MIKtlfY LIBRARY MNIVEISITY Of CALIFOtNIA GIFT OF GUIDE TO THE MINERAL COLLECTIONS IN THE ILLINOIS STATE MUSEUM STATE OF ILLINOIS FRANK O. LOWDEN, GOVERNOR DEPARTMENT OF REGISTRATION AND EDUCATION FRANCIS W. SHEPARDSON, PH.D., LL.D., DIRECTOR STATE MUSEUM DIVISION A. R. CROOK, PH.D., CHIEF SPRINGFIELD BOARD OF MUSEUM ADVISERS Administration and Fine Arts: CHARLES L. HUTCHINSON, A.M., Corn Exchange National Bank, Chicago Botany: CHARLES F. MILLSPAUGH, M.D., Field Museum, Chicago Ethnology: CHARLES L. OWEN, A.B., Field Museum, Chicago Manufacturing and Business: EDWARD W. PAYNE, State Bank, Springfield Zoology: HENRY B. WARD, PH.D., University of Illinois, Urbana A FREE INSTITUTION FOR THE PEOPLE : TO PROMOTE SCIENCE TO PROMOTE ART TO PROMOTE BUSINESS Hours: Week Days: 8 A.M. till 12 noon, 1:30 P.M. till 5 P.M. Saturdays: 8 A.M. till 3 P.M. LETTER OF TRANSMITTAL STATE MUSEUM, SPRINGFIELD August 31, 1919 Francis W. Shepardson, LL.D. Director, Department of Registration and Education DEAR SIR: For the purpose of increasing the usefulness of the collections in the State Museum a series of guidebooks was planned a few years ago. The first to be printed was the General Guide, which appeared in 1914 and which is now exhausted. Herewith is submitted a Guide to the Mineral Collections, upon which the chief has been working in moments which could be spared from other work for the past several years. Hoping that it may prove of service to students of mineralogy and also to those visitors whose interest is of a general character, I am Yours very respectfully, A. R. CROOK, Chief, State Museum Division GUIDE TO THE MINERAL COLLECTIONS IN THE ILLINOIS STATE MUSEUM e V By A. R. CROOK, PH.D. Chief, State Museum Division, Department of Registration and Education SPRINGFIELD, ILLINOIS 1920 Published October 1920 Composed and Printed By The University of Chicafco Press Chicajo, Illinois, U.S.A. PREFACE In the following pages an attempt has been made to so describe the minerals constituting our constantly growing collections as to emphasize the most important ones and at the same time to present to the reader a good idea of the science of mineralogy. The average visitor approaches the subject as a child would and just as the human race has done. When early man wandered up stream courses and found a gold nugget he doubtless was attracted by its yellow color, in time noticed the weight, softness, etc., and learned to use it as an ornament. The child does the same, using the senses of sight, feel, taste, and smell in making the acquaintance of any strange sub- stance. Hence the physical characteristics form, color, hardness, and weight of various minerals are described, and then their chemi- cal constituents, geological and geographical relations, and use are given. By becoming acquainted with various minerals the visitor obtains a knowledge of the science. In preparation of this work the writer has used chiefly Dana's, Mier's, Lacroix's, and Tschermak's mineralogies and Tutton's and Groth's crystallographies, in addition to individual articles in U.S.G.S. reports, scientific journals, etc. Especial thanks are due Professor O. C. Farrington for painstak- ing revision of the manuscript, Professor W. S. Bayly for careful reading of the proof, and the University of Chicago Press for the thorough manner in which their part of the work has been done. Professor Farrington supplied photographs for Plates IV, XVIII, XlXa, and XXVIIa. Plate VIb is after W. M. Foote, and Plate la is reproduced by permission of B. F. Buck & Co. The other illus- trations are by the writer. A. R. CROOK August, 1919 43927; IX TABLE OF CONTENTS LIST OF ILLUSTRATIONS xi" ABBREVIATIONS ...... xxi INTRODUCTION . ... . . . . i CLASS I. ELEMENTS . . .'.-.. ....... . . . 5 LIST OF ELEMENTS AND THEIR ATOMIC WEIGHTS . . V . . . 45 CLASS II. SULPHIDES ., . - . 46 CLASS III. SULPHANTIMONITES, SULPHARSENITES ...'.. 68 CLASS IV. HALOIDS ... . 76 CLASS V. OXIDES ....'.,.,..,... 82 CLASS VI. CARBONATES . . . . ... . . . . . . 112 CLASS VII. SILICATES . 132 CLASS VIII. NIOBATES, TANTALATES 175 CLASS IX. PHOSPHATES, ETC '. 175 CLASS X. BORATES, URANATES . i ... ... . . 177 CLASS XL SULPHATES, CHROMATES, TELLURATES . .... . 179 CLASS XII. TUNGSTATES, MOLYBDATES 185 CLASS XIII. ORGANIC ACID SALTS 187 CLASS XIV. HYDROCARBONS 187 SUMMARY 194 NAMES OF MINERALS ....;.. ... 196 THE USES OF MINERALS . .... ... . 197 HISTORY OF THE STUDY OF MINERALS .......". 198 LIST OF MINERALS 202 INDEX 279 XI LIST OF ILLUSTRATIONS PAGE FIG. i. MODEL OF OCTAHEDRON; PREVAILING OUTLINE OF DIA- MOND . . , ; . 5 FIG. 2. AXES . ..." / .;'* . 6 FIG. 3. METHOD OF CONSTRUCTING CRYSTALLOGRAPHIC AXES . 7 FIG. 4. CONSTRUCTION OF AN OCTAHEDRAL PLANE .... 7 FIG. 5. COMPLETED OCTAHEDRON . . ... . . . 8 FIG. 6. MODEL OF TRAPEZOHEDRON . . . ... . 9 FIG. 7. COMPLETED TRAPEZOHEDRON . 9 FIG. 8. MODEL OF TRISOCTAHEDRON . -. 10 FIG. 9. TRISOCTAHEDRON COMPLETED ....... 10 FIG. 10. MODEL OF HEXOCTAHEDRON . 12 FIG. ii. HEXOCTAHEDRON COMPLETED 12 FIG. 12. GROWTH OF UNSHADED PLANES OF THE WOODEN OCTA- HEDRON PRODUCE THE GLASS TETRAHEDRON COVER- ING IT . . . . 12 FIG. 13. RIGHT-HANDED TETRAHEDRON 12 FIG. 14. WOODEN OCTAHEDRON INCLOSED BY GLASS TETRAHEDRON 13 FIG. 15. LEFT-HANDED TETRAHEDRON 13 FIG. 16. INTERPENETRATING SUPPLEMENTARY TETRAHEDRONS (TETRAHEDRAL TWINS) 13 FIG. 17. TETRAHEDRAL TWIN WITH CORNERS TRUNCATED . . 14 FIG. 18. MODEL OF RIGHT-HANDED HEXATETRAHEDRON . . . 15 FIG. 19. CONSTRUCTION OF HEXATETRAHEDRON 15 FIG. 20. INTERPENETRATING TRUNCATED TETRAHEDRONS BEVELED BY HEXATETRAHEDRONS . . . . . . . 16 FIG. 21. MODEL OF "SPINEL TWIN" . . . ..j.*!...,;.. "... ' 17 FIG. 22. DRAWING OF SPINEL TWIN . . ,','" . ... 17 FIG. 23. Two KINDS OF AXES OF SYMMETRY . . . '. ' . 18 FIG. 24. DOTTED LINES SHOW DIRECTION OF PLANES OF SYMMETRY IN CUBE 19 FIG. 25. ANGLES OF INCIDENCE AND REFRACTION . . . . 19 FIG. 26. MODEL OF ORTHORHOMBIC BrpYRAMio . . . . 25 FIG. 27. ORTHORHOMBIC PYRAMIDAL PLANE AND AXES . ... 25 FIG. 28. OBTUSE BIPYRAMID CHARACTERISTIC OF SULPHUR . . 26 FIG. 29. MODEL OF BRACHYDOMES AND MACROPINACOIDS . . 26 FIG. 30. UPPER BRACHYDOME PLANES . ....:* . . 26 FIG. 31. MODEL OF MACRODOMES AND BRACHYPINACOIDS . . v 27 FIG. 32. UPPER MACRODOMES . . -,,,,.. v. ,.,,*. ,v 27 xiii xiv LIST OF ILLUSTRATIONS PAGE FIG. 33. PRISM AND BASAL PLANES 27 FIG. 34. BASE, MACROPINACOID, AND BRACHYPINACOID ... 28 FIG. 35. MODEL or BASE, MACRO- AND BRACHYPINACOID ... 28 FIG. 36. MODEL OF PRISM, BRACHYPINACOID, AND BRACHYDOME . 28 FIG. 37. RIGHT-HANDED SPHENOID . . .> 28 FIG. 38. SULPHUR, USUAL HABIT . . 29 FIG. 39. SULPHUR, SPHENOIDAL HABIT . . . . . ,, . 29 FIG. 40. AXES or MONOCLINIC CRYSTAL . ..... 30 FIG. 41. CUBE . . . . . ... ... . 33 FIG. 42. TETRAHEXAHEDRON MODEL . . .... . 35 FIG. 43. CONSTRUCTION OF TETRAHEXAHEDRON 35 FIG. 44. MODEL OF A DODECAHEDRON 39 FIG. 45. CONSTRUCTION OF A DODECAHEDRON 40 FIG. 46. STIBNITE CRYSTAL .... . . . . . . 47 FIG. 47. CUBE TRUNCATED BY OCTAHEDRON . .... . 49 FIG. 48. MODEL OF CUBE TRUNCATED BY OCTAHEDRON ... 49 FIG. 49. GALENA, Jo DAVIESS COUNTY, ILLINOIS . . . . 50 FIG. 50. MODEL OF PLANES APPEARING ON GALENA * 50 FIG. 51. TWIN LAMELLAE IN GALENA . . . *. . . . 51 FIG. 52. SPHALERITE . . . . . . .. .* . 53 FIG. 53. MODEL OF THREE-FACED TETRAHEDRON, A TRISTETRAHEDRON 54 FIG. 54. CONSTRUCTION OF TRIGONAL TRISTETRAHEDRON . . . 54 FIG. 55. SPHALERITE Y / . . . . . . . . . 54 FIG. 56. ACUTE PRIMARY BIPYRAMTD ....... . 57 FIG. 57. OBTUSE PRIMARY BIPYRAMTD . ... . . . . . 57 FIG. 58. MODEL OF SECONDARY BIPYRAMID . . . -. . . 58 FIG. 59. DITETRAGONAL BIPYRAMID ....... . . 58 FIG. 60. MODEL OF DITETRAGONAL BIPYRAMID . . . . . 58 FIG. 61. PRIMARY PRISM 59 FIG. 62. SECONDARY PRISM . . . . . . .... 59 FIG. 63. MODEL OF DITETRAGONAL PRISM 59 FIG. 64. COMBINATION OF PRIMARY PRISM, SECONDARY PRISM, SEC- ONDARY BIPYRAMID, AND DITETRAGONAL BIPYRAMID 59 FIG. 65. MODEL OF BISPHENOID .60 FIG. 66. CHALCOPYRITE 60 FIG. 67. CHALCOPYRITE, FRENCH CREEK, PENNSYLVANIA ... 60 FIG. 68. CHALCOPYRITE, NEUDORF 61 FIG. 69. PYRITOHEDRON DERIVED BY DISAPPEARANCE OF TETRA- HEXAHEDRAL PLANES DARKENED, AND GROWTH OF THE OTHER PLANES 62 FIG. 70. MODEL OF A DIPLOID . 62 FIG. 71. MODEL OF COMBINATION OF PYRITOHEDRON AND CUBE . 63 LIST OF ILLUSTRATIONS XV PAG3 FIG. 72. MARCASITE . . . . . ._-'-'.*. . . . 64 FIG. 73. MARCASITE ..... " . ... 64 FIG. 74. " SPEARHEAD PYRITES " . . . / . ; . . 65 FIG. 75. " COCKSCOMB PYRITES " . ... . .> . ^. . 65 FIG. 76. ARSENOPYRITE . . .: . . . . ~\ .' . 67 FIG. 77. ARSENOPYRITE . . . . . . .' ... 67 FIG. 78. SYMMETRY PLANES OF A DITRIGONAL POLAR CRYSTAL . 68 FIG. 79. AXES OF HEXAGONAL SYSTEM - . . . ". .- . 68 FIG. 80. MODEL OF PRIMARY PYRAMID .... . . 69 FIG. 81. BASAL SECTION SHOWING RELATION OF PRIMARY, SECOND- ARY, AND DlHEXAGONAL PYRAMIDS AND PRISMS . . 69 FlG. 82. MODEL OF DlHEXAGONAL BlPYRAMID ..... ... . 69 FIG. 83. MODEL OF PRIMARY HEXAGONAL PRISM . : . * . . 70 FIG. 84. SECONDARY HEXAGONAL PRISM ... . . . 70 FIG. 85. MODEL OF DIHEXAGONAL PRISM ., . . . . . 70 FIG. 86. RHOMBOHEDRON RESULTING FROM DISAPPEARANCE OF DARKENED PLANES OF THE INTERIOR FIGURE HEXAGONAL BIPYRAMTD . ... . . . 71 FIG. 87. MODEL OF POSITIVE SCALENOHEDRON . . . . . 71 FIG. 88. MODEL OF SCALENOHEDRON TRUNCATED BY RHOMBO- HEDRON . .... . . . . . 71 FIG. 89. MODEL OF TRUNCATED PRISM .... . . 71 FIG. 90. PYRARGYRITE, CRYSTAL FORM . . . . . . 72 FIG. 91. PREVAILING FORM OF TETRAHEDRITE . . . . . 73. FIG. 92. CHARACTERISTIC FORM OF TETRAHEDRITE . . . . 73; FIG. 93. TENNANTITE (SCHWATZITE) ... . . . . 74. FIG. 94. MODEL OF SANDBERGERITE . . , , . . 74 FIG. 95. HALITE CUBE FROM SALT BRINE ,. . ^ ,. ., . . . 77 FIG. 96. FLUORITE 78 FIG. 97. FLUORITE . 78- FIG. 98. MODEL OF FLUORITE TWIN 79, FIG. 99. QUARTZ; PRISM AND RHOMBOHEDRON 83, FIG. 100. QUARTZ . . v . 83 FIG. 101. A FORM OF QUARTZ COMMON AT ALSTON MOOR, ENGLAND 83 FIG. 102. QUARTZ '. , . ; .. ,. . 83 FIG. 103. QUARTZ; POSITIVE LEFT TRIGONAL TRAPEZOHEDRON . 84 FIG. 104. QUARTZ; POSITIVE RIGHT TRIGONAL TRAPEZOHEDRON . 84 FIG. 105. Two RIGHT-HANDED QUARTZ CRYSTALS TWINNED . . 85 FIG. 106. BRAZIL TWIN; RIGHT- AND LEFT-HANDED QUARTZ CRYSTALS INTERPENETRATING . . . .85. FIG. 107. BRAZIL TWIN. Two RIGHT-HANDED CRYSTALS JUXTA- POSED 86 FIG. 108. QUARTZ; BOURG DE OISANS TWIN 86 xvi LIST OF ILLUSTRATIONS PAGE FIG. 109. QUARTZ ETCHED WITH HYDROFLUORIC ACID; A, LEFT- HANDED; B, RIGHT-HANDED 86 FIG. no. AIRY'S SPIRAL IN RIGHT-HANDED CRYSTAL . ... 88 FIG. in. CUPRITE 92 FIG. 112. ZINCITE . . . . . . *. . :. . . 93 FIG. 113. CORUNDUM . .' . . 94 FIG. 114. CORUNDUM . . 95 FIG. 115. CORUNDUM WITH TWINNING LAMELLAE PARALLEL TO R . 95 FIG. 116. CROSS-SECTION OF DICHROSCOPE . . . ... , .. . 96 FIG. 117. DIRECTION OF VIBRATION OF Two RAYS OF LIGHT PASSING THROUGH CALCITE PRISM . . . . . .96 FIG. 118. RUBY . . . ; . 97 FIG. 119. SAPPHIRE . ..... . .... 97 FIG. 1 20. MODEL OF RHOMBOHEDRON . ' . . . .. . . 98 FIG. 121. HEMATITE 99 FIG. 122. TABULAR HEMATITE CRYSTAL TWINNED PARALLEL TO THE PRISM . . y . . . . . . . .99 FIG. 123. MANGANITE , . . ... / . . . 100 FIG. 124. MANGANITE '. . . . ..-.,.. 100 FlG. 125. GOETHITE . . . . . . .. . . . 102 FIG. 126. GOETHITE . ..... . . . v . . . 102 FIG. 127. SPINEL TWIN . . . '1 . . .... . 105 FIG. 128. SPINEL .- , . . . . .' . . . .105 FIG. 129. MAGNETITE . , . . . . . . . . 106 FIG. 130. CASSITERITE .... ... . . . . . 108 FIG. 131. CASSITERITE . . . . . . . . . .108 FIG. 132. RUTILE , . .'...... . . .109 FIG. 133. RUTILE TRIPLET no FIG. 134. RUTILE OCTET no FIG. 135. CALCITE. POSITIVE RHOMBOHEDRON; CLEAVAGE RHOM- BOHEDRON . . . ... . . . '. 113 FIG. 136. CALCITE. NEGATIVE RHOMBOHEDRON . . . .113 FIG. 137. CALCITE. NEGATIVE ACUTE RHOMBOHEDRON . . .114 FIG. 138. CALCITE, SCALENOHEDRON 114 FIG. 139. CALCITE, PRISM AND NEGATIVE OBTUSE RHOMBOHEDRON 114 FIG. 140. CALCITE, SHOWING PRISM, NEGATIVE OBTUSE RHOMBO- HEDRON, AND BASE -. ' . . 114 FIG. 141. CALCITE; COMBINATION OF SCALENOHEDRON AND RHOM- BOHEDRON . . . . . ,'; ... . 114 FIG. 142. CALCITE RHOMBOHEDRON .... . . : . 114 FIG. 143. CALCITE SCALENOHEDRON ... . . . 115 FIG. 144. CALCITE SCALENOHEDRON 115 LIST OF ILLUSTRATIONS xvii PAGE FIG. 145. CALCITE PRISM . . . . 115 FIG. 146. CALCITE SCALENOHEDRON . . . ~ . ' . . . 116 FIG. 147. CALCITE SCALENOHEDRON . . - . . ... . 116 FIG. 148. CALCITE ETCHED WITH DILUTE HYDROCHLORIC ACID . 118 FIG. 149. DOLOMITE ETCHED WITH DILUTE HYDROCHLORIC Aero . 118 FIG. 150. ELASTICITY COEFFICIENT or CALCITE . . . . . 119 FIG. 151. ELASTICITY COEFFICIENT OF DOLOMITE . . . .119 FIG. 152. GLIDE PLANES IN CALCITE . . . . . . . 119 FIG. 153. ARAGONITE. ..... . .. . . . .123 FIG. 154. BASAL SECTION OF ARAGONITE TRIPLET . / . . 124 FIG. 155. B ASAL SECTION OF ARAGONITE; INTERPENETRANT TRIPLET 124 FIG. 156. WITHERITE . . ... . . ... .125 FIG. 157. CROSS-SECTION OF WITHERITE . . .... . 125 FIG. 158. CERUSSITE . . .- . . . . . . . 127 FIG. 159. CERUSSITE " . . . . . 127 FIG. 1 60. THREE CERUSSITE CRYSTALS INTERPENETRATING PAR- ALLEL TO PRISM PLANES . . v ; . . . . 127 FIG. 161. AXES OF MONOCLINIC CRYSTAL . ... . ' . . . 128 FIG. 162. MONOCLINIC BIPYRAMID . . . . . * 129 FIG. 163. ORTHODOMES AND CLINODOMES . .'-... . . . 129 FIG. 164. MODEL OF PRISM AND BASAL PLANE . . . . . 130 FIG. 165. MALACHITE SECTION .. .... ... . 130 FIG. 1 66. AZURITE CRYSTAL, SHOWING ALSO POSITION OF OPTIC AXES AND AXIAL PLANE 131 FIG. 167. MODEL OF AN ORTHOCLASE CRYSTAL ... . . 134 FIG. 1 68. ORTHOCLASE . . ' . . . . . " . . . 134 FIG. 169. ADULARIA ORTHOCLASE . . . . ... . 134 FIG. 170. MODEL OF CARLSBAD TWIN, INTERPENETRATING . . 134 FIG. 171. BAVENO TWIN, COMPOSITION FACE . . .... 134 FIG. 172. MANEBACH TWIN, COMPOSITION FACE . . . .134 FIG. 173. ORTHOCLASE SECTION; AXIAL PLANE, ANGLE OF EXTINC- TION 135 FIG. 174. ORTHOCLASE (ADULARIA); AXIAL PLANE . . . -. . 136 FIG. 175. ORTHOCLASE; POSITIVE AND NEGATIVE DIRECTION OF EXTINCTION 136 FIG. 176. TRICLINIC AXES OF COPPER SULPHATE; No AXES AT RIGHT ANGLES . . . 139 FIG. 177. ALBITE . . . . : . . * ... . 140 FIG. 178. ALBITE, SHOWING ALBITE LAW ., V . . . . 140 FIG. 179. ALBITE, PERICLINE TWIN . . . . ,. . . 141 FIG. 1 80. ALBITE; AXIAL PLANE . . 141 FIG. 181. ALBITE SECTION . 141 xviii LIST OF ILLUSTRATIONS PAGE FIG. 182. ALBITE SECTION . . .141 FIG. 183. RHOMBIC SECTION OF ANORTHITE ,142 FIG. 184. ANORTHITE, SHOWING POSITION OF AXIAL PLANE AND BISECTRIX 142 FIG. 185. MICROSCOPIC SECTION OF LEUCITE BETWEEN CROSSED NICOLS . . ? 145 FIG. i860. DIOPSIDE . . . , . '. 147 FIG. 1 86ft. PHOTOGRAPH OF DIOPSIDE FROM CANTLEY, QUEBEC, CANADA . . . ..... . . . 147 FIG. 187. DIOPSIDE ...... v 7 * 148 FIG. 1 88. DIOPSIDE, SHOWING OPTIC AXES, ACUTE BISECTRIX, AXES OF ELASTICITY 148 FIG. 189. AUGITE .... . . . . . . . 148 FIG. 190. AUGITE TWIN . 148 FIG. 191. AUGITE CROSS-SECTION PERPENDICULAR TO PRISM PLANES 149 FIG. 192. ENSTATITE, SHOWING PARALLEL EXTINCTION . . . 149 FIG. 193. DIOPSDDE, SHOWING OBLIQUE EXTINCTION ANGLE . .149 FIG. 194. RHODONITE . .151 FIG. 195. ANTHOPHYLLITE, AXIAL PLANE AND OPTIC AXES . .152 FIG. 196. HORNBLENDE 154 FIG. 197. HORNBLENDE .. ...'..';..'.'.' 154 FIG. 198. HORNBLENDE SECTION PERPENDICULAR TO PRISM . .154 FIG. 199. HORNBLENDE , i, ".-... r ' '. . , '. . . 154 FIG. 200. ANTHOPHYLLITE; PARALLEL EXTINCTION . . . .155 FIG. 201. TREMOLITE; EXTINCTION ANGLE 155 FIG. 202. HORNBLENDE; EXTINCTION ANGLE 155 FIG. 2030. PHOTOGRAPH OF BERYL FROM BRAZIL 157 FIG. 2036. BERYL .... . . . . " . . .. . 157 FIG. 204. GARNET . . ... . . .... . . . 158 FIG. 205. GARNET . . , t . . . . . . . . . 159 FIG. 206. GARNET . .... 159 FIG. 207. ZIRCON 161 FIG. 208. ZIRCON ... . 161 FIG. 209. TOPAZ 162 FIG. 210. TOPAZ, SHOWING OPTIC AXES AND AXIAL PLANE . . 162 FIG. 211. TOURMALINE 164 FIG. 212. TOURMALINE 164 FIG. 213. TOURMALINE, ANALOGOUS END . . . . ' . .165 FlG. 214. FOUR-TWINNED CRYSTALS OF STILBITE .... l66 FIG. 215. STILBITE SHEAF 166 FIG. 216. LEUCITE 167 FIG. 217. NATROLITE 168 LIST OF ILLUSTRATIONS xix PAGE FIG. 218. MUSCOVITE . . .' . . . : . . . 169 FIG. 219. MUSCOVITE: PRESSURE FIGURE, PERCUSSION FIGURE, OPTIC AXES . . . . ... . .169 FIG. 220. BIOTITE; AXIAL PLANE 171 FIG. 221. BASAL SECTION OF BIOTITE, SHOWING POSITION OF AXIAL PLANE AND PERCUSSION FIGURE 171 FIG. 222. APATITE , . ,. . ; > . * . . . . . . 175 FIG. 223. BARITE ... . 179 FIG. 224. BARITE . . * 179 FIG. 225. BARITE 179 FIG. 226. CELESTITE 180 FIG. 227. ANGLESITE 181 FIG. 228. ANGLESITE 181 FIG. 229. GYPSUM . . . * , . . ^ 2 FIG. 230. GYPSUM . . . . 182 FIG. 231. GYPSUM . . 182 FIG. 232. GYPSUM TWINNED BY JUXTAPOSITION 183 FIG. 233. GYPSUM, TWINNED BY INTERPENETRATION . . .183 FIG. 234. WOLFRAMITE 185 FIG. 235. WULFENITE 186 FIG. 236. WULFENITE . . . 186 PLATE I. a, PREVAILING FORMS OF THE DIAMOND. G. F. WILLIAMS COL- LECTION; b, GLASS MODEL OF CULLINAN DIAMOND, THE LARGEST DIAMOND EVER FOUND. PLATE II. CONSTRUCTION OF RIGHT-HAND UPPER OCTANT OF TRISOCTA- HEDRON ABOVE AND OF TRAPEZOHEDRON BELOW. PLATE III. CONSTRUCTION OF ONE OCTANT OF HEXOCTAHEDRON. PLATE IV. DENDRITIC COPPER FROM CALUMET AND HECLA MINING REGION, MICHIGAN. PLATE V. MUKEROP METEORITE, ONE-SIXTH NATURAL SIZE. FELL IN AMALIA-GOAMUS, WEST AFRICA. PLATE VI. a, STIBNITE, JAPAN; b, MOLYBDENITE FROM ALDFIELD, PONTIAC COUNTY, QUEBEC, CANADA. PLATE VII. a, GROUP OF PYRITE CUBES, SHOWING STRIATIONS, CENTRAL CITY, COLORADO; b, PYRITE. A PYRITOHEDRON AND CUBES, COLO- RADO. PLATE VIII. MARCASITE, Jo DAVIESS COUNTY, ILLINOIS. PLATE IX. MARCASITE DISKS, GULF MINE, SPARTA, RANDOLPH COUNTY, ILLINOIS. xx LIST OF ILLUSTRATIONS PLATE X. MARCASITE, SHOWING RADIATED INTERNAL STRUCTURE. PLATE XL MARCASITE COATING GALENA, MARSDEN MINE, Jo DAVIESS COUNTY, ILLINOIS. PLATE XII. FLUORITE GROUP FROM ROSICLARE, HARDIN COUNTY, ILLINOIS. PLATE XIII. a, FLUORITE CUBES, ROSICLARE, ILLINOIS; b, OCTAHEDRONS CLEAVED OUT BY TEN- YEAR-OLD BOY, SHOWING EASE AND REGU- LARITY OF CLEAVAGE. PLATE XIV. a, SMOKY QUARTZ, "CAIRNGORM," FROM MONTANA; b, QUARTZ, MONTGOMERY COUNTY, ARKANSAS. PLATE XV. QUARTZ GROUP, MONTGOMERY COUNTY, ARKANSAS. PLATE XVI. QUARTZ, "BOURG DE OISANS" TWIN, HOT SPRINGS, ARKANSAS. PLATE XVII. AMETHYST, THUNDER BAY, LAKE SUPERIOR. PLATE XVIII. Moss AGATE, INDIA. PLATE XIX. a, BOTRYOIDAL HEMATITE, CUMBERLAND, ENGLAND; b, LIMONITE, HARDIN COUNTY, ILLINOIS. PLATE XX. CALCITE, WEBB CITY, MISSOURI. PLATE XXI. a, CALCITE, "DOG-TOOTH SPAR," JOPLIN, MISSOURI; b, CALCITE, "ICELAND SPAR," SHOWING DOUBLE REFRACTION. PLATE XXII. CALCITE, JOPLIN, MISSOURI. PLATE XXIII. CALCITE SCALENOHEDRON, ROSSIE, ST. LAWRENCE COUNTY, NEW YORK. PLATE XXIV. a, CALCITE, JOPLIN, MISSOURI; b, QUARTZ GEODE WITH LARGE FLAT RHOMBOHEDRAL CRYSTALS, ST. FRANCISVTLLE, MISSOURI. PLATE XXV. a, ARAGONITE CRYSTALS FOUR INCHES IN DIAMETER, CIANCIANA, SICILY; b, STALACTITES, BISBEE, ARIZONA. PLATE XXVI. a, MICROCLINE, "AMAZON STONE," PIKE'S PEAK, COLO- RADO; b, MICROCLINE, PIKE'S PEAK, COLORADO. PLATE XXVII. a, GARNETS; DODECAHEDRON FROM SALIDA, COLORADO, TRAPEZOHEDRON FROM NORTH CAROLINA, AND COMBINATION FROM FORT WRANGEL, ALASKA; b, A DODECAHEDRON NEARLY FOUR INCHES IN DIAMETER FROM SALIDA, COLORADO. PLATE XXVIII. a, TOURMALINE DOUBLY TERMINATED; VARIOUSLY COLORED CRYSTAL FROM MESA GRANDE, CALIFORNIA; b, BLACK, WELL-CRYSTALLIZED SPECIMEN FROM HADDAM, CONNECTICUT. PLATE XXIX. a, APATITE, RENFREW, CANADA; b, BARITE, ALSTON MOOR, ENGLAND. PLATE XXX. GYPSUM, SHOWING FISHTAIL TWIN AND CURLED FORM. PLATE XXXI. GYPSUM, "SELENITE," WAYNE COUNTY, UTAH. ABBREVIATIONS a, b, c = Crystallographic axes a, b, C = Direction of greatest, medium, and least elasticity a, j8, 7 = Greatest, medium, and least index of refraction a, j8, 7 = Angles between crystallographic axes e = Direction of the extraordinary ray or its index of refraction 2 E = Apparent value of axial angle in the air 7 a = Maximum biref raction 2 H = Value of axial angle when mineral is immersed in oil n = Index of refraction p = Axial angle of red light 2 V = True value of angle between optic axes v = Axial angle of violet (blue) light co = Index of refraction of the ordinary ray XXI INTRODUCTION Minerals play a large part in the annual increase in wealth and in the comfort of the inhabitants of Illinois. The state is not usually thought of as a mineral-producing region, as is Colorado, Montana,, or California, and the fact is not usually known that the money value of the minerals obtained in this state exceeds that of any state west of the Mississippi River. But such is the case. During the year preceding the world- war the total value of mineral products in Illinois amounted to more than one hundred and seventeen millions of dollars, while that of California, the nearest competitor, was only one hundred and one millions, and Colorado and Montana together fell even farther be- hind Illinois in mineral production. The use of minerals is an index of civilization. Man is the only member of the animal kingdom to utilize minerals; and the more primitive his place in human society, the less does he do so. The whole fabric of civilization depends upon iron, copper, gold, and other metals, and upon coal, building stone, and clays. The people of our state produce some of these substances in great quan- tities and use all kinds of minerals from all corners of the globe. Some minerals occur in extensive deposits in the state, others are scattered here and there. The majority of those described in the following pages have been found within the region and many of the others are very useful for our people. While more than a thousand different minerals are known, only about one hundred are common enough to claim our special attention. These one hundred are well illustrated in the museum collections. Many visitors, while having a general idea of the subject, are unable to say just what a mineral is. Upon investigation they learn that a mineral is a natural, inorganic, homogeneous, solid, liquid, or gas. When solid, it is usually crystallized. Artificial substances such as are produced in laboratories, chemical works, iron foundries, etc., are excluded from the definition, although they often show perfection of form and purity of constitution. Min- eralogy is concerned with natural products. GUIDE TO MINERAL COLLECTIONS The term inorganic excludes all forms of living substance every- thing that grows by internal activity, that has the power of assimila- tion and reproduction, that has sensibility and usually slight chemical stability. A mineral may have had an organic origin. For example, the carbon of a piece of graphite may have been at one time in a tree. The tree died and with the loss of oxygen and hydrogen was converted into peat. The loss of oxygen and hydrogen continuing, the peat or lignite was changed into bituminous coal, then into anthracite, and finally into graphite. It is not the origin but its present condition which places a substance in the mineral kingdom. The term homogeneous indicates that the substance throughout is the same at one point as another, has the same arrangement, and shows the same properties. This separates a mineral from other inorganic substances such as rocks. A rock is made up of a mass of minerals. Usually a mineral is a solid. Some minerals for example, water and mercury are ordinarily liquid but may be changed into solids by freezing: water at 32 and mercury at 40 F. All minerals are solid under certain conditions. Minerals are usually crystallized; that is, they have a definite internal structure which is often shown by their external form. There are a few exceptions, such as turquoise and opal, and other substances which are solidified from gases or liquids so rapidly or under such other unfavorable conditions that the molecules are unable to properly arrange themselves. These minerals are said to be amorphous. They may be regarded as minerals that are unsuccessful or are of weak molecular attractions. Ordinarily a mineral has just as definite a shape as has a bird or a flower. It has less opportunity than a flower to develop a perfect external form, since it is usually crowded by its neighbors. The growing crystal soon reaches a place where its planes touch those of its neighbors and its perfection is impaired. But though the bounding planes are distorted and irregular, the internal arrangement is so orderly and definite that the smallest fragment has the same structure as a perfect crystal. This regularity of architecture in the mineral world is a fact of far-reaching importance. It discloses one of the great laws of the universe, a law as beautiful and universal as the law of gravitation, the conservation of energy, or the development of species. INTRODUCTION 3 The law of crystallization affects every particle of mineral matter in the world, and more than that, in the universe as well. The results are seen alike in the minutest' forms and on a gigantic scale. The most beautiful colors in the world the pure colors of the spectrum are exhibited by minerals in accordance with this law. Minerals are the most abundant and most valuable substances in the world. If all the vegetation in the world the great masses of weeds in Sargasso Seas, the myriads of land weeds, the flowers and grains, all the trees of the mighty forests if all of these were placed in an immense pile and to this pile were added all the lower animals, all mankind, and all the buildings in the world, the mass would be gigantic. But, if in another pile were heaped the minerals of which the world is composed, the first pile would be as a grain of sand to a mountain, so small as to be well-nigh invisible. In quantity minerals are of the greatest importance. In quality the same is true. They are unsurpassed in enduring beauty and value. Some diamonds like the Kohinoor, Regent, or the Cullinan are valued more highly than any other objects of the same size in the world. A ruby worth half a million dollars is so light in weight that it could be sent by mail across the continent for two cents. Mineral ornaments such as vases, tables, and columns in the palaces of the wealthy and in the great museums will remain unchanged in beauty and pleasure-giving power for many long years. Minerals are as beautiful as flowers and infinitely more permanent. Though the same sun with all diffusive rays Blush in the rose and in the diamond blaze, We prize the higher effort of his power And justly place the gem above the flower. 1 An acquaintance with minerals is useful in many trades and pro- fessions. The doctor of medicine and the pharmacist may be inter- ested in minerals as the source of drugs. The lawyer may be helped by some knowledge of mineralogy, especially in mining cases. The minister furnished by this science with an insight into the structure of the universe is better able to find "sermons in stones." From 1 Alexander Pope. 4 GUIDE TO MINERAL COLLECTIONS the study of the mineral composition of his soil the farmer is aided in soil improvement and in making " bread from stones." The physicist repeatedly uses minerals in his study of the laws of heat, light, and electricity. Even more dependent upon minerals as a source of materials for study and experiment is the chemist. For the geologist? the prospector, the miner, the assayer, and the metallurgist, min- eralogy is a fundamental science, one without which they cannot well work. Thus the mineral collections in the museum have a twofold claim upon the interest of the visitor: first, because they well illustrate the mineral resources of this state, and second, because they show the composition of the world and the uses which our people make of minerals to increase the comfort of living and their happiness. The visitor will naturally begin his inspection of this collection with the minerals that are the most simple in their composition those that are composed of but one chemical substance, the so-called elements. He will find that while there are about two dozen of them which occur in some abundance as minerals, not more than twelve are common enough to claim his attention. These are: diamond, graphite, sulphur, arsenic, antimony, bismuth, gold, silver, copper, mercury, platinum, and iron. Each of these is noteworthy because of its beauty or utility or because it shows some peculiar property. All of them except antimony, bismuth, mercury, and platinum have been found in the state. Diamond, graphite, and sulphur are non- metals; antimony and bismuth, brittle metals; gold, silver, copper, platinum, and iron, malleable metals; and mercury, a liquid metal under ordinary conditions. Together, these minerals constitute the most prominent representatives of Class I. PLATE I * a, Prevailing forms of the diamond. G. F. Williams collection b, Glass model of Cullinan diamond, the largest diamond ever found CLASS I. ELEMENTS Diamond There are several reasons for studying the diamond first, though Illinois is not a diamond-producing state. Not more than a dozen diamonds have been found here and they are immigrants brought in by glaciers which formerly slid down from the north, carrying all kinds of minerals collected from a wide area and scattering them here and there over two- thirds of the state. The chief source of the diamond is the Kimberley region in South Africa, but no people are more partial to the diamond as a gem than are the citizens of this state. Every woman has or expects to have one, and every man should at some time buy one ! The diamond is easily premier among gems. It is a fine example of a successful mineral. Its character is positive. It deserves the most extended study. While studying it we gain an insight into the whole mineral world. The Illinois State Museum con- tains a few examples of the diamond, and glass models of the most famous diamonds of history. If one examines a hand- ful of diamonds as they are taken from the mines at Kimberley (Plate I) or as they come uncut to Amsterdam, London, or New York City, he will observe that the greater number of them are shaped like two pyramids placed base to base forming an eight- sided figure called an octahedron (Fig. i). Some of them are flat, triangular flakes, others globules, and nearly all are somewhat dis- torted and pitted, with some planes well developed and others small. The larger faces were formed on that side of the crystal which had FIG. i. Model of octahedron; vailing outline of diamond. pre- 6 GUIDE TO MINERAL COLLECTIONS the most abundant material to draw from, while the small faces, like the smaller birds in a nest, receiving the least food, have not had equal opportunity for growth. But while the different faces vary in size, the angles between them are always the same. They are said to be constant, and illustrate the "law of constancy of angle " a law of far-reaching importance, since because of it minerals can readily be identified and classified. The natural shape of a mineral is one of the first characters to notice. What anatomy is to the student of the human body, cell structure to the morphologist, and architecture to the builder, crystal form is to the mineralogist. It is one of the fundamentals. The purpose of study of the form of minerals is not only to recognize and picture the external form but to understand the internal structure as well, since they are dependent upon each other. The architecture of the dia- mond may be better understood if JL+ the planes which occur on natural crystals can be represented by a drawing. Fortunately it is only necessary to measure off certain points and connect them by straight lines a much simpler task than it FIG. 2. Axes would be to draw the structures seen in the plant and animal worlds. Anyone can draw the shapes which diamonds exhibit. First draw three lines or axes which intersect each other at right angles (Fig. 2). In drawing these figures we use the method most generally employed, which is called " clinographic projection." The eye is supposed to be elevated a trifle above the crystal and removed an infinite distance so that the lines in the drawing do not converge as in ordinary perspective. Those parallel in the crystal are parallel in the drawing. To erect the axes, a templet cut out of cardboard may be con- structed in the following manner (Fig. 3) : Draw a vertical line MM' and NN' at right angles to it. Divide NN' into six equal divisions. At the second and fourth divisions _.**. ELEMENTS draw lines parallel to MM'. From N f mark N'O equal to one divi- sion. From draw a straight line through P to^O'. ad is the front to back axis of our crystal. From a draw aR parallel to N'N. From R draw RP. From S draw Sb parallel to NN'. From b draw bP and extend to b. bb is the horizontal axis extending from right to left. Twice OP gives the length of the c axis. These axes form the founda- tion for the construction of the axes used all through the work. An excellent discussion of the subject may be found in Tutton's Crystal- lography. 1 We always call the vertical line (Fig. 2) c; the horizontal M N 1 R O c M' FIG. 3. Method of constructing crystallographic axes. FIG. 4. Construction of an octa- hedral plane. line, extending from right to left, b; and the one extending from the front backward, a. The upper half of the c axis, the right half of b, and the front of a are said to be positive; the others, negative. To draw any given plane mark the points at which it would intersect the axes. In the octahedron (Fig. i) each plane intersects the three axes at points equally distant from the center. Then to draw an octahedral plane measure off equal distances on each axis and connect these points with straight lines (Fig. 4). To complete the octahedron, which has eight such planes, draw similar planes in each of the other octants (Fig. 5). 'Seepages 382-439. 8 GUIDE TO MINERAL COLLECTIONS The relation of the axes to each other was expressed by an Eng- lish mineralogist, W. H. Miller, of Cambridge (d. 1880), as a ratio, a: b : c. The portion measured off on each axis is written as a denomi- nator. Then the ratio which represents the octahedral plane is -:-:-, and its symbol is (in) which is read as one, one, one. When simply (in) is used, the right-hand upper octant is meant. The left-hand upper octant would c have the symbol (111) [read one, minus one, one]; the right-hand lower (111), the left-hand lower (in), the right-hand upper back (in), the left-hand upper back (in), etc. The diamond, like some other minerals, is symmetri- cally built. It has the same molecular structure in all directions. Light, heat, and electricity travel through it with the same ease and rapidity in the direction of all three of the axes, and the corrosive action of sol- vents is the same in all parts. Its axes are of the same value and interchangeable, and hence a numeral like i may be substituted for the letters a, b, and c and the ratio - : - : - then becomes -:-:-. This iii iii cleared of fractions yields i : i : i. The numbers in this ratio, i : i : i, constitute the " parameters" of the octahedral plane, since they define the position of the plane. The parameter of another plane might be 1:2:2 or 2:1:2, etc. The plane which has the parameter 1:2:2 represents a ratio - : - : and its symbol is (211) (Fig. 6). Since each of the three axes are equal, we can apply the 2 to each axis in turn and hence obtain three planes in every octant. FIG. 5. Completed octahedron 6- Construction of right-hand upper octant of a trisoctahedron above, and of a trapezohedron below. ELEMENTS Parameters 2:i:2 2:2:i Ratios I.I.I 2*1*1 III I*2'l I.I.I 1*1*2 Symbols (211) (121) (112) To construct these three planes in the right-hand upper octant (Plate II, lower diagram) measure off unit's distance on a and draw a line (red) cutting b at twice unit's distance, one cutting c at twice unit's distance, and one connecting the ends of b and c. Then from unit's FIG. 6. Model of trapezohedron FIG. 7. Completed trapezohedron distance on b draw lines (blue) cutting a and c at twice unit's dis- tance, and connect the ends. Finally, beginning at unit's distance on c draw lines (green) cutting a and b at twice unit's distance and connect the ends. These lines will determine the position of planes which will intersect each other so as to form three trapezoids in the octant. When the same plan is followed for the other octants there results a trapezohedron (Figs. 6 and 7). Having constructed figures with the symbol (in) and (211), the next in order will be one with the symbol (221) (Fig. 8). Its ratio will be -:-:- and its parameter 1:1:2. Just as in the case of the 221 10 GUIDE TO MINERAL COLLECTIONS trapezohedron, the numerals may be applied to each of the axes in turn. Thus writing the parameters, ratios, and symbols for the right-hand upper octant w.e obtain the following: Parameters Ratios III III III Symbols (221) (122) (212) Draw a line (red) cutting a and b at unit's distance and c at twice unit's distance (Plate II, upper diagram). From unit's distance FIG. 8 Model of trisoctahedron FIG. 9. Trisoctahedron completed on b draw lines (blue) cutting a at twice unit's distance and c at unit's distance. From unit's distance on c draw lines (green) cutting a at unit's and b at twice unit's distance. These lines determine the position of planes which intersect within the octant so as to produce triangles. The resulting planes are called trisoctahedral planes and the figure produced by continuing the process in each octant is called the trisoctahedron (Figs. 8 and 9). PLATE III Construction of one octant of hexoctahedron ELEMENTS II The next form in point of complexity is one whose planes intersect each axis at different distances (Fig. 10). For example, its parameter might be i : - : 3 ; its ratio then would be -:-:-, and its symbol (321). Since each number in the parameter is different, each of the three axes would be intersected at two points different from unity and there would result two planes at each corner of the octant, making six planes where the octahedron has but one. Writing the parameters, ratios, and symbols as before, the follow- ing result: Parameters Ratios Symbols 3 III , N i:-:3 ----- (3 21 ) a 3 2 i ;| 3 :i:3 I v : i (23I) 3=1=1 Proceed in the construction as was done with the octahedron, trapezohedron, and trisoctahedron. To construct, begin at unit's distance on a (Plate III) and draw a line (red) cutting b at three halves unit's distance and one cutting c at three times unit's distance. Com- plete the triangle by joining f& and 3^. Begin at unit's distance on b and draw a line (blue) cutting a at three halves unit's distance and one cutting c at three times unit's distance. Join f# and $c. Again from unit's distance on b draw other lines (blue dotted) cutting a at three times unit's distance and c at three halves. Join the ends. Continue the construction from c (with green) and a (with red dotted) as indicated and the six planes of the octant will be produced. They are called the hexoctahedral planes. The same operation repeated in each octant produces a hexoctahedron (Figs. 10 and n). 12 GUIDE TO MINERAL COLLECTIONS The faces above described are those most characteristic of the diamond, but usually faces of any one form do not make up the whole crystal. Sometimes planes of one form predominate and small FIG. 10. Model of hexoctahedron FIG. ii. Hexoctahedron completed FIG. 12. Growth of unshaded planes of the wooden octahedron produce the glass tetrahedron covering it. FIG. 13. Right-handed tetrahedron faces of another modify the corners. Often two crystals will inter- penetrate, each crystal having only half of its faces developed. If the right-hand upper octant and every alternate octant of the octa- hedron should grow to the exclusion of the other faces, a tetrahedron ELEMENTS (Figs. 12 and 13) would result. If the left-hand upper octant and each alternate octant were developed, a left-handed or negative tetrahedron would be produced (Figs. 14 and 15). FIG. 15. Left-handed tetrahedron FIG. 14. Wooden octa- hedron inclosed by glass tetrahedron. When two supple- mentary tetrahedrons interpenetrate, the form represented in Figure 16 results. It is called an interpenetrating tetrahe- dral twin. Where an octa- hedron would have sharp edges, these tetrahedral twins have re-entrant angles. Now if the projecting corners of each tetrahe- dron were truncated by the faces of the other tetrar hedron, a form resembling an octahedron would result, but trie re-entrant angles, instead of the characteristic edges, would reveal its true structure. This is a very common occurrence in the diamond (Fig. 17). FIG. 1 6. Interpenetrating supplementary tetrahedrons (tetrahedral twins). 14 GUIDE TO MINERAL COLLECTIONS Just as with the octahedron, so also with the trapezohedron, trisoctahedron, or the hexoctahedron, a portion only of the faces might be developed. If the right-hand upper octant and every alternate octant of a hexoctahedron were produced at the expense of their neighbors, a right-handed hexatetrahedron would result (Figs. 1 8 and 19). FIG. 17. Tetrahedral twin with corners truncated A left-handed or negative hexatetrahedron would be produced if the left-hand upper and every alternate octant were developed at the expense of their neighbors. A right-handed and a left-handed hexatetrahedron interpenetrating and having the corners truncated by tetrahedral planes give rise to one of the most characteristic forms of the diamond (Fig. 20). Upon taking up a diamond, one first notices the prevailing octahedral form, but closer inspection reveals the re-entering angles, and in these angles the slightly inclined hexatetrahedral planes may be recognized. ELEMENTS 15 Another form of twinning in the diamond is that which results when an octahedron is cut through the middle by a plane parallel to an octahedral face and one-half of the octahedron is turned 90 (as shown in Figs. 21 and 22). Diamonds of this sort are called " suture" stones by diamond dealers and by crystallographers "spinel twins/' since they are even more commonly found among specimens of the mineral named spinel. All of the above forms the octahedron, the trapezohedron, trisoctahedron, hexoctahedron, tetrahedron, and hexatetrahedron agree in this, that they are symmetrical in the same directions. If FIG. 1 8. Model of right-handed hexatetrahedron . FIG. 19. Construction of hexatet- rahedron. any of these forms were divided parallel to these directions, one-half would be just like the other. These directions are: first, parallel to any one of the three crystal- lographic axes, a, b, and c (Fig. 23); second, parallel to any one of the four axes perpendicular to the octahedral planes; third (Fig. 24), parallel to the six planes which would pass through the edges of a cube. Since this symmetry is best represented in a mineral called tetrahedrite, it is named the tetrahedrite class of symmetry. By the above study we have become acquainted with facts in regard to the crystallography of the diamond and, more than that, with facts which are needed to understand the forms of a hundred 16 GUIDE TO MINERAL COLLECTIONS other minerals as well. All of these minerals agree in this, namely, that the molecules which compose them arrange themselves similarly along three lines of equal length at right angles to each other, the a, b, and c axes. Hence these minerals are placed together in one of the six great groups in which all minerals are classified the group known as the Regular System. FIG. 20. Interpenetrating truncated tetrahedrons beveled by hexatetrahedrons As wood has certain directions in which it readily splits and con- trary to which it breaks in an irregular manner, so the diamond has a direction in which it readily splits or " cleaves," namely, parallel to the octahedral planes. By taking advantage of the cleavage, diamond cutters are more readily able to fashion the gem into the desired shape. Cleavage is so easily obtained that it is difficult to break or " fracture " the diamond. When it is broken and not cleaved or split, the fractured surfaces are pitted or rounded like a shell. Consequently the fracture is said to be conchoidal. Contrary to popular report, the diamond is brittle and easily shattered. Many valuable gems have been destroyed by the finders, ELEMENTS who failed to recognize the difference between hardness and tenacity. For centuries it has been a tradition that if a diamond were laid upon an anvil and struck by a hammer, both anvil and hammer would fly to pieces before the diamond was broken. Pliny said that the only way to "subdue" a diamond is to "soften it in warm goat's blood"! Although the diamond is brittle, it is the hardest of minerals. FIG. 2i. "Spinel twin" model. Twin- ning plane (in). FIG. 22. Drawing of spinel twin Scale of Hardness To measure the hardness of minerals a scale 1. Talc 2. Gypsum 3. Calcite 4. Fluorite 5. Apatite 6. Orthoclase 7. Quartz 8. Topaz 9. Corundum 10. Diamond has been arranged which consists of ten minerals so chosen that, beginning with the softest, each succeeding mineral is hard enough to scratch the one before it in the scale. Talc, which is the softest, is given as No. i in this list, and diamond as No. 10. The finger-nail can scratch any mineral below 3, and a knife-blade any below 6. When the weight of the diamond is compared with that of an equal volume of water, the diamond is found to be three and one- half times as heavy as water, i.e., its specific gravity is 3 .5. It is much heavier than glass (sp. gr. about 2.5), which is most commonly employed to imitate it, or quartz (sp. gr. 2.6), the most abundant mineral that resembles diamond, or phenacite, " the Specific Gravity of 1. Glass 2.5 2. Quartz 2.6 3. Phenacite 2.9 4. Topaz 3 . 5 i8 GUIDE TO MINERAL COLLECTIONS deceiver" (sp. gr.=3), which is sometimes worn to represent the more valuable gem. The diamond shows color from two causes: first, because of actual coloring materials in it; and second, because it divides a ray of enter- ing light into the colors of the spectrum. The coloring matter is usually some metallic oxide which does not change when heated. Sometimes the coloring matter is organic material which does fade when heated or held in sunlight. Many shades are seen red, yel- low, green, blue, indigo, brown. Yellow and brown are the most com- mon among African dia- monds. Brown may deepen into black, as in the opaque ''carbons." Green is not so common. Blue and red are the rarest, and when these colors are pure, the dia- mond exhibiting them is the most valuable gem in the world. About half of all diamonds found are white or colorless. The color or "fire" which they then show is due to the fact that a ray of light which enters at an angle is refracted or turned very markedly from its course and is divided into rays of different wave- lengths. The result obtained by dividing the angle which the entering light makes with a perpendicular erected to the surface of the mineral (called the angle of incidence, i in Fig. 25) by the angle which the ray makes with the perpendicular prolonged after it has entered the mineral (called the angle of refraction, r in the figure) is called the index of refraction. Thus FIG. 23. Two kinds of axes of symmetry n = Sin I sin r ELEMENTS 19 The index of refraction n has a different value according to the kind of light used. For blue light in the diamond it is 2.465; for red, 2.402. That is, a blue ray is turned farther from a straight line than is a red ray. Now the difference between these indexes, 0.063, * s called the dispersion. Both the refraction and disper- sion of diamonds are high in comparison to the refraction and dispersion of other minerals. Because of its high refraction the diamond is unusually brilliant. It is said to show "life." Because of its high dispersion it has a remarkably vivid play of colors or "fire." Mean Refractive Index of Ice 1.31 Salt i . 54 .Quartz 1.55 Topaz 1.62 Glass i . 80 Cinnabar 3 .02 Dispersion of Fluorite .006 Quartz .025 Diamond .063 ^^TI ~--^\ \ / r^ i \ / \ / \ / \ I \ s X \ / \ \ / *X /\ ^ \ / \ / \ / / \ / \ ./,.