.O. B=Fb : 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. LAXMAITKITE (pho*plwchrmwU\ Near vimquelinite, but held to be a pLoepho-chioraate. Beresof OXYGEN COMPOUNDS. SULPHATES. 387 6. SULPHATES. ANHYDROUS SULPHATES. Barite Group. BARITE. Barytes. Heavy Spar. Schwerspath, Germ. Orthorhombic. /A 7= 101 40', O A 14 = 121 50' ; 6 : I : d = 1-6101 700 701 Cheshire. : 1-2276 : 1. O A 1 = 115 42' ; \-\ A -t, top, =. 102 IT ; 14 A !-, 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; i-i imperfect. Also in globular forms, fibrous or lamellar, crested ; coarsely laminated, laminae convergent and of ten 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, ray, blue, red, or brown, dark brown. Transparent to translucent opaque, ometimes fetid, when rubbed. Optic-axial plane brachydiagonal. Comp. BaS0 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 sulphate, this will not be absorbed by the coal when treated in powder with soda. Insoluble in acids. Diflf. 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 th<- gaugue of the ore. It is met with ir. secondary limestone, sometimes forming distinct veins. and often in crystals along with calcite and celestite. At Dufton, in Westmoreland. Eng 388 DESCEIPTIVE 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 Roy a 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. y CELESTITE. Orthorhombic, I f\ I 104 2' (103 30'-1 04 30'), <9 A 1-i = 121 19i' ; c : I ; d = 1-6432 : 1-2807 : 1. O A 1 = 115 38', A l- = 127 56' A 1, mac., = 112 35', 1 A 1, brack, = 89 1 distinct ; i-l less distinct. lar; occasionally granular. 26'. Cleavage : O perfect ; Also fibrous and radiated ; sometimes globu- 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. Pyr., 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 ; Chauniont Bay, Scoharie, and Lockport, N. Y. ; also the Rossie lead mine ; at Bell's Mills, Blair Co. , Penn. Named from coelestis, celestial, in allusion to the faint slrade of blue often presented by the mineral. BARYTOCELESTITE. Celestite containing barium sulphate 26 p. c. (Griiner), 20-4 p. c. (Turner). 1-1 A 14=74 54', -iA-H=100 J 35', on crystals from Imfeld in the BinnenthaJ (Neminar). DrammondL, Lake Erie* Norton, Hanover. OXYGEN COMPOUNDS. - SULPHATES, ETC. 389 ANHYDRITE, Orthorhombic. 7 A 1= 100 30', O A l-l = 127 19' ; c : I : & = 1-3122 : 1-2024 : 1. 14 A 14, top, = 85. Cleavage : ?4 very per- fect ; i4 also perfect ; O somewhat less so. Also iibrous, lamellar, granular, and sometimes impalpable. The lamellar and columnar varieties often curved or contorted. H.=3-3'5. G.=2-S99-2-9S5. Lustre : i-l and i-l some- what pearly ; O 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 fibroua _ varieties, splintery. Optic-axial plane parallel to i-l, or Stassfurt. plane of most perfect cleavage; bisectrix normal to 0\ Grailich. Var. () Crystallized ; cleavable in its three rectangular directions. (5) fibrous; either parallel, or radiated, or plumose, (c) Fine granular, (d) Scaly granular. Vulpinite is a scaly granular kin; I 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 ia the tripestone (Gekrosvlein). Comp. 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 14. 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. ANGLESITE. Bleivitriol, Germ. Orthorhombic. 7A7= 103 43', O A 14 = 121 20J', Kokscharof; c:l\a= 1-64223 : 1-273634 : 1. O A 1-i = 127 48' ; O A 1 = 115 35 J' ; \-l A 1-2, top, = 75 35 y. 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 -J4 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 opaque. Fracture conchoidal. Yery 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 (F.=1'5). On charcoal in O. 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. Obs. This ore of lead was first observed by Monnet as a result of the decomposition oi 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 aa CaSO 4 -r3BaSO 4 . Occurs in small crystals at Beaujeau, France ; Badenweiler, Baden. DOLEROPHANITE (Scacchi). Cu 2 SO 5 . In minute crystals. Monoclinic. Color brown. Vesuvius. HYDROCYANITE (Scacchi). Anhydrous copper sulphate, CuS0 4 . Color sky-blue. Very soluble. Vesuvius. APHTHITALITE, Arcanite. K 2 S0 4 =Potash 54-1, sulphuric acid 45*9=100. Vesuvius. THENARDITE. Sodium sulphate, Na 2 S0 4 . Spain; Vesuvius. LEADHILLITE. Orthorhombic. /A 7= 103 16', O A 14 = 120 10' ; c:l.d = 1-7205 : 1-2632 : 1. Hernihedral in 1 and some other planes ; hence monoclinic in aspect, or rhombohedral when in compound crystals. Cleavage : i4 vary perfect ; i-l in traces. Twins, f. 712, consisting of three crystals ; twinning plane, l-i (see f. 298, p. 97) ; also parallel with I. OXYGEN" COMPOUNDS. SULPHATES. 391 H. =2-5. G. = 6 26-6-44. Lustre of i-l pearly, other parts resinous, some- what adamantine. Color white, passing into yellow, green, 711 712 or gray. Streak un colored. Transparent translucent. Conchoid al fracture scarcely observable. Rather sectile. Comp. Formerly accepted for- mula, PbS0 4 +BPbCO 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 a O, and Hintze, Pb 7 C 4 S 2 O 2l +2H 2 0. Analyses: 1. Laspeyres; 2, Hintze: SO 3 C0 a PbO H 2 O 1. 8-14 8-08 81 -i>l 1-87=100, Laspeyres. 2. 817 9-18 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. CALEDONITE. Monoclinic (Schrauf). H. =2-5-3. G. =6*4. Color bluish-green. R 2 SO S + aq (Flight), with R=Pb : Cu=7 : 3, or 5PbS0 4 +3H_CuO, + 2H..,PbO 2 . This requires : Sulphuric trioxide 19-1, lead oxide 65 '2, copper oxide 11 '4, water 4'3=100. Leadhills, Scot- land ; Red Gill ; Retzbanya ; Mine la Motte, Missouri. L AN AKKITE. Monoclinic. H. =2-2*5. G. =6-3-6*4. Color pale yellow, or greenish- white. Transparent. Composition as formerly accepted, PbS0 4 + PbC0 3 . New analyses by Flight, and by Pisani, show the absence of both carbon dioxide and water ; composition accordingly Pb 2 S0 5 =PbS0 4 4-PbO, which requires : Lead sulphate 57-G, lead oxide 42'4=100. Leadhills ; Siberia, etc. GLAUBERITE. Monoclinic. O=Q -= 0-8454 : 0-8267 : 1. '16', /A I =83 20', A 14 = 136 30'; c : b : a Cleavage : O perfect. H. = 2-5-3. G. 2-64-2-85. Lustre vitreous. Color pale yellow or gray; sometimes brick-red. Streak white. Fracture conchoidal ; brittle. Taste slightly saline. Comp. Na 2 CaS 2 0=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. 392 DESCRIPTIVE MINERALOGY. HYDKOUS SULPHATES. MIRABILITE. Glauber Salt. 15', /A 7=86 31', (9 A 14 = 130 19'; c:b:d Cleavage : i-i perfect. Usually in efflorescent Transparent Monoclinic. 6 y =72 = 1-1089 : 0-8962 : 1. crusts H.= 1-5-2. G. = l-481. Lustre vitreous. Color white, opaque. Taste cool, then feebly saline and bitter. Comp. Na 2 S0 4 +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. Very soluble in water ; the solution gives with barium salts the reaction for sulphuric acid. Falls 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 River, Eocky Mountains. MASCAGNITE, BOUSSINGAULTITE (cerbolite), LECONTITE, and GUANOVTJLITE are hydrous sulphates containing ammonium. GYPSUM. Monoclinic. C= 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', 14 A 14 = 128 31' ; c : l> : a = 0-9 : 2-4135 : 1. O A 1 = 125 35', A 24=145 41', 1 A 1 = 143 42', 24 A 24= 111 42'. Cleavage : (1) i-l 9 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) O, or basal, imperfect, but affording a nearly smooth surface. Twins : 1. Twin- nmg-plaiie common (f. 717) ; also 14, 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. O-XTGEN COMPOUNDS. bJLPHATES. 393 II. = 1-5-2. G. = 2-314:-2'328, when pure crystals. Lustre of i-\ 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. () 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. CaS0 4 + 2aq= Sulphur trioxide 40 '5, lime 32'(i, 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 watar 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. Ob.3. 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. It is 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 O^ana in Spain ; in the clay of Shotover Hill, near Oxford ; at Montmartre, near Paris. A noted locality of alabaster occurs at Castelino, 35 in. 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 Canfield, 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 sy mine tricalJy 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 hi compact fibrous masses. H.= 2-5-3. G.=2'76S9. Lustre resinous or slightly pearly. Streak red. Color flesh- or brick-red, sometimes yellowish. "Translucent opaque Taste bitter and astringent, but very weak. Comp. 2RSO 4 +aq, where E=Ca : Mg : K 2 in the ratio 2:1:1; that is, K 2 MgCa 2 S 4 O 19 -I- 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 Bcluble in water, leaving a residue of calcium sulphate, which dissolves in a large amount oi water 391 DESCRIPTIVE MINERALOGY. Obs. Occurs at the mines of Ischl, Ebensee, Aussee, Hallstatt, and Hallein in Ausiria, with common salt, gypsum, and anhydrite ; at Berchtesgaden in Bavaria ; at Vic in Lorraine. The name Polyhalite is derived from iru\vs, many, and oAs, salt, in allusion to the numbet of salts in the constitution of the mineral. SYNGENITE, v. Zepharovich ; Kaluszite. Rumpf. Near polyhalite. Composition RSOu-f- aq, with R=Ca : K 2 = l : 1, that is, K 2 CaS O 8 +aq= Potassium sulphate 53'1, calcium sul- phate 41 '4, water 5 -5 = 100. Monoclinic. Occurs in small tabular crystals in cavities in halite at Ralusz, East Galicia. KJESERITE. MgS0 4 +aq= Sulphur trioxide 58*0, magnesia 28-0, water 18-0=100. Stass- furt. PICROMERITE is K a MgS vi O (J +Gaq= Sulphur trioxide 39'8, magnesia 9'9, potash 23 4, water 26-9=100. Vesuvius; Stassfurt. BLOEDITE. Composition NaoMgS.0 8 + 4aq= Sulphur trioxide 47-9, magnesia 12-0, soda 18-6, water 21 '5 =100. Salt mines of Ischl ; also in the Andes. STMONYITE (TacJiermak) is identical. IXEWEITE. 2Na2MgS 2 O 8 +5aq= Sulphur trioxide 52'1, magnesia 13 0, soda 20 2, watei 14-7=100. From Ischl. EPSOMITE. Epsom Salt. Bittersalz, Gtrrm. Orthorhornbic ic, and generally hemihedral in the octahedral modiiications. /A 1= 90 34', O A l-l = 150 2' ; c : I : d = 0-5706 : 1-01 : 1. I-i A !-, basal, = 59 27', 14 A 1-t, basal, = 59 56'. Cleavage : brachydiagonal, perfect. Also in botryoidal masses and delicately librous crusts. H. = 2'25. G.=1'751; 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, magnesia 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. CHALOANTHITE. Blue Vitriol. Kupfervitriol, Germ. Triclinic. Ohl= 109 32', O A /' = 127 40', /A 1' = 123 10', O A 1 =125 38', 0At-i = 120 50', 0A*-* = 103 27'. Cleavage: /imper- fect, /' very imperfect. Occurs also amorphous, stalactitic, reniform. II.=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. CuSO 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 localitief OXYGEN COMPOUNDS. SULPHATES. 395 are the Bammelsberg mine, near Goslar, in the Harz ; Fahlun in Sweden ; at Parys mine. Anglesey ; at various mines in Co. of Wicklow ; Rio Tinto mine, Spain. Found at the Hiwassee copper mine, and other mines, in Polk Co. , Tennessee ; at the Canton mine, Georgia ; at Copiapo, Chili, with stypticite. When purified it is employed in dyeing operations, and in the printing of cotton and linen, and for various other purposes in the arts. It is manufactured mostly from old sheathing, copper trimmings, and refinery scales. Other vitriols are: MELANTERITE, iron vitriol ; PISANITE, iron-copper vitriol; GOSLAR- ITE, zinc vitriol; BIEBEKITE, cobalt vitriol ; MORENOSITE, nickel vitriol ; CUPROMAGNESITE, copper-magnesium vitriol (Vesuvius). These are all alike in containing 7 molecules of watex of crystallization. ALUNOGEN (Haarsalz, Germ.). AlS 3 Oi 2 +18aq= Sulphur trioxide 36 '0, aluininal5'4, watei 48-6100. Taste like that of alum. Vesuvius; Konigsberg, Hungary. COQUIMBITE. FeS 3 Oi2+9aq= Sulphur trioxide 42-f, iron sesquioxide 28'5, water 28*8= 100. Coquimbo, Chili. ETTRINGITE (Lehmanri). Analysis, S0 3 16 -64, A10 3 7-7G, CaO 27 '27, H^O 45'82. In hexa- gonal needle-like crystals from the lava at Ettringen, Laacher See. Alum and HalotricJiite Groups. Here belong : TSCIIERMIGITE, ammonium alum. KALINITE, potassium alum, or common alum. MENDOZITE, sodium alum. PICKERINGITE, magnesium alum. APJOHNITE, man- ganese alum. BOSJEMANNITE, mangano -magnesium alum. HALOTRICHITE, iron alum. Also RCEMEUITE, and VOLTAITE. OOPIAPITE. Hexagonal (?). Loose aggregation of crystalline scales, or granular massive, the scales rhombic or hexagonal tables. Cleavage : basal, perfect. In- crnsting. H.=1'5. G.=2*14, Borcher. Lustre pearly. Color sulphur-yellow, citron-yellow. Translucent. Oomp. Fe 2 S 5 21 + 13aq ; G^eS^ 2 + fl 6 5e0 8 + 36H 2 O = Sulphur trioxide 41-9, iron sesquioxide 33 '5, water 24'5 = 100. Pyr., etc. Yields water, and at a higher temperature sulphuric acid. On charcoal be- comes magnetic, and with soda affords the reaction for sulphur. With the fluxes reactions for iron. In water insoluble. Obs Common as a result of the decomposition of pyrite at the Rammelsberg mine, near Goslar in the Harz, and elsewhere. This species is the yellow copperas long called misy, and it might well bear now the name Misylite. RAIMONDITE. Composition Fe 2 S 3 Oi5+7aq. FIBROFERRITE (stypticite). Composition . BOTRYOGEN is red iron vitriol, exact composition uncertain. Fahlun, Sweden. BARTHO LOMITE, West Indies, is related. IIILEITE. Fe S 3 Oia+12aq. Occurs as a yellow efflorescence )n graphite from Mugraa, Bohemia (Schrauf). ALUMINITE. Ken if orm, massive ; impalpable. H.nrl-2. G.=l-66. Lustre dull, earthy. Color white. Opaque. Fracture earthy. Adheres to the tciigue ; meagre to the touch 396 DESCRIPTIVE MINERALOGY Comp A-lSO 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, become* 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. AlSO c + 3aq. G.=2'80. Occurs near 'Chachapoyas, in Peru. ALUNITE, Alaunstein, Germ, Composition K 2 2Vl 3 S 4 0.22 + 6aq. Rhombohedral. Also massive, fibrous. Forms seams in trachyte and allied rocks. Tolf a, near Rome ; Tuscany ; Hungary ; Mt. Dore, France, etc. LOWIGITE. Same composition as alunite, but contains 3 parts more of water. Tabrze, Silesia. \:f\ LINARITE. Bleilasur, Kupferbleispath, Germ. Monoclinic. C = 77 27' ; /A I, over i-i, = 61 36', O A 1-1 = 141 5', c:b:d = 0-48134: : 0-5819 : 1, Hessenberg. Twins: twinning-plane i-i common ; O A O' = 154 54'. Cleavage : i-i very perfect ; O less so. H.=2'5. Gr. 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)S04+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- land ; near Schneeberg, rare; in Dillenburg ; atRetzbanya; inNertschinsk; and near Beresof in the Ural ; and supposed formerly to be found at Linares in Spain, whence the name. BROCHANTITE. Monoclinic. O = 89 27*'. 1 A /= 104 6i', O A 14 = 154 12' ; c : l\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 Nisehne-Tagilsk, mono- clinic triclinic ; IV. lEonigine from Russia, and a fourth variety from Retz- banya, monoclinic (or orthorhornbic). Also in groups of acicular crystals and drusy crusts. Cleavage : i-l very perfect ; / 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 + 3H 2 p=CuSO4 + 3H 2 Cu0 2 =Sulphur trioxide 17'71, copper oxide 70 '34, water 11 '95 =100. This formula belongs to type IV., above ; the warringtonite corresponds more nearly to CuS0 4 +uHaCuO^-t-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 Konigite} 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. LANGITE. CuSO 4 +2HoCuOj + 2aq. In crystals and concretionary crusts of a blue color. G.=3-5. Cornwall. CYANOTRICIIITE, Lettsomite. Kupfersammterz, Germ. In velvety druses. Color blue. A hydrous sulphate of copper and aluminum. Moldava in the Banat. WOODWARDITE, near Che above. KIIONKITE. CuS0 4 + Na 2 S0 4 + 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.} PHILLIPITE. CuS0 4 +FeS s Oi 2 +waq. In irregular fibrous masses, not prismatic. Coloi blue. In the cordilleras of Condes, Santiago, Chili (Domeyko.} ENYSITE. Occurs in stalactitic forms in a cave. H.=2-2'4. G. =1-59. Color bluish- green. B.B. infusible. Analysis: S0 3 8'12, A10 3 29'85, CuO 16D1, CaO 1'35, HO 39'42, Si0 2 3-40, C0 2 1-05=100. Near St. Agnes, Cornwall (Collins, Min Mag., 1. p. 14.) URANIUM- SULPHATES. There are included here joliannite, uranochalcite, medjidite, zippeite, voylianite, uraconite. These are secondary products found with other uranium minerals at Jofcchimsthal* TELLURATES. MONTANITE. Incrnsting ; without distinct crystalline structure. Soft and earthy. Lustre dull to waxy. Color yellowish to white. Opaque. Oomp. Bi 2 TeO 6 + 2aq=: Tellurium trioxide 26-1, bismuth oxide 68'6, water 5'3=100. Fyr., etc. Yields water in a tube when heated. B.B. gives the reactions of bismuth and tellurium. Soluble in dilute hydrochloric acid. Obi. Incrusts tetradymite, at Highland, in Montana ; Davidson Co., N. C. 398 DESCRIPTIVE MINERALOGY. 7. CAKBOSTATES. ANHYDROUS CARBONATES. Calcite Group. CALCITE. Calc Spar. Kalkspath, Gvrm. Khombohedral. E^E, terminal, = 105 5', (9 A 7? = 135 23'; 0*854:3. Cleavage: R highly perfect. 719 720 721 722 723 ANGLES OP RHOMBOHEDRONS. Term. Edge. i(-i) 150 2 !(_$) 134 57' B(-'R) 105 5' 166 9' 153 45' 135 23' Term. Edge. -$ 95 28' 2(-2) 78 51' 4(-4) 65 50' 727 0/\R 129 2 116 52' 104 17' ANGLES OF SCALENOHEDRONS. Edge X (f. 724). J- 8 138 3 5' P 128 15' * 104 38' i 109 r Y. 159 24' 146 LO' 144 24' 134 28' Z. 64 54' 90 20' 132 58' 150 44' Edge X. 130 37' -* 107 38' -i* 117 23' -2 8 92 9' Y. 164 1' 145 15' 149 43' 153 16' Z. 67 41' 124 39' 102 25 135 1 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) 2J?. (4) i^ff, the vertical axes of the two forms inclined to one another 127 34:'. (5) Pris- matic plane *-2. (6) plane i (see p. 95). Also fibrous, both coarse and fine; sometimes lamellar; of ten 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 subvitreous 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 Derbyshire Alston-Moor. Comp., Var. Calcite is calcium carbonate, CaC0 3 =r 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-i ef meting Spar (Doppels- path, Genn.}. 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 400 DESCRIPTIVE MINERALOGY. ment occur abort and stout because abbreviated by an abrupt termination in a broad 0, or an obtuse rhombohedron (as or .72), or a low scalenohedron (as ^ 3 ), or a combination 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 Nen.ours, 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 much harder and effervesces with acids. Argentine (Schieferspath), a pearly lamellar calcite, the lamellae more or less undulating ; color white, grayish, yellowish, or reddish. Aphriti, in its harder and more sparry variety (ScJiaumspath) is a foliated white pearly calcite, near argentine ; in its softer kinds (Schawnerde, Silvery Chalk, Ecume de Terra 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 (Succharoidal 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. SheU-marble includes kinds consisting 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 of 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. Hydraulic limestone is an impure limestone. The varieties in the United States contain 20 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 to 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 grains are minute rounded concretions, looking somewhat like the roe of a fish, the name coming from 'woy, egg. It occurs among all the geological formations, from the Lower Silurian to the most recent, and ifc 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 of the Hot Springs at Carlsbad in Bohemia. Deposited from calcareous springs, streams, or in caverns, etc. (a) Stalactites are the calcareous cylinders or cones that hang from the roofs of limestone caverns, and which are formed from 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 that drop from the roofs, or from sources over the bottom or sides ; cones of it sometimes rise from the floor to meet the stalactites above. (c) Oak-sinter, Travertine, Gale Tufa. Travertine ( Confetto diTuoli) is of essentially the eame 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 is scores of feet in thickness. It has a very cavernous and irregularly banded structure, owing fco its mode of formation. (d) Agaric mineral; Rock-milk (Bergmilch, Montmilcfi, Germ.) is a very soft, white material, breaking easily in the fingers, deposited sometimes in caverns, or about sources holding lime in solution. OXYGEN COMPOUNDS. CARBONATES. 401 (4) 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, bxit 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 iii cold acid. Diff. Distinguishing characters : perfect rhombohedral cleavage ; softness, can be scratched with a knife ; effervescence in cold dilute acid ; inf usib.ility. Less hard and of lower specific gravity than aragonite. 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 TJ. States prominent localities are : in N. 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., at the lead mine, Middletown In N. Jersey, 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 j at Quincy. 111.; at Hazle Green, Wis. In Nova Scotia, at Partridge L DOLOMITE. Rhombohedral. 7? A 72 = 106 15', <9 A 72 = 136 84'; c = 0-8322. R varies between 106 10' and 106 20'. Cleavage : R 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 : l=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. jR/\^=106 23' ' 106 10'. Cobaltiferous. Colored reddish ; G-. =2 '921, 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 MINERALOGY. (5). 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 iit. prob- able. ^Pyr., etc. B. B. acts like calcite, but does not give a clear mass when f used with soda on platinum foil. Fragments thrown into cold acid are very slowly acted upon", while in powder 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 U. 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. Khombohedral. R A R 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. Oomp. CaC0 3 +FeC0 3 +(CaMgC 2 6 ). Here, according to Boricky, a? may have the values *, 1 $, ih , 2, 3, 4, 5, 10. The varieties having the five higher values of x he calls paran- kcrite, while the others are normal ankerite. If =1, the formula is equivalent to 2CaC0 3 -t- MgCO 3 +FeCO 3 , and requires: Calcium carbonate 50, magnesium carbonate 21, iron carbon- ate 29=TLOO. 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. Rf\R = 107 29', O^E = 136 56' ; c 0-8095. Cleavage: rhombohedral, perfect. Also massive; granular, to very com- pact. H.=3-5-4-5. G.=3-3-08, 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 fiat conchoid al. Var. Ferriferous, Breunerite ; containing several p. c. of iron protoxide; Gr.=3-3'2, white, yellowish, bro\vnish, rarely black and bituminous; often becoming brown on exposure, and hence called Brown Spar. Comp. Magnesium carbonate, MgCO 3 = Carbon dioxide 52 4, magnesia 47 '6 = 100 ; but iron often replacing some magnesium. Pyr., etc. B. K resembles ealcite and dolomite, and like the latter is but slightly acted upon by cold acids ; in powder is readily dissolved with effervescence in warm hydrochloric 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 opliidite of OXYGEN COMPOUNDS. CARBONATES 403 Bunt) ; 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 Barehills, near Baltimore, Md. ; in Penn., at West Goshen, Chester Co. ; near Texas, Lan- caster Co. ; California. MESITITE and PISTOMESITE come under the general formula (Mg,Fe)C0 3 ; with the formoi Mg : Fe=2 : I ; with the latter^=l : 1. )^ SIDERITE. Spathic Iron. Chalybite. Eisenspath, Germ. Khombohedrul. R A R = 107, O A R = 136 37' ; c = 0-81715. The faces often curved, as below. Cleavage : rhom- bohedral, perfect. Twins : twinning-plane J-. 