NRLF B M IflE 755 UNIVERSITY OF CALIFORNIA. MAR 141893 ^Accessions 7Vo.5~o5~/ > , Class No. 189 SYSTEMATIC MINERALOGY BASED ON A NATURAL CLASSIFICATION, WITH A GENERAL INTRODUCTION. BY THOMAS STERRY HUNT, M.A., LL.D., ^ AUTHOR OP "CHEMICAL AND GEOLOGICAL ESSAYS," "MINERAL PHYSIOLOGY AND PHYSIOGRAPHY," " A NEW BASIS FOR CHEMISTRY," ETC. SECOND EDITION. THE SCIENTIFIC PUBLISHING CO., 27 PARK PLACE, NEW YORK. 1892. EARTH eat; IJBRARY COPYRIGHTED, 1891, BY THE SCIENTIFIC PUBLISHING COMPANY. JAMES DOUGLAS, SCHOLAR, SKILLED METALLURGIST, AND FRIEND OF A LIFE-TIME. CONTENTS. PAGES PREFACE xiii-xvii CHAPTER I. THE RELATIONS OP MINERALOGY 1-4 Natural history and natural philosophy, or physiogra- phy and physiology, 1. The three kingdoms of nature, 2. Descriptive and systematic mineralogy, 2. Dynamics, chem- istry and biotics, 3. Tabular classification of the natural sci- ences, 4. CHAPTER II. MlNERALOGICAL SYSTEMS 5-13 Werner, Mohs and Jameson ; the natural-history method, 5. Breithaupt, Weisbach, C. U. Shepard, J. D. Dana, 6. Chemical system of Berzelius as adopted by Rammelsberg and Dana ; Groth, 7. The system of Mohs and its modifica- tions, 8. Porodic or colloid bodies, 10. Spars as defined by Mohs and by Breithaupt, 11. Defects of both the natural- history and the chemical methods, 12. Possibility of recon- ciling the two, 13. CHAPTER III. FIRST PRINCIPLES IN CHEMISTRY 14-25 Chemical or intrinsic change, 14. Metamorphosis and metagenesis, 15. Relations of gas, liquid and solid ; the ab- solute zero of temperature, 16. Effects of pressure ; change of state; co-efficient of expansion by heat, 17. Critical points of vaporization and of solidification ; varying co- efficient of expansion in heated liquids, 19. Dense or poly- meric vapors under pressure ; studies of Andrews and others, 20. Polymerism or intrinsic condensation in vapors and in - solids, 22. Chemical and mineralogical form ; colloid and crystalline bodies ; metallicity, 24. CHAPTER IV. CHEMICAL ELEMENTS AND NOTATION 26-49 Equivalent weights and symbols, 26. Division of the elements into natural groups ; Newlands, Mendeljeff, Lothar Meyer, De Chancourtois, 28. Table of the periodic law ; prediction of new elements, 30. Relations of the several groups ; negative and positive qualities, 32. The law of oc- taves ; elements of group VIII., 33. The cerium metals and allied rare elements, 35. Aluminum and its functions, 36. vi Contents. PAGES 37-49 Relations of the various groups considered, 37. Distinction between protoxyds and sesquioxyds, 39. Mineralogical signs of Berzelius, 40. A monadic notation and its application, 41. Specific gravity of vapors ; gallium, indium and aluminum chlorids, 44. Four chemical divisions of the mineral king- dom, 45. Distribution of chemical elements, 46. Meteoric masses ; their mineralogy, 48. CHAPTER V. SPECIFIC GRAVITY 50-57 The law of volumes ; hydrogen as the unit of weight, 50. Integral weights of water and of solids, 52. Expansion of solids by heat, 55. Determination of specific gravity of solids, 56. CHAPTER VI. THE CO-EFFICIENT OF MINERAL CONDENSATION. 58-75 The problem hitherto considered insoluble ; Gibbs, Ros- coe, Victor Meyer, Louis Henry, 58. Its solution attempt- ed, 60. Chemical species and mineral species, 61. Illustra- tions of polymerism; formaldehyde, hydrocarbons, 62. Raoult's cryoscopic method; its significance, 64. Graham and Pickering on polymerization and allotropism, 67. The case of iron sulphids, 69. High equivalent weights of solid species, 70. Fixing an arbitrary chemical unit ; quartz and calcite, 73. CHAPTER VII. THE THEORY OF SOLUTION 76-85 Its importance; solution defined, 76. Spontaneous sep- aration in solutions, 78. Guthrie on cry ohyd rates ; Tilden and Shenstone on solution at high temperatures, 79. The case of sodium sulphate, 80. Soluble and insoluble conditions of bodies ; calcium carbonate ; the nascent state, 82. Con- clusions of Mendel jeff, 83. Water in plutonic phenomena, 84. Studies of metallic alloys and mattes, 84. CHAPTER VIII. RELATIONS OF CONDENSATION TO HARDNESS AND INSOLUBILITY 86-101 The scale of hardness; changes by heat; pyrognomic minerals, 86. Varying co-efficients of condensation in ele- ments, 88. In various isomeric compounds, 89. Effects of fusion on density, 90. Solubility as related to condensation ; studies by H. C. Bolton, 91. By J. B. Mackintosh ; action of fluorhydric acid, 93. Conclusions, 99. CHAPTER IX. CRYSTALLIZATION AND ITS RELATIONS 102-134 Crystalline systems, 102. Isomorphism considered, 105. Crystalline admixtures, 108. Views of v. Waltershausen and Contents. vii PAGES 108-134 of Tschermak, 109. Pseudomorphism by chemical alteration, 111. Survival of the fittest in the mineral kingdom, 114. Pseudomorphism by replacement, 115. Silicification of wood, 116. Silicates in organic remains, 119. Endogenous, indige- nous and exotic rocks, 120. Metasomatism or transmutation, 121. Hypotheses of Genth and of Julien, 122. Envelopment of minerals, 124. Skeleton, hollow and composite crystals, 126. Rounded crystals, 128. Porodic or colloid species, 129. Studies of palagonite by Bunsen, 130. The crenitic process, 131. Concretionary veins, granitic and others, 132. Contem- poraneous formation of crystalline silicates, 133. Supposed hydration of species, 134. CHAPTER X. THE CONSTITUTION OF MINERAL SPECIES 135-154 Polymerism ; complex formulas and high equivalents, 135. Examples in silicates and carbonates, 136. Law of progres- sive or homologous series, 137. Isomeric and anisomeric homologues, 138. Compound inorganic acids, polytungstates, etc. ; Wolcott Gibbs, 139. Relations of alumina and other triad oxyds, 141. Aluminates, silicates, aluminisilicates, 142. Chemistry of ultramarine, 143. Sulphids, arsenids, etc., 144. Complexity of mineral species, 145. Halides and amphides ; positive and negative oxyds, 146. Genesis of phosphates ; two hypotheses, 147. Different views of the constitution of albite, 149. Individuality of the mineral species, 150. Defini- tion by Persifor Frazer, 151. Chemistry of the sugars, 152. Inadequacy of chemical formulas, 153. CHAPTER XI. A NEW MmEBALoaiCAL CLASSIFICATION 155-166 Plan of the new system ; four classes, 155. Class I. or Metallaceae ; Glances and Blendes, or Lamprites and Minia, 155. Metallometallata and Spathometallata, 156. Orders in Class I., 157. Classes II. , III. and IV. ; Halidacese, Oxydaceaa, and Pyri- caustaceae, 158. Interdependence of chemical and natural- history characters, 159. Breithaupt's orders of Stones and Ores, 159. Orders of Mica, Spar and Gem of Mohs, 159. Sclerites, Spathi, Zeolithi, and Grammites of Breithaupt, 160. Porodini or Colloids, 161. Spathoid, Hydrospathoid, Phylloid and Adamantoid types, 161 . Salts or Salinoids, 161. Solutions and gases not mineral species, 162. The Metalloid type, 162. List of mineralogical types, 163. The establishment of orders, 165. Relations of alumina in silicates, 166. Functions of other triad oxyds, 166. Their relations to tetrad, diad and monad oxyds, 166. CHAPTER XII. MINEKALOGICAL NOMENCLATURE 167-175 The terminal syllable in most mineralogical names, 167. viii Contents. PAGES 16&-174 Systematic nomenclature of Mohs ; examples, 168. Latin nomenclatures proposed by Dana and by Breithaupt, 170. Re- lations of specific gravity in classification, 171. Dana's Latin nomenclature examined, 172. Breithaupt's Latin nomencla- ture examined, 173. Respective positions of chemical and natural-history characters in the new classification and no- menclature, 174. CHAPTER XIII. SYNOPSIS OF MINERAL SPECIES 176-203 Their scientific and trivial names ; generic characteris- tics, 176. (Orders and genera as follows :) 1st Class, METALLACE^E. I. METALLINEA : 1, Metallum ; 2, Metallinum, 177. II. GALENINEA : 1, Thiogalenites ; 2, Se- lenogalenites ; 3, Tellurogalenites, 178. III. DIAPHORINEA : 1, Arsenodiaphorites ; 2, Stibiodiaphorites ; 3, Bismutodiaphor- ites, 179. IV. PYRITINEA: 1, Pyrites; 2, Pyritinus, 180. V. CHLOANTHINEA : 1, Phosphochloanthites ; 2, Arsenochloan- thites ; 3, Stibiochloanthites ; 4, Arsenodyscrasites ; 5, Stibio- dyscrasites, 181. VI. LAMPROTINEA : 1, Arsenolamprotites ; 2, Mesolamprotites, 182. VII. SPATHOMETALLINEA : 1, Spatho- metallinum, 182. VIII. SPHALERINEA : 1, Sphalerites, 182. IX. RHODOPYRITINEA : 1, Arsenofulvites ; 2, Stibiofulvites ; 3, Mediofulvites, 183. 2d Class, HALIDACEJE. I. FLUORINEA : 1, Fluorites ; 184. II. CHLORINEA : 1, Murialus ; 2, Muriates. III., IV. BROMINEA, IODINEA : 1, Bromites ; 2, lodites, 184. 3d Class, OXYDACE^E. I. OXYDINEA: 1, Hydroxy- dites ; 2, Protolithus ; 3, Crystallithus, 185. II. BORATINEA : 1, Borasalinites ; 2, Boratinus ; 3, Borites, 186. III. SPINEL- LINEA : 1, Spinellus ; 2, Allospinellus, 187. IV. CARBONINEA : 1, Carbosalinites ; 2, Hydrocarbonites ; 3, Carbonites ; 4, Halicarbonites, 187. V. SILICINEA : 1, Pectolithus ; 2, Chry- solithus; 3, Amphibolus ; 4, Pyroxenus ; 5, Phenacites; 6, Zirconius ; 7, Eritimites ; 8, Picrolithus ; 9, Porosilicites, 188. VI. BORISILICINEA : 1, Boricrystallithus ; 2, Borisilicites, 190. VII. ARGILLINEA : 1, Zeolithus ; 2, Agrolithus, 191. 3, Sea- polithus; 4, Alcalites; 5, Phengites ; 6, Astrites, 192. 7, Idocrasius ; 8, Epidotus ; 9, Granatus ; 10, Granatinus ; ll r Acmitodes, 193. 12, Beryllus ; 13, Spodiolithus ; 14, Poro- dites ; 15, Amorphites ; 16, Topazius ; 17, Pyrauxites, 194. 18, Argillithus. 195. VIII. BORARGILLINEA ; 1, Turmalinus ; 2, Axinites, 195. IX. TITANINEA : 1, Titanites ; 2, Paratita- nites, 195. X. STANNINEA, 196. XI. COLUMBOTANTALINEA : 1, Tantalites ; 2, Columbites ; 3, Paracolumbites, 196. XII. WOLFRAMINEA : 1, Wolframites, 196. XIII. MOLYBDINEA: 1, Molybdites, 197. XIV. CHROMATINEA: 1, Chromatites, 197. Contents. ix PAGES 197-m XV. NITRATINEA : 1, Nitrasalinites ; 2, Nitrates, 197. XVI. PHOSPHATINEA : 1, Eutelites ; 2, Phosphatites ; 3, Apatites ; 4, Phosphasclerites ; 5, Callaites ; 6, Cacoxenites, 197. XVII. ARSENINEA : 1, Pharmacolites ; 2, Mimetites ; 3, Arsenascle- rites, 199. XVIII. VANADINEA, 200. XIX, STIBIINEA, 200. XX. SULPHATINEA : 1, Arcanites ; 2, Vitriolites ; 3, Sulpha- tites ; 4, Sulphatosclerites ; 5, Alumen ; 6, Sulphaluminites ; 7, Amarantites ; 8, Pararcanites ; 9, Parasulphatites, 200. XXI. SELENINEA. XXII. TELLURINEA, 202. 4th Class, PYRICAUSTACEJE. I. CARBATINEA : 1, Graph- ites ; 2, Adamas. II. HYDROCARBATINEA. III. ELAINEA. IV. CERATINEA. V. RETININEA. VI. ASPHALTINEA. VII. AN- THRACINEA, 202. CHAPTER XIV. THE METALLACEOUS CLASS 204-22S Orders of Metallacese, 204. Genus Metallum and its two divisions, 206. Their variations in hardness and in condensa- tion, 208. The atomic or molecular hypothesis, 209. Metalli- num ; the semi-metals, 209. Galeninea, or galena and allied species ; sulphids, selenids and tellurids, 210. Diaphorinea, or galena-like sulphantimonids and sulphobismuthids, 213. Ex- amples of progressive series, 213. Pyritinea and its two gen- era, Pyrites and Pyritinus, 216. Bornite, cassiteropyrite, etc., 218. Chloanthinea ; metallic arsenids and antimonids, 220. Lamprotinea ; pyrites-like sulpharsenids, etc., 222. The Spathometallate subclass defined; color, and relations to light, 223. Spathometallinum; sulphur, phosphorus, etc., 224. Spha- lerites ; spathoid "sulphids, 225. Rhodopyritinea ; nomencla- ture ; signification of fahlerz, 226. Spathoid sulpharsenids and sulphantimonids ; Arsenofulvites, Stibiofulvitcs, 227. CHAPTER XV. THE HALIDACEOUS CLASS 229-232 Its nomenclature, 229. Fluorites ; the aluminic fluorids, 230. Chlorids; the genera Murialus and Muriates, 231. Bromites and lodites. 232. CHAPTER XVI. THE OXYDACEOUS CLASS 233-325- Oxydata and Amphidata, 233. Three genera of Oxydinea, 234. Hydroxydites, 235. Protolithus, including various oxyds and oxysulphids, 236. CrystallitKus ; relations to spinels, 237. Genera of Amphidata, 238. Boratinea and its three genera, 239. Warwickite and the question of titanic trioxyd, 240. Spinellus ; replacement of alumina by some other triad oxyds, 241. Allospinellus ; magnetite, chromite and related species ; uraninite, 242. Carbonates ; salinoid species, 244. Carbon- ites or carbon-spars, 245. Halicarbonites, 246. Silicinea and Contents. PAGES 247-380 its various genera, 247. Pectolithus ; distinguished from zeolites, 248. Chrysolithus, 249. Amphibolus; its principal types, 250. Pyroxenus, its principal types, 251. Associa- tion of amphibole and pyroxene, 252. Phenacites ; its great condensation, 252. Zirconius; variations in density, 253. The genus Eritimites, 254. Picrolithus ; talc and pyrallolite, 255. Porosilicites ; colloidal; serpentine, chrysocolla, etc., 256. Sepiolite, glauconite, 257. Borisilicinea, 258. Argil- linea or aluminisilicates ; separation from Silicinea, 258. Eelation to subaerial decay ; argil or clay, 259. Homologous series of aluminisilicates, 260. The name feldspar, 262. Zeo- lithus ; hydration of zeolites, 263. Agrolithus ; the various feldspars ; petalite, iolite, 266. Scapolithus ; melilite, milarite, 270. Alcalites; lapis lazuli, cancrinite. 272. Agrolithus, Scapolithus, Zeolithus and Alcalites compared, 274. Phen- gites ; nomenclature and history, various micas, 275. As- trites ; the chlorites ; venerite, 277. Idocrasius ; prehnite, glaucophane, pargasite, etc., 279. Epidotus ; jadeite, saus- surite ; its history, 280. Orthite ; its hydrous fo-ms, their origin, 281. Granatus ; etymology ; various types of garnet, 282. Granatinus; staurolite, sapphirine, chloritoid, arden- nite, 284. Acmitodes ; alumina replaced by ferric oxyd ; acmite, lievrite, etc., 285. Beryllus ; emerald and euclase, 287. Spodiolithus ; relations of spodumene, 287. Porodites; fahlunite and pinite, their formation, 288. Amorphites ; obsidian and other volcanic glasses ; often hydrous, 290. Specific character of these bodies, 292. False distinction between rock and mineral, 292. Pumice, its origin, 292. To- pazius ; andalusite, kyanite, etc., 293. Pyrauxites ; kaolin and pholerite; nacrite, 294. Kaolin from scapolite, beryl, etc., 296. Argillithus ; chemical clays ; allophane, halloysite, etc., 297. Borargillinea ; tourmaline; studies by Rammelsberg, 298. Analyses by Riggs, 299. Axinites, 300. Titanites, pyrophane, perowskite, rutherfordite, 301. Paratitanites, sphene, astrophyllite, 302. Stanninea, cassiterotantalite ; supposed stannic silicate, 303. Columbium and tantalum ; niobium, a synonym of columbium, 304. Tantalites ; Colum- bites, 306. Fergusonite ; its hydrous forms, 307. Paracolum- bites, 307. Wolframites, 308. Chromatites, 309. Molybdites, 309. Nitrasalinites, 310. Phosphates ; their subdivisions, 310. Eutelites; Phosphatites, 312. Apatites ; chloriferous and fluor- iferous phosphates, 313. Phosphasclerites ; amblygonite and montebrasite, 314. Hypothesis of hydroxyl, 315. Compounds with negative hydrogen, 316. Plumbogummite, 316. Gal laites ; turquoise, wavellite, etc., 316. Cacoxenites, 317. Ar- senates ; Pharmacolites, 318. Mimetites ; Arsenasclerites, 319. Vanadites, 320. Antimonates and antimonites, 320. Sul- Contents. XI PAGES 321-335 phates ; Arcanites, 321. Vitriolites, 321. Sulphasclerites, 322. Alums, 322. Sulphaluminites, 323. Amarantites ; Par- arcanites ; Parasulphatites, 324. Selenates and tellurates, 325. CHAPTER XVII. THE PYRICAUSTACEOUS CLASS 326-345 The new designation for carbonaceous combustible bodies, 326. Subdivisions of the class, 326. Different forms of carbon ; Graphite ; its mineralogical history, 327. Diamond ; its history and geological relations, 328. Hydrocarbonaceous minerals ; resins, 331. Coals and pyroschists, 332. Various series of hydrocarbons, 333. Gaseous hydrocarbons, 333. Petroleum; pa raffines, 334. Sulphur in petroleum, 335. Change of petroleum into asphalt, 335. Petroleum in limestones, 336. Ozocerite or mineral wax, 337. Geology of petroleum ; surface oil-wells of Ontario, 337. Petroleum in the Trenton limestone ; Lima oil of Ohio, 338. In Silurian and Devonian limestones, 338. Genesis of petroleum ; three hypotheses, 339. First, that it is formed in the earth's interior, 339. Second, that it comes from the distillation of coal and related matters, 340. Opinions of J. P. Lesley and others, 340. Third, that it is formed directly from organic matters, 341. The latter hy- pothesis maintained, 342. Animal and vegetal organisms alike may contribute to its formation, 343. Flaming and anthracitic coals, 343. Local conditions of production of anthracite, 343. It is not a result of a change of naming coals, 344. Anthra- cites of Pennsylvania and South Wales, 344. The several orders of native hydrocarbonaceous bodies, 345. CHAPTER XVIII. MINERAL HISTORY OF WATERS 346-375 Atmospheric and surface waters, 346. The rivers Ottawa and St. Lawrence, 347. Action of soil on percolating waters, 349. Secular changes in oceanic waters, 349. The primeval ocean, 350. Modern sea-water, 351. Results of its evapora- tion, 351. Calcium chlorid in the ancient ocean, 352. Bitter saline springs, 353. The Boston Artesian well, 354. Ancient brines and rock-salt, 355. Calcium salt of Stassfurth, 357. The Cambrian salt-horizon of North America, 357. Cambrian salt-rocks of Hindostan, 358. Porosity of dolomites and sandstones, 359. Saline and alkaline springs of St. Law- rence valley, 359. Waters of Saratoga and Ballston, 361. Geological relations of these various springs, 362. Soda-lakes of western North America, 363. Excess of carbonic acid in native soda-deposits, 364. Source of this acid in acidulous springs, 364. Borates in waters, 365. Potassium salt in surface-waters, 365. Its removal by aquatic vegetation, 366. Formation of glauconite, pinite and related species, 366. xii Contents. PAGES 367-375' Magnesian silicates ; their formation, 367. Soluble silicates in waters, 368. Magnesian or sepiolite marls, 369. Separa- tion of lime carbonate from sea-water, 369. Formation of dolomite, 370. The notion of dolomitization rejected, 370. Simultaneous production of magnesian carbonate and gyp- sum, 371. Anhydrite and its geological relations, 372. Sul- phuretted waters, 373. The plutonist fallacies of Button, 374. The neptunism of Werner, 375. GENERAL INDEX 377-379 INDEX OF MINERAL NAMES 381-391 For a revision of the genus MURIATES (page 184), see farther page 232. UNIVERSITY /FORN1A. PEEFAOE. THE publication of this volume is the fulfilment of a long- -cherished plan. When in 1845, forty-six years since, the writer began the study of mineralogy under his venerated teacher, the late Charles Upham Shepard, the antagonism between the Natural- History method, as it was called, and the Chemical method of classification in mineralogy was the subject of much debate. The former, originated by Werner, and published in 1815, had been farther developed by Mohs, and proposed to arrange the species of the mineral kingdom " solely by agreements and differences in ex- ternal characters." As introduced to students in the English language in 1820 by Jameson, who was aided by Mohs, this method was declared to be " totally independent of any aid from chemistry." Berzelius, on the other hand, had put forth a chem- ical system of classification in 1815, and still another, also chem- ical, in 1824. This latter was developed by Rammelsberg in his ** Handworterbuch des Chemischen Theils Mineralogie," in 1841, with a first supplement in 1843. Mineralogical classifications on a chemical basis were not, however, wanting before the time of Ber- zelius. Without going back to still earlier dates, we may note those of Hausmann and of Haiiy, both published in 1813 ; while Clarke, of Cambridge, England, put forth an elaborate chemical system in 1818. Cleaveland, in the second edition of his treatise on "Mineralogy and Geology," in 1822, gives an excellent discus- sion of the questions between the Natural-History method (or, as he also called it, the Mineralogical method) of Mohs and Jameson, and the Chemical method, referring at the same time to the sys- tems of Haiiy, Clarke and Berzelius ; while he himself also adopted a chemical system. A classification on a chemical basis is, more- over, set forth in the English treatise on "Mineralogy," by Will- iam Phillips, of which a revised and augmented American edi- tion, wherein is cited with approval the then recent work of Ram- melsberg, was published in 1844 by Francis Alger, of Boston. The Natural-History method, as expounded by Mohs, was adopted in the United States by Charles Upham Shepard in the three editions of his " Mineralogy " published in 1835, 1844 and 1857, xiv Preface. in the first of which, moreover, the nomenclature of Mohs was also employed. Meanwhile James D. Dana had published a treatise under the name of "A System of Mineralogy," in 1837, also on the basis of the Natural-History method, but with a Latin binomial nomenclature of his own. A second edition of his work appeared in 1844, wherein the chemical system of Rammelsberg is given in an appendix. In his third edition, in 1850, however, as is set forth with many other details in Chapter II. of the present volume, Dana abandoned the Natural-History method, and with it his own no- menclature, employing for mineral species only the trivial names, and adopting, with some modifications, the Chemical method, as expounded by Rammelsberg. The disciples of the Chemical method, for the most part, still regard physical characters, though we find in later times, in the " Tabellarische Uebersicht der Min- eralien " of Groth, a mineralogical classification in which hardness, specific gravity, color, lustre, and in fact all physical characters save the geometric forms of crystalline species are ignored, so that the votaries of the Chemical method may say that for cryptocrys- talline and uncrystalline minerals at least, they have a system "totally independent of any aid from natural history" In 1836 and 1841 appeared the first and second volumes of Breithaupt's " Handbuch der Mineralogie," in which the Natural-History method was followed and a new Latin nomenclature was proposed. An intelligent student in mineralogy, having thus set before him in various text-books the two rival methods, could not fail to be impressed by the radical opposition between them, and to ask whether some mode of reconciliation might not be found. After much study of the question during some years, the writer came to believe that by an extension of the doctrine of homologous or pro- gressive series in chemistry, and a consideration of the varying de- grees of intrinsic condensation, or, as it was designated at the time, the relations of atomic volume, it would be possible to " enlarge and simplify the plan of chemical science, and lead to a correct mineralogical system." This was said in 1853, and having in the interval published several papers on the subject, it was farther de- clared in 1863, in a note to the French Academy of Sciences,* that the doctrine of polymerism in mineral species, and the connection between specific gravity, hardness and chemical characters, "in- volve principles of great importance in mineralogy, and will form * Comptes Rendus de VAcad. des Sciences, 1863, Ivi., 1256 ; and in an English transla- tion, Amer, Jour. Science, xxxvi., 426-438. Preface. xv the basis of a new system of classification, which will be at the same time chemical and natural-historical." The principles thus stated were farther explained in 1867, in an essay on "The Objects and Method of Mineralogy," * where they were designated " the basis of a true mineralogical classification." They moreover embodied a new chemical philosophy, which was finally set forth in 1887, and again in 1888, in a volume entitled "A NEW BASIS FOB CHEMISTRY." In a paper published in 1885 on "A Natural System in Mineralogy," there was given a historical sketch of the writer's efforts up to that time to elaborate such a system, and with it a tentative classification of native silicates ; all of which appeared in his "MINERAL PHYSIOLOGY AND PHYSIOG- RAPHY." Of the defects and shortcomings of this first attempt, so far as the silicates are concerned, no one is probably so well aware as the author. His aim in the mineralogical system here proposecl^ as ex- plained in Chapter XL, has been to observe a strict jceriformity to chemical principles, and at the same time to retain all that is valu- able in the Natural-History method ; the two opposing schools be- ing reconciled by showing that when rightly understood, chemical and physical characters are really dependent on each other, and present two aspects of the same problem, which can never be solved but by the consideration of both. Differences in specific gravity between two or more solid species do not become intelli- gible until we know the equivalent weights of these species as de- duced from chemical investigation. It is not the specific gravity itself but the relation of this to the equivalent weight which must be taken into account. Hence it was thought proper in the introductory chapters of the present volume to explain in a somewhat elementary manner such principles of physics and chemistry as seem necessary for a clear understanding of this relation. The nature of chemical change, the connections between gases, liquids and solids, the periodic law, the principles of progressive series and of chemical homology, of solution, and those of polymerization, or rather of intrinsic condensation, and the relation of condensation to hard- ness and to chemical indifference, have therefore been dwelt upon at some length. The problem of determining the co-efficient of con- densation in liquid and solid species has, moreover, been discussed * Amer. Jonr. Science, 1867, xliii., 203-206; also "Chemical and Geological Essays," pp. 453-458. xvi Preface. in a separate chapter ; while a new and simplified chemical notation, which is believed to be advantageous for the purposes of the min- eralogist, has been set forth. The subject of mineral constitution, and the theoretical questions therein involved, are treated in Chap- ter X., in connection with which may be read the paragraphs 403, 404, on pages 314-316. The question of a scientific nomenclature in mineralogy is one of much importance. The barbarisms of the trivial names now universally employed are only too evident, while the endeavors to replace them by something better have been many. As prelimi- nary to a farther attempt of the kind, it seemed desirable to give some account of those successively proposed by Mohs, J. D. Dana, and Breithaupt. How far the writer has succeeded in his effort to construct a new nomenclature must be left to his colleagues to decide. While following, so far as appeared practicable, that of Breithaupt, he has been led to devise one which is in great part novel. Whether his groupings of species into genera will satisfy mineralogists remains to be seen. Some of these groups are but tentative, and may require farther subdivision, but he can claim the merit of having followed a definite plan and created a binomial Latin nomenclature which is consistent and logical. Following the discussion of this question in Chapter XII. will be found a Synopsis of Mineral Species, which gives a connected view of the nomenclature adopted, with the scientific and the trivial names of the species recognized in the present treatise. In the next three chapters are considered the orders, genera and species which make up the first three classes in the present system, the species of each genus being tabulated with their scientific and trivial names, while opposite them, in separate columns, are given for each species the calculated value of the chemical unit = p, the specific gravity = d, and the reciprocal of the co-efficient of con- densation = v / being the quotient got by dividing p by d. These values are given only to the first decimal place, for the obvious reason that the determinations of specific gravity are but approxi- mations, and do not, for the most part, admit of greater precision. The hardness of each species on the scale of Mohs, and an indica- tion of its geometric form, in the case of crystalline species, are in- serted in the table. In describing the several orders, genera and species, there is given an explanation of the nomenclature here adopted, together with a discussion of their more important historical and chemical Preface. xvii relations. In Class IV., where the species are for the most part undefined, the writer has introduced certain details with regard to the more important bodies, graphite, diamond, petroleum and coals, upon which more precise information than is to be found in other mineralogical treatises was much to be desired. In the final chap- ter various questions connected with natural waters in their mineral relations have been discussed, with many new facts and considera- tions which throw light upon several important problems in miner- alogy and geology. It will be evident that the plan of this volume does not re- quire a statement of the elementary principles of Descriptive or Determinative Mineralogy, which are well set forth in many re- cent treatises. That of Prof. E. S. Dana (1885) contains in Part L, on Physical Mineralogy, a compendious exposition of the subject, supplemented by appendices on crystallography ; while the volume of Prof. G. J. Brush (1875) on Determinative Mineralogy and Blowpipe Analysis leaves little to be desired. That cff Prof. E. J. Chapman on Blowpipe Practice, with Original Tables for the Determination of all known Minerals (1880), is also to be highly recommended. Dr. Persifor Frazer, moreover, has lately published (1891) a third and completely rewritten edition of his Tables for the Determination of Minerals, based essentially on the plan pur- sued by Weisbach. The chemical formulas and characters, and the natural associations of each species, given in addition, make this compendium one of much value to the mineralogical student. The writer has to acknowledge his obligations for important aid in preparing this work to many friends, among whom are Messrs. F. W. Clarke, of Washington ; Persifor Frazer, of Philadelphia ; W. O. Crosby, of Boston ; Sir William Dawson and B. J. Harring- ton, of Montreal ; G. Christian Hoffmann, of Ottawa ; and George F. Kunz and the late James B. Mackintosh, of New York. He is, moreover, much indebted to Mr. George lies, also of this city, for his critical skill in the final revision of the printed text. He counts himself fortunate in having been able to carry out the pur- pose so long entertained of giving to the world a Systematic Min- eralogy which is " at the same time chemical and natural-histori- cal," and proposes, if health and strength permit, to complete and publish a Descriptive Mineralogy. NEW YORK, September, 1891. SYSTEMATIC MINERALOGY. CHAPTER I. THE RELATIONS OF MINERALOGY. 1. The knowledge of the material universe as displayed in the earth with its gaseous envelope, and the starry heavens, is called Natural Science. This knowledge may be considered under two heads : 1st, Descriptive ; and 2d, Rational and Philosophical ; the former making what is commonly called Natural History, and the latter Natural Philosophy. As the terms Physical and Physiologi- cal are often applied to such science, it is well to remember that the signification of the two words "natural" and "physical" (the first derived from the Latin and the second from the Greek) is the same, and involves the notion of birth and growth ; which can be predi- cated of all material things. The word Physiography means liter- ally a description of physical things, or of nature in general, and is hence equivalent to the term Natural History, while Physiology means the logic of physical things, or the reason of nature,* and corresponds to Natural Philosophy. The words physiologist and naturalist were formerly synonymous in the English language, and all questions of so-called natural philosophy were until the present century included under the general head of Physiology, as may be seen in the abstracts of the papers of the Royal Society of London, published in 1720. 2. The study of the processes and functions of plants and animals is known as physiological botany and physiological zoology, or as vegetal and animal physiology, and we may with scientific cor- rectness and with great advantage employ the term mineral physi- * " Rationem naturae quam physiologiam Graeci appellant." (Cicero, De Nat. Deorum, I., 4.) 2 Systematic Mineralogy. ology. The usage which, without any apparent good reason, has lately grown up of restricting the use of the word physiology to the organic kingdoms, and of employing the more general and compre- hensive term physics in a similar manner for the mineral kingdom, does not conduce to clearness of conception. In the study of each of these three kingdoms of nature, which divide the physical uni- verse between them, we have, 1st, The sensible characters of the various objects, together with their resemblances and their differ- ences, by which they may be classified, arranged, and designated ; and 2d, Their genealogical history ; that is to say, their origin, growth, and transformations, which includes the relation of these objects to one another and to external forces. From this method there result in each one of the three kingdoms certain subdivisions of natural or physical science. Thus, in the vegetal and animal king- doms, we have under the head of the Natural History, or the physi- ography of living things (which we may call Biophy siography) what are known as Descriptive Botany and Descriptive Zoology, includ- ing the details of structure designated Organography, and farther, under the same head, Systematic Botany and Systematic Zoology. These have for their object to arrange the individuals of these king- doms in species, genera, orders, and classes, and to give proper des- ignations so as best to show their natural affiliations. Under the head of the Natural Philosophy or general physiology of these two kingdoms (which we may call Biophysiology, and which con- siders not structure but function), we have the process of develop- ment of organs Organogenesis and the generation of external forms Morphology besides the study of the processes which be- long to Physiological Botany and Zoology. 3. In the mineral or inorganic kingdom in like manner we have under General Physiography the subdivisions of Descriptive and Systematic Mineralogy. The assumption by many solid species of a crystalline individuality, characterized by definite geometrical forms, gives rise to the study of Crystallography, which is thus an adjunct to Descriptive Mineralogy. Passing thence into the do- main of General Physiology, we find Physiological Mineralogy to include the whole record of the origin, growth, and transformations of mineral species, or in other words, their chemical history. In the organic kingdoms the problems of structure are considered under the heads of Organography and Organogenesis, to which cor- respond Crystallography and Crystallogenesis. In the mineral ^kingdom structure is apparent in crystalline species. In colloids, The Relations of Mineralogy. 3 liquids, and gases, however, individuation has not asserted itself, and of such species structure cannot be predicated. The relations of Descriptive Mineralogy to Geography and to Geognosy (including- Petrography), and of Physiological Mineralogy to Geogenesis, will be evident to the reader. These last two divisions of terrestrial science are comprehended under the popular term Geology. 4. In the case of other worlds (which are the subjects of astron- omical study) we have in like manner their Physiography, embracing Descriptive and Systematic Astronomy, while their Physiology gives us Theoretical Astronomy, in which we bring to the study of the- heavenly bodies the knowledge gathered from their movements, their mass, and the facts which the telescope and the spectroscope have made known to us regarding their analogies with the inor- ganic kingdom as observed on our own planet. 5. The various relations of the three kingdoms of nature are per- haps best understood by considering the activities which appear in matter under three heads. All of those manifestations of force which are neither chemical nor vital, including besides ordinary motion, those of sound, temperature, radiant energy, electricity, and mag- netism, are here embraced under the common title of Dynamics, corresponding to what in popular language is called Physics. Thi& general use of the term Dynamics is adopted by Thomson and Tait in their treatise on Natural Philosophy, and is sanctioned by Clerk Maxwell, Helmholtz, and Clifford among other recent stu- dents. In this, moreover, they were to a certain extent anticipated by Berzelius, who, in the third edition of his treatise on Chemistry, in 1842, included electricity, magnetism, light, and heat, all of which he regarded as affections of matter, comparing their phenom- ena with those of sound under the common term of Dynamides, as resembling forces. Rising above this dynamic plane we next rec- ognize in matter the intervention of Chemism, or Chemistry, giving rise to chemical and so-called mineral species, which attain in crys- talline form a static individuality. On a still higher plane appear the kingdoms of organized matter, seen in individuals which are in constant and active relations with the external world, and exhibit the phenomena of life or vitality, which we have included under the head of Biotics. It may be said that the phenomena of matter when considered without reference to specific differences, are dy- namic, but with relation to these same differences are both dynamic and chemic, while the phenomena of the organic kingdoms are alike dynamic, chemic, and biotic. Systematic Mineralogy. 6. These explanations will help us to understand the true relations of the natural sciences to each other, and also the respective prov- inces of Dynamics, Chemistry, and Biotics. They will, moreover, serve to make plain the position of Mineralogy considered in its true sense as the study of the dynamical and chemical relations of INORGANIC NATURE. ORGANIC NATURE. 1 * MINERAL PHYSIOGRAPHY. BlOPHYSIOGRAPHY. 02 H i fJ Astronomy, descriptive. Organography. o 3 S "e ^ Mineralogy, Botany and Zoology, H S 1 1 descriptive and systematic. descriptive and J Geognosy. Geography. systematic. 02 ^ 1 * MINERAL PHYSIOLOGY. BlOPHYSIOLOGY. tf 4 1 ? ID H g 1 k | Dynamics. Chemistry. Biotics. 1 ^ i Astronomy, theoretical. Organogenesis. Morphology fc ^11 Mineralogy, physiological. Botany and Zoology, ^ "e Geogenesis. physiological. fe; all inorganic or mineral species, whether found in nature or pro- duced in the chemist's laboratory. The accompanying table, copied, with slight revision, from one published by the author in 1883, will show the view of the relations of the sciences which we have here sought to present. Mineralogical Systems. CHAPTER II. MINERALOGICAL SYSTEMS. 7. Although Mineralogy in its wider sense includes all chemical species, it is as a branch of Natural History restricted to native species. Many of these have from early times been the subjects of descriptions based, as in the case of plants and animals, upon their more obvious characters. Their hardness, specific gravity, external form, color, taste and smell, and their behavior when ex- posed to the action of fire, serve to distinguish the various native mineral species, and formed the basis of a classification which first took a definite shape near the close of the eighteenth century in the hands of the illustrious Werner. His system, we are told, was based on "the natural alliances and differences which exist between minerals," by means of which he " established and arranged the greater number of species of the mineral kingdom solely by agree- ments and differences in external characters," grouping the various minerals in classes, families, genera, species, sub-species, and kinds. While chemical characters were not overlooked in the larger divis- ions proposed, Werner regarded the intervention of chemistry as but a provisional expedient, and doubted the possibility of con- structing a system in which the external and the chemical charac- ters should be conjoined. 8. Werner, who died in 1817, was succeeded as Professor of Mineralogy at Freiberg by Fred. Mohs, who in 1822-24 published in two volumes his " Grundriss der Mineralogie," which was after- wards translated into English by W. Haidinger, and published in Edinburgh in 1825. Before the first appearance of his work, how- ever, Mohs had been in Edinburgh, and had aided Jameson in the preparation of a third edition of the latter's " System of Mineral- ogy," published in 1820. In the preface to this work, which de- velops the ideas of Mohs, it is declared that the system there adopted, and called the Natural History method, is in accordance with the views of Werner, and that it is " founded on what are popularly called external characters, and is totally independent of any aid from chemistry." This was, moreover, in the opinion of Jameson, the only method "by which minerals could be scientifi- 6 Systematic Mineralogy. cally arranged and rightly determined." Physical characters inde- pendent of chemical composition constituted, in the language of Mohs, the " characteristic " of mineral species, and served as the basis of his classification. This system of Mohs, as set forth by Jameson and by himself, at once found favor with naturalists, and was adopted by Breithaupt, Werner's successor at Freiberg, of whose " Handbuch der Mineralogie " three volumes were published in 1836, 1841, and 1846 ; the fourth and last volume never having ap- peared. A brief synopsis of twenty -two pages, printed by that author in 1855, supplies the characters of the orders which would have been included in the fourth volume, and thus enables us to complete the outline of the system as set forth by Breithaupt. Albin Weisbach, who has succeeded him at Freiberg, published in 1875, and in a later edition in 1884, his "Synopsis Mineralogica," a farther exposition of the Natural History system of Mohs. In place of the trivial names hitherto adopted in mineralogy, and still generally in use, Mohs proposed an ingenious but somewhat cum- brous German nomenclature, descriptive in its nature, which was translated by Haidinger into English, and was adopted by Jameson. Breithaupt, on the other hand, essayed a Latin binomial nomencla- ture for genera and species. 9. Charles Upham Shepard, in 1835, in the first edition of his " System of Mineralogy," adopted both the classification of Mohs and his nomenclature as translated by Haidinger. In the second and third editions of this same work, in 1844 and 1852-1857, while retaining with slight modifications the classes and orders of Mohs, Shepard abandoned his nomenclature, and reverted to the trivial names previously and still in general use. James D. Dana, in the first and second editions of his " System of Mineralogy," in 1837 and 1844, adopted the Natural History method of Mohs.* He more- * In 1844 he wrote: " We would not say that the system of Mohs, adopted in this trea- tise as the natural system, is perfect ; yet, whether we consider it chemically or mineral- ogically, it will be found to approach more nearly to such a system than any other that has been proposed. 1 ' Again, he adds : " The striking beauties of the system [of Mohs] will forcibly impress the minds of those who give it the attention it merits." (J. D. Dana, " Min- eralogy," 2d ed., pp. 130, 134.) In 1850, however, his views had undergone a complete change, as announced in the Preface to his third ed., referring to which in 1854 he writes : " The system of Mohs, valuable in its day, had subserved its end, and that, in throwing off its shackles for the more consistent principles flowing from recent views on chemistry, the many difficulties in the way of perfecting a new classification led the author to an arrange- ment which should * serve the convenience of the student, without pretending to strict science/ " He adds, referring to the first and second editions : " The arrangement of Mohs, followed in the main in those editions, cannot stand the test of the developments of science. Even on the assumed ground of being a natural system, it is in many parts singularly arti- ficial." (* Mineralogy," 4th ed., pp. 6, 355.) Mineralogical Systems. 7 over devised a Latin terminology for the orders, as well as a Latin binomial nomenclature of his own for genera and species, which has, however, never found favor, and was dropped by himself in his third edition, in 1850, when he abandoned also the Natural History method of Mohs. 10. Already in 1815 Berzelius had proposed a purely chemical system of mineralogical classification, based upon his electro-chem- ical hypothesis, in which all compounds were regarded as made up of an electro-positive or basic, and an electro-negative or acidic portion. He brought together in a single family all compounds containing the same electro-positive portion, and arranged the fam- ilies among themselves according to the degree of the electro-posi- tivity of the metal ; each family being divided into orders, arranged according to the degree of the electro-negativity of the acidic por- tion. The arbitrary nature of this system being made manifest by the discovery of isomorphism by Mitscherlich, Berzelius in 1824 proposed a new arrangement, dependent on the electro-negative or acidic portion of the compound, which in its essential features has since been adopted by chemical mineralogists, and notably by Ram- melsberg, who in 1841 published his " Chemical Mineralogy." Such a classification, avowedly taken from Rammelsberg, was given as an alternative scheme by Dana in his second edition, while still re- taining the natural history classification. In his third edition, in 1850, Dana put forth a new chemical classification, "in which the Berzelian method was coupled with crystallography." Since that time an essentially chemical system has been followed by him in his later editions of 1854 and 1868, and in the "Text-Book of Min- eralogy" of EdwardS. Dana in 1882. Such a system somewhat modified was adopted by Naumann, and is set forth in the twelfth edition of his " Elemente der Mineralogie," revised and edited by F. Zirkel in 1885. The chemico-crystallographic conception of mineral classification finds its simplest expression in the " Tabel- larische Uebersicht der Mineralien " of Groth (2d edition, 1882), where the trivial name, together with the crystalline form and the chemical formula of the species are given, without any reference to hardness, specific gravity, or any other physical characters whatever. 11. For the better understanding of the student it will be well to give an analysis of the Natural History system of Mohs, with a notice of some of the changes introduced by his followers. Mohs, and, after him, Shepard included all native minerals in three 8 Systematic Mineralogy. classes : I. Saline bodies, sapid if solid ; together with all liquids and gases. II. All insoluble minerals having a specific gravity above 1.8 ; water being unity. III. Resins and coals. 12. The second class which, as will be seen, included all insoluble mineral species, save the resins and coals, was divided by Mohs into fifteen orders, as follows : 1, Haloide ; 2, Baryte ; 3, Kerate ; 4, Terene ; 5, Malachite ; 6, Mica ; 7, Steatite ; 8, Spar ; 9, Gem ; 10, Ore; 11, Metal; 12, Pyrite ; 13, Glance; 14, Blende; 15, Sulphur. The order Spar as defined by Mohs included not only all zeolites, scapolites and feldspars, with sodalite, nepheline and leucite, but petalite, spodumene and cyanite, as well as pyroxene, amphibole, wollastonite and epidote, these last four being made species of the genus Augite-Spar. Other genera were Schiller - Spar; Disthene-Spar, including cyanite ; Triphane- Spar, com- prising spodumene and prehnite ; Pet aline- Spar for petalite ; Azvre-Spar for lapis-lazuli and lazulite ; Feld-Spar, embracing adularia, albite, anorthite, labradorite and scapolite. In the ge- nus Kouphone- Spar were grouped not only leucite and sodalite, but the characteristic zeolites mesotype, laumontite, harmotome, analcite, chabazite, stilbite and heulandite. With these was also placed apophyllite, while datolite was assigned to a new genus Dystome-Spar. 13. In adopting the system of Mohs, Charles Upham Shepard in 1844 subdivided the order SPAR, and established a new order, ZEOLITE, in which were included with the zeolites, sodalite, nephe- line, and leucite, the other genera in the order SPAR of Mohs being left as before. J. D. Dana, on the contrary, enlarged this order, renamed by him CHALCINEA, by adding to it a large part of the order MICA of Mohs, including all the true micas then known. He, on the other hand, removed epidote from the alliance with pyroxene made by Mohs, and placed it in its proper position, with garnet and idocrase, in the order GEM, called by Dana HYALINEA. This, for the rest, embraced all the species which had been therein included by Mohs, whom Dana followed by placing cyanite and fibrolite with the Spars, while andalusite was arranged with the Gems. 14. Breithaupt, who in his Handbuch introduced many changes into the system, made four classes : I. SALES (Salts) ; II. LAPIDE (Stones) ; III. MINERS (Ores) ; IV. INFLAMMABILIA (Combusti- bles). He thus divided in two the second class of Mohs, in which he is followed by Weisbach. In the above arrangement, as in that of Mohs, soluble carbonates, sulphates, borates, chlorids, etc., Mineralogical Systems. 9 are placed in the first class, far away from the insoluble ones, and thus a ready solubility in water at ordinary temperatures is made a class distinction. Passing to the second class, Breithaupt recognized nine orders, as follows : 1, Phyllites, including gypsum, pharmacolite, cobalt-bloom, uranite, chalcophyllite, etc. ; 2, Chal- cites / some harder and denser green-colored phosphates, arsenates, carbonates, etc., including malachite, azurite, olivenite, and, also, the silicates dioptase and chrome-garnet, or ouwarovite ; 3, Spathi (spars), including besides all the carbon-spars, or carbon- ates of lime, magnesia, baryta, strontia, iron, manganese, zinc, lead, etc. ; sparry sulphates, as anhydrite, celestite, barytine ; cryo- lite, fluorite ; sparry phosphates, as apatite, arsenates, chromates, tungstates, molybdates, and even certain silicates, such as eulytite and datolite ; 4, Cerates, comprising the chlorids and iodids of silver and mercury ; 5, Porodini, amorphous, colloidal, or porodic species, to be again mentioned below ; 6, Micce (micas), including besides true micas, chlorites and talc, certain non-silicated species, micaceous in structure, such as brucite, hydrargillite and pyrosma- lite ; 7, Zeolithi (zeolites), comprising besides the true zeolites, the silicates apophyllite and dysclasite, and the phosphate wavellite ; 8, Grammites, embracing, besides the feldspars, scapolites, petalite, leucite, sodalite and related silicates, the great family of am- phiboles and pyroxenes, with chondrodite; silicates like wollastonite, troostite and willemite, calamine, pectolite, epidote, spodumene, prehnite, cyanite and fibrolite, and finally the phosphates, ambly- gonite and lazulite ; 9, Sclerites, including garnet, helvine, idocrase, beryl, phenacite, euclase, tourmaline, axinite, dichroite, chryso- lite, topaz, zircon, staurolite, andalusite, sphene, quartz, periclase, spinel, corundum, chrysoberyl, boracite and diamond ; besides opal, tachylyte, obsidian, pitchstone and similar amorphous or porodic species, which he included in one genus, Amorphites. 15. In class three of Breithaupt, MINERS (ores) are five orders : 1, Aerce (oxydized ores), including the native oxyds of iron and manganese, both anhydrous and hydrous, with chromite, ilmenite, and various titanates, columbates, tantalates, tungstates and molyb- dates, also cuprite, zincite, pitchblende, cassiterite, rutile, and related species, with such silicates as lievrite, cerite, orthite, allanite and thorite ; 2, Pyrites ; the harder compounds of the metals, iron, cobalt, nickel, etc., with sulphur, arsenic and antimony, of which pyrite, millerite, smaltite, arsenopyrite and niccolite are types, and including also iridosmium ; 3, Metalli ; native metals and alloys ; 10 Systematic Mineralogy. 4, Lamprites or Glances ; the compounds of silver, lead, copper, mercury and molybdenum, with sulphur, selenium, tellurium, arsenic, bismuth and antimony ; Minia or Blendes, including sul- phids of zinc, cadmium, manganese, mercury and arsenic, and also sulpharsenides and sulphantimonides like the red silver ores. Class four, Inflammabilia, or combustibles, included four orders : 1, Sulphur / 2, Hesince / 3, Bitumina ; 4, Carbones. 16. Weisbach published in 1875, in his "Synopsis Mineralogi- ca," a modification of the system of Mohs. Class I. of Weisbach, HYDROLYTE or Salts, includes compounds soluble in water, while Class II., LITHE or Stones, is divided into three orders : 1, Kuph- oxyde ; 2, Pyritite (silicate), including four families : a, Sklerite ; Z>, Zeolite ; c, Phyllite ; J, Amorphite ; and 3, Apyritite (non-sili- cate). Class III., METALLITE or Ores, is divided into four orders ; 1, Halometallite ; 2, Metalloxyde ; 3, Metalle ; 4, Thiometalle, the last including three families : a, Pyrite ; 5, Galenite (Glances) ; c, Cinnabarite (Blendes). Class IV., KAUSTE or Combustibles, includes five orders : 1, Ametalle (Sulphur) ; 2, Anthracite (Coals); 3, Asphaltite (Pitches); 4, Rhetinite (Resins); 5, Paraffine (Waxes). 17. The oxyds are divided between the Kuphoxyde and the Met- alloxyde, or those of the lighter and the heavier metals. In Halo- metallite are found the silicates of yttrium, zirconium, thorium, cerium, zinc, copper, iron, and manganese, together with colum- bates, tantalates, tungstates, chromates, as well as arsenates, phos- phates, sulphates, carbonates, fluorids, and chlorids of the heavy metals ; the corresponding compounds of the lighter metals coming under the order Apyritite of Class II. In a second edition of the Synopsis, in 1884, the Halometallite are made an order in a new class called Metallolithe or Metalstones ; while the order Asphal- tite is divided by separating it from the order Elaoite (Petroleums). His three families of Halometallite, namely, Pyrite, Galenite, and Cinnabarite, correspond to the three orders of Pyrites, Lamprites, and Minia of Breithaupt. 18. To Breithaupt is due the merit of having already in 1836 recognized the wide distinction between crystalline and amorphous or structureless, opal-like gelatinous or vitreous bodies ; whether hydrous and of aqueous origin, as opal, allophane, chrysocolla and serpentine, or anhydrous and of igneous origin, as obsidian. Regard- ing these as the result of a process of induration or coagulation, he designated them as porodic* (German, porodisch, from the * " Handbuch der Mineralogie," I., 324. See also in Weisbach's " Oaracteres Minera- logici" (1880), pp. 21-33, his observations on Amorphite. Mineralogical Systems. 11 Greek Ttopoao to harden, coagulate or make callous), and in his Class III. established an order called Porodini, in which were included a great many porodic or colloidal silicates, together with some oxyds, as well as the colloidal sulphates, phosphates and arsenates. He subsequently, as we have seen, recognized the wider significance of this character by making in the order Scle- rites a genus, Amorphites, which he declared to be porodic, includ- ing opal, pitchstone, tachylyte and obsidian. Still farther, in his class MINERS, under the order Aerea, he proposed several porodic genera, comprising various colloidal oxyds, such as asbolite, psilo- melane and urangummite. Weisbach also, it will be noted, follow- ing Breithaupt, has made of the colloidal silicates an order, Amorphite. It was not until some years later that Graham, who was not acquainted with the distinction established by Breithaupt, made his remarkable investigations of porodic substances, which he designated colloids. 19. In comparing the nomenclature of Mohs with that of Breit- haupt we note that the designation of Spars or Spathi is applied to two widely unlike groups of species. The order SPAR of Mohs included not only zeolites but all of the feldspars, scapolites and related species besides, amphibole, pyroxene, and in fact the greater number of crystalline silicates, with the exception of those of the order of MICA, and those harder species which, like garnet, idocrase, tourmaline, beryl, etc., were embraced in his order GEM. The order SPATHI of Breithaupt, however, embraced calc spar, pearl spar, bitter spar, heavy spar and fluor spar, and many related species, as already noticed, but, with two or three exceptions, no silicates. The species included in the order Spar of Mohs are placed by Breithaupt in his order GRAMMITES, while his order SCLERITES corresponds to the Mohsian order GEM. The order MICA is made by both of them to include the same group of silicated minerals. Weisbach, however, makes of these a family, PHYLLITES; while Breithaupt, as we have seen, employs the same term to designate an order of soft, non-silicated, foliated species, of which gypsum, pharmacolite, erythite and uranite are examples. 20. The term Spar, as commonly applied, connotes a certain hard- ness, transparency or translucency, and crystalline structure which are independent of chemical composition. These sparry or spathoid characters are shared by sulphids like sphalerite, cinnabar and proustite ; by oxyds like zincite and senarmontite ; by silicates like the zeolites, feldspars, petalite and scapolites ; tungstates like 12 Systematic Mineralogy. scheelite ; chromates like crocoisite ; phosphates like apatite > sulphates like anhydrite, barytine and anglesite ; carbonates like calcite, dolomite, siderite and smithsonite ; and fluorids like fluorite and cryolite. Again, the phylloid, micaceous or foliated structure belongs not only to graphite and to sulphids like molybdenite, covelline, sternbergite, friesite and tetradymite, but to oxyds like brucite, to silicates like the true micas and chlorites, as well as to talc and to pyrophyllite, and, as we have seen, to the sulphates, phosphates and arsenates which constitute the order Phyllites of Breithaupt. So, also, the porodic or colloidal character belongs not only to certain oxyds and silicates, but to sulphates, phosphates and arsenates. Again, the hardness and transparency which char- acterize the order Gem belong to the diamond, to oxyds like quartz, rutile, corundum, diaspore, spinel and chrysoberyl ; to sili- cates like chrysolite, garnet, beryl, tourmaline, spodumene, andalu- site, topaz and zircon. 21. Notwithstanding the work of the learned exponents of the Natural History method, the later views of Berzelius, as adopted and modified by Rammelsberg, Naumann, Dana and others, now prevail among students of mineralogy, with whom the results of the chemical analysis of species are generally considered as of paramount significance ; while hardness, specific gravity, crystal- line form and optical characters assume a secondary value in classification, and are regarded as important chiefly in connection with determinative mineralogy. The conception of a true natural method, which, although but partially understood, was at the basis of the system of Mohs, has been generally lost sight of ; the order which the naturalist finds in the organic is no longer apparent in the inorganic world, as presented in modern mineralogical text- books ; and this state of things has contributed not a little to the comparative neglect into which systematic mineralogy has of late years fallen. As to the complete divorce between physical and chemical char- acters in the study of mineral species, maintained by Werner, Mohs, and his followers, there seems to have underlaid it the notion of framing a system which, as in botany and zoology, shall be available for the purposes of determination without the destruc- tion of the individual. It is to be noted, however, that characters dependent upon chemical differences, such as the presence or ab- sence of certain acids, alkaloids and groups of essential oils, are not without significance in determining the natural affinities of Mineralogical Systems. 1& plants ; and, moreover, that as we descend the scale of being from the highly organized forms of the animal and vegetable world to the simple crystal or the amorphous colloid mass, the external char- acters which serve to show likeness and difference become fewer, and are often obscure and ill-defined. Again, a natural system is not one subordinate to the end of identifying species, but should consider objects in all their alliances and relations. Such a system, as long since defined by John Ray, is one which neither brings to- gether dissimilar species nor separates those which are nearly allied; and the most important resemblances and differences in the mineral kingdom are, in many cases, those which can only be de- termined by chemical investigation. 22. If, however, we regard as mistaken those who in their search after a natural system in mineralogy have rejected the aid of chemistry, it must be said, on the other hand, that the chemical mineralogists who, disregarding the relations of density and hard- ness, or relegating them to a secondary rank, build systems on the results of chemical analysis, are false to chemical science itself. There exist, in fact, inherent and necessary relations between the physical characters and the chemical constitution of inorganic bodies which serve to unite and reconcile the natural -historical and the chemical methods in mineralogy. A physico-chemical study of the mineral kingdom, having in view these relations, will enable us, while remaining faithful to the traditions of Werner and of Mohs, to frame a classification which it is believed will merit the title of a Natural System in Mineralogy. 14 Systematic Mineralogy. CHAPTER III. FIEST PRINCIPLES IN CHEMISTEY. 23. A general view of some of the principal facts of chemistry, and of certain phenomena which are intimately connected with chemical changes, is a necessary preliminary to the study of min- eralogy. The observations of chemists have made known the existence of a number of kinds of matter, specifically distinct, which they have agreed to call chemical elements for the reason that all other known kinds may be resolved into two or more of these. Of these elements there are between sixty and seventy, well-defined and readily distinguishable from one another, which will be considered more at length in the next chapter. By the study of these elementary species and of the kinds of matter to which they give rise by their transformations, their combinations and their interactions, we discover that definite and constant laws of weight, of measure and of number preside over all chemical operations. 24. Matter is susceptible of changes of measure or volume of two kinds. (1) Those produced from without, by variations of tem- perature and of pressure, which changes are constant and regular. Since these effect no essential alteration in species, they may be called extrinsic changes, or, as the result of external dynamic agencies, mechanical changes. (2) Those which, in the language of the late Thomas Andrews in his remarkable studies on gases and vapors, are called "internal disturbances; " and which effect specific alterations in character. These constitute chemical, or what may be designated as intrinsic changes, and differ from the last inas- much as instead of being constant and regular they are periodic and subordinated to definite and unforeseen relations of volume. 25. These intrinsic changes in matter connote chemical pro- cesses. In chemical union we have intrinsic contraction or conden- sation, which has been variously described as interpenetration, compenetration, identification, unification and, by Herbert Spen- cer, as integration. In chemical decomposition we have intrinsic expansion or intrinsic division. These intrinsic changes may be either homogeneous, involving one species of matter only, or hetero- First Principles in Chemistry. 15 geneous, involving two or more species. The first includes so- called polymerization and depolymerization, which may be described respectively as homogeneous intrinsic union and homogeneous in- trinsic division that is to say, a homogeneous chemical operation by intrinsic contraction or by intrinsic expansion, constituting what the writer has elsewhere called collectively chemical meta- morphosis. Those intrinsic changes which involve two or more species have in like manner been included under the title of chem- ical metagenesis; the process being one of heterogenequs intrinsic union or of heterogeneous intrinsic division. In the former, intrinsic contraction involves volumes of unlike species, while in the latter intrinsic expansion resolves a species into two or more unlike spe- cies. Both elemental and compound species may be subjects of intrinsic condensation or polymerization. Moreover the body re- sulting from a union, either homogeneous or heterogeneous, of compound species may afterwards suffer division in a different sense, and thus give rise to species unlike those which united, resulting in what is generally called double decomposition; which always im- plies a temporary union followed by division. The relations to vol- ume of all such changes are most simple and evident in the cases of gases and vapors, but the same laws of intrinsic contraction and expansion by volumes apply alike to gases and vapors and to the liquid and solid species formed by their condensation. In all of these chemical changes temperature and pressure play an important part ; and beyond certain limits the extrinsic changes thereby pro- duced themselves provoke chemical changes. These, in their turn, are accompanied by thermic disturbances, the study of which is the object of thermo-chemistry. 26. All chemically stable forms of matter may theoretically, by sufficient elevation of temperature, assume, even under the greatest pressure, a gaseous condition, the more or less polymeric vapors thus produced being subject to intrinsic expansion or depolymeriza- tion on diminution of pressure ; while by reduction of temperature they pass, as may be seen under favorable conditions, through suc- cessive polymerizations or processes of intrinsic contraction into liquid or solid species ; the passage from the vaporous to the liquid state being apparently continuous. The ideal gas is wholly obedient to the extrinsic influence of pressure, according to Boyle's law, while the ideal solid is wholly indifferent thereto. These ideal forms are, however, constant only within certain limited ranges of temperature, beyond which most of even the so-called 16 Systematic Mineralogy. permanent gases become liquid or solid by intrinsic changes; while the solids themselves are in many cases the subjects of intrinsic expansion or contraction without losing their solid state, as in the so-called allotropic changes of sulphur, phosphorus, arsenic, tin and calcium carbonate, and very many other bodies. We are thus brought face to face with the fact of existence of matter in the three states of liquid, solid and gas, and with the changes of state, as they are called that is to say, the passage of solids into liquids, vapor or gas, and the condensation of gas and vapor into liquid and solid forms. Of the same order of operations are the changes in specific gravity and other characters constituting cjiem- ical metamorphosis, which species may undergo while still retaining their respective states of gas, liquid or solid, as already noticed in many cases of so-called polymerism and allotropism. 27. Before proceeding farther it is well to consider some ele- mentary facts relating to the extrinsic changes produced alike in gases, liquids and solids by variations in temperatures and in press- ure, referring the student to more extended treatises for details. The ideal or perfect gaseous state of matter is nearly realized through greater or less ranges of temperature and pressure by many gases, such as hydrogen, nitrogen, oxygen, atmospheric air, as a mixture of the two, methane, carbon monoxyd, and by many vapors ; as that of water above 100 at the ordinary atmospheric pressure of 760 mm. In these the effect of augmentation of tem- perature at constant pressure is to produce a constant and regular increase of volume, which amounts for each degree of the centi- grade thermometric scale to -^ 5 part of the volume of the gas or vapor calculated for 0. In accordance with this law the volume is doubled at 273, while at 273 it should, if the law still held good, disappear altogether. This point of extreme cold has, how- ever, never been attained in experiment, and we now know more- over that at temperatures much above 273, all the above-named gases except hydrogen undergo a change of state, becoming liquids and solids, neither of which are amenable to the same law of extrinsic contraction as gases. These changed forms, however, re- quire for their production and preservation not only great cold, but a pressure much exceeding the normal atmospheric pressure of 760 mm. The temperature of 273, deduced from the extrinsic contrac- tion of gases, and arbitrarily named the absolute zero of temper- ature, is conveniently adopted as the zero of a scale on which to indicate in degrees centigrade the melting point of all bodies. First Principles in Chemistry. 17 On this scale it is evident that the melting point of ice, which is on the ordinary thermometric scale, becomes +273. 28. The effect of increased pressure on the perfect gas at con- stant temperature is to diminish its volume in a regular and con- stant manner. Taking its volume at a pressure of 760 mm., or one atmosphere, as the unit, this at constant temperature under a press- ure of two atmospheres is reduced to one-half, at three atmospheres to one-third, and at four atmospheres to one-fourth. Conversely, if the pressure is reduced to one-half of an atmosphere the volume of the gas is doubled, while at a pressure of one-third it is tripled, and at one-fourth quadrupled ; the volume of the gas, at constant tem- perature, being inversely as the pressure, in accordance with the law pointed out by Boyle and subsequently elaborated by Mar- riotte. Beyond a certain point, which for each gas or vapor varies according to temperature and pressure, this law fails, owing to the intervention of a change of state. Liquids, as is well known, no longer obey Boyle's law, and their compressibility, on the contrary, though variable for different species, is so slight in the case of the commoner liquids, as water and mercury, that it can only be rec- ognized by delicate experiments, and in ordinary operations is dis- regarded. Solids, it may be affirmed, are even less compressible than liquids ; the apparent exceptions to be noted farther on in some species, as sulphur in certain conditions, tin in its gray form, and ice (which by pressure is changed into water), are connected with chemical or intrinsic change. The observation of Spring, that some metals under great pressure undergo a certain temporary re- duction of volume, is perhaps connected with such a chemical change, as will be noticed farther on. It is only the perfect or ideal gas which is entirely subject to the extrinsic influence of press- ure as seen in Boyle's law. The ideal solid is incompressible. 29. The true gas in like manner, as we have seen, has a regular and constant rate of expansion by heat, the co-efficient of expansion for all such bodies having been found to be sensibly -g^of their volume at for each degree centigrade of temperature. In solids, however, it is very unlike for different species. The co-efficient of cubic expansion for various solids, between and 100 has been found, approximately, as follows for each degree : platinum, .000026 ; iron, .000036 ; gold, .000044 ; copper, .000050 ; silver, .000058 ; lead, .000083. That for cassiterite is .000016 ; for rutile, .000032 ; for magnetite, .000029 ; for hematite, .000040 ; for pyrite, .000034 ; for sphalerite, .000036 and for galena, .000068. For calcite, .000075 ; for 18 Systematic Mineralogy. dolomite and siderite, .000035 ; for aragonite, .0000647 ; for barite, .0000581 ; for celestite, .0000608 and for fluorite, .0000623. For orthoclase it is .000022 ; for zircon, tourmaline, garnet and idocrase from .000021 to .000028 ; for beryl, .000016, and for diamond only .00000354. Compared with these we find the cubic expansion of various kinds of glass to be from .000021 to .000030, and that of Bayeux porcelain from to 1000, .0000108. The co-efficient of expansion for fixed and difficultly fusible solids is nearly constant for all temperatures far removed from that at which change of state takes place. This, however, often occurs below fusion, as may be seen in the case of aragonite passing into calcite at a low red heat, and of quartz taking on a lower specific gravity. These facts with regard to the expansion of solid species are here noted for their bearing on the determination of specific gravities, a ques- tion to be considered farther on in Chapter V. 30. The co-efficients of expansion or dilatation, for liquids, though variable, are generally nearly constant for any given species through a considerable range of temperature at the ordinary atmos- pheric pressure. In the case of many liquids heated, under greater pressure, to temperatures above their boiling point, the co -efficient of dilatation is found to augment with the elevation of tempera- ture. The deviations thus observed for many liquids, as well as by many gaseous and solid species, from the constant rates of ex- pansion which characterize the ideal gas on the one hand and the ideal solid on the other are apparently due to chemical transforma- tion or change of state / the relations of which to temperature and pressure we shall now proceed to consider before discussing in de- tail the facts in relation to these varying co-efficients in liquid species. The vapor of water above 100, at the normal pressure, behaves like a true gas, but below that point is resolved into a liquid ; 1698 volumes of the vapor at 100, and 760 mm. pressure, condensing into a single volume of water at the same temperature. If the pressure be reduced one-half, water boils at about 82, but if doubled it boils at 122, while at ten atmospheres, its boiling point is 182, at twenty atmospheres, 214, and, by calculation, at fifty atmospheres, 266 ; the vapor, at these higher temperatures, being subject to Boyle's law. At a temperature a little above 400, water, under pressure, suffers a change of state, and assumes a gaseous condition with a volume equal to about four times its bulk in the liquid state. First Principles in Chemistry. 19 31. A like change takes place in other volatile liquids. This point for alcohol is about 234, when the vapor is found to exert a pressure of about 63 atmospheres ; and for ethyl oxyd, 190, at a pressure of 36.9 atmospheres. Similar facts have been observed for ethyl chlorid, carbon disulphid and other vo- latile liquids, all of which, above certain temperatures, assume the condition of dense vapors, differing widely from true gases in their relations to temperature. The same is true for liquids which are not permanent at the ordinary atmospheric pressure. Thus carbon dioxyd, which, within a considerable range of temperature and pressure, acts as a true gas, when exposed to a pressure of 38.5 atmospheres at 0, becomes liquid. Even oxygen and nitrogen, as already remarked, at great pressures and still lower tempera- tures, assume the liquid state, and at still lower temperatures all of these liquids become solid. Above 309, however, carbon dioxyd passes, like water, alcohol and ethyl oxyd, into a dense vapor, which a pressure of 300 or 400 atmospheres fails to reduce to a liquid state. Similar results are obtained with nitrogen monoxyd. The point at which liquids thus pass into vapor, under pressure, is called the critical point, and it is supposed that all such bodies have their critical point of vaporization ; or, in other words, at sufficiently high temperatures, will assume a gaseous condition, under any pressure. On the other hand it would appear that below a certain temperature, the critical point of solidification^ they will all pass into the solid state. This point is lowered by pressure for water, which expands in solidifying,* and is raised by pressure for bodies which, unlike this, contract in becoming solid. Thus, all species of matter which do not suffer heterogeneous dissociation by heat pass, at sufficiently elevated temperatures, into the gaseous condition. 32. The co-efficient of expansion of the ideal gas is constant, as is also that of the ideal solid. That of liquids, and also of the dense vapors formed from these under pressure above the critical point of vaporization, is, however, subject to great variations, and rises rapidly with augmentation of temperature ; a fact of much significance, which is best illustrated by some examples. Begin- ning with mercury, we find its co-efficient of dilatation, for 1 nearly constant, increasing slowly from .000179 at 0, to .000184 at 100, to .000189 at 200, to .000194 at 300, and to .000196 at 350 ; its * Moisson at a temperature estimated at 13000 atmospheres caused ice to melt at -18, and kept water liquid at -5. 20 Systematic Mineralogy. boiling point being 35725. Water, from 4 to 100 has a co-efficient of dilatation of .00043 nearly, but from 4 to 1508, the mean co- efficient is not less than 000.67; that from 998 to 1508, according to Mendeljeff, being .001157. Alcohol, boiling at 784, has a mean co-efficient of dilatation for 1 from to 10 of .00105, which rises slowly to .00137 between 60 and 70, and to .00146 between 70 and 80. From 80 to 999 it is .00160, and from the last point to 1309 rises to .00193. Ethyl oxyd, boiling at 349, has from to 782 a mean co-efficient of dilatation of .00193 ; from this point to 998 it is .00270, thence to 1312 it equals .00337, and between the last point and 157 augments to .00420 ; its critical point, ac- cording to Sajotschewsky, being 190. Sulphur dinoxyd, boiling at 10 under atmospheric pressure, shows from that temperature to a co-efficient of expansion of .00192, above which it .augments rapidly; being approximately .00528 between 100 and 110, .00650 between 110 and 120, and .00863 between 120 and 130. Carbon dinoxyd, which boils at 782, and passes the critical point of va- porization at 309, presents a still more striking case of augmentation of the co-efficient of dilatation by increase of temperature. From -10 to 5 it is .0047, but between 15 and 20 is .0097, and be- tween 20 and 25 is .0127. It will be noted that this liquid under pressure, when approaching the critical point, has already a co-effi- cient of dilatation more than three times the constant co-efficient of hydrogen and atmospheric air, which is .00366. 33. This remarkable change in the rate of expansion, which serves to distinguish liquids, as they approach the critical point, alike from the perfect gas and from the ideal solid, is apparently due to incipient and partial changes of state; which we regard as in all cases chemical in their nature, whether seen in the phenomena of liquefaction, of vaporization, and the conversion of vapors and liquids into solids, or in the intrinsic periodic changes of specific gravity to which matter alike in gaseous, liquid, and solid forms is subject ; and which are to be carefully distinguished from the ex- trinsic changes, regular and constant in character, which we have already considered as effected alike by temperature and pressure in gases. 34. The phenomena presented by dense vapors under pressure when exposed to variations of temperature or of pressure led An- drews to declare that "the ordinary gaseous and the ordinary liquid states are only widely separated forms of the same condition of matter, and may be made to pass into one another by a series First Principles in Chemistry. 