- \- 1 \ /**' v L^^ FIG. 24. Dotted lines show direction FIG. 25. Angles of incidence and of planes of symmetry in cube. refraction. Some diamonds which have a bluish tinge after being held in the sunlight emit light in the dark, i.e., become phosphorescent. Many phosphoresce after being rubbed on wood or while being subjected to an electric discharge in a vacuum or while exposed to radium emanations. Positive electricity is developed in the diamond by friction. The diamond is worthy of its place as the leading gem, not only because of its hardness, brilliancy, and beauty of color, but also because of its permanency in the presence of corrosive gases and liquids. The air and moisture do not affect it. Ordinary acids 20 GUIDE TO MINERAL COLLECTIONS cannot dissolve it. A solvent composed of sulphuric acid and potas- sium bichromate acts upon it slowly. At a high temperature (goo C. ) in an oxygen flame, the diamond burns to carbon dioxide just as pure charcoal does, and sometimes leaves an extremely light ash that retains the original crystal shape and consists of iron, calcium, magnesium, and silicon which were present as impurities. Though used as a gem for many hundreds of years, it is only within comparatively recent times that cutting of the diamond has been resorted to to enhance its beauty. Cutting and polishing are accom- plished by the use of diamond dust imbedded in a tin disc or an iron plate. Besides its use as a cutting tool, in its less well-crystallized forms it is extensively used to make drills. The diamond drill is one of the most useful implements invented for piercing rock in the search for valuable ores. The drills are made from the forms of diamond called bort and carbonado. Bort has radial fibrous structure, curved drusy surface, and is dark in color. Carbonado is somewhat compact, altogether without cleavage, slightly porous, black like charcoal, and somewhat harder than ordinary diamond. It is valuable for drills. Diamonds have been found in nearly every part of the globe, yet for some cause or other in quantities worth mentioning only in regions less than 30 from the equator.' A line following their most abundant occurrence would begin in southeastern Australia and extend east- ward to South America; there, dividing into two branches, would pass in one branch north of the equator to British Guiana, and in the other, south to Bahia in Brazil. The northern branch extended would finally reach India, most prolific of ancient localities, and the southern branch would reach South Africa at Kimberley, the most productive of modern regions. In India diamonds were first found and prized as gems. Most of the famous historical gems came from there. That field is now exhausted. The New South Wales fields yield about sixty thousand dollars' worth a year, British Guiana twice that amount, and Brazil five times that amount, while South Africa so far surpasses these regions as to make them hardly worth mentioning. It easily produces twenty-five million dollars' worth annually. In India, Australia, South America, and also in a few localities in the Urals, and in Wisconsin, Michigan, Illinois, etc., diamonds ELEMENTS 21 have been found in sands and gravels in which they were imbedded when the original rock containing them was broken up and trans- ported by glaciers or flowing streams. In the Kimberley region, however, they occur in a greenish-blue igneous rock called kimberlite, a sample of which is shown in Case i . The kimberlite occupies crater-like basins, sometimes nearly half a mile in diameter and of unknown depth, in the Triassic rocks of that region. In Arkansas kimberlite has been found and has yielded a few diamonds. Meteorites often contain minute diamonds. Glass models of diamonds of unusual size and value, several of which have been long known and owned by kings and other celeb- rities, are shown in Case i. No diamond is more famous than the Kohinoor. It weighs 106 carats and is valued at more than half a million dollars. It was found in India six hundred years ago (1304 A.D.) and for centuries was fought for or purchased by various rulers. It is now exhibited among the English crown jewels in London. The Regent, which weighs 136 carats and is valued at six hundred thousand dollars, has had a most eventful history from the time when it was found in India by a slave, stolen from him by a sailor, bought and sold at ever-increasing price, till it came to sparkle in the hilt of Napoleon's sword, and finally, as one of the gems of the French Republic, was placed where it could ever after be inspected by all who cared to see it in the priceless collections of the Louvre, Paris. The next is the Orloff, 193 carats, valued at half a million dollars, shaped so as to fit in the eye socket of an idol in India, from which it was stolen by a French soldier, finally purchased by Prince Orloff who sold it to Catherine II of Russia; and when last heard of it was in the Winter Palace, Petrograd. Still larger is the Jubilee, 239 carats, valued at two million dollars, found in South Africa in 1895, and now in England. The largest diamond ever found was the Cullinan (Plate I), named after the discoverer of the Premier Diamond Mine, South Africa. It was picked up in a shallow pit in that mine in January, I 95 J by a foreman, who was given ten thousand dollars for his good 22 GUIDE TO MINERAL COLLECTIONS fortune in recognizing it. It weighed uncut 3,025! carats, or about one and one-quarter pounds, and was valued at three million dollars. The Transvaal Republic donated it to King Edward VII of England, who, it was hoped, would place it unaltered in a museum to show for all time the largest diamond ever found. But the king had it cut into eleven brilliants four of which are yet larger than any others known. Many diamonds smaller than those mentioned above are interesting because of their history. ' The South Star, the largest diamond found in Brazil (in 1853) weighs 125 carats, is valued at four hundred thousand dollars, and is now owned by a prince in Bztroda, India. The Shah of Persia, 86 carats, now in Petrograd, has the shape of a four-sided prism with inclined ends. No diamond has had a more varied history than the Sancy. It was found in India and, after being in the possession of Charles the Bold, who lost it on a battlefield, then among the jewels of the French Count De Sancy, then of Queen Elizabeth, then of Louis XIV, then of the King of Spain, and then of a Russian Prince Demidoff, has again been taken back to India by a native prince. All of the above-named are beautiful white stones. There are some colored ones greatly prized, as, for example, the yellow Floren- tine and the blue Hope diamond. The Florentine, found in India, is now among the Austrian state jewels, after having been owned by Charles the Bold, Pope Julius, and the Empress of Austria. The Hope diamond is the most famous of all colored stones. It is of a vivid blue. It has been owned by wealthy and titled people in Italy, France, and England, and now is in the possession of a family in Washington, D.C. SUMMARY Diamond. C. Regular; tetrahedrite class of symmetry: (m), (321); supplementary twins of tetrahedrons and contact twins on (in). Cleavage parallel (in) perfect; brittle; fracture conchoidal. Hardness = i o ; gravity =3.52. Colorless, yellow, brown, purple, red, blue; luster, greasy; trans- parent ; refraction very strong, n = 2 . 41 7 ; dispersion very strong = o . 063. Infusible; soluble in sulphuric acid and potassium bichromate. Australia, South America, South Africa. ELEMENTS 23 Graphite Graphite (ypafaiv, "to write"), another form of pure carbon, though not abundant in Illinois, is scattered in flakes through gneisses and other rocks which have been strewn over the state. It is a mineral so useful in many of our activities that it could not be spared. What, for example, would the people of the state do without lead pencils, lampblack, stove polish, graphite paints, and lubricants? The specimens on exhibit came from New Jersey, Ottawa, Canada, and Ceylon, of which localities the last has yielded the greatest quantities of the finest quality. While the diamond is very pronounced in its shape, graphite is a mineral of weak molecular attraction. Its external form is not marked and, since it is opaque and cannot be studied under the micro- scope, there is even some doubt as to what its system of crystallization really is, although it is classified as hexagonal. Usually it occurs in leafy or scaly flakes disseminated in rocks that originally were like limestone but have been changed by heat into marble or into other metamorphic rocks. Often it is segregated into compact, granular, or earthy masses forming veins in gneisses and schists. While diamond is the hardest of substances, there is no mineral softer than pure graphite; while diamond is transparent and of light color, graphite is opaque and black ; while diamond is a non-conductor of electricity, graphite is a good conductor. These differences are probably due to different arrangement of the atoms in the molecule, the graphite molecule containing three atoms, while that of the diamond contains nine. Graphite is greasy to the touch, flexible, i in hardness, 2 in specific gravity, infusible, and insoluble. Its specific heat is similar to that of the diamond. By specific heat is meant the heat required to raise one gram of a substance through one degree Centigrade. Taking as the unit the amount of heat required to raise one gram of water one degree in tempera- ture, graphite requires only .12 and diamond .18 as much. In the electric arc, diamond can be converted into graphite or graphite to diamond by varying the conditions. Graphite is chiefly used for pencils, stove polish, paint, crucibles, and lubricants. In early days only the purest graphite could be 24 GUIDE TO MINERAL COLLECTIONS employed for "lead pencils" since the "leads" were cut out of the solid material. Now material containing much foreign matter is pulverized and washed to free it from impurities, mixed with clay, and burned. The amount of clay used and the heat employed determine the degree of hardness of the pencil. Graphite is a valuable paint where heat is to be resisted. For the same reason because of its extreme infusibility, and for its reducing action, i.e., its tendency to keep oxygen away from molten metals it is employed for crucibles. As a lubricant it is useful for heavy machinery or wherever heat would destroy other lubricants. All of these uses are well illustrated in the graphite case. SUMMARY Graphite. C. Hexagonal (?); in plates, scales, masses. Cleavage basal, perfect; flexible. Hardness=i; gravity=2; black; streak gray; luster, metallic. Ceylon, Siberia, Canada, Mexico. Sulphur One of the most interesting sights in one of America's most charm- ing parks the Yellowstone National is a group of hills, the highest of which rises a few hundred feet above the surrounding country and is called "Sulphur Mountain." It is composed of siliceous and cal- careous material mingled with vast quantities of sulphur. From the yellowish-gray mass here and there sulphurous vapors arise, and in many places sulphur springs burst forth and run in rivulets down the side of the hill, leaving behind a yellowish- white trail. In many places on the hill the sulphur is quite pure, earthy in character, and yellowish-gray in color. The cavities from which fumes are escaping are often lined with deposits of pure yellow sulphur that hang in clustered crystalline masses and have been formed by the sublimation of sulphurous vapors. Sublimation deposits characteristic of volcanic regions do not furnish fine crystals such as may be obtained from Sicily, where in the marly limestones hot waters laden with sulphur in solution have deposited their burden under favorable conditions and produced large crystals. Samples of sulphur from the Yellowstone and from Sicily are shown. Illinois occurrences are limited to whitish masses remaining from decomposition of iron sulphide or calcium sulphate. ELEMENTS The structure of the sulphur crystal differs from that of a diamond, since sulphur has three well-defined directions in which light, heat, electricity, and various chemical reagents act with different ease and rapidity. Hence a sulphur crystal is represented by three axes of different lengths, which cross each other at right angles. These axes characterize the Orthorhombic System. In the regular system we found all axes equal; in the orthorhombic they are all unequal. The vertical axis c may be greater or less than the lateral axis b. Of the two lateral axes, the longer is always chosen as the b axis and the shorter as a. FIG. 26. Model of orthorhombic bipyramid FIG. 2 7 . Orthorhombic midal plane and axes. pyra- Since these axes represent different lengths and values, they cannot be interchanged as they were in the regular system. Upon them three different kinds of planes may be constructed: first, those which intersect all the axes; second, those which intersect two axes and are parallel to the third; and third, those which intersect one axis and are parallel to two. i. Planes which intersect three axes are called pyramid planes. They correspond to the octahedral planes of the regular system. When they intersect all three axes at unit's distance, the typical bipyramid results (Fig. 26). Figure 27 shows the construction of the pyramidal plane. 26 GUIDE TO MINERAL COLLECTIONS If the c axis is intercepted at one-third unit's distance, as is often the case with some planes that are found on sulphur, an obtuse bipyramid is produced (Fig. 28). 2. Besides pyramid planes occur the so-called dome planes (from domus, " house," since they are like a roof). They inter- sect two axes and are parallel to one of the lateral axes (Figs. 29-32). The plane which is paral- FIG. 28. Obtuse bipyramid (113) character- lel to the short axig ig the istic of sulphur. , -, , , , u brachydome, i.e., the short FIG. 29. Model of brachydomes and macropincacoids. FIG. 30. Upper brachydome planes (on). dome (Figs. 29 and 30). That one parallel to the long axis is called the macrodome, i.e., the long dome (Figs. 31 and 32). The domes do not produce closed figures unless united with each other or with some other planes. In Figures 29 and 31 they are closed by planes called pinacoids. Prism planes (Fig. 33), like domes, are parallel to one axis; but it is always the c axis to which a prism is parallel. The symbol of the prism may be (no) or (210), etc. ELEMENTS 27 3. The third kind of planes consists of those parallel to two axes and intercepting one axis. They are called pinacoids (from " plane") (Figs. 34 and 35). 1 FIG. 31. Model of macrodomes and FIG. 32. Upper macrodomes (101) brachy pinacoids . The basal pinacoid, or base, is parallel to a and b and intercepts c (ooi). The brachypinacoid (short pinacoid) is parallel to the c and to the shorter of the two lateral axes, the a, but intercepts the b (oio). The macropinacoid (long pinacoid) is parallel to c and to the longer of the lateral axes, but intercepts the a (100). Figure 36 shows a combination of prism (no), brachypinacoid (oio), and brachy dome (on). Pyramids, domes, prisms, and pina- coids complete the list of holohedral forms in the orthorhombic system. If the right-hand upper octant of a pyramid and each alternate octant were developed at the expense of their neighbors, a right-handed bisphenoid would be produced (Fig. 37). A left-handed or negative bisphenoid would result if the left-hand upper octant and alternate octants grew at the expense of their neighbors. FIG. 33. Prism (no) and basal (ooi) planes. 28 GUIDE TO MINERAL COLLECTIONS I I 4- i FIG. 34. Base, macropinacoid, fie. 35. Model showing base, macro- and brachypinacoid. a nd brachypinacoid. FIG. 36. Model of prism (no), brachypinacoid (oio), and brachydome (on). FIG. 37. Right-handed sphenoid (in). ELEMENTS 29 In sulphur these bisphenoids (in) are commonly united and modified by basal (ooi), dome (on), and obtuse pyramid planes (113) (Figs. 38 and 39). In Figure 39 the left-handed sphenoid predominates while the right-handed appears as a very small plane. In Figure 38 they are of nearly equal size, but an edge instead of a corner where the a and b axes are intersected shows that the prevailing form is not a bipyra- mid but rather two bisphenoids. -113 FIG. 38. Sulphur, usual habit FIG. 39. Sulphur, sphenoidal habit Study of the sulphur crystal has shown that if the b axis is taken as unity, the a axis is .8 and the c is 1.9. Therefore to construct the various planes write parameters, ratios, and symbols as before. Ordinary bipyramid (Fig. 28) Obtuse bipyramid (Fig. 30) Brachydome bipyramid (Fig. 32) Macrodome bipyramid (Fig. 34) Prism bipyramid (Fig. 35) Similarly for the pinacoids. If melted sulphur is quickly cooled, the molecules do not have opportunity to arrange themselves and the resulting mass is without Parameters Ratios Symbols .8:1:1.9 .8 - 1 . 1.9 (ill) I * I .8 i 1 .9 2.4:3:1.9 (lI3) i *i* 3 oo :i:i.9 .8 .1. i-9 (on) o "x" i .8:00:1.9 .8 . i . 1-9 (xox) i 'o' i .8:1:00 .8 I 1-9 (no) i 'i' 30 GUIDE TO MINERAL COLLECTIONS definite form. It is said to be amorphous. If it is slowly cooled, crystals are formed similar to those occurring in nature but differing in this respect, that they slant downward parallel to the a axis, so that the front angle between the c and a axis, /3, is greater than 90 (Fig. 40). The basal plane, being parallel to the lateral axes, slants forward. The crystals cannot be classed in the orthorhombic system but are in the monoclinic. (Monoclinic means having one inclination.) After a time, however, these monoclinic crystals become dull and fall to pieces, since their molecules tend to arrange themselves in the more stable form of the ortho- |C" rhombic crystal. Orthorhombic crys- I tals can be obtained artificially by I allowing sulphur to crystallize from /3 ^ ^0 i ' solution in carbon disulphide. (\/__ -~&r Sulphur cleaves very imperfectly, parallel to the base (ooi) and to the prism (no). It is brittle and shows conchoidal surfaces when broken. Hardness = 2; gravity = 2; luster, greasy, resinous, adamantine. It allows F.G. 4o.-Axes of a monoclinic 1! g ht tO P aSS ^"^ ^perfectly, i.e., crystal, it is translucent. Its average angle of refraction is ^ = 2.04. Since the density of its molecules varies in different directions, a ray of entering light is divided into two rays. These rays vibrate at right angles to each other and are differently refracted. The dispersion or difference between the angle of greatest and least refraction is 0.29. The heat conductivity is so low that the warmth of the hand is enough to cause a sulphur crystal to crackle, as may be noticed when a crystal is held near the ear. Sulphur becomes elec- tric by friction; volatilizes easily, forming sulphur dioxide; is insoluble in acids. Hundreds of thousands of tons are mined in Sicily annually. Spain, France, and Germany produce smaller amounts. Louisiana, Texas, Nevada, and Utah are the chief source of the domestic supply. In 1916 the first two states supplied 98 per cent of the sulphur ob- tained in the United States. ELEMENTS 31 SUMMARY Sulphur. S. Orthorhombic; symmetry holoaxial (sulphur class): (in), (113), (on), (101), (ooi). Cleavage very imperfect (ooi), (no); brittle; fracture conchoidal. Hardness=2; gravity =2. Yellow, orarige, white; luster resinous; translucent; refraction strong, ^=2.04; double refraction very strong, positive. Fusible; insoluble in acid; soluble in carbon disulphide. Sicily, Spain, France, Germany, Louisiana, Texas. Arsenic A small mass of native arsenic from Austria represents the usual appearance of this mineral. It somewhat resembles slag from a metal furnace or some kinds of lava, since it shows a rounded, twisted surface, like a bunch of grapes crowded together, and is dull lead gray or blackish on the surfaces which have long been exposed to the air. The fresh surfaces are tin white and show the short radiating needles which build up individual portions of the mass. It is brittle, less than 4 in hardness, and 5 . 7 in specific gravity. Native arsenic furnishes but little of the arsenic used in medicine and the manufacturing arts. SUMMARY Arsenic. As. Hexagonal. Cleavage (oooi); botryoidal, reniform, massive; brittle, conchoidal. Hardness = 3 . 5 ; gravity =5. 6. Silver white; tarnishes lead gray to black; streak white. Volatilizes without fusing, tinges flame blue, yields dense white fumes; odor of garlic. Colorado, Chile, Saxony, Austria. Antimony and Bismuth These two brittle metals are very similar in their occurrence, properties, and uses. They do not develop well-defined crystals, but are usually found in grains, incrustations, or aggregations of scales which form masses. Bismuth is sectile and is the softer of the two, being about 2 in the scale, while antimony is 3. Bismuth is the heavier of the two, having a specific gravity of 9, while that of anti- mony is 6. Bismuth is somewhat reddish in hue; antimony is tin 32 GUIDE TO MINERAL COLLECTIONS white. Both are metallic in luster, soluble in nitric acid, easily fusible and volatile. Both are found in association with silver, iron, arsenic, sulphur, and quartz. One hunting for these minerals should examine crystalline rocks. The localities most noteworthy on account of specimens of anti- mony and bismuth are Saxony, Bohemia, and Japan. Many of the ores of precious metals in our western states contain these metals. Antimony and bismuth are used in medicine and for the manu- facture of alloys for type metal, babbitt metal, and other metals of low fusing-point. SUMMARY Antimony. Sb. Hexagonal; symmetry dihexagonal alternating (cal- cite class). Cleavage parallel (oooi) perfect, parallel -%R fair; brittle; fracture uneven. Hardness = 3 . 5 ; gravity = 6. 6. Tin white; luster metallic; opaque. Easily fusible, volatile; oxidizes in nitric acid. Germany, France, Japan, Australia. Bismuth. Bi. Hexagonal; symmetry dihexagonal alternating (calcite class). Cleavage parallel (oooi) perfect, parallel -$R fair; sectile; fracture hackly. Hardness=2; gravity = 9. White with reddish tinge; luster metallic. Easily fusible; volatilizes; soluble in nitric acid. Germany, Bohemia, Colorado. Gold Probably there is more general interest in this mineral than in any other that is found in the earth's crust. It was doubtless the first metal to be used by primitive man, since it is found in the beds of streams to which men would come for water and which were their highways from earliest times. Its glitter would attract the attention. When once its acquaintance was made, it would be easily recognized again, since it does not tarnish or rust, is very heavy, being 19 times as heavy as water, and so soft and malleable that it can be given various shapes and employed in many ways. These qualities would lead men to use it long before they would notice or use the more abundant metals such as iron. It is found in the earliest tombs, such as those at Kertsch in the Crimea, in northern ELEMENTS 33 Africa, and western Asia. Cloisonne work made in Egypt three or four thousand years ago shows skill in the use of gold. The beauty of color, ease of working, weight and permanence of gold, render it a mineral of great value. But, however great its intrinsic worth, were it as common as quartz, for example, its value would be decreased. Thus is it over all the earth That which we call the fairest And prize for its surpassing worth Is always rarest. Iron is heaped in mountain piles And gluts the laggard forges, But gold flakes gleam in dim denies And narrow gorges. The snowy marble flecks the land In heaped and rounded ledges, While diamonds hide beneath the sand Their starry edges. 1 Gold is found usually in quartz veins, in pyrite and other sul- phides, or in sands and gravels. In quartz it occurs as fine threads or thicker wires that run singly or are bunched into mossy or treelike masses (arborescent). Sometimes it is in scales or grains isolated at times or packed to- gether so as to form lenses or nuggets. Wiry and granular masses alike are rounded, twisted, and so distorted as to give little suggestion of crystal faces. How- ever, an exposed end of one of 1 these grains or threads, one which has had opportunity to F IG . 4 i. Cube develop in a cavity uncrowded by quartz or some other mineral, may show crystal faces clearly enough developed to permit of study and to make possible the 1 J. G. Holland, "Bitter Sweet." 34 GUIDE TO MINERAL COLLECTIONS conclusion that the structure of gold agrees with that of the diamond, the molecules being so arranged as to place it in the regular system. , Besides the octahedron (m), two other forms appear, namely, the cube (100) (Fig. 41) and the four-sided cube (tetrahexahedron, 210) (Figs. 42 and 43). To construct the cube, write the notation as before. Since the axes are interchangeable, six planes will be produced. The parameters of the front, right side, and top are as follows: Parameters i : oo : oo oo : i: oo oo ; oo ; i Ratios III 1*0*0 III o'i'o III I'Q'I Symbols (100) (oio) (ooi) A cube with four faces in each cubic face (Figs. 42 and 43) results when one of the three axes is intersected at twice unit's distance, for example. Ratios III' 2'l'o III I ' 2' O III O'2'l III O*I*2 II I 2'o'l III I*O*2 Parameters i:2:oo oo 11:2 2 : oo : i Symbols (210) (120) (021) (012) (201) (102) Gold crystals are usually small, distorted, and so grouped that to study and decipher them is a difficult matter. The gold contained in pyrites and metallic sulphides is so finely divided as to be invisible. It is mechanically included in the sulphides and not chemically united with the sulphur. In nearly every country in which gold is mined, it ELEMENTS 35 was first discovered in sands and gravels, and such deposits until within the last fifty years have been the chief source of the metal. Like diamonds, gold has been able to withstand the friction to which it was subjected while being washed from the original ledge. Diamonds resisted the friction because of their hardness ; gold because of its tenacity; both have endured because of their insolubility and slight affinity for oxygen. The condition of gold in alluvial deposits varies from dust of microscopic fineness to nuggets many pounds in size. In California a nugget weighing 161 pounds was FIG. 42. Tetrahexahedron model FIG. 43. Construction of tetrahexa- hedron. found. The largest nuggets have been discovered in Australia, three weighing over 200 pounds having been found there. The largest of them, the " Welcome," weighed 248 pounds. The origin of nuggets of such size has been a matter of much speculation, since no masses of similar size have been found in veins. It has been suggested that small particles carried downstream were welded together by the impact of water-tossed gravel until a large nugget was formed, or that the nuggets have grown by accretion of gold from some percolating solution. Polished and etched surfaces of nuggets, however, show crystalline structure. This would be wanting in welded gold, and there is an absence of the onion-like structure that would be expected if the gold were deposited by accre- tion from solution. Hence it may be concluded that the nuggets 36 GUIDE TO MINERAL COLLECTIONS were originally in quartz veins and have been rounded in the down- ward journey from some high ledge to the resting-place in which they were discovered. As to the origin of gold, nothing is known. The same may be said in regard to all elements. All that is known is something of the method of their transference and deposition. Light is shed on the subject by the fact that many fresh waters and all sea waters contain gold in appreciable quantities. There is nearly one grain of gold (five cents' worth) in every ton of ocean water. Then in all the oceans there is about seventy-five billion dollars' worth. Gold in solution, possibly as a telluride, chloride, or cyanide, was carried by waters and deposited by them upon neutralization, cool- ing, or evaporation. Though the surfaces of gold crystals are rounded and often look as if melted, their appearance is not due to fusion but to their manner of crystallization. The origin of the gold is the same as the origin of the vein material inclosing it quartz, fluorite, and calcite. All of these minerals are commonly deposited from aqueous solutions. Gold melts at 1200 C. and forms such perfectly spherical globules that by microscopical measurements it is possible to estimate the amount of gold in a globule and hence to dispense with fine balances in assaying. Gold is soluble in aqua regia only (a combination of nitric [HNO 3 ] and hydrochloric [HC1] acids). Sulphur and oxygen do not unite with gold, and hence it remains bright in nature or when worn as an ornament. All gold contains silver in solid solution. As the amount of silver increases, the alloy becomes paler, lighter, and more liable to dissolve in nitric acid. Most Hungarian gold contains 30 per cent of silver, California gold 10 per cent, Australian gold (Mount Morgan, Queens- land), reputed to be the purest, only .3 per cent. Platinum, copper, and iron minerals, calcite, fluorite, quartz, feldspar, amphibole, and pyroxene, mica, garnet, and zircon, are the minerals most usually found with gold. The rocks in which gold-bearing veins are found are igneous rocks such as granites, syenites, and porphyries; or metamorphic rocks such as gneisses and schists. The richest veins are usually at places of contact of different kinds of rock. California, Nevada, Colorado, Montana, and South Dakota have been the chief producers of gold in this country since the discovery of ELEMENTS 37 the metal in California in 1848. The only gold found in Illinois is an occasional piece contained in some rock transported from northern re- gions by the glaciers of Pleistocene times. There are no deposits of commercial importance. In spite of this fact, the procession of people who hope to discover such deposits or think they have done so will never end. They bring to the museum iron sulphide (pyrite), decay- ing mica (vermiculite), and other minerals, confident that they have found valuable deposits of precious metal; and when disillusioned are dejected. At one time the United States, at another time South Africa, leads the world in gold production, while Australia ranks third. Gold is a metal useful in all places where hardness and toughness are not desired but where insolubility, permanence in the air, beauty of color, softness, and ductility are sought. Since the earliest times it has been used for personal adornment and for ornaments for the home, the church, and the palace. It is universally favored as a medium of exchange. SUMMARY Gold. Au. Regular; holosymmetric; distorted (in), (100), (210); fibers, plates, grains. Malleable; ductile; fracture hackly. Hardness = 2.5; gravity = 19.3. Gold yellow, metallic, opaque. Fusible at 1200 C.; soluble in aqua regia. Western North and South America, South Africa, Australia. Silver Silver resembles gold in its mode of occurrence, crystal habit, and physical properties. Chemically it is not so stable as gold, being readily affected by acid fumes and liquids. It is rarely found in placer deposits, but occurs most commonly in wiry, mossy, flaky, or granular forms in veins. Sometimes large pure masses are discovered. One of the most famous was an eight-hundred-pound mass found in Peru. Another from Kongsberg, Norway, weighing five hundred pounds, is preserved in Copenhagen. Crystals of silver are usually so distorted that their form is difficult to decipher, but under favorable circumstances octahedrons (in), cubes (100), and tetrahexahedrons (210) can be distinguished. Like gold, silver has no direction of easy separation (cleavage). When broken, the fractured surfaces are splintery. It is inferior to 38 GUIDE TO MINERAL COLLECTIONS gold in its malleability and ductility, as it is possible only to beat leaves of it so thin that it requires one hundred thousand leaves to form a pile one inch in height, and one grain can be drawn out into four hundred feet of wire. Gold, however, can be beaten into leaves thin enough to require two hundred and eighty-two thousand leaves to form an inch-high pile, and one grain can be drawn into five hundred feet of wire. Silver is unsurpassed as a conductor of electricity. Its conduc- tivity is placed at 100 per cent, that of copper at 93 per cent, and platinum at 16 per cent. One thousand degrees Centigrade of heat are required to melt it. When fused it can absorb twenty times its bulk of oxygen, which it gives off upon cooling, causing it to blossom into arborescent forms. It is readily soluble in nitric acid. It unites with sulphur so easily that to keep silver bright is a very difficult task. The chief source of the metal is not native silver but sulphides such as argentite, proustite, tetrahedrite, etc., minerals which will be described later. The association, occurrence, and localities of silver are nearly identical with those of gold. The United States has for many years been one of the principal producers, as well as the chief consumer, of silver. It is estimated that the ocean contains over two million tons of silver worth more than $38,000,000,000. Silver is used extensively for coinage, for making household articles, for photographic purposes, and in various other ways. SUMMARY Silver. Ag. Regular, holosymmetric ; (100), (210), (in); twinned on (in). Threads, wires, plates, grains, masses. Malleable; ductile; fracture hackly. Hardness = 2.5; gravity = 10. 5. White, metallic, opaque. Fusible at 1050 C. ; soluble in nitric acid. Cordilleran states in both North and South America, Australia, Ger- many. Copper Copper is similar in its physical characteristics, association, and occurrence to the two minerals just described, but is more abundant. PLATE IV Dendritic copper from Calumet and Hecla mining region, Michigan. ELEMENTS 39 In the rare crystal faces discernible, possibly the tetrahexahedron (210) and dodecahedron (no) (Fig. 44) are more common than they are in gold and silver. The dodecahedron (no) can be constructed from the following parameter (Fig. 45) : Parameter 1:1:00 Ratios III 1*1*0 Symbols (no) Wiry and arborescent forms are common. Masses of remarkable size have been found. One of the largest was 45 feet long and weighed 420 tons. It was found in the " Minnesota Mine" in Michigan. That region has produced more pure copper than any other in the world. The copper is disseminated in breccias, conglomerates, and basalts, or is collected in veins of calcite, fluorite, anal- cite, and quartz which pene- trate the basalt. Often a cavity is filled partly with copper and partly with silver. If these metals had been de- posited from a fused mass, they would have been united in an alloy rather than stand- ing side by side. Evidently FlG . 44 ._ Mo del of a dodecahedron they were formed from a solution, and the more difficultly soluble silver was first deposited and later the copper. Copper is redder than gold and much more soluble. It is one of the most useful of metals, being used for electrical purposes and for many domestic and commercial articles. The United States has produced about three times as much copper as the rest of the world together. Arizona, Montana, and Michigan are the leading states in production. In the two former the ores are chiefly sulphides and carbonates; in Michigan, native copper. GUIDE TO MINERAL COLLECTIONS Glacial drift from the north has brought nuggets of copper, some of them weighing more than 50 pounds, and scattered them widely over Illinois. One (No. 695) found in the drift in Peoria County weighs i8f pounds. A hole was cut through it by the finder so that it could be used on a C rope to close a gate. No. 693 from Macon County weighs 17 f pounds and is covered with the fine green de- posit with which time paints old copper domes of churches and palaces. This deposit is formed when carbon, oxygen, and water unite with copper to produce the copper carbonate called malachite. No. 3383 is an irregular nugget (n| pounds) which shows the scratches made by the rocks over which the nugget was pushed while frozen in a glacier. No. 259, a small nugget from Jersey County, was found farthest south of any specimen in the collection. SUMMARY Copper. Cu. Regular, holosymmetric; elongated (210); twinned on (in); threads, wires, masses. Malleable; ductile; fracture hackly. Hardness =2.5; gravity =8.9. Copper red, metallic, opaque. Fusible at 1100 C., soluble in nitric acid. Michigan, Arizona, New Mexico. Mercury Mercury is the only element which is liquid at ordinary tempera- ture. It solidifies at 40 C. and in so doing crystallizes in the regular system. It unites so readily with sulphur that it is rarely found uncombined with that element. Cinnabar, HgS, is the chief source of the metal. FIG. 45. Construction of a dodecahedron ELEMENTS 41 Mercury is used in making medicine, in "silvering" mirrors, and in the manufacture of toys, but chiefly as a means of collecting finely divided gold in placer mining and in the free milling process. About the same time that gold was discovered in California, fortunately quicksilver was found at New Almaden, some fifty miles south of San Francisco. The United States is at present the leading country in the pro- duction of cinnabar, from which mercury is obtained. The famous old Spanish localities now take second rank. Nature has not provided any deposits of mercury in Illinois. Nor do we need it as much as do some other states. SUMMARY Mercury. Hg. Liquid, amorphous; at 40 C. Regular. Gravity =15. White, metallic, opaque. Volatilizes, sublimes. California, Spain. Platinum Platinum is a steel-gray, metallic, moderately hard, exceedingly heavy mineral occurring in small flat grains in alluvial deposits. The world's supply has been obtained practically from the Ural Mountains alone. If its appearance and characteristics were more widely known among prospectors, other localities might be added to the list of producers. Because of its peculiar utility and rarity, platinum is at present unsurpassed in commercial value by any metal. Its especial useful- ness depends upon its resistance to heat. Over 2000 C. are required to melt it. This, in addition to its insolubility, makes it serviceable for dental purposes, for crucibles, wire, and foil to be used in chemical laboratories and manufacturing plants and for electrical purposes. The attempt to find some metal which will take the place of plati- num has been unsuccessful. The United States uses about half of all the platinum produced in the whole world. The crystal form of platinum, being similar to that of gold, silver, and copper, presents nothing new for consideration. Platinum is very finely disseminated in gravels derived from ser- pentine and syenite, and large placers may be expected only in very 42 GUIDE TO MINERAL COLLECTIONS old land areas which have been subjected to protracted degradation. The Ural Mountains furnish such conditions. Small percentages of platinum are often obtained from sulphides of antimony, arsenic and copper, and in chromite. The placers of the Ural Mountains, Columbia, and California contain, associated with platinum, other minerals of high specific gravity such as gold, cas- siterite, magnetite, hematite, chromite, and rutile. SUMMARY Platinum. Pt. Regular; holosymmetric ; grains and nuggets. Malle- able; ductile; fracture hackly. Hardness = 4.5; gravity=i9; chemically pure, 21. Steel gray. Infusible; soluble in nitre-hydrochloric acid (aqua regia). Nijni Taguilsk (Urals) ; Columbia, South Africa, Canada, Wyoming, California. Iron Iron so readily unites with oxygen, sulphur, and other elements that it rarely occurs native. Consequently, while minerals contain- ing iron are numerous and abundant, pure iron is rare. Yet it is one of the most interesting of minerals because of its origin. Some of it is terrestrial and some meteoric in origin. Terrestrial iron is found as small imbedded particles in basalt, peridotite, and serpentine three kinds of dark rocks abundant in many mountain regions and in deposits derived from the disinte- gration of these rocks. Gold and platinum are usually associated with terrestrial iron. At several places on the west coast of Greenland, especially at Disco Island, large masses of iron occur which are regarded as origi- nating from deep-seated portions of the earth, since the basalts of the region contain scattered grains and globules of iron. Meteoric iron illustrates the fact that the science of mineralogy is concerned not only with this earth but with the universe as well. Until within the last one hundred years the idea prevailed that meteorites were portions of this earth which had been thrown out of volcanoes with such velocity as to reach great heights and then to fall back with enormous speed. But as the composition of meteorites became known and the circumstances connected with their fall were investigated, students of the subject were convinced that they are fragments of other heavenly bodies the dust of the universe. PLATE V Mukerop meteorite, one-sixth natural size. on page 44 was cut from the center of this mass. Fell in Amalia-Goamus, West Africa. Section mentione ELEMENTS 43 Myriads of them enter the earth's atmosphere. At night they are seen to flash in the heavens when they are ignited by the friction generated in their fall through the earth's atmosphere. Many enter the atmosphere at such an angle that they leave it without touching the earth; many are totally consumed as they fall; some reach the earth's surface as cosmic dust, as grains, or even as masses many tons in weight. In 1894 at Cape York, in the northern part of Green- land, a mass weighing 36 tons was found and three years later brought by R. E. Peary to New York City. It was called by the Eskimos "Ahnighito" or "The Tent." Occasionally a meteorite has been seen as it fell and has been picked up while still warm. Those which have been observed in the air and then found are called " falls." Their number is less than the so-called " finds," which are not seen to fall but are simply picked up. Several hundred " falls" and "finds" have been collected and described. A meteorite entering the atmosphere may have an astonishingly high velocity something like 45 miles a second but because of the resistance of the air be reduced in velocity and strike the earth's sur- face with small force. Meteoric stones fell upon the ice at Hessle, Sweden, and rebounded without either breaking the ice or being themselves shattered. The heat generated by the friction with the air fuses the surface of the meteorite, especially on the front side, and causes the melted material to flow back in waves, making a kind of "varnish." Meteorites are usually pitted with thumblike impres- sions. Since the heating is sudden, the surface may be fused while the interior is still cold. The unequal expansion causes them to explode with loud report and to scatter over wide territory. According to constitution there are three kinds of meteorites: first, those consisting almost wholly of iron (siderites) ; second, those having a cellular matrix of iron in which stony matter is imbedded (siderolites) ; and third, those composed almost entirely or wholly of stony matter (aerolites). Meteoric iron is massive, but its crystalline structure can be readily discerned when it is etched with diluted nitric acid, since triangular markings usually appear on the surface. They are due to the presence of nickel. The form and the widths of the bands depend upon the percentages of nickel present. The figures resulting 44 GUIDE TO MINERAL COLLECTIONS are called Widmanstatten figures, after the man who first studied them. The largest meteorite ever discovered in the United States and one of the most interesting is the Willamette iron. It was found 19 miles south of Portland, Oregon, in 1902. It weighs 15 tons and is now in the American Museum of Natural History. Meteorites have been found in our neighboring states, Michigan, Indiana, Kentucky, Missouri, Iowa, and Wisconsin, but thus far not a single example has been reported in Illinois. All accounts of the finding of meteorites in this state have upon investigation proved to be untrue. There appears to be no reason why falls may not occur here at any time. If people are more observant, we may some time discover and preserve these messengers from the great waste spaces. The largest meteorite exhibited in the collection (No. 4064) is a 1-inch- thick section from 13 to 15 inches in diameter and weighing 13! pounds avoirdupois. It was cut from the Mukerop meteorite which fell in southwestern Africa (Plate V). The following also are shown: a dozen examples of the Canon Diablo, Arizona, meteorite (No. 3385); about fifty of the Holbrook, Arizona; one from Eddy County, New Mexico (Sacramento Mountains, No. 3384); Sheridan County 3 Kansas (Saline, No. 4106); Lyon County, Kansas (Admire, No. 4104); Phillips County, Kansas (Long Island, No. 4109); Iowa County, Iowa (Homestead, No. 4107, and Forest, No. 4108); Emmet County, Iowa (No. 1730); Bullitt County, Kentucky (Salt River, No. 4103); Kent County, Michigan (Grand Rapids, No. 4103); and state of Mexico, Mexico (Toluca, No. 4101). SUMMARY Iron. Fe. Nickel usually present. Regular; (in), (100); massive lamellar; cleavage parallel (100) perfect; malleable; fracture hackly. Hardness = 4.5; gravity=7.5. Gray to black, metallic, magnetic Infusible; soluble in acid. Greenland, and in meteorites of wide distribution. ELEMENTS 45 LIST OF ELEMENTS AND THEIR ATOMIC WEIGHTS Name Combining Weight Oxygen = 1 6 Aluminium, Al 27 Antimony, Sb 1 20 Argon, Ar 39 Arsenic, As 75 Barium, Ba 137 Beryllium, Be 9 Bismuth, Bi 208 Boron, B . . . 1 1 Bromine, Br 79 Cadmium, Cd 112 Caesium, Cs 132 Calcium, Ca 40 Carbon, C 12 Cerium, Ce 140 Chlorine, Cl 35 Chromium, Cr 52 Cobalt, Co 59 Columbium, Cb 94 Copper, Cu 63 Dysprosium, Dy 162 Erbium, Er 167 Europium, Eu 152 Fluorine, F 19 Gadolinium, Gd 157 Gallium, Ga 70 Germanium, Ge 72 Glucinum, Gl 9 Gold, Au 197 Helium, He 4 Hydrogen, H i Indium, In 114 Iodine, 1 127 Iridium, Ir 193 Iron, Fe 56 Krypton, Kr 83 Lanthanum, La 139 Lead, Pb 207 Lithium, Li 7 Lutecium, Lu 1 74 Magnesium, Mg 24 Manganese, Mn 55 Name Combining Weight Oxygen = 1 6 Mercury, Hg 200 Molybdenum, Mo 96 Neodymium, Nd 144 Neon, Ne 20 Nickel, Ni 59 Nitrogen, N 14 Osmium, Os 191 Oxygen, O 16 Palladium, Pd 107 Phosphorus, P 31 Platinum, Pt 195 Potassium, K 39 Praeseodymium 141 Radium, Ra 226 Rhodium, Rh 103 Rubidium, Rb 85 Ruthenium, Ru. 102 Samarium, Sm 150 Scandium, Sc 44 Selenium, Se 79 Silicon, Si 28 Silver, Ag 108 Sodium, Na 23 Strontium, Sr 88 Sulphur, S 32 Tantalum, Ta 181 Tellurium, Te 127 Terbium, Tb 159 Thallium, Tl 204 Thorium, Th 232 Thulium, Tu 168 Tin, Sn 119 Titanium, Ti 48 Tungsten, W 184 Uranium, U 239 Vanadium, V 51 Xenon, Xe 131 Ytterbium, Yt 172 Yttrium, Y 89 Zinc, Zn 65 Zirconium, Zr 91 CLASS II. SULPHIDES The next group of minerals which would naturally claim the attention of the visitor is that which embraces minerals consisting of a mixture of sulphur with some metal like antimony, molybdenum, lead, silver, copper, zinc, mercury, or iron. From the twenty-five or more minerals in the group, thirteen are common; and while but eight of them are found in Illinois, all are used here and all are of interest, since they show marked properties. They are stibnite, molybdenite, galena, argentite, chalcocite, sphalerite, cinnabar, pyrrhotite, erubescite, chalcopyrite, pyrite, marcasite, and arsenopyrite. Stibnite Stibnite, a sulphide of antimony (Sb 2 S 3 ) is the chief source of the metal, antimony. Its crystals are often large and beautiful. They resemble sulphur crystals since their structure is different in three directions. The planes which are usually developed are prisms and pinacoids. Several pyramid planes are of common occurrence. The crystals are holohedral. Basal planes are wanting. The long needle- like crystals often terminate in a flat pyramid (113), as shown in Figure 46. The ratio of the axes a:b:c is .99: i : i .01, differing thus but slightly from a mineral in the regular system. Applying these values and using the parameter as usual, the following result: Parameters Ratios Symbols .OQ I I . OI 2.97:3:1.01 :: ("3) .00 I I.OI / N oo :i;oo (oio) o 'i' o Some crystals of stibnite are of remarkable size and beauty. One of the finest specimens in any museum may be seen in the British Museum. It is a group of crystals eighteen inches long and termi- nated by lustrous pyramid faces. It came from the antimony mines 46 PLATE VI a, Stibnite, Japan b, Molybdenite from Aldfield, Pontiac County, Quebec, Canada. SULPHIDES 47 at Shikoku, Japan, a locality which has furnished a larger number of remarkable specimens than any place in the world. Our largest specimen, No. 3784 (Plate VI a), comes from the same place. Other samples are from Portugal, Australia, and the western United States. Stibnite crystals are often twisted, curved, and warped. The most usual occurrence is that of massive forms with bladelike or fibrous structure. The mineral cleaves easily parallel to the brachypinacoid, and shows nicks and horizontal lines at right angles to the c axis, indi- cating " glide planes" parallel to the base (ooi). These glide planes make it possible for the crystals to bend, and explain their curved and twisted form. That the mineral is in the orthorhombic sys- tem can easily be illustrated by the difference in rapidity with which heat is transmitted in differ- ent directions. Senarmont's method is to coat a brachypinacoid plane with wax and touch it with the point of a hot wire. The wax is melted more rapidly in the direction of the c axis than in the direction of a. Consequently the resulting figure is an ellipse. Roentgen's method, similar in prin- ciple, is to breathe upon a face, touch it with the point of a hot wire, then sprinkle lycopodium crystal, powder upon it. When shaken, the powder drops from the mineral where it was dry. The form of the clean space is an ellipse with the long axis parallel to the c axis. Stibnite is found with other sulphides (argentite, galena, sphalerite, cinnabar) and with barite and quartz in veins in granite and gneiss. The ancients used stibnite as a pigment to darken eyebrows. Its chief use at present is as a source of antimony. SUMMARY Stibnite. Sb 2 S 3 ; Sb = 7i.8 per cent, 8 = 28.2 per cent. Ortho- rhombic; (no), (in), (113), (oio). Massive, bladed, fibrous, granular. Cleavage (oio) perfect; glide planes (ooi); slightly pliable; fracture conchoidal. Hardness=2; gravity = 4. 