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. Oomp., 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. Some varieties contain 8-10 p. c. MnO. The principal varieties are the following : (1) Ordinary, (a) Crystallized, (b) Concretionary = Spherosiderite ; in globular concretions, either solid or concentric scaly, with usually a fibrous structure, (c) Granular to compact mas* *we. (a) 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 ; Gr. =3'0-3'8, or mostly 3 15 -3 '05. Pyr., eto. 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 uitre 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 as 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 .AT. Fork, at the Sterling ore bed in Antwerp, Jefferson Co. ; at the Rossie iron mines, St. Lawrence Co. In JV. 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 many parts of the country. RHODOCHROSITE.* Dialogite. Manganspath, Germ. Ehombohedral. 72 AT? = 106 51', O A R = 136 31i'; c = 0-8211. Cleavage : 72, perfect. Also globular and botryoidal, having a columiiai structure, sometimes indistinct. Also granular massive ; occasionally ira palpable; iucrustiiig. 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 ?; 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. Dissolves with effervescence in warm hydrochloric acid. On exposure to the air changes to brown, and some 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 Schemriitz and Kapnik in 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 of Austin, Nevada ; at Placentia Bay, Newfoundland. Named rlwdochrosite from f>6$ov y a rose, and xp&vis, color ; and dialogite, from SmAo-y^, doubt. SMITHSONITE. Calamine pt. Galmei pt. Zinkspath, Germ. Khombohedral. Rl\E~ 107 40', 0/\R = 137 3' ; c = 0-8062. R 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 imperfectly conchoidal. Brittle. Comp., Var. ZnC0 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) botryoidal 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 drusy surfaces in the cavities ; " dry-bone" of American miners. Pyr.j 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 calamine 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 Raibel in Cariu- thia; Moresnet in Belgium. In England, at Roughten Grill, Alston Moor, near Matlock, in the Mendip Hills, and elsewhere ; in Scotland, at Leadhills; in Ireland, at Donegal. In the U. States, in jY. 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. ARAGONITE. Ortliorhombic 7 A 7 = 116 10', O A 14 = 130 50' ; comiriy 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 orn: La closely related to that of epidote (Ber. Ak. Wien, July 3, 1871). BISMUTITE. Wismuthspath, Germ. In implanted acicular crystallizations (pseudomorphous) ; also incrtisting or amorphous ; pulverulent. H.=4-4'5. Gr.=6'86-6'909. Lustre vitreous, when pure; sometimes dull. Color white, mountain-green, and dirty siskin-green ; occasionally Btraw-yellow and yellowish-gray. Streak greenish-gray to colorless. Sub- translucent opaque. Brittle. Comp. 2Bi 8 C 3 O, 8 f 9H 2 0, Kamm. (S. Carolina) = Carbon dioxide 6 '38, bismuth oxido 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 Schneeberg 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 (TJrankalk, Germ.). Carbonates of uranium and calcium, from the decomposition of uraninite. Exact composition doubtful. SCHROCKTNGERITE 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 2 C>4 4- 3aq. Compact; earthy. In brown- coal of Koloseruk, near Bilin; also in black shales at Kettle Point; in Bosanquet, Canada. MELLITE (Honigstein, Qerm.\ Tetragonal. In octahedrons ; also massive, honey -yellow, reddish, or brownish, rarely white. Al Ci 2 OnH-18aq=:Aluniina 14 '36, mellitic acid 40'30, water 45 34=100. Arteru, Thuringia ; Luschitz, Bohemia ; Walchow, Moravi* ; Nertschinsk, 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 C n H 2n+2 - Here belong the liquid naphthas, the more volatile parts of petroleum ; also the butter-like solids scheererite and chrismatite. PETROLEUM. Mineral oil. Kerosene. Bergol, Steinol, Erdol, 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 09. 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 olil'erous shales and limestones the oil of cen 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 southei-n 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 Olefiant or Ethylene series. General formula CnH^. Here belong the pittolium group of liquids, or pittasphalt 8 (mineral tar), and the paraffins. 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. G-. about '85-0 -98. Melting point for the following species, 33-9Q\ 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 : URPF/miTE. Consistency of soft tallow. Melting point 39 C. Soluble in cold ether. Urpeth Collierv. 414 DESCRIPTIVE MINERALOGY. HATCHETTITE. In thin plates or massive. Color yellowish, or greenish- white ; blackent 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. Colorless 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 litumiuDus 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 of 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 6w, smeU t and /c^pof , wax, in allusion to the odor. ELATERITE. Massive, soft, elastic; often like india-rubber, though sometimes hard and brittle. It is found at Castleton in Derbyshire, in the lead mine of Odin, along with lead ore and calcite, in compact renif orm or fungoid masses, and is abundant. Also reported from St. Bernard's Well, Edinburgh, etc. ZIETRISIKITE and PYBOPISSITE belong here. (c) The Camphene Series. General Formula C n II 2n _ 4 . FICHTELITE. 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 the rings of growth and throughout the texture of pine wood (identical in species with the modern Pinus sylvestris) from peat beds in the vicinity of Redwitz in the Fichtelgebirge, North Bavaria. In peat near Sobeslau ; in a log of Pinus Australis. HAIITITE. Resembles fichtelite, but melts at 74-75 C. Found in a kind of pine, like fichtelite. but of a different species, the Pence acerosa Unger, belonging to an earlier geological epoch. From the brown-coal beds of Oberhart, near Gloggnitz, not far from Vienna. Reported also from Rosenthal near Koflach in Styria, and Pravali in Carinthia. DraiTE 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. Color white. In nature found only impure, being mixed with cinnabar, clay, and some pynte and gypsum in a brownish -black earthy material, called from its combustibility and the presence of mercury, inflammable cinnabar (Quecksilberbranderz). Idria, Spain. ARAGOTITE, from 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-J-, or less. Some of the more important are : GEOCERITE. Wax-like. Color white. Melting point near 80 C. ; after fusion solidifies as a yellowish wax, hard but not very brittle. Soluble in alcohol of 80 p. c. C 2 H 5 6O 2 = Carbon 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- sisting of acicular crystals. Color white. Melting point 80-83 C. After fusion has the aspect of a yellowish brittle wax. Soluble easily in hot absolute alcohol and ether, but slightly in alcohol of 80 p. c. C 34 H6 6 O 2 = Carbon bO'59, hydrogen 13'42, oxygen 5 '99 = 100. Burns with a bright flame. Occurs at the Gesterwitz brown coal deposit, in a dark brown tayer. HYDROCARBON COMPOUNDS. 415 SUCCINITE. Amber. Succin, Ambre, Fr. Bernstein, Germ. In irregular masses, without cleavage. H. 2-2'5. G.=l'065~l*081. Lustre resinous. Color yellow, sometimes reddish, brownish, and whitish, often clouded. Streak white. Transparent translucent. Tasteless. Elee- tr ; c on friction. Fuses at 287 C., but without becoming a flowing liquid. Comp. Ratio f or 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 Berzelius, it consists mainly (85 to 90 p. c.) of a resin which resists all solvents (properly the species succinite), along with two othe* 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. O'bs. Occurs abundantly on the Prussian coast of the Baltic ; occurring 1'rom 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. In 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. Thia is inferred both from its native situation with coal, or fossil wood, and 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 t]/ e/crpov, 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 of remarkable electrical properties. Other related resins are: COPALITE (retitiite pt.) from Highgate Hill, near London; KHANTZITE, Nieuburg ; WALCHOWITE, Walchow, Moravia ; AMBKITE, N. Zealand ; BATH- VILLITE, occurring in the torbanite, or Boghead coal of Bathville, Scotland ; torbanite is related to it. SLEQBURGITE, bciiRAUFiTE, AMBROSINE, DUXITE. XYLORETINITE (hartine). C : H : O=40 : 64 : 4. BOMBICCITE, C : H : O 13 : 7 : 1, in lignite in the valley of the Arno, Tuscany. LEDCOPETRITE. C : H : O=f>0 : 84 : 3. Ges- terwitz, near Weissenf els. EUOSMITE. C : H : O 34 : 29 : 2, from the brown coal at Baiershof 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 I H=5 I 5^ Or less. Insolu- able in ether or alcohol. TASMANITE and DYSODILE are remarkable in containing sulphur, replacing part of the oxygen. The ACID OXYGENATED HYDKOCARBONS include Butyrellite (Bogbutter), Succinellite, Dopplerite, etc., etc. 416 DESCEIPTIVE MINERALOGY. APPENDIX TO HYDKOCAKBONS. ASPHALTUM. Bitumen. Asphalt, Mineral Pitch. Bergpech, E 'dpech, Qeim. Asplialtum, or mineral pitcli, is a mixture of different hydrocarbons, part of which are oxygenated. Its ordinary characters are as follows: Amorphous. 5. = 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 0., 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. Bat 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 Dahnatia ; 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. GRAIIAMITE, Wurtz. Resembles the preceding in its pitch-black, lustrous appearance; H. 2; Gr. =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 oi] of turpentine, and in its very imperfect fusion when heated. It has H. = 1-2; Gr. =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. It occurs slaty massive ; color brownish- or greenish-black ; thin splinters colophonite- brown by transmitted light ; streak light brown, amber-brown ; H.=l -5 ; G-.=l '220 ; 1 'ISb', 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 tule dees not 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. 417 MINERAL COAL The distinguishing characters of Mineral Coal are as f olloTvs : 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.=:0*5-2*5. G.= 1-1-80. Lustre dull to brilliant, and either earthy, resinous, or subrnetallic. Color black, grayish-black, brownish-black, and occasionally iridescent ; also sometimes dark brown. Opaque. Fracture conchoidal uneven. Brittle ; rarely somewhat sectile. Without taste, except from impurities present. Insoluble or nearly so in alcohol, ether, naphtha, and benzole. Infusible to subf 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 on destructive destination ; or (2) on the nature of these volatile compounds, for ingredients of 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- ture conchoidal. 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 per cent, 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- taining more volatile matter ; and an intermediate variety is called free-burning anthracite. BITUMINOUS COALS (Steinkohle 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 the 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 Pechkolile in German), a firm compact texture, are rather fragile compared with anthra- cite, and have Gr. =1*14-1 '40. The brown coals have often a brownish-black color, whence the 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-l*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 COAL. A bituminous coal which softens and becomes pasty or semi-viscid in the 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 30 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 dif- 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 conchoidal fracture and smooth surfaces; color dull black or grayish-black. On distillation it affords, after drying, 40 to 66 ol volatile mat- ter, 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 the manufacture of such oils. It graduates into oil-producing coaly shales, the more compact of which it much resembles. 5. TORBANITE. A variety of cannel coal of a dark brown color, yellowish streak, without lustre, having a subconchoidal fracture; H. =2 '25 ; G. = 1*17-1 '2. Yields over GO p. c. of volatile matter, and is used for the production of burning and lubricating- oils, paraffin, illu- minating gas. From Torbane Hill, near Bathgate in Linlithgowshire, Scotland. Also called Boghead Cannel. 6. BROWN COAL (Braunkohle Germ.* Pechkohle pt. Germ., Lignite\ The prominent characteristics of brown coal have already been mentioned. They are non-caking, but afford a large proportion of volatile matter They are sometimes pitch-black (whence Pechkohle pt. Gei'm.), but often rather dull and brownish- black. G. = ri5-l '3 ; sometimes higher from impurities. It is occasionally somewhat lamellar in structure. Brown coal is often called lignite. But this term is sometimes restricted to masses of coal which still retain the form of the original wood. Jet is a black variety of brown coal, compact in texture, and taking a good polish, whence its use in jewelry. 7. EARTHY BROWN COAL (Erdige Braunkohle) is a brown friable matfrial, sometimes form- ing layers in beds of brown coal. But it is in general not a true coal, a considerable part of it being soluble in ether and benzole, and often even in alcohol; besides affording largely of oils and paraffin on distillation. Comp. Most mineral coal consists mainly, as the best chemists now hold, of oxygenated, 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 irds a red ash on burning, there is reason for believing this true. But 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 rein containing sulphur (see TASMANITE, p. 415), gives reason for inferring that it may exist in 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 92-56 333 2 "53 1-58 2. Caking Coal, Northumberland 78 -69 (rOO 10-07 2 -87 1'51 1 "36 8. Non-Caking Coal, Zwickau 80'25 4'01 1098 0'49 2'99 1-57 4. Cannel Coal, Wigan 80'07 5'53 8'10 2-12 1 '50 2-70 5. Torbanite, Torbane Hill 04-02 8-90 5 "66 0'55 0'50 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 fracturings, 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 psat 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 l r nited 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. Cancel coal is found near G-reensburg, Beaver Co., Pa., in Kenawha Co , Va., at Peytona, 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. SUPPLEMENTAKY 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 of an intimate mixture of albite and muscovite. From Goshen, Mass. ALASKAITE, Konig. 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 Rammelsberg, from Moro- cocha, Peru, is pure Ag 2 S + Bi 2 Sn. ALBITE, p. 323. Has been made artificially, identical in form and composition with natu- ral crystals, by Hautefeuille. AMBLYGONITE, p. 369. Penfield has analyzed specimens from Penig, Montebras, 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: A1 2 P 2 8 + 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 bergamas- kite by Lucchetti. Occurs in a hornblende porphyry. Monte Altino, Bergamo, Italy. Phaactinite (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 manganapatite 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. ARAGOXITE, p. 405. A variety from the Austin mine, Wythe Co., Va., afforded 7'29 p.c. PbCO a . AKCTOLITE, Blomstrand. A doubtful silicate, composition near prehnite, prismatic angle near hornblende. Hvitholm, near Spitzbergen. 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- p, not one of the true micas. ite and zircon in El Paso Co., Colorado. , . . ber of the pyroxene group, not one of the true micas. Occurs with arfvedsonit ATELTNE (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 2 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 2011, Fe 2 3 2*52, MnO 0-79, MgO 8'30, CaO 13'47, Na.O 2'72, K 2 O 1-36, H 2 4-71 = 100*02. In limestone at Balvraid, 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. = 1. G. = 4;03. White. o 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. Color gray. Lustre metallic. Composition, 6PbS + Bi 2 S 3 = S 14-78, Bi 21 36, Pb 63 '84 = 100. From the Baltic Lode, Park Co., Colorado. 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 Sjogren ; 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 In spherical forms, with concentric, fine fibrous radiated structure. Regarded as an anhydrous bismuth carbonate. From Neustadtel, Schneeberg, Saxony. BLOMSTRANDITE, LindstrSm. 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. 881. On the crystalline system, see p. 183. BOWLINGITE, Hannay. A soft, soapy, green substance, containing silica, alumina, iron, ig sine Clyde, 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 O 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. Mangaiibrucite (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. j CABRERITE. Occurs in crystals (isomorphous with erythrite) at the zinc mines of Lau- rium, Greece An analysis by Damour corresponds to M 3 As 2 B -\-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 O e , 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 i-i - 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 S 4- 2RH 2 + 2aq, with R = Fe principally, also Mn. This requires: P 2 5 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 eosphorite by Brush Dana. Orthorhombic. In prismatic crystals (see fig.), near chil- drenite. /A/= 104 19' ; p f\p (1 Al) = 133 33' (front), = 118 58' (side). Here /, and a (i-l) = 2-i and O of childrenite. Also mass- ive, cleavable to compact. Cleavage parallel a (i-T) 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 : o). Percentage composition : P 2 3 30-93, A1 2 3 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 rnanganesian phosphates in a vein of pegmatite at Branch ville, Conn. CHLORALLUMINITE, Scacchi. Hydrous aluminum chloride from Vesuvius. CHLOROMAGNESITE, Scacchi. Hydrous magnesium chloride from Vesuvius. Sischofite /Ochsenius and Pfeiffer) from Leopoldshall, Prussia, has the composition MgCl 2 + 6 aq. Crystalline, massive, foliated or fibrous. Color w T hite. 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. v CHRYSOCOLLA, p. 338. Pilarite, from Cnili, is an aluminous variety, 16'9 p.c. Ai 2 3 . CHRYSOLITK, p. 300. NeocJirysolito (Scacchi) is a manganesian variety from Vesuvius. A variety from Zermatt, containing 6 p.c. TiO 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- gummite (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 Rhon. Clinophceite, from the same source, occurs in blackish green microscopic crystals; formula 5R 2 S0 4 4 [R 2 ]H 6 6 + 5 aq, with [R 2 ] = Fe 2 ,Al 2 , and R 2 = Fe,K 2 ,Na 2 . CLTNTONITE, 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 Branchville, Conn., having the composition MnCb 2 6 + MnTa 2 6 ; 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. CORONGUITE, 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, Nordrnark, Sweden. COSSYRITE, Foerstner. Near amphibole in form, but triclinic, and with I A /' = 114 5'. Cleavage prismatic. G. = 3*75. Color black. An analysis gave : Si0 2 43'55, A1 2 3 4-96, Fe,0 3 7'97, FeO, 32'87, MnO 1-98. CuO 0'39, MgO 0'86, CaO 201, 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). CRAIGTONITE, Heddle. Doubtful mineral, contains A1 2 3 , Fe 2 3 , MgO, etc. Dendrites 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, Scacclii. 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. part 51-5, DANALITE, p. 302. Occurs at the iron mine of Baitlett, K H. (Wadsworth). DANBURITE, p. 311. Occurs (G. J. Brush and E. S. Dana) well crystallized and abundant at Russell, N. Y. Orthorhombic, homceomorphous with topaz and like it in habit. I /\1 = 122 52' (topaz = 124 17'), w /\w = 54 58' (topaz = 55 20'), d /\d = 97 7' (topaz = 96 6'). Common forms as in figures, w = 4-?-, d = l-l, l=i-2, n = i-4, r 2-2. Color pale wine or honey yellow, colorless. Transparent. Composition CaB 2 Si 2 08, 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 (Chaper) in the province of Siena, Pian Castagnaio, Tuscany. Analysis gave Friedel : () C0 3 29*09, A1 2 3 35"89, Na 2 1913, H 2 12-00, MgO 1'39, CaO 0-42. DELESSITE, p. 356. More or less related to the chloritic delessite are: Subdelessite from the Thiiringer Wald ; Hullite, Camrnoney Hill, near Belfast, Ireland. DESCLOIZITE, p. 367. Occurs in the Sierra de Cordoba, Argentine Republic ; perhaps also in Arizona, Composition of South American mineral (Rammelsberg) RaV^O^ + RH 2 2 , with R Pb (56 p.c.), Zn (17 p.c.) BrackebuscMte from Cordoba, Argentine Republic, occurs in small striated crystals. Color black. C'omposition 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, fi= 61 30 . CA = 118 30', CAP = 118 52', c/\s = 97 58' ; c = 0, p =1, s = 2, a- = - 3- Com monly foliated to micaceous. Cleavage basal perfect. H. = 3 '5-4. G. = 3'338-3'34b. Lustre vitreous, on c pearly. Color various shades of green. Composition 4R 3 P 2 8 + 3aq. with R=Mn,Fe,'a,Na 2 , requiring: P a O 40-05, FeO 12-69, MnO 25 '04, CaO 11-85, Na 2 6-56, H 2 3-81 = 10J. 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 phytocoliite ; empirical formula CioH 22 Oi8. 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) : $i0 2 29-85, A1 2 3 66'02, Fe 2 O 3 1-01, 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. DYSANALYTE, Knop. The perofskite 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 H + 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, Nies. Monoclinic ; often in druses and in radiated crusts. Cleavage ortho- diagonal. H. = 3-4. Lustre vitreous. Color red brown to dark hyacinlh red. Streak Sallow. Composition (Streng) 2Fe 2 P 2 8 -- Fe 2 H fl O e + 5 aq. From the'Eleonore mine on the iinsberg, 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. ELROQUITE, 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. ENTSITE, 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 identical. EPSOMITE, p. 394. Reichardtite (Krause) is a massive variety from Stassfurt and Leo- poldshall. 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. 323. 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 ALSi 2 O 8 = Si0 2 47-51, AL0 3 40 61, Li 2 11-88 100. Branehville, Conn. EULYTITE, p. 302. Pseudo rhombohedral according to Bertrand. EUSYNCHITEIS (Eammelsberg) 4Pb 3 V 2 8 + 3Zn 3 V 2 8 . Araoxene is 2(Pb,Zn) 3 V 2 8 + (Pb,Zn) 3 As 2 O 8 . Tritochorite (Frertzel) is related, composition R 3 V 2 8 , with R = Pb (54 p.ck 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 8 + 9 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 Branehville, 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 show 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 and i-l are as follows : With With i-l Albite -f 4 to +3 +18 Varieties between Albite ) , 1 and Oligoclase \ 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 -16 to -18 29 C Anorthite -38 -40 FERGUSONITE, 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. FILLOWTTE, G. J. Brush and E. S. Dana. Monoclinic ; pseudo-rhombohedral. Gener- ally in granular crystalline masses. H. = 4'5. G. =3'43. Lustre subresinous to greasy. Color wax yellow, yellowish to reddish brown. Composition 3R 3 P 2 8 + aq, with R = Mn, Fe, Ca, Na 2 ; requiring : P 2 O 5 40'19, FeO 6-80, MnO 40-19, CaO 5'28, Na 2 5'84, H 2 O 1-70 = 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 Na 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. Sjogren. 