21 of gradations so gentle that the passage shall nowhere present any interruption or break of continuity. They are only distant stages of a long series of physical changes." For carbon dioxyd, he asserted that under certain conditions " it is impossible to say whether it is gas or liquid ; " while, according to him, " a vapor may be defined to be a gas at any temperature under its critical point." These observations and conclusions have since been abundantly confirmed by many other experimenters. According to farther investiga- tions by Hannay and Hogarth these dense vapors behave like liquids, dissolving salts not otherwise volatile ; while alcoholic solutions of these salts pass integrally, above the critical point, into the condition of dense vapors; "affording a farther proof of the perfect continuity of the liquid and the gaseous states, and also a complete proof of the solubility of solids in gases." * 35. We have already maintained that changes of s,tate from gas to liquid and solid, and the reverse, are always chemical in their na- ture, so that the " series of physical changes " insisted upon by Andrews is really at the same time a series of chemical changes. These dense vapors, though formed under great pressure, and readi- ly dissociated by the diminution thereof, owe their existence as such not to mechanical or extrinsic condensation, but to intrinsic condensation, or so-called polymerization, as is shown by the fact that their tension is far less than that demanded by Boyle's law. It was long since pointed out by W. Allen Miller that the dense vapors of alcohol and ethylic oxyd formed just above the critical points of these liquid species have tensions far less than belong to the normal vapors ; and moreover that the abnormally dense vapors of these liquids on augmentation of temperature not only present a much greater rate of expansion than air or water vapor, but in- stead of being like these constant therein, show a rapidly increasing co-efficient of dilatation. Andrews found that carbon dioxide at 607, under a pressure of 223 atmospheres, is reduced to one-447th, or less than half the volume that should belong to the normal gas at this temperature and pressure, according to Boyle's law. The dense vapor of ethylic alcohol affords a more striking example of the same fact, since, according to Messrs. Ramsay and Young, a gramme of this liquid, which has at 4 a volume of 1.2403 cubic centimetres, acquires at the critical point a volume of about 3.5 cubic centimetres ; so that the specific gravity of the vapor, by their * See Hannay and Hogarth, Proc. Roy. Soc., London, xxix., 325, and Chemical JVettw, xli., 108-106 ; also " A New Basis for Chemistry," 2d ed., p. 187. 22 Systematic Mineralogy. observation at 243, with a pressure of about 63 atmospheres, is nearly 0.28, water being 1.00.* This corresponds to a four-fold in- trinsic condensation, or to 4(C 2 H 6 O), since the normal vapor of al- cohol, calculated for the above temperature and pressure, should, in obedience to the extrinsic influences of temperature and pressure, have a specific gravity of 0.0681, or one-fourth of the number ob- served. 36. From the facts here set forth we may then conclude to the existence, under pressure, of a gas or vapor 2(CO 2 ), and of another 4(C 2 II 6 O), which are products of polymerization or intrinsic condensation, marking stages in the process of conversion of the normal gas or vapor into the liquid state ; a process which, notwith- standing the instability of these intermediate forms under reduced pressure, is subordinate to the same relations of volume as are ob- served in the more or less stable polymerizations of pentene, C 4 H 5 , acetylene, C 2 H 2 , and other hydrocarbons. The cases of oxygen, Og, and its more condensed form of ozone, O 3 ; and that of sulphur, which, from its normal vapor, having a density corresponding to Sjj, passes into the denser vapor, S 6 , before reaching the state of liquid sulphur, are examples of the same kind. Similar facts are known in the case of the vapors of iodine, of arsenic and of phos- phorus. The various forms of solid sulphur, selenium, phos- phorus, arsenic, silicon, carbon, tin, silver, and many other bodies, both simple and compound forms which differ from each other alike in specific gravity, hardness, color, lustre, and electrical re- lations, as well as in their relations to heat, to solvents, and to the animal economy are familiar to chemists as examples of so-called allotropy, and mark stages in the farther intrinsic condensation of these bodies, giving rise to new species marked at once by aug- mented density with increase of hardness, infusibility, insolubility, and indifference to chemical change. To this subject we shall recur farther on. 3V. The question of the greater or less stability of condensed forms under changed conditions of temperature and pressure is one of much interest in the present connection. Without adverting farther to the great instability alike of condensed gaseous oxygen or ozone, and of dissociated or monad iodine vapor, of which the first very readily undergoes intrinsic expansion and the second in- trinsic condensation, or to the various facts more or less familiar to * " On the Thermal Properties of Alcohol," Philos. Trans., 1886, part i. First Principles in Chemistry. 23 chemists touching the analogous changes in various hydrocarbons, we may notice several cases in regard to solid species which have a more immediate mineralogical interest. The less dense forms of solid sulphur, known as plastic and prismatic sulphur, pass slowly under ordinary conditions into the denser octahedral form, but im- mediately when submitted to great pressure, as shown by Spring j who has also found the same agency to transform the lighter and amorphous form of arsenic, specific gravity 4.7, into the denser crystalline species, specific gravity 5.7. A very slight pressure, and a gentle elevation of temperature, suffice to change the gray and brittle form of tin, specific gravity 5.8, into the white and malleable form, specific gravity 7.3. The changes of phosphorus from one state to another are also readily effected, while no means has yet been devised to convert graphite into diamond or diamond into graphite. 38. The cases of carbon dinoxyd and silicon dinoxyd, two bodies which, from analogy, we should expect to offer many points of similarity, present a striking contrast with regard to the stability of their polymeric or condensed forms. Carbon dinoxyd is a gas which only by great pressure at a temperature below 309 can be reduced to a liquid; and this, when solidified, is very volatile and readily passes, without fusion, into a gaseous state at the ordinary temperature and pressure. Silicon dinoxyd, on the contrary, is a solid, appearing in two crystalline states as tridymite, sp. gr. 2.30, and quartz, sp. gr. 2.65, both of which are extremely fixed. When quartz is fused by the intense heat of the electric furnace of Cowles, as observed by the author, a partial volatilization takes place.* Carbon nitrid presents in its chemical history reactions which may be compared both with those of carbon dinoxyd and silicon dinoxyd. As cyanogen, C 2 Na, it is a gas, which under pressure at 274 becomes liquid, and at still lower temperatures a crystalline solid: characters recalling those of carbon dinoxyd. When, how- ever, this very volatile liquid is heated under pressure to between 350 and 500, it is slowly changed into the brownish black solid polymer known as paracyanogen. This substance is best formed by the prolonged heating of the mercuric cyanid in a closed tube to about 440, the proportion of the cyanogen thus trans- formed depending on the temperature and the pressure. When * " A New Basis for Chemistry 24 Systematic Mineralogy. heated alone to 800 in a closed tube, or at a lower temperature in a current of nitrogen or of carbon dinoxyd, paracyanogen is again transformed into cyanogen. 39. From what has gone before, it will be understood that the production of liquid or solid species involves two and in many cases three distinct operations. First, the production of the elements themselves by the stochiogenic process, which in former times, and by ways unknown to us, gave rise to them. Second, in the case of compounds, the union of two or more of these elements in certain definite proportions by what we have designated chemical meta- genesis. These compounds are either the result of a direct heter- ogeneous integration or direct union of the different species, or else of such a union followed by subsequent division or disintegration in a different sense ; resulting in two or more new species by what is called double decomposition, as already explained (25). In the next stage, the normal chemical species, whether elemental, on the one hand, or compound and the result of metagenesis on the other, becomes the subject of a chemical metamorphosis by con- densation. Upon the normal or theoretical chemical form is thus superinduced the mineralogical form, which involves the greater or less intrinsic contraction (polymeric condensation) of the normal chemical species often gaseous or volatile, but frequently un- known to us and the assumption by it of a solid state; in which it has greater specific gravity and a certain hardness, fixity and insolubility, and is metallic or non-metallic, colloidal or crystalline. 40. The colloid is not possessed of individuality, but upon non- crystalline matter, in the greater number of solid species, is again superinduced the crystalline form; this being the geometric shape assumed by the crystalline individual, which connotes a certain structure, apparent in the cleavage, the varying hardness and the thermic, optical and electrical relations of the crystal, but is, not- withstanding its value in determinative mineralogy, the least essen- tial or most accidental form of the mineral species. The significance involved in the note of metallicity is very apparent when we con- sider the metallic and non -metallic conditions presented by sele- nium and phosphorus, the similar dual condition of the sulphids of mercury and antimony, the non-metallic and sparry character of one form of each of these, and of the native sulphids of zinc, cadmium, arsenic and many double sulphids ; as well as the singu- lar metallic characters assumed by the tungsten bronzes and the dinoxyd of vanadium. First Principles in Chemistry. 25 41. We have said that all mineralogical species, so far as known, are the result of intrinsic condensation or so-called polymerization of normal chemical species, because, as will be shown farther on, there is reason to believe that the true equivalent weights of all solid or liquid mineralogical species are multiples by some num- ber, generally very elevated, of the equivalent weight belonging to the normal chemical species. Before proceeding with the dis- cussion of this question of equivalent weights, which involves the determination of the co-efficient of condensation that of specific gravity, we shall consider the chemical history of the elements, the laws of their combination by measure, number and weight, and the real nature of chemical union or solution.* * For a detailed account of the question of polymeric or condensed vapors from the time of the early studies of Cagniard de la Tour, in 1832, the reader is referred to Chap- ter XIV. of the author's "New Basis of Chemistry," 3d edition, or to the French transla- tion thereof, " Un Systeme Chimique Nouveau ; " also to his essay entitled " The Founda- tions of Chemistry" in the American Chemical Journal for September, 1888, and the Chemical News, vol. Ixviii., pp. 193, 305, 213. 26 Systematic Mineralogy. CHAPTER IV. CHEMICAL ELEMENTS AND NOTATION. 41. It was said at the beginning of the last chapter that the num- ber of well-known elementary bodies in chemistry is between sixty and seventy. The first table in the present chapter gives in al- phabetical order, with their symbols, the numerical values of sixty-eight of these bodies. It will be understood that any one of these symbols, when written with a capital letter, and without a co-efficient, denotes not only the element in question, but a definite proportion thereof corresponding to the value opposite it. Thus H = 1 of hydrogen, O 16 of oxygen, and Na = 23 of sodium, while Na g O = 62 of an oxyd of sodium. The numbers here affixed are in most cases but approximations, being the nearest whole numbers. Thus oxygen itself, given as 16(H = 1), is a little below that value, and is now generally regarded at 15.96, though recent re- searches tend to show a still lower figure, probably about 15.9. As many of the other numbers have been calculated with reference, either directly or indirectly, to the value of 16 for oxygen, it is clear that a revision will introduce small differences, which, how- ever, are of minor importance for our present purpose. 42. These numbers have been variously designated as propor- tional, combining and equivalent weights, and as atomic or molecu- lar weights. They show the proportions in which these elements unite with one another and often replace each other in similar com- binations. But a given element may have more than one combin- ing or equivalent weight, as in the case of copper, in the two chlorids in which respectively 63 and 31.5 parts of the metal unite with 35.5 parts of chlorine, replacing in each case 23 parts of sodium or 1 part of hydrogen; to which these two proportions of copper may both be said to be equivalent. The terms " atomic " and " molecular " weights, based on the assumption of the existence of atoms, and of molecules made up of two, three, four or more atoms, are objectionable as founded on an unproved hypothesis. The question of the term to be employed is complicated by that of the different valencies of the same element, as seen in the case of cop- per, and as will be more fully shown in the succeeding paragraphs. Chemical Elements and Notation. Table of Elementary Bodies, with their Symbols and Relative Weights. Symbol. Weight Symbol. 1 Weight Aluminium Al 27 Manganese Mn 55 Antimony (Stibium). . A rsenic .... Sb As 120 75 Mercury (Hydrargyr.) Molybdenum Hg Mo 200 96 Barium Ba 137 Nickel Ni 59 Beryllium (Glucinum) Be 9 Nitrogen N 14 Bismuth Bi 208 Osmium Os 191 Boron B 11 o 16 Bromine Br 80 Palladium Pd 106 Cd 112 Phosphorus p 31 Caesium . Cs 133 Platinum Pt 194 Calcium Ca 40 Potassium (Kalium) K 39 Carbon c 12 Rhodium . . . Rh 104 Ce 140 Rubidium Rb 85 Chlorine Cl 35 5 Ruthenium Ru 102 Chromium Or 52 Scand ium Sc 44 Cobalt Co 59 Selenium . Se 78 Columbium Cb 94 Silicon Si 28 Copper (Cuprum) . Cu 63 Silver (Argentum) Ao- 108 Didymium Di 147 Sodium (Natrium) .tt-5 Na 23 Erbium Er 166 Strontium Sr 87 Fluorine F 19 'Sulphur 32 Gadolinium Gd 156 Tantalum Ta 182 Gallium Ga 69 Tellurium Te 125 Germanium Ge 72 Thallium Tl 204 Gold (Aurum) Au 197 Thorium Th 231 Hydrogen H 1 Tin (Stannum) Sn 118 Indium In - 113 Titanium Ti 48 Iodine I Tunsrsten ("^Tolfram) W 184 Iridium Ir 192 Uranium Ur 240 Iron (Ferrum) Fe 56 Vanadium .... V 51 Lanthanum La 1QQ Ytterbium Yb 173 Lead (Plumbum) Pb 207 Yttrium Y 88 Lithium Li 7 Zinc Zn 65 Magnesium .... Me- 24 Zirconium . . . Zr 90 H5 28 Systematic Mineralogy. The essential fact is, however, while having these in view, to fix the proportions in which these elements combine; some standard, as that of hydrogen, being taken as unity. The numerical values thus determined, with due regard to the principle of valency, may be correctly designated the proportional or relative weights of the elements. 43. The relations between these elementary species are best shown by arranging them in the order of their proportional weights from the lowest to the highest. Chemists have long recognized the existence of natural groups among these elements, characterized by the proportions in which they unite with oxygen, with hydro- gen, and with the halogens, FC1, Br, I ; and often moreover by certain physical resemblances between the elements or their analo- gous compounds. Of these groups we may note the following ex- amples : I. The alkali-metals, Li, Na, K, Rb, Cs ; all very light, fusible and readily oxydable, which form colorless oxyds, R 2 O, ex- tremely soluble in water, eminently caustic and alkaline ; while the corresponding chlorids RC1 are neutral, and also very soluble. These oxyds and chlorids are comparable to water, H 2 O, and to chlorhy- dric acid, HC1. II. Metals of the alkaline earths, Ca, Sr, Ba, which yield strongly basic and more or less soluble alkaline oxyds, RO ; with corresponding chlorids, RC1 2 . With these are more or less closely connected Be, Mg, Zn, and Cd. III. Elements like Al, Ga, and In, yielding oxyds, R^Og, and chlorids, RC1 3 , which, unlike those of the two preceding groups, are readily volatile. IV. Elements like C, Si, Ti, forming oxyds, ROg, and also chlorids, RC1 4 ; the first two named also uniting with H to form volatile hydrids. V. Ele- ments like N, P, As, Sb, which have for their oxyds R 2 O 3 and R 2 O 5 , and yield moreover volatile chlorids, RC1 3 and RC1 5 , besides hydrids, RH 3 . VI. Elements like S, Se, and Te, which form acidic oxyds, RO 2 and RO 3 , and in some cases chlorids, RC1 6 . VII. Ele- ments like F, Cl, Br, I, which have for their highest oxyds RgO?. 44. It was pointed out by J. A. R. Newlands in 1864 that if the chemical elements are arranged in the order of their equivalent weights, beginning with Li = 7, they, with some apparent excep- tions, fall naturally into the seven groups above named. These in fact present a curious analogy with the octaves in the ordinary musical scale ; the eighth term becoming the first of a second oc- tave, and the fifteenth the first of a third octave. This remark- able discovery was therefore at first designated as the Law of Octaves. Farther inquiry shows that while this law can be traced The Periodic Law. 29 throughout the whole range of chemical elements, it is compli- cated by the occasional intervention of an eighth group. The study of these curious relations, now generally included under the title of the Periodic Law, has since been pursued by Odling and Lothar Meyer, and especially by Mendeljeff ; * the second table in this chapter is a reproduction, with some revision, of one by the last-named chemist. It will be noticed that in this table the elements are arranged in eight vertical groups, and in twelve hori- zontal series, presenting, however, many vacancies, which may yet be filled up by farther discoveries. Of these groups the first seven are each farther divided by Mendeljeff into two parts. Those which fall into the even series, namely, the 2d, 4th, 6th, 8th, 10th and 12th, and those which fall in the uneven or odd series, namely, the 3d, 5th, 7th, 9th and llth series, are in most cases more nearly related to each other, and constitute respectively in Mendeljeff's table the subgroups a and b of each of the first seven groups. He moreover has noted the predominant basic or positive character of the members of the even series, or the subgroups a; and the more acidic or negative character of the subgroups b, or the odd series. 45. To this there are not wanting exceptions, since Na and Mg are found under b, while all the elements in the 2d series, with the exceptions of Li and Be, are notably acidic or negative in their * In the proceedings of the Royal Society of London for 1887-88, vol. 43, p. 195, in an account of the anniversary meeting, Nov. 30, 1887, it is said : '* The Davy medal for the year 1882 was awarded by the council to Professor Mendeljeff and Lothar Meyer conjointly, 'For their Discovery of the Periodic Relations of the Atomic Weights,' . . . now known as the Periodic Law. . . . But while recognizing the merits of the chemists of other nations we are not to forget our own countryman, and accordingly the Davy medal for the present year has been awarded to Mr. John A. R. Newlands, for his discovery of the Periodic Law of the Chemical Elements. Though in the somewhat less complete form in which the law was enunciated by him it did not at the time attract the attention of chemists, still, in so far as the work of the two foreign chemists above mentioned was anticipated, the priority belongs to Mr. Newlands." The late Beguyer de Chancourtois, a distinguished French geologist, philosopher and mystic, had already in 1862 and 1863 arranged the chemical elements in the order of their combining weights, employing for this purpose those which had been in 1858 adopted by Cannizaro ; and had, moreover, attempted to show that simple numerical relations exist not only between the combining weights, but between all the physical and chemical characters of allied elements. According to de Chancourtois " the properties of bodies are the properties of numbers." Arranging the elements on a spiral called by him the telluric helix (vis tellurique) the great discovery of Newlands and Mendeljeff was before him, yet he failed to recognize what now seems obvious therein, the law of octaves and the periodicity of functions first pointed out by Newlands in 1864. The various notes on this subject by de Chancourtois, which appeared in the Comptes Rendus de r Academic des Sciences in 1862 and 1863, are resumed by him in a volume entitled " Vis Tellurique, classement naturel des corps simples ou radicaux, obtenu au moyen d'un systeme de classification helicoidal et numerique," Mallet-Bachelier, Paris, 1863, with a graphic rep- resentation of the helix. An extended notice of these by P. J. Hartog, under the title of "A first Foreshadowing of the Periodic Law," appears in Nature for Dec. 26, 1889. 30 Systematic Mineralogy. THE PERIODIC LAW. M ENDELJEPp's TABLE, WITH ADDITIONS. 1 2 3 I. a. 6. II. a. b. III. a. b. IV. a. 6. V. a. 6. VI. a. b. VII. a. b. vin. H 1 Li 7 Be 9 B 11 C 12 N 14 O 16 F 19 Na 23 M 24 Al 27 Si 28 P 31 S 32 Cl 35.5 4 K 39 Ca 40 Sc 44 Ti 48 V 51 Cr 52 Mil 55 Pe Co 56 59 Ni 59 5 Cu 63 Zn 65 Ga 69 Ge 72 As 75 Sc 78 Br 80 6 Rb 85 Sr 87 Y 88 Zr 90 Cb 94 Mo 96 Kullli 102 104 Pd 106 7 Agr 108 Cd 112 In 113 Sn 118 Sb 120 Te I 1251 127 8 Cs 133 Ba 137 La 138 Ce 140 Di 147 9 Gd 156 Er 166 10 11 Yb 173 Ta 182 W 184 Os Ir 191 192 Pt 194 Au 197 2W Tl 204 Pb 207 Bi 208 212 12 Th 231 _ U 240 _ 1- chemical relations. Lothar Meyer, rejecting this subdivision of the groups, determines their positions therein by their relative condensation, and thus puts Na, Mg, Al, and Li in a, and N, O, and F in b / the change affecting only the 2d and 3d series. It will be noted that there are many resemblances, functional and otherwise, not only among successive members of the same group or subgroup, but also among consecutive members of the same series ; the four elements adjacent to any given element in the table being called by Mendeljeff its " atomic analogues." From these relations this chemist was enabled to predict the discovery and the properties of two unknown elements, scandium and gallium, which were soon afterwards fdund, and likewise of germanium ; which has been more recently recognized, and which we have inserted in the table. The discovery of this latter element, it should be said, had already been predicted by Newlands in 1864.* Recent observations show the existence of a new element in the llth series, belonging to * " The Discovery of the Periodic Law," by J. A. R. Newlands, 1884, p. vi., 8. The Periodic Law. 31 VI. b, related to Te, and having a weight of 212, apparently the same which has been designated austrium. 46. In group I. of the table are included the elements regarded as monovalent or monad, forming chlorids with one proportion of chlorine ; while in group II. are those called, for an equally obvious reason, divalent or diad. In group III. are triad or trivalent, in IV. tetrad or tetravalent, in VI. hexad or hexavalent, and in VII. heptad or heptavalent, elements. Among those which in the table are placed in group VIIL, two, namely, Ru and Os, give rise to volatile oxyds, RO and others to complex chlorids corresponding to RC1 8 , thus establishing their title to be called octad or octovalent ; a designation which has been extended to the whole group. Thus the number assigned to each group in the table marks its supposed maximum quantivalence. 47. The alternate arrangement of the elements into two sub- groups serves to bring out certain facts of great significance, besides those already noted. Thus group La includes all the light alkali- metals, with the apparently anomalous exception of Na, placed at the head of b, and followed by Cu, Ag, and Au, dense metals yielding insoluble or sparingly soluble chlorids MCI. In group II. no such marked difference exists between a and b, magnesium being placed in b, where it is followed by Zn, Cd, and Hg, all volatile metals. In group III., on the contrary, the characters of the two subdivisions are marked. Omitting for the present B, whose rela- tions (like all the members succeeding of the 2d series to those be- low them) are anomalous, we find the subgroup b distinguished from a by the fact that its members, or at least Al, Ga, and In, are metals yielding readily volatile chlorids, and also hydrous double sulphates with potassium or ammonium, of which common alum is the type. Thallium offers an exception to this, but its characters do not assimilate it to the subgroup a, which will be noticed far- ther on. 48. In group IV., passing over C, whose resemblances in the elemental state are with Si, we have, following the latter in b, the distinctly metallic elements Ge, Sn, and Pb, while the relations of a serve to connect them rather with Si than with these. In group V., setting aside in like manner N, we find in the fixed elements of a a contrast to the more or less volatile metalline elements of b. A similar contrast is apparent between the two subgroups of VI., where the volatile elements of b differ widely from the dense and fixed associates of a. The same unlikeness is seen between the 32 Systematic Mineralogy. dense metal Mn of group VII. a, and the volatile haloid elements of b. The characters of many of the subgroups b recall the observa- tion of Mendeljeff, already cited, as to the generally acidic or nega- tive relations of the elements in the odd series which make up these subgroups, and suggest a farther examination of the whole subject of these relations. In the electro-chemical hypothesis of Berze- lius, certain relations between different elements, or between their oxygen and sulphur compounds, were distinguished by the terms electro-negative and electro-positive, or by the corresponding signs of minus and plus ( +). As synonymous with these, the names of acidic and basic, halogen ous and basylous, or of chlo- rous and zincous, have been employed. While none of these are free from objections, we may perhaps employ the terms negative and positive (without the Berzelian prefix) as the least so, while occasionally making use of acidic and basic as synonymous there- with. A reference to Mendel Jeff's table of the periodic law will suffice to show that the elements in most of the odd series in the first seven groups are more markedly negative than those of the corresponding even series. If we except the 2d series, which is anomalous in other respects, we note evidences of this predominance of negative relations in the odd subgroups of VII. Jin Cl, Br, I ; of of VI.& in S, Se, Te ; of V.b in P, As, Sb ; of IV.b in Si, Ge, Sn, Pb ; and of III. b in Al, Ga, In. 49. Farther inspection moreover shows that the relations of negative and positive between the members of each subgroup, which seem confounded, as it were, in the 2d series, become respectively more strongly defined and augmented as we proceed to higher series. Beginning with group I. we note the strong basicity and ready solubility of the oxyds of a; characters which are hgwever fully shared by that of Na at the head of b. Of the scarcely soluble oxyds of the metals succeeding in this subgroup, cuprous oxyd is a strong base, since, as I have long since shown, it decomposes a solution of MgCl, even in the cold, with precipitation of magnesic hydroxyd and formation of cuprous chlorid.* The basic properties of silver oxyd are also well marked, those of aurous oxyd being apparently less so. In II. a the compara- tively feeble positive relations of beryllic oxyd led Berzelius and others after him to regard it as a sesquioxyd nearly related to alumina. Be is, however, clearly a diad, and is followed by Ca, Sr and Ba, with increasing equivalent weights and augmenting positive * " Contributions to the Chemistry of Copper," Amer. Jour. Science, 1870, vol. xliv. The Periodic Law. 33 characters. Again, in II. J, the action of heat on the hydrous chlorids of Mg and Zn shows these elements to be less positive than Cd ; while the strongly basic HgO not only decomposes a solution of ZnCl, but separates potassium hydroxyd from a solution of KI, to form a double potassio-mercuric iodid. In III. a the negative B is followed by the positive Sc, and by Y, La and Yb, which are strongly basic. Again in III. b, A1 2 O 3 is at once negative to oxyds of groups I. and II., with which it forms compounds known as alumi- nates, and positive to the strongly negative or acidic oxyds of groups V., VI. and VIL, forming with them salts which if soluble are not very stable. The basic or positive character augments progressively in Ga and In. 50. In IV. a the strongly negative character seen in CO 2 is less marked in TiO 2 ; and ZrO 2 , like alumina, while negative to many oxyds, sustains to others positive relations, playing the part of a base. The positive character is still more marked in CeOg, while ThO 2 is strongly basic, its hydrate, like those of Y, La, Ba, Ca and Cd, absorbing carbon dinoxyd from the atmosphere. In V.#, where negative characters are strongly marked in the triad and pentad oxyds of P and As, the triad oxyd of Sb is feebly and that of Bi more strongly basic ; while in VLa the hexad oxyds of Cr, Mo and W are more or less strongly negative, and that of IT is posi- tive. The negative energies of VI. b and VII. J, so far as known, progressively diminish with the increased equivalent, and in the for- mer TeO 2 is already feebly basic, uniting, like A1 2 O 3 , alike with pos- itive and with negative oxyds. Too little is yet known to establish similar comparisons in VIII., and I. may perhaps offer an exception, but for all the other groups it may be said that the positive or l>asic energy varies directly, and the negative or acidic energy inversely as the combining weight of the element. 51. Hydrogen (H) stands alone in the 1st series of the table, no element having yet been discovered between it and lithium. For the first eighteen elements, beginning with Li and ending with V in the 4th series^ the law of octaves is clearly marked, and in accordance therewith we should expect after three terms having analogies with N, O and F, a fourth analogous to Na marking the first term of the 5th series. In place of four such elements, how- ever, we find no less than seven heavy metallic elements, namely V, Cr, Mn, Fe, Co, Ni, Cu; the last taking a place beneath Na in group L, while the three preceding elements constitute group VIII. Of these elements, those ranged in groups VI., VII., VIII. are in 34 Systematic Mineralogy. their ordinary combinations diads and sometimes triads. From Cu, as a monad of the 5th series, with its sparingly soluble chlorid,* the law of octaves is traced without interruption to group V. in the 6th series, where we again meet with a succession of heavy metals, apparently seven in number, Cb, Mo, ?, Ru, Rh, Pd and Ag; the last taking its place as a monad in the Vth series, as the first term of a new octave. In the 10th series the law of octaves is a third time interrupted by the intervention of a similar succession of heavy metals, Ta, W, ?, Os, Ir, Pt, Au; which last is made the first of a new octave in the llth series. In the 6th and 10th series we have indicated the as yet undiscovered elements corresponding to Mn by a heavy dash. It may be conjectured that farther discov- eries will show similar conditions to the above in the 8th and 12th series. The law of octaves is thus periodically interrupted by the appearance of these associations of heavy metals; three of which in each case make up the superadded group VIII. of their respec- tive series. To make this more plain, these interpolated metals are marked in the table by black-faced letters, and their probable places, where unknown, by heavy dashes ; the elements conforming to the law of octaves being designated by ordinary letters, and their sup- posed place by light dashes. 52. The valencies assigned in the table to the elements in the various groups and subgroups next require consideration. Of those in group L, the monad character of the alkali-metals forming only chlorids, RC1, is unquestioned. Cu, however, more generally plays the part of a diad, yielding CuCl 2 , and the existence of a lower chlorid of silver serves to make the relations of Ag some- what uncertain ; while Au in its soluble chlorid, AuCl 3 , is a triad. In group II. the diad character is invariable, so far as known, for all the elements which form only soluble chlorids, MCla, with the ex- ception of Hg, which also yields an insoluble chlorid, HgCl, analo- gous to those of Cu, Ag, Au; and Cd, which has lately been found to yield a peculiar subchlorid. A similar anomaly is met with in the case of Tl, which, while placed in group III. ft, as a triad, and giving T1C1 3 , also plays the part of a monad, yielding a sparingly soluble chlorid, T1C1, and a soluble highly basic alkaline oxyd, T1 2 O, comparable with those of the alkal-imetals. The triad * Cuprous chlorid is described as insoluble in water. The writer, however, finds that 1000 parts of water at 100 dissolves 1.35 parts of CuCl, a portion of which crystallizes out on cooling; the liquid at 14 still retaining about 0.90 parts of the cuprous chlorid. Trans. Amer. Inst. Mining Engineers (1881), x., 11, note. The Periodic Law. 35 characters of Al, Ga and In, in the same subgroup, are well marked in their oxyds and their ordinary chlorids, RC1 3 ; but re- cent inquiries show for each of these the probable existence of diad forms, to be noticed farther on. 53. The elements ranged in III. a, so far as known, form, with the exception of B, but a single non-volatile chlorid, RC1 3 . We have already noticed the acidic character of B 2 O 3 , and the marked basicity of the higher members of this subgroup. From the comparative rarity of the elements Sc, Y, La and Yb, it has come to pass that A1 2 O 3 has been assumed as the type of the basic triad oxyds. The differences between its chemical relations and those of the oxyds of the elements before mentioned have given rise among chemists to differences of opinion, which are still farther complicated by the intimate relations between these ele- ments, and especially between La and the triad forms of Ce and Di, which in the table are assigned places in groups IV. and V. in the same series with it positions still questioned by many chem- ists. Di, in fact, presents but slight resemblances to Cb and Ta, the elements above and below it in the same subgroup, and, while yielding an unstable higher oxyd, said to be Di 2 O 5 , forms a strongly basic oxyd, Di 2 O 3 , which is closely related to La-jOg. Ce, in like manner, while yielding a basic oxyd, CeO^ like those of Zr and Th, also gives an oxyd, Ce 2 O 3 , much resembling the triad oxyds of La and Di. 54. The chemical relations of these three triad oxyds are, in fact, so close that they are almost always found associated in nature, and are only with difficulty separated from each other. From their strongly basic relations, the neutral character and the crystalline forms of their salts, these three elements have been by many chemists regarded as diads, with equivalents two-thirds of those assigned to them in the table that is to say, of 92, 94 and 98, approximating to that of Cd; with the hydrous sulphate of which the sulphates alike of La, Ce and Di, together with that of Y (also regarded as diad), are isomorphous. Farthermore, it has been noted that La, Ce and Di are all three malleable metals, with specific gravities of 6.2-6.7, near to Mg in fusibility and, if we regard them as diads, in condensation ; while they present, so far as known, no analogies with the elements of the subgroups in which they are placed in Mendeljeff's table. It is farther to be remarked of these three triad oxyds of Li, Ce and Di (frequently designated as the cerium metals), that in native silicates, fluorids and fluocar- 36 Systematic Mineralogy. bonates they apparently replace CaO and other diad oxyds. It is to be noted that the calcined oxyds of lanthanum and didymium are so strongly basic that they readily decompose a solution of ammonium nitrate at the temperature of ebullition, expelling am- monia and forming nitrates of lanthanum and didymium ; while eerie oxyd remains undissolved. 55. Closely related to these metals is samarium, found with them in samarskite, and in thorite, and most nearly resembling didymium, which itself, according to recent investigations, appears to include three closely allied metals. The names of erbium, gadolinium and ytterbium have been given to rare elements found in gadolinite and samarskite, together with yttrium, scandium, and several others named phillipium, terbium, decipium, dysprosium, thulium and holmium ; all of which are described as yielding triad oxyds. The distinctness of many of these bodies is still ques- tioned, and their chemical history is as yet very imperfectly known. They are found for the most part in small quantities, and in rare minerals, and are separable from each other with dif- ficulty, by fractional precipitation, guided by spectroscopic study. Several of them may possibly find a place in the now unoccupied places in Mendel Jeff's table. The analogies of the 4th, 6th and 10th series favor the existence of triad forms for the six vacancies succeeding Di in the 8th series. 56. Meanwhile in the present state of our knowledge, it would seem that the only known oxyd of La should be regarded as a typical triad oxyd of the subgroup III. a, having at the same time close chemical analogies, not only with those above and below it, but with similar triad oxyds of the succeeding elements Ce and Di in the same series. As regarding farther the subgroup III. 5, we have already alluded to the double relation of aluminic oxyd, A1 2 O 3 , as playing both an acidic and a basic part in combination. The sig- nificance of this is the greater from the fact that, apart from the small number of simple aluminous silicates, more than one-half of the native silicates known in mineralogy contain alumina. These compounds of silica, alumina and other oxyds may with propriety be regarded as aluminisilicates, in which not only the silica but the alumina plays a negative or acidic part ; similar to that of boric oxyd in borosilicates like datolite and danburite, or in boralumini- silicates like the tourmalines. Alumina presents in this respect close analogies with the triad oxyds of Cr, Mn and Fe, which resemble it closely in their power to replace aluminic oxyd in the The Periodic Law. 37 double salts known as alums, in their feebly basic relations, and in their disposition to take a negative or acidic part. This latter character is very marked in the case of Cr 2 O 3 in solutions, and appears also in the case of Fe 2 O 3 and Mn 2 O 3 ; as we see manifested in magnesioferrite, franklinite and certain ferriferous spinels. These same triad oxyds may replace A1 2 O 3 wholly or in part in the aluminisilicates ; while the corresponding triad oxyd of Ti, and perhaps also that of V, appears to play a similar part. 57. In group IV.a we have noted the triad oxyds of Ti and Ce ; while in IV. 5, Sn, though shown to be a tetrad by its chlorid, SnCl 4 , and its oxyd, SnO^ presents in its stannous compounds the re- lations of a diad. The same is true of Ge and of Pb, which last in its ordinary relations is a diad, having close relations with group II. In its unstable chlorid, PbCl^, its oxyd, PbO 2 , and in plumbic ethide, Pb(C 2 H 5 ) 4 , it however exhibits tetrad relations which give it a place in group IV. In group V. the principal oxydized compounds of the elements are R 2 O 3 and R 2 O 5 , showing for these a triad or a pentad character. The sesquioxyds of Sb, Di and Bi are basic, the last two markedly so ; while vanadic sesquioxyd also presents basic characters. The existence, however, of compounds like N 2 O, NO, NOg, and of sim- ilar compounds of V, of POg, of AsS, of SbO 2 , and finally of BiCl^ BiO, BiO 2 and BiS 2 , shows clearly that the elements of this group may also play the pari of monads, diads and tetrads. A tetrad oxyd, TaO 2 , is known, and, although not yet discovered, may be as- sumed in the cases of Cb and Di. In the various simple and com- plex sulphids which are so numerous in the mineral kingdom, the elements As, Sb and Bi enter as diads. 58. While the hexad character is apparent in the elements of group VI., their diad and tetrad relations are also seen in VI. a, the former conspicuously in the chromous chlorid and salts, and the latter in the molybdic tetrachlorid. These various relations are also very apparent in the elements of VI. b. In TeO 8 we have an oxyd which like A1 2 O 3 , has both negative and positive relations. Again, in the heptad group, VII., the oxyds of chlorine, C1 8 O and ClOjj, and the compounds of manganese, MnCl 2 and MnO^ show clearly the lower valencies of the elements of this group. The triad part played by Mn in common with Ti, V, Cr and Fe has already been noticed. 59. The metals of group VIIL, found in the 4th, 6th and 10th series, next require notice. Those in the 4th series are diads in 3$ Systematic Mineralogy. their ordinary saline combinations, and through Cu in the next series, which is most frequently diad, are connected with the diad Zn in group II. The metals Ru, Rh, Pd, Os, Ir and Pt give, with the exception of Rh, two chlorids, RC1 2 and RCl^ ; showing thus both diad and tetrad characters. Rh, morever, which yields but a single chlorid, RhCl 3 , marking a triad type, gives an oxyd, RhO 2 . Ru also gives a similar oxyd, and moreover an oxyd, Ru 2 O 7 , corre- sponding to that of manganese in group VII. Two of these so- called platinum metals, namely Ru and Os, yield volatile oxyds, RuO and OsO 4 . In native species these platinum metals are almost always alloyed with each other or with iron. Two excep- tions, however, are known ; the pyritous laurite is a ruthenic sul- phid in which the metal plays a triad part, while in the native arsenid of platinum, sperrylite, the metal enters as a tetrad. 60. The relations apparent between the three consecutive ele- ments of this group in each of the three series are not less evident than those presented by the consecutive elements in different and separate groups. We have referred to the triad forms assumed alike by Fe, Mn, Cr, V, and even by Ti ; in all cases giving rise to feeble bases, yielding highly colored salts, and apparently, at least in the case of Ti, Cr, Mn and Fe, replacing Al in combination. The three metals Ru, Rh and Pd, with the succeeding Ag, and the other three, Os, Ir and Vt, with Au, constitute the so-called noble metals ; while immediately following the latter are the related Hg, and the two soft heavy fusible metals, TI and Pb, which have with each other, and with Au and Hg, many chemical resemblances. The characters which connect the oxyds of Al and Si have already been noticed ; while those between B, C and, it may be added, Si in its elemental state, are worthy of note. The intimate relations and close resemblances between the triad forms of La, Ce and Di have already been insisted upon. 61. Reviewing the whole subject, we find that the elements ranged in group I. of the table are known as monads only, with the exception of Cu, w T hich also acts as a diad, and of Au, which assumes, in many combinations, a triad part. In group II. the elements are known only as diads, with the exception of Hg, which also assumes a monad form. In group III. the triad character of the various elements is only varied by the fact that TI has also a monad form, and that the other elements of III. 5, Al, Ga and In, may give rise to diad, and the latter even to monad forms, under certain conditions to be noticed farther on. To the tetrad relations The Periodic Law. 31> of group IV. must be excepted the occasional triad part which Ti, in common with the four succeeding elements in the same series,, is capable of assuming, and also the similar triad form of Ce. The diad part played in IV. b by Si, Ge, Sn, and especially by Pb, is also to be noted. In the elements of group V. the triad and pentad characters of many of their combinations are well marked, and the triad oxyds of Di and Bi are strong bases. We have already no- ticed the diad character frequently displayed by most of this group,* which is particularly marked in the metalline combinations of V.. In group V. hexad characters are marked in Cr, Mo, W, and IT,. from the strongly acidic CrO 3 to the distinctly basic UO 3 . It is to be remarked, however, that in the only native sulphid of this group, that of Mo, this element is diad ; while the triad rela- tions of Cr are well known. Moreover, while the hexad character of the elements of VI. b is well marked, they generally play the part of diads in their metallic compounds. In group VII. the heptad Mn is well known to be, in other oxydized compounds, diad, triad, tetrad, and, it is claimed, octad ; like certain elements of group VIII., in which, as already noted, tetrad, triad, and diad relations are also displayed. 62. It was formerly supposed by chemists that wide differences separated the sesquioxyd bases from the so-called protoxyd bases ;. under which head, before clear notions of the question of valency prevailed, were included all those oxyds which we have noticed above as monad, diad or tetrad ; and in addition, those of Y, La, and the lower oxyds of the other cerium metals, Ce and Di. The ele- ments Ga, In and Tl being then unknown, the sesquioxyd bases were represented only by A1 2 O 3 and the closely related chromic, manganic and ferric oxyds, which share with aluminic oxyd the ambiguous alternately basic and acidic character apparent in its various combinations with more negative or more positive oxyds. The distinction thus originating has been perpetuated to a great extent in nomenclature, with unfortunate results. It is now clear that with the exception of A1 2 O 3 (perhaps Ga 2 O 3 and In 2 O 3 ) and the triad forms of Ti, V, Cr, Mn and Fe, the monad, diad, triad, tetrad and even hexad bases may replace each other in combi- nation without materially changing the type of the combination. This is seen by the manner in which Ca and Ba appear in the aluminisilicates such as zeolites, scapolites and feldspars ; and are themselves replaced by diad forms of Mn and Fe in many other silicates ; as well as by the triad forms of La, Ce and Di both in. silicates and in fluorids. 40 Systematic Mineralogy. In order to represent these relations by what may be designated as a monadic notation, it is necessary to divide the received form- ulas of the oxyds in question by twice the oxygen co-efficient ; by which we obtain what may be called the chemical unit for each oxyd. Thus, for monads like Na 2 O, and diads, CaO, we divide by 2 ; for triads like A1 2 O 3 and La 2 O 3 , by 6 ; for tetrads like SiO 2 and ThO 2 , by 4 ; and for hexads like UO 3 by 6. Thus in each case the chemical unit for the element is that portion which is united with 8 parts of oxygen ; O = 16-v-2 = o = 8. 63. The same intimate relation exists among acidic or negative elements as among basic ones, and demands a similar notation. The negative or acidic portion is in many cases as complex, and embraces elements from as many groups as the positive or basic portion. Here also the chemical unit will be represented by the ^quantity of each element united with 8 parts of oxygen ; the received formula for triad oxyds being divided as before by 6, for tetrads by 4, for pentads like Cb 2 O 6 by 10, and for hexads by 6. It is hardly necessary to remind the reader that one half portion of diad oxygen (o = 8) is the equivalent of the monads F and Cl. 64. Attempts to simplify the ordinary chemical notation have not been wanting ; chemists are familiar with the device of indi- cating the amount of oxygen in oxydized compounds by dots or points placed over the symbol of the element ; and in like manner of commas to represent sulphur. A horizontal bar across the cap- ital letter of the symbol, or beneath it, indicated two equivalents of the element, and a black-faced letter was also used to the same end. Berzelius, however, proposed a farther simplication for oxydized compounds, which consisted in suppressing the points, as signs of oxydation, and employing italic letters to designate oxyds ; while different degrees of oxydation in a given element were indicated by the use of capital and current letters. Thus taking Fe as the symbol for iron, Fe represented the higher or sesquioxyd, and fe the protoxyd of the same metal. The italic letter in all cases rep- resented the compound of the element with one portion of oxygen (O = 8). Thus, lime being, in the chemical notation of the time, CaO, alumina A1 2 O 3 , silica SiO 3 , ferric oxyd Fe 8 O 3 , and ferrous oxyd FeO, the italic signs Ca, Al, Si, Fe, fe represented the com- pounds of these elements with eight parts of oxygen ; and the -co-efficients affixed to these signs after the manner of exponents in algebra showed the oxygen-ratios. CaStf represents a silicate of lime in which the ratio of the oxygen in the lime is to that in the A Monadic Notation. 41 silica as 1:2; and the value of the sign remains unchanged, whether silica be SiO 2 , or SiO 3 as Berzelius supposed. These new symbols, which Berzelius called mineralogical signs, to distinguish them from the ordinary chemical signs or symbols, while most advanta- geous for oxydized compounds, could not be extended to sulphids, fluorids or arsenids, or to compounds like oxychlorids and oxy- fluorids.* To meet this difficulty, and to retain as far as possible the advantages of these mineralogical signs, the writer has devised what is here presented as a monadic notation, wherein all the elements are indicated, and their ratios clearly shown; the valencies being designated by the use of current letters of three different kinds. By the use of this notation it is optional to represent a compound according to a dualistic or a unitary conception. Thus orthoclase, an aluminisilicate of potassium, may be written either si w a4<>i5-ki<>i or si^a^o^. 65. This monadic notation, adopted by the writer as early as 1854, and farther set forth in 1885, was in 1890 modified by the introduction of different fonts of type to represent the valencies of the elements, as will be explained, f The strictly monad elements of group I. are represented by small roman letters, followed in each case by the co-efficient ; thus, h 1? li D na^ kj, rbj, cs! ; as are also the haloid elements of group VII., f u clj, fr r i> *i > while those monads which are also in some cases diad or triad are indicated by a duplication of the initial letter in the same type, thus: ccuj, hhg : , aau 1? ttlj. The diads of group II. are also represented by the same small roman letters ; bcj, mg^ ca^ srj, cdi, ba ly hgi. The same notation is extended to the diad forms of Oe, Sn and Pb from group IV., thus : ge x , sn^ pfy; to the diad forms of group V., as seen in N, P, As, Sb and Bi, thus: n lf p x , as l5 sbj, bij ; to those of S, Se and Te in group VI., as well as to the diad forms of Cr, Mn, of Fe, Co, Ni, and of the other metals of group VIII., as ru 1? pd D OS!, ir 1? ptj. It will be remembered that for all these diads the numerical value of the symbols as here given is one-half that ordinarily assigned to these elements, the corresponding haloid compounds being MXj, while for the monads these are MX. 66. The triad forms are distinguished by being printed in small italic letters, and include besides the elements of group III., b ta al^ * These mineralogical signs were adopted by Beudant, whose clear discussion of the matter may be consulted with profit. See his " TraitS de Mineralogie," 2d ed., 2 vols., 1830- 32, vol. i., pp. 385-387. t ** Chem. and Qeol. Essays," p. 443 ; " Mineral Physiology," p. 292, and Chemical News, June 6, 1890. 42 Systematic Mineralogy. sCj, ga^ yi^ in^ la^ gd y yb^ tl lf the triad form au 1} together with: those of t^ VH cr mn^fe^ rh ly also the triad forms of ce lt di l9 ofp lf as lf sb^ and bi v All of these correspond to haloid compounds, MXg, and have numerical values one-third of those represented by the or- dinary symbols. For convenience, the hexad basic uranic oxyd is included with the triads. The tetrads of group IV. are repre- sented by small black-faced letters, thus : d, si t , ti lf ge lf zr lt sn l9 ce!, pbj, th!. To these we may add the tetrad forms, Vj, sb^ and bi x ; together with those of mou w lf mn lf fe lf and of the platinum metals, with the exception of rhodium. All of these correspond to haloid compounds, MX, and the symbols here adopted have a nu- merical value one-fourth of that ordinarily assigned to these ele- ments. 67. Coming now to the pentad forms assumed by the elements, in group V., corresponding to M 2 O 5 , in which forms, so far as known, they exhibit only negative or acidic relations, it appears simpler for our present purposes to make of them an exception ; and instead of introducing a new style of symbol to make use- for these negative oxyds of the diad form (which, though met with in the other members of this group, is assumed for Cb, D, and Ta), and to write their formulas with monadic oxygen, thus :. B2<>5> P2<>5, v 2 o 5 , as 2 o 5 , sb 2 o 5 , cb 2 o 5 , ta 2 o 5 , bi 2 o 5 . The same license may be extended to the hexad forms of group VI. ; by which we get ^o^ sejOg, tejOg, cr^g, mOjOg, WjO,,. In view of the basic part played by the hexad uranic oxyd, we have already assigned it a place as an, appendix to the triads : U 2 o 3 =3(?y 1 o 1 ). 68. To resume, the notation here proposed employs the ordinary chemical symbols, which, for all monad and diad forms of the ele- ments, are written in small roman letters, and for all triad forms in small italic letters. For the basic elements of the first three groups, which present, in the case of Cu and Hg, both monad and diad forms, and in Au and Tl, monad and triad forms, the monad is distinguished by a duplication of the initial letter of the monad symbol. Tetrad forms of group IV. and subsequent groups are represented by small black-faced letters. These symbols in all cases represent the numerical values corresponding to 8 parts of oxygen, 16 of sulphur, and 35.5 of chlorine. To avoid the introduction of other forms of letters, the pentad and hexad compounds of the elements of the succeeding groups are represented as compounds of the diad forms of these elements with monadic oxygen or mo- nadic sulphur, or haloids, as above. Unlike the ordinary chemical A Monadic Notation. 43 notation in which, in the case of single portions of an element, the co-efficient is understood, the monadic notation demands the affixing in all cases of the co-efficient, for the purpose of separating and of keeping distinct, in the absence of capital letters, the consecutive symbols. In tabulating the symbols here proposed, however, we omit the co-efficient, but give for each symbol its numerical value. It should be distinctly understood that this system is not in- tended to replace the ordinary notation, except so far as it may be convenient for the purposes of the mineralogist, as already explained. It has not, therefore, been deemed necessary to discuss its possible extension to the oxygen compounds of groups VII. and VIII. Monadic Notation : Symbols and their Values. ag..l08 ce... .47 ga...34.5 mn ..26 pb . . 52 ta ...91 al....!3.5 ce...35 gra...23 raw... 17. 3 pt ...97 te....62.5 al . . . 9 cd ...66 gd. . . 52 mn..l3 pt. ..48.5 th. ..58 as ...37.5 cl 35.5 ge...36 mo . .48 rh ...34.7 ti... 16 as ...25 co ...29.5 ge...!8 mo. .24 rb ...85 ti. . . .12 aau. 197 cs.,.133 h 1 n 7 ru .51 ttl . .204 aw... 65. 7 cr 26 hhg.200 n 4.7 ru ...34 tl 68 b 3.7 cr 17.3 hg..lOO na . . .23 ru...25.5 u ...120 ba...68.5 cu.,.31.5 i. ...127 ni ...29.5 s ....16 i* ... .40 be... 45 ecu ..63 in 66.5 os ... 96 sb ...60 V....26.5 M...104 di....73.5 in ...37.7 OS... 48 sb ...40 V....17 bi ...69 di . .49 ir....96 o 8 se ...39 w. ...92 br... 80 er....55 ir . . . 48 p ....15.5 si ....7 w ...46 c 6 f 19 k ... .39 p.... 10.3 sc... 14.7 y ....29.3 c 3 fe. . . .28 la. . . .46 nrl W n ^Q 7/7) 57 7 Uil tlO SIl . . . O J //< ' aWf * i ca...20 /.... 18.7 li 7 pd ..26.5 sn. ..29.5 zn ...32.5 cb ...47 fe... 14 mg ..12 pb.. 103.5 sr....43.5 zr...22.5 69. To show the application of this system we here give the ordinary formulas of several well-known aluminisilicates, together with their formulas under the new notation : Anorthite Al 8 O 8 .2SiOj4- MO = aZ 8 o 8 si 4 o 4 .m 1 o 1 Leucite Al 8 O 8 .4SiO 8 + MO = a2 a o s si 8 o 8 .m 1 o 1 Albite Al 8 O 8 .6SiO 8 + MO = aZ 8 o 8 si ll o ll .m 1 o i Meionite 3Al 8 O 8 .6SiO 8 +4MO = aZ,o 9 si 18 o 18 .m 4 o 4 Garnet Al 2 O 8 .3SiO a +3MO = aZ 8 o 8 si 6 o e .m $ o 8 Zoisite 4A1 2 O 8 . 9SiO 8 +6MO = aZ 8 o 8 si 8 o 8 .m^ 44 Systematic Mineralogy. The new formulas, in which m = a monad portion of a monad 1 or diad base, corresponding to 8 parts of oxygen, will suffice to show the simplicity of the monadic notation here proposed ; which gives at once the oxygen -ratio, and distinguishes the monads and diads from the triad and tetrad elements. The numerical value calculated for the new formulas (0 = 8) divided by the sum of the oxygen co-efficients, gives the mean value (p) of the oxyd-unit ; which, in its turn, divided by d, the specific gravity (water = unity) gives the reciprocal of the co-efficient of condensation of the species (p -r- d = v). These monadic formulas may be farther condensed by uniting in one term the oxygen co-efficients, when albite will become a4 s iu m ii6> and meionite algSi^m^o^. In this way andalu- site and cyanite are a^si^y and topaz is a J si 2 (o 4 f 1 ). The farther applications of this notation will be considered at length in a sub- sequent chapter. 70. The specific gravity of the vapors of their volatile chlorids has served to fix the combining weights of many elements ; but it is to be noted that the densities of these vapors in many cases undergo, by changes of temperature, intrinsic homogeneous changes like the vapors of certain of the elements themselves. Thus, as is well known, the vapor of hexad sulphur, S 6 , passes at a higher temperature to a diad vapor, Sg, and diad iodine vapor, I 2 , to a monad vapor, I 19 the elements in both cases resuming the denser polymeric forms on reduction of temperature. Similar metamor- phoses are familiar in many composite species, and have been ob- served in several of the metallic chlorids ; frequently complicated, however, by partial heterogeneous decomposition, as a result of the elevation of temperature. Thus the vapor of ferrous chlorid preserves between 1300 and 1400 the normal density correspond- ing to FeCl 2 ; while ferric chlorid has at low temperatures the den- sity required by the formula Fe 2 Cl 6 , but is partly reduced by de- polymerization to FeCl 3 at 448. Above this point it undergoes a partial heterogeneous dissociation, a portion being converted into ferrous chlorid and free chlorine ; so that we have no longer Fe-jClg, but an admixture of FeCl 3 with FeCl 2 and Cl; about one-third being converted in ferrous chlorid at 750. The chlorid of gallium, Ga 2 Cl 6 , undergoes similar changes by heat, while indium yields not less than three distinct volatile chlorids, InCl 3 , InClg, and InCl 3 ;. thus presenting the characters alike of triad, diad and monad, although no oxygen or sulphur compounds corresponding to these diad and monad chlorids are as yet known. The Periodic Law. 45 71. Alumininic chlorid has, like ferric chlorid, a vapor-density at low temperatures corresponding to A1 2 O 6 , but a little below 835 attains the normal density of A1C1 3 . Above 935 it appears ta undergo a partial heterogeneous dissociation, like FeCl 3 , the liber- ated chlorine attacking the containing platinum vessel ; a reaction implying the production of a diad aluminous chlorid, A1C1 2 . The quantivalence of the elements thus appears to be a function of tem- perature ; heat, which is the general agent of dissociation or disin- tegration, breaking up the higher chlorids as well as the higher oxyds and sulphids. According to lately published observations by Hampe, it appears moreover that when cryolite, a crystalline compound of fluorid of sodium with aluminic fluorid, A1F 3 , is fused out of contact of air with metallic aluminium, a portion of this is taken up, and a new crystalline body is formed, in which the sodium fluorid is combined with aluminous fluorid, A1F 2 . The triad char- acter of Al under ordinary conditions is sustained by the late de- terminations by Combes of the vapor-density of the acetylacetonate,. which is that required by the formula A1(C 5 H 7 O 2 ) 3 . 72. The assumption that the characteristic monad, diad, triad and oxyds of the first three groups in the table of the periodic law rep- resent the maximum degrees of oxydation for these elements is not strictly true, since higher, though less stable, oxyds are known not only for the alkali-metals, but for Mg, Zn and Cd, besides a higher oxyd of Al. When we come to the tetrads of group IV., we find, besides the typical RO 2 , oxyds of tin, SnO 3 , and of zirconium Zr 2 O 5 and ZrO 3 . For the metals of the succession, Cr, Mn, Fe, etc., the number of higher oxyds is multiplied. Mn, Fe and Ru give rise to compounds corresponding to CrO 3 ; while for Mn the existence of a volatile oxyd MnO, corresponding to OsO and RuO, has been both affirmed and denied. 73. The distribution and the modes of occurrence of the chemi- cal elements in native mineral species may here be briefly con- sidered ; and to this end it is proper so far to anticipate the state- ment of the system adopted in the present treatise as to say that all mineral species are divided on chemical grounds into four great classes, designated : I., METALLACE^E ; II., HALIDACE^E ; III., OXY- DACEJE ; IV., PYRICAUSTACE^E. The first or metallaceous class embraces the metals and semi-metals with sulphur, selenium, phos- phorus and arsenic, and all their compounds with one another ; the second or halidaceous class includes all the compounds of the haloid elements, fluorine, chlorine, bromine, and iodine ; the third 46 Systematic Mineralogy. or oxydaceous class all oxydized species, except a few oxydized hydrocarbons which find a place in the fourth or pyricaustate and 5.20, for well-defined pyritohedral crystals. On the other had, marcasite itself may vary in specific gravity from 4.75 to abut 5.00 (4.987), with a hardness on the scale of Mohsof 6.0-6.5; wile the denser isometric species attains 6.5-7.0. The latter stikes fire strongly with steel, giving a faint sulphurous odor ; mrcasite, on the contrary, feebly, giving a strong odor. Differ- eces in color and in texture also distinguish the denser from the lijhter sulphide. A. A. Julien, who has lately examined this ques- tm with great care, concludes that we have in these minerals of itermediate density an intermingling of two disulphides of unlike egrees of condensation. Each of these species would thus be Amorphous, and might include admixtures of the other.* It is ifficult to conceive any other explanation of these facts, which are Tecisely what we should expect in the case of admixtures of poly- neric bodies like the hydrocarbons noted above. It will be found >hat an admixture of three parts of a disulphide of iron, sp. gr. 5.18, * A. A. Julien, N. Y. Acad. Sci., 1886. 1887, Vol. in., No. 12, Vol. IV., Nos. 3, 5, 6, 7. 70 Systematic Mineralogy. and two parts of one of sp. gr. 4.75, would give a mean sp. gr. of 5.00 ; which is that assigned by many observers to pyrite, and very near the maximum specific gravity of marcasite. Similar differences in density are met with among the ortfio- rhombic and isometric arsenides of cobalt, nickel and iron, rejre- sented by the general formula MAs^ as shown in safflorite And smaltite, verified by the recent studies of MacCay. Another jex- ample of the kind, uncomplicated by the question of dimorphism,, is seen in sodium chloride. Several careful observers concuf in giving for specimens of this substance at ordinary temperatures a sp. gr. of about 2.25 (2.20, 2.23, 2.26) ; and others, apparently equally worthy of confidence, have found about 2.00 (2.01, j.03, 2.06, 2.08), while the greater number of observations range f*om 2.14 to 2.20. These wide variations in density in such a famliar species are the more remarkable for the reason that the chloides of potassium and ammonium present no such notable variatbns. A similar condition of things is apparent in crystals of zircon, p,nd many other cases might be cited showing that we have, as in the case of the iron disulphides, variable admixtures of two minral species with the same centesimal composition but of unlike on- densation. 107. It will now be apparent that we have to deal with pro- cesses of condensation belonging alike to chemical species am to mineral species. Thus, for example, with acetylene, pentine nd their polymers, we have in each case chemical species havh a common centesimal composition with widely different co-efiicicits of chemical condensation, as is apparent when we compare tleir vapor-densities ; which, moreover, present no simple or appaimt relations to their specific gravities in the liquid or solid state. V"e may recall in this connection the already cited case of formalle- hyde of which the equivalent weight is fixed by its vapor-densty as well as by Raoult's method with those of xylose, glucose ad the related sugars and amyloid bodies ; species in which tie chemical condensation presents a very wide range. In these casjs we are enabled by vapor-density, by the cryoscopic method, or e'lb by direct chemical analysis, to determine the minimum value f the chemical integer, and in this latter way we are led to assign } many cases very elevated numbers, as seen in such compounds the cobaltamine salts and the polytungstates ; the simplest admi sible formulas of which give integral weights of thousands or ten of thousands. The Co-efficient of Condensation. 71 108. The cases which we have just considered show in chemical species of related centesimal composition, as in formaldehyde, xylose, glucose, the higher sugars, the dextrines and soluble starch,, integral weights rising from 30, 150 and 180 to numbers which cannot be less than thousands. These figures suggest for chemical species a range of integral weights which may conceivably rise to- that of the mineral species itself. Instead of being, as in glucose and other sugars, a multiple of the chemical integer by a high number, the co-efficient for the mineral species becomes a small one ; as in the case of the dextrines and soluble starch, or of the cobaltamines and the polytungstates. So far as is yet known, how- ever, there intervenes, in all cases, a greater or less polymerization, the study of which will be found to have important thermo-chemi- cal relations. If we consider the four groups of sugars represented chemically by xylose and arabinose (C 5 ), glucose (C 6 ), saccharose (C 12 ), and rani- nose (C 18 ), but having for the mineral species essentially the same specific gravity, assumed to be 1.5, we shall have for the co-effi- cients of the mineral species respectively the numbers 214, 180, 94 and 54, corresponding to a common integral weight, therefor, of 32,100 ; xylose being 214(C 5 H 10 O 6 ), glucose 180(C 6 H 12 O 6 ), etc. In the case of the volatile polymeric hydrocarbons already mentioned, octodecylene (CH 2 ) 18 , cerotene (CH^, and melene (CH^ assum- ing the specific gravities assigned for the solids, namely 0.19 '0.8$ and 0.89, to be correct we have respectively the co-efficients for the solid mineral species of 67, 48 and 45. Melene will be 45 (CH^, cerotene 48 (CH^, and octodecylene 67(CH 2 ) 18 . 109. The ammonio-cobalt salts, from the results of chemical analysis, have necessarily high integral weights for the chemical species, and have assigned to them densities of about 1.7-1.8 ; the former figure corresponding to an integral weight for the mineral species of about 36,380. The minimum chemical weight for the orthometaphosphate of luteocobalt ( = 2540) would demand a co- efficient for the mineral species of 14, since 14 X 2540 = 35,580. In like manner the soluble crystalline hydrous polyphosphotung- states have for sodium salts, according to Scheibler, specific grav- ities of 3.84-3.98, and for a barium salt 4.3. We find no determi- nation of specific gravity for the highly complex polyphosphovana- date to which Gibbs assigns a chemical weight of 20,058, and which, should its co-efficient of polymerization be 4, would have a specific gravity of 3.75, nearly. More or less uncertainty must,, 72 Systematic Mineralogy. however, still exist with regard to the true chemical formulas, and consequently to the integral weights of chemical species of such complex constitution as those now under consideration. Under the name of tungsten-bronzes have been conveniently included sev- eral anhydrous crystalline bodies, metallic in lustre, conductors of electricity, and highly electro-negative, which are nevertheless oxy- dized compounds of tungsten and an alkali-metal. The tungsten- bronze first described by Wohler is, in the opinion of Gibbs, prob- ably 16WO 3 .4WO 3 .7Na 2 O ( = 5002). To this has been assigned a specific gravity of 6.617 ; to another sodium species, 7.28 ; and to a potassic species, 7.60. 110. It will be clear to those who have followed the preceding argument, that in cases where neither the vapor-density nor the cryoscopic method can be invoked that is to say, in non-volatile and insoluble mineral species we have not the means of determin- ing the integral weight of the chemical species which by its subse- quent condensation generates such mineral species ; or of discover- ing whether this may have attained that condensation by a single step or by successive stages. Thus, by hypothesis, a solid like retene might be generated directly by the intrinsic condensation of acetylene, or from benzene ; the production of the latter hydro- carbon marking an intermediate stage in the progress of homo- geneous integration. What stages, if any, intervene in the passage from the soluble normal calcium carbonate to the insoluble crystal- line mineral species, calcite and aragonite, we may never know ; though from the existence of these two mineral species of identical centesimal composition, with different degrees of condensation and of solubility in acids, corresponding to the differences observed in the various polymers of many hydrocarbons, aldehydes, etc., we may with great probability suspect the existence of intermediate and unstable stages of condensation in calcium carbonate. The same argument applies equally to the unlike forms of silicon dioxide, tridymite and quartz, differing both in specific gravity and in solubility, to the two forms of iron disulphide, and to other cases too many to recall. 111. We can in very many cases recognize at least two distinct stages of polymerization in the passage of a given chemical species, either simple or compound, into a mineral species. The first stage is seen when the vapor of sulphur (S 2 ) passes by intrinsic condensa- tion into the denser vapor (S 6 ) ; gaseous acetylene into the vapor of benzene, of cinnamene, or of retene ; or when formaldehyde The Co-efficient of Condensation. 73 dissolved in water is changed to an aqueous solution of formose. The second stage is seen in the passage of the dense sulphur vapor, the polymerized hydrocarbon vapors, or the dissolved formose, into liquid or solid forms. For the great multitude of mineral species of which the corresponding volatile or soluble species are unknown to us, the means of marking these separate stages are wanting, and we have but two data : the specific gravity of the mineral species, water being unity, and the equivalent weight as deduced from the results of chemical analysis ; d = the specific gravity and p = the equivalent weight. This latter, for compound species, may be calculated from the simplest formula which represents intelligibly the results of such analysis, or as we have elsewhere proposed as the basis of a wider comparison which will include all metallic oxides, salts and haloid compounds by the adoption for p of a still simpler and an arbitrary unit. For all such species " we assume as the unit for p a weight including that of H = 1, of Cl = 35.5, or of O -T- 2 = 8. By thus adopting a combining weight of 8.0 for oxygen, we get a unit which gives a common term of comparison for oxides, sulphides, chlorides, fluorides ; and for intermediate compounds like the oxysulphides and oxyfluorides common in native species." 112. For the metalline species which constitute Class L, includ- ing unoxydized metals and their compounds with one another, and with arsenic, antimony, bismuth, sulphur, selenium and tellurium, it has been found more convenient to divide the formula by the sum of the valencies therein represented ; so that for all such species the unit p gives not the mean integral weight of an oxygen-com- pound in which O = 8, but that of the chemical element, corre- sponding to S = 16, to Fe = 28, to Ag = 108, to As = 37.5, Sb = 60, and Bi = 104 ; represented respectively by s to fej, ag t , as 1} sfy bij, in the monadic notation, pages 41-44. While gold and, in some cases, copper combine as monads, the lat- ter very often plays the part of a diad, as do the other metals, with few exceptions. Tin and germanium, molybdenum and platinum, however, appear as tetrads in their rare metalline compounds. The elements of the group consisting of nitrogen, phosphorus, arsenic, antimony and bismuth in many of their combinations with oxygen^ hydrogen and the halogens assume the part of triads and pentads. Their assumption of diad relations is, however, seen in oxyds and sulphids like NO, NS, NSe, AsS, SbTe, BiO, BiS, and also in PIjj, AsBr 2 and BiCl 2 . This diad character they apparently 74 Systematic Mineralogy. present alike in their elementary state and in their metallic com- pounds. 113. Since the arbitrary mean chemical unit p thus assumed rep- resents in all cases an aliquot part of the chemical species, however simple or however complex, which by its final intrinsic condensa- tion has generated the mineral species whose specific gravity (= d) is known, it follows that the equation p -f- d = v, giving in v the reciprocal of the co-efficient of condensation, permits a ready com- parison of the relative condensation in mineral species ; upon which,, as we have elsewhere endeavored to show, the hardness and the chemical indifference of solids depend. It will be remembered that p, which represents the equivalent weight of the chemical unit, corresponds, in the last analysis, to the specific gravity of that unit, presumed to be gaseous hydrogen gas at standard temperature and pressure being unity (H = 1) while d represents the specific gravity of the liquid or solid min- eral species, liquid water at its point of condensation at standard pressure being unity (1 = 21,400). The value deduced from this conventional p is readily adapted to any rational formula which may be admitted for the species in question. Thus quartz, repre- sented as silicon dioxide, SiO 2 = 60-4-4= 15 = JP/ and this being divided by 2.65, the specific gravity of quartz, we find v = 5.66, which for SiO 2 gives v = 22.64. We have then the proportion 22.64 : 21,400 :: 1 : 945. In other words, if simple silicon dioxide passes directly into the mineral species quartz, the co-efficient of condensation is approxi- mately 945, or perhaps 950 (SiO 3 ). Should it be found, as is proba- ble, that silicon dioxide in its soluble colloidal condition is a polymer of greater or less equivalent weight, represented by (SiO 2 ) 10 or by (SiOg)^ the above co-efficient therefor would be divided by these numbers ; the total co-efficient of mineral con- densation, comprising two or even more stages, being in each case the same. That its integral weight is very high would appear from the late experiments with Raoult's process by Sabaneeff ; who found the reduction of the freezing-point by colloid silica to be so slight that the values in all cases came within the limits of errors of observation ; * as would appear to be also the case with soluble starch. 114. To take another example, calcite, CCaO 3 = 100 -r- 6 = * Jour. Buss. Phys. Chem. Oes., 1889, p. 615 ; cited Am. Jour. Science, July, 1890, p. 87. The Co-efficient of Condensation. 75 16.66 = jt>. Dividing p by 2.73, as the specific gravity of calcite, we find v = 6.10 nearly, which for CCaO 3 gives v = 36.6, 36.6 : 21,400 : : 1 : 584. The condensation from CCaO s to calcite of specific gravity 2.73, is thus represented by 584(CCaO 3 ). Here, too, as in the case of silicon dioxide, it is probable that there exists an intermediate polymer, represented by a soluble form of carbonate of lime, long since noticed by the writer, and noticed in the next chapter. These numbers thus arrived at for quartz and for calcite are, of course, but approximations, since the exact equivalent weights of oxygen and of silicon are still uncertain, and since, moreover, there are small variations in the specific gravity of the mineral species themselves, from which Breithaupt with much plausibility conjectured, in the case of calcite, the existence of several species, rhombohedral in form, with specific gravities rang- ing from 2.652 to 2.754. At the same time we must not overlook the calcium carbonate, aragonite, harder and less soluble in acids, with a specific gravity of 2.94, showing a higher intrinsic conden- sation than any calcite. 76 Systematic Mineralogy. CHAPTER VII. THE THEORY OF SOLUTION. 115. It has been asserted in the preceding chapter, that liquid and solid species are, so far as known, always the result of polyme- rization ; and are generated from chemical species, which them- selves are either gaseous, or exist for the most part in a state of solution, water being the usual solvent. For a more complete understanding of this important question, it will be necessary to consider at some length the phenomena of solution. These were discussed by the writer in 1855 in an essay entitled "Thoughts on Solution and the Chemical Process," * and farther in a review of the subject in 1888, on "The Theory of Solution,"! from which extracts are here given. After showing the vague notions as to the nature of solution held by Berzelius, Dumas and Mitscherlich, and noting that Turner and Griffin had, among others, affirmed the chemical nature of solution, it was maintained that solution is chemical union, and farther that "all chemical union is nothing else than solution. The uniting species are, as it were, dissolved in each other, for solution is mutual." The same idea was expressed in 1874 by say- ing, " The type of the chemical process is found in solutions, from which it is possible, under changed physical conditions, to regener- ate the original species." It had already been said in 1853, "Solu- tion is the result of that tendency in nature which constantly leadg to unity, condensation and identification;" and further, "Solution is chemical union, as is indicated by the attendant condensation." 116. In support of this view, it was pointed out in 1855 that " aqueous solution presents all the phenomena of chemical combina- tion ; " among which were then enumerated " homogeneousness," " more or less perfect identification of volume," " the changes of temperature which attend the process," and also the " changes of color," seen in the solution of some compounds, as in the case * See the American Journal of Science for January, 1855, and the Chemical Gazette for the same year ; also the writer's *' Chemical and Geological Essays " (1874 and 1878, pp. 448-452). t Read before Section B of the British Association for the Advancement of Science* at Bath, September, 1888, and published in its Proceedings and in the Chemical News for October, 1888. The Theory of Solution. 77 of the chlorides of copper and nickel. It was further noted that " the liquid state of these combinations is often an accident of tem- perature. Alum, and the rhombic phosphate of soda, Na 2 HP0 4 .!OH 2 O, are liquids at 212 F, and the bihydrated sulphuric acid, H 2 S0 4 .2H 2 0, is a crystalline solid below 46 F." This was followed by an argument to the effect that the instability of some of these hydrous compounds is not to be urged against their chemical nature, " since chemical affinity may be very feeble in degree." It was further said, "the precipitation of the [hydrated] sulphates of cerium, lanthanum, and calcium from their solutions by heat, and that of most other salts by cold, is chemical decomposition." 117. The case of arsenic terchloride was then noticed, which unites with a certain amount of water, yielding a well-defined solu- tion, and subsequently, by the addition of a larger amount, is disso- ciated in a different sense, so as to give chlorhydric acid and ar- senic teroxide ; thus illustrating the theory of double decomposition. The capacity of sulphuric acid to combine with a great amount of water was next considered, Gay Lussac having shown that this acid will absorb from an atmosphere saturated with moisture fif- teen times its own weight, while, according to Griffin, the condensa- tion which attends the union of sulphuric acid with water is still perceptible with 6000 equivalents of water to one of acid. It was then added, "there appears, however, to be with many bodies a limit beyond which the affinity for water is satisfied. The liquids, being then mechanically intermixed, gradually separate by reason of their difference in density, as is observed in dilute alcohol, and probably in some saline solutions and in metallic alloys." Refer- ence was then made to the statements on this point to be found in " Gmelin's Handbook of Chemistry," * and also to some later statements with regard to the asserted separation of dilute alcohol into layers of greater or less hydration. 