Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/403

Rh MINERALOGY 385 G. =57 to 6-3. M oasily. Sol. in n. acid. C.c. : chloride of lead 40, protoxide of lead 60. Meiidip Hills, and Brilon in Westphalia. 68. SCHWARTZEMBERGITE, Pbl + 2PbO. Rhombohedral ; in thin crusts. H. =2 to 2 5 Adamantine. Honey-yellow. Desert of Ata- cama. 69. ATACAMITE, CuCl + 3CuO,H 2 0. Right prismatic ; ooP (J/) 112 25, P&amp;gt; (P) 106 10, ool x) (h) (fig. 275); also reniform. Cl. h perfect. Semitransparent ; vitreous. Emerald - green ; streak apple- green. B. 15. fuses, leaving cop per. Easily soluble in acids. C.c. : copper protoxide 55 85, copper 14 86, chlorine 16 61, water 12 68. Atacama, Chili; Tarapaca, Peru; Bolivia; Burra- Burra, Australia ; Serra de Bembe, Ambriz, Africa ; Vesu vius and (?) Etna. 70. TALLINGITE, CuCl, H 2 + 4CuO, H 2 0. In crusts. H. =3; G. =3 5. Bright blue to greenish blue. Translucent ; brittle. Botallack in Cornwall. Fig. 275 (sp. 69). 71. PERCTLITE, Cubic (com. of figs. 26, 30, 33, 36). H. -2. Vitreous. Sky-blue. Sonora in Mexico. 72. CONNELLITE. Hexagonal (fig. 276). b : r 143 10 ; r : r 132 50 . Crystals acicular. Vitreous ; translucent. Vitriol-blue. A chloride and sulphide of copper. Wheal Unity and Wheal Damsel (Cornwall). OXIDES OF METALS. 1. S0BOXIDES AND PROTOXIDES. 73. CUPRITE, Cu 2 . Cubic (figs. 22, 30, 33, 26, with 39, 40). Compact and granular. Cl. octahedral ; brittle. H. =3 5 to 4 ; G. =57 to 6. Transparent and opaque ; adamantine. When transparent, crimson ; when opaque, cochineal or brick-red. Often tarnished grey. B. B. becomes black, fuses, and is reduced on charcoal. Soluble in acids and in ammonia. C.c. : 88 9 copper, 11 1 oxygen. Cornwall, Siberia, Banat, Chessy near Lyons, Linares in Spain, Urals, South Africa, Burra-Burra. Valuable copper ore. Chalcotrichite consists of cubes elongated so as to become fibrous. Tile-ore is a ferruginous variety. Hepatic copper, liver ore, or pitchy copper ore seems to be a product of the decomposition of chalcopyrite. Delafossite, Cu 2 + Fe,j0 3, from Bohemia and Siberia. 74. WATER, H 2 . Hexagonal, when solid, in complex twins in snow crystals ; rhombohedric by cleavage, in ice. H. =1 5; G. = 918. Hence 1000 of water = 1089 5 of ice, or water expands T Vth in freezing. Trans parent ; vitreous. Colourless, but in bulk pale emerald-green. R 117 23&quot;. Cl. basal. Water when pure colourless, in mass bluish green. Occurs in centre of geodes of chalcedony in China ; of druses of quartz in California and many other countries ; in zeolitic cavities to the amount of several gallons in the Faroes, also in the Hebrides, &c. Water of the ocean, from holding saline matters in solution, has G. = 1 027 to 1 0285. Waters of saline lakes contain sometimes 26 per cent, of salts, and have G. 1 212. Besides its vast bulk in the ocean, water occurs in enormous amount in the solid form, often as water of crystallization in rocks and minerals, e.g., zeolites. Igneous rocks in some districts are converted largely into saponite, which contains 25 per cent, of water. Water is the standard for specific gravities of solids and liquids ; 1 cubic inch at 60 F. and 30 inches of the barometer weighs 252 458 grains ; 1 litre weighs 1000 grammes. 75. PERICLASE, MgO. Cubic; in cubes and octahedrons. Cl. do. H. =6; G. =3 6 to 375. Transparent ; vitreous. Grey to dark green. B.B. infusible. Sol. in acids. C.c. : magnesia, with 6 to 8 of iron oxide. Somma. 76. BUNSENITE, NiO. Cubic ; in octahedrons. H. = 5 5 : G. = 6 4. Vitreous. Pistachio- green. Johann-Georgenstadt. 77. ZINCITE, ZnO. Hexagonal and granular. Cl. basal. H. =4 to 4 5 ; G. =5 4 to 5 5. Adamantine ; translucent. Blood- or hyacinth-red ; streak orange-yellow. B.B. infusible, but phosphoresces. C.c. : zinc 80-26, oxygen 1974; sometimes with manganese peroxide. Valuable ore of zinc. Franklin and Sterling in New Jersey. 