6. Steel gray; metallic; opaque. Easily fusible (i in the scale) ; volatilizes; soluble in hydrochloric acid. Japan, Hungary, Australia, California. / \j I p , i ^ 4 -~1 - |no 010 i i i i FIG. 46. Stibnite 48 GUIDE TO MINERAL COLLECTIONS Molybdenite Molybdenite, the sulphide of molybdenum (MoS 2 ), is a soft metallic mineral, bluish lead gray in color. It occurs in six-sided (hexagonal) tabular crystals in quartz veins (Plate VI b). In soft- ness, color, and form it closely resembles graphite but can be distin- guished by the fact that the color is bluish and the mark left on paper (the " streak") is bluish, while the color and streak of graphite are lead gray. Molybdenite (gravity = 4. 7) is also more than twice as heavy as graphite. Its crystals are often striated horizontally, taper toward the top because of the decrease in the diameter of its constituent lamellae, and show glide planes. Foliated, scaly, and granular particles some- times are scattered through the containing quartz and at other times concentrated in the masses. With it are often found other sulphides such as pyrite and chalcopyrite. It has been deposited from solution in crystalline rocks, such as pegmatite granite, gneiss, and granular limestone. The chief sources of supply in the United States recently have been California, Colorado, Montana, Maine, and Washington. None is found in Illinois. Molybdenum compounds are used in coloring silk, leather, and porcelain blue. They have a limited use in chemical laboratories for the determination of phosphorus; in the manufacture of steel a frac- tion of a per cent of molybdenum hardens the steel and changes its coefficient of expansion. SUMMARY Molybdenite. MoS 2 ; Mo =60 per cent, 8 = 40 per cent. Hexagonal; plates, scales; cleavage parallel (oooi). Flexible; sectile. Hardness=i; gravity = 4.y. Bluish gray; metallic; opaque; greasy. Infusible; soluble in nitric acid. California, Colorado, Montana, Washington, Maine, Canada, and many European localities. Galena Because of its physical properties and its importance commer- cially, galena, the sulphide of lead (PbS), is an interesting mineral. It is found in great masses or disseminated in limestone, as in the Mississippi Valley region, and in veins in crystalline rock, as in the SULPHIDES 49 Cordilleran region. In the Cordilleras the galena is usually argen- tiferous and consequently one of the chief sources of silver in this country. In the Mississippi Valley region it contains practically no silver but is associated with the zinc sulphide, sphalerite. Galena is mined in many places in both hemispheres, but probably in no place more extensively than in Missouri and Idaho. In early days in the Mississippi Valley region the avocation of the farmers was often the quarrying of galena for lead from which to cast bullets in time of war and for making pewter ware in time of peace. Some galena is found in Pope and Hardin counties in Illinois in connection - 1 -I- FIG. 47. Cube truncated by octa- hedron. FIG. 48. Model of a cube truncated by an octahedron. with the fluorite mined there, and some is produced in the north- western portion of the state. Scattered crystals may be detected in the "Niagara" limestone at different places. The finest samples shown in the museum collection are from Jo Daviess County. No. 421 is a cube whose corners are truncated with octahedron planes. It measures over three inches each way and weighs yf pounds (Fig. 49). No. 3396 is another smaller cube, and No. 267 is a large mass which has been incrusted with iron sulphide (marcasite). Where the incrustation has broken off, the underlying galena may be seen. When one sees this pronounced crystallization he is impressed with the fact that when minerals have the opportunity they have a form as well defined as that of a flower. 50 GUIDE TO MINERAL COLLECTIONS Galena is soft, heavy, lead gray, metallic, and opaque. It crys- tallizes readily, so that even massive forms when cleaved show the structure, and well-formed crystals are very common. The usual habit is fine cubes with the corners truncated by octahedrons (Figs. 47 and 48). The octahedrons may be enlarged so as to almost dis- place the cube, or they may become so small as to disappear. The cube faces are often formed by very flat four-faced cube planes (hko\ h and k representing any two different numbers. If h = 4 and k = i, the symbol is (410), a tetrahedron often met with. 2 inch FIG. 49. Galena, Jo Daviess County, Illinois. FIG. 50. Model of planes appear- ing on galena. Crystals often exhibit the dodecahedron (no) in combination with the cube and octahedron (Fig. 50). Cleavage is so perfect that a single blow of a hammer will shatter a crystal into multitudes of little cubes whose faces may show stria- dons parallel to the lower right-hand trisoctahedron (441) due to twining lamellae parallel to that plane (Fig. 51). Since glide planes can be produced in this direction by pressure, the striae may be due to that cause. Galena which contains from, i to 2 per cent of bismuth has octahedral cleavage. When heated enough to drive off the bismuth, the cleavage becomes cubic. Singularly, galena containing Bismuth does not decrepitate when heated, as does ordinary galena, nor is SULPHIDES FIG. 51. Twin lamellae in galena parallel to (441). there a change in its specific gravity. Further, with the change in crystalline structure, there is no decrepitation such as occurs in ordi- nary galena. Galena usually contains small amounts of silver sulphide, and as the amount present increases, the galena loses its coarse cubic struc- ture and becomes finely granular. When covered with a layer of wax and touched with the point of a hot wire, the wax melts in a circle, showing that galena is in the regular system. Argentite, sphalerite, chalco- pyrite, pyrite, fluorite, quartz, calcite, and rhodochrosite accom- pany galena in limestones or in crystalline rocks. Since galena furnishes the lead of the world, it is one of the most useful of minerals. Lead is used in plumbing, in the manufacturing of paint, medicine, alloys, shot, etc. SUMMARY Galena. PbS; Pb = 86.6 per cent, 8 = 13.4 per cent. Regular; holosymmetric ; (100), (in), (no), (221). Cleavage (100) perfect; fracture even; nearly sectile. Hardness = 2.5; gravity = 7 . 5. Lead gray; metallic; opaque. Easily fusible, decrepitates; soluble in nitric acid. Mississippi Valley, Cordilleran region. Argentite Argentite, the sulphide of silver (Ag 2 S), is one of the chief sources of the metal. It closely resembles galena but does not occur in such distinct crystals. Usually it is in the form of dendritic, scaly, earthy, or granular masses. It does not cleave as readily as galena but is sectile. It is associated with the same minerals and is found in crys- talline rocks such as are wont to contain gold, silver, and other precious minerals. The best crystal shown, No. 3822, was obtained at Guanajuato, Mexico. 52 GUIDE TO MINERAL COLLECTIONS SUMMARY Argentite. Ag 2 S; Ag=87.i per cent, 8=12.9 per cent. Regular, holosymmetric; (100), (no). Cleaves imperfectly parallel (100), (no); sectile; fracture sub-conchoidal. Hardness = 2 . 5 ; gravity = 7.3. Color and streak lead gray; metallic; opaque. Melts readily; soluble in nitric acid. In the mountain ranges in western North and South America, and in many European and Australian localities. Chalcocite In Arizona during 1918 nearly as much copper was produced as was obtained from Michigan, Montana, and Utah combined. The ore consists chiefly of chalcocite (Cu 2 S), a mineral which is dark lead gray in color, metallic, and opaque, and occurs in granular or compact masses. It resembles argentite in general appearance, but is more brittle and is often tarnished blue or green when the addition of sulphur changes the chalcocite (Cu 2 S) to covellite (CuS), or the addition of iron changes it into erubescite (Cu 3 FeS 3 ) . While chal- cocite crystallizes in the orthorhombic system, well-formed crystals are rare. Since the angle between the prism planes (no) is 60, chalcocite often looks as if it were a hexagonal mineral. When several crystals are twinned about the prism planes, the form is even more deceptive. Chalcocite is found in connection with other sulphides at many localities in the Cordilleran range. No example has been reported in Illinois. SUMMARY Chalcocite. Cu 2 S ; Cu = 79 . 8 per cent, S = 20 . 2 per cent. Orthorhom- bic; a:&:c=o.58:i:o.97. Common planes (no), (ooi), (023), (113); twinned on (no), (032); cleavage imperfect (no); sectile; fracture conchoidal. Hardness =2. 5; gravity =5. 7. Lead gray; streak black; metallic;, opaque. Easily fusible; soluble in nitric acid. Cordilleran region, England, Germany. Sphalerite Many localities in which lead is abundant are also famous because of their great deposits of sphalerite (ZnS). The early German miners who were seeking lead were disappointed when they found sphalerite SULPHIDES 53 instead, and therefore called it Blende from blenden, "to deceive." "Sphalerite," from the Greek, has the same meaning. Pure sphalerite has the color of resin. See the specimen from Spain (No. 3765). Usually it is dark because of impurities like iron, cadmium, manganese, tin, thallium, indium, and gallium that are often present in varying quantities. Some sphalerite contains as much as 20 per cent of iron. Miners call the dark varieties "Black Jack." See specimens from Colorado, Kansas, and Missouri. Gal- lium and indium were first discovered in sphalerite. Sphalerite occurs, as do most of the other sulphides, when igneous rocks such as granites, diabases, and porphyries are in contact with metamorphic rocks such as gneisses, schists, and granular limestones, especially where these rocks have been fissured and sub- sequently cemented by vein-forming materials. In the Mississippi Valley region, however, sphalerite usually is found in beds or is scattered through the limestone. Well-crystallized specimens are seen to follow the laws of the regular FIG. 52. Sphalerite system and to illustrate the same class of symmetry as that which is shown by the diamond, the " tetrahedrite class." Common forms such as that in Figure 52 are combinations of tetrahedrons (in), dodecahedrons (no), and trapezohedrons (311). The tetrahedrons are positive and negative, and upon the alternate octants only occur the planes which together would produce the hemihedral form called the three-faced tetrahedron (311) (Figs. 53 and 54). Supplementary tetrahedrons combined with cubes are characteristic (Fig. 55). The positive and negative tetrahedrons may be distinguished by the difference in their size, by their differing smoothness, by the different markings which their faces show when they are etched with dilute hydrochloric acid, and by a pyro-electric test. To make this test cut a plate parallel to a face of each of the two tetrahedrons in turn. Insulate, connect with an electroscope, and touch with the point of a heated wire. One tetrahedron will become positively electrified, and the other negatively. 54 GUIDE TO MINERAL COLLECTIONS Twin lamellae parallel to tetrahedral faces are common in the sphalerite of many localities. Stibnite, galena, afgentite, pyrite, marcasite, chalcopyrite, fluorite, quartz, calcite, and barite are the associates of sphalerite. FIG. 53. Model of a three-faced tetrahedron, a tristetrahedron. FIG. 54. Construction of trigonal tristetrahedron. FIG. 55. Sphalerite The region around Joplin, Missouri ,. has produced probably more sphalerite than has any other locality in the world, and Illinois is the leading state in zinc smelting from these ores. The museum collection contains also specimens from Alston Moor, England, and Kapnik, Hungary, two places famous for their many fine crystals. Sphalerite is the most important source of zinc, and the metal obtained from it is used in galvanizing iron, in zinc plating, in paint manu- facture, and in medicine. SUMMARY Sphalerite. ZnS; Zn = 6; per cent, 8 = 35 per cent. Regular, tetra- hedrite class; (in), (no), (311), (100). Cleavage perfect parallel (no);, brittle; fracture conchoidal. Hardness =3. 5; gravity =4. Yellow, adamantine, translucent; refrac- tion 7^=2.37. Fusible with difficulty; soluble in hydrochloric acid. Kansas, Missouri, Illinois, Wisconsin, Colorado, Utah, Montana, Europe. SULPHIDES 55 Cinnabar Though mercury occurs sometimes uncombined in nature, the chief source of the metal is cinnabar (HgS). Cinnabar, a word used in India two thousand years ago, means "red resin" and is well applied, since the color of the mineral is bright red and the streak vermilion. See specimens No. 3401 and No. 3893. Impurities make it brown or slaty (No. 593). Crystals of cinnabar are rare. The mineral is notable for its refractive power, the ordinary ray (o>) being more strongly refracted than it is in diamond. co = 2 .85. Further, a ray of light entering the crystal in almost any direction is divided into two rays which vibrate at right angles to each other. That is, .it is " doubly refracted." One ray is called the ordinary (co) and the other the extraordinary (e). When the difference between them is great, the double refraction or "birefringence" is said to be strong. In cinnabar e co = o . 3 5 . Of late years more cinnabar has been produced in the United States than in any other country, and of this production the greater part is furnished by California. None is found in Illinois. SUMMARY Cinnabar. HgS; Hg=86.2 per cent, 8=13.8 per cent. Hexagonal; "quartz class": (1010), (oooi), rhombohedrons (ion); c= 1.145. Cleav- age good, parallel (1010); fracture uneven. Hardness =2. 5; gravity =8. 2. Cochineal red; streak vermilion; luster, metallic, adamantine; translucent. Refraction very strong, (0=2.85; birefringence, positive, very strong ((0 = 0.35). Circular polarization very strong. Volatile; soluble in nitric acid. New Almaden, California; Spain; and south Russia. Pyrrhotite Pyrrhotite (-jrvppos, "reddish") is a bronze-colored, magnetic iron sulphide, which occurs in massive forms and is often lamellar in structure. Its crystallization is so imperfect as to leave doubt concerning its true nature, and, being opaque, its optical properties can shed no light on the question. However, its structure is probably such as characterizes the hexagonal system. 56 GUIDE TO MINERAL COLLECTIONS There is also doubt as to the chemical composition of pyrrhotite. Different formulae have been given to it, ranging from Fe6S 7 to FenS I2 . The formulae all agree closely with the monosulphide FeS, troilite, which is a mineral not known on the earth but common in some meteorites. Pyrrhotite is not so abundant as other iron sulphides. The iron which it contains cannot be separated from the sulphur without great difficulty. However, in some localities, as at Duck town, Ten- nessee, immense quantities of sulphuric acid are made from it. Nickel and cobalt are often present in paying quantities, and the nickelifer- ous pyrrhotite of Pennsylvania, Canada, and Norway is an important source of those metals. SUMMARY Pyrrhotite. FenSi 2 ; Fe = 56 to 61 per cent; 8 = 44 to 39 per cent. Hexagonal plates, masses. Brittle; fracture uneven. Hardness = 4; gravity = 4. 6. Bronze yellow; streak grayish black; metallic; opaque; magnetic. Fusible; soluble in nitric acid. Appalachian and Cordilleran systems; Europe. Erubescite Erubescite, the "blushing ore" (Cu 3 FeS 3 ), owes its beauty to the ease with which it tarnishes. It is called also bornite, variegated copper, horseflesh ore, peacock ore. When freshly broken it has a coppery or bronzy color, but soon tarnishes to a vivid blue or purple. Its color is its most interesting characteristic. Granular or compact masses are the most usual, but sometimes crystals in cubes can be distinguished. As is always the case, the crystals represent the purest condition. Cornwall, England, South Africa, and some of the Cordilleran states furnish the best crystals and the most abundant supply of erubescite. Our best samples were obtained in Colorado (No. 3753) andJNew Mexico (No. 2195). SUMMARY Erubescite. Cu 3 FeS 3 ; Cu=55. 5 per cent, Fe= 16.4 per cent, 8 = 28. i percent. Regular; (100); twinned on (in); cleavage imperfect, parallel (in); slightly sectile; fracture sub-conchoidal. SULPHIDES 57 Hardness=3; gravity =5. Pinchbeck brown, bronze, tarnished blue; streak grayish black; metallic; opaque. Fusible; soluble in nitric acid. With other copper ores in Colorado, Montana, South Africa. Chalcopyrite Very closely related to erubescite in chemical composition but much more pronounced in physical characteristics and commercial importance is chalcopyrite (CuFeS 2 ), i.e., copper pyrite, a name given by Henckel in 1725 when a difference between this and pyrite was FIG. 56. Acute primary bipyramid FIG. 57. Obtuse primary bipyramid for the first time noticed. Chalcopyrite and chalcocite are the chief sources of copper today. Lustrous, clean-cut crystals of chalcopyrite are common, and were early studied by crystallographers who thought they were in the regular system until, in 1822, accurate measurements showed that the c axis is 0.985 when a and b are unity. Hence the crystals are in the Tetragonal System, that system in which the c axis is longer or shorter than the a and b, the a and b axes are equal, and all three axes are at right angles. The symbol (i 1 1) indicates a bipyramid which is acute when the c axis is longer than the lateral axes (Fig. 56), or obtuse when the c axis is shorter than the others (Fig. 57). Since the lateral axes are equal and interchangeable, a form whose symbol is (101) will be a secondary bipyramid, instead of one con- sisting of dome planes, as in the orthorhombic system (Fig. 58). GUIDE TO MINERAL COLLECTIONS Symbols such as (211) or (331), etc., indicate the ditetragonal bipyramid (Figs. 59 and 60), since the two or three can be applied to each lateral axis in turn, thus indicating two planes in each octant. Similarly there are three prisms: a pri- mary, (no) (Fig. 61); a secondary turned 45 to it, (100) (Fig. 62); and a ditetragonal prism, (210) (Fig. 63). These with the basal plane represent the simple holohedral forms of the system. Figure 64 shows a combination of several of these planes. Hemihedral forms are constructed on the same plan as were those in the systems here- tofore described. For example, when the alternate pyramid faces only are developed, a bisphenoid results (Fig. 65). It may FIG. 58. Model of a secondary bipyramid. FiG/5Q. Ditetragonal bipyramid FIG. 60. Model of a ditetragonal bipyramid. be either positive or negative. If the planes in alternate octants of a ditetragonal pyramid are developed, the tetragonal scaleno- hedron is produced. Tetragonal scalenohedrons possess two planes SULPHIDES 59 of symmetry intersecting at right angles in the c axis, which is an axis of alternating symmetry. They are so well represented a* 1 I l FIG. 61. Primary prism FIG. 62. Secondary prism FIG. 63. Model of a ditetragonal prism. FIG. 64. Combination of primary prism (no), secondary prism (100), secondary bipyramid (101), and ditet- ragonal bipyramid (211). in chalcopyrite that the class has been called the " chalcopyrite class of symmetry." Figure 66 represents the most usual chalcopyrite crystal. It is composed of the positive scalenohedron. Pyramid planes with the 6o GUIDE TO MINERAL COLLECTIONS symbol (201) often appear on the edges. The scalenohedrons may be either acute or obtuse. Figure 67 represents a form composed of the prism (no), scaleno- hedrons (in) and (101), and the basal plane (ooi). Two kinds of twins are common. In one the twinning plane is (in) and produces a form so similar to the twin characteristic of the mineral spinel as to be called the " spinel twin." (The "spinel twin" proper is a form in the regular system.) The faces of one of the scaleno- hedrons are bright, while those of the other are dull. In the second form of twinning, a central crystal (201) is surrounded by four other crystals which are joined on the primary pyramid plane (in), FIG. 65. Model of a bisphenoid 021 110 11O FIG. 66. Chalcopyrite FIG. 67. Chalcopyrite, French Creek, Pennsylvania. forming a composite twin (Fig. 68). As is generally the case with all minerals, massive forms are the rule and evident crystals the exception. The color of chalcopyrite is bronze yellow and its streak is greenish black. Because of surface alterations it readily tarnishes, and takes PLATE VII a, Group of pyrite cubes, showing stria- tions, Central Cityj Colorado. b, Pyrite. A pyritohedron and cubes, Colorado SULPHIDES 6 1 on beautiful iridescent colors. The vivid blue is due to the forma- tion of covellite (CuS). The Cordilleran region from Arizona to Montana furnishes large quantities of chalcopyrite. Many fine crystals have been found at French Creek, Pennsylvania, the Hartz Mountains, and Cornwall, SUMMARY Chalcopyrite. CuFeS 2 ; 01 = 34. 5 per cent, Fe = 30.5 per cent, 8 = 35 per cent. Tet- ragonal; symmetry ditetragonal alternating (chalcopyrite class); a: c= 1:0.985. Common forms (in), (101), (211), (ooi), (201), (114,) (441) ; twinned about normal of (in). Brittle; fracture conchoidal. FlG . 68. Chalcopyrite, Hardness = 4; gravity = 4. 2. Brass yellow, Neudorf. Twinned paral- tarnishes blue; streak greenish black; metallic; lei to (in), opaque. Fusible; soluble in nitric acid. Western United States, Pennsylvania, Harz, Cornwall. Pyrite This iron sulphide is more abundant than any mineral thus far considered. It is found in all kinds of rocks, with all kinds of mineral associates, and in all parts of the world. In Illinois it occurs in the underlying rocks the shale, limestone, and sandstone, and in the sand and gravel carried in by Pleistocene glaciers. The name pyrite (irvp, Greek "fire") was used by Dioscorides and Pliny in the first century after Christ for minerals which gave sparks when struck by the hammer, and was applied not only to minerals in which the sparks are due to the combustion of the mineral itself but to hard minerals like flint in which the sparks are due to glowing particles intensely heated by the friction. Pyrite differs from the iron sulphide already considered, pyrrho- tite, in being neither magnetic nor bronze colored, and from the copper iron sulphide, chalcopyrite, in being brass yellow and not deep yellow as in chalcopyrite. It occurs as masses, large and small crystals, and minute yellow specks in sedimentary, igneous, and metamorphic rocks. 62 GUIDE TO MINERAL COLLECTIONS Two forms of crystals are common and several others abundant. One of the most typical is that which has the outline of a cube (100) (Plate Vila), but whose true symmetry is indicated by the striations on each face. These striations show that the cube is built up by repetition of many planes of a form which is so characteristic of pyrite as to have been named the " pyritohedron " (pentagonal dodecahedron) (Plate VII b). The pyritohedron is formed when the alternate- quarters of the four-faced cube (the inner part of FIG. 69. Pyritohedron derived by disappearance of tetrahexahe- dral planes darkened, and growth of the other planes. FIG. 70. Model of a diploid Fig. 69) are developed, beginning with the plane (210). The black strips with which the glass faces of the outer figure are bound mark the pyritohedron. Clear-cut pyritohedrons are so common that every collector can obtain them. Occasionally a form shown in Figure 70, called a diploid, is found. It results when the plane (321) and each alternate plane in the right-hand octant of the hexocta- hedron and the planes of the like symbol in the other octants are developed to the exclusion of their neighbors. Both the diploid and the pyritohedron agree in this, that if revolved around any one of the four octahedral axes, i.e., the lines extending through the center of the crystal and perpendicular to an octahedral plane (Fig. 23), each of its faces would be in the position previously occupied by the adjoining face three times during a com- plete revolution. The faces are said therefore to have four trigonal SULPHIDES axes. If revolved around the crystallographic axes (#, b, c) the planes are in similar positions twice during a complete revolution and hence these axes are called digonal axes. Since planes through any two of these digonal axes (a and c, or b and c, or a and b) are planes of sym- metry, the digonal axes are called didigonal axes. Pyrite crystals have three didigonal axes. Their faces are in pairs about a center. Hence the pyrite class of the regular system has a center, three planes, three didigonal and four trig- onal axes of symmetry. This symmetry is called tesseral central symmetry. Cube, octahedron, pyrito- hedron, and diploid appear in various combinations. The edges of the pyritohedron (210) are truncated by the cube (100) (Fig. 71). Etching with aqua regia produces figures symmetri- cally arranged in respect to the cube planes. Sulphides of nickel and FIG. 71. Model of a combination of cobalt are often found in py- pyritohedron (210) and cube (100). rite as isomorphous inter- mixtures, i.e., mixtures of substances having the same crystalline form. Chalcopyrite, marcasite, and silver sulphide are often associated with it. The most important impurity, however, is gold, which is often present as a metal scattered through the pyrite in invisible particles. Much of the gold of the world is now obtained by crushing, roasting,, smelting, and cyaniding pyrites, and much of the placer gold may have originally come from the same source. The chief use of pyrite is in the manufacture of sulphuric acid, sulphur, and iron oxide to be employed as polishing powder and paint. Iron for steel manufacture cannot be obtained from it, since thorough separation of the sulphur is almost impossible and a fraction of i per cent remaining in the iron renders it brittle while hot. GUIDE TO MINERAL COLLECTIONS SUMMARY Pyrite. FeS 2 ; Fe = 46.6 per cent, 8 = 53.4 per cent. Regular; pyrite class: (100), (in), (210), (321), (421). Supplementary twins; granular; massive; brittle; fracture conchoidal. Hardness = 6; gravity =5.1. Pale brass yellow; streak greenish black; metallic; opaque. Burns on charcoal and gives off SO 2 ; fuses to magnetic globules; soluble in nitric acid. Ubiquitous. Marcasite The same chemical composition is ascribed to marcasite as to pyrite, namely, FeS 2 . But there are pronounced physical differences. Marcasite crystallizes in the orthorhombic system and in the holo- symmetric class. The crystals have a center of symmetry; three planes of symmetry intersecting at right angles in the crystallo- graphic axes; and the c axis is a didigonal axis of symmetry, that is, if revolved around the c axis the planes assume similar positions twice in one wT^^OlS complete revolution, making the c // /* >/~Voi2. axis a digonal axis. Since planes of symmetry intersect in this axis, it is called a didigonal axis. A form j i n Oil FIG. 72. Marcasite FIG. 73. Marcasite common to marcasite is composed of the prism (no), base (ooi), and brachydomes (on) and (013) (Fig. 72). Prisms of marcasite are usually terminated by various brachydome planes (Fig. 73). Isolated crystals are rare. Because of multiple twinning they gener- ally show jagged outlines and re-entrant angles. Before marcasite was distinguished from pyrite, these forms were called "spearhead pyrites," " cockscomb pyrites," " radiated pyrites," "hepatic pyrites," PLATE VIII Marcasite, Jo Daviess County, Illinois PLATE IX Marcasite disks, Gulf Mine, Sparta, Randolph County, Illinois SULPHIDES 65 etc. Four or five individuals consisting of various dome and basal planes twinned parallel to the prism produce the "spear-head pyrites" (Fig. 74). "Cockscomb pyrites" result from repeated twinning par- allel (no) so as to produce individuals parallel to each other (Fig. 75). The prisms are short and the striated basal plane long. Radi- ated, nodular, and stalactitic forms are abundant (Plate VIII). More marcasite than pyrite is found in Illinois. No. 3287 from Sparta shows disks which are not surpassed in abundance and perfec- tion by any locality (Plate IX). Plate X shows a portion of a large radiated mass and Plate XI a coating of marcasite on cubes of galena which are resting upon a. -no L10 FIG. 74. "Spearhead pyrites" FIG. 75. " Cockscomb pyrites " botryoidal mass of sphalerite, well illustrating the association of the sulphides. Haidinger (1845), recognizing the orthorhombic form of mar- casite, reserved Pliny's term pyrite for the regular form and applied the old Moorish word "marcasite" to the orthorhombic. It is a. common error to use the name pyrite when marcasite is meant. Marcasite is orthorhombic, white in color and streak, not as heavy and more easily decomposed than pyrite. Even in museum cases it disintegrates and becomes covered with white efflorescent iron sul- phate (melanterite) and forms sulphuric acid which attacks the material upon which it rests. Its instability may be due to minute spicules of troilite (FeS), a mineral heretofore identified in meteorites only. When marcasite is heated to 200 C. in a sealed tube with a copper sulphate solution, it yields a solution entirely ferrous. Pyrite 66 GUIDE TO MINERAL COLLECTIONS treated in the same way yields a solution 19.9 per cent ferrous and II 80 . i per cent ferric. Hence the formula of marcasite is FeS 2 while III II that of pyrite is 4FeS 2 and FeS 2 . Since marcasite is most common in limestones and shales, and pyrite in crystalline rocks, their physical differences are doubtless due to their origin marcasite having been hastily deposited from cold solutions, and pyrites slowly deposited from hot solutions, pyrite rep- resenting the more successful molecular grouping and showing that metamorphism produces in the lower zones of the earth's crust min- erals of more complete symmetry, higher specific gravity, and greater hardness than those found in the upper zones. Marcasite has been made in the laboratory from an acid solution and with temperatures not above 300 C. When the solution was neutral, pyrite crystals were formed. The most favorable conditions were found to be an acidity amounting to about i . 2 per cent free sulphuric acid and a temperature of 100. At 450 marcasite changes to pyrite. Both marcasite and pyrite are common fossilizing material because of the reducing action which decaying organisms exert upon iron sulphate solutions. Marcasite decomposing in moist air forms sulphuric acid, which can change the limestones surrounding it to gypsum: SUMMARY Marcasite. FeS 2 ; Fe = 46.6 per cent, $-=53.4 per cent. Ortho- rhombic; holosymmetric; a:b:c = o. 766: i: i. 234; forms (no), (ooi), (on), (018); twinned on (no). Crystals grouped, nodular, stalactitic, radiated, massive. Cleavage imperfect (lu); brittle; fracture uneven. Hardness = 6; gravity = 4. 8. Pale brass yellow; streak greenish gray; metallic; opaque. Soluble in nitric acid. Fuses readily. Ubiquitous. Arsenopyrite Arsenopyrite resembles marcasite in its crystallography (Figs. 76 and 77) but is whiter, has a black streak, and is softer and heavier. It often contains as high as 9 per cent of cobalt in the form of an isomorphous intermixture of the cobalt sulphide, glaucodot. Arseno- PLATE X Marcasite, showing radiated internal structure PLATE XI Marcasite coating galena, Marsden Mine, Jo Daviess County, Illinois SULPHIDES 67 pyrite is the chief source of arsenic, a metal used principally in the manufacture of Paris green, in various medicinal compounds and embalming fluids, and in glass and enamel manufacture. FIG. 76. Arsenopyrite FIG. 77. Arsenopyrite SUMMARY A rsenopyrite. FeAsS ; Fe = 34 . 3 per cent, As = 46 . o per cent, 8 = 19.7 per cent. Orthorhombic ; holosymmetric; a:b:c = o. 677:1:1. 08; (no), (on), (014); twinned on (101); massive; cleavage fair (no); brittle; fracture uneven. Hardness =5.5-, gravity = 6. Silver white ; streak grayish black. Soluble in nitric acid. Freiberg, Cornwall, Ontario, Washington. CLASS III. SULPHANTIMONITES, SULPHARSENITES PYRARGYRITE GROUP Pyrargyrite, a silver sulphantimonite, and proustite, a silver sul- pharsenite, called the "ruby silver ores" because of their wine-red color when fresh, are excellent examples of isomorphism, since they crystallize in forms very similar and with angles nearly identical, though one contains antimony and the other arsenic. Their structure places them in the hexagonal system, and their symmetry is said to be "di trigonal polar" (tourmaline class). It is polar, inasmuch as the crystals are different at different ends. If the difference is not shown by developed planes, it may nevertheless be disclosed by the -c FIG. 78. Symmetry planes of a di- trigonal polar crystal. FIG. 79. Axes of hexagonal system stria tions on the prism planes, since the striations are not symmetrical toward both ends. The symmetry is ditrigonal, since three planes of symmetry intersect in the c axis, and if the forms are revolved around this axis the planes are in a similar position three times in one com- plete revolution (Fig. 78). In the hexagonal system are grouped those crystals which have three lateral axes of equal length intersecting each other at 60, and perpendicular to them a vertical axis longer or shorter than they are. The method of naming the axes can be understood from Figure 79. The holosymmetric (holohedral) forms are three pyramids and three 68 SULPHANTIMONITES, SULPHARSENITES 69 prisms, and the ratios are always given thus : a-.bia^.c. The sum of the intercepts on the first three is always zero. If (hkU) represents any FIG. 80. Model of a primary pyramid symbol, then h-\-k-\-i=o. The pri- mary pyramid (Fig. 80) is a form whose parameter is i : oo : i : i and whose symbol is (1011). Parameter 1:00 :i:i Ratio a b di c 1*0" i "i Symbol (lOll) The diagonal (or " secondary") pyramid, whose relation to the pri- mary pyramid is shown in Figure 81, is one whose parameter is 2 : 2 : i x : 2. Parameter 2 : 2 : ij : 2 +CC -a. FIG. 81. Basal section show- ing relation of primary, second- ary, and dihexagonal pyramids andprisms. I=(ioTi),II=(ii2i). 111= (2131). Ratio I I I I l'l*2*I FIG. 82. Model of a dihex- agonal bipyramid. Symbol (II2I) GUIDE TO MINERAL COLLECTIONS The dihexagonal pyramid (Fig. 82) is a form whose parameter may be ^3: 1:3. Parameter 3 Ratio a b a* c Symbol (2131) FIG. 83. Model of a primary hexag- onal prism. FIG. 84. Secondary hexagonal prism FIG. 85. Model of a dihex- agonal prism. The relation of all three of these pyramids to each other is shown by a ground plan of the lateral axes (Fig. 81). The c axis is simply a point. The three prisms are similar and their symbols are identical with those of the three pyramids, save that the number applied to the c axis is always zero (see Figs. 83, 84, 85). Two hemihedral forms are common; first, that which results when the unit pyramid planes in alternate sextants only are developed. If the start is made with the front sextant (noi), a positive rhombohedron (R) results (Fig. 86). If the start is made with (oiii), a negative rhombo- SULPHANTIMONITES, SULPHARSENITES 71 hedron ( R) is produced. If the two planes in each alternate sextant of a dihexagonal pyramid are developed, a scalenohedron is formed FIG. 86. Rhombohedron (R) resulting from disappearance of darkened planes of the interior figure a hexagonal bipyramid. FIG. 87. Model of a positive scalenohedron. FIG. 88. Model of a scalenohedron FIG. 89. Model of a prism truncated truncated by a rhombohedron (R). by negative %R. (2131) (Fig. 87). A positive rhombohedron and scalenohedron are united in Figure 88, while in Figure 89 a prism is truncated by the negative \ rhombohedron, \R. GUIDE TO MINERAL COLLECTIONS FIG. 90. Pyrargyrite, crystal form. Crystals of pyrargyrite and proustite occur in forms which are combinations of the secondary prism (1120) terminated above with the plus rhombohedron (1011), the flat minus rhombohedron (0112), and the flat scalenohedron (2134), while below appear the scaleno- hedrons (213!) and the rhombohedrons (011:2) and (0114) (Fig. 90). As usual with most minerals, well- developed crystals are rare. Ordinarily pyrargyrite and proustite occur in masses. Pyrargyrite varies in color from the darkest varieties, which are of a deep ruby shade in thin splinters, to the light- est varieties, which are clear wine color. Upon exposure to light, pyrargyrite becomes dead black. It should therefore be sheltered from light if the reddish color is to be preserved. The streak of pyrargyrite is purplish red, while that of proustite is scarlet. Like minerals in all systems other than the regular, these minerals divide entering light into two rays vibrating at right angles to each other and hence differently refracted. One of the rays is called the ordinary (w) and the other the extraordinary (e). SUMMARY Pyrargyrite. Ag 3 SbS 3 ; Ag = 59 . 8 per cent, Sb = 2 2 . 5 per cent, 8=17.7 percent. Hexagonal; ditrigonal polar (tourmaline class) ; 0:^=1:0.789; (1120), (1161), (0112), (2131), (2134), (0114); massive. Cleavage imperfect (1161) and (1010); brittle; fracture conchoidal. Hardness =2. 5; gravity =5. 8. Black to ruby, streak purplish red; metallic; adamantine; translucent. Refraction strong; mean refractive index in sodium light is 2 . 98 (stronger than that of diamond, and surpassed by cinnabar alone, 3.02). Easily fusible; soluble in nitric acid. Guanajuato, Mexico; Chili; Cordilleran states. Proustite. Ag 3 AsS 3 ; Ag = 69-4 per cent, As =15. 2 per cent, 8=19.4 per cent. Crystallography similar to pyrargyrite ; a : c = i : o . 304. Physical properties similar to pyrargyrite, but color lighter and streak scarlet. (0=2.94. Localities similar to pyrargyrite. SULPHANTIMONITES, SULPHARSENITES 73 TETRAHEDRITE GROUP In this group are two well-crystallized copper minerals, tetra- hedrite (Cu 3 SbS 3 ) and tennantite (Cu 3 AsS 3 ), which are related to each other as were the two silver minerals, pyrargyrite and proustite. So definite are they in crystal habit that they have been chosen to furnish the name of a crystal class, the tetrahedrite class (already illustrated by the diamond). The tetrahedron (in) is always developed, sometimes alone (Fig. 91), but usually combined with other tetrahedrons, trapezo hedrons, and dodecahedrons. A common combination is a positive 111-2 110 110 111 FIG. 91. Prevailing form of tetra- hedrite. FIG. 92. Characteristic tetrahedrite. form of tetrahedron (in) with edges beveled by positive and negative three- faced tetrahedrons (211), and with corners truncated by the minus tetrahedron (111) and beveled by the dodecahedron (no) (Fig. 92). The negative tetrahedron appears as a small triangle on each corner and is usually dull or pitted with triangular markings, while the positive faces are bright. When complementary forms of a three-faced tetrahedron (211) are present, the positive form is often striated perpendicularly, while the negative is striated parallel to the dodecahedron edge which it truncates. The edges and corners of one tetrahedrite crystal often project from the faces of another a kind of twinning derived by a half-turn of the projecting crystal about a line normal to (in). In tennantite, dodecahedral or cubic faces usually predominate (Fig. 93). 74 GUIDE TO MINERAL COLLECTIONS The old German miners called both of these minerals (tetrahedrite and tennantite) Fahlerz ("pale ore"), and that term included several varieties which were later divided and named according to the locality in which they are found or according to some peculiarity due to varying composition. They contain not only copper, antimony, arsenic, and sulphur, but of ten. bismuth, lead, silver, mercury, zinc, and iron in varying amounts, vicariously replacing each other. Some of the varieties are the following: (i) freibergite (Freiberg, Saxony) often contains as much as 30 per cent of silver and is lighter than ordinary tetrahedrite in color; (2) schwatzite (Schwatz, FIG. 93. Tennantite (schwatzite) FIG. 94. Model of sandbergerite Tyrol) contains 16 per cent mercury and occurs in black, drusy, dodecahedrons; (3) binnite (Binnenthal, Switzerland) appears in brilliant cubic crystals; (4) sandbergerite contains zinc and shows a tendency to develop large faces of the three-faced tetrahedron (211) (Fig. 94). Tetrahedrite crystals are often coated with brassy, drusy chal- copyrite (Cornwall). They can all be recognized by polar symmetry, metallic luster, absence of cleavage, and reactions for copper, together with either arsenic or antimony. Massive tetrahedrite is worked in Germany, Cornwall, and in many places in the Cordilleran states as a source of copper and silver. SULPHANTIMONITES, SULPHARSENITES SUMMARY 75 Tetrakcdrite.Cu 3 SbS 3 ; Cu = 46.8 per cent, Sb=2g.6 per cent, 8 = 23.6 per cent. Regular; symmetry ditrigonal polar; (in), (ni), (no), (211); twinning axis the normal to (in); brittle; fracture sub- conchoidal. Hardness = 3. 5; gravity = 4. 7. Lead gray; streak dark brown; metallic; opaque. Fusible; soluble in nitric acid. Germany, Bohemia, Cornwall, western United States. CLASS IV. HALOIDS THE SALT GROUP The two most important minerals of this group are halite, sodium chloride (common salt), and sylvite, potassium chloride. Being sol- uble in water, they may be distinguished by their taste. While both are saline, sylvite is bitter. Sylvite the sal digestivus syfoii of the old pharmacists has long been used for medicinal and chemical purposes. It was first dis- covered in the volcanic sublimations of Vesuvius, but larger quan- tities and finer specimens are now obtained at Stassfurt, Germany. Halite has the distinction of being the mineral most largely used as a food. Other minerals furnish food for plants and thus indirectly sustain the life of man, but halite is the only mineral which is eaten in its natural state. It is also one of the most useful of minerals in chemical and manufacturing industries glass manufacture, chlorine and soda works, etc. Halite is the most abundant salt in ocean water, and in many seas in arid regions in various parts of the world. Salt Lake, Utah, contains 20.19 P er cent sodium chloride; the Dead Sea, Palestine, only 7 .8 per cent. The Dead Sea contains more magnesium chloride, about 1 1 per cent, and about 2 per cent of potassium chloride. Its total content of salts exceeds that of Salt Lake, being about 25 per cent. By the evaporation of such seas in preceding geological periods, great beds of salt have been laid down. Such are those of New York, Michigan, Louisiana, Kansas, Nevada, and other states. The New York bed most utilized is seventy-five feet thick and lies at a depth of from one thousand to two thousand feet below the surface. The salt is obtained there, as it is in Michigan, Louisiana, Kansas, and other places, by driving pipes down to the bed, forcing hot water down to dissolve the salt, and carrying the brine thus produced up to evaporating basins, where it is collected, purified, and made ready for market. In some places salt is mined just as is coal. The great chambers remaining after the removal of mountainous masses of salt 76 HALOIDS 77 in some of the mines of Germany, Austria, and Russia are among the most interesting and beautiful underground caverns that are to be found. Salt obtained by evaporation of brines often exhibits skeletal cubes with cavernous faces (Fig. 95). Natural crystals show quite perfect cubes. Ordinarily both halite and sylvite occur in granular and massive condition and contain mag- nesium chloride, magnesium sulphate, and calcium sulphate as impurities. When pure, salt is transparent and color- less. But varying tints of yellow, red, and blue are common. The coloring material is usually some iron oxide. It has been sug- gested that the deep blue color in salt (see No. 3288 from Stassfurt) may be due to metallic potassium. Both halite and sylvite are highly dia- thermanous, allowing free passage of heat as other transparent bodies allow passage of light, and cleavage blocks are used to inclose gases in a tube with transparent ends which will readily transmit heat rays. SUMMARY Halite. NaCl; Na = 3Q.4 per cent, Cl = 6o.6 per cent. Regular; (100); massive. Cleavage perfect (100) ; brittle; conchoidal. Hardness = 2 . 5 ; gravity =2. 2. Colorless; streak white; vitreous; transparent; refraction weak, n= i . 54. Soluble in three volumes of water; taste saline; fusible. Lakes in arid regions, New York, Michigan, Louisiana, Kansas, Ger- many, Poland, Russia. FIG. 95. Halite cube from salt brine. Sylvite. KC1; K = 52.4 per cent, = 47.6 per cent. Regular; sym- metry holoaxial; (100); massive. Cleavage perfect (100); brittle; frac- ture uneven. Hardness=2; gravity =1.9. Colorless; streak white; vitreous; transparent; refraction, 11=1.49. Soluble in three volumes of water; taste saline, bitter; fusible. Volcanic regions; Stassfurt. 78 GUIDE TO MINERAL COLLECTIONS Fluorite Fluorite (CaF 2 ) occurs commonly in beautiful, clear-cut cubic crystals. Few minerals show their crystal form so plainly. The edges of the cubes are often beveled by the four-sided cube (310) (Fig. 96) or by a hexoctahedron (421) (Fig. 97). The flat four-faced cube is so characteristic that it has been called the "fluoroid." The most typical twinning of fluorite is that where two cubes interpenetrate about a line normal to (in) with the result that the corners of one cube project from the faces of the other (Fig. 98). At a point where these corners emerge, the cube face is raised into low " vicinal" faces which form a flat four-faced cube with very high parameters, for example, 32:1:0. " Vicinal" faces often replace FIG. 96. Fluorite FIG. 97. Fluorite simple faces with low parameters. Multitudes of minute cubic crystals often cover the faces of the large cubes without detracting from their luster, since the minute faces are parallel to the large ones. Fluorite also occurs in granular and compact masses. Its cleavage is remarkably perfect, yielding octahedrons (Plate XIII). This trait, together with its vitreous luster, aids in the ready identification of the mineral. The cubic faces have a higher luster than have the cleavage faces. Natural octahedrons are usually dull. Fluorite displays many beautiful colors. Large yellow cubes with corners beveled by (421) are found at Mehenoit, Cornwall; and transparent yellow cubes (see No. 503), at Durham. Beautiful purple crystals, No. 502 from Alston and No. 3852 from Cumberland, are shown. Pink and rose-red octahedrons are found near Chamonix, and at the island of Siglio (near Elba). Beautiful green, plum- PLATE XII Fluorite group from Rosiclare, Hardin County, Illinois PLATE XIII a, Fluorite cubes, Rosiclare, Illinois b, Octahedrons cleaved out by ten-year-old boy, showing ease and regularity of cleavage. HALOIDS 79 colored, and amethystine crystals from the north of England adorn many museums. Since the colors are in layers parallel to cubic faces, some lilac cubes have a yellow center (Derbyshire) and some a deep green center. Amethystine (Nos. 3296 and 3297), green (Nos. 2278 and 2567), and colorless (No. 1788) specimens, all from Rosiclare, Hardin County, give an idea of the color of Illinois occur- rences. Large crystal groups are shown in Nos. 708 and 958. No. 908 is a typical massive specimen. The most complete exhibit of Illinois fluorite is shown in the cases devoted to the eco- nomic exhibits. When specimens of fluorite are heated, they lose in weight and color, and hence are thought to owe their color to hydro- carbon compounds. No rela- tion has been traced between composition and color. Green and red crystals are strongly phosphorescent, that is, if heated above 212 F. or held in sun- light, when taken into a dark room they are luminous. The phenomenon called "fluores- FIG. 9 8.