118. The theory of solution thus advanced, embraces : 1st. The conception that in the process of aqueous solution there are formed definite compounds with water, accompanied with all the phenom- ena of chemical union. 2d. That in these compounds of a single proportion of a salt or other species with many proportions of * Cavendish Society's Ed., i., p. 111. 78 f Systematic Mineralogy. water, there are definite limits beyond which the further addition of water gives rise (A) to decomposition, involving a new arrange- ment of the elements of the previously united bodies (double de- composition) ; or (B) to simple admixtures of one definite solution or liquid species with another less dense solution, or with water. 3d. That these compounds are separable in a solid state by changes of temperature, or (theoretically at least) in a liquid state by the influence of gravity. 4th. That liquidity is but an accident of so- lution, since it is a state depending on temperature and on pressure ; which state may be assumed by all species, whether elemental or compound. 119. The recent studies of Traube and Neuberg* have confirmed the previous observations of Bodlander, showing that solutions of ammonium sulphate in dilute alcohol separate spontaneously, by augmentation of temperature, into layers of unlike densities ; the proportion of alcohol increasing and those of water and sulphate decreasing in the upper layer. Similar results are got with alcoholic solutions of other sulphates, with phosphates and carbonates, and with the hydroxides of potassium and sodium. Examples of admixtures of aqueous solutions are seen in the case of phenol and water, which when heated mix in all propor- tions, but on cooling separate into two layers, the lower a solution of phenol in water, and the upper a solution of water in phenol. Aniline, and many other bodies present similar reactions with water below 100 C., and like results are got through the agency of press- ure at still higher temperatures. Thus salicylic acid heated with water in a sealed tube to above 100 gives a solution which separates suddenly, on cooling to 91, into two layers ; each of which, accord- ing to Alexeeff,t grows turbid independently as cooling goes on. 120. According to the observations of Messrs. Hannay and Ho- garth a saturated alcoholic solution of anhydrous calcium chloride, when heated under pressure, separates at 230 into a lighter and a denser layer, which latter at 255 dissolves, but reappears when the pressure is taken off. Regarding this they remark that " a combination of the chloride with part of the alcohol evidently occurs, and at a higher temperature diffusion takes place until the fluid is quite homogeneous." Similar phenomena were observed with the alcoholic solution of ferric chloride. They found, moreover, that (as already noticed in 34) alcoholic solutions of potassium * Zeit. Physikalisch Chem., i., 509-515. t Butt. Soc. Chim., II., 38, 145. The Theory of Solution. 79 iodide, and of the cobaltous and ferric chlorides, among others, pass integrally, at temperatures somewhat above the critical point of pure alcohol, into dense vapors, which, in the case of the chlorides named, retain their characteristic colors ; while the absorption- spectrum of cobaltous chloride, as well as that of an alcoholic solu- tion of chlorophyll, remains unchanged above the critical point. More than this, it was found that the dense vapor of alcohol at 300 dissolves solid potassium iodide. These remarkable observa- tions, which seem to show the integral volatilization of solutions, and their passage into dense polymeric vapors, as well as the solu- bility of solids in such vapors, and the separation of apparently homogeneous solutions, at elevated temperatures under pressure, into distinct layers of different densities, deserve more attention than they have yet received from chemists.* 121. In "A New Basis for Chemistry " the question of solution has been considered at some length. The views of Guthrie and of Spencer Pickering on so-called molecular equivalents are there discussed, together with the bodies described by the former as cryohydrates and sub-cryohydrates. These, it is said, may be re- garded as " very fusible definite crystalline compounds containing many portions of water to a single portion of a salt or alkaloid." Contrary to the view maintained by Guthrie that in these com- pounds the " constituents are not in the ratio of any simple multiple of their chemical equivalents," it is maintained that their composi- tion does not present " a deviation from the law of definite propor- tions," but " is only an expression of that law in a higher form." It is there further said, " Messrs. Tilden and Shenstone, in their studies of the great solubility in water of salts when near their melting-points, have described compounds which, unlike the cry- ohydrates, are homogeneous liquids, containing, in the case of somewhat fusible compounds like silver nitrate and benzoic acid, very small proportions of water ; from which the experimenters are led to conjecture for bodies an indefinite solubility in water under proper conditions of temperature and pressure. f It is, how- ever, easy to understand from the high equivalent weights of such dense liquids (which from their viscosity are probably colloidal) that compounds with water may exist in which the proportion of the latter, though definite, is so small a fraction that it would be * See Hannay and Hogarth, Chemical News, xli., p. 103, and Proc. Roy. Soc., xxs., pp. 178, 484 ; also Ramsay, ibid., p. 334. t Philosophical Transactions, 1884 ; Part I., pp. 23-36. 80 Systematic Mineralogy. neglected in the ordinary processes of analysis. . . . These two cases of apparently homogeneous compounds on the one hand, liquids existing at high temperatures, with very small proportions, and, on the other, solids at low temperatures, with very large pro- portions of water are alike illustrations of the complex form- ulas and high equivalent weights which we have so long main- tained." 122. In connection with the studies of Tilden and Shenstone, the writer has elsewhere recalled* the fact of the existence of combined hydrogen in many ignited bodies at the atmospheric pressure. Such are the hydroxides of barium, sodium and potas- sium, and certain vitreous borates of the latter metals, long since described by Laurent, which, at a red heat and in tranquil fusion, hold an amount of hydrogen equal to 1.2 and 1.3 percent, of water. The presence of water in talc, and even in epidote, beryl, and eu- clase, is well known, while perlite and pitchstone are hydrous glasses differing from obsidian in containing from 2.0 to 8.0 per cent, of water. All of these are examples of the stability at elevated temperatures of solid compounds in which water exists dissolved that is to say, chemically combined. They differ in degree only from the hydroxide of magnesium, or from zeolites like laumontite, and salts like the efflorescent hydrated sodium carbonate and borate. 123. Many points in the theory of solution are well illustrated by the example of sodium sulphate. This is found to be most soluble at 20, when 100 parts of water dissolve 52.76 parts of the anhydrous salt, yielding a solution which possesses a certain de- gree of stability, and retains its liquid form at ordinary tempera- tures in closed vessels, but by agitation is readily changed in great part into crystals of the decahydrate, Na 2 SO,.10H 2 0, having a specific gravity of 1.47 to 1.48 ; which contain for the 52.76 of sodium sulphate 66.80 parts of water, or more than two- thirds of the solvent liquid. This hydrate has its point of maxi- mum solubility in water at 34, while that for the anhydrous salt, as we have seen, is 20. The crystallized decahydrate is slowly changed at 34 into a liquid ; melting in its water of crystallization. From this liquid, as from the original solution, by a reduction of * " Mineral Physiology and Physiography," pp. 219-223. The Theory of Solution. 81 temperature, or by contact with alcohol, crystals of a new com- pound, the heptahydrate, are deposited. These, which are much harder than the last, are very unstable, and, after removal from the liquid, become milk- white by a heat of 15, or by contact with a foreign body, and are changed, with a considerable rise of temperature, into an admix- ture of the anhydrous and the decahydrated sulphate. This latter, in dry air at ordinary temperatures, loses its combined water, and passes into the anhydrous salt. A similar decomposition also takes place when a saturated solu- tion of sodium sulphate is heated above 40 ; crystals of the hard and very dense anhydrous salt specific gravity 2.64 to 2.73 being deposited. These are more or less completely re-dissolved on cooling, until the temperature reaches 18, when the formation of crystals of the heptahydrate begins, and the previously separated anhydrous sulphate itself is gradually converted into the same hy- drate. When a liquid containing an excess of crystals of the heptahydrate is heated to 27, these melt, like those of the decahy- drate, and the solution will then yield crystals of the anhydrous salt. From all these facts Lowel concluded, in 1857, that sodium sulphate exists in three distinct forms in aqueous solutions ; namely, as a decahydrate, as a heptahydrate and as the anhydrous salt.* The decahydrate is readily dissociated below 34 into heptahydrate and water, and above 34 into the anhydrous salt and water ; while the unstable heptahydrate is itself readily transformed into an admixture of the anhydrous salt and the decahydrate. 124. We may regard the various liquids obtained with sodium sulphate and water as liquid forms of the decahydrated, the hepta- hydrated and the anhydrous sodium sulphate, intermingled with water, or, at certain transition temperatures, with each other. From such admixtures any one of these sulphated species may not only separate, under slight provocation, in a crystalline form, but also under favorable conditions (which for obvious reasons are not easily attained in practice) in a liquid form, under the influence of gravity, as already suggested. In this view of solution, there is not only in change of pressure (as long since shown by Sorby), but *For the data here employed the reader is referred to " Watts's Dictionary of Chem- istry," sub voce, Sulphates of Sodium, and also to Lowel's paper in the Ann. de Chimie et de Physique, xhx., 32-58. 82 Systematic Mineralogy. in change of temperature, in evaporation, in dilution, and in crys- tallization, a constant making and unmaking of chemical species. In the mingling of liquids, wherever change of volume is apparent, chemical change is going on. When that ceases it may be assumed that admixture takes the place of solution. All precipitation and all crystallization from solution thus involve chemical change ; and all chemical species may theoretically exist in soluble states, from which they pass into polymeric mineral species, often insoluble. 125. Solution being as above defined, chemical union, and the liquid condition, as distinguished from the gaseous or the solid con- dition, but an accident dependent upon temperature and pressure, the solubility of any body in a liquid such as water is simply an evidence of its capacity to form a liquid combination, more or less stable, with water. A great many species exhibit a temporary solubility in water, so that when generated in aqueous mixtures they remain for a longer or shorter time in solution before sepa- rating in an insoluble condition. Examples of this are seen in gypsum, in strontium sulphate, and in ammonio-magnesian phos- phate ; while the existence of modifications very soluble in water of the oxyds of silicon, titanium, tin, tungsten, and of aluminic, chromic and ferric oxyds is well known. The evidence furnished by the modes of occurrence of many of these crystallized oxyds, as well as of silicates, sulphids, arsenids, etc., in veinstones, shows that under certain conditions these also have been held in aqueous solution. 126. Some illustrations of the temporary solubility of carbon- ates may here be given. As long since described by the writer, on adding a solution of sodium bicarbonate to carbonated water hold- ing calcium and magnesium chlorids, there are obtained super- saturated solutions, containing at the ordinary temperature and pressure from 3.4 to 4.1 grams of calcium carbonate to the litre. These solutions, however, after a few hours, spontaneously deposit the greater part of this in a crystalline form (accompanied with about 3.0 per cent, of magnesium carbonate) ; the liquid, though charged with carbonic acid, retaining in permanent solution only about 0. 8 grams of calcium carbonate. In like manner supersaturated solutions may be prepared containing of ferrous carbonate, at the ordinary temperature and pressure, 5.0 grams, of which two thirds are spontaneously deposited, after several hours of repose in closed vessels, as a white crystalline hydrated carbonate.* * "The Genesis of Certain Iron Ores," Can. Naturalist , 1880 ; new series, ix., 431. The Theory of Solution. 83 127. Supersaturated solutions of carbonates may also be got with- out any excess of carbonic acid. It was found that the recent pre- cipitate produced by a solution of sodium carbonate in one of cal- cium chlorid is readily soluble in an excess of the latter salt, or in a solution of magnesium sulphate. The transparent, almost gela- tinous magma which results when the above solutions are mingled is immediately dissolved by a solution of magnesium sulphate. In this way it is easy to obtain solutions holding besides three or four hundredths of hydrated magnesium sulphate, 0.8, and even 1.2 grams of calcium carbonate, besides 1.0 gram of magnesium car- bonate to the litre ; the only other substance present being the sodium chlorid equivalent to these carbonates. Such a solution has an alkaline reaction, and is tolerably permanent. After eighteen hours of repose it still held 0.72 grams of calcium carbonate, but after a few days deposited the whole of this in transparent crys- tals of the penta-hydrate ; retaining, however, all its magnesium carbonate, which was precipitated in large part by boiling. The addition of alcohol in the cold at once throws down from these supersaturated solutions the whole of the calcium carbonate. This solubility of the yet uncondensed carbonate in neutral solutions, which are without action upon it after it has passed into a crystal- line form, is an example of the so-called nascent state. It was said in 1872, "it will probably one day be shown that for the greater number of those oxygenized compounds which we call in- soluble, there exists a modification soluble in water." Later results have justified and still farther extended this conclusion, since modi- fications of sulphids previously described as insoluble, of sulphur itself, and even of metallic silver, soluble in water, have been ob- tained. Theoretically, all substances, whether elementary or com- pound, may exist in a gaseous or a soluble form, and it is this con- dition which constitutes the nascent state of bodies.* 128. Views similar to these as to the nature of solution have since 1886 been ably maintained by Mendel jeff, who recognizes the fact that aqueous solutions are definite chemical combinations, which in many instances can be got in crystalline condition by reduction of temperature ; as in the case of the compounds of alcohol and of sulphuric acid with water. Evidences of such definite combina- tions of these existing in the liquid state are obtained by the study * " On Lime and Magnesia Salts," Amer. Jour. /Set., 1866, vol. xlii.; "A New Basis for Chemistry, 1 ' pp. 98-98, also " Mineral Physcology," etc., pp. 167-169. 84 Systematic Mineralogy. of their densities, and in other cases from the variations in elec- trical conductivity. * 129. The observations of Tilden and Shenstone cited above, to the effect that small portions of water uniting with saline bodies give rise to compounds which are liquid at temperatures much below the point of dry fusion, have an important bearing on the part which water is supposed to play in plutonic and volcanic phenomena, where it is known to exist with silicated rocks, under strong pressure at high temperatures. "From this union there result hydrated compounds, which are more fusible than the anhy- drous rocks, and are decomposed in the transformations that take place during the cooling, with diminution of pressure, which accom- panies the eruption of these materials. The water thus set at liberty may be disengaged in vapor, and with it certain other volatile matters met with in volcanic emanations. In other cases, however, under a high pressure still maintained, and at a tempera- ture above the critical point of vaporization, the water may be liberated in the state of a dense polymeric vapor, holding in solu- tion mineral matters which, through cooling, are at length deposited either from the vapor itself, or from the liquid resulting from its condensation, as crystalline species." f 130. Similar facts to those observed by Tilden and Shenstone are known in other combinations into which water does not enter. The great fusibility of many metallic alloys, and the effect of small quantities of carbon in reducing the fusing point and other- wise modifying the characters of iron, are familiar examples. Regarding all cases of so-called solution as chemical union, we may notice the existence of compounds, apparently homogeneous, of iron, not only with carbon, but with small portions of silicon, of sulphur, of phosphorus, of chromium, of manganese and of nickel ; which change notably the characters of the iron. Similar to these are the solution of oxygen in molten copper and in molten silver. Many of these compounds are stable only at certain high tempera- tures, and are dissociated on cooling ; as when the dissolved oxygen is given off from silver during its solidification. Ordinary carbu- retted cast iron, which under certain conditions solidifies into a very hard, white, brittle crystalline carbide, under others is dissoci- * See in this connection farther the author's paper on " The Theory of Solution," cited above; also Ostwald's "Zeitschrift fiir Physikalische Chemie," 1887, p. 379 ; and Trans. Chem. Soc. of London, Oct., 1887, p. 778; farther, Crompton on "The Electrical Conductivity of Aqueous Solutions," ibid., Jan., 1888. t See the author's essay (in French), " Les schistes cristallins," read before the Inter- national Geological Congress, in London, September, 1888, and published in the Transac- tions thereof ; also in an English translation in Nature^ for Sept. 37, 1888. The Theory of Solution. 85 ated into a mixture of soft gray iron, with intermingled crystalline plates of metalloidal carbon or graphite ; which are again readily taken into combination on the application of heat, and reproduce the carburetted iron. The examination of ingots of cast iron or of steel shows a segregation of certain constituents from the mass during the process of cooling ; while variations in the composition of different portions of ingots of alloys, as those of silver and copper, give evidence that the separation of mixtures noticed in the case of aqueous and alcoholic solutions, by the influence of gravity, comes into play also in fused and slowly cooling metals. 131. Another remarkable example has lately been noticed by Moore in the case of a molten nickel-iron regulus, containing twenty- five per cent, of sulphur, from which during slow cooling there crys- tallize out brilliant plates, malleable and ductile, of metallic nickel alloyed with a little iron ; the result of dissociation during cooling of a sulphid containing more nickel than it could retain in solution.* The separation of metallic copper in filaments, known as moss copper, from copper regulus, which is a similar rich sulphid, is another case in point ; and the writer has long since described a copper matte which was found to contain magnetite in grains, to- gether with metallic iron and sulphid of copper ; products formed by the dissociation in cooling of a fluid molten regulus got from the smelting of roasted cupriferous pyrites. This matte held forty- five per cent, of copper, with a little zinc, and was strongly mag- netic. When oxydized by nitric acid or by bromine it left more than ten per cent, of pure magnetic oxyd of iron. It moreover precipitated freely metallic copper and lead from solutions of these metals, and gave up to dilute acids the larger part of its iron, with evolution of free hydrogen and hydrogen sulphid gases ; the latter apparently formed by the action of nascent hydrogen upon the metallic sulphid. From all these observations the finely granular matte was regarded as an intimate mixture of metallic iron, mag- netite and sulphids.f Without extending farther the discussion of similar facts it will be evident that we may have in liquids, whether they be aqueous solutions or the results of igneous fusion, more or less com- plex combinations, which are subject in many cases to dissociation in cooling ; and that through change of temperature there is, as has been already said, a constant making and unmaking of species. * Chemical News (1887), Ivi., 3. + Trans. Amer. Assoc. Adv. Science, 1873, p. 143 ; also, " New Basis for Chemistry," p. 164. 86 Systematic Mineralogy. CHAPTER VIII. BELATIONS OP CONDENSATION TO HARDNESS AND INSOLUBILITY, 132. From the nature of the process of condensation involved in chemical union, by which a greater or less number of volumes is condensed into a single volume, it follows that specific gravity in solids and in liquids, as well as in gases and vapors, will vary directly with their integral weights. Other and not less important results follow from this process ; since, other things being equal, the hardness or mechanical resistance to abrasion augments with increased condensation. Hence the value of v, which is the recip- rocal of the co-efficient of condensation, will be found to diminish with the increase of hardness of the species. This is conveniently represented on the scale of Mohs, in degrees from 1 to 10 ; in which 1, talc ; 2, gypsum ; 3, calcite ; 4, fluorite ; 5, apatite ; 6, orthoclase ; 7, quartz ; 8, topaz ; 9, corundum ; 10, diamond. The scale proposed by Breithaupt, in which the same range is divided into twelve in- stead of ten parts, is seldom used. 133. The resistance of bodies to chemical change or change of state, that is to say, to fusion and volatilization ; and farther to the chemical action of various reagents, such as water, acids and alkalies, will be found to vary, in like manner, with the condensa- tion. This is so far true that W. Spring, in speaking of the more condensed and comparatively inactive red phosphorus as compared with the ordinary fusible, volatile, colorless and active species, aptly speaks of it as a deadened body (un corps amorti). The occurrence of similar changes connected with condensation in vari- ous compounds has not escaped the attention of chemists. Gmelin notes the vivid incandescence from internal change which takes place when many amorphous bodies are heated to low redness ; by which process they acquire " greater specific gravity, greater hard- ness and less solubility." This change is observed in titanic, tan- talic, molybdous, chromic, and ferric oxyds ; in magnesium pyro- phosphate, and in certain artificial arsenates and antimonates, as well as in native minerals like euxenite, gadolinite and allanite. Such as these were called by Scheerer pyrognomic species, and were adduced by him as evidence that the granitic veinstones in which they are found were not formed at very elevated tempera- Relations of Condensation to Hardness, etc. 87 tures. The change is not connected with loss of volatile matter, since water, and in the case of ammonio-magnesian phosphate, the ammonia itself may be expelled, without affecting the change marked by incandescence ; which only takes place at a higher tem- perature.* 134. In considering, in 1863, the question of differences in con- densation as exemplified between the various carbon-spars, horn- blende and pyroxene, tibrolite and cyanite, and especially between meionite and zoisite, it was said, "the augmentation in density, in. hardness, and in chemical indifference ... is doubtless to be ascribed to a more elevated equivalent, or, in other words, to- a more condensed molecule. "f Again, in 1867, in discussing these and other examples in mineral species, it was said, " the hardness of these isomeric or allotropic species, and their indifference to chemical reagents, increase with their condensation, or, in other words, vary inversely with their empirical equivalent volumes ; so- that we here find a direct relation between chemical and physical properties."]; The conclusion then reached was, in fact, that for re- lated solids, hardness and chemical indifference increase with thecon- densation of the species ; or, in other words, vary inversely as the empirical equivalent, or so-called atomic volume, represented by v .- atomic weight . , p V^ = atomic volume = -^- = v. specific gravity a This is in accordance with earlier observations as to the tenacity and hardness of metals and alloys. Wertheim, from his experi- ments, concluded (as had Guyton Morveau long before) that the order of the common metals for tenacity and for hardness is prac- tically the same, and announced in 1841 that the tenacity varies directly as the quotient of the specific gravity divided by the atomic weight : specific gravity _ d 1 atomic weight p v ' This conclusion was confirmed by the studies of Calvert and Johnson, in 1859, on the hardness of metals and alloys ; by those of * See in this connection Gmelin's Handbook, Cavendish Soc. ed., I., 106, 107 ; also- the writer's "New Basis for Chemistry," p. 88. t Comptes Rendus de VAcad. des Sciences, June 29, 1863 ; and in English, Amer. Jour. Science, xxxvi., 426. t Amer. J&ur. Science, xlviii., 203. See further, "A New Basis for Chemistry," Chap- ter VII., and also Appendix to the 2d edition. 88 Systematic Mineralogy. Karmarsch on the tenacity of metallic wires ; and by those of Bot- tone, in 1873, also on the hardness of metals ; the latter maintain- ing that for homogeneous bodies of uniform texture, the hardness and tenacity vary together, in accordance with the law enunciated by Wertheim. The law thus arrived at by various investigators for the hardness and tenacity of metals and alloys is identical with that independently deduced, not only for the hardness but for the indifference to chemical changes, of related silicates, carbonates, and oxides. 135. This subject, which is one of great significance, will be more fully illustrated farther on in describing the various orders of minerals, but a few examples may here be given. Thus, in the metals, the hardness, infusibility and resistance to chemical action will be found to diminish rapidly with the diminution of the co- efficient of condensation, or, in other words, with the increase of the value of v, calculated in the manner above described ; the differ- ences being the more striking for the reason that among these elementary species we have the widest range of physical and chemical characters known among solids. Taking the equivalent weights already given in the table of the periodic law (page 30), and the best determinations of specific gravity, we find for the light, soft, readily fusible and very oxydable alkali-metals, the following values for v: caesium, 70; rubidium, 56; potassium, 44; sodium, 24; lithium, 12. Barium gives 36.5; strontium, 34.9; cal- cium, 25.4; magnesium, 13.8; and the hard and refractory beryl- lium somewhat less than 5.0. For copper we have 7.2; silver, 10.2; gold, 10.2; solid mercury being 13.9; lead, 18.1; thallium, 18.1; cadmium, 12.9; aluminum, 10.6, and zinc 9.1. Tin in its white malleable form (sp. gr. 7.3) gives for v = 16.1, and in its gray brittle state (sp. gr. 5.8) = 20. Passing to the harder and less fusible metals, chromium, manganese, iron, cobalt and nickel, we have for v numbers from 6.7 to 7.7. Of the six metals of the platinum group, the three having specific gravities of about 12, namely, ruthenium, rhodium and palladium, give for v values from .4 to 9.2 ; and the denser ones, osmium, iridium and platinum, with specific gravities 21.5-22.5, give 8.6-9.1. If, however, remem- bering that these harder and heavier metals generally act as diads and tetrads, we divide, in accordance with the plan adopted below in the case of their oxydized compounds, the value of v for the iron group by two, and of the platinum group by four, we shall have for the first, values of from 3.4 to 3.8, and for the second, 2.1 to 2.5. Relation of Condensation to Hardness, etc. 89 We find for bismuth 21.1, for antimony, 17.9, and for crystalline arsenic, 13.2, and the same value for crystalline metallic phos- phorus ; while for colorless non-metallic phosphorus v = 17.0, and for amorphous arsenic about 16.0. It is well to note in this con- nection the two crystalline forms of carbon. Of these graphite, which may be defined as a metallic state of carbon, with sp. gr. 2.25, gives for v = 5.3 ; while the non-metallic diamond, with sp. gr. 3.5, gives v = 3.4. 136. Passing now to complex species, we revert for our calcula- tions to the monadic notation, and to the values for p as set forth in 69. For the sparry carbonates, (CMO 3) ) calcite, CCaO 3 = 100 -j- 6 = p = 16.66, which divided by the specific gravity, d = 2.73, gives for the value of v 6.1. For dolomite, chalybite and diallogke, v = 5.2, for magnesite and smithsonite, v = 4.7, and for aragonite, v = 5. 7, nearly. A similar mode of calculation is applied to silicates and oxyds. Passing from the above carbonates to the corresponding sili- cates, SiMO 3 , we have in the calcium silicate, wollastonite, specific gravity 2.92, a value for v = 6.62 ; for the manganese silicate, rhodonite, sp. gr. 3.68, v = 5.92. For tremolite, and various other amphiboles, the value of v is about also 5.7 to 5.9 ; while for the species of pyroxene it is from 5.4 to 5.5. Of these various silicates, wollastonite is readily decomposed by chlorhydric acid, while rhodonite and amphibole are slightly attacked thereby, and the pyroxenes still less. Of the two silicates, zoisite and meionite, which, if not isomeric, are, very nearly so, the harder species, zoi- site, which resists the action of chlorhydric acid, has v = 5.3, while the softer species, meionite, which is readily attacked by the same acid, has v = 6.5. Of the two crystalline forms of silicon dinoxyd, quartz has for v = 5.65, while tridymite (sp. gr. 2.3), gives v = 6.52. Of these, the latter is readily soluble in a boiling solution of sodium carbonate, by which quartz is scarcely attacked. In farther illustration of these differences, it may be noted that the value of v as above calculated for various feldspars and scapo- lites, equals 6.8-6.2 ; for the micas, 5.9-5.6 ; for garnet, epidote and tourmaline, 5.4-5.1 ; for staurolite and spodumene, 4.9 ; and for andalusite, topaz, fibrolite and cyanite, 5.0-4.5, approxi- mately. In the subaerial decay of crystalline rocks, while feld- spars and scapolites among aluminiferous silicates are kaolinized, the micas, notwithstanding their laminated structure, are much less readily changed ; and garnet, epidote, tourmaline, andalusite, and 90 Systematic Mineralogy. topaz are found unaltered, with the quartz, corundum, spinel, cassi- terite and magnetite left behind by the decay of the feldspathic rocks ; a process in which even amphiboles, pyroxenes, and chryso- lite share. " The greater stability of those [silicates] which belong to the more condensed types is shown in their superior resistance to decay, and is thus of geological significance." 137. In the cases already cited in 133, it has been shown that many substances at a low red heat undergo condensation, becoming at the same time harder and less soluble. In others, however, a high temperature, especially if carried to the point of fusion, pro- duces a contrary result. Thus quartz when fused yields an un- crystalline glass having a specific gravity of about 2.22, which, like tridymite, is readily soluble in a boiling solution of sodium carbonate. It even undergoes a partial change of this kind by long exposure to a high temperature below its point of fusion. Zoisite, garnet, idocrase, beryl, and many other dense adman- toid silicates, are by fusion changed in like manner into softer and less dense states. Thus zoisite, or rather, saussurite, specific grav- ity 3.4, melts into a soft glass, with specific gravity 2.8, and after strong ignition, even without fusion, becomes partially soluble in acids, which had previously no action upon it. So epidote by ig- nition has its specific gravity reduced from 3.40 to 3.20 ; while the specific gravity of garnet is reduced one fifth by fusion, and that of idocrase from 3.34 to 2.94. Beryl, specific gravity 2.65-2.69,. fused before the oxyhydrogen blowpipe, gives a clear glass, scratched by quartz, with specific gravity 2.42. The change of state which these various silicates and quartz undergo by the action of heat shows that they have not been formed by igneous fusion, nor yet at very high temperatures ; while the increased solubility which is attendant upon their thus diminished condensation finds very many illustrations, some of which will be given farther on. 138. The sparry carbonates, noticed above, afford remarkable il- lustrations alike of augmenting hardness and increasing insolubility with the diminution of v. The readiness with which even dilute acids in the cold attack calcite is well known, while aragonite is less readily attacked thereby ; dolomite, chalybite, and diallogite, which are harder, present a greater resistance to acids ; while the still harder and more condensed magnesite and smithsonite ara scarcely attacked by the same acids except when aided by heat. By the use of cold dilute acetic acid, as first pointed out by Karsten, or of carbonated water, the writer has found it possible to effect Eelation of Condensation to Hardness, etc. 91 separations of calcite, dolomite and magnesite with approximate accuracy.* According to the observations of Bischof, a limestone containing 11.5 of magnesian carbonate gave to the prolonged action of water saturated with carbonic acid abundance of carbonate of lime, but no carbonate of magnesia. In experiments by the writer upon a pure dolomite, either alone or intermingled with carbonate of lime, a slight solvent action was noted, the proportions dissolved from an admixture of equal parts of carbonate of lime and dolomite being as 24 : 1. 139. A series of studies on the action of vegetal acids and some other solvents on various mineral species, made a few years since by Dr. H. Carrington Bolton, is very instructive in this con- nection ; and the more so as his extended researches, although undertaken without any reference to the question of condensation, furnish remarkable confirmations of the observations already an- nounced, and of those to be considered subsequently. Bolton, in fact, published in 1877 and 1880 tne results got by the action of such acids, and especially of citric acid, which he found to be the most efficient, chiefly upon native oxydized species, both in the cold and at the temperature of ebullition. He farther studied the effect of solutions of citric acid mixed with nitrate of sodium, with fluorid of ammonium, and with iodid of potassium, and extended his experiments to the action of iodine itself, in the presence of water, upon metalline species. The object proposed in all these investigations was, as he tells us, "the practical application of these methods to the examination of minerals in the field." f He found the action of a saturated solution of citric acid in the cold to be nearly as potent as that of chlorhydric ; and to a less degree, and in the order named, that of tartaric, oxalic, malic and other vegetal acids. While calcite is readily attacked by the citric solution, smithsonite is, like diallogite and dolomite, feebly attacked; magnesite and siderite apparently resisting its action. Of oxyds, citric acid dissolves brucite in the cold, and zincite and cuprite on boiling ; while hematite, magnetite, franklinite and chromite, like corundum, spinel and chrysoberyl, are not attacked thereby. The oxyds of manganese decompose the citric acid with disengagement of carbonic dinoxyd. * "On the Salts of Lime and Magnesia," Amer. Jour. Science (1859), vol. xxviii., part III., 28-42 ; ibid. (1866), vol. xlii., 70-80, 103-110. t Bolton, " The Application of Organic Acids to the Examination of Minerals," part i., 1877. Annals N. Y. Acad. Sciences, Vol. L. ; and part ii., ibid., ii., 1880. Also a Table of Results, 1880, and "The Behavior of Natural Sulphids with Iodine and Other Reagents," 1877. Annals, Vol. L 92 Systematic Mineralogy. 140. The same acid in the cold attacked the following silicates, those named in italics being completely decomposed : pectolite y apophyllite, calamine, rhodonite, willemite, wollastonite, laumon- tite, thomsonite, natrolite, mesolite, lapis lazuli, nephelite, pro- chlorite, chrysocolla. By boiling citric acid datolite was completely decomposed, while tephroite, ilvaite, serpentine and chrysolite were more or less acted upon, and prehnite, phlogopite, gieseckite, jeff- erisite and masonite were feebly attacked. Elsewhere we are told by him that chrysolite, chondrodite, prehnite are " hardly attacked by citric acid alone ; " and we have no quantitative results, save for those species already noted as completely decomposed by the acid. Farther we learn that diopside, asbestus, talc, the various feldspars, leucite, wernerite, iolite, petalite, idocrase, zoisite, tourmaline, staurolite, biotite, muscovite, lepidolite, ripidolite, andalusite, fib- rolite, cyanite, topaz, zircon and kaolin are not attacked by citria acid even when heated. As regards native sulphids, galenite, stibnite, pyrrhotite and sphalerite are slightly attacked by a solution of citric acid even in the cold, with disengagement of hydrogen sulphid, but more rapidly when heated. The same is true of bornite, and to some extent of bournonite. Pyrite, marcasite, argentite, chalcocite, chalcopyrite, molybdenite, cinnabar, niccolite, smaltite, ullmannite, arsenopyrite and tetrahedrite resist the action of citric acid. Pyr- rhotite may thus be distinguished from pyrite, and bornite from chalcocite or chalcopyrite. Alabandite is readily attacked in the cold, and by heat is completely soluble. The arsenids, clausthalite and leucopyrite are completely dissolved by citric acid in the cold, without liberation of gas. 141. The action of the nitro-citric and iodo-citric mixtures, as studied by Bolton, is complicated by other affinities than those of the acids for bases, and is of less significance than the preceding ; while the mixture of citric acid with ammonium fluorid, liberating fluorhydric acid, attacked more or less various silicates not acted upon by citric acid alone. The iodo-citric mixture attacks, even in 'the cold, stibnite, argentite, chalcocite and sphalerite, and with the aid of heat completely decomposes galenite and cinnabar ; molyb- denite, however, resisting. When placed in contact with iodine and water, the pulverized sulphids, stibnite, argentite, galenite, cinnabar and sphalerite are easily attacked, and by heat are completely decomposed. Bornite also is readily acted upon, and gives by heat an abundant deposit Relation of Condensation to Insolubility. 95 of cuprous iodid, but of this compound chalcocite, though attacked,, gives little if any. Pyrrhotite, moreover, is strongly attacked by iodine in the cold, and pyrite but incompletely ; indeed, according to earlier observations by Prof. Henry Wurtz, an aqueous solution of iodine, in the dark, may be employed to separate pyrrhotite from pyrite. Of seventeen native sulphids thus examined by Bolton, all save molybdenite were more or less attacked by iodine in presence of water, but for those partially decomposed thereby quantitative results are still desirable. 142. It was many years since observed by the writer that a so- lution of cupric chlorid with sodium chlorid, which readily dissolves copper from chalcocite and rich cupriferous mattes, attacks chal- copyrite more slowly, while pyrite resists its action. It is in virtue of this inferior resistance of chalcopyrite to decomposition that cupriferous iron pyrites (a mixture of pyrite and chalcopyrite) slowly gives up the greater part of its copper when exposed to air and moisture, through the solvent influence of ferric salts formed by oxydation, and moreover (as in a recently applied process) to lixiviation by acids and oxydizing liquids ; the action of which chalcopyrite resists less than the more condensed pyrite.* 143. The decomposing action of chlorhydric and citric acids on mineral silicates is complicated by the fact that the silica, which is present in varying quantity in different species, and is moreover separated either in a gelatinous or a pulverulent condition, inter- feres with and vitiates the result of the process. Fluorhydric acid, which, while it combines with the bases, forms a soluble and vola- tile compound with the silica, is, however, free from this objection. Its ready action upon glass, feldspars and many similar silicates, had long been known to chemists, and it was farther observed that staurolite, zircon, pyroxene and chrysolite resist more or less completely its action a fact which had been taken advantage of by Lechartier and Linnemann, and especially by Fouque and Mi- chel-Levy in the analysis of mixtures of silicates. Prof. J. B. Mack- intosh has availed himself of this reagent to make an important study of a large number of mineral silicates. In a preliminary note in July, 1886, and farther in 188Y,f he has set forth his results, of which we make the following digest. Fouque and Michel-Levy had already observed that in treating with fluorhydric acid a vol- * " Contributions to the Chemistry of Copper," 1870, Amer. Jour. Science, (3), xlix. t "On the Action of Hydrofluoric Acid on Silica and Silicates," School of Mines Quarterly, vol. iv., no. 7, and Jour. Amer. Chemical Society, vol. viii., no. 9. See also " Mineral Physiology," etc., p. 687 ; and " A New Basis for Chemistry," pp. 56-5. 94 Systematic Mineralogy. canic rock, consisting of " a mixture of amorphous material and of crystalline minerals, the amorphous portion was first attacked, then the feldspars, and next the chrysolite, the magnetite, the amphi- bole and the pyroxene." Extending his observations, Mackintosh has investigated to some length the behavior of a large number of silicates, and of silica in various conditions, when submitted to the action of more or less concentrated fluorhydric acid. The etching or eroding action of this acid of a given strength differs very greatly for different mineral silicates, and Mackintosh has given lists of those which are and those which are not " visibly etched " thereby ; fifty-five in number. In these lists he has, moreover, in- dicated some which are " slightly," or " very slightly attacked," or are " etched with difficulty ; " species which, as he elsewhere ob- serves, appear "to be on the border line, and which sometimes seem to be unattacked ; while at other times, by longer exposure or by treatment of a different surface, a slight action becomes evi- dent." He farther gives a list of species with which by this action quantitative results were obtained. "In these experiments the minerals were reduced to an average size of three hundredths of a cubic millimetre, by careful sizing, and one gram of each sample was taken for each experiment. The samples were all treated for one hour with an excess of dilute fluorhydric acid (9.0 per cent.) at the ordinary temperature of the laboratory ; all conditions being, so far as possible, the same. At the expiration of that time the acid was poured off, the residues were carefully washed and dried, and, where any insoluble fluorids or products resulting from the decom- position of the mineral were present, they were removed by the use of a fine bolting-cloth before weighing the residue of unattacked mineral." 144. From these various data, furnished, with few exceptions, by Mackintosh, we have constructed the four following tables : A. Silicates not visibly etched by fluorhydric acid. B. Silicates more or less attacked by the same acid. C. Silicates visibly etched by fluorhydric acid. D. Quantitative results from certain silicates of table B. In preparing these lists we have added to A staurolite, and to C anorthite, from the observations of others, and have moreover introduced into B amphibole and augite, shown by the results given in D to belong to this intermediate class. Mackintosh, in the presentation of his results, has adopted, to represent the com- Relation of Condensation to Insolubility. 95 position of the silicates, formulas based on the monadic notation of the present writer (pages 41-43), of which he says that they " dif- fer from the ordinary formulas in that the quantities represented by the symbols of the elements are all equivalent to one atom of hydrogen. The co-efficients thus represent the oxygen-ratios of the constituents, and the formulas are very much simplified." For these formulas, and for the values of p calculated therefrom for the various species here noticed, the reader is referred to the tables given in the classification of the orders of Silicates, farther on. The specific gravity = d, and the value of v ( =p -r- d) t to- gether with the percentage of silica for each species, and, in table A. Silicates not visibly etched by dilute Fluorhydric Acid. d. V. #SiO 2 d. V. Si0 2 3.28 5.48 54 Beryl 2.70 5.52 67 EnsttititG 3 10 5 54 60 TODOZ . . 3.65 5.04 34 Danburite 3.00 3.50 5.12 5.37 48 36 Andalusite .... Cyanite 3.35 3.66 4.83 4.42 38 38 3.40 5.40 38 Zircon 4.70 4.84 33 Zoisite 3 35 5 32 44 Talc 2.60 6.07 63 -A.xin.it6. ...... 3.27 5 53 48 Muscovite 3.12 5.68 46 Tourmaline . . . Staurolite Spodumene. . . . 3.05 3.75 3.18 5.36 4.92 4.88 38 29 64 Lepidolite Ripidolite Margarite 3.00 2.70 2.99 5.61 5.70 5.54 46 31 33 _Z), the proportion of silicate left undissolved after exposure of an hour to the action of an excess of dilute fluorhydric acid, being given as determined by Mackintosh. 145. Of the species named in table , it is said by Mackintosh that tremolite, idocrase and datolite are (like phlogopite and bio- tite) " very slightly attacked," and that tremolite is " slightly at- tacked by long exposure ;" while prehnite also is " slightly attacked," and "etched with difficulty." The force of these qualifications is explained when we find from table D that tremolite, with another variety of amphibole, and with augite, lost from 2.47 to 2.64 of their weight during an exposure of one hour to the action of the dilute fluorhydric acid. This in the same time dissolved only 5.40 of chrysolite, and 8.59 of prehnite, although dissolving 43.4 of leu- cite, 66.3 of orthoclase, 69.2 of rhodonite, and 100.0 willemite and 96 Systematic Mineralogy. of halloysite. In the case of halloysite, which was rapidly disinte- grated, an insoluble residue of undetermined nature remained. Willemite was so quickly attacked that of a massive variety, 86.78 and of a crystallized specimen, 92.09 per cent, were dissolved after fifteen minutes exposure' to the action of the dilute acid. With labradorite, and with datolite, a coating of calcium fluorid was formed by the action of the acid, which interfered somewhat with the process of decomposition. 146. Quartz submitted to the same treatment as the preceding silicates was but slightly attacked by the dilute acid, losing in one hour only 1.56 per cent.; while of opal 77.28 per cent, were dis- solved. Crystals of quartz exposed for an hour to an acid of 54 per cent, were slightly but visibly etched ; the action being more marked on artificial surfaces than on the natural planes of crystals. B. Silicates more or less attacked by dilute Fluorhydric Acid. d. V. #Si0 2 d. V. #SiO 2 *Tremolite .... 2.97 5.88 57 Datolite 2.99 5.35 37 *.A.mphibole 3 21 *Prehnite 2.95 5 64 44 * Ausrite 3.30 3.40 5.67 37 *Chrysolite Fayalite .... 3.40 4.35 5.38 5.86 45 27 Phlogopite .... Biotite 2.85 3.00 6.35 6.06 40 41 The surfaces thus etched show a variety of markings, some having apparently no relation to the crystalline form. Mackintosh adds, however, "the twining structure is also developed, showing the complex nature of the crystal. On artificial surfaces the twining structure is made very evident." He elsewhere says, " The differ- ences in the amounts dissolved from different quartz crystals seem to have much more than merely chemical significance, and to be connected with those molecular dissimilarities which cause the dif- ferences between right-handed and left-handed quartz, the occur- rence of plagihedral faces, and of those rhombohedral faces which differ in angle from the primitive form." A specimen of artificially- made tridymite was found to be readily soluble in dilute fluor- hydric acid. The fusion of quartz is well known to yield a vitreous product of much reduced density. In the electrical furnace of Messrs. Cowles, the writer found it easy to obtain fused masses thereof^ Relation of Condensation to Insolubility. many ounces in weight. This material when in powder was found to have a specific gravity of 2.22, and lost in an hour, by the action of fluorhydric acid, 11.02 per cent.; while parallel experiments with uncalcined quartz gave a loss of from 1.28 to 1.70 per cent. The same powdered quartz, by long-continued ignition over a blast- lamp, was found by Mackintosh to have its specific gravity re- duced to 2.62 ; while its partial change of state was shown by the fact that such calcined specimens lost by fluorhydric acid from 4.23 to 5.35 per cent, of their weight. 147. The slag from an iron cupola-furnace, when rapidly cooled, gave to Mackintosh a vitreous mass having a specific gravity of C. Silicates visibly etched by dilute Fluorhydric Acid. d. V. #Si0 8 d. V. #SiO 2 Wollastonite 2 92 6 62 52 *Albite 2 62 6 24 68 *Willemite. . . . *Rhodonite. . . . Apophyllite . . . Pectolite 4.18 3.62 2.35 2 78 6.63 6.06 6.44 6 57 28 47 53 55 *Oligoclase *Labradorite... Anorthite *Petalite . . 2.65 2.70 2.75 2 42 6.27 6.28 6.32 6 33 62 55 43 78 Gala/mine .... 3 50 6.87 25 *Iolite 2 67 6 31 49 Heulandite. . . . 2 20 6.58 59 "Wernerite 2 70 6.44 48 Stilbite 2 20 6.46 57 *Orthoclase . . . 2.54 6 83 64 Hcirrnotome 2 45 6 82 46 *Leucite. 2 56 7 09 55 Chabazite .... 2.19 6.41 52 Jeff eri site . . 2 30 6 50 34 2.29 6.86 55 *Serpentine 2.53 5 78 42 Natrolite 2.25 7.03 47 *Halloysite 2.40 5.75 43 2.77, which was increased, when reduced to powder, to 2.81. The same slag slowly cooled was opaque and crystalline, having a specific gravity in mass of 2.34, which was raised by pulverization to 2.97. Of the first, dilute fluorhydric acid, as before, dissolved in an hour 68.8 per cent., and of the second only 9.6 per cent. M. W. lies had already called attention to the practical application of this fact in the analysis of furnace-slags ; which if suddenly cooled are vitreous and soluble, but if slowly cooled become crystalline and insoluble in acids. The reader will note in like manner the ready solubility of the amorphous or porodic species serpentine and halloysite in fluorhydric acid, which is greater than would be expected for crystalline species with a similar value of v. 98 Systematic Mineralogy. 148. The nature of the bases in the silicates compared in these experiments is not to be lost sight of in considering the solvent power of an acid, whether fluorhydric or another. In the case of the former to satisfy the affinity of one portion of f ^ = 19, there are required of be x = 4.5, of al = 9, of nag! = 12, of caj = 20, of mnj = 27.5, of fcj = 28, and of zn x = 31.5. From this it will follow that the dissolving action of fluorhydric acid of a given strength on silicates of similar condensation will be greater with those of bases of the higher equivalent weights. Hence we find a reason for a D. Quantitative results with Silicates and dilute Fluorhydric Acid. d. V. #Si0 8 % dissolved. 1. Tremolite 2.97 5.88 57 2.47 2. Amphibole 3.21 2.64 3. Augite 3.30 2.61 4. Chrysolite 3.40 5.38 45 5.40 2.95 5.64 44 8.59 6. Albite 2.62 6.34 68 23.10 7. Oligoclase 2.61 6.41 66 35.25 2.70 6.28 55 24.60 9 Petalite 2.42 6.33 78 28 97 10. lolite 2.67 6.31 49 47 34 11. Orthoclase 2.54 6.83 65 43.45 12 Leucite 2.56 7.09 55 66 30 13 Rhodonite 3 63 6 06 47 69 2 14 Willemite 4 18 6 63 28 100 00 2.53 5.78 42 80 67 16 Halloysite 2 40 5 75 43 100 00 more ready solubility of silicates like willemite and rhodonite, than might at first be looked for from their ascertained values for v. A similar relation is apparent when we consider that s^ = 7 is equivalent to t^ = 12 ; so that the solvent effect of fluorhydric acid on a mineral like titanite, v = 5.65, which according to Mackintosh is visibly etched by the acid, is not to be compared with its action on a silicate of similar condensation ; since titanite contains besides 30.0 per cent, of silicon dinoxyd, not less than 40.0 per cent, of ti- tanium dinoxyd, readily soluble in fluorhydric acid. The solubility of titanite in chlorhydric acid, for a similar reason, is well known. Relation of Condensation to Insolubility. 99 149. As regards the localities of the minerals quantitatively ex- amined in table D, No. 1 is a lime-magnesia amphibole from Gov- erneur, New York ; 2 and 3 are amphibole and augite from Tep- litz, Bohemia, the analyses of which were not known ; 5 is from Paterson, New Jersey; 7 from Haddam, Conn.; 9 from Sweden ; 10 from Finland ; 11 from Pike's Peak, Colorado ; 13 and 14 from Franklin, New Jersey. Of this list, the specimens numbered 1, 2, 3, 4 and 5 are also given in table B, where they are marked by a star, prefixed ; while the others are found in table (7, similarly dis- tinguished. The values d and v, like the other figures, are those given by Mackintosh in his published results. 150. A study of the fifty-five native silicates above considered, not less than that of the slags and the different forms of silicon dinoxyd, is thus found to present no exception to the law of the re- lation of condensation in these species to their resistance to dilute fluorhydric acid ; while it shows at the same time that this resist- ance, in the case of the more or less soluble species, is modified to a certain extent by the variations in the equivalent weight of the bases combined with the silica. Farther experiments in elucida- tion of these relations might be advantageously made in two di- rections. First, by the comparison of species of identical centes- imal composition, but of different condensation ; or in other words, having the same value for jo, but with different values for d, and consequently for v. Second, by the comparison of species of simi- lar condensation, but with different bases ; having thus different values for p and for c?, but a common value for v. Examples of the two categories are given below in tables E and F ; to which the most approved determinations of d = specific gravity, with the values of p, as already calculated, and the resulting value of v, the reciprocal of the co-efficient of condensation, are appended. 151. A marked example of chemical difference bet ween two states of the same body is afforded by magnesian carbonate. The rhom- bohedral crystalline magnesite, as given in table E 9 has a hardness of 4.5, a specific gravity of 3.00, and is scarcely attacked by acids in the cold. When, however, the hydrous compound of magnesium carbonate and potassium acid -carbonate, described by H. Deville, is exposed to a temperature between 70 and 150, water and a por- tion of carbon dinoxyd are expelled, and there remains a mixture of soluble potassium carbonate with an anhydrous magnesium car- bonate, having the same centesimal composition as the stable insol- uble magnesite. It however slowly absorbs water and is converted 100 Systematic Mineralogy. into a hydrous carbonate, and is even soluble in water, giving a so- lution from which a crystalline hydrous magnesian carbonate sep- arates.* The specific gravity of this soluble magnesian carbonate is not known, but will doubtless be found much less than that of E. Species of Identical Composition but of Unlike Condensation. P- d. V. P- d. V. Pyrite 20.0 5.19 3 85 Zircon 22 75 4.70 4.84 Marcasite . . . 20 4 75 4 21 Zircon 22 75 4 05 5 61 Quartz 15 2 65 5 66 Sciussurite 17 80 3 35 5 32 Tridymite 15 2 30 6 50 Meionite ... . 17 80 2 74 6.49 Rutile 20 4 2 4 76 Jadeite 16.88 3 32 5.08 Octahedrite . . . 20 3.8 5 26 Diovre . . 16.89 2.64 6.39 Cyanite . 16 2 3.66 4 42 Aragonite 16.6 2 94 5.66 -A.ndcilu.sit6 16 2 3 35 4 83 Calcite 16 6 2 73 6.10 F. Related Species with Different Bases but of Like Condensation. P- d. V. P- d. V. Magnesite 14.0 3.00 4.66 Bromlite 24.7 3.70 6.67 Smithsonite. . '. 20.8 4.45 4.67 Strontianite . . . 24.5 3.65 6.71 Cerussite 44.5 6.60 6.74 Dolomite 15.3 2.90 5.27 Diallogite 19.1 3 60 5.30 Enstatite 17.20 3.10 5.54 Pyroxene . . . 18 66 3 40 5 49 Celestite 25.7 3.96 6.48 Barite 29.1 4.50 6.46 magnesite. Magnesium oxyd itself furnishes an example of differ- ent degrees of condensation. As got by calcining the hydroxyd at 350, it has a specific gravity of 3.20 or less ; which is raised by a bright red heat to 3.60, or approximately that of the crystallized species periclase.f * Engel. C&mpte Rendu de VAcad. des Sciences, Oct. 26, 1885, p. 814 ; also "Min- eral Physiology," etc., p. 169. t Ditte, cited in Clarke's " Constants of Nature," Part I., rev. ed. (1888), being a Table of Specific Gravities a compilation of great value to the student. Relation of Condensation to Insolubility. 101 152. It would be easy to furnish other examples for these two tables. As regards E, it is not certain whether the slight correc- tion applied by Tschermak to meionite and dipyre, as scapolites, should be retained, and if so, whether it should also be extended to saussurite and jadeite ; but as it would only change the value of v in the first from 17.80 to 17.83, the question is not essential for our present comparison.* In F\ it is not improbable that siderite may be found by careful determinations to have v the same as dolomite and diallogite. A nearly pure enstatite (mg^fe^) is there com- pared with a pyroxene the bases of which are ca^mgffe^. The comparative solubility of these, and of other silicates given in table E, as well as those of the forms of silicon dinoxyd and of titanium dinoxyds, might be tried with fluorhydric acid of greater or less strength, and that of the various carbonates with dilute acetic or carbonic acid ; while solutions of iodine, or of ferric or of cupric chlorid, might be advantageously used for the examination of the various metalline species. It should be considered that for such comparisons as those in table F, the amount of the species added to an excess of the attacking liquid should be proportioned to the equivalent weight of the solid, as represented by the value of p. These suggestions for farther experiment in the directions indi- cated, may serve to show whether other factors than the co-efficient of condensation and the equivalent weight of the species in rela- tion to the solvent, are concerned in the question of the insolu- bility and chemical resistance of species. f * For a discussion of the relations of these silicates see the author, " Compte Rendu de 1'Acad. des Sciences," June 29, 1863, and in translation in Amer. Jour. Science for Nov., 1863 (p. 427) ; also " Chem. Geol. Essays," pp. 445-447. t James Buckton Mackintosh, of New York, died of pneumonia, April 15, 1891, while this chapter, devoted in large part to his important studies of the relation of condensa- tion to insolubility in silicates, was printing. In his early death, at the age of thirty-four years, chemistry loses not only an able experimenter and a skillful analyst, but an intell- igence which by its philosophic grasp had already given promise of the highest attain- ment in his chosen science. 102 Systematic Mineralogy. CHAPTER IX. CRYSTALLIZATION AND ITS RELATIONS. 153. The greater number of solid species are capable of assum- ing crystalline forms, and the study of these and their relations presents many points of interest to the mineralogist. Before pro- ceeding to their consideration it will be well to give a concise view of the different crystalline systems. The inspection of any crys- tal, if it be not too highly modified, will suffice to show that it may be conceived of as symmetripally built up around certain lines or axes, which have definite and constant relations to the crystal it- self ; and which vary in their number, their relative lengths, and their inclination to each other. We may thus reduce all crystals to six systems, which are as follows : I. Isometric. The forms of this system, also named Regular, Cubic or Tesseral, may be described as built up around three axes of equal length, intersecting each other at right angles. Of these forms the most important are the cube, the regular octahedron, and the rhombic dodecahedron ; which may be generated by com- plete or holohedral replacements of the solid and the lateral angles of the cube itself. What is called hemihedral modification gives rise, by replacement of alternate angles of the cube, to the regular tetrahedron ; while by a similar replacement of the lateral angles is generated the pentagonal dodecahedron, or so-called pyritohedron. Examples of the isometric system are seen in galenite, fluorite, garnet and diamond ; also in pyrite, noticeable* for its parallel hemihedral modifications ; while in fahlerz or tetrahedrite the in- clined hemihedral modifications are displayed. II. Tetragonal. The forms of this system, which is also known as Quadratic, Square Prismatic, and Pyramidal, have, like the last, three axes at right angles to each other ; the two lateral ones being of equal length, while the vertical axis is either longer or shorter than these. This right square prism gives rise to the square-based octahedron, and also, by hemihedral modification, to a tetragonal tetrahedron. Examples of this system are seen in the scapolites, idocrase and zircon, and of its tetrahedral form in chalcopyrite. III. Hexagonal. This system is characterized by four axes, of Crystallization and its Eelations. 103 which three are equal and inclined to each other at angles of 60 ;, while the fourth, the vertical or principal axis, is perpendicular to these. This hexagonal prism, which is seen in apatite, nephelite, and beryl, gives rise by its holohedral modifications to the pyra- midal dodecahedron, or double six-sided pyramid. It is subject ta many hemihedral modifications, the most important being that by which from the pyramidal dodecahedron is derived the rhombohe- dron ; as seen in calcite, quartz, tourmaline, and the red silver ores. This derivative is so characteristic and important in crystallography that the Hexagonal system has been appropriately divided into two- parts ; a Hexagonal section and a Ehombohedral section. IV. Orthorhombic. This, also called the Right Prismatic sys- tem, is characterized by three axes of unequal lengths, at right angles to each other. Its most noticeable forms are the right rec- tangular prism, the right rectangular-based octahedron, the right rhombic prism, and the right rhombic-based octahedron. From these last is derived the name of the Orthorhombic system, examples of which are seen in aragonite, enstatite, topaz, and bournonite. V. Clinorhombic. In this, also called the Monoclinic or Oblique Prismatic system, of the three axes all may be unequal. Two of these, the secondary ones, are placed at right angles to each other ; the third or principal axis being oblique to the one and perpendic- ular to the other. The chief forms referred to this system are like those of the last, save that the prisms and octahedrons are all oblique, whence the name of Clinorhombic. To this group belong orthoclase, augite, epidote, and spodumene. VI. Anorthic. In this, which is also known as the Triclinic or Doubly Oblique Prismatic system, are included forms which may be referred to three axes, all of which are oblique to each other, and all may be of different lengths. The principal forms are the doubly oblique prism and the doubly oblique octahedron. Ex- amples of this doubly oblique or Anorthic system are seen in albite and anorthite, in axinite and in cyanite. For convenience in tabulation, the names of the seven types of crystalline forms above noticed, including the two divisions of the Hexagonal system, will be designated by initial letters. Thus, I, Isometric ; T, Tetragonal ; H, Hexagonal ; R, Rhombohedral ; O, Orthorhombic ; C, Clinorhombic ; A, Anorthic. 154. Many crystals readily cleave parallel to all the planes of their primary form, as seen in the cubical cleavage of galenite, the dodecahedral of sphalerite, the octahedral of fluorite, and the 104 Systematic Mineralogy. rhombohedral of calcite; while in others perfect cleavage is found in one plane only, as in orthoclase and the micas ; or else, as in quartz, the species is uncleavable. The unlike cleavages in different planes, and their unlike erosion by fluorhydric acid (as noticed in 146), serve to show the structural differences, and the subordination of parts to function, apparent in all crystalline forms, save in those of the isometric system. They are, of course, absent in colloidal or non-individualized species. Many other illustrations of the structural differences in all prismatic crystals may here be men- tioned ; among them the varying lengths of the unlike axes, and the different inclinations of these to each other in the oblique systems, determining the angles of the secondary forms, and thus enabling the crystallographer to classify still farther the species belonging to any given system, and to arrange them in what are designated isomorphous groups. The character of hemimorphism must also be noticed, that is to say, the existence of unlike modifi- cations of the two extremities of a prismatic species ; examples of which are seen in tourmaline, topaz and calamine. The two extremities of such crystals may develop opposite electrical polar- ities when heated. The capacity of conducting heat for crystals of the isometric system is, like that of colloidal species, the same in all directions ; while crystals of the tetragonal and hexagonal systems conduct heat equally well in all directions perpendicular to the vertical axis ; and those of the other three systems, having axes of three different lengths, conduct unequally in the directions of these. Similar differences are disclosed by the action of light on the crystals of these different systems. Differences in color are also observed in many transparent species when viewed in the direc- tions of unlike axes, giving rise to what is designated pleiochroism. This is shown, among other minerals, in chrysoberyl, andalusite, zircon, tourmaline and iolite ; which latter from its remarkable dis- play of two colors, has received the synonym of dichroite. 155. The fact that species more or less unlike in chemical com- position crystallize in forms which are either identical, or differ slightly from each other in angle, early attracted the attention of chemists, and the farther study of such cases led Mitscherlich to announce what has been called the law of isomorphism ; namely, that bodies having a similar chemical constitution have also the same crystalline form, as determined by the measurement of their angles ; reference being had to the primary form to which the Isomorphism. 105 crystal is reducible. Substances, the chemical similarity of which is either not at all apparent, or can only be sustained by very doubtful analogies, have, however, often been included in one and the same isomorphous group. We propose to give, by way of illus- tration of the law of isomorphism, some well known and unques- tionable 'examples of isomorphous groups, and then to proceed to show the frequent misapplication of the principle. Aluminic, ferric, chromic, manganic and gallic sulphates unite with sulphates of potassium, ammonium, rubidium, caesium and thallium to form the definite hydrated double salts with 12H 2 O, called alums, crystallizing in the isometric system. Again, the aluminic, ferric and chromic oxyds are known to crystallize in similar rhombohedral forms, and may replace each other more or less completely in silicates, without change in the crystalline forms of these. In certain natural carbonates or carbon-spars, the metals magnesium, calcium, strontium, barium, iron, manganese, cobalt, zinc and lead, may replace each other, wholly or in part, in isomor- phous rhombohedral or orthorhombic forms. The sulphates of magnesia, zinc, cobalt, nickel and iron crystallize with the same amount of water, 7H 2 O, in isomorphous forms of the clino- rhombic system ; and, moreover, unite with sulphate of potash or of ammonium to form isomorphous double salts with 6H 2 O, also crystallizing in clinorhombic forms. The sulphates of barium, strontium and lead are also isomorphous, and corresponding sul- phates, selenates and chromates crystallize in similar forms. The same is true of like hydrated phosphates and arsenates of sodium ; and of the chlorophosphates and chloroarsenates of calcium and of lead. 156. These examples may suffice, and it is now necessary to call attention to the fact that while in many of these cases, as in the alums, the hydrated phosphates and arsenates, and the single and double hydrated sulphates of the magnesium group, the condensa- tion, as indicated by the value of v, is similar ; in other cases, as in the rhombohedral and the orthorhombic carbon-spars, the conden- sation varies considerably ; as may be shown by comparing calcite with dolomite and with magnesite, or aragonite with strontianite and witherite. Thus, while in the alums, and the hydrated salts just mentioned, we have isomorphous relations between compounds of strictly similar, or what has been called metameric constitution ; we find in the two groups of carbon-spars, in wollastonite and augite, and in many other cases, examples of isomorphism between 106 Systematic Mineralogy. what we have called isomeric homologues ; that is to say, between compounds of analogous constitution, more or less condensed or polymerized ; in which the common difference is the same with that of the first term of the homologous series. Isomorphisms pertain- ing to a third category are seen in those bodies which present in their constitution homologies of the second kind ; being what are termed anisomeric homologies, in which the common difference is unlike the first term of the homologous series. Examples of this are seen in the scapolites, represented by marialite and meionite, and in the feldspars, the known extremes of the series of which are anorthite and albite. In these two series, while the ratios be- tween alumina and the positive element, represented by lime or an alkali, are constant, that of the silica varies through a wide range ; the intermediate species of the respective series, however, having the same condensation. The question of these homologous rela- tions will be considered at length in the next chapter. 157. Having thus shown by examples the legitimate application of the doctrine of isomorphism, and the extension of it which is justified by a consideration of the laws of polymerization and of progressive series, we proceed to notice some of the extremes into which the advocates of the doctrine have been led, and the errors which have resulted therefrom. Referring, by way of illustration, to an extended article on Isomorphism by the learned editor him- self, in " Watts's Dictionary of Chemistry," we find there a table,, said to exhibit " the most important and best established examples of isomorphism." These are arranged according to the crystallo- graphic systems, in groups ; and the subdivisions of these groups "include those also which correspond in atomic constitution." Among these will be found, besides the examples given in 155, a group in which the rhombohedral carbon-spars are coupled with rhombohedral nitrates of potassium and sodium. In another group, with the orthorhombic carbon-spars are included both orthorhombic potassium nitrate and bournonite, a sulphid of antimony, lead and copper ; in a third, sulphates of baryta and lead with the perchlor- ates and permanganates of potassium ; in a fourth, the hydrated magnesian sulphate series with sulphid of antimony ; and in a fifth, borax with augite. 158. A striking example of the extension of the notion of isomorphism is found in most mineralogical text-books where with pyroxene are classed not only wollastonite and rhodonite (which last, though anorthic in crystallization, is nearly isomorphous with Isomorphism. 107 pyroxene), but acmite, aegerite, spodumene and petalite, while arfvedsonite and glaucophane are arranged with amphibole ; as may be seen in J. D. Dana's Manual, and in the last edition of Zirkel's Naumann. Breithaupt, in fact, in 1847, included both spodumene and acmite in his genus Pyroxenus, and, later, Descloi- zeaux asserted the isomorphism of petalite with spodumene. Breit- haupt had however already rightly assigned to petalite a place among the true feldspars, and in this is followed by Groth ; who, for the rest, adopts the same grouping for the species as Dana and Zirkel. Without adverting farther to the many unnatural associations apparent in the isomorphous groups previously cited from Watts, we may proceed to notice the case of the silicates just named ; since they afford striking examples of the grave errors into which an exaggerated notion of the significance of crystalline form, unguided by a proper consideration of chemical and physical characters, has led modern mineralogists. The peculiar relations of alumina lead us to regard those silicates into which it enters, as constituting an order distinct from simple silicates ; the alumina, with certain triad oxyds replacing it (as ferric, chromic and man- ganic oxyds), forming with the silica a complex negative or acidic group. Apart from this fundamental fact, which serves to differ- entiate simple silicates like wollastonite, rhodonite, amphibole and pyroxene from aluminisilicates like petalite and spodumene, regard should be had to the great differences in hardness, condensation and solubility of the minerals compared. Wollastonite, amphibole and pyroxene are three species of very unlike condensation, as shown by the respective values of v ; which, for the first, is about 6.6, and for the various pyroxenes about 5.5 ; that for amphibole being about 5.9. Moreover, wollastonite is readily decomposed by chlorhydric acid, while amphibole and pyroxene resist its action ; and dilute fluorhydric acid, as we have seen, reveals similar differ- ences. 159. Coming now to the aluminisilicates, petalite and spodu- mene, we find for the former v = 6.3, or very near that of the true feldspars, anorthite, labradorite and albite ; like which it is readily attacked by dilute fluorhydric acid. Spodumene, on the contrary, resists its action, and having v = 4.9, is one of the most highly condensed silicates known, taking its place near to zoisite, jadeite, epidote and garnet, in which last two the alumina may be to a greater or less extent replaced by ferric or by manganic 108 Systematic Mineralogy. sesquioxyd ; while in zoisite and in jadeite several hundredths of soda are met with. Closely related with these are the soda-bear- ing silicates, acmite and arfvedsonite, in which the triad oxyd is wholly ferric, with values for v from 5.3 to 5.5. Here also belong glaucophane and gastaldite ; which are aluminisilicates, having v = 5.6, and approaching in composition to epidote and to zoisite. Thus it would appear that the group of so-called isomorphous silicates of which pyroxene and amphibole were taken as repre- sentatives, has been made to include species which not only differ in hardness and insolubility, but belong to different genera, and even to different orders. This confusion has come from a persis- tent following out of the single character of crystalline form, without regard to chemical or to other physical characters ; and helps to show the need of a wider and more scientific basis for mineralogical classification than that hitherto adopted. While intimate relations are apparent in very many cases between certain crystalline forms and chemical constitution, the secondary importance of these is illustrated by the well-known fact that the same chemical species is frequently dimorphous ; that is to say, it may crystallize in two different systems, while preserv- ing its hardness, its density, and all its other physical characters un- changed. Examples of this are seen in sphalerite and wurtzite ; in orthoclase and microcline ; in eulytite and agricolite ; and in anda- lusite and fibrolite. 160. Intimately connected with the question of isomorphism, and with that of intermediate species, as in the scapolites and feldspars, is the question of crystalline admixtures. That species truly isomorphous may crystallize upon each other is a fact long since established by experiments with the different alums ; as when ammonia-alum is deposited on potash -alum, or a chromic upon an aluminic alum. In the case of homologous fatty acids, as of the series (CH 2 )nO5, we may have admixtures of two, in which n = 2 and n = 4, in such proportion as to give the centesimal composition corresponding to n = 3. Having facts like these in view, the wri- ter in 1854, after making many analyses of anorthic feldspars, was led to propose the hypothesis that the intermediate species of these might be regarded " as isomorphous mixtures of albite with anor- thite, sometimes with small admixtures of orthoclase." Von Wal- tershausen had also put forth the same view in 1853, but it was not until 1864 that Tschermak, to whom is generally given the credit of this hypothesis, advanced the same notion ; which from its Intermediate Species. 109 plausibility has found general favor with mineralogists. Mean- while, after reconsidering the whole subject, the present author in 1886 declared against the hypothesis in the following language : " With regard to this conception of the nature of these inter- mediate feldspars, it should be noted that the chemical difficulties in the way of verifying it are much greater than in the case of sol- uble compounds ; where, as in the case of the fatty acids just men- tioned, solution and separation by fractional precipitation are pos- sible ; or where differences in volatility may be appealed to. While a definite feldspar-species having the composition assigned to lab- radorite doubtless exists in nature, it is nevertheless true that a mixture of proportions of anorthite and albite containing equal parts of alumina would give a centesimal composition identical with that assigned to labradorite ; just as the composition of a fatty acid may be simulated by a mixture of its higher and lower homo- logues. In so far as the view of von Waltershausen and myself, since adopted by Tschermak, is true, the action of acids capable of attacking the basic feldspars will enable us to discriminate between admixtures and definite intermediate species. That the latter should occur in nature is, a priori, probable from the composition of the parallel series of the zeolites, in which occur well-crystal- lized species, having the ratios (excluding the water) of the inter- mediate feldspars ; and also from the evidence of species like hy- alophane and leucite. The late observations by Tschermak as to the action of acids on various scapolites go far to show that these are not admixtures but integral compounds. The intermediate scapolites of the meionite-marialite series are imagined by him to be, not as once proposed by von Waltershausen and myself, crystal- line intermixtures, but binary combinations, in different propor- tions, of the two silicates, meionite and marialite. He notes (1), compounds holding one equivalent of marialite to two of meionite, which are almost or completely soluble in acids ; (2) compounds with one of meionite to two of marialite incompletely soluble ; and (3) compounds with more than the latter proportion of marial- ite insoluble in acids. This variation in solubility will, in the chemist's eyes, be a sufficient reason for rejecting the notion that they are admixtures. These intermediate scapolites, like the feld- spars labradorite and oligoclase, and the various zeolites between thomsonite and stilbite, must be regarded as distinct species." * * "Mineral Physiology," p. 342. 110 Systematic Mineralogy. This will be farther considered in treating of these silicates in the order Argillinea. 