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 ; analvsis (Lind- strom : Si0 2 34'55, PbO 34"S9, MnO 2001, CaO 4'89, MgO 3'68, alk., ign. 1 88=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. Triciinic, complex twins, according to Schrauf and v. Lasaulx. GUANAJUATITE, Fernandez, 1873. The same mineral as that afterward called frenzelite (p. 223). Composition (Mallet), Bi 3 Se a , with a little Se replaced by S. Silaonite is a mechanical mixture of this mineral and native bismuth. GUNNTSONITE, Clarke and Perry (Am. Chem. Journ., iv., 140). A massive substance, of a deep purple color, mixed with calcite. An analysis, after deducting 12-75 CaC0 3 , yielded CaF 2 74-89, CaO 11-44, Si0 2 6-87, A1 2 3 5'95, Na 2 0-85 = 100. Probably an impure fluorite ; perhaps altered ; certainly not a homogeneous mineral. GUEJARITE, Cumenge. Orthorhombic ; in prismatic crystals, form near that of chalco- stibite. H. - 3*5. G. = 5'03. Color steel gray. Composition Cu 2 Sb 4 S 7 or Cu 2 S + 2Sb 2 S 3 . From the copper mines in the district of Guejar, Andalusia. GUMMITE. This decomposition product of uraninite occurs in considerable masses at the Flat Rock mine, Mitchell Co., N. C. GYROLITE, p. S2S.Tobermorite of Heddle, is near gyrolite and okenite. Massive. Color pinkish white. G. = 2-423. Analysis : Si0 2 46-62, A1 2 3 3-99, F 2 3 0'66, FeO 1-08, CaO 33-98, K 2 0-57, Na 2 0'89, H 2 1211 = 99 -81. Filling cavities in rocks near Tobermory Island of Mull. > HALLOYSITE, p. 352. Indianaite of Cox, is a white porcelain clay, useful in the arts, occurring in considerable beds in Lawrence Co., Indiana. HANNAYITE, vom Rath. In triclinic prismatic crystals. G. = 1*893. Composition gsRtOie + 8 aq. Occurs in guano of the Skipton Caves, Victoria. HATCHETTOLITE, J.L. Smith. Isometric, habit octahedral. H. = 5. G. = 4 -77-4-90. Lustre resinous. Color yellowish brown. Translucent. Fracture conchoidal. A columbo-tan- talate of uranium and calcium, containing 5 p.c. water ; closely related to pyrochlore. With samarskite in the mica mines of Mitchell Co., N. C. HAYESINE. According to N". H. Darton, this borate occurs sparingly with datolite and cal- cite at Bergen Hill, N. J. HEDYPHANE, p. 367. A variety from Langban contains (Lindstrom) 8 p.c. BaO. Mono- clinic (Des Cloizeaux), and perhaps isomorphous with caryinite, p. 422 ; this would sepa- rate it from mimetite. HELDBURGITE, Liidecke. In minute tetragonal crystals, resembling guarinite. Color yellow. H. = 6*5. Composition unknown. In feldspar of the phonolyte of the Heldburg, near Coburg. HELVITE, p. 302. Occurs at the mica mine near Amelia Court House, Amelia Co., Vir- ginia. In crystals and crystalline masses, of a sulphur-yellow color, imbedded in ortho- 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.c. CuO). West Phenix mine, Cornwall. HERREXGRUNDITE, Brezina (= Urvolgyite, Szabo). In spherical groups of six-sided tabu- lar crystals (monoclinic). Cleavage basal perfect. H. = 2*5. G. = 3*132. Lustre vitreous, pearly on cleavage face. Color emerald to bluish green. A hydrous basic sulphate of copper, allied to langite. From Herrengrund (= TIryolgy) in Hungary. DESCRIPTIVE MINERALOGY. 429 HESSITE, p. 228. Pseudo-isometric (triclinic) according to Becke, but the conclusion is not beyond question. HET^ROLTTE (Hetairite), Gr. E. Moore. In botryoidal coatings, with radiated structure. H. =5. Gr. = 4 983. Stated to be a zinc hausmannite. Occurs with chalcophanite at Sterling Hill, New Jersey. HEUBACHITE, Sandberger. In thin soot-like incrustations, also dendritic. Color black. A hydrous oxide of cobalt and nickel. Heubachthal, near Wittichen, Baden. HEULANDTTE, p. 347. Oryzite of Grattarola may be identical with heulandite. In minute white crystals, resembling rice grains (opv^a, rice). Elba. HIBBERTITE, Heddle. A lemon-yellow powder in kammererite ; in composition probably a mixture of magnesium hydrate and calcium carbonate. From the chromite quarry in the island of Unst, Scotland. HIERATITE, Cossa (Trans. Acad. Line., III., vi., 14). A potassium fluo-silicate, 2KF -f SiF 4 , obtained in octahedral crystals from an aqueous solution of part of stalactitic concre- tions found at the fumarolesof the crater of Volcano. The concretions have a grayish color, a spongy texture, rarely compact, and consist of hieratite, lamella of boracic acid, with selensulphur, arsenic sulphide, etc. HOMILTTE, Paijkull. Near gadolinite and datolite in angles and habit. H. = 4 '5-5. G. = 3 '34. Lustre resinous to vitreous. Color black or blackish brown. Translucent in thin splinters. Composition FeCaB 2 Si 2 Oi , or analogous to datolite. From the Stocko, near Brevig, Norway. HOPEITE. Composition probably Zn 3 P 2 O 8 + 4 aq. Orthorhombic. Altenberg. HUBNERITE, p. 383. Found (Jenney) near Deadwood, Black Hills, Dakota. Also in rho- dochrosite at Adervielle, in the Hautes Pyrenees. HUNTILITE, Wurtz. An impure massive mineral from Silver Islet, Lake Superior, re- garded as a basic silver arsenide. HYALOTEKITE, NordenskiOld. Coarsely crystalline, massive. H. = 5-5*5. G. = 3 '81. Lustre vitreous to greasy. Color white to pearly gray. Analysis (incomplete) : Si0 2 39 62, PbO 25-30, BaO 20 66, CaO 7 '00, ign. 0'82, A1 2 3 K 2 O, etc., tr. From Langban, Sweden. HYDROCERUSSITE, Nordenskiold. A hydrous lead carbonate, occurring' in white or color- less crystalline plates on native lead at Langban, Sweden. HYDROFRANKLINITE, Rcepper. A hydrous oxide of zinc, manganese and iron, occurring in brilliant regular octahedrons, with perfect octahedral cleavage. Sterling Hill, N. J. Never completely described. HYDROPHILITE, Adam. Calcium chloride ; see chlorocalcite, p. 260. HYDRORHODONITE, Engstrdm. A hydrous silicate of manganese (MnSiOa + aq). Massive, crystalline. Color red brown. Langban, Sweden. ILESITE, Wuensch. In loosely adherent crystalline aggregates. Color white. Taste bitter, astringent. Composition (M. W. lies) RSO 4 + 4 aq, with R = Mn : Zn : Fe = 5 : 1:1. Occurs in a siliceous gangue in Hall Valley, Park Co., Colorado. IODOBROMITE, y. Lasaulx. Isometric, octahedral. GK = 5-713. Color sulphur yellow, sometimes greenish. Composition 2Ag(Cl,Br) + Agl. From the mine "SchQne 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 that it is in fact terrestrial. JAMESONITE, p. 251. Occurs in Sevier Co., Arkansas, with other ores of antimony. JAKOSITE. Occurs in tabular rhombohedral crystals at the Vulture mine, Arizona (Silliman), and at the Arrow mine, Chaffee Co., Colorado (Konig). Composition K 2 SO 4 -+- Fe 2 S 3 O 12 + 2Fe 2 H 6 O 6 . KENTBOLITE, Damour and vom Rath. In minute orthorhombic crystals, grouped in sh eaf -like forms like stilbite. H. = 5. G. =6'19. Color dark reddish brown. Composition probably Pb 2 Mn 2 Si20 9 . From Southern Chili. KRENNERITE, vom Rath (Bunsenin, Krenner). Orthorhombic ; in vertically striated prismatic crystals. Color silver white to brass yellow. Lustre metallic, brilliant. A tellu- ride of gold, perhaps related to calaverite. Nagyag, Transylvania. LAUTITE, Frenzel G-enerally massive. H. =3-3*5. G = 4'96. Metallic. Color iron black. Formula given CuAsS, but very probably a mixture. Lauta, Marienberg, Saxony. LAWRENCITE, Daubree. Iron protochloride occurring in the Greenland native iron, etc. LEADHILLITE, p. 390. Susannite is very probably identical with leadhillite. LEIDYITE, K5nig. 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 leucite has been made by Hautefeuille ; optical character as of natural crystals. LEUCOCH*ALCITE, Sandberger. In slender, nearly white crystals. According to an imper- fect description, an arsenical tagilite. Wilhelmine mine in'the Spessart. LEUCOPHANITE, 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 a 28-98, A1 2 3 6-99, Fe a 3 8 '16, MgO 29 '78, CaO 7 '37, uSIa 2 1'32, K,0 tr., H 2 17 "29 = 99 '89. Reichenstein, Silesia. LIBETHENITE, p. 373. Pseudo-orthorhombic, monoclinic, according to Schrauf. LISKEARDITE, Maskelyne. Massive, incrusting. Color white. Stated to have the compo- sition AloAs^O^lGHaO. Not fully described. Liskeard, Cornwall. LTVINGSTONITE, 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, Al a O, 0'57, FeO 1-25, MnO tr., CaO 17'27, MgO 0'38, K 2 3 38, Na a OO-08, H 2 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 Te0 4 . A decomposition product of coloradoite, Keystone mine, Magnolia District, Colorado. DESCRIPTIVE MINERALOGY. 431 MALLARDITE, Carnot. In colorless cystalline fibrous masses. Composition MnS0 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. MARMAIROLTTE. 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 O. Langban, Sweden. MATRICITE, Hoist. In crystalline masses. H. = 3-4. G. 2 -53. Color gray. Feel reasy. A hydrous silicate of magnesium, near villarsite, but with one molecule H 2 O. m the Krangrufva, Wermland, Sweden. grec Fro MELANOTEKITE, Lindstrom. Massive, cleavable. H. = 6'5. G. 573. Lustre metallic to resinous. Color black to blackish gray. Composition Pb 2 Fe 2 Si 2 09 (analogous to ken- trolite). With magnetite and yellow garnet at LSngban, 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. Phlogopites : Phlogopite, Zmnwaldite. ( Lepidolite, Muscovites : -j 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 (dyo/iios, contrary to law} and meroxene 1 (or sometimes n = 1, and r > 1), in other words, by multiplying through by 3, in this case, the symbol takes the form a : %b : fc,* or, as abbreviated, $-$ (fPf)- 1' ne symbol a:\b:*c properly belongs to the plane MNE (f. 751), which is parallel to, and hence crystallographically identical (p. 11) with the plane Special values of tlie indices 7i, &, I. It is obvious that several distinct cases are possible : (1) The three indices 7i, k, I are all greater than unity, then including the various pyramidal planes. The number of similar planes corresponding to the general form j hkl / 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 corresponding to this index. Thus the symbol (hkQ), = a : nb : oo c, or nn : b : so c (p. 11), belongs to the planes parallel to the vertical axis c, as shown in f. 752. They are called prismatic planes. The symbol (/tOZ), = a : oo b : me (p. 11) belongs to the planes par- allel to the axis 6, as in f. 753. The symbol (O&Z), oo a : b : me, belongs to the planes parallel to the axis , f . 754. 752 753 55 001 (3) Two of the indices may be zero, the symbol (AH) then becomes (001), - cca . i : , the basal plane, f. 755 ; (010), = coa : b : a>c; and (100), a : x : xe. These are the three diametral or pinacoid planes. The symbol (010) represents the clinopinacoid (i-l)ot the Monoclinic system, and (following Groth) the Irachypinacoid (i-l) of the Orthorhombic. Similarly (hW) belongs to the oriho- * The symbol is written here in this order to correspond with the (h k I) of Miller ; on page 10, and subsequently, the reverse order ? 2 c : $b : a was adopted for the sake of uni- formity with Naumann' 8 abbreviated symbols. MILLER S SYSTEM OF CRYSTALLOGRAPHY. 443 domes of the Monoclinic, and the macrodomes of the Orthorhombic system ; also (QJcT) belongs to the clinodomes of the former, and the brachydom.es 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. 750 the com- mon centre of the crystal and sphere is at 0, the normal to the plane b meets the surface of the sphere at B, of b' at B', of d and c, 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 ro 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 be situated at the opposite extremity of the diameter of the sphere normal to this plane, the great circles then appear either as area 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 bn.d between tiie two planes. This fact, that the arc of a great circle intercepted between tha 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 mn.de 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 7-17 consequently meet the spherical surface at their poles. When the axial angles are not 90% this is no longer true. In ail cases, however, the following relation holds good between the cosines of the angles made by a plane with the axes : OK -.n = But from the equation (1) before given, by the introduction of the values of OH, OK, OL, we obtain : -- cos PX = - cos PY = - cos PZ. (2) 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). Itelatwns beticeen 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 (hkl) and (pgr) lie in the same zone, that the following- equation most hold good : ua cos XQ + \b cos YQ + we cos ZQ = 0. where u = kr Iq, v = lp hr, w = hq kp. The letters u, v, w are called the symbol of the zone or great circle PR. Every plane (a?y2) 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 I 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. Examples of the methods 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 h k I h k In this case XXX p q r p q u = kr Iq ; v = lp hr ; vr = hq kp. u = 0; v = l; w =0. Consequently every plane (hkl) in the zone named must answer the condition : \ih + vtt 4- vrl = 0, that is, in this case k = 0. The general symbol is consequently (hQl). Compare tm ooioo (2) For the zone (001), (010), in a similar manner: u = 1, v = 0, w = 0, and the equation of condition becomes 7i = 0, and the general sym- bol is (Qkt). Compare f. 759. (3) For the prismatic zone between (100) and (010), the general symbol will be found to be (hkto). Compare f. 759. 758 (4) For the pyramidal zone between the basal plane (001) and 00100 the unit prism (110), we have the scheme : 1 1 1 In general uvw Hence n = 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-i, and in the zone H 3-3, 2-2, 1, l-l. The indices, uvw, for the first zone 1-t (Oil), I (110), are, obtained as above, ti = i, v = 1, w = 1. Again, for the zone between i-l (010), l-l (101), the zone indices, efg, are, e = 1, f = 0, g = 1. The indices (Md), for the plane (2-2) 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. : i v In this case 11111 e f g e f h = gv f w ; k = ew gu ; I f u ev. The plane has consequently the symbol (121). MILLER S SYSTEM OF CRYSTALLOGRAPHY. 445 3-3, 2-2, etc., the indices, as 759 For the zone of plane_s, lettered on the figure (f. 758) already shown, are e = 1, f = 0, g = .l, and consequently the equation cf condi- tion reduces to h = 7, and the general symbol is hkh. This zone is shown on the spherical projection, f. 759, and in- cludes the planes 010 (i4\ 131 (3-3), 121 (2-2\ 111 (1), 101 (1-1), and so on. A second oxamp e of the above method is afforded by the plane lettered 2-2 in f. 7o8. It lies in the zone i-l (100) to 1-2 (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-i (101), whose indices, efg, are, e = l,f = l,g = l. Its own symbol (hkl) is deduced as above : 01101 The symbol is consequently (211). The position of this plane is shown on the spherical projection, f. 759, as also that of the zone first mentioned above, whese indices were u = 0, v = 1, w = 1, and for which the equation (3) consequently reduces to Jc = I ; the general symbol is then (hkK), the planes 100 (i-i), 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-$ (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. Method* of Calc'dation.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 interf acial 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 b sm B = Sin A = sm a sin h tan b tan/A tana sin b cosB cos B = tanB - sn i tan a tan h tan b sin a cos b cos h = cos a cos b cos h = cot A cot B In oblique angled spherical triangles : cos A sm B = cos a (1) Sin A : sin B sin a : sin b ; (2) Cos a = cos b cos c + sin b sin c cos A ; (3) Cot b sin c = cos c cos A + sin A cot B ; (4) Cos A = cos B cos C + sin B sin C oos <3. 446 ATFENDIX. In calculation ifc 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. 7GO), having the following indices, viz. : P = (hM), 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 ~~ < V Q.R) ' (P.S) * Here (P ' Q) = **""** = lp ~ hr = hq ~ kp (Q.R) gw rv rupw pv qv? (S.R) _ wy zv _ zu xw _xv yu (P.S) ~ kz-ly ~ Ix - hz ~ liy - kx ' By means of the above equation it is possible to deduce the indices or imgle of a fourth plane, when those of the three others are given. In the application of thia 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 P(MJ), and Q(pqr) in this zone : h tan_PA = ,fc = J p ' tan QA ~~ q ~ r ' h _ k tan PB _ I ~p ~~ q ' tan QB ~ ? 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 (hkQ), 01 a dome (hOl) or (Q/d), between two pinacoid planes 90 from another, we have : li _ tan (100) (110) U _ tan (001) (7iOZ) m k _ tan (001) (QM) Ic ~ tan (100) (AJfe6) ; / ~ 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 OP 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 iii 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 (5) of un equal length; all at right angles. MILLERS SYSTEM OF CKVSTALLOGKAPIIY. 447 III. Hexagonal System. Three equal lateral axes (, k>l. 2. [hkk] ; h->k. 3. \7ihk] ; h>k. 4. [Ill] ; h = k = l = l. 5. [MO] ; I = 0. 6. [110] ; h - k = 1 ; I = 0. 7. [100] ; A = 1, A = I = 0. NAUMANN. ma : ma a : ma a : a na : cca a : ooa ooa : ooa [m-n]. [m-m}. [m\. ' [IJ. [*-]. The seven distinct forms corresponding to these symbols are as follows, taken in the same order as on \ p 14-20, where the forms are described : Cube (f. 7(51). Symbol [100], including the six planes (100), (010), (100), (OlO), (001). (001). See also the spherical projection (f. 7b'6). 781 763 764 763 [ill] [110] [100] [111] [100] [110] [111] Octahedron _(f. 762). Symbol [111], Jncluding the eight planes taken in order shown in t. 762, (in), (ill), (ill), (Hi), (ill), (Hi), (Hi), (Hi). * In general the indices of any individual plane are written (fikt), 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 sinrjlar planes of the cube. 448 APPENDIX. Dodecahedron (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 b repeated. It is to be noticed that the distance between two contiguous poles of [100] and [110] is 45 (seef. 766) ; between those of [100] and [111] it is 54 44', and between (110) and (111) it is 35 16'. f Moreover, the angle between (111) and (111) is 70 32', and between (111) and (111), 109 28'. 766 [211] [3111 Tetragonal trisoctaJiedron (f. 767, 768). Symbol [hkk], with /*>&, comprising twenty-fom similar planes. Trigonal trisoctahedron (f. 769). Symbol \Jihk], with h >k, also embracing twenty -four like planes. 769 [221] [210] [310] [321] Tetrahexahedron (f. 770. 771). Symbol \7ikft\ including twenty-four like planes. As seen on the spherical projection (f. 766), the planes of the form [7*^0] lie in a zone with the dodeca- hedral planes, between two pinacoid planes. Hexoctahedron (f. 772), [hkl\. This is the most general form in the system, including the forty-eight planes enumerated on p. 447. Their position (h = 3, k = 2, I = 1) is shown on the spherical projection (f. 766). B. Hemihedral Forms. There are two kinds of hemihedral forms observed, as shown on p. 20: (1) ihehemihofa Jtedral, 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\hkl}^ and the second kind produces parallel hemihe- drone, indicated by the symbol Tt\hld\. The resulting forms in the several cases are as follows MILLER'S SYSTEM OF CKYSTALLOttKAPHY. 449 INCLINED HEMIHEDRISM. Tetrahedron (1). Symbol /cflll]. The plus tetrahedron (f. 778) includes the four planes (111), (111), (111), (111). The minus tetrahedon (f. 774) includes the planes (111), (111), (111), (ill). Hemi-trisoctahedrom. The symbol K[hkk] denotes the solid shown in f. 775, and K[hhk\ the solid shown in f . 776. They are the hemihedral forms of the tetragonal and trigonal brisoctahedrona respectively. Hemi-hexoctahedron. The same kind of hemihedrism applied to the hexoctahedron pro- duces the form shown in f. 777, having the general symbol K\hJd\. 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 T[7*A;0], and of th latter, ir[7ik\ ; they are shown in f. 778-782. 778 779 780 781 7T[210] [210] 7T[120] 7r[210] [100] 7T[321J Tetartohedral forms of several kinds are possible in this system, but they are of small piactical interest. Mathematical delations of the Isometric System. (1) The distance of the pole of any plane P(hkl) from the cubic ( or pinacoid) planes is gfven by the following equations. These are derived from equation (2), p. 443. Here PX(=PA) is the distance between (Tiki) and (100); PY(=PB) is the distance between (hkl) and (010); aud PZ(=PC) that between (hid) and (001). The following equations admit of much simplification in special cases, for (7*&0), (hhk), etc. cos 2 PB = cos 2 PC = (2) The distance between the poles of any two planes (Tiki) and (pqr) is given by the fol- lowing equation, which in special cases may also be more or less simplified : p O _ ^ ~ Tip + kg + Ir + & + P) (p* r*)' (3) Calculation of the values of A, k, Z, for the several forms. (a) Tetragonal trisoctaht dton (f. 767). B and G are the supplement angles of the edges as lettered in the figure. cos B = 29 A 2 + 2k v cosC 2hk 450 APPENDIX. A 3 2/fc 2 I or the heinihedral form (f . 775), cos B = - - ^. (b] Trigonal trisoctahedron. The angles A and C are, as before, the supplements of the uiterfacial angles of the edges lettered as in f . 709. For the hemihedral f orm (f. 776), cos B = -^~ * . Tetrahexdliedron (L 770), 7i a 2hk For the hemihedral form (1 778), cos A" = - 2 ~ . cos C" = ^ II -\- 1C II Eexoctaliedron (f. 772). 7i a + 2&Z _ w + k*-^P cos A = --- c os B = cos C = For the hemihedral form K\m\ (f. 777), cos B' = W -tf + p A:Z -f- lh + lik Foi 7r[Mq, cos A = . ; cos C = For planes lying in the same zone the methods of calculation given on p. 444 and p. 446 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). II. TETRAGONAL SYSTEM. In the Tetragonal System, since the vertical axis c has a different length from the two equal lateral axes, the index Z, referring to it, is never exchangeable for the other indices, h and A;. The general form \Jikl\ consequently embraces all the planes which have as their symbols the different arrangements of 7i, k, 1, in which I always holds the last place. We thai obtain : hu nu m m m m m MI hkl m W Tiki khl W TM khl A. Holohedral Forms. According to the values of 7^, k, and I in this general form (A = 0, k = , etc.), different cases may arise. By this means we obtain a list of all the possible distinct holohedral forma iu tliis system. They are analogous to those of the Isometric System. MILLER. NAUMANN. \. [hkl}\ 7i>k. a na : me [m- 2. [hid] ; h = k. a 3. [JiQl] ; // or k = 0. a 4. [hkti] ; h>k, I = 0. a 5. [110] ; h = k = 1, I = a a a : me [m] . oo a : me [m-i\. na : ooc [*-wj, a : x c [/]. oo : ex; c [*'-'] * L J 7 6. [100] ; A; = 0, I = 0. _ L - -, 7. [001] ; 7i = &:=0. a:ooa:c [0]. MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 451 The forms answering to these general symbols (compare f. 790; are as follows : Basal planes. Symbol [001], including the planes (001) and (001). Prisms. (a) Diametral prism, or_that of the second series (f. 783). Symbol [1001. in eluding the four planes (100), (010), (100), (010). () 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. 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 [hW] in- cluding eight similar planes. The form [101] is shown in f. 786. (b) Octahedrons of the first, or unit series. Symbol [hkl\, embracing eight similar planes. The form [111] is shown in f. 787. 