-Modd of fluorite twin cence" is named from this mineral, since it is best illustrated when some richly colored speci- mens are held in the sunlight. They become hazy at a slight depth below the surface and diffuse from this superficial layer a plum-blue color. When viewed by transmitted light, they are light green. This fluorescence is due to transformation of light rays within the mineral, so that those emitted are of greater wave-length than those which entered. Fluorite is low in refraction ( = i .43). Were colorless iso tropic crystals more abundant, the mineral would find extensive use in the manufacture of lenses and microscopic objectives where achromatic light is desired. It is used in the production of ultra-violet rays, for making vases and ornaments (Derbyshire, England), and for enamel and glass manufacture; but the largest quantities are employed as a 8o GUIDE TO MINERAL COLLECTIONS flux in iron smelting and in similar operations where a fluid slag is sought. Being the only common mineral which contains fluorine in any large proportion, fluorite is the chief source of hydrofluoric acid. Moissan used it for vessels and stoppers in experiments on the isola- tion of fluorine, since it is one of the few substances which is not attacked by the gas. Fluorite occurs chiefly associated with metallic ores, calcite, barite, and in tin-bearing veins which are marked by the presence of other minerals containing fluorine, such as topaz, lepidolite, tourma- line, and apatite. Illinois leads all other states in the production of fluorite, some years more than a million dollars' worth having been sold, greatly to the advantage of the steel industry, the manufacture of enameled bath tubs, the production of hydrofluoric acid, etc. SUMMARY Fluorite. CaF 2 ; Ca=5i.i per cent, F = 48.g per cent. Regular; holosymmetric; (100), (310), (421). Massive; interpenetrant twins on axis normal to (in). Cleavage, perfect (in); brittle; fracture sub- conchoidal. Hardness = 4; gravity = 3. 2. Purple, blue, green, yellow, brown; streak white; vitreous; transparent. Refraction weak (to =1.44); dis- persion weak. Fusible; soluble in nitric acid. England, Germany, France, Illinois, Kentucky, Colorado. Cryolite Cryolite is a colorless or pure white translucent mineral composed of sodium and aluminium fluoride (Na 3 AlF 6 ). It is well named " ice- stone" (xpvos, " frost" and \ldos, " stone") because of the trans- lucence of its white masses, because of its low melting-point (a splinter fuses in a candle flame), and because it has been obtained in the greatest amounts in the land of ice, West Greenland, where it was discovered near the town of Ivigtut in 1795. It was long the only source of aluminium and is still an important ore, though today bauxite, a brownish, earthy, hydrated aluminium oxide (A1 2 O 3 +2H 2 O) found in quantities in the southern states, furnishes most of the alu- minium of commerce. Free crystals of cryolite are so rare that the author has never noticed one. Optical examination of crystalline HALOIDS 81 masses and etching with sulphuric acid, however, show the crystals to be repeatedly twinned and to belong to the "triclinic system." In masses they resemble cubes placed in parallel position. Their cleav- age also appears to be parallel to cubic planes, hence it is easy to mistake their crystallography. The cleavage, oblique stria tions, and hardness (2.5) distinguish cryolite from colorless fluorite and similar minerals. Heated with sulphuric acid, cryolite gives off hydrofluoric acid (HF). SUMMARY Cryolite. Na 3 AlF6j Na=32.8 per cent, Al=i2.8 per cent, F~ 54.4 per cent. Triclinic; (no), (ooi), (101); massive; cleavage, perfect, parallel (ooi), nearly perfect parallel (no), (101) ; brittle; fracture uneven. Hardness = 2 . 5 ; gravity = 3. Colorless; vitreous; transparent; refrac- tion weak, /3=i.36; birefringence weak, positive. Easily fusible; soluble in sulphuric acid. Greenland. CLASS V. OXIDES Of the minerals which consist of one or more basic elements united with oxygen, about seventeen are abundant and important. The oxides of silicon, that is, quartz, chalcedony, and opal, will be considered first; and second, the oxides of the metals, such as cu- prite, zincite, corundum, hematite, spinel, magnetite, franklinite, chromite, cassiterite, rutile, pyrolusite, manganite, goethite, and limonite, will be taken up next. Quartz Quartz (SiO 2 ) is the most abundant mineral in the world. It is the chief constituent in the sands of the deserts and of the ocean shores, in the great layers of sandstone and quartzite which underlie the plains and outcrop in the mountains, and in most of the rocks that form the cores of mountain ranges. No mineral has received more study than quartz. It furnished that thoughtful Danish physician, theologian, and geologist, Steno (1669), material with which to establish the "law of the constancy of a crystal angle," and it has been the subject of study for mineralogists ever since, seeming still to be able to reward the investigator with new facts. The Greeks thought quartz to be ice so thoroughly frozen as to have lost the power of melting, and hence named it Kpuo-raXXos, that is, "ice," and today many persons say crystal when they mean quartz. The name "quartz" is an old German mining term used since the sixteenth century and now common to many languages. Crystals of quartz are more abundant than those of any other mineral. They occur in the hexagonal system, and their symmetry is trigonal holoaxial, i.e., they have no plane nor center of symmetry but if revolved around the c axis their planes occupy similar positions three times during a complete revolution. Prism (loio) and rhombohedron (1011) planes are nearly always present and combined, as shown in Figure 99. In Hungary and Brazil are found crystals which contain these planes only. It will be seen that when revolved around the c axis an upper rhombohedron 82 PLATE XIV a, Smoky quartz, "cairn- gorm," from Montana. b, Quartz, Montgomery County, Arkansas PLATE XV Quartz group, Montgomery County, Arkansas OXIDES 83 would be in the front three times during a complete revolution; hence the crystals are "trigonal." Several planes occur with such regularity that, for sake of abbre- viation, to represent them a letter is used instead of the symbol, for FIG. ioo. Quartz FIG. 99. Quartz; prism and rhombo- hedron. FIG. 101. A form of quartz common at Alston Moor, England. FIG. 102. Quartz example, R stands for the plus rhombohedron (ion), z for the minus rhombohedron (oin), m for the prism (1010), 5 for the right trigonal pyramid (1121), and x for the right plus trapezohedron (5161) (Figs. 100-102). The construction of the right and left plus trapezohedrons 84 GUIDE TO MINERAL COLLECTIONS is explained below (see Figs. 103 and 104). Rarely is a crystal termi- nated by a single rhombohedron, as in Figure 102. The usual termination is a combination of plus and minus rhombohedrons, R (ion) and z (om), of different sizes. Sometimes R and z are so nearly of the same size as to resemble a unit pyramid (Fig. 101). ' In some crystals, like those from Alston Moor, England, the prism planes are very small or disappear, and the result resembles a bipyramid (Fig. 101). But their trigonal character can be discovered by heating them and plunging them into water, when they cleave FIG. 103. Quartz; positive left trig- FIG. 104. Quartz; positive right onal trapezohedron. trigonal trapezohedron into imperfect rhombohedra. In some crystals the right edge between R and m is truncated by the plane 5 whose symbol is (1121) (Fig. 102). It has the direction of the diagonal pyramid, yet occurs but three times instead of six, so is recognized as a hemihedral form of the diagonal pyramid called the "right trigonal pyramid." The left trigonal pyramid appears on the left-hand side. The trigonal pyramid is often accompanied by a trapezohedral face x (5161). Figures 103 and 104 show right-handed and left-handed trapezohedrons. They result when the alternate upper sextants of a scalenohedron and the corresponding sextant below are developed. The trapezo- hedral planes are marked by the letter x. The right- and left- handed crystals may be distinguished in three ways: first, in a PLATE XVI Quartz, Bourg de Oisans twin, Hot Springs, Arkansas OXIDES right-handed crystal the x plane is below the right-hand corner of the rhombohedron; second, the direction of the zone z s x m is that of the thread of a right-handed screw; and third, the striae on s are parallel to the edge sR. Twinning in quartz crystals is common according to three laws: first, two crystals of the same sort, both right-handed or left-handed, may be united parallel to the c axis in interpenetrant twins (Fig. 105). Thus x may appear at each corner and R and z in the same plane. However, since R is usually smooth and bright, while z is pitted or X- K FIG. 1 05 . T wo right-handed quartz crystals twinned parallel to c axis. X - FIG. 106. Brazil twin. Right- and left-handed quartz crystals interpene- trating. coated, they may be distinguished from each other. The boundaries of the two interlacing crystals show a zigzag pattern. Second, right- handed and left-handed crystals interpenetrate parallel to the c axis and at the same time parallel to the diagonal prism (1120). In this case twinning is betrayed by the x and z faces (Fig. 106). This is called the Brazil twin. Figure 107 shows two right juxtaposed Brazil twins. Third, Bourg de Oisans in Dauphiny (France) has long been noted for fine quartz crystals twinned in the manner shown in Figure 108 (Nos. 3307, 3308, and 3315). Recently Japan has furnished the museums of the world with a large number of these twins. They are united parallel to the diagonal pyramid (1122) so that the c axis and the line of union form a zigzag. 86 GUIDE TO MINERAL COLLECTIONS Quartz illustrates not only the geometrical but the optical, elec- trical, thermal, and chemical features of crystals as well. Optical properties throw much light upon its internal structure. The con- nection between geometrical and electrical properties may be illus- trated as follows: The three horizontal axes are polar (i.e., not symmetrical around the center), for one end of each axis emerges through a prism edge that is truncated by the planes 5 and x, and the other through a prism lacking these planes. Since the horizontal axes are polar, they exhibit pyro-electric polarity. Finely powdered red lead and sulphur are sifted through a piece of cloth, thus becoming electrified by friction. The red lead is positive, the sulphur negative. When they touch the heated quartz crys- tal, the s and x faces become negatively electrified on cooling, i.e., attract the red lead. FIG. 107. Brazil twin. Two right-handed crystals juxta- posed. A B FIG. 108. Quartz twinned on (1122). Bourg de Oisans twin. FIG. 109. Quartz etched with hydrofluoric acid; A, left-handed; B, right-handed. The action of caustic alkalies or hydrofluoric acid in nature or in the laboratory produces different effects on different planes, and thus the right-handed and left-handed nature of the crystals can be made evident (Fig. 109). The etching shows that the forms are related to each other as are a right and left glove, and hence they are said to be entantiomorphous. OXIDES 87 The manner of crystal growth is shown by some specimens of quartz which within the transparent outer crystal have different layers of cloudy material forming outlines of the planes at different stages of the crystal's development. This is called "ghost quartz." "Capped quartz" has an inner kernel separated from the outer by a layer of clay or other substance which permits them to be taken apart. "Twisted quartz," while seeming to consist of a single warped crystal, in reality is composed of many individuals, each turned through a small angle so as to produce a spiral effect. Quartz is practically lacking in cleavage. Only by heating and plunging in cold water can rough rhombohedrons be obtained. Intergrowths of right- and left-handed quartz break with a wavy surface, producing "ripple fracture," while the ordinary fracture is conchoidal. As might be expected in a mineral so abundant and so varied in its surroundings and mode of formation, quartz exhibits great variety in form and appearance. Rock crystal, or mountain crystal, as it was called by indefatigable collectors who sought fine specimens in the mountain fastnesses of Switzerland and the Tyrol, is a clear, transparent variety well marked in crystallization. It was formed in non-resistant rocks like clay and sandstone, or in cavities in igneous or metamorphic rocks, which afforded it opportunity to develop its own planes (see Nos. 1772 to 1779, 3896, etc.). Crystals of remarkable size have been found in the Alps, Brazil, Japan, and Madagascar. 'A crystal twenty-five feet in circumference was found in Madagascar. A famous cave in the Berner Oberland in Switzerland yielded five hundred tons of quartz crystals. Herkimer County, New York, is noted for its beautiful, transparent crystals. Little Rock, Arkansas, has annually furnished countless souvenirs of this kind to the tourists in that region (Nos. 473, 1775, etc.). Multitudes of geodes found at Warsaw in Hancock County, Illinois, varying in size from a hazelnut to nodules a foot or more in diameter are lined with clear quartz crystals. There is hardly a state in the United States in which fine quartz crystals have not been found. Clear crystals have long been used for ornaments. Beautiful transparent globes as much as six inches in diameter have been cut from quartz found in Japan. 88 GUIDE TO MINERAL COLLECTIONS Inclosures of foreign substances may add to the beauty of the mineral. Crystals from Herkimer County, New York, often inclose anthracite flakes. Spangles of mica and of hematite produce the shimmer seen in aventurine quartz. Fibrous actinolite, asbestos, or rutile needles produce beautiful effects. Silky fibers of asbestos or of quartz replacing them give a peculiar band of color to the opalescent quartz called "cat's eye" (a name more properly applied to a variety of chrysoberyl) . The golden yellow crocidolite from South Africa owes its beauty to this cause. Cavities shaped like a quartz crystal and containing water or liquid carbon dioxide are often seen. There are several varieties based on color: milk quartz (No. 1773) is white and opaque, morion (No. 4645) is black, smoky quartz (No. 3312) brown. Morion and smoky quartz, abundant in the Alps, are colored by a hydro- carbon which disappears upon heating. When cut into gems smoky quartz is called "cairn- gorm." A clear yellow quartz also colored by hydrocarbon is named citrine. Prase (No. 3225) is green from needles of actinolite. Rose quartz abundant in the Black Hills is pale red from solution of salts of titanium or man- ganese (Nos. 1681, 3323, 4513). Amethyst, a violet quartz, has long been one of the most popular of semiprecious stones (Nos. 4458, 588, 589, 3319, etc.). Its color is thought to be due to manganese, though upon heating to a temperature of 250 it changes to yellow. The color is often irregularly distributed, white, opaque layers alternat- ing with transparent violet and brown layers (Plate XVII). Micro- scopic examination shows alternating layers of right- and left-handed lamellae. Where the right and left layers are mingled, converging light produces lines known as "Airy's spirals" (Fig. no). The interpenetration of right- and left-handed layers produces roughly striated surfaces. The more strongly colored parts are "biaxial," that is, they have two directions in which light is not doubly refracted. FIG. no. Airy's spiral in right- handed crystal. PLATE XVII Amethyst, Thunder Bay, Lake Superior OXIDES 89 Upon heating, the biaxial character disappears, showing that it, as well as the color, is due to easily destructible material. Beautiful violet specimens are found in Brazil, Ceylon, the Urals, Colorado, and north of Lake Superior. By some authors all quartz showing Airy's spirals is called amethyst, whatever the color. Quartz quite commonly replaces organic substances, producing such objects of permanent beauty as silicified wood; or fills cavities formerly occupied by fluorite, calcite, barite, etc., assuming the shape of these minerals, thus producing pseudomorphs. A cube of quartz may be a pseudomorph after fluorite; fibrous quartz, a pseudomorph of fibrous gypsum; cellular quartz, the capping of calcite crystals later dissolved by water. Quartz is the great repairing agent of nature, since it so commonly cements crevices in rock layers and microscopic fissures in minerals. SUMMARY Quartz. SiO 2 ; Si=46.y per cent, = 52.3 per cent. Hexagonal; symmetry, trigonal holoaxial (quartz class). a:c=i:i.i. w=(ioio), R=(ioii), 2=(oiii), s=(ii2i), #=(5161). Twinned on m (1010) or (1122). Massive, cleavage parallel R very imperfect; brittle; fracture conchoidal. Hardness=y; gravity =2. 65. Colorless; vitreous; transparent, 0^=1.544. Uniaxial; double refraction, positive weak; rotary polariza- tion, strong. Infusible before blowpipe; insoluble in acid. Ubiquitous. Chalcedony Chalcedony is identical with quartz in chemical composition and in many physical properties, but differs in several respects. First, it never shows crystal planes but occurs in translucent or opaque botryoidal, reniform, or stalactitic masses composed of microscopic fibers. Second, the fibers composing it are optically biaxial. Quartz is uniaxial. The refractive index and fusing-point of chalcedony differ from those of quartz. Chalcedony is waxy or greasy in luster, and somewhat splintery in fracture. It is much more soluble in potassium hydrate than is quartz. It is deposited from aqueous solution, and is found in veins or other cavities in various kinds of rocks. Usually it has banded structure 90 GUIDE TO MINERAL COLLECTIONS and shows a great variety of colors. The banding is due to alternation of different-colored layers of chalcedony, quartz, and opal. There are many varieties. The translucent, waxy, cream- colored, slightly banded variety is chalcedony proper. The red variety is called carnelian; the brownish-red, sard; the leek-green, plasma; the apple-green, chrysoprase (No. 3324); chalcedony with blood-red spots of jasper, heliotrope (No. 3329). Agate (Nos. 496- 99, etc.) is composed of successive bands of chalcedony, carnelian, jasper (No. 568), smoky quartz, amethyst, etc., that have been laid down in the lining of a cavity, the outer band being formed first and the others successively until the cavity has been more or less filled. Usually the last stages permit of the formation of good quartz crystals. The fineness of some of the layers is a cause of wonder, and as the cavities often have no visible outlet, the manner in which the silicon reached its resting-place is enigmatical unless it be explained as being due to the solidification of colloidal silica. Sometimes the solution has deposited curvilinear layers first, and later parallel bands per- fectly horizontal (No. 496). Such deposits are prized for cameo cutting. The figure is cut in one layer and the background in a layer of different color. When the layers are black and white, the material is called onyx. When red or brown, sardonyx. In moss agate (Nos. 4398 and 1851), banding is inconspicuous, but dendritic inclu- sions of chlorite, manganese oxide, and other substances occur. Flint (No. 3330) is a translucent to gray, brown, or nearly black chal- cedony consisting largely of the remains of diatoms, sponges, and other marine organisms. The best variety is found in the chalk cliffs of England. Hornstone, as its name implies, resembles horn in color and in streaked appearance. It is more brittle, splintery, and soluble than flint, and less pure. Chert is still farther removed from flint in these respects. Its color is white or gray, and the impurities are calcareous and arenaceous substances. Jasper is a creamy, brown, or red chalcedony containing ferruginous, calcareous, or arenaceous substances as impurities. These last four-named varieties border very closely upon rock species because of their impurities. A final step is represented by granular to massive silica, which occurs in large bodies and forms the rock called quartzite. PLATE XVIII Moss agate, India OXIDES 91 SUMMARY Chalcedony. SiO 2 ; 81=46.7 per cent, = 53.3 per cent. Crypto- crystalline, apparently amorphous, concretionary, botryoidal, stalactitic, arborescent. Brittle; fracture conchoidal. Hardness = 7 ; gravity =2.6. Waxy, yellow, red, brown, translu- cent to opaque; optically biaxial, thus differing from quartz, which is uniaxial. Infusible; insoluble. Ubiquitous. Opal Opal differs from quartz and chalcedony in constitution, since water forms a part of its molecule (SiO 2 and H 2 O). When water occurs in quartz it is mechanically, not chemically, included and is given off with a cracking noise (decrepitation) when the quartz is heated above the boiling-point (100 C.). In opal it is chemically combined in definite proportion, constituting most commonly about 10 per cent of the mass. At the moment of solidification a molecule of silica attracts one or more molecules of water, called the water of constitution, in distinction to mechanically included water. It is held scarcely more firmly than are the different molecules which con- stitute water itself, and is given off upon heating to 100 C. Opal differs from quartz not only in composition but in physical characteristics also. It lacks crystal form, lines cavities with layers which on their free sides are botryoidal, reniform, or stalactitic, is softer and lighter than quartz, has a greasy luster, and is completely soluble in hot potassium hydrate. Of the several varieties, the most important is precious opal (Nos. 3741 and 4725), which is highly prized for gems in spite of its opacity, low refraction, and moderate hardness. Its beauty depends upon the wonderful play of colors which the thin films composing it cause by their difference in refractive index. For centuries near Czerwenitza, Hungary, beautiful yellow, red, green, and blue opals have been found disseminated through an altered trachyte. Similar rock near Queretaro, Mexico (No. 3334), furnishes a fiery red opal without much play of color, the so-called fire opal. Blue and green opals of great beauty are obtained from nodules of brown jaspery limonite in Queensland (No. 3741). At all these localities opals of various other shades also are found. GUIDE TO MINERAL COLLECTIONS A perfectly transparent colorless and glassy opal found in botry- oidal masses is called hyalite. Because of strain due to the solidi- fication of the original jelly mass, it often shows double refraction. Siliceous sinter is fibrous, stalactitic, porous, or powdery opal deposited by hot waters in Yellowstone Park, Iceland, and New Zealand. Its structure is influenced by the algae which live in the water, just as blades of grass determine the form of ice deposited on them by winter's rain. The shapes of the sinter or geyserite are often fantastic and beautiful. SUMMARY Opal. SiO 2 -H 2 O. Amorphous; brittle; fracture conchoidal. Hardness=6; gravity = 2. Colorless, white, red, brown, yellow, gre.en, blue. Vitreous. Infusible; yields water; soluble in potassium hydrate. Hungary, Bohemia, Australia, Mexico, Idaho, Montana. A. THE MONOXIDES Minerals composed of an equal number of atoms of a bivalent metal and of oxygen are called monoxides. The two leading examples are cuprite and zincite. Cuprite Cuprite (Cu 2 O), or "red copper ore," contains the largest per cent of copper (88.8 per cent) of any mineral except native copper. It occurs in well-formed crystals which exhibit the cube (100), octahedron (in), dodecahedron (no), trapezohedron (211), and trisoctahedron (221). A typical crystal is shown in Figure in. Granular aggregates and dense masses are common. Fresh sur- faces of cuprite have a shining red appearance like proustite, but the streak is brownish red, while FIG. in. Cuprite that of proustite is scarlet. Cu- prite is the harder of the two minerals. It is found in mineral veins where chalcocite and chalco- pyrite have been subject to oxidizing agencies. Hence many veins loo V OXIDES 93 which above the water line contain cuprite are composed of sul- phides, chalcocite, chalcopyrite, etc., below that line. Cuprite is often coated with malachite, a green copper carbonate, and at times the change extends throughout the crystal without destroying the external form. There are three varieties of cuprite: first, the ordinary crys- tallized form described above; second, " chalcotrichite " "plush copper ore," consisting of slender fibers as fine as a hair, elongated in the direction of a cube edge or a cube diagonal; third, "tile ore," a brick-red, earthy mixture of cuprite and limonite. SUMMARY Cuprite. Cu 2 O; Cu = 88.8per cent, O=n. 2 per cent. Regular (in), (100), (no); brittle; fracture uneven. Hardness = 3 . 5 ; gravity = 6. Cochineal red; streak brownish-red. Metallic, adamantine ; translucent; refraction very strong, 00 = 2.85. Fusible; soluble in strong hydrochloric acid. In Cordilleran states hydrochloric acid. Zincite In Sussex County, New Jersey, zincite (ZnO) occurs in quantities sufficient to make it a profitable source of zinc (Nos. 314, 315, 524, 747). It is of brownish or deep red color, and has a characteristic orange-yellow streak. It is usually massive, but when crystals are found they are in the hex- agonal system and " hemimorphic " or "polar," since their planes are not sym- metrically arranged around the center (Fig. 112). Some specimens of zincite contain as much as 7 per cent of man- ganese oxide (MnO), which is present in solid solution as an isomorphous mixture. r^,, .... ,.j ,- . . FIG. 112. Zincite That it is a solid solution is suggested by the fact that with increase of the amount of manganese the mineral becomes more yellow. SUMMARY Zincite. ZnO; Zn = 8o/3 per cent, 0=19.7 per cent. Hexagonal. Symmetry, dihexagonal polar. Cleavage, perfect (oooi), (1010). Brittle; fracture subconchoidal. 94 GUIDE TO MINERAL COLLECTIONS Hardness = 4; gravity =5. 6. Blood red, streak orange; luster, sub- adamantine; translucent; double refraction positive. Infusible; soluble in hydrochloric acid. New Jersey. B. THE SESQUIOXIDES Minerals having three atoms of oxygen to two of another element, usually a metal, are called sesquioxides. As examples we select co- rundum and hematite. Corundum Since very early in human history corundum (A1 2 O 3 ) has been recognized and used by man. The words sapphire and ruby occur in literature two thousand years old. Sapphire is blue corundum and ruby the red variety. Ordinary corundum, being non-transparent and unattractive in color, did not early arrest attention. When cleaved, its fragments resemble feldspar, one of the most abundant of minerals, and hence would not be easily recognized. Though the name corundum is an old Hindu word, the mineral was first brought from China to Europe, and was first OOO1 analyzed by a German, Klaproth, in 1787. A third variety of corundum, emery, is granular and dark in color because mixed with iron oxides such as magnetite. The name "emery" is of Greek origin, and some of the isles of Greece, especially Naxos, were long the FIG. 113. Corundum chief source. The ancient lapi- daries used it for grinding and polishing, and today its use is very extensive, although pure corun- dum is preferable, being superior to emery in hardness. Sapphire, ruby, ordinary corundum, and emery differ only in purity of chemical composition, color, and in structure. Emery is the least pure, is opaque, and occurs only in grains. Corundum and the transparent varieties crystallize in good hexagonal crystals of rhombohedral symmetry (calcite class).. While the sapphire and ruby are rare, corundum is abundant and may best be taken as the representative of the species. Figure 113 shows a common and typical OXIDES 95 form. It is composed of a rhombohedron truncated with a basal plane. In such a crystal it is evident that there are three planes of symmetry intersecting in the c axis, and that if the mineral were revolved around this axis the planes would repeat themselves three times during a complete revolution. Thus the c axis is an axis of trigonal symmetry. The three horizontal axes are axes of binary symmetry. More common than the simple crystals are those composed of rhombohedrons R (idi), dihexagonal pyramids (2423), diagonal prisms (1120), and base (0061) (Fig. 114). Repetition of dihexagonal pyramid planes of different inclination to the c axis produces undulating prisms and rounded crystals. Often 422 FIG. 114. Corundum FIG. 115. Corundum with twinning lamellae parallel to R. twinning lamellae parallel to the rhombohedron (ion) cause stria- tions on the basal plane and divide the crystal into sextants (Fig. 115). When the basal plane is polished, these striations reflect the light in such a manner as to produce a beautiful six-rayed star ("asterism"). The largest amount of corundum has been found as water- worn pebbles, which, though rounded, usually retain their crystal shape because of their great hardness. Coarse pieces and granular masses intergrown with mica are also characteristic. In the Boston Society Natural History Museum is a group of large corundum crystals weighing several hundred pounds. True cleavage is wanting, but there is a lamellar separation parallel to R and the base, due to layers of twin crystals. 96 GUIDE TO MINERAL COLLECTIONS Vitreous luster is characteristic. Few minerals have as great variety of color. Colorless examples are rare. When the trans- parent or translucent varieties are red, they are called ruby. If of the shade known as "pigeon blood," they are more highly prized than any other gem. When deep blue to lilac in color, they are called sapphire; yellow to brown, oriental topaz; green, oriental emerald; purple, oriental amethyst a good example of the common tendency to call one object by the name of another in order to enhance its value a tendency which should be resisted. The color is due to oxides of iron or chromium. Sapphire exposed to action of radium bromide assumes successively green, light-yellow, and dark-yellow tints, while ruby develops in succession shades of violet, blue, green, and yellow. They regain their original color upon heating. W FIG. 116. Cross-section of dichro- FIG. 117. Direction of vibration of scope. two rays of light passing through calcite prism. In corundum (as in other transparent minerals not belonging to the regular system) the color depends upon the direction in which light passes through the crystal. Hence false gems can be readily separated from genuine ones. The mineral needs only to be examined through a dichroscope (S, "two," xP^Ma, " color") (Fig. 116), an instrument consisting of a metal tube three inches long fitted with a weak lens at the end a to be held to the eye and having a small square opening at the end b against which the mineral to be examined is held. In the tube is a cleavage rhomb c of calcite (CaCO 3 ), a transparent mineral which has the power of dividing a ray of entering light into two rays that vibrate in planes at right angles to each other and consequently make a single point appear double (Plate XXI). Such a thickness of calcite is chosen as to make the square opening appear like two openings side by side. The transmitted light vibrates in the direction indicated by the arrows in Figure 117. One ray of light is called the ordinary (co) and the other the extraordinary (e). OXIDES 97 When a piece of colored glass is placed on the square opening, both images have the same color. If a ruby is placed on the opening, the ordinary ray (co) looks deep red, while the extraordinary (e) is violet red. A sapphire appears deep blue for the ordinary ray () and greenish blue for the extraordinary (e) (Figs. 118 and 119). Rubies and sapphires are found in granite, basalt, gneiss, mica and chlorite schist, granular limestone and dolomite, and in gravels derived from them. The finest sapphires have been obtained in Ceylon, the most valuable rubies in Burma. Montana and North Carolina furnish valuable sapphires, rubies, corundum, and emery. D FIG. 1 1 8. Ruby FIG. 119. Sapphire The examples shown come from widely distributed localities: rubies from Burma (No. 3339), sapphires from Kashmir (No. 3341) and from Queensland (No. 3340), corundum from North Carolina (No. 3342) and New Jersey (Nos. 506 and 519), emery from Massa- chusetts (No. 1254). SUMMARY Corundum. A1 2 O 3 ; Al= 52 . 9 per cent, = 47 . i per cent. Hexagonal, symmetry rhombohedral (calcite class). 0:^=1:1.363. R (ion), (2423), (1120). Parting or pseudo-cleavage ; brittle; fracture conchoidal. Hardness=g; gravity =4. Many colors, vitreous, transparent, dichroic, refraction strong, 00=1.768. Double refraction, negative weak. o> e = o.oo8. Infusible; insoluble. North Carolina, Montana, Idaho, India. Hematite Of all minerals in the mineral kingdom, none is more important from a human standpoint than hematite (Fe 2 O 3 ), inasmuch as it is the mineral which furnishes the greatest quantity of iron a metal upon which modern civilization is founded and which may be said to furnish a standard of development of a people. 9 8 GUIDE TO MINERAL COLLECTIONS In appearance hematite varies greatly with its physical condition. When well crystallized it is metallic, black, 6 . 5 in hardness and 5 in specific gravity. When earthy and friable it is submetallic, red, soft, and of low specific gravity. Hematite is isomorphous with corundum, that is, it has the identi- cal shape, though it is a different chemical substance. The best crystals are found in igneous rocks. The island of Elba has for many years furnished beautiful crystals which show the same rhombo- hedral symmetry already studied in corundum. The rhombohedron R (1011) occurs alone (Fig. 120) or combined with a negative flat rhombohedron %R (0112). Rounded crystals (Fig. 121) composed of a flat rhombohedron %R (1014), the ordinary rhombohedron R (1011), and the bipyramid (2243) are characteristic. Tabu- lar crystals composed of a broad basal plane (oooi), truncating short rhombohedrons R (1011), and secondary prism planes (1120) often twinned parallel to a prism plane are common (Fig. 122). They are often so grouped as to form rosettes, "iron roses." FIG. 120. Model of a rhombohedron _ .. . . . . ... (101 1) =R Individual crystals of minute size occurring in myriads some- times constitute great masses of ore and form the variety called mica- ceous hematite. The fine scales of this variety of hematite are usually imperfectly cemented so that they easily rub off and give a false impression of the hardness of the mineral. When heated in a reducing flame, the mineral loses its red color and becomes magnetic but does not melt. The electrical con- ductivity of hematite has been accurately measured and is found to be two times as great in the vertical as in the horizontal direc- tion of the crystal. Hematite is one of nature's most universal paints. It colors the rocks red and brown and yellow as it varies in amount and in its degree of oxidation. About 6 per cent of the PLATE XIX Botryoidal hematite, Cumberland, England , Limonite. Hardin County, Illinois OXIDES 99 earth's crust is iron and a large part of iron is in the form of hematite. Illinois has no workable deposits, but the mineral occurs in flakes, incrustations, or red ochreous balls, or as coloring matter in all parts of the state and in massive micaceous or compact pieces in the drift. In many parts of the world granular hematite (No. 1581) forms such extensive deposits as to furnish the largest source of iron. Well- crystallized lustrous hematite is capable of receiving a high polish and reflects the light as does a looking-glass, and hence has been called " specularite " (Nos. 3894 and 3895). The fibrous and columnar varieties are composed of individual threads or pencils more or less parallel and ending in rounded grapelike (botryoidal) (No. 3343) or 1011 __ 11ZO 2245 FIG. 121. Hematite FIG. 122. Tabular hematite crystal twinned parallel to the prism. kidney-shaped (reniform) surfaces and exhibiting curvilamillar mark- ings in various places (No. 3345). Botryoidal masses break up into conical forms known as " pencil ore." Masses that are earthy and soft enough to adhere to the fingers like graphite, and usually bright red in color, suggested a name for the mineral (hematite, "blood- stone") to Theophrastus three hundred years before Christ (Nos. 343, 608, and 4496). Thin flakes such as may be seen in microscopic slides appear blood red in transmitted light, just as the powder does in ordinary light. The great deposits of hematite in Michigan, Minnesota, Wis- consin, and Alabama make it possible for the United States to lead the world in the production of iron. 100 GUIDE TO MINERAL COLLECTIONS SUMMARY Hematite. Fe 2 O 3 ; Fe = 70 per cent, O = 30 per cent. Hexagonal ; sym- metry dihexagonal, alternating (calcite class). a:c= 1.3656. R (ion), $R (0112), %R (1014), (1120), (2243), (oooi). Cleavage (parting) parallel R and (oooi) imperfect; brittle; fracture uneven. Hardness = 6 ; gravity = 5.2. Iron black to blood red ; streak brownish red or purple; metallic; in thinnest pieces translucent and red. Infusible alone before blowpipe; powder difficultly soluble in concen- trated hydrochloric acid. Elba, Switzerland, New York to Alabama, Minnesota, Wisconsin, and Missouri. C. HYDRATED SESQUIOXIDES Three minerals may be chosen to represent this group. They are: Manganite Mn 2 O 3 H 2 O Goethite Fe 2 O 3 -H 2 O Limonite 2 Fe 2 O 3 3H 2 O Manganite From a mineralogical point of view manganite (Mn 2 O 3 -H 2 O) is of more importance than pyrolusite, though not so commercially, since ,O01 JOO 101 FIG. 123. Manganite FIG. 124. Manganite twinned par- allel to (011). pyrolusite and another manganese oxide, psilomelane, are mined in great quantities, while manganite is comparatively rare. Manganite is well denned in its physical and chemical characteristics. It occurs in steel gray to black, moderately hard (hardness, 4), ortho- rhombic prisms, which are usually grouped in bundles and striated vertically. The prisms end in basal planes and are striated hori- OXIDES zontally (Fig. 123). The customary planes are (210), (no), (120), (oio), (in), (101), (on), and (021). Twins parallel to (on) are common (Fig. 124). Fibrous, radiated, and granular forms are rep- resentative (No. 3356). Manganite is formed by deposition of manganese oxide in many springs and often replaces other minerals, assuming their forms, i.e., becoming a pseudomorph. For example, at Ilfeld, Germany, man- ganite (No. 3357) replaces calcite, and since the calcite has been deposited from an aqueous solution it is natural to conclude that manganite has a like origin. On the other hand, manganite changes into pyrolusite by loss of water. The process which occurs in nature is imitated by slow heating of manganite with free access of air. Pyrolusite is often found with a manganite core, showing that the process is but partially completed. SUMMARY Manganite. Mn 2 O 3 -H 2 O; Mn 2 O 3 = 89.7 per cent, H 2 O=io.3 per cent. Orthorhombic. a:6:c = 0.844 : i : o. 545 ; (ooi), (in), (on), (101), (no), (oio), (210), (120), (021); twinning parallel (on); cleavage parallel (oio) perfect; brittle; fracture uneven. Hardness = 4; gravity = 4. 4. Steel gray; streak reddish black; sub- metallic; opaque. Infusible; soluble in hydrochloric acid with evolution of chlorine. Hartz Mountains, Michigan, Colorado. Goethite Goethite (Fe 2 O 3 'H 2 O), named in honor of the poet Goethe, who was interested in mineralogy as well as in other natural sciences, is an iron hydrate occurring in lustrous brown or black orthorhombic prisms terminated with pyramids (No. 547). The usual planes (Fig. 125) are (no), (210), (oio), (in), '(on), and rarely (ooi). Prism planes are often striated. Columnar forms and capillary crystals radially grouped are common. The last are called " needle iron stone." Columnar and capillary crystals bunched together in radiated and concentric masses which end in rounded sur- faces are said to be "reniform." Goethite also occurs in thin red scales composed of (100), (oio), (401), (on) (Fig. 116). Multitudes of these fine scales attached on one side produce a mass with velvety luster. Because of their color they are called "ruby mica," and in &UIIDE TO MINERAL COLLECTIONS the finest scales are transparent, reddish yellow, and under the micro- scope dichroic, i.e., exhibit two different colors when the light travers- ing them is allowed to vibrate first in one and then in another direction through a dichroscope (see p. 96). Thus are they easily distin- guished from scales of hematite, which are monochroic. Goethite crystals are common alteration products in secondary cavities, and give rise to a bronze sheen and opalescent tint. When goethite is heated it gives off water, becomes red, and changes to hematite. 210 --O1O FIG. 125. Goethite 401 100 FIG. 126. Goethite Further heating with some reducing agent makes it black and mag- netic, and heating continued until all the oxygen is removed produces pure iron. Goethite is much less abundant than either hematite or magnetite, but is a common associate of these and other iron ores in veins. Bohemia, Cornwall, Connecticut, the Lake Superior region, and Colorado yield the best crystals. SUMMARY Goethite. Fe 2 O 3 'H 2 O; Fe 2 3 = 89-9 per cent, H 2 O = io.i per cent. Orthorhombic. a:b:c = o. 913: 1:0.607; (no), (210), (on), (in), (ooi), (401), (oio), (100). Cleavage parallel (oio) perfect; brittle; fracture uneven. Hardness=5; gravity =4. Brown to black; translucent; double refraction positive; dichroic. Fusible with difficulty to magnetic bead; soluble in hydrochloric acid. Bohemia, Cornwall, Connecticut, Michigan, Colorado. OXIDES 103 Limonite Much more common than goethite is the fibrous, dense, or earthy iron hydrate, limonite (2Fe 2 O 3 '3H 2 O) named from \einuv, the Greek for a moist grassy place, since it is found as a brownish-yellow deposit in bogs. It causes the iridescent slime seen in sluggish streams and pools, replacing the decaying vegetable matter. The rusting of iron is simply a change to limonite. There are several varieties founded upon form, origin, and condition of the mineral in deposits. First, there is the fibrous, radial, curvilaminar limonite, often with black glazed (No. 1881) or opalescent lustrous surface (No. 3359), lining cavities and geodes, and hanging in stalactites in caves (Nos. 2571 and 244); second, dense compact limonite (No. 298), in veins where it has been deposited by circulating waters which have gathered it from the surrounding decomposing rocks; third, extensive beds formed by waters circulating above ground and emptying into ponds. These beds are often oolitic (No. 1747), i.e., composed of myriads of small grains, among which are found fragments of algae, foraminifera, bryozoans, etc. Such deposits are analogous to the fourth variety bog iron ore, forming today in swamps and making granular, nodular, concretionary, earthy, or sandy masses. On the bottom of many lakes is a black mud from which small grains of limonite are separating. Measurements made in Sweden show that deposits six inches thick have been formed in twenty years. The fifth variety consists of grains as large as a pea (pisolitic). The grains often show concentric structure and fill clefts in limestone and are cemented together in clumps. Sixth, constantly associated with the denser limonite and other iron ores is a yellowish-brown, soft, porous mass called yellow ochre. It is porous because it is a rem- nant left after the dissolution of other materials. That limonite is a secondary mineral derived from such minerals as siderite and also from pyrite, hematite, and magnetite, is evident because the form of the original crystal is often retained the rhombo- hedrons of siderite, cubes of pyrite, octahedrons of magnetite, and hexagonal plates of hematite. Different stages of the process show different proportions of the original crystals still unaffected. All the steps of the transition from original to derived material can be traced. The brown streak of limonite, its inferior hardness and weight, and the presence of water distinguish it from hematite. It is 104 GUIDE TO MINERAL COLLECTIONS harder and lighter than the crystallized goethite and contains more water. Because of the ease with which limonite fuses, it was probably the first mineral to be used by man as a source of iron. SUMMARY Limonite. 2Fe 2 O 3 3H 2 O; Fe 2 O 3 = 88.5 per cent, H 2 0=i4-S per cent. Amorphous, fibrous, concentric, dense, earthy. Hardness =5. 5; gravity = 3. 8. Dark brown; streak yellow brown; submetallic; opaque. Fusible to magnetic bead ; soluble in hydrochloric acid. Scotland, Sweden, Connecticut, New York, Pennsylvania, Alabama, Ohio, Illinois. D. ALUMINITES, FERRITES, MANGANITES, CHROMITES The chief minerals of this group, all of which crystallize in the regular system with the octahedron as a common form, are Spinel MgO-Al 2 O 3 Manganit e FeO Fe 2 O 3 Franklinite (Fe,Zn,Mn)O- (Fe,Mn) 2 O 3 Chromite FeO-Cr 2 O 3 Spinel. Spinel is a mineral useful as a gem because of its beauty and hard- ness. The minute quantities of various elements which replace a part of the Mg or Al in the typical formula MgO A1 2 O 3 produce differ- ent colors. For example, the dark green to black opaque spinel (ceylonite) contains Fe. The yellowish- or greenish-brown variety (picotite) contains Fe and Cr, and the grass-green variety (chlor- spinel) contains Fe and Cu. But the typical spinel approaching most nearly the formula MgO*Al 2 O 3 is of a beautiful clear red color, generally transparent, and called precious spinel. The purest red is called ruby spinel; the orange red, rubicelle; and the violet, the almandine spinel. From earliest times precious spinel was prized as a gem, but was not distinguished from ruby until Rome de ITsle studied it (1783), though these minerals differ in crystal form, cleavage, optical proper- ties, hardness, and density. The specific gravity of spinel is 3.5, while that of ruby is 4; spinel is only 8 in hardness, while ruby is 9. OXIDES 105 Spinel shows no pleochroism and is iso tropic, i.e., it allows the light to pass through it similarly in all directions, as would be expected of a mineral crystallizing in the regular system. In gem-bearing sands of Ceylon, Burma, and Siam, which have long been the source of precious spinel, are found small, sharp-edged octahedrons and typical spinel twins, where the octahedral face is the twinning plane (Fig. 127). The corners of the octahedrons are FIG. 127. Spinel twin FIG. 128. Spinel often beveled by trapezohedrons and the edges by dodecahedrons, giving the crystal a rounded appearance. Dark-colored varieties occur in abundance at Vesuvius, in New York, New Jersey, and North Carolina. SUMMARY Spinel. MgO-Al 2 O 3 ; MgO=28.2 per cent, Al 2 O 3 = 7i.9 per cent. Regular; holosymmetric; (in).. Cleavage imperfect parallel (in); brittle; fracture conchoidal. Hardness = 6; gravity =3. 