78. MASSICOT, PbO. Massive ; scaly crystalline. H. =2 ; G. 7 8 to 8. Sulphur- or lemon-yellow ; often contains iron. Popocatepetl in Mexico. 79. MELACONITE, CuO. Cubic; compact. H. =3 to 4; G. =6 to 6 3. Black. B.B. infusible ; soluble in acids. Cornwall, Leadhills, Lake Superior, Burra-Burra. 80. TENORITE, CuO. Oblique prismatic ; occurs in thin scales of metallic lustre on lava of Vesuvius. Colour black and dark-red. 2. SESQUIOXIDES. 81. CORUNDUM, A1 2 3. Hexagonal ; R 86 4. Twins common. Cl. rhombohedral, and basal. Excessively tough, and difficultly frangible. H. = 9 ; G. = 3 9 to 4 2. Transparent or translucent ; vitreous, but pearly to metallic on basal face. B. B. unchanged. As Corundum, white, grey, and greenish, frequently with bronzy lustre on basal face. C.c. : alumina, with a little peroxide of iron. China, Ceylon, Bohemia, Malabar, Macon in North Carolina (one crystal 300 Ib weight). Emery is compact, crystalline, granular ; grey to indigo-blue. Asia Minor, Naxos, Spain, Greenland, America. Corundum is used when crushed for cutting and polishing gems in China and India, emery in powder for grinding. Alumina oc curs also in a purer state in transparent crystals of vari ous tints of colour. When red and of the colour of pigeon s blood they are termed Rubies ; these come from Syriam in Pegu, Ava, Ceylon, Bohemia, and near Expailly. When 5 carats in weight a ruby is twice the value of a diamond of the same size, when 10 carats three times the value. When blue the crystal is the Sapphire, found chiefly in Ceylon and Pegu ; when green it is the Oriental Emerald, when yellow the 277. Fig. 278. Oriental Topaz, when purple the Oriental Amethyst, the adjective here distinguishing them from the true or occidental stones of the same name. Other tints of colour also occur, but with the excep tion of the red and blue they are seldom pure or deep. The prism when cut with a hemispherical dome sometimes displays a six- rayed star, either of a bright gold or a silvery white colour, upon a greyish blue ground. These receive the name of Asteria Sapphires. The same crystal frequently shows portions of even three different tints. When perfectly devoid of colour, they are called Water Sapphires ; such are little inferior to the diamond in brilliancy, but do not disperse rays of light to the same extent. 82. HEMATITE, Fe 2 3. Hexagonal and rhombohedral ; R 86&quot;. Crystals rhombohedric, prismatic, and tabular. Twins with axes parallel. Cl. R, and basal ; fracture conchoidal; brittle. H.=5 5 to 6 5; G. =5 1 to 5 3. Opaque, but in thin laminae transparent and blood-red. Brilliant metallic lustre, iron-black to steel-grey, often brilliantly tarnished of red, yellow, green, and blue tints ; streak cherry-red. B.B. in the inner flame becomes black and magnetic. Sol. in acids. C.c.: iron 70, oxygen 30. The following are varieties or subdivisions: Elba Iron Ore, highly modified rhombohedral crystals, often bril liantly tarnished. Specular Iron Ore, in thin flat crystals, often from volcanoes, as on the island of Ascen sion ; this variety includes Micaceous Iron, thin, lamellar, and curved, and Red Iron Froth, scaly. Red Haema tite, in botryoidal and stalactitic forms, which are internally com posed of radiating fibres, and often have a concentric structure ; the external red to a brownish red hue. Pis 280. surface has a dark Compact and Ochrcy varieties, with more or less aluminous impurity, pass into Reddle or red chalk, and when still more earthy into jaspery and columnar ores. This ore is very commonly distributed: micncoous iron at Pitfichie in Aberdeen and Birnam in Perthshire ; red hanuatite at Leadhills and at X T. 49