784 [100] [001] [110] [210] [101] [111] Octagonal Pyramids. The general symbol [hkl] embraces, as already shown, sixteen like planes, which together form the octagonal pyramid shown in f . 788. 788 789 \h1d\ 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. Hemiliedral Forms. Among the hemihedral forms there are to be distinguished three classes, as shown on p. 28 et seq. I. Sphenoidal hetnihedrons, corresponding to the inclined hemihedrons of the isometric system. They are indicated by the symbol 7r[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 n[hkl\. 3. Trapezoidal hemihedrons, hemiholohedral like those just mentioned, but vertically alternate. They have the symbol K."\hkl]. 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), 01C = PB), 001 (= PC) are given by the following equations: 08 ' PA = ; COS * PB = C S ' PC = These may also be expressed in the form : (2) For the distance between the poles of any two planes (hkt), (pqr), we have in general : cos PQ _ _ x/ [(h 2 + k-y* + JV] [(p* + q*)t- + r'V] ' 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 (pgr) 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) (A&O) =-|. Determination of the axis c. This follows from equation (1), p. 446, which, for* this case becomes : ^ cos PA = - cos PC, (a - 1,. For an octahedron (7*00 in the diametral series, we have : tan (7iOZ)(OOJ)=y. For the unit octahedron (111), we have : tan (111) (001). cos 45 = 6. III. HEXAGONAL SYSTEM. The Hexagonal System and its hemihedral, or rhombohedral, division are both included by Miller in his RIIOMBOHEDRAL SYSTEM (see p. 462). All hexagonal and rhombohedral forms 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 hexagorial 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 13. 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 MILLEKS 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 1806 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, c, 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 7i, &, 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)j or, in full, - a : a : na : inc. Thus the plane 3-| (3P) has the full symbol, 3a : a : f a : 3c, or to correspond with the other symbols it must be written, 3a : \ a : a : 3c. The reciprocals of the latter indices are $ : $ : 1 : J, 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 : e or in Naumann's abbreviated form 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 /i, /, or I of the form (hkli) need bo 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 , 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 /*, 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 : IfO (hkli) (hkli} (Uki) (hlki) (klhi) (Ikhi) (Ihki (IhJd (khli) In this general form [hkli] the following special cases are possible, each one giving riM to an independent form or group of forms, as seen below : 454 APPENDIX. BEAVAIS-MILLEB. NAUMANN.* [1122] ; [OAW] ; [0111]; A=l, A: = 0.\ [MZO]; =0 [1120]; e = 0,A = A; = [0110] ; * = 0, k = 0, h [0001] ; h = A; = I = 0. 1 . /* . u> , t/io \7n-nj 2a : 2a : a : me 2a : 2a : a : c [m-2] [1-2] a : a : a : me [m] ooa : a : a : c [1] n T a : na : a : oo e [i-n] 2a :2a a : oo c [i-2] oo a : a : a : oo c [-^] oo a : oo a : oo a : c [0] A. HoloJiedral Forms. rhc 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 friven in the table. Basal planes. Symbol (0001) and (0001). Prisms.. //,) The unit prism (/). General symbol [01 10], including (s-e f. 793 794) the six planes with the following symbols: (0110), (1100), (1010), (0110), (1100), (1010). (b) The diagonal prism (f-2). General symbol [1_1_20], including (f. 793, 795) the follow- ing six planes : (1120), (1210), (2110), (1120), (1210), (2110). (c) The dihexagonal prism (i-ii). General symbol [hklQ}, embracing the following twelve planes mentioned in order : (A*70), (MO), (MO), (7^0), (ZteO), (MZO), (MZO), (AZfcO), (*BM)), (ZMO), (WO), (M/0). Hexagonal pyramids, or Quartzoids. (a) The pyramids of the first or wm' series. General symbol [OMt] 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 h = k = i = I. The planes of this form (f. 796) are shown on the projection, f. 793. 794 795 [0110] [1120] [0111] [hkli] (fr) Pyramids of the second, or diagonal series. General symbol [A&2&&*], including twelve 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 [M7i], including the twenty- four planes enumerated on p. 453. * The ordot of the terms in the symbols below is made to correspond to that of the indicei MILLER S SYSTEM OF CRYSTALLOGRAPHY. 455 B. Hemttiedral Forms. The most important of the hemihedral forms in this system are as foil >ws : 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 798 *[7iklf\. It is common on apatite. 2. RHOMBOKEDRAL hemihedrism. These included here are hemiholohedral, and vertically alternate. They are indicated in general by K\hkli\. This class is import- ant, since it embraces the RHOMBOHEDRAL DIVISION. (a) Rhombohedrons. Symbol K[0hhi] ; the unit, or fundamental rhombohedron (+R, f. 798) has the svmbol K[01Il], including the six planes: (Olll), (1011), (1101), (lOll), (1101), (0111). The negative rhombohe- dron (-R, f. 799^ includes the planes: (1101), (Olll), (1011), (Olll), (1011), (1101). (ft) ScalenoUdrons (f. 800). Symbol K\hkli]. 3. GYROIDAL, or trapezohedral hemihedrism. The forms here included are holohemihedral, and vertically alternate. They are indicated by K" [hkli] , see p. 39. 4. TETRATOIIEDRISM. This may be (1) rhombohedral, indicated by Kir[hkli] ; or (2) trapezohedral (eryroidal), as common on quartz, having the gen- eral symbol KK" \Iikli]. Mathematical Relations of tlie Hexagonal System. In the Hexagonal System, as has been explained, the symbol in general has the form [hkli]. where the algebraic sum of h, k, 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 J7, K, (= a = 1) oblique (120 and 60 J ) 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 (hkli], (pqrt) lie, are given by the scheme : h k i h k XXX p q t p q u = kt qi v = ip ht w = hq kp. (1) The distances (see f. 793) of the pole of any plane (Jikli) from the poles of the plane* (1010), (0110), (1100), and (0001) are given by the following equations: cos PA = cos (MX) (1010) = cos PB = cos (hkU) (0110) = cos PM = cos (MM) (1100) . oc* PC = cos (hkli) (0001) = 456 APPENDIX. (2) The distance (PQ) between the poles of any two planes (7ikli) and ( pqrt) is given by th equation : Bit + 2c*(hg + pk + 2hp + 2kg) po _ ~ hk}] [8? + W(p> + q* + pg)]' (3) For special cases the above formula becomes simplified ; it serves to give the value of the normal angles for the several forms in the system. They are as follows : (a) Hexagonal Pyramid [Qhhi], f. 796, cos X (terminal) .= g ., + ^, ,, ; cos Z (basal) - g ., + ^. For the hexagonal pyramids of the second series [Qh2h2i] the angles have the same value, (ft) Dihexagonal Pyramid [hkli], cos X (see f . 797) = ?! cos Y (see f . 797) = ^ cos Z (basal) = k. h> k. h = k. [Okl] \ h = 0. [hkO] ; I = 0, h > k. L&ftOJ; I = o, h > k. lllO] ; [100] ; h, k = k = I . I, 0. l- 0. [010] ; h = I = 0. [001] ; h = k = o. & : nb : me [m-n] nti:b :mc [m-n d:b :m'c []. A : co b : me [m-l]. oo ti : b : me [m-l]. & : nb : GO c [i-h]. na : b : oo c [i-n]. & : 6 :_ooc [I]. d : oo& : ooc Mi cod : b : ooc []. 00$ : GO& : c [0]. IV. ORTHORHOMBIC SYSTEM. The Orthorhombic System is characterized by three unequal rectangular axes, c, , a.* Tfce indices 7i, &, I may be either plus or minus, in the general form [hkl], but they are not exchangeable, since they refer to axes of different lengths. This general symbol then embraces the following planes : (hkl) (hkl) (khi) (hkl) (hkl) (Jikl) (hkl) (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. These symbols belong to the various distinct forms of this system, as follows : Pinacoids.(a) Basal plane. Symbol [001], including the two planes (001) and (001). (b) Macropinacoid. Symbol [100], including the plane [1001, and [100] opposite to it. (c) Brachypinacoid. Symbol [010], including the planes [010] and [010]. Prisms, (a) Unit prism (1). Symbol 110, including four planes, (110), (110), (110), (110). (b) Macrodiagonal and brachydiagonal prisms, having respectively the symbols [JikO] and [khO], 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 [hOl] ; and (b) brachydiagonal, or br achy domes, with the symbol [Okl]. In each case the symbol embraces four similar planes. Octahedrons or Pyramids. The 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), (HI), (Hi), .(Hi), (111). Of the general pyramids two cases are possible, either [hkl] or \khl\, when h>k, these correspond respectively to the prisms [hkQ] and [khQ]. They are the macrodiagonal and brachydiagonal pyra- mids of Naumann ; thus 2-2 (= a: 26 : 2c) is [211], according to Miller, and 2-2 (= 2$ : b : 2b) is [121]. no * 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 macropinacoid has the symbol (}00\ and the brachypinacoid the symbol (010) ; similarly the macrodomes are in general cl the brachydomes (Qkl). 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 Orthorhombic System. (1) For the distance between the pole of any plane P (hkl) and the pinacoid planes we have in general : cos 2 PA = cos 2 (hkl) (100) = h ^ + %% + ^ cos 5 PB = cos 2 (hkl) (010) = Wj cos' PC = cos' (Ml) (001) = (2) For the distance (PQ) between the poles of any two planes (hkl) and (pqr) : hpb^c 2 + kqa"c* -\- Ira^b"* COS PQ = -= - . : V[A 2 & 2 c 2 + &Vc 2 + Z*o^"] [_p 8 6V + faP& + rW& 2 ] (3) For planes lying in a zone, the general relation (p. 446) is to be employed. For the special cases, practically of most importance, the simplified equations which follow are used, (4) To determine the lengths of the axes, the general equation may be employed : T- cos PA = ^ cos PB = 4 cos PC. h k I Here PA, PB, PC are the distances from the pole of any plane (hkl) to the pinacoid planes (100), (010), (001) respectively. The brachydiagonal axis, &, 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 (hkO) (100) = -^ bh tan PB = tan (Qkl) (010) = ^ tan PC = tan (hOl) (001) = ^ V. MONOCLINIC SYSTEM. tn 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, gQ2 c is vertical, b the orthodiagonal axis, and d the clinodiagonal axis oblique to c, but at right angles to b. The symbol [hkl] embraces only four similar planes in the most general case, for 3/90 in consequence of the obliquity of one of the axes, 1>ho quadrants \ above in front correspond alone to those below and bonind, and / those above behind correspond to those below in front. This is / I seen clearly in the projection of f. 803. For h, k, 1 the symbol [hkl\ includes two distinct forms, viz. : (1) (hkt) and (2) (hid) (hkl) (hkl) The various forms are as follows : MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 459 Pinacoids. Base [001]. Orthopinacoid [100]. Clinopinacoid [010]. Each symbol, of course, comprehending two planes only. 804 Crocoite. ^ Prisms. (a) Unit prism [110], == d : b : ooc (J) of Naumann. This symbol embraces foul similar prismatic planes, (b) Orthodiagonal prisms [7i&0], where h > k, the poles of these prisms fall on the prismatic zonal circle between 100 and 110 (see f. 803). They correspond to the prisms i-n (= d : nb ' : ooc) of Naumann. (e) Clinodiagonal prisms. Symbol [MO], li > k, lying between (110) and (010). They correspond to i-h ( nd_ : b : ooc) of Naumann. Domes. (a) Hemi-orthodomes, including two cases, (101) and (101), the minus domes of Naumann (opposite the obtuse angle) ; and also (101) and (101)), the plus domes of Naumann (opposite the acute angle ft), (b) Clinodomes. Symbol [O&Z] , embracing four similar planes (0fe)(0&), (0*2), (Qk). The clinodome [Oil], equivalent to 14 (=00 d : b : w:'), is one case in this form. Pyramids. The pyramids are all hemi-pyramids. (a] The symbol [7ihl\ includes the unit pyramids in a zone between [110] and [001]. (b) The symbol [hkl] includes two sets of hemi- pyramids, whose indices have been given on p. 416, corresponding respectively to P and +P of Naumann. If h is greater than k these are orthodiagonal pyramids, corresponding to (d : nb : oo c) of Naumann. The symbol \khl] on the same supposition includes two sets of planes, like those of p. 45S, and differing only in being dinodiagoncd ; equivalent to (nd : b : GO e) of Naumann. The orthodiagonal planes lie between the zone (100), (001) and (110), (001), while theclino- diagonal are between the latter zone and (010) (001), as is seen on f. 803, which gives the projection for f. 804. Mat7iematical Relations for the Monoclinic System. (1) The distances of the pole of any plane (Jikl) from the pinacoid planes are given by the frUowing equations : cos PA = cos (MJ) (100) = PB = "" W (010) = sin' $ + IWb* + IWah't. coe ' COB PC = co, (UQ (OOn = V AW + K'a V sin 8 f + 27 + MUaPc cos ft 460 APPENDIX. (2) The distance between any two planes may be axpressed 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. (8) For the relation between the planes in a zone the general equation before given holds good : cot PS cot PR _ (PQ) . (SR) coTPGj^"cot PR ~~ (QR) . (PS)' (4) For all zones passing through the clinopinacoid (010), the value of PR may be taken as 90, and the above equation consequently simplified : h_ _ k_ tanPB _ J_ ~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 as to read : h sin PrA _ p sin QYA _ a T * sin PYG ~~r ' sin QYC ~ T ; k sin PYA _ q_ sin^QYA _ b_ T ' cotPY "~ r " cot QY " ~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 between the given plane P or Q with the clinopinacoid. VI. 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 brachy diagonal axis, a. The position assumed for the axes is shown in f. 259, p. 80. The general symbol [MZ], which includes eight similar planes in the orthorhombic system, is here resolved into four independent forms, embracing two opposite planes only. They are thus : m M ( 9\ ( m "> (<\\ ( ?lk ^ u\ $$& (1) (hkl) (2) (Iikt) (3) (hkl) (4) (hkl) These correspond respectively to mP'n (1), m'Pn (2), mP,n (3), m.'Pn (4) of Naumann, 01 m-n, m-n, m-n', m-ri ', 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 : o>c), and [010] the brachy pinacoid (i-l coa:b: ocC'. Planes having the symbol [7<0f] are then macrcdomes ; and those of the symbol [Qkl] are*brachy- domes. Similarly then pyramids (h > k) of the form [7^] are macrodiagonal planes, and those of the form (hkl) are brachydiagonal planes. The unit prism consists of two independent forms (110), (110) (I'=ooP/), and (110;, (110) (I =00 ',P). Mathematical Relations 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 fche most important relations (given by Schrauf) are as follows: MILLER'S SYSTEM OF CRYSTALLOGRAPHY. 461 If the angle between the axes X and Z = i), between X and Y = and between Y and Z = | (see f. 757) ; if also o, , y are the corresponding angles between the pinacoid planes then and where Also cos ft cos 7 cos a sin ft sin 7 !OS ,p X = *^A. cos y cos a cos 3 sin y sin a k' } a-c' 2 A- COS ft COS a COS ) cos- PZ = Mi = [1 + 2 cos a cos j8 cos 7 (cos-' a + cos 2 & + cos" 7)]. M, = 7i'W sin 2 o + &'Vc 2 sin 2 + f-Vft 2 sin 2 7 + 2rte (M> cos ft sin o sin 7 + hko cos 7 sin o sin ft + kla cos a sin /3 sin 7). cos 2 AX = sin 2 a cos BY = sin 2 ft ' cos CZ = A, sin- 7 When PX, PY, PZ have been found by calculation, then the following equation gives the relation of the axes : -^- cos PX = -=- cos PY = 4- cos PZ. ft K I As seen in f . 805. cos PX = sin PEG sin PB = sin PCB sin PC ; cos PY = sin PGA sin PC = sin PAC sin PA ; cos PZ = sin PAB sin PA = sin PB A sin PB ; and also from these it follows that - sin PAC = sin PAB ; sin PCB = sin PCA. h h = 180 - CAB ; = 180 - ABC ; = 180 - ACB. RELATIONS OP THE Six CRYSTALLINE SYSTEMS IN RESPECT TO SYMMETRY. From a careful study of the spherical projections for the successive systems a very cleai 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 . 706) : 1st, the three diametral zones : 1. (100), (010), (100). 2. (100), (001), (100). 3. (010), (001), (010). Also the diagonal zones : 4. (110), (001), (110). 5. (110), (001), (110). C. (100), (Oil), (100). 7. (100), (Oil), (100). Tetragonal System (f . 790) : 1. (100), (010), (100). Also: 4. (110), (001), (110). 8. (010), (101), (010). 9. (010), (101), (010). 2. (100), (001), (100). 3. (010), (001), (010). 5. (110), (001), (110). 462 APPENDIX. Hexagonal System (f. 793) : 1. (1010), (0001), (1010). 4. (1120), (0001), (1120). Orlhorlumbic System (f. 801) 1. (100), (010), (100). H&nodinic System (f. 804) : 2. (0110), (0001), (0110). 5. (1210), (0001), (1210). 7. (1010), (0110), (1100). 2. (100), (001), (100). 1. (100), (001), (100). In the Tridinic System there is no plane of symmetry. 3. (1100), (0001), (1100). 6. (2110), (0001), (2110). 3. (010), (001), (010). THE RnOMBOHKDRAL DIVISION OF MlLLER. The following projection (f. 806) is added in order to show the relation of the forms in the Hexagonal and Rhombohedral Systems as 806 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 (/_= [0110]) has the symbols : (211), (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, [hid} and [efg] ; the symbol [hkl} hence belongs to the plus scalenohedron, and [ffg} to the minus. In this as in other cases it is true that : e = h + 2k + 21, f = 2h-k + 21, g- 27i + 2k - I. The dihexagonal prism includes the six planes of the form [//&0] , and the remain- ing six of the form [efO], 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, so that the rays of light fall from it on the crystal in parallel lines. The plane on which the crystal is projected is termed the plane of projection. This plane rnay be at right angles to the ver- tical axis, may pass through the vertical axis, or may intersect it at an oblique angle. These different positions give rise, respectively, to the HORIZONTAL, VERTICAL, and OBLIQUE pro- jections. 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 ORTHOGRAPHIC, in the second CLINOGRAPHIC. In the horizontal position of the plane of projection, the projection is always orthographic. In the other positions, it may be either orthographic or clinographic. It is generally preferable to employ the vertical position and clinograpnic projection, and this method is elucidated in the following pages. PROJECTION OP THE AXES. The projection of the axes of a crystal is the first step preliminary to the projection of the form of the crystal itself. The projection of the axes in the isometric system, which are equal and intersect at right angles, is here first given. The projection of the axes in the other systems, with the exception of the hexagonal, may be obtained by varying the lengths of the projected isometric axes, and also, when oblique, their inclinations, as shown beyond. Isometric System. When the eye is directly in front of a face of a cube, neither the sidei 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 8, and 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 CG appears of its actual length. On revolving the whole through a number of degrees equal to BMB' (5) the axes have the position exhibited hi the dotted lines. The projection of the semiaxis MB is now lengthened to MN, and that of the semi- axis MC 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 ft'N, M, and c H) will be di- rectly proportional to the lengths of the lines B N, BM, and C'H. It is usual to adopt such a revolution 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 6'N to MN by 1 : i Suppose r to equal 3 and s to equal 2, then proceed as follows : 464 APPENDIX. B B is the pro- Draw two lines AA', H'H (f. 808), intersecting one another at right angles. Make MH = MH' = b. Divide HH' into 3 (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, S 6 and extend the same to the vertical N'. jection of the front horizontal axis. Draw BS parallel with MH and connect SM. From the point T in which SM intersects BN, draw TC par- allel with MH. A line (CC') 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 ; AA' is the vertical o axis. If, as here, r = 3, and s 2, then S = 18 26', and e = 9 28', for cot 8 = r, and cot e = rs. Tetragonal and OrthorJiombic Systems. The axes AA', CC', 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 d = I. Monodinic System,. The axes c and d in the monoclinic system are inclined to one another at an obliqe angle 0. To project this inclination, and thus adapt the isometric axes to a monoclinic form, lay off (f . 809) on the axis MA, Mrt = MA cos 0, and on the axis BB' (before or behind M, according as the inclination of d on c, in front, is acute or obtuse) Mb = MB x sin 0. From the points b and a, 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, C'C, 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. Triclinic 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 b, 7, and a and c, 0. BB' is the analogue of the brachydi : gonal, and CC 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, M6'= 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 soctiou and c, is oblique. ON THE DRAWING OF FIGURES 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 Z>, their oblique inclinations may be given them as follows: Lay off on MA (f. 810), Ma = MA xcos , and on the axis BB' (brachy diagonal), M6 MB' x sin 0. By completing the parallelogram M#. E'&, the point E' is determined. Make ME = ME ; EE is the projected brachy diagonal. Again lay off on MA, ~M.a'= MA x cos a, and on MD', to the left. Mrf MD' x sin a. 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 as is AA' and the horizontal axes EE' (brachy diagonal) and FF' (macrodiagonal) thus obtained, ofre 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 5, 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 8 YMY'. In this position the axis MY is projected upon MP, MU' upon MN, and MZ on MH. Dcsgnating 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 projection will be as follows : I : II : III =1 : 2 : 3. Let us take r (= PM : HM) equal to 3, and s (= 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 construe tion : 1. Draw the lines AA, HH (f. 812) at right angles with, and bisecting, each other. Let HM = 6, or HH 2l> 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 ; UU' 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 Q 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. 81 1 ; for in the triangle NHV, the angle HNV is an angle of 30, and HN iMH. MV is therefore the radius of the circle (f. 811). Make therefore MA = MA'= MV ; AA' is the vertical axis, and YY', UU', ZZ' are the projected horizontal axes. The vertical axis has been constructed equal to the horizontal axes. Its actual length in different hexagonal or rhombohedral forms may be laid off according to the method sufficiently explained. 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 then answer all subsequent requirements. Whenever needed for use, these axes may be transferred to a sheet of paper, and then adapted in length, or inclination, or both, to the case in hand. 30 466 APPENDIX. PROJECTION OP TUB FORMS OP CRYSTALS. 1 , Simple forms. When the axial cross has been constructed for the given species, the unit 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 c meet; they make the parallelogram, abed, which is a transverse section of the prism, par- allel to the base. Through a, b, c, d draw lines parallel and equal to the vertical axis, making the parts above and below these points equal bo the vertical semiaxis. Then, connect the extremities of these lines by lines parallel to ab, be, cd t da, and the figure will be that of the diametral prism, corresponding 1 o 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-l ; in the monoclinic, the prism 0, i-i* *-l ; in the triclinic, 0, i-l, i-i. The unit, vertical prism hi 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 BCB C is a transverse section of such a prism parallel to its base. It is the prism 0, I, in each of the systems excepting the triclinic, and in that 0, 1, 1' ; a square prism in the tetrago lal 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, 814 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 b illustrated by f . 