161. Apart from facts to be noticed farther on, whereby the intimate association of distinct species is made readily apparent, it is, however, well known that the microscopic study of many crys- talline minerals reveals the presence in them of enclosed crystals, often very minute, of other species. This is readily apparent where differences in geometrical form, color, and relations to polar- ized light exist ; but for obvious reasons is difficult to establish when we have to do with isomorphous and closely related species which present none of these differences. Thus, if with aluminic and ferric or chromic potash-alums, instead of depositing the two salts successively upon a nucleus of one or the other species, we mingle their solutions; or, for another example, take mixed solutions of the sulphates of iron (ferrous sulphate) and related metals, we may obtain, in either case, crystals of hydrated salts in which the proportions of the several metals are not in any simple ratio. If, however, we consider that these crystalline salts are the results of great condensation, and have high integral weights, it is con- ceivable that the crystals in question may yet be definite chemical compounds. Bearing in mind the elevated equivalents deduced from the results of chemical analysis in the case of certain salts like the polytungstates mentioned in Chapter VI., we may note that the potash-alumina alum, with a chemical unit, A1K(SO 4 ) 2 .- 12H 2 O = 474, has, with a specific gravity of 1.75 in its crystalline state, a co-efficient of condensation nearly represented by 79. The heptahydrated ferrous sulphate of iron, with a specific gravity of 1.90, gives, in like manner, a co-efficient of 146. It should be remem- bered that these numbers are calculated from formulas taking O = 16 ; and that with the doubts still existing as to the exact value of oxygen, and moreover with the variations in the density of the salts as given by different observers, it is possible that the num- bers above deduced for the co-efficients may differ by one or two units from the truth. If then crystalline alum be represented by 80[AK1(S0 4 ) 2 .12H 2 0], a small portion of ferric oxyd got from certain crystals of alu- mina-alum (amounting by assumption to 0.21) may either come from the mechanical intervention of a minute portion of fer- ric alum, or else may belong to a definite compound including 79A1 and iFe ; the small amount of iron being as essential to the Pseudomorphism. Ill integrity of this particular species as the single portion of VOg, or of SiOjj, is to the integrity of the complex polytungstates ; or as the 0.25 of hydrogen to iodoform, CHI 3 . Similar cases may be noted in the carbon-spars, in which small quantities of certain bases make their appearance, giving rise to a great many slight variations in the composition of these crystalline anhydrous carbonates. The results of the study of such bodies as these, and of the complex polytungstates, polymolybdates, polyphosphates, etc., will probably furnish many evidences that the small quantities of different mat- ters hitherto ascribed to mechanical admixtures may be elements essential to the constitution of the species. 162. Closely related to the questions just discussed are certain points made evident in considering some of the many facts brought together in what is vaguely called pseudomorphism. Under this head have been included several distinct and unlike cases, in which substances are made to assume forms belonging to other bodies, either organic or inorganic ; these false forms being aptly named pseudomorphous or epigenetic. These various cases may be con- veniently classed under two heads chemical alteration, and sub- stitution or replacement. Of pseudomorphism by chemical alteration, a good example is presented when a crystal of ferrous carbonate (siderite) loses its carbon dinoxyd, and absorbing oxygen and water passes into hydrous ferric oxyd ; or when a crystal of pyrite (ferrous disulphid), in like manner, by the loss of sulphur and the peroxydation and hydration of the iron, gives rise to the same product. In some instances the resulting hydrous peroxyd is rearranged by solution and deposition in the form of concretionary cryptocrystalline limonite ; but in others the product retains unchanged the shape of the crystalline carbonate or sulphid, and in the case of the former still exhibits its characteristic rhombohedral cleavage. The masses resulting from this process of chemical alteration or epigenesis are said to be limonite-pseudomorphs after sider- ite or pyrite. In like manner, crystals of cuprite (cuprous oxyd) may be changed into the hydrous cuprous carbonate, malachite ; which, if retaining the crystalline form of the oxyd, is said to be a pseudomorph after cuprite. The volume of the solid prod- uct of alteration is rarely the same as that of the parent spe- cies. Thus, in the conversion of siderite into limonite, the resulting pseudomorph is found to be porous ; the contraction in volume which takes place in the conversion of a pure siderite of specific 112 Systematic Mineralogy. gravity 3.6 with a limonite of the same specific gravity, being, by calculation, 19.5 per cent. This process of contraction, as we have elsewhere pointed out, causes, in the case of epigenesis and rear- rangement of massive ferrous carbonate, a concretionary structure, which has proceeded from without inwards ; the layers of limo- nite forming successive shells or layers, and enclosing a cavity sometimes partially filled with insoluble sand, included in the massive siderite and eliminated in the course of solution and redeposition of the iron-oxyd ; or at other times enclosing in a nucleus of unchanged siderite. Of this nature are the geodes of limonite found in certain deposits, and known as bomb-shell ore, setites or eagle-stones.* The conversion into limonite of the above specific gravity of pyrite of specific gravity 5.0, would be accom- panied by an augmentation of volume of 10.7 per cent. Similar phenomena to those observed in siderite are said to occur in the oxydation of galenite (lead sulphid), and its conversion into sul- phate of lead ; masses of which are found to contain nuclei of unchanged sulphid. 163. A farther example of the chemical alteration of mineral species by the action of atmospheric agents, that is to say of water with oxygen and carbonic acid, is seen in the process of kaoliniza- tion ; by which feldspars, scapolites, and other chemically related species, losing alkalies and lime, and therewith a portion of sili- ca, and fixing water, become changed into the hydrous silicate of alumina known as kaolin or porcelain -clay. In rocks thus decayed, and especially in granitic veinstones, large crystals of orthoclase are sometimes found, retaining their cleavage, but changed into soft and earthy kaolin ; and are thus pseudomorphs after orthoclase. Beryl also, according to the observations of Damour and Muller, undergoes a similar change, from the loss of its protoxyd base. Leucite crystals, as observed by Ram- melsberg, and by the present writer, are found apparently changed to kaolin, but containing a portion of soda, probably derived from an external source, and thus allied in composition to analcite,f which may then be said to be a pseudomorph after leucite. The farther consideration of these matters may be reserved for another place ; but it should be said that the complete conversion of orthoclase to kaolin is effected by the removal therefrom of the *"The Genesis of Certain Iron Ores," Ainer. Assoc." Adv. Science, 1880, and Can. Naturalist for Dec., 1880, ix., 484; also "Mineral Physiology," p. 263. t "Mineral Physiology," p. 371. Pseudomorphism. 113 whole of the alkali, and two-thirds of the silica.* This is, in fact, liberated in a soluble form, together with the alkali, and being thus dissolved in water, plays an important part in other chemical processes to be noticed farther on. 164. Alkaline or earthy sulphates in watery solutions become reduced, if oxygen be excluded, by the action of many organic matters, to the state of sulphids. These last are either decomposed by any carbonic acid present, with production of hydrogen sulphid, or else exist dissolved as sulphids of alkaline and earthy bases ; forming, in one case or the other the ordinary sulphurous mineral waters.* Such waters, especially at elevated temperatures, doubt- less play an important part in the solution, deposition and altera- tion of the mineral species met with in their subterranean circula- tion; and serve to explain some remarkable pseudomorphous changes, which are probably produced by such waters. Thus crystallized pyromorphite, a chlorophosphate of lead, is found changed into galenite, a pseudomorph of which there are remarkable examples. It is evidenrt that such a process of sulphuration of oxydized com- pounds may have many applications. 165. Other and not less important changes may take place through the intervention of saline waters, independent of the action either of sulphids or of oxygen ; such changes being due to the greater or less insolubility therein of different mineral species. When, by the chemical action of such waters on a given species, a more soluble compound is formed, it may be carried away ; but if less soluble it remains behind. Thus its greater fixity or insolu- bility removes the newly formed compound from the sphere of action, as in ordinary cases of precipitation ; its conservation being due to its chemical stability under the circumstances. Examples of this are seen in the formation of certain softer hydrated mag- nesian and aluminous species by epigenesis from harder and more condensed species. In discussing this method of chemical altera- tion, it has been elsewhere said of the mineral known as pinite, " The constancy in composition, and the wide distribution of pinite, show that it is a compound readily formed, and of great stability. Such being its character, it might be expected to occur as a fre- quent product of the aqueous changes of other and less stable sili- cates. It is met with in veinstones, in the shape of crystals of nephelite, iolite, scapolite, feldspars and spodumene ; from each of * " Chem. Geol. Essays," pp. 158-163, from "Geol. Survey of Canada," 1863-66, pp. 272- 77, and farther in the present volume, in a chapter on Mineral Waters. 114 Systematic Mineralogy. which it is supposed to have been formed by epigenesig. Itt frequent occurrence as an epigenic product is one of the many examples to be met with in the mineral kingdom of the law of 'the survival of the fittest.' It is, however, difficult to assign such an origin to beds of pinite [described by the names of dysyn- tribite and parophite], which are probably the results of original deposition or of diagenesis." * 166. Similar observations apply to the magnesian hydrated sili- cate, serpentine, which, while manifestly in many cases formed di- rectly, like the other magnesian silicates, sepiolite and talc, by pre- cipitation from water, is also, from its insolubility, a residual or epigenic product of the hydrous alteration of other silicates, as chrysolite, enstatite and pyroxene, f It is only in cases where these amorphous or porodic silicates, piuite and serpentine, can be shown to be the results of the epigenic change of crystalline species, as above, that they can be described as pseudomorphous minerals. To conclude, as some have done, that since the hydrous aluminous silicates included under the name of pinite are in certain cases ap- parently the results of epigenic changes of iolite or of nephelite ; and that serpentine in like manner has been derived from chryso- lite, enstatite or pyroxene all pinite and all serpentine are therefore of epigenic origin is as illogical as it would be to contend from the production of malachite by epigenesis from cuprite, and of galenite from pyromorphite, that all malachite and all galenite are of epi- genic origin. 167. In pseudomorphs of the first class that is to say, those produced by chemical alteration, as has been explained the space occupied by the original species continues to be occupied by some of its elements, modified by subtractions and additions, but still retaining the form of the first species ; as is seen in the compounds of iron, copper, lead, alumina, and magnesia in the instances noted. Pseudomorphs of the second class are those produced by deposition in vacant spaces left by the removal of some matter, either crystal- lized or of organic shape ; the form of which is assumed by the ma- terial that displaces it or is substituted therefor. Hence the term * " Mineral Physiology," pp. 163-165. This question has since been discussed by Mr. E. A. Ridsdale, who in 1888 published a suggestive essay entitled, "Notes on Organic Evolution," wherein he speaks of the production and conservation of more stable species, .as above described, as a gradual " selection of inert forms ; " and further, as "a survival of the most inert. 11 But as inertness consists in stability and in fitness to resist alike the chemical and the mechanical agencies which destroy other species, it is evident that iiis phraseology is but another statement of the formula of " the survival of the fittest." t " Mineralogical Evolution," Proc. B. A. A. Science, Bath, 1888, Section B. Pseudomorphs by Replacement. 115 of pseudomorphs l>y replacement, or by substitution, which is gen- erally given to these examples. This process of producing false forms by moulding presents two different and unlike cases; namely, those in which the substitution is simple, or effected by a single operation ; and those in which it is complex, involving, as in the case of certain organized tissues, two distinct and consecutive pro- cesses. The first case, or that of simple substitution, is seen alike in crystalline minerals and in organic forms. Thus, in veins and other cavities, through chemical changes effected by circulating waters, crystals once deposited are not only altered but in many cases are wholly dissolved ; while the unlike surrounding species, being unattacked, constitute moulds to be subsequently filled by other minerals. In this way quartz, either crystalline or chalce- donic, is sometimes found in cavities left by the solution of calcite, barite, fluorite or datolite ; of which various species it assumes the external form. Other solutions, in their turn, may dissolve and remove quartz itself, as will be noticed farther on. 168. Farther examples of simple replacement are seen in the case of the calcareous remains of animals enclosed in more or less porous dolomite or quartz rock ; from which infiltrating waters sub- sequently remove the more soluble calcareous structure, leaving cavities to be subsequently filled by other matters, as with silica, hematite, calcite or dolomite ; thus giving by simple replacement casts or moulds of the organic forms. Remarkable examples of these phenomena were long since described by the writer from a stratified mass of very pure crystalline dolomite, about 160 feet thick, known as the Guelph division, found in the Silurian series of western Ontario ; where it immediately overlies the Niagara lime- stone, also dolomitic. The shells of species of Megalomus, Pen- tamerus, Murchisonia, and Pleurotomaria, common in certain beds of the Guelph dolomite, have been in most cases removed by solu- tion. " The shell was simply enveloped in the rock, and by its solution has left only a cavity corresponding to its exterior. At other times, the interior of the shell was also filled with the dolo- mite, so that the cavity corresponds only to the thickness of the shell ; of which the markings both of the interior and exterior sur- faces are preserved. More rarely, the cavities thus formed have been filled up by calcareous matter, apparently replacing the sub- stance of the shell, and in one place great numbers of encrinal fragments have been replaced by a white sparry dolomite, whose color contrasts with the yellowish hue of the base." * This stra- * Geology of Canada, 1863," p. 624. 116 Systematic Mineralogy. turn, in which the organic forms replaced by the dolomite were very distinct from the including crystalline dolomitic base, was, however, like the adjacent non-fossiliferous beds in composition. Analysis in both cases showed the mass to be a pure dolomite, con- taining less than one per cent, of insoluble matter, and from fifty- three to fifty-four of carbonate of lime, with a trace of iron. 169. In still other cases, shells imbedded in non-magnesian lime- stone, and unfilled, or but partially filled with the calcareous sedi- ment, have had the vacant spaces subsequently filled by infiltra- tion with quartz, calcite, or dolomite, by a process similar to that which has effected the deposition of these species in mineral veins or geodes. Remarkable examples of this are seen in many local- ities in the Trenton division of the Ordovician series in the St. Lawrence valley, in Canada, where in bluish non-magnesian lime- stones are found yellowish crystalline dolomitic casts of the interior of Orthoceras, Murchisonia and Pleurotomaria, sometimes hold- ing in drusy cavities crystals of quartz or of dolomite ; thin veins of which latter species also intersect the limestones.* In this case, the original cavity of the organic form, and in that of the Guelph dolomite, the mould left by its solution, has been filled up with the infiltrated mineral species. 1 70. These two distinct and unlike cases of simple replacement are sometimes united in the same specimen, giving rise to the com- plex replacement mentioned above ; a process which deserves special study for the reason that it has been generally misunderstood ; and moreover because from its misinterpretation grave errors have arisen which have assumed considerable theoretical importance. A typical case of this process is presented by the complete silicifi- cation of wood, giving rise to what J. D. Dana has called " quartz pseudomorph after wood." G. Bischof, who wrote at length on pseudomorphism, asserted that " the pseudomorphic process may be imagined to consist either in direct conversion of the original min- eral into the new substance ; or in a series of intermediate changes, the results of which are minerals successively more and more distinct from the original in composition, and nearer to the final product." f Bearing in mind the distinction between pseudomorphs by altera- tion, and those by replacement, which are now under consideration, he properly observes that " from the nature of the process of dis- placement-pseudomorphism only the first change can take place." * "Geology of Canada," 1863, p. 630. t Bischof, "Chem. Geology," Cavendish Soc., ed. 1854, 1., cap. ii. Pseudomorphs by Replacement. 117 In the displacement of barite by quartz, Bischof supposes that " a particle of quartz replaces each particle of sulphate of baryta re- moved ; here there is no intermediate stage." In like manner he speaks of the silicification of wood as effected by an infiltration of waters holding silica in solution ; although there is no evidence that he was in 1854 familiar with the results of the completed process, which does not appear to have been then known to Goeppert. 171. So far as the writer is aware, the first statement of the true nature of the complex process of replacement which is seen in the complete silicification of wood, was made by himself, in 1864. Goeppert had already found in his studies of specimens from Hun- gary, the pores of the wood filled with silica ; while the organic tissue, more or less completely changed into coal or lignite, still remained, and was liberated when the silica was dissolved by fluor- hydric acid. In other specimens, according to him, this organic matter had subsequently disappeared, leaving spaces vacant or filled with water.* Sir William Dawson, however, in examining silicified exogenous woods from Antigua, afterwards found the organic tissue itself replaced by silica ; the whole of the woody fibre having disappeared, and its place being occupied by silica distinguished by a difference of color from that filling the place of the vessels ; precisely as in the encrinitic dolomite rock mentioned above, the dolomite replacing the crinoidal stems is distinguished from that surrounding them. Having, through the kindness of Sir William, examined the specimens of silicified wood showing these various phases, the writer concluded that the complete silicification had necessarily been effected at two periods ; the process consisting (1), in filling the pores of the wood with silica ; (2), in the removal by slow oxydation and solution of the organic tissue, thus leaving a silicious skeleton, as seen by Goeppert ; and (3), the filling of the ^mpty spaces thus left by a farther deposition of silica." f 172. Subsequent studies by J. Arthur Phillips, published in 1873, of the silicified woods found in the auriferous gravels of California, served to confirm the various observations of Goeppert, Dawson, and the writer. Phillips found that the trunks of exo- genous trees, which are abundant in those gravels, are " either silicified, or converted into a lignite often containing a considerable * Goeppert, "Plantes Fossiles." t "The Silicification of Fossils," Feb., 1864, Can. Naturalist, new series, 1. 46, embody- ing the observations both of Dawson and the writer; also"Chem. and Geol. Essays," p. 286. 118 Systematic Mineralogy. amount of iron pyrites." . . . "Fragments are sometimes met with of which one portion had been more or less completely con- verted into lignite previous to silicification. In such cases, speci- mens may be obtained having the appearance of jet and opal, respectively ; each portion distinctly retaining the original struc- ture of the wood." We have thus in these deposits the three species, sometimes in a single specimen unsilicified lignite, silicified lignite, and opalized wood. " The transition from silicified wood to silicified lignite was exceedingly gradual, one end of the log being black, with a somewhat hackly fracture, while the color of the other end was yellowish white, and its fracture conchoidal ; both dis- tinctly retained their original woody structure." . . . The results of analysis [given by Phillips] " show that although every trace of organic matter has disappeared in the silicified wood, the silicified lignite produced from the same tree still retains about fourteen per cent, of carbonaceous matter." The latter contained about eighty per cent., and the opalized wood over ninety-two per cent, of silica ; besides water, and small portions of alkalies, lime and iron oxyd. The specimens were from Nevada City, CaL, in gravels capped by volcanic overflows, and regarded by Newberry as of later pliocene age.* 173. These observations the writer was able to confirm and ex- tend in 1877, at the Blue Tent gold placer-mine in Nevada Co., Cal. The lower portions of the nearly upright trunks were found to consist of lignite, non -silicified, and readily combustible when dried ; while the gradual silicification of the lignite, and its final opalization, were apparent in the same trunk when traced upwards from the unoxydized bluish or greenish gravel, holding pyrites, into the upper gravel ; in which the pyrites had been oxydized, and the numerous contained pebbles of greenstone or diorite had be- come rusty in color, and earthy in texture, exfoliating and par- tially kaolinized. The lignite therein becomes more or less com- pletely silicified, being sometimes converted into agatized masses, often with drusy cavities lined with quartz crystals ; and at other times only penetrated or injected with silicious matter, which has filled the pores of the exogenous wood ; the vegetable tissue of which still remains, often incrusted with crystals of quartz. In still other cases, a slow subsequent decay of the tissue in these co- niferous woods has left the silicious casts in the form of bundles of * Phillips, Gecil. Magazine, Mar., 1873, vol. x. Pseudomorphs by Replacement. fibres, which have been mistaken for asbestus.* " The silica by" which the tissues are thus successively filled and replaced is that which is set free in the decay of the silicates in the gravel. The lignite in the undecomposed and unoxydized portions of this gravel which lie below drainage-level is as yet unsilicified." Similar ob- servations by the late Prof. W. C. Kerr, subsequently published, fully confirm this view of the process of the kaolinization as one go- ing on by the action of meteoric waters in the auriferous gravels of North Carolina ; where also the liberated silica effects the silicifi- cation of imbedded trunks of trees. 174. To resume: the stages of the process of complete silicifica- tion in the auriferous gravels in California, are the following : (1) Conversion of the woody trunks into lignite, often more or less py- ritiferous ; as seen in the bluish unoxydized gravel below the drainage-level ; (2) Gradual silicification of the lignite in those portions of the gravel which, from the downward penetration of atmospheric waters, become the subject of oxydation and kaolini- zation ; the silica set free filling the pores of the lignite, giving a brown silicified mass. (3) Removal of the lignitic matter, as ob- served by Goeppert, leaving silicious casts of the vessels ; (4) Final filling-up of the spaces left by its removal, giving rise to fully silicified wood, like the specimens examined by Dawson and analyzed by Phillips. Casts of the vessels in brilliant crystalline pyrite, liberated, like the silicious casts, by the subsequent decay of the tissues, have also been observed by Dawson in carboniferous strata in Nova Scotia. 1 75. The same process of filling-up cavities presented by organ- ized structures, or left by solution or by decay, is, moreover, seen not only in silica, and in calcite and dolomite, but in many other minerals, including various silicates ; not only colloidal as glauco- nite and serpentine, but crystalline species. Examples of the latter have been examined and described in detail by Dawson and- myself. One of these is in a Silurian limestone from near Wood- stock, New Brunswick, made up of broken organic remains with a calcareous cement. The pores of contained crinoidal joints are therein filled with a crystalline silicate, which on surfaces etched by an acid appears as "a congeries of curved, branching and anastomosing cylindrical rods of the injected mineral, sometimes forming a complete network, and exhibiting under a microscope * Trans. Amer. Jour. Min. Engineers, 1880, vol. viii., pp. 452, 456; also Amer. Jour. Set., May, 1880, and, with farther additions, in Can. Naturalist, new series, IX., 436. 120 Systematic Mineralogy. coralloidal forms, with a white frost-like crystalline aspect, resem- bling the variety of aragonite known as flos ferri. The same crystalline mineral, as observed by Dawson, occasionally fills the interstices between the larger fragments of organic forms in the limestone, and was, according to him, evidently deposited before the calcite, which cements the whole mass." The separated mineral was found on analysis to be a hydrous silicate of alumina, mag- nesia, ferrous oxyd and potash ; having, apart from the water, the oxygen-ratios of zoisite, near to jollyte in composition, and has been named hamelite for Monsignor Hamel of Quebec.* 1 76. Here also may be noticed a mineral which is found in veins in the anthracite, and, in its accompanying black shales of carbon- iferous age, at Portsmouth, Rhode Island. This substance is some- times seen penetrating quartz, but in its pure state appears as a grayish -green mass, consisting of fine transverse, flexible fibres, resembling chrysotile or amianthus ; with which it has been con- founded. Its analysis, however, shows it to be near prochlorite in composition, although containing considerable alkali.f A hydrous silicate not unlike hamelite has also been described by the writer as forming casts of small gastropods in a paleozoic limestone from the island of Anglesea ; and others resembling it have been met with in a fossiliferous limestone of carboniferous age in Ohio.| 177. The relations of all these to serpentine, and to glauconite and similar silicates found under analogous conditions alike in re- cent marine deposits and in ancient rocks, as in glauconites from the Cambrian, and the still older Eozoon, need not here be recalled. It is sufficient to note that this process of deposition alike of silica, of calcite, of dolomite, of pyrite, and of various silicates, both crystalline and uncrystalline, in cavities presented by organized structures, or left by solution or decay, is identical with that which, in all periods, has given rise to the formation of minerals in geodes or veinstones ; and has generated the masses which, when found on a large scale, are best described as endogenous rocks. This term implies that such mineral masses, whether great or * Amer. Jour. Science, 1871 (3), I., 379, and " Mineral Physiology," 193 ; also Dawson, "The Dawn of Life," pp. 120-123, with figure of a portion of a crinoid injected with hame- lite, p. 103. t A portion from a vein about an eighth of an inch wide, gave by analysis : silica, 27.80 ; alumina, 21.80 ; ferrous oxyd, 26.10 ; magnesia, 8.96 ; lime, 2.01 ; potash, 2.69 ; soda, 4.24 ; volatile, 9.30 = 102.90. A subsequent microscopic examination of the material ana- lyzed showed the presence therein of interspersed films of pyrites ; thereby vitiating to some extent the results of the analysis, which deserves to be repeated on a portion of the mineral purified by the aid of bromine-water. * "Mineral Physiology," pp. 194-195. Metasomatosis. 121 small, are formed by interior growth ; as contrasted with masses produced by chemical or mechanical deposition at the earth's sur- face, which are properly designated indigenous rocks / and also with masses which are erupted in a more or less plastic condition through these, from below, and are thus foreign or exotic rocks.* 178. The process of deposition in an enclosed space, by which one mineral species is made to assume the form of another, or else of some organized structure, is evidently very distinct from the process of alteration to which all masses, whether exotic, indige- nous or endogenous, are subject ; the latter, however, more especially so from the conditions of their formation, and the ready access to them of various aqueous solutions. It seems, however, to have es- caped the attention of many who have written upon this matter, that the process of deposition, which in certain cases leads to the replacement of one substance by another, as when silica takes the place of crystals of calcite or of fluorite, or, in the stem of a plant, successively of its vacant spaces and of its solid tissues to none of which has it any direct chemical relation differs fundamentally from the process of alteration. Moreover, the preservation of the details of organized structure in completely silicified wood is only possible through a process limited by its very nature to such organisms, and effected by successive replacements, as already ex- plained. The vague notion that such a process, which owes the very conditions of its success to the structure imposed by organization on living matter, could be extended to mineral masses which have no such structure has, however, been the source of a great many more or less contradictory hypotheses ; which, it is not too much to say, have been a bar to scientific progress, and the source of grave errors. To write in this place the history of these vagaries in de- tail would be unprofitable, but we shall give some examples. 1 79. The doctrine of transmutation or metasomatism, which as- sumes that all the chemical elements, not only of a plant, or a crystal in a vein or cavity, but of a great mass of indigenous or exotic rock, may disappear, and be replaced by something as distinct therefrom as opal is from lignite, or granite from limestone, was in fact maintained a generation since by certain geologists ; and still finds a place in some text-books. Thus it was taught by Blum, Volger and Bischof, that limestone might be changed into gneiss or granite ; while King and Rowney maintained, on the con- trary, that the great beds and masses of crystalline limestone in * " Mineral Physiology," pp. 72, 73. 122 Systematic Mineralogy. the ancient gneissic series of Scandinavia and of North America were at one time beds of gneiss, of diorite and of other silicated rocks, but had suffered transmutation. Following the views of Volger, Pumpelly, as late as 1873, suggested that the bedded petrosilicious porphyry of pre-Cambrian age, in Missouri, with its included magnetite, hematite and manganese ores, may have been derived by a process of metasomatosis from a limestone, parts of which have been replaced by the oxyds of iron and manganese ; " while the porphyry now surrounding the iron ores may be due to a pre- vious, contemporaneous, or subsequent replacement of the lime- carbonate by silica and silicates." * 180. This doctrine of transmutation, as expounded by one school, thus proceeded to assume the conversion of an abundant and widely distributed rock, like limestone, into granite, gneiss, serpentine, petrosilex, and crystalline iron ores ; while according to another school, quartz, diorite and serpentine might themselves be trans- muted into limestone. Such, in brief, were some of the conclusions deduced from certain real and, in other cases, supposed examples of pseudomorphism by alteration and by replacement. Most crystal- line rocks, in accordance with another popular hypothesis, were called " metamorphic ; " and being, according to the above teach- ings, regarded as having been the subjects of pseudomorphic or metasomatic changes, it was declared that " metamorphism is pseudomorphism on a broad scale." f 181. A farther illustration of the development of this hypoth- esis of transmutation, and of its contradictions, is seen in the op- posed views of Genth and Julien as to certain minerals of the crystalline schists of the Blue Ridge ; which both of these mineral- ogists have studied with much care and patience. These crystal- line schists include besides gneissic, hornblendic and serpentinic rocks, stratified masses of a rock composed in great part of chrys- olite ; associated with which are many other crystalline minerals. All of these Genth supposed to have been derived from pre-exist- ing beds of corundum, or crystalline alumina, itself of unknown origin, which by subsequent hydration, chemical alteration and metasomatosis, has been changed to bauxite, diaspore, spinel, opal, * "Mineral Physiology," p. 103, from "Geol. Surrey of Missouri, 1873," "Iron Ores," etc., pp. 25-27. t See for a discussion of this matter, the writer in reply to J. D. Dana, in Amer. Jour. Science, July, 1872, reprinted in "Chem. and Geol. Essays," pp. 313-327; also Preface to. the same volume, 2d ed., pp. xxviii-xxxi : and farther, " Mineral Physiology," pp. 98-103 ; also especially a farther reply to Dana, June, 1875, Proc. Boston Soc. Nat. Hist., xviii.^ Metasomatosis. 123 and a great number of aluminiferous silicates ; including fibrolite, cyanite, tourmaline, various micas, and probably some feldspars ; as also magnesian silicates of the chlorite group. The final result of these changes has been " in many instances a pretty thorough alteration of the original corundum into micaceous and chloritic schists or beds ; or, as Prof. Dana would express it, ' a pseudomor- phism on a broad scale.' " * We here cite the words used by Genth in 1873. 182. Julien, on the other hand, who has since attentively studied these rocks and minerals in the field, declared in 1883 that chryso- lite, and not corundum, has been the point of departure for the crystalline schists in question. He moreover says that while some of the beds of chrysolite remain unchanged, others have been con- verted into strata of cellular chalcedony or quartz, of serpentine, of steatite, of actinolite-schist, of tremolite-schist, and of a diorite or gabbro made up of albite and smaragdite and including corundum, sometimes with margarite. Within these rocks are veins and fis- sures carrying corundum, with various other species ; enstatite, actinolite, talc, ripidolite, etc. With regard to the supposition of Genth, Julien remarks that the notion that these rocks and min- erals " have been derived from the alteration of corundum finds not the least confirmation from my studies, and is indeed strongly con- tradicted by the facts observed in the field. The corundum itself is in all cases, both in the veins and in the particles found in the gabbro, a secondary or alteration-product." f It may, perhaps, be permitted that a chemist, keeping in view alike the associations of these various minerals, and the processes by which many of them may be produced in the laboratory, should reject both of the mutually exclusive hypotheses of Genth and Julien. In opposition to the priority assigned by these chemists respectively to the very unlike minerals corundum and chrysolite, the writer finds it more reasonable to believe that these other species diaspore, spinel, quartz, amphibole, pyroxene, enstatite, feldspars, micas and chlorite, were, like corundum and chrysolite themselves, separately and independently deposited, either contem- poraneously or successively from aqueous solutions. 183. As regards the arguments drawn from the intimate asso- * Genth, Proc. Amer. Philos. Soc., Sept., 1873, and July, 1874; also "Mineral Physiol- ogy, 1 ' pp. 100-101. t Julien, Proc. Bost. Soc. Nat. Hist., 1883, xxiii., 147 ; also, "Mineral Physiologry," pp. 101-102. 124 Systematic Mineralogy. ciation of these various minerals with corundum or with chrysolite, and the supposed existence of intermediate species, while we can say that in these " lie the materials for a history," it is well to in- quire, with Sir Warrington Smyth, whether in many of these cases " we are obliged to conclude that there has been, historically speak- ing, an actual transition from the one to the other" species. The various associations of rocks and minerals in nature, when inter- preted according to the canons of the pseudomorphic school, seem, as that writer has further observed, " to offer a premium to the in- genious for inventing an almost infinite series of possible combina- tions and permutations." * This subject was so well discussed by Delesse, in 1859, that we cannot do better than repeat his argu- ments. Since, in some cases, a mineral is found to be surrounded by another clearly resulting from its chemical alteration, certain mineralogists have supposed that wherever one mineral species en- closes another there has been epigenesis by chemical change. A crystallized mineral species frequently includes a large, and even a predominating portion, of another; and the combination is then con- sidered by many of the school in question as an example of partial pseudomorphous change. In such instances, however, the question arises whether we have to do with the results of envelopment, or of chemical alteration ; to resolve which it becomes necessary to study carefully the phenomena of envelopment. The difficulty in decid- ing whether we have to do with envelopment, or with epigenesis, increases when the enveloped mineral becomes so abundant as to obscure the enveloping species ; or when the two become intimately mingled. The final result of this process of envelopment is thus to give rise to mixed mineral aggregates, owing their external forms to the crystallizing energy of one of the constituents, which may be present in so small a quantity as to be completely obscured by the other matter present. f The imitative forms thus resulting, though differing totally in their origin from the pseudomorphs by chemical alteration or by replacement already described, may still be called pseudomorphs ; though in a sense very different from that in which the term is used by the school in question. 184. We are now prepared to discuss the question of the en- velopment of minerals, as distinguished both from chemical altera- tion and from replacement. At the same time, it should be said that the partial chemical alteration from without may leave a nu- * Smyth, Address as Prest. Geol. Soc., London, 1867. i t Delesse on " Pseudomorphs," 1859; Ann. des Mines (5). xvi., 317-392. Pseudomorphs by Envelopment. 125 cleus of unchanged mineral, as in the case of siderite or of cuprite imbedded in limonite or in malachite; or in certain cases, apparently, of chrysolite enveloped in serpentine. Apart from such examples of enclosure we have now to consider successively, (1) symmetrical envelopment or associ- ation ; (2) non-symmetrical envelopment ; (3) the formation of crystalline shells ; and (4) the filling of these with foreign min- eral aggregates, non-symmetrically arranged. In the first case, or that of symmetrical envelopment, one mineral species is so enclosed within the other that the two appear to form a single crystalline individual. Examples of this are seeen when prisms of cyanite are surrounded by staurolite, or staurolite crystals completely envel- oped in those of cyanite ; the vertical axes of the two prisms cor- responding. Similar cases are seen in the enclosure of a prism of red in an envelope of green tourmaline, of allanite in epidote, and of various minerals of the pyroxene group in one another. This phenomenon of symmetrical envelopment, as remarked by Delesse, shows itself with species which are generally isomorphous and of related chemical composition. Of a similar association, an exam- ple is furnished by feldspar crystals from the lava of Krakatoa ; which are sometimes made up of labradorite, and sometimes of an- orthite; while others show a composite structure. Sections of these last were attacked by chlorhydric acid, which dissolved a layer of anorthite, leaving behind clean and well-defined labradorite ; thus showing a mechanical association of two isomorphous species.* Allied to this is the case of perthite, a banded red and white cleav- able feldspar made up of alternate layers from one to two milli- metres in thickness, of albite and orthoclase, the latter with some microcline. 185. Very unlike to the above are those cases of envelopment in which no relations of crystalline symmetry or of similar chemi- cal constitution can be traced. As well known examples of this kind may be mentioned crystals of staurolite enclosing grains of quartz ; which amount in some cases to more than one-third of the weight, and may be dissolved by prolonged digestion with fluor- hydric acid, leaving the staurolite behind. The farther studies of v. Lasaulx show, moreover, that garnet, mica, magnetite and brookite may also be present as disseminated impurities in stauro- * Br&m, Compte Rendu de VAcad. des Sciences, ciii., 170. For a more detailed dis- cussion of this matter see the author's " Chemical and Geological Essays," pp. 388-290 ; also, " Mineral Physiology," etc., pp. 293-296 and 340-342. 126 Systematic Mineralogy. iite. The so-called crystallized sandstone of Fontainebleau, with the external form of calcite, may hold from 50 to 65 per cent, of grains of quartz, mechanically enclosed in well-defined rhombohe- dral crystals ; and similar crystallized aggregates of gypsum and silicious sand are met with. Very similar to these are the crystals with the form of orthoclase, which sometimes consist in large part of a granular mixture of quartz, mica and orthoclase, with a little cassiterite, and in other cases, contain two-thirds their weight of the latter mineral, with an admixture of orthoclase and quartz. Crystals with the form of scapolite, but made up, in a great part, of mica, seem to be like cases of envelopment, in which a small proportion of one substance in the act of crystallization, includes a large portion of foreign material, which so masks the crystalliz- ing envelope that this becomes overlooked, as of secondary import- -ance. The substance which, under the name of houghite, has been described as an altered spinel, is found by analysis to be an admix- ture of voelknerite with a variable proportion of spinel, which, in some specimens, does not exceed eight per cent., but to which, nevertheless, these masses appear to owe their more or less com- plete octahedral form. Crystals of dark colored amphibole some- times contain magnetite disseminated in such excess that the ilicate appears like a cement enclosing the grains of the oxyd. As remarked by Zirkel, even a small proportion of amphibole gives its crystalline form to the aggregate, in which magnetite greatly predominates. 186. Still another case of envelopment is known, in which crys- tals externally homogenous are found to consist of a shell,, some- times very thin, including other minerals, which differ widely in composition from the envelope, and have, moreover, with it no apparent relations either crystalline or chemical. More rarely the shells are empty. We have in the first place to inquire as to the origin of these hollow or skeleton-crystals, which have in most instances, however, been subsequently filled up. Certain ortho- clase crystals with hollowed-out or hopper-shaped faces, were long since described by Fournet as resulting from the formation of a frame or skeleton of a crystal, when the material was not sufficient for their completion. Such a process is not unfrequently seen in crystallization, whether from fusion, solution or vaporous conden- sation ; giving rise in some cases to external depressions and in others to internal cavities in the resulting crystals. A familiar example of this is seen in the prismatic crystals deposited in the Pseudomorphs by Envelopment. 127 cooling of an aqueous solution of potassium nitrate, which present interior cavities, sometimes traversing the axis of the prism, giving rise to tubular crystals. Kunz has described such hollow crystals of quartz found in a sandstone in Arizona, often grouped around a nucleus of chalcedony. These prisms, with pyramidal termina*- tions, are thin shells, and are sometimes half an inch in diameter.* 187. Small hollow prisms of red and of green tourmaline are com- mon in the granitic veinstone of the famous locality in Paris, Maine, f More frequently, however, the subsequent process of deposition has filled such cavities with other minerals. Thus hollow prisms of tourmaline are found to contain crystals of orthoclase or of mica, and a hexagonal prism an inch in diameter, from Haddam, Conn., was seen to enclose within a thin shell of apparently homogenous beryl a granular mixture of orthoclase and quartz, holding small crystals of garnet and tourmaline ; a mixture similar to that of the enclosing granitic veinstone. A prism of yellow idocrase, half an inch in diameter, from a vein in Grenville, Quebec, composed chiefly of orthoclase and pyroxene, is seen, when broken across, to consist of a thin shell filled with a confused aggregate of crystalline orthoclase, including a small prism of zircon. In like manner large crystals of zircon from northern New York, in similar veins, are sometimes thin shells filled with calcite. Garnet crystals are also found, the walls of which are no thicker than paper, en- closing in different examples, crystalline calcite, epidote, chlorite and quartz ; while crystalline shells of leucite may, in like manner, enclose feldspar. Leucite crystals themselves often include au- gite, magnetite and portions of vitreous matter, which are frequently symmetrically arranged. In some cases the materials enclosed show evidences of slow and alternate deposition. Dodecahedral crystals from Auburn, Maine, described by Kunz, are made up of successive layers of garnet and calcite, of which two minerals not less than twelve were found in a crystal twelve centimeters in diameter. A prism thirty centimetres long and twenty-two in diameter, externally of beryl, from Auburn, Maine, was found to consist of twenty-five layers of this mineral, with twenty -five of an aggregate of albite, quartz and muscovite ; which also filled the centre. The hexagonal form of the thin successive layers of beryl was sharply defined. J * Amer. Juor. Science (III.) xxxiv., p. 477. t See the author on " Granitic Rocks and Veinstones," Amer. Jour. Set., 1871-72, and "Chem. and Geol. Essays," pp. 201, 211-214. % Trans. Amer. Assoc. Adv. Science, vol. xxxiv., p. 240, and also a private com- munication. 128 Systematic Mineralogy. 188. Facts of a different order are presented by the rounded crystals of quartz and some other minerals, long since noticed by the late Prof. Emmons in the Laurentian veinstones of North America. The quartz crystals in question, sometimes have their angles so much rounded that the crystalline form is nearly or quite effaced, the surfaces being at the same time smooth and shining. Moreover, as described by the writer, crystals of calcite and of apatite in the same veins present similar characters. At the same time, crystals of orthoclase, pyroxene, titanite and zircon associated with these rounded crystals (as observed by Emmons for orthoclase in contact with quartz) preserve their sharpness of .outline; a fact supposed by him to be due to a subsequent partial fusion. The crystals of apatite in many of these veins in Ontario, whether in drusy cavities or imbedded in cleavable calcite, are often rounded or cylindrical masses. This rounding of the angles in the various kinds of crystals in question is, in the writer's opinion, due to the solvent action of the heated waters from which the minerals of these veins have been deposited ; crystals previously formed having been partially redissolved, as the result of some change in the temperature or the chemical composition of the waters. Thus, heated solutions of alkaline carbonates or bicarbonates would attack and dissolve apatite and quartz, while without action on crystals of feldspar or of pyroxene ; both of which, as is known may be artificially formed in such liquids. That this process of solution has been renewed at intervals in the filling of these min- eral veins, is shown by the fact observed by the writer of rounded crystals of calcite, enclosed in a large crystal of quartz, the angles of which were also nearly obliterated. Large terminated prisms of quartz are also found embedded in bornite, in Leeds, Quebec, with their angles much rounded, and their faces concave, having lost their polish, and being coated with a green film, apparently of a copper silicate. From the mode of their arrangement, it is evident that these crystals lined drusy cavities in a quartz vein, and were partially redissolved previous to the deposition of the copper sul- phid. Similar examples have since been found in a cupriferous vein in Virginia. 189. The crystalline form of a mineral species, being the geo- metric shape assumed by the crystalline individual, which con- notes a certain structure apparent in the cleavage and in the ther- mic, optical and electrical relations of the crystal is, notwithstand- ing its value in determinative mineralogy, the least essential ; or in Porodic or Colloid Bodies. 129 other words, the most accidental form of the mineral species itself. This is made apparent by the fact that, as already pointed out, the same chemical species may assume two distinct crystalline forms, its hardness and specific gravity remaining the same. In many cases we have to do with massive minerals, which are nevertheless cryptocrystalline ; that is to say, crystalline in their intimate structure, as is shown by microscopic examination, especially with the aid of polarized light. There are besides, how- ever, a large number of bodies which are completely structureless or amorphous. The characters of these have been studied by many chemists, notably by Fuchs, Graham and Regnault, among^ others.* Breithaupt, who already, in 1836, recognized the import- ance in mineralogy of amorphous bodies, designated by him porodic, had, as we have shown in Chapter II. (14), proposed an order, Porodini, and subsequently a genus, Amorphites. This distinction has, moreover, been insisted upon by his successor, Weisbach. To the class of porodic bodies belong all natural and artificial glasses, and all other amorphous substances destitute of marks of crystalline structure, whether of aqueous or igneous ori- gin. Gums, dextrine and glue are examples, and many other sub- stances, both soluble and insoluble, are capable of assuming tempo- rarily the porodic condition. Graham, who had already contributed greatly to our knowledge of this condition of matter, but to whom the work of Breithaupt was unknown, discovered subsequently their peculiar relation to liquid diffusion, and taking glue or gelatine as the type, proposed for them the designation of colloids, as distin- guished from crystalline bodies, called by him crystalloids.f The substantive colloid, and the corresponding adjectives colloid and colloidal have since been generally adopted, and the latter will be used as synonymous with porodic in these pages. 190. Graham, whose studies threw great light upon the subject of colloids of aqueous origin, conceived that they might have high- er equivalent weights than the corresponding crystalloids ; but so far as known, colloids pass by intrinsic condensation, with augmenta- tion of specific gravity and evolution of heat, into crystalloids. It is however true that colloids have much higher equivalent weights than the corresponding gaseous or dissolved chemical spe- cies which by subsequent polymerization generate the crystalline * Gmelin's " Handbook of Chemistry," Cavendish Soc. Ed., 1848, vol. i., 102-107. t Graham, " Liquid Diffusion applied to Analysis." Philos. Trans. 1861. See, for a far- ther discussion of this subject, the author's " Mineral Physiology," etc., pp 374, 375 and 383, note ; also " A New Basis for Chemistry," pp. 54 and 132. 130 Systematic Mineralogy. mineral species. This conclusion, expressed by the writer in 1887, has since been verified by various determinations, by Raoult's method, of the integral weight of colloids, such as the dextrines, inulin, glycogen and soluble starch ; and also of the soluble tung- stic and molybdic and silicic acids. It was because soluble col- loids appear to mark the passage from crystallizable chemical species to crystalline mineral species that the writer in 1886 was led to speak of palagonite and other hydrous colloidal silicates as mineral protoplasm.* 191. These porodic or colloidal bodies, whether hydrous or an- hydrous, whether of aqueous or of igneous origin, are often more or less unstable and prone to assume a crystalloid condition. Thus viscid colloidal sulphur slowly assumes a crystalline structure at ordinary temperatures, and if heated to 93 rapidly undergoes a similar change ; the temperature, from intrinsic condensation, rising to 110, and the process being marked by a considerable increase in specific gravity. Colloidal or vitreous sugar also slowly suffers a similar change, but if after fusion it is cooled to 38, and then, when still viscid, rapidly wrought and drawn out into threads, its temperature rises in a few minutes to 80, and it becomes changed into crystalline grains. The writer has elsewhere described a some- what similar case, when the cold dilute nitric solution of the mixed cerium metals is precipitated by a solution of oxalic acid. The in- soluble oxalates then separate as a viscid colloidal mass which, when wrought in the hands, soon grows hot and changes into an incoherent crystalline powder. In like manner the vitreous trans- parent colloidal arsenic teroxyd slowly passes, at ordinary temper- atures, into an opaque granular mass, and many silicate glasses, at temperatures below fusion, are devitrified and converted into an aggregate of crystals, which by a greater heat melt and are again changed to glass. Many cases may be cited also of transform- ation like that of the cerium oxalate, where amorphous precipitates, under water, pass into a crystalline state ; examples of this are seen in calcium carbonate, in hydrous magnesium carbonate, and in lead malate.f In these transformations, so far as known, there is an augmentation of density, attended with evolution of heat as the result of intrinsic condensation. 192. A remarkable example of the change of colloid into crys- talline matter is furnished by the observations of Bunsen on palag- * Mineral Physiology," etc., pp. 183, 374. t Ibid., pp. 169-171. The Crenitic Process. 131 onite, an amorphous highly hydrated substance resulting from the action of heated waters on certain basaltic rocks ; which, when ex- posed to heat, develops crystalline chabazite in its substance, and is thereby transformed into a zeolitic amygdaloid. When frag- ments of amorphous native palagonite are rapidly heated in the flame of a lamp, according to Bunsen, cavities are formed therein, filled with a white matter, which by a lens is recognized as crys- talline chabazite. It is " the amorphous portion of the basalt that gelatinizes with acids which is the part forming zeolites." Palag- onite, from the mode of its formation, is a colloidal hydrated mixture of silicates, having besides the elements of a zeolite like chabazite, an excess of alumina, together with iron oxyd and more or less magnesia, and may, as Bunsen has shown, be artificially formed from basalt.* We have in this case a most instructive example of the results of the successive action of water and heat in transforming an igneous uncrystalline rock into crystalline min- eral species, and one which, as we have elsewhere sought to show, affords a key to the origin of the great mass of crystalline silicated rocks that make up the older terranes, by what we have desig- nated as the crenitic process, f 193. This process of generating crystalline mineral species, though somewhat modified in its conditions, and to a greater or less degree obscured by the intervention of mechanical sediments, has moreover been continued through all subsequent ages down to the present time. Recalling the examples of deposited silicates already noticed in 1 75, and referring the reader elsewhere for a detailed dis- cussion of results, we may note some illustrations which help to throw light upon the part played by this process in the production of crys- talline minerals. The formation of concretionary or endogenous gra- nitic veins (1V7) is a casein point, of which striking examples may be seen, under favorable conditions, not only in the more ancient terranes, but in those of paleozoic and of mesozoic age. The large vertical dykes of doleritic or allied basic eruptive rocks which intersect the fossiliferous Ordovician (Trenton) limestones at Mon- treal, Canada, enclose banded granitic veins, apparently filling fissures therein. These veins, sometimes twelve inches or more in thickness, may be traced considerable distances, and are made of coarsely crystalline white orthoclase, with quartz, sometimes lining * Bunsen, "Recherches sur la formation des roches volcaniques en Islande," (1853). .. de Chim. et de Phys. (3) xxxvui., 215-289. Also " Mineral Physiology," pp. 129, 130. t "Mineral Physiology," pp. 132-134, et seq.; also pp. 241-245. 132 Systematic Mineralogy. druses with distinct crystals, and more rarely with amphibole, biotite, magnetite and other minerals. 194. In like manner, the diabase of mesozoic age, of Bergen Hill, New Jersey, is traversed by veins from one to four inches thick, .alike of quartz and of flesh red orthoclase, the two species some- times intermingled. With the orthoclase are moreover found zeo- lites, pectolite, apophyllite and datolite, and more rarely galenite, pyrite and chalcopyrite, as has been well described by Mr. Kunz. In other localities, not only orthoclase, but albite, garnet and tour- maline are also found, apparently as secretions, in the midst of similar basic eruptive rocks. The whetstone or coticulite of the Ardennes in Belgium is shown by the chemical and microscopic studies of Renard to consist of rounded grains or minute crystals -of a manganese-alumina garnet (spessartite), with others of green tourmaline, and probably of chrysoberyl, included in a base of fine hydrous mica ; sometimes with pyrophyllite in fissures, and with intersecting veins of quartz. Layers of this aggregate from one to ten centimeters thick, pale yellow in color and conchoidal in fracture, are interstratified with and graduate into a fine grained schist, itself with transverse cleavage, made up chiefly of similar mica, but containing besides the garnets, etc., laminae of hematite, and carbonaceous grains. The evidence of contemporaneous for- mation of the various species in these ancient argillites is clear.* Again, in the beds of siderite extensively mined as an ore of iron in the Cleveland district in England, which are of the mesozoic (Oolitic) period, the residue left by the action of chlorhydric acid contains, besides small crystals of quartz, great numbers of well-defined microscopic crystals of titanium oxyd (octahedrite) and with these, according to Rutley, in smaller number, crystals of zircon and of tourmaline, f 195. The oxide of tin, cassiterite, which, like quartz, occurs crystallized in ancient granitic veinstones, appears like it to have been deposited from solutions in recent times. Collins, in the " Transactions of the Royal Geological Society of Cornwall," has described his examinations of deer's horns from the tin-bearing gravels of the region, which are impregnated with cassiterite, and even contain visible crystals of the mineral. Some of these horns *Dick, " Mem. Qeol. Survey Gt. Brit.," 1856, I., p. 95; also Rutley, "Rock-forming Minerals," p. 138. t Renard, "Sur la comp. mineralogique du coticule," Mem. de VAcad. Roy. de la JBelgique, 1877 ; also, by the same, "The Belgian Whetstones," Month. Micros. Jour., 1877, xvii., 369, and " Mineral Phys.," pp. 422, 435. The Crenitic Process. 133 are so rich in tin -ore as to be sought by the smelter. A specimen examined by Collins, of the horn of the red deer ( Cervus elaphus) contained 2.6 per cent, of oxide of tin and 1.6 per cent, of pyrites ; both of which were seen by the microscope to be inclosed in the cells of the horn.* The process of stannification is thus, like that of silicification, one in progress in modern times, though under conditions as yet unknown to us. Zeolites, and related hydrated silicates, are found in de- posits in the ancient masonry constructed by the Romans around certain thermal springs in France, f Moreover it has been shown that the formation of a crystalline zeolite, phillipsite, is now going on abundantly in the depths of the Pacific Ocean. The crystals, which are either simple, twinned or in spheroidal groups, are sel- dom over half a millimeter in diameter, and are supposed by Mur- ray and Renard, who have described them, to be due to a transfor- mation of amorphous basic igneous silicates allied to palagonite, into the zeolite, on the one hand, and the associated red clay of these deep-sea areas on the other ; the action going on at the tem- perature near 0, which there prevails.! 196. The contemporaneous formation of orthoclase and zeolites observed in basic eruptive rocks, as in the Keweenian series on Lake Superior, and elsewhere, shows that the production of an anhydrous or a hydrous species may depend upon slight variations in condition. An instructive illustration of this is found in the observation of de Senarmont, who found that in the decomposition of an aqueous solution of aluminic chlorid under pressure, at ele- vated temperatures, there were formed not only crystals of corun- dum, but distinct crystals of the hydrous species, diaspore. Again, Friedel et Sarrasin, in similar experiments, with heated alkaline solutions containing silica and alumina, in sealed tubes, obtained crystals of albite, and, with certain variations in the composition of the liquid, crystals of the zeolite, analcite. As a farther and a striking example of the production at ( will of anhydrous and hydrous species, may be cited the experiments, on a large scale, of Behr on the crystallization of dextrose. The solutions of this, within very narrow limits of temperature and concentration, yield crystals either of anhydrous or of hydrous dextrose ; and under cer- * Smithsonian Report, 1882 ; " Progress of Geology." t See the studies of Danbree thereon, resumed in "Mineral Physiology," pp. 150-155. J Nature, June 5, 1884, p. 133, and " Mineral Physiology," p. 154. 134 Systematic Mineralogy. tain conditions admixtures of the two species may even be obtained as the result of contemporaneons crystallization.* By such a process as this, it is maintained by the writer, the operation of permeating waters and watery solutions, has effected a progressive differentiation of a primary porous basic plutonic mass ;, abstracting from it, and depositing, alike in veins and in beds, both the indigenous and the endogenous crystalline masses of the earth's crust. As this action, both in ancient as in modern times, has been affected by the agency of springs, it has been designated as a crenitic process. A similar process, under condi- tions which, from the nature of things, is but imperfectly under- stood, apparently still goes on, under great pressure, in abyssal depths of the ocean, f 197. As regards the association in nature of species differing from each other in the presence and absence of water, as the zeolites and the corresponding feldspars, mineralogists have been disposed to admit as a general principl that the hydrous species have been derived from one previously anhydrous. Thus, it is said, diaspore may come from the hydration of corundum, and limonite from hematite. In like manner, it is conjectured that certain hydrous zirconic silicates result from a hydration of zircon, and fahlunite from iolite ; while hydrous minerals having the composition of al- lanite are supposed to be the results of hydration of a previously anhydrous species, and even the monohydrated and trihydrated columbates of yttria (fergusonite) are in like manner described as secondary products. In opposition to this view it has been maintained by the writer that in such cases we have to do either with successive production of anhydrous and hydrous species, under slightly varying conditions, or else a subsequent dehydration of a previously hydrated com- pound. It seems to have been overlooked that many hydrous species are unstable, and that the presumption is generally in favor of a loss of water, rather than the contrary. Thus, in opposition to the notion of the hydration of ferric oxyd, it will be remembered that the artificial hydrate becomes anhydrous in the presence of water even at 100. This conception of the hydration of anhydrous mineral species comes from the hitherto generally received notion of the igneous as opposed to the aqueous origin of crystalline minerals. The subject will be farther considered in a subsequent chapter. * Behr, Jour. Amer. Chem. Soc., 1882, iv., 11, and " Mineral Physiology," 504. t For a full discussion of the crenitic hypothesis, see " Mineral Physiology," pp. 134- 189 and 941-245. The Constitution of Mineral Species. 136 CHAPTER X. THE CONSTITUTION OF MINERAL SPECIES. 198. The investigations by chemists during the first half of thia century, of substances derived directly or indirectly from the or- ganic world, led to the artifical divisions of organic and inorganic chemistry. In the former, the study of various hydrocarbons, alcohols, ethers, glycerids, acids and bases, often complex in con- stitution, and having more or less elevated integral weights, fre- quently, moreover, constituting members of progressive series, seemed to differentiate the chemistry of the bodies of the carbon- series from that of those non-carbonaceous substances which were included in the domain of inorganic or mineral chemistry. The conception of polymerism was already familiar by examples among the hydrocarbons and cyanogen compounds, before it was extended to so-called inorganic species. In 1847, however, we find Favre and Silbermann, from their thermo-chemical studies, led to the con- clusion that crystallized salts should be represented by formulae which are multiples, by some whole number, of those deduced from analysis. Graham, again, from his studies in liquid diffusion, sup- posed the existence of similar polymers in solutions ; while the present writer, in 1848, proposed to regard charcoal, graphite and diamond as so many "polymeric modifications of elemental car- bon," and also cited the dense sulphur-vapor, then known, as an example of polymerism.* The law of progressive and homologous series had, at this time, been recognized only in hydrocarbonaceous species, and its extension to other compounds makes an epoch in chemical theory ; leading as it does to the conclusion that the chemical formulas of many mineral species are very complex, and have integral weights far higher even than those hitherto admitted for hydrocarbonaceous bodies, 199. The earliest statement, so far as the writer is aware, of the application of the doctrine of complex formulas, of high equiv- alent weights, and of homologous relations, to mineral or inorganic chemistry will be found in a paper by him, in 1853. Therein it was contended that isomorphous solid species, at least, " have the* * " A New Basis for Chemistry," pp. 10-13, 39, 40, 113. 136 Systematic Mineralogy same equivalent volume, so that their equivalent weights (as in the case of vapors) are directly as their densities ; and the equiva- lents of mineral species are as much more elevated than those of the carbon-series as their specific gravities are higher." Referring to the latter, "the hydrocarbonaceous or so-called organic species," and to the law of progressive or homologous series, it was said that "it may be expected that mineral species will exhibit the same general relations as those of the carbon-series, and the principle of homology be greatly extended in its application. The history of mineral species affords many instances of isomorphous silicates whose formulas differ by 7i(O 2 M 2 ) ; as the tourmalines, and the sili- cates of alumina and of magnesia." 200. It was then farther declared that the native mineral car- bonates or carbon -spars must be represented as polycarbonates, having not less than from " twelve to eighteen equivalents of base replaceable, so as to give rise to a great number of species," among which the relations of their densities were said to "indicate the existence of several homologous genera which are isomorphous." In subsequent papers, in 1853 and 1854, attempts were made to show that in these polycarbonates n(CMO 3 ) the different val- ues of n might be not less than 22, 25, 30, 36 and 40. Similar elevated formulas were also given in 1853 for various poly silicates ; a,s in the cases of pyroxene, amphibole and wollastonite, and of the feldspars, albite, anorthite and orthoclase. In this connection moreover, the complex silicates containing chlorides, carbonates and sulphates were considered, and were compared to basic salts ; * while the variations in the ratios of silica and alumina in nearly related species, and the apparent partial replacement therein of silica by the latter, then imperfectly understood, were noted, in 1854, as seeming to invalidate the distinction between silica, as the negative or acidic member, and the positive or basic member of these oxydized compounds, in which alumina was at that time still generally included. P. A. v. Bonsdorff, however, from his studies of aluminous augites and amphiboles, had already been led to * "Theory of Chemical Changes and Equivalent Volumes," Am. J. Sci., xv., 226-334 ; Phil. Mag. (4), v., 526, and in a German translation in the Chem. Centralblatt of Leipsic for the same year (p. 849) ; also in the author's " Chem. and Geol. Essays," pp. 427-437. Far- ther, 4t The Constitution and Equivalent Volume of Mineral Species," Am. J. Set., xvi., 203- 218, and, in abstract, in "Chem. and Geol. Essays," p. 438, etc. Also, " Illustrations of Chemical Homology," Proc. Am. Asso. Adv. Sci., 1854, pp. 237-247 ; also in abstract, Am. ^J. Sci. for September of the same year ; and noticed, with extracts, in the author's "Chem. and Geol. Essays," p. 438 et seq. The whole question is farther discussed in Mineral Physiology," etc., pp. 288-295. Homologous Series. 137 suppose that in these minerals alumina should be regarded as a negative or halogenous element, replacing a portion of silica, in the ratio, SiO 2 : A1 2 O 3 ; a view which was supported by Scheerer.* The relations of alumina in combination will be considered more at length farther on. Besides the general application of the principle of homologous or progressive series, we had thus extended to the bodies of inorganic or mineral chemistry, on the one hand, the conception of many equivalents of replaceable base, and on the other of many equiva- lents of the acidic or negative element ; which might be either car- bonic, silicic or boric oxide, or might include with the latter, alumina, sulphuric or phosphoric oxyd, fluorine or chlorine ; thus leading to the recognition of the existence of polybasic salts in which the negative or acidic might be as complex as the positive or basic member. 201. Before proceeding farther, it will be well to recall briefly the principal facts in the history of the doctrine of progressive series, which, not less than the doctrine of multiple proportions, and the facts of polymeric condensation, serves to illustrate the law of numbers in nature. f This doctrine of series, which appears to have been first enunciated in chemistry by James Schiel of St. Louis, Mo., in 1842, and adopted by Charles Gerhardt in 1844, was by them made to show that hydrocarboriaceous bodies differing from each other by (CH 2 )n, have similar functions, and may be repre- sented by a common formula ; constituting what was called by Gerhardt, a homologous series. The present writer, in 1853, at- tempted to extend this doctrine to other compounds, maintaining that bodies differing by (OH 2 )n, (OM 2 )/& and (SM 2 )w might, like those differing by (CH 2 )n, be homologous ; these formulas being, in the notation of the time, (O 2 H 2 )yi, (O 2 M 2 )n, (S 2 M 2 )n and (C 2 H 2 )7i. The principle of progressive series was thus to be extended from hydrocarbonaceous bodies to other compounds of the mineral kingdom, as was then attempted to be shown in the case of native silicates and carbonates. Still farther, in 1855, it was claimed that various considerations " lead us to admit an intimate relation between bodies differing by H 2 ; " whence a similar relation might * Gmelin's Handbook," Cavendish Soc. ed., iii., 403, note. f " Thou hast ordered all things in measure and number and weight. 1 " This dictum, in its Latin version, " Omnia mensura et numero et pondere disposuisti,' 1 Liber Sapi- entiae. Cap. XL, is the motto of the author's " New Basis for Chemistry," in which see also p. 69, note. 138 Systematic Mineralogy. be expected between bodies differing by M 8 , as was subsequently maintained. 202. The formulas of homologous bodies present series in arith- metical progression, in which the first term may be the same as the common difference, as in the olefine series, (CH 2 )n / or unlike the common difference, as in the compound ammonias, NH3 . . . (CH 2 )/. Each of these cases is illustrated in the chemical history of many mineral species. The series in which the common difference is the same as the first term has since been designated by the writer as isomeric homologues, while all other progressive series may be ap- propriately named anisomeric homologues. The first are evidently examples of simple homogeneous intrinsic condensation or poly- merization, and were illustrated by the more or less dense carbon- spars, such as calcite, aragonite, dolomite and magnesite ; while ex- amples of series of the second class, or anisomeric homologues, were shown in the various feldspars, amphiboles and tourmalines.* 203. It was not until after many years that this conception of the general application of the doctrine of progressive series was adopted by other chemists. Illustrations of it, however, were not wanting, and Wolcott Gibbs, following up the researches of Marignac, and the later ones of Scheibler, by his own remarkable studies of the polytungstates, described them in 1877 as homologous or progres- sive series ; " the homologizing term," as he has designated the com- mon difference, being 2(WO 3 ), and the values of the co-efficient n varying from 2 to 12 and even to 30. \ Other striking examples of the recurrence of homologous series might be cited ; one of the most notable is that furnished by the double sulphids of antimony and lead, of which zinkenite and meneghinite are examples. These, in our monadic notation, are represented by The values of n in the species known are 1, 1 J, l, 2, 3, 4, 5, 6 ; or rather, multiplying by four, to avoid fractions, are 4, 5, 6, 8, 12, 16, 24, 32 ; while for corresponding silver compounds the values of n are 20 and 48. 204. Apart from -the general extension of the law of homolo- gous series, we have mentioned, as serving to systematize mineral * The student will find this whole subject discussed at length in *' A New Basis for Chemistry," pp. 40-50, and 155-182 ; also in " Mineral Physiology," etc., pp. 386-390. t See farther, for a discussion of this question, " Mineral Physiology," etc., pp. 384-394. Compound Inorganic Acids. 139 chemistry, the doctrine of polybasic acids, polymeric in origin, as was suggested for carbonates and silicates. This conception, though .advanced in 1853, did not find favor among chemists until 1860, when Adolphe Wurtz again put forth the notion of polysilicates ; citing in connection therewith, the metastannates of Fremy, in which the negative element consists of 5(SnO 2 ). The similar me- tatungstates or tetratungstates, the pyroborates, the polyphos- phates of Fleitmann and Henneberg, including tetraphosphates and dekaphosphates, and the not less complex phosphates of Wallroth, with 9(P 2 O 5 ), soon showed that such a polymerism is not excep- tional in negative or halogenous oxides. A complexity of a higher order than that of polymerism is, however, observed in many cases, as already noticed in Chapter VI. (91), and requires farther consideration. The associations with natural silicates, as integral parts of the species, of portions of sulphate, carbonate, borate, sulphid, chlorid and fluorid, are exam- ples of a principle of wide application, in virtue of which different negative or acidic substances of the same, or of unlike valencies, unite to form what Wolcott Gibbs, whose generalizations on the subject constitute a most important contribution to theoretical chemistry, has called compound inorganic acids. These composite mineral acids may be defined as combinations of two or more negative or acidic oxides, often of different groups ; frequently attaining very high equivalent weights, and often of comparatively small saturating power. The high integral weight, the limited basicity, and the partial instability of these complex acids and their salts, are well illus- trated in the phosphomolybdate of ammonia formed in the ordi- nary method for determining phosphorus thereby. This insoluble compound, when precipitated in presence of an excess of chlorhy- dric or nitric acid, contains 12MoO 3 .PO,.(NH 4 ) 8 , besides 2NO 3 .H 2 O or 2HC1.H 2 O, constituting a nitro- or a chlor- hydro-phospho-dodekamolybdate ; but by desiccation at 150, these volatile acids and water are expelled, leaving the phosphomolyb- date, with 3.78 per cent of phosphoric oxide, P 2 O 6 . 205. For the purposes of illustration it may be well to note some of these acids and their salts, in which we shall follow the notation 140 Systematic Mineralogy. adopted for them by Gibbs. The boritungstates of Klein are rep- resented respectively by BA.7WO3 B 2 O 3 -12WO 3 -f 4RA B 2 O 3 .14WO 3 4-3KA In the complex molybdates described by Struve and by Parmentier are two aluminimolybdates AlA.12MoO 3 besides corresponding chromic and ferric compounds, and a man- ganimolybdate, Mn 2 O 3 .16MoO 3 -j- sRgO.HgO. These same sesquioxides may also, according to Gibbs, unite at the same time both with phosphoric and molybdic oxides to form still more complex bodies. We have, moreover, silicotungstates, phosphotungstates, vanadotungstates, arsenotungstates, antimono- tungstates, and even stannophosphomolybdates and stannophospho- tungstates of various degrees of complexity ; in which the negative or acidic member is made up of tetrad, pentad and hexad oxides united. Besides the tetrad oxides, SiO 2 and TiOg, other tetrad forms, as VO 2 , MoOg, and WO 2 may enter, and, in addition to the pentad oxides named, triad oxides of phosphorus and arsenic. Portions of the oxygen in molybdic and tungstic hexad oxides may be replaced by fluorine ; while hydrocarbon radicles, as ethyl, methyl and phenyl, appear also to be capable of entering into these compounds. In the case of the silicotungstates of Marignac, two types are known, in which SiO 2 is united respectively with 10WO 3 and 12WO 3 ; while, as Gibbs has shown, the silica therein may be replaced by the oxyds of platinum, selenium, tellurium, etc. The oxyds of tin, titanium, zirconium, columbium and tantalum also appear to form similar combinations with the tungstates and molybdates. In the phosphotungstates, according to Gibbs, we have a homologous series, the extreme terms of which, so far as known, are P 2 5 -6W0 3 + <3H 2 . . . .PA-24WO 3 + 6H 2 O ; the common difference being 2WO 3 . All of these series of salts The Relations of Alumina. 