5. Red, yellow, green, black; streak white; luster vitreous; transparent; refraction high,'w = 1.715. Infusible; soluble with difficulty in sulphuric acid. Burma, Ceylon, Appalachian region. Magnetite The third mineral in importance as a source of iron is magnetite, which derived its name, according to Pliny, from the shepherd Magnes, who found his iron-pointed staff attracted by the mineral while he was wandering over Mount Ida. It is the most magnetic of all io6 GUIDE TO MINERAL COLLECTIONS FIG. 129. Magnetite minerals, sometimes possessing polarity and attracting particles of iron to itself (loadstone) (No. 334). Usually it is simply itself attracted by a magnet. Because of its magnetism it is easily sepa- rated from the sands of the ocean or lake or the streams, in which it is found in abun- dance. In various sedimentary deposits in igneous and in metamorphic rocks it occurs as grains, granules, and masses. Crystals of magnetite show most com- monly octahedral (No. 3346) and dodeca- hedral forms in which the dodecahedron is striated parallel to the octahedral edges (No. 548), because of oscillatory combina- tion (Fig. 129). The magnetism and the black streak of magnetite distinguish it from hematite. SUMMARY Magnetite. FeO Fe 2 O 3 ; FeO = 3 1 per cent ; Fe 2 O 3 = 69 per cent. Regu- lar; holosymmetric; (in), parting, parallel (in); brittle; fracture uneven. Hardness = 6; gravity =5. 8. Black; streak black; metallic; opaque. Magnetic, sometimes polar. Fusible with difficulty; powder easily soluble in hydrochloric acid. Scandinavia, Urals, Altai Mountains, New York, Pennsylvania, New Mexico, North Carolina. Franklinite Franklinite closely resembles magnetite in form, color, hardness, and weight, but has a browner streak, is more commonly rounded on its octahedral edges, and is but slightly magnetic. Its usual associa- tion with the red zinc oxide (No. 3348), zincite, renders its determina- tion by physical means less difficult, but chemical test (search for a zinc incrustation on charcoal or the amethystine color of manganese in the borax bead) is necessary for its accurate determination. The mineral receives its name from Franklin Furnace, New Jersey, where it has been found in great quantities. SUMMARY Franklinite. (Fe,Zn,Mn)O.(Fe,Mn) 2 O 3 . Regular; holosymmetric; (111); rounded grains. Resembles magnetite in physical properties, but is slightly magnetic and browner in streak. OXIDES 107 Hardness = 6 ; gravity = 5. Infusible, soluble in hydrochloric acid. Franklin Furnace, New Jersey. Chromite Chromite resembles magnetite and franklinite in form and color (No. 543), but is slightly softer (hardness 5.3) and lighter (gravity, 4.5). The best. means of identifying it is to test for the green color which it gives to a cold borax bead. Chromite owes its importance to the fact that it furnishes prac- tically all the chromium used in the arts and manufactures. Chro- mium compounds are used to color porcelains and enamels green, and to dye calicoes, etc. Their most important use of late years, however, has been to harden steel. Before the world-war nearly a million dollars' worth of chromite was imported annually, a few thousand dollars' worth only being produced in this country. As a result of government inves- tigation and encouragement production of domestic chromite was greatly increased. It is found in rocks consisting chiefly of olivine and serpentine. SUMMARY Chromite. FeO Cr 2 O 3 ; FeO = 32 per cent, Cr 2 3 = 68 per cent. Regu- lar; holosymmetric (in); granular, massive; uneven; fracture brittle. Hardness =5. 5; gravity = 4. 5. Black, yellowish red in very thin sections; dark brown. Infusible; insoluble in acids, decomposing when fused with sodium sulphate. New Caledonia, Bohemia. E. DIOXIDES The minerals in this group contain two atoms of oxygen to one of the basic element. Those which most merit attention are : Cassiterite SnO 2 Rutile TiO 2 ' Pyrolusite Mn0 2 Cassiterite This mineral, the only important source of tin, has been known since earliest times and was used by the ancients to make bronze. In color it is usually dark brown or black. It is hard (hardness, 6.5), io8 GUIDE TO MINERAL COLLECTIONS heavy (gravity, 7), insoluble, and infusible, and is usually in the form of rounded grains and pebbles or short stout crystals. The color of cassiterite depends upon impurities such as iron oxide (Fe 2 O 3 ), tantalum oxide (Ta 2 O s ), etc. Pure varieties, which are rare, are colorless, transparent, and lustrous, and, were they a little harder, would be much prized for gems. In Mexico yellowish varieties are found, and Australia has yielded some fine red speci- mens; but most cassiterite is black. Owing to its hardness, weight, and stability, it occurs in stream deposits as "stream- tin" and has been successfully mined in the Malay Peninsula, Australia, the Black Hills, and California. In primary deposits it is persistently associated with certain acidic 101 101 JIO 010 FIG. 130. Cassiterite lit" FiG. 131. Cassiterite twinned on (oil) igneous rocks, such as granites and pigmatites, where it has crystallized in short, stout tetragonal crystals, usually twinned. Simple crystals (Fig. 130) composed of (m), (no), (100), (101) are rarer than the twin forms which are so characteristic. The twinning plane is parallel (on), as shown in Figure 131. Prism planes are usually striated parallel to c. Basal planes are almost unknown. Slender prisms, having acute, di tetragonal pyramids such as (321) in addition to the more usual pyramids, occur rarely and are called " needle tin." Some of the massive varieties have a radiated fibrous structure, are arranged in curvilaminar layers of different shades, and in a botryoidal surface lack the luster of the ordinary crystal. Being remarkably dull and wooden, they are called "wood tin." Little brown-banded spherical nodules with the same fibrous structure are called "toad's OXIDES 109 eye tin" in Cornwall, which has long been the most productive tin region. The minerals associated with cassiterite suggest its origin. They are commonly apatite, fluorite, zinnwaldite, topaz, and tourmaline all of which contain fluorine and lead to the thought that vapors contain- ing fluorine were influential in the deposition of cassiterite. Daubree produced cassiterite artificially by the action of steam on tin fluoride. But cassiterite is produced in two other ways also. Violet-colored simple crystals have been made in tin works by the oxidation of metallic tin, and cassiterite has been found replacing organic remains and cementing nodules, as would be the case were it deposited from solution, or from vapors. The chief uses of cassiterite are as a source of tin for plating and the manufacture of alloys. SUMMARY Cassiterite. Sn0 2 ; Sn = 78 . 6 per cent, 0=21.4 per cent. Tetragonal ; holosymmetric. a:c= 1:0.672. (in), (100), (no), (101), (210), (321); twinned on (101); cleavage parallel (100) imperfect; brittle; fracture sub-conchoidal. Hardness = 6 . 5 ; gravity =7. Brown or black; streak gray; adaman- tine; translucent; 00=1.997; double refraction positive; c (0 = 0.097. Insoluble; with soda on charcoal yields tin. Cornwall, Malay Peninsula, Wyoming, and Dakota. Rutile Rutile (TiO 2 ) is a source of titanium, an element used for giving a yellow color to glass, for hardening steel, and for various chemical purposes. Its hardness is the same as that of cassiterite (6.5), and its color and form are very similar, but it is redder (rutilus, Latin for "red") and has a yellowish-brown streak instead of a grayish streak. It is only 4 . 3 in specific gravity and cleaves readily to (100) and (no), hence is easily distinguished from cassiterite. It occurs in stout crystals (Nos. 3354 and 3355), in acicular and twin crystals, and in masses (No. 3197). The stout crystals (Fig. 132), nearly duplicating those of cassiterite, consist of the following planes: (100), (no), (on), all of which may be vertically striated, and (in) and (101). no GUIDE TO MINERAL COLLECTIONS Twinning parallel to (on) is very common (Fig. 133) and the twins are often repeated six or eight times till they form a complete ring with the different individuals inclined to each other in a zigzag with angles of 65 35" (Fig. 134). Acicular crystals varying from the finest threads to needles and blades of some thickness often penetrate other minerals such as quartz. FIG. 133. Rutile triplet twinned on (on). FIG. 134. Rutile octet twinned on (on). The beautiful yellowish-red or brown fibers in quartz are called fleches d 'amour. In some groups the needles cross each other at the twinning angle and form a reticulated skeletal plate called "sagenite" (=net). SUMMARY Rutile. Ti0 2 ; Ti=6o per cent, 0=40 per cent. Tetragonal; holo- symmetric. 0:^=1:0.644. (100), (110), (310), (in), (101); twinned on (101); cleavage, parallel (100), (no); brittle; fracture uneven. Hardness = 6. 5; gravity = 4. 3. Reddish brown; streak yellowish brown; metallic; adamantine; translucent; w= 2.616; double refraction positive strong, e 0^ = 0.287. Infusible; insoluble. Switzerland, Virginia, North Carolina, Florida, Arkansas, Alaska. Pyrolusite Pyrolusite (MnO 2 ) is an amorphous, black, soft (hardness, 2) mineral used in glass manufacture to clear the glass from green and brown colors (Nos. 541 and 1838). Because of its usefulness in this OXIDES in respect it has received its name (irvp, " fire " ; Xueiu, " to wash"). Large quantities are employed also as a flux in iron manufacture. It has no crystal form of its own, but borrows its form of manganite, from which it is derived by the loss of water. Brazil and Russia before the war supplied the United States with the greatest part of the manganese ore needed. About one million tons of ore came from Russia in 1913. In 1916 more than that amount was produced in the United States. SUMMARY Pyrolusite. MnO 2 ; Mn = 63.2 per cent, = 36.8 per cent. Pseu- domorph after manganite, showing radiated fibrous structure, but usually massive, earthy, soiling the fingers. Hardness=2; gravity=5- Gray to black; streak black. Infusible; soluble in warm hydrochloric acid. Minnesota, Arkansas, California, Virginia, Russia, Brazil. CLASS VI. CARBONATES CALCITE GROUP CALCITE GROUP HEXAGONAL Calcite CaCO 3 Dolomite CaMg(CO 3 ) 2 Magnesite MgCO 3 Siderite FeCO 3 Rhodochrosite MnCO 3 Smithsonite ZnCO 3 Calcite Calcite is one of the most important and interesting minerals in the world, both because of its beauty and abundance, and because of its usefulness from a scientific and practical standpoint. The history of calcite is the history of mineralogy. In abundance it is surpassed by quartz alone. Its crystals occur in such profusion, variety, and beauty as easily to have attracted the attention of mineralogists and to have continually furnished them with material for study. This study has led to important results. About the time that the Dane, Steno, noted the regularity of the angles on quartz and announced the law of the constancy of angle, a countryman of his, Erasmus Bartholinus (1670), was working with the splendid calcite crystals then recently discovered in Iceland (No. 3832); and in his book Experimenta Crystalli Islandici described the remarkable cleavage and the double refraction which calcite shows more satisfactorily than does any other mineral. Twenty years later the Hollander Huygens, famous for his undulatory theory of light, extending Bartholinus' study of calcite, was able to formulate the laws of double refraction the laws of a phenomenon which could not be explained by the corpuscular theory of Newton. For many years following, while discussion of the cor- puscular and wave theories of light was at its height, calcite was carefully studied by the advocates of both theories. As the result of such study Malus (1808) discovered the polarization of light. Today calcite is much used in optical researches because of its effect on light, being employed for "nicol prisms" in microscopes, both for purely scientific and for commercial purposes. 112 PLATE XXI a, Calcite, "dog-tooth spar," Joplin, Missouri b, Calcite, "Iceland spar," showing double refraction CARBONATES No mineral shows more planes and combinations of planes than does calcite. More than two hundred forms and seven hundred com- binations have been described. There are four distinct habits of crystallization rhombohedral, scalenohedral, prismatic, and tabular. The fundamental form is the rhombohedron, R (ion), (Fig. 135), in which the mineral always cleaves, and so readily that it is difficult to produce a fracture in any other direction (Nos. 3460 and 3832). As an independent form this plane is rare but is found on crystals from near Bologna, Italy, and is a predominant form on the calcite from Iceland (" Iceland spar"). The obtuse rhombohedron, ^R (0112) (Fig. 139), is common. Figure 137 represents another common acute rhombo- hedron. The scalenohedron which furnishes the so-called "dog FIG. 135. Calcite. Positive rhombo- hedron (ioii)=R; the cleavage rhom- bohedron. FIG. 136. Calcite. Negative rhom- bohedron (oin) = R. tooth spar" (Fig. 138) (Nos. 3446, 3458, etc.) is a form of frequent occurrence. Prism planes also appear (No. 3450), modified usually with rhombohedron planes as in Figure 139, where the rhombohedron is negative, %R. If the prisms are short and a basal plane is present, tabular crystals similar to Figure 140 result. Sometimes they are as thin as paper and grouped parallel to one another so as to give the effect of cleavage which is peculiar to slate, hence the variety is called " slate spar." Scalenohedrons are usually modified by rhombohedrons (Fig. 141). All these forms agree in having three planes of symmetry, which are diagonal to the lateral crystallographic axes, and intersect in the vertical axis c, the axis of trigonal symmetry. Such symmetry is so typical as to have been named after calcite the "calcite class." GUIDE TO MINERAL COLLECTIONS There are four types of twins: (i) A common type is that in which two crystals are united by juxtaposition on the basal plane. Figure 142 shows a rhombohedron and Figure 143 a scalenohedron twinned according to this law. If the crystals overlap, filling the FIG. 137. Calcite. Neg- ative acute rhombohedron (0221) = 2 R. FIG. 138. Calcite, scalenohedron. FIG. 139. Calcite, prism and negative obtuse rhombohedron. FIG. 140. Calcite, showing prism, nega- tive obtuse rhombo- hedron, and base. FIG. 141. Calcite; FIG. 142. Calcite. combination of scaleno- Rhombohedron twinned on hedron and rhombohe- (oooi). dron. re-entering angles, cleavage lines will disclose the twinning. (2) More common than the foregoing is that type whose twinning plane is \R (0112). In this case the cleavage planes of the two individuals are parallel. Figure 144 shows a juxtaposed twin of this sort charac- teristic of crystals from Guanajuato, Mexico. Twinning lamellae PLATE XXII Calcite, Joplin, Missouri; (2131) and (3145) PLATE XXIII Calcite scalenohedron, Rossie, St. Lawrence County, New York CARBONATES 115 parallel to %R have been commonly produced in calcite by pressure, and in thin sections under the microscope are so characteristic as to furnish the best means of distinguishing the mineral. They well illustrate secondary twinning such as may be artificially produced in calcite and is especially pronounced in " Iceland spar." (3) The type of twinning parallel to the cleavage rhombohedron R, though rare, is shown in scalenohedrons and prisms (Figs. 145 and 146). In these twins one cleavage plane only is parallel to the two individuals. FIG. 143. Cal- cite scalenohedron twinned parallel to (oooi). FIG. 144. Calcite scalenohedron twinned parallel to (0112) = %R. FIG. 145. Calcite prism twinned par- allel to R. (4) The type where the twinning plane is the acute negative rhombo- hedron (0221) produces forms which closely resemble those of the second class, but here the cleavage planes of the different individuals are not parallel (Fig. 147). Some calcite crystals exhibit asterism, i.e., when a candle flame is viewed through them it appears as a radiating star of light. This is due to systems of hollow tubes parallel to each other in three direc- tions, and is produced where the " gliding surfaces" of the negative rhombohedron %R intersect each other. Calcite is useful for nicol prisms because the ordinary ray while passing through it is so greatly refracted (00 = 1.658). The extraor- dinary ray is allowed to pass through the prism, being but slightly affected by the Canada balsam whose index is nearly that of the extraordinary ray. (For balsam e = i . 536.) n6 GUIDE TO MINERAL COLLECTIONS A microscopic section of calcite rotated above the polarizer when the analyzer is removed shows high relief if the ordinary ray is allowed to pass through, and relief so low as to be almost invisible when the extraordinary ray passes through. When calcium carbonate crystallizes from aqueous solution in veins or other cavities, it forms the ordinary variety of calcite. If it is deposited from springs or streams by evaporation in a more or less granular condition it forms travertine, calc tufa, stalactites, and stalagmites. If it is composed of fragments or organic remains cemented by calcareous or other cements, it forms chalk, oolite, and FIG. 146. Calcite twinned parallel to R. scalenohedron FIG. 147. Calcite scalenohedron twinned parallel to (0221). limestone. If the limestone has been metamorphosed by heat and pressure so as to become crystallized, it forms marble. Among some of the localities the following are famous because of the abundance and beauty of their crystallized varieties. In Iceland near Eskif- jordhr a cavity 36 feet long, 15 feet wide, and 10 feet high in dolomite rock was found filled with clear crystallized calcite. The prevailing forms were rhombohedrons (ion) with edges beveled by scaleno- hedrons (2131) and (3145), and scalenohedrons terminated by (1011) or (3145). Their surfaces were often corroded or coated with other minerals such as stilbite. In England the lead, iron, and ftuorite mines of Derbyshire, Dun- ham, and Cumberland (Nos. 3450, 3451, and 3452) have furnished fine crystals which now ornament museums in all parts of the world. Many beautiful crystals come from the Hartz Mountains. They are PLATE XXIV a, Calcite, Joplin, Missouri; (2131) and (3145) b, Quartz geode with large flat rhombohedral crystals, St. Francisville, Missouri CARBONATES 117 commonly prismatic planes and tabular forms. The silver mines of Guanajuato, Mexico, have furnished twin crystals of great beauty and variety. Among many famous localities in the United States may be mentioned St. Lawrence County, New York (No. 4657); the Lake Superior copper mines with their complex crystals which often contain spangles and wires of copper; and the Wisconsin, Illinois (Nos. 698 and 699), and Missouri (No. 3459, etc.) lead and zinc mines with their rhombohedrons and scalenohedrons. The geodes of Keokuk contain numerous large flat crystals (Nos. 686, 691, 672). At Joplin, Missouri, many large, beautiful, honey-yellow scaleno- hedrons (2131) terminated by rhombohedrons R (1011) and the striated %R have been found. The acute terminal edges of these scalenohedrons (2131) are often replaced by striated and rounded faces (Nos. 3886, 3899, 3890, also Plate XXIII). SUMMARY Calcite. CaCO 3 ; CaO = s6 per cent, CO 2 =44 per cent. Hexagonal; symmetry dihexagonal alternating (calcite class); a :c= 1:0.854. R, %R, 4R; twinned on (oooi), (0112), (1011), (0221). Cleavage parallel R perfect; brittle; fracture conchoidal. Hardness = 3; gravity =2. 7 2. Colorless; vitreous; transparent; refraction strong, (0 = 1.658; double refraction very strong, positive, 2 60 Labradorite AbAn 3 40 3 3,2 6 2 8 IIT 7 2 72 Bytownite AbAne 46 6 34 4 i 6 17 4 2 74 Anorthite CaAl 2 Si 2 Os 43 2 36.7 o. 2O I 2 7v. . Fusible to magnetic mass. Partly soluble in hydrochloric acid. Common with labradorite in granular eruptive rocks in Labrador. Greenland, Norway, New York. MONOCLINIC PYROXENES The monoclinic section of py- roxenes is more important than either the orthorhombic, already considered, or the triclinic, which will be studied later. The chief monoclinic pyroxenes are Diopside and Augite These two minerals occur in short, stout, green to black crys- tals in igneous rocks, and are nearly as abundant as is the feldspar in these rocks (Nos. 3676, 3677,3680). Diopside (Nos. 3429 and 3430) is clear pale green in color. Some- times a crystal is darker at one to? FIG. 1 86a. Diopside FIG. 1866. Photograph of diopside from Cantley, Quebec, Canada: (in), (100), (101), (no), (100), (oio); about 1 2 inches long. J48 GUIDE TO MINERAL COLLECTIONS end than at the other, and also differently terminated at the opposite ends. The usual shape of the crystal is illustrated in Figures 186-88. In composition diopside is a silicate of calcium and magnesium, CaMg(SiO 3 ) 2 . 01 10) 110 FIG. 187. Diopside FIG. 188. Diopside, showing optic axes, acute bisectrix, axes of elasticity Hi \ 100 A no .010 100 110 _.oio FIG. 189. Augite FIG. 190. Augite twin parallel to (100) Augite is dark green or black (No. 343 1) Tne crystals are usually terminated with pyramidal planes, while prism and pinacoid planes are both well developed. Twins parallel to the orthopinacoid are common (Figs. 189 and 190). SILICATES 149 While iron is usually present in both diopside and augite, it is more abundant in the latter. Diopside lacks aluminum. There- fore the pyroxenes are often divided into non-aluminous (diopside) and aluminous (augite) varieties. Light green or white diopside is abundant in crystalline limestones and dolomites. Green or black augite is common in granite or eruptive rocks (No. 3433). When black basalt decomposes, augite crystals sometimes fall out and may be easily collected in quan- tities. A thin section of augite cut perpendicular to the c axis when FIG. ioi. Augite cross-section per- , , . pendicular to prism planes. W * d Under the nucroscope 001 too FIG. 192. Enstatite, showing parallel FIG. 193. Diopside, showing oblique extinction. extinction angle of 38. shows fine cleavage lines parallel to the prism planes. These lines form an angle of nearly 90 with each other and the outline of the figure is eight-sided (Fig. 191). The eight-sided outline, the cleavage angle, and lack of pleochroism aid in distinguishing augite from horn- blende. Hornblende presents a six-sided figure with cleavage line forming an angle of 124, and furthermore is strongly pleochroic. Fragments or thin sections of the members of the pyroxene group may be recognized by their extinction angle. A section of enstatite 150 GUIDE TO MINERAL COLLECTIONS cut parallel to the brachypinacoid and viewed in parallel light between crossed nicols becomes dark when the c axis is parallel to one of the cross-hairs of the microscope (Fig. 192). Diopside when so examined must be turned clockwise about 38 before it becomes dark (Fig. 193). Augite requires even a greater angle of revolution, sometimes being as large as 54. In each case the angle of extinction increases with the amount of iron present. SUMMARY Diopside. CaMg(Si0 3 ) 2 ; CaO = 25.g per cent, MgO=i8.5 per cent, SiO 2 =55-6percent. Monoclinic; a:b:c=i. 0921:1:0. 5893. /3=io55o'. (no), (100), (oio), (ooi), (101), (in), (221). Twinned on (100). Cleavage perfect parallel (no), imperfect parallel (100), (oio). Brittle; fracture conchoidal. Hardness = 5 . 5 ; gravity =3. 3.- Light green; vitreous; transparent. Mean refraction (y8) = i.68i, maximum (y) = 1.703. Double refraction positive, strong; 70 = 0.030. Axial plane (oio). Acute bisectrix inclined 37 35' to c and the obtuse bisectrix inclined below a in front 21 45' (Fig. 193). Axial angle (2 E) = 68. Fusible; insoluble. In crystalline limestones and dolomites, both east and west, and in the drift. Augite. MgksioVj Fe A is also always present. Augite has nearly the same character as diopside, but contains A1 2 O 3 and Fe 2 O 3 in addition to calcium and magnesium silicates, and is darker in color. More readily fusible than diopside. In granitic and eruptive rocks the world over. Jadeite Jadeite is a compact, tough, alkaline pyroxene having the compo- sition NaAl(SiO 3 ) 2 . It is 7 in hardness and 3.3 in specific gravity, is translucent, and varies in color from blue and green to white. When carved and polished it has a soft waxy luster which is very pleasing, and for that reason it has been used for many hundreds of years as material for carving into ornaments, vases, etc. Being tough and hard, it is very enduring. SILICATES 151 SUMMARY Jadeite. NaAl(SiO 3 ) 2 ; Na 2 0=i5.4 per cent, A1 2 O 3 =25.2 per cent, SiO 2 =59-4 per cent. Monoclinic; massive, sometimes granular, slightly fibrous; fracture splintery; very tough. Hardness=y; gravity =3. 3-. Greenish, bluish, white; waxy, dull, translucent; 2 7=72. Fuses readily; not attacked by acids after fusion; different from saussurite. Burma, Thibet, Mexico. TRICLINIC PYROXENE The triclinic pyroxene rhodonite (podov, "a rose") is a beautiful red mineral which, because of its hardness (6) and fine color, is used for ornaments such as brooches, cuff buttons, watch charms, ink- wells, paper weights, vases, mantelpieces, and table tops. In the Urals masses of such size have been found as to be available for tomb- stones. In the late Czar's lapid- ary shops at Petrograd some years ago, the author saw an oblong block of rhodonite 7X4X3 feet in size, being carved for a sar- ^ ( f ^ ||o|O cophagus for royalty, and which was valued at six hundred thou- sand dollars. |0 When crystals of rhodonite F IG . 194 Rhodonite occur, as is often the case in Nor- way, England, and New Jersey (No. 3438), they are tabular (Fig. 194) in form or stout like augite. Rhodonite is a silicate of manganese (MnSiO 3 ) but usually con- tains calcium, iron, and in New Jersey zinc. SUMMARY Rhodonite. MnSi0 3 ; MnO=54.i per cent, Si0 2 =45-9 per cent. Triclinic; a:b:c=i .073:1:0.621. a = 103 18', /? =108 44', 7 = 87 39'. (no), (oio), (ooi), (221). Cleavage (110), (no), perfect; (ooi), fair. Brittle; fracture uneven. 152 GUIDE TO MINERAL COLLECTIONS Hardness=6; gravity =3. 6. Red; vitreous; translucent. Mean refraction (/?) = 1.73. Double refraction negative, weak; y a = o.oio. Axial plane is inclined at 63 to (110) and 38 to (ooi). Acute bisectrix inclined 51 47' to the normal of (110) and 51 40' to the normal of (ooi). Axial angle (2 = 79; pv. Infusible; difficultly soluble. Urals, Brazil, Japan, Utah, Colorado, California, Missouri. Cyanite This mineral (No. 3496), which easily attracts attention because of its blue color (/cuapos, "blue"), occurs in long, flat, bladed crystals that show a remarkable difference in hardness in different directions. Across the blades, that is, parallel to the edge made by the macro- pinacoid (100) and base (ooi), the hardness is 7, while along the crystal, that is, parallel to the edge formed by the macropinacoid (100) and brachypinacoid (oio), the hardness is only 4.5. When Haiiy discovered this property, he named the mineral disthene (dis and Oevos, " double strength"). When cyanite is heated at 1350 C. without changing its chemical composition (Al 2 SiO s ) it is transformed into a fibrous mineral of uniform hardness (6.5), lighter specific gravity (3.2; cyanite is 3.6), and straight extinction. The mineral is called sillimanite, and is characteristic of some gneisses and schists. Compact sillimanite (sometimes wrongly called jade) was used in prehistoric times in the manufacture of ornaments and implements. SUMMARY Cyanite. Al 2 SiO s ; A1 2 3 = 63 per cent, Si0 2 = 37 per cent. Triclinic; a:b:c=o.Sgg: 1:0.697. (ooi), (100), (oio), (no). Cleavage parallel (100) perfect; (oio) imperfect. Brittle; fracture fibrous. Hardness =7 across the crystal, 4.5 parallel to the edge (100); (oio); gravity =3. 6. Blue to white; vitreous; transparent. (3 = i.j2. Double refraction negative; y a = o.oi6. Axial plane inclined 30 to edge (100); (oio). Acute bisectrix normal to 100: 2 H = ioo. Infusible; insoluble. Alps, northern England, Appalachians, Cordilleras. 164 GUIDE TO MINERAL COLLECTIONS Tourmaline This mineral is worthy of notice for three reasons: first, because it is abundant in igneous and metamorphic rocks; second, because it is used in making optical instruments such as " tourmaline tongs" (see below, p. 166); and third, because the beautiful red, pink, and green varieties are used as gems (Plate XXVIII). Tourmaline is literally found "from Maine to California." Paris, Maine (Nos. 444, 454, 4062), has long been reputed for its magnificent red and green crystals, and more recently San Diego County, California (Nos. 3511, 3788, 3789, 3790), has furnished the museums of the world with handsome groups of red tourmaline (rubellite) in a lavendar mica, lepidolite. The tourmalines of Illinois are all emigrants from northern FIG. 211. Tourmaline FIG. 212. Tourmaline regions. Black is the prevailing color, and they are usually imbedded in gneisses and granites. Among the most famous foreign localities may be mentioned the region near Ekaterinburg in the Urals, where a coarse granite contains smoky quartz, albite, green and pink mica, and red and fine black tourmaline. At Campologna, Switzerland, calcite, corundum, diaspore, mica, and green tourmaline are found in a granular dolomite. The granite of the island of Elba consists of quartz, orthoclase, albite, mica, pink beryl, red garnet, and red and black tourmaline. The best gem tourmalines are obtained in Ceylon. Tourmaline crystals (Nos. 357 and 3505) (Figs. 211 and 212) are usually prismatic, often elongated, sometimes terminated at one end, PLATE XXVIII a, Tourmaline doubly terminated; variously colored crystal from Mesa Grande, California. b, Black, well-crystallized specimen from Haddam, Con- necticut. SILICATES 165 rarely at both ends. Occasionally they are flat crystals. Prisms are strongly striated vertically. This striation, the triangular cross- sections, and absence of cleavage serve to distinguish this mineral from black pyroxenes and amphiboles. The chemical constitution of tourmaline is complex and is still the subject of much discussion. Generally speaking, it is a borosili- cate of aluminum, iron, or chromium, of magnesium, and of the alkalies sodium, potassium, and lithium. The following varieties may be distinguished: Black, iron tourmaline (Fe 4 Na 2 B6Al I4 H 8 Si I2 O6 3 ) ; gravity =3. 2. Red, green, colorless; alkali tourmaline (NaLiK^BeAl^HgSinOej) ; gravity = 3. Brown; colorless; magnesium tourmaline (Mg I2 B6Al IO H8Si I2 06 3 ) ; gravity = 3. Green; chromium tourmaline (chromium replacing a portion of the aluminium) ; gravity = 3.1. Transparent crystals (No. 3788) are often differently colored at the different ends, and some are banded with two or three different shades of color, as may be observed in a section parallel to the base. Early in the eighteenth century it was discovered that red tourma- line crystals brought from Ceylon when heated became positively electrified at one end and nega- tively at the other. When any tourmaline crystals after heating are beginning to cool, if they are dusted with finely powdered red lead (-f) and sulphur ( ), one end the negative, the "analogous end" attracts the red lead, while FIG. 213 Tourmaline, analogous the other the positive or "antilo- end. gous end" attracts the sulphur. The negative end (No. 3791) usually shows a basal plane and the rhombohedron (R) over the trigonal prism (1010) (Fig. 213). The positive end is usually acute owing to the development of pyramids. All tourmalines absorb the ordinary ray much more completely than they do the extraordinary, consequently black varieties look green or i66 GUIDE TO MINERAL COLLECTIONS blue with the ordinary ray (o) and brown or red with the extraordi- nary (e). Brown crystals cut parallel to the optic axis transmit only the extraordinary ray, and can be used as polarizer and analyzer. Two such sections held in wire rings constitute " tourmaline tongs." SUMMARY r^rwa/^e. (FeCrNaKLi) 4 Mg I2 B6Al I 6H 8 Si I2 O63. Hexagonal; sym- metry ditrigonal polar; a:c= 1:0.4477. (oooi), (1011), (0221), (1010), (1120), (3251). Cleavage imperfect parallel (1011). Brittle; fracture subconchoidal. Hardness = 7; gravity =3.1. Black, brown, red, green, colorless; vitreous; translucent; 00 = 1.64. Double refraction strong, negative; w =0.017. Pleochroic; pyro-electric. Fusible; insoluble. Maine to California, Urals, Alps. ZEOLITE GROUP The zeolites (eco, "I boil") are white, pearly, light (gravity, 2), soluble minerals, which boil before the blowpipe because the two to FIG. 214. Four-twinned crystals of stilbite. FIG. 215. Stilbite sheaf six molecules of water of crystallization contained in them are loosely held. The different members of the group are so-called " secondary minerals" since they result from the decomposition of other minerals, chiefly feldspar, leucite, etc., in disintegrating igneous rocks. From seventeen representatives three may be chosen to indicate the nature of the group. Stilbite The most attractive characteristic about this mineral is its pearly sheaflike crystals (Nos. 3255 and 3514), which result from twinning SILICATES 167 of monoclinic crystals parallel to the base and orthodome in such a manner as to produce interpenetrating twins. The crystals are flattened parallel to the clinopinacoid, which is also a plane of easy cleavage. The basal cleavage is imperfect. The basaltic rocks found in many places in New Jersey, Michigan, the Cordilleras, Scotland, etc., contain in their cavities fine groups of stilbite crystals. SUMMARY Stilbite. CaAl 2 Si 6 Oi6+6H 2 O; CaO = 8.94 per cent, A1 2 3 = 16.31 per cent, Si0 2 = S7.si per cent, H 2 = i7.24 per cent. Some Na 2 usually replaces a portion of the Ca. Monoclinic; 0:6: 6 = 0.7623:1: 1:1940. /? = 5o5o' (ooi), (oio), (no). Twinned parallel (ooi) and (101). Cleav- age parallel (ooi). Brittle; fracture uneven. Hardness = 3.5; gravity =2.2. White ; vitreous ; transparent ; ft = 1.498. Double refraction, strong, negative; y a = 0.006. Axial plane (oio) acute bisectrix inclined 85 to normal of (ooi) and 34 to the normal of (100). 2 = 51. 5. Fusible (2.5). Decomposed by hydrochloric acid. In disintegrating igneous rocks in the Cordilleras, Appalachians Scotland, etc. Analcite The second representative of the zeolites to claim our attention is analcite (No. 3576), one of the best illustrations of the trapezohedral crystals among minerals (Fig. 216). More rarely analcite occurs in cubes with corners truncated by the trapezohe- drons. Small crystals are often beautiful and glossy. The larger ones are usually opaque and white or pink. SUMMARY Analcite. Na 2 Al 2 Si 4 O I2 +2H 2 O; Na 2 =14.1 per cent, A1 2 O 3 = 23 . 2 per cent, Si0 2 =54.5 per cent, H 2 O = 8.2 per cent. Regular; (211), (100). Brittle; fracture uneven. Hardness = 5.5; gravity =2.2. #=1.487. Fusible (2.5). Gelatinizes in hydrochloric acid. Same regions as other zeolites. FIG. 216. Leucite Colorless; vitreous; transparent. i68 GUIDE TO MINERAL COLLECTIONS FIG. 217. Natrolite Natrolite Natrolite (No. 3517) is closely related to analcite in chemical composition inasmuch as it contains one less molecule of SiO 2 , but differs markedly in form since it crystallizes in the orthorhombic system and occurs in long prisms that end in very flat pyramids. It is the commonest of fibrous zeolites, usually constituting masses in cavities. Beautiful tufts of acicular crystals are found in the cavities of basalt. So fusible is it that it melts in a candle flame, imparting the yellow color characteristic of burn- ing sodium. SUMMARY 110 Natrolite Na 2 Al 2 Si 3 O IO 2H 2 O ; Na 2 O = 16 . 32 per cent, A1 2 O 3 =26.86 per cent, SiO 2 =47.36 per cent, H 2 O = g\46 per cent. Orthorhombic; a:b:c = 0.978:1:0.354. (no), (in). Cleavage parallel (no) perfect. Brittle; fracture uneven. Hardness = 5 . 5 ; gravity =2. 2. Colorless; vitreous; transparent. /8=i.479. Double refraction positive, strong; ya = o.oi2. Axial plane (oio). Acute bisectrix normal to (ooi). 2 =99; pv. Pleochroism feeble ; transparent, white; vitreous. Fusible with difficulty; insoluble. In granites, gneisses, mica schists, in all mountain ranges. New Hampshire, South Carolina, South Dakota, Colorado, New Mexico, and California. Biotite Black mica, named biotite after Biot, the celebrated French mineralogist, is the magnesian mica (H,K) 2 (Mg,Fe) 2 Al 2 (SiO 4 ) s (Nos. 3535, 3536, 1240, 1768, 453). SILICATES 171 In this mica the axial plane is usually parallel to the chief per- cussion figure, which, as noted above, is parallel to the brachypinacoid (oio). Such biotite is said to be a brachy diagonal mica, or mica of the second class. Whether muscovite or biotite is the more abundant mica is difficult to say, since both abound in nearly all kinds of igneous rocks. Biotite decomposes more readily than muscovite and forms such minerals as chlorite, epidote, quartz, and iron oxide. Its FIG. 220. Biotite; axial plane parallel to (oio). FIG. 221. Basal section of biotite, showing position of axial plane and percussion figure. characteristic color is black, but while undergoing decomposition it assumes red and green shades. It is strongly pleochroic and appar- ently uniaxial. Fine crystals are found at Vesuvius. SUMMARY Biotite (H,K) a (Mg,Fe) a Ai 2 (SiO 4 ) 3 ; K 2 O=7.64 per cent, MgO = 2i .89 per cent, H 2 O = 4.02 per cent, F = o.8g per cent, Fe 2 O 3 =7.86 per cent, A1 2 O 3 = 16.95 P er cent, SiO 2 =39-3o per cent. A little FeO, MnO, CaO, and Na 2 O are usually present. Monoclinic; a:b:c=o. 577:1:3. 2 74. /3=9o. (no), (in), (ooi), (oio), (221). Twinning plane parallel to (no), combination face (ooi). Cleavage parallel to (ooi) perfect; laminae elastic; fracture uneven. Hardness = 2.5; gravity = 2 . 86. Black, pleochroic ; a green, /? and y dark brown. Translucent; luster vitreous; streak colorless. Plane of optic axes parallel to (oio). Acute bisectrix inclined 30' to the perpen- dicular of (ooi). J3=i.6. Double refraction negative, strong; y a= 0.04; p Si0 2 =46.5 per cent, H 2 = i4 per cent. Water is driven off at 330. Monoclinic. Scales flexible, inelastic; friable to compact; unctuous, plastic. Hardness=2.s; gravity =2. 6. White, blue, yellow, red, green; luster pearly to earthy; translucent. Biaxial, negative. Infusible; insoluble. Blue color with cobalt solution. Many eastern and middle states, such as Massachusetts, Delaware, Georgia. Illinois, etc. PLATE XXIX a, Apatite, Renfrew, Canada b, Barite, Alston Moor, England CLASS VIII. NIOBATES, TANTALATES CLASS IX. PHOSPHATES, ARSENATES, VANADATES, ANTIMONATES, NITRATES Apatite Apatite is a mineral of great commercial importance, occurring in metamorphic limestones and in granites often as well-formed crystals (No. 3551) varying from microscopic size to dimensions of a foot or more (Plate XXIX0) . As usual, the more nearly perfect crystals with well-terminated ends occur in cavities. Their prevailing color is blue, green (No. 3550), yellow, or brown. Among the most beautiful apatite crystals found are little limpid hexagonal prisms contained in crystalline schists in the St. Gothard and Unter- sultzbachthal. Microscopic crystals are found in a variety of igneous rocks. The planes most commonly appearing (Fig. 222) are the follow- ing: (1010), (1120), (1011), (1121), (oooi). The prisms are usually vertically striated. Apatite resembles beryl in appearance, but is softer, has imperfect cleavage parallel to the base, and a high, refractive index. Chemically there are two varities of apatite: the ordinary, which contains fluorine; and the less common, in which fluorine is replaced by chlorine. According to physical condition there are two kinds which are even more markedly different than are the two chemical varieties. The first is pure crystallized apatite, which is found filling veins and as inclusions in metamorphic rocks (Nos. 3666, 3709, 3712). The second is phos- phorite (No. 4307), the white, structureless variety, organic in origin and occurring in extensive beds in the Carolinas and Tennessee. It has resulted by the concentration of phosphatic material which was previously disseminated through sands and sandstone. 1010 FIG. 222. Apatite 176 GUIDE TO MINERAL COLLECTIONS The crystallized apatite is found in most of the Appalachian states and iri the drifts over the middle states in granular limestone and in granites, gneisses, and schists, and in veins in iron ores. Apatite is one of the most important of all minerals to man, inasmuch as it is the chief source of phosphorus, a chemical substance indispensable to plant growth. SUMMARY Apatite. CasF(P0 4 ) 3 ; CaO = 5S-5 per cent, P 3 O S =42.3 per cent, F=3.8 per cent. Hexagonal; symmetry hexagonal equatorial; a:c= 1:0.7346. (101), (1011), (1121), (2131). Cleavage parallel to (oooi), 1610). Brittle; fracture conchoidal. Hardness = 5 ; gravity =3.2. Colorless ; luster vitreous ; transparent ; w = i . 646. Double refraction negative, weak ; w c = o . 004. Fusible with difficulty; soluble in hydrochloric acid. Ottawa County, Quebec, Canada; Bolton, Massachusetts; Crown Point, New York; New Jersey. Pyromorphite Pyromorphite (No. 507) is a lead chloro-phosphate found in quantities in upper levels of lead mines, where it has been forming during the decomposition of lead sulphide. It was named pyro- morphite because, when fused before the blowpipe, upon cooling it solidifies with many facets (irvp, "fire"; AWP$I?> "form"). These facets are not true crystal faces. The true crystals are composed of prisms and basal planes which produce barrel-shaped forms because of aggregation and curvature of the prisms. A violet color is shown by large hexagonal prisms occasionally, but the prevailing color is green or brown. SUMMARY Pyromorphite. Pb5Cl(PO 4 )3; PbO = 82.3 per cent, P 2 5 =i5.7 per cent, Cl= 2 . 6 per cent. Hexagonal; symmetry hexagonal equatorial. (1010), (1011), (oooi). Cleavage parallel (1010), (1011) imperfect. Brittle; fracture sub- conchoidal. Hardness =3. 5; gravity =7. Green; luster resinous. Translucent; ( IIO )> C 001 )* C 111 )- Cleavage perfect (100); fracture conchoidal. Hardness = 2 ; gravity = 1.7. White, vitreous, translucent; /3= i . 47. Double refraction negative ; 7 a = o . 004; acute bisectrix normal to (oio) ; 2 =59; p>v. Fusible, swells up; soluble in water; sweetish. Thibet, Peru, California, Nevada. Colemanite. Ca 2 B60n.5H 2 0; CaO=27.2 per cent, B 2 O 3 =5o.9 per cent, H 2 O =21.9 per cent. Monoclinic, prismatic class ; a:b:c=o.fj: 1:0.541; 18=70; (no), (301), (100), (oio), (ooi), (in), (021), (221). Cleavage (o i o); fracture uneven. Hardness =4; gravity =2. 4. Colorless, white; translucent, vitreous; "-1.5902. Fusible, exfoliates; soluble in hot hydrochloric acid; insoluble in water. California, Chile. Boracite. Mgs(MgCl) 2 B I 6O 30 ; MgO = 31.4 per cent, Cl= 7 . 9 per cent, B 2 O 3 =62.5 per cent. Dimorphous; crystals formed above 265 C., regular; below that, orthorhombic; (no), (100), (in), (in), (211). Cleavage (in) imperfect; brittle; fracture conchoidal. Hardness=7; gravity =3. Colorless, vitreous, translucent. Double refraction; /?= 1.667; T a = o.on; 2 7=90. Fusible, swells up; soluble in hydrochloric acid. Stassfurt, Prussia. 177 178 GUIDE TO MINERAL COLLECTIONS Uraninite The uranate uraninite is of interest because it is a source of uranium, of radium, and of helium. Its composition is doubtful, inasmuch as a large number of rare elements are present. In addi- tion to oxides of uranium, thorium, lead, iron, and calcium, small quantities of the following have been found: zirconium, cerium, lanthanum, didymium, yttrium, erbium, helium, manganese, sodium, potassium, silicon, phosphorus, and hydrogen. Its composition may be expressed by the formula U 3 0g. Uranium compounds are used in the laboratory for the determination of phosphorus and zinc, in the manufacture of pigments, glazes, and special steels. SUMMARY Uraninite. U 3 Os. Regular, (in), (no), (100). Crystals rare, crystalline masses, botryoidal groups. Brittle; fracture conchoidal. Hardness =5.5; gravity =9.5. Brown, black ; luster dull. Infusible; soluble in nitric and sulphuric acids; radio-active. Colorado, Cornwall, Austria. CLASS XI. SULPHATES, CHROMATES, TELLURATES Class XI, containing the sulphates, chromates, and tellurates, is an outstanding class because of at least four commercially and scientifically interesting minerals, namely, barite, celestite, anglesite, and gypsum. Barite Barite, or heavy spar (/3apus, "heavy"), so named since it is nearly twice as heavy as other white minerals like calcite or gypsum, is important because of its fine crystals, its great masses, and its usefulness. FIG. 224. Barite no ~^J "I FIG. 223. Barite FIG. 225. Barite The crystals are usually flat (Nos. 3562 and 3556), and consist of large basal planes with short prisms, as in Figure 223. Forms composed of dome planes elongated parallel to the a axis (Fig. 224) are not uncommon (No. 4060). Cleavage pieces take the form of Figure 225, and the position of the axes is indicated by the cleavage, which usually shows pearly cracks. Prismatic cleavage is good. Aggregates of crystals produce rounded masses from which acute prism edges protrude. Radiated, columnar, and massive (No. 3559) forms are common, though a white, earthy, massive condition is most characteristic. Discoloration by iron is usual. Inorganic phosphorescence was first discovered when an Italian investigator in the early part of the seventeenth century heated 179 i8o GUIDE TO MINERAL COLLECTIONS barite on charcoal and noticed that in the dark it continued to emit a glow, due to the reduction of the sulphate to sulphide. Barite is found in veins and masses with ores oi lead, antimony, and iron in limestones, especially in Georgia, Missouri, and Tennessee. It is used in the manufacture of white paint, filler for paper, barium for chemical and medicinal uses, etc. Nearly four hundred thousand dollars' worth of barite was produced in the United States in 1915. SUMMARY Barite. BaSO 4 ; BaO = 65.7 per cent, $03=34.3 per cent.- Ortho- rhombic; a:b:c=o. 815:1:1. 314. (ooi), (no), (102), (on), (122), (in). Cleavage parallel (no) and (ooi) perfect; brittle; fracture uneven. Hardness = 3 ; gravity =4.5. Colorless ; luster vitreous ; transparent ; 18=1.637. Double refraction positive, strong; 7 a = o.oi2. Axial plane (oio); acute bisectrix perpendicular to ( i oo); 2^=64; pv. Inclined dispersion. Easily fusible (3) . Soluble in hydrochloric acid. Michigan, New York, Virginia, Ohio, Iowa, Alabama, Arkansas, and the Cordilleran states. CLASS XII. TUNGSTATES, MOLYBDATES 100 no The class of tungstates and molybdates contains but few min- erals and those few are of slight importance. One example of each may be considered: the tungstate, wolframite; and the molybdate, wulfenite. Wolframite Wolframite (No. 3533), a black mineral accompanying cassiterite in tin-bearing regions, and greatly resembling cassiterite in appear- ance, is the chief source of tungsten, an element being used in an increasing degree in manufactures. Well-formed monoclinic crystals resembling those shown in Figure' 234 are common, but bladed, lamellar, or granular forms are more abun- dant. Its perfect cleavage parallel to (oio) and its stibnite-like luster aid in distinguishing it, although otherwise it is a somewhat diffi- cult mineral to identify, since blowpipe re- actions for tungsten are masked by the presence of the iron and manganese in its formula, (FeMn)WO 4 . After wolframite is boiled in aqua regia, tungstic oxide appears as a yellow residue. Tungsten steel is especially valuable for permanent magnets, cutting tools, wires for electric purposes, etc. Tungsten is also used as a dye which renders cotton less inflammable. Wolframite is found in veins in Cornwall, Zinnwald, Black Hills, North Carolina, and Missouri. SUMMARY Wolframite. (FeMn)WO 4 ; FeO varying from 2 to 19 per cent, MnO from 6 to 22 per cent, WO 3 = 76 per cent. Monoclinic; holosym- metric. Cleavage parallel (oio) perfect, parallel (100) imperfect. Brittle; fracture uneven. Hardness = 5. 