814 and f . 815. In the former case it is required to draw the trigonal trisoo tahedron, whose symbol i 2 ON THE DRAWING OF FIGURES OF CRYSTALS. 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 the 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. 810, will be obtained. Similarly in f. 8-5, the octagonal pyramid 1-2 is constructed; the figure shows the planeu 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 m 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 giver:. Projection of Simple Iscmetric 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. 10). 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 bcale, 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 f and r' respectively given by the following equations ; those of the octahedron being taken as a unit : , _ 2mn (m + ri) , _ n 1 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 i-2 I * i i i-3 f i 8-1 i * 2-2 4-2 f * 3-3 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 hemihednd 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 ri) mn + (m ri) ' 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 Y^^l an a _ v^) mav be pro j ec t e( L <* 2 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, W(f.76,p.20) 2 -(f.86) | 1 468 APPENDIX. The paraUel 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 o - , may be found by the for- By means of these formulas, the situation of two points, a m(n }} , n(m mulas + and - mn 1 mn I and b (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 f, c', of these lines will be the vertices of the unsymmetrical solid angles, those marked c of the form - -- - and those marked 8' of the form [m-n] 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. (f. 100, P . 23) Coord, of the unsym. S. A. Trigonal interaxis. -^-f- (sim. f. 92) Co5rd. of the unsym. S. A. [4-2] -^ (1 92) Projection of a Rhombohedron. To construct a rhombohedron, lay off verticals tr^ough the extremities of the horizontal axes, and make the parts both above and below these e ctremities 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 poin-s E or E', rhombohedrons in different positions, raR, or mR, will be constructed. Scalenohedron. The scalenohedron m n admits of a similar construction with the rhombohe dron mR. 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 mR 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, upon 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 ol 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 th? 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 fco 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- nung, 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 *-2, a, 1< 1,2-2, l-l, 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 intersect! on- 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 length, must be adapted to the species in hand. For andalusite the axial ratio is c : b : a = ! 712 : 1'014 : 1 ; hence the vertical axis c must have a length -71 of what it now has, and the lateral axis one 1 "01 ; these required lengths are determined in a moment with a scale of equal parta The next step is to draw the predominating form, the prism 1. Obviously its intersection- edges are parallel to the vertical axis, and its basal edges, intersecting 0, are parallel to ps, tq in the projection (f . 820). The planes 4, and i- 5 are now to be added, whose intersections with each other and with 1 are parallel to c. The position of one edge, 7/-2, having been taken, that of the other on the other side is determined by the point where a line parallel tc 4:70 APPENDIX. the axis b meets the basal edge of the prim. Similarly the position of the same prismatic edges behind are given by the intersection of lines from front to rear parallel to the axis a. 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 1-1 il 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 1-1 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 i-2 and 14. Similarly for i-2 on the right, the two points of intersection are c, and the point where n'n and gap, 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 in 4 ersection-edge, whiel 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 2i : b : 2 .?, or c : %b : a ; and hence intersects the horizontal plane (f. 820) in the lines as (right), at (left), and aq, a'p (behind). Hence the intersection-edge of 7, 2-2, l-i 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 ?/ (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 forma 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 823 824 M axes. Suppose that f. 822 represents the diametral prism of an orthorhombic crystal. Here obviously the edge e = 2e, e = 2b, e = 2L The plane 1 (c : b : d) may be laid off on it by taking from the angle a equal portions of the edges e, e, e, for instance, conveniently one ON THE DRAWING OF FIGURES OF CRYSTALS. 471 half of each, hence the plane appears as mno. Again the plane 2 (2c : b : a) is laid off by taking the unit lengths of the edges e (6), and e (a) and twice the unit length of e (c)< the plane is then mub. Again, the plane 4-2" (4 : b : 21) takes the position npb, since ap = 2c, ap ^&, and an = a, the ratio of the edges (axes) being the same as in the symbol. So also the plane 2-2 (2c : 2b : d) has the position rmo, since ao = c, ra = 6, and ar = $#, 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 for the given form are at once obtained. For example, the intersect! on- edge for 1, and the basal plane, as also for 1 and 2, it is the line mn ; for 1 and 4-2 it is the dotted line joining the common points n 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 j8a. The direction of the required intersection-edges being obtained in this way, they are used to construct the crystal itself, being transferred to it in the usual way. In f. 823 they have been placed upon the diametral prism, and when this process has been completed for the other angles, and, too, the domes e\ 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 the axes of the second individual, or semi- individual, hi the position in which they are brought by the revolution 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-i, and (2) on an axis normal to f-f. 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 = I -441, b - 2'112, d = 1). The twinning-plane f-| (fc : I : fa) 825 has the position MNR. It is first necessary to construct a normal from the centre O to this plane. If perpendiculars be drawn from the centre to the lines MX, NR, MR, they will meet them at the points z, y, z, dividing each line into segments proportional to the squares of the adjacent axes ;* or N# : M# = ON 2 : OM 2 . In this way the points x, y, z are fixed, and linea * This is true since the axial angles are right angles. In the Monoclinic System two ol the axial intersections are perpendicular, and they are sufficient to allow of the determina- tion of the point T, as above. In the Triclinic System the method needs to be slightly modified. 472 APPENDIX. 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-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^t), the point V the place ' (NT T/8'), and so on. The lines joining 1 these points ^ ft', x, and the common centre O will be the new axes corresponding to MO, NO, RO. In order to obtain the unit axes corresponding to t-, b, d it is merely necessary to draw through c a line parallel to MT^t, meeting ^uO at 7, then ^Oy' is the new vertical axis corresponding to cOc', also &O& corresponds to bOb', and aOa' corresponds to aOa'. These three axes then are the axes for the second individual in its twinned po&ition ; 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-Z, the construction is more simple. It is obvious the axis is the line 62, and using this, as before, the new axes are found ; /cO/c' corresponds to cOc' (sensibly coinciding with bb), since 0Af-2 = 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. Thus in 1 827 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. Calcite. 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. BINGIIAM. Massive pyrite, galenite, blende, andalusite. BLUE HILL B AY. Arsenical iron, molybdenite! galenite, apatite! fluorite! black tourma- line (Long Cove), black oxide of manganese (Osgood's farm), rhodonite, bog manganese, wolframite. BOWDOIN. Rose quartz. BOWDOINIIAM. Ueryl, molybdenite. BRUNSWICK. Green mica, garnet! black tourmaline! molybdenite, epidote calcite mus covite, feldspar, beryl. BUCKFIELD. Garnet (estates of Waterman and Lowe), iron ore, muscovite/ tourmaline' magnetite. CAMDAGE FARM (Near the tide mills), molybdenite, wolframite CAMDEN. Mode, galenite, epidote, black tourmaline, pyrite, talc, magnetite. CAHMEL (Penobscot Co.). Stibm'te, pyrite, made. COR INN A. 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. Hose quartz, garnet, feldspar, scapolite, graphite, muscovite. 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 Sya tern of Mineralogy, 1868. 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 (hebron'te), rubettiteJ indicolite, green tourmaline, mica, beryl, apatite, albite, childrejiite, cookeite. JEWELL'S ISLAND. Pyrite. KATAHDIN IKON WORKS. Bog-iron ore, pyrite, magnetite, quartz. LETTER E, Oxford Co. Staurolite, macle, copperas. LINN/EUS. Hematite, limonite, pyrite, bog-iron ore. LITCHFIELD. Sodalite, cancrinite, el&olite, zircon, spodumene, muscovite, pyrrhotite. LUBEC LEAD MINES. - Galenite, chalcopyrite, blende. MAOHIASPORT. Jasper, epidote, laumontite. MADAWASKA SETTLEMENTS. Vwianite. MINOT. Beryl smoky quartz. MONMOUTII. Actinolite, apatite, elceolite, zircon, staurolite, plumose mica, beryl, rutile. MT. ABRAHAM. Andalusite, staurolite. NORWAY. Chrysoberyl! molybdenite, beryl, rose quartz, orthoclase, cinnamon garnet. ORR'S ISLAND. Steatite, garnet andalusite. OXFORD. Gar 'net , beryl, apatite, wad, zircon, muscovite, orthoclase. PARIS. Green/ red! black, and blue tourmaline! mica! lepidolite! feldspar, albite, quart* crystals/ rase quartz, cassiterite, amblygonite, zircon, brookite, beryl, smoky quartz, spodu- mene, cookcite, leucopyrite. PARSONSFIELD. Vesuvianite / yellow garnet, pargasite. adularia, scapolite, galenite, blende, chalcopyrite. PERU Crystallized pyrite. PHIPPSBURG. Yellow garnet / manganesian garnet, vesuvianite, pargasite, axinite, laumon- tite ! chabazite, an ore of cerium ? POLAND. Vesuvianite, smoky quartz, cinnamon garnet. PORTLAND. PreJmite, actinolite, garnet, epidote, amethyst, calcite. POWNAL. Black tourmaline, feldspar, scapolite, pyrite, actinolite, apatite, rose quartz. RAYMOND. Magnetite, scapolite, pyroxene, lepidolite, tremolite, hornblende, epidote, orihc- clase, yellow garnet, pyrite, vesuvianite. ROCKLAND. Hematite, tremolite, quartz, wad, talc. RUMFORD. Yellow garnet, vesumanite, pyroxene, apatite, scapolite, graphite. RUTLAND. Allanite. SANDY RIVER. Auriferous sand. SANFORD, York Co. Vesuvianite / albite, calcite, molybdenite, epidote, black tourmaJine, labradorite. SEAIISMONT. Andalusite, tourmaline. SOUTH BERWICK. Macle. STANDISII. Columbite ! STREAKED MOUNTAIN. Beryl! black tourmaline, mica, garnet. THOM ASTON. Calcite, tremolite, hornblende, sphene, arsenical iron (Owl's head), blacL 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 pyrite. WINDHAM (near the bridge). Staurolite, spodumene, garnet, beryl, amethyst, cyanite, tourmaline. WINSLOW. Cassiterite. WINTIIROP. Staurolite, pyrite, hornblende, garnet, copperas. WOODSTOCK. Graphite, hematite, prehnite, epidote, calcite. YOBK. B&ryl, 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. AMIIERST. Vesuvianite, yellow garnet, pargasite, calcite, amethyst, magnetite. BARTLETT. Magnetite, hematite, brown iron ore in large veins near Jackson (on ll Bold face mountain "), quartz crystal*, smoky quartz. BATH. Galenite, chalcopyrite. BEDFORD. Tremolite, epidote, graphite, mica, tourmaline, alum, quartz. BELLOWS FALLS. Cyanite, staurolite, wavelJite. BRISTOL. Graphite. AMERICAN LOCALITIES. 475 c 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. C HOYDEN. lolite ! chalcopyrite, pyrite, pyrrhotite, blonde. ENFIELD. Gold, galenite, stauroJite. green quarts. FKANOESTON. Soapstone, arsenopyrite, quartz crystals. FRANCONIA. Hornblende, staurolite! epidote! zoisite, hematite, magnetite, black and red manganesian gurnets, arsenopyrite (danaite), chalcopyrite, molybdenite, prehnite, green quartz, malachite, azurite. GILFORD (Gunstock Mt.). Magnetic iron ore, native "loadstone." GOSHEN. Graphite, black tourmaline. GILMANTOWN. Tremolite, epidote, rnuscovite, tournialiae, limonite, red and yellow quartz crystals. GRAFTON. Mica! (extensively quarried at Glass Hill, 2 m. S. of Orange Summit), albitef blue, green, and yellow beryls! (1 in. S. of 0. Summit), tourmaline, garnets, triphylite, apa- tite, fluorite. GRANTIIAM. Gray staurolite! GROTON. Arsenopyrite, blue beryl^ rnuscovite crystals. HANOVKR. Garnet, a boulder of quartz containing rutile/ black tourmaline, quartz, cya- nite, labradorite, epidote. HAVERIIILL. Garnet! arsenopyrite, native arsenic, galenite, blende, pyrite, chalcopy- rite, magnetite, marcasite, steatite. HILLSBORO' (Campbell's mountain). Graphite. HINSDALE. Rhodonite, 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, zoisite^ 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. MKKBTMACK. Rutile! (in gneiss nodules in granite vein). MIDDLETOWN. Rutile. MONADNOCK MOUNTAIN. Andalusite, hornblende, garnet, graphite, tourmaline, ortho- clase. MOOSILAUKE MT. Tourmaline. MOULTONBOROUGH (Red H\\l).Hornbende, bog ore, pyrite, tourmaline. NEWINGTON. Garnet, tourmaline. NEW LONDON. Beryl, molybdenite, rnuscovite crystals. NEWPORT. Molybdenite. ORANGE. Blue beryls/ 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, inela- conite, chalcocite, ripidolite. PELHAM. Steatite. PIERMONT. Micaceous iron, barite, green, white, and brown mica, apatite, titanic iron. PLYMOUTH. Coluuibite, beryl. RICHMOND. lolite! rutile, steatite, pyrite, anthophyllite, talc. RYE. Chiastolite. SADDLEBACK MT. Black tourmaline, garnet, spinel. SHELBURNE. Galenite, black blende, c.'ndcopyrite, pyrite, pyrolusite. SPRINGFIELD. Beryls (very large, eight inches diameter), manganesian garnets! black tourmaline ! in mica slate, albite, mica. SULLIVAN. Tourmaline (black), in quartz, beryl. SURREY. Amethyst, calcite, galenite, limonite, tourmaline. SWAN^EY (near Keene). Magnetic iron (in masses in granite). 476 APPENDIX. TAMWORTH (near White Pond). Galenite. UNITY (estate of James Neal). Copper and iron pyrites, chlorophyUite, green mica, racfc ated actinolite, garnet, titaniferous iron ore, magnetite, tourmaline. WALPOLE (near Bellows Falls). Made, staurolite, mica, graphite. WARE .Graphite. WARREN. Chalcopyrite, blende, epidote, quartz, pyrite, tremolite, galenite, rutile, tale, molybdenite, cinnamon stone ! pyroxene, hornblende, beryl, cyanite, tourmaline (massive). WATERVILLE Labradorite, chrysolite. WESTMORELAND (south part). Molybdenite! apatite! blue feldspar, bog manganese (north village), quartz, fluorite, chalcopyrite, oxide of molybdenum and uranium. WHITE MTS. (Notch near the "Crawford House")- Green octahedral fluorite, quarta crystals, black tourmaline, chiastolite, beryl, calcite, amethyst, amazonstoue. WILMOT. Beryl. WINCHESTER. Pyrolusite, rhodochrosite, psilomelane, magnetite, granular quartz, spodu- mene. VERMONT. ADDISON. Iron sand, pyrite. ALBURGH. Quartz crystals on calcite, pyrite. ATHENS. Steatite, rhomb spar, actinolite, garnet. BALTIMORE. Serpentine, pyrite ! BABNET. Graphite. BELVIDERE. Steatite, chlorite. BENNINGTON. Pyrolusite, brown iron ore, pipe clay, yellow ochre. BERKSHIRE. Epidote, hematite, magnetite. BETHEL. Actinolite! talc, chlorite, octahedral iron, rutile, brown spar in steatite. BRANDON. Braunite, pyrolusite, psilomelane, limonite, lignite, white clay, statuary marble ; fossil fruits in the lignite, graphite, chalcopyrite. BRATTLEBOROT.TGH. Black tourmaline in quartz, mica, zoisite, rutile, actinolite, scapolite, spodumene, roofing slate. BRIDGEWATER. Talc, dolomite, magnetite, steatite, chlorite, gold, native copper, blende, galenite, blue spinel, chalcopyrite. BRISTOL. Rutile, limonite, mariganese 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. CHITTENDEN. Psilomelane, pyrolusite, brown iron ore, hematite and magnetite, galenite, iolite. COLCHESTER. Brown iron ore, iron sand, jasper, alum. CORINTH. Chalcopyrite (has been mined), pyrrhotite, pyrite, rutile, quartz. COVENTRY. Ehodonite. CRAPTSBURY. Mica in concentric balls, calcite, rutile. DERBY. Mica (adamsite). DUMMERSTON. Rutile, roofing slate. FAIR HAVEN. Roofing slate, pyrite. FLETCHER. Pyrite, magnetite, acicular tourmaline. GRAPTON. The steatite quarry referred to Graf ton is properly in Athens ; quartz, acti- nolite. GOILFORD. Scapolite, rutile, roofing slate. HARTFORD. Calcite, pyrite ! cyanite in mica slate, quartz, tourmaline. IRASBURGH . 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. MoBh'TOWN. Smoky quartz! steatite, talc, wad, rutile, serpentine. MORRISTOWN. Galenite. MOUNT HOLLY. Asbestus, chlorite. NEW FANE. Glassy and aabestiform actinolite, steatite, green quartz (called chrysopraae AMEEICAN LOCALITIES. 477 at the locality), chalcedony, drusy quartz, garnet, chromic and, titanic iron, rhomb jyvw, serpentine, rutile. NORWICH. Actinolite. feldspar, brown spar in talc, cyanite, zoisite, chalcopyrite, pyrita PITTSFORD. Brown iron ore, manganese ores. PLYMOUTH. Siderite, magnetite, hematite, gold, galenite. PLYMPTON. Massive hornblende. PUTNEY. Fluorite, brown iron ore, rutile, and zoisite, in boulders, staurolite. READING. Glassy actinolite in talc. READSBORO\ uiasty actinolite, steatite, hematite. RIPTON. Brown iron ore, augite in boulders, octahedral pyrite. ROCHESTER. Jlutile, hematite cryst. , magnetite in chlorite slate. ROCKINGHAM (Bellows Falls). Cyanite, indicolite, feldspar, tourmaline, fluorite, caioite, prehnite, 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, copperas. THETFORD. Blende, galenite, cyanite, chrysolite in basalt, pyrrhotite, feldspar, roofing slate, steatite, garnet. TOWNSIIEND. Actinolite, black mica, talc, steatite, feldspar. TROY. 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, zaratito. VERSHIRE. Pyrite, chalcopyrite, tourmaline, arsenopyrite, quartz. WARDSBORO'. Zoisite, tourmaline, tremolite, hematite. WARREN. Actinolite, magnetite, wad, serpentine. WATERBURY. Arsenopyrite, chalcopyrite, rutile, quartz, serpentine. WATERVILLE. Steatite, actinolite, talc. WEATHERSFIELD. Steatite, hematite, pyrite, tremolite. WELLS' RIVER. Graphite. WESTFIELD. Steatite, chromite, serpentine. WESTMINSTER. Zoisite in boulders. WINDHAM. Glassy actinolite, steatite, garnet, serpentine. WOODBURY. Massive pyrite. WOODSTOCK. Quartz crystals, garnet, zoisite. MASSACHUSETTS. ALFORD. Galenite, pyrite. ATHOL. Allanite, fibrolite (?), epidote! babingtonite ? AUBURN. Masonite. BARRE. Rutile! mica, pyrite, beryl, feldspar, garnet. GREAT BARRINGTON. Tremolite. BEDFORD. Garnet. BELCHERTON. Allanite. BERNARDSTON. Magnetite. BEVERLY. Columbite, green feldspar, cassiterite. BLANFORD. Serpentine, anthophyllite, actinolite! chromite, cyanite, rose quartz in boulders. BOLTON. Scapolite ! petalite, sphene, pyroxene, nuttalite, dioptide, boltonite, apatite, mag- nesite, rhomb spar, allanite, yttrocerite ! cerium ochre ? (on the scapolite), spinel. BOXBOROUGH. Scapolite, spinel, garnet, augite, actinolite, apatite. BRIGHTON. Asbestus. BRIM FIELD (road leading to Warren). lolite, adularia, molybdenite, mica, garnet. CARLISLE. Tourmaline, garnet! scapolite, actinolite. CHARLESTOWN. Prehnite, laumontite, etilbite, chabazite, quartz crystals, melanolite. CIIELMSFORD. Scapotite (chelmsfordite), chondrodite, blue spinel, amianthus! tone quartz. 478 APPENDIX. CHESTER. Hornblende, scapolite, zoisite, spodumene, indicolite, apatite, magnetite, chro- mite, etilbite, heulandite, analcite and chabazite. At the Emery Mine, Chester Factories.- Corundum, margarite, diaspore, epidote, corundophilite, chloritoid, tourmaline, menaccan- ite ! rutile, biotite, indianite ? andesite ? cyanite, amesite. CIIESTKIIFIELD. Blue, green, and red tourmaline, cleavelandite (albite), lepidolite, smok$ quartz, microlite, spodumene, cyanite, apatite, rose beryl, garnet, quartz crystals, staurolito^ eassiterite, columbite, zoisite, uranite, brookite (eumanite), scheelite, anthophyllite, boinite. CON\V AY. Pyrolusite, fluorite, zoisite, rutile! ! native alum, galenite. CUMMIN GTON. Rhodonite! cummingtonite (hornblende), marcasite, garnet. DEDHAM. Asbestus, galeuite. DEERFIELD. Chabazite, heulandite, stilbite, amethyst, carnelian, chalcedony, agate. FITCHBURQ (Pearl Hill). Beryl, staurolite! garnets, molybdenite. FOXBOROUGH. Pyrite, anthracite. FRANKLIN. Amethyst. GOSHEN. Mica, albite, spodumene! blue and green tourmaline, beryl, zoiaite, smoky quartz, columbite, tin ore, galenite, beryl (goshenite), pihlite (cymatolite). GREENFIELD (in sandstone quarry, half mile east of village). Allophane, white and greenish. HATFPELD. Barite, yellow quartz crystals, galenite, blende, chalcopyrite. HAWLEY. Micaceous iron,, massive pyrite, magnetite, zoisite. HEATH. Pyrite, zoisite. HINSDALE. Brown iron ore, apatite, zoisite. HUBBARDSTON. Mdftxive pyrite. LANCASTER. Cyanite, chiastolite! apatite, staurolite, pinite, andalusite. LEE. Tremolite! sphene! (east part). LENOX. Brown hematite, gibbsite(?) LEVERETT. Barite, galenite, blende, chalcopyrite. LE YDEN . 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. MFLBURY. Vermiculite. 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, amethyst, corundum, vermiculite (pelhamite). PLAINFIELD. Cummingtonite,, pyrolusite, rhodonite. RICHMOND. Brown iron ore, gibbsite! ollophane. ROCKPORT. Danalite, cryophytlite, annite, cyrtoUte (altered zircon), green and white ortho- clase. ROWE. Epidote, talc. SOUTH ROYALSTON. Beryl// (now obtained with great difficulty), mica/ / feldspar/ allanitc. Four miles beyond old loc., on farm of Solomon Hey wood, mica / beryl! jeldspar J menaccanite. RUSSEL Schiller spar (diallage ?), mica, serpentine, beryl, galenite, chalcopyrite. SALEM. In a boulder, cancrinite, sodalite, elaeolite. SAUGUS. Porphyry, jasper. SHEFFIELD. Aabestus, pyrite, native alum, pyrolusite, rutile. SHELBURNE. Rutile. SHUTESBURY (east of Locke's Pond). Molybdenite. SOUTHAMPTON. Galenite, cerussite, anglesite, wutfenite, fluorite, barite, pyrite, chalcopy- rite, blende, corneous lead, pyromorphite, stolzite, chrysocolla. STERLING. tipodumene, chiastolite, siderite, arsenopyrite, blende, galenite, chalcopyrite pyrite, sterlingite (damourite). STONEHAM. Nephrite. AMERICAN LOCALITIES. 