141 are soluble in water, and crystallizable, generally assuming clino- rhombic or anorthic forms. 206. The relations of alumina, and certain other allied triad oxyds, may now be noticed. Half a century since, when the doc- trine of valency was unknown, all basic oxyds were divided into protoxyds (or suboxyds) on the one hand, and sesquioxyds on the other. At that time gallium, indium and thallium were undiscov- ered, and the sesquioxyds were chiefly represented to the chemist by aluminic, and the corresponding chromic, manganic and ferric triad oxyds ; to which might be added the rare oxyds of bismuth and uranium, and also that of beryllium, then erroneously reckoned in the same category. Certain chemical analogies led Berzelius,, to whom we owe the first accurate knowledge of zirconia, to regard it also as a sesquioxyd, Zr 2 O 3 ; and this view was henceforth gener- erally adopted by chemists (with the exception of Gmelin, who wrote it ZrO), until the determinations of the vapor-density of the volatile zirconic chlorid showed that zirconia, like silica, (which Ber- zelius made SiO 3 ) was to be regarded as a tetrad oxyd. In those days also, scandium and ytterbium were still unknown, and yttrium and lanthanum oxyds, together with the corresponding oxyds of cerium and didymium, were universally regarded as protoxyds* Hence alumina, with the so-called peroxides of chromium, mangan- ese, and iron, which replace it in alums (together with beryllic and zirconic oxides), became to chemists the type of sesquioxides. The contrast between these and other basic oxides was such as to influ- ence strongly the chemical classification of natural silicates, into so- many of which alumina enters. It was in accordance with these views, farther impressed upon chemical mineralogy by the author- ity of Rammelsberg, that the writer attempted, in 1885, the divis- ion of all such silicates into three parts : (1) protosilicates, or non- aluminous silicates, like chrysolite ; (2) protopersilicates, or silicates of alumina and protoxides, like -orthoclase ; (3) persilicates, or sili- cates of alumina without protoxides. At the same time, the sesqui- oxides of Cr, Mn and Fe were rightly (and zirconic oxide wrongly) regarded, as in certain cases, more or less completely replacing alu- mina. The oxide of beryllium was, however, reckoned as a pro- toxide. Apart from the erroneous position thus assigned to zirconia, the fallacy underlying this time-honored distinction between protoxides and sesquioxides will be apparent when it is considered that it is not the sesquioxide or triad character of alumina which determines 142 Systematic Mineralogy. its relations in these silicates, and in other combinations, but its po- sition intermediate between negative and positive triad oxides; which makes it acidic to monad and diad positive or basic oxides, on the one hand, and basic to the more strongly negative oxides, on the other. 207. Bonsdorff had, in fact, made a first step towards the concep- tion of compound inorganic acids when he proposed to consider alum- ina as partially replacing silica in certain natural silicates. Alum- inic, like boric oxyd, may thus be coupled not only with tetrad silicic oxyd, but with pen tads like phosphoric oxyd, with hexad oxyds, like molybdic oxyd, and with monad elements, as chlorine and flu- orine, to form complex negative or halogenous bodies. An exam- ple of this is seen in the two aluminimolybdates of Parmentier, no- ticed above ; where, as is also shown, aluminic oxyd may be replaced by chromic, ferric and manganic triad oxyds. More than one-half of the native silicates known to mineralogy (without counting the small number of simple aluminous silicates, hydrous and anhy- drous) contain aluminic oxyd together with some more distinctly basic oxyd. The triad oxyds of chromium, manganese and iron (and even of titanium) may occasionally replace aluminic oxyd in these silicates, not in virtue of their triad constitution, but because of their relatively negative character, which brings them near to it chemically. It will be found, as before noted (54), that the markedly basic triad oxyds, like those of yttrium, lanthanum, ceri- um and didymium do not replace aluminic oxyd, but, on the con- trary, take the place of diad oxyds. The same may be asserted of the basic tetrad oxyds of zirconium and thorium. Among native oxydized aluminous species, besides the com- pounds of alumina with pentad and hexad oxyds, may be dis- tinguished : (1) Aluminates, including non-silicated compounds of aluminic oxyd with one or more basic oxyds, as in the spinels. (2) Aluminisilicates, in which a complex aluminisilicic acid is combined with one or more basic or positive oxyds. (3) Simple silicates, in which aluminic oxyd may be supposed to enter, as in its phosphates and sulphates, as a positive or basic element, but which it may also be permitted to regard as generated by the more or less complete elimination of water from normal aluminisilicic hydrates ; which are thereby at last converted into anhydrids of the complex acids, containing, in the case of topaz, fluorine in addition. In alumini- silicates like the tourmalines we have also boric oxyd as a con- stituent of the negative portion ; and in other cases, chlorine, sulphuric oxyd, or even sulphur itself, as in lapis lazuli. Compound Inorganic Acids. 143 208. Besides the complex salts already mentioned, we may add chloroborates, chlorocarbonates, chlorophosphates, fluorophos- phates, chlorosulphates and carbosulphates ; as also carbosilicates, silicotitanates and phospharsenates, in which two negative oxyds of the same valency are united ; examples of all of which will be given farther on. The tendency to the formation of these salts of complex acids is in some cases very marked, as in the case of nitro- phospho-dodekamolybdate of ammonium, noticed above ; which separates as an insoluble crystalline yellow precipitate from strong- ly acid solutions, and is well known to chemists from its impor- tance in the detection and determination of small amounts of phos- phorus. Another noticeable example is afforded by boracite, which, while found in nature under circumstances showing its Aqueous origin, has been artificially made, alike by igneous fusion, and by the action of heated water, under pressure, on mixtures containing sodium borate and magnesium chlorid.* Besides an amorphous magnesium borate, there are thus formed crystals of the -dense, hard, gem-like boracite ; a chloroborate, which may be repre- sented by 8B 2 O 3 -6MgClO.MgCl 2 = C^B^O^ -f Mg 7 O 6 . 209. The fact that in the soluble hydrous polytungstates, hy- drocarbon radicles like methyl, ethyl and phenyl, may enter, helps to break down the barrier, not yet wholly removed, which once separated the so-called organic and inorganic compounds. Even the stability of insoluble silicates is not proof against similar -changes, as shown in the case of artificial lapis lazuli or ultrama- rine. This, which is got as a blue, green or violet crystalline pow- der, appears to be essentially a peculiar sodium aluminisilicate, in which the oxygen is partially replaced by sulphur. By digestion with a solution of silver nitrate a yellow substance is obtained in which silver replaces sodium, and this with ethyl iodide yields a compound into which the alcohol radicle enters, and which, by sub- sequent treatment with sodium chloride, gives off ethyl chloride and regenerates blue ultramarine. The silver in the yellow species may also be replaced by potassium or by lithium, the last giving also a blue ultramarine. Similar compounds are obtained from ultramarine with the iodides of amyl, allyl and benzyl, f Acetic * De Gramont, Butt. Soc.franq. de Mineralogie, xiii., No. 7. t For a summary of the results of the study of ultramarine by Neumann, Philipp and -de Forcrand, see Watts, Diet. Chem., 3d Suppl., 3069-2071. 144 Systematic Mineralogy. acid and even solutions of alum decompose ultramarine with dis- engagement of hydrogen sulphid. It is probable that only their great insolubility prevents us from getting somewhat similar re- sults with more highly condensed silicates, such as the feldspars, micas and tourmalines. The experiments of Eichhorn upon the reactions between solu- tions of chlorids and pulverized chabazite, a crystalline hydrous aluminisilicate of calcium, are instructive. This substance, in a so- lution of sodium chlorid, exchanges a large portion of its calcium for sodium, but if the resulting sodium compound be placed in a so- lution of calcium chlorid, a portion of lime again enters into the silicate, replacing sodium ; while by the action of a solution of po- tassium chlorid both of the above bases are in part replaced by potassium. In like manner chabazite may be made to exchange a part of its calcium for ammonium, which in its turn may be replaced by potassium, sodium, or calcium by the aid of the corresponding chlorids.* 210. The application of the conception of complex acids is not confined to oxydized and haloid compounds, but extends to metal- line species as well. Here, however, the cases are less complicated, since we have to deal with but three negative groups, namely, (l) that of sulphur, selenium and tellurium ; (2) that of arsenic, anti- mony and bismuth ; (3) that of the compounds of the last two groups ; that is to say, the sulphids of arsenic, of antimony and of bismuth, and probably in some cases the selenids and tellurids of these last three elements. The natural compounds which have been represented as sulphids of arsenic, antimony or bismuth uni- ted with a sulphid of some positive metal, as lead, silver, copper, mercury, zinc or iron corresponding to the oxysalts, arsenites, ar- senates, antimonates, etc. are numerous, and have been described as sulphosalts. Of these, intermediate species containing the two or even the three negative sulphids are met with, which may be compared with carbosilicates and silicotitanates among oxydized species. 211. The extension of the doctrine of homologous series to min- eral species like the polytungstates and molybdates, the higher members of which have necessarily very elevated integral weights, serves to show the importance of small variations in the composi- tion of definite crystalline species ; since very small portions of * Amer. Jour. Sci. (2) xxviii., 72.; and "Chem. and Geol. Essays," p. 96. Complexity of Mineral Species. 145 different substances may not only occur as necessary elements in such a compound, but may even change essentially its chemical relations. Thus in a complex tungstate containing 12WO 3 = 2784, the addition of SiO 2 = 60 suffices to determine the production of a new type, with changed basicity. In like manner, the addition to a compound containing 24WO 3 = 5568, of P 2 O 5 = 142, gives a new and distinct acid type. Similar illustrations might be drawn from the salts of the cobaltamines, and from many other com- pounds. Moreover, according to the views maintained in this treatise, the values just cited, which are the lowest permitted by the results of chemical analysis, must be several times multiplied to represent the true integral weight of the polymer which con- stitutes the solid mineral species. In such compounds, partial sub- stitutions and small additions, affecting but slightly the centesimal composition of a species, may nevertheless be as essential to its chemical constitution as the small amounts of silicic and phosphoric oxyds added to the polytungstates. Such substitutions and ad- ditions would, however, if found in ordinary analyses of mineral species, be disregarded as impurities not essential to the composi- tion. The small amounts of sulphur, of fluorine, of chlorine, of hydrogen, of boron, and of phosphorus, so often met with in native silicates, are not to be looked on as accidental ingredients, but as essential parts of highly complex integers. Farther and more critical chemical analyses are necessary before we can fully know the constitution of dense insoluble species ; and the great difficulty is to decide how far these small portions of elements are due to impurities, and how far they are elements necessary to the con- stitution of the species ; questions which in many cases can only be solved by much care and study. It is well to remember in this connection the effect of minute quantities of various elements in modifying the characters of metals ; as in the cases of iron, copper and gold, to which some reference has already been made in. a previous chapter (ante 130). 212. Having considered the question of progressive or homol- ogous series, we may proceed to notice that of the constitution of saline compounds. An important distinction is at once apparent between the compounds of the various elements with fluorine, chlorine, bromine and iodine on the one hand ; and those with oxygen, sulphur, selenium and tellurium on the other. To the com- pounds of the first group, of which common salt or sodium chlorid is the type, Berzelius, who first clearly defined the relations in question. 346 Systematic Mineralogy. gave the name of haloid salts (Greek afy, sea-salt) ; fluorine, chlorine, bromine and iodine being designated as halogenous ele- ments y whence the name of Haloidaceae or Halidaceae, which we retain for Class II. in the present system of classification. For the second group, the saline compounds were by Berzelius regarded, in the case of oxydized species, as combinations of two oxyds, the one acidic or negative, and the other basic or positive ; for which reason oxygen, and, moreover, sulphur, selenium and tellurium (each of which may replace it), were by him designated amphi- genous elements that is to say, generators both of acids and of bases. The resulting compounds were thus called by him amphide salts. Other chemists have proposed to assimilate these to the halide salts, by the assumption of hypothetical compound radicles. Thus, according to Berzelius, calcium carbonate is an amphide salt, CO 2 .CaO, formed by the union of carbon dinoxyd with calcium oxyd, while the hypothesis in question would make it CO 3 Ca, or a compound of calcium with an unknown CO 3 , cor- responding to fluorine in the haloid salt F 2 Ca, calcium fluorid. Each mode of representation has had, and still has, its advocates, but the advantage of simplicity appears to rest with the Berzelian, which dispenses with a class of imaginary negative radicles, is at the same time more convenient, and serves to make more apparent what is after all a wide distinction, that between halide and am- phide salts. It will therefore be maintained in the classification of oxydaceous species in the present treatise.* Its recognition in the nomenclature of the metalline sulphids, selenids and arsenids is, however, complicated by the intervention of the elements of the arsenic group, and it was thought, so far as the interests of classifi- cation are concerned, unnecessary to insist upon it farther than to point out, as has been already done, the parallelism between oxy- salts and sulphosalts ; both being considered as amphide in consti- tution. 213. It is now in order to consider the relations of compound negative oxyds (the nature of which has already been set forth), to positive or basic oxyds. These negative oxyds may not only fix water and other positive oxyds and hydroxyds, but fluorids and chlorids ; giving rise to species alike hydrated and anhydrous, and * See for a clear statement of the two views, Gmelin's " Handbook of Chemistry," -Cavendish Soc. ed., ii., 15. Fremy has lately argued strongly for the Berzelian defi- nition, Chem. Neux, Ixii., 250, from Jour, de Pharm. et de Chimie (5) xxi., no. 7. For an important essay on the halides, and their relations to amphides, see Remsen, Amer. Chem. Journal, xi., 291-319. The Genesis of Phosphates. 147 often of considerable complexity. This may be illustrated by the example of phosphorus pentoxyd, written in monadic notation p 2 o 5> which, in the presence of an excess of alkaline base, unites with three proportions, forming the normal orthophosphates, p a o 6 .3(m 1 o 1 ). The fixing-power of phosphorus pentoxyd is not, however, lim- ited to the production of tribasic compounds. These may unite with various proportions of water, w(h 1 o 1 ), and, moreover, with fixed positive oxyds, forming what are called basic salts ; which are generally described as compounds of normal tribasic phosphate with oxyds and with water. Such copper salts, in which the values of n are 4, 5 and 6, are found crystallized in nature, with various proportions of water ; libethenite, ehlite and phosphorochalcite being examples; while in the corresponding native copper arsenates the values of n are not only 4, 5 and 6, but 8. In like manner, crystalline hydrated aluminic phosphates, are found, having values for n of 3, 4, 5 and 6 ; similar ferric phos- phates are also known. The fallacies involved in the doctrine of valency, as now maintained, were anticipated by Charles Gerhardt, who in 1848 insisted that so-called basic or subsalts, such as those just mentioned, should be regarded as really neutral salts of distinct types ; the tribasic orthophosphates being as truly basic salts when compared with metaphosphates, as are the pentabasic and hexbasic cupric phosphates when compared with the tribasic phosphates. Gerhardt also then prepared and described two crystalline nitrates of lead, njjOg.pbaO^Oi, and n 2 o 5 .pb 4 o 4 .h 3 Os, both of which retain their combined water up to 200.* From a mingled aqueous solution of tribasic sodium phos- phate and sodium fluorid with excess of sodium hydroxyd are de- posited hard transparent isometric crystals of a fluorophosphate, which, when dissolved in pure water, are resolved by dissociation * "Chem. and Geolog. Essays," pp. 466-487. 148 Systematic Mineralogy. into sodium fluorid and orthophosphate. This complex salt is a type of the fluorophosphates, represented among native insoluble species by amblygonite, apatite and pyromorphite ; in which last two chlorine may partially or wholly replace fluorine. The ratio between the phosphate and the fluorid is not always, as above, 1 : 1, but in some cases apparently 2 : 1 or 3:1. Thus tribasic orthophosphates not only fix n^o^, ^m^), ^(h^), and ^(mih^), but also n^jij) and r^mjC^) ; that is to say, water, oxyds, hy- droxyds, fluorids and chlorids. In other words, we find replacing oxygen o l not only f l and cl w but the group hjO 2 (the hypo- thetical hydroxyl) ; giving rise to a tetrabasic hydroxyphosphoric acid, which is to orthophosphoric acid what glycollic or hydroxy- acetic, or lactic or hydroxypropionic, are to the normal acetic and propionic acids. 214. The student of chemistry accustomed to consider compounds like the ordinary nitrates, sulphates and carbonates, which are an- hydrous salts generated, according to the Berzelian view, by the union of a negative and a positive oxyd, both alike destitute of hy- drogen, may lose sight of the fact that, apart from the carbonates, all the other salts of the carbon-series include in the negative ele- ment a portion of hydrogen, for which, though it is not replaceable by a metal, fluorine, chlorine or bromine may be substituted, as for example in chloracetates and bromosuccinates. That salts of other than the carbon-series may also contain hydrogen as part of the negative element is shown by the case of the polyphosphomolyb- dates already mentioned (204), where a seemingly neutral am- monium salt may include the elements of either chlorhydric or nitric acid, which are expelled, together with water, by a temper- ature of 150. The various phosphoric acids may be regarded as derived from the water-type either, as was conceived by Ad. Wurtz, by im- agining monobasic, dibasic and tribasic radicles of phosphorus oxyds replacing successively one, two and three proportions of hy- drogen ; or otherwise, as was maintained by the writer, by the suc- cessive formation of phosphoric acids, by the reaction first of phos- phorus pentoxyd on HgOj, and then of the resulting monobasic acid with additional equivalents of water ; the polymerization of the sec- ond product yielding the tetrabasic pyrophosphate ; while the tri- basic orthophosphate is derived from 3(H 2 O 1 ), and a tetrabasic fluorophosphate, like that noticed above, from 4^0!). This mode Constitution of Silicates. 149 of explaining the genesis of these acids has the advantage of dis- pensing with all hypothetical radicles.* 215. Various ingenious attempts have been made, and are still made, to represent the supposed constitution of salts, and especially of the more complex silicates. The feldspar, albite, gives by anal- ysis a result which is expressed below, alike in ordinary and in monadic notation. As examples of the various manners in which the constituent elements of this species have been supposed to be grouped, we will give four other formulas. Berzelius, who conceived silica to be SiO 3 , regarded the feldspar as an anhydrous alum, and represented it accordingly. Gmelin, who had come to regard silica as SiOa, proposed a second formula, and J. D. Dana, after having in 1854 copied the formula of Berzelius, proposed, in his "Miner- alogy " of 1868 (p. 204), two alternative ones. His reasons for these the reader may consult, when he will learn that in the formula 4 what is by Dana called " the surplus silica," is basic, while in 5 it may be " all accessory." 1. Albite 6SiO 8 .Al 2 O 8 .Na 8 O = si^c^na^!,, Analysis. 2. " SiO 8 .NaO + 3SiO 8 .Al s O 8 Berzelius. 3. " 3SiO 3 .NaO + 3SiO 8 Al 2 O 8 Gmelin. 4. " ; (|Na 8 + 1 AP + |sTf )Si J. D. Dana. 5. " (pr'a 3 + f Ai)Si + 3Si J. D. Dana. 216. Similar illustrations, though less complicated than these * The successive generation of the acids in question may be thus shown in monadic notation : 2(p a o s )-f-h a o a = 2(p a h l Ot) = metaphosphoric acid (monobasic), ZfpahiOe) -f h 2 o a = p*h 4 o 14 = pyrophosphoric acid (tetrabasic), P4h*o 14 4-h a o a = 2(p a h 3 o 8 = orthophosphoric acid (tribasic), 2(p a h 3 o 9 )-f h a f a = 2(p a h 4 o 8 .f 1 ) = fluorophosphoric acid (tetrabasic), 2(p,h s o 8 ) + h 4 o 4 = Stpah^Os.hiO,) = hydroxyphosphoric acid (tetrabasic). The conception of water, H a O, and its polymers 2(H a O) and 3(H a O), as types of mono- basic, bibasic and tribasic oxydized species was originally set forth by the present writer in 1848. This hypothesis of the water-type has many advantages over the alternative one since proposed and here stated. The student will find a historical account of the matter in a paper on " The Theory of Types in Chemistry," published in the American Journal of Science for March, 1861, and reprinted in the author's " Chemical and Geological Essays," pp. 459-469. Therein is cited the testimony of Wolcott Gibbs, in 1858, who, after referring to his previous attribution of the theory of water-types to Gerhardt and Williamson, adds : "In this I find I have not done justice to Mr. T. Sterry Hunt, to whom is exclu- sively due the credit of having first applied the theory to the so-called oxygen acids, and to the anhydrides ; and in whose earlier papers may be found the germs of most of the ideas on classification usually attributed to Gerhardt and his disciples." See farther a paper by the present writer entitled " The Foundations of Chemistry," in the American Chemical Journal for September, 1888. 150 Systematic Mineralogy. last two, may be found in other and later writers. We have already referred to Tschermak's conclusion that the intermediate feldspars and scapolites of their respective series are not, as once suggested "by v. Waltershausen and myself, simply crystalline admixtures of isomorphous species ; but definite compounds of those species which mark the extremes of these series, united in ratios of 1:2; 1:3; 2 : 3, etc. Again, in the micas, Tschermak supposes that by the union in various proportions of a non-magnesian silicate allied to muscovite with a non-aluminous magnesian silicate having the composition and ratios of chrysolite the magnesian micas, like bio- tite and phlogopite, may be generated. Rammelsberg has, more- over, represented chlorite as made up of a hypothetical silicate united with a hydroxyd of alumina, and Kengott has put forth sim- ilar views, while many others might be mentioned. All such spec- ulations, from the time of Berzelius down, are without any real value or significance. At best, it can only be said of certain of these proposed formulas that they may help to explain the trans- formations of a species under given conditions. They are, in fact, devised to explain a certain class of reactions, and we may con- struct from other points of view other formulas which are equally plausible. 217. The present writer, perceiving the errors growing out of such views as to the constitution of mineral species, wrote in 1853, " These hypotheses are based on the notion of dualism, which has no other foundation than the observed order of generation." "A body may divide into two or more new species, yet it is evident that these did not pre-exist in it from the fact that a different di- vision may yield other species, whose pre-existence is incompatible with the last." The object of chemical formulas, it was farther said, is to " serve to show what changes are possible in any body r and to what new species it may give rise by its changes."* In 1874, in resuming the above argument, while maintaining the doc- trines of polymerism and of progressive series, it was said of the received formulas of mineral species, that they "are not to be looked upon as expressing any pre-existing relations in the compo- sition of the species ; which is not to be regarded as a compound, but as an individual" The arrangements of the chemical ele- ments in formulas, it was added, " only serve to make apparent the * " Considerations on the Theory of Chemical Changes," Amer. Jour. Sci., March* 1853 ; reprinted in " Chem. and Geol. Essays," p. 428. Frazer on Mineral Formulas. 151 numerical relations which have been found to govern the trans- formations of the higher species." * 218. In 1875 Dr. Persifor Frazer published, with the title of "Tables for the Determination of Minerals," a translation from the- German of Weisbach, in an Introduction to which he calls attention to the question of mineral formulas, and says in language which merits the emphasis given it by its author : " Every true mineral is a definite chemical compound, or ele- ment, homogeneous throughout its parts, and capable of expression in a formula which represents at least the proportions in which the atoms of the same or different elements are associated together in its molecule. " Its molecule is a distinctive whole the unit of its mass and incapable of division so long as the mineral retains its character- istic properties / and any formula which represents the mineral as consisting of two compounds is in antagonism with this funda- mental principle, and can convey no clear idea of unity to the mind." He farther declares his belief that one of the greatest obstacles to mineral formulation " has been the notion of the comparative sim- plicity of mineral species, whereas, in fact, they are generally poly- mers of a high order." In a second edition, in 1877, Frazer again insists on the principle of "the unity of the mineral molecule ;" while in a third and much enlarged edition, just published, in 1891,, he reprints from the Introduction, the passage emphasized above,, and expresses his satisfaction that the principle for which he then contended, that "of the unity of the mineral molecule, in opposi- tion to the theory of Prof. J. D. Dana, has been tacitly conceded by all modern writers, including Prof. Dana himself." f 219. In illustration of the formulas and the notation adopted by Frazer in his recent volume, the following examples are given. Retaining Faraday's terms anion and Jcation or cathion for the elements, which in electrolysis are liberated respectively at the anode or positive and the cathode or negative pole, he follows " the practice adopted in the earlier edition of placing the cathions- as much as possible first, and the anions last ; " that is to say, put- ting the positive or basic element first, and the negative or acidic * " Chem. and Geol. Essays," p. 439. t It may be said, however, that so late as 1885 the doctrine maintained by Tscher- mak, still finds a place in his " Lehrbuch der Mineralogie ; " where see under Skapolith, p. 466 ; Plagioklas, p. 465 ; Chlorit, p. 506, and Meroxen, p. 515. 152 Systematic Mineralogy. element second, as usual in chemical notation. While sodium chlorid is NaCl, calcium carbonate is not CaO.CO 2 , but CaCO 3 ; the positive and negative elements following each other without any interposed sign of addition (as . or +), such as is interposed before what is regarded as water of crystallization. We have thus the following formulas : Pyroxene MgCa(SiO 3 ) 2 Deweylite MgH 4 Si 8 O 18 Anorthite AlCaSi a AlO 8 Albite Al(Nak)Si 8 O 8 Meionite Al 2 (AlO)Ca 4 (Si 2 AlO 8 ) 8 Laumontite Al 2 (OH) 4 Ca(Si 2 O 6 ).2H 8 O Analcite AlNa(SiO 8 ) 3 .H 2 O Epidote Al 2 (Al.OH)Ca 8 (SiO 4 ) 8 Muscovite (K,Na)H,Al 8 (SiO 4 ) 8 220. The lessons to be learned from the chemistry of the sugars .fire full of instruction in this connection. Beginning with saccha- rose, without speaking of its transformation by heat into a mixture of dextrose and levulosan, with various other products at higher temperatures, we may note that in aqueous solution it undergoes the vinous fermentation ; being, after inversion, readily broken up into ethylic alcohol and carbon dioxyd. A similar solution, under somewhat different circumstances, undergoes the lactic fermenta- tion, being integrally changed into lactic acid, or rather, a lactate ; which latter, if the fermentation be properly continued, is resolved into a butyrate, with disengagement of carbon dioxyd and hy- drogen gases. The subsidiary production of small portions of man- nit e in the lactic, and of succinate, glycerol and amylic alcohol in the vinous fermentation, need not be here discussed. Going still farther, it is to be observed that besides the so- called glucoses, C 6 H 12 O 6 , there are now known to be many other sugars having the same centesimal composition as these, but with other equivalent weights. These are seen in arabinose and xylose, C 5 H 10 O 5 , formerly confounded with the glucoses, and moreover in the remarkable series of related sugars represented by C 7 H U O 7 , C 8 H 16 O 8 and C 9 H 18 O 9 ; not to mention others still lower in the series than xylose. These bodies, which may all be represented as va- rious polymers of CH 2 O, are shown by their combinations with cy- Constitution of Mineral Species. 153 anhydric acid and with phenylhydrazine to have the various equiv- alent weights above assigned, for their chemical species ; which are confirmed by the application of Raoult's cryoscopic method. More than this, the sugars of the same equivalent weight present among themselves very many examples of isomerism. Thus in the group of the so-called hexoses, C 6 H 12 O 6 , not less than eight isomers are known, all susceptible of the vinous fermentation ; while the numer- ous heptoses (C 7 ), and the three octoses (C 8 ), are not f ermentescible. Nonnose, however (C 9 ), readily undergoes the alcoholic fermenta- tion. These, which are some of the results of the recent brilliant series of studies by Emil Fischer, are of great significance, and help us to understand that since we cannot apply to the fixed and insoluble silicates such modes of investigation as the nature of the sugars renders possible, we have no certainty that in the case of mineral oxyds, sulphids and silicates, we are not dealing with bodies which, while physically very similar, have differences in constitution as great as these sugars (ante 99). 221. When we pass from bodies like the sugars, made up of but three elements united in simple ratios, to others far more complex, like the cobaltamines, the polymolybdates and the polytungstates, we learn that the simplest admissible formulas for these lead to integral weights of thousands, as in the borotungstate of sodium of Klein, and in the hydrous phosphorovanadotungstate of barium described by Gibbs, which are respectively : B 2 O 3 .14WO 3 . -f sNa^ = 3,504 3P 2 O 5 .VA-VO 2 .60WO 8 .18BaO + 150H 2 O = 20,058. When we farther consider that each portion of barium, sodium, phosphorus, boron, oxygen and hydrogen in these formulas is an essential part of these crystalline unities, we attain a better concep- tion of the extreme complexity to be found in mineral species, as has been repeatedly set forth in preceding paragraphs (91, 107, 109, 161, 211). The chemist who, with such facts before him, attempts to calcu- late from the results of chemical analysis formulas for silicates like the chlorites, the micas, the epidotes and the tourmalines, soon finds how inadequate are the principles ordinarily recognized, and is led to conclude that did we possess a knowledge as complete of these natural silicates as of the artificial salts in question, we should find our present formulas for these silicates even though as elab- 154 Systematic Mineralogy. orate as those devised by Frazer for muscovite and epidote, and by Riggs for tourmaline (to be noticed later) are but approxima- tions. They however serve to fix with sufficient accuracy the values of p, and the co-efficient of condensation. This imperfection must pertain to all our formulas for mineral species, save for such as cal- cite, barite, fluorite, and for some metalline sulphids and arsenids ; which for purity and definiteness may be compared with artificially crystallized substances. CHAPTER XL A NEW MINEKALOGICAL CLASSIFICATION. 222. The student of the preceding chapters will now be prepared to consider the new system of classification here proposed for the mineral kingdom. In Chapter II. have been set forth the prin- ciples alike of the Chemical method of Berzelius, both in its earlier and in its later form, as adopted and modified by Rammelsberg and his followers ; and the Natural History method of Werner and Mohs, as subsequently developed by Jameson, Shepard, J. D. Dana, Breithaupt and Weisbach. The present writer, as the result of many years of study, has devised what he has elsewhere described as a Natural System in mineralogy,* designed to unite the advan- tages of both the Chemical and the Natural History methods. It is therein made apparent that not only the specific gravity of solid species but their different degrees of hardness, and their greater or less chemical indifference by which is meant their resistance to change by the action of water and of acid or alkaline solutions are dependent upon their chemical constitution ; or in other words, upon their greater or less intrinsic condensation or polymerization, as already set forth in Chapter VIII. 223. The proposed system has thus a chemical basis, the min- eral kingdom being divided on chemical grounds into four classes ; namely, I. METALLACEJS ; II. HALIDACE^E ; HI. OXYDACE^E ; IV. PYRICAUSTACE^E (combustible or fire-making species). These are again subdivided into orders, genera and species. In Class I., which we designate Metallaceae, are included the non-oxydized metalline minerals, embracing the metals, their alloys, and all their compounds with sulphur, selenium, tellurium, phos- phorus, arsenic, antimony and bismuth. These, as set forth in Chapter II., are, in the natural-historical classification of Mohs and his followers, comprised in four orders Pyrites, Metals, Glances and Blendes (Pyrites, Metalli, Lamprites and Minia of Breithaupt). The metals and their various alloys are included in the same class with sulphids, selenids, tellurids, phosphids, arsenids, antimonids, bismuthids, sulpharsenids, sulphantimonids, etc., for the reason * " Mineral Physiology," etc., p. 279. 156 Systematic Mineralogy. that the resemblances between the typical and malleable metals,, such as gold, silver, lead, copper, nickel and iron, and the elemen- tary metalline species, tellurium, arsenic, antimony and bismuth, are such that the compounds of these with the metals above named cannot well be separated from alloys. This metalline class we divide into two subclasses, which we have designated Metallometallata and Spathometallata, based upon the radical differences in physical characters which distinguish the great groups of the Glances and the Blendes. The first subclass includes the Glances or Lamprites that is to say, simple sulphids like galena, argentite, chalcocite, metacinnabar, stibnite and molyb- denite ; selenids like eucairite and clausthalite ; tellurids like altaite, sylvanite and tetradymite ; sulpharsenids like enargite ; sulphantimonids like bournonite and stephanite , sulphobismuthids like emplectite and kobellite. To Metallometallata also belongs the order Pyrites of Mohs. This not only includes the harder simple sulphids as marcasite, pyrite, siegenite and laurite, and as pyrrhotite, chalcopyrite and millerite ; but arsenids such as smalt - ite, leucopyrite and niccolite ; antimonids like breithauptite, hors- fordite and dyscrasite ; sulpharsenids like arsenopyrite and cobalt- ite ; sulphantimonids like ullmannite ; and sulphobismuthids like grunauite. In this same subclass, for reasons already given, belong the Metalli, embracing the metals and alloys ; including metallic arsenic, antimony and bismuth, and also the metallic forms of selenium and of phosphorus. 224. In the second subclass, designated Spathometallata, the metals are not represented by any known species, but by the non- metallic forms of selenium and phosphorus, and by the various modifications of sulphur. This subclass includes, moreover, simple sulphids like sphalerite, wurtzite, greenockite, hauerite, oldhamite, cinnabar and realgar ; sulpharsenids like proustite and tennantite ; and sulphantimonids like pyrargyrite and miargyrite. The opaci- ty and lustre of the compound species of the first subclass, and their occasionally sectile character, connect them closely with the typical metals. On the other hand, the transparency, the absence of metallic lustre and aspect from the species of the second sub- class recall the physical characters of oxyds like zincite, cuprite and senarmontite ; with which they are connected through the oxy- sulphids, voltzite and kermesite. It is to recall these resemblances to sparry oxydized species, that we have given the name of Spatho- metallata to this subclass, which corresponds to the Blendes of Divisions of the Metallacece. 157 Mohs, the Minia of Breithaupt, and the Cinnabarite of Weisbach r but includes, moreover, sulphur and certain forms of selenium and phosphorus. It is worthy of note that not only the elements selenium and phosphorus, but the sulphids of mercury and of anti- mony, are found in two distinct forms, and belong to each of these subclasses. 225. In the fourfold division hitherto adopted for the minerals which we have grouped in Class I., the order Glance or Lamprites has been made to include not only the softer simple sulphids like galena and chalcocite, but physically similar double sulphids con- taining also arsenic, antimony, or bismuth, of which bournonite and emplectite are representatives. Upon chemical grounds it is now proposed to divide the Glances into two orders; namely, Galeninea, to include the simple sulphids ; and Diaphorinea, for those double sulphids which, together with lead, silver or copper, contain ar- senic, antimony and bismuth. Again, the order Pyrites was made to include not only the hard simple sulphids like those of iron, nickel, cobalt and ruthenium, but arsenids like smaltite and leucopyrite, and, moreover, sulpharsenids like arsenopyrite and cobaltite. For chemical reasons we now divide the Pyrites of Mohs into three orders ; namely, Pyritinea, for the sulphids of iron, nickel, cobalt, etc.; Chloanthinea, for the arsenids, of which smaltite is a type ; and Lamprotinea, for the hard sulpharsenids. Again, in the second subclass or Spathometallata, from the Blendes proper or simple sulphids, represented by sphalerite and cinnabar, we separate the double sulphids containing arsenic and antimony, represented by the red silver ores, proustite, pyrargyrite^ etc.; making two orders, Sphalerinea and Rhodopyritinea. The metals proper and alloys, as in the scheme of Mohs, constitute in the first subclass an order apart, Metallinea ; while in the second subclass sulphur and the non-metallic forms of selenium and phos- phorus form another order, Spathometallinea. The class Metallacesa is thus, on grounds partly natural-historical and partly chemical, divided into two subclasses and nine orders, which are as follows : 1. Metallinea ; 2. Galeninea ; 3. Diaphorinea ; 4. Pyritinea ; 5. Cloanthinea ; 6. Lamprotinea ; 7. Spathometallinea ; 8. Sphaler- inea ; 9. Rhodopyritinea. 226. The study of these orders is complicated by the fact that sulphur in them is often replaced wholly or in part by selenium and tellurium, giving rise to selenids and tellurids, or to interme- diate species, which might with propriety constitute suborders. 158 Systematic Mineralogy. The same observations hold good with regard to those orders which may contain antimony or bismuth instead of arsenic, or else are in- termediate compounds' holding any two or all three elements. We have here repeated the problem of complex inorganic acids, which has been discussed at length with regard to oxydized compounds in the preceding chapter. We may, in fact, look upon sulphur, selenium and tellurium, and upon the sulphids of arsenic, antimony and bismuth, as negative or halogenous bodies united with positive or basylous metals, or metallic sulphids, to form sulphosalts, as they have been designated; in which sulphur is sometimes wholly or par- tially replaced by selenium or by tellurium. The farther discus- sion of these points will, however, be reserved for consideration in treating of the orders themselves. Class II., called Halidaceae, comprises four orders, namely, Fluorids, Chlorids, Bromids and lodids. Intermediate species of the last three are met with, and it is to be noted that complex halogenous members are found, like oxychlorids, chloroborates ? chlorosilicates, and chlorophosphates and fluorophosphates, which serve as connecting links between Classes II. and III. 227. In Class III., including oxydized species, and designated Oxydaceae, are arranged under different orders the Oxyds, Borates, Carbonates, Aluminates, Silicates, Aluminisilicates, Phosphates, Arsenates, Sulphates, etc. Many examples of mixed or interme- diate species, having for their negative member a more or less com- plex inorganic acid, are met with in this class, and sometimes assume great significance, as in the Aluminisilicates named above, constituting a very important order; while others will be mentioned farther on. It is well to consider that the negative like the positive member in mineral compounds may be assumed to have in all cases a more or less elevated equivalent ; and that it is formed either by homogeneous union, as in polycarbonates and polysilicates, or by heterogeneous union, as in aluminisilicates, borisilicates, titano- columbates, etc. Class IV., denominated Pyricaustaceae, and including all carbon- aceous combustible species, is divided into two subclasses. One of these, which may be designated Carbata, includes the forms of carbon, graphite and diamond; the other, Hydrocarbata, comprises petroleum, resins, asphalt and coals. 228. It will be seen from this concise statement that the divid- ing of mineral species into classes, and these again into orders in the proposed system, is based entirely on chemical grounds, with The Orders Mica, Spar and Gem. 159 the single exception of the separation into two parts of Class I. The farther division of these orders into genera will, however, be founded essentially on natural-historical characters, which at this stage of the process of classification assume a paramount impor- tance. It would seem to be from a failure to see the true relations and significance of these that while one school has made them supreme, the other has rejected them more or less completely in favor of a purely chemical or chemico-crystallographic arrange- ment. Rightly understood, both physical characters and chemical constitution find their place in a natural system of classification ; and this can only be attained by a judicious combination of the two, the final justification of which is made apparent by showing, as we have here sought to do, their interdependence. 229. In noticing in Chapter II. the classes and orders adopted for mineral species by Mohs, and subsequently modified by Breit- haupt, we have seen that the former united in one class all the insoluble species of our Classes L, II. and III. ; and that the latter, while separating them into two classes, named respectively Lapide (Stones) and Mineras (Ores), still included in the latter class, together with the heavier oxydizeu and saline compounds, some of the heavier silicates, such as cerite, orthite, lievrite and thorite ; besides the whole of the very different group of metals, sulphids, arsenids, etc., which make up Class I. of the present system. The character of specific gravity alone determined this division of Stones from Ores ; thus separating species chemically allied, and bringing together others most unlike, giving thereby a striking example of the unfortunate results of the misapplication of an im- portant physical character. 230. Mohs adopted as orders in his system, Mica, Spar and Gem. Of these, the first two names were retained by Breithaupt, who, however, applied the name Sclerites to the minerals which Mohs had included in the order Gem. Weisbach, in turn, adopts the name Sklerite for one such division and Phyllite (Mica) for another. The application of the terms Mica and Spar as designations of orders, furnishes us an instructive lesson. The characteristic cleavage of the Micas made easy of recognition this order, which included alike micaceous silicates like the true micas and chlorites, with talc and pyrophyllite, and various non-silicated species resem- bling these in structure ; among which were placed sulphates like gypsum, phosphates like uranite, arsenates like chalcophyllite, oxyds like brucite, and even elemental species like graphite ; all of which 160 Systematic Mineralogy. were by Mohs comprised in his order Mica. A similar latitude was given by him to the order Gem ; which included not only many hard and gem-like silicates, such as idocrase, garnet, chrysolite, tour- maline, staurolite, andalusite, zircon, phenakite and beryl, but bora- cite, quartz, corundum, chrysoberyl, spinel and diamond. Again r the order Spar, as defined by Mohs, while excluding species like calcite, dolomite, barytine and fluorite, was made to include a number of species which properly belong to his order Gem. Exam- ples of this are seen in epidote, spodumene, cyanite and fibrolite, pyroxene, amphibole and opal, which are classed by Mohs among Spars, with feldspars and scapolites ; while iolite is placed in the order Gem. If, however, we take into account their hardness, condensation and insolubility, it will be found that epidote, spodu- mene, fibrolite and cyanite belong, with garnet, idocrase and stau- rolite, in the order Gem of Mohs ; while the relations of iolite are with petalite and the feldspars, in the order Spar as defined by him ; and that the uncrystalline colloid opal should find a place in neither of these orders. Moreover the affinities of amphibole and of pyroxene separate them from wollastonite and other Spars, and assign them a place among the Gems. 231. Breithaupt, as we have seen in Chapter II., also recognized an order of Spars (Spathi) ; made up, however, of an entirely differ- ent group of minerals from the order Spar of Mohs. Breithaupt included therein all the so-called carbon-spars or crystalline car- bonates of calcium, magnesium, barium, strontium, iron, manga- nese, zinc, lead, etc. (some of which are familiarly known as calc- spar, bitter-spar, pearl-spar, brown-spar, spathic iron) ; together with apatite, sparry sulphates like anhydrite, celestine, barytine or heavy spar; sparry arsenates, chromates, molybdates and tungstates; fluorids like fluor-spar and cryolite, and even certain silicates, as eulytite and datolite. Meanwhile, the species of silicates which make up the order Spar of Mohs were comprised by Breithaupt in his order Grammites, placed between the orders Zeolithi and Scle- rites. The word Spar (Latin, spatum or spathum ; Fr. and Ger., spath) in popular language serves to denote a lustrous crystalline mineral, with a certain regularity of structure, and is as well exem- plified by the feldspars and scapolites as by the carbon-spars, heavy spar and fluor spar. Another example of an extension in the application of a term is found in the history of 'colloid or porodic bodies. For these, Breit- haupt at first constituted an order, called by him Porodini, but sub- Soluble or Salinoid Species. 161 sequently proposed in the order Sclerites, a porodic genus, desig- nated by him Amorphites, for certain porodic silicate minerals which did not find a place in the order Porodini ; and later still other porodic genera, including many colloid oxyds. 232. The conclusion from all these facts is plain. The types of structure indicated by the terms, Mica, Spar, Gem and Colloid are general, and cannot be restricted to any one order of mineral species. The same may be said of the type Zeolite, proposed by Shepard for an order, and after him adopted by Breithaupt and Weisbach ; which must also be extended to other minerals than the true zeolites. When thus understood, these types become of importance in subdividing orders. In fact, all of the five types above mentioned will be found repeated alike in the Silicates and Aluminisilicates. It is precisely at this stage in classification that the advantage of natural-history characters becomes apparent. Their attempted introcjuction at an earlier period has only served to confuse the student, as may be seen from the brief history here given of the use of the terms Mica and Spar as names of orders. In applying these distinctions in the present system we employ adjectives, such as Spathoid and Colloid. The softer and hydrous spathoid type, seen in the zeolites, in pectolite, apophyllite, etc., may be conveniently designated as Hydrospathoid; while the harder and more condensed species hitherto recognized in the orders Gem and Sclerites will be called Adamantoid ; and the order Mica, or the micaceous type, Phylloid. The fibrous character occasionally observed in many species is, unlike the Phylloid, not fundamental, but an accidental development of prismatic crystallization, which may occur in Hydrospathoid, Spathoid and Adamantoid types ; as is seen in certain zeolites, and in chrysolite, in gypsum and calcite, in hexagonal zinc sulphid, in limonite, in amphibole, in tourmaline, and in fibrolite. 233. In the systems of Mohs and his successors sapid, saline or acid bodies were made a class apart, designated as Salts (Hydro- lyte of Weisbach). In a system having a chemical basis like that here proposed, it would be a grave error to place not only in differ- ent orders, but in different classes, species chemically so closely re- lated as borax, hydroboracite and boracite. We therefore include all soluble species in a Salinoid type in their respective orders. While water in a liquid or solid state constitutes a distinct min- eral species, it is evident from what has been said in Chapter VII. , that matters as they occur dissolved in natural waters cannot be sub- 162 Systematic Mineralogy. jects of mineralogical classification ; since, except in the case of saturated or otherwise definite solutions of particular salts, these saline liquids are mixtures of unknown constitution. They were therefore rightly excluded by Breithaupt. The same may be af- firmed of the atmosphere and of other natural gases. 234. Adamantoids are, like Hydrospathoids and Spathoids, sparry in character. Moreover, the division between Spathoid and Ada- mantoid is not based wholly on hardness ; since some species which we must regard as Spathoid equal or surpass in hardness certain others to which we assign a place among Adamantoids. A greater degree of condensation, marked by a smaller value of v, and, other things being equal, a greater resistance to the action of sol- vents, however, serves to distinguish the latter type ; as is seen when the Spathoids, petalite and iolite, are compared with the Adaman- toids, spodumene and beryl, or wollastonite with amphibole. There is, however, a gradation from one of these types to the other, so that the dividing line between the two is to some extent a matter of convention. 235. Passing now to the Metallaceous class, it will be remem- bered that we have already pointed out its natural division into two parts ; one of which, from the spar-like characters of most of its species, and from the absence of the metallic aspect, we have distinguished as. Spathometallata. So far as known, the species of this division, with the exception of the Phylloid, orpiment, are to be referred to the Spathoid type. The species of the other di- vision, Metallometallata, on the contrary, are metallic in aspect, opaque, and moreover present such differences in structure, and especially in hardness, that it becomes desirable to choose special designations. The Salinoid and Hydrospathoid types are of course absent from these species, and it does not appear that we have among them any Colloids. Metalline characters are, however, not confined to the metals and the non-oxydized compounds of these, which make up the division Metallometallata of this same class ; as appears from the tungsten-bronzes. These are metallic in aspect, strongly electronegative, and conductors of electricity ; properties which they share with the nitrocyanid of titanium, and apparently with vanadous oxyd. No native oxydized species of the Metalloid type are, however, known. 236. The differences in structure, hardness and condensation observed among the species of the orders which we have included in the division Metallometallinea, will permit us to indicate the Various Mineral Types. 163 types analogous to the Adamantoid, Spathoid and Phylloid already defined, and which may be distinguished as Metalladamantoid, Metallospathoid and Metallophylloid. To the first belong metals like iridosmium and platiniridium, sulphids like laurite and pyrite, arsenids like sperrylite and smaltite, and sulpharsenids like arseno- pyrite and cobaltite ; with degrees of hardness from 5 to 7. To the second or Metallospathoid type will belong the softer pyritous species, the arsenids like algodonite, besides sulphids like galena and chalcocite, and sulphantimonids like bournonite ; having a range of hardness from 2.5 to 4.0. To the third or Metallophylloid type are to be referred the still softer micaceous or foliated species, such as molybdenite, sternbergite, wehrlite, tetradymite and stib- nite ; with hardness of from 1.0 to 2.0. We are thus led to recognize in description the following min- eralogical types : 1. SALINOID, as in soluble borates, carbonates, sulphates and chlorids. 2. HYDKOSPATHOID, as in apophyllite, calamine, stilbite, and in gibbsite, goethite, hydromagnesite, azurite, gypsum, vivianite and erythrite. 3. SPATHOID, as in sulphur, sphalerite, cinnabar, realgar and proustite ; in wollastonite, willemite, feldspars, iolite, petalite ; in cuprite, zincite, calcite, siderite, bary te, apatite, fluorite and cryolite. 4. ADAMANTOID, as in boracite, phenakite, zircon, chrysolite, pyroxene, garnet, epidote, tourmaline, spodumene, topaz ; and in quartz, rutile, cassiterite, hematite, spinel, chrysoberyl, corundum and diamond. 5. PHYLLOID, as in talc, muscovite, chlorite, pyrophyllite ; and in brucite, chalcophyllite and uranite. 6. COLLOID, as in chrysocolla, serpentine, pinite, obsidian, allo- phane, opal, bauxite and urangummite. 7. METALLOPHYLLOID, as in molybdenite, sternbergitete, trady- mite and graphite. 8. METALLOSPATHOID, as in copper, gold, platinum ; and in pyr- rhotite, galena, chalcocite, algodonite and bournonite. 9. METALLADAMANTOID, as in iridosmium, laurite, pyrite, sperry- lite, smaltite, arsenopyrite, and in the tungsten-bronzes.* * Those who wish to follow in detail the development of the new system in the au- thor's various papers from 1853 to 1886 will find it set forth in an essay in the Transac- tions of the Eoyal Society of Canada," vol. III., sec. Hi., which is republished, with some additions, in his " Mineral Physiology and Physiography " (Boston, 1886, pp. 279-401), under the title of " A Natural System in Mineralogy, with a Classification of Native Silicates." 164 Systematic Mineralogy. 237. In establishing on chemical grounds the orders into which the four classes of mineral species are to be divided, an ar- rangement according to the groups given in the table of the per- iodic law will, with certain modifications, be found desirable. Though the dualistic conception of the constitution of salts may be regarded as conventional, its employment in treating of compounds formed by heterogeneous integration offers many advantages. Hence the distinction between negative, halogenous or acidic, on the one hand, and positive, basylous or basic on the other, familiar to chemists, will be adhered to alike for compounds of two ele- ments, as in simple sulphids and chlorids, and for more complex species like sulpharsenids, silicates and phosphates. Referring to the groups in the table of the periodic law (page 30), it may be said that for oxydized species the distinction of negative and posi- tive is not recognizable under group I., and scarcely under group II., save in the unstable compounds of the alkalies with beryllic oxyd ; suggesting a feebly negative character in the latter. In group III., however, a decided negative or acidic relation appears in boric and aluminic oxyds ; which give rise to borates and aluminates with various basic oxyds. These same negative characters are much more developed in group IV., where oxyds of carbon, silicon, titan- ium and tin give rise to important compounds with basic oxyds. The same is still farther true of group V., where only antimony, didymium and bismuth oxyds assume a distinctly positive or basylous type ; while in group VI. positive characters are restricted to uranic oxyd and to the diad chromic oxyd. The similar oxyd of manganese forms the only exception to the generally negative character of group VII. ; while on the contrary the diad and tetrad forms of the elements of group VIII. are distinctly basylous. The triad oxyd of iron, and the corresponding oxyds of manganese, chromium, and apparently of vanadium and titanium, are like alu- minic oxyd, feebly basylous when not negative in their relations. 238. The designating of the orders in mineralogy is compli- cated by the frequent occurrence of complex negative or halo- From it are taken the quotations found in Chapter II. of the present volume. The reader may farther consult an essay by the author on " The Classification and Nomenclature of Metalline Minerals," in the " Proceedings of the American Philosophical Society" for May 4, 1888. See farther, " The Study of Mineralogy," read before Section B of the British Association for the Advancement of Science in September, 1888, and published in its "Proceedings." The last two papers will be found republished in the Chemical News of London for August 10 and 17, and in that for October 12, 1888. As will be seen above, many important changes have since been made in the subdivisions of the classes ; and also in raising to the rank of orders in Class I. the groups to which the designation of tribes had been provisionally given. Orders in Classification. 165 genous constituents, as already explained (226). Thus we have borisilicates, aluminisilicates, carbosilicates, sulphosilicates, sul- phatosilicates, fluorosilicates, chlorosilicates, chlorophosphates and fluorophosphates, silicotitanates, titanocolumbates, etc. For these composite species might be established as many orders or suborders ; but as their introduction would complicate the classification, and, moreover, hinder comparison between species often very closely allied in chemical and physical characters, it is deemed expedient to include them, in most cases, with the order which is named from their more prominent negative element. Thus, the only known chloroborate, boracite, is placed in the order of Borates ; and the few fluorophosphates and chlorophosphates, with the order of sim- ple Phosphates. In certain cases, however, the importance and the considerable number of such complex salts, and, moreover, the existence of wide differences between them and the simple salts to which they are nearest akin, is such as to make it expedient to create for them distinct orders. Such, it may be affirmed, is the case with the great group of Aluminisilicates, with very varying proportions of aluminic and silicic oxyds ; which are at once quite distinct from the simple Aluminates on the one hand and the sim- ple Silicates on the other. The distinctness of the Borisilicates and the Boraluminisilicates has, moreover, been deemed sufficient to de- mand for them separate orders ; but the compounds in which titanic, ferric, chromic and manganic triad oxyds replace wholly or in part aluminic oxyd have been included in the order of Aluminisilicates. Most of the species of this order may be described as compounds having for their negative or halogenous constituent aluminic and silicic oxyds in various proportions, united with some basylous oxyd, as in the feldspars, micas and zeolites ; and occasionally with water only, as in the hydrous aluminisilicates like pyrophyllite and kaolin. In simple anhydrous compounds of aluminic and silicic oxyds, as cyanite and dumortierite, the alumina may be supposed to enter as a positive or basylous element ; or they may be re- garded as generated by the complete elimination of water from normal aluminisilicic hydrates, which are thereby converted into anhydrids of these complex acids. The same alternative views may be extended to the simple phosphates and sulphates of alumina. 239. The presence or absence in natural silicates of alumina (or a replacing triad oxyd) is a fact of fundamental importance in their history. Salts of the alkaline metals, as well as of calcium and magnesium, exist in greater or less abundance dissolved in all ter- 166 Systematic Mineralogy. restrial waters. The carbonates of the latter two are also readily soluble as bicarbonates ; while aluminic salts, for obvious reasons, are absent, or present only in traces in such natural waters. These unlike- relations explain the fact that the process of subaerial decay, while removing more or less completely from silicates, alkalies, lime and magnesia, together with a large proportion of the silica, leaves behind alumina as an insoluble silicate. Iron and manga- nese, which in their diad forms frequently replace lime and magnesia in silicates, share with these bases the solubility in carbonated waters, but when by oxydation they pass to the condition of higher oxyds, they partake of the insolubility of aluminic oxyd ; which they often replace wholly or in part in silicates. These considera- tions, which bear closely on the decay and the generation of sili- cates in the earth's crust, serve to give additional significance to the distinction upon which we have insisted between simple silicates and aluminisilicates in classification. It may farther be remarked that for species of similar condensation and hardness the chemical indiiference of the aluminisilicates is greater than that of the sim- ple silicates ; a fact explained by the comparative insolubility of alumina and aluminous silicates in atmospheric waters. 240. As has been elsewhere explained (206), there is no ground for the long-maintained distinction bet ween prot oxyd and sesquioxyd bases ; while beryllia and zirconia are not, as was once held, triad oxyds. Moreover, the peculiar relations of aluminic oxyd in com- bination are due not to its triad character, but to the fact that it is a feeble base, and plays rather a negative than a positive part ; a character which it shares with the triad oxyds of chromium, man- ganese and iron. Again, the triad oxyds of higher equivalent weight, as those of yttrium, lanthanum and ytterbium (like the triad forms of cerium, didymium and bismuth, and the hexad oxyd of uranium), are all distinctly basylous, and replace diad oxyds, at least in the cases of yttrium, lanthanum, cerium and didyinium. A similar part is also apparently played by the tetrad zirconic and thoric oxyds. Farthermore, the diad oxyds of calcium, barium and strontium, in zeolites and feldspars, appear to replace more or less completely the monad oxyds of sodium and potassium ; while cal- cium is replaced by sodium in the insoluble crystalline double car- bonate of magnesium and sodium, rightly designated by its discov- erer, H. Deville, a soda-dolomite. From all these considerations we disregard, in the monadic notation, the conception of valency^ and make all the basylous oxyds interchangeable. 167 CHAPTER XII. MINERALOGICAL NOMENCLATURE. 241. The popular or trivial names given to mineralogical species are of various and very unlike origins. Apart from some which have come down to us from classic antiquity, they have for the most part been devised within a century by Werner, Haiiy and others. Many of these names are of Greek derivation, and serve to mark some peculiarities of the species ; other names have been given to designate the localities of the species, or in compliment to the discoverer or some other person. The termination ite, corre- sponding to the Greek suffix ites or itis, was generally given by Werner, and has been adopted in a great number of cases, though mineralogists have often departed from that sound rule. In many names terminating in lite the suffix is still ite, as in tremolite, petal- ite, apophyllite, but in other cases the suffix itself is lite (Greek ?u6of y a stone), as in pectolite, zeolite, natrolite, iolite, cryolite. In a few examples we have the suffix tyte, as in eudialyte, dysana- lyte and tachylyte (Greek Mio, to dissolve or loosen), in allusion to the degree of solubility or the fusibility of the species.* The or- dinary designations of minerals are for the greater part single names, but in a few cases double names like fluor spar, heavy spar, are employed. 242. Attempts have not been wanting from the time of Lin- naeus to devise a systematic nomenclature, and to unite under ge- neric names related species. Of these attempts, the most noted, and the only one which has ever attained a measure of success, is that of Mohs, whose ingenious German nomenclature was rendered into English and adopted by Jameson in his " System of Mineralogy " in 1820. This nomenclature was also employed by Shepard in his report on the Geology of Connecticut, in 1837, and in his "Treatise on Mineralogy " in 1835. Therein he also adopted the classification of Mohs, and gave the names of the latter, translated into English, * The usage now followed by some teachers to write the names of certain rocks, as argillite, diorite, phonolite and quartzyte, thus : argiilyte, dioryte, phonolyte and quartz- yte, while they still adhere to granite and syenite, is not only false orthography, but tends to mislead the student by suggesting a wrong etymology. The name of trachyte is wholly exceptional, since it comes from the Greek rpa^v^j rough, in allusion to the texture of the rock thus called. 168 Systematic Mineralogy. as the only synonyms of the trivial names under which the various mineral species were alphabetically arranged. In a later edition, in 1857, however, Shepard, while retaining the classes and orders of Mohs, rejects any attempt to define genera, and is thus led to regard a systematic nomenclature as undesirable. He therefore gives only the trivial names, including a few synonyms, and omits all reference to the nomenclature of Mohs. A similar course as to nomenclature is followed by Zirkel in his editions of Naumann, and by Tschermak. Breithaupt, however, in his list of synonyms, is careful to give the names of Mohs, as is also J. D. Dana in the second edition of his " System of Mineralogy," but they are stricken out from the otherwise pretty complete synonymy of species given in his later editions.* 243. One defect in the nomenclature of Mohs was that it was constructed in accordance with a classification which left much to be desired ; although it would not be difficult so to revise that nomen- clature as to correspond with a new division of the mineral kingdom into classes, orders and genera. A greater objection to it, however, is found in the fact that it was framed in the German language, and while readily rendered into English, could not be easily trans- lated into Latin. A scientific nomenclature for general adoption in mineralogy should, however, be, like those employed in botany and zoology, in the Latin language, and the establishment of such a nomenclature has been the subject of several attempts. 244. It is well that a system of nomenclature so complete and so ingenious as that of Mohs, though now set aside, should not be forgotten. It was in part trinomial, giving successively the species, genus .and order of each mineral. In the order GEM, however, it was not deemed necessary to repeat the name of the order ; so that the names therein are binomial. The German names, as rendered into English for Jameson's book, suffered from imperfect and in- felicitous translation, and still more from errors of the press. Shep- ard, however, rendered them correctly and elegantly, and moreover extended the nomenclature to species which were unknown at the time when Mohs aided Jameson in the preparation of his "System." It is accordingly from Shepard's "Mineralogy" of 1835 that the following examples are taken, it being understood that only some prominent species of certain genera from the orders Haloide and Baryte are here given. * This suppression apparently coincides with the remarkable change in Mr. Dana's opinions as to the system of Mohs, recorded in the note to page 6. Nomenclature of Mohs. 169 Order HALOIDB. Rhombohedral Lime-Haloide Calcite. Prismatic Lime-Haloide Aragonite. Macrotypous Lime-Haloide Dolomite. Staphyline Lime-Haloide Magnesite. Octahedral Fluor-Haloide Fluorite. Rhombohedral Fluor-Haloide Apatite. Hemi-prismatic Fluor-Haloide Wagnerite. Prismatic Fluor-Haloide Yttrocerite. Rhombohedral Alum-Haloide Alunite. Prismatic Cryone-Haloide Cryolite. Prismatic Gypsum-Haloide Anhydrite. Order BABYTB. Prismatic Hal-Baryte Barite. Di-prismatic Hal-Baryte Witherite. Prismatoidal Hal-Baryte .Celestite. Peritomous Hal-Baryte Strontianite. Hemi-prismatic Hal-Baryte Barytocalcite. Macrotypous Parachrose-Baryte Dialogite. Brachytypous Parachrose-Baryte Siderite. Prismatic Parachrose-Baryte Triplite. Axotomous ZinoBaryte Willemite. Rhombohedral Zinc-Baryte Smithsonite. Prismatic Zinc-Baryte Calamine. Habroneme Copper-Baryte Malachite. Azure Copper-Baryte Azurite. Prismatic Lead-Baryte Anglesite. Di-prismatic Lead-Baryte Cerussite. Brachytypous Lead-Baryte Pyromorphite. Cupreous Lead-Baryte Caledonite. Kerasene Lead-Baryte Phosgenite. Hemi-prismatic Lead-Baryte Crocoisite. Pyramidal Lead-Baryte Wulfenite. Staphyline Lead-Baryte Plumbogummite. Pyramidal Tungsten-Baryte Scheelite. Octahedral Tungsten-Baryte Microlite. Prismatoidal Tungsten-Baryte Xenotime. Tetarto-prismatic Tungsten-Baryte Monazite. Peritomous Tungsten-Baryte Thorite. 170 Systematic Mineralogy. 245. A binomial Latin nomenclature was proposed by Brochant early in the present century, and James D. Dana, in the first and sec- ond editions of his "System of Mineralogy," in 1837 and 1844, while adopting the natural-history classification of Mohs, devised a Latin terminology for the orders, as well as a binomial Latin nomenclature for the genera and species. We have already, in Chapter II., discussed that classification, and the modifications pro- posed therein by Dana. In his third edition, however, in 1850, he abandoned both the classification of Mohs and his own systematic nomenclature, returning to the trivial names. His Latin designa- tions were, however, given as synonyms in Alger's edition of " Phil- lips's Mineralogy," in 1844. Breithaupt, in the first volume of his " Handbuch der Mineral - ogie," published in 1836, had already declared himself in favor of a Latin binomial nomenclature, which in his second and third volumes, in 1841 and 1847, he applied to the species therein de- scribed ; being his Classes I. and II., together with Order 1 of Class III., which included Aerae or oxydized ores. The remaining orders of this class Metalli, Pyrites, Lamprites and Minia corresponding to our class of Metallaceae, and also his Class IV., Inflammabilia, were reserved for the fourth volume, which was never published ; and the completed nomenclature, so far as the writer is aware, has not been given to the world.* From what appears in the published volumes, covering about three-fourths of the species then known, we are enabled to study the system of nomenclature proposed, and to compare it with that published by Dana in 1837 ; which has with it very few points of accord either in the constitution or in the designation of the genera and species, but which, like it, has failed to secure recognition by the students of mineralogy. 246. Both Dana and Breithaupt, following Mohs, established the orders on natural-historical characters, and then proceeded on chemical grounds to subdivide these orders into genera and spe- cies, as Mohs had done before them. The plan proposed by the present writer for a systematic Latin nomenclature differs radi- cally from the method of both of these mineralogists, which it re- verses ; inasmuch as it bases the orders upon chemical composition. These again are arranged on natural-historical grounds in genera, * There exists a brief analysis of his classification, entitled " Die Charaktere der Klassen und Ordnung des Mineral-Systems," August Breithaupt, zweite Ausgabe, Frei- berg, 1855 ; in which constant reference is made to the pages of the "Handbuch," up to the close of Classis III., Minerse, Ordo 1, Aerse, but no farther. Relation of Density to Chemical Equivalent. 171 in which the species are defined chemically. A method of pro- cedure so unlike those hitherto attempted, yields of course results very different from them, and, it is believed, much more nearly approaching to a natural system. As before explained, the great physical differences which by the natural-history school have been made the basis of orders have a much wider significance, and are essentially repeated in species found in groups so unlike, that they would by a chemist be placed not merely in different orders but in different classes. 247. The connection above maintained between chemical and physical or natural -history characters, and the subordination of the latter, will appear on examination to be logical and necessary ; the two being really dependent on one another, and presenting two aspects of the same problem, which can only be solved by the con- sideration of both. Thus, the relations of specific gravity between two solid species cannot be understood until we know their equiva- lent weights, as deduced from chemical analysis of the species in question ; since it is not the specific gravity in itself, but the pro- portion between this and the equivalent weight which is to be taken into account. To illustrate this by an example : of two rhombohedral carbon-spars, one, that with magnesium, has a specific gravity of 3.0, and another, that with zinc, of 4.5. From these differ- ences they were assigned by Mohs to two distinct orders ; the first, magnesite, to Haloide, as Staphyline Lime-Haloide ; and the second, smithsonite, to Baryte, as Rhombohedral Zinc-Baryte ; which latter order in his classification included all such minerals having a spe- cific gravity above 3.2. Yet the densities of these two closely related species are really in the proportion of their equivalent weights ; CMgO 3 = 84, and CZnOg = 125. If we divide these num- bers by the respective specific gravities we have (p -r- d = v), for the magnesium carbonate, 27.78, and for the zinc carbonate, 27.96 ; or in the notation which we have adopted for the oxyd-unit (111), 4.63 and 4.66. The condensation in the two species is thus the same.* Moreover, as has elsewhere been shown, other things being equal, the hardness and resistance to solution of a species are inversely as the value of v, or directly as the condensation. These various * Breithaupt had already in 1841 made these minerals species of one genus, Carbon- ates, in his order Spar. Shepard, moreover, subsequently increased the range of specific gravity for the order Haloide so as to include therein both smithsonite and barite (Min- eralogy, 3d ed., 1844). The specific name Staphyline refers to the botryoidal forms sometimes assumed by magnesite. 172 Systematic Mineralogy. relations can only be made apparent when chemical analysis has first determined the composition of a complex species, and per- mitted us to fix its chemical equivalent. Then, and then only, are we in a position to rightly understand the significance of specific gravity and hardness, which, with those of solubility and insolu- bility, are the fundamental characters upon which the natural- history method has been constructed. Hence the necessity of beginning a truly natural system with a knowledge of the chemis- try of the species, by founding upon a chemical basis the classes and orders, which are to be then subjected to the natural -history method for their subdivision into genera (ante 21, 22). 248. In carrying out the proposed plan for a systematic nomen- clature, it was deemed desirable by the writer to select for the designation of genera and species names which by their orthography would suggest, as far as practicable, the trivial nomenclature with which the student is supposed to be familiar ; or in cases where this was not feasible, to employ terms which may indicate some distin- guishing character. Moreover, following essentially, as is fitting, the guidance of the periodic law in chemistry Metals, Sulphids, Arsenids, Fluorids, Chlorids, in accordance with a principle long since recognized, fall necessarily into different orders ; while among oxydized species, Borates, Carbonates, Silicates, Phosphates, Sul- phates, etc., will also constitute distinct orders. 249. Dana's systematic nomenclature followed no definite rules. The silicates were for the most part arranged in genera, such as Mica, Zeolus, Scapolus, Spatum (for the feldspars), Avgitus, Car- bunculus, etc., in accordance with the principle just stated ; but this was not strictly adhered to. Thus we find among soluble salts, two genera, Alumen and Vitriolum, proposed for certain sulphates ; besides a third genus, Picralum, made up of sulphates, chlorids and nitrates, distinguished from the preceding genera by their bitter saline taste. In another genus, Fluellus, following Mohs, the phosphates, apatite and wagnerite are joined with fluor- ite ; while in a genus, Margaritus, with talc, chlorite, pyrophyllite and other silicates, is included the mica-like magnesian hydrate, brucite. 250. In the farther extension of his nomenclature, Dana aban- doned the plan of basing the genera, as in the silicates, upon the negative or halogenous portion, and, like Mohs, founded them on the positive or basylous portion. Thus we have, among others, the genera, Zincalus, Arealus, Cronalus and Cypralus, respectively, for Latin Nomenclatures of Dana and Breithaupt. 173 oxydized compounds of zinc, iron, lead and copper ; including car- bonates, sulphates, phosphates, oxyds, and even silicates of these metals. In the first-named genus, the silicates, calamine and wil- lemite are joined with smithsonite, as in the genus Zinc-Baryte of Mohs ; in the second, with phosphates and arsenates of iron, is the micaceous chlorif erous silicate, pyrosmalite ; and in the third, the oxyds massicot and minium are grouped with lead carbonates, sulphates, phosphates, etc.; while in Cypralus, with malachite, azurite, euchroite and atacamite are joined the silicates, dioptase and chrysocolla. 