5; gravity =7. 3. Black; streak reddish brown; luster metallic; opaque. Fusible (3) to magnetic bead. Decomposed by hydrochloric acid. North Carolina, Missouri, South Dakota. 185 FIG. 234. Wolframite i86 GUIDE TO MINERAL COLLECTIONS Wulfenite This molybdate (Nos. 3528 and 3531), PbMoO 4 , is a heavy, red, resinuous mineral which occurs in granular masses, and often in thin, tabular, square crystals (Fig. 235), or less commonly in acute pyramids (Fig. 236). Were it not so brittle and soft, it would be one of the most FIG. 235. Wulfenite FIG. 236. Wulfenite prized of gems, since it is beautiful in color and has a high luster. Commercially it is of small value because of its rarity. SUMMARY Wulfenite. PbMoO 4 ; PbO = 6o.7 per cent, MoO 3 = 39.3 per cent. Tetragonal; symmetry, tetragonal polar. 0:^=1:1.577. (ooi), (102), (in), (320). Cleavage parallel (in) good. Brittle; fracture sub- conchoidal. Hardness = 3 ; gravity =6.7. Red ; streak white ; luster adamantine ; translucent; o> = 2.402. Double refraction negative, strong; (06 = 0.098. Easily fusible (2) ; soluble in hydrochloric acid. Arizona, New Mexico, California, Missouri, Pennsylvania. CLASS XIII. ORGANIC ACID SALTS The organic acid salts, oxalates and mellates, which constitute Class XIII are rare and unimportant, hence we may pass at once to the next class. CLASS XIV. HYDROCARBONS Though the members of this class are all of organic origin, yet they have been so changed .by the loss of some constituent as to rank as mineral substances. Several of them are amorphous. Others retain the structure of the substance from which they were derived. Some of them may be most properly classified as rocks, but since they constitute part of a series they are here included. The most abundant representatives are the fossil resins, asphalt, heavy and light oils, gas, and coal. Fossil Resins Amber is a fossil resin occurring in amorphous masses which vary in size from small grains or droplets to chunks a foot or more in diameter. It was exuded from ancient conifers or leguminous trees, and buried by drifting sands in recent geological formations in Spain, Sicily, Germany, etc. It is characterized by conchoidal fracture, softness (hardness, 2), low specific gravity (gravity, i.i), yellowish to brown color, greasy luster, and translucency. It shows fluo- rescence, is negatively electric, melts at about 287 and burns with a bright flame and an agreeable odor. It is composed of carbon, hydrogen, and oxygen (C^H^At); C = 78.93 per cent, H = io.55 per cent, = 10.52 per cent. It is used in the manufacture of buttons, beads, pipestems, varnish, amber oil, and acid. Copal is a kind of amber which contains a larger proportion of hydrogen and melts at a lower temperature (210). It is slightly harder than amber (hardness, 2.5). It is the dried sap of leguminous and coniferous trees which are found in many parts of the world, such as New Zealand, Australia, Madagascar, the east and west Coasts of 187 i88 GUIDE TO MINERAL COLLECTIONS Africa, and various places in South America. Nine-tenths of the copal used is obtained from deposits buried sometimes as deeply as twenty feet and often no doubt thousands of years old. All varieties of amber are used chiefly as material from which to manufacture varnish. Insects imprisoned in the gum as it was exuding from trees have been preserved with remarkable fidelity, so that not only are their most delicate membranes intact, but in many cases an idea of the original color can be obtained. ' Asphalt This hydrocarbon is of indefinite composition. It is black, burns with a pitchy odor and is slightly heavier than water (gravity, i .1; hardness, 2). It melts at 100 C. and ignites readily with black smoke and bright flame. At a sufficiently low temperature it shows conchoidal fracture. It is soluble in ether. It occurs in beds or lakes in the island of Trinidad and in veins or disseminated through sandstone or limestone in Kentucky, Cali- fornia, etc. It forms one of the most satisfactory paving materials when mixed with sand and broken limestone. It is used for roofing, for calking material on ships, for paint on metal and woodwork, and as an adulterant of rubber goods. Petroleum Petroleum is one of the most important of mineral substances, being second only to coal and iron in the contribution which it yearly makes to the wealth of mankind. It has been found in many coun- tries, but nowhere so extensively as in the United States. It occurs in strata from the Ordovician to the Pleistocene. It has been produced by the distillation under great pressure of both animal and vegetable substances. Petroleum, or "rock oil," is composed of a variety of oils, form- ing a series from the volatile and easily flowing oils to viscous oils, lubricating oils, and greases. It consists chiefly of the paraffines (C n H 2n+2 ) in Pennsylvania and of the naphthenes (C 6 H I2 ) in the Caucasus. The color varies from dark brown to greenish, and the gravity from 0.7 to 0.9. Petroleum shows a distinct fluorescence. Benzine, naphtha, gasoline, kerosene, lubricating oil, vaseline, dye- stuffs, and other chemicals are derived from petroleum. HYDROCARBONS 189 Pennsylvania long held chief place in the production of petroleum, but recently California has surpassed her, and Ohio, Indiana, Illinois, Kansas, Oklahoma, and Texas have all shown remarkable pools. Mexico and the Caucasus are increasing in productiveness. Natural Gas Closely associated with petroleum and having the same origin is natural gas. It too consists mainly of the lower paramne methane (CH 4 ) and ethane (CH 3 ), and also carbon monoxides, carbon dioxide, hydrogen, neon, and the new gas.helium, so necessary for war balloons. Coal Coal consists of solid hydrocarbons derived from vegetable growths of former geological ages. Trees, shrubs, weeds, mosses, and especially spores of cryptogams contributed to its formation. More than five hundred different species of plants have been identified among those concerned in the production of coal. Among them are six species of algae; two hundred and fifty species of ferns; eighty- three species of lycopods, that is, club mosses whose powder is used for fireworks, medicines, etc. ; thirteen species of equisetites, that is, rushes, horsetails, etc.; sixty sigillarids, whose trunks were ribbed and scarred like giant cacti; twelve species of noggerathia with over- lapping scales on their trunks and pinnate leaves; forty-four astero- phyllites; and three species of cycads, the sago palms. All of the above were acotyledons, the lowest form of vegetable life. They comprise five-sixths of all the plants which have been identified in coal. The remaining one-sixth were fifteen species of coniferous trees and fifteen of the palms. All of the above-named species are similar to vegetation which thrives in a warm, moist climate today. These plants, grown in swamps or near lakes and rivers, were deposited in beds, buried under mud that later turned to stone, and by the loss of hydrogen and oxygen were converted into coal. Cross-sections of coal fields in all parts of the country point to such a history. At the bottom of a coal field occurs a conglomerate such as would form on a new shore line. This is covered by sandstone that indicates long action of the waves and gradual decrease in their severity. Next comes shale, and then clay, "fire clay," such as would be formed in the shallow waters of ponds into which sluggish streams I go GUIDE TO MINERAL COLLECTIONS carry silt. These are followed by the coal from a few inches to several feet in thickness, such as might be formed in a peat swamp. The lowest coal bed in Illinois is called coal No. i. This is covered by gray shale showing subsidence of the swamp and burial under mud: Further subsidence brought conditions favorable to formation of sandstone. Re-elevation introduced other shale and fire-clay forma- tions which, in their turn, were followed by swamps in which coal No. 2 was formed. This shifting of the shore line was repeated many times in some localities, as is indicated not only by the differ- ent coal seams but also by their containing rocks. There are a dozen different beds in Illinois. Mollusks, fishes, and amphibians buried in these deposits and changed to stone give further light upon the history of coal. Coal is found in five geological systems, from the middle Tertiary down through the upper Cretaceous, the lower Jurassic (Oolite), and the Triassic to the Carboniferous. Of these systems the Carbonif- erous far surpasses all others in production. In America there are seven extensive coal regions. The first is that included in Acadia, Nova Scotia, New Brunswick, and Rhode Island. The coal measures of Nova Scotia are 7,000 feet thick and contain 76 seams. In Rhode Island and Massachusetts a graphitic anthracite is found. The second region, covering 70,000 square miles along the Appa- lachians, includes the famous coal fields of Pennsylvania, Ohio, Mary- land, Virginia, West Virginia, Kentucky, Tennessee, and Alabama. In some portions of this field the coal measures are 4,000 feet thick. From no region of the world has more or better anthracite and bituminous coal been obtained. The third field occupies about 7,000 square miles in Michigan, where the productive Carboniferous is but about 300 feet thick. Indiana and Illinois, with approximately 1,000 feet of Carboniferous strata covering 58,000 square miles, comprise the fourth field one of the most actively worked and most remunerative. At one time, continuous with this field was that which now con- stitutes the fifth field, covering 94,000 square miles. It is found in Iowa, Missouri, Arkansas, and Texas. Here the Carboniferous rocks are thicker than in any other portion of America but not for that reason more promising. HYDROCARBONS 191 The sixth region is one of scattered character, occurring chiefly in Montana, Wyoming, Colorado, Utah, and Arizona. On the Pacific Coast is the seventh region, embracing Washington, Oregon, and Cali- fornia. Altogether there are more than 335,000 square miles of known coal-bearing territory in North America. The anthracite area covers less than 1,000 square miles. Half of this is in Massachusetts and Rhode Island, where the anthracite is almost without fuel value because of its graphitic character and con- sequently no production has been reported in recent years. Colorado contains 15 square miles. Pennsylvania has a field covering 470 square miles. From this latter region practically all the anthracite produced in the United States is obtained. The total coal produc- tion in the United States in 1915 was valued at six hundred and eighty-six million dollars. More than a thousand million tons of coal are used in the world each year, and of this amount the United States furnishes the greatest part. Before the world-war Great Britain came next in production, followed in descending order by Germany, Austro-Hungary, France, Belgium, Russia, Japan, India, Canada, New South Wales, Spain, South African Republic, and New Zealand. Coal was first used in London in 1240. After people had been using it for sixty-six years a law was passed against it on account of the smoke, which was declared to spoil ladies' complexions and clothes! As early as 1552 men began to fear all the coal in the world would soon be exhausted! In 1698 the first mention of coal in the United States was made by Father Hennepin as occurring near Fort Creve Coeur on the Illinois River near the place where Peoria now stands. Anthracite was discovered in Rhode Island in 1760. Being graphitic in character it was not used, and even the excellent variety which occurs in Pennsylvania lay unutilized for forty years after its presence was known. All early use of coal was very local owing to lack of transportation, but with the advent of coal, trans- portation and the growth of cities became a possibility. As society is now constituted, no mineral substance could be spared with greater difficulty, and, in fact, without coal modern civili- zation would be impossible. Railroads, steamships, and great manu- facturing plants would disappear. Men would miserably perish in winter's cold or all be driven to the tropics. 192 GUIDE TO MINERAL COLLECTIONS PQ g &.J2 PQ 3.1 V) If) MM fi 3 *3oCJCJCJc^P-iOU 3 - HYDROCARBONS 193 One pound of coal in a good engine will produce six-horse-power for one hour. One ton will produce thirteen-thousand-horse-power; and since some railroads use ten thousand tons per day, they have the equivalent of the work of one hundred and thirty million horses for one hour without the necessity of feeding the horses. It is estimated that one pound of coal can produce as many foot pounds of energy as one man in one day. Three hundred pounds will furnish as much power as one man per year. Then if half the coal produced in the United States in 1915 were used as a source of power, it could do .the work of sixteen hundred million men. This furnishes one expla- nation of the remarkable growth in wealth of the United States in the last fifty years a growth which has not been equaled before in the history of the world. In using coal so lavishly we are drawing on the energy stored in the earth by the slow growth and trans- formation of a succession of swamps and forests requiring the sun- shine of millions of years. The disappearance of the coal supply is but a question of time. In less than 300 years workable coal seams will probably be exhausted in Europe. Those in other parts of the world will last longer. But coal producers and users should seek to avoid the wasteful methods which at present prevail in: (i) mining, (2) removal, and (3) in use in furnace, stove, and fireplace. The following table shows the typical proportions of carbon, hydrogen, oxygen, and nitrogen in the transformation of wood to anthracite. CHEMICAL CHANGES IN TRANSFORMATION OF WOOD TO COAL Carbon Hydrogen Oxygen and Nitrogen Wood CQ 6 A.1 Peat C.Q 6 *to 22 Lignite 60 52 oo or Bituminous coal 82 5" 12 2 Anthracite coal nc 2 1 2 ? SUMMARY Having proceeded thus far, the visitor to the museum has made the acquaintance of about 100 different minerals. Many more are worthy of his interest and attention; yet this number is sufficient to give an idea of the minerals which constitute the world, and which are used by man for ornament, for medicine, as the source of metal, for building material, and in many other ways. Such a study furnishes results similar to those which would be obtained by a student of human society who went into a community of some 1,200 inhabitants and made the acquaintance of 100 differ- ent people engaged in different occupations, holding different respon- sibilities, and showing varied attainments. One who has finished such a study would have a fair idea of the whole community. So one who has passed through the museum, noting carefully the minerals shown and giving attention to their physical and chemical laws, their geography, geology, and relation to human activities, has a good idea of the whole mineral world. It is not necessary for him to study all the thirteen hundred different species and varieties of minerals. However, for one who wishes to go farther, a compre- hensive list of minerals is given on pages 202 to 275; and for further study he is referred to the books listed on page 200. No country is better supplied with minerals than the United States, and few countries make as good use of their resources in this regard as we do. The world-war resulted in stimulating mineral production in this country. For a number of minerals we had been accustomed to go to foreign countries; for antimony we had gone to China, for chromium to New Caledonia, for graphite to Ceylon, for magnesite to Greece, for manganese and platinum to Russia, for sulphur to Sicily, for tin to Singapore, for vanadium to Peru. But with increased difficulty of ocean transportation, prospectors and producers became increasingly active in the search for and the mining of these minerals. So the time is near at hand when the United States may be nearly independent in regard to the minerals necessary for the activities of its people. 194 SUMMARY 195 In 1915 the total wealth added to the country by our minerals was two billion three hundred and ninety-three million dollars. New minerals and chemical substances are being constantly dis- covered, and with their discovery new ideas and inspiration is gained by advanced workers in various departments of science. Most prominent among recent advances are those which have been made by men studying the ultimate constitution of matter. NAMES OF MINERALS Among the minerals which we have seen, the name of one at least, kaolinite, is of Chinese origin; two are of Singhalese origin: corundum and tourmaline; three are of Arabic origin: marcasite, amber, and talc. Bismuth, zincite, and hornblende are taken directly from the German; while gold, silver, and iron are old Anglo-Saxon words. Many minerals are named after some geographical locality, such as aragonite, anglesite, labradorite, muscovite, strontianite, tremolite. Others are named after men distinguished in the science of mineral- ogy or otherwise biotite, dolomite, goethite, franklinite, magnesite, magnetite, proustite, smithsonite, tennantite, witherite. A still larger number were derived from the Latin language: sul- phur, antimony, platinum, mercury, stibnite, argentite, erubesite, tetrahedrite, sylvite, fluorite, cassiterite, rutile, spinel, cerussite, mangenite, albite, enstatite, actinolite, garnet, celestite, asphalt. And finally, a still larger number of mineral names originate from the Greek: diamond, graphite, copper, molybdenite, galena, chalco- cite, sphalerite, cinnabar, pyrrhotite, chalcopyrite, pyrite, arseno- pyrite, pyrargyite, halite, cryolite, chalcedony, cuprite, hematite, chromite, pyrolusite, limonite, calcite, siderite, rhodochrosite, mala- chite, azurite, orthoclase, microcline, oligoclase, anorthite, hypersthene, pyroxene, diopside, augite, rhodonite, barite, gypsum. 196 THE USES OF MINERALS Minerals contribute toward the welfare of mankind in manifold ways. Many of the harder, more brightly colored, or highly refract- ing minerals since earliest times have been used as objects of personal adornment, and today among the most prized of all material objects are such minerals as diamonds, rubies, sapphires, emeralds, aqua- marine, amethyst, agates, turquoise, tourmaline, olivene, rhodonite, and malachite. The metals, together with their sulphides, oxides, carbonates, and silicates, play a weighty role in the life of men of all races and all stages of development. The condition of society would be materially different were there no gold, silver, platinum, copper, iron, tin, zinc, lead, paladium, chromium, aluminium, manganese, magnesium, mer- cury, antimony, or bismuth. Some minerals form foods without which it would be well-nigh impossible for men to exist. For example, salt and the minerals which are the source of the alkalies are almost indispensable to life. The number of minerals which are used in the arts and manu- factures is large and important. Sulphur, phosporus, soda, potash, chlorine, fluorine, and calcium contribute largely to the wealth of men. Attention has already been called to the indispensable character of the hydrocarbon compounds. Without them modern civilization would be an impossibility. Minerals as rock constituents form mountains and plains, and by their decomposition furnish the ultimate food supply of mankind. The study of minerals in their capacity of soil-formers is one of sur- passing interest. 197 HISTORY OF THE STUDY OF MINERALS The science of mineralogy, depending as it does upon physics, chemistry, and other well-developed sciences, has been one of the latest to be pursued, although from very early times minerals were used for ornaments, weapons, and domestic utensils. While ancient literature abounds in references to minerals, little more was known about them in early times than their external form. Hebrew litera- ture mentions the use of clay, niter, salt, sand, and sulphur, as well as of gold, silver, copper, emerald, agate, chalcedony, carnelian, jasper, onyx, sardonyx, topaz, ruby, and sapphire. Aristotle, 322 B.C., who is reputed by his admirers "to have known something of every science," has given no evidence of acquaint- ance with minerals. Several references to the subject in his writings are thought to have been interpolations made later by other writers. Pliny, 79 A.D., was the first Latin writer to describe minerals, and his accounts are usually so incomplete as to leave doubt as to the minerals to which they apply! Avicenna (d. 1036), an Arabian doctor of medicine born near Bokhara, distinguished salts, metals, minerals, and stones. Agricola (d. 1555), a German doctor born in Joachims Thai, used the terms quartz and spar, and noted the hardness, cleav- age, form, and luster of certain minerals. This is a short list to cover all the years to the seventeenth century. But during the latter part of the seventeenth century a number of men began to be inter- ested in the subject, Robert Boyle (1691) investigating their chemis- try, Niccolas Steno discovering the constancy of crystal angles, and Bartholinus noting the double refraction of calcite. During the eighteenth century Linnaeus, the great classifier, attempted to classify minerals according to their form, while Cronstedt attempted a chemical classification. Two Frenchmen, Rome de ITsle and Rene Just Haiiy, were enthusiastic investigators in crystallography. De ITsle described and pictured many forms. Haiiy discovered laws underlying them. Jealousy of each other's work made them enemies. Haiiy enjoyed recording de ITsle's errors while correcting them. But their work formed the basis of later work in crystallography. 198 HISTORY OF THE STUDY OF MINERALS 199 During the nineteenth century the study of minerals was pursued by many workers and the advancement in many lines assumed admirable proportions. In Germany, Weiss developed the idea of systems of crystallization, Mohs investigated the natural history of minerals, and Werner studied chemical classification and developed determination of minerals by simple physical characteristics. In Germany, France, England, and America the number of workers increased, some pursuing the subject of crystal formation, as did Bravais, Sohncke, Naumann, Miller, and Liebisch; others working at the chemical side of the subject, as, for example, Berzelius, Rose, Bunsen, Mitscherlich, Plattner, and Rammelsberg; still others studying optical mineralogy, noting particularly the relation of form to physical properties Brewster, Senarmont, Des Cloizeaux, Zirkel, Sorby, Wollaston. The systematic side of the subject was developed by Beudant, Breithaupt, Groth, and Dana. Fouque, Michel Levy, and Daubree gave attention to the artificial formation of minerals- The increase in interest in the subject of mineral study has come largely from advance in mining and in the use of minerals in arts and manufactures. The study has been and is naturally one of materials rather than of laws; but as the science has progressed, the principles and laws have been gradually perceived and formulated. In the development of the science, contributions have been made to other sciences: to physics, knowledge of optical and electrical phenomena; to chemistry, knowledge of new substances; to geology, light on the origin, composition, and decay of rocks; to metallography, facts concerning the contents and treatment of ores. Within the last fifty years the number of workers in mineralogy has increased to such an extent that the list is an extensive one and the science has been brought to great perfection in various lines. In the United States many excellent books on the subject have been written. No work has ever surpassed in completeness that of James Dwight Dana. His System of Mineralogy, which first appeared in 1837, has passed through six editions. After the elder Dana's death the Manual of Mineralogy, which first appeared in 1848 and has passed through thirteen editions, and the Textbook of Mineralogy, which first appeared in 1877, were rewritten, enlarged, and kept up to date, first by Edward Salisbury Dana and later by William E. Ford. Among many books which have appeared during the "last 200 GUIDE TO MINERAL COLLECTIONS dozen years, the following may be noted especially. In them there has been a general endeavor to present this rather difficult science in such a manner as to render it more attractive to the general student. Increasing use is made of diagrams, of models, and of photographs of minerals. Anyone wishing to pursue the subject further should con- sult the following excellent works: Bayley, W. S., Descriptive Mineralogy. D. Appleton & Co., 1917. Brush, G. J., and Penfield, S. L., Determinative Mineralogy and Blow- pipe Analysis. John Wiley, 1907. Butler, G. M., Handbook of Minerals. John Wiley, 1908. Erni, H., and Brown, A. P., Mineralogy Simplified. Philadelphia, 1901. Farrington, 0. C., Meteorites. Lakeside Press, 1915. , Gems and Gem Minerals. Lakeside Press, 1902. Fulton, A. E. H., Crystallography and Practical Crystal Measurement. Macmillan Co., 1911. Gratacap, L. P., Popular Guide to Minerals. D. Van Nostrand Co., 1912. Groth, P., and Jackson, B. H., Optical Properties of Crystals. John Wiley, 1910. Iddings, J. P., Rock Minerals. John Wiley, 1906. Johannsen, Albert, Determination of Rock-Forming Minerals. John Wiley, 1908. Kraus, E. H., Descriptive Mineralogy. George Wahr, 1911. Kunz, G. F., Gems and Precious Stones of North America. New York. Lewis, J. V., Determinative Mineralogy. John Wiley, 1915. Merrill, G. P., Rocks, Rock Weathering, and Soils. John Wiley, 1906. , Non-Metallic Minerals. Macmillan Co., 1904. Moses, A. J., and Parsons, C. L., Mineralogy, Crystallography, and Blowpipe Analysis. D. Van Nostrand Co., 1909. Phillips, A. H., Mineralogy. Macmillan Co., 1912. Pirsson, L. V., Rocks and Rock Minerals. John Wiley, 1908. Van Horn, F. R., Lecture Notes on Mineralogy. Cleveland: 1903. Winchell, N. H. and A. N., Elements of Optical Mineralogy. D. Van Nostrand Co., 1909. An attractive little monthly magazine, The American Mineralogist, edited by Edgar T. Wherry, to be obtained of H. W. Trudell, Phila- delphia, describes new minerals and records events of interest to mineralogists. Economic Geology, Mineral Industry, American Jour- nal of Science, Science, and other journals contain many articles on mineralogy. Various state geological reports and those of the United States Geological Survey are full of interesting and valuable information concerning occurrence and production of minerals. COMPREHENSIVE LIST OF MINERALS 2O2 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form I. ELEMENTS i. Diamond .... c Regular 2. Bort c Regular 3. Carbonado c Massive 4. Cliftonite c Massive 5 Graphite c Hexag 6 Schungite c Amorph 7. Sulphur s Ortho. 8. Selensulphur . SeS Ortho. 9. Arsenic As Hexag. 10. AUemonite SbAs 3 Hexag. 1 1 . Tellurium Te Hexag. 1 2 . Antimony Sb Hexag. 13. Bismuth Bi Hexag. 14. Zinc Zn Hexag. 15. Gold Au Regular 16. Electrum Au Ag Regular 17. Silver Ag Regular 18. Copper 19. Mercury ~ Cu Hg Regular Amorph. 20. Lead Pb Regular 2 1 . Amalgam (Ag,Hg) Regular 22. Arquerite (Ag I2 Hg) Regular 23. Kongsbergite (Ag, 2 Hg) Regular 24. Tin Sn Tetrag. 25. Platinum Pt Regular 26. Iridium Ir Regular 27. Iridosmine IrOs Hexag. 28. Nevyanskite 29. Siserskite 30. Palladium IrOs IrOs Pd Hexag. Hexag. Regular 31. Allopalladium Pd Hexag. 3 2 . Iron Fe Regular 33. Awaruite FeNi 2 Regular 34. Josephinite Fe 2 Ni s Regular 35. Meteoric Iron 36. Kamacite Fe Fei 4 Ni Regular Regular 37. Taenite FCnNIn Regular 38. Plessite Fe n Nin Regular 39. Cohenite (Fe,Ni,Co) 3 C Regular 390. Schreibersite (Fe,Ni,Co),P Tetrag. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 203 No. Color Hard- ness Gravity Locality Chief Constituent or Use I. Colorless IO 3-5 Kimberley Gem 2. 3- Dark Black IO IO 3-5 3-5 Kimberley Kimberley }Drills 4- Black 2-5 2. I Meteorites Carbon 5- Black I 2 Ceylon Pencils 6. Black I 1.9 Russia Carbon 7- Yellow 2 2 Sicily Drugs 8. Reddish Sicily Selenium 9- Tin white 3-5 5-6 Freiberg 1 10. Tin white 3-5 6.2 Andreasberg fDrugs ii. Tin white 2 6.1 Colorado J 12. 13- White Reddish 3 2-5 6.6 9.8 Japan Western U.S. JAlloys 14. White 2 6.9 Australia Zinc 15- Yellow 2-5 T 9 Western U.S. Coin 16. Amber 2-5 15 Urals Gold 17- White 2-5 II Western U.S. Coin 18. Red 2.5 8.9 Michigan Wire 19. White 17. C California Amalgamation 20. Gray i-5 O 3 "3 Colorado Lead 21. Whit2 3 14 Sweden, S. America ) 22. White 3 TO Sweden, S. America Silver 23- White 3 14 Sweden, S. America J 24. White 2 7 Siberia, N.S. Wales Tin 25- White 5 21 Urals Dentistry 26. Regular 6 22 Urals Pen points 27. White 6 21 Urals, S. America 28. White 6 J 9 Urals, S. America [irdium and 2Q. White 6 21 Urals, S. America J osmium 30. 3 1 ' Steel gray Steel gray 4 II Brazil Hartz JPalladium 32. Iron black 4 7 Meteorites 33- Gray 5 8 New Zealand 34- Gray 5 8 Oregon 35- Gray 4 7 Meteorites 36. Gray 4 7 Meteorites Iron and nickel 37- Gray 4 7 Meteorites 38. Gray 4 7 Meteorites 39- Tin white 6 7 Meteorites 390. Tin white 6 7 Meteorites t 2O4 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form II. SULPHIDES i. Sulphides of Semi-Metals 40. Realgar AsS Mono 41. Orpiment 42. Stibnite As 2 S 3 Sb 2 S 3 Mono. Ortho 43. Metastibnite Sb 2 S 3 44. Bismuthinite 45. Guana juatite .... Bi 2 S 3 Bi 2 Se 3 Ortho. Ortho 46. Tetradymite Bia(Te,S), Hexasr 47. Joseite Bi,Te,Se Hexasr 48. Wehrlite Bi 3 Te 2 Hexas 49. Molybdenite MoS 2 Hexacr 2. Sulphides of Metals a. Basic 50. Dyscrasite Ag 3 Sb-Ag 6 Sb Ortho 51. Horsiordite 52. Huntilite CucSb AgiAs Ortho. Ortho 53. Animikite 54. Domeykite Ag 9 Sb Cu 3 As Ortho. Ortho 55. Algodonite CueAs Ortho 56. Whitneyite CiipAs Ortho 57. Chilenite AgfiBi Amorph 58. Stiitzite Ae d Te Hexag b. Monosulphides 59. Galena . PbS Ref^ular 60. Cuproplumbite 61. Alisonite 62. Altaite. . . Cu 2 S-2PbS 3 Cu 2 S-PbS AgTe Massive Massive Regular 63. Clausthalite PbSe Regular 64. Tilkerodite 65. Naumannite (PbCo)Se (Ag 2 Pb)Se Regular Regular 66. Argentite Ag 2 S Regular 67. Jalpaite (Ag,Cu) 2 S Regular 68. Hessite 69. Petzite Ag 2 Te (Ag Au) 2 Te Regular JMassive 70. Aguilarite Ag 2 S Ag 2 Se Regular 71. Berzelianite Cu 2 Se Dend. 72. Lehrbachite PbSe-HgSe Massive 73. Eucairite Cu 2 Se Ag 2 Se Regular 74. Zorgite (PbCu 2 Ag 2 )Se Massive 75. Crookesite . 76. Umangite (CuTlAg) 2 Se CuSe Cu 2 Se Massive Massive 77. Chalcocite 78. Stromeyerite Cu 2 S (Ag,Cu) 2 S Ortho. Ortho. 79. Sternbergite 80. Frieseite AgFe 2 S 3 Ag 2 Fe s Ss Ortho. Ortho. 81. Acanthite Ag 2 S Ortho. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 205 No. Color Hard- ness Gravity Locality Chief Constituent or Use 40. 41. Aurora red Yellow 1-5 1-5 3-5 3-5 California Utah, Wyoming JArsenic 42. A -2 Lead gray Brick red 2 5 Japan Nevada JAntimony *w 44. White, iridescent 2 6 England, N.C. 45- Bluish gray 2 6 Mexico 46. Steel gray i-5 7 North Carolina Bismuth 47- Steel gray 2 7-9 Brazil 48. Steel gray 2 8-4 Hungary 49- Lead gray 1-5 4-6 Washington Molybdenum 5- Tin white 3-5 9-5 Hartz Mts. Silver C I Tin white 8.8 Mytilene Copper A< c;2 Tin white 7 Lake Superior r^r^ Ic-M C-2 White / Q Lake Superior | Silver JO CA. Tin white V 7 e Lake Superior 1 0*r cc. Tin white / 7 6 Lake Superior [Copper 00 <6. Reddish white / * w 8-4 Houghton, Mich. r^r^ 57- Silver white 2 Chile ^ol\rp>r 58. Lead gray Nagyag i onver 59- Lead gray 2-5 7 Missouri, Colorado Lead 60. Dark blue 6 Chile in 61. Indigo blue 6 Chile r Copper 62. Tin white 3* 8.1 Chile, Colorado Lead 63- Lead gray 3 8 Hartz Mts. IT wr\ 64. Lead gray 8 Hartz Mts. rj_/eau 65- Iron black 2-5 8 Hartz Mts. 66. 67. Lead gray Lead gray 2-5 7 6 Western U.S. Mexico Silver 68. Lead gray 2-5 8 Boulder, Colo. '*. 69. Iron black 2-5 9 California Gold 70. Iron black 2-5 7-5 Mexico Silver 71- Silver white 2 6-7 Sweden Copper 72. Iron black 7-8 Hartz Mts. Mercury 73. Lead gray 7 ^ Chile Is* 74- Lead gray 2 / o 7 Hartz Mts. ^Copper 75- Lead gray 3 6.9 Sweden Silver 76. Cherry red 3 5-6 Argentina Copper 77- Lead gray 2 5 Montana Copper 78. Steel gray 2-5 6 Siberia, Colorado 79- 80. Pinchbeck .brown Dark gray I 2-5 4-2 4 Saxony Joachimsthal Silver It, Iron black 2-5 7 Joachimsthal 206 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form II. SULPHIDES continued 82. Sphalerite ZnS Regular 83. Marmatite ZnS-FeS Regular 84. Przibramite ZnS CdS Regular 85. Metacinnabarite HgS 86. Guadalcazarite 87. Tiemannite HgS- ZnS HgSe Regular Regular 88. Onofrite Hg(S-Se) Regular 89. Colorado! te HgTe Regular 90. Alabandite MnS 9 1 . Oldhamite CaS Regular 92. Pentlandite (Fe,Ni)S Regular 93. Troilite FeS Hexasr 94. Cinnabar HgS Hexag 95. Covellite CuS Hexag 96. Greenockite CdS Hexag 97. Wurtzite ZnS Hexaer 98. Erythrozincite ZnS- MnS 99. Millerite NiS Hexasr TOO. Beyrichite NiS* Hexag 101. Hauchecornite (Ni,Co) 7 (S Sb Bi) 8 Tetrag 102. Niccolite NiAs Hexag 103. Breithauptite NiSb Hexacr 104. Pyrrhotite FcuSiz Hexasr c. Intermediate 105. Horbachite 4Fe 2 S 3 Ni 2 S 3 Hexag 106. Polydymite Ni 4 S s Regular 107. Griinauite Ni 4 S s -Bi 2 S 3 Regular 108. Sychnodymite (Co,Cu) 4 S 5 Regular 109. Melonite Ni 2 Te 3 Hexag. no. Bornite ( = Erubesite) in. Linnaeite . 3 Cu 2 S-Fe 2 S 3 (Ni Co Fe) 3 S 4 Regular Regular 112. Daubreelite 113. Cubanite. FeS-Cr 2 S 3 CuFe 2 S 4 Regular 1 14. Carrollite CuCo 2 S 4 Regular 115. Chalcopyrite CuFeS 2 Regular d. Bisulphides 116. Pyrite FeS 2 Regular 117. Hauerite MnS 2 Regular 1 1 8 . Smaltite-chloanthite 119. Cobaltite CoAs 2 -NiAs 2 CoAsS Regular Regular 1 20. Gersdorffite NiAsS Regular i2i. Corynite ... . Ni(As,Sb)S Regular 122. Willyamite CoS 2 NiS 2 CoSb 2 NiSb 2 Regular 123. Ullmannite NiSbS Regular 124. Kallilite Ni(Sb Bi)S Massive 125. Sperrylite PtAs 2 Regular 126. Laurite RuS 2 Regular COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 207 No. Color Hard- ness Gravity Locality Chief Constituent or Use 82. Yellow 3-5 3-9 Missouri | 83. Dark brown 2 .Q Cornwall \Zinc O 84. Dark brown 3-5 O V 3-9 Hungary 1 85- Grayish black 3 7 California 86. 2 7 Gaudalcazar. ]VIex. 87. Steel gray 2-5 / 8 Hartz Mts. Mercury 88. Blackish gray 2-5 8 Mexico 89. Iron black 3 8 Colorado 90. Iron black 3-5 3-9 Colorado Manganese 91. Pale brown 4 2-5 S.C. Meteorites Calcium 92. Bronze yellow 3-5 4.6 Norway Nickel 93- Tombac brown 4-7 4-7 Meteorites Iron 94. Reddish brown 2 8 Spain, California Mercury 95- Indigo blue i-5 4-5 Chile Copper 96. Yellow 3-5 4-9 Scotland Cadmium 97- Brownish black 3-5 3-9 Peru \7irtr> 98. Red 2 3-9 Siberia riI!C 99. Brass yellow 3-5 5 Saxony IOO. Lead gray 3 4-7 Westerwald IOI. Bronze yellow 5 6 Westphalia Nickel IO2. Copper red 5 7 Sweden 103. Red 5 7-5 Andreasberg 104. Bronze 3-5 4-5 Pennsylvania Sulphur 105. Steel gray 4-5 4 Horback V 106. Gray 4-5 4-5 Griinau j^Nickel 107. Steel gray 4-5 5 Griinau I 108. Steel gray 4.7 Siegen Cobalt 109. Reddish white T^ / California Nickel no. III. Copper Steel gray 3 5-5 is Chile Sweden Cobalt 112. Black 5~ IVteteoric iron Chromium 113- 114- Bronze Steel gray 4 5-5 4 4-8 Cuba Maryland r Copper US- Yellow 3-5 4 Western U.S. Copper 116. Yellow 6 5 Everywhere Sulphur 117. Brown 4 3 Hungary Manganese 118. 119. Tin white Silver white 5-5 5-5 6 6 Saxony Sweden JGobalt 120. 121. Silver white Silver white 5-5 4-5 6 5-9 Sweden Olsa }Nickel 122. Silver white 5 7 New South Wales Cobalt 123. 124. Steel gray Bluish gray 5-5 6 Germany Germany JNickel 125. Tin white 6 10 Canada Platinum 126. Iron black 7-5 6-9 Borneo Ruthenium 208 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form II. SULPHIDES continued 127. Skutterudite CoAs 3 Regular 1 28. Nickel-skutterudite. . . 129. Bismuto-smaltite (Ni,Co,Fe)As 3 Co(As,Bi) 3 Massive Massive 130. Marcasite FeS 2 Ortho 131. Lollingite FeAs 2 Ortho. 132. Leucopyrite Fe 3 As 4 Ortho. 133. Geyerite Fe(AsS) 2 Ortho. 134. Arsenopyrite FeAsS Ortho. 135. Danaite FeCoAsS Ortho. 136. Saffiorite CoAs 2 Ortho. 137. Rammelsbergite 138. Glaucodot NiAs 2 (Co,Fe)AsS Ortho. Ortho. 139. Alloclasite Co(As,Bi)S Ortho. 140. Wolfachite 1400 M^aucherite Ni(As-Sb)S Ni 3 As 2 Ortho. Tetrag. e. Tellurides 141. Sylvanite (Au Ag)Te 2 Mono. 142. Krennerite (Au,Ag)Te 2 Ortho. 143. Calaverite (Au,Ag)Te 2 Mono. 144. Nagyagite Au 2 Pbi 4 Sb 3 (S,Te) 24 Ortho. /. Oxysulphides 145. Kermesite Sb 2 S 2 O Mono. 146. Voltzite Zn s S 4 O Globules COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 209 No. Color Hard- ness Gravity Locality Chief Constituent or Use 127. Tin white 6 6-7 Norway ) 128. Gray New Mexico [Cobalt I2O Tin white 6 Q Zschorlau *y 130. Yellow 6-5 W . VJ 4-8 Bohemia Sulphur I3I- Silver white 5-5 7 Lolling-Huttenberg Arsenic 132. Silver white 5-5 7 Lolling-Huttenberg I 122. 6.8 Saxony [Arsenic oo 134- Silver white 5-5 6 Freiberg 135- 136. Gray Tin white 5-5 4-5 6 7 Franconia Saxony }Cobalt 137- Tin white 5-5 7 Saxony Nickel 138. J 39- Tin white Steel gray 5 4-5 5-9 6.6 Chile Orawitza JCobalt 140. 1405- Silver white Reddish 4-5 5 6 7 Wolfach Thuringen }Nickel 141. Steel gray i-5 7-9 Nagyag | 142. 143- Silver white Yellow 2-5 8 9 Nagyag, Colo. California, Colo. Gold 144. Lead gray i 6.S Nagyag J 145- Red i 4-5 Hungary Antimony 146. Red 4 3-6 Joachimsthal Zinc 2IO GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form III. SULPHO-SALTS i. Sulpharsenites, etc. a. Acidic 147. Livingstonite HgS-2Sb 2 S 3 Ortho 148. Chiviatite 2PbS '3Bi a S 3 Ortho 149. Cuprobismutite 3Cu 2 S'4Bi 2 S 3 Ortho 150. Rezbanyite 4PbS'5Bi 2 S 3 Ortho b. Meta 151. Zinkenite PbSb 2 S 4 Ortho 152. Andorite ) T 53' Webneritel- 2(Pb,Ag,Sb),S6 Ortho 154. Sundtite J 155. Sartorite PbS-As 2 S 3 Ortho 156. Emplectite Cu 2 S Bi 2 S 3 Ortho 157. Chalcostibite Cu 2 S Sb 2 S 3 Ortho 158. Galenobismutite PbS-Bi 2 S 3 Ortho 159. Berthierite FeS-Sb 2 S 3 Ortho 160. Matildite Ag 2 S Bi 2 S 3 Ortho 161. Miargyrite Ag 2 S-Sb 2 S 3 Mono. 162. Lorandite TlAsS 2 Mono. c. Intermediate 163. Plagionite 5PbS-4Sb 2 S 3 Miono 164. Schirmerite 3(Ag 2 ,Pb)S-2Bi 2 S 3 Ortho 165. Klaprotholite . 3Cu 2 S'2Bi 2 S 3 Ortho 166. Binnite 3Cu 2 S-2As 2 S 3 Regular 167. Warrenite 3PbS-2Sb 2 S 3 Ortho. 168. Jamesonite Pb 2 Sb 2 S s Ortho. 169. Dufrenoysite 2PbS-AS 2 S 3 Ortho. 1 70. Rathite 2PbS-As 2 S 3 Ortho. 171. Cosalite 2PbS-Bi 2 S 3 Ortho. 172. Kobellite 2PbS-(Bi,Sb) 2 S 3 Ortho. ' 173. Brongniardite . . PbS-Ag 2 S-Sb 2 S 3 Regular 1 74. Semseyite 7PbS-3Sb a S 3 Mono. 175. Schapbachite PbS-Ag 2 S-Bi 2 S 3 Ortho. 176. Freieslebenite (Pb,Ag 2 ) s -Sb 4 Su Mono. 177. Diaphorite (Pb,Ag 2 ) s -Sb 4 Sn Ortho. 1 80. Boulangerite Pb 3 Sb 2 S6 Ortho. 181. Embrithite ioPbS'3Sb 2 S 3 Ortho. d. Ortho 182. Bournonite (Pb,Cu 2 ) 3 Sb 2 Se Ortho. 183. Aikinite 3(Pb Cu 2 )S-Bi 2 S 3 Ortho. 184. Wittichenite 3Cu 2 S-Bi 2 S 3 Ortho. 185. Stylo typite . . 3(Cu 2 ,Ag 2 ,Fe)S-Sb a S 3 Ortho. 186. Lillianite 3PbS-BiSbS 3 Ortho. 187. Guitermanite 3PbS-As 2 S 3 Ortho. 188. Tapalpite 3Ag 2 (S,Te)-Bi 2 (S,Te) 3 Ortho. 189. Pyrargyrite Ag,SbS, Hexag. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 211 No. Color Hard- ness Gravity Locality Chief Constituent or Use 147. Lead gray 2 4-8 Mexico Mercury 148. Lead gray 6.9 Chiviato Lead 140. Bluish black 6 Colorado Copper Li ry * 150. Lead gray 2-5 6 Hungary ^Y Lead ISI. Steel gray 3 5 Hartz Lead 152. | 153- [Dark gray 3 5 Felsobanya Silver 154- J I SS- Dark gray 3 5 Binnenthal 156. Tin white 2 6 Saxony Tp,ad I 57- Gray 3 4-75 Hartz LrfCcLU. 158. Lead gray 3 6-9 Sweden 159. Steel gray 2 4 Saxony Antimony 1 60. 161. Gray Iron black 2 2 6.9 5 Peru Saxony jSilver . 162. Red 2 5 Allchar Thalium 163. Lead gray 2 -5 5 Wolfsberg Lead 164. Lead gray 2 6 Colorado Silver 165. 166. 167. Steel gray Steel gray Grayish black 2 2-5 4-6 4 Wittichen Tyrol Colorado }Copper J. \J / 168. Steel gray 2 5-5 Cornwall 169. 170. Lead gray Lead gray 3 3 5-5 5-5 Tyrol Tyrol Lead 171. Steel gray 2-5 6 Mexico 172. Steel gray 6 Sweden, Colorado */* 173- Black 3-5 5.9 Mexico SUver 174. Gray Bismuth 185. Iron black 3 4-7 Chile Antimony 186. Steel gray Sweden IT j 187. Bluish gray 3 S.9 Colorado JLead 188. Gray 3 7.8 Mexico Bismuth 189. Black 2.5 5.7 Andreasberg Silver 212 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form III. SULPHO-SALTS continued 190. Proustite Ag^AsS* Hexag 191. Sanguinite A A ? Ag 3 ASo 3 Hexaer 192. Falkenhaynite 3Cu 2 S*Sb 2 S 3 Regular 193. Pyrostilpnite 3Ag 2 S-Sb 2 S 3 Mono. 1 94 Rittingerite AgjoAszSeg M^ono e. Basic 195. Tetrahedrite 196. Freibergite. 197. Schwatzite 198. Tennantite CusSb 2 S 7 Cu8Sb 2 S 7 -Ag 2 S Oi8Sb 2 S 7 -HgS Cu8As 2 S 7 Regular Regular Regular Regular loo. Tordanite 4PbS'As 2 S 3 Mono. 200. Menenghinite 4PbS-Sb 2 S 3 Ortho. 201. Stephanite Ag s SbS 4 Ortho. 202. Geocronite 5PbS-Sb 2 S 3 Ortho. 203. Beegerite 6PbS-Bi 2 S 3 Regular 204. Kilbrickenite 6PbS-Sb 2 S 3 Massive 205 Polybasite Ag 9 SbS 6 Mono. 206. Pearceite 9 Ag 2 S As 2 S 3 Mono. 207. Polyargyrite 1 2 Ag 2 S Sb 2 S 3 Regular 2. Sulphar -senates, etc. 208. Enargite Cu 3 AsS 4 Ortho. 209. Clarite Cu 3 AsS 4 Mono. 210. Luzonite Cu 3 AsS 4 Massive 211. Famatinite 212. Xanthoconite 3 Cu 2 S-Sb 2 S s 3Ag 2 S-As 2 S s Ortho. Hexag. 213 Epiboulangerite 3PbS-Sb 2 S s Ortho. 214. Epigenite 4Cu 2 S 3FeS As 2 S 5 e Ortho. 215. Stannite Cu 2 FeSnS 4 Regular 216. Argyrodite AgjjGeSe Regular 217. Canfieldite AggSnS6 Regular 218. Franckeite Pb s Sb 2 Sn 2 S I2 Massive 219. Cylindrite Pb 6 Sb 2 Sn6S M Massive 220. Sulvanite 3Cu 2 S-V 2 S s Massive COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 213 No. Color Hard- ness Gravity Locality Chief Constituent or Use 190. IQI Scarlet Red 2 2 5-S Freiberg Chile jSilver *y* IQ2. Gray black 4-8 Joachims thai ) Copper o.y 193- IQ4- Red Iron black 2 2 4 5-6 Andreasberg Chile Jt^lr jSilver 195- Iron black 3 4 Hartz Copper 196. Steel gray 4 8 Hartz Silver and copper IO7 Iron black *r * *-* ir Hartz ! "ft 198. Iron black 3 4 Freiberg jCopper 199. 200. Lead gray Lead gray 3 2-5 6 6 Tyrol Tuscany }Lead 201. Iron black 2 6 Freiberg Silver 2O2. Lead gray 2-5 6 Sweden } 2O3. Gray 6 Colorado Lead " W O 2O4. Lead gray 6 Ireland 205. Iron black 2 6 Mexico ) 2O6. Iron black 3 6 Colorado, Montana Silver 207. Iron Black 2.5 6.9 Wolfach ) 208. Black 3 4 Peru 20 9 . 210. Gray Steel gray 3-5 3-5 4 4 Baden Luzon Copper 211. Gray 3-5 4-5 Argentina 212. Orange yellow 2 5 Freiberg Silver 21.3. Gray 6 Altenberg Lead 214. Steel gray 2 tr Baden Copper 215. Steel gray O 4 4 South Dakota X_xV^/V,l. Tin 216. 217. Steel gray Black 2-5 6 5-5 Freiberg Bolivia }Silver 218. 219. Blackish gray Blackish gray 2-5 5-5 5 Bolivia Bolivia }Lead 220. Bronze 3 4 Australia Copper 214 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form IV. HALOIDS i. Anhydrous 221. Calomel Hg 2 Cl 3 Tetrae 222. Nantokite Cu 2 Cl 2 Regular 223. Marshite , Cu 2 I 2 Regular 224. Halite NaCl Regular 225. Huantajayite 2oNaCl-AgCl Regular 226. Sylvite KC1 Regular 227. Sal ammoniac NH 4 C1 Regular 228. Cerargyrite AgCl Regular 229. Embolite Ag(Br,Cl) Regular 230. Bromyrite AgBr Regular 231. lodobromite . . . . 2AgCl-2AgBr-AgI Regular 232. Miersite Ag 2 I 2 Regular 233. Cuproiodargyrite. . . . 234. lodyrite CuI-Agl Agl Incrust. Hexaer 235. Fluorite CaF 2 Regular 2350. Yttrofluorite (Ca 3 ,Y 2 )F 6 Regular 236. Hydrophilite CaCl 2 Regular 237. Chloromagnosite 238. Scacchite MgCl 2 MnCl 2 Regular Regular 239. Chloralluminite A1C1 3 -XH 2 O Regular 240. Molysite FeClj Incrust. 241. Sellaite . . MgF 2 Tetrag. 242. Lawrencite FeCl 2 Hexag. 243. Cotunnite PbCl 2 Ortho. 244. Tysonite (Ce,La,Di)F 3 Hexag. 245. Cryolite Na 3 AlF 6 Mono. 246. Chiolite 5NaF-3AlF 3 Tetrag. 247. Hieratite 2KF-SiF 4 Regular 2. Oxy chlorides, etc. 248. Atacamite Cu 2 ClH 3 O 3 Ortho. 249. Percylite PbCuO 2 H 2 Cl 2 Regular 2490. Boleite PbCuCl 2 (OH) 2 4AgCl Regular 2496. Cumengite PbCuCl 2 (OH) 2 4AgCl Tetrag. 250. Matlockite Pb 2 OCl 2 Tetrag. 251. Mendipite Pb 2 O 2 Cl 2 Ortho. 252. Laurionite PbClOH Ortho. 253. Fiedlerite PbClOH Mono. 254. Penfieldite Pb 3 OCl 2 Hexag. 255. Daviesite Pb-O-Cl Ortho. 256. Schwartzembergite.. . 257. Fluocerite Pb(I,ClJ 2 2PbO (Ce,La,Di)aOF 4 Hexag. Hexag. 258. Nocerite 2(Ca,Mg)Fe-(Ca,Mg)O Hexag. 259. Daubreeite 2Bi 2 O 3 -BiCl 3 -3H 2 O Amorph. 3. Hydrous 260. Carnallite * KMgCl 3 6H a O Ortho. 261. Douglasite 262. Bischofite 2KCl-FeCl 2 2H 3 O MgCl 2 -6H 2 O Mono. Mono. 263. Kremersite KC1 NH 4 C1 2 FeCl 2 H 2 O Regular COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 215 No. Color Hard- ness Gravity Locality Chief Constituent or Use 221. 222. 223 Gray Colorless Oil brown I 2-5 6 3-9 Spain Chile New South Wales Medicine }Copper 224. 22 ^ Colorless White 2.5 2 2 Kansas, Louisiana Chile }Salt 226. 227. 228. 229. 230. 231. 272. Colorless White Pearl gray Grayish green Yellow Greenish Yellow 2 I-S I I 2 i-5 1.9 i-5 5-5 5-8 5-7 Stassfurt Vesuvius Colorado, Nevada Chile Mexico Nassau New South Wales Potassium Medicine Silver 233- 234. 235- 23Si 236 Yellow Yellow Blue Yellow White 2 i-5 4 4 5-6 5-6 3 3 2 C Peru New Mexico Illinois Norway Vesuvius Jlodine Flux Yttrium, fluorine Chlorine 237 White Vesuvius Magnesium 238 White Vesuvius 230 White Vesuvius ^Chlorine 24.O Red Vesuvius 241. 242. Colorless Green 5 2-9 Savoy Meteorites Fluorine Iron ''4.3. White 5 Vesuvius Lead 244. 245- 246. 24.7 Wax yellow Colorless Snow white Gray 4-5 2-5 3-5 6 2-9 2.8 Pike's Peak Western Greenland Ilmen Mts. Vulcano Cerium >Aluminum Potassium 248. 24.Q. Green Blue 3 2 t; 3-7 Arizona Mexico Copper 2490. 2406. Indigo blue 3 5 Lower California Lead and copper 250. 251. 2 C2 Yellowish White Colorless 2-5 2-5 7 7 Cromford England Greece 2 C3 Colorless Greece Lead 2 <\A. White Greece 2 C C. Colorless Sierra Gorda 256. 257- 2^8. Honey yellow Yellow White 2 4 6 5-7 Atacama Sweden Italy Cerium Fluorine 259- 260. 261. 262. 263. Yellow White Colorless Colorless Red 2 I I 6 1.6 2 1.6 Bolivia Stassfurt Stassfurt Prussia Vesuvius Bismuth Magnesium ichlorine 2l6 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form IV. HALOIDS continued 264. Erythrosiderite 2KCl-FeCl 3 -H 2 O Ortho. 265. Tachhydrite 266. Fluellite CaCl 2 -2MgCl 2 -i2H 2 A1F 3 -H 2 O Hexag. Hexag 267. Prosopite 268. Pachnolite CaF 2 - 2 Al(F,OH) 3 NaF-CaF 2 -AlF 3 -H 2 O Mono. Mono. 269. Thomsenelite .... NaCaAlF 6 -H 2 O Mono. 270. Gearksutite 271. Ralstonite CaF 2 -Al(F,OH) 3 -H 2 (Na 2 Mg)F 2 3 A1(F,OH) 3 2H 2 O Earthy Regular 272 Tallingite Cu s (OH) 8 Cl 2 -4H 2 O Botry 273. Footeite 8Cu(OH) 2 CuCl 2 4H 2 O Mono. 274. Yttrocerite (Y Er,Ce)F 3 -sCaF 6 -H 2 O Earthy COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 217 No. Color Hard- ness Gravity Locality Chief Constituent or Use 264. Red Vesuvius 26 1 ?. Yellow Stassfurt | Chlorine 266. Colorless 3 2 Cornwall 267. Colorless 4-5 2.8 Colorado 268. Colorless 3 2.9 Colorado Fluorine 269. Colorless 2 2.9 Colorado 270. White 2 Colorado 271. Colorless 4-5 2 -5 Greenland 272. 273. Blue Blue 3 3-5 Cornwall Arizona J Copper 274. Blue 4 3 Sweden Yttrium 218 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form V. OXIDES i. Oxides of Silicon 27 <. Ouartz SiO 2 Hexag 276. Star quartz SiO 2 Hexag 277. Amethyst SiO 2 Hexag 278. Rose quartz 2 79 Citrine Si0 2 SiO 2 Hexag. HcxaAbrasives 32^. Colorless 3-7 California Drugs O 3 326. White 2-5 3-8 Portugal Arsenic 327- 328. White White 2 2-5 5-3 5 Quebec New Brunswick ^Antimony -22Q, Straw yellow 4 -2 Cornwall Bismuth O V* 330- White 2 ^ O 5-9 Boulder, Colo. Tellurium 331- Straw yellow I 4-5 Pennsylvania Molybdenum 332. Yellow North Carolina Tungsten OO * 333- 334- Yellow Yellow 4 4 4 5 Spain Arkansas >Antimony 335- Red 3-5 5-8 W. United States 1 336. Red 3-5 5-8 Arizona Copper 337- Brown 3-5 5-8 Arizona J 338. Colorless i o.-9 Cold regions Ice 339- Grayish 6 3-6 Sweden Magnesium 340. Green 5 5 Sweden Manganese 34i. Green 5 6 Johanngeorgen- stadt Nickel 342. Red 4 5 New Jersey Zinc 343- Yellow 2 8 Mexico Lead 344. 345- Black Black 3 5 5-8 5-8 Tennessee Arizona > Copper . 