479 STURBRTDGE. Graphite, garnet, apatite, bog ore. SWAMPSCOT. OrtMte, feldspar. TAUNTON (one mile south). Paracolumbite (titanic iron). TURNER'S FALLS (Conn. River). Chalcopyrite, prehnite, chlorite, chlorof Kccite, siderite malachite, magnetic iron sand, anthracite. TYRING HAM. Pyroxene, scapolite. UXBRIDGE. G-alenite. WARWICK. Massive garnet, radiated black tourmaline, magnetite, beryl, epidote. WASHINGTON. Graphite. WESTFIELD. Schiller spar (diallage), serpentine, steatite, cyanite, scapolite, actinolite. WESTFORD. Andalusite ! WEST HAMPTON. Galenite, argentine, pseudomorphous quartz. WEST SPRINGFIELD. Prehnite, ankerite, satin spar, celestite, bituminous coal. WEST STOCKBRIDGE Hematite, fibrous pyrolusite, siderite. WIIATELY. Native copper, galenite. WILLIAMSBURG. Zoisite, pseudomorphous quartz, apatite, rose and smoky quartz, galenite pyrolusite, chalcopyrite. WILLIAMSTOWN. Gryxt. quartz. WINDSOR. Zoisite, actinolite, ruttte! WORCESTER. Arsenopyrite, idocrase, pyroxene, garnet, amianthus, bucholzite, siderite, galenite. WORTHINGTON. 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. WOONSOCKET. Cyanite. CONNECTICUT. BERLIN. Barite, datolite, blende, quartz crystals. BOLTON. Staurolite, chaloopyrite. BRADLEYVILLE (Litchfield). Laumontite. BRISTOL. Chalcocite! chakopyrite, barite, bornite, talc, aUophane, pyromorphite, Golcite, malachite, galenite, quartz. BROOKFIELD. Galenite, calamine, blende, spodumene, pyrrhotite. CANAAN. Tremollte and white augite ! in dolomite, canaanite (massive pyroxene). CHATHAM. Arsenopyrite, smaltite, chloanthite (ehathamite), scorodite, niccolile, beryl, rrythrite. CHESHIRE. Barite, chalcocite, bornite cryst., malachite, kaolin, natrclite, prehnite, ohaba ite, datolite. CHESTER. Sttlimanite/ zircon, epidote. 480 APPENDIX. CORNWALL. Graphite, pyroxene, actinolite, spJicne, scapolite. D ANBURY. Danburite, oligoclase, moonstone, brown tourmaline, orthoclasej pyroxene, parathorite. FARMINGTON. Prehnite, chabnzite, agate, native copper; in trap, diabantite. GRANBY. Green malachite. GREENWICH. Black tourmaline. HADDAM. Chrysoberyl ! beryl! epidote! tourmaline! feldspar, garnet! iolite! oligxiase, thlorophyllite ! automolite, magnetite, adularia, apatite, columbite! (hermannolite), zircon (calyptolite), mica, pyrite, marcasite, molybdenite, allanite, bismuth, bismuth ochre, bismu- 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, chal-copyrite, 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. Sillimanite, monazite / zircon, iolite, corundum, feldspar. OXFORD, near Humphrey sville. Cyanite, chalcopyrite. PLYMOUTH. Galenite, heulandite, fluorite, chlorophyltite ! garnet. HEADING (near the line of Danbury). Pyroxene, garnet, KOARING BROOK (Cheshire). Datolite! calcite, prehnite, saponite. ROXBURY. Siderite, blende, pyrite! ! galenite, quartz, chalcopyrite, arsenopyrite, limon- to. SALISBURY. Brown iron ore, ochrey iron, pyrolusite, triplite, turgite. SAYBROOK. Molybdenite, stilbite, plumbago. SEYMOUR. Native bismuth, arsenopyrite, pyrite. SIMSBURY. 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, tuugstic acid, siderite, mispickel, argentiferous galenite, blende, scapolite, tourmaline, garnet, albite, augite, graphic tellurium (V), 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, snowj gypsum. COEYMAN'S LANDING. Gypsum, epaom salt, quartz crystals at Crystal Hill, three milea outh of Albany. GUILDERLAND. Petroleum, anthracite, and calcite, on the banks of the Norman's Kill two miles south of Albany. WATEKVLIET. Quartz crystals, yellow drusy quarta. AMERICAN LOCALITIES. 481 AM/EGHANY CO. CUBA. Calcareous tuta, 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. SPRINGPORT. At Thompsou's plaster beds, sulphur f selenite. SPRINGVILLE. Nitrogen springs. CLINTON CO. ARNOLD IRON MINE. Magnetite, epidote, molybdenite. FINCH ORE BED. Calcite, green and purple fluor. CHATAUQUE CO. FIIEDONIA. Petroleum, carburetted hydrogen. L AON A. Petroleum. SHERIDAN. Alum. COLUMBIA CO. AUSTERLITZ. Earthy manganese, wulfenite, chalcocite ; Livingstor lead mine, vitreous silver ? CHATHAM. Quartz, pyrite in cubic crystals in slate (Hillsdale). CANAAN. Chalcocite, chalcopyrite. HUDSON. Epidote, selenite! NEW LEBANON. Nitrogen springs, graphite, anthracite ; at the Aiicram lead mine, galen- ite, barite, blende, wulfenite (rare), chalcopyrite, calcareous tufa; near the city of Hudson, epsom salt, brown spar, wad. DUTCHESS CO. AMENIA. Dolomite, limonite, turgite. BECKMAN. Dolomite. DOVER. Dolomite, tremolite, garnet (Foss ore bed), staurolite. limonite. FISIIKILL. Dolomite ; near Peckville, talc, asbestus, graphite, hornblende, augite, actino* lite, hydrous anthophyllite, limonite. NORTH EAST. Chalcocite, chalcopyrite, galenite, blende. PAWLING. Dolomite. RHINEBKCK. Calcite, green feldspar, epidote, tourmaline. UNION VALE. At the Clove mine, gibbsite, limonite. ESSEX CO. ALEXANDRIA. Kir by' s graphite mine, graphite, pyroxene, sea/polite, sphene. CROWN POINT. Apatite (eupyrchroite of Emmons), brown tourmaline/ in the apatite, chlorite, quartz crystals, pink and blue calcite, pyrite ; a short distance south of J. C. Ham- mond's house, garnet, scapdite, chalcopyrite, aventurine feldspar, zircon, magmetie iron (Peru), epidote, mica. KEKNE. Scapolite. LEWIS. Tabular spar, coloplionite, garnet, labradorite, hornblende, actinolite; ten miles south of the village of Keeseville, mispickel. LONG POND. Apatite, garnet, pyroxene, idocrase, coccolite! ! scapolite, magnetite, blue calcite. MclNTYRE. Labradorite, garnet, magnetite. MORIAH, at Saudford Ore Bed. Magnetite, apatite, allanite ! lanthanite, actinolite, and feldspar ; at Fisher Ore Bed, magnetic iron, feldspar, quartz; at Hall Ore Bed, or ''New Ore Bed," magnetite^ zircons; on Mill brook, calcite. pyroxene, hornblende, albite; in the town* of Moriah, magnetite, black mica ; Barton Hill Ore Bed, albite. NEWCOMB.- Labradorite, feldspar, magnetite, hypersthene. , PORT HENRY. Brown tourmaline, mica, rose quartz, serpentine, green and black pyroxene, hornblende, cryst. pyrite, graphite, wollastonite, pyrrhotite, adularia ; phlogopite ! atCheevei Ore Bed, with magnetite and serpentine. ROGER'S ROCK. Graphite, wol/Mstonite, garnet, coloplionite, feldspar, adularia, pyroxene^ vphene, ooccolite. SCHROON. Calcite, pyroxene, chondrodite. TICONDEROGA. Graphite! pyroxene, saJdite, sphene, black tourmaline, cacoxene? (Mt Defiance). WESTPORT. Labradorite, prehnite, magnetite. WILLSBORO'. Wollastonite, coloplionite, garnet, green coccolite, hornblende. ERIE CO. ELLTCOTT'S MILLS. Calcareous tufas. 31 482 APPENDIX. FRANKLIN CO. CHATEAUGAY. Nitrogen springs, calcareous tufaa. MALONE. Massive pyrite, magnetite. GENESEE CO. Acid springs containing sulphuric acid. GREENE CO. CATSKILL. Calotte. DIAMOND HILL. Quartz crystals. HERKIMER CO. FAIRFIELD. Quartz crystals, fetid barite. LITTLE FALLS. Quartz crystals f barite, calcite, anthracite, pearl spar, smoky quarts f one mile south of Little Falls, calcite, brown spar, feldspar. MIDDLEVILTE. Quartz crystals! calcite, brown and pearl spar, anthracite. NEWPORT. Quartz crystals. SALISBURY. Quartz crystals ! blende, galenite, pyrite, chalcopyrite. STARK. Fibrous celestite, gypsum. HAMILTON 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, cJialcodite, siderite, millerite, red Jiematite, crya taliized quartz, yellow aragonite, niccoliferous pyrite, quartz crystals, pyrite ; at Oxbow, cal- cite! porous coralloidal heavy spar; near Vrooman's lake, calcite! vesuvianite, phlogopite ! pyroxene, sphene, lluorite, 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 pseudomorpJious after pyroxene, apatite. NEW CONNECTICUT. 8phene, brown phlogopite. OMAR. Beryl, feldspar, hematite. PHILADELPHIA. Garnets on Indian river, in the village. PAMELIA. Affaric mineral, calc tufa. PIERREPONT. Tourmaline, sphene, scapolite, hornblende. PILLAR POINT. Massive 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). tica polite / wollastonite, green coccolite, feldxpar, tremolitft, pyroxene ! sphene.! ! mica, quartz crystals, drusy quartz, cryst. pyrite, pyrrhotite, blue calcite, serpentine, rcnsselaerite, zircon, graphite, chlorite, hematite, bog-iron ore, iron Band, apatite. GREIG. Magnetite, pyrite. LOWVILLE. Calcite, fluorite, pyrite, galenito, blende, calc tufa. MARTINSBURGH. 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. CANAJOHABIE. 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. Tremolitc,pyroxene, mica, tourmaline, pyrites, rutile, dolomite. HARLEM. Epidote, apophyllite, stilbite, tourmaline, vivianite. lamellar feldspar, mica. NEW YORK. Serpentine, amianthus^ actinolite, pyroxene, hydrous anthophyllite, garnet, ataurolite, molybdenite, graphite, chlorite, jasper, necronite, feldspar. In the excavations foi the 4th Avenue tunnel, 1875, harmotome, stilbite, chabazite, heulandite, etc. AMERICAN LOCALITIES. 483 NIAGARA CO. LEWISTON. Epsomite. LOCKPOHT. Celestite, caltite, selenite, anhydrite, fluorite, dolomite, blende. NIAGARA PALLS. -Calcite, fluorite, blende, dolomite. ONE1DA CO. BOONVILLE. Calcite. wollastonite, coccolite. CLINTON. Blende, lenticular argillaceous iron ore; in rocks of the Clinton Group, stronti anite, celestite, the former covering the latter. ONONDAGA CO. CAMILLUS. Selenite and fibrous gypsum. COLD SPUING. Axinite. MANLIUS. Gypsum and fluor. SYHACUSE. Serpentine, celestite, selenite, barite. ORANGE CO. CORNWALL. Zircon, chondrodite, hornblende, spinel, massive feldspar, fibrous epidote, hudsouite, menaccanite, serpentine, coccolite. DEER PARK. Cryst, pyrite, galenite. MONROE. Mica! sphene! garnet, colophonite, epidote,^ chondrodite, allanite, bucholzite, brown spar, spinel, hornblende, talc, menaccanite, pyrrJwUte, pyrite, chromite, graphite, raa- tolyte, moronolite. At WILKS and O'NEiL Mine in Monroe. Aragonite, magnetite, dimagnetite (pseud. ?), jen- kinsite, asbestus, serpentine, mica, hortonolile. At i Two PONDS in Monroe. Pyroxene! chondrodite, Itornblende, scapolite! zircon, sphene, apatite. At GREENWOOD FURNACE in Monroe. Chondrodite, pyroxene / mica, hornblende, spinel, scapolite, biolite! menaccanite. At FOREST OP DEAN. Pyroxene, spinel, zircon, scapolite, hornblende. TOWN OP WARWICK, WARWICK VILLAGE. Spinel! zircon, serpentine! brown spar, pyrox- ene ! hornblende ! pseudf Amorphous steatite, feldspar ! (Rock Hill), menaccanite, clintonite, tourmaline (R. H. ), rutile, sphene, molybdenite, arsenopyrite, marcasibe, pyrite, yellow iron sinter, quartz, jasper, mica, coccolite. AMITY. Spinel! garnet, scapolite, hornblende, vesuvianite, epidote! clintonite! magnetite, tourmaline, warwickite, apatite, chondrodite, talc! pyroxene! rutile, menaccanite, zircon^ corundum, feldspar, sphene. calcite, serpentine, schiller spar (?), silvery mica. EOENVILLE. Apatite, chondrodite ! hair-brown hornblende ! tremolite, spinel, tourmaline, warwickite, pyroxene, sphene, mica, feldspar, mispickel, orpiment, rutile, menaccanite, score- dite, chalcopyrite, leucopyrite (or lollingite), allanite. WEST POINT. Fddspar, mica, scapolite, sphene, hornblende, allanite. PUTNAM CO. BREWSTER, Tilly Foster Iron Mine. Chondrodite! (also humite and clino- hurnite) crystals very rare, magnetite, dolomite, serpentine pseudomorphs, brucite, enstatite, ripidolite, biotite, acbinolite, apatite, pyrrhotite, fluorite, albite, epidote, sphene. CARMEL (Brown's quarry). Anthophyllite, schiller spar (?), orpiment, arseuopyrite, epi- dote. COLD SPRING. Chabazite, mica, sphene, epidote. PATTERSON. WJiit", pyroxene ! calcite, asbestus, tremolite, dolomite, massive pyrite. PIIILLIPSTOWN. Tremolite, amianthus, serpentine, sphene, diopside, green coccolite, horn blende, sc3ntine title, magnesite. ROCKLAND CO. CALDWELL. Calcite. GRASSY POINT. Serpentine, actinolite. HAVERSTRAW. Hornblende, barite. LADEN TOWN. Zircon, malachite, cuprite. PIERMONT. Datolite, stilbite, apophyllite, stellite, prehnite. thomsonite. caloite, chabazite STONY POINT. Cerolite, lamellar hornblende, asbestus. 484 APPENDIX. ST. LAWRENCE CO. CANTON. Massive pyrite, calcite, brown tourmaline, spliene, ser- pentine, talc, rensselaerite, pyroxene, hematite, chalcopyrite. DEKALB. Hornblende, barite, fluorite, tremolite, tourmaline, blende, graphite, pyroxene, quartz (spongy), serpentine. EDWARDS. Brown and siloery mica ! scapolite, apatite, quartz crystals, actinolite, trerW' 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 (near Somerville). GOUVEBNEUR. Galcite ! serpentine! hornblende! scapolite! orthoclase, tourmaline! ido- orase (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, clwndrodite, spinel ; two miles north of Somerville, apatite, pyrite, brown tourmaline! ! HAMMOND. Apatite! zircon! (farm of Mr. Hardy), 0r/i0cte0(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, phlogopite (Pope's Mills), barite OGDENSBURG. Labradorite. PITCAIRN. Satin spar, associated with serpentine. POTSDAM. Hornblende! eight miles from Potsdam, on road to Pierrepont, feldspar , tourmaline, 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, angles! te, octahedral fluor, black phlogopite. Elsewhere in ROSSIE. Calcite, barite, quartz crystals, chondrodite (near Yellow Lake), feldspar/ pargasite f 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 t apatite, graphite, aragonite (in iron mines). SCHOHARIE CO. BALL'S CAVE, and others. Calcite, stalactites. CARLISLE. Fibrous barite, cryst. and Jib. calcite. MIDDLEBURY. Anthracite, calcite. SHARON. Calcareous tufa. SCHOHARIE. Fibrous celestite, strontianite ! cryst. pyrite! SENECA CO. CANOGA. Nitrogen springs. SULLIVAN CO. WURTZBORO'. Galenite, blende, pyrite, chalcopyrite. TOMPKLNS 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. JOIINSBURG. Fluorite! zircon! ! graphite, serpentine, pyrite. WASHINGTON CO. FORT ANN. Graphite, serpentine. GRANVILLE. Lamellar pyroxene, massive feldspar, epidote. WAYNE CO. WOLCOTT. Barite. AMERICAN LOCALITIES. 485 WESTCHESTER CO. ANTHONY'S NosE.Apatife, pyrite, calcite ! in very large tabulai crystals, grouped, and sometimes incmsted with drusy quartz. DAVENPORT'S NECK. Serpentine, garnet, sphene. EASTCHESTER. Blende, pyrite, chalcopyrite, dolomite. HASTINGS. Tremolite, white pyroxene. NEW ROCHELLE. Serpentine, brucite, quartz, mica, tremolite, garnet, magnesite. PEEKSKILL. Mica, feldspar, hornblende, stilbite, sphene ; three miles south, emery. RYE. Serpentine, chlorite, black tourmaline, tremolite. SINGSING. Pyroxene, tremolite, pyrite, beryl, azurite, green malachite, cemssite, pyromor phite, anglesite, vauquelinite, galenite, native silver, chalcopyrite. WEST FARMS. Apatite, tremolite, garnet, stilbite, heulandite, chabazite, epidote, sphene YONKERS Tremolite, apatite, calcite, analcite, pyrite, tourmaline. YORKTOWN. Sittimanite, monazite, magnetite. NEW JERSEY. ANDOVER IRON MINE (Sussex Co.). Willemite, brown garnet. ALLEN TOWN (Monmouth Co.). Vimanite, dufrenite. BELVILLE. Copper mines. BERGEN. Calcite! datolite! pectolite (called stellite) ! analcite, apop7iyllite ! gmelinite : preluiite, sphene, stilbite, natrolite, heulandite, laumontite, cJiabazite, pyr-ite, pseudomorphoua steatite, imitative of apophyllite, diabantite. BRUNSWICK. Copper mines; native copper, malachite, mountain leather. BUY AM. Chondrodite, spinel, at Roseville, epidote. CANTWELL'S BRIDGK (Newcastle Co.), three miles west. Vivian ite. DANVILLE (Jemmy Jump Ridge). Graphite, chondrodite, augite, mica. FLEMINGTON. Copper mines. FRANKFORT. Serpentine. FRANKLIN and STERLING. Spinel! garnet ! rJiodonite ! willemite ! franklinite ! zintite ! dysluite! hornblende, tremolite. chondrodite, white scapolite, black tourmaline, epidote, pink calcite, mica, actinolite, augite, sahlite, coccolite, asbestus, jeffersonite (augite), calamine, graphite, fluorite, beryl, galenite, serpentine, honey-colored sphene, quartz, chalcedony, amethyst, zircon, molybdenite, vivianite, tephroite, rhodochrosite, aragonite, sussexite, chal- eophanibe, roepperite, calcozincite, vanuxemite, gahnite. Also algerite in gran, limestone. FRANKLIN and WARWICK MTS. Pyrite. GREENUROOK. Copper mines. GRIGGSTOWN. Copper mines. HAMBURGH. One mile north, spinel! tourmaline, pJdogopite, Jiornblende, limonite, hematite. HOBO KEN. Serpentine (marmolite) , brucite, nemalite (or fibrous brucite), aragonite, dolo- mite. HURDSTOWN. Apatite, pyrrhotite, magnetite. IMLEYTOWN. Vivianite. LOCK WOOD. Graphite, chondrodite, talc, augite, quartz, green spinel. MONTVILLE (Morris Co.). Serpentine, chrysotile. MULLICA HILL (Gloucester Co.). Vivianite lining belemnites and other fossils. NEWTON. Spinel, blue, pink, and white corundum, mica, vesuvianite, Jiornblende, tourma- line, scapolite, rutile, pyrite, talc, calcite, barite, pseudomorphous 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 Morgantown, green malachite, native copper, chrysocolla, magnetite, allophane, pyrite, chalcopyrite, aragonite, apatite, talc ; two miles N. E. from Jones's mine, graphite, sphene ; at Steel e's mine, one mile N.W. from St. Mary's, Chester Co., magnetite, micaceous iron, coccolite, brown garnet. EEADING. Smoky gtmrte'crystals, zircon, stilbite, iron ore, near Pricetown, zircon, allan- Ifce, epidote ; at Eckhardt's Furnace, attanite with zircon ; at Zion's Church, molybdenite ; * See also the Report on the Mineralogy of Pennsylvania, by Dr. F A. Genth, 1875. 486 APPENDIX. near Kutztown, in the Crystal Cave, stalactites ; at Fritz Island, apovhyttite, thomsonite, chaba \lte, 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, coccolite, sphene, green mica, calcite, wollastonite,^ glassy feld' epar 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. A VOND ALE. Asbestos, 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 gray cyanite, the gray cyanite is found loose in the soil, in crystals ; on the farms of Dr. Kwyn, Mrs. Foulke, Wm. Gibbons, and Saml. Entrikin, amethyst. At Strode's mill, asbestus, mag- nesite, anthophyllite, epidote, aquacrepitite, oligoclase, drusy quartz, cottyrite? 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 Black Horse Inn, indurated talc, rutiJe ; on Amor Davis' farm, orthite! massive, from a grain to lumps of one pound weight ; near the paper-mill on the Brandywine, zircon, associated with titaniferous iron in blue quartz. WEST BRADFORD. Near the village of Marshalton, green cyanite, rutile, scapolite, pyrite, staurolite ; at the Chester County Poor-house limestone quarry, chesterlite ! in crystals im- planted on dolomite, rutile / in brilliant acicular crystals, which are finely terminated, cal- cite in scalenohedrons, zoisite, damourite f in radiated groups of crystals on dolomite, quartz crystals ; on Smith & McMullin's farm, epidote. CHARLESTOWN. Pyromorphite, cerussite, galenite, quartz. COVENTRY. Allanite, near Pughtown. SOUTH COVENTRY. In Chrisman's limestone quarry, near Coventry village, angilc. sphene, graphite, zircon in iron ore (about half a mile from the village). EAST FALLOWFIELD. Soapstone. EAST GOSHEN. Serpentine, asbestus, magnetite (loadstone), garnet. ELK. Menaccanite with inuscovite, 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, chromite in octahedral crystals, deweylite, radiated mag nesite, aragonite, staurolite, garnet, asbestus, 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! I chabazite, sphene. 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 lite, black tourmaline, margarite, sunstone, asbestus, anthophyllite, steatite* near Tywn'f 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, muscovite, orthocluse, bismutite. CHICHESTKR. Near Trainer's mill-dam, beryl, tourmaline, crystals oi feldspar, kaolin; on Wm. Eyre's farm, tourmaline. CONCORD. Crystals of mica, crystals of feldspar, kaolin abundant, drusy quartz of a blue and green color, meerschaum, stellated tremolite, some of the rays 6- in. diameter, antho- phyllite, fibrolite, acicular crystals of rutile, pyrope in quartz, amethyst, actinolite, mangane- sian garnet, beryl ; in Green's creek, pyrope garnet. DARBY. Blue and gray cyanite, garnet, staurolite, zoisite, quartz, beryl, chlorite, mica, limonite. EDGEMONT. Amethyst, oxide of manganese, crystals oi feldspar ; one mile east of Edge mont Hall, rutile. in quartz. GREEN'S CREEK. Garnet (so-called pyrope). HAVERPORD. Staurolite with garnet. MARPLE. Tourmaline, andalusite, amethyst, actinolite, anthophyllite, talc, radiated actin- olite in talc, chromite, drusy quartz, beryl, cryst. pyrite, menaczanite in quartz, chlorite. MIDDLETOWN. Amethyst, beryl, black mica, mica with reticulated magnetite between the plates, manganesian garnets! large trapezohedral crystals, some 3 in. in diameter, indurated talc, hexagonal crystals of rutile, crystals of mica, green quartz! anthophyllite, radiated tour- maline, staurolite, titanic iron, fibrolite, serpentine ; at Lenni, chlorite, gieen and bronze vermiculite ! green feldspar ; at Mineral Hill, fine crystals of coi*undum, one of which weighs If lb., actinolite in great variety, bronzite, green feldspar, moonstone, suiutone, graphic granite, magnesite, octahedral crystals of chromite in great quantity, beryl, chalcedony, asbestus, fibrous hornblende, rutile, staurolite, melanosiderite, hallite ; at Painter's Farm, near Dismal Run, zircon with 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. Anlhophyllite, tremolite, radiated asbestus, radiated 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, picrolite7~-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! ripidolite! kammererite! baltimorite, chromic iron, williamsite, chrysolite! marmolite, picrolite, hydromagnesite, dolomite, magnesite, aragonite, calcite, serpentine, hematite, menaccanite, genthite, chrome-garnet, bronzite, millerite ; at Low's mine, hydro- magnesite, 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, pyrite in cubes and various modifications, an thopJtyllit e ; near Rock Springs, chalcedony, carnelian, moss agate, green tourmaline in talc, titanic iron, chromite, octahedral magnetite in chlorite ; at Reynolds's old mine, calcite, talc, picrolite, chromite ; at Carter's chrome mine, brookite. GAP MINES. Chalcopyrite, pyrrhotite (niccoliferous), millerite in botryoidal radiations, t/fofanite ! (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?), vauquelinite, rutile at Pequea mine ; fom- miles N.W. of Lancaster, on the Lancaster and Harrisburg Railroad, calamite, galenite, blcude ; pyrite ir cubic crystals is found in great abundance near the city of Lancaster ; at the Lancaster zin* mines, calamine, blende, tennantite ? sriiths&mte (pseud, of dolomite), aurichalcite. AMERICAN LOCALITIES. 