251. In the metalline class, Dana designated by the name Py- ritinea the order Pyrites of Mohs and Breithaupt, including, as they had done, not only the harder sulphids, but arsenids and sulph- arsenids ; thus embracing on natural-historical grounds in one order what we have for chemical reasons divided into three. The Glances- of Mohs (Lamprites of Breithaupt), called by Dana Galmea y include, as we have seen, not only simple sulphids and selenids, but the sulpharsenids and sulphantimonids. These two orders are, as in the case of the oxydized species above, arranged in genera (except in Lycites) according to the basylous or positive elements ; so that we have, as examples, Cobaltites, Cyprites, Lunites and Plumbites. In the first of these we find united linnaeite, smaltite and cobaltite; in the second, chalcocite, berzelianite (copper selenid), tetrahedrite, tennanite and bournonite ; while stibnite and the va- rious double sulphids of lead and antimony are included in the genus Zycites. 252. In the nomenclature of Breithaupt, as in those of Mohs and Dana, the same natural -historical orders are divided into gen- era on chemical grounds. Breithaupt, however, has greatly multi- plied genera, as will be seen from the fact that of soluble salts alone, including Alumen and Vitriolum, he has 20 genera ; while there are of Phyllites 6, of Ohalcites 12, Spathi 27, of Porodini 33, of Mica 7, of Zeolithus 14, of Grammites 17, of Sclerites 22, and of Aerea 26 ; making a total of 184 genera, many of them comprising large numbers of species. For the corresponding orders Dana has but 81 genera. In farther illustration, it may be noted that for the minerals included by Dana in the four genera, Zeolus, Spatum, Scapolus and Augitus, with a total of 37 species, Breithaupt has not less than 17 genera, including 87 species. We have thus en- deavored to point out certain defects in the three systems of no- menclature here examined, defects due in the first place to a false 174 Systematic Mineralogy. principle in classification ; secondly, to the want of consistent plan in carrying out the nomenclature, and finally, on the part of Breit- haupt, to a disposition to assign specific and even generic values to small differences in characters and composition. 253. Breithaupt was correct in principle when he made of rhom- bohedral carbon-spars, represented by calcite, dolomite, siderite, rhodocrosite, magnesite and smithsonite, a genus, Carbonites y to which he might however have properly added the prismatic carbon- spars, such as aragonite, strontianite and witherite ; of which he has made two other genera in his order Spar. He was also right in making a genus Pyroxenus, although he erred in including therein the species acmite and spodumene ; which latter has nothing in common with the pyroxenes save a coincidence in crystalline form with some species of the genus. Dana in like manner was correct, according to the principle which we have defined, in proposing a similar genus, Augitus, in which, while excluding spodumene, he too, wrongly included acmite, and also amblygonite ; a crystalline fluorophosphate of alumina and lithia, which Haidinger before him had designated as a species of Augite-Spar. Dana's genus, Zeolus, was also sound, save that he thereon joined with tru.e zeolites, species like apophyllite, pectolite and dysclasite, which are not properly zeolites. He was wrong, however, in propos- ing as a genus, Cobaltites, not for a group of species of which cobaltite should be the type, but for various cobaltif erous minerals ; including with cobaltite the chemically very unlike compounds, smaltite and cobaltic pyrites or linnseite. A similar criticism ap- plies to his genera, Pyrites, Cyprites, Lunites, etc.; as well as to the oxydized genera Arealus, Cronalus and Cypralus, as al- ready noticed. These genera, unlike those named above (Augi- tus and Zeolus), are established on chemical grounds, and named from their basylous elements. In this latter mode of designating genera, Dana followed Mohs who, as we have seen, divided his order Baryte, for example, into genera on the same chemical grounds ; making Hal-Baryte, Lead-Baryte, Zinc-Baryte, Copper- Baryte, etc., and describing the species in these several genera from their crystalline form, or from some other external character. 254. We have in the present system sought to show that the only sound rule in mineralogical classification is to divide the natural species of the mineral kingdom, on essentially chemical grounds, into classes and orders. These latter, from physical differences and resemblances, are then arranged in genera, the farther definition Latin Nomenclatures of Dana and Breithaupt. 175 of which, as species, is the work of chemistry. Thus, while a natural mineralogical classification must evidently both begin and end in a chemical method, the position therein of a natural-historical method, intervening between the orders on the one hand and the species on the other, is not less marked. The error of those chem- ists who would frame a mineralogical classification without the aid of physical characters is not less grave than that of the natu- ralists who have thought it possible to build up such a classification without the aid of chemistry ; while the attempts hitherto made to unite the two in a mixed method cannot, from a scientific point of view, be considered as successful. If the examination of the question of nomenclature has led to a criticism alike of the associations and the names proposed in the now abandoned schemes of Mohs, Dana and Breithaupt, it has been in no invidious spirit ; but solely with a view of drawing therefrom lessons as to what appear to the writer to be right and wrong ways of classification and of nomenclature ; and to make <;lear certain principles which may serve as guides in any farther attempts in a similar direction. 176 Systematic Mineralogy. CHAPTER XIII. SYNOPSIS OP MINERAL SPECIES. 255. Having set forth in the last two chapters the general plan of the new mineralogical system, and the principles to be followed in nomenclature, we proceed to give a concise view of the classes, orders, genera and species here recognized, and the names adopted for them ; followed, in the case of each species, by its trivial name. In this latter, so far as possible in the confused synonymy now prevailing, we have followed J. D. Dana, whose judgment therein is generally sound and judicious. The explanations of the terms adopted for orders and genera (when not, as is generally the case, sufficiently obvious), will be given in the subsequent chapters de- voted to the discussion of the minerals of the several classes. The characters prefixed in the synopsis to each genus need little explanation, the significance of the various types having been already shown in 236. The letter H refers to the hardness on the scale of Mohs (132). Instead of giving the specific gravity, it has been made plain in 24V, that it is not the specific gravity itself (sp. gr. = d), but the relation of this to the chemical equivalent, (i= p), which is the fact of cardinal importance in the density of the species. This relation, as expressed by v =p -r- c#, gives the re- ciprocal of the co-efficient of condensation (113). The expression " j&T> 4. v<4 " is to be read, " Hardness greater than 4 ; v less than 4." ; and "J?<4 ; v>6," "Hardness less than 4 ; v greater than 6." The species in each genus are numbered, and when a species not known in a native state, as Phosphorus, is mentioned for il- lustration, it is marked with a star. 177 SYNOPSIS OF THE NATIVE MINERAL SPECIES TABULATED IN THIS VOLUME. CLASS I METAXLACEJE. SUB-CLASS A METALLOMETALLATA. ORDER I METALLINEA. GENUS 1. METALLUM. a. Native Metals and Alloys. 1 M. osmirideum .......................... Newjanskite. 2 * iridosmeum ........................... Sysserskite. 3 " irideum .............................. Iridium. 4 " platinirideum ........................ Platiniridium. 5 " platineum ............................. Platinum. 6 " ferroplatineum ....................... Iron-platinum. 7 " palladeum ...................... . ..... Palladium. 8 " ferreum .............................. Iron. 9 " niecoloferreum ........................ Awaruite. b. Native Metals and Alloys. H<. v>6. 10 M. cupreum ............................. Copper. 11 " plumbeum ............................ Lead. 12 ' aureum ........... . .................. Gold. 13 ' argenteum .......................... Silver. 14 ' aurargenteum ....................... Electrum. 15 ' argentomercureum ................... Amalgam. 16 ' mercureum .......................... Mercury. 178 Systematic Mineralogy. Genus 2. METALLINUM. Semi-Metals. H<. * M. phosphoreum ......................... Phosphorus. 1 " arseneum ................. . ........... Arsenic. 2 " arsenostibeum ................ . ....... Allemontite. 3 " stibeum .............................. Antimony. 4 " bismuteum ........................... Bismuth. 5 " seleneum .... ......................... Selenium. 6 " tellureum ........... ..Tellurium. Order II. GALENINEA. Genus 1. THIOGALENITES. Metallic Sulphids. H< 4. v > 6. 1 T. molybdeus Molybdenite. 2 " stibeus . . . .Stibnite. * bismuteus Bismuthinite. ' argentoferreus Sternbergite. * cupricus Cantonite. ' cuprosus Chalcocite. 8 4 5 6 7 ' Harrisi Harrisite. 8 " plumbeus Galenite. 9 " argenteus Argentite. 10 " argentocuprosus Stromeyerite. 11 " germanicus Argyrodite. 12 " mercuricus Metacinnabar. Genus 2. SELENOGALENITES. Metallic Selenids. H< 4. v > 7. 1 S. cuprosus Berzelianite. 2 " plumbeus Clausthalite. 3 bismuteus Frenzelite. 4 " argentocuprosus Eucarite. 5 " mercureus Tiemannite. ^ " plumbomercureus Lehrbachite. 7 " argenteus Naumannite. 8 " cuproplumbeus Zorgite. 9 " thalleus . Crookesite. Synopsis of Species. 179 Genus 3. TELLUROGALENITES. Metallic Tellurids. H< 4. 9. 1 T. argenteus Hessite. 2 " argentaureus Petzite. 3 " mercureus Coloradoite. 4 " plumbeus Altaite. 5 " aureus Calaverite. 6 " Sylvanites Sylvanite. 7 " auroplumbeus Nagyagite. 8 " bismuteus Tetradymite. 9 " niccoleus Melonite. Order III. DIAPHORINEA. Genus 1. ARSENODIAPHORITES. Metallic Sulpharsenids. H< 4. u>6. 1 A. terplumbeus Guitermannite. 2 " quadriplunibeus Jordanite. Genus 2. STIBIODIAPHORITES. Metallic Sulphantimonids. H< 4. v > 6. 1 S. plumbeus Zinkenite. 2 " Plagionites Plagionite. 3 " sesquiplumbeus Warrenite. 4 " biplumbeus Jaraesonite. 5 " terplumbeus Boulangerite. 6 " quadriplumbeus Meneghinite. 7 '* quinqueplumbeus Geocronite. 8 " sexplumbeus Kilbrickenite. 9 " Brongniardius Brongniardite. 10 " quinquargenteus Stephanite. 11 " perargenteus Polyargyrite. 12 " argentoplumbeus Freieslebenite. 13 " typicus Diaphorite. 14 " cuproplumbeus Bournonite. 15 " argentocuprosus Stylotypite. 16 " cuprosus Chalcostibite. 17 " semicuprosus Guejarite. 18 " ferreus Berthierite. 19 " thiocuprosus. Fatiminite. 20 " thioplumbeus Epiboulangerite. 180 Systematic Mineralogy. Genus 3. BISMUTODIAPHORITES. Metallic Sulphobismuthids. H< 4. v > 7. 1 B. subplumbew Chiviatite. 2 ' plumbeus Galenobismutite. 3 ' biplumbeus Cosalite. 4 ' sexplumbeus Beegerite. 5 * argenteus Alaskaite. 6 ' sesquiargenteus Schirmerite. 7 ' cuproplumbeus Aikinite. 8 " sesquieuprosus Klaprothite. 9 " cuprosus Emplectite. 10 " tercuprosus Wittichenite. Order IV. PYRITINEA. Genus 1. PYRITES. Metallic Sulphids. H > 5. v<5. 1 P. rutheneus. Laurite. 2 ' vulgaris Pyrite. 3 ' secundus Marcasite. 4 * cobalteus Linnaeite. 5 niecoleus Siegenite. 6 ' cuprocobalteus Carrollite. 7 " chromieus Daubreelite. Genus 2. PYRITINUS. Metallic Sulphids. H< 5. v>5. 1 P. ferreus , .Troilite. 2 " niecoleus Millerite. 3 " proximus Polydomite. 4 " Beyriehii Beyrichite. 5 " magnetwus Pyrrhotite. 6 " Bornites Bornite. 7 " erubescens Bornite. 8 " varius Homichlyn. 9 " cupricus Chalcopyrite. 10 " Cubanites Cubanite. 11 " stanneus Cassiteropyrite. Synopsis of Species. 181 Order V. CHLOANTHINEA. Genus 1. PHOSPHOCHLOANTHITES. Metallic Phosphid. H> 6. v < 4. 1 P. ferroniccoleus Schreibersite, Genus 2. ARSENOCHLOANTHITES. Metallic Arsenids. J9 r >5. v <6. 1 A. platineus Sperrylite. 2 " niccoleus Niccolite. 3 " cobaltoferreus Safflorite. 4 " Rammelsbergii Rammelsbergite. 5 " semiferreus Loellingite. 6 " ferreus Leucopyrite. 7 " eobalteus Smaltite. 8 " typicus Chloanthite. 9 " perarseneus Skutterrudite. 10 " manganosus Kaneite. Genus 3. STIBIOCHLOANTHITES. Metallic An timonids. J5T>4. -y<8. 1 8. niccoleus Breithauptitc. j3 " cuprosus Horsfordite. Genus 4. ARSENODTSCRASITES. Metallic Arsenids. H< 5. v > 6. 1 A. cuprosus Domeykite. 2 " tercuprosus Algodonite. 3 " percuprosus Whitneyite. 4 " argenteus , Arsenargentite. Genus 5. STEBIODYSCRASITES. Metallic Antimonids. H< 4. v >8. 1 8. argenteus Dyscrasite. 2 " terargenteus Dyscrasite. 3 " perargenteus Animikite. 182 Systematic Mineralogy. Order VI. LAMPROTINEA. Genus 1. ARSENOLAMPROTITES. Metallic Sulpharsenids. JJ > 5. v<5. 1 A. ferreus Mispickel. 2 " cobalteus Cobaltite. 8 " niccoleus Gersdorffite. 4 ' niccolocobalteus . . . .Glaucodot. Genus 2. MESOLAMPROTITES, etc. Kindred to the preceding genus. J3">4. v ? 1 Mesolamprotites niccoleus Corynite. 2 " " Wolfachite. 3 " " Alloclasite. 4 Stibiolamprolites niccoleus Ullirannite* 5 Bismutolamprotites niccoleus Grunauite. Sub-Class B. SPATHOMETALLATA. Order VII. SPATHOMETA LLINEA. Genus 1. SPATHOMETALLINUM. Spathometalloids. H< 3. v > 7. 1 8. sulphureum Sulphur. 2 seleneum Selenium. 3 " selenosulphureum Selensulphur. * " phosphor Phosphorus. * " arseneum .. Arsenic. Order VIII. SPHALERINEA. Genus 1. SPHALERITE& Spathoid Sulphids. H< 5. v >5. 1 S. semimanganosus Hauerite. 2 " manganosus Alabandite. 3 " cuprosus Covellite. 4 " zinceus Sphalerite. Synopsis of Species. 183 5 S. parazinceua Wurtzite. 6 " ferrozinceus Christophite. 7 " cadmeus Greenockite. 8 " calcareus Oldhamite. 9 " mercureus Cinnabar. 10 " arseneus Orpiment. 11 " perarseneus Realgar. 12 " stibeus . . .Metastibnite. Order IX. RHODOPYBITINEA. Genus 1. AESENOPULVITES. Spathoid Sulpharsenids. H< 5. v > 6. 1 A. subcuprosus Binnite. 2 " plumbeus Sartorite. 3 " biplumbeus Duf renoysite. 4 " argenteus Proustite. 5 " cuprosus Fatiminite. 6 " cuprozinceus Tennantite. 7 " thiocuprosus Enargite. 8 " thioargenteus .,,,,.,. .Xanthoconite. Gtenus 2. STIBIOFULVITEa Spathoid Sulphantimonids. H< 4. v > 6. 1 8. mercureus Livingstonite. 2 " subargenteus Miargyrite. 3 " argenteus Pyrargyrite. 4 " parargenteus Pyrostilpnite. 5 " plumbargenteus Polytelite. 6 " cuprosus .Tetrahedrite. 7 " cuprargenteus Freibergite. 8 " mercureus . , Spaniolite. 9 " superargenteus Polybasite. 10 " thiocupreus Fieldite. Genus 8. MEDIOFULVITES. Kindred to the last two genera. (Annivite, Studerite, Rittingerite, etc.). 184 Systematic Mineralogy. Class II. HALIDACEJE. Order I. FLUORINEA. Genus 1. FLTJORITES. Spathoid. H< 6. 1 F. calcareus Fluorite. 2 * magneseus Sellaite. 3 ' cereus Tysonite. 4 ' Cryolithus Cryolite. 5 ' nivalis Chiolite. 6 ' glaeialis Chodnewite. 7 ' natrocalcareus Pachnolite. 8 " decipiens Prosopite. 9 " aluminous.. ..Fluellite. Order II. CHLORINEA. Genus 1. MURIALUS. Salinoid. H< 3. -y>8. 1 M. natricus Halite. 2 " kalieus Sylvite. 3 " volatilis Sal ammoniac. 4 " kalimagneseus Carnallite. 5 " magneseus Bischoffite. 6 " calcareomagneseus Tachyhydrite. Genus 2. MURIATES. Spathoid. H< 3. v >20. 1 M. argenteus Kerargyrite. 2 l ' cuprosus Nantoquite. 3 '* plumbeus Cotunnite. 4 " mercurosus Calomel. Orders III. and IV. BROMINEA : IODINEA. Genera 1 and 2. BROMITES : IODITES. Kindred to the preceding genus. H< 3. v > 20. 1 Bromites argenteus Bromargyrite. 2 lodites argenteus lodargyrite. Synopsis of Species. 185 Class III. OXYDACE^E. Sub-class a. OXYDATA. Order I. OXYDINEA. Genus 1. HYDROXYDITES. Spathoid and Colloid. H< 6. v >4.5. 1 H. ruber Turgite. 2 " lamellosus Goethite. 3 " limosus Limonite. 4 " Limnites Limnite. 6 " manganicus Manganite. 6 " aluminicus Gibbsite. 7 " argilleus Bauxite. 8 " siliceus Opal. 9 " hydromagneseus Brucite. 10 " hydromanganosus Pyrochroite. 11 " hydricus Ice. 12 " uranicus Gummite. 13 " niger Psilomelane. Genus 2. PROTHOLITHUS. Chiefly Spathoid. H < 6.5. v >5. 1 P. manganosus Manganositc. 2 " magneseus Periclase. 3 " niccoleus Bunsenite. 4 " zinceus Zincite. 5 " cuprosus Cuprite. 6 " cupricus Tenorite. 7 " plumbeus Massicot. 8 " plumbieus Plattnerite. 9 " arseneus Arsenolite. 10 " stibeus Senarmontite. 11 " sulphostibeus Kertuesite. 12 " sulphozinceus Voltzite. 186 Systematic Mineralogy. Genus 3. CRYSTALLITHU& Adamantoid. JT>5.5. v< 7. 1 C. aluminicus Corundum. 2 " ferricus Hematite. 3 " Martialis Martite. 4 " ferrititanicus t . . .Menacannite. 5 " manganicus Braunite. 6 " vulgaris Quartz. 7 triplex Tridymite. 8 " rutilis Rutile. 9 " Brookianus Brookite. 10 " octahedrus Anatase. 11 " stanneus Cassiterite. 12 " Polianites... , .Polianite. Sub-class b. AMPHIDATA. Order II. BOEATINEA. Genus 1. BORAS ALINITE& Salinoid. H< 3. v > 6. 1 B. natricus Tincal. 2 " hydricus Sassolin. 3 " ammoniatus Larderellite. Genus 2. BORATINTJa Spathoid. H< 5. v > 4. 1 B. calcareus Colemanite. 2 " natrocalcareus Ulexite. 3 " manganosus Sussexite. Genus 3. BORITES. Adamantoid. JH">5. v< 6. 1 B. ehloromagneseus Boracite. 2 " aluminikalicus Rhodizite. 3 " aluminicus JeremejewitCr 4 " titanicus Warwickite. Synopsis of Species. 187 Order III. SPINELLINEA. Genus 1. SPINELLUS. Adamantoid. H>6. v < 6. 1 S. berylleus Chrysoberyl. 13 " hydricus Diaspore. 3 " magneseus Spinel. 4 " zinceus Gahnite. -5 " ferreus Hercynite. Genus 2. ALLOSPINELLUS. Adamantoid, kindred to the last. H>5. v< 6.5. 1 A. mediochromicus Chromite. 15 " chromicus Chromite. 3 " ferricus Magnetite. 4 " ferrimagneseus Magnesioferrite. 5 " ferrimanganosus Jacobsite. 6 " ferrizinceus Franklinite. 7 " manganicus Hausmannite. 8 " manganicupreus Crednerite. 9 M uranicus . . . .Uraninite. OrderlV. CARBONINEA. Genus 1. CARBOSALINITES. Salinoid. H< 4. v>5. 1 O. natrocalcareus Gaylussite. 2 " typicus Urao. 3 " hydronatricus Natron. 4 " natreus . . . .Thermonatrite. Genus 2. HYDROCARBONITES. Chiefly Spathoid. H< 5. v >5. 1 H. magneseus Hydromagnesite. 2 " cceruleus Azurite. 3 " cupreus Malachite. 4 " cuprozinceus Aurichalcite. 5 " niccoleus Texasite. 6 " zinceus Hydrozincite. 7 " alumimcus Dawsonite. 8 " lanthaneus Lanthanite. 9 " bismuteus Bismutite. 10 " uranicus.. UranothaUite. 188 Systematic Mineralogy. Genus 3. CARBONITE& Spathoid. H4. 1 C. cdlcareus Calcite. 2 " calcareomagneseus Dolomite. 3 " calcareoferreus Ankerite. 4 " magneseoferreus , Breunnerite. 5 " ferreus Siderite. 6 " manganeus Rhodocrosite. 7 " cobalteus Sphaerocobaltite. 8 " zinceus Smithsonite. 9 " magneseus Magnesite. 10 " paracalcareus Aragonite. 11 " baryteus Witherite. 12 " Alstonius Alstonite. 13 " barytocalcareus Bary tocalcite. 14 " stronteus Strontianite. 15 " plumbeus Cerussite. 16 " parazinceus Parasmithsonite. Genus 4. HALICARBONITES. Spathoid. H< 5. v > 5. 1 H. calcareocereus Parisite. 2 " cereus Bastnaesite. 3 " plumbeus Phosgenite. Order V. SILICINEA. Genus 1. PECTOLITHUS. Chiefly Spathoid. H > 3. v < 1. 1 P. vulgaris Pectolite. 2 " lamellaris Apophyllite^ 3 " Okeni Okenite. 4 " recens Plombierite^ 5 " Xonaltites Xonaltite. 6 " cupricus Dioptase. 7 " zinceus Calamine. 8 " manganosus Friedelite. 9 " chloroferreus Pyrosmalite. Synopsis of Species. 189 Genus 2. CHRYSOLITHUS. Spathoid. H< 8. v > 5. 1 C. magneseus Forsterite. 2 " nobilis Chrysolite. 3 " ferreus Fayalite. 4 " calcareus Monticellite. 6 " fluoromagneseus Chondrodite, 6 " manganosus Tephroite. 7 " zinceus Willemite. 8 " plumbeus Ganomalite. 9 " bismuteus Eulytite. Genus 3. AMPHIBOLUa Adamantoid. H>5. . v< f 7. 1 A. dibits Tremolite. 2 " radiatus Actinolite. 3 " floridus Anthophyllite. 4 " magneseus Kupfferite. 5 " ferromagneseus Cummingtonite. Genus 4. PYROXENUS. Chiefly Adamantoid. 1Z">4.5 v<1. 1 P. magneseus Enstatite. 2 " ferromagneseus Hypersthene. 3 " albus Malacolite. 4 " ferrocalcareus Hedenbergite. 5 " manganosus Rhodonite. 6 " calcareus . . ; . . .Wollastonite. Genus 5. PHENACITES. Adamantoid. ^Z">7. v< 5. 1 P. decipiens ............................. Phenacite. 2 " Bertrandius . . ......... Bertrandite. Genus 6. ZIRCONIUS. Adamantoid. H > 6. v < 6. 1 Z. nobilis Zircon. 2 " minor . . Auerbachite. 190 Systematic Mineralogy. Genus 7. ERITIMITES. Chiefly Spathoid. H< 7. v >5. 1 E. cerew Cerite. 2 " thoreus . . . Thorite. 3 " yttreus Yttrialite. 4 " Oadolini Gadolinite. 5 " uranothoreus Thorogummit( 6 ' ' uranocalcareus Uranotil. 7 " natreus Catapleiite. 8 " calcareus Eudialyte. 9 " manganeus Laveriite. 10 " xantheus , Helvite. 11 " zinceus Danalite. 12 " albus r Leucophane. Genus 8. PICROLITHUS. Spathoid and Phylloid. H< 5. v>5. 1 P. triplex Villarsite. 2 ligneus Picrolite. 3 " foliaceus , Thermophyllite 4 " sericeus Chrysotile. 5 " odorus Picrosmine. 6 " mollis Talc. 7 " prismaticus Pyrallolite. Genus 9. POROSILICITES. Colloid. H<4. v>5. 1 P. communis Serpentine. 2 " Laurentianus Retinalite. 3 " gummosus Deweylite. 4 " spumosus Aphrodite. 5 " detergens Sepiolite. 6 " niccoleus Genthite. 7 " cupricus Chrysocolla. 8 " ferreus ? Glauconite. Order VI. BORISILICINEA. Genus 1. BORICRYSTALLITHU& Adamantoid. H>6. v< 6. 1 B. nobttis. . Danburite. Synopsis of Species. 191 Genus 2. BORISILICITES. Spathoid. H< 6. v > 5. 1 B. calcareus Datolite. 2 " ferrocalcareus Homilite. Order VII. ARGILLINEA. Genus 1. ZEOLITHU& Spathoid. H< 6.5. v >6. 1 Z. Thomsoni Thomsonite. 2 " Gismondii Gismondite. 3 " natreus Natrolite. 4 " medius Mesolite. 5 " Edingtoni Edingtonite. 6 " Levynii Levynite. 7 " ccesius Pollucite. 8 " Analcites Analcite. 9 " Laumontii .' . . .Lanmontite. 10 " Phillipsii Phillipsite. 11 " Chabasites Chabasite. 12 " Faujasii Faujasite. 18 " Beudantii Hypostilbite. 14 " baryteus Harmotome. 15 " stronteus Brewsterite. 16 " Heulandii Heulandite. 17 " splendens Stilbite. Genus 2. AGROLITHUS. Spathoid. H < 7. v > 6. 1 A. calcareus Anorthite. 2 " medius Bytownite. 3 " Labradorensis Labradorite. 4 " insignis Lavalite. 5 ' Andesianus Andesite. 6 ' Oligoclasius Oligoch 7 8 9 10 11 ' albus Albite. 1 microclinus Microcline. ' orthotomus Orthoclase. ' baryteus Hyalophane. Petalites. .. Petalite. 12 " magneseus lolite. 192 Systematic Mineralogy. Genus S. SCAPOLITHU& Spathoid. H< 6.5. v>6. 1 8. minor Meionite. Werneri Wernerite. Paranthinus Eckebergite. major Mizzonite. Porcellanites Dipyre. Andradii Marialite. flavus Melilite. Oehleni Gehlenite. Milarites . . . .Milarite. Genus 4. ALCALITES. Spathoid. H< 6. v >6.5. 1 A. muriatus Sodalite. 2 " vitriolatus Nosite. 3 " gypseus Hattyene. 4 " carbonatus Cancrinite. 5 " sulphureus Lapis lazuli. 6 " natreus Nephelite. 7 " kalicus.. ..Leucite. Germs 5. PHENGITES. Phylloid. H<5. v>5. 1 P. Lepidolithus Lepidolite. hemidomaticus Zinnwaldite. fusilis Cryophyllite. hydratus Cookeite. Muscoviticus Muscovite. Euphyllites Euphyllite. baryteus Oellacherite. Margarites Margarite. 9 " Chrysophanus Seybertite. 10 " Meroxenus Biotite. 11 " Phlogopites Phlogopite. Genus 6. ASTRITES. Phylloid. H< 3. v >6.5. 1 A. Lophoites Prochlorite. 2 " Ripidolithus Eipidolite. 3 " chromifer Penninite. 4 " flavus Jeffersite. 5 " cupreus Venerite. 6 " Thuringites Thuringite. 7 " Cronstedii Cronstedite. Synopsis of Species. 193 Genus 7. IDOCRASIUS. Adamantoid. H>5.5. v<6. 1 /. phlogogenius Vesuvianite. 2 " hydratus Prehnite. 3 " Glaucophanus Glaucophane. 4 " Gastaldianus Gastaldite. 5 " amphibolus Pargasite. 6 " albus Leucaugite. Genus 8. EFIDOTUS. Adamantoid. H > 6. v < 6. 1 E. caleareus Zoisite. 2 " vulgaris Epidote. 3 " manganicus Piedmontite. 4 " cereus Orthite. 5 " tenax Saussurite. 6 " Damourii.. . Jadeite. Genus 9. GRANATTJS. Adamantoid. H > 6. v < 6. 1 O. Grossularius Grossularite. 2 " Pyropus .Pyrope. 3 " Almandinus -. Almandite. 4 " manganosus Spessartite. 5 " ferricalcareus Andradite. 6 " chromaticus .. Ouvarovite. Genus 10. GRANATINUS. Adamantoid. 1T>6. v< 6. 1 G. decussatus Staurolite. 2 " caeruleus Sapphirine. 3 " viridis Chloritoid. 4 " secundus Ottrelite. 5 " manganosus Ardennite. Genus 11. ACMITODES. Adamantoid. H > 5.5*. v< 6. 1 A. insignis Acmite. 2 ** secundus Arfvedsonite. 8 " Babbingtonii Babbingtonite. 4" Hvaites Lievrite. Melanotekite, Kentralite. 194 Systematic Mineralogy. Genus 12. BERYLLUS. Adamantoid. fZ">6.5. v< 6. 1 B. smaragdus Beryl. 2 " Euclasius. . . .Euclase. Genus 13. SPODIOLITHUS. Adamantoid. H>6. v <6. 1 S. triphanus .Spodumene. Genus 14. PORODITES. Colloid. H< 4. v> 5. 1 P. Jollytes Jollyte. 2 " Fahlunites Fahlunite. 3 " medius Hygrophilite. 4 " Bravaisii Bravaisite. 5 " Parophites Finite. Genus 15. AMORPHITES. Colloid. T>4. v? 1 A. Obsidian Obsidian. 2 " perlaceus Pearlite. 3 " piceus Pitchstone. 4 " Tachylytes Tachylyte. 5 " Palagonites Palagonite. Genus 16. TOPAZIUS. Adamantoid. jff>6.5. v< 5.5. 1 T. nobilis Topaz. 2 " crucifer Andalusite. 3 " Sillimanii Fibrolite. 4 " caeruleus Kyanite. 5 " Damourii Dumortierite. 6 " hydratus Zunyite. Genus 17. PYRAUXITES. Phylloid. H< 2. v >5. 1 P. insignis Pyrophyllite. 2 " Nacrites Nacrite. 3 " squamosus Pholerite. 4 " Sinensis Kaolin. 5 " Bavaricus . . Keramite. Synopsis of Species. 195 Genus 18. ARGILLITHU& Colloid. H< 4. 1 A. Collyrites ............................ Collyrite. 2 " Allophanus ........................... Allophane. 3 " Glagerites ............................ Glagerite. 4 " Halloysii ............................ Halloysite. Order VIII. BORARGILLINEA. Genus 1. TURMALINUS. Adamantoid. H>6.5. v< 5.5. 1 T.litheus Rubellite. 2 " ferreus Schorlite. 3 " magneseus Coronite. Genus 2. AXINITES. Adamantoid. .ff>6.5. #< 6. 1 A. calcareus Axinite. Order IX. TITANINEA. Genus 1. TITANITES. Spathoid. JZ"<6. v ? 1 T. calcareus Perowskite. 2 " manganosus Pyrophane. 3 " zirconeus Mengite. 4 " yttreus Polymignite. Genus 2. PARATITANITES. Chiefly Spathoid. H< 6.5. v ? 1 P. calcareus Sphene. 2 " cereus Tschewkinite. 3 " zirconeus Oerstedite. 4 "ferreus Astrophyllite. 5 " cereocalcareus Mosandrite. 196 Systematic Mineralogy. Order X. STANNINEA. Cassiterotantalite, Nordenskioldine, Stannite, Br. Order XI. COLUMBOTANTALINEA. Genus 1. TANTALITES. Adamantoid. H>5. v<6. 1 T. verus. . . . .Tantalite. Genus 2. COLUMBITES. Adamantoid. H> 5. v <6. 1 C. verus . Columbite. 2 " ponderosus Columbite. 3 " yttreus Yttrocolumbite. 4 " Fergusonii Fergusonite. 5 " uranicus Samarskite. 6 " uranocalcareus. ... Hatchettolite. Genus 3. PARACOLUMBITES. Adamantoid. H>5. v ? 1 P. silicozirconeus Woehlerite. 2 natrocalcareus Pyrochlore. 3 uranyttreus Euxenite. 4 titanocalcareus Dysanalyte. 5 yttreus Polycrase. 6 thoricereus uSSschynite. Order XII. WOLFRAMINEA. Genus 1. WOLFRAMITES. Spathoid. H< 6. v > 5. 1 W. ferreus Ferberite. 2 " manganosus Hubnerite. 3 " calcareus Scheelite. 4 " plumbeus Stolzite. Synopsis of Species. 197 Order XIII. MOLYBDINEA. Genus 1. MOLYBDITES. Spathoid. H<4. v>5. 1 M. plumbeus Wulf enite. 3 " calcareus. . . .Powellite. Order XIV. CHROMATINEA. Genus 1. CHROMATITES. Spathoid. H< 4. v >6. 1 C. plumbeus Crocoite. 2 " sesquiplumbeus Phoenicite. Order XV. NITRATINEA. Genus 1. NTTRASALINITES. Salinoid. H< 3. v >6. 1 N.kalicus Potash Niter. 2 " natricus SodaNiter. 3 " baryteus Baryta Niter. 4 " calcareus . . .Lime Niter. 5 " magneseus Magnesia Niter. Genus 2. NITRATES. Phylloid. H < 3. f. cupricusS Gerhardtite. Order XVI. PHOSPHATINEA. Genus 1. EUTELITES. Chiefly Spathoid. H< 4. v >5. 1 E. Brushianus .......................... Brushite. 2 *' Julianus ............................. Metabrushite. 3 " Shepardii ............................ Monetite. 4 " magneseus ............................ Newburyite. " ammoniomagneseus ................... Struvite. 198 Systematic Mineralogy. , Genus 2. PHOSPHATITES. Spathoid. H< 6. v > 5. 1 P. zinceus Hopeite. 2 " natromanganeus Dickinsonite. 3 " manganeus Reddingite. 4 " Hureaulites Hureaulite. 5 " Vivianites Vivianite. 6 " Ludlamites Ludlamite. 7 " Libethenites Libethenite. 8 " Tagilites Tagilite. 9 " Ehlites Ehlite. 10 " percupreus Phosphorochalcite. 11 " uranicalcareus Uranite. 12 " uranibaryteus Uranocercite. 13 " uranieuprieus Torbernite. Genus 3. APATITES. Spathoid. H< 6.5. v > 5. 1 A. natroberylleus Beryllonite. 2 " calcareoberylleus Herderite. 3 " magneseus Wagnerite. 4 " fluorocalcareus Fluorapatite. 5 " chloroplumbeus Pyromorphite. 6 " yttreus Xenotime, 7 " cereus Monazite. 8 " lithioferreus Triphylite. 9 " fluoromagneseus Triplite. 10 " lithiomagneseus Lithiophilite. 11 " natromanganeus Natrophilite. 12 " hydromanganeus Triploidite. Genus 4. PHOSPHASCLERITES. Spathoid. H > 4. 5. v < 7. 1 P. Uthicus Amblygonite. 2 " hydrolithicus Montebrasite. 3 " hydromagneseus Lazulite. 4 " hydroferreus Childrenite. 5 ' ' hydromanganeus Eosphorite. 6 " hydrocalcareus Goyazite. Genus 5. CALLAITES. Spathoid. H>3. v2. v< 7. 1 C. Strengites Strengite. 2 " Eleonorites Eleonorite. 3 " viridis Krausite. 4 " vulgaris Cacoxenite. Order XVII. ARSENINEA. Genus 1. PHARMACOLITES. Spathoid and Phylloid. H< 6. v > 6. 1 P. Haidingeri Haidingerite. 2 " vulgaris Pharmacolite. 3 * ' calcareomagneseus Wapplerite. 4 " magneseus Hornesite. 5 " calcareocobalteus Roselite. 6 " cobalteus Erythrite. 7 " niecoleus Annabergite. 8 " zinceus Adamine. 9 " ferreus Symplesite. 10 " manganeus Allatakite. 11 ' Conichalcites Conichalcite. 12 " Olivenites Olivenite. 13 " Euchroites Euchroite. 14 " Erinites Erinite. 15 " Tirolites Tirolite. 16 " Clinoclasius Clinoclase. 17 ' ' Chalcophyllites Chalcophyllite. 18 " bismutoeupricus Mixite. 19 " bismuteus Rhagite. 20 " bismutouranicus Walpurgite. 21 " uranicalcareus Uranospinite. 22 " uranicuprieua Zeunerite. 23 " uranieus Tragerite. Genus 2. MIMETITES. Spathoid. H < 5. v>8. M. plumbeus Mimetite. Genus 3. ARSENASCLERITES. Spathoid. H< 6. v>6. A. ferronatreus. Durangite. Berzelliite. Scorodite, Pittizite, Liroconite. 200 Systematic Mineralogy. Order XVIII. VANADINEA. Spathoid. JET<5. v ? Vanadinite, Endlichite, Dechenite, Volborthite, Descloizite, Mottramite, Psittacinite, Pucherite. Order XIX. STIBIINEA. Atopite, Bindheimite, Rivotite, Romeite, Nadorite. Order XX. SULPHATINEA. Genus 1. ARCANITES. Salinoid. H< 4. v>G. 1 A. kalicus Arcanite. 2 " natrieus Thenardite. 3 " ammoniatus Mascagnite. hydronatricus Mirabilite. natrocalcareus Glauberite. magneseus Kieserite. Astrdkanites Bloedite. natromagneseus Loewite. 9 *' kalicalcareus -. Syngenite. 10 Tcalimagneseus Polyhalite. 11 " gypseus Gypsum. Genus 2. VITRIOLITES. Salinoid. H< 4. u>5. 1 V. magneseus Epsomite. 2 ' zinceus Goslarite. 3 ' ferreus Melanterite. 4 ' niccoleus Moresonite. 5 ' cobalteus Bieberite. 6 * manganosus Mallardite. 7 ' cupricus Chalcanthite. Synopsis of Species. 201 Genus 3. SULPHATITE& Spathoid. H< 4. v > 5. 1 S. cupriplumbeus Linarite. 2 " Caledonites Caledonite. 3 " Langites Langite. 4 " Brochantites. . . .Brochantite. Genus 4. SULPHATOSCLERITE& Spathoid. H < 4. w>5. 1 S. baryteus Barite. 2 " stronteus Celestite. 3 " calcareu* Anhydrite. 4 " plumbeus Anglesite. 5 " diplumbeus Lanarkite. Genus 5. ALUMEN. Salinoid. H< 2. v>7. 1 A.capillaris Keramohalite. -2 " kalicus Potash alum. 8 " natricus Mendozite. 4 " magneseus Pickeringite. ^5 manganosus Bosjemanite. Genus 6. SULPHALUMINITES. Spathoid chiefly. H< 4. v>6. 1 S. Websterianus Aluminite. 2 '" secundus Faraluminite. 3 " kalicus Alunite. 4 " zinceus Zincaluminite. 5 " chloricupricus Spangolite. Genus 7. AMARANTITES. Salinoid. H< 3. 1 A. Coquimbites .......................... Coquimbite. % *' natreus ............................... Ferronatrite. 3 " insignia .............................. Amarantite. 4 " Copiapites ............................ Copiapite. 5 " ferreus ............................... Roemerite. 202 Systematic Mineralogy. Genus 8. PARARCANITES. Salinoid. H< 4. -y>6. 1 P. cTdorokalicus Kainite. 2 " chloromagneseus Sulphohalite. 3 " carbonatreus . . . .Hanksite. Genus 9. PARASULPHATITES. Spathoid. H< 3. v > 7. 1 P. carbopZwmbews Leadhillite. Order XXI. SELENINEA. Selenate of lead ; Chalcomenite, Molybdomenite, Cobaltomenite. Order XXII. TELLUBINEA. Magnolite, Montanite, Ferrotellurite. Class IV PYRICAUSTACE.E, Sub-Class A CARBATA. Order I CARBATINEA. Genus 1. GRAPHITES. Metallophylloid. Hi. v 5.3. \ Graphites mollis Graphite. Genus 2. ADAMAS. Adamantoid. H 10. v 3.4. 1 Adamas octahedricus Diamond. Sub-Class B. HYDROCARBATA. Order II. HYDROCARBATINEA. Whewellite, Oxalite, Mellite. Synopsis of Species. 203 Order III. ELAINEA. Petroleums. OrderlV. CERATINEA. Mineral Waxes. Order V. RETININEA. Fossil Resins. Order VI. ASPHALTINEA. Solid Bitumens. Order VII. ANTHRACINEA. Coals, Lignites, etc. 256. In the preceding synopsis there have been named in the first three classes, as follows : Class I. Metallaceae 167 species. Class II. Halidaceae 21 species. Class III. Oxydaceae 464 species. Making in all 652 species. With these figures we may compare the numbers given by Zirkel in his edition of " Naumann's Mineralogie " in 1885, wherein, including graphite and diamond, but excluding other bodies which are embraced in Class IV. (not here recognized as distinct species), he arrives at 649 species. In the present attempt at classification, while we have divided garnet into five, and tourmaline into three species, we have designedly omitted many species of doubtful or of minor importance, as will be noticed farther on in discussing the various orders. 204 Systematic Mineralogy. CHAPTER XIY. THE METALLACEOUS CLASS. 257. The four great chemical classes of the mineral kingdom, their nomenclature and their divisions, have been briefly set forth in Chapter XL, where the two subclasses and the nine orders of the first or metallaceous class are given (223-225). It is now proposed to take up successively, in this and the three following chapters, these four classes ; the present one being devoted to the considera- tion of the orders, genera and species of the Metallaceae. Orders of Class I. METALLACE^E. Subclass A. METALLO-METALLATA. 1. METALLINEA : All true metals and alloys ; together with what are sometimes called the semi-metals, namely, antimony, bis- muth, tellurium ; and the metallic forms of selenium, phos- phorus and arsenic. Genera: Metallum and Metallinum. 2. GALENINEA : All simple metallic sulphids, selenids and tellurids having a hardness below 4.0 on the scale of Mohs, and occa- sionally sectile like the metals. Genera: Thiogalenites, Seleno- galenites, Tellurogalenites and Mesogalenites / the latter in- cluding mixed or intermediate species. 3. DIAPHOKINEA : Double metallic sulphids containing besides the metals proper, the sulphids, etc., of arsenic, antimony and bis- muth, and having a hardness below 4.0. They may be de- scribed as sulphosalts, of which the sulphids of the three ele- ments last named constitute the negative or halogenous, and sulphids of copper, lead, silver, zinc and iron, the positive or basylous member. This order, like the last, includes four prin- cipal genera, namely, Arsenodiaphorites, Stibiodiaphorites, Bismutodiaphorites, and Mesodiaphorites ; to which may be added a fifth, in which selenium replaces sulphur wholly or in part. 4. PYBITINEA : Simple sulphids of the true metals, with hardness above 3.0 ; including two genera, Pyrites and Pyritinus. Metallinea. 205 5. CHLOANTHINEA: Phosphids, arsenids, antimonids and bismuthids, having a hardness above 3.0, and including five genera : Phos- phochloanthites, Arsenochloanthites, Stibiochloanthites, J$is- mutochloanthites, Arsenodyscrasites and Stibiodyscrasites. fl. LAMPROTINEA : All sulpharsenids, sulphantimonids and sulpho- bismuthids having a hardness above 3.0, including four genera : ArsenolamprotiteSy jStibiolamprotites, JBismutolamprotites and Mesolamprotites. Subclass B.SPATHO-METALLATA. 7. SPATHOMETALLINEA : Sulphur, and non-metallic forms of phos- phorus, selenium and arsenic. One genus : Spathometallinum. 8. SPHALEEINEA : Sparry simple sulphids like zinc blende, cinnabar, realgar and orpiment ; hardness below 3.0. One genus : Sphal- erites. 9. RHODOPYRITINEA : Sparry double sulphids of arsenic and anti- mony with various metals; hardness below 5.0. Three genera : Arsenofulvites, StiMofulvites and Mediofulmtes. 258. Of the above orders, it may be repeated that 1 corresponds to the Metals of Mohs ; 2 and 3 to the Glances (Galinea of Dana, Galenite of Weisbach) ; 4, 5 and 6 to the Pyrites of Mohs, Breit- haupt and Weisbach (Pyritinea of Dana) ; and 8 and 9 to the Blendes of Mohs, the Minia of Breithaupt and the Cinnabarite of Weisbach. In an earlier attempt at this subdivision of Metallaceae, the present orders were by the writer ranked as tribes ; and the names of Bourn on oidese and Proustoidese for 3 and 9, and of Smaltoidese and Arsenopyritoideae for 5 and 6, were employed. It seems better, however, for the designations of the orders to reject alike those of personal origin, and those compounded with the name of a chemical element, or referring thereto. Hence the change now adopted to terms of classic etymology, based, with but one exception, on trivial names already given to characteristic species in the respective orders. The names of galena and pyrites, how- ever, have, besides their antiquity, the sanction of modern usage as types of orders ; so that it would be regarded as an affectation of pedantry to reject from our nomenclature designations based upon them. The rule thus adopted for orders has been extended to genera, so far as their positive or basylous elements are concerned. The chemical principle involved in the present nomenclature, how- ever, demands a recognition of the negative elements in the desig- 206 Systematic Mineralogy. nation of the genera ; while for species the basylous element and local and personal names will alike find places. Order 1. METALLINEA. 259. Comparatively few of the metals are found in nature un- combined. Thus, of the so-called native metals, those of the platinum group are alloyed with each other, or with iron. This, in its turn, is generally combined with nickel, whether in terrestrial masses, or in those of meteoric origin ; while gold is almost always alloyed with silver, and sometimes with mercury or palladium. To study aright the metals, their specific gravity, hardness, etc., we must in most cases have recourse to artificial products. We pro- pose in this order two genera: Metattum, for the true metals and alloys, which, with the exception of amalgam, are malleable, in- cluding mercury itself when solid : Metallinum, for the semi- metals, including tellurium, bismuth, antimony, and the metalline forms of selenium, arsenic and phosphorus. All of these are brittle. Genus 1. METALLUM. 260. The native species included in this genus may be arranged in two divisions, corresponding to the two types which we have designated Metalladamantoid and Metallospathoid (236) ; the first including the difficultly fusible metals, with a hardness of from 4.0 to 7.0 ; and the second the more fusible, with a hardness below 4.0. The composition and the physical characters of most of the native species in this genus are subject to such variations that it is diffi- cult to fix them, or to determine the limits of the species. The native alloys of iridium and osmium, with H = 7.0, and density from 19.3 to 21.2, contain from about 20 per cent, to 25, 55 and even 75 per cent, of iridium. Of these, the two extremes have been pro- posed as distinct species ; the heavier and the richer in iridium being named sysserskite, and the lighter, newjanskite. The so-called native platinum, with H = 4.5 6.0 and density from 14.2 to 17.6, is very variable in composition, and contains besides a dominant proportion of platinum and small amounts of all the other platinum metals, occasionally with copper, from 5 to 19 per cent, of iron ; it being magnetic, and occasionally magneti-polar. Other specimens Metallinea. 207 contain iridium in still larger proportions, amounting to more than 75 per cent, in the so-called native iridium ; while intermediate forms have been named iron-platinum and platin -iridium. Native palladium is in like manner alloyed with some platinum and irid- ium, and a native compound of gold and palladium with a little silver has been described. In like manner, native iron is generally alloyed with nickel, of which the proportion may amount to 20 per cent., often with small portions of cobalt and of copper. In these alloys, however, it is clear that the nickel is not uniformly distributed ; and it is very probable that the specimens of native platinum are in like manner admixtures of related species. In a native alloy of nickel and iron found in New Zealand, and named awaruite, the former metal predominates, the ratio of Ni : Fe = 2 : 1. 261. The alloys of gold and silver are not less variable in their composition, from gold containing a few hundredths of silver to compounds in which the silver predominates ; including what was called by the ancients electrum. The native amalgams of mer- cury with gold and with silver present similar variations, and among these crystalline silver amalgams have been observed con- taining from 26.4 to 43.0, 86.0 and even 95.0 per cent, of silver. Native copper is generally comparatively pure, or alloyed only with a small amount of silver ; and the same may be said of the rare species, native lead. Such being the condition of things, it is evident that in the present state of our knowledge it is useless to define more closely the different species of the genus Metallum ; the principal ones of which are however enumerated in the table below. METALLUM. Section a. form P d V H xl 1 M osmiTideum 48 ?.1 ?, 8 6-7 H 2 * ' iTidosffieuvfi Sysserskite 48 ?,1 9! 3 6-7 H 3 " irideum . . . ir. 48 fl1 3 8 6-7 H 4 " fylcLtini/ridBUTfi Platiniridium . 48 91 9, 8 6-7 T 5 " platineuvn . . . Platinum pti 48 31 2,8 5 T 6 " ferropl&tineum . 6 T pdi 26.5 11 5 3 8 5 r H 8 " ferreum Iron fei 28 7 8 8 7 4 5 T 9 '* niccoloferTBuwi I 208 Systematic Mineralogy. Section b. form P d V H i xl 10 M cuprewn Copper . . ecu, 63 8 9 7 3 T 11 " pluinbeuin Lead pbi 103.5 11 5 9 1.5 T 12 " ctuTBum Gold aau, 197 19 3 10 ?, 3 T 13 " ctrgenteum .... Silver a/ST-i 108 10 5 10,3 3 T 14 " CLUTdToent eum . . . . T 15 " ctrgentomeTcureum T 16 " mercureum Mercury hhff. 200 14 9! 14 ?, T The metals above named are all, so far as observed, isometric in crystallization, with the exception of palladium, which has also been observed in hexagonal forms, and the alloys of iridium with osmium, which are also hexagonal in crystallization. 262. It may here be repeated, as already explained (page 103), that the crystalline form of the species is indicated in the column under xl by an initial capital letter; H = Hexagonal and I = Isomet- ric. The species in the above table are arranged on natural-histori- cal grounds, not in the order of their specific gravity or density, but in the order of their condensation. Of the first six spe- cies, it has been shown above that they are made up in various proportions of osmium, iridium and platinum, with small and variable amounts of palladium, rhodium, ruthenium and iron, the presence of any of which would reduce somewhat the equivalent, = p, and also the density of the species = d. As, however, the equivalent weights assigned to the three tetrad metals concerned are from 191 to 194, we may take as a mean 192, which will make the unit-weight of the monad, as represented by iri and pti = 48. This with d= 21 (instead of 21.5 22.5, the observed specific gravity of these metals in a state of purity), will give v = 2.3 ; which will be as close an approximation as can be expressed with a single deci- mal. It is worthy of note that the value of v for the tetrad palla- dium (as also those of the closely related rhodium and ruthenium), is represented by the same figure. This value for many other metals not found in the native state has been already given in 135. It will be remembered that in the monadic notation here adopted, the monads of tetrad elements are designated by bold, those of triads by italic, and those of diads and monads by roman letters ; Metallinea. 209 while those of diads and triads, which also play the part of monads, are distinguished by the reduplication of the initial letter in roman, as in ecu, hhg and aau (68). In the case of the intermediate or compound species in the table, the variations in composition are such that no attempt is made to fix for them the value of p, given as formula under "form" and of d. It is worthy of notice that the more condensed metals are less easily amalgamated than the others. 263. The cases of platinum, iron and lead present exceptions to the general inverse relation between the hardness, = H, and v / but when we recall the influence of small portions of foreign matters in changing the hardness of metals, as shown by the addition of a little tin to copper, and of still smaller quantities of carbon to iron, with but little change in specific gravity, it is evident that some principle not yet well understood is here involved. It will be apparent that in arranging the metals in a series with an increasing value of v, according to their relative condensation, we are applying the natural-history method, and thus showing their division between the types of Metalladamantoid and Metallo- spathoid, to which the two sections of the genus respectively belong. The value designated by v, though called in the language of the atomic or molecular hypothesis, the atomic volume, really represents the co-efficient of condensation, of which it is the reciprocal. The designation " atomic volume " involves the double hypothesis of the existence of atoms, and of their variation in dimensions ; whereas the facts known to us serve only to demonstrate intrin- sic alterations in the volume of a given weight of matter while undergoing chemical change. Genus 2. METALLINUM. 264. In this genus are included those brittle metallic elements, bismuth, antimony, arsenic and tellurium, which have sometimes been called semi-metals. The first three named serve to connect the species of the genus with nitrogen and phosphorus. The latter appears in two forms, one metallic in aspect, a conductor of electricity, insoluble and very stable, which takes its place in the present genus ; while the more common, soluble and very combusti- ble form is included in the genus Spathometallinum. The ordinary red phosphorus is probably an intermediate species, whose affini- ties are with the present genus. In like manner, the metalline species, tellurium, through the metalline form of selenium, connects 210 Systematic Mineralogy. the true metals with sulphur and with oxygen. It will be noted that the species of this genus, from their comparatively small con- densation, as shown by the values of v, and from their inferior hardness, are all to be referred to the Metallospathoid type. METALLINUM. form P d V H xl * M. phosphoreum Phosphorus. . . . Di 15 5 9, 3 6 7 ? R 1 " arseneum Arsenic asi 37.5 5 7 6 6 3 5 R 2 " arsenostibeum Allemontite .... sbiasa 43 6,2 7 3.5 R 3 ' ' seleneum Selenium . . . S6i 39 4 8 8 1 | ? 4 " stibeum. Antimony sbj 60 6 7 9 3 R 5 tf tellureum Tellurium ... . te. 62 5 6 3 9 9 9, R 6 " bismuteum bi. 104 9 9 10 915 R Order 2. GALENINEA. 265. In the second order of the first class are included all simple sulphids, selenids and tellurids of the metals proper, of bismuth, and of antimony, which have opacity, metallic lustre, and a hardness not above 3.0. Compounds containing, at the same time with the metals proper, arsenic, antimony, or bismuth, are referred to the third order. Galenite, the native sulphid of lead, is taken as the type, from which are derived the names alike of the order itself and of the four genera into which it is divided ; which are desig- nated as follows : Thiogalenites, for all the sulphids of the order, the prefix being from the Greek Otiav, sulphur ; Selenogalenites, including the selenids ; Tellurogalenites, including the tellurids ; and MesogaUnites, including the mixed or intermediate species ; which may contain any two or all three of the halogeneous or neg- ative elements, sulphur, selenium and tellurium. Genus 1. THIOGALENITES. 266. In the genus Thiogalenites we find as basylous elements "besides silver, copper both as monad and diad ; mercury, iron, lead, bismuth, antimony, and molybdenum and germanium. In arranging Galeninea. 211 the mineral species in the table we have forborne to follow the augmenting value of v, as in the two genera preceding, for the reason that it appeared desirable, by other juxtapositions, to make more apparent certain other relations. THIOGALENITES. form. P d V H xl 1 T molybdeus Molybdenite.. mo. So . . 26 6 4 4 6 1 5 H? Stibnite sb 9 So .. 83 6 4 6 7 3 ?, () 3 " bismuteus Bismuthinite. bioSo . 51 ?. 6 6 7 7 9, o 4 " argentocupreus . 5 ' ' cupreus Sternbergite . Cantonite . . . ag^e^. ccu^s, .. 28.7 33 4.2 4 2 6.8 7 8 2.0 2 5 T Chalcocite . . . CCU 1 S 1 ... 39 5 5 8 6 8 3 o 7 * ' Harrisi Harrisite CCUiSi . 39 5 4 5 8 8 I 8 " plumbeus Galenite . . . T)b, Si . 59 7 7 5 7 9 2 5 I 9 " argenteus Argentite . . . clST, 81 . . 69 7 3 8 5 9, 5 I 10 " argentocupreus.. 11 " germctnicus . ... Stromeyerite. Argyrodite agiCCUjSjj atr.-ffei s., 50.8 47 6.3 6 1 8.1 7 7 2.5 9, 5 O c 12 " mercureus Metacinnabar heTiS, . 58 7 8 7 4 3 I 267. With molybdenite, and sternbergite or flexible silver ore, which are characteristically phylloid in type,the flexibility of its lam- inae may perhaps also permit us to place stibnite. Near to stern- bergite in composition and in density are friesite and argyropyrite, which, with Zirkel, we include provisionally with that species. The name of cantonite is given to a copper sulphid with hexahedral cleavage, and a density of 4.2 (near to that found by Karsten for an artificial sulphid of the same composition, 4.16). This we have represented as a cuprous disulphid having the same centesimal composition as covellite, which finds a place in the order SPHALE- RINEA. In harrisite, we have another copper sulphid, also with hexa- hedral cleavage, agreeing in composition with chalcocite, but having a lower density, and according in condensation with argentite. Genth has suggested that these isometric copper sulphids with cubical cleavage, have resulted, in some way, from a transformation of galenite, of which the crystalline structure has been preserved. A little reflection will show that the supposed genesis of a mineral species is not a question for the mineralogist ; and, moreover, that 212 Systematic Mineralogy. such an origin, if proved, would not affect the value, as mineral species, of substances whose chemical composition and crystalline form, structure and density are well defined. The case presented by chalcocite and harrisite is similar to that offered by pyrite and rnarcasite, or by smaltite and safflorite. The name of acanthite has been given to a sulphid of silver supposed to be orthorhombic, but its distinctness has been questioned, the crystals being perhaps only distorted isometric forms. An isometric sulphid closely resem- bling argentite, but containing some copper, and intermediate in composition between this and stromeyerite, has been described under the name of jalpaite. "Under the names of cuproplumbite and alisonite have also been described double sulphids of lead and copper, which are by some regarded as but mechanical mixtures of galena and chalcosite. Digenite also is, perhaps, an admixture of two sulphids, and thus is riot mentioned in the table. Genus 2. SELENOGALENITES. 268. The second genus of the present order comprises, as already explained, the various metallic selenids, which have much resem- blance to the corresponding sulphids ; with a hardness not exceed- ing 3.0, and containing, besides the metals, silver, copper, lead, mercury and bismuth, the rare element thalium. The species hitherto recognized are given in the following table. None of them, so far as known, present a phylloid type. It should be said that there are double selenids of lead and copper with other pro- portions of these metals than are assigned to zorgite ; and also that under the name of lehrbachite are selenids with varying propor- tions of lead and mercury. SELENOQALENITES. form. P d V H xl 1 S. cuprosus Berzelianite. CCU 1 86], . , 51 6.7 7.6 2.5 ? 2 * * plumbeus . , Clausthalite pbiS6i . . 71 9, 8,8 8.1 2.5 T 3 " bismuteus Frenzelite . . bi P S6q 65 6.6 9.9 3.0 4 " argentocuprosus . . 5 " fflBTCUTBUS Eucairite . . . Tiemannite . ccujagiSeg hST-iSSt . 62.2 69 5 7.5 8 9 8.3 8 5 3 ? T 6 " plumbomercureus. . Lehrbachite. Naumannite hgipbise 2 . ae^se, .... 70 78 5 7.9 8 2 8.9 8.9 2.5 I ? 8 * ' cuproplumbeus .... 9 " thalleus Zorgite Crookesite. ccuipbiseg ccu 7 th 1 se 8 61 79 7.0 6.9 8.7 11.4 3 ? ? Diapliorinea. 213 Genus 3. TELLUROQALENITES. 269. This genus order comprises the various tellurids, all of which, like the corresponding sulphids and selenids, have a hardness of not over 3.0. It will be noticed that in hessite, petzite, coloradoite and altaite, the ratio between the tellurium and the basylous element is as 1: 1, while in calaverite and sylvanite it is as 4: 1, and in melonite the ratio is 2:3. Closely related to sylvanite is the species nagya- gite, which is a tellurid of lead with a variable amount of gold, and, moreover, contains in different examples from to 3.0 to 9.0 and 11.0 per cent, of sulphur; the equivalent ratios of tellurium and sulphur being in one case as 1 : 2, and in another as 1 : 3. A little selenium is also sometimes present in the mineral. In considering these results of chemical analyses, it will be remembered that owing to the great difference in the equivalent weights of the three negative elements in question, 1.00 of sulphur replaces 2.44 of selenium and 3.90 of tellurium. Near to tetradymite are two bismuthic tellurids which contain more or less sulphur and a little selenium, and have been named wehrlite and joseite. All of these, like sylvanite and nagyagite, are phylloid in structure. These intermediate species, when more fully known and studied, may probably form an intermediate genus, Mesogalenites, but for the present are included with Tellurogalenites. TELLUROGALENITES. form. P d V H xl I ? ? I ? C R H 1 T. cirgenteus Hessite agitej ag 8 aau 1 te 4 . ng^ pbitej aau!te 4 .... agiaauitea. bLte, . 85.2 96.4 81.2 83 89.4 80.5 65.7 49.3 8.5 9.0 8.6 8.2 9 8.3 7.2 7.9 ? 9.9 10.0 9.4 9.9 9.9 9 7 9.1 2.5 2.5 3.0 3.0 2.5 1.5 1.5 1.5 2 " argentaureus. . . 3 " mercureus Coloradoite. . Altaite Calaverite... Sylvanite. . . . Nagyagite . . . Tetradymite. Melonite 4 " pluiribeus .... 6 " Sylvanites . . . . 7 " auroplumbeus. . 8 ' ' bismuteus 9 " niccolcus ni s te 8 Order 3. DIAPHORINEA. 270. The Glances of Mohs include two well-defined chemical groups, the first of which comprises the simple sulphids, selenids, 214 Systematic Mineralogy. and tellurids of the order GALENINEA. The second embraces a large number of species not unlike the last in aspect, having a hardness below 4.0, and consisting of double sulphids ; containing copper, lead, silver and iron together with a sulphid of arsenic, antimony or bismuth. The chemical difference or unlikeness of this second group suggests for it the name of DIAPHOBINEA (Greek dm^opof, different). It happens also that the trivial name of diaphorite has been given to an antimonial species of this group, and it is proposed to arrange the species of the order in three genera : 1. Arseno- diaphorites ; 2. Stibiodiaphorites ; 3. Bismutodiaphorites. Re- garding these various compounds as sulphosalts, in which the halo- genous or negative portion is in some cases a pentasulphid, but more often a trisulphid of arsenic, antimony or bismuth, the gen- eral formulas (x = the negative element) are X 2 s 3 .n(m 1 s 1 ) and X 2 s 5 .n(m 1 s 1 ). Genus i. ARSENODIAPHORITES. 271. Two species named below appear to represent this genus, guitermannite and jordanite, in which the halogenous portion is arsenic trisulphid. There are also two rare and little known spe- cies, corresponding to arsenic pentasulphid, namely, clarite and epigenite ; but it is not certain whether their place is not with enargite in the order RHODOPYEITINEA. ARSENODIAPHORITES. form. P d V H xl A. terplumbeus Guitermannite. as 2 pb a s 6 ... 42 6.0 7.0 3 ? " quadriplumbeus Jordanite as s pb 4 s 7 ... 46 6.4 7.2 3 Genus 2. STIBIODIAPHORITES. 272. The large number of species met with in this genus is due to the great differences in the proportions between the antimony and the basylous metals ; the formulas presenting an example of homologous or progressive series very worthy of notice, which has already been cited (203). Diaphorinea. 215 STIBIODIAPHORITES. form. P d V H xl Zinckenite sbopb, s< 41 4 5 3 7 7 3 o 2 " Plagionites Plagionite SboPbi .OK.SA.Q K . 48 3 5 4 7 8 3 5 C 3 " sesquiplumbeus . . 4 " biplumbeus Warrenite Jamesonitc .... sb 8 pb 1 . 5 s 4 . B .... SboPboSie . 48.4 45 3 5 8 1 2 5 c? o 5 " terplumbeus 6 " quadriplumbeus . 7 " quinqueplumbeus 8 ' ' sexplumbeus Boulangerite. . . Meneghinite . . . Geocronite Kilbrickenite sb 8 pb s s e sb 2 pb 4 s 7 sb 2 pb 5 s 8 47.8 49.7 51 52 1 6.0 6.3 6.5 6 4 8.0 7.9 7.8 8 1 3 3 3 9, 5 ? c o ? 9 " Brongniardius. . . 10 " quinquargent eus Brongniardite. . Stephanite. .... sbgagipbjSg.... sboasTrSa. 45.7 58 5 5.9 8 3 7.7 7,8 2.5 ?, 5 I o 11 " perargent BUS Polvarfirvrite . sboaer-i 081 r 57 1 7 8 1 ft 5 T 12 " argentoplumbeus. 13 " typicus Freieslebenite. . Diaphorite . sbgagipb^gSg.B ibid 47.1 ibid 6.2 5 9? 7.6 8 2.5 ft 5 C O 14 " cuprosoplumbeus. 15 " argentocuprosus . 16 ' ' cuprosus Bournonite .... Stylotypite Chalcostibite. . sbgCCUjpbaSg... sb 2 m 8 s 6 .. sboCCUtS, . 44.2 35 85 3 5.8 4.8 4 8 7.6 7.3 7 3 2.5 3 3 5 o o 17 * ' semicuprosus 18 " ferreus ... Guejarite Berthierite. . . . sb 2 ccu. 4 s s . 6 sbofei s.. 34.6 80 3 5.0 4 7.0 7 6 3.5 3 o? 19 *' thiocuf)Tus FatirniiiitG SboCCUaSo 33 6 4 6 7 3 3 5 o 20 ' ' thio'Dlumbcus . Epiboulangerite sboDboSo 43 6 3 6 8 o In order to show more clearly the progressive series in the present genus the formulas are written in some cases with frac- tional co-efficients. The pentasulphid negative of the last two species is indicated by the specific names, P. thiocupreus and P. thioplumbeus. Genus 3. BISMUTODIAPHORITES. 273. The species of this genus offer a progressive series nearly as complete as the preceding, with which it has many resem- blances. 216 Systematic Mineralogy. BISMUTODIAPHORITES. form. P d V H xl 1 B. subplumbeus .... 2 ' ' plumbeus bi b s 53 6 9 7 7 I O O O Galenobismutite Cosalite bi 2 pb 1 s 4 bi 2 pb 2 s 5 bi s pb 6 s 9 bi s ag 1 s 4 bi 2 ccu 1 s 4 bi 2 ccu 3 s e .... 53.6 55.8 57.2 54.3 55.2 52.2 46.8 47.8 44.8 6.9 6.7 7.3 6.9 6.7 6.8 5.6 6.3 5.0 7.7 8.2 7.8 7.9 8.2 8.1 7.9 7.6 8.9 3.5 3 2.5 2.5 2.0 2.5 3 " biplumbeus 4 " sexplumbeus .... 5 * ' ctrgenteus , 6 " sesquiargent eus. . 7 " cuprosoplumbeus 8 " sesquicuprosus. . 9 ' ' cuprosus Schirmterite .... Klaprothite Emplectite Wittichenite . . . 10 " tercuprosus In J3. subplumbeus, to avoid a fraction not easy to represent, we have multiplied the formula by 3. Kobellite is a species inter- mediate in proportions between cosalite and beegerite, but contains ten per cent, of antimony, and may represent an intermediate genus, Mesodiaphorites. Order 4. PYRITINEA. 274. The name pyrites was applied in a very vague manner by the ancients, both to stones resisting fire and to those which, from their hardness, yielded sparks of fire when struck. Dioscorides, however, speaks of pyrites which was smelted for copper, either cupriferous iron pyrites or chalcopyrite itself, which was called by German naturalists in the sixteenth century copper pyrites (kup- ferkies). Later, in the eighteenth century, pyrrhotite and fahlerz were described as magnetic pyrites and gray copper pyrites. The extension of the term to sulphuretted minerals softer than common pyrites is thus sanctioned by long usage, and modern naturalists have not hesitated to include under that title metallic sulphids having a hardness of not over 3.5. We propose for convenience in description to divide the present order into two genera, as fol- lows : 1. Pyrites, includes various sulphids of iron, cobalt, nickel and copper, and also of chromium and ruthenium, having a hard- ness above 5.0. 2. Pyritinus, embraces sulphids of iron and of nickel, with copper and tin, having a hardness of from 3.5 to 5.0. Neither selenids nor tellurids are as yet known to occur in this order, unless it be the little-known nickel tellurid, melonite, which has been provisionally included in the order GALENINEA. Pyritinea. Genus 1. PYRITES. 217 form. P d V H xl 1 P rutheneus Laurite ru,s, . 25 7 3 6 7,5 T 2 * ' vulgaris Pyrite fe,So . , 20 5,2 8,9 7 T 3 ' ' secundus Marcasite . . . feiS a . 20 4.8 4.2 6.5 O Linnseite. . . . CO Q S^ . 21 8 5 4 4 5.5 T 5 " niccoleus Siegenite (co,ni)oS,, 21.8 5 4.4 5.5 T 6 " cuprocobalteus . . . Carrollite . . . Daubreelite. . COgCUjS^ fe 1 crSA . 22.1 9,0 6 4.9 5 4.5 4 1 5.5 ? I v The basylous metals in this genus enter as diads with the excep- tion of ruthenium, which in the rare mineral laurite appears to act as a triad, corresponding to the sesquioxyd and the trichlorid. The chromiferous sulphid, daubreelite, the only native unoxydized compound of chromium known, is found in certain meteoric masses with metallic iron. Genus 2. PYRITINUS. form P d V H xl 1 p. ferreus Troilite feiSi . 2?, 4 8 4 6 4 H 2 " niccoleus Millerite nitS! 22.7 4.6 4.9 3.5 R 3 " proximus Polydonaite. . . ni,Sr . . 2?, 4 8 4 6 4 5 T 4 " Beyrichius . . . Beyrichite ni 5 8 7 21.6 4.7 4.6 3.5 ? 5 " sesquiferreus . Horbachite .... fe 1 . 6 ni. 6 s 8 .. 20.9 4.4 4.7 4 ? 6 " magneticus . . . Pyrrhotite fe,s 8 21.6 4.6 4.7 4 H 7 " Bornites .... Bornite (6) cu,fes<> . . P-4 R 5 4 8 4 T 8 " erubescens Bornite(a) cu 5 fe 1 s 4 . . . 25 4 I 9 ** VariUS Homichlyn .... CU.fCoS^ . 28 8 4 5 5 8 4 T 10 " cupricus Chalcopyrite . . cuifejs^.. 22.9 4.3 5.3 3.5 T 11 " Cubanites Cubanite cu 1 fe 8 s 4 . . . 21.6 4.1 5.3 4 I 13 " stanneus Cassiteropyrite cu 8 sn 2 fe 1 s 4 23.8 4.5 5.3 4 I * (Artificial) fe 4 ni 8 s 26.7 ? 275. It will be remarked that the species of this genus present remarkable variations in the ratios between the metals and sul- 218 Systematic Mineralogy. phur. In troilite and millerite the proportion 1: 1 obtains, and in what have been named pentlandite and niccopyrite we have simi- lar compounds, containing both nickel and iron. In pyrrhotite, the ratio is found to be 7 : 8, in polydomite 4 : 5, in beyrichite 5 : 7, and in horbachite 2 : 3. Again, in chalcopyrite, in which the copper may be regarded as diad, we have the ratio 1: 1, and in cubanite 3:4. In the so-called variegated copper ores are included appar- ently three or more species with different ratios. That designated in the table as bornite (a) according to Dr. Harrington (private communication), gives the appended formula, and contains 63 per cent, of copper ; while bornite (#), with the formula usually assigned to the species, contains 55 per cent., and the homichlyn of Breithaupt, also a variegated copper ore, only 44 per cent, of copper. A massive ore near this last in composition has been described by Genth with the name of barnhardtite. We note in the three species last cited from the table ratios between the metals and sulphur of 4 : 4, 5 : 4, and 6 : 4. This second ratio is also seen in cassiteropyrite (tin pyrites) into which tin enters as a tetrad. It is worthy of note that in an artificial crystallized matte de- scribed by Mackintosh, and inserted in the table for comparison, this ratio becomes 6:1. The density and hardness of this product have not been determined, and it may belong to the preceding genus, Pyrites. The hardness of the copper-iron sulphids in- cluded in Pyritinus, is such as to lead to the conclusion that the copper therein enters as a diad and not as a monad ; which latter would give values for p and v much greater than for other species of the same hardness. The density of 5.6 assigned by Rammels- berg to millerite is seemingly an error. It is not in accord with that given by Kengott, and adopted in the above table, and more- over indicates a species much harder than millerite, which would take a place in the genus Pyrites. Order 4. CHLOANTHINEA. 276. In this order are included the compounds of the metals proper with phosphorus, arsenic, antimony and bismuth. While many artificial phosphids are known, but a single one is found in nature, the phosphid of iron and nickel, to which the name of schreibersite has been given, which occurs in masses of meteoric iron. The chief arsenids of this order are hard pyrites-like species, of which niccolite, smaltite and chloanthite are representatives f Chloanthinea. 219 the latter has been taken as a type, -giving the name both to certain genera, and to the order itself. Breithauptite, an antimonid of nickel, resembles the preceding arsenids in hardness. The arsen- ids and antimonids of copper and silver are however softer and less condensed, and are well represented by the antimonid of silver, which has received the name of dyscrasite, and from which the genera including them are named. We distinguish in this order the following genera: 1. Phospho- chloantliites, already mentioned, with a hardness of 6.5. 2. Arseno- chloanthites includes arsenids of platinum, cobalt, nickel, iron and manganese, having a hardness of 5.5 to 6.5. 3. Stibiochloanthites, with a single species, having a hardness of 5.0. 4. Arsenody sera- sites includes arsenids of copper, and probably of silver, having a hardness below 5.0. 5. Stibiodyscrasites includes antimonids of silver with a hardness below 5.0. The little known compounds of silver and of gold with bismuth, which have been named chilenite and maldonite, may perhaps form a bismuthic genus allied to the last. Genus 1. PHOSPHOCHLOANTHITES. form. P d 7.2 V H 6.5 xl ? P. ferroniccoleus . . Schreibersite. . fegniipi... 25 3.5 Genus 2. ARSENOCHLOANTHITES. form. P d V H xl 1 S. platineus 1)1,118,. 43 10 6 4 6 5 T 2 " niccoleus .... Niccolite Ul 3,g , 38 5 7 3 4 6 5 5 H 3 " cobaltoferreus Safflorite COofCiSfl . 34 8 7 8 4 8 6 O 4 " Rammelsbergi Rammelsbergite . ni 1 as 2 .. .. 34.6 7.2 4.8 5.5 5 " scmiferreus. . Loelingite fe,aso . 34 3 7 4 9 5 5 O 6 " ferreus Leucopyrite fe Q as,i . 33 4 7 4 8 5 5 o 7 " cobalteus Smaltite co 1 as 2 ... 34.8 6.5 5.3 5.5 I 8 ' ' typicus Chloanthite ni,as... 34 8 6 5 5 3 5 5 I 9 " perarseneus . . Skutterudite cc^as,, . . . 35.5 6.8 5.2 6 I 10 " manganosus . . Kaneite mi^aSi .. 32.5 5.6 5.8 5? 9 220 Systematic Mineralogy. 277. This genus serves to illustrate many points of mineralogi- cal interest : 1st, The different ratios between the negative ele- ment, arsenic, and the positive or basylous metal. These are seen in niccolite, kaneite and sperrylite (wherein platinum enters as a tetrad) with 1 : 1 ; in loelingite, smaltite, chloanthite, rammelsbergite and safflorite, with 2 : 1 ; in skutterudite 3:1; while in different inter- mediate arsenids which have been referred to smaltite and leu- copyrite the ratios 4 : 3, 3 : 2, 5 : 4, 3 : 5 and 5 : 2 have been observed. 2d, The variations in density from 6.5 to 7.3 in what was originally included under the title of smaltite (speisskobalt) are due partly to these differences in composition, partly to imperfect determina- tions of density, and partly also to different degrees of condensa- tion, which moreover coincide with differences in crystalline form. Apart from the highly condensed sperrylite, are to be noted the denser species, safflorite, rammelsbergite, leucopyrite and loelingite, orthorhombic in crystallization, and the lighter isometric species, smaltite, chloanthite and skutterudite. The porosity of the massive variety of safflorite had led more than one observer to assign to it a density of 6.83-6.85, but McCay has found for the same miner- al, crushed and freed from included air, a density of 7.167 (7.18, Breithaupt).* The lighter and denser forms of this arsenid are intimately associated, crystals of true smaltite being implanted in massive safflorite, so that mechanical admixtures of the two spe- cies may very well occur. In the above table we have given only the principal species, omitting those with intermediate ratios. Genus 3. STIBIOCHLOANTHITES. 278. To a genus with this name, in which antimony replaces arsenic, we ref er the antimonid of nickel, breithauptite, which is less condensed than the corresponding arsenid, niccolite, having for v a value like that of the little-known kaneite. Here also the newly-discovered antimonid of copper, horsfordite, may perhaps belong, if not to the genus Stibiodyscrasites, noticed below. STIBIOCHLOANTHITES. form. P d V H xl 1 8 niccoleus . Breithauptite . 44 7 7 6 5 9 5 H 2 " cuprosus Horsfordite . . ccu K sb.> . . 63 8 8 7 4-5 * Amer. Jour. Science, 1885, (3) xxiv., 369. Chloanthinea. 221 Genus 4. ARSENODYSCRASITES. 279. Under this name are included certain arsenide of copper, which are much inferior in hardness to the preceding genera of this order, and probably contains copper as a monad. The name of huntilite was proposed in 1879 by Prof. H. Wurtz, for a crys- talline arsenid from Silver Islet, Lake Superior, from the analysis of which he deduced the formula AsAg 3 (as 2 ag 3 ) ; describing it as having a hardness below 2.5, and a specific gravity of 7.47. Already in 1877, however, Hannay described under the name of arsenargen- tite a crystallized species from Saxony, with a specific gravity of 8.825, and yielding arsenic 18.43, silver 81.37; which corresponds to the formula proposed by Wurtz. ARSENODYSCRASITES. form. P d V H xl 1 A. sesquicuprosus. Domeykite ccu s as 2 . . 53 7.5 7.0 3.5 ? 2 " tercuprosus .... Algodonite ccugas!,. 56.6 7.6 7.4 4.0 ? 3 ' ' pereuprosus. . . . Whitney ite ccu^asj 58.4 8.4 7.0 3.5 ? 4 " argenteus Arsenargentite a&TocLSo . . 79 8 8 8 9 ? Genus 5. STIBIODYSCRASITES. 280. To the genus Stibiodyscrasites are referred certain native compounds of antimony and silver, which have been described by the trivial name of dyscrasite, containing from 64 to 84 per cent, of silver. These extremes correspond with agjsbj^ and ag^sbj, but there are probably other and intermediate compounds. The name of animikite has been proposed for another antimonid of silver, which was found with the silver arsenid above noticed, at Silver Islet. STIBIODYSCRASITES. form. P d V H xl 1 S. argenteus Dyscrasite .... ag^ .. 84 9.4 9.0 3.5 O 2 " terargenteus Dyscrasite ag^ . . 96 10 9.6 3.5 3 " perargenteus . . . Animikite ag 9 sb 2 . . 99 9.5 10.5 .... ? 222 Systematic Mineralogy. Order 6. LAMPROTINEA. 281. The present order contains certain double sulphids of cobalt, nickel and iron, together with arsenic, antimony or bismuth ; presenting a group of species which by their hardness and conden- sation are distinguished from the Diaphorinea, and resemble the last two orders. It includes cobaltite, mispickel and glaucodot, besides other less known antimonial and bismuthic species. The name of Lamprites, (Gr. Aa//^, brilliant or shining) was given by Breithaupt to the great division of the Glances ; including our orders, 2, 3 and 4, as well as the present. In the absence among the species of this order of any trivial name suitable for generic purposes, we propose that of Lamprotites. The order LAMPEOTINEA will thus embrace four genera, as follows: 1, Arsenolamprotites ; 2, Stibiolamprotites ; 3, Bismutolamprotites ; 4, Mesolamprotites ; but the number of species in this order is comparatively few, and with the exception of those of the arsenical genus, they are included in a second table together with three species representing lamprotites. Genus 1. ARSENOLAMPROTITES. form. P d V H xl 1 A. ferreus Mispickel fe,as,s, .. ?n ?, 6 4 5 5 5 o 2 " cdbdlteus Cobaltite co,aSiSi . 917 7 6 1 4 5 5 5 T 3 " niccoleus Gersdorffite . nii JLSiSi . . 27 7 6 9! 4 5 5 5 T 4 " niccolocobalteus Glaucodot . . . (co^as.^ 27.7 5.5 O 282. The ferrous species becomes in some cases cobaltif erous, and offers a transition to glaucodot, which, like it, is orthorhombic ; while the other two species are isometric, a dimorphism similar to that noticed in Arsenochloanthites. Some varieties of mispickel show other ratios than that above given, and have been described under the names of pacite and geyerite. It is probable that further studies will make known several such species with varying propor- tions of constituents, as in the genus just named ; the symbols of the associated negative metals being given in parenthesis in the formula. Lamprotinea. Genera 2, 3, 4. MESOLAMPROTITES, etc. 223 form. P d V H xl 1 Stibio. niccoleus. . . Ullmannite. . ni lS b lSl . 35.2 6.7 5.2 5 I 2 Bismu. niccoleus . . ni bi s 5 1 4 5 T 3 Meso. niccoleus. . . . Corynite .... nl 1 (as f 8b) 1 8 1 .... 6.0 ... 5 I 4 " niccoleus.... Wolfachite . . ni 1 (as,sb) 1 s 1 6.4 O 5 " cobalt eus . . . Alloclasite. . co 1 (as,bi) 1 s 1 .... 6.6 ... 4.5 O Sub-Class B. SPATHOMETALLATA. 283. In this second division of the great class Metallacae, as already set forth, are included all those native sulphids which are not distinctly metalline in aspect ; corresponding to the order Blende of Mohs, the Minia of Breithaupt, and the Cinnabarite of Weisbach. In this division Weisbach, the latest exponent of the natural- history method, embraces not only sphalerite, greenockite, cinnabar, orpiment, realgar and the two sulphids of manganese, but covel- lite. To these are added the various red silver ores, and also, by Weisbach, the species enargite. The gray copper ores known as fahlerz, including tetrahedrite and tennanite are, -however, by him included among the Glances, and accordingly in the present classification would find a place in the order Diaphorinea. We think, however, that they should be included in the same order with the red silver ores. The blackness of their streak passes into red- dish gray, brown, and even cherry red in the zinciferous varieties ; while thin scales of the mineral are sometimes translucent, and transmit a reddish light. Breithaupt, indeed, gave the trivial name of copper blende (kupferblende) to the zinciferous tennanite from Freiberg. 284. It is to be noted that cuprous compounds, as cuprous chlorid, are blackened by exposure to the light, and it is known that the red silver ores, as Fletcher has shown, undergo a similar change by its action ; being perhaps, like selenium, metallized by exposure to solar light. It would be desirable to make experiments on the color of thin layers of fahlerz, and the action of light thereon. Meanwhile, for the reasons above given, we include these ores, together with enargite and some other closely related species, in 224 Systematic Mineralogy. the sub-class of the Spathometallata. The oxysulphids, kermesite and voltzite, generally placed with the Blendes, are connecting links between the sparry sulphids and the oxyds, for which reason we shall include them with the latter. Tschermak has upon chemical grounds unitedthe varieties of fah- lerz, including tennanite, together with enargite and the red silver ores, in one group with the metalline double sulphids like pla- gionite and emplectite ; erecting all of these into an order des- ignated Fahle, distinct from Glances on the one hand and from Blendes on the other ; thereby disregarding the fundamental dis- tinction which guided the founders of the natural-history method in separating the metalline from the sparry non-metallic sulphids. In the present sub-class are included also the non -metallic forms of arsenic, .phosphorus and selenium, and the various known forms of sulphur. These, however, with the exception of orthorhombic crystalline sulphur, selenium, and the sulphid of selenium, are not known as native species. It is to be noted that a vitreous non-metallic form of tellurium has been obtained, allied to amorphous or colloid sulphur, and it is possible that a metalline form of sulphur corresponding to those of selenium and tellurium may be produced. Order 7. SPATHOMETALLINEA. Genus SPATHOMETALLINUM. p d V H xl 1 S sulphureum 16 9, 8 9, o 2 " selencum Selenium 861 . . 89 4 5 8 1 C 3 " selenosulphureum * " phosphoreum .... * " arseneum Phosphorus . . . Arsenic Pi ..-. aSi , . 15.5 37.5 1.8 4.7 8.6 8.0 I Order 8. SPHALERINKA. 285. This order is well represented by the sparry species zinc blende, called also, from its non-metallic and deceptive aspect, sphalerite ; from which has been derived the name alike of the order and of the single genus in which all its species are included. Sphalerinea. 225 Genus 1. SPHALERITES. 286. It is worthy of remark that while the sulphids of iron are found in the order PYRITINEA, a considerable proportion of iron may unite with zinc in the present order and genus. The value of p, as calculated for christophite in the table, corresponds to zn 2 fej, and the name of marmatite has been given to another ferriferous blende in which the ratio is 3:1. Wurtzite or hexagonal zinc sulphid is identical with spiauterite, the hexagonal crystallization of which had been already recognized by Breithaupt. It is to be noted that these dimorphous forms have the same condensation ; while green- ockite, isomorphous with wurtzite, has a less condensation, agreeing therein with the sulphid of arsenic and with cinnabar. From the comparatively small density of covellite, which, if regarded as cupric monosulphid, gives with <# = 4.6, a value forv = 5.2, we are led to regard it as a cuprous disulphid, as represented above in the table. A similar observation applies to the isometric form of the same sulphid, cantonite, in the genus Thiogalenites. The two manganese sulphids have an exceptional degree of condensation. Covellite and orpiment, from their softness and their eminently foliated structure, belong to the phylloid type, while the other species of the genus are clearly spathoid. SPHALERITES. form. P d V H xl 1 S. semimangonosus Hauerite mn,s.j 19 8 3 5 5 1 4 I 2 ' * manganosus .... 3 " cuprosus Alabandite. . Covellite .... mn^! CCUiSa . 21.7 83 4.0 4 6 5.4 7 ?. 3.5 ?, I H 4 " zinceus (a) 5 " zinceus (6) Sphalerite . . . Wurtzite . . zn l s l zn,Si 24.2 94 9 4.0 4 6.0 6 4.0 4 I H 6 ' ' ferrozinceus .... 7 " cadmeus Christophite. Greenockite (zn.fe^Sj... cdi si 23.5 36 3.9 4 9 6.0 7 3 4.0 3 5 I 8 " calcareus Oldhamite . . ca,Si 18 2 6 7 4 o I 9 " mercuricus 10 " arseneus Cinnabar.... Orpiment .... hgjsi asoSo ... 58. 94 6 8.1 3 4 7.2 7 2 2.5 ? H O 11 " perarseneus Realgar aSiSi .. 26 7 3 5 7 6 9! c 12 " stibeus Metastibnite . sboSo .. 83 6 4 9, 8 9 226 Systematic Mineralogy. Order 9. RHODOPYBITINKA. 287. It remains to consider in this sub-class the species which correspond to the DIAPHORINEA of the preceding, and may be de- scribed as compounds in which the negative member is a sulphid of arsenic or of antimony, while the positive consists of sulphids of various metals, chiefly silver, copper, lead and mercury ; with the addition of zinc and iron, and rarely of cobalt. The red color and the translucency seen in the red silver ores is, as already remarked, more or less apparent in the cupriferous species collectively known as fahlerz in German, or gray copper ores. The extension of the name pyrites to soft sulphids like chalcopyrite and magnetic pyrites, which have a hardness below 4.0, and even to fahlerz itself, which was in the last century called gray copper-pyrites (pyrites cupri griseus), will justify the application to the order in question of the name of RHODOPYKITINEA, or red pyrites ; the redness which is apparent in powder, or in thin portions, being not less marked than the superficial grayness. Indeed, the word fahl (or fal in old German) is the equivalent of fallow, Engl., fauve, Fr., andfulvus, Latin ; adjectives which signify reddish or yellowish, rather than gray, in color. The order Fahle, as proposed by Tschermak (284), is far too wide in its scope, while the name of fahlite was given by Breithaupt to tetrahedrite or fahlerz, and from its Latinized form we may with advantage derive names for the genera into which the present order is here divided, as follows : 1. Arseno- fulvites, including proustite, tennantite and other apparently re- lated arsenical species. 2. Stibiofulvites, including pyrargyrite, with other red silver ores, and much of the so-called fahlerz. 3. Mediofulvites, intermediate arsenico antimonial species, as certain forms of fahlerz. Genus 1. ARSENOFULVITES. 288. The chemical type of both tennantite and tetrahedrite is, like that of jordanite and meneghinite in the order DIAPHOR- INEA, as 2 ni 4 s 7 . . . sb 2 m 4 s 7 . Both of those are plumbeous species, but a related antimonial plumbeous species of the present order, polytelite, containing Sphalerinea. 227 some silver and a portion of zinc, serves to connect them chem- ically with the zinciferous tennanite and with tetrahedrite. Both in Arsenofulvites and Stibiofulvites there are, however, included species in which other ratios than the above of arsenic and anti- mony are met with, as in the corresponding order DIAPHORINEA. Like that order, moreover, RHODOPYRITINEA includes also other species which must be represented as containing pentasulphids of arsenic and antimony. They are, however, made species of the genera already named. ARSENOFULVITES. form. P d V H xl 1 A. sub-cuprosus. 2 " plumbeus 3 " biplumbeus . Binnite Sartorite D uf renoy site . assccu^s^. asapb^ aSopboSe . . 30.2 34.6 40 3 4.5 5.4 5 5 7.0 6.4 7 3 3 3 8 I O O 4 " argenteus... . 5 " cuprosus 6 " cuprozinceus . 7 " thiocuprosus. Proustite Tennantite. . . Tennantite . . Enargite as 2 ag 8 s e as 8 ccu 4 s 7 aSgCCUgZnjS,. aSoCCUoSo . 45 33.7 31.4 5.5 4.5 4.4 8.2 7.5 7.1 3.5 R I I O 8 " thioargenteus. Xanthoconite as s ag 4 s 9 48.4 5.2 8.3 2.0 R Enargite is placed in this order on the authority of Weisbach. The little known species, luzonite, and clarite, which with a similar composition, differs from it in crystalline form, should perhaps be included in the order DIAPHORINEA. Both enargite and xanthocon- ite have arsenic pentasulphids as the negative members, as their specific names indicate. Genus 2. STIBIOFULVITES. 