346. Various 9 4 Appalachians Abrasives 347- 348. Blue Red 9 9 4 4 Ceylon Upper Burma JGems 349- Black 9 4 New York Abrasives 350- Red 6 5 New York 35 1 - Black 6 5 Elba 352. Brownish red 6 5 New York Iron 353- Red 3 5-4 Minnesota 354- Brownish black 3 3 Minnesota 355- 356. Iron black Iron black 6 5 4-8 4-5 East U.S. East U.S. Jlron 357- Red 5 4-5 Sweden Manganese 358. Red 8 3-5 New York ) 359- Red 8 3-6 New York ^Gems 360. Brown 8 3-5 New York I 222 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form V. OXIDES continued 361. Chlorospinel MgO-(Al,Fe) 2 O 3 Regular 362. Picotite-chrome spinel 363. Hercynite (Mg,Fe)0-(Al,Fe,Cr)A FeAl 2 O 4 Regular Regular 3 64 Ga.hn.ite ZnAl 2 O 4 Regular 365. Automolite 366 Dysluite ZnAl 2 O 4 (Zn,Fe,Mn)0 (Al,Fe) 2 O 3 Regular Regular 367 Kreittonite (ZnFe,Mg)O(Al,Fe) 2 O 3 Regular 368 Miagnetite FeO-Fe 2 O 3 Regular 360 Franklinite (Fe,Zn,Mn)O- (Fe,Mn) 2 O 3 Regular 370. Magnesioferrite 371. Jacobsite 372 Chromite MgFeO 4 (Mn,Mg)0-(Fe,Mn) 2 3 FeO-Cr 2 O 3 Regular Regular Regular 3 7 ? Chrvsoberyl . BeAl 2 O 4 Hexag. 374 Alexandrite BeAl 2 O 4 Hexag. ?7c Cat's eve BeAl 2 O 4 Hexag. 176 Hausmannite Mn 3 O 4 Tetrag. 377 JVlinium Pb 3 O 4 Powder. 378 Crednerite Cu 3 Mn 4 O 9 Mono. 379 Pseudobrookite Fe 4 (TiO 4 ) 3 Ortho. 380 Braunite 3Mn 2 O 3 -MnSiO 3 Tetrag. 381 Bixbyite FeO-MnO 2 Regular d. Dioxides 382 Cassiterite SnO 2 Tetrag. 383 Stream tin SnO 2 Tetrag. 384 Polianite . . MnO 2 Tetrag. 385 Rutile TiO 2 Tetrag. 386 Nigrine TiO 2 (+2%Fe 2 O 3 ) Tetrag. 387 Ilmenorutile TiO 2 (+io%Fe 2 O 3 ) Tetrag. 388 Plattnerite PbO 2 Tetrag. 380 Baddeleyite ZrO 2 Mono. 390 Octahedrite TiO 2 Tetrag. ?QJ Brookite .... TiO 2 Ortho. 392 Pyrolusite MnO 2 Amorph. e. Hydrous Oxides ao3 DiasDore A1 2 O 3 -H 2 O Ortho. 394 Goethite Fe 2 O 3 -H 2 O Ortho. ?o< M^antranite Mn 2 O 3 -H 2 O Ortho. 396 Limonite 2Fe 2 O 3 -3H 2 O Amorph. 3O7 Bo ore 2Fe 2 O 3 -3H 2 O Amorph. 398. Clay ironstone OQQ Turgite 2 Fe 2 O 3 -3H 2 O 2Fe 2 O 3 -H 2 O Amorph. Amorph. 400. Xanthosiderite 401 Bauxite Fe 2 O 3 -2H 2 O A1 2 O 3 2H 2 O Amorph. Grains 402 ^^ocheinite . . A1 2 O 3 -2H 2 O Grains 403 Brucite MgO-H 2 O Hexag. 404 Pyrochroite MnO-H 2 O Hexag. 40 'C Gibbsite A1 2 O 3 -H 2 O Mono. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 223 No. Color Hard- ness Gravity Locality Chief Constituent or Use 36l Green 8 3-5 New York Gems 362! Brown 8 4 N.Y. and N.J. 363- Black 7-5 3-9 Ronsberg Iron 364- Green 7-5 4 New Jersey 365- Green 7-5 4 Sweden 366. Brown 7-5 4 Pennsylvania Zinc 367. Black 7 4 Brazil 368. Iron black 5-5 5 Adirondacks Iron Black 6 5 New Jersey Zinc 37- Iron black 6 4-5 Vesuvius Magnesium Black 6 4-7 Sweden Manganese 372. Black 5-5 4-5 W. United States Chromium 373- Green 8-5 3-5 Urals 374- Green 8-5 3-6 Urals Gems 375- Greenish 8-5 3-6 Ceylon 376. Black 5 4.8 Sweden Manganese 377- Red 2 4.6 Baden Lead 378. Iron black 4-5 4-9 Friedrichsrode Manganese 379- Dark brown 6 4 Transylvania Titanium 380. Dark brown 6 4-7 Hartz Manganese 381- Black 6 4-9 Utah Iron 382. Black 7 7 Malay Peninsula \ Tin 383- Black 7 7 Malay Peninsula > jLin 384. Steel gray 6 4-9 Bohemia Manganese 385- Red 6-5 4 Arkansas I 386. Black 6-5 4 Arkansas ^Titanium 387. Black 5 Ilmen Mts. J o / 388. Iron black 5-5 8-5 Idaho Lead 389. Colorless 6-5 5-5 Ceylon Zirconium 39- 39 1 - Brown Brown 5 5-5 3-8 3-8 Rhode Island Arkansas >Titanium 392. Black 2 4-7 Alabama Manganese 393- White 6-5 3 North Carolina Aluminum 394- Brown 5 4 Pa., Colorado Iron 395- Black 4 4 Colorado Manganese 396, Brown 5-5 3-8 Minnesota 397- Brown 2 3-8 Minnesota 398. Brown 2 3-8 Widespread Iron 399- Brown 2 4-1 Connecticut 400. Yellow 2-5 4-1 Hartz Mts. 401. 402. Gray Gray 3 3 2-5 2-5 Arkansas Carniola JAluminum 403- White 2-5 2 New York Magnesium 404. White 2-5 3-2 New Jersey Manganese 405- White 2.5 2 New York Aluminum 224 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form V. OXIDES continued 406. Sassolite B 2 O 3 -3H 2 O Triclin 407. Hydro talcite Al 2 O 3 -6MgO-isH 2 O Hexag. 468. Pyroaurite FeA-aMgO-isHaO Hexag. 409. Chalcophanite (Mn,Zn)O 2MnO 2 2H 2 O Hexag. 410. Psilomelane 411. Wad H 4 MnO s H 4 MnO s -H 2 O Massive Amorph 412. Bog manganese H 4 MnO 5 -H 2 O Amorph. 413. Asbolite H 4 MnO 5 -H 2 O-CoO Amorph. 414 Lampadite H 4 MnO s H 2 O (Co Cu) O Amorph. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 225 No. Color Hard- ness Gravity Locality Chief Constituent or Use 406. 407. 4.08 White White White I 2 1-4 2 California Norway Sweden Boric acid JMagnesium 409. 410. 411. 412. 413- 414. Iron black Iron black Black Black Black Black 2-5 6 6 6 3-9 4 3 3 3 New Jersey Arkansas Germany Germany Germany Germany Manganese 226 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form VI. CARBONATES i. Anhydrous 415. Calcite 416. Dog-tooth spar 417. Nail-head spar 418. Iceland spar 419. Fontainebleau lime- stone 420. Satin spar 421. Argentine 422. Aphrite 423. Saccharoid. limestone. 424. Shell marble 425. Lumachelle 426. Ruin marble 427. Lithographic stone. . . 428. Hydraulic limestone. . 429. Chalk 430. Oolite 431. Pisolite 432. Stalactite 433. Stalagmite 434. Calc sinter 435. Travertine 436. Agaric mineral 437. Rock meal 438. Thinolite 439. Dolomite 440. Magnesite 441. Breunnerite 442. Mesitite 443. Pistomesite 445. . Siderite 446. Spherosiderite 447. Rhodochrosite 448. Smithsonite 449. Sphaerocobaltite 450. Aragonite 451. Flos fern 452. Tarnowitzite . . . '. . . . . 453. Witherite 454. Bromlite 455. Strontianite 456. Cerussite 457. Barytocalcite 458. Bismutospharite 459. Parisite 460. Bastnasite 461. Phosgenite 462. Northupite CaCO 3 CaC0 3 CaC0 3 CaC0 3 CaC0 3 CaC0 3 CaC0 3 CaC0 3 CaC0 3 CaC0 3 CaCO 3 CaC0 3 CaC0 3 CaCO 3 , also SiO 2 ,Al 2 O 3 , etc. CaC0 3 CaC0 3 CaCO 3 CaC0 3 CaC0 3 CaC0 3 CaC0 3 CaC0 3 CaCO 3 CaCO 3 (Ca,Mg)C0 3 MgC0 3 MgC0 3 -H 2 2MgC0 3 -FeCO 3 MgCO 3 -FeCO 3 FeCO 3 FeC0 3 MnC0 3 ZnC0 3 CoC0 3 CaC0 3 CaC0 3 CaC0 3 -PbCO 3 BaC0 3 (Ba,Ca)CO 3 SrC0 3 PbC0 3 BaCO 3 -CaCO 3 Bi 2 (CO 3 ) 3 -2Bi 2 O 3 (CaF)(CeF)Ce(C0 3 ) 3 (PbCl) 2 C0 3 MgC0 3 -Na 2 CO 3 -NaCl Hexag. Hexag. Hexag. Hexag. Hexag. Hexag. Lamellar Lamellar Crypto. Shelly Chatoy. Brecci. Massive Massive Massive Granular Grains Cylind. Cylind. Incrust. Incrust. Grains Grains Grains Hexag. Hexag. Hexag. Hexag. Hexag. Hexag. Concret. Hexag. Hexag. Hexag. Ortho. Stalact. Stalcat. Ortho. Ortho. Ortho. Ortho. Mono. Spherical Hexag. Hexag. Tetrag. Regular COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 227 No Color Hard- ness Gravity Locality Chief Constituent or Use 4I5- Colorless 3 2-7 Ubiquitous V 416. Colorless 3 2-7 Missouri ^Calcium 417. Colorless 3 2-7 Missouri I 418. Colorless 3 2.7 Iceland Prisms 419. Colorless 3 2.7 France 420. Colorless 3 2-7 France 421. White 3 2-7 France 422. White 3-5 2.7 France 423- Yellow 3 2-7 France 424. Yellow 3 2-7 Carinthia 425. Dark brown 3 2-7 France 426. Brown 3 2.7 Italy 427. Buff' 3 2-7 Solenhofen 428. 429. Buff White 3 3 2-7 2.7 Virginia England Calcium 430- White 3 2.7 Missouri 43 1 - White 3 2.7 Missouri 432. White 3 2-7 Kentucky 433- White 3 2-7 Kentucky 434- White 3 2.7 Yellowstone Park 435- White 3 2-7 Tivoli 436. White 3 2.7 Caverns 437- White 3 2-7 Paris 438. Yellow 3 2-7 Nevada 439- White 3-5 2.8 Illinois Building 440. Colorless 4 3 Greece | 441. 442. White Yellowish 4 3-5 3 3 Massachusetts Traversella >Magnesium 443- Yellowish 3-5 3 Traversella j 445- 446. Gray Brown 3-5 3-5 3-8 3-8 Germany E. United States Jlron 447- Red 4 3 Colorado Manganese 448. White 5 4 Pennsylvania Zinc 449. Red 4 4 Saxony Cobalt 450. Colorless 3-5 2.9 New York, Illinois 451. White 3-5 2.9 New York, Illinois Calcium 452. White 2 .0 Silesia 453- 454- Colorless White 3-5 4 V 4-2 3-7 England England JBarium 455- Colorless 3-5 3-7 New York Strontium 456: Colorless 3-5 6 Cordilleras Lead 457- White 4 3-6 Cumberland Barium 458. Yellow 3 7 Saxony Bismuth 459- Yellow 4-5 4 Colombia Cerium 460. Yellow 4 4-9 Colorado Lanthanum 461. White 2.7 6 England \T Aorl 462. White California f-ueau 1 228 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form VI. CARBONATES continued 2. Hydrous 463. Teschemacherite HNH 4 CO 3 Ortho 464. Malachite CuCO 3 -Cu(OH) 2 Mono 465. Azurite 2CuCO 3 -Cu(OH) 2 Mono 466. Chessylite 2CuCO 3 -Cu(OH) 2 Mono. 467. Aurichalcite 2(Zn,Cu)CO 3 *3(Zn,Cu)(OH) 2 Mono. 468. Hydrozincite 469. Hydrocerussite 470. Dawsonite ZnC0 3 -2Zn(OH) 2 2PbCO 3 -Pb(OH) 2 Na 3 Al(CO 3 ) 3 2 A1(OH) 3 Earthy Hexag. Mono 471. Thermona trite Na 2 CO 3 -H 2 O Ortho. 472. Nesquehonite MgCO 3 -3H 2 O Ortho. 473 Natron Na 2 CO 3 -ioH 2 O M!ono 474. Pirssonite CaCO 3 Na 2 CO 3 2H 2 O Ortho 475. Gaylussite 476. Lanthanite CaOVNa 2 C0 3 - 5 H 2 La 2 (CO 3 ) 3 -9H 2 O Mono. Ortho. 477. Trona Na 2 CO 3 HNaCO 3 2H 2 O Mono. 478. Hydromagnesite 479. Hydrogioberite 480. Lansfordite 3MgC0 3 -Mg(OH) 2 -3H 2 MgC0 3 -Mg(OH) 2 - 2 H 2 3MgCO 3 Mg( OH) 2 2 iH 2 O Amorph. Compact Triclin. 481. Zaratite NiCO 3 -2Ni(OH) 2 -4H 2 O Stalact. 482. Remingtonite CaCO 3 -H 2 O Incrust. 483. Tengerite YCO 3 -H 2 O Pulver. 484. Bismutite Bi 2 O 3 -CO 2 -H 2 O Amorph. 485. Uranothallite 486. Liebigite 2CaCO 3 -U(CO,) 2 -ioH 2 O CaCO 3 (UO 2 ) CO 3 2oH 2 O Ortho. Concret. 487. Voglite (UCa Cu)Co 3 -H 2 O Scales COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 229 No. Color Hard- ness Gravity Locality Chief Constituent or Use 463- Yellow 1-5 1-4 Africa Lead 464. Green 3-5 4 Arizona I 465- Blue 3-5 3-7 Arizona [Copper 466. Blue 3-5 3-7 France J 467. Green 2 3-5 France \ 468, White 2 3-5 Pennsylvania jZinc 469. Colorless 2 6 Sweden Lead 470. 471. White White 3 i 2 Tuscany Nevada >Aluminum 472. Colorless 2-5 1.8 Pennsylvania Magnesium 473- 474- Gray Colorless i 3-5 2-3 Egypt California (Sodium 475- White 2-3 1.9 Utah 476- White 2-5 2.6 Pennsylvania Lanthanum 477- Gray 2-5 2 Nevada Sodium 478. White 3-5 2 New Jersey ] 470- Gray 2 Italy [Magnesium *T / V 480. White 2-5 Pennsylvania 481. Green 3 2 Texas Nickel 482. Rose 2 Maryland Cobalt 483. White Texas Ytterium 484. White 4 6.8 South Carolina Bismuth 485- Green 2 Bohemia | 486. Green 2 Joachims thai [Uranium 487. Green Joachims thai *t?f / / 230 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form VII. SILICATES i. Anhydrous a. Disilicates 488. Petalite LiAl(Si 2 O s ) 2 Mono 489. Milarite HKCa 2 Al 2 (Si 2 O s )6 Hexag 490. Eudidymite HNaBeSijOg Mono 49 1 Epididymite HNaBeSi 3 O 8 Ortho 492. Orthoclase KAlSijOs IVIono 493 . Adularia KAlSijOg Mono 494. Valencianite KAlSi 3 O 8 IVIono 495. Sanidine KAlSijOg JVIono 496. Rhyacolite KAlSi 3 O 8 JVIono 497. Loxoclase KAlSijOg 7Na 2 O Mono 498. Murchisonite KAlSi 3 O 8 Mono. 499. Perthite KAlSi 3 O 8 Mono 500. Hyalophane (K 2 Ba)Al 2 (SiO 3 ) 4 Mono 501. Microcline KAlSi 3 O 8 Triclinic 502. Amazonstone . KAlSi 3 O 8 Triclinic 503. Chesterlite KAlSi 3 O 8 Triclinic 504. Anorthoclase KAlSi 3 O 8 Triclinic 505. Albite NaAlSi 3 O 8 Triclinic 506. Peristerite NaAlSi 3 O 8 Triclinic 507. Pericline NaAlSi 3 O 8 Triclinic 508. Cleavelandite NaAlSi 3 O 8 Triclinic 509. Oligoclase *Ab 3 Ani Triclinic 510. Sunstone *Ab 3 Aih Triclinic 511. Andesine *Ab 3 An t Triclinic 512. Labradorite *AbjAn z Triclinic 513 Maskelynite *Ab 3 Ani Grains 514. Anorthite CaAl 2 Si 2 O 8 Triclinic 515. Indian! te CaAl 2 Si 2 O 8 Triclinic 516. Cyclopite CaAl 2 Si 2 O 8 Triclinic 517. Celsian BaAl 2 Si 2 O 8 Triclinic b. Metasilicates 518. Leucite KAl(SiO 3 ) a Ortho. 519. Pollucite H 2 Cs 4 Al 4 (SiO 3 )9 Regular 520. Enstatite MgSiO 3 Ortho. 521. Chladnite MgSiO 3 Ortho. 522. Bronzite MgSiO 3 Ortho. 523. Hypersthene (Fe,Mg)SiO 3 Ortho. 524. Bastite (Fe,Mg)SiO 3 Ortho. 525. Peckhamite 2(Mg Fe)SiO 3 -(Mg,Fe)SiO 4 Ortho. 526. Pyroxene Ca(Mg,Fe)Si 2 O6 (Mg,Fe) (AlFe) 2 Si 2 O6 Mono. 527. Diopside CaMg(SiO 3 ) 2 Mono. 528. Malacolite CaMg(SiO 3 ) 2 Mono. 529. Alalite CaMg(SiO 3 ) 2 Mono. 530. Traversellite CaMg(SiO 3 ) 2 Mono. 53 1 . Violan CaMg(SiO 3 ) 2 Mono. * Ab = Albite ; An = Anorthite. COMPREHENSIVE LIST Of* MINERALS LIST OF MINERALS 231 No. Color Hard- ness Gravity Locality Chief Constituent or Use 488. Colorless 6 2 Massachusetts Lithium 489. Colorless 5 2-5 Switzerland. Potassium 490. White 6 2-5 Norway 491. White 5-5 3-5 South Greenland 492. Colorless 6 2-5 California 493- Colorless 6 2-5 Switzerland 494. Colorless 6 2-5 Valencia 495- Colorless 6 2-5 Valencia 496. Colorless 6 2.5 Monte Somma 497- Colorless 6 2.5 New York 498. Red 6 2.5 England 499- Red 6 2-5 Ontario 500. Red 6 2.8 Sweden 501. White 6 2.5 Pike's Peak 502. White 6 2.5 Pike's Peak SOS- 504. White White 6 6 2.5 2-5 Pennsylvania Pennsylvania Rock forming 505- White 6 2.6 E. United States 506. White 6 2.6 E. United States So?- White 6 2.6 E. United States 508. Bluish 6 2.6 New Hampshire 509- White 6 2.6 New York 510. White 6 2.6 Norway SIL White 5 2.6 Rocky Mts. 512. Gray 5 2.7 New York 5 J 3- Colorless 5 2.7 Meteorites Si4. White 6 2.7 Mt. Vesuvius 5i5- White 6 2-7 India 516. White 6 2.7 Cyclopean Island 5i7. Colorless 6 3 Sweden 518. Colorless 5-5 2.5 Vesuvius Si9. White 6-5 2.9 Maine 520. Gray 5-5 3 New York 521. Gray 5-5 3 Meteorites 522. Green 5-5 3 New York 523- Brownish green 5 3 New York 524- 525- Green Yellow 3-5 2-5 3-2 Hartz Meteorites Rock forming 526. White 5 3 Igneous rocks 527- Light green 5-5 3-3 Igneous rocks 528. Light green 5-5 3-3 Sweden 529- Green 5-5 3-3 Piedmont 530. Green 5-5 3-3 Traversella 531- Blue 5-5 3-3 Italy 232 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form VII. SILICATES continued 532. Canaanite 533. Lavrovite 534. Hedenbergite 535. Sahlite 536. Baikalite 537. Coccolite 538. Diallage ." 539. Omphacite 540. Schefferite 541. Jeffersonite 542. Augite 543. Leucaugite 544. Fassaite 545. Acmite 546. Spodumene 547. Hiddenite 548. Jadeite 549. Chloromelanite 550. Nephrite 551. Wollastonite 552. Pectolite 553. Rosenbuschite 554. Wohlerite 555. Lavenite 556. Rhodonite 557. Bustamite 558. Fowlerite 559. Babingtonite 560. Hiortdahlite 561. Anthophyllite 562. Gedrite 563. Amphibole 564. Tremolite 565. Actinolite 566. Nephrite 567. Asbestus, amianthus. . 568. Mountain leather . . . . 569. Mountain cork 570. Smaragdite 571. Uralite 572. Cummingtonite 573. Dannemorite 574. Griinerite 575. Richterite 576. Breislakite 577. Hornblende..... 578. Edenite 579. Koksharovite 580. Pargasite CaMg(Si0 3 ) 2 CaMg(Si0 3 ) 2 CaFe(SiO 3 ) 2 CaFe(SiO 3 ) 2 CaFe(Si0 3 ) 2 CaFe(Si0 3 ) 2 CaFe(SiO 3 ) 2 CaFe(SiO 3 ) 2 CaMg(Fe,Mn)(SiO 3 ) 2 Like schefferite+Zn CaMg(Si0 3 ) 2 CaMg(Si0 3 ) 2 CaMg(Si0 3 ) 2 NaFe(Si0 3 ) 2 LiAl(Si0 3 ) 2 LiAl(SiO 3 ) 2 NaAl(SiO 3 ) 2 NaAl(SiO 3 ) 2 NaAl(SiO 3 ) 2 CaSiO 3 HNaCa 2 (Si0 3 ) 3 6CaSiO 3 - 2Na 2 ZrO 2 F 2 - (TiSiO 3 TiO 3 ) Ca IO Na 5 Fe 3 Nb 2 Zr 3 Sii O 42 (Na,Ca,Mn,Fe) (F,Zr,O)Si 2 O 6 MnSiO 3 Like rhodonite +Fe,Ca Like rhodonite+Fe,Ca,Zn (Ca,Fe,Mn)Si0 3 (Na 2 ,Ca)(Si,Zr)0 3 (Mg,Fe)Si0 3 Like anthophyllite+Al CaMgFe[MnNa 2 K 2 H 2 (SiO 3 ) 4 ] CaMg 3 (Si0 3 ) 4 Like tremolite+Fe CaMg 3 (Si0 3 ) 4 CaMg 3 (Si0 3 ) 4 CaMg 5 (Si0 3 ) 4 CaM g3 (Si0 3 ) 4 CaMg 3 (Si0 3 ) 4 CaMg 3 (Si0 3 ) 4 Like actinolite+Mg Like actinolite+Mn FeSiO 3 (K 2 ,Na 2 ,Mg,Ca,Mn,Fe) 4 (Si0 3 ) 4 (K 2 ,Na 2 ,Mg,Ca,Mn) 4 (Si0 3 ) 4 Ca(MgFe) 3 Si0 3 ) 4 - CaMg 2 Al 2 (Si0 4 ) 3 Ca(MgFe) 3 Si0 3 ) 4 - CaMg 2 Al 2 (Si0 4 ) 3 Ca(MgFe) 3 Si0 3 ) 4 - CaMg 2 Al 2 (Si0 4 ) 3 Ca(MgFe) 3 Si0 3 ) 4 - CaMg 2 Al 2 (SiO 4 ) 3 Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Mono. Triclinic Triclinic Triclinic Triclinic Triclinic Ortho. Ortho. Mono. Mono. Mono. Compact Fibrous Fibrous Fibrous Fibrous Fibrous Fibrous Fibrous Fibrous Fibrous Fibrous Mono. Mono. Mono. Mono. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 233 No. Color Hard- ness Gravity Locality Chief Constituent or Use S3 2 - Gray 5- 3-3 Connecticut 533- Green 5- 3-3 East Siberia 534- Black 5- 3-5 Sweden 535- Green 5- 3-5 Sweden 536. Green 5- 3-5 Siberia 537- Dark green 4 3 Mountains 538. Green 4 3 Mountains 539- 540. Brown Brown 4 4 3 3 Mountains Mountains Rock forming 541- Dark 6 3 New Jersey 542. Green 5-5 3-3 E. United States 543- White 6-5 3 E. United States 544- Green 6-5 3 Vesuvius 545- Gray 6 3-5 Colorado 546. Green 6-5 3 Massachusetts 547- Green 6-5 3 Massachusetts 548. Green 6-5 3 Asia Ornaments 549- Dark green 6-5 3 Asia Rock forming 550. Green 6-5 3 Asia Ornaments 55 1 - White 4-5 2.8 New York 552. White 5 2.6 New Jersey 553- White 5 2.6 Norway Rock forming 554- Yellow 5-5 3-4 Norway 555- Yellow 6 3-5 Norway 556. Red 6 3-5 Russia 557- Red 6 3-5 Mexico 558. Red 6 3-5 New Jersey Ornaments 559- Black 5-5 3 Norway 560. Yellow 5-5 3 South Norway 561. Brown 5-5 3 North Carolina 562. Brown 5-5 3 North Carolina 563. Green 5 2-9 Mountains Rock forming 564. Gray 5 2-9 Mountains 565- Green 5 3 Mountains 566. Green 6 2-9 Mexico Ornaments 567- Gray 3 2-9 Mountains ) 568. Gray 3 2-9 Mountains Cloth 569- Gray 3 2-9 Mountains J 570. Green 3 2.9 Alps . 571- Green 3 2.9 Alps 572. Gray 3 3 Massachusetts 573- Brown 3 3 Sweden 574- Brown 3 3-7 Sweden 575- Brown 3 3-7 Sweden Rock forming 576. Brown 3 3-7 Vesuvius 577- Black 5-5 3 Vesuvius 578. Gray 5-5 3 New York 579- Gray 5-5 3 New York 58o. Green 5-5 3 Finland 234 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form VII. SILICATES continued 581. Kataforite Ca(MgFe) 3 (SiO 3 ) 4 - CaMg 2 Al 2 (SiO 4 ) 3 Mono. 582. Kupfferite Ca(MgFe) 3 (SiO 3 ) 4 CaMg 2 Al 2 (SiO 4 ) 3 Mono. 583. Syntagma tite Ca(MgFe) 3 (SiO 3 ) 4 -CaMg 2 Al 2 (SiO 4 ) 3 Mono. 584. Bergamaskitc Ca(MgFe) 3 (SiO 3 ) 4 -CaMg 2 Al 2 (SiO 4 ) 3 Mono. 585. Kaersutite .... .(-Mg) m Like amphibole-|-Ti Mono. 586. Hastingsite Contains much Na Mono. 587. Glaucophane NaAl(SiO 3 ) 2 - (Fe,Mg)SiO 3 Mono. 588 Gastaldite NaAl(SiO 3 ) 2 - (Fe Mg)SiO 3 Mono. 5880 Riebeckite 2NaFe(SiO 3 ) 2 -FeSiO 3 Mono. 589. Crocidolite NaFe(SiO 3 ) 2 -FeSiO 3 Mono. 590. Abriachanite NaFe(SiO 3 ) 2 -FeSiO 3 Amor. 5Qoa. Arfvedsonite . . 4Na 2 O 3CaO i4FeO (Al,Fe) 2 3 2 iSiO 2 Mono. 591. Crossite Like arfvedsonite+Na Mono. 592. Barkevikite Like arfvedsonite+Na 593. Aenigmatite Na 4 Fe,,AlFe(SiTi)i 2 O 3 8 Triclinic ^94. Beryl. . Be 3 Al 2 Si6Oi 8 Hexag. 595. Emerald. Be 3 Al 2 Si6Oi8 Hexag. 596. Aquamarine BejAlaSieOig Hexag. 597. Davidsonite . . . Be 3 Al 2 Si6Oi8 Hexag. 598. Eudialyte Na I3 (Ca,Fe) 6 Cl(Si,Zr) 20 O S2 Hexag. 599. Eucolite Na I3 (Ca,Fe) 6 Cl(Si,Zr) 2 oO s2 Hexag. 600. Elpidite Na 2 O ZrO 2 6SiO 2 3H 2 O 601. Catapleiite H 4 (Na 2 ,Ca)ZrSi 3 On Hexag. 602 Cappelenite 3BaSiO 3 2Y 2 (SiO 3 ) 3 sYBO 3 Hexag. 603. Melanocerite i2(H 2 Ca)SiO 3 -3(Y,Ce)BO 3 -2H 2 (Th,Ce) Hexag. 604. Caryocerite O 2 F 2 -8(Ce,La,Bi)OF 6(H 2 ,Ca)Si0 3 2 (Ce,Da,Y)BO 3 3H 2 (Ce, Hexag. 605. Streenstrupine 606. Tritomite Th)0 2 F 2 - 2 LaOF Ti,Th,Ce^,La,Di,Al,Fe,Mn,Ca,Na,H, silicate 2(H 2 Na 2 Ca)SiO 3 - (Ce,La,Di,Y)BO 3 - Hexag. 607. Leucophanite H 2 (Ce,Th,Zr)0 2 F Na(BeF)Ca(SiO 3 ) 2 Hexag. Ortho. 608. Meliphanite NaCa 2 Be 2 FSi 3 Oi Tetrag. 609. lolite H 2 (Mg,Fe) 4 Al8Sii O 37 Ortho. 610. Bonsdorffite 611. Fahlunite . . . H 2 (Mg,Fe) 4 Al8Sii O, 7 , altered H 2 (Mg,Fe) 4 Al 8 Sii O 37 , altered Ortho. Ortho. 612. Pyrargillite H 2 (Mg,Fe) 4 Al8SiioO 37 , altered Ortho. 613. Esmarkite H 2 (Mg,Fe) 4 Al 8 Si IO O 37 , altered Ortho. 614. Raumite H 2 (Mg,Fe) 4 Al 8 Sii O 37 , altered Ortho. 615 Chlorophylli te H 2 (Mg,Fe) 4 Al8Sii O 37 , altered Ortho. 6 1 6. Aspasiolite H 2 (Mg,Fe) 4 AlSiioO 37 , altered Ortho. 617. Polychroilite 618. Barysilite H 2 (Mg,Fe) 4 Al8Si I0 37 , altered Pb 3 Si 2 O 7 Ortho. 619. Ganomalite Pb 3 Si 2 O 7 -(Ca,Mn) 2 SiO 4 Tetrag. (Pb Ba Ca) B 2 (SiO 3 )i 2 621 Barylite Ba 4 Al 4 Si 7 O 24 622 Roeblingite 5(H 2 CaSiO 4 ) 2(CaPbSO 4 ) c. Orthosilicates 623 Nephelite K 2 Na 6 AlSi 9 O 24 Hexag. 624 Elaeolite K 2 Na 6 AlSi 9 O 24 Hexag. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 235 No. Color Hard- ness Gravity Locality Chief Constituent or Use 58i. Green 5-5 3 Norway 582. Deep green 5-5 3 Tunkinsk Mts. 583. Black 5-5 3 Vesuvius 584. Black 5-5 3 Italy 585. Brown 5 3 North Greenland 586. Brown 5 3 Ontario 587. 588. Blue Blue 6 6 3 3 California Corsica Rock forming 5880. Black 6 3 Ireland 589- Blue 4 3 Rhode Island 59- Blue 4 3 Scotland SQoa. Black 6 3 Colorado 59 1 - Black 6 3 California 592. Black 6 3 Southern Norway CQ2 Black a Southern Norway oVO* 594- Green 7-5 2.6 E. United States ) 595- Green 7-5 2.6 E. United States ^Gems 596. Green 7-5 2.6 E. United States / 597- Green 7-5 2.6 Scotland . 598. Red 5 2.9 Western Greenland 599- Red 5 2.9 Norway 600. 2 S South Greenland 601. Yellow 6 o 2.8 Norway 602. Brown 6 4.4 Norway 603. Brown 6 4 Norway 604. Brown 6 4 Norway 605. Brown 4 3 Greenland 606. Brown 5 4 Norway 607. Green 4 2.9 Norway 608. Yellow 5 3 Norway Rock forming 609. Blue 7 2.6 Connecticut 610. Blue 7 2.6 Finland 611. Various 7 2.6 Sweden 612. Various 7 2.6 Helsingfors 613.- Various 7 2.6 Norway 614. Various 7 2.6 Finland 615- Various 7 2.6 Maine 616. Various 7 2.6 Kragero 617. Various 7 2.6 Kragero 618. White 3 6 Sweden 619. Colorless 3 5-7 Sweden 620. White 5 3-8 Sweden 621. Colorless 7 4 Sweden 622. White 3 3 New Jersey 623. 624. Colorless Brown 5 5 2-5 2-5 Vesuvius Maine rRock forming 236 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form VII. SILICATES continued 625. Gieseckite 626. Eucryptite , 627. Kaliophilite 628. Cancrinite 629. Microsommite 630. Sodalite 631. Haiiynite 632. Noselite 633. Lazurite 634. Helvite 635. Danalite 636. Eulytite 637. Zunyite 638. Garnet 639. Grossularite 640. Cinnamon-stone .... 641. Hyacinth 642. Succinite 643. Romanzovite 644- Pyrope 645. Rhodolite 646. Almandite 647. Spessartite 648. Andradite 649. Topazolite 650. Demantoid 651. Colophonite 652. Melanite 653. Pyreneite 654. Rothoffite 655. Allochroite 656. Polyadelphite 657. Bredbergite 658. Aplome 659. Titaniferous garnet. . 660. Yttergranat 661. Uvarovite 662. Schorlomite 663. Partschinite 664. Agricolite 665. Chrysolite 666. Olivine 667. Hyalosiderite 668. Iddingsite 669. Monticellite 670. Forsterite 671. Hortonolite K 2 Na 6 Al 8 Si 9 O 24 -nH 2 O LiAlSi0 4 KAlSiO 4 H 6 Na6Ca(NaC0 3 ) 2 Als(SiO 4 ) 9 (Na,K)i Ca 4 Al I2 Si I2 O S2 SCl 4 Na 4 (AlCl)Al 2 (SiO 4 ) 3 Na 2 Ca 2 (NaSO 4 -Al)Al 2 (SiO 4 ) 3 Na 4 (NaSO 4 -Al)Al 2 (Si0 4 ) 3 Na 4 (NaS 3 -Al)Al 2 (Si0 4 ) 3 (Mn,Fe) 2 (Mn 2 S)Be 3 Si0 4 ) 3 (Fe,Zn,Mn) 2 [(Zn,Fe) 2 S]Be 3 (Si0 4 ) 3 Bi 4 (Si0 4 ) 3 (Al(OH,F,Cl) 2 ) 6 Al 2 (Si 6 4 ) 3 II III R 3 R 2 (SiO 4 ) 3 Ca 3 Al 2 (Si0 4 ) 3 Ca 3 Al 2 (Si0 4 ) 3 Ca 3 Al 2 (Si0 4 ) 3 Ca 3 Al 2 (Si0 4 ) 3 Ca 3 Al 2 (Si0 4 ) 3 M g3 Al 2 (Si0 4 ) 3 Mg 3 Al 2 (Si0 4 ) 3 Fe 3 Al 2 (SiO 4 ) 3 Mn 3 Al 2 (Si0 4 ) 3 Ca 3 Fe 2 (Si0 4 ) 3 Ca 3 Fe 2 (Si0 4 ) 3 Ca 3 Fe 2 (Si0 4 ) 3 Ca 3 Fe 2 (Si0 4 ) 3 Ca 3 Fe 2 (SiO 4 ) 3 Ca 3 Fe 2 (SiO 4 ) 3 (CaMg) 3 Fe 2 (SiO 4 ) 3 (Mg,Ca 3 (Fe 2 (Si0 4 ) 3 (Mg,Ca) 3 Fe 2 (Si0 4 ) 3 (Mg,Ca) 3 Fe 2 (Si0 4 ) 3 (Mg,Ca) 3 Fe 2 (Si0 4 ) 3 3 CaO- (Fe,Ti,Al) 2 3 - 3 (Si,Ti)0 2 3CaO-(Fe,Ti,Y,Al)YO 3 Ca 3 Cr 2 (SiO 4 ) 3 Ca 3 (FeTi) 2 (SiTi)0 4 ) 3 (Mn,Fe) 3 Al 2 Si 3 I2 Bi 4 Si 3 O t2 (Mg,Fe) 2 Si0 4 (Mg,Fe) 2 SiO 4 (Mg,Fe) 2 Si0 4 +Fe (Ca,Mg,Fe) 2 SiO 4 CaMgSiO 4 Mg 2 Si0 4 (Fe,Mg,Mn) 2 Si0 4 Pseudo. Hexag. Hexag. Hexag. Hexag. Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Regular Mono. Mono. Ortho. Ortho. Ortho. Ortho. Ortho. Ortho. Ortho. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 237 No. Color Hard- ness Gravity Locality Chief Constituent or Use 625. Brown 5 2.6 New York 626. Colorless 5 2.6 Connecticut 627. Colorless 6 2 Mt. Somma 628. 629. Gray Colorless 5 5 2 2 Maine Vesuvius Rock forming 630. Gray 5 2 Maine 631. Blue 5-5 2 Vesuvius 632. Grayish 5-5 2 Andernach 633. Blue 5 2 Chile Ornaments 634. Yellow 6 3 Virginia 635. Red 5-5 3 Colorado 636. Brown 4-5 6 Saxony 637. Brown 7 2.8 Colorado 638. Red 6-5 3 Mountains 639- Pale green 6-5 3-5 Ceylon 640. Brown 6-5 3-5 Ceylon 641. Brown 6-5 3-5 Ceylon 642. Yellow 6-5 3-5 Piedmont 643- 644. Brown Red 6-5 6.5 3-5 3-7 Russia Bohemia Rock forming 645- Red 6-5 3-7 North Carolina 646. Red 6-5 3-9 Pennsylvania 647. Red 6-5 4 Colorado 648. Yellow 6-5 3-8 Portugal 649. Green 6-5 3-8 France 650. Green 6-5 3-8 Mountains 651. Brown 6-5 3-8 Mountains 652. Black 6-5 3-8 Mountains 653- Black 6-5 3-8 Mountains 654- Brown 6-5 3-8 Mountains 655. Brown 6-5 3-8 Mountains 6 5 6. Yellowish brown 6-5 3-8 New Jersey ( Rock forming 657- Yellowish brown 6-5 3-7 Sala and gems 658. Brown 6-5 3-7 Siberia 659- Black 6-5 3-7 Siberia 660. Black 6-5 3-7 Norway 661. Green 7-5 3 Canada Rock forming 662. Black 7 3-8 Arkansas 663. Yellow 6-5 4 Transylvania 664. Yellow 2 Johanngeorgen . Bismuth 665. Green 6-5 3 Virginia 666. Green 6-5 3 Virginia 667. Green 6-5 3 Baden 668. Brown 2.8 California Rock forming 669. Gray 5 3 Arkansas 670. White 6 3 Vesuvius 671. Yellow 6 3-9 New York 2 3 8 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form VII. SILICATES continued 672. Fayalite Fe 2 SiO 4 Ortho 673. Knebelite (Fe,Mn) 2 SiO 4 Ortho 674. Tephroite Mn 2 SiO 4 Ortho 675. Willemite Zn 2 SiO 4 Hexag 676 Phenacite Be 2 SiO 4 Hexasr 677 Trimerite (Mn,Ca) 2 SiO 4 Be 2 SiO 4 Triclinic 678 Dioptase ... H 2 CuSiO 4 Hexaiz 679. Friedelite H 7 (MnCl)Mn 4 Si 4 Oi 6 Hexag 680. Pyrosmalite H 7 ([Fe,MnJCl) (Fe,Mn) 4 Si 4 Oi6 Hexag 681. Meionite Ca 4 AkSiRock forming 246 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form VII. SILICATES continued 8 Rock forming 8^7 Green 2 . 3 North Carolina Nickel u o / 8 5 8. Green i o 2.7 Vermont Lubricants 859. Gray i 2-5 Virginia Soapstone 860. White i 2.5 Virginia 861. White i 2-5 New York ^Lubricants 862. White 2 2 Asia Minor J 863. Green 2-5 2 Saxony Nickel f 864. Reddish 2-5 Italy Magnesium 865. 866. White Green I I 2 Scotland Verona >Rock forming 867. Green 2 2 New Jersey Fertilizer 868. Yellow 2 2 Sweden Rock forming 869. White 2 2.6 Delaware 870. White 2 2 Germany 871. White 2 2 France 872. White I 2 Illinois 873- Green 2 2 Illinois 874. White 2 2 Indiana 875. Greenish 2 2 France 876. Brown 2 2 Illinois 877- Brown 2 2 California 878. White I 2 Arkansas 879. White I 2 Argentina 880. White I 2 St. Jean Ode-Cole 881. White I 2 France 882. 883. 884. 885. White Blue White Green I 3 i 3 2.8 1.8 2 1.9 North Carolina Pennsylvania Pyrenees Alabama Brick, fire clay, pottery, and rock forming 886. Brown 5 3 Norway 887. White 3-5 1.8 New Jersey 888. Yellow 3-5 1.8 North Carolina 889. Green 2 2 New Jersey 890. Yellow 2-5 i-7 Pennsylvania 891. Yellow 2-5 i.7 France 892. Green I i-7 Saxony 893- Green I i-7 Menzenberg 894. Green I 2-3 Bohemia 895- Black 3 2-5 Sweden 896. Yellow i 2.9 New Jersey 897- Brown 3 2.8 Sweden 898. Black 3 2.6 Sweden 248 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form Vila. TlTANATES 899. Titanite CaTiSiO 5 IVIono 900. Sphene . . . CaTiSiOs M^ono 901. Ligurite CaTiSiO s Mono 902. Spinthere CaTiSiOg Mono 903. Lederite 904. Titanomorphite CaTiSiO s CaTiSiOs Mono. Mono. 905. Greenovite 906. Grothite CaTiSi0 5 CaTiSiO s Mono. M^ono 907. Keilhauite i5CaSiTiO s - (Al,Fe,Y) 2 (Si Ti)O s ]VJono 908. Guarinite CaTiSiO s Ortho 909. Tscheffkinite iSCaSiTiO s - (Al Fe Y) a (Si Ti)O s JVIassive 910. Astrophyllite (Na K)4(Fe.Mn) 4 Ti(SiO4)4 Ortho 911. Johnstrupite Ce,Ca,Na,Ti,Fe, silicate Mono. 912. Mosandrite Ce,Ca,Na,Ti,Fe, silicate Prism. 913. Rinkite Ce Ca Na Ti Fe silicate Mono 914. Neptunite Ce Ca Na Ti Fe silicate Mono 915. Perovskite 916. Knopite CaTi0 3 CaTiO 3 , much Ce Regular Regular 917. Dysanalyte 918. Geikielite 6(Ca,Fe)TiO 3 (Ca,Fe)Nb 2 O 6 MgTiO 3 Regular Missive COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 249 No Color Hard- ness Gravity Locality Chief Constituent or Use 899. Brown 5 3 Massachusetts 900. Brown 5 3 Massachusetts 901. Yellow 5 3 Massachusetts 902. Green 5 3 Massachusetts 93- Brown 5 3 Massachusetts 904. White 5 3 Massachusetts 90S- Red 5 3 Massachusetts 906. Brown 6 3 Dresden 907. Black 6-5 3-5 Norway 908. Yellow 6 3 Mt. Somma Rock forming 909. Black 5 4-5 Ilmen Mts. 910. Yellow 3 3 Colorado on. Green Norway V 912. Brown 4 2.9 Norway > 9*3- Brown 5 3 Greenland ' 914. Black 5 3 South Greenland 9*5- Yellow 5-5 4 New York 916. Black Sweden 917. Black 5 4 Baden 5 918. Black 6 4 Ceylon 250 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form VIII. NIOBATES, TANTA- LATES 919. Pyrochlore 920. Hatchettolite (G,Nb,Ti,Th,Ce,Ca,Fe,U,Mg,NaF,) O (G,Nb,Ti,Th,Ce,Ca,Fe,U,Mg,NaF ) -O Regular Regular 921. Microlite Ca 2 Ta 2 O 7 Regular 922. Pyrrhite Ca 2 Ta 2 O 7 +Nb,Ti,Ce,Na Regular 923. Fergusonite (Y,Er,Ce)(Nb,Ta)O 4 Tetrag 924. Sipylite Er Nb O 4 Tetrag. 925. Columbite-tantalite . . 926. Tapiolite (Fe,Mn)(Nb,Ta) 2 6 Fe(Ta,Nb) 2 O 6 Ortho. Regular 927. Yttro tan tali te . ... W,Sn,Y,Er,Ce,U,Fe,Ca,H,Nb, tantalate Ortho. 928. Samarskite G,Sn,W,U,Ce,Di,La,Y,Er,Fe,Mn,Ca, Ortho. 929. Annerodite H,Nb, tantalate Pyroniobate of U,Y Ortho. 930. Hielmite Y Fe Mn Ca Sn Nb tantalate Ortho 931. Aeschynite Ce Th,Fe,Ca,Nb, titanate Ortho. 032. Polvmiffnite Ce,La,Di,Fe,Ca,Nb,Zn,Sn,Th, titanate Ortho. 933. Euxenite Y,Er,Ce,U,H,Nb, titnate Ortho. 934. Polycrase G,Nb,Y,Er,Ce,U,Fe,Ta,H 2 O, titanate Ortho. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 251 No. Color Hard- ness Gravity Locality Chief Constituent or Use 919. Brown 5 4 Norway 920. Brown 4-7 North Carolina 921. Yellow 5-5 5 Massachusetts 922. Yellow Urals 923- Black 5-5 5-8 Carolinas 924. Black 6 4-8 Virginia 925. Iron black 6 5 N. England states 926. Black 6 7 Finland 927. Black 5 5-5 Sweden Rock forming 928. Black 5 5-6 North Carolina 929. Black 6 5-7 Norway 930. Black 5 5-8 Sweden 931. Black 5 4-9 Ilmen Mts. 932. Black 6 4-7 Norway 933- Black 6-5 4-9 Norway 934- Black 5 4-9 South Carolina 252 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form IX. PHOSPHATES, ARSE- NATES, ETC. i. Anhydrous 935. Xenotime YPO 4 Tetrae 936. Monazite (Ce,La,Di)PO 4 Mono 937. Berzeliite (CaMgMn) 3 As 2 Og Regular 938. Monimolite (Pb Fe Ca) 3 Sb 2 O8 939. Carminite Pb 3 As 2 O8- ioFeAsO 4 Ortho 940. Pucherite BiVO 4 Ortho 941. Triphylite LiFePO 4 Ortho 942. Lithiophilite . . . LiMnPO 4 Ortho 943 . Natrophilite NaMnPO 4 944. Beryllonite NaBePO 4 Ortho 945. Apatite (CaF,Cl)Ca 4 (PO 4 ) 3 Hexajj 946. Moroxite (CaF,Cl)Ca 4 (PO 4 ) 3 Hexajr 947. Lasurapatite (CaF,Cl)Ca 4 (PO 4 ) 3 Hexag 948. Francolite (CaF Cl)Ca 4 (PO 4 ) 3 949. Manganapatite (CaF, Cl) Ca 4 (PO 4 ) 3 + Mn Hexag. 950. Phosphorite 951. Eupyrchroite 952. Staffelite . . . . (CaF,Cl)Ca 4 (P0 4 ) 3 (CaF,Cl)Ca 4 (P0 4 ) 3 (CaF,Cl)Ca 4 (PO 4 ), Concret. Concret. Concret 953. Earthy apatite; osteo- lite Altered apatite Earthy 954. Pyromorphite (PbCl)Pb 4 (PO 4 ) 3 Hexag. 955. Polysphaerite 956. Miesite (PbCl)Pb 4 (C0 4 ) 3 +Ca (PbCl)Pb 4 (PO 4 ) 3 +Ca Hexag. Hexag. 957. Nussierite Impure polysphaerite 958. Mimetite (PbCl)Pb 4 (AsO 4 ) 3 Hexag CKQ. Campylite (PbCl)Pb 4 (AsO 4 ) 3 +P Hexag 960. Endlichite Pb s Cl(As VO 4 ) 3 Hexag. 96 1 . Vanadinite (PbCl)Pb 4 (VO 4 ) 3 Hexag. 962. Hedyphane (Pb,Ca,Ce) 4 (AsO 4 ) 3 Mono. 963. Svabite Ca(F,Cl,OH) Ca 4 (AsO 4 ) 3 Hexag. 964. Wagnerite (MgF)MgPO 4 Mono. 965. Spodiosite 966. Triplite (CaF)CaP0 4 (Fe,Mn)PO 4 Mono. Mono. 967. Talktriplite 968. Triploidite . ... (Fe,Mn,Ca,Mg)P0 4 (Fe 3 ,Mn,OH)PO 4 Mono. Mono. 969. Adelite (MgOH)CaAsO 4 Mono. 970. Tilasite (Mg,FOH)CaAsO 4 Mono. 971. Sarkinite (MnOH)MnAsO 4 Mono. 972. Herderite (CaF)BePO 4 Mono. 973. Hamlinite . . Al 3 Sr(OH) 7 P 2 O 7 Hexag. 974. Durangite 975. Amblygonite Na(AlF)AsO 4 Li(AlF)PO 4 Mono. Triclinic 2. Basic 976. Olivenite Cu 3 As 2 O 8 -Cu(OH) 2 Ortho. 977. Libethenite Cu 3 P 2 8 -Cu(OH), Ortho. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 253 No. Color Hard- ness Gravity Locality Chief Constituent or Use 935- Brown 4 4 G:orgia 936. Red 5 4-9 Connecticut 937- Yellow 5 4 Sweden 0^8 Brown 6 e Pajsberg VO 0> 939- 940. Red Brown 2-5 4 * 4 6 Nassau Saxony Rock forming 941. Gray 4-5 3 Massachusetts 942. Yellow 4-5 3 Connecticut 943- Wine yellow 4-5 3 Connecticut 944. Colorless 5-5 2.8 Maine 945- Green 5 3 Maine 946. Blue 5 3 Arendal 947- Sky blue 5 3 Siberia 948. Grayish green 5 3 England . 949- Green 5 3 Delaware Phosphorus 95- Green 5 3 Spain 95 1 - Gray 4-5 3 New York 952. Yellow 4 3 Staffel 953- Green 3-5 6-5 New York 954- Green 3-5 6-5 Pennsylvania 955- Brown 5-8 Cornwall 956. Brown 5 Bohemia 957- Yellow 5 France 958. Yellow 3-5 7 Pennsylvania Lead 959- Brown 7 Cumberland 960. Brown 2.7 6.6 Arizona 961. Red 2.7 6.6 Arizona 962. White 4 5 Sweden 963- Colorless 5 3-5 Sweden } 964. White 5 3 Austria >Rock forming 965- Ash gray 5 2.9 Sweden / 966. Gray 4 3 Connecticut 967. 968. Gray Brown 4 4-5 3-6 Horrsjoberg Connecticut Phosphorus 969. Yellow 5 3-7 Sweden 970. Yellow 5 3-7 Langban Rock forming 971. Red 4 4 Sweden ) 972. White 5 2-9 Maine ^Manganese 973- Colorless 4-5 3 Maine j 974- Orange red 3-9 Mexico Arsenic 975- White ..., 3 Maine Phosphorus 976. 977- Green Green 3 4 4 3-6 Utah Cornwall >Copper 254 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form IX. PHOSPHATES, ARSE- NATES continued 978. Tarbuttite Zn 3 P 2 8 -Zn(OH) 2 Zn 3 As 2 O 8 -Zn(OH) 2 (Pb,Zn) a (OHJVQ4 PbZnCuV 2 O 8 PbV 2 6 (Cu,Ca) 3 V 2 8 -(Cu,Ca)(OH) 2 (Pb,Fe,Mn) 3 V 2 8 -H 2 (Pb,Cu) 4 (OH) 2 V 2 8 -H 2 O (Pb,Cu) 4 (OH) 2 V 2 8 -H 2 Cu 3 As 2 O 8 -3Cu(OH) 2 Cu 3 As 2 O 8 -2Cu(OH) 2 Cu 3 P 2 O 8 -2Cu(OH) 2 Cu 3 P 2 8 . 3 Cu(OH) 2 Mn 3 As 2 O 8 -3Mn(OH) 2 Mn 3 As 2 O 8 -3Mn(OH) 2 +H 2 O FeP0 4 -Fe(OH) 3 (Fe,Mn)Al 2 (OH)P0 4 Ca 3 P 2 3 - 2 Al(OH) 2 Ca 3 Al(P0 4 ) 3 -Al(OH) 3 Ca 3 Fe(As0 4 ) 3 . 3 Fe(OH) 3 Mn 3 As 2 O 8 -4Mn(OH) 2 2 (Al,Mn) AsO 4 5Mn(OH) 2 MnAsO<-2Mn(OH) 2 (Al,Mn)As0 4 . 4 Mn(OH) 2 Mn,Ca,Ce,Li,Ca,Mg, arsenate Sb,Fe,Mn,Pb,Ca,Mg,HSP, arsenate ioMnO-(Sb,As) 2 O 5 H 2 Bi 3 AsO 8 (NH 4 )MgPO 4 -6H 2 Ca 3 P 2 O 8 -H 2 O Mg 2 P 2 O 7 4 (Ca 3 P 2 O 8 + Ca 2 P 2 O 7 ) Zn 3 P 2 8 -H 2 (Mn,Ca,Fe,Na 2 ) 3 (PO 4 ) 2 -fH 2 O Fe,Mn,Ca,Na,Li, hydrous phosphate (Ca,Co,Mg) 3 As 2 8 - 2 H 2 O Ca 2 MnAs 2 O 8 -2H 2 O Ca 2 MnP 2 O 8 -2H 2 O (Ca,Fe) 3 P 2 8 -2^H 2 Mn 3 P 2 8 - 3 H 2 (Ca,Mg) 3 As 2 8 -6H 2 Cu 3 As 2 O 8 -5H 2 O Fe 3 P 2 O 8 -8H 2 O Fe 3 As 2 O 8 -8H 2 O Mg 3 P 2 O 8 -8H 2 O Mg 3 As 2 8 -8H 2 O Co 3 As 2 O 8 -8H 2 O Triclinic Ortho. Ortho. Massive Massive Ortho. Mono. Coatings Coatings Mono. Concent. Mono. Massive Mono. Mono. Ortho. Mono. Mono. Mono. Tetrag. Mono. Mono. Ortho. Hexag. Ortho. Hexag. Ortho. Mono. Ortho. Amor. Massive Ortho. Hexag. Mono. Triclinic Triclinic Triclinic Triclinic Ortho. Ortho. Ortho. Mono. Mono. Mono. Mono. Mono. 979. Adamite 980. Descloizite 98 1 . Eusynchite 982. Dechenite 983. Calciovolborthite . . . . 984. Brackebuschite 985. Psittacinite 986. Mottramite 987. Clinoclasite 988. Erinite . 989. Dihydrite. ... 990. Pseudomalachite . . 991. Chondrarsenite 992. Xantharsenite 993. Dufrenite 994. Lazulite 995. Tavistockite 996. Cirrolite 997. Arseniosiderite 998. Allacite . . 999. Synadelphite 1000. Flinkite 1001. Hematolite 1002. Retzian 1003. Arseniopleite 1004. Manganostibiite ..... 1005. Atelestite 3. Normal Hydrous 1006. Struvite 1007. Collophanite 1008. Pyrophosphorite 1009. Hopeite 1010. Dickinsonite ion. Fillowite 1012. Roselite 1013. Brandite 1014. Fairfieldite 1015. Messelite 1016. Reddingite 1017. Picropharmacolite 1018. Trichalcite 1019. Vivianite 1 020. Symplesite . . . 1021. Bobierrite 1022. Hoernesite 1023. Erythrite COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 2 55 No. Color Hard- ness Gravity Locality Chief Constituent or Use 978. Brown 3-5 4 Rhodesia \7i nr 979- Yellow 3-5 4 Chile fZ^lIlC 980. Red 3-5 5-9 Arizona Lead 981. Red 3 5-5 Baden 982. Red 3 5-6 Bavaria 983- 084. Green Black 3 3-8 Thuringa Argentina Vanadium V T" 08 1C Green Montana VJ t 086 Black England yuw. 987. Green 2 -5 4 Cornwall 9 88. 989. Green Green 4 4-5 4 4 Cornwall Urals Copper 990. Dark green 4 3 Rheinbreitenbach 991. 002 Yellow Yellow 3 Sweden Sweden ^Manganese yy " 993- Green 3-5 3 New York Phosphorus 994. Blue 5 3 North Carolina Gems QQC. White Devonshire i yyo 996. Yellow 5 3 Sweden >Phosphorus 997- Brown i 3 France Arsenic 998. Red 4 3 Sweden 999. IOOO. Black Brown 4 4 3-8 Sweden Sweden Manganese IOOI. Red 3-5 3 Nordmark 1002. Brown 4 4 Nordmark Arsenic IOO3 Red Sweden Arsenic iv -"~'G' IOO4 Black . Sweden Manganese J. UU^.. 1005. Yellow 3 6 Saxony Bismuth 1006. White 2 1.6 Victoria Lead 1007. 1008. Colorless White 2 3 2 2 Sombrero Islands West Indies ^Phosphorus 1009. White 2-5 2-7 Altenberg Zinc IOIO. IOII. Green Yellow 3-5 4 3 3 Connecticut Connecticut >Phosphorus IOI2. 1013. Red Colorless 3 5 3-5 3-6 Saxony Sweden jArsenic IOI4. White 3-5 3 Connecticut ) 1015. Colorless 3-5 Hesse ^Phosphorus 1016. White 3 3 Connecticut J IOI7. White Missouri Arsenic xvsj. i 1018. Green 2 Turginsk Copper 1019. Colorless i-5 2-5 New Jersey Phosphorus IO2O. Indigo 2-5 2.9 Carinthia Arsenic IO2I. Colorless Norway Phosphorus IO22. 1023. White Red i i-5 2.4 2-9 Hungary California > Arsenic 256 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form IX. PHOSPHATES, ARSE- NATES continued 1024. Annabergite 1025. Cabrerite Ni 3 As 2 O 8 -8H 2 O (Ni,Mg) 3 As 2 O8 8H 2 O Mono. Miono 1026. Kottigite Zn 3 As 2 O 8 -8H 2 O M^ono 1027. Rhabdophanite ( Y,Er) 2 O 3 (La,Di) 2 O 3 P 2 O 3 H 2 O M!ono 1028. Churchite Ce 2 O 3 CaO PD 2 O 5 H 2 O Mono 1029. Scorodite FeAsO 4 -2H 2 O Ortho. 1030 Strcngite FePO 4 -2H 2 O Ortho 1031. Phosphosiderite 1032. Barrandite IO 33 Variscite 2 FeP0 4 . 3 H 2 (Al,Fe)P0 4 - 2 H 2 O A1PO 4 -2H 2 O Ortho. Ortho. Ortho 1034 Callanite A1PO 4 -2^H 2 O Ortho 1035 Zepharovichite .... A1PO 4 -3H 2 O Ortho 1036. Koninckite FePO 4 -3H 2 O Ortho. 4. Acid Hydrous 1037. Pharmacolite ... . HCaAsO 4 -2H 2 O Mono. 1038 Haidingerite HCaAsO 4 -H 2 O Ortho. 1039. Wapplerite HCaAsO 4 -3^H 2 O Mono. 1040. Brushite HCaPO 4 -2H 2 O Mono. 1041. Martini te H 2 Ca s (PO 4 ) 4 ^H 2 O Hexag. 1042. Newberyite 1042^. Stercorite HMgP0 4 - 3 H 2 HNa(NH 4 )PO 4 -4H 2 O Ortho. Mono. 1043 Hureauli tc H 2 Mn s (PO 4 ) 4 -4H 2 O Mono. 1044 Forbesite H 2 (Ni,Co) 2 As 2 O 8 8H 2 O Mono. 5. Basic Hydrous 1045 Isoclasite Ca 3 P 2 O 8 Ca(OH) 2 4H 2 O Mono. 1046. Hemafibrite 1047 Euchroite Mn 3 As 2 O 8 3Mn(OH) 2 2H 2 O CUiAszOg Cu(OH) 2 6H 2 O Ortho. Ortho. 1048 Conichalcite (Cu,Ca) 3 As 2 O 8 (Cu,Ca) (OH) 2 - H 2 O Ortho. 1049. Bayldonite (Pb,Cu) 3 As 2 O 8 (Pb,Cu) (OH) 2 - H 2 O Mono. 1050. Tagilite 1051. Leucochalcite Cu 3 P 2 8 Cu(OH)- 2 H 2 Cu 3 As 2 O 8 Cu(OH) 2 2H 2 O Mono. Mono. i o "5 2 Volb orthi t6 (Cu,Ca,Ba) 3 (OH) 3 VO 4 -6H 2 O Ortho. 1053 Cornwallite Cu 3 As 2 O 8 2 Cu (OH) 2 H 2 O Ortho. 1054 Tyrolite Cu 3 As 2 O 8 2Cu(OH) 2 7H 2 O Ortho. 1055 Chalcophyllite 7CuO As 2 O 5 i4H 2 O Hexag. 1056 Veszelyite ... ... 7 (Zn,Cu s ) (P, AS) 2 O S 9H 2 O Mono. 1057. Wavellite 4A1PO 4 2 A1(OH) 3 9H 2 O Ortho. 1058. Fischerite A1PO 4 -A1(OH) 3 -2|H 2 O Ortho. 1059. Peganite A1(PO 4 ) A1(OH) 3 i^H 2 O Orhto. 1060. Turquois A1PO 4 -A1(OH) 3 -H 2 O Amorph. 1 06 1 Wardite 2A1 2 O 3 -P 2 O S -4H 2 O Crusting 1062 Sphaerite 4A1PO 4 -6A1(OH) 3 Ortho. 1063. Liskeardite ( Al,Fe) AsO 4 2 (Al,Fe) (OH) 3 5H 2 O Ortho. 1064. Evansite 2A1PO 4 -4A1(OH) 3 - 1 2H 2 O Ortho. 1065. Coeruleolactite 1066 Augclitc 3 Al 2 3 2PaO s .ioH 2 2A1 2 O 3 -PA-3H 2 O Mono. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 2 57 No. Color Hard- ness Gravity Locality Chief Constituent or Use 1024. Green 2 Nevada 1 1025. Green 2 2.9 Spain iArsenic IO26. Red 2-5 3 Schneeberg J 1027. Brown 3-5 3-9 Cornwall Rare elements 1028. Smoke gray 3-5 3 Cornwall Cerium IO2Q. Green 3-5 3 Utah Arsenic 1030. Red 3 2.8 Virginia 1031. Red 3-7 2.7 Germany 1032. Gray 4-5 2-5 Bohemia 1033. Green 4 Utah Phosphorus 1034. Green 3-5 2-5 Lockmariaquer 1035. White 5-5 2-3 Bohemia 1036. Yellow 3-5 2-3 Belgium 1037. White 2 2.6 Joachimsthal Arsenic 1038. 1039. White Colorless !-5 2 2 2 Joachimsthal Joachimsthal Rock forming Arsenic 1040. Colorless 2 2 Caribbean Sea 1041. Yellowish 2.8 Western India 1042. White 3 2 Victoria Phosphorus 1042!. White 2 1.6 Peru 1043. Yellow 5 3 Connecticut 1044. White 2.5 3 Atacama Arsenic 1045. White I 2.9 Joachimsthal Calcium 1046. Red 3 3-5 Sweden Manganese 1047. Green 3-5 3 Hungary 1048. . Green 4 4 Utah 1049- Green 4 5 Cornwall 1050. Green 3 4 Urals 1051. White Germany 1052. Green 3 3 Urals Copper I53- Green 4 4 Cornwall 1054. Green i 3 Utah JOSS- Green 2 2 Utah 1056. Blue 3-5 3-5 Banat 1057. White 3 2 Saxony ] 1058. Green 5 2-4 Urals I Phosphorus 1059. Green 3 2.4 Saxony J 1060. Green 6 2.6 New Mexico Gems 1061. Green 5 2.7 Utah Phosphorus 1062. Gray 4 2-5 Bohemia 1063. White Cornwall 1064. Colorless 4 1.9 Hungary Aluminum io6s. White Pennsylvania j* 1066. Colorless 2.7 Sweden 258 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form IX. PHOSPHATES, ARSE- NATES continued 1067. Berlinite 2 A1 2 -O 3 2P 2 O S -H 2 4A1 2 3 - 3 P 2 S -3H 2 P 2 O s -Al 2 -0 3 ,MnO,CaO,H 2 0, etc. 6FeAsO 4 2Fe(OH) 3 - 1 2H 2 O 2Fe 3 P 2 O 8 Fe(OH) 2 8H 2 O FeP0 4 Fe(OH) 3 - 4 iH 2 2FeP0 4 -Fe(OH) 3 . 2 iH 2 O 2 AlP0 4 -2Fe(OH) 2 . 2 H 2 2 AlPO 4 -2Fe(OH) 2 -2H 2 O Ca 3 Fe 2 (As0 4 ) 4 2 FeO(OH) - 5 H 2 O Ca 3 Fe 2 (P0 4 ) 4 - Fe(OH) 3 8H 2 O Ca 3 Fe 2 (PO 4 ) 4 1 2Fe(OH) 3 - 6H 2 O 4 FeP 2 8 Fe 2 OF 2 (OH) 2 - 3 6H 2 O Cu6Al(AsO 4 ) s 3CuAl(OH) s 2oH 2 O Cu 2 (FeO) 2 As 2 8 - 3 H 2 Fe,Cu,Ca,Al,H, phosphate CuO 3Fe 2 O 3 2P 2 O S - 8H 2 O 5Fe 2 3 -P 2 O s - S H 2 Fe,Zn,Ca,Mg,Al,H, phosphate Ca 3 Al IO P 2 O 23 -9H 2 O PbO 2 A1 2 O 3 P A 9H 2 O Cu(U0 2 ) 2 P 2 8 -8H 2 Cu(U0 2 ) 2 As 2 8 -8H 2 O Ca(U0 2 ) 2 P 2 8 -8H 2 Ca(U0 2 ) 2 As 2 8 -8H 2 Ba(U0 2 ) 2 P 2 8 -8H 2 (UO 2 ) 3 P 2 O 8 -6H 2 O (U0 2 ) 3 As 2 8 -i2H 2 O' Bi IO (U0 2 ) 3 (OH) 24 (As0 4 ) 4 2 BiAsO 4 -3Bi(OH) 3 2oCuO Bi 2 O 3 5 AsA 2 2H a O Ca 2 Sb 2 O 7 Pb 3 Sb 2 8 - 4 H 2 O CaSb 2 O 4 PbClSbO. Pb 4 As 2 O 7 -2PbCl 2 Pb 4 Sb 2 7 - 2 PbCl a CuO,AS 2 O 3 2FeO-Sb 2 O s FeO-Sb 2 O s -sFeO-TiO a 5CaO-2Ti0 2 -3Sb 2 Os Pb,Ca,Ti, antimonate Cu,Hg,Fe,S, antimonate Massive Compact Massive Regular Mono. Tufts Mono. Ortho. Ortho. Ortho. Mono. Mono. Mono. Mono. Mono. Mono. Triclinic Triclinic Amorph. Tetrag. Hexag. Tetrag. Tetrag. Ortho. Ortho. Ortho. Powder Mono. Triclinic Triclinic 1068 Trolleite 1069. Attacolite 1070. Pharmacosiderite . . . . 1071. Ludlamite 1072. Cacoxenite 1073. Beraunite 1074. Childrenite 1075. Eosphorite 1076 Masapilite 1077 Calcioferrite 1078 Borickite 1079. Richellite . . . . 1080. Liroconite 1081. Chenevixite 1082. Henwoodite 1083. Chalcosiderite 1084. Andrewsi te 1085 Kehoeite 1086 Goyazite 1087. Plumbogummite 1088. Torbernite 1089. Zeunerite 1090. Autunite 1091. Uranospinite 10921 TJranocircite 1 093 . Phosphuranylite 1094 Trogerite 1095. Walpurgite 1096. Rhagite 1097 M!ixite 6. Antimonates 1098. Atopite Regular Amorph. Tetrag. Ortho. Tetrag. Ortho. Tetrag. Ortho. Ortho. Regular Regular Earthy 1099 Bindheimite 1 1 o i Nadorite 1102. Ecdemite 1103. Ochrolite 1 103(1. Trippkeite 1104 Tripuhyite 1105 Derbylite 1106. Lewisite 1107. Mauzeliite 1108. Ammiolite COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 2 59 No. Color Hard- ness Gravity Locality Chief Constituent or Use 1067. Colorless 6 2.6 Germany } 1068. Green 5-5 3 Sweden ^Phosphorus /: Salmon red J 1070. Green 2-5 2-9 Utah / Arsenic 1071. Green 3 3 Cornwall 1072. Yellow 3 3 Pennsylvania IO73 Brown Bohemia Phosphorus 1074. White 4-5 3 Maine I75- Pink 4-5 3 Connecticut 1076. Black 4-5 3-5 Mexico Arsenic 1077. Yellow 2 2 Bavaria 1078. Brown 3-5 2.6 Bohemia Phosphorus 1079. Yellow 2 2 Belgium I080. 1081. Blue Green 2 3-5 2.8 3-9 Cornwall Utah Arsenic 1082. Blue' 4 2.6 Cornwall 1083. Green 4 3 Cornwall 1084. Bluish green 4 3 Cornwall Phosphorus 1085. 2 -3 South Dakota 1086. White 5 3 Brazil 1087. Yellowish 4 4 Brittany Lead 1088. Green 2 3 Cornwall 1089. Green 2 3 Cornwall 1090. Yellow 2 3 North Carolina 1091. Green 2 3 Saxony Uranium 1092. Green 3-5 Voigtland IOCH. Yellow North Carolina vo 1094. Yellow 3 Saxony 1095. 1096. Yellow Yellow 3-5 5 5-7 6 Saxony Saxony >Bismuth 1097. Green 3-5 5 Utah Copper 1098. Yellow 5-5 5 Sweden Antimony 1099. Gray 4 4 Arkansas Lead 1 100. Yellow 5-5 4-7 Piedmont Antimony IIOI. Yellow 3-5 7 ' Algeria 1 IIO2. Yellow 2-5 7 Sweden Lead IIO3. Yellow Chile j XW O 1103*1. Bluish green Brazil Copper 1104. Greenish yellow 5 Brazil Antimony 1105. Black 5 4 Brazil Titanium 1106. Yellow 4 Brazil \ 1107. Brown "(3 5 Sweden ^Antimony 1108. Scarlet Chile J / 260 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form IX. PHOSPHATES, ARSE- NATES continued 7. Mixed Phosphates . 1109. Diadochite 2 Fe 2 O 3 2 SO 3 P 2 Oi 1 2H 2 O Mono. i no. Destinezite 2Fe 2 O 3 2SO 3 P 2 O S 1 2H 2 O Earthy 1 1 1 1 . Pitticite Fe,S, arsenate Massive ii 12. Svanbergite Ca,Al,S, phosphate Hexag. 1 1 13 Beudantite Fe,Pb,S AS, phosphate Hexag. 1114. Lindackerite 1115 Liinebergite 3 NiO 6CuO - S0 3 2 As 2 s - 7H 2 O 3MgO B 2 O 3 P 2 O S 8H 2 O Ortho. Earthy 1116. Lossenite 2PbSO 4 3 (FeOH) 3 As 2 O 8 1 2H 2 O Ortho. 8. Nitrates, etc. 1117. Soda niter 1118. Niter NaNO 3 KNO 3 Hexag. Ortho. 1119. Nitrocalcite Ca(NO 3 ) 2 -nH 2 O 1 1 20. Nitromagnesite Mg(NO 3 ) 2 -nH 2 O n 2 1 . Nitrobarite Ba(NO 3 ) 2 Regular 1 1 22. Gerhard tite Cu(NO 3 ) 2 -3Cu(OH) 2 Ortho. 1123. Darapskite NaNO 3 -Na 2 SO 4 -H 2 O Tetrag. 1124. Nitroglauberite 6NaNO 3 - 2Na 2 SO 4 3H 2 O Tetrag. 1125 Lautarite Ca(IO 3 ) 2 Mono. 1126 Dietzeite yCa(IO 3 )2 '8CaCrO 4 Mono. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 261 No. Color Hard- ness Gravity Locality Chief Constituent or Use nog. Yellowish 3 2 Thuringia Phosphorus i no Yellowish Belgium \. IIII. Brown 2 2 Saxony >Arsemc III2. Yellow 5 3 Sweden Phosphorus 1113. Green 4 4 Cork Lead 1114. Green 2 5 Joachimsthal Copper 2 Hannover Phosphorus ri 16. Brownish Greece Arsenic 1117. White 2 Nevada 1118. White 2 2 Egypt IIIQ. Gray Kentucky Fertilizer 1 1 20. White Kentucky II2I. Colorless Chile 1122. Green 2 3 Arizona Copper 1123. Colorless Chile Soda 1124. White Atacama Sodium 1125. 1126. Colorless Yellow 3 4-5 3-7 Atacama Atacama Iodine 262 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form X. BORATES, ETC. 1127. Sussexite 2 (Mn,Zn,Mg) O B 2 O 3 H 2 O Ortho. 1128. Ludwigite 3MgO B 2 O 3 FeO Fe 2 O 3 Ortho 1129. Pinakiolite 3MgO B 2 O 3 MnO Mn 2 O 3 Ortho. 1130. Nordenskioldine 1131. Jeremejevite CaSn(BO 3 ) 2 A1BO 3 Regular Hexag. 1132. Hambergite Be 2 (OH)BO 3 Ortho. 1133. Szaibelyite 2Mg s B 4 Oii-3H 2 O Ortho. 1134. Boracite MgvCLBrfOso Regular 1135 Ascharite 3Mg 2 B 2 O s -2H 2 O Amorph. 1136 Rhodizite K Al Cs Rb,Na,Ca,Mg,Al, borate Regular 1137. Warwick! te 6MgO FeO 2TiO 2 3B 2 O 3 Ortho. 1138. Howlite H s Ca 2 B 5 SiOi 4 Ortho. 1139. Lagonite ... . Fe 2 O 3 '3B 2 O 3 -3H 2 O Earthy 1140. Larderellite (NH 4 ) 2 O-- 4B 2 O 3 4H 2 O Mono. 1141. Colemanite CazBeOu 5H 2 O Mono. 1142. Pinnoite MgB 2 O 4 -3H 2 O Tetrag. 1143. Heintzite K 2 O 4MgO 9B 2 O 3 1 6H 2 O Mono. 1144. Borax Na 2 B 4 O 7 -ioH 2 O Mono. 1145. Ulexite NaCaB 5 O 9 '8H 2 O Fibers 1146. Bechilite CaB 4 O 7 -4H 2 O Crusts 1147. Hydroboracite 1148. Sulfoborite CaMgB 6 On-6H 2 3MgSO 4 2Mg 3 B 4 O 9 1 2H 2 O Mono. Ortho. 1149. Uraninite Pb,Th,G,Ce,La,Y,Ca,N,Fe,H, uranite Regular 1150. Uranniobite . ... Pb,Th,G,Ce,La,Y,Ca,N,Fe,H, uranite Regular 1 15 it Broggerite Pb,Th,G,Ce,La,Y,Ca,N,Fe,H, uranite Regular 1152. Cleveite Pb,Th,G,Ce,La,Y,Ca,N,Fe,H, more U Regular 1153. Nivenite Pb,Th,G,Ce,La,Y,Ca,N,Fe,H, more U Regular 1154. Pitchblende Pb,Th,G,Ce,La,Y,Ca,N,Fe,H,more U Regular 1155. Carnotite K 2 O 2U 2 O 3 V 2 O S 3H 2 O Earthy 1156. Gummite (Pb,Ca,Ba)U 3 SiOi 2 6H 2 O Amorph. 1157. Yttrogummite (Pb,Ca,Ba)U 3 SiO I2 6H 2 O+ Y Earthy 1158. Thorogummite (Pb,Ca,Ba)U 3 SiOi 2 6H 2 O+Th Earthy 1159. Uranosphaerite (BiO) 2 U 2 O 7 '3H 2 O Globular COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 263 No. Color Hard- ness Gravity Locality Chief Constituent or Use 1127. 1128. II2Q. 1130. II 3 I. 1132. 1133. II34- 1135. White Green Black Yellow Colorless White White White White 3 6 11 7-5 3 7 3 3-9 3-8 4 3 2 3 2-9 i .9 New Jersey Hungary Sweden Norway Mt. Soktuj Norway Hungary France Germany Manganese Magnesium Manganese Zinc Boron Berylium 1136. II37- II 3 8. Il^g. White Brown White Yellow 8 3 3-5 3 3 2 Urals New York Nova Scotia Tuscany II4O. Yellow Tuscany II4I. 1142. 1143- 1144. H45- 1146. Colorless Yellow Colorless White White Gray 4 3 4 2 I 2 3 2 1.6 1.6 California Stassfurt Stassfurt Nevada Nevada Tuscany > Boron 1147. 1148. 1149. 1150. II5I. II 5 2. 1153- IIS4- 1155. White Colorless Gray Gray Gray Gray Black Black Yellow 2 4 5-5 5-5 5-5 5-5 5-5 5-5 1.9 2 9 9 9 8 8 Caucasus Germany Connecticut Norway Norway Norway Texas Colorado Utah Rare elements 1156. II57- IIS8. II59- Yellow Black Brown Red 2-5 5 4 2-3 3-9 4 6 North Carolina Norway Texas Saxony 264 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form XI. SULPHATES, ETC. i. Anhydrous Sulphates 1 1 60. Mascagnite (NH 4 ) 2 SO 4 Ortho 1161. Tavlorite 5K 2 SO 4 -(NH 4 ) 2 SO 4 Concret. 1162. Thenardite 1163. Aphthitalite Na 2 SO 4 (K,Na) 2 SO 4 Ortho. Hexag. 1164. Glauberite Na 2 SO 4 -CaSO 4 Mono. 1165. Langbeinite K 2 Mg 2 (SO 4 ) 3 Hexag. 1166. Barite BaSO 4 Ortho. 1167. Bologna stone BaSO 4 Ortho. 1168. Cawk BaSO 4 Ortho. 1169. Michel-levyte BaSO 4 Ortho. 1 1 70. Celestite SrSO 4 Ortho. 1171. Apotome SrSO 4 Ortho. 1172. Anglesite PbSO 4 Ortho. 