489 LEBANON" CO. CORNWALL. Magnetite, pyrite (cobaltiferous), chalcopyrite, native cop* per, azurite, malachite, chrysocolla, cuprite (hydrocuprite), oMophane, brochantite, serpentine, quartz pseudomorphs ; galenite (with octahedral cleavage), fluorite, covellite, hematite (mi caceous), opal, asbestus. LEHIGH CO FRIEDENSVILLE. At the zinc mines, calamine, smitJisonite, hydrozincite, massive blende, greenockite, quartz, allophane, zinciferous clay, mountain leather, aragonite, sauconite ; near Allentown, magnetite, pipe-iron ore ; near Bethlehem, on S. Mountain, allanite, 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 CIIEKRY VALLEY. Calcite, chalcedony, quartz; in Poconac Valley, near Judge Mervine's, cryst. quartz. MONTGOMERY CO. CONSHOHOCKEN. Fibrous tourmaline, menaccanite, aventurine quartz, 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, galenite, pyromorphite, cernssite, wulfenite, anglesite, barite, calamine, chalcopyrite, malachite, chrysocolla, brown spar, cuprite, covellite (rare), mela- conite, libethenite, pseudomalachite. WHITE MARSH. At D. 0. Hitner's iron mine, five and a half miles from Spring Mills, limonite in geodes and stalactites, gothite, pyrolusite, wad, lepidocrocite ; at Edge Hill Street, North Pennsylvania Railroad, titanic iron, braunite, pyrolusite; or.e mile S.W. of Hitner's iron mine, limonite, velvety, stalactitic, and fibrous, fibres three inches long, turgite, gothltc, pyrolusite, velvet manganese, wad ; near Marble Hall, at Hitner's marble quarry, white mar- ble, granular barite, resembling marble ; at Spring Mills, limonite, pyrolusite, gothite ; at Flat Rock Tunnel, opposite Manayunk, stilbite, heulandite, chabasite, ilvaite, beryl, feldspar, mica. LAFAYETTE, at the Soapstone quarries. Talc, jefferisite, garnet, albite, serpentine, zoisite, etaurolite, chaloopyrite ; at Rose's Serpentine quarry, opposite Lafayette, enstatite, serpen- tine. NORTHUMBERLAND CO. Opposite SELIM'S GROVE. Calamine. NORTHAMPTON CO. BUSHKILL TOWNSHIP. Crystal Spring on Blue Mountain, quartz crystals. Near EASTON. Zircon! (exhausted), nephrite, coccolite, tremolite, pyroxene, sahlite, limonite, magnetite, purple calcite. WILLIAMS TOWNSHIP. Pyrolusite in geodes in limonite beds, gothite (lepidocrocite) at Glendon. PHILADELPHIA CO. FR A NKFORD. Titanite in gneiss, apophyllite ; on the Philadelphia, Trenton and Connecting Railroad, basanite ; at the quarries on Frankford Creek, stilbite, molybdenite, hornblende ; on the Connecting Railroad, wad, earthy cobalt ; at Chestnut Hill, magnetite, green mica, chalcopyrite, fluorite. FAIRMOUNT WATER WORKS. In the quarries opposite Fairmount. autunite ! torbernite, crystals of feldspar, beryl, pseudomorphs after beryl, tourmaline, albite, wad, menaccanite. GOHGAS' and CREASE'S Lane. Tourmaline, cyanite, staurolite, hornstone. Near GERMANTOWN. Slack tourmaline, laumontite, apatite; York Road, tourmaline, beryl. HESTONVILLE. Alunogen, iron alum, orthoclase. HEFT'S MILL. Alunogen, tourmaline, cyanite, titanite. MANAYUNK. At the soapstone quarries above Manayunk, talc, steatite, chlorite, vermicu- lite, anthophyUite, staurolite, dolomite, apatite, asbestus, brown spar, epsomite. MEAGARGEE'S Paper-mill. Staurolite, titanic iron, hyalite, apatite, green mica, iron gar- nets in great abundance. McKiNNEY's Quarry, on Rittenhouse Lane. Feldspar, apatite, stilbite, natrolite, heulan- dite, epidote, hornblende, erubescite, malachite. SCHUYLKILL FALLS. Chabazite, titanite, fluorite, epidote, muscovite, tourmaline, pro- fhlorite. 8CHUYLKILL CO. TAMAQUA, near POTTSVILLE, in coal mines. KaottniU. YORK CO. Boruite, rutile in slender prisms in granular quartz, calcite. 490 APPENDIX. DELAWARE. NEWCASTLE CO. BRANDYWINE SPRINGS. BucJiolzite, fibrolite abundant, sahlite, pyroz ene ; Brandywine Hundred, muscovite, enclosing reticulated magnetite. DIXON'S FELDSPAR QUARRIES, six miles N. W. of Wilmington (these quarries have been worked for the manufacture of porcelain). Adularia, albite, oligodase, beryl, apatite, cinna- mon-*tone! ! (both granular like that from Ceylon, and crystallized, rare), magnesite, 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, spodumene, fibrolite. Near NEWARK, on the railroad. Sphaerosiderite on drusy quartz, jasper (ferruginous opal), cryst. spathic iron in the cavities of cellular quartz. WAY'S QUARK Y, two miles south of Centreville. Feldspar in fine cleavage masses, apatite^ mica, deweylite, granular quartz. WILMINGTON. In Christiana quarries, metalloidal diallage. KENNETT TURNPIKE, near Centreville. Cyanite and garnet. HARFOKD 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 Yivianite. MARYLAND. BALTIMORE (Jones's Falls, If mile from B.). Chabazite (haydenite), heulandite (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- eopyrite, linnseite (carrollite) ; at Patapsco Mines, near Finksburg, bornite, malachite, siegen- ite, linnceite, remingtonite, magnetite, chalcopynte ; at Mineral Hill mine, b&rnite, 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 asbestus, 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 galenite iu dolomite. MONTGOMERY Co. Oxide of manganese. SOMERSET and WORCESTER Cos., north part. Boa-iron ore, vivianite. ST. MARY'S RIVER. Gypsum! in clay. PTLESVILLE, Harford Co. Asbestus mine. VIRGINIA AND DISTRICT OF COLUMBIA. ALBEMARLE Co., a little west of the Green Mts. Steatite, grapJdte, galenite. AMHERST Co., along the west base of Buffalo ridge. Copper ores, allanite, eta AtJGtSTA Co. At Weyer's (or Weir's) cave, sixteen miles northeast of Staunton, anyromorphite, galenite, blende, malachite, black copper, wavellite, garnet, stilbite ; five milea from Washington mine, on Faust's farm, gold, tetradymite, oxide of bismuth and tellurium, montanite, chalcopyrite, limonite, spathic iron, epidote ; near Squire Ward's, gold in crys- tals, electrum. FRANKLIN Co. At Partiss mine, diamonds. GASTON Co. Iron ores, corundum, margarite ; near Crowder's Mountain (in ^vbat TOM 492 APPENDIX. formerly Lincoln Co.), lazulite, cyanite, garnet, graphite ; also twenty miles northeast, neai south end of Clubb's Mtn., lazulite, cyanite, talc, rutile, topaz, pyropJiyllite ; 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, chalcopyrite (worked for copper), quartz, siderite. The North Carolina Copper Co. are working the copper ore at the old Fentress mine ; at Deep River, compact pyrophyllite. (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. LTNCOLN 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, pyromelane, 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- eite. MITCHELL Co. Samarskite, 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, pseiidomorphmts quartz f, chalcedony, corundum in small crystals, epidote, pyrope, brookite, zircon, monazite, rutherfordite, samarskite, quartz crystals, itacolumyte ; on the road to Cooper's Gap, cyanite. STOKES AND SURRY 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 '5 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 DTST. At Pendleton, actinolite, galenite, kaolin, tourmaline. CHARLESTON. Selenite. CHEOWEE 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. D AR LINGTON. 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, Ezell's inine. LAURENS DIST. Corundum, damourite. NEWBERRY DIST. Leadhillite. PICKEN'S DIST. Gold, manganese ores, kaolin. RICIILAND DIST. Chiastolite, novaculite. SPARTANBURG DIST. Magnetite, chalcedony, h>maHte ; at the Cowpens, limonite, graphite limestone, copperas ; Morgan mine, leadhillite, pyromorphite, cerussite. SUMTER DIST. Agate. UNION DIST. Fairforeat gold mines, pyrite, chalcopyrite. YoKK DIST. Limestones, whetstones, witherite, barite, tetradymite. AMERICAN LOCALITIES. 493 GEORGIA. BURKE AND SCRIVEN Cos. Hyalite. CHEROKEE Co. At Canton Mine, chaleopyrite, galenite, clausthalite, plumbogumrnite, aitchcockite, arsenopyrite, lanthanite, harrisite, cantonite, pj romorphite, automolite, zinc, ataurolite. cyanite ; at Ball-Ground, spodumene. CLARK Co., near Clarksville. Gold, xenotime, zircon, rutile, cyanite, hematite, garnet, quartz. BADE Co. Halloysite, near Rising- Fawn. FANNIN Co. Staurolite! chalcopyrite. HABERSHAM Co. Gold, pyrite, chalcopyrite, galenite, hornblende, garnet, quartz, kaolinite, eoapstone, 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, tetradymite, pyrrhotite, 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. TDSCALOOSA Co. Coal, galenite, pyrite, vivianite, limonite, calcite, dolomite, cyanite, steatite, quartz crystals, manganese ores. BENTON Co. Antimonial lead ore (boulangerite ?) TALLAPOOSA Co., at Dudleyville. 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, calcite, barite, celestite. OWEN Co. Galenite, barite. TENNESSEE. BROWN'S CREEK. Galenite, blende, barite, celestite. CARTER'S Co., foot of Roan M.t.S2); some tetradymite (p. 233). 2. Fumes selenial or telluric. CLAUSTHALITE (p. 236); TETRADYMITE (p. 233). 3. NATIVE ARSENIC, ANTIMONY, BISMUTH, and TELLURIUM (pp. 226, 227.) Some CINNA* BAR (see above) has a metallic lustre. Part II. YIELDING FUMES READILY IN THE OPEN TUBE, BUT NOT WHOLLY VAPORIZABLE. 1. LUSTRE UNMETALLIC. 1. Fumes sulphurous alone. SPHALERITE (p. 237), infusible; GREENOCKITE (p. 242). 2. Fumes sulphurous, and (a) antimonial; or (/3) arsenical, yield a bead of silver with Boda on charcoal. (a) MIARGYRITE (p. 249); PYRARGYRITE (p. 252). 9) Hatchettolite (p. 428).. Manganosite (p. 431). . . Senarmonite (p. 284).. Embolite (p. 260) PHABMACOSIDERITE (p. 376) BORACITE (p 381) FLUORITE (p. 263) Nitrobarite (p 433) .... Microlite (p 359) CERARGYRITE (p. 2GO) . . Huantajayite (p. 259).. lodobromite (p. 429)... Bromyrite (p. 260) CUPRITE (p. 266) HELVITE (p 302) G \RNET (p 302) D \NALITE (p. 302) . . . Hauerite (p l ^44) DIAMOND (p 228) Eulytite (p. 302) Periclasite (p. 267) Bunsenite (p. 267) B. LUSTRE METALLIC (and SUBMETALLIC). Spec. Gravity Hardness. Spec. Gravity Hardness Cubanite (p 245) 4-03-4-2 4 Skutterudite (p. 246) . . 6-7-6-8 6 PEROFSKITE (p. 270) CHROMITE (p 274) 404 4-3-4-6 5-5 5-5 Polyargyrite (p. 257) . . Laurite (p 247). . . . 6-97 6-99 25 7 above TENNANTITE (p. 256) . . . Binnite

1) R. . . Eudialyte (p. 299) R. .. TOURMALINE (p. 829) R. ANKERITE (p. 493) R. . . APATITE (p 364) Cerito (p 340) Fluocerite (p. 264) jGREENOCKITE (p. 242) . . ZINCITE (p. 266) lodyrite (p. 2GO) PROUSTITE (p 253) R. . . PYRARGYRITE (p. 252) R iSchwartzembergite (p. 262) Phenacite (p. 301) R. . . Seybertite (p. 858) Tysonite (p. 439) PYROMORPHITK; (p. 306). VANADINITE (p. 867) MIMETITE (p. 366) . . . Friedelite (p. 302) R... Breunerite (p. 402) R . . Wurtzite (p. 242) CORUNDUM (p. 267) R. . . B. LUSTRE METALLIC (and SUBMETALLIC). Spec. Gravity Hardness.' Spec. Gravity Hardness. GRAPHITE (p 230) 2-1-2-23 1-2 Allemontite (p 227) . 613-62 8-3-5 Chalcophanite (p. 283). . PYRRUOTITE (p. 241) MOLYBDENITE (p. 233). . MENACCANITE (p. 289) R HEMATITE (p. 268) R. . . 3-91 4-4-4-7 4-4-4-5 4-5-5 4-5-53 2-5 3-5-45 1-1-5 5-6 5-5-6-5 1 ANTIMONY (p. 227) R. . . TEDRADYMITK (p. 233). . NICCOLITE (p. 242) Breithauptite (p. 243). . Joseite (p. 2-33) 6-6-6-7 7-2-7-9 7-3-7-7 7-54 7-93 3-3-5 2 5-5-5 5-5 soft. Beyrichite (p. 241) 4-7 3-3-5 Wehrlite (p 233) 8-44 1-2 MILLERITE (p. 241) R . . PYRARGYRITE (p. 252) R ARSENIC (p. 226) R TELLURIUM (p. 227) 4-6-5-65 5-7-59 5-93 6-1-6-3 3-3-5 2-25 3-5 2-2-5 CINNABAR (p. 240) R . . BISMUTH (p. 227) IRIDOSMINE (p. 224) 9-0 9-73 19-3-21 2-2-5 2-2-5 6-7 The crystals of the following species are sometimes PSEUDO-HEXAGONAL (see pp. 96, 97, and 188-190) as a result of repeated twinning : Aragonite, cerussite, chrysoberyl, jordanite, leadhillite, milarite, stephanite, strontian- ite, witherite, zinkenite. The species of the mica group and most of those of the chlorite groups are also PSEUDO- HEXAGONAL, the true form (monoclinic) approximating very closely to that required by the hexagonal system. IV. CRYSTALLIZATION ORTHORHOMBIC. A. LUSTRE UNMETALLIC. Spec. Gravity Hardness. Spec. Gravity Hardness, Struvite(p. 37.) Lecontite (p 392) 1-65-1 7 2 -2'5 ZOISITE (p. 308) Dufrenite (p 378) 3-1-3-38 3-2-3-4 G-6'5 3'5-4 Aphthitalite (p. 390)... Mascagnite (p. 3;)2) EPSOMITE (p 394) . 1-73 173 1 *75 3-3-5 2-25 2 25 CALAMINE(p. 389) ? Astro phyllite (p. 313). HYPERSTHENE (p 280; 8-16-0-9 3-32 3-89 4-5-5 3 5-6 Fauserite (p. 394) Mtre (p 379) 1-89 1-94 2-2-5 2 Euchroite (p. 373) DIASPORE (p 279) 3-39 3-3 3'5 3-5-4 6'5 7 Erythrosiderite (p. 261). Newberyite (p. 432). . . . Goslarite (p. 395) 204 2-2-5 CHRYSOLITE (p. 300). . . . Uranospinite (p. 379) . . ! ORPIMENT (p 231). . . 3-3-3-5 345 3-48 6-7 2-3 1-5-2 SULPHUR (p. 228) 207 1-5-2-5 Guarinite (p. 336) 8'49 6 NATROLITE (p. 342^ ?Pilinite(p. 344) ?Gismondite (p. 341).. Etidnophite (p. 344) 2-17-2-25 2-26 2-265 2-27 5-5-5 45 5-5 Serpierite (p. 436) Langite(p. 897) TRIPHYLITE (p. 369) .... TOPAZ (p. 332) 3-5 354-3-6 3-4-3-68 2-5-3 5 8 THOMSONITE (p. 342)... WAVELLITE (p. 376). . . . 2-3-2-4 2-34 5-55 34 Ardennite (p. 310) TRIPLITE (p 369) 3*62 3-4-3-8 6-7 4-5-5 SCORODITE (p. 375) Forsterite (p. 300) 3-1-3-3 3-2-3-33 3-5-4 6-7 STAUROLITE (p. 336) 3-4-3-8 7-7-5 DETERMINATION OF MINERALS. 521 Spec. Gravity Hardness.! Spec. Gravity Hardness. Forest te (p. 347) KAOLINITE (p. 351) 2-41 2-4-2-63 1-25 Uranocircite (p. 439). . . CHRYSOBKRYL (p. 274\ . 3-53 3-5-3-84 8-5 Peganite (p. 378) Milarite (p. 4-52) 2-5 2-5-2-59 3-3-5 5-5-6 STRONTTANITE (p. 406) . Knebelite (p. 300) 3-6-3-71 3-71 3-5-4 6-5 Kieserite (p. 394) lOLLTF (p 301) 2-o2 2 56 '67 2-5 7-7-5 LlBETBENITE (p. 373) . . Bromlite (p 406) 3 6-3 -3 37 4 4-4-5 LANTHANITE (p. 410). - . TALC (p. 348) Aspidolite (p 312) .... 2-0-2-67 2-6-2-8 2-72 2-5-3 1-1-5 1-2 ATACAMITE (p. 261) Claudetite (p. 284)...-, Hortonolite (p. 800) 3-76-3-9 3-85 391 3-3-5 6-5 PYROPHYLLITE (p. 349).. PHLOGOPITE (p 312) 2-75-2-9 2 '78 2'85 1-2 2-5-3 CELESTITE (p. 888) Rrepperite (p. 300) 8-9-3-98 8-8-4-08 3-3-5 5-5-6 Haidingerite (p. 371). . . PREHNTTE (p 340) 2-85 2-8-2-9 1-5-2-5 6-6-5 Sternbergite (p. 240) ... Cervantite (p. 284) 4-21 4-08 1-1-5 4-5 Strengite (p 43?) 2-87 3-4 Tephroite (p 300) . . . 4-4-12 5'5-6 ARAGONITE (p 40") ) 2 '93 3-5-4 BROOKITE (p. 277) 4-03-4-23 5-5-6 ANHYDRITE (p 389) 2-9 2-98 3 3'5 GGTHITE (p 280) 4-4-4 5-5 -5 Herdei'ite (p 370) 2 98 5 OLIVENITE (p. 373) 4-1-44 3 Villarsite (p. :M)) Fluellite (p 264) 2-99 4-5 3 WITHERITE (p. 406) BARITE (p. 387) 4-3 4-3-4-7 3-3-75 2-5-3-5 Danburite (pp 311 424) 3 7-7-25 Molybdite (p. 284) 4-5 1-2 Manganocalcite (p. 406). Diaclasite (p. 291) Kupffcrite (p. 298) ... 3-04 3-0~> 3-08 4-5 3-5-4 5-5 EUXENITE (p. 862) Polymignite (p. 362)... Polycrase (p. 362) 4-6-5 4-7-4-85 5-1 6-5 6-5 5'5 Seybertite (p. 358) Tyrol ite (p 3T4). 3-3-1 3-3-1 4-5 1-2 JESCHYNITE (p. 862) Cotunnite (p 261).. . 4-9-5-14 5-24 5-6 soft. Reddingite (p. 435) AUTUNITE (p. 379) ANTHOPHYLLITE (p 295) 3-10 3-05-3-19 3-1-3-2 3-35 2-25 5-5 . VALESTINITE (p. 284). . . Descloizite (p. 367) Pucherite (p 367) 5-57 5-84 5-91 2-5-3 3-5 4 ANDALUSITE (p. 331). . . HUMITE (p 327) . 3-1-3-2 3-1-3-24 75 6-6 '5 ANGLESITK (p. 889) Kentrolite (p 430) 6-1-6-89 6-19 2-75-3 5 Monticellite (p. 300) Eosphorite (p. 423) CHILDRENITE (p 377) . . 3-3-25 3-13 3-18-3 24 5-5-5 5 4-5-5 LEADHILLITE (p. 390).. . CERUSSITE (p. 407) Nadorite (p. 870) 6-26-6-44 6-48 7-02 2-5 3-3-5 3 ENSTATITE (p. 290) 3-1-3-3 5-5 iMendipite (p. 2(52) 7-7-1 2-5-3 B. LUSTRE METALLIC (and SUBMETALLIC). Spec. Gravity Hardness. Spec. Gravity Hardness. ILVAITE (p. 309) MANGANITE (p. 280) Chalcostibite (p. 250). . . EXARGITE (p. 257) Epigenite (p 25S) .... 3-7-4-2 4-2-4-4 4-25-5 4-44 5-5-6 4 3-4 3 3-5 JAMESONITE (p. 251) . . . CHALCOCITE tp. 239) COLUMBITE (p. 360) BOURNONITE (p. 2f)3) . . . Diaphorite (p 252) . . . 5-5-5-8 5 5-5-8 5-4-6-5 5-7-5-9 5-90 2-3 25-3 6 2-5-3 2-5-3 Spathiopyrite (p. 246).. STIBNITE (p. 232) Famatiuite (p. 258) Klaprotholits (p. 251).. MARCASITE (p. 247) Livingstonite (p. 232) . . Stylotypite (p. 254) PYROLUSITE (p. 278). . . . 4-5 4-52 4-57 4-6 4-7-4-85 4-81 4-79 4-82 6-7 2 3-5 2-5 6-o-5 2 3 2-25 :Glaucodot (p. 248) Aikinite (p. 254) POLYBASITE (p. 257) STEPHANITE (p. 256) Stromeyerite (p. 240). . . Wolfachite (p. 247).... lArsenopyrite (p. 247).. . Jordanite (p. 251) 6-0 6-16-8 621 627 6-2-6-3 6-37 66-4 6-4 5 2-2-5 2-3 2-2-5 2-5-3 5-5 5-5-6 Wittichenite (p. 254). . . Guejarite (p 428) 5 5-03 3-5 35 iGeocronite (p. 257) Allocla^ite (p 248) . . . 6-4-6-6 66 2-3 4-5 Guana juat ite (p. 233) . . Emplectite (p. 250) ZlNKENITE (p. 250) SARTORITE (p. 250) SAMARSKITE (p. 361) DUFRENOYSITE (p 251). 5-15 5-1-5-26 5-35 5-39 5-45-5-7 5 5-5 '6 22-5 3-3-5 3 5-5-6 3 iBlSMUTHTNITE (p. 232). . i Leucopyrite (p. 248) . . . [LoUingite (p. 248) ACANTHITE (p. 239) jTANTALITE (p. 359) ^HESSITE (p 238) 6-4-7-2 62-7-3 6-8-8-7 7-1*6-7-3 7-8 8 '3-8 -6 2 5-5-5 2-5 6-6-5 2-3-5 YTTROTANTALITE (p. 361).. 5-4-5-9 5-5-5 Krennerite (p. 430) DYSCKASITE (n. 234).. 9-4-9-8 3-5-4 APPENDIX. CRYSTALLIZATION MONOCLINIC. A. LUSTRE UNMETALLIC. Spec. Gravity! Hardness. Spec. Gravity llardnesa Natron (p. 409) MlRABILITE (p. 392)... BORAX (p 381) 1-42 1-48 1-72 1-8-2-2 1-9 1-99 2-04 2-11 2-14-2-18 2-1-2-4 2-09-2-2 2-20 2-2 2-3-2-33 2-3-2-4 2-25-2-6 225-2-38 2-25-2-36 2-43 2-4-2-5 2-4) 2-4-2-6 2-58-2-68 2-6-2-8 2-65-2-8 2-6-273 2-6-2-85 2-7-3-1 2-7-3-1 2-78-2-9 2-8-3 2-8-2-9 2-8-2-96 2-9 2-92 2-9-3 2-93-3 2-97 2-99 2-9-3-4 2-95 1-1-5 1-5-2 2-2-5 2-2-5 2-3 2-2-5 2-5-3 2-5-3 3-5 5-5-5 35-4 4-4-5 3-5-4 1-5-2 25-3-5 2-5 3-5-4 4-4-5 4-5-5 6-6-5 4-5 6 6-5 1-5-2 2-2-5 5 2-2-5 2-5-3 2*5-3 2-2-5 4-5-5 5-5-5 6-6-5 1-2 2-5 1-5 2-5 25-4 3-5-4 3-5-4-5 5-6 2-2-5 WAGNERITE (p. 363). . . Kottigite (p. 372) 3-07 3-1 3-12 3-1-319 3-312 3-1 3 13 3-19 3-1-3-24 3-1-3 24 3-2-3-3 3-4-2 3-25-3-5 3-2-3-5 3-2-353 3-34 334 34-4 3-43 3-4-3-6 3-4-3-56 3-45-3-6 3-7 3-5-3-83 3-64-3-66 3-7 3-76 3-7-4-01 3-8-3-9 3-96 3-95-4-03 4-4-5 4-2-4-25 4-2-4-36 4-9-5-26 5-2-5-24 5-3-5-45 5-5-5-78 5-77 5-8 5-9-6-1 6-3-7 6-4 6-45 7-14 5-5-5 2-5-3 3-5 6-5-7 5-6 7-5 2-5 2-25 6-6-5 6-6-5 6-7 5-5-6 6-7 5-6 6 4-5-5 3-5-4 6-5 4-5 1-5-2 5-5-5 5-5-6 6-5 3-5-4 4 4-5-5 3-5-4 3-5-4 5 6-5-7 2 2-5-3 5-5-5 2-2-5 2-5 2-5-3 3 2-5-2 2-2-5 2-5-3 3-5-4 45 Ludlamite (p. 372) SPODUMENE (p. 295). . . LAZULITK (p. 375) Copperas (p. 394) GAY-LUSSITE (p. 409). . Botryogen (p. 395) Whewellite (p. 412). . . . TRONA (p. 408) . ... EUCLASE (p 333) Herrengrundite (p. 428) Johannite (p. 397) Hydromagnesite (p. 409) SCOLECITE (p. 343) CHONDRODITE (p. 327). ICLINOHUMITE (p. 328). . PlBROLITE (p. 331) ALLANITE (p. 308) STILBITE (pp. 346, 437) PHILLIPSITE (pp. 345, 433) EPIDOTE (p 307) HEULANDITE (p. 347).. GYPSUM (p. 392) GIBBSITE (p. 282) PYROXENR (p. 292) Acmite (p ^94) 'Homilite (p. 429) Syngenite(p. 394) LAUMONTITE (p. 338). . EPISTILBITE (p. 347) . . . Brewsterite (p. 347) Petalite ( p 295). Dickinsonite (p. 425). . . |Piedmontite(p. 308)... Fillowite (p. 427) REALGAR (p. 231) TIT \NITE (p. 335) . . HARMOTOME (p. 346). . . ORTHOCLASE (p. 325). . . VIVIANITE (p. 371) RIPIDOLITE (p. 356) . . . PECTOLITE (p. 337). . . . PHARMACOLITE (p. 370) GLAUBERITE (p. 391). . . BIOTITE (p. 312), LEPI- DOLITE and other MICAS '^Egirite (p. 294) Keilhauite (p. 3S6) AZURITE (p 411) BARYTOCALCITE (p. 408) iTriploidite (p. 439) Chalcomenite (p. 422). . MALACHITE (p. 411). . . BROCHAXTITE (p. 396). Trogerite (p 379) Durangite (p 370) MUSCOVITE (p. 313) Vaalite (p 3,35) . Gadolinite (p. 309).... | Pyrostilpnite (p. 252). . : CLINOCLASITE (p. 374). . MONAZITE (p. 368), Tur- nerite WOLLASTONITE (p. 291) DATOLITE (p. 334) HYALOPHANE (p. ;>22). . Prochlorite (p. 357) Corundophilite (p. 353). Isoclasite (p. 373) CRYOLITE (pp 264. 424) Thomsenolite (p. 438). . PACHNOLITE (p. 265). . . Leucophanite (pp. 300, 430) jMlARGYRITE (p. 249). . . 'LlNARITR (p 396) < VAUQUELINITE (p. 386). Laxraannite (p. 386) . . . iWalpurgite (p. 379)... 'CROCOITE (p. 385) Lanarkitetp. 391) Caledonite (p. 391;.... iMegabasite (p. 383) Hubnerite(p. 383) MARGARITE (p. 357). . . AMPHIBOLE (p 296) ERYTHRITE (p. 372) ... B. LUSTRE METALLIC (and SUBMETALLIC). Spec. Gravity Hardness. Spec. Gravity Hardness, ALLANITE (p. 308) Clarite (p 253) . 3-4-2 4*46 5-5-6 3'5 Meneghinite (p. 256).. . FREIESLEBENITE (p 252) 6-34 6-6-4 2-5 2-2-5 Crednerite (p. 278) MlARGYRITE (p. 249). . . Plagionite (p. 251) 4-9-5-1 5-2-5-4 5-4 4-5 2-2-5 2-5 WOLFRAMITE (p. 383). . SYLVANITE (p. 248). . . . 7-1-7-55 8-8-3 5-5-5 1-5-2 DETERMINATION OF MINERALS. 523 CRYSTALLIZATION TRICLINIC. Spec. Gravity Hardness. Spec. Gravity Hardness. SASSOLITE fp 380) 1-48 1 Ebonite CD 425") 4-5 Hannayite (p 428). . . . 19 AMBLYGONITE (p 369) 3-3-11 6 CHALCANTHITE (p. 394). Wapplerite (p. 371) Microcline (p. 326) 2-21 2-48 2-54 2-5 2-2-5 Fairfieldite (p. 426).... AXINITE (p. 310) Babingtonite (p. 295) 3-15 3-27 3-3-3-37 3-5 6-5-7 55-6 ALBITE (p. 323) OLIGOCLASE (p. 323^ LABRADORITE (p 321) 2-59-2-65 2-65-2 69 2-67-2-76 6-7 6-7 6 CYANITE (p. 332) RHODONITE (p. 294) Veszelyite (p 373) 3-4-37 3 4-3-7 3-5 5-725 5-5-6-5 4 MONETITE (p. 4-->2) 2'75 3-5 Roselite (p. 372) . :i-5--3-58 3-5 ANDESITE (p. 322) 2-61-2-74 6 ? BROCHANTITE (p. 396 \ 3-8-3-9 3-5-4 ANORTHITE (p. 321). . . . 2-66-2-78 6-7 Pseudomalachite (p.374) 4-4-4 4-5-5 HI. AUXILIARY TABLES. A. Minerals whose Hardness is equal to, or greater than, 7 (Quartz 7). Hardness. Quartz (p. 284) 7 Tridymite (p. 288) Danburite (p. 311) Boracite (crystals) (p. 381) Cyanite (p. 332) Tourmaline (p. 329) Garnet (p. 302) lolite (p. 311) Staurolite (p. 336) Schorlomite (p. 337) 7 7 7 I. 5-7-25 VI. 6-5-7-5 III. 6-5-7-5 I. 7-7-5 IV. 7-7-5 IV. 7-7-5 Cryst.* III. (R) III.? IV. (R) Hardness. Cryst. Euclase (p. 333) 7'5 V. Zircon (p. 314) 7 '5 II. Andalusite (p. 331) 7 '5 IV. Beryl (p. 299) 7 '5-8 III. Phenacite (p. 301) 7-5-8 III. (R) Spinel (p. 271) 8 I. Topaz (p. 332) 8 IV. Chrysoberyl (p. 274) 8'5 IV. Corundum (p. 267) 9 III. (R) Diamond (p. 228) 10 I. The following minerals have hardness equal to 6-7, or 6-5-7. Iridosmine, III. Cassiterite, II.; Diaspore, IV.; Chrysolite, IV.; Spodumene, V. ; Epidote, V. ; Ardennite, IV. ; Gadolinite, V. ; Fibrolite, V. ; Feldspars, VI. ; Axinite, VI. B. Unmetallic Minerals which are distinctly FOLIATED in some of their varieties. 1. Micaceous: easily separable into very thin laminae, flexible to slightly brittle. a. MICAS (pp. 311 to 315): laminae tough and elastic, except when they have under- gone alteration; Anhydrous. Here are included the species: Phlogopite; Biotite; Musco- vite; Lepidolite; Cryophyllite. These graduate into the HYDRO-MICAS (pp. 353, 354), in which the laminae are inelastic and more or less brittle. Here belong: Fahlunite; Margarodite; Damourite; Paragonite; Cookeite; Eu- phyllite; Oellacherite, etc. ; and related to these, Margarite. Lepidomelane is another mica (anhydrous or nearly so) whose folia are nearly in- elastic. Astrophyllite is a micaceous member of the pyroxene family. 6. CHLORITES (355 to 357) : laminae tough but mostly inelastic; hydrous ; color gen- erally dark-green. Here are included : Penninite ; Ripidolite ; Prochlorite, etc. These are related to the VERMICULITES (p. 355^ in which the laminae are less tough, being more or less brittle: Jefferisite; Pyrosclerite, etc. c. Pyrophyllite. Talc, sometimes rather micaceous, laminae soft, and somewhat greasy to the feel. Brucite is related in character, but differs chemically in being soluble in acids. d. Torbernite, color deep-green; Autunite, color yellow to bright-green, laminae brittle. * Here, as elsewhere, , I. = Isometric; II. = Tetragonal; III. = Hexagonal; IV.=Ortho rhombic; V Monoclinic; VI. =Tricliuic. 24: APPENDIX. 2. Not properly micaceous, though separable more or less easily into thin laminae. Ghloritoid (p. 858^ and Seybertite (p. 358) .ire foliated, the laminae not separating aasily. So also Bronzite, Hypersthene, Diallage, and Marmolite. Gypsum sometimes occurs in soft, separable larninse (var. Selenite), slightly flexible Zincite and Erythrite are sometimes foliated but not separable. C. Unmetattic Minerals uJiich in some of their varieties have a FIBROUS structure. 1. Easily separable into flexible fibres. A&bestus (=amphibole) ; Crocidolite ; Cbrysotilc (= serpentine); Anthrosiderite. 2. Fibrous, not easily separable ; structure graduating into columnar. Anhydrous Silicates: Enstatite ; Wollastonite ; Fibrolite ; also, though more properlj columnar in structure : Cyanite ; Epidote ; Tourmaline. Hydrous Silicates, Zeolites mostly : Thomsonite ; Okenite ; Natrolite ; Scolecite ; Pecto- lite ; Carpholite. Also some Serpentine. Phosphate* ; Arsenates : Wavellite ; Cacoxenite ; Pharmacolite ; Dufrenite ; Olivenite Vivianite ; Pyromorphite. SulpJiates: Anhydrite; Barite ; Celestite; Gypsum. Carbonates: Calcite; Rhodochrosite ; Magnesite; Hydromagnesite ; Aragonite; Mala- chite. Also: Brucite (jiemalite); Sussexite; Ulexita. GENEEAL INDEX TO MINEEAL SPECIES Abriachanite, 420. Acadialite, 344. Acanthite, 239. Achrematite, 385. Achroite, 330. Acmite, 294. Actinclite, 297. Adamine, Adamite, 373 ; 420. Adelpholite, 363. Adular, Adularia, 325. ^Egirine, ^Egyrite, 294 Aerinite, 350. ^Eschynite, 362. Agalmatolite, 349, 352. Agaric mineral, 400. Agate, 286. Aglaite, 420. Agricolite, 302. Aikinite, 254. A j kite, 4:15. Akanthit, . Acanthite. Akmit, . Acmite. Alabandite, 237. 