289. In livingstonite, as in cinnabar and metacinnabar, mercury appears as a diad, but in spaniolite, where it replaces in part monad copper or monad silver, it too enters as a monad. In the mercurial fahlerz, as in some tennantite, the metals zinc and iron are absent, or present only in minute proportions. Fieldite appears to be, like enargite, a pentasulphid species. 228 Systematic Mineralogy. STIBIOFULVITES. form. P d V 7.8 8.0 8.4 H xl 1 8 mcrcuricus Livingstonite Miargyrite . . . Pyrargyrite.. Pyrostilpnite. Polytelite. . . . Tetrahedrite. Freibergite. . . Spaniolite.... Polybasite.. . Fieldite sbohsr - So. - 37.7 41.7 49.1 49 1 4.8 5.2 5.8 2.0 2.5 2.5 2.0 3 3 3 2.5 O C R O I I I I C ? 2 " subargenteus . . . 3 " argenteus (a) . . .. 4 " argenteus (6) 5 " plumbargenteus 6 ' ' cuprosus sb aTiS^ gV) a on through the amphide salts, of which elements of groups V. and! VI. characterize the negative or acidic members. It will be well to write for compounds of the triad oxyds of aluminum, iron, chromi- um, titanium, manganese, the syllables alumini, ferri, chromi, titani, etc. This will prevent the confounding of them with titanates and chromates, and also with diad ferrous, chromous and possible aluminous compounds. The use of the third vowel of the alphabet will moreover serve to recall the fact that these terms designate triad oxyds. Sub-Class A. OXYDATA. Order 1. OXYDINEA. 297. The species of this sub-class are included in a single order, and in three genera. Beginning with hydrous species, we include a number of hydrous oxyds under the generic name of Hydroxy- dites. In the second place is a group of anhydrous oxyds, chiefly basic or positive in character, which we designate Protolithvs* The third genus includes various triad and tetrad negative oxyds, of which the most common and the most characteristic species is quartz, to which belongs properly the name of " crystal," given it by the Greeks, who imagined it to be water congealed by intense cold. This designation, since extended to other transparent sub- stances such as glass, and even to the definite geometric forms assumed by solids which are not transparent, may still, with historic truth and fitness, be employed as the generic name of a group of natural species remarkable for distinctness and beauty of crystal- line form, and having quartz, itself, the original rock-crystal, as its most common and most conspicuous species. We therefore desig- nate the third genus as Crystallithus. Oxydinea. 235 Genus 1. HYDROXYDITES. 298. Of the above genus the first three species are hydrous ferric oxyds of definite constitution. The name of limnite has been given to a fourth and more highly hydrated oxyd, which, in some cases at least, contains, besides the amount of water indicated in the formula, a greater or less portion of an organic acid, and constitutes a. variety of iron ore. The crystalline species manganite cor- responds to goethite in composition, and by the loss of water and its well-known tendency to peroxydation, passes into what has been called pyrolusite. This, as Breithaupt long since pointed out, is but polianite of epigenic origin, still retaining the external HYDROXYDITES. form. P d 4.5 4.4 4.1 4.4 2.3 V H xl ? O ? 1 H. ruber Turgite Goethite Limonite . . . Limnite Manganite. . Gibbsite. . . . Bauxite Opal. . /e 6 o 6 .laq . . /e 8 o 8 .laq.. /e s o 2 .laq . . /eiOi.laq.. 77m 8 o s .laq. aZ 1 o 1 .laq. aZ 3 o s .laq . . 24.1 22.2 20.8 17.8 22 13 15 5.3 5.0 5.1 5.0 5.6 5.5 5.5 5.5 4 3 2 " lamellosus 3 ' ' limosus 4 " Limnitcs 7 ' ' argilleus 8 " siliceus 9 " hydromagneseus . . 10 " hydromanganosus. 11 " hydricus Brucite Pyrochroite Ice mgjOi.laq. imiiOj.laq. h 8 o 2 14.5 22.2 18.0 2.4 92 6.0 19.6 2 2.5 1.5 R H 13 " niger Jfsilonielane form of manganite, and presenting an apparent softness very unlike that of the indigenous polianite (301). After the crystalline species gibbsite, we place bauxite, a porodic species, generally impure from an admixture of hydrous iron oxyd. Most of the analyses of bauxite, as Dana has remarked, lead to the formula given in the table, making it isomeric with the dense crystalline species diaspore, which, for reasons assigned farther on, we have included in the order SPINELLINEA, it forming a connect- ing link, as it were, between that order and the present. Opal is an amorphous porodic form of silica, more or less hydrated. The hydrates of silica, when artificially formed, are well known to be 236 Systematic Mineralogy. very unstable, and to lose the greater part of their combined water at temperatures below 100 C. Here also we place, for convenience, the crystalline hydrous species, brucite and pyrochroite, and water itself, in its solid form of ice. 299. The name of psilomelane is given to a common form of amorphous or cryptocrystalline manganic peroxyd, which, however, is often combined with a portion of baryta, and even of alkali, to- gether with more or less oxyd of copper and cobalt. Under this name, however, are included both hydrous and anhydrous massive manganese oxyds, doubtless representing more than qne species. The more highly hydrous substance known as wad is an earthy manganese peroxyd, varieties of which, containing considerable amount of oxyds of cobalt and of copper, have been respectively named asbolan and lampadite. Gummite is an amorphous hydrated uranic oxyd, more or less impure, which has been compared in composition to limnite ; while a variety of it has been named eliasite. It is to be observed that of the species named in the table, opal, bauxite, gummite, and probably limnite, are porodic or colloid bodies* Genus 2. PROTOLITHUS. 300. Of this second genus the first three species are rare and very little known, but, like zincite and cuprite, are spathoid in structure. The steel-gray metallic-looking native cupric oxyd which has been named tenorite is lamellar, yellowish brown, and transparent in thin plates. Melaconite, which is massive or rarely in isometric shapes, is probably an uncrystalline form of the same cupric spe- cies, which is apparently, like massicot, phylloid in type. Here also we place provisionally the little known species, plattnerite, and also arsenolite and senarmontite, since these two oxyds, though triad in type find in this same genus their nearest allies. Pris- matic forms of these last two oxyds have been named claudetite and valentinite ; while cervantite is a higher oxyd of antimony than the last, and is also prismatic. Two native oxysulphids have been observed, which present connecting links between Class I. and the present ; these are voltzite and the red translucent antimony- blende, or kermesite, which we have placed in the table. Both of these oxysulphids are non-metallic and spathoid in character, the former recalling the similar character of zinc sulphid ; while in the case of the antimony sulphid we have noted the existence of two Oxydinea. 237 forms, the metalline stibnite and the red non -metalline metastibnite. An oxysulphid of bismuth has been described by the name of kare- Unite, but further analyses of it are to be desired. Mention should here be made of so-called telluric ochre or tellurous oxyd, TeO 2 ; and also of molybdic and tungstic ochres, earthy forms of MoOj and WO 3 , the existence of which as native species has been ob- served. PROTOLITHUS. form. P d V H xl 1 P. manganosus. . Manganosite. . mn l0l 35.5 5.2 6.8 5.5 I 2 ' ' magneseus P e ri c 1 us i te me* o 20 3,7 5 4 6 T 3 " niccoleus Bunsenite ni o * 37.5 6.4 5,8 5.5 T 4 " zinceus Zincite zn,o, . 40.5 7 2 4 H 5 * ' cuprosus Cuprite CCUjOj 63 ft 11 8 3 5 T 6 " cupricus Tenorite 39.5 6 9, 6 4 C? 7 " plumbeus Massicot 111.5 9.5 12.1 .... O? 8 " plumbicus. . . . Plattnerite..,. pb^ 59.8 9.4 6.3 H? 9 " arseneus Arsenolite .... as, o, .. 33 3 7 8 9 1 5 T 10 " stibeus Senarmontite . stojOj 48 5 3 9 2.0 T 11 " sulphostibeus. Kermesite 53.3 4.6 11.6 1.5 C 12 " sulphozinceus Voltzite zn 6 o lS4 .... 46.9 3.8 12.2 3.5 ? Genus 3. CRYSTALLITHUS. 301. In arranging the species of the genus Crystallithus in the present table regard has been had in the first place to chemical con- siderations. We note in the two triad oxyds at the top remarkable differences in condensation, as shown in the values of v, that of corundum being even below that of polianite. Again, in quartz and tridymite, in rutile and in anatase, we have notable examples of similar differences with the same centesimal composition. In hematite and martite we find, as also in the cases of silicic and titanic dinoxyds, examples of dimorphism. Menacannite or titanic iron presents some problems in its composition, being variable in constitution. The most highly titanic variety has been regarded as made up of titanic and ferric oxyds, as in the present table, containing generally, however, an excess of ferric oxyd. At the same time it may be looked upon as a titanate of ferrous oxyd ? 238 Systematic Mineralogy. and some examples of the mineral contain from twelve to four- teen per cent, of magnesia, which may be regarded as replacing ferrous oxyd, thus giving an amphid constitution to the species approaching that of the spinels, as will be noticed under the genus Attospinettus in the order SPINELLINEA. CRYSTALLITHUS. form. p d V H xl 1 C. aluminicus Corundum... Hematite. . . . Martite 17 26.7 26.7 25.3 26.3 15 15 20 20 20 37.5 21.8 4 5.3 5.3 4.7 4.8 2.65 2.3 4.2 4.2 3.8 6.7 5.0 4.2 5.0 5.0 5.4 5.5 5.66 6.5 4.8 4.8 5.2 5.6 4.4 9 6.5 6.5 6.0 6.5 7 6 6.5 6.0 6.0 6.0 7.0 R R I R T R A T O T T T 2 " ferricus 3 " martialis 4 " ferrititanicus... 5 " manganicus .... 6 " vulgaris Menacannite Braunite .... Quartz . . . f ':::. 7 " triplex Tridymite . . . Rutile j. 8 " rutilus 9 " Brookii Brookite Anatase Cassiterite.. . Polianite .... iS;:::: 10 " octohedrus 11 " stanneus 12 " Polianites. ..... Sub-Class B. AMPHIDATA. 302. In this division of the Oxydaceae are included all the oxy- dized species of Class III. with the exception of the three genera of Oxydata already noticed in the sub-class A. The orders in the sub-class Amphidata which, in the present state of mineralogical knowledge, it is deemed proper to recognize among native species; are the following : 2, Boratinea or Borates ; 3, Spinellinea, includ- ing aluminates, together with those species containing triad oxyds performing functions similar to those of alumina, as ferric, chromic, manganic and titanic oxyds ; 4, Carboninea or Carbonates ; 5, Sili- cinea or Silicates ; 6, Borosilicinea or Borosilicates ; V, Argillinea or Aluminisilicates ; 8, Borargillinea ; 9, Titaninea ; 10, Stanninea ; 11, Columbotantalinea ; 12, Wolframinea ; 13, Molybdinea ; 14, Chromatinea; 15, Nitratinea ; 16, Phosphatinea ; 1 7, Arseninea ; 18, Vanadinea ; 19, Stibiinea ; 20, Sulphatinea ; 21, Seleninea ; 22, Tellurinea. Boratinea. Order 2. BORATINEA. 239 303. The species in this order may be grouped in three genera. The first consisting of a few salinoid species for which the name of Borasalinites is proposed, while the second includes several spathoid species under the generic name of Boratinus. In the third place are found some remarkable adamantoid species, embracing the species boracite and rhodizite, to which the name of Borites, proposed by Breithaupt for these two species, is applied. Genus 1. BORASALINITES. 304. In this genus we include native borax or tincal and sasso- lin, to which may be added larderellite, an ammonium borate. BOKOSALINITES. form. P d V H xl 1 B. ncttricus . . . Tincal . . 11 ?- 1 7 6 6 2 5 r, 6 17 "***! * 2 " hydricus. . . . Sassolin .... fciOj.laq 10.3 1.5 6.8 1 A 3 " ammoniatus Larderellite Genus 2. BORATINUS. 305. Of the present genus colemanite is a well-defined spathoid species ; ludwigite, apparently an admixture of a crystalline hydrated ferromagnesian borate with limonite and magnetite ; while after sussexite and ulexite we have several hydrated borates of lime, magnesia and soda in hydroboracite, szabelyite, crypto- morphite, bechilite, etc., which are too poorly defined for definite consideration. BORATINUS. form. P d V H xl 1 B. ccilccireus .... Colemanite &aCa>oOi i.Saa . 1?- 9 9, 4 5 4 4 f! 2 " natrocalcareus Ulexite.... b l9 ca, a na,iO al .I8aq 12.3 1.7 7.4 ? 3 " manganosus . . Sussexite . . 6 3 mn 1 mg 1 6 5 .6aq. 16.7 3.4 5.0 3 ? 240 Systematic Mineralogy. Genus 3. BORITES. 306. The four species here included in the above genus are- all remarkable in composition. Boracite, containing a small amount of chlorine, is in fact a chloroborate, and the tendency to its pro- duction is so strong that when the requisite elements are brought together, whether by igneous fusion or by aqueous solution with heat under pressure, this singularly hard and dense crystal- line compound is formed (208). In jeremejewite we have an anhydrous compound of aluminic and boric oxyds, and in rhodizite the same elements united with an alkali. As regards warwickite, the above formula is recalculated from the analysis by J. Lawrence Smith, with which it agrees closely. In representing it as a com- pound in which titanic and ferric oxyds replace aluminic oxyd, it is proper to recall the writer's earlier studies of this mineral,. BORITES. form. P d V H xl 1 B. chloromagneseum Boracite froAlUSTftOoaCli . 14 85 3 4 7 7 T 2 " aluminikalicus. . . 3 " dluminicus Rhodizite.... Jeremejewite fc^aZjek^, .. 17.3 14 3 3.3 3 3 5.2 4 3 8 5 f> I H 4 " titanicus Warwickite. . betiofeiYngfiQ, fi . 17 3 3 4 5 1 6 n published in two papers in 1846 and 1851. In the latter he called attention to the fact that its hardness is 6.0, its color copper red, with a somewhat metallic lustre, which had given it among col- lectors the name of hypersthene ; while its powder, of a dark pur- plish brown, becomes light reddish brown by calcination. It was noticed moreover that it is decomposed by heating with sul- phuric acid, giving a dark blue mass, decolorized by solution in water. From these circumstances it was suggested in 1846 that the titanum in this mineral exists not as TiO 2 , but as sesquioxyd, Ti 2 O 3 . To this view Rammelsberg then objected, though he, in common with other chemists, has since come to admit the presence of this form of titanum in various silicates, as Scheerer had already done in a titanic iron ore. The name of enceladite was given by the writer in 1846 to large crystals with a hardness of 3. and a specific gravity of 3.188, and a less perfect cleavage, which con- tained silica and alumina equal to one-third their weight, with Spinellinea. 241 7.3 per cent, of water. This substance, in accordance with the vague notions of the time, was described as the result of an altera- tion of warwickite,* but is apparently one of the many examples ^f the enclosure of a foreign substance in the jJrocess of crystalliza- tion, similar to that of grains of quartz in calcite, or of cassiterite in orthoclase (185). Order 3. SPINELLINEA. 307. This order is represented by the spinels, of which the nor- mal type may be described as a definite anhydrous compound of aluminic oxyd, considered as negative or acidic, with a positive or basic diad oxyd. Ferric, chromic, titanic and manganic triad oxyds may replace wholly or in part the aluminic oxyd, and even the hexad uranic oxyd has apparently a similar function. The formula of these compounds is thus: n^Oj -f- m 3 o s = m 3 o 4 . It is however probable that there exist related compounds with other ratios between the negative and positive members, having a general formula m^ -f- ^(mjOj), in which n, instead of being = 3, as in true spinels, is less, or more often, greater than this. The name of Spin- ellus, early given to the gems of this order, and employed by Breit- haupt, is retained for the aluminous spinels; while the ferric, chromic, manganic and titanic genus will form a distinct genus, Allospinellus. Genus 1. SPINELLUS. 308. The chemical history of the spinels is somewhat compli- cated. We place at the head of the genus the beryllic species, chrysoberyl, since, though differing in crystalline form from the typical spinels, it is chemically representative. For a like reason, diaspore, similar to it in hardness and in condensation, in which the basic member is h^, finds a place next it. The magnesia of the red spinel or balas ruby is replaced to a greater or less extent by ferrous oxyd in the dark green spinel, also called ceylanite ; while a bright green variety designated chlorospinel contains a little cupric oxyd, and in hercynite and gahnite ferrous and zincous oxyds replace more or less completely the magnesia. The alumina in some of these spinels is partly replaced by ferric oxyd, and in a black variety, called picotite, by chromic oxyd to the * Amer. Jour. Science (2), ii., 30, and xi., 352. 242 Systematic Mineralogy. extent of seven or eight per cent.; while in chromite this replace- ment is more or less complete, as seen in the two formulas given in the table, in the second of which, moreover, the magnesia is in part replaced by ferrous 6"xyd. SPINELLUS. form. P d V H xl 1 S. berylleus Chrysoberyl. . CLla\)GlO A . 15 6 3 8 4 1 8 5 O 2 " hydricus 3 ' ' magncseus Diaspore Spinel aZ 3 h 1 o 4 dloTQSiOA . 15 17 8 3.5 3 5 4.3 5 7 8 T Gahnite GtZoZDl OA M 9 4 5 5 1 7 T 5 " ferreus Hercynite nl 9 f&,o A ?,1 7 4 5 4 7 T Genus 2. ALLOSPINELLUS. 309. In magnetite we have a ferric spinel, two varieties of which, named as distinct species, have the ferrous oxyd replaced by magnesia and by manganous oxyd. Franklinite is a zinciferous fer- ric spinel in which manganic replaces a portion of the ferric oxyd ; while hausmannite is apparently a manganese compound corre- sponding to magnetite. Menacannite has been regarded as a com- pound similar to spinel, in which titanic oxyd replaces alumina or ferric oxyd, and some analyses correspond to that formula, while in others an excess of ferric oxyd appears to be present. A titanic iron ALLOSPINELLUS. form. P 23.9 28 29 25 28.9 29.7 28.6 d 4.3 4.6 5.2 4.6 4.8 5.1 4.8 V 5.5 6.0 5.6 5.4 6.0 5.8 5.9 H 5.5 5.5 6 6 6 6 5.5 xl I T 1 A. mediochromicus . 2 ' ' chromicus Chromite aZjcr 2 fe. 5 mg. 6 o 4 cMe^ /e 8 fe!0 4 /g TYJCT o., Chromite Magnetite Magnesioferrite. Jacobsite . . 3 " ferricus 4 " ferrimagneseus. . 5 " ferrimanganosus 6 " ferrizinceus .... /PoinnT o, . Franklinite Hausmannite. .. (/e,mw) 8 zn 1 o 4 . .. 7 " manganicus 8 " manganicupreus 9 ' ' urctnicus I Spinellinea. 243 containing magnesia, referred to under the genus Crystallithus, ap- proaches in composition to a titaniferric spinel, ^/ej.mg^. Cred- nerite is apparently an example of deviation from the normal spinel formula, since the value of n therein is not 3 but 2, while in many titanic irons it is much higher. The recognition of a homologous series, as above explained, constituting a passage towards oxyds like corundum, hematite and martite, of the order Oxydinea, serves to explain the existence of various compounds intermediate in com- position between magnetite and martite (301). The suggestion that these have resulted from subsequent alteration by a more or less complete peroxydation of magnetite, though often advanced, can scarcely be seriously maintained when we consider that the min- eralogical associations of magnetite are such as to forbid the notion that it has ever been exposed to high temperature or oxydizing agencies, and moreover the fact that magnetite, so far as our exper- ience goes, is an exceedingly permanent and unalterable species. 310. The composition of uraninite is doubtful ; the various speci- mens referred to that species differ considerably in composition, and range in specific gravity from 5.0 to 8.0 and even to 9.7. They moreover contain besides oxyds of uranium, greater or less propor- tions of oxyd of lead, besides variable amounts of oxyds of thorium, yttrium, and the cerium metals. Still more remarkable is the occa- sional presence therein of nitrogen in an unknown state of combi- nation, sometimes to the extent of 2.5 per cent. Certain of the so- called uraninites are readily decomposed by dilute acids, in which others are nearly insoluble ; some are crystalline, while others are apparently uncrystalline ; and others, instead of being anhydrous, contain water up to 4.0 per cent. To two hydrous forms the names of nivenite and clevite have been given, while an anhy- drous one has been called broggerite. It is not improbable that a normal uraninite, analogous in formula to spinel, may exist, but our knowledge of the whole matter is as yet very imperfect. Such a species, in which the positive element should be either uranous oxyd or the admixtures of those mentioned as generally found with uranic oxyd in the mineral above, would give for p = 50 to 53, and with d = 9.7, a value of v = 5.5 5.6. All the native aluminates known are hard and much condensed, and, with the exception of diaspore, anhydrous. What has been described as a crystalline hydrous aluminate of magnesia, with the name of voelknerite or hydrotalcite, appears to be a mixture of aluminous magnesian hydrates and carbonates. 244 Systematic Mineralogy. Order 3. CARBONINEA. 311. The species in this order are arranged in four genera, the first consisting of salinoids under the name of Carbosalinites, the second of hydrous and basic carbonates, called Hydrocarbonites, the third including the carbon-spars, for which we assume the name of Carbonites, already given by Breithaupt to the rhombohedral species, and the fourth Halicarbonites, embracing two remarkable fluorocarbonates and a chlorocarbonate. Genus 1. CARBOSALINITES. The salinoid carbonates embrace besides a hydrous double car- bonate of calcium and sodium several sodium carbonates, including the monohydrate, thermonatrite, and the decahydrate, natron ; be- sides an intermediate compound which has been described as a sesquicarbonate. The late careful studies of Chatard have shown that this substance, variously known as trona and urao, may be represented as a hydrous combination of monocarbonate and dicar- bonate of sodium, or as in the accompanying table. It may be formed artificially under conditions described by Chatard.* CARBOSALINITES. form. P d V 6.0 6.6 7.3 9.7 H xl C C C 1 C. natrocalcareus 2 " typicus. . . . Gaylussite. . . . Urao Cgna^a^g^aq C 4 na 3 h 1 o 18 .4aq c^naiOg.lOaq . . Cjnaj.Og.laq. . . 13.4 14.1 11 15.5 1.9 2.14 1.5 1.6 2.5 3 1.5 1.5 3 " hydronat reus. . 4 " natreus Thermonatrite Genus 2. HYDBOCABBONITES. 312. The hydrous carbonates of this genus include a number of well-defined species, besides several others the precise composition of which is not certain. Such are hydrodolomite and lancasterite. In addition to uranothallite, other uranic carbonates, as liebigite and vogtite have been named. A hydrous bismuth carbonate has been found in several localities, but the analyses show a somewhat variable composition, and its formula is uncertain. * Amer. Jour. Science (3), xxxviii., 59. Carboninea. HYDROCARBONITES. 245 form. P d V H ,/ 1 H. magneseus . . . 2 " caeruleus 3 " cupreus Hydromagnesite Azurite Malachite C 8 mg 4 o 10 .4aq.. C 2 cu 3 o 7 .laq C- CU O t lllO 13 21:4 00 2.2 3.8 4 5.9 5.6 R R 4 \ C r 4 ' ' euprozinceus. 5 " niccoleus Aurichalcite. . . . C 2 zn 3 cu 8 o 9 .3aq . 22.6 17 o 7 6 3 2 3 C 6 ' * zinccus H yd rozincitc C* zn Or 3ao 00 1 7 o 7 " aluminicus . . 8 " lanthanicus. . 9 " bismuteus Dawsonite Lanthanite Bismut ite c 1 aZ 8 na 1 .o 8 .2aq . 14.4 17.1 2.4 2.7 6 , 6.0 6.3 3 2 4 5 C 10 " uranieus Uranothallite. . . CK 1*7*0 caOi e.lOaa 16 3 ? Genus 3. CARBONITES. 313. In the genus Carbonites are arranged the anhydrous sparry carbonates, both rhombohedral and prismatic. Of these only the principal ones are given in the table above. Intermediate species, to many of which names have been given, abound in the rhombo- hedral spars, being due to more or less complete replacements of the bases, lime, magnesia, iron, manganese and zinc by one another, and occasionally to the intervention of a little baryta, strontia, or lead oxyd. Similar variations occur also in the prismatic species, and small portions of strontia are frequently met with in arago- nite, while a cerussite with a portion of zinc oxyd has been desig- nated iglesaite. It is worthy of note that the calcic carbonate in its rhombohedral and prismatic forms of calcite and aragonite exhibits different densities, while the corresponding zinc carbonate, in like manner dimorphous, presents in both forms the same con- densation. The variations in specific gravity of calcite, according to the numerous observations of Breithaupt, from 2.754 to 2.652, are probably examples of variations in condensation in this rhombohe- dral form ; but for ordinary purposes that of 2.73 (or 2.7) assigned by Breithaupt to what he found the most common density of cal- -cite, is generally accepted.* The progressive augmentation of hardness and the diminution of solubility in acids coinciding with * See, for a detailed notice of Breithaupt's observations, the author's " New Basis for Chemistry," pp. 103-105. 246 Systematic Mineralogy. the increased condensation, as shown by the diminished value of its co-efficient v, has been already insisted upon (138), and is well shown in the present table of species. CARBONITES. form. P d V H 3 4 4 4 4 4 4 5 4.5 4 3 4 3 3.5 3 5 xl 1 C calcareus Calcite 16.7 15.3 18.0 16.7 19.3 19.2 19.8 20.8 14.0 16.7 32 8 2.7 2.9 3.1 3.4 3.7 3.7 4.1 4.4 3.0 2.94 4.3 3.7 3.7 3.7 6.6 4.5 6.0 5.3 5.8 5.3 5.2 5.2 4.8 4.7 4.7 5.7 7.6 6.7 6.7 6.6 6.6 4.6 R R R R R R R R R O O O C O O 2 " calcareomagneseus 3 " calcareoferreus . . . 4 " magneseoferreus . . 5 " ferreus CiCa.5fe.gOg . Ciing. 5 fe. 5 o 8 Ankerite Breunnerite Siderite 6 " manganosus c mn o 7 * ' cobalteus Sphaerocobaltite. Smithsonite Magnesite CCiOiOo . . 8 " zinceus 1 9 " magnescus 10 " paracalcareus .... 11 " baryteus Aragonite Witherite c ha 12 '* Alstoni Alstonite Cj Da. gCa. gOg . Cjpbi Og ..... 24.7 24.7 24.5 44.5 20.8 13 " barytocalcareus... Barytocalcite. . . . Strontianite Cerusite Parasmithsonite. . 16 *' parazinceus ... . Genus 4. HALICABBONITES. 314. With the rare fluorocarbonates parisite and bastnaesite or harmatite, is here included kischtimite, apparently a variety of the first. In the same genus, Halicarbonates, is placed provisionally, the chlorocarbonate phosgenite. HALICARBONITES. form. P d V H xl 1 H. calcareocereus . Parisite . . . Cgcegca^fi . 27 4.4 6.1 4.5 H 2 " cereus Bastnaesite CoCe a o fi fi . 81 4 5 ?r 6 4 5 H 3 " plumbeus Phosgenite c 1 pb o o o cl i . . . 68 6 8 10 8 i T Silicinea. 247 Order 5. SILICINEA. 314. The silicates are in the present system separated into two principal orders, one containing alumina, which in some cases may be partially or wholly replaced by the related titanic, chromic,, manganic or ferric triad oxyds. This constitutes the order ARGIL- LINE A, to be described farther on. Our present object is to consider the non-aluminous order, which we designate SILICINEA, premising that between the two will be noticed a small subordinate order containing boric oxyd, and named BOBISILICINEA. The species of the important order Silicinea may with propriety be arranged in the following generas : Pectolithus, including a group of which pectolite is the type, with other calcareous species ; the related ones, calamine, dioptase, friedelite, and the chloriferous ferrous species, pyrosmalite. All of these are distinctly spathoid in their charac- ters, except the last, which is a well marked phylloid, and was by Breithaupt included in the order of Micas. All of the silicates of this genus are hydrated, and are decomposed by chlorhydric acid with separation of gelatinous silica, as indicated by the name, of pec- tolite.* Chrysolithus includes a group of anhydrous silicates more- condensed than the last, which are still, however, attacked and pectised by the action of chlorhydric acid. In this genus, besides the typical chrysolite or olivine, are related silicates of magnesia, zinc, iron and manganese, the lead-silicate, ganomalite and the bis- muthic silicate eulytite. In the next place, we find two related groups of species which are known by the general names of amphi- bole and pyroxene or augite. Dana, in his early classification, took the latter name for a genus, Augitus, which he made to include both ; but we follow Breithaupt in making two genera, Amphibolus and Pyroxenus, for the reason that there is at the same time a difference in condensation, and a more or less complete parallelism in the chemical composition of species to the two divisions. 315. We place next Phenacites, including the remarkable beryl- lie species, phenacite, and also bertrandite, like it adamantoid, and differing from it only in being hydrated. Following this is Zir- conius, the name applied by Breithaupt to the ordinary zircon or * The designation pektolith was given by v. Kobell in 1829 to the species which we have made the type of the genus, from the Greek irrjKTds, or rather from Tny/crjf , jelly, whence also come the words pectin, pectose and pectisation, referring to jellies and their production. The name pectolite is, however, wrongly said, on the authority of J. D. Dana (Webster's Dictionary), to be derived from pecten, Latin, a comb, and to belong to a hydrous silicate of alumina, lime and soda. 248 Systematic Mineralogy. hyacinth, with which we place the related species auerbachite. Following these two genera, characterized by the rare elements ber- yllium and zirconium, we find another group of silicates remarkable for containing thorium, the cerium-metals and yttrium, with its attendant elements, ytterbium, gadolinium, etc., and in some cases also uranium. To this group, of exceeding interest and import- ance to the chemist, we give the generic name of Eritimites (Greek fpm//or, precious), and include therein besides cerite, thorite, yttrialite, gadolinite and thorogummite, certain rare zirconic and beryllic silicates. We have next a group of hydrous magnesian silicates of which picrolite is the type, and which is, therefore, desig- nated Picrolithus, a name applied by Breithaupt to some of the species. In the last place, is a group of distinctly colloid or porodic hydrous silicates, including besides magnesian species, others con- taining copper and nickel, to which we give the name of Porosili- cites. Genus 1. PECTOLITHUS. 316. The first three species of this genus have been by most mineralogists confounded with the zeolites, which have with them certain resemblances, but are aluminous silicates, and as such belong to the order Argillinea. Apophyllite is notable as a fluo- riferous species, whose composition is represented most intelligibly by the formula given in the table. Pyrosmalite, again, is a chlo- rif erous species, and one of curious interest. Besides the silicates of copper, zinc and manganese, mention should be made of conarite, which appears to be a crystalline nickel-silicate probably belong- ing to this genus. PECTOLITHUS. form. P d V H xl 1 P. vulgaris 2 " lamellosus. . . 3 " Okeni Pectolite . . . Apophyllite. Okenite .... Plombierite . Xonaltite... Dioptase. . . . Calamine . . . Friedelite... Pyrosmalite sijgca^a^.laq. . siiCaiOg.KM^.Saq Si 4 ca 1 o 6 .2aq sijjCajOg.Saq Si 2 c ai o 3 .iaq Si 2 cu 1 o 3 .laq siiZnjOjj.^aq 18.4 15.9 15.1 15.2 18.5 19.9 24 19.1 21.6 2.8 2.4 2.3 2.7 3.3 3.5 3 3.2 6.6 6.6 6.6 6.8 6.0 6.8 6.4 6.7 5 5 5 ? 5 5 5 4.5 C T ? R O R R 4 ' ' recens 5 " Xonaltites... 6 " cupricus .... 7 " zinceus 8 " manganeus. . 9 " chloriferreus Si 8 fe 8 o 5 .laq(|cl) ... Silicinea. 249 Genus 2. CHRYSOLJTHUS. 317. In this genus we notice besides the typical chrysolite or peridot, the purely magnesian form, fosterite or boltonite, and the little known fayalite ; a partial replacement of magnesia by iron giving rise alike to peridot and to the intermediate species, horton- olite. It is worthy of note that fayalite appears, like monticellite, tephroite and willemite, to be less condensed than the first two species in our table ; while ganomalite and eulytite are still less so. In accordance with this greater condensation, while all these silicates are decomposed by chlorhydric acid, it was found by Mackintosh (145) that chrysolite resists the action of fluorhydric acid, which readily and completely dissolves willemite. Besides the rare ganomalite, is a less known species, hyalotekite, which, from an in- complete analysis, appears to be essentially a double silicate of lead and barium ; and still another, barysil, apparently a simple barium, silicate. 6oth of these will probably find a place in this genus. A silicate of bismuth identical in composition with eulytite occurs in <;linorhombic form, and has been named agricolite, and a massive mineral which appears to be a silicate of bismuthic and ferric oxyds, has been called bismutoferrite. CHRYSOLITHUS. form. P d V H xl 1 C magneseus . Forsterite siiHieTtOo . 17 5 3 3 5 3 7 O Chrysolite . siimgr.ofe.iOo. . 18 8 3 4 5 4 7 O 3 " ferreus Fayalite .... siife,o 9 . 25 , 5 4 1 6,1 6,5 4 " CdlCCLTBUS Monticellite. siiingf. ,.ca. rOo . 19 5 3 2 6 1 5 5 O 5 " fluoromagneseus. 6 ' ' mangcineus .... Chondrodite Tephroite . . Si 8 mg 4 o 6 . 5 f. 5 .. si, inn ,o., . 18.6 25 3 3.2 4 1 5.8 6 1 6.5 6 o Willemite . . 27 7 4 2 6 6 5 5 H 8 " plumbeus Ganomalite . si c pboCa.,Oi 1 43 7 5 7 7 6 3 T 9 " bismuteus Eulytite .... siibi, , 46 6 1 7 5 4 5 T Genus 3. AMPHIBOLUS. 318. The varieties, or rather the sub-species, of this genus are very numerous and their nomenclature is somewhat perplexing. It will suffice for the present to select a few distinct and representative examples. Beginning with tremolite, a pure lime-magnesia amphi- 250 Systematic Mineralogy. bole, we pass through partial replacement of magnesia by ferrous oxyd to actinolite, and through a complete replacement to antho- phyllite, a lime-iron amphibole ; while in kupfferite we have a nearly pure magnesia-amphibole, and in cummingtonite one in which the magnesia is to a large extent replaced by ferrous oxyd. The name of griinerite has been given to what appears to be a. purely ferrous amphibole, and that of hermannite to a similar manganesian species. Between these types there are many inter- mediate species. AMPHIBOLUS. form. P d V H xl 1 A., albus Tremolite siomsrl^arOo . . 17 3 3 5 8 5 5 O 2 " radiatus Actinolite sigHig 1 7 ca. gfe.jCo 17 7 8 5 9 5 5 r, 3 " floridus 4 " magneseus Anthophyllite . . Kupfferite si 2 mgf feo 8 sioimr afc.iOo 18 17 2 3.2 f* 5.6 5 7 5.5 5 r> r 5 " ferromagneseus.. Cummingtonite . sioinerlfefOo ., 90 9 8 3 6 1 5 5 o Amphibole assumes fibrous forms, as in tremolite, and is often radiated, as in actinolite, passing into the soft, flexible, silky variety which constitutes true asbestus or amianthus. Most of the so- called asbestus found in commerce is however chrysotile. A finely granular or compact variety of tremolite, generally greenish -white in color, is known as nephrite or jade, and serves for the fabrica- tion of weapons or ornaments, to which, from its tenacity, it is well fitted. This is not however to be confounded with a much harder and heavier mineral, like it in aspect, and also known as jade or saussurite, to be mentioned later ; which is an aluminous silicate,, related to garnet and to epidote. Genus 4. PYBOXENUS. 319. In this genus, beginning with a purely magnesian pyroxene enstatite, we pass through bronzite, which contains more or less ferrous oxyd, to hypersthene, the formula of which as given below is deduced from the writer's analysis of that from the granitoid norite rocks, made up of andesite, hypersthene and menacannite, from Cha- teau Richer, Quebec. Passing next to the colorless and often trans- parent lime-magnesia pyroxene, malacolite, we find near it diallage,. Silicinea. 251 in which the magnesia is partially replaced by ferrous oxyd, and which is to malacolite what bronzite and hypersthene are to en- statite. Hedenbergite is a black lime-iron pyroxene in which the magnesia is wholly replaced by ferrous oxyd, while jeffersonite is a similar species in which the magnesia is partially replaced by oxyds of zinc and manganese. In rhodonite we have a manganesian silicate with the general formula of pyroxene, sometimes containing a little zinc oxyd, and often impure from an intermixture of carbonates. Wollastonite is a lime-silicate, with the ratios of pyroxene. The species and varieties intermediate between the first four named in the above table are very numerous, and we have only selected these as chemically typical of the genus. PYROXENUS. form. P d V H xl 1 P. magneseus Enstatite .... siging^a 16.7 3.1 5.4 5.5 O 2 " ferromagneseus Hypersthene. si 2 mgffeo s . 18.4 3.4 5.4 6 O 3 " albus Malacolite . . . sica>. K nQgr. E Oo 18 3 3 5 4 5 5 f! 4 " ferrocalcareus . . Hedenbergite si 8 ca. 5 fe. 5 o s . 20.7 3.6 5.7 5.5 C 5 " manganosus . . . Rhodonite . . . Si 8 mn 1 o 8 . . . 21.8 3.7 5.9 5.5 A Wollastonite. sioCaiOo 19 8 9, 9 6 6 5 C 320. It will be kept in mind that the two genera, amphibole and pyroxene, are distinguished by differences in crystallization, and that while the clinorhombic prisms of the former are from 124 to 125, those of the latter are about 87. In this respect wollasto- nite agrees with pyroxene, as does also rhodonite which, though anorthic in crystallization, is approxmatively isomorphous with pyroxene. The most important point to be noted in the relations of these kindred genera is their differences in condensation. This is very evident when we compare the first four species of Amphi- bolus, which are best known (v = 5.7, 5.8, 5.9), with the first three of Pyroxenus (v = 5.4, 5.4, 5.4), and with Wollastonite (v = 6.6). (The specific gravities of cummingtonite, hedenbergite and rhodonite require farther examination.) It was from this comparison of the relative condensation of pyroxene, amphibole and Wollastonite that the writer, in 1853, insisted that these represent three homologous isomeric types ; a relation afterwards recognized by Dana, in 1868, 252 . Systematic Mineralogy. so far as pyroxene and amphibole are concerned. In this connec- tion it is to be remarked that wollastonite is attacked and dis- solved by chlorhydric acid, which does not decompose amphibole nor augite, and a similar difference is noted in their behavior with dilute fluorhydric acid. Wollastonite is to be regarded as spathoid, while the others are adamantoid in type. Pyroxene, like amphi- bole, often assumes fibrous and granular forms. The two species, moreover, are frequently intimately associated in the same aggre- gate, and under circumstances which show that small variations in the conditions may determine the production of the one or the other species. The writer many years described and analyzed specimens of both found together on the Madawaska river in Canada, where well-terminated dark green crystals of amphibole, nearly an inch in diameter (sp. gr., 3.05), are unsymmetrically joined with still larger crystals of greenish white pyroxene (sp. gr., 3.27), which has crystallized afterwards and partially enclosed the amphibole ; both of the minerals occurring with black tourma- line in calcite, constituting a veinstone or endogenous rock in the ancient Laurentian gneiss. Other examples of similar associations are not wanting, and in some cases the amphibole has evidently been deposited upon the pyroxene, while twin crystals of the two species united are met with ; from all of which facts we may con- clude that they may be formed simultaneously.* 321. A mere coincidence of crystalline form among anisometric crystals is, as has been already shown (158), a very inadequate foundation on which to base a chemical or a mineralogical relation. It was, however, on this ground that Breithaupt included in his genus Pyroxenus, both spodumene and acmite, and in Amphibolus the species arfvedsonite. Following this indication, Zirkel has added to these, in what he calls the Pyroxene series, petalite and babbingtonite, and in the Amphibole series, glaucophane and gas- taldite, all of which species will be considered in the order AR- GILLINEA. Genus 5. PHENACITES. 322. Of the genus Phenacites the two species known are re- markable for their condensation, and for the fact that they differ chemically in the hydration of bertrandite. * " Geology of Canada," 1863, pp. 466, 467. Silicinea. PHEN ACITES. 253 form. P d V H xl 1 O. nobilis...... Phenacite. . . . 13 7 3 4 6 8 "R, 2 " Bertrandi . Bertrandite . siibeiOjj.iaq . . . 13.2 3 5.1 7 Genus 6. ZIRCONIUS. 323. In the genus Zirconiys the principal species presents con- siderable variations in density. While most zircons give from 2.6 to 4.7, to which figures other less dense ones are raised by ig- nition, the small transparent crystals from Auvergne have a sp. gr. of 4.86 ; and other, though rare specimens, give only 4.02 4.04 ; which latter, in an example described by A. H. Church, was not changed by ignition. We give in the table the density 4.7,. premising that 4.9 gives v = 5.6. The question of the lower den- sity, and its significance, requires farther examination, the more so as a density of 4.06 has been assigned to auerbachite, which seems to be a silicate of zirconia with different ratios, and gives, with a density of 4.0, a value for v = 5.3. Zircon, while it resists the action of chlorhydric and even of fluorhydric acid, is to some ex- tent attacked by digestion with heated concentrated sulphuric acid. ZIRCONIUS. P d v H xl 1 O. nobilis Zircon sltziv),.. .... 27.7 4.7 5.9 7 T 2 ' * minor. Auerbachite. . 9,1 9, 4 5 3 6 5 T Genus 7. ERITIMITES. 324. In assigning chemical formulas to the species which we have grouped in the genus Eritimites, we are met by the fact that the bases present in many of them include not only the triad oxyds of the three so-called cerium metals, namely lanthanum, cerium and didymium, but also, under the head of yttria, the oxyds of several elements closely related thereto, and separable from one another 254 Systematic Mineralogy. only with great difficulty. Besides yttria itself, are, in many cases, rbia, ytterbia, gadolinia, and probably other related oxyds of higher equivalents, and also in some cases scandia, with a lower equivalent. In the formulas here given the three triad oxyds of the cerium metals are represented by the common formula c^Oj with a value for ce=47, which is about the mean of the three ; while yt^Qt is made to represent not only yttria itself but the other related oxyds just referred to. Berzelius found some yttria in cerite itself. Here also is apparently the place of the rare silicate uranotil, which, according to Genth, has the composition assigned ERTTTMITES. form. P d V H 5.5 5 5.5 7 4 3 6 5.5 6 6 4 xl 1 E. cereus. 2 " thoreus Cerite si ce o 'a 31 30 25.7 25.1 31.6 22.5 19.2 20.3 22.9 23.3 18.8 4.9 4.7 4.6 4.3 4.5 3.9 2.8 3 3.5 3.4 3.4 3.0 6.3 6.4 5.5 5.8 7.0 5.8 6.8 6.8 6.5 7.0 6.3 O T C T 0? H R C I I Thorite si th o laq 3 " yttreus Yttrialite sLt/Sthio... 4 " Gadolini (jadolinite si., ?/i .rbei ca. -Or 5 " uranothoreus . 6 " uranocalcareus 7 " natricus Thorogummite Uranotil Catapleiite .... Eudialyte . siaWithj.5ca.506.2aq.... Si 4 ^ 6 ca 1 o 11 .6aq 8 "' calcareus S**G* 9 " manganeus. , . . 10 " xantheus Lavenite Helvite Danalite Si 2 b ei (fe,2n)fo 4 si Si 16 be 6 ca 5 na 8 o 26 f 8 .... 12 " albus Leucophane . . . in the table. What has been called uranophane is perhaps the same species. In addition to all these rare elements, we note the presence in the minerals of this genus, of the tetrads, zirconium and thorium, of beryllium and uranium. Besides the silicates of zirconia with lime and alkalies, named in the above table of the genus Eritimites, there have been described as hydrous zirconic species, malacone and cyrtolite. Analyses of the latter differ con- siderably, as do the densities assigned to it, which vary from about 3.3 to 4.0. The analysis by Nordenskiold gives, for the lightest of these, notable proportions of yttria, of the cerium oxyds, and lime, with 12.0 per cent, of water. It is probable that more than one species is confounded under this name. The cyrtolite from Llano Silicinea. 255 Co., Texas, with H. = 5.0, and a specific gravity of 3.65, as noted by Mackintosh, is attacked by chlorhydric acid, with solution of zir- conia and separation of pulverulent silica. The rare mineral helvite is an example of a native sulphosilicate, in which part of the oxygen is replaced by sulphur. Danalite is a similar compound, in which the manganese is replaced in part by zinc and in part by iron. Leucophane is another beryllic species, noteworthy as con- taining both sodium and fluorine. The name of melinophane or melitophane has been given to a mineral which seems to be identi- cal with the last. Genus 8. PICROLITHUS. 325. We have next to notice the genus Picrolithus^ with its hy- drous magnesian silicates, some of which are still imperfectly known. In picrolite itself, and in thermophyllite, we have crystalline sili- icates with a specific gravity of about 2.6. These have the compo- sition of serpentine, which we place in the next genus. It is not however improbable that we have in these two a prismatic and PICROLITHUS. form. P d V H xl 1 P. triplex "Villarsite si.HlGT.iO IclQ 16 5 3 5 5 8 o 2 " figneus Picrolite si.m2ToO-.2aa . 15 R 9! 6 5 9 4 5 ? 3 " foliaceus... . 4 '* sericeus .... Thermophyllite . si 4 mg 3 o 7 .2aq si^imToCv 2aa 15.3 15 3 2.6 2 2 5.9 7 2 ? ? 5 " odorus Picrosmine sLmeToOft.laq. . 15 6 9 7 5 8 3 ? 6 " mollis Talc sii nmsr^Oi 4.14&Q 15 7 2 7 5 tf I O? 7 * * prismaticus Pyrallolite siinlllST.Oi. 1-ia.O 15 7 2 7 5 8 Q D? *10 iJJ &4 v/ 14* J -^ a '4 < fibrous and a phylloid form of the silicate which, in an amorphous colloid form, constitutes ordinary serpentine. Marniolite is near to thermophyllite, though seemingly more hydrated. It is further to be noticed that the massive granular silicate which has been described as bowenite, with a hardness of 5.5, and a specific gravity of about 2. 7, has also the composition of picrolite, and sustains to it a relation apparently like that of nephrite to tremolite, con- stituting with it a single species. Chrysotile, having the same 256 Systematic Mineralogy. centesimal composition as these, seems, from several concordant ob- servations, to have a specific gravity of about 2.2 (2.142, 2.220, 2.238). This, if confirmed, would show another and a less con- densed species, which would be to picrolite and bowenite what amphibole is to pyroxene. Talc, which we place in this genus, pre- sents some little variation in composition, affording from 59.0 to 63.0 per cent, of silica, and from less than 1.0 to 5.0 and 6.0 per cent, of water. From the nature of the mineral it is difficult to have guarantees of its purity ; while it is possible that there are still confounded under that name two or more closely related species. We have assumed in the above table a formula which agrees closely with many analyses, and is moreover identical with that of rensselaerite or pyrallolite. This, in the writer's experience, has been found definite and constant in composition, and is appar- ently a distinct species, which seems to take the place of talc in the older crystalline or Laurentian rocks. Genus 9. POROSILICITES. 326. In this genus we have grouped a number of distinctly amor- phous porodic or colloid hydrous silicates, some of them closely related to those of the last genus. The name of serpentine is retained for the colloid form of the silicate represented therein by picrolite and bowenite. The differences observed between serpen- tine, retinalite and deweylite (near to which comes cerolite) are such as to show variations alike in composition and in condensa- tion, but the limits of these as species are not well defined. The t POROSILICITES. form. P d V H 1 P. communis. . . . Serpentine. . si 4 mg s o 7 .2aq . . 15.3 2.6 5.9 3 2 " Laurentianus Retinalite . . si 4 mg 3 o 7 .2iaq . 15 2.4 6.2 3 3 " gummosus. . . . Deweylite . . si 4 mg 2 o 5 .3aq.. 14 2.2 6.4 3 4 " spumosus Aphrodite . . si 2 mg 1 o 3 .faq.. 13.3 2.2 6.0 5 " deter gens Sepiolite si 3 mg 1 o 4 .laq .. 14.8 2 6 " niccoleus Genthite si 3 ni 2 o 5 .3aq ... 18.4 2.4 7.6 3 7 " cupricus . . . Chrysocolla. sioCu, o , .2ao . . 17 5 9, 4 7 R 3 8 " ferreus ? Glauconite. . Silicinea. 357 niccolic species, which has been named genthite, has apparently a similar formula to deweylite, and there appear to be gradations from the one to the other ; the so-called garnierite being sometimes more and sometimes less magnesian, and passing into genthite. Chrysocolla is a cupric colloidal silicate which varies, in many examples, from the formula here given. From the nature of things, compounds which have not been individualized by crystallization may be expected to present admixtures and variations in their composition. 32 7. Sepiolite is a species of much interest, inasmuch as it is found in uncrystalline sediments, and presents a little-understood phase in the formation of magnesian silicates ; a process which has gone on in comparatively modern times, on a considerable scale, and in favorable conditions may still be active. Glauconite which, in like manner, is an amorphous silicate, is found in recent sediments, and is even now in process of formation at the bottom of certain parts of the ocean, where it fills the cavities in foraminiferous shells and other organic forms. Analyses show considerable variations in the composition of glauconite essentially a hydrous silicate of iron-oxyd and potash, it sometimes contains a considerable portion of alumina, which in the glauconite of the newer mesozoic rocks is as much as 9.0 p. c., while in other cases it falls to 1.5 p. c., though many paleozoic glauconites are still more aluminous. The iron is partly ferrous, but in large part in the ferric condition, perhaps as a result of subsequent oxydation. It seems probable, in the present state of our knowledge, that we have in most glauco- nites a greater or less admixture of an aluminous mineral allied to a zeolite in composition ; while glauconite itself is a ferrous potassic hydrous silicate allied to pectolite and to apophyllite, and having essentially the ratios of sepiolite. Order 5. BORISILICINEA. 328. The distinctness of the few native species in which the negative element consists of boric oxyd coupled with silica is such as to warrant their separation alike from silicates and from alu- minisilicates as an order apart, with the name of BORISILICINEA. In like manner, we find a small group of boraluminisilicates which will be described farther on as another order, under the name of BORARGILLINEA. 258 Systematic Mineralogy. Genus 1. BORICBYSTALLITHUS. 329. Of the three borisilicates known, one, danburite, is remark- able for its great hardness, and its resistance to acids, which gives it a place among adamantoids. It may be distinguished by the ge- neric name of Boricrystallithus. BORICRYSTALLITHUS. form. P d V H sol B. nobilis . . . Danburite . . . boSi^caiOo . 15 4 8 5 1 7 O Genus 2. BORISILICITES. 330. The other two borisilicates are less hard and less condensed than the last, and are -readily attacked by chlorhydric acid. They may be called BorisUicites. BORISILICITES. form. P d V H Ofl B. calcareus Datolite b 8 si 4 ca 2 o 9 .laq. 16. 2.9 5.5 5 C " ferrocalcareus Homilite .... b 8 si 4 ca 2 fe 1 o 10 . 18.7 3.3 5.7 5 C Order 7. ARGILLINEA. 331. As already explained, those silicates which include in their composition alumina, or one of the triad oxyds that may be re- garded as replacing it, are placed in a separate order. In SILICINEA the negative or acidic member is silicon dinoxyd, coupled in BORI- SILICINEA with boric oxyd, while in the present order the same sili- con oxyd is coupled in various proportions with aluminic oxyd, form- ing aluminisilicates, which it is proposed to distinguish by the col- lective name of ARGILLINEA. This division of the natural silicates is a very obvious one, but has been for the most part overlooked. Beudant, however, in his attempt at a chemical system in miner- alogy, divided silicated minerals into aluminous silicates, repre- sented by cyanite ; silico-aluminates, represented by the micas ; and Argillinea. 259 non-aluminous silicates like zircon ; insisting at the same time upon the subdivisions among silico-aluminates, of fluoriferous, chlorif- erous, sulphatic and boric species.* The present writer, more- over, in 1863 adopted the division of natural silicates into the non-aluminous and aluminous groups, therein following Beudant.f 332. The propriety alike of this distinction, and of the designa- tion proposed for the aluminisilicates (= alumino-silicates), will be made more apparent when we consider the results of the subaerial decay of crystalline rocks ; or in other words, the transformation of certain of their mineral species under the combined influences of water, oxygen and the carbon-dinoxyd of the atmosphere. The silicates proper which are common in these crystalline rocks, are amphibole, pyroxene, and chrysolite ; the subaerial decay of which has been studied by Ebelmen and by others. Its result, as is well known, is the complete removal, by solution, of the lime and mag- nesia of these minerals, together with the greater part of the silica - r ferrous oxyd, however, being peroxydized and left behind in an insoluble condition, unless dissolved by the reducing action of organic matters. Serpentine, moreover, undergoes a similar change. Chrysolite is more resistant than amphibole and pyroxene, and accordingly we find in many localities sands made up in good part of grains of chrysolite. J Zircon is the only other simple silicate which is commonly found in this condition, associated with which may be quartz, rutile, corundum, cassiterite, hematite, menacan- nite, and the spinels, including magnetite and chromite. 333. Turning now to the more complex silicates which, with lime, magnesia and alkalies, contain at the same time alumina, and which are widely represented in the crystalline rocks by the various feldspars, and to a less extent by the scapolites, we find, as the result of their subaerial decay, the removal by solution of the first-named bases, as before, together with a proportion of the silica ; while the remainder of this, united with the alumina, and combined with water, constitutes the insoluble residue known as clay or argil (Latin, argilla), whence the name of AKGILLINEA proposed for these minerals, whose negative element may be rightly regarded as being not silica but argil. It may here be noted in passing that these are, however, species belonging to the order Argillinea, which, from their great hardness and condensation, resist the ordinary agents of * Beudant, " Trait6 de MinSralogie " (1830), 2d ed., vol. i. t " Geology of Canada," 1863, p. 463. t " Mineral Physiology," etc., pp. 30-34 and 368. 260 Systematic Mineralogy. subaerial decay, and consequently are found with zircon, quartz, and the various oxyds named, in the sands resulting from the decomposition and subsequent disintegration of crystalline rocks. Such are garnet, epidote and staurolite, not to mention simple aluminisilicates such as andalusite and topaz, besides tourmaline, and to a certain extent, various micas. 334. But while the broad distinction above noted is conspicuous in the case of the two most abundant families of native silicated minerals, that of the feldspars on the one hand, and that of the amphiboles and pyroxenes on the other, there are apparent excep- tions in the case of the two last named which demand our especial study. Although the typical forms alike of amphibole and of pyroxene contain neither alumina nor any of the oxyds which, like ferric, manganic and chromic triad oxyds, sometimes replace it, many examples are known of species which, while having the crystalline form, hardness and other external characters of these minerals, contain portions of alumina which may equal six or eight per cent., and even in some cases twice that amount. In these instances there is at the same time a notable diminution in the silica, and the view was hence suggested by v. Bonsdorff, and sup- ported by Scheerer, that alumina is to be here regarded as replacing silica in the proportion represented by A1 8 O 3 = 2SiO2, so that by making it was possible to bring the formulas of these aluminous species in accordance with those of non-aluminous amphiboles and pyroxenes.* 335. The application to the solution of the problem thus pre- sented of the principles of polymerism and of homology which have since been recognized, now permits another explanation of this apparent replacement, which is here set forth in detail for the first time. As shown in a previous chapter (203, 205), the concep- tion of polymerism of negative or acidic oxyds put forward in 1853 in the case of silicates and carbonates, was soon after supple- mented by the recognition of polystannates, polyphosphates, poly- molybdates and polytungstates, often of very high equivalents. With this, moreover, came the discovery that besides this homo- geneous condensation or polymerism there is often also a hetero- geneous condensation, in virtue of which these groups unite with other negative oxyds in different proportions. In this way are * Gmelin's " Handbook of Chemistry," Cavend. Soc. Ed., iii., 403. Argillinea. 2G1 generated homologous compounds in which the first term is unlike the common difference. Examples of this are seen in the silico- tungstates, in similar phosphotungstates, and again in the bori- tungstates and the aluminimolybdates. These compounds are, for the most part, soluble in water, and hydrated, but certain of the polytungstates are anhydrous and insoluble. 336. The many native aluminous silicates afford illustrations on a still broader scale of such homologous series of complex nega- tive or acidic oxyds, by the study of which much light is thrown upon the history of these mineral species. We find therein, in fact, the existence of a great homologous series of aluminisilicates com- parable in extent and completeness to those previously known among the hydrocarbons. The general formula of these complex negative oxyds is or rather a multiple of this, so that in order to avoid fractional values for n, and the objection of high numbers in calculation, it will be better to write the formula in monadic notation, thus : A comparison of well-known silicates with this general formula will show for the negative element therein values for n from 3 in sapphirine, and 8 in chloritoid, andalusite and kyanite, to 16 in thomsonite, meionite, sodalite, anorthite and muscovite ; 20 in iolite and wernerite ; 24 in natrolite, garnet, prehnite, lepidolite and ripidolite ; 30 in idocrase and spodumene ; 32 in leucite and hyalophane ; 36 in oligoclase, melilite, pargasite and phlogopite ; 48 in orthoclase, albite and stilbite ; 60 in petalite, and 96 in leucau- gite ; the latter being a so-called aluminous pyroxene containing about seven per cent, of alumina. Still higher members of this homologous series doubtless exist, in which the value of the first term, or, in other words, the proportion of alumina, becomes stochio- metrically insignificant. 337. In studying the order Argillinea it is clear that we have to deal with three kinds of compounds : First, the amphids, in which the negative element is combined with positive oxyds, either with or without the addition of water, as in the zeolites and feld- spars ; second, the hydrates of the negative element, as in pyro- phyllite and kaolin ; and third, the anhydrids like topaz and anda- 262 Systematic Mineralogy. lusite. In arranging in genera these numerous species we begin with those hydrated sparry species, the zeolites, which of them- selves constitute a large genus, and were subdivided by Breithaupt into not less than fourteen genera. The generic name of Zeolithus,, here adopted, was employed by Cronstedt in 1756. Many of these zeolites differ from each other, chemically, chiefly in the proportion of combined water, a matter which will be noticed at length far- ther on. 338. Coming next are the feldspars, a large and important group of anhydrous spathoid species, which it is proposed to include in a single genus. The name of feldspar is of German origin, and was given because the mineral is common in the masses of crystal- line rock met with in certain regions in the fields (Felderi). It appears in the form of felt-spat in Wallerius, in 1747, while feld- spath was given by Cronstedt in 1780, and later by Werner in 1879, and by Mohs in 1804. Hausmann in 1813 wrote feldstein. Before this date, and early in the century, English writers had adopted the vicious spelling, felspar, and Kir wan called a compact f eld- spathic rock, felsite. Later, in 1847, Breithaupt, who, as we have seen (23), refused the designation of spar to minerals of this character, substituted for feldspar the name, in Latin form, of felsites, as if from the German fels. As, however, the word feld- spar is, in any case, barbarous in its etymology, it becomes desi- rable to change it, and to substitute in its place the name Agroli- thus (Gr. aypof, field, and A/%, stone). To devise such a name is not to invent but simply to translate. The use and significance of the different designations given to various species of this genus, as orthoclase, albite, anorthite, etc., will be noticed farther on. 339. Following the plan adopted in the preceding orders, we shall here notice briefly the other genera into which it is proposed to divide the remaining species of the order. After Zeolithus and Agrolithus is placed Scapolithus, a group of species having close relations with the last, followed by another group including, with nephelite and leucite, the species sodalite, nosite, haiiyene and can- crinite, comprised in the genus Alcalites. Coming now to the micas and the chlorites, these are included under two genera, Phengites and Astrites. Succeeding species are arranged in the crystalline genera, Idocrasius, Epidotus, Granatus, Granatinus, Acmitodes, JBeryllus, and Spodiolithus, followed by two genera of uncrystalline or amorphous species, Porodites and Amorphites, which last completes the amphid genera of the order. The hydrates Argillinea. 263 of the negative element are represented by the crystalline genus Pyrauxites and the uncrystalline genus Argillithus, while the anhydrids of the order are included in the genus Topazius. Genus 1. ZEOLITHUS. 340. The zeolites are hydrous aluminisilicates, the bases being for the most part lime and soda, which replace one another more or less completely in the same species. Not infrequently they contain more or less potash, and more rarely baryta and strontia ; while in the rare species pollucite analysis shows the base to be ZEOLITHUS. form. P d V H xl 1 Z. Thomsoni.. Thomsonite . si 4 aZ 3 ca 1 o 8 .24aq. 16.1 2.4 6.8 5 2 " Gismondii . Gismondite. . 8i 4 aZ,ca 1 o 8 .4aq .. 14.6 2.3 6.4 5 T 3 " natreus Natrolite si 6 al s na, 1 o 10 .2a*i. 15.8 2.3 6.8 5 4 " medius Mesolite sieaZaCa^Q.Saq . 15.3 2.3 6.6 5 C 5 " Edingtoni.. Edingtonite . sigaZgba^o.Saq . 18.8 2.7 6.1 4.5 T 6 " Levynii Levynite .... sigaZgCajOjo.Saq . 14.5 2.2 6.6 4 B 7 " caeseus Pollucite sisaZgmjOia.laq.. 21.8 2.9 7.5 6 I 8 " Analcites... Analcite Bl 8 al t 'na, 1 o 19 .2suq_. 15.7 2.3 6.8 5.5 I 9 " Laumontii . Laumontite . 8i 8 oZ 8 ca 1 o 18 .4aq. 14.9 2.3 6.5 3.5 C 10 " Phillipsii . . Phillipsite . . . sigaZgCajOig.Saq . 14.5 2.2 6.6 4.5 C 11 " Chabasites. Chabazite . . . sigaZgCaiC^.Gaq . 14.2 2.1 6.7 4.5 B 12 " Faujasii Faujasite. . . . 8i 1 oZ 8 ca 1 o 14 .lOaq 13.3 2.0 6.6 5 I 13 " Beudantii.. Hypostilbite . sijoaZjjCaiO^.eaq 14.1 2.2 6.4 4 02 14 " baryteus . . . Harmotome . si to aZ 8 ba 1 o 14 .5aq 17.0 2.5 6.8 4.5 C 15 " stronteus. . . Brewsterite. . siigaZgSrjOie.Saq. 15.6 2.4 6..5 5 C 16 " Heulandii . Heulandite... si^aZgCa^e.Saq 14.5 2.2 6.6 4 C 17 " splendens... Stilbite si 12 aZ 8 c ai o 16 .6aq 14.1 2.2 6.4 4 C two-thirds caesia and one-third soda. Edingtonite and harmotome are barytic species, while brewsterite contains chiefly strontia with smaller portions of baryta and lime. Under the name of thomson- ite are included sub-species in which, as in the so-called ozarkite, three-fourths of the base is lime, and others in which as large a pro- portion is soda. Natrolite is essentially a soda-zeolite, while lime predominates in the closely related mesolite, and the name of 264 Systematic Mineralogy. scolecite is given to a mineral having the same general formula as the last two named, but containing lime, to the exclusion of soda. Small portions of potash are found in many zeolites, while in phil- lipsite it occurs in notable proportion. In fixing the value of p in the present table, it is to be said that, with the exception of the few cases noted, the calculation has been made as if lime alone was present ; the difference between the value thus arrived at and that which would obtain were soda substituted, being so small as to be within the limits of error in the case of species of which the specific gravity is so imperfectly determined as in most of this genus. In- deed it may be remarked that with the exception of the feldspars, the tourmalines, topaz, emerald and a few other gems, with quartz and calcite, our knowledge of the specific gravity of mineral species is still in a very imperfect state. It should be said that the above table of the genus Zeolithus includes only the more important and characteristic zeolites, and that many species having place in our text-books are omitted. Farther, it is to be said that in the case of thomsonite, the late studies of Cross and Hillebrand of the remarkable deposits of zeo- lites in the basalt of Table Mountain in Colorado have shown that the mineral having the general character of thomsonite, and there associated with stilbite and with laumontite, is more silicious than thomsonite itself, being intermediate in composition between it and natrolite, and approaching to the ratios of iolite and bytownite in the genus Agrolithus ; while apparently a definite compound which may constitute an intermediate species.* 341. The water in zeolites is retained with various degrees of force, a greater or less portion of it being readily lost or regained in most cases by slight changes of temperature or of atmospheric humidity. Some varieties of laumontite effloresce by exposure to the air ; that is to say, they become opaque, and finally crumble from a partial loss of water, so that to preserve the crystals unchanged they must be kept in moist air or in water. Many observations by different observers are recorded, but the careful comparative exper- iments of Damour, made many years since, throw so much light on this question of the water of zeolites that a partial abstract of them is here given. The minerals having in all cases been reduced to a coarse powder, and kept in a room where the temperature varied from 12 to 18, were submitted to the following experi- * " Mineral Physiology, 1 ' pp. 13&-142. Argillinea. 265 merits, a gramme being used in each case. Stilbite, containing 19.20 per cent, of water, lost after a month in perfectly dry air 3.6 per cent., which it regained after exposure to free air for two days. At 100, in an hour it lost 1.3, and after another hour, at 150, 13.0 per cent., but after five days in free air this loss was reduced to 3.1 per cent. Harmotome, with 14.7 of water, lost in dry air after six months, 4.3, and by a temperature gradually raised to 190, and maintained at this point for two hours, 13.5 per cent.; the whole of which it regained by exposure to free air for twenty-four hours. Heulandite, with 15.8 of water, lost in dry air, after a month, 3.75 per cent., which it wholly regained after twenty-four hours in free air. Heated to 190 for two hours, it lost 12.3 per cent., a great part of which it regained in free air ; but after two months the loss was still 2.1 per cent. Chabazite, containing 22.4 per cent, of water, lost in two hours at 300, 19.0 per cent., the whole of which was again absorbed after forty-eight hours in free air. Levynite, with 21.0 per cent, of water, lost in dry air, in nine months, 6.4, but after twenty-four hours in free air not only regained its loss but aug- mented 0.3 per cent.; while after exposure to a humid atmosphere for a month it gained not less than 7.2 per cent., which it lost again in free air. Faujasite is still more hygroscopic ; containing 27.0 per cent, of water, it lost not less than 15.0 during a month in dry air, but by exposure to free air for two days the loss was reduced to 0.6 per cent., after which the weight of the material varied from 0.2 to 0.3 per cent., according to the condition of the atmosphere. In an hour, from 50 to 55, it lost 15.2, and between 60 and 65, for another hour, 16.4 per cent., but after three days in free air the loss was reduced to 0.2 ; while at 100, in an hour, the loss was not less than 21.0 per cent., which after three days in free air was reduced to 0.1 per cent. Scolecite, with 13.9 per cent, of water, on the contrary, lost nothing in dry air, or at 100, but at 160 lost 4.3 per cent., and at 300 during two hours, 5.0, the whole of which it regained after twenty-four hours in free air. Mesotype, with 9.7 per cent, of water, did not change in dry air, but at 150 lost 5.0, at 240, 9.5 per cent., and finally, after one and a-half hours, at 290, lost 9.6 per cent., all of which it regained after two days in free air, augment- ing moreover 0.3 per cent. Thomsonite, with 13.3 per cent., was scarcely changed in moist or dry air, but lost 6.10 at 280, while after forty days in free air this loss was reduced to 1.5 per cent. Analcite showed no change in moist or dry air, but lost at 310, 266 Systematic Mineralogy. after two hours, 7.0 per cent., which it did not regain in free air.' 342. The intumescence which the minerals of this genus present when heated before the blowpipe, which has given to them the name of zeolites, would seem to indicate that a melting takes place before the complete expulsion of the water ; or, in other words, that the zeolite is partially liquefied in its combined water. The zeolites are all attacked by acids with pectization or separation of gelatin- ous silica. The zeolites are for the most part so similar in chemical com- position that in choosing specific designations for them it has been found convenient to adapt in many cases to the new nomenclature their trivial names. The minerals of this genus have been with justice described as hydrated feldspars, and farther observations as to their relation will be given in connection with the next genus. Genus 2. AGROLITHUS. 343. Of the species of the important genus Agrolithus which includes, with some others, all of the minerals usually designated as feldspars, we notice first that of the well-known series of which the two terms are anorthite and albite, between which in the table we have placed five intermediate species. In a previous chapter AGROLITHUS. form. P d V H xl 1 A., cdlcareus Anorthite . . . By townite . . . Labradorite . Lavalite Andesite .... Oligoclase . . . Albite siiaZgcajOg sigaZgCaiOj, ... si^ca^o ... sifdZgiia^n ... sigCtZ 3 na 1 o ls . . . sigaZjjna^s. .. si 18 aZ 3 n ai o 16 .. si^al^o^ ... si^aZgknOig .. si 8 aZ 8 bakio 12 . si^aZJiiOsg ... 8i 5 aZ 8 mgffeo 9 . 17.4 17.1 16.9 17.0 16.8 16.7 16.4 17.4 17.4 19.4 15.3 16.8 2.75 2.73 2.70 2.69 2.68 2.65 2.62 2.54 2.54 2.80 2.42 2.67 6.3 6.3 6.3 6.3 6.3 6.3 6.3 6.8 6.8 6.9 6.3 6.3 6 6 6 6 6 6 6 6 6 6 6 6 A A A A A A A A C C C H 2 " medius 3 " Ldbradorensis . 4 ' ' insignis 5 " Andesianus .... 6 " Oligoclasius. . . . 7 " albus 8 " microclinus 9 " orthotomus 10 " baryteus Microcliu Orthoclase . . Hyalophane . Petalite lolite 11 " Petalites 12 " magneseus * Damour, 1837, Ann. de Chim. de Phys., III., liii. Argillinea. 267 (160), the question of the relations of these to each other has been already discussed, as well as the grounds upon which the present writer formerly maintained, with v. Waltershausen, that all of them might be regarded as crystalline intermixtures of the two extremes, and consequently that the intermediate species then already named were not to be admitted to that rank. That such mixtures exist, is undoubted, but the writer has long since aban- doned as untenable the view held by him in 1854, and as late as 1863,* and afterwards advocated by Tscherinak, believing on the contrary in the distinctness and integrity of the intermediate species ; in which nevertheless the evidences of mechanical inter- mixtures are numerous, as will be shown farther on. It was under the influence of that early hypothesis that he, in 1854, rejected the claims of bytownite, and what he has since called lavalite, to the title of species. The evidences of a feldspar intermediate between anorthite and labradorite, alike in the indigenous gneissoid rocks of the Norian series and in intrusive granitoid masses of paleozoic age, has been shown in several analyses by the writer, and by others. The name bytownite, by Thompson in 1836, has priority over that of barsowite given by H. Rose to a similar feldspar in 1839. That of lavalite is now given to a feldspar intermediate between labra- dorite and andesite, found in more than one locality in the Norian rocks in Canada, and remarkable for the great size and beauty of its lavender blue semi-transparent individuals, often three or four inches in length by an inch in thickness ; as already described in 1855.f Other species, intermediate between oligoclase and albite, may no doubt be recognized. The further argument as to the independence of these feldspars will be noticed after a consideration of the genera Scapolithus and Alcalites. The composition of the feldspars in question varies from a purely calcareous species, anor- thite, to a purely natreous species, albite ; though to these there are exceptions, since small quantities of soda are sometimes met with in anorthite, and of lime in albite, while a little potash may occur alike in these and in the intermediate species ; in which the lime diminishes and the alkali augments as we pass from the less to the more silicious species. Magnesia is generally absent, or present in small quantities only, though in anorthite it occasionally rises to four or five per cent. * "Geology of Canada, 1863," p. 480. f L.i E. andD. Philos. Mag., May, 1855 ; " On Some Feldspathic Eocks ; " analyses ix., 268 Systematic Mineralogy. 344. The condensation in all these feldspars is essentially the same, and serves to distinguish them from the next three species, mi- crocline, orthoclase and hyalophane, in which v is notably higher. The crystallization of the anorthite-albite series is doubly oblique or anorthic, while orthoclase and hyalophane are clinorhombic. Microcline, while having the same chemical composition and den- sity, differs from orthoclase only in being anorthic in crystalliza- tion. It is scarcely distinguishable from orthoclase, with which it is often intimately associated, except by, the use of polarized light. In the green feldspar known as Amazon stone, microcline is thus found mixed with orthoclase, and occasionally also with albite. Again, in the so-called perthite, a banded red and white feldspar, found in large cleavable individuals, the white layers, of one or two millimetres in thickness, are albite, and the similar red ones an admixture of orthoclase and microcline, colored by included laminae of hematite. It has been found possible to separate the red and white layers in perthite, and to show the former to be a pot- ash-feldspar with the specific gravity of orthoclase, and the latter a soda-feldspar with the specific gravity and composition of albite. The occurrence of microcline is now known to be very frequent, and it may be said that this particular feldspar has received an attention more than sufficient when it is considered that it differs from orthoclase solely by a little variation of geometric form, which causes it to be included in a distinct crystalline system. 345. Other facts with regard to the intimate associations of dif- ferent feldspars may here be noticed. Thus in the eruptive dolerites of New Jersey the late Mr. Hawes found that the crushed feld- spathic portion could, by the aid of Sonstadt's solution, be separated into two parts, a lighter with the composition of andesite, and a heavier having that of labradorite. In the lava of Krakatoa, already noticed, while some crystals were of anorthite and others of labradorite, others still were found to be made up of these two feldspars, from which the first could be removed by solution in acid, leaving behind the labradorite (184). In like manner, in a lava from Santorin, labradorite is associated with albite and with anorthite. It is probably, as was suggested by Hawes, a question of slight change of condition whether two or more feldspars shall be formed by division or an intermediate species be produced. "We may go farther, and say that it depends upon similar con- ditions whether a feldspar or zeolite, an anhydrous or a hydrous species shall be formed. Orthoclase occurs, like zeolites, in amyg- Argillinea. 269 daloids with chalcedony, and both it and albite are found in veins in the mesozoic diabases of Massachusetts and New Jersey, together with various zeolites, as shown by the observations of Emerson and of Kunz. In the ancient amygdaloids of the Keween- ian series on Lake Superior also, as shown by Whitney, and since more fully by Pumpelly, orthoclase is found with laumontite, analcite, prehnite and epidote, alternating with and even posterior to the zeolites. Garnet, tourmaline, axinite, sphene and magnetite are also found in these associations, and under similar conditions.* 346. As regards the composition of microcline and orthoclase, while potash generally predominates therein, sometimes to the exclusion of soda, at other times a considerable portion of this base enters, from two to three up to seven or eight per cent. Baryta, in small amounts, up to two or three per cent., is occasion- ally met with in orthoclase. Hyalophane, a feldspar in form and condensation like the last, but with the general formula of andesite, contains chiefly baryta, with some potash. An anorthic form of this feldspar corresponding to microcline has been met with, besides another clinorhombic feldspar, unnamed, which also con- tains a little baryta, and is intermediate in composition between hyalophane and orthoclase. We have followed Breithaupt in including petalite in this genus, to which it unquestionably be- longs, and we retain for it, as well as for oligoclase and microcline, the specific names given by that mineralogist. lolite or cordier- ite we have also placed in the genus, as a magnesian feldspar. Magnesia, which in other feldspars is seldom over one or two or -at most five per cent., is here the predominant base, though accom- panied by from four to ten per cent, or more of ferrous oxyd. Genus 3. SCAPOLITHUS. 347. This genus was formerly regarded as having between the oxygen of the contained aluminic and the positive or basic oxyds the ratio of 2 : 1, that of the feldspars being 3:1. The recent careful studies of Tschermak have, however, shown that this ratio for the scapolites is more correctly expressed by 2J : 1, or 9 : 4. In fact, a series of scapolites corresponding to the anorthite-albite series among the feldspars, has for its extremes meionite and marialite ; the intermediate scapolites, wernerite, eckebergite, mizzonite and dipyre or courzeranite, corresponding to each one of the interme- * Mineral Physiology, pp.420, 121, 138, 143. 270 Systematic Mineralogy. diate feldspars, with the exception of oligoclase, no representative of which is as yet known in the scapolite series. As will be seen by reference to the present table of the genus, these scapolites may be represented as derived from the corresponding feldspars by the addition, in each case, of m^ (m = ca or na). As regards the specific names given to the true scapolites the first six species SCAPOLITHUS. form. P 17.8 17.5 17.3 17.0 16.9 16.7 18.9 19.5 16.4 d V 6.5 6.5 6.4 6.5 6.5 6.4 6.5 6.5 6.3 H xl T T T T T T T T O Meionite. .. Wernerite . Eckebergite Mizzonite. . Dipyre .... Marialite . . Melilite. . . . Gehlenite 2.75 2.7 2.7 2.6 2.6 2.6 2.9 3 2.6 5.5 5*. 5 5.5 5.5 5.5 5.5 5 6 6 2 " Wernerii.... 3 " Paranthinus. 4 " major 5 " Porcellanites . 6 " Andradii.... 7 " flavus 8 " Gehlenii 9 " Milarites Milarite. . . . in the table S. minor and S. major are translations of their trivial names ; S. Wernerii recalls the original name of the species, while that of S. Paranthinus or paranthite was given by Breithaupt to a scapolite apparently corresponding to eckebergite. S. Andradii commemorates the name of d'Andrada, the Portuguese mineralogist who first recognized and named scapolite as a mineral species ; and who was also the fortunate discoverer both of petalite and of spodumene. 348. The porcelain spar or passauite of Fuchs, found near Passau in Bavaria, was by Breithaupt regarded as a feldspar, and by him named felsites Porcellanites. Later examinations, however, show the mineral to be a scapolite, which from the analysis of Schaf- hautl was regarded as probably eckebergite, somewhat altered. A later analysis of the fresh unchanged material, by Wittstein, cited by Zirkel, however, shows a composition more silicious, and nearer to dipyre than eckebergite, or even than mizzonite. It is not improbable that more than one species of the genus may occur in the region where this porcelain spar abounds. Meanwhile the name of 8. Porcellanites is provisionally given to dipyre, as in the Argillinea. 