1173. Anhydrite CaSO 4 Ortho. 1174. Vulpinite CaSO 4 Scaly 1175. Tripstone CaSO 4 Concret. 1176. Zinkosite 1177. Hydrocyanite 1178. Crocoite ZnS0 4 CuS0 4 PbCrO 4 Ortho. Ortho. Mono. 1179. Leadhillite 4PbO-SO 3 -2CO 2 -H 2 O Mono. 1180. Susannite 4PbO-SO 3 -2CO 2 -H 2 O Mono. 1 1 8 1 . Sulphohalite 3Na 2 SO 4 -2NaCl Regular 1182. Caracolite Pb(OH)Cl-Na 2 SO 4 Ortho. 1183. Kainite. . MgSO 4 -KCl-3H 2 O Mono. 1184. Connellite Cu IS (Cl,OH) 4 SO l6 - i5H 2 O Hexag. 1185. Spangolite Cu 6 AlClSO IO -9H 2 O Hexag. 1186. Hanksite 9Na 2 SO 4 -2Na 2 CO 3 -KCl Hexag. 1187. Misenite HKSO 4 Mono. 1 188. Brochantite CuSO 4 -3Cu(OH) 2 Ortho. 1189. Lanarkite Pb 2 SO s Mono. 1190. Dolerophanite Cu 2 SO s Mono. 119^. Caledonite 1192: Linarite 2 (Pb,Cu)0-S0 3 -H 2 O (Pb,Cu)SO 4 (Pb,Cu) (OH) 2 Ortho. Mono. 1193. Antlerite 3CuSO 4 -7Cu(OH) 2 Massive 1194. Alumian A1 2 O 3 -2SO 3 Hexag. 2. Hydrous Sulphates a. Normal 1195. Lecontite (Na,NH 4 ,K) 2 SO 4 -2H 2 O Ortho. 1196. Mirabilite Na 2 SO 4 -ioH 2 O Mono. 1197 Kieserite MgSO 4 -H 2 O Mono. 1198. Szmikite MnSO 4 -H 2 O Amorph. 1 1 oo. Gypsum CaSO 4 -2H 2 O Mono. 1 200. Selenite CaSO 4 -2H 2 O Mono. 1201. Satin spar : CaSO 4 -2H 2 O Mono. 1 202. Alabaster CaSO 4 -2H 2 O Mono. 1203 Ilesite (Mn,Zn Fe)SO 4 -4H 2 O Mono. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 265 No. Color Hard- ness Gravity Locality Chief Constituent or Use 1160. Yellow White 2 2 1-7 Etna Chincha Islands jSulphur 1162. 1163. 1164. ii6 Calcium Zinc 1177. Green Vesuvius Copper 1178. 1179. 1 1 80. 1181. 1182. Red Yellow Yellow Yellow Colorless 2-5 2-5 2-5 3 4.5 5-9 6 6 - 2 Arizona Scotland Scotland California Atacama [Lead Sulphur Lead 1183. 1184. 1185. 1186. 1187. White Blue Green White White 2 3 2 3 2 3 3 2-5 Stassfurt Cornwall Arizona California Naples Sulphur >Copper Sodium Potassium 1188. 1189. IIQO. Green White Brown 3-5. 2 3-9 5 Colorado Scotland Vesuvius EeaT r Copper 1191. 1192. IIQ3. Green Blue Green 2-5 2 6 5 3 -0 California California Arizona JLead Copper 1194. HOS. White Colorless 2 2 2-7 Spain Central America Sulphur lc j- 1196. 1197- 1198. 1199. I2OO. I2OI. I2O2. I2OV White White White White White White White Green i-5 3 5 5 5 -5 5 i 2 3 2 2 2 2 Salt Lake, Utah Stassfurt Hungary Michigan Michigan Michigan Michigan Colorado > Sodium Magnesium Manganese ^Piaster Ornaments Manganese 266 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form XI. SULPHATES, ETC. continued 1 204. Epsomite MgSO 4 -7H 2 O Ortho 1 205 . Goslarite ZnSO 4 -7H 2 O Ortho 1206. Morenosite 1207. Melanterite 1208. Mallardite 1209. Pisanite NiS0 4 -7H 2 FeS0 4 - 7 H 2 MnS0 4 -7H 2 (Fe,Cu)SO 4 -7H 2 O Ortho. Mono. Mono. M!ono 1210 Salvadorite (Cu,Fe)SO 4 -7H 2 O ]VIono 121 1. Bieberite CoSO 4 -7H 2 O M!ono 1212. Chalcanthite CuSO 4 -5H 2 O Triclinic 1213. Syngenite CaSO 4 -K 2 SO 4 -H 2 O ]Vlono 1214. Loweite MgSO 4 Na 2 SO 4 2^H 2 O Tetrae 1215. Blodite MgSO 4 Na 2 SO 4 4H 2 O jyjono 1216. Leonite MgSO 4 -K 2 SO 4 -4H 2 O M!ono 1217. Boussingaultite (NH 4 ) 2 SO 4 MgSO 4 6H 2 O ]VIono 1218. Picromerite MgSO 4 -K 2 SO 4 -6H 2 O M!ono 1219. Polyhalite 2CaSO 4 MgSO 4 K 2 SO 4 2H 2 O jVIono 1 2 20. Pickering! te MgSO 4 -Al 2 (SO 4 ) 3 -22H 2 O Mono 1 22 1. Halotrichite FeSO 4 A1 2 (SO 4 ) 3 24H 2 O Mono. 1222. Apjohnite MnSO 4 A1 2 (SO 4 ) 3 24H 2 O Mono. 1223. Dietrichite (Zn,Fe,Mn)SO 4 -Al,(SO4V22H0 Mono. 1224. Masrite Fe,Ms,Mn,Co,Al, sulphate Fibrous 1225. Coquimbite Fe 2 (SO 4 ) 3 -9H 2 O Hexag 1226. Quenstedtite Fe 2 (SO 4 ) 3 -ioH 2 O JV^ono 1227. Ihleite Fe 2 (SO 4 ) 3 -i2H 2 O Efflor 1228. Alunogen Al 2 (SO 4 ) 3 -i8H 2 O Mono. 1229. Krohnkite CuSO 4 -Na 2 SO 4 -2H 2 O Mono. 1230. Phillipite CuSO 4 Fe 2 (SO 4 ) 3 wH 2 O Mono. 1231. Ferronatrite 3Na 2 SO 4 Fe 2 (SO 4 ) 3 6H 2 O Hexag. 1232. Romerite FeSO 4 -Fe 2 (SO 4 ) 3 -i2H 2 O Triclinic 1233. Natrochalcite Na 2 SO 4 - Cu 4 (OH) 2 (SO 4 ) 2 - 2H 2 O Mono. b. Basic 1 234 Langite CuSO 4 -3Cu(OH) 2 -H 2 O Ortho. 1235. Herrengrundite 1236. Kamarezi te 2 (CuOH) 2 S0 4 Cu(OH> 2 3 H 2 O (CuOH) 2 SO 4 Cu(OH) 2 6H 2 O Mono. Ortho. 1237. Cyanotrichite. . 1 238 Serpierite 4CuO-AlA'SO 3 -8H 2 O Cu,Zn, sulphate Ortho. Ortho. 1239. Copiapite 2 Fe 2 O 3 5 SO 3 1 8H 2 O Mono. 1 240. Castanite Fe 2 O 3 2SO 3 -8H 2 O Mono. 1241. Utahite 3Fe 2 O 3 -2SO 3 -7H 2 O Hexag. 1242. Amarantite Fe 2 O 3 -2SO 3 -7H 2 O Triclinic 1243. Fibroferrite Fe 2 O 3 '2SO 3 -ioH 2 O Mono. 1 244. Raimondite 2Fe 2 O 3 '3SO 3 7H 2 O Hexag. 1245. Carphosid erite 3 Fe 2 O 3 4SO 3 i oH 2 O Hexag. 1246. Glockerite 2Fe 2 O 3 -SO 3 -6H 2 O Earthy 1247. Knoxvillite Cr,Fe,Al,H, sulphate Ortho. 1 248. Redingtonite Cr Fe Al H, sulphate Ortho. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 267 No. Color Hard- ness Gravity Locality Chief Constituent or Use 1204. 1205. 1206. 1207. 1208. White White Green Green Colorless 2 2 2 2 1-7 1.9 2 1.8 Kentucky Montana Galicia Utah Utah Medicine Zinc Nickel Iron Manganese 1 200. Blue Turkey \- I2IO. Green Chile JCopper I2II. Red I Bieber Cobalt 1212. I2I 3 . 1214. I2IS. 1216. Blue Colorless Yellow Colorless White 2-5 2 2 2 2 2 2 2 Arizona Galicia Austria Chile Germany Copper Potassium Sodium Magnesium Potassium 1217. White 1.6 Tuscany Magnesium 1218. White 2 Vesuvius Potassium 1219. I22O. Red White 2 I 2 Austria Colorado Calcium } 1221. Yellow New Mexico Li 1222. 1223. Yellow Yellow 1.5 2 1-7 Tennessee Hungary >Alummum 1224. EsrvDt 1225. 1226. 1227. White Red Yellow 2 2 2 2 I 8 Chile Chilel Bohemia |lron 1228. I22Q. I23O. White Blue Blue 1-5 2.5 1.6 1.9 Bohemia Atacama Chile Aluminum JCopper I2 3 I. 1232. 1233- 1234. 1235- 1236. 1237. Gray Brown Green Blue Green Green Blue 2 3 4 2 2 3 2 2 2 3 3 3 Chile Chile Chile Cornwall Hungary Greece Utah Sodium Iron Copper Copper 1238. Green Greece 1239. I24O. 1241. Yellow Brown Yellow 2-5 3 2 2 Chile Chile Utah 1242. 1243. 1244. 1245- 1246. 1247. 1248. Red Yellow Yellow Yellow Brown Yellow Pale purple 2 2 3 4 2 1.8 3 2 i-7 Chile Chile Bolivia Greenland Harz California Knoxville Iron Chromium 268 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form XL SULPHATES, ETC. continued 1249. Cyprusite 7Fe 2 O 3 A1 2 O 3 ioSO 3 i4H 2 O Hexag 1250. Aluminite A1 2 O 3 -SO 8 -9H 2 O Mono 1251. Paraluminite 2Al 2 O 3 -SO 3 -i5H 2 O Mono. 1252. Felsobanyite 2Al 2 O 3 -SO 3 -ioH 2 O Ortho. 1253. Botryogen MgO FeO Fe 2 O 3 4SO 3 1 8H 2 O Mono 1254. Siderona tri te 2Na 2 O Fe 2 O 3 4SO 3 yH 2 O Ortho 1255. Voltaite 5 (K 2 ,Fe)O - 2 (Al,Fe) 2 O 3 ioSO 3 i sH 2 O Regular 1256. Metavoltine 5 (Ka 2 Na 2 ,Fe)O 3F 2 O 3 1 2SO 3 i8H 2 O Hexag. 1257. Alunite K 2 O 3 A1 2 O 3 4SO 3 6H 2 O Hexag. 1258. Jarosite K 2 O 3 Fe 2 O 3 4SO 3 6H 2 O Hexag. 1259. Lowigite K 2 O-3A1 2 O 3 -4SO 3 -9H 2 O Hexag. 1260. Ettringite 6CaO A1 2 O 3 3SO 3 33H 2 O Hexag. 1261. Quetenite MgO Fe 2 O 3 3SO 3 i3H 2 O Mono. 1262. Zincaluminite 2ZnSO 4 4Zn(OH) 2 6 A1(OH) 3 5H 2 O Hexag. 1263. Johannite U,Cu,H, sulphate Mono. 1 264. Uranopilite 3. Tellurates 1265. Montanite CaU 8 S 2 3I -2 5 H 2 Bi 2 O 3 -TeO 3 -2H 2 O Incrust. Earthy 1266. Emmonsite Fe,H, tellurate Mono. 1267. Durdenite Fe 2 (TeO 3 ) 3 -4H 2 O Massive 1268. Chalcomenite CuSeO 3 2H 2 O Mono. 1269. Molybdomenite Pb, selenite Ortho. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 269 No. Color Hard- ness Gravity Locality Chief Constituent or Use 1249. Yellow 2 Cyprus Iron 1250. White I I Halle 1 1251. White Halle } Aluminum 1252. Snow white I 2 Hungary J 253- Red 2 2 Sweden | 1254. Yellow 2 2 Chile 1255- Green 3 2 Naples /.iron 1256. Yellow 2 2 Persia j 1257. White 3-5 2-5 Colorado Aluminum 1258. Yellow 2-5 3 Utah Iron 1259. Yellow 3 2 Upper Silesia Aluminum 1260. Colorless 2 1-7 Prussia Calcium 1261. Brown 3 2 Chile Iron 1262. White 2 2 Greece Zinc 1263. 1264. Green Yellow 2 3 Joachimsthal Tohanngeorgenst'dt >Uranium 1265. Yellow Montana } Bismuth 1266. 1267. Green Yellow 5 2 Arizona Honduras JTellurium 1268. 1269. Blue White 3 Argentina Argentina } Selenium 2 7 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form XII. TUNGSTATES, MOLYB- DATES 1270. Wolframite (Fe,Mn)WO 4 Mono. 1271. Hiibnerite MnWO 4 Mono. 1272 Scheelite CaWO 4 Tetrag 1273. Cuprotungstite 1274. Po wellite CuWO 4 CaMoWO 4 Crystal. Tetrag. 1275. Stolzite . PbWO 4 Tetrag. 1276. Raspite PbWO 4 Mono. 1277. Wulfenite PbMoO 4 Tetrag. 1278. Reinite FeWO 4 Tetrag. 1279. Belonesite MgMoO 4 Tetrag. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 271 No. Color Hard- ness Gravity Locality Chief Constituent or Use 1270. Black 5 7 Connecticut | 1271. 1272. Brown White 5-5 4-5 7 5-9 Nevada North Carolina >Tungsten 1273. Green 4 Chile j 1274. Yellow 3-5 4 Michigan Molybdenum 1275- 1276. Green Yellow 2.7 2 7.8 Zinnwald New South Wales >Tungsten 1277. Green 2.7 6.7 Arizona Molybdenum 1278. 1270. Brown White 4 6.6 Japan Vesuvius Tungsten Molybdenum 272 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form XIII. ORGANIC ACIDS Oxalates, Mellates 1280. Whewellite CaC 2 O 4 -H 2 O Mono. 1281. Oxammite (NH 4 ) 2 C 2 O 4 -2H 2 O Ortho. 1282 Humboldtine 2FeC 2 O 4 -3H 2 O Capill. 1283 Mellite Al 2 Ci 2 Oi 2 -i8H 2 O Tetrag. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 273 No. Color Hard- ness Gravity Locality Chief Constituent or Use 1280. Colorless 2 ^ Saxony Calcium 1281. Yellowish Peru Ammoni u m 1282. 1283. Yellow Yellow 2 2 2 i-S Bohemia Bohemia Iron Mellitic acid 274 GUIDE TO MINERAL COLLECTIONS COMPREHENSIVE Composition Form XIV. HYDROCARBONS 1284. Scheererite IVIono 1285. Hatchettite . . _g-o/. jj_ I -m' Mono 1286. Paraffin C = 85%; H=is% Amorph 1287. Ozocerite .... C = 86%; H=i4% Amorph 1288. Zietrisikite 1289. Chrismatite CnRm. C = 8 4 .6%; H=i S . 4 % C = 8o%; H = 2o% Amorph. Amorph. 1290. Urpethite 1291. Fichtelite 1292. Napalite Ci S H 2 s. C 3 H 4 . C = 8 5 .8%; H=i 4 .2% C = 8 7 .2%; H=i2.8% C = 89.8%; H=io.2% Amorph. Mono. Amorph. 1293. Amber = 78.9%; H=io.5%; Amorph. 1 294. Succinite CnHm O=io.6% = 78 9%; H=io *%; Amorph. 1295. Retinite . . 0=io.6% Amorph. 1296. Gedanite . . Amorph. 1297. Glessite 1298. Rumanite Amorph. Amorph. 1299. Copalite = 85.6%; H=n.4%; Amorph. 1300. Bathvillite CnRm. = 3% Amorph. 1301. Tasmanite 1302. Dysodile CnRm. CnRm. Ash = 3i% C = 79%; H = io%; O = s%; C = 6 9 %;H=io%;O=i6%; Scales Scales 1303. Geocerite C 28 H,,6O 2 . S = 3%; N=2% C = 79%; H=i3%; O = 8% Waxy 1304. Leucopetrite C = 82%; H=n%; O = 7% Waxy 1305. Pyroretinite C 40 H6 O C = 8o%; H = 9 %; O=n% Resinous 1306. Dopplerite C H Cr- T C7 TT i-C7 C\ A O7 . Amorph. 1307. Idrialite C 42 H I4 O. N=i% C = 9i%; H = 6%; = 3% Earthy 1308. Posepnyte 1309. Petroleum, naphtha. . 1310. Pittasphalt C 22 H 36 4 . CwHaw+2 C = 72%; H=io%; O=i8% Plates Amorph. Viscid 1311 Asphaltum Amorph. 1312 Elaterite Amorph. 1313. Albertite Amorph. 1314. Grahamite C H 2 Amorph. 1315. Gilsonite 1316. Mineral coal 1317 Anthracite CnH 2 -f-2 Amorph. Amorph. Amorph. 1318 Bituminous coal Amorph. 1319 Coking coal CH 2 Amorph. 1320. Non-coking coal 1321. Cannel coal. 1322. Torbanite 1323. Lignite CH 2W Amorph. Amorph. Amorph. Amorph. 1324. let Amorph. 1325. Peat .... CH 2 Amorph. COMPREHENSIVE LIST OF MINERALS LIST OF MINERALS 275 No. Color Hard- ness Gravity Locality Chief Constituent or Use 1284. Resinous I Switzerland Chemicals 1285. 1286. White Yellowish I 9 Switzerland England [Paraffin 1287. Brown Q Sicily 1288. Brown _ r y 9 Utah 1280. Yellow Q Saxony y 1290. Brown V .8 Urpeltz 1291. White Bavaria 1292. Brown 2 California Technical 1293. Yellow 2 i Baltic coast purposes 1294. Yellow 2 i Baltic coast J !295- Brown Germany 1296. Brown Baltic Technical 1297. Brown 2 i Baltic purposes 1298. Brown 2 i Roumania 1299. Yellow i Tropics Varnish 1300. Brown 2 i Scotland 1301. Brown 2 i Tasmania Technical 1302. Yellow I . 2 Sicily purposes 1303. White \Veissengels 1304. White I . 2 \Veissengels I 3>S- Yellow 2 I Bohemia 1306. Black 2 I Styria Technical 1307. White Idria purposes 1308. Green 9 California 1309. Brown .6 United States - - 1310. Greenish brown Pennsylvania }0il 1311. Black i California 1312. Brown 9 Derbyshire ISIS- Black I Nova Scotia Technical 1314- 1315- Black Black 2 2 West Virginia Utah purposes 1316. Black 2-5 United States 1317- 1318. Black Black 2 2-5 Pennsylvania Pennsylvania I 3 I 9- 1320. Black Black 2 2 5 .5 Virginia Illinois >Fuel 1321. 1322. Black Brown 2 2.2 5 . i West Virginia Scotland 1323- Brown 1-5 . i Western states 1324. 1325- Black Brown i-5 i .1 . i Wales Scotland Jewelry Fuel GENERAL INDEX GENERAL INDEX The number preceding each mineral following is the page number. 590. 774- 81. 748- 545' 565- 979' 969. 493' 436. 291. 664. 70. 183- 90. I2O2. 529. 55- 374- .55- 61. 998. 725- 10. 655- 139- 3i- 883. 646. 62. 1194. 1250. 1257. 1228. 809. 21. 1242. Abbreviations, xxi Abriachanite, 234 Acadialite, 242 Acanthite, 204 Achroite, 240 Acmite, 232 Actinoliie, 232 Adamite, 254 Adelite, 252 Admire, 44 Adularia, 134, 230 Aenigmatite, 234 Aerolites, 43 Aeschynite, 250 Agaric Mineral, 226 Agate, 90, 218 Agricola, 198 Agricolite, 236 Aguilarite, 204 Ahnighito, 43 Aikinite, 210 Airy's spiral, 88 Alabandite, 206 Alabaster, 264 Alalite, 230 Albertite, 274 Albite, 140, 230 Alexandrite, 222 Algodonite, 204 Alisonite, 204 Allacite, 254 Allanite, 240 Allemonite, 202 Allochroite, 236 Alloclasite, 208 Allopalladium, 202 Allophane, 246 Almandite, 159, 236 Altaite, 204 Alumian, 264 Aluminite, 268 Aluminium, 45 Alunite, 268 Alunogen, 266 Alurgite, 244 Amalgam, 202 Amarantite, 266 the list number used in the List of Minerals; that 502. Amazonstone, 230 1293. Amber, 187, 274 975. Arnblygonite, 252 830. Amesite, 244 277. Amethyst, 88, 218 567. Amianthus, 232 1108. Ammiolite, 258 Amorphous, 2 563. Amphibole, 152, 232 782. Analcime, 242 781. Analcite, 167, 242 704. Andalusite, 238 511. Andesine, 139, 230 152. Andorite, 210 648. Andradite, 159, 236 1084. Andrewsite, 258 1172. Anglesite, 181, 264 1173. Anhydrite, 264 53. Animikite, 204 1024. Annabergite, 256 929. Annerodite, 250 803. Anomite, 242 514. Anorthite, 139, 142, 230 N 504. Anorthoclase, 138, 230 561. Anthophyllite, 232 1317. Anthracite, 192, 274 850. Antigorite, 244 Antimonates, 175 12. Antimony, 31, 45, 202 1193. Antlerite, 264 945. Apatite, 175, 252 422. Aphrite, 226 747. Aphrizite, 240 831. Aphrosiderite, 244 1163. Aphthitalite, 264 1222. Apjohnite, 266 658. Aplome, 236 758. Apophyllite, 240 1171. Apotome, 264 596. Aquamarine, 156, 234 450. Aragonite, 122, 226 735. Ardennite, 240 5900. Arfedsonite, 234 421. Argentine, 226 66. Argentite, 51, 204 Argon, 45 216. Argyrodite, 212 279 280 GUIDE TO MINERAL COLLECTIONS Aristotle, 198 22. Arquerite, 202 Arsenates, 175 9. Arsenic, 31, 45, 202 1003. Arseniopleite, 254 997. Arseniosiderite, 254 325. Arsenolite, 220 134. Arsenopyrite, 67, 208 567. Asbestus, 155, 232 413. Asbolite, 224 1135. Ascharite, 262 305. Asmanite, 218 616. Aspasiolite, 234 1311. Asphaltum, 188, 274 910. Astrophyllite,248 248. Atacamite, 214 1005. Atelestite, 254 1098. Atopite, 258 1069. Attacolite, 258 699. Auerlite, 238 1066. Augelite, 256 542. Augite, 147, 232 467. Aurichalcite, 228 365. Automolite, 222 1090. Autunite, 258 285. Aventurine, 218 Avicenna, 198 33. Awaruite, 202 Axial plane, 131 727. Axinite, 240 465. Azurite, 130, 228 Babbitt metal, 32 559. Babingtonite, 232 389. Baddeleyite, 222 726. Bagrationite, 240 536. Baikalite, 232 Bayly, W. S., ix, 200 1166. Barite, 170, 264 Barium, 45 592. Barkevikite, 234 1032. "Barrandite, 256 Bartholinus, 112, 198 621. Barylite, 234 618. Barysilite, 234 457. Barytocalcite, 226 297. Basanite, 218 Base, 28 Basic Phosphates, 256 524. Bastite, 230 847. Bastite, 244 460. Bastnasite, 226 1300. Bathvillite, 274 401. Bauxite, 222 Baveno Twin, 134 1049. Bayldonite, 256 Bayley, W. S., ix, 200 1146 203 1279 896 1073 584 785 877 1067, 159 739 594. 944. ?* 937. 1113, 100. I2II, 1099, 166, 801, 262. 329. 13- 44- 484. 129. 458. 1318. 381. 1215. 1021. 412. 397- 876. 2490. 1167. 610. 1144, 1078. no, Bechilite, 262 Beegerite, 212 Belonesite, 270 Bementite, 246 Beraunite, 258 Bergamaskite, 234 Bergmannite, 242 Bergseife, 246 Berlinite, 258 Berthierite, 210 Bertrandite, 240 Beryl^^, 234 Beryllium, 45 Beryllonite, 252 Berzelianite, 204 Berzeliite, 252 Berzelius, 199 Beudantite, 260 Beyrichite, 206 Biaxial, 89 Bieberite, 266 Bindheimite, 258 Binnite, 210 Biot, 170 Biotite, 170, 242 Bipyramid, 25 Birefringence, 55 Bischofite, 214 Bisectrix, 130 Bismite, 220 Bismuth, 31, 45, 202 Bismuthinite, 204* Bismutite, 228 Bismuto-smaltite, 208 Bismutospharite, 226 Bisphenoid, 29 Bituminous coal, 274 Bixbyite, 222 Black Jack, 53 Blodite, 266 Board of Museum Advisers, iii Bobierrite, 254 Bog Manganese, 224 Bog Ore, 222 Bole, 246 Boleite, 214 Bologna Stone, 264 Bonsdorffite, 234 Boracite, 177, 262 Borates, 177 Borax, 177, 262 Borickite, 258 Bornite, 56, 206 Boron, 45 Bort, 20, 202 Boston Society, 95 Botryoidal, 89, 99 GENERAL INDEX 281 1253' Botryogen, 268 180. Boulangerite, 210 Bourg de Oisans Twin, 85 182. Bournonite, 210 1217. Boussingaultite, 266 849. Bowenite, 244 Boyle, 198 Brachydome, 26 Brachypinacoid, 27 984. Brackebuschite, 254 1013. Brandite, 254 380. Braunite, 222 Bravais, 199 657. Bredbergite, 236 576. Breislakite, 232 103. Breithauptite, 206 Breithaupt, 199 441. Breunnerite, 226 Brews ter, 199 762. Brewsterite, 242 1188. Brochantite, 264 1151. Broggerite, 262 Bromine, 45 454. Bromlite, 226 230. Bromyrite, 214 173. Brongniardite, 210 522. Bronzite, 230 391. Brookite, 222 Brown, A. P., 200 403. Brucite, 222 Brush, 200 1040. Brushite, 256 Buck and Company, ix 720. Bucklandite, 240 301. Buhrstone, 218 Bunsen, 199 341. Bunsenite, 220 557. Bustamite, 232 Butler, G. M., 200 512. Bytownite, 139 1025. Cabrerite, 256 315. Cacholong, 218 1072. Cacoxenite, 258 Cadmium, 45 Caesium, 45 280. Cairngorm, 88, 218 1320. Caking coal, 274 740. Calamine, 240 143. Calaverite, 208 1077. Calcioferrite, 258 983. Calciovolborthite, 254 415. Calcite, 112, 226 Calcium, 45 434. Calc-sinter, 226 434. Calc-Tufa, 116 1191. Caledonite, 264 1034. Callanite, 256 * 221. Calomel, 214 959. Campylite, 252 532. Canaanite, 232 Canada balsam, 129 628. Cancrinite, 236 217. Canfieldite, 212 1321. Cannel coal, 274 Canon Diablo, 44 602. Cappelenite, 234 1182. Caracolite, 264 Carbon, 45 3. Carbonado, 20, 202 Carbonates, 112 Carlsbad Twin, 134 939. Carminite, 252 260. Carnallite, 214 287. Carnelian, 90, 218 1155. Carnotite, 262 742. Carpholite, 240 1245. Carphosiderite, 266 114. Carrollite, 206 604. Caryocerite, 234 897. Caryopilite, 246 382. Cassiterite, 107, 222 1240. Castanite, 266 806. Caswellite, 242 601. Catapleiite, 234 284. Cat's-eye, 218 375. Cat's Eye, 222 1 1 68. Cawk, 264 866. Celadonite, 246 1170. Celestite, 180, 264 517. Celsian, 230 886. Cenosite, 246 228. Cerargyrite, 214 744. Cerite, 240 Cerium, 45 456. Cerussite, 127, 226 333. Cervantite, 220 360. Ceylonite-Pleonaste, 220 773. Chabazite, 242 121 2. Chalcanthite, 266 286. Chalcedony, 89, 218 77. Chalcocite, 52, 57, 204 1268. Chalcomenite, 268 409. Chalcophanite, 224 1055. Chalcophyllite, 256 115. Chalcopyrite, 57, 206 1083. Chalcosiderite, 258 157. Chalcostibite, 210 336. Chalcotrichite, 220 429. Chalk, 226 840. Chamosite, 244 1 08 1. Chenevixite, 258 296. Chert, 90 466. Chessylite, 228 282 GUIDE TO MINERAL COLLECTIONS Chester, 124 503. Chesterlite, 230 705. Chiastolite, 238 1074. Childrenite, 258 57. Chilenite, 204 246. Chiolite, 214 148. Chiviatite, 210 521. Chladnite, 230 239. Chloralluminite, 214 Chlorine, 45 814. Chloritoid, 244 237. Chloromagnesite, 214 549. Chloromelanite, 232 890. Chloropal, 246 836. Chlorophaeite, 244 615. Chlorophyll! te, 234 361, Chlorospinel, 222 991. Chondrarsenite, 254 731. Chondrodite, 240 1289. Chrismatite, 274 372. Chromite, 104, 107, 222 Chromium, 45 373. Chrysoberyl, 222 889. Chrysocolla, 246 665. Chrysolite, 236 288. Chrysoprase, 90, 218 852. Chrysotile, 244 1028. Churchite, 256 879. Cimolite, 246 94. Cinnabar, 55, 206 640. Cinnamon-Stone, 236 996. Cirrolite, 254 279. Citrine, 88, 218 209. Clarite, 212 326. Claudetite, 220 63. Clausthalite, 204 354. Clay Iron-stone, 220 398. Clay-ironstone, 222 Cleavage, 16 508. Cleavelandite, 230 1152. Cleveite, 262 4. Cliftonite, 202 821. Clinochlore, 244 987, Clinoclasite, 254 Clinodomes, 129 741. Clinohedrite, 240 733. Clinohumite, 240 Clinopinacoid, 129 722. Clinozoisite, 240 Cloisonne work, 33 1316. Coal, 190 Cobalt, 45 119. Cobaltite, 206 537. Coccolite, 232 130. Cockscomb pyrite, 65 1065. Coeruleolactite, 256 39. Cohenite, 202 1319. Coking Coal, 274 1141. Colemanite, 177, 262 Colloidal Silica, 90 1007. Collophanite, 254 884. Collyrite, 246 651. Colophonite, 236 89. Colorado! te, 206 925. Columbite-Tantalite, 250 Columbium, 45 352. Columnar hematite, 220 Comprehensive list, 201 1048. Conichalcite, 256 863. Connarite, 246 1184. Connellite, 264 1299. Copalite, 274 1239. Copiapite, 266 18. Copper, 38, 45, 202 1225. Coquimbite, 266 1052. Cornwallite, 256 829. Corundophilite, 244 346. Corundum, 94, 220 121. Corynite, 206 171. Cosalite, 210 243. Cotunnite, 214 687. Couseranite, 238 95. Covellite, 206 Crayon, 173 378. Crednerite, 222 306. Cristobalite, 218 589. Crocidolite, 234 1178. Crocoite, 264 Cronstedt, 198 838. Cronstedite, 244 75. Crookesite, 204 591. Crossite, 234 245. Cryolite, 80, 214 Crystal form, 2 113. Cubanite, 206 Cube, 33 Cullinan diamond, 22 2496. Cumengite, 214 572. Cummingtonite, 232 335. Cuprite, 92, 220 149. Cuprobismutite, 210 233. Cuproiodargyrite, 214 60. Cuproplumbite, 204 1273. Cuprotungstite, 270 730. Cuspidine, 240 707. Cyanite, 163, 238 1237. Cyanotrichite, 266 516. Cyclopite, 230 219. Cylindrite, 212 694. Cyprine, 238 1249. Cyprusite, 268 GENERAL INDEX 283 792. Damourite, 242 Dana, ix, 199 135. Danaite, 208 635. Danalite, 236 700. Danburite, 238 573. Dannemorite, 232 1123. Darapskite, 260 708. Datolite, 238 Daubree, 109, 199 259. Daubreeite, 214 112. Daubreelite, 206 597. Davidsonite, 234 255. Daviesite, 214 470. Dawsonite, 228 982. Dechenite, 254 833. 061658^244 650. Demantoid, 236 1105.. Derbylite, 258 Des Cloizeaux, 199 980. Descloizite, 254 1 1 10. Destinezite, 260 855. Deweylite, 246 832. Diabantite, 244 1109. Diadochite, 260 538. Diallage, 232 i. Diamond, 5, 202 177. Diaphorite, 210 393. Diaspore, 222 Dichroscope, 96 1010. Dickinsonite, 254 1223. Dietrichite, 266 1126. Dietzeite, 260 989. Dihydrite, 254 Dimorphism, 123 527. Diopside, 147, 230 678. Dioptase, 238 Dioscorides, 61 Dioxides, 107 Diploid, 62 686. Dipyre, 238 Dispersion, 19 Disulphides, 206 Ditetragonal Bipyramid, 58 Ditetragonal Prism, 58 Ditrigonal polar, 166 Doctor of Medicine, 3 > Dodecahedron, 72 416. Dog-tooth Spar, 226 1190. Dolerophanite, 264 439. Dolomite, 117, 226 Dome, 26 54. Domeykite, 204 1306. Dopplerite, 274 Double refraction, 55 261. Douglasite, 214 Drills, 20 993. Dufrenite, 254 169. Dufrenoysite, 210 749. Dumortierite, 240 974. Durangite, 252 1267. Durdenite, 268 917. Dysanalyte, 248 50. Dyscrasite, 204 366. Dysluite, 222 1302. Dysodile, 274 Dysprosium, 45 953- IIO2. 578. 783- 624. 1312. 16. 600. 229. 181. 595- 349- 1266. 156. 208. 960. 520. 1075- 213. 834- 491. 717. 214. 763. 1204. 1023. 264. 98. 613- 1260. 73- 1047. 599- 710. 626. 598. 636. 95i. 835. Earthy Apatite; Osteolite, 252 Ecdemite, 258 Edenite, 232 Edingtonite, 242 Elaeolite, 234 Elasticity coefficient, 119 Elaterite, 274 Electrum, 202 Elements, 4 Elements, List of, 5, 45 Elpidite, 234 Embolite, 214 Embrithite, 210 Emerald, 156, 234 Emery, 94, 220 Emmonsite, 268 Emplectite, 210 Enargite, 212 Endlichite, 252 Enstatite, 146, 230 Entantiomorphous, 86 Eosphorite, 258 Epiboulangerite, 212 Epichlorite, 244 Epididymite, 230 Epidote, 238 Epigenite, 212 Epistilbite, 242 Epspmite, 266 Erbium, 45 Erinite, 254 Erni, 200 Erubiscite, 56 Erythrite, 254 Erythrosiderite, 216 Erythrozincite, 206 Esmarkite, 234 Ettringite, 268 Eucairite, 204 Euchroite, 256 Eucolite, 234 Euclase, 238 Eucryptite, 236 Eudialyte, 234 Eulytite, 236 Eupyrchroite, 252 Euralite, 244 284 GUIDE. TO MINERAL COLLECTIONS Europium, 45 981. Eusynchite, 254 933. Euxenite, 250 1064. Evansite, 256 Extraordinary ray, 55 611 1014 192 211 544 672 1252 923 1231 1243 1291 253 ion 310, 1058, 1000, 295' 322. 45i- 266. 257 419' 273- 1044- 670. 558- 2l8. 948. 369- . 196. 176. 860. 679. 80. 796. 869. Fahlerz, 74 Fahlunite, 234 Fairfieldite, 254 Falkenhaynite, 212 Famantinite, 212 Farrington, O. C., ix, 200 Fassaite, 232 Fayalite, 238 Felsobanyite, 268 Fergusonite, 250 Ferrites, 104 Ferronatrite, 266 Fibroferrite, 266 Fichtelite, 274 Fiedlerite, 214 Fillowite, 254 Finds, 43 Fire Opal, 218 Fischerite, 256 Flinkite, 254 Flint, 218 Float stone, 220 Flosferri, 226 Fluellite, 216 Fluorescence, 79 Fluorine, 45 Fluocerite, 214 Fluorite, 78, 214 Fontainebleau Limestone, 226 Foote, W. M., ix Footeite, 216 Forbesite, 256 Ford, 199, 200 Forest,3 Forsterite, 236 Fossil resins, 187 Fouque, 199 Fowlerite, 232 Fracture, 16 Franckeite, 212 Francolite, 252 Franklinite, 106, 222 Freibergite, 212 Freieslebenite, 210 French chalk, 246 Friedelite, 238 Frieseite, 204 Fuchsite, 242 Fuller's Earth, 174 Fulton, 200 711. Gadolinite, 238 Gadolinium, 45 364. Gahnite, 222 59. Galena, 48, 204 158. Galenobismutite, 210 Gallium, 45 619. Ganomalite, 234 755. Ganophyllite, 240 638. Garnet, 158, 236 857. Garnierite, 246 588. Gastaldite, 234 475. GayLussite, 228 270. Gearksutite, 216 1296. Gedanite, 274 562. Gedrite, 232 692. Gehlenite, 238 Geikielite, 248 918. Geikielite, 248 General Guide, v 856. Genthite, 246 1303. Geocerite, 274 202. Geocronite, 212 1 122. Gerhardtite, 260 Germanium, 45 120. Gersdorffite, 206 133. Geyerite, 208 321. Geyserite, 92, 218 Ghost quartz, 87 405. Gibbsite, 222 625. Gieseckite, 236 794. Gilbertite, 242 1315. Gilsonite, 274 311. Girasol, 218 768. Gismondite, 242 1164. Glauberite, 264 138. Glaucodot, 208 684. Glaucolite, 238 867. Glauconite, 246 587. Glaucophane, 234 326. Glaudetite, 220 1297. Glessite, 274 Glide planes, 47 1246. Glockerite, 266 Glucinum, 45 778. Gmelinite, 242 Goethe, 102 394. Goethite, 101, 222 15. Gold, 32, 45, 202 1205. Goslarite, 266 1086. Goyazite, 258 1314. Grahamite, 274 893. Graminite, 246 5. Graphite, 23, 202 Gratacap, 200 96. Greenockite, 206 905. Greenovite, 248 639. Grossularite, 159, 236 GENERAL INDEX 285 Groth, ix, 200 906. Grothite, 248 107. Grunauite, 206 574. Grunerite, 232 86. Guadalcazarite, 206 45. Guanajuatite, 204 908. Guarinite, 248 187. Guitermanite, 210 1156. Gummite, 262 1199. Gypsum, 182, 264 757. Gyrolite, 240 Haidinger, 65 1038. Haidingerite, 256 224. Halite, 76, 214 872. Halloysite, 246 Haloids, 76 1 22 1. Halotrichite, 266 1132. Hambergite, 262 973. Hamlinite, 252 Hancock County, 87 ' 1 1 86. Hanksite, 264 972. Harderite, 252 Hardin County, 79 Hardness, Scale of, 17 766. Harmotome, 242 729. Harstigite, 240 586. Hastingsite, 234 1285. Hatchettite, 274 920. Hatchettolite, 250 1 01. Hauchecornite, 206 117. Hauerite, 206 Haiiy, 198 631. Haiiynite, 236 804. Haughtonite, 242 376. Hausmannite, 222 775. Haydenite, 242 Heat conductivity, 30 534. Hedenbergite, 232 962. Hedyphane, 252 1143.' Heintzite, 262 -290. Heliotrope, 90 Helium, 45 634. Helvite, 236 1046. Hemafibrite, 256 350. Hematite, 97, 220 1001. Hematolite, 254 Hemihedral, 70 Hemimorphic, 93 Hennepin, 191 1082. Henwoodite, 258 130. Hepatic Pyrite, 64 363. Heroynite, 222 1235. Herrengrundite, 266 777. Herschelite, 242 68. Hessite, 204 Hexagonal system, 68 Hexatetrahedron, 15 Hexoctahedron, 12 761. Heulandite, 242 547. Hiddenite, 232 930. Hielmite, 250 247. Hieratite, 214 560. Hiortdahlite, 232 895. Hisingerite, 246 History of Study of Minerals, 198 894. Hoeferite, 246 1 02 2. Hoernesite, 254 Holbrook, 44 Holland, J. G., 33 Holoaxial, 82 Homestead, 44 709. Homilite, 238 Hope diamond, 22 1009. Hopeite, 254 105. Horbachite, 206 577. Hornblende, 153, 232 296. Hornstone, 90, 218 51. Horsfordite, 204 671. Hortonolite, 236 Hours, iii 1138. Howlite, 262 225. Huantajayite, 214 1271. Hiibnerite, 270 837. Hullite, 244 691. Humboldtilite, 238 1282. Humboldtine, 272 732. Humite, 240 52. Huntilite, 204 1043. Hureaulite, 256 Hutchinson, Charles F., iii Huygens, 112 641. Hyacinth, 236 696. Hyacinth, 238 319. Hyalite, 218 500. Hyalophane, 138, 230 667. Hyalosiderite, 236 620. Hyalotekite, 234 Hydrated sesquioxides, 100 428. Hydraulic limestone, 226 Hydrous Sulphates, 264 1147. Hydroboracite, 262 Hydrocarbons, 187 469. Hydrocerussite, 228 1177. Hydrocyanite, 264 Hydrofluoric acid, 81 Hydrogen, 45 479. Hydrogiobertite, 228 478. Hydromagnesite, 228 790. Hydronephelite, 242 313. Hydrophene, 218 236. Hydrophilite, 214 407. Hydrotalcite, 224 286 GUIDE TO MINERAL COLLECTIONS Hydrous carbonates, 228 Hydrous chlorides, 214 Hydrous oxides, 222 468. Hydrozincite, 228 523. Hypersthene, 146, 230 338. Ice, 220 418. Iceland Spar, 115, 226 Iddings, J. P., 200 668. Iddingsite, 236 1307. Idrialite, 274 1227. Ihleite, 266 1203. Ilesite, 264 387. Ilmenorutile, 222 356. Ilmenite, 220 734. Ilvaite, 240 874. Indianai te, 246 515. Indianite, 230 746. Indicolite, 240 Indium, 45 754. Inesite, 240 324. Infusorial Earth, 220 Intermediate plagioclases, 143 Intermediate oxides, 220 Iodine, 45 231. lodobromite, 214 234. lodyrite, 214 609. lolite, 234 26. Iridium, 45, 202 27. Iridosmine, 202 32. Iron, 42, 45, 202 1045. Isoclasite, 256 Isomorphism, 122 300. Itacolumite, 218 371. Jacobsite, 222 Jackson, B. H., 200 Jade, 156 548. Jatfeite, 150, 232 67. Jalpaite, 204 168. Jamesonite, 210 697. Jargon, 238 1258. Jarosite, 268 298. 845- Xr, 90, 218 isite, 244 541. Jeffersonite, 232 1131. Jeremejevite, 262 Jersey County, 40 1324. Jet, 274 1263. Johannite, 268 Jo Daviess County, 49 Johannsen, Albert, 200 911. Johnstrupite, 248 199. Jordanite, 212 47. Joseite, 204 34. Josephinite, 202 Jubilee, 21 585. Kaersutite, 234 1183. Kainite, 264 627. Kaliophilite, 236 124. Kallilite, 206 36. Kamacite, 202 1236. Kamaresite, 266 826. Kammererite, 244 Kaolins, 246 869. Kaolinite, 174, 246 581. Kataforite, 234 1085. Kehoeite, 258 907. Keilhauite, 248 737. Kentrolite, 240 145. Kermesite, 208 1197. Kieserite, 264 204. Kilbrickenite, 212 Kimberley, 5 Kimberlite, 21 Klaproth, 94 165. Klaprotholite, 210 673. Knebelite, 238 916. Knopite, 248 1247. Knoxvillite, 266 172. Kobellite, 210 Kohinoor, 21 579. Koksharovite, 232 23. Kongsbergite, 202 1036. Koninckite, 256 752. Kornerupine, 240 823. Kotschubeite, 244 1026. Kottigite, 256 Kraus, E. H., 200 367. Kreittonite, 222 263. Kremersite, 214 142. Krennerite, 208 1229. Krohnkite, 266 Kryptom, 45 Kunz, G. F., 200 582. Kupfferite, 234 512. Labradorite, 139, 230 Lacroix, ix 1139. Lagonite, 262 414. Lampadite, 224 1189. Lanarkite, 264 763. Langbanite, 240 1165. Langbeinite, 264 1234. Langite, 266 480. Lansfordite, 228 476. Lanthanite, 228 Lanthanum, 45 1140. Larderellite, 262 947. Lasurapatite, 252 772. Laubanite, 242 769. Laumontite, 242 252. Laurionite, 214 126. Laurite, 206 GENERAL INDEX 287 1125. Lautarite, 260 555. Lavenite, 232 533. Lavrovite, 232 242. Lawrencite, 214 743. Lawsonite, 240 Lawyer, 3 994. Lazulite, 254 633. Lazurite, 236 20. Lead, 45, 202 1179. Leadhillite, 264 1195. Lecontite, 264 903. Lederite, 248 72. Lehrbachite, 204 770. Leonhardite, 242 1216. Leonite, 266 799. Lepidolite, 172, 242 808. Lepidomelane, 244 Letter of transmittal, v 543. Leucaugite, 232 822. Leuchtenbergite, 244 518. Leucite, 145, 230 1051. Leucochalcite, 256 1304. Leucopetrite, 274 607. Leucophanite, 234 132. Leucopyrite, 208 779. Levynite, 242 Lewis, J. V., 200 1106. Lewisite, 258 977. Libethenite, 252 486. Liebigite, 228 Liebisch, 199 1323. Lignite, 192, 274 901. Ligurite, 248 1 86. Lillianite, 210 396. Limonite, 103, 222 1 19 2. Linarite, 264 1114. Lindackerite, 260 in. Linnaeite, 206 Linnaeus, 198 1080. Liroconite, 258 1063. Liskeardite, 256 List of Illustrations, xiii 942. Lithiophilite, 252 Lithium, 45 427. Lithographic Stone, 226 870. Lithomarge, 246 147. Livingstonite, 210 131. Lollingite , 2 08 Long Island, 44 162. Lorandite, 210 1116. Lossenite, 260 1214. Loweite, 266 1259. Lowigite, 268 497. Loxoclase, 230 1071. Ludlamite, 258 1128. Ludwigite, 262 425. Lumachelle, 226 1115. Lunebergite, 260 Lutecium, 45 210. Luzonite, 212 714. Mackintoshite, 238 Macon County, 40 Macrodome, 27 Macropinacoid, 25 370. Magnesioferrite, 222 440. Magnesite, 120, 226 Magnesium, 45 368. Magnetite, 105, 222 464. Malachite, 128, 228 528. Malacolite, 230 1208. Mallardite, 266 Malus, 112 Manebach Twin, 134 949. Manganapatite, 252 824. Manganchlorite, 244 Manganese, 45 395. Manganite, 100, 222 Manganites, 104 805. Manganophyllite, 242 340. Manganosite, 220 1004. Manganostiibite, 254 130. Marcasite, 63, 208 811. Margarite, 244 793. Margarodite, 242 688. Marialite, 238 83. Marmatite, 206 851. Marmolite, 244 223. Marshite, 214 1041. Martinite, 256 355. Martite, 220 1 1 60. Mascagnite, 264 513. Maskelynite, 230 817. Masonite, 244 1224. Masrite, 266 343. Massicot, 220 1 60. Matildite, 210 250. Matlockite, 214 1400. Maucherite, 208 1107. Mauzeliite, 258 1076. Mazapilite, 258 68 1. Meionite, 238 652. Melanite, 236 603. Melanocerite, 234 307. Melanophlogite, 218 738. Melanotekite, 240 1207. Melanterite, 266 690. Melilite, 238 608. Meliphanite, 234 1283. Mellite, 272 109. Meionite, 206 251. Mendipite, 214 200. Menenghinite, 212 317. Menilite, 218 288 GUIDE TO MINERAL COLLECTIONS 19. Mercury, 2, 40, 45, 202 802. Meroxene, 242 Merrill, G. P., 200 442. Mesitite, 226 787. Mesolite, 242 1015. Messelite, 254 85. Metacinnabarite, 206 Metallurgist, 4 Metasilicates, 230 43. Metastibnite, 404 1256. Metavoltine, 268 35. Meteoric Iron, 202 Meteorites, 21, 42 161. Miargyrite, 210 Micas, 1 68 1169. Michel-levyte, 264 921. Microlite, 250 501. Microcline, 137, 230 629. Microsommite, 236 Miers, ix 232. Miersite, 214 956. Miesite, 252 489. Milarite, 230 314. Milk Opal, 218 281. Milky Quartz, 218 Miller, W. H., 8, 199 99. Millerite, 206 Millspaugh, Charles F., iii 958. Mimetite, 252 Miner, 4 Mineral, Definition of, i 1316. Mineral coal, 274 Minerals, Abundance of, i Minerals, Numbers of, i Mineral production of 111., i Minerals, uses of, i, 287 Minister, 3 377. Minium, 222 Minnesota Mine, 39 1196. Mirabilite, 264 1187. Misenite, 264 Mitscherlich, 199 1097. Mixite, 258 685. Mizzonite, 238 Mohs, 199 Moissan, 199 Molybdates, 270 49. Molybdenite, 204 Molybdenum, 45 331. Molybdite, 220 1269. Molybdomenite, 48, 268 240. Molysite, 214 936. Monazite, 252 938. Monimolite, 252 Monoclinic axes, 30 Monoclinic system, 30, 129 Monosulphides, 204 Monoxides, 92 1265. Montanite, 268 669. Monticellite, 236 880. Montmorillonite, 246 492. Moonstone, 135 760. Mordenite, 240 1206. Morenosite, 266 Morion, 88 946. Moroxite, 252 912. Mosandrite, 248 986. Mottramite, 254 Moses, A. J., 200 569. Mountain Cork, 156, 232 568. Mountain Leather, 156, 232 Mukerop, 44 498. Murchisonite, 230 791. Muscovite, 168, 242 noi. Nadorite, 258 144. Nagyagite, 208 417. Nail-head Spar, 226 Names of minerals, 196 222. Nantokite, 214 1292. Napalite, 274 1233. Natrochalcite, 266 784. Natrolite, 168, 242 943. Natrophilite, 252 473. Natron, 228 Natural gas, 189 Naumann, 199 65. Naumannite, 204 Neodymium, 45 Neon, 45 898. Neotocite, 246 623. Nephelite, 234 550. Nephrite, 232 566. Nephrite, 156, 232 914. Neptunite, 248 472. Nesquehonite, 228 28. Nevyanskite, 202 1042. Newberyite, 256 878. Newtonite, 246 102. Niccolite, 206 Nickel, 45 128. Nickel-Skutterudite, 208 Nicol prism, 115, 129] 386. Nigrine, 222 Niobates, Tantalates, 175 1118. Niter, 260 Nitrates, etc., 260 1 121. Nitrobarite, 260 1119. Nitrocalcite, 260 Nitrogen, 45 1124. Nitroglauberite, 260 1 1 20. Nitromagnesite, 260 1153. Nivenite, 262 258. Nocerite, 214 GENERAL INDEX 289 1320. Non-coking coal, 274 891. Nontronite, 246 1130. Nordenskioldine, 262 751. Nordmarkite, 240 462. Northupite, 226 632. Noselite, 236 957. Nussierite, 252 1103. Ochrolite, 258 Octahedron, 5 390. Octahedrite, 222 780. Offretite, 242 756. Okenite, 240 91. Oldhamite, 206 509. Oligoclase, 139, 230 445. Oligonite, 226 976. Olivenite, 252 666. Olivine, 236 539. Omphacite, 232 88. Onofrite, 206 292. Onyx, 90, 218 430. Oolite, 226 308. Opal, 91, 218 316. Opal-agate, 218 854. Ophicalcite, 244 Ordinary ray, 55 Organic acid salts, 187 Orloff, 21 41. Orpiment, 204 492. Orthoclase, 133, 230 Orthodomes, 129 Orthopinacoid, 27 Orthorhombic system, 25 Osmium, 45 818. Ottrelite, 244 Owen, Charles L., iii Oxalates, Mellates, 272 1281. Oxammite, 272 Oxides, 82 Oxy chlorides, 214 Oxygen, 45 789. Ozarkite, 242 1287. Ozocerite, 274 268. Pachnolite, 216 30. Palladium, 45, 202 1286. Paraffin, 274 798. Paragonite, 242 1251. Paraluminite, 268 345. Parameleconite, 220 Parameters, 8 Paramorph, 123 Paramorphism, 123 580. Pargasite, 232 459. Parisite, 226 Parsons, C. L., 200 663. Partschinite, 236 683. Passauite, 238 Payne, Edward W., iii Peacock ore, 56 206. Pearceite, 212 320. Pearl sinter, 218 Peary, R. E., 43 1325. Peat, 192, 274 525. Peckhamite, 230 552. Pectolite, 232 1059. Peganite, 256 Penfield, S. L., 200 254. Penfieldite, 214 825. Penninite, 244 Pentagonal dodecahedron, 62 92. Pentlandite, 206 Peoria County, 40 Percussion figure, 169 249. Percylite, 214 339. Periclase, 220 507. Pericline, 141 ; 230 506. Peristerite, 230 915. Perovskite, 248 499. Perthite, 230 488. Petalite, 230 1309. Petroleum. Naphtha, 188, 274 69. Petzite, 204 776. Phacolite, 242 Pharmacist, 3 ' 1037. Pharmacolite, 256 1070. Pharmacosiderite, 258 676. Phenacite, 238 1230. Phillipite, 266 Phillips, A. H., 200 765. Phillipsite, 242 807. Phlogopite, 242 871. Pholerite, 246 868. Pholidolite, 246 461. Phosgenite, 226 Phosphates, 175, 260 Phosphorescence, 19 950. Phosphorite, 252 Phosphorus, 45 1031. Phosphosiderite, 256 1093. Phosphuranylite, 258 820. Phyllite, 244 702. Physalite, 238 1220. Pickeringite, 266 362. Picotite-Chrome Spinel, 222 723. Picroepidote, 240 853. Picrolite, 244 1218. Picromerite, 266 1017, Picropharmacolite, 254 724. Piedmonite, 240 Pinacoid, 27 1129. Pinakiolite, 262 892. Pinguite, 246 797. Finite, 242 2 go GUIDE TO MINERAL COLLECTIONS 1142. Pinnoite, 262 Pirsson, L. V., 200 474. Pirssonite, 228 1209. Pisanite, 266 431. Pisolite, 155, 226 443. Pistomesite, 226 1154. Pitchblende, 262 1310. Pittasphalt, 274 mi. Pitticite, 260 163. Plagionite, 210 290. Plasma, 218 Plaster of Paris, 182 25. Platinum, 41, 45, 202 Plattner, 199 388. Plattnerite, 222 Pleistocene, 37 38. Plessite, 202 Pliny, 6 1 1087. Plumbogummite, 258 Polar, 68, 93 384. Polianite, 222 519. Pollucite, 230 656. Polyadelphite, 236 207. Polyargyrite, 212 205. Polybasite, 212 617. Polychroilite, 234 934. Poly erase, 250 106. Polydymite, 206 1219. Polyhalite, 266 932. Polymignite, 250 955. Polysphaerite, 252 Pope County, 79 1308. Posepnyte, 274 Potassium, 45 1274. Powellite, 270 Praeseodymium, 45 289. Prase, 218 309. Precious Opal, 218 Preface, ix 728. Prehnite, 240 Prism, 27 828. Prochlorite, 244 267. Prosopite, 216 Prospector, 4 190. Proustite, 68, 212 84. Przibramite, 206 379. Pseudobrookite, 222 990. Pseudomalachite, 254 Pseudomorph, 123 827. Pseudophite, 244 873. Pseudosteatite, 246 410. Psilomelane, 224 985. Psittacinite, 254 759. Ptilolite, 240 940. Pucherite, 252 703. Pyonite, 238 Pyramid, 25 612. Pyrargillite, 234 189. Pyrargyrite, 68, 210 653. Pyreneite, 236 116. Pyrite, 206 Pyritohedron, 62 408. Pyroaurite, 224 919. Pyrochlore, 250 404. Pyrochroite, 222 392. Pyrolusite, no, 222 954. Pyromorphite, 176, 252 644. Pyrope, 159, 236 357. Pyrophanite, 220 1008. Pyrophosphorite, 254 882. Pyrophyllite, 246 I 3S- Pyroretinite, 274 680. Pyrosmalite, 238 193. Pyrostilpnite, 212 526. Pyroxene, 230 Pyroxene group, 145 922. Pyrrhite, 250 104. Pyrrhotite, 55, 206 275. Quartz, 82, 218 303. Quartzine, 218 299. Quartzite, 90, 218 1226. Quenstedtite, 226 1261. Quetenite, 268 Quincy, 124 Radium, -45 1244. Raimondite, 266 271. Ralstonite, 216 Rammelsberg, 199 137. Rammelsbergite, 208 1276. Raspite, 270 170. Rathite, 210 614. Raumite, 234 40. Realgar, 204 353. Red Ocherous hematite, 220 1016. Reddingite, 254 1248. Redingtonite, 266 Refraction, Index of, 18, 19 Regent diamond, 21 Regular system, 16 1278. Reinite, 270 482. Remingtonite, 228 Rene Just Haiiy, 198 Reniform, 99 861. Reneselaerite, 246 312. Resin Opal, 218 Resins, 187 848. Retinalite, 244 1295. Retinite, 274 1002. Retzian, 254 150. Rezbanyite, 210 1027. Rhabdophanite, 256 GENERAL INDEX 291 1096. 1136, 447. 645. 556. 496, 1079. 575. 5 88a, 913 194, 437. 643 622, 1 100, 1232, 810, 553- 278. 654- 713- 348. 359- 426. 1298. 843. 385- 423- 136. 283. 227. 535. 816. 1210. 928. 195- 191. 495- 865. 347- Rhagite, 258 Radium, 45 Rhodizite, 262 Rhodochrosite, 121, 226 Rhodolite, 236 Rhodonite, 151, 232 Rhombohedron, 70, 114 Rhyacolite, 230 Richellite, 258 Richterite, 232 Riebackite, 234 Rinkite, 248 Rittingerite, 212 Rock, 2 Rock Island, 124 Rock-meal, 226 Roentgen, 47 Romanzovite, 236 Rome de L'Isle, 104, 198 Roeblingite, 234 Romeite, 258 Romerite, 266 Roscoelite, 244 Rose, 198 Roselite, 254 Rosenbuschite, 232 Rose- quartz, 218 Rothoffite, 236 Rowlandite, 238 Rubidium, 45 Ruby, 95, 220 Ruby Spinel-Magnesia Spinel, 220 Ruin-marble, 226 Rumanite, 274 Rumpfite, 244 Ruthenium, 45 Rutile, 109, 222 Saccharoidal limestone, 226 Safflorite, 208 Sagenite, 218 Sal Ammoniac, 214 Saline, 44 Salite, 232 Salmite, 244 Salvadorite, 266 Salt, 76 Salt, Origin of, 77 Salt River, 44 Samarekite, 250 Samarium, 45 Sancy, 22 Sandbergite, 74 Sanguinite, 212 Sanidine, 230 Saponite, 246 Sapphire, 94, 220 282. Sapphire-quartz, 218 753. Sapphirine, 240 689. Sarcolite, 238 293. Sard, 90 293. Sardonyx, 90, 218 Sargasso Seas, 2 971. Sarkinite, 252 155. Sartorite, 210 406. Sassolite, 224 420. Satin Spar, 226 1 201. Satin Spar, 264 238. Scacchite, 214 Scalenohedrons, 72, 114 Scandium, 45 175. Schapbachite, 210 1272. Scheelite, 270 1284. Scheererite, 274 540. Schefferite, 232 164. Schirmerite, 210 771. Schneiderite, 242 662. Schorlomite, 236 390. Schreibersite, 202 885. Schrotterite, 246 6. Schungite, 202 256. Schwartzembergite, 214 197. Schwatzite, 74, 212 786. Scolecite, 242 1029. Scorodite, 256 718. Scorza, 238 Selenium, 45 1200. Selenite, 182, 264 8. Selensulphur, 202 241. Sellaite, 214 174. Semseyite, 210 Senarmont, 47 327. Senarmontite, 220 862. Sepiolite, 246 795. Sericite, 242 846. Serpentine, 172, 244 1238. Serpierite, 266 Sesquioxides, 94 812. Seybertite, 244 Shah of Persia, 22 424. Shell-marble, 226 Shepardson, F. W., iii, v 444. Siderite, 120, 226 Siderolites, 43 1254. Sideronatrite, 268 Silicates, 132 294. Siliceous sinter, 218 302. Silicified wood, 218 Silicon, 45 706. Sillimanite, 238 17. Silver, 37, 45, 202 Sinter, 92 924. Sipylite, 250 29. Siserskite, 202 2Q2 GUIDE TO MINERAL COLLECTIONS 815. Sismondine, 244 127. Skutterudite, 208 118. Smaltite-Chloanthite, 206 570. Smaragdite, 232 875. Smectite, 246 448. Smithsonite, 121, 226 630. Sodalite, 236 1117. Soda Niter, 260 Sodium, 45 Sohncke, 199 Sorby, 199 South Star, 22 864. Spadaite, 246 1185. Spangolite, 264 Spearhead pyrite, 65 Specific gravity, 17 Specific heat, 23 351. Specular hematite, 220 Specularite, 99 125. Sperrylite, 206 647. Spessartite, 159, 236 1062. Sphaerite, 256 449. Sphaerocobaltite, 226 82. Sphalerite, 52, 206 900. Sphene, 248 446. Spherosiderite, 226 358. Spinel, 104, 220 Spinel Twins, 1 7 902. Spinthere, 248 965. Spodiosite, 252 546. Spodumene, 232 952. Staffelite, 252 432. Stalactites, 116, 226 433. Stalagmite, 116, 226 215. Stannite, 212 276. Star-quartz, 218 750. Staurolite, 240 859. Steatite, 246 Steno, 81, 198 201. Stephanite, 212 10420. Stercorite, 256 79. Sternbergite, 204 334. Stibiconite, 220 42. Stibnite, 46, 204 767. Stilbite, 166, 242 841. Stilpnomelane, 244 881. Stolpenite, 246 1275. Stolzite, 270 383. Stream Tin, 222 605. Streenstrupine, 234 1030. Strengite, 256 842. Strigovite, 244 78. Stromeyerite, 204 455. Strontianite, 126, 226 Strontium, 45 1006. Struvite, 254 58. Stutzite, 204 185. Stylotypite, 210 Subsilicates, 240 Sublimation deposits, 24 642. Succinite, 236 1294. Succinite, 274 1148. Sulfoborite, 262 Sulphantimonites, 68 Sulpharsenates, 212 Sulpharsenites, 68, 210 Sulphates, 179 Sulphides, 46 Sulphides of metals, 204 1181. Sulphohalite, 264 Sulpho-salts, 210 7. Sulphur, 24, 45, 202 Sulphuric acid, 56, 63 220. Sulvanite, 212 Summary, 194 154. Sundtite, 210 510. Sunstone, 230 1 1 80. Susannite, 264 1127. Sussezite, 262 963. Svabite, 252 iii2. Svanbergite, 260 108. Sychnodymite, 206 141. Sylvanite, 208 226. Sylvite, 76, 214 Symbol, 8 Symmetry axes, 18 1020. Symplesite, 254 999. Synadelphite, 254 1213. Syngenite, 266 583. Syntagma tite, 234 1133. Szaibelyite, 262 1198. Szmikite, 264 265. Tachhydrite, 216 37. Taenite, 202 1050. Tagilite, 256 858. Talc, 172, 246 967. Talktriplite, 252 272. Tallingite, 216 1 88. Tapalpite, 210 926. Tapiolite, 250 Tantalum, 45 978. Tarbuttite, 254 452. Tarnowitzite, 226 1301. Tasmanite, 274 995. Tavistockite, 254 1161. Taylorite, 264 Tellurates, 268 330. Tellurite, 220 ii. Tellurium, 45, 202 483. Tengerite, 228 198. Tennantite, 212 344. Tenorite, 220 674. Tephroite, 238 GENERAL INDEX 293 Terbium, 45 463. Teschemacherite, 228 46. Tetradymite, 204 195. Tetrahedrite, 72, 212 Tetragonal system, 57 Tetrahedral Twins, 13 Tetrahedron, 13 Tetrahexahedron, 34 719. Thallite, 238 Thallium, 45 887. Thaumasite, 246 1162. Thenardite, 264 471. Thermonatrite, 228 Theophrastus, 99 438. Thinolite, 226 Thin section, 1 29 269. Thomsenolite, 216 788. Thomsonite, 242 698. Thorite, 238 Thorium, 45 1158. Thorogummite, 26*2 716. Thulite, 238 Thulium, 45 839. Thuringite, 244 87. Tiemannite, 206 970. Tilasite, 252 337. Tile ore, 220 64. Tilkerodite, 204 24. Tin, 45, 202 Titanates, 248 659. Titaniferous garnet, 236 899. Titanite, 248 Titanium, 45 904. Titanomorphite, 248 701. Topaz, 162, 238 649. Topazolite, 236 1322. Torbanite, 274 1088. Torbernite, 258 745. Tourmaline, 164, 240 Trapezohedron, 9 530. Traversellite, 230 435. Travertine, 116, 226 564. Tremolite, 153, 232 Triassic, 21 1018. Trichalcite, 254 Triclinic system, 139 304. Tridymite, 218 677. Trimerite, 238 941. Triphylite, 252 966. Triplite, 252 968. Triploidite, 252 323. Tripolite, 220 1 1 03 a. Trippkeite, 258 1175. Tripstone, 264 1104. Tripuhyite, 258 Trisoctahedron, 10 606. Tritomite, 234 1094. Trogerite, 258 93. Troilite, 206 1068. Trolleite, 258 477. Trona, 228 909. Tscheffkinite, 248 Tschermak, ix 1054. Tyrolite, 256 244. Tysonite, 214 Tungstates, 185 Tungsten, 45 332. Tungstite, 220 399. Turgite, 222 1060. Turquois, 256 Tutton, ix 1145. Ulexite, 262 123. Ullmannite, 206 76. Umangite, 204 University of Chicago Press, ix 571. Uralite, 232 Uranates, 177 1149. Uraninite, 178, 262 Uranium, 45 1150. Uranniobite, 262 1159. Uranosphaerite, 262 1091. Uranospinite, 258 1092. Uranocircite, 258 888. Uranophane, 246 1264. Uranopilite, 268 485. Uranothallite, 228 1290. Urpethite, 274 Use of minerals, 197 1241. Utahite, 266 661. Uvarovite, 159, 236 494. Valencianite, 230 328. 'Valentinite, 220 961. Vanadinite, 252 Vanadium, 45 Van Horn, F. R., 200 1033. Variscite, 256 819. Venasquite, 244. 844. Vermiculite, 244 693. Vesuvianite, 238 1056. Veszelyite, 256 Vicinal faces, 78 531. Violan, 230 1019. Vivianite, 254 487. Voglite, 228 1052. Volborthite, 256 1255. Voltaite, 268 146. Voltzite, 208 Von Lang, 146 1174. Vulpinite, 264 411. Wad, 224 964. Wagnerite, 252 294 GUIDE TO MINERAL COLLECTIONS 1095. Walpurgite, 258 1039. Wapplerite, 256 Ward, Henry B., iii 1061. Wardite, 256 167. Warrenite, 210 1137. Warwickite, 262 1057. Wavellite, 256 153. Webnerite, 210 48. Wehrlite, 204 Welcome Nugget, 35 764. Wellsite, 242 Werner, 199 682. Wernerite, 238 Wherry, E. T., 200 1280. Whewellite, 272 56. Whitneyite, 204 Willamette, 44 675. Willemite, 238 122. Willyamite, 206 Winchell, A. M., and N. H., 200 721. Withamite, 240 453- Witherite, 125, 226 184. Wittichenite, 210 402. Wocheinite, 222 554. Wohlerite, 232 140. Wolfachite, 208 1270. Wolframite, 185, 270 Wollaston, 199 551. Wollastonite, 232 318. Wood Opal, 218 1277. Wulfenite, 186, 270 97. Wurtzite, 206 992. Xantharsenite, 254 813. Xanthophyllite, 244 400. Xanthosiderite, 222 212. Xanthosonite, 212 935. Xenotime, 252 Yellowstone National Park, 24 Ytterbium, 45 660. Yttergranat, 236 712. Yttrialite, 238 Yttrium, 45 274. Yttrocerite, 216 2350. Yttrofluorite, 214 1157. Yttrogummite, 262 927. Yttrotantalite, 250 813. Zanthophyllite, 244 481. Zaratite, 228 Zeolites, 166 1035. Zepharovichite, 256 1089. Zeunerite, 258 1288. Zietrisikite, 274 14. Zinc, 45, 202 1262. Zincaluminite, 268 342. Zincite, 93, 220 151. Zinkenite, 210 1176. Zinkosite, 264 800. Zinnwaldite, 242 695. Zircon, 160, 238 Zirconium, 45 Zirkel, 199 715. Zoisite, 238 74. Zorgite, 204 637. Zunyite, 236 14 DAY USE RETURN TO DESK FROM WHICH BORROWED EARTH SCIENCES LIBRARY This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. LD 21-40m-5,'65 (F4308slO)476 General Library University of California Berkeley Z7Z