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, r o. Andradite. Alloclasite, 248. Allophane, 341. Allophite, 3~)6 Almandin, Almandite, 303. Alshedite, 438. Aistonite, . Bromlite. Altaite, 237. Alum, Native, 895. Alumina == Aluminum oxide. Aluminum carbonate, 410. chloride, 260. fluoride, 264, 265. fluo-silicate. 332, I Aluminum hydrate, 279, 282. hydro - sulphate, 395. mellate, 412. oxide (Alumina), 267. phosphate, 375, 376, 377, 378, 439. silicate, 831, 332, 341, 349, 351. sulphate, 395, 396. Aluminite, 395. Alunite, 396. Alunogen, 395. 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, 392. Amphibole, 296; 420. Analcite, Analcime, 343. Anatase, 277. Andalusite, 331. Andesine, Andesite, 322. Andradite, 304. Andrewsite, 378. Anglesite, 389. Anhydrite, 389. Animikite, 420. Ankerite, 402. Annabergite, 372. Annerodite, 423. Annite, 313. Anomitc, 431. Anorthite, 321. Antholite, . Anthophyllite. Aiithophyllite, 295. Anthracite, 417. Anthracoxenite, 415. Antigorite, 351. Antillite, 351. Antimonblende, 284. Antimonbliithe, v. 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, 232. ochre, 437. oxide, 284, 437. sulphide, 232. Apatite, 364; 420. Aphanesite v. Clinoclasite. Aphrite, 400. Aphrizite, 330. Aphrodite, 349. Aphrosiderite, 356. Aphthalose,Aphthitalite,390. Apiohnite, 395. Aplome, 304. Apophyllite, 340; 421. Aquacreptite, 351. Aquamarine, 299. Araoxene, 426. Aragonite, 405; 421. Aragotite, 414. Arcanite, 890. Arctolite, 421. Ardennite, 310. Arequipite, 421, Arfvedsonite, 298; 421. Argentine, 4uO. Argentite, 235. Argentopyrite, 437. Argyropyrite, 487. Arite, 243. Arkansite, 278. i Arksutite, 365. 526 GENERAL INDEX. Arquerite, 225. Arragonite, 405. Arrhenite, 421. Arsenargentite. 421, Arsencisen, 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, 878. Arsenite, v. Arsenolite. Arsenolite, 284. Arsenopyrite. 247. Asbestus., 297. Blue,. Crocidolite. Asbolan, Asbolite, 283. Asmanite, 288; 421. Asparagus-stone, 365. Aspasiolite, 353. Asphaltum, 410. Aspidolite, 312. Astrakanite, 10. Blodite. Astrophyllite, 313; 421. Atucamite, 261. Atelestite, 378. Ateline, Atelite, 262; 421. Atopite, 421. Augite, 293. Aurichalcite, 410. Auriferous pyrite, 220. Auripigmentum, 232. Automolite, 272. Autunite, :579; 421. Aventurine quartz, 286. ieldspar, 322, 323, 325. Axinite, 310. Azorite, 359. Azurite, 411. Babingtonite, 295. Bagrationite, v. Allanite. Baikalite, v. Sahlite. Balvraiditc, 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, 351. Bastnasite, 408, 439. 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. Bcrgpech, 410. Bergseife, v. Halloysite. Bergtheer, 0. Pittasphalt. Berlauite, 436. Beruardinite, 435. Bernstein, 415. Beryl, 299; 421. Beryllium aluminate, 274. silicate, 299, 300, 301, 302, 333. Berthierite, 251. Berzelianite, 237. Berzeliite, 421. Beyrichite, 241. Bhreckite, 422. Bieberite, 395. Biharite, 353. Bimsstein, v. Pumice. Bindheimite, 379. Binnite, 251; 250. Biotite, 312, Bischofite, 423. Bismite, 284. Bismuth, Acicular (aikinite), 254. Native, 227. Telluric, 233. Bismuth arsenate, 377, 379. blende(eulytite),302. carbonate, 412, 422. chloride. 262. glance, 2J2. nickel (griinauite), 237. ochre, 284. oxide, 284. selenide, 233. silicate, 302. silver, 420. Bismuth oulpnide, 232. tellurate, 397. telluride, 233. Bismuthinite, 282. Bismutite, 412. Bismutoferrite, 302. Bismutosphaerite, 422. Bittersalz, 394. Bitter spar, Bitterspath, 6. Ekdemite, 425. Ekebergite, 316. Ekmannite, 354, Ela3olite, 316. Elaterite, 414. Electrum, 221. Eleonorite, 426. Ellonite , 426. Elroquite, 426. Embolite, 260. Embrithite, v. Boulangerite. Emerald, 299. Emerald nickel, 410. Emery, 268. Emplectite, 250. Enargite, 257. Enceladite, v. Warwickite. Enophite, 436. Enstatite, 290. Enysite, 397. Eosite, 385. Eosphorite, 423. Ephesite, 354. Epiboulangerite, 254. Epidote, 307. Epigenite, 258. Epistilbite, 347; 426. [426. Epsom Salt, Epsomite, 394; Erbsenstein, 400. Erdkobalt, 283. Erdol, 416. Erdpeeh, 416. Eremite, v. Monazite. Erilite, 426. Erinite, 374. Eriochalcite, 426. Erubescits, 237. Erythrite, 372. Erythrosiderite, 261. Erythrozincite, 426. Esmarkite, 353. Essonite. 304. Ettringite, 395. Eucairite, 235. Euchroite, 373. Euclase. 333; 436. Eucolite, 299. Eucrasite, 426. Euciyptite, 426. Eudialyte, Eudyalite, 299. Eudnophite, 344. Eugenglanz, . Polybasite. Eukairite, v. Eucairite. Euklas, 333. Eulytine, Eulytite, 302; 426. Eumanite, 278. Euosmite, 415. Euphyllite, 354. Eusynchite, 426. Euxenit3, 362. Fahlerz, 255. Fahlunite, 353. Fairfieldite, 426. Famatinite, 258. Faserquarz, 298. Fassaite, 293. Faujasite, 344. Fauserite, b91. Fayalite, aoO. Feather ore. 251. Federerz, 251. Feitsui, 309. Feldspar Group, 319; 426. Felsite, 323, 326. Feldspath, v. Feldspar. Fergusonite, 362; 427. Ferroilinenite, 360. Ferrotellurite, 427. Feuerblende, 252. Feuerstein, 287. Fibroferrite, 395. Fibrolite, 331. Fichtelite, 414. Fillowite, 427. . Fiorite, 289. Fireblende, 252. Flint, 287. Float-stone, 2S9. Flos ferri, 405. Fluellite, 264. Fluocerite, 264. Fluor-apatite, 365. Fluor, Fluorite, 263; 427. Fluor Spar, 263. Flussspath, 263. Foliated tellurium, v. Nagya- gite. Fontainebleau limestone, 400. Foresite, 347; 427, Forsterite, 300. Fowlerite, 294. Francolite. 365. Franklandite. 427. Frank Unite, 273. Fredricite. 438. Freibergite, 255. Freieslebenite, 252. Frenzelite, 233. Freyalite, 427. Friedelite, 302. Frieseite, 437. Frigidite, 438. Fuchsite, 314. Gadolin, Gadolinite, 309; 427. Gahnite, 272. Galena, Galenite, 235. Galenobismutite, 427. Galmei. 339, 404. Ganomalite, 427. Garnet, 302; 427. ! Garnierite, 351 ; 427. j Gastaldite, 298. j Guanovulite, 392. Gay-Lussite, 409. Gearksutite, 265. Gedanite, 435. Gehlenite, 331. Geierite, . Geyerite. Gekrosstein, 389. Gelbbleierz,384. Genthite, 351. Geocerite, 414. Geocronite, 257. Geomyricite, 414. Gersdorffite, 246. Geyerite, 248. Geyserite, 289. Gibbsite, 282. Gieseckite,352; 317. Gigantolite, 353. Gilbertite, 353. Gillingite, 354. Ginilsite, 428. Girasol, 289. Gismondine, Gismondite, 341 ; 428. Giufite, 432. Glanzkobalt, n. Cobaltite. Glaserite, 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. GoldTelTuride, 248, 249, 430. Goldtellur, v. Sylvanite. Goshenite, 299. Goslarite, 395. Gothite, 280. Grahamite, 41C. Grammatite, 297. Granat, 302. Graphic tellurium, 248. Graphite, 230. Graukupfererz, 0. Tennantite. Gray antimony, 232. copper, 255. Greenockite, 212. Greenovite, 335. Grenat, v. Garnet. Grochauite, 357. Grossularite, 303. Grttnauite, 237. Griinbleierz, 366. Guadalcazarite, 241. Guanajuatite. 2:)3; 428. Guanipite, 433. Guano, 365. 530 GENERAL INDEX. Guarinite, 336. Guejarite, 428. Giimbclite, 353. Gummite, 428. Gunnisonite, 428. Guyaquillite, 415. Gymnite, 351. Gyps, v. Gypsum. Gypsum, 392. Gyrolite, 838; 428. Haarkies, 241 ; 247. Haarsalz, 395. Haddamite, 432. Hafnefiordite, 823. Hagemannite, 265. Haidingerite, 371. Halite, 259. Hallite, 355. Halloysite, 352; 428. Halotrichite, 395. Hamartite, 408, 438. Hannayite, 428. Harmotome, 346. Harrisite, 240. Hartite, 414. Hatchettite, Hatchettine, 414. Hatchettolite, 428. Hauerite, 214. Haughtonite, 431. Hausmannite, 277. Haiiyne, llaiiynite, 318. Haydenite, 344. Hayesine, 428. Haytorite, 335. Heavy spar, 387. Hebronite, 370; 420. Hedenbergite, 293. Hedyphane, 367; 428. Heldburgite, 428. Heliotrope, 286. Kelvin, Helvite, 302; 428. Hematite, 263. Brown, 280. Henwoodite, 378. Hercynite, 272. Herderite, 370. Hermannolite, 361. Herrengrundite, 428. Herschelite, 344. Hessite, 288; 429. Hessonite, -o. Essonite. Hetserolite, Hetairite, 429. Heteromorphite, v. Jameson- ite. Heubachite, 429. Heulandite, 347; 429. Hexagonite, 298. Hibbertite, 429. Hiddenite, 436. Hielmite, 361. Hieratite, 429. Highgate resin, 415. Hisingerite, 354. Hrernesite, 371. Hofmannite, 435. Holzopal, v. Wood Opal. Holz Zinn, 275. Homilite, 429. Honey-stone, Honigstein,412. Hopeite, 429. Horbaehite. 241. Hornblende, 296. Horn silver, 200. Hornstone, 287. Horse-flesh ore, ID. Bornite Hortonolite. 300. Houghite, 28:2. Hovite, 410. Howlite, 382. Huantajayite, 259. Hiibnerite, 383; 429. Hullite, 425. Humboldtine, 412. Humboldtilite, 303. Humboldtite, 334. Huminite, 4:,5. Humite, 327, 328, 423. Huntilite, 429. Bureau 1 . ite, 372. Huronite, 353. Hyacinth, 304, 305. Hyalite, 289. Hyalophane, 322. Hyalosiderite, 3GO. Hyalotekite, 429. Hydrargillite, 282. Hydrargyrite, 267. Hydraulic limestone, 400. Hydrobiotite. 436. Hydrocastorite, 433. Hydrocerussits, 429. Hydrocuprite, 266. Hydrocyanite, 390. Hydrodolomite, 410. Hydrofluorite, 264. Hydrofranklinite, 429. Hydroilmenite, 431. Hydromagnesite, 409. Hydro-mica Group, 353. Hydrophilite, 429. Hydrophite, 351. Hydrorhodonite, 429. Hydrotalcite, 282. Hydrotitanite, 271. Hydrozincite, 410. Hygrophilite, 353. Hypargyrite, 250. Hypersthene, 290.^ Hypochlorite, 302. Ice spar, 325. Iceland spar, 399. Idocrase, 205. Idrialine, Idrialite, 314. Ihleite, 395. Ilesite, 429. Ilmenite, 269. Ilsemannito, 284. Ilvaite, 309. Indianaite, 428. Indianite, 321. Indicolite, 330. lodargyrite, 2(iO. lodobrornite, 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, 860. oxalate, 412. oxide, 268, 272, 279, 280. phosphate, 869, 371, 372, 378, 426, 437. silicate, 300, 354. sulphate, 895. sulphide, 211, 243, 247. sulph-antimonite, 251. tantalate, 359. tellurate(?)4'27. tungstate, 383. Iron pyrites, 243. White, 247. Ironstone, Clay, 269, 281, 403. Iserine, 'isorite, 270. Isoclasite, 373. Itacolumyte, 229. Ivigtite, 354. Ixolyte, 414. Jacobsite, 272. Jade, Common, 297. Jadeite, 409. Jamesonite, 251 ; 430. Jargon, 305. Jarosite, 430. Jasper, 287. Jaulingite, 415. Jefferisite, 355. Jeffersonite, 293. Jenkinsite, 351. Jet, 418. Johannite, 397. Jollyte, 854. Jordanite, 251. Joseite, 233. Julianite, 256. GENERAL INDEX. 531 N. B. Many names spelt with an initial K in German, begin with C in English. Kalait, 377. Kaligliramer, 313. Kalinite, 395. Kalk-Harmotome, v. Phillips- ite. Kalk-uranit, 379. Kalkspath, 398. Kalk-volborthit, 374. Kallait, 377. Kaluszite. 394. Kammererite, 355. Kainmkies, 247. Kaolin, Kaolinite, 351. Karelinite, 284. Karyinite, 422. Katzenauge, 286. Keatingine, 295. Keilhauite, 336. Kelyphite, 436. Kenngottite, 250. Kentrolite, 430. Kerargyrite, 260. Kermes, Kermesite, 284. Kerolith, v. Cerolite. Kerrite, 355. Kiesel, v. Quartz. Kieselkupfer, 338. Kieselwismuth, 302. Kieselzinkerz, 339. Kiescrite, 394. Killinite, 353, 436. Kischtimite, 408. Kjerulfine, 368. KJaprotholite, 251. Klinochlor, 356. Knebcdite, 300. Kobaltbluthe, 372. Kobaltglanz. 246. Kobaltkies, v. Linnaeite Kobaltnickelkies, 245. Kobellite, 254. Kochelite, 363. Kochsalz, 259. Koflachite, 435. Kohle, v. Coal. Kokkolit. v. Coccolite. Kongsbergite, 225. Konigine, 396. K,onlite, 414. Koppite, 359. Korarfveite, 368. Kottigite, 372. Korund, v. Corundum. Kotschubeite, 357. Koupholite, 340. Krantzite, 415. Kreittonite, 272. Kremersite, 261. Krennerite, 430. Krisuvigite, 397. Kronkite, 397. Krugite, 434. Kupferantimonglanz, 250. Kupferbleispath, 396. Kupferglanz, 239. Kupferglimroer, 375. Kupferindig, 249. Kupferkies, 244. Kupferlasur, 411. Kupfernickel. 242. Kupfersammterz, 397. Kupferschaum, 374. Kupferschwiirze, 267. Kupfferite, 29(5. Kupfer-uranit, 378. Kupfer-vitriol, 394. Kupferwismuthglanz, 250. Kyanite, 332. Labradorite, 321. Labrador feldspar, 321. Lagonite, 382. Lampadite, 283. Lanarkite, 391. Langite, 397. Lanthanite, 410. Lapis-lazuli,JJ18. Larderellite, 383. atrobite, v. Anorthite. Laumonite, Laumontite, 338. Laurite, 247. Lautite, 430. Lawrencite, 430. Laxmannite, 386. Lazulite, 375. Lead, Argentiferous, 233. Black (graphite), 230. Corneous (phosgenite), 4C8. Native, 226. Leadantimonate, 370, 379. arsenate, 306. arsenio-molybdate, 385. carbonate, 407. chloride, 261. chloro-carbonate, 408. chromate, 385, 386. molybdate, 384. oxichloride, 262. oxide, 267, 277. phosphate, 366. selenide, 236. selenite, 432. silicate, 427, 429, 430, 431. sulphate. 389, 390, 391. sulphato-carbonate, 391. sulphide, 235. sulpharsenite, 250, 251. sulphantimonite, 250, 251, 253, 254. snlpho-bismuthite, 252, 421,427. Lead telluride, 237, 249. tungstate, 384. vanadate.367; 374,426, Leadhillite, 390; 430. Leberkies, v. Marcasite. Lecontite, 392. Ledererite. 345. Lederite. 336. Lehrbachite, 237. Leidyite, 430. Lennilite, 436. Leopoldite, 260. Lepidoiite, 314. Lepidomelane, 313. Lepidophaeite, 440. Lernilite, 436. Lesleyite, 354. Lettsoinite, 397. Leucaugite, 293. Leuchtenbergite, 357. Leucite, 318; 430. - Leucochalcite, 430. Leucomanganite, 426. Leucopetrite, 315. Leucophanite, 300; 430. Leucopyrite, 248. Leucotilc, 430. Leviglianito, 241. Levyne, Levynite, 343. Lherzolyte, 271. Libethenite, 373; 430. Liebigite, 412. Lievrite, 309. Lignite, 418. Ligurite, 336. Limbachite, 351. Lime = Calcium oxide, t\ Calcium. Limestone, 400, 401 Limonite. 280. Linarite, 396. Linna3ite, 245. Linsenerz, 374. Lintonite, 438. Lionite, 437. Liroconite, 374. Liskeardite, 430. Lithionglimmer, 314. Lithiophilite, 438. Lithographic Stone, 400. Lithomarge, 352. Livingstonite, 232; 430. Loganite, 356. Lollingite, 248. Louisite, 430. Loweite, 394. Lowigite, 396. Loxoclase, 326. Luckite, 431. Ludlamite, 372. Ludwigite, 380. Luneburgite, 382. Luzonite, 258. Lydian stone, 287. 532 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, 260,261, 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. Magneteisenstein, 272. Magnetic iron ore, 272. Magnetic pyrites, 241. Magnetite, 272. Magnetkies, 241. Magnoferrite, 273. Magnolite, 430. Malachite, Blue, 411. Green, 411. Malacolite, 293. Maldonite, 221. Malinowskite, 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, 201'. sulphide, 237, 244. sulphate, 431, 437. tantalate, 359, 437. tungstate, 383. Manganglanz, 237. Manganite, 280. Manganocalcite, 406. Manganophyllite, 312. Manganosiderite, 435. Manganosite, 431. GENERAL INDEX. Mangansp^th, 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. Marmatite, 238. Marmolite, 350. Martite, 269. Mascagnine. Mascagnite, 392. Maskelynite, 322. Mason ite, 358. Massicot, 267. Matlockite, 262. Matricite, 431. Maxite, 391. Medjidite. 397. Meerschaum, 349. Megabasite, M83. Meionite, 315. Melaconite, 267. Melanglanz, v. Stephanite. Melanite, 304. Melanochroite, 386. Melanophlogite, 289. Melanosiderite, 281. Melanotekite, 431. Melanothallite, 431. Melanterite, 395; 431. Melilite, Mellilite, 306. Melinophane, 300. Meliphanite, 300; 431. Mellite, 412. Meionite, 249. Menaccanite, 269, 431. Mendipite, 262. Mendozite, 395. Meneghinite, 256. Mengite, 362. 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, *%jh ; 431. Michaelsonite, 3C~ Microcline, 326. Microlite, 359; 431. Microphyllites,Microplakites, 322. Microsommite, 317. Middletonite, 41o. Mikroklin, v. Microcline. Milarite, 432. Millerite, 241. Mimetene, Mimetite, 366 ; 432. Mimetese, Mimetesite, 366. Mineral coal, 417. oil, 418. pitch. 416. tar, 413. Minium, 277. Mirabilite, 392. Mispickel, 247. Misy, 395. Mixite, 432. Mizzonite, 316. Molybdanglanz, 233. 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:.2. Monrolite, 332. Montanite, 397. Montebrasite, 370; 420. Monticellite, 800. Montmartite, v. Gypsum. Montmorillonite, 349. Moonstone, 323, 324, 325. Mordenite, 432. Morenosite, J395. Moroxite, 365. Mosandrite, 309. Mottramite, 374. Mountain cork, 297. leather, 297. Muckite, 435. Muromontite, 308. Muscovite, 313. Musenite, v. Siegenite. Madeleisenstein, 280. Nadelerz, 254. Nadelzeolith, 342. Nadorite, 370. Nagyagite, 249; 432. Namaqualite, 282. Nantokite, 260. Naphtha, 413. Naphthaline, 414. GENERAL INDEX. 533 Natrolite, 342; 432. Natron, 409. Natronborocalcite, 381. Naumannite, 235. Needle ore, v, Aikinite. Neraalite, 282. Neocftrysolite, 423. Neocyanite, 432. Neotocite, 354. Nepheline, Nephelite, 316. Nephrite, 297, 432. Neudorfite, 435. Newberyite, 433 . Newjanskite, 224. Newportite, 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. Niekelarsenikglanz, 246. Nickelarsenikkies, 246. Nickelbliithe, 372. Nickel-Gymnite, 351. Nickeikies, 241. Nickelsmaragd, 410. Niobite, 360. Nitre, 379. Nitrobarite, 433. Nitrocalcite, 379. Nit.roglauberite, 379. Nitromagnesite, 379. Nocerine, Nocerite, 433. Nohlite, ;^62. Nontronite, 350. Nosean, Nosite, 318. Noumeaite, Noumeite, 351. Nuttalite, v. Wernerite. Ochre, red, 269. Octahedrite, 277; 433. (Ellacherite, 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, 265; 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, Peiminite, 855. Penwithite, 433. Percylite, 262. Periclase, Periclasite, 267. Peridot, 300, 330. Perikline, Periklin, 324. Peristerite, 324. Perlglimmer, 357. Perthite, 326. Perofskite, 270; 433. Perowskit, 27Q. Petalite, 295; 433. Petroleum, 413. Petzite, 2;i9. Phacolite, 344. Phaeactinite, 420. Pharmacolite, 370. Pharmacosiderite, 376; 433. Phenacite, Phenakit; 301 ; 433. Phengite, 431. Philadelphite, 439. Phillipite, 397. Phillipsite, 345; 433. Phlogopite, 312. Phoanicochroite, 386. Pholerite, 352. Phosgenite, 408. Phosphocerite, 364. Phosphochalcite, 374. Phosphochromite, 386. Phosphorite, 365. Phosphuranylite, 434. Phyllite, 358. Physalite, 333. Phytocollite, 425. Piauzite, 416. Picite, 434. Pickeringite, 395; 434. Picotite, 271. Picranalcite, 420. Picroallumogene, 434. Picrolite, 351. Picromerite, 394. Picropharmacolite, 371. Pictite, 336. Piedmontite, 308. Pihlite, 349. Pilarite, 423. Pilinite, 344. Pilolite, 434. Pimelite, 351. Pinite, 352. Pisanite, 395. Pisolite, 400. Pistacite, Pistazit, 307. Pistomesite, 403. Pitchblende, 274. Pittasphalt, 413. Pitticite, Pittizit, 379. Plagiocitrite, 434. Plagioclase, 319. Plagionite, 251. Plasma, 286. Plaster of Paris, 93. Platinum, Native, 223; 434. Platiniridium, 224. Pleonaste, v. Spinel. Plumbago, 230. Plumbaliophane, 341. Plumbogummite, 377. Plumbomanganite, 4a4. Plumbostannite. 434. Plumbostib, v. Boulangerite. Polianitc, 278. Pollucite, Pollux, 299. Polyargite, 353. Polyargyrite, 257. Polybasite, 257. Polycrase, 362. Polychroilite, 353. Polydymite, 434. Polyhalite, 393; 434. Polymignite, 362. Poonahlite,343. Porcellophite, 351. Posepnyte, 435. Potassium chloride, 260. chromate (?), 437. 534 GENERAL INDEX. Potassium nitrate, 879. silicate, 313, 825. 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, 25:1. Prussian blue, Native, 37J. Przibramite, 2;j8, 280. Pseudobrookite, 434. Pseudocotunnite, 261. Pseudomalachite, 374. Pseudonatrolite, 434. Pseudophite, 356. Psilomelano, 2S2 ; 434. Psittacinite, 374. Pucherite, 367. Purple copper, 237. Pycnite, v. Topaz. Pyrallolite, 848. 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. Kadiated, 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, 435. 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. Ref dans kite, 351. Reichardtite, 426. Reinite, 4 5. Reissitc, 426. Remingtonite, 410. Rensselaerite, 348. Resanite, 339. Resin, Mineral, 415, 435. Restorm elite, 353. Ketinalite, 351. Retinite, 415. Reussinite, 41 5. Rhabdophane, 435. Rhaetizite, 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. j salt, 259. Rcemerite, 395. Roepperite, 300. Rcesslerite, 371. Rogenstein, 400. Rogersite, 435. Romeine, I?omeite, 370. Roscoelite, 367; 435 Rose quartz, 286. Roselite, 372; 435. Rosterite, 420. Rosthornite, 415. Rosite, 353. Rothbleierz, 385. Rotheisenerz, 268. Rothgiiltigerz, 252, 253. Rothkupi'ererz, 266. Rothnickelkies, 242. Rothoffite, 303. Rothzinkerz, 266. Rubellite, 330. Rubislite, 4a5. Ruby, Spinel, Almandine,271 Oriental, 268. Ruby-blende, v. Pyrargyrite. Ruby silver 25'2, 253. Rutherfordite, 362. Rutile. 276; 435. Ryacolite, v. Rhyacolite. Sahlite, 293. Sal ammoniac, 260. Salmiak. 200. Salt, Common, 259. Samarskite, 301 ; 435. Sammetblende, 280. Sanidin, 325. Saponite, 352. Sapphire. 208; 330. Sarawakite, 435. Sarcolite, 316. Sarcopside, 369. Sard, 287. Sardonyx, 287. Sartorite, 250. Sassolite, Sassolin, 380. Satin-spar, 393, 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, 43". Schorlomite, 337; 435. Schraufite. 415. Schreibersite, 242. Schrifterz, Schrift-tellur, 248 Schrockingerite, 412. Schuchardtite, 486. 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. 535 Sellaite, 264. Semeline, 335. Scraseyite, 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, 245. Silaonite, 233; 428. Silberamalgam, 225. Silberglanz, 2-'>5. Silberhorncrz, '-260. Silberkupferglanz, 240. Silbervvismuthglanz, 420. Silex. v. Quartz. Silicified wood, 286. Siliceous sinter, 287, 289. Siliciophite, 4 ; !6. Silicoborocalcite, 382. Siltimanite, 331. Silver, 223. Antimonial, 234. Bismuth, 420. Horn, 260. Native, 223. Euby, 252, 253. Vitreous, 285. Silver antimonide, 234. chloride, 260. . bromide, 260. iodide, 260. selenide, 235. sulph-antimonite, 250, 2,)2, 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, 392. Sommite, 316. Sonnenstein, v. Sunstone. Sonoma it e, 434. Spargelstein, 365. Spathic iron, 403. Spathiopyrite, 246. Spear pyrites, 247. Speckstein, 348, 352. Specular iron, 268. Speerkies, 247. Spessartite, 304. Speiskobalt, 245. Sphaerocobaltite, 436. Sphaerosiderite, 403. Sphaerostilbite, 346. Sphalerite, 237; 436. Sphene, 335. Spiauterite, 242. Spinel, 271. Spinthere, 335. Spodiosite, 436. Spodumene, 295; 436. Sprodglaserz, 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. Stuzite, 437. Stylotyp, Stylotypite, 254. Subdelessite, 425. Succinellite, 415. Succinite, 415. Sulphur, Native, 228. Sunstone, 323, 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, 373. Talc, :-!48. 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, 248. Native, 227; 437. Tellurium oxide, 437. Tellursilber, 238. Tellurwismuth, 238. Tengerite, 410. Tennantite, 256; 438. Tenorite, 267; 438. Tephroite, 300. Tequesquite, 438. Tequixquitl, 438. Tesseralkies, 246. Tetradymite, 233. Tetrahedrite, 255; 438. Thaumasite, 438. Thenardite, 390; 438. Thinolite, 438. Thomsenolite, 265; 438. Thomsonite, 342; 438. Thorite, 340; 438. Thulite, 309. Thuringite, 358. Tiemannite, 237. Tile ore, 266. Tin, Native, 226. Tin ore, Tin stone, 275. oxide, 275. pyrites, v. Stannite. 536 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, v. Ulexite. Tobermorite, 428. Tocornalite, 260. Topaz, ;?32 ; 438. False. 286. Topazolite, 304. Torbanite, 415, 418; 438. Torbernite, Torberite, 378. Totaigite. 436. Tourmaline, 329, 438. .Travertine, 400. Tremolite, 297. Trichite, 110. Triclasite, H53. 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, 329. 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, 274. 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, 395. 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. Wehriite, 233. Weissbleierz, 407. Weissite, 353. Weisspiessglaserz, 284. Wernerite, 316. Werthemanite, 396. Westanite, ;]32. Wheelerite, 415. Wheel-ore, 253. Whewellite, 412. Whitneyite, 235. Wichtine, Wichtisite, 299. Willcoxite, 358. Willemite, 301. Williamsite, 351. Wilsonite, Jj53. Winklerite, 372. Winkworthite, 382. Wiserine, 277. 364. Wismuth, Gediegen, 227. Wismuthglanz, 232. Wismuthocker, 284. Wismuthspath, 412. Wither! te, 406. WittichenitOa04. 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. Wiirfelerz, 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 f carbonate, 404, 410. GENERAL INDEX. 537 Zinc ore, Red, 266. oxide, 266, 273. silicate, 801, 339. sulphate, 395, 440. sulphide, 237, 242. Zincaluminite, 440. Zincite, 266. Zinkbliithe, 410. Zinkenite, 250. Zinkspath, 404. Zinnerz, Zinnstein, 275. Zinnkies, 245. Zinnober, 240. Zinnwaldite, v. Lepidolite. ! Zippeite, 397. 1 Zircon, 304; 440. i Zoisite, 308. | Zoblitzite, 351. ! Zonochlorite, 340. Zorgite, 237. Zwieselite, 369.