271 table, until farther investigation shall have settled the question. The decomposition of this scapolite gives rise to a porcelain-clay differing somewhat in composition from that of the more silicious feldspars, as will be seen farther on. The base in the less silicious scapolites is chiefly lime, which is to a great extent replaced in the more silicious ones by soda, together with variable amounts, gen- erally small, of potash. Small quantities of chlorine are met with in many scapolites, varying from traces to 2.7 per cent. 349. The species melilite or humboldtilite and gehlenite are appended to the scapolite genus, since, although they have not the same general formula, their affinities are with the scapolites. Melilite, which occurs in many eruptive rocks, is also found in furnace -slags, and may be made artificially by fusion. The native species often contains more or less soda and magnesia, and may have the alumina in part replaced by ferric oxyd. An artificial melilite has been made both with and without ferric oxyd. Sar- colite is nearly related to this species, if not identical with it. Native gehlenite, in like manner, often contains a little ferric oxyd, but is also found in furnace-slags, when it is without iron, and contains a little sulphur, amounting in a specimen examined by Percy to 1.5 per cent. We here place milarite, which has been referred to the zeolites on the one hand, and compared with petalite on the other. Ludwig represents the small amount of water contained in this mineral as replacing a portion of the fixed bases. If we take one-sixth of the positive element to be potassium and one-sixth hydrogen, we arrive at the formula given for milarite in the above table. It is to be repeated that, in the writer's opinion, our chemical formulas in many cases, as in the present, although serving to show the inter- relations of species, are but approximative (221). We have already noticed (160) the relations of the scapo- lites to acids, and the reasons for including them among spathoids. The feldspars, in the same way, though they resist the action of chlorhydric acid, except in the case of anorthite, are ranked as spathoids, since they are all readily attacked by dilute fluorhydric acid, and, moreover, easily suffer subaerial decay, giving, at least in the case of the more silicious species, a residue of kaolin. Genus 4. ALCALITES. 350. We pass next to this remarkable genus, characterized by an unusual proportion of alkalies, and hence named by Breithaupt 272 Systematic Mineralogy. Alcalites. In tnis genus he included, besides leucite, sodalite, nosite, haiiyene and lapis lazuli, to which we add the related can- crinite (since made known) and nephelite. Of these minerals, leucite has the same general formula as andesite and hyalophane, but with a base of potash, and is, moreover, less condensed than either ; while nephelite approaches anorthite, or rather is a species intermediate in ratios between anorthite and bytownite, having as its positive element, however, soda with a little potash. Of the remaining species, which are, as regards composition, the most ALCALITES. form. P d V H xl 1 A., muricitus . . Sodalite ... sii#X, na, Ou. Hna., cli) . 19 4 9, 3 8 4 5 5 T 2 " vitriolatus. Nosite si^ftZQiiaiOa.^diaiSiO,.) 17 7 2 4 7 3 5 5 T 3 " aypseus. . Haiiyene si4dZ 3 na 1 Og.4(ca 1 s 1 O4) 17 6 9, 5 7 5 5 T 4 " carbonatus. 5 ' ' sulphureus. Cancrinite. . Lapis lazuli . 8i 4 aZ 8 na 1 o 8 4(c 1 na 1 o 8 ). 17.2 2.5 9, 4 7.0 5.5 5 5 I T 6 " natricus . . 7 " Tcalicus .... Nephelite.. . Leucite si 4 . 5 aZ 8 na 1 o 8 . 5 8i 8 oZ 8 k 1 o 18 18 18.1 2.6 2.6 6.9 7.0 5.5 H T noteworthy of the genus, they may be represented as a silicate having the composition of a soda-anorthite, united, not as in meio- nite with calcium oxyd, but, in the case of sodalite, with sodium chlorid, in nosite with sodium sulphate, and in haiiyene with calcium sulphate, as in the formulas given in the table. It should be clearly understood that the adoption of these formulas is but an expedient to bring before the eye the nature and proportions of the contained elements, and that no dualism in constitution is intended to be expressed thereby. Near in composition to nosite is microsommite, while under the name of ittnerite has been described a hydrous species closely related to haiiyene. 351. Lapis lazuli is a species having affinities with nosite and with haiiyene, and remarkable for its deep blue color, which makes it a valuable pigment, known as ultramarine. Its chemical compo- sition is not clearly understood, though it is now made artificially on a large scale by calcining a mixture of an aluminous silicate, such as kaolin, with sodium carbonate and sulphur. The compo- sition of the artificial product varies considerably, but like the Argillinea. 273 natural species, it is apparently a sulphato-aluminisilicate related to nosite, but more silicious, and holding, besides much oxydized sulphur, a small portion so combined that it is liberated as hydro- gen sulphid by the action of even feeble acids ; which decompose it, with gelatinization, like nosite and haiiyene. At the same time, as has already been pointed out (209), this artificial ultramarine does not give a sulphid with silver solutions, but on the contrary a yellow substance containing silver, from which it is possible, in the humid way, to regenerate the blue ultramarine. 352. We come next to the consideration of cancrinite, which has been regarded as nephelite that has taken up carbonate of lime and water. The proportion of carbon dioxyd contained therein is, how- ever, much greater than that required to unite with the lime present, which shows that it must be integrally combined ; forming, in fact, a mg p ,.Oi r.4ao 15 6 a 7 5 8 1 5 H 3 " chromifer... 4 " fldvus Penninite . . Jefferisite si 6 (aZ 3 . B cr. B )mg 5 .o 14 .4aq sirfaZafei^mfiTaOi 24aa 15.6 15 8 2.7 2 3? 5.8 2 1 5 R ? 5 " eupricus . . . Venerite... siio(aLfei)merr.MCu 9 . K Oo.8aq. 17 9 9, ? 6 ' ' Thuringites . Thuringite 8i(otZof6i)feoO fi .2aci . , 19 5 3 9, 6 1 9, p 7 " Cronstcdii . Cronstedite si^ffiofeoOi n.3aci 91 3 5 6 o 5 R 278 Systematic Mineralogy. The formula here given for the latter represents a variety in which chromic oxyd replaces a portion of alumina, and which has been described by the names of rhodochrome and kammererite. Near to these is the cupric species venerite, of which the chemical composition and microscopic characters alike show its distinctness.* The name of jefferisite has been given to a mineral provisionally placed in this genus, which resembles the so-called vermiculite, * The species which was described by the writer in 1876 is found in the Jones (or Johannes) mine, in Carnarvon, Bucks County, Pennsylvania, long known as a large de- posit of magnetite associated with chalcopyrite, malachite, chrysocolla, and a substance which had hitherto been called clay-carbonate ore, of which several thousand tons, yielding from six to seven per cent, of copper, had up to that time been mined and utilized in smelting. These ores are found in the Taconian crystalline schists of the region, the so-called Primal slates of Rogers, and the mineral in question is distributed in greater or less abundance through several feet of the strata, alternating with layers of a coarser granular material, poor in copper, the whole marked with ferruginous bands which coin- cide with the bedding, and are intersected with veins of quartz. Layers of half an inch or more in thickness were found to contain ten or twelve per cent, of copper. *' These pure portions have a pea-green or apple-green color when moist, becoming greenish-white on drying, when the mass falls into a powder, which is seen under the microscope to consist of minute, transparent, shining scales, mixed, however, with some grains of quartz and a small portion of magnetite. A qualitative examination of this material showed that it contains no carbonates, and is not of the nature of a clay, but consists of a hydrous silicate of magnesia, copper-oxyd, alumina, and iron-oxyd. It is but feebly attacked by dilute acids, while strong acids, and notably sulphuric acid diluted with two or three parts of water, and aided by a gentle heat, readily and completely de- compose it, with separation of flocculent silica, which, by solution in dilute soda-lye, is readily separated from the accompanying quartz and magnetite. A single somewhat rough analysis made in this way gave for 100 parts : insoluble sand, 14.10 ; silica, 24.60 ; alumina, 13.00; magnesia, 15.15; ferric oxyd, 7.11; cupric oxyd, 15.30; water, 11.50 = 100.70. The qualitative examination of a considerable portion of another and less pure specimen gave an appreciable quantity of zinc and a distinct trace of nickel. A portion of the specimen of this copper-silicate of which the analysis is given above, was freed by careful washing alike from the coarser grains and from the lighter portion, which re- mained long suspended in water. The material thus purified was somewhat richer in copper than before, and has been carefully analyzed by my friend, Mr. George W. Hawes, of New Haven, who found : insoluble sand, 6.22 ; silica, 28.93 ; alumina, 13.81 ; ferric oxyd, 5.04 ; ferrous oxyd, 0.27 ; magnesia, 17.47 ; cupric oxyd, 16.55 ; water, 12.08 = 100.37. This, deducting the insoluble matter, gives, for 100 parts : silica, 30.73 ; alumina, 14.67 ; ferric oxyd, 5.35 ; ferrous oxyd, 0.29 ; magnesia, 18.55 ; cupric oxyd, 17.58 ; water, 12.83 = 100.00. This, as remarked by Mr. Hawes, gives, on calculation, an oxygen-ratio between prot- oxyds, sesquioxyds, silica, and water, of 4 : 3 : 6 : 4, very nearly, which puts this mineral, if it be a homogeneous substance (as its microscopic characters would indicate), among the chlorites, some of which it resembles very closely in its atomic ratios. Before the blow- pipe, on charcoal, it swells, then fuses quietly into a black globule, giving the usual reac- tions for copper. The iron is almost wholly in the state of sesquioxyd, as shown by two determinations of the amount of protoxyd of iron, which gave, respectively, 0.27 and 0.29 per cent. This copper-chlorite appears, alike from its physical and chemical characters, to constitute a distinct mineral species, for which I propose the name of VBNERITE, in allusion to the mythological and alchemistic name of copper." ("A New Ore of Copper and its Metallurgy," Trans. Amer. Inst. Mining Engineers^ iv., 325.) A microscopic examination of this curious chlorite will suffice to show its distinctness, and the judgment of Hawes thereon is confirmed by that of Descloizeaux, according to his private com- munication to the writer. Argillinea. 279 and is perhaps a partially decomposed and hydrated magnesian mica. In thuringite and cronstedite we have examples of the par- tial and the complete replacement in this genus of alumina by ferric oxyd. Genus 7. IDOCKASIUS. 358. Passing from the phylloids to the denser and adamantine species of the order we have, as already mentioned in 339, first the genus Idocrasius. Under this name (from that of idocrase origi- nally given by Haiiy) Breithaupt has indicated not less than six species, all of which would probably come under the head of the original idocrase, the vesuvian of Werner, with the exception of colophonite. Much of the mineral bearing that name, though gen- IDOCRASIUS. form. P d V H xl 1 I. phlogogenius. Vesuvianite . SirCtZoCEoOt . 19.3 3.4 5.7 6.5 T 2 " hydratus Prehnite sieoZ.ca.On.laq 17.1 3 5.7 6.5 C 3 " Glaucophanus Glaucophane si 9 aZ 8 mg 2 fe. 6 na. B o 14 . 17.3 3.1 5.6 6.5 C 4 " Gastaldianus. Gastaldite . . . si 6 aZ 3 fe. 6 na. 5 o 9 17.4 3 5.6 6.5 C 5 " amphibolus.. . Pargasite. . . . 8i,oZ 1 mg 1 . B fe. B o 6 .... 17.7 3.1 5.7 6 C 6 " albus Leucaugite . . sigaZjCaamgjjOja 17.9 3.2 5.6 6.5 C erally regarded as a garnet, is, according to Breithaupt, a variety of idocrase. Here we place prehnite, a hydrous species whose con- densation and insolubility assign it a position here rather than among the zeolites,- where it was placed by Shepard. To this same genus also are referred three species, namely, glaucophane, gastal- dite and pargasite, which, as they have the crystalline form of am- phibole, have hitherto been included with it ; and moreover leuc- augite, another aluminous species having the crystalline form of pyroxene. Genus 8. EPIDOTUS. 359. Coming next to Epidotus, we include in this genus alike the pure lime-epidote or zoisite, and the ordinary epidote in which ferric oxyd replaces a portion of alumina, piedmontite in which manganic sesquioxyd plays a similar part, and orthite or allanite ; 280 Systematic Mineralogy. which is regarded as a cerium-epidote, wherein the triad oxyds of the cerium metals replace not alumina but lime. To these we add saussurite, which appears to be chemically similar to zoisite, but is more condensed, and jadeite. It will be noticed that while the positive element in epidote and zoisite is lime, this in saussu- rite is replaced, to the extent of three or four hundredths, by soda. The jadeite of Damour is a more silicious species than these, related to zoisite as dipyre is to meionite, and here, as in the more silicious scapolites and feldspars, the replacement of the lime by soda is EPIDOTUS. form. form. p d V H xl 1 E. cdlcareus . . . 17 8 8 5 4 O 2 ' ' vulgaris Epidote SiottZf K f&. r Cell Oa . 19 4 3 4 5 7 O 3 " manganieus 4 " cereus Piedmontite . Orthite 19.3 20 5 8.4 3 8 5.7 5.4 ... C c 5 '* tendx Saussurite si al ca o 17 8 3 4 5.2 6 " Damourii . . Jadeite Si gttZgllJljOg 17.2 3.3 5.2 ... c? nearly complete. Until the late inquiries of Tschermak had shown that the oxygen ratio between these bases and the alumina is as 4 : 9,, it had been regarded as 1 : 2 ; zoisite and saussurite were hence con- sidered as isomeric with meionite, and jadeite with dipyre. As it is, the calculated values of p for the two formulas are the same to the first place of decimals, being in both cases 17.8 ; so that the argument drawn from the comparison of the species by the writer in 1863* is not affected thereby. As then suggested, we may look for species between jadeite and saussurite, corresponding to the in- termediate feldspars and scapolites. 360. Much interest is attached to saussurite for the reason that under the names of jade and nephrite more than one species of white or greenish-white mineral is known to have been employed alike among the Chinese, and among pre-historic races on both continents, for ornamental carvings. While some of this material has the hardness, specific gravity and chemical composition of amphibole, as already noticed (318), other specimens of it have a * Comptes Rendus de VAcad. des Sciences, June 29, 1863; also "Chem. and Geol. says," p. 446. Argillinea. 281 greater density, with a hardness and a composition which have led us to refer it to the present genus. The name of euphotide was- given by Haiiy to a rock found in Switzerland and in Corsica,, composed of diallage and a white compact mineral called by him feldspath tenace, and by de Saussure, the elder, jade. The late ProL Arnold Guyot having made a collection of erratic masses of this rock y and traced them to their source in Monte Rosa, generously placed them at the service of the writer, who was thus enabled to study the typical euphotide and its constituent jade, to which the younger Saussure had given the name of saussurite. Previous observers had, for the most part, confounded unlike substances of very differ- ent hardness, specific gravity and chemical composition under the common name of jade. Many, misled perhaps by Hauy's designa- tion, had described and analyzed feldspars near to or identical with labradorite, which is often present as an element in the composite rock in question. Saussure himself, however, found for jade a specific gravity of 3.26, Mohs 3.34, and Naumann 3.40 ; my own observations giving from 3.33 to 3.38. To the more silicious jade recognized in specimens from China, in 1863, Damour gave the name of jadeite. It will be seen in the table that the condensation for both of these species is considerably greater than for ordinary epidote. A late writer remarks to the effect that saussurite varies in composition from labradorite to zoisite, a confusion for which, since the publication of the writer's results in 1859, there is no excuse.* 361. The numerous analyses of orthite present great varieties alike in specific -gravity, hardness, solubility in acids, and in opti- cal characters ; moreover, while generally anhydrous, one variety contains not less than 12.0 per cent, of water, is yellowish in color,, and has a specific gravity of from 2.8 to 3.0. This, which has been called xanthorthite, I have elsewhere suggested is apparently related to the zeolites. The ordinary forms of the mineral, dark brown or black in color, have specific gravities varying from 3.3 to 4.1. Optical examination farther shows that while true orthite is clino- rhombic, and often well crystallized, much of the material bearing that name is isotropic, and is apparently amorphous. Sjogren sup- poses the mineral to have been at first deposited by infiltration, in a gelatinous form, and subsequently in part crystallized, while another part remains in a colloidal or porodic state. Similar ob- * " Contributions to the History of Euphotide and Saussurite, 1859," Amer. Jour* Science, II. , xxvii. 282 Systematic Mineralogy. servations have been made in the case of gadolinite, and it may be remarked, in passing, that the extension of a similar view to many other cases appears, in the present state of our knowledge, far more probable than the contrary hypothesis, which imagines a hydration of previously crystallized anhydrous species, whether orthite, zircon or corundum (197). Genus 9. GRANATUS. 362. The name of Granatus * was given by Albertus Magnus in the thirteenth century to the gem known to the Latins as carbun- culus, which probably included the ruby or red corundum, as well as the red garnet. In later times the name of granatus (Fr. grenat) or garnet has been extended to minerals of various colors, which are so closely connected with each other as to constitute a single genus. The composition of the garnets varies greatly within cer- tain limits, and it is possible, on chemical grounds alone, to divide them into several species. (1.) We have in the first place a garnet having for its negative element an aluminisilicate while the positive is a lime-silicate. This alumina-lime garnet con- stitutes what is known as grossularite, essonite, or cinnamon-stone, which is either white or yellowish, reddish, or pale green in color, from the presence of small quantities of other bases. (2.) The base in a second species is in large part magnesia, with a little lime and some ferrous oxyd, besides an amount of chromium, perhaps as chromous oxyd, equal in some cases to three or four per cent. This constitutes pyrope, the fine red Bohemian garnet. (3.) Another red garnet, the so-called almandite, has for its base in great part fer- rous oxyd, sometimes with a little lime or magnesia, while in (4) manganous oxyd is the predominant base, with, however, some f er- * We are told by one mineralogical writer that this name was given in allusion to the flower, and by another to the seeds of the pomegranate, both of which are red in color. This fruit, the malum punicum of the Romans, was also called granatum. The ovary of an insect known as coccus, which is found in a species of oak, being much used in dyeing a red color, was from its granular form known as granum ; whence the name of Granada given to the Spanish province from which came large quantities of this precious dye. From this was derived the word grain, used by English writers from the time of Chaucer in the fourteenth century, to designate a scarlet or crimson color. It is a plausible conjecture that both the granatum of the Romans and the granatus of Albertus Magnus were derived, like the English word grain as a color, from this red granum. In early English the pomegranate is called the "garnet-apple." See on this etymology '*' Marsh, Lectures on the English Language," lecture iii. Argillinea. 283 rous oxyd. This is distinguished by the name of spessartite. In some of the preceding garnets a portion of the alumina may be re- placed by ferric oxyd, a substitution which at length becomes com- plete, making a ferric garnet (5) in which the base is generally lime, sometimes replaced in part by manganese. The ferric-lime garnets have been by Dana embraced under the name of andradite, and include great varieties of color. Some of them are black, the GBANATUS. form. P d 3.5 3.7 4.2 4.2 4 3.5 V H 7 7 7 7 7 7 xl 1 G. grossularius . . 2 ' ' Pyropus Grossularite. Pvrope . . si 2 fl/ 1 ca 1 o 4 . . 18.7 18.7 20.7 20.6 21.2 20.7 5.5 5.0 5.0 5.0 5.3 5.6 I I I I I I si8aZimg.5fe.B04 si 2 a^ife 1 o 4 8i 8 aZ 1 mn 1 o 4 siofc-iCBitOA . 3 " Almandinus . . 4 " manganosus . . 5 " ferricalcareus . 6 " chromaticus. . . Almandite . . Spessartite . . Andradite . . . Ouvarovite . . si 2 c7" 1 ca 1 O4 . . so-called melanite ; others dark red, known as colophonite (see in this connection the genus Idocrasius) ; others still, dark green in color, or even pale yellowish and transparent, are the so-called topazolite. It is worthy of note that these light green and yellow- ish garnets, while containing as much as thirty per cent, of ferric oxyd, resemble grossularite in color. (6) The alumina in garnets is sometimes partially replaced by chromic oxyd, giving a pure green garnet, and in ouvarovite the replacement is complete. In rare cases a little yttria has been found in garnets, and titanic oxyd, sometimes to the amount of seven or eight per cent. The conclusion has been reached by Knop and Rammelsberg, and also by Konig, that in these cases a portion at least of the titanium is present as sesquioxyd, replacing alumina,* as was in a similar case suggested by the writer as long ago as 1846 (306). A highly titaniferous silicate described by the name of schorlomite, which has also been called ferrotitanite, is in like manner supposed to be a titanic garnet. 363. The garnets are adamantine in character, with a hardness of 6.5-7.5, resisting alike chlorhydric and fluorhydric acids, and are greatly condensed. Their specific gravity generally varies from * Amer. Jvur. Science, xxxiii., 425. 284 Systematic Mineralogy. 3.5 to 4.3, but in some cases is said to fall below the first figure named. So far as it is possible to fix the value of v, it would seem to vary from 5.0 to 5.4 and 5.6, as shown in the table. It is not improbable that in the garnets, as in the carbon-spars, the pyrox- enes and the epidotes, different species may present different degrees of condensation. To determine this question, however, will require many careful studies of specific gravity, confirmed with the analyses of characteristic specimens. Breithaupt, fifty years since, proposed in the genus Granatus not less than ten species, some of which cannot be maintained. We retain, however, the names which we can identify with the six species named in the above table, Genus 10. GRANATINUS. 364. The mineral known as staurolite, also called grenatite and granatite, the prismatoidal garnet of Mohs, is constituted a genus with a single species, by Breithaupt, as Staurolithus diagonalis. Wishing to unite with it sapphirine and some other species, we have devised the generic name of Granatinus. The two species just GRANATINUS. form. P d V H xl 1 G. decusscitus Staurolite . 18 1 3 7 5 7 O 2 ' ' caeruleus Sapphi rine 17 ?- 3 4 5 7 5 "I 4 1 6** 3 " viridis Chloritoid . siaaZgfeiOg.laq 18 3.5 5.1 6.5 C 4 " secundus... Ottrelite. . . si 6 aZ 4 fe ] o 11 .Haq... 16.3 3.3 5.0 6.5 T 5 " manganosus Ardennite . rf.crf.tvnn.o^.aaq 18.9 3.7 5.1 6-7 O named are remarkable as the least silicious known in the order AR- GILLINEA ; the value of n in the homologous series being for stauro- lite 7, and for sapphirine 3. Staurolite generally occurs in micaceous schists, and is in most cases impure, including greater or less quan- tities of quartz, besides in other cases, as already noted (185), mica, garnet, magnetite and brookite. We place here the chlori- toid of Rose (the chloritspath of Fiedler) which, for some unex- plained reason, has been classed by Dana among the hydrous micas. His chloritoid group includes besides this species, clinochlore, mar- garite and thuringite, and is placed just before seybertite. Zirkel Argillinea. 285 moreover makes it a member of the same group with seybertite, and Tschermak also puts it between the micas and the chlorites. Chloritoid, however, differs widely from all these minerals in its hardness, brittleness and condensation ; while its lamellar structure gives it no more title to a place among them than does the similar structure in hypersthene, in apophyllite or in foliated albite. In its physical characters, as regards hardness and condensation, as well as in composition, and in its mode of occurrence, it has many points of resemblance with staurolite. We therefore assign it a place in the genus Granatinus. Masonite and sismondine are probably only impure forms of chloritoid, but the similar ottrelite appears, from the analysis of Klement and Renard, to be a distinct and more silicious species, to which we assign a place in the above genus. Here also we place, provisionally, ardennite, a manganesian species containing, like the last two named, a little water, and moreover a certain amount of vanadium, equal to about 9.0 per cent, of V 2 O 6 (sometimes in part replaced by arsenic), which per- haps enters as a triad oxyd, as in the mica, roscoelite, by which sup- position we get very near the formula given above. In its hardness and condensation, as well as in composition, ardennite thus presents many analogies with the minerals of this genus. A small portion of the manganous oxyd in ardennite is replaced by lime and mag- nesia. Staurolite also contains more or less manganese, partially replacing iron, and in one variety is found about seven per cent, of zinc oxyd. Some analyses of staurolite give from one to two per cent, of water, but others show it to be anhydrous. Genus 11. ACMITODES. 365. We have seen in the micas, the chlorites, the epidotes and the garnets, that aluminic oxyd may be replaced partially and even wholly by the corresponding ferric, chromic and manganic oxyds, and to a certain extent by vanadic and probably by titanic sesqui- oxyd. The non -aluminous species resulting from such complete sub- stitutions should, strictly speaking, constitute separate orders, but inasmuch as the replacement is often but partial, so that there are intermediate compounds marking the passage from the aluminic to the ferric or other species, it is more convenient, for the purposes of comparative study, to consider them in the order ARGILLINEA. In acmite and arfvedsonite we have two important species, wholly ferric, in both of which the positive element is principally soda, 286 Systematic Mineralogy. with a little lime and ferrous oxyd. These two minerals, having respectively the crystalline forms of pyroxene and amphibole, have been by mineralogists united therewith, though they have only this mimetic resemblance, and differ from them fundamentally in chemical constitution. Aegirite, which has been made a distinct species, is probably identical with acmite, with which arfvedsonite also agrees in composition and specific gravity, while crocidolite is probably a fibrous form of the latter. Here also is apparently the place of the ferric silicate, babbingtonite, the analysis of which by Kammelsberg leads to the formula assigned in the table. Lievrite ACMITODES. form. P d V 5.5 5.5 5.9 6.2 6.4 6.5 H 6 6 6 6 6.5 ? xl C C A O ? 1 A., insignis Acmite ... sig/egnaj.Ojjj . siJ^naiO^... sij^caffefo^ Si 5 /e 2 ca 1 fe 2 o 10> Si4/e 8 pb a o 9 .... Si 4 ran 8 pb 2 o 9 .. . 19.2 19.2 20.1 22.8 40.3 40.2 3.5 3.5 3.4 3.7 5.7 6.2 2 " secundus Arfvedsonite. . . Babbingtonite.. Lievrite 3 " Babbingtonii.. 4 " Hvaites 5 " ferriplumbeus . 6 " manganiplumb. Melanotekite . . Kentralite or ilvaite is a similar ferric silicate, having for its positive elements lime and ferrous oxyd. Different observers have assigned to this mineral a specific gravity of from 3.7 to 4.1. Since, however, its hardness is rather under than over 6, and since it gelatinizes with chlorhydric acid, it is probable that the lower figure, which is assigned in the table, is near the truth, and that the higher specific gravity of certain specimens is due to the inclusion of foreign matter, perhaps, as suggested by J. D. Dana, of goethite. Mean- while we place here, provisionally, two rare and little-known lead- silicates, melanotekite and kentralite, containing ferric and man- ganic oxyds. These minerals also are decomposed by chlorhydric acid, and may probably be included in the present genus. Genus 12. BERYLLUS. 366. The Greeks gave this name to a sea-green colored precious stone of which Pliny speaks as probably " the same, or certainly of like nature, with the smaragdus " or emerald ; a conclusion sustained by modern mineralogy. The positive element in beryl is chiefly Argillinea. 287 the oxyd of beryllium or glucinum, but small portions of alkalies are also present, and in one variety has yielded 0.88 per cent, of by fixing lithium fluorid, lijfj, generates ambly- gonite, as in the table; or otherwise, with lithium hydroxyd, (l^hiOg) gives rise to monebrasite. It is by assuming the fluorif erous ambly- gonite as the normal species that montebrasite is said to be formed by the replacement of fluorine by hydroxyl ; that is of f t by h^. The simpler statement that the two species are alike derivatives of a normal tribasic phosphate, which has fixed, in the one case, an equivalent of a fluorid, and in the other an equivalent of a hydroxyd, has the merit of dispensing with a hypothetical radicle. A farther extension of the same principle is seen in childrenite and eosphorite, which have fixed a second equivalent of a hydroxyd ; while in goyazite is seen the integration of a third equivalent. 404. It may here be noted that while, as shown in 69 and 111, the value of p in anhydrous and in ordinary hydrous species is got by dividing the equivalent deduced from the empirical formula in monadic notation, by the sum of the oxygen co-efficients, or of those of the elementary bodies which may wholly or in part replace 316 Systematic Mineralogy. oxygen, a different case is presented in those compounds which include a portion of negative hydrogen. Such are the ordinary acids of the carbon series, and in the mineral kingdom certain com- plex phosphates, as already set forth in 213, 214, and as seen in Phosphasclerites. When the normal species fixes instead of n^clj, D^O! or hjOj, a hydroxyd, m 1 h 1 o 2 , the group h,o 8 becomes the equiva- lent of o 1? Sj, clj, and f l? and must be counted as a unit in calculating the value of p. 405. The curious amorphous substance containing lead-phos- phate and alumina, which has been named plumbogummite, may here be mentioned, to say that the observations of Damour and of others show great variations in its composition. Different specimens yield from 8 to 15 per cent, of phosphorus pentoxyd, from less than 3.0 to 34.0 per cent, of alumina, and from 35 to over 70 per cent, of lead-oxyd ; while the amount of water is variable, and the specific gravity ranges from 4.0 to 6.4. From one analysis by Damour it would appear that we have in so-called plumbogummite an amor- phous lead-phosphate near to pyromorphite, and in other cases an admixture of a similar phosphate with an aluminic hydrate ap- proaching gibbsite in composition. Genus 5. CALLAITES. 406. The trivial name of callaite has been given to the tur- quoise, which is supposed to be the callais of Pliny, and is an alu- minic phosphate colored by a small amount of cupric oxyd. This species, which is either porodic or cryptocrystalline, suggested the generic name of Callaites alike for the turquoise and for the crystalline species which we have placed within the table. From the specific gravity of turquoise it is inferred that its composition CALLAITES. form. P d V H xl 1 C. speciosus. . . . Turquoise . PsaJaOs.SCaZ^o^.Saq. 16.8 2.8 6.0 6 ? 2 " Peganites . . . Peganite . . p 2 aZ s o 8 .3(aZ 1 h 1 o 8 ).3aq. 16.2 2.5 6.5 4 O 3 " Fischeri Fischerite . p 2 aZ 3 o 8 .3(aZ 1 h 1 o 2 ).5aq. 15.3 2.5 6.1 4 O 4 " Wavellites.. Wavellite . Ps( aZ 8 o 8 .2(aZ 1 h 1 o 2 )4aq.. 15.0 2.5 6.0 4 O 5 " Variscianus. Variscite . . p 2 aZ 1 o 6 .2(aZ 1 h 1 o 2 )2aq.. 15.8 2.4 6.6 4 Arseninea. 317 is best represented by the formula in the table, and the same may be said of the other and less condensed species which are placed in the same genus. The composition of wavellite is doubtful, from the fact that from one to two per cent, of fluorine has been found in some analyses, but is perhaps as in the table ; while the constitution of variscite may also be as there represented. Other aluminic phosphates allied to turquoise have been described by the names of evansite, amphitalite and cirrolite, but their characters and their composition are not well defined. Genus 6. CACOXENITKS. 407. The ferric species, which we have included in the genus Cacoxenites, are rare and but little known. CACOXENITES. form. P d V H xl 1 C. Strengites.. Strengite. . . . p2/e 8 o 8 .4aq.... 15.6 2.9 5.4 4 O 2 " Eleonorites. Eleonorite... P8/e 4 . 5 o 9 . B .4aq. 16.1 .. . . .. . . 4 C 3 " viridis Kraurite Pofe^oi T.Baq . . 18 4 8 5 5 8 4 o 4 " vulgaris ... Cacoxenite. . . p2/e 6 0n-12aq.. 14.7 2.4 6.0 ? Order 17. ARSENINEA. 408. In this order are included all those compounds in which arsenic pentoxyd constitutes the negative or acidic portion. Less numerous and less important mineralogically than the phosphates, they may be included in three genera. Genus 1. PHARMACOLITES. Of these arsenates the first, and by far the largest, is one which corresponds to Phosphatites, and from pharmacolite, the trivial name of a characteristic species, is here designated Pharmacolites (Greek ^//a/cof, poison). 318 Systematic Mineralogy. PHARMACOLTTES. form. P d V H 2.5 2.5 3 1 3.5 2.5 2.5 3.5 3.5 4 4.5 3 4 4.5 2 3 2 4 5 3.5 2.5 2.5 xl 1 P. Haidingeri Haidingerite . . Pharmacolite. . 19.8 17.3 15.7 15.4 22.5 18.7 18.7 27.0 18.4 25.0 25.1 28.2 21.0 27.5 20.7 27.1 21.6 25.1 32.1 29.6 25.1 25.7 25.2 2.9 2.7 2.5 2.5 3.5 3.0 3.0 4.3 2.9 3.8 4.1 4.6 3.4 4.1 3.1 4.4 2.7 2.7 6.8 5.7 3.5 3.5 3.2 6.8 6.4 6.3 6.2 6.4 6.2 6.2 6.3 6.4 6.5 6.1 6.1 6.2 6.7 6.7 6.2 8.0 9.8 4.7 5.2 7.2 7.4 7.8 O C A C O C C R C C O O C R C? A O T C 2 ' ' vulgaris asca 2 o 7 .6aq 3 " calcareomagneseus . 4 " magneseus Wapplerite .... Hornesite. . as 2 ca 1 mg 1 o 7 .8aq 5 " calcareocobalteus . . 6 " cobalteus Roselite Erythrite Annabergite . . . as a ca 2 (co.mg) 1 o 8 .laq. as 2 co a o 8 .8aq as 2 ni 3 o 8 .8aq 7 " niccoleus 8 " zinceus 9 " ferreus Symplesite .... Allatakite Conichalcite . . . Olivenite Euchroite Erinite Tirol! te Clinoclase as 2 fe s o 8 .8aq 10 " manganeus 11 " Conichalcites as 2 cu 2 ca s o 9 .4aq as 2 cu 4 o 9 .laq as 2 cu 4 o 9 .7aq as 2 cu B o 10 .2aq as s cu 6 o 10 .9aq aSoCii Oi 1 3ao 12 " Olivenites 13 " Euchroites . . . 14 " Erinites 15 " Tirolites . 16 " Clinoclasius 17 " Chalcophyllites Chalcophyllite. Mixite asoCUuOin 12aQ 18 ' ' bismutocupricus . . . 19 " bismuteus Rhagite Walpurgite. . . . Uranospinite . . Zeunerite Troegerite as s bi 4 o 9 .4aq as 2 b! 1 w 4 o 10 .5aq 20 ' ' bismuturaneus 21 " uranocalcareus 22 " uranocupricus 23 " uranicus Genus 2. MIMETITES. Genus 3. ARSENASCLERITES. 409. In a second genus is a plumbic species corresponding to pyromorphite, which has been named mimetite, whence the generic name of Mimetites. More or less nearly allied to this are the species berzeliite, and two little-known anhydrous nickel arsenates which have not yet received trivial names. In addition to these are two aluminic species; one durangite, which is fluoriferous, represents amblygonite, and is referred to a genus Arsenasclerites. Besides these is liroconite, a highly hydrous aluminic species con- taining also cupric oxyd. Mention should moreover be made of Vanadinea. MIMETITES. 319 form. P d V H xl M. plumbeus. . Mimetite . . asaphscv^phjcli) . 59.4 7.2 8.5 4 H scorodite, a ferric arsenate corresponding to strengite. The name of pittizite has been given to an amorphous ferric arsenate con- taining also some sulphate. Two native species in which arsenic tritoxyd is the negative element may here be mentioned. They ekdemite, a chloriferous arsenite of lead, and trippkeite, a ARSENASCLERITES. ( form. P 23.7 d V H xl A. ferrinatreus . Durangite . . . as 8 aJ 8 -6/e.50 8 fi. 4 5.9 5 C cupric arsenite of unknown composition. In the present state of our knowledge it seems prudent, while ranging mimetite and durangite in their respective genera, to give the other arsenical species named a place in an appendix to the order. Order 18. VANADINEA. 410. The pentoxyd of the fixed metal vanadium presents in its combinations close analogies with those of phosphorus and arsenic pentoxyds, which are apparent in the few native vanadates. Genus 1. VANADITES. The plumbic species, vanadinite, corresponds to pyromorphite and to mimetite. An intermediate species, in which, besides vana- dic oxyd, phosphoric and arsenic pentoxyds are present, has been named endlichite. As regards the other species named in the table under the head of Vanadites, it will be well to wait for farther knowledge before attempting their arrangement in genera, and their systematic nomenclature. The name of psittacinite has been given to a species near mottramite in composition. It will be 320 Systematic Mineralogy. remembered that roscoelite and ardennite have been included in the order ABGILLINEA as silicates, holding apparently vanadic trit- oxyd. VANADITES. form. P d 5.8 3.5 7.2 5.9 6.2 5.8 V H xl O H H O 1 Dechenite . . Volborthite. Vanadinite . Mottramite. Pucherite . v 2 pbl^znlo 8 .... VjjCUgca^.laq . . VgpbgOs.Kp^cli). V 8 cu 8 pb 8 o 10 .2aq. VabiaOi 1 39.8 23.6 56.5 40 31.5 37.4 6.8 7.0 7.8 6.8 5.1 6.4 3.5 3 3 3 4 3.5 2 3 4 5 6 Descloizite. . V 2 pb 2 zn 2 o 9 .2aq . . Order 15. STIBIINEA. 411. A few native antimonates have been observed. Atopite is essentially an antimonate of lime with some soda ; bleiniere or bind- heimite, a massive hydrous antimonate of lead ; while the name of rivotite has been given to a supposed antimonate of copper, con- taining also much carbon dinoxyd. The name of romeite desig- nates a supposed antimonite of lime, and that of nadorite has been given to a chloriferous antimonite of lead. All of these compounds are rare and as yet but imperfectly known. Order 19. SULPHATINEA. 412. This order comprises those native compounds in which sul- phuric tritoxyd is the sole or the principal negative element, and which are included in the general designation of sulphates. The soluble or salinoid species of this order are many, and may be ar- ranged in not less than three groups, constituting as many genera. Genus 1. ARCANITES. In the first, besides the sulphates of potash, soda and ammonia^ are several double sulphates of alkalies with lime and magnesia, with which we include also the magnesian sulphate, kieserite, and gypsum. The name of arcanite, from an alchemistic designation Sulphatinea. 321 of the salt, was given by Haidinger to the potassic sulphate, which suggests the generic title of Arcanites here adopted. ARCANITES. form. P d V 8 6.5 9.0 7.5 6.2 5.5 7.3 6.1 7.0 7.5 6.2 H 3 2.5 2.5 2 2.5 3 3.5 3 2.5 3.5 2 xl O O c c c T C C 1 A. kalicus Arcanite . . s, k, o, . 21.7 17.7 16.5 11.4 17.4 13.8 16.7 14.6 18.2 21.0 14.3 2.7 2.7 1.8 1.5 2.8 2.5 2.3 2.4 2.6 2.8 2.3 2 " natricus Thenardite. Mascagnite Mirabilite . Glauberite m Kieserite . . Bloedite . . . Loewite . . . Syngenite . Polyhalite . Gypsum . . . s na, 1 Q. 3 " ammoniatus .... 4 " hydronatricus . . 5 " natrocalcareus. . 6 *' magneseus 8 1 (n 1 h A )o A . S,IHfir..O,. laO 7 " Astrakanites . . . 8 " natromagneseus. 9 " kalicalcareus ... 10 " kalimagneseus . . 11 " gypseus s s na 1 mg 1 o 8 .4aq . . . S 8 na 1 mg 1 .o 8 .2iaq. . SgkiCajOg.laq S 4 k 1 mg 1 ca 8 o 16 .2aq. S 1 ca 1 o 4 .2aq Genus 2. VITRIOLITES. In the second are various sulphates, designated as vitriols by the older chemists, whence the generic name of Vitriolites. These, with the exception of epsomite, are the result of secondary pro- cesses that is to say, they are formed by the oxidation of metallic sulphids. VITRIOLITES. form. P d V H xl 1 V. magneseus 2 " zinceus Epsomite Goslarite . S 1 mg 1 o 4 .7aq. 11.2 14 3 1.7 9, 6.6 6 5 2 9, O o 3 " ferreus Melanterite . siifeiO^.7aa . 1?. 6 1 9 6 6 9, c 4 ' ' niccolcus Moresonite si, nii o .7u< i . 12 7 ft 6 5 9, o 5 " eobalteus 6 * ' mangctnosus Bieberite Mallardite. . S 1 co 1 o 4 .7aq.. s 1 mniO I t.7aQ. 12.7 1?r 6 o 7 * ' cupricus Chalcanthite. SiCU^A.Saq. . 13 8 2 3 6 2 5 A 322 Systematic Mineralogy. Genus 3. SULPHATITES. Following these we have a group of insoluble basic metallic sulphates included under the generic name of Sulphatites. SULPHATITES. form. P d V H xl 1 S. cupriplumbeus. Linarite .... SjCUipbjOg.laq . 33.3 8.5 6.0 3 C 2 " Caledonites Caledonite.. S 6 cu 3 pb 7 o 86 .5aq. 38.1 6.4 6.0 3 3 " Langites Langite .... s^u^Of^aq 20.3 3.5 5.9 2.5 O 4 " Brochantites . . Brochantite. Sl cu 4 o 7 .3aq 22.5 3.9 5.9 3.5 O Genus 4. SULPHATOSCLERITES. The anhydrous sulphates of baryta, strontia, lime and lead- oxyd, somewhat harder than the last, constitute the genus Sulpha- toselerites. SULPHATOSCLERITES. form. P d V H xl 1 S baryteus Barytine .... Si \)Bii OA . 29 1 45 6 4 3 5 O 2 " stronteus Celestine .... SiSl*iO,i . . . 22.9 4,0 5.7 3.5 O 3 ' ' calcctreus Anhydrite SiCaiO ( . 17 3 5 7 3 5 O 4 " plumbeus Anglesite. . . . Sit)biOA. R7 9 6,3 6 8 O 5 " diplumbeus Lanarkite. .. S ipb 8 o 6 52.6 7.0 7.5 2.5 C Genus 5. ALUMEN. 413. Making, as in the case of silicates and phosphates, a dis- tinction between non-aluminous and aluminous species, we may regard the compounds of alumina and sulphuric oxyd as constitut- ing a negative group, without, however, establishing for them a distinct order. We place together in a single genus, Alumen^ the various alums or soluble aluminic sulphates. While the typical alum is a hydrous double sulphate of alumina and potash, as in the table, Sulphatinea. 323 the potassium may be replaced not only by sodium and by am- monium, but by magnesium, manganese and iron, yielding so- called alums, of which examples are given in the table of the genus. ALUMEN. form. P d V JET xl 1 A. capillaris . . . Keramohalite. s al o 6a 2 " kalicus Potash alum. s al k o 24 11 8 1 75 6 8 ? 5 I 3 " natricus Mendozite .... S 4 a/ 8 na 1 o 16 .24aq. 4 " magneseus . . Pickeringite. . S 4 a/ 8 mg 1 o 16 .24aq 5 " manganosus. Bosjemanite . . s 4 aZ 8 mn 1 o le .24aq Genus 6. SULPHALUMINITES. Under the generic name of Sulphaluminites are provisionally arranged insoluble simple aluminic sulphates, and also compounds SULPHALUMINITES. form. P d V H xl 1 S. Websterianus . 2 " secundus Aluminite .... Paraluminite . Alunite Zincaluminite. Spangolite SiCtZsOe.Oaq Si ttZ,.Oa.loao . . 11.5 1.7 6.4 1 Por 8 " kalicus 840^022.634 So^/oZn^Ooi .ISaci . . 14.8 13.8 20.4 2.8 2.3 3.1 5.3 6.0 6.6 3.5 3 2.5 R H R 4 " zinceus 5 " chlorocupricus SgaZaCUuOgo-CUjCli.lSaq like alunite, zincaluminite, and spangolite and lettsomite, a group of species requiring farther study. Genus 7. AMARANTITES. The ferric sulphates, in which ferric oxyd replaces alumina, give rise to many species, some of which contain also ferrous oxyd, soda or magnesia. They are hydrous, crystalline and more or less completely soluble in water, but are of minor mineralogical inter- est. We therefore give in the table the names and the formulas of 324 Systematic Mineralogy. a few species only, which are included under the generic name of Amarantites, from the trivial designation of one of the species. AMARANTITES. form. P d V H #Z 1 A. Coquimbites. . 2 ' * natreus Coquimbite. . Ferronatrite . S 1 /e 1 o 4 .3aq SofVi Ha, .2aq . . 15 6 2.1 ... 2.5 H 3 " insignia 4 " Copiapites . . . 5 " ferrcus Amarantite. . Copiapite. . . . Roemerite . . . S2/e 3 o 9 .7aq S6/e 6 o 21 .13aq.... s^/VjofeiOi c.l2aci. . 14 13.7 2.0 2.1 2,2 7 6,2 1.5 ? A Genus 8. PARARCANITES. 414. Three remarkable soluble salts are known, which may be described as compounds of sulphate with chlorid, and of sulphate with carbonate. These species, kainite, sulphohalite and hanksite, PARARCANITES. form. P d V H xl 1 P. chlorolccilicus . . . Kainite sm{roO<>.kicL .6aa 16 6 9, 1 6 6 n 2 " chloromagneseus . 3 " c&rbonatreus . . Sulphohalite. Hanksite. . SanagOia.mgiClj ... s .na.d ,..dnaiOf, 20.1 17 7 2.5 * 6 8.0 6 8 3.5 3 i H being allied to Arcanites, we place in a genus apart, designated Pararcanites. Genus 9. PARASULPHATITES. A sulphato-carbonate of lead, leadhillite, is referred to a new genus, Parasulphatites. PARASULPHATITES . form. P d V H xl P. carboplumbeus. Leadhillite S 1 pb 1 o 4 .c 3 pb 3 o 9 . .... 65 .... 25 C Tellurinea. 325 Order 20. SELENINEA. 415. A native selenate of lead has been observed in which selenic tritoxyd is the negative element. Moreover, there have been found associated with selenids of lead and cobalt in Chile, crystalline species which, as the result of qualitative examination, have been found to be, respectively, a hydrous selenate of copper, which is named chalcomenite, and selenates of lead and cobalt, designated respectively molybdomenite and cobaltomenite. With these was also found crystalline selenic tetroxyd. Order 21. TELLURINEA. Native compounds, in which telluric oxyd constitutes the negative element, are rare and but little known. The existence of tellurate of iron, one of mercury named magnolite, and one of bismuth named montanite, have, however, been shown. 326 Systematic Mineralogy. CHAPTER XVII. THE PYRICAUSTACEOUS CLASS. 416. Those mineral species which he included in his fourth- class, embracing the bitumens, mineral resins and coals, were as combustible bodies by Breithaupt designated Inflammabilia, a term for which Weisbach has since substituted in German the name of JKauste (Greek, xawif, a burning). The extended sense given in modern language to words of this etymology, and espe- cially the use of the term eremacausis to denote the slow oxydation or combustion without fire, which goes on in the decay of wood and similar matters, suggests the need of a word clearly designating what has been called "pyral combustion," or burning with fire. Hence the name Pyricaustaceae has been devised, together with the English word pyricaustate, which was first proposed in 1885.* It will be noted that sulphur, included by Breithaupt and by Weisbach in this class of combustible or inflammable bodies, is in the present system placed in Class I., by the side of selenium, so that Class IV. has only to do with bodies of the carbon series. Moreover, those derivatives of carbon in which the negative element is carbon dinoxyd, comprising the carbonates, have already been considered in the order CARBONINEA in Class III. The bodies of this fourth class are divided on chemical grounds into two sub- classes, which we designate C^BATA and HYDROCARBATA, each in- cluding many orders. For our present purpose it suffices to recog- nize in the first sub-class a single order, embracing the elemental forms of native carbon, graphite and diamond, ^hich constitute two genera in the order CARBATINEA ; while in the second sub-class are included all native hydrocarbonaceous bodies. In these, besides the essential elements, carbon and hydrogen, are often found oxy- gen, nitrogen, sulphur, and various fixed mineral elements ; the whole divided into several distinct orders. It is obvious that the extension of this system to artificial compounds would lead to a general classification of the bodies of the carbon series, or so-called organic chemistry, a consideration foreign from our present pur- pose. * "Mineral Physiology," p. 380. Carbatinea. 327 Order 1. CARBATINEA. 417. The differences noted in the metallic and non-metallic states of selenium and phosphorus are still more marked in the three states of carbon known as graphite, diamond and amorphous carbon. The markedly phylloid or micaceous character of graphite, its softness, opacity, metallic lustre and its electrical conductivity, offer the strongest contrast to the diamond, the hardest and most condensed element known, a non-conductor of electricity, and pre- senting chemical relations widely differing from graphite. While graphite, diamond and amorphous carbon, as charcoal, alike unite with oxygen at an elevated temperature, forming carbon dinoxyd, graphite by the action of a mixture of potassic chlorate and nitric acid undergoes a peculiar change, being converted into a yellow crystalline transparent body, somewhat soluble in water, which contains both hydrogen and oxygen, and has been designated gra- phitic acid and graphitic oxyd (to which the formula C u H 4 o 6 is assigned). This was described by Brodie as an oxyd of graphon, a supposed condition of carbon in which its integral weight is no longer 12, but 33. Neither diamond nor amorphous carbon exhibit, this reaction. Genus 1. GRAPHITES. 418. The modes of its occurrence in nature show that graphite has a two-fold history. Its frequent appearance as a product of the transformation of. imbedded carbonaceous matters is seen in the conversion of anthracite into a more or less perfect graphite ; while on the other hand it appears as a crystalline mineral in veinstones, enclosed alike in calcite, quartz, orthoclase, pyroxene and mica, as well as forming by itself solid masses, generally made up of broad crystalline laminae, often at right angles to the sides of the vein. Repeated layers of graphite may thus occur, separated from each other, and from the enclosing wall, by the crystalline minerals named. This graphite is sometimes nearly or quite free from for- eign matters, but often includes calcite and pyrite in considerable quantities, crystalline apatite and various silicates. These graphite- bearing veins are found in the crystalline rocks of the Laurentian period ; which also include disseminated graphite alike in the gneisses, the crystalline limestones and the beds of magnetite.* * Many details with regard to graphite and the modes of its occurrence will be found in the "Report of the Geological Survey of Canada, 1863-66," pp. 212-323, in an. essay on "The Mineralogy of the Laurentian Limestones," which is reprinted in the 21st report of the Regents of the University in the State Cabinet of New York. 328 Systematic Mineralogy. 419. Graphitic carbon may be obtained both by igneous and by aqueous reactions. Its separation in a crystalline form from molten cast-iron is well known. On the other hand, it is got from the carbonaceous matter resulting from the slow decomposition of dilute cyanhydric acid, and from the cyanids contained in the mother-liquors in the manufacture of soda. When these are treated at a high temperature with sodium nitrate, the carbon GRAPHITES. form. P d V H xl 1 Graphites wiollis. Ci . 1ft 9, 95 5 3 1 T? separates as graphite. According to other observations the con- tained cyanogen compounds "are decomposed at a certain con- centration of the liquid with formation of ammonia and graph- ite." * From the mode of its occurrence, alike in beds of carbonate of lime and of magnetite, it is evident that native graphite has been formed in the moist way, and has, under conditions not yet understood, been deposited, like the minerals associated with it, in the veins from solutions. Genus 2. ADAMAS. 420. The origin and the association of the diamond present many points of interest; and we shall first consider these questions with reference to the occurrence of the gem in Hindostan, in Brazil, in the southern Atlantic states of the American Union and in the Ural Mountains. While it is generally found in alluvial or quaternary deposits, the source of the diamond in all of the regions named appears to be a series of crystalline schists known in Brazil as the Itacolumite group, while in the Bundelkund district in Hin- dostan similar strata have been named the Lower Vindhyan series. A lithologically analogous group in the southern Urals is also diamond -bearing. These schists in Brazil, where they have been carefully studied, consist in great part of quartzites, granular and sometimes flexible, with argillites and soft unctuous strata contain- *,., E. & D. Philos. Mag. (4), xxi., 541; also Watts' "Dictionary of Chemistry," edition by Morley & Muir, I., 685. Carbatinea. 329 ing hydrous micas and chlorite, together with beds of specular schistose iron ore (itabirite), and great masses of crystalline lime- stones. The close resemblances between these rocks and the Lower Taconic series of the eastern United States were pointed out in 1856 and 1860 by Oscar Lieber, who then insisted on the diaman- tiferous character of the two regions. Subsequently, from a study of a collection of these rocks from the province of Minas Geraes in Brazil, in 1876, the writer was enabled to verify the correctness of Lieber's comparisons. In both regions the schists are traversed by quartz veins, containing, among other minerals, crystallized lazu- lite and rutile, and in Brazil the Itacolumite series has been clearly shown, by the observations of Gorceix and of Derby, to be ADAMAS. form. P d V H xl 1 Adamas octahedricus . . Diamond . . their number as known, 230 Mineral kingdom, its four divisions, 45y 155 Molybdates, complex, 139-140 Monadic notation, 41, 44 Muria, 229 Muriates, 231 Nascent state, 83 Natron lakes, 363 Natural-history method in mineralogy, 5, 159, 171 Negative and positive in chemistry, 3^ ; 146 Neptunism, 375 Ocean, primeval, 350 Octaves, law of, 28, 33 Olefines, 63, 333 Oil wells. Ste Petroleum Orders in mineral classification, 157, 165" Organic remains, replacement of, 119 Oxydata, 233 Oxygen, equivalent weight of, 26, 52 Palagonite, its history, 131 Paracyanogen, 23 ParaflSnes, 333 Periodic law, 29 Petroleum, history of, 333 hypotheses as to its origin, 339 Phosphates, genesis of, 147, 149 Phosphorus, various forms of, 86 mineralogical relations of, 209, 224 Phylloid type, 161 General Index. 379 Finite, 114, 369 Plutonic phenomena, 84, 291, 374 Polycarbonates. See Carbonates Polymerism, illustrations of, 58, 63, 67, 69, 135 Polymolybdates. See Molybdates Poiytungstates. See Tungstates Porodic bodies, 10, 24, 129, 160 Positive and negative in chemistry, 32, 146 Potassium salts in waters, 365 Pressure in relation to chemical change, 17 Progressive series. See Homologous se- ries Protoplasm, mineral, 130 Protoxyds and sesquioxyds, 39 Pseudomorphism considered, 111 by alteration, 111 by replacement, 115 Pyricaustates, 158, 326 Pyrites, two forms of, 69 in organic shapes, 119 order of, 156 signification of name, 216 Pyrognomic minerals, 86 Quartz, integral weight of, 73 fusion of, 97 solubility of, 96 Raoult's cryoscopic method, 64 Rhodopyritinea, order of, 226 Rocks, porosity of, 358 endogenous, indigenous and exotic, 120 Salinoid type, 161 Salt deposits, 356 Saratoga, waters of, 361 Scapolites, supposed constitution of, 109 Sclerites, order of, 159 Sea-weeds, ashes of, 366 Semi-metals, 209 Sesquioxyds and protoxyds, 39 Signs, mineralogical, of Berzelius, 41 Silicates, of magnesia, 367 in organic forms, 119 in natural waters, 368 Silicification of wood, 116 Silicotungstates. See Tungstates. Skeleton crystals, 126 Soda lakes, 363 UtodittTn sulphate, studies of, 80 Solidification, critical point of, 19 Solubility, its relation to condensation, 90 Soluble forms of matter, 82 Solution, theory of, 76 Spars defined, 11 order of, 160 Spathi, order of, 160 Spathoid type, 161 Species, chemical and mineral, defined, 61,66 Starch, integral weight of, 65 State, change of, 17 nascent, 83 Stones, order of, 151 Sugars, chemistry of, 62, 64, 71, 152 Sulphids, constitution of, 144 Sulphur, mineral relations of, 224 in petroleum, 335 Sulphuretted waters, 373 Sulphuric acid waters, 374 Survival of the fittest, 114, 288 Symbols of the elements, 26 Terpene, 62, 333 Tin, two forms of, 65, 68 Titanium, nitrocyanid of, 162 triad oxyd of, 240, 300 Toluene, 333 Transmutation. See Metasomatosis Trivial names in mineralogy, 176 Tungstates, 71, 308 Tungsten bronzes, 72, 139 Types, mineralogical, 163 Ultramarine, chemistry of, 143, 272 Unit, an arbitrary chemical, 73 Vaporization, critical point of, 19-20 Vapors, density of, 21, 44 Veins, concretionary, 120, 131 Volcanic phenomena, water in, 84 glasses, 290 Volumes, law of, 50 Water, integral weight of, 52 Waters, surface, 346 of rivers, of ocean, 365 saline, alkaline, sulphuretted, 373 action of soil on, 349 fixed at high temperatures, 80 Wood, Silicification of, 116 Zeolites, artificial production of, 133 Zirconia, chemical relations of, 141 INDEX OF MINERAL NAMES. THE names of orders are in capitals, and those of genera in italics, while trivial names are in roman ; thus, AEGILLINBA, Agro- Albite. Amblygonite, 315 Ambrite, 331 Amianthus, 250 AmorphiteSy 290 Amphibolus, 250 Amphitelite, 317 Analcite, 263 Anatase, 238 Andalusite, 293 Andesite, 266 Andradite, 283 Anglesite, 322 Anhydrite, 322, 372 Animikite, 221 Ankerite, 246 Annabergite, 318 Annerodite, 307 Annivite, 228 Anorthite, 266 Anthophyllite, 250 ANTHRACINEA, 343 Anthracite, 343 Antimony, 210 Antimony blende, 236 Apatite, 313 Apatites, 313 Aphrodite, 236 Apophyllite, 248 Aragonite, 246 Arcanite, 321 Arcanites, 321 Ardennite, 284 Arfvedsonite, 286 Argentite, 211 ARGILLINBA, 258 Argillithus, 297 Acanthite, 212 Acmite, 286 Acmitodes, 286 Actinolite, 250 Adamas, 329 Adamine, 318 Aeschynite, 307 Agalmatolite, 294 Agricolite, 249 Agrolithus, 266 Aikinite, 216 Alabandite, 225 Alaskaite, 216 Albertite, 336 Albite, 266 Alcalites, 272 Algodonite, 221 Alisonite, 212 Allanite, 281 Allatakite, 318 Allemontite, 210 Alloclasite, 223 Allophane, 297 Allospinellus, 243 Almandite, 283 Alstonite, 246 Altaite, 213 Alumen, 322 Aluminite, 323 Alums, 323 Alunite, 323 Amalgam, 208 Amarantite, 324 Amarantites, 324 Amazon stone, 267 Amber, 331 382 Index of Mineral Names. Argyrodite, 211 Argyropyrite, 211 Arsenargentite, 221 Arsenasclerites, 318 Arsenic, 210 ARSENINEA, 317 Arsenochloanthites, 219 Arsenodiaphorites, 214 Arsenodyscrasites, 221 Arsenolamprotites, 222 Arsenolite, 237 Asbestus, 250 Asbolan, 236 Aspasiolite, 289 ASPHALTINEA, 345 Asphaltum, 335 Astrites, 277 Astrophyllite, 302 Atacamite, 232 Auerbachite, 253 Aurichalcite, 245 Awaruite, 207 Axinite, 300 Axinites, 300 Azurite, 245 Babbingtonite, 286 Balas ruby, 241 Barnhardtite, 218 Barysil, 249 Baryta nitre, 310 Barytine, 322 Bastnaesite, 246 Bauxite, 235 Bechtelite, 239 Beegerite, 216 Berthierite, 215 Bertrandite, 253 Beryl, 287 Beryllonite, 313 Beryllus, 287 Berzelianite, 212 Berzeliite, 318 Beyrichite, 217 Bieberite, 321 Bindheimite, 320 Biotite, 276 Bischofite, 231 Bismuth, 210 Bismutinite, 211 Bismutite, 245 Bismutodiaphorites, 216 Bismutoferrite, 249 Bitumen, 334 Bleiniere, 320 Bloedite, 321 Boltonite, 249 Boracite, 240 BORARGILLINEA, 298 Borasalinites, 239 BORATINEA, 239 Boratinus, 239 Borax, 239 Boricrystallithus, 258 BORISILICINEA, 258 Borisilicites, 258 Borites, 240 Bornite, 217 Bort, 330 Bosjemanite, 323 Boulangerite, 215 Bournonite, 215 Bowenite, 255 Braunite, 238 Bravaisite, 289 Breithauptite, 202 Breunnerite, 246 Brewsterite, 263 Brochantite, 322 Broggerite, 243 Bromargyrite, 232 Bromites, 232 Brongniardtite, 215 Bronzite, 251 Brookite, 238 Brucite, 235 Brushite, 312 Bunsenite, 237 Bytownite, 266 Cacoxenite, 317 Cacoxenites, 317 Calamine, 248 Calaverite, 213 Calcite, 246 Caledonite, 322 Index of Mineral Names. 383 Callaite, 316 Callaites, 316 Calomel, 232 Cancrinite, 272 Cantonite, 211 CARBATINEA, 327 Carbon spars, 246 Carbonites, 246 Carbosalinites, 244 Carbunculus, 283 Carnellite, 231 Carrollite, 217 Cassiterite, 238 Cassiteropyrite, 217 Cassiterotantalite, 303 Catapleiite, 254 Celestite, 322 CERATINEA, 345 Cerite, 254 Cerolite, 256 Cerussite, 246 Ceylanite, 241 Chabazite, 144, 263 Chalchanthite, 321 Chalcocite, 211 Chalcomenite, 325 Chalcophyllite, 318 Chalcopyrite, 217 Chalcostibite, 215 Chiastolite, 293 Childrenite, 315 Chilenite, 219 Chiolite, 230 Chiviatite, 216 CHLOANTHINEA, 219 Chloanthite, 219 Ohlorapatite, 313 CHLORINEA, 230 Chlorite, 277 Chloritoid, 284 Chloropal, 298 Chlorospinel, 241 Chodnewite, 230 Chondrodite, 249 Christophite, 225 CHBOMATINEA, 309 Chromatites, 309 Chromite, 243 Chrysoberyl, 242 Chrysocolla, 256 Chrysolite, 249 Chrysolithus, 249 Cinnabar, 225 Cinnamon stone, 283 Cirrolite, 317 Clarite, 227 Claudetite, 236 Clausthalite, 212 Cleveite, 243 Clinochlore, 318 Coals, 232 Cobaltite, 222 Coccinite, 232 Colemanite, 239 Collyrite, 297 Colophonite, 279, 283 Coloradoite. 213 Columbite, 306 Columbites. 306 Columbotantalites, 304 Conarite, 248 Conichalcite, 318 Cookeite, 276 Copalite, 331 Copiapite, 324 Copper, 208 Coquimbite, 324 Cordierite, 266 Coronite, 299 Corundum, 238 Corynite, 223 Cosalite, 216 Cossaite, 289 Cotunnite, 232 Covellite, 225 Crednerite, 230 Crocoite, 309 Cronstedite, 277 Crookseite, 212 Cryolite, 230 Cryophyllite, 276 Cryptomorphite, 239 Crystallithus, 238 Cubanite, 217 Cummingtonite, 250 Cuprite, 237 384 Index of Mineral Names. Cuproplumbite, 212 Cyanite, 293 Cyrtolite, 254 Danalite, 254 Danburite, 258 Damourite, 276 Datolite, 258 Daubreelite, 217 Daubreite, 232 Dawsonite, 245 Dechenite, 320 Descloizite, 320 Deweylite, 256 Diallogite, 246 Diamond, 329 DIAPHORJNEA, 214 Diaphorite, 215 Diaspore, 242 Dichroite, 266 Dickinsonite, 312 Digenite, 212 Dioptase, 248 Dipyre, 270 Disthene, 294 Dolomite, 246 Domeykite, 221 Duf renoysite, 227 Dumortierite, 293 Durangite, 319 Dysanalyte, 307 Dyscrasite, 221 Eckebergite, 270 Edingtonite, 263 Ehlite, 312 Ekdemite, 319 Elaeolite, 272 ELEAINEA, 333 Eleanorite, 317 Electrum, 209 Eiiasite, 236 Embolite, 232 Emerald, 287 Emplectite, 216 Empyrodox quartz, 291 Enargite, 227 Enceladite, 240 Endlichite, 319 Enstatite, 251 Eosphorite, 315 Epiboulangerite, 215 Epidote, 280 Epidotus, 280 Epsomite, 321 Erinite, 318 Eritimites, 254 Erythrite, 318 Esmarkite, 289 Essonite, 283 Eucairite, 212 Euchroite, 318 Euclase, 287. Eudialyte, 254 Eulytite, 249 Euosmite, 331 Euphyllite, 276 Eutelites, 312 Euxenite, 307 Evansite, 317 Fahlerz, 226 Fahlite, 226 Fahlunite, 289 Fatiminite, 215 Faujasite, 263. Fayalite, 249 Ferberite, 308 Fergusonite, 134, 306, 307 Ferronatrite, 324 Ferrotitanite, 283 Fibrolite, 293 Fichtelite, 331 Fieldite, 228 Fischerite, 316 Fluellite, 230 Fluocerine, 230 Fluocerite, 230 Fluorapatite, 313 FLUOBINEA, 229 Fluorite, 230 Fluorites, 231 Forsterite, 249 Franklinite, 242 Freibergite, 228 Freieslebenite, 215 Index of Mineral Names. 385 Frenzelite, 212 Friedelite, 248 Friesite, 211 Fuchsite, 276 Gadolinite, 254 Gahnite, 242 GALENINEA, 210 Galenite, 211 Galenobismutite, 216 Ganomalite, 249 Gastaldite, 279 Garnet, 282 Garnierite, 257 Gaylussite, 244 Gearksutite, 230 Gehlenite, 270 Genthite, 256 Geocronite, 215 Gerhardtite, 310 Gersdorffite, 222 Geyerite, 222 Gibbsite, 235 Gismondite, 263 Glagerite, 297 Glauberite, 321 Glaucodot, 222 Glauconite, 257, 366, 3i Glaucophane, 279 Goethite, 235 Gold, 208 Goslarite, 321 Goyazite, 315 Granatinus, 284 Granatus, 282 Graphite, 327 Graphites, 327 Greenockite, 225 Grossularite, 283 Grunauite, 228 Griinerite, 250 Guejarite, 215 Guitermannite, 214 Gummite, 235 Gypsum, 321 Haidingerite, 318 Halicarbonites, 246 Halite, 231 Halloysite, 297 Hamelite, 120, 246 Hanksite, 324, 365 Hannayite, 311 Harmotome, 263 Harrisite, 211 Hatchettolite, 306 Hauerite, 225 Hausmannite, 242 Hauyene, 272 Heavy spar, 322 Helvite, 254 Hematite, 238 Hercynite, 242 Herderite, 313 Hermannite, 250 Heulandite, 263 Hiddenite, 287 Homichlyn, 217 Homilite, 258 Hopeite, 312 Horbachite, 217 Hornesite, 318 Horsfordite, 220 Hortonolite, 249 Hubnerite, 308 Humboldtilite, 271 Huntilite, 221 Hureaulite, 312 Hyalophane, 266 Hydroboracite, 239 Hydrocalcite, 243 Hydrocarbonites, 245 Hydrodolomite, 244 Hydromagnesite, 245 Hydroxydites, 235 Hydrozincite, 245 Hygrophilite, 289 Hypersthene, 251 Hypostilbite, 263 Ice, 235 Idocrase, 279 Idocrasius, 279 Idrialite, 331 Ilvaite, 286 Indiaaaite, 298 386 Index of Mineral Names. lodargyrite, 232 IODINEA, 232 lodites, 232 lolite, 266, 269 Iridium, 207 Iron, 207 Iron-platinum, 207 Ittnerite, 272 Jacobsite, 242 Jade, 250, 280 Jadeite, 280 Jalpaite, 212 Jamesonite, 215 Jeffersite, 277 Jeremejewite, 240 Jollyte, 289 Jordanite, 214 Joseite, 213 Kainite, 324 Kammererite, 278 Kaneite, 219 Kaolin, 295 Kaolinite, 295, 297 Karalenite, 237 Kentralite, 286 Keramite, 295 Keramohalite, 323 Kerargyrite, 232 Kermesite, 237 Kerosene shale, 332 Kieserite, 321 Kilbrickenite, 215 Kischtimite, 246 Klaprothite, 216 Kobellite, 216 Koenleinite, 331 Kraurite, 317 Kupfferite, 250 Kyanite, 293 Labradorite, 266 Lampadite, 236 LAMPROTINEA, 222 Lanarkite, 322 Lancasterite, 244 Langite, 322 Lanthanite, 245 Lapis lazuli, 272 Larderellite, 239 Laumontite, 263 Laurite, 217 Lavalite, 266 Lavenite, 254 Laxmannite, 309 Lazulite, 315 Leadhillite, 324 Lepidolite, 276 Lettsomite, 323 Leucite, 272 Leucophane, 254 Levynite, 263 Libethenite, 312 Liebigite, 244 Lievrite, 286 Lignite, 332 Lime nitre, 310 Limnite, 235 Limonite, 235 Linarite, 217 Liroconite, 318 Lithiophilite, 313 Livingstonite, 228 Loellingite, 219 Loewite, 321 Ludlamite, 312 Ludwigite, 239 Luzonite, 227 Magnesia nitre, 310 Magnesite, 246 Magnesioferrite, 242 Magnetite, 243 Magnolite, 325 Malachite, 245 Malacolite, 257 Malacone, 254 Maldenite, 219 Mallardite, 321 Manganite, 235 Manganosite, 237 Marcasite, 69, 217 Marialite, 270 Marmolite, 255 Martinsite, 311 Martite, 208 Index of Mineral Names. 387 Masonite, 284 Massicot, 237 Matlockite, 232 Mediofulvites, 228 Megabromite, 232 Meionite, 270 Melaconite, 236 Melanite, 283 Melanotekite, 286 Melanterite, 321 Melihte, 271 Melinophane, 255 Mellite, 332 Meionite, 213 Menacannite, 238, 300 Mendipite, 232 Mendozite, 323 Meneghinite, 215 Mengite, 301 Mercury, 208 Mesodiaphorites, 216 Mesogalenites, 213 Mesolite, 263 Metacinnabar, 211 Metallinum, 209 Metallum, 206 Metastibnite, 225 Miargyrite, 228 Microbroraite, 232 Mtcroclin, 266 Microsommite, 272 Milarite, 271 Millerite, 217 Mimetite, 319 Mimetites, 319 Mirabilite, 321 Mispicke), 222 Mixite, 318 Mizzonite, 270 Molybdenite, 211 Molybdic ochre, 237 MOLYBDINEA, 309 Molybdites, 309 Molybdomenite, 325 Monazite, 313 Monetite, 312 Monite, 311 Montanite, 325 Montebrasite, 314, 315 Monticellite, 249 Moresonite, 321 Mosandrite, 302 Mottramite, 320 Murialus, 231 Muriates, 232 Muscovite, 276 Nacrite, 296 Nadorite, 320 Nagyagite, 213 Natrolite, 263 Natron, 244 Natrophilite, 313 Naumannite, 212 Nephelite, 273 Nephrite, 250 Newberyite, 312 Newjanskite, 207 Niccolite, 219 Nitrates, 310 NlTRATINEA, 310 Nitre, 310 Nitrosalinites, 310 Nivenite, 243 Nontronite, 298 Nordenskioldine, 303 Norite, 272 Obsidian, 290 Octahedrite, 132, 238 Oellacherite, 276 Oerstedite, 302 Okenite, 248 Oldhamite, 225 Oligoclase, 266 Olivenite, 318 Olivine, 247 Opal, 235 Orpiment, 225 Orthite, 281 Orthoclase, 266 Ottrelite, 284 Ouvarovite, 283 OXYDINEA, 234 Ozarkite, 263 Ozocerite, 337 388 Index of Mineral Names. Pachnolite, 230 Pacite, 222 Pagodite, 294 Palagonite, 290 Palladium, 207 Paracolumbites, 807 Paraffines, 334 Paraluminites, 323 Paranthite, 270 Pararcanites, 324 Parasmithsonite, 246 Parasulphatites, 324 Paratitanites, 302 Pargasite, 279 Parisite, 246 Passauite, 270 Pearlite, 290 Pectolite, 248 Pectolithus, 248 Penninite, 277 Percylite, 232 Periclasite, 237 Peridot, 249 Perowskite, 301 Perthite, 268 Petalite, 266, 269 Petzite, 213 Pharmacolite, 318 Pharmacolites, 318 Phenacite, 253 Phenacites, 253 Phengites, 275, 276 Phillipsite, 263 Phlogopite, 276 Phoenicite, 309 Pholerite, 295 Phosgenite, 246 Phosphasclerites, 314 PHOSPHATINEA, 311 Phosphatites, 312 Phosphochalcite, 312 Phosphocliloanthites, 219 Phosphorus, 210, 224 Pickeringite, 323 Picrolite, 255 Pterolithus, 255 Picrosmine, 255. Piedmontite, 280 Finite, 289 Pitchstone, 290 Pittizite, 319 Plagionite, 215 Platiniridium, 207 Platinum, 207 Plattnerite, 237 Plombierite, 248. Plumbogummite, 316 Polianite, 235, 238 Pollucite, 263 Polyargyrite, 215 Poly basite,. 228 Polycrase, 307 Polydomite, 217 Polyhalite, 321 Polymignite, 301 Polytelite, 228 Porcelain spar, 270 Porodites, 288 Porosilicites, 256 Potash nitre, 310 Powellite, 309 Prehnite, 279 Prochlorite, 277 Prosopite, 230 Protolithus, 236 Proustite, 227 Psilomelane, 235 Psittacinite, 319 Pucherite, 320 Pumice, 292 Pyrophane, 301 Pyrallotite, 255 Pyrargyrite, 228 Pyrauxites, 295 Pyrite, 69, 217 Pyrites, 217 PYBITINEA, 216 Pyritinus, 217 Pyrochlore, 307 Pyrochroite, 235 Pyrolusite, 235 Pyromorphite. 313 Pyrope, 282 Pyrophyllite, 295 Pyroxenus, 251 Pyroschist, 332 Index of Mineral Names. 389 Pyrosmalite, 248 Pyrostilpnite, 228 Pyrrhotite, 217 Quartz, 89, 96, 238 Quincite, 369 Rammelsbergite, 219 Realgar, 225 Reddingite, 312 Rensselaerite, 256 Retinalite, 256 Resins, mineral, 331 RETININEA, 331, 345 Rhagite, 318 Rhodizite, 240 Rhodochrome, 278 Rhodonite, 251 RHODOPYRITINEA, 226 Ripidolite, 277 Rittingerite, 228 Rivotite, 320 Rock salt, 231 Romeite, 320 Roemerite, 324 Roscoelite, 276 Roselite, 318' Rubellite, 299 Rutherfordite, 301 Rutile, 238 Safflorite, 219 Sal-ammoniac, 231 Samarskite, 306 Sapphirine, 284 Sarcolite, 271 Sartorite, 227 Sassolin, 259 Saussurite, 280 Scapolite, 270 Scapolithus, 270 Scheelite, 308 Schirmerite, 216 Schorlite, 299 Schorlomite, 283 Schreibersite, 219 Schwartzembergite, 232 Scleretinite, 331 Scorodite, 319 SELENINEA, 325 Selenium, 210, 224 Selen-sulphur, 224 Selenogalenites, 212 Sellaite, 230 Senarmontite, 237 Sepiolite, 257, 369 Serpentine, 256 Seybertite, 276 Siderite, 246 Siegenite, 217 SILICINEA, 247 Sillimanite, 293 Silver, 208 Skulterudite, 219 Smaltite, 219 Smithsonite, 246 Soda dolomite, 166 Soda nitre, 310 Sodalite, 272 Spangolite, 323 Spaniolite, 228 Sperrylite, 219 Sphaerocobaltite, 246 Sphaerulite, 292 SPHALERINEA, 225 Sphalerite, 225 Sphalerites, 225 Sphene, 302 Spinel, 242 SPINELLINEA, 241 Spinellus. 242, 243 Spodiolithus, 287 Spodumene, 287 STANNINEA, 303 Stannite, 303 Staurolite, 284 Stercorite, 31 1 Sternbergite, 211 Stephanite, 215 STIBIINEA, 320 Stibnite, 211 Stibiochloanthites, 220 Stibiodiaphorites, 215 Stibiodyserasites, 221 Stibiofulvites, 228 Stilbite, 263 Strengite, 317 390 Index of Mineral Names. Stromeyerite, 211 Strontianite, 246 Struvite, 312 Studerite, 228 Stylotypite, 215 Sulphaluminite, 323 Sulphaluminites, 323 SULPHATINEA, 320 Sulphatites, 322 Sulphatosclerites, 322 Sulphohalite, 324 Sulphur, 224, 326 Sussexite, 239 Sylvanite, 213 Sylvite, 231 Symplesite, 318 Syngenite, 321 Sysserskite, 207 Szabelyite, 239 Tachyhydrite, 231 Tachylyte, 290 Tagilite, 312 Talc, 255 Tantalite, 306 Tantalites, 306 Tapiolite, 305 Telluric ochre, 237 TELLUBINEA, 325 Tellurium, 210 Tellurogalenites, 213 Tennantite, 227 Tenorite, 237 Tephroite, 249 Tetradymite, 213 Tetrahedrite, 228 Texasite, 245 Thenardite, 321 Thermonatrite, 244 Thermophyllite, 255 Thiogalenites, 211 Thomsonite, 263 Thorite, 254 Thorogummite, 254 Thuringite, 277 Tiemannite, 212 Tincal, 239 Tirolite, 318 TITANINEA, 300 Titanite, 302 Titanites, 301 Topaz, 293 Topazius, 293 Topazolite, 283 Torbanite, 332 Torbernite, 312 Tourmaline, 132, 298 Tremolite, 250 Tridymite, 89, 238 Triphane, 287 Triphyllite, 313 Triplite, 313 Triploidite, 313 Trippkeite, 319 Trogerite, 318 Trona, 244, 364 Troosite, 217 Tschewkinite, 302 Tungstic ochre, 237 Turgite, 235 TurmalinuSi 298 Turquoise, 316 Ulexite, 239 Ullmanmte, 223 Uraninite, 242 Uranite, 312 Uranocercite, 312 Uranophane, 254 Uranospinite, 318 Uranothallite, 245 Uranotil, 254 Urao, 244 Valentinite, 236 VANADINEA, 319 Vanadinite, 320 Vanadites, 320 Variscite, 316 Vauquelinite, 309 Venerite, 278 Vermiculite, 277 Vesuvianite, 279 Villarsite, 253 Vitriolites, 321 Vivianite, 312 Index of Mineral Names. 391 Voelknerite, 243 Vogtite, 249 Volborthite, 320 Wad, 236 Wagnerite, 313 Walpurgite, 318 Wapplerite, 318 Warrenite, 215 Warwickite, 240 Wavellite, 316 Wax, mineral, 337 Wehrlite, 213 Wernerite, 270 Whitneyite, 221 Willemite, 249 Witherite, 246 Wittichenite, 216 Woehlerite, 307 Wolchonskoite, 298 Wolfachite, 223 Wolfram, 308 Wolframites, 308 Wollastonite, 251 Wulfenite, 309 Wurtzite, 225 Xanthoconite, 227 Xenotime, 313 Xonaltite, 248 Yenite, 286 Yttrialite, 254 Yttrocerite, 229 Yttrocolumbite, 306 Yttrotitanite, 302 Zeolites, 263 Zeolithus, 263, 266 Zeunerite, 318 Zincaluminite, 323 Zincite, 237 Zinkenite, 215 Zinnwaldite, 276 Zircon, 253 Zirconius, 253 Zoisite, 280 Zbrgite, 212 Zunyite, 293 WHat tHe Critics say of Dr. T. Sterry Hunt's Worts. *T ?> y - 7 ur readers are aware that a French translation of Dr. Hunt's -Nevv Basis for. hemistry" was published in Paris in 1889. We are now permitted by Dr de Kroustchoff, the eminent chemist and mineralogist of St. Petersburg , to say that he has in hand a translation into Russian of a selection from the works of Dr. Hunt. The translatiens will be published next year and will form the first volume of a series of scientific classics to be toll owed by other volumes of similar selections from French and German Will well repay a most careful study. Chemical News, London. D v, r ; H ^ fc ^f - always suggestive, and his words are always entitled to great weight. Public Opinion, Washington. They are all subjects which cannot fail to interest any one possessing a liking for either geology or mineralogy.-Letogr/i Quarterly, Bethlehem, Pa. Among the most creditable monuments of American science. It would require almost a volume to notice the points worthy of attention. North American Review, New York. The geological literature of the latter half of the nineteenth century will always bear a profound impress derived from the labors of Dr. Hunt. American Geologist, Minnesota. His investigations have covered a wider field than those of most modern writers. Thoroughness, accuracy and learning characterize the author's work. Medical ana Surgical Journal, Boston. His high reputation and the honors which he has received from learned societies, both at home and abroad, give the best assurance of the valuable character of his labors. Popular Science Monthly, New York. Shows the most thorough familiarity with all that is known up to the present time of the various sciences on which the arguments are based, and will take a foremost place among the philosophical treatises of the day. Dominion Annual Register. He has distinguished himself as one of the most original of the scientific investigators and thinkers of America, and his opinions thus set forth, toward what is probably the end of his life's work, are not to be lightly re- garded. Railroad Gazette, New York. We find in these volumes a patient, mature and thoroughly trained physicist, drawing to a conclusion which he verily believes to be triumphant the scientific evidence by which he has worked out not only the dream of his own youth, but the dream of the youth of science herself. Science, New York. Dr. Hunt is equally eminent as a geologist and chemist, and his volumes have the breadth which comes of the complete mastery of the two most important provinces of science. His style has the clearness which can only be won by a teacher in love with his subject. Publishers' Weekly, New York. Perhaps no scientist of the present day combines in so great degree the highest literary skill with the most thorough knowledge of the chief depart- ments of science. As an original investigator, more particularly in the fields of chemical geology, mineralogy, and mineral physiology and physiography, Dr. Hunt's eminent services have won the admiration of the scientific world. Engineering and Mining Journal, New York. CHEMICAL AND GEOLOGICAL KSSAYS BY THOMAS STERRY HUNT, M.A..LL.ID., Author of "Mineral Physiology and Physiography," "A New Basis for Chemistry," "Systematic Mineralogy," etc. FOURTH EDITION. JUST PUBLISHED. WITH NEW PREFACE. ., &2.5O- CONTENTS. Preface; 1. Theory of Igneous Rocks and Vol canoes; II. Some Points in Chemical Geology ; III. The Chemistry of Metamorphic Rocks; IV. The Chemistry of the Primeval Earth; V. The Origin of Mountains; VI. The Probable Seat of Vocanic Action; VII. On Some Points in Dynamical Geology; VIII. On Limestone, Dolomites and Gypsums; IX. 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SHARPLESS, of the Houghton Mining School, writes : "One who has occasion to read up the recent advances of lixiviation processes will appreciate the work which has been done by the author in compiling and in original research, and the profession should extend its thanks to Mr. Stetefeldt for his successful effort ' to fill up a gap in metallurgical literature.' " PROF. BRUNO KERL, in a review of this book which he prepared for the Berg- und Huettenmaennische Zeitung, of Berlin, says: "All the defects of the old process have been overcome by the Russell process as described by Mr. Stetenfeldt in his book, which fills a real gap in metallurgical literature. ... Its translation into German would be a very desirable addition to our literature." JOHN HEARD, JR., Mining Engineer, writes: "This treatise is the most valuable indeed the only valuable one on lixivia- tion. The amount of careful, intelligent, original and compiled research is enor- mous ; the tables and drawings must be invaluable and, indeed, indispensable to any manager of a lixiviation plant, and the figures there recorded are more convincing arguments as to the value and range of lixiviation as a method of extracting silver from certain ores than the author's dogmatic deductions. SCIENTIFIC PUBLISHING COMPANY, 27 PARK PLACE, NEW YORK. THE MINING CODE OF THE REPUBLIC OF MEXICO. WITH THE Begulations for the Organization of the Mining Deputations and the Schedule for the Levying of Pees and Dues, with all the Latest Official Circulars and Decisions of the Mining Section of the Ministry of Publis Works and with the Laws of June 6th, 1887, upon the Taxation of Mines and their Products, the Concession of Mining Territory an! the Purchase of a Process for the Treatment ofOres, TRANSLATED FROM THE OFFICIAL EDITION IN THE ORIGINAL SPANISH, BY RICHARD E. CHISM, MINING ENGINEER, MEMBER OF THE AMERICAN INSTITUTE OF MINING ENGINEERS. THE SCIENTIFIC PUBLISHING COMPANY, 27 PARK PLACE, NEW YORK. THE UNANIMOUS OPINION OF THE BEST CRITICAL JUDGMENT OF THE WORLD IS THAT THIS WORK IS THE MASTERPIECE OF LITERARY, ARTISTIC AND TYPOGRAPHICAL ART. GEMS AND PRECIOUS STONES OF NORTH AMERICA A POPULAR DESCRIPTION OF THEIR OCCURRENCE, VALUE, HISTORY, ARCHAEOLOGY, AND OF THE COLLECTIONS IN WHICH THEY EXIST, ALSO A CHAPTER ON PEARLS AND ON REMARKABLE FOREIGN GEMS OWNED IN THE UNITED STATES ILLUSTRATED WITH EIGHT COLORED PLATES AND NUMEROUS MINOR ENGRAVINGS BY GEORGE FREDERIC KUNZ, Gem Expert with Messrs. Tiffany &* Co., special agent of the United States Geological Survey and of the Eleventh United States Census^ member of the Mineralogical Society of Great Britain And Ireland* the Imperial Mineralogical Society of St. Petersburg, the Soci^te Francaise de Mine"ralogie* etc. Price, - - $10.00 SCIENTIFIC PUBLISHING COMPANY, 27 PARK PLACE, NEW YORK. MINING ACCIDENTS AND THEIR PREVENTION. BY SIR FREDERICK AUGUSTUS ABEL With Discussion by Leading Experts. Also, the United States, British and Prussian Laws relating to the Working of Coal Mines. Frice, - $4.OO in Cloth. CONTENTS : Mining Accidents. By Sir Frederick A. Abel. With discussion by President Bruce, of the British Institute of Civil Engineers; and Prof. Arnold Lupton, C. Tylden Wright, Emerson Bainbridge, William Morgans, Sydney F. Walker, Col. Paget Mosley, Henry Hall, Col. J. D. Shakespear, Stephen Humble, Sir George Elliot, Sir Warington Smyth, A. R. Sawyer, A. Giles, R. Bedlington, Edward Combes, George Seymour, Henry Harries, William Cochrane, James Ashworth, J. B. Atkinson, W. N. Atkinson, Bennett H. Brough, T. Foster Brown, S. B. Coxon, C. Le Neve Foster, W. Galloway, Max Georgi, W. S. Gresley, J. A. Longdon, A. R. Sennett, M. H. N. Story Maskelyne, Arthur Sopwith, A. L. Steavenson, A. H. Stokes and others. List of safety appliances, with description of detachment of mineral from its bed, carriage of mineral to the surface, difficulties attendant on the presence of gases, etc. Safety lamps (oil and spirit), safety lamps (electric) and other appli- ances. The Mining Laws of Colorado, Illinois, Indiana, Iowa, Kansas, Ken- tucky, Maryland, Missouri, Ohio, Pennsylvania, Washington, West Vir- ginia and Wyoming; also those of Great Britain and Prussia add a feature of great value for these laws have never before been collected or published in accessible form. Of the unanimously favorable criticisms of this book, we have only space to quote one : " It is a work that should be in the hands of every intelligent man connected with a colliery, no matter what his position. It is as valuable to the intelligent miner as it is to the mining engineer or the colliery official." Colliery Engineer. SCIENTIFIC PUBLISHING COMPANY, 87 PARK PLACE. NEW YORK. 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