Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/414

Rh 396 MINERALOGY 246. CLARITE, 3CuS + AsS. Oblique prismatic. Cl. clinodiagonal. Ordinary form ooP, ooP oo, OP, mP. H. =3-5; G. - 4 -46. Dark bluish grey. Kinzig- thal in Baden. Luzonite is similar. 247. FAMATINITE, 3CuS + SbS. Right prismatic. Typical form OP, ooP, ooPoo, cP3. Massive or renitbrm. H. =3 5; G. =4 57. Copper-red to grey ; streak black. Famatina Mts. in the Argentine Republic, and Cerro de Pasco in Peru. 248. CHIVIATITE, 2PbS + 3Bi 2 S 3. Foliated, massive. G. =6 9. Metallic. Lead-grey. Chiviato in Peru. 249. EPIGENITE, 6RS + As 2 S 5. Right prismatic. ooP 110 50. Steel-grey. H. =3 5. Witti- chen. 250. EPIBOULANGERITE, 3PbS + Sb 2 S 5. Right prismatic. G. =6 3. Metallic. Blue-black. Altenburg in Silesia. 251. XANTHOCON, 2(3AgS + As 2 S 3 ) + (3AgS + As 2 S 5 ). Hexagonal rhombohedral. R : OR 110 30. Crystals thin hex agonal tables ; brittle, easily frangible. H. = 2 to 2 5 ; G. = 5 to 5 2. Translucent; adamantine. Orange-yellow or brown; streak darker. In the closed tube fuses easily, becomes lead-grey. C.c. : 63 &quot;4 silver, 147 arsenic, and 21 9 sulphur. Himmelsfiirst mine at Freiberg. 252. PYROSTILPNITE (Fire-blende). Oblique prismatic ; crystals like stilbite. OP 139 12. Twins on orthodiagonal. H. =2;G. =4 2. Lustre pearly, and adamantine. Colour hyacinth-red and bright-yellow. Seetile. C.c.: 62 - 3 silver, with sulphur and antimony. Freiberg, Andreasberg, Przibram. OXYSULPHURETS. 253. KERMESITE, Sb0 3 + 2SbS 3. Oblique prismatic ; crystals oopoo, OP, acicular and diverging ; seetile. H. = 1 to 1 5 ; G. = 4 5 to 4 6. Translucent ; adamantine. Cherry-red ; streak similar. Sol. in h. acid. In potash solution becomes yellow, and dissolves. C.c.: 75 3 antimony, 19 8 sulphur, 4 9 oxygen. Braunsdorf, Przibram, Pernek near Bbsing (Hungary), Allemont, Southham (Canada). 254. VOLTZINE, ZnO + 4ZnS. Incrusting. H. =4 5; G. =37. Yellow. Pontgibaud and Joachimsthal. 255. KARELINITE, 3BiO + BiS. H. = 2; G. = 6 6. Metallic. Lead-grey. Zavodinski in the Altai. 256. BOLIVITE, BL,0 3 + Bi,S 3. Rhombohedral. From Bolivia. SELENITES. 257. CHALCOMENITE, CuSe + 2H 2 [ = CuO, Se0 2 + 2H 2 0]. Oblique prismatic, C 108 20. G. -=376. Bright blue. Trans parent. C.c.: selenious acid 48 2, copper oxide 35 4, water 15 3. Cerro de Cacheuta (Mendoza, Argentine Republic). NITRATES AND BORATES. 258. NITRATINE, Na. 2 N&quot;,[ - Na 2 0, N 2 5 ]. Rhombohedral ; R, 106 30. Tarapaca in Peru. Used in the arts as a substitute for nitre ; but deliquesces in moist air. 259. NITRE (Saltpetre), K.N,[ = K 2 0, N 2 5 ]. Right prismatic. oP (M) 118 49 ; 2Poo (P) 70 55 ; Poo 109 52 ; ooPoo (h) (fig. 275) ; isomorphous with aragonite. Acicular, capillary, or pulverulent.^ Cl. indistinct; fracture conchoidal. H. == 2 ; G. = 1 9 to 2. Semitransparent ; vitreous or silky. Colour less, white, or grey. Taste saline and cooling. Deflagrates when placed on hot charcoal ; and B.B. on platina wire melts very easily, colouring the flame violet. C.c. : 46 6 potash and 53 4 nitric acid, but always more or less impure. In the limestone caves of many countries; Hungary, Spain, India. Used for producing nitric acid, in glass making, medicine, and the manufacture of gunpowder. 260. NITROCALCITE, CaN 2 + H 2. Fibrous or pulverulent. White or grey. C.c.: 30 8 lime, 59 3 nitric acid, and 9 9 water. Limestone caves of Kentucky ; on old Avails and limestone rocks. 261. NlTROMAGNESlTE, MgN 2 + H 2. Taste bitter. In the same places, and similar to nitrocalcite. 262. BORACITE, 2Mg 3 B 4 + MgCl. Tesseral and hemihedral (figs. 63, 253, 359). Cl. octahedral, im- perfect ; fracture conchoidal ; brittle. H. -7; G. =2-9 to 3. Transparent or translucent ; vitreous or adamantine. Colourless or rhite, often greyish, yellow ish, or greenish. Becomes polar electric by heat. B.B. fuses with difficulty to a clear yellowish bead, which on cooling forms a white opaque mass of needle-like crystals ; at the same time colours the flame green. Sol. in h. acid. C.c. : 62 5 boracic acid, 26 9 magnesia, 7 9 chlorine, and 27 mag nesium. Liineberg, Segeberg in Holstein, Fig. 359. Stassfurt. 263. STASSFURTITE. In very minute prismatic crystals. White. C.c. same as bora- cite, and thus perhaps dimorphous. Stassfurt. 264. RHODIZITE, 2Ca 3 B 4 (?). H. =8 and G. =3 3 to 3 42; agrees in most characters with boracite. Pyro-electric. Mursinsk in Siberia. 265. LUDWIGITE, 2MgB + FeFe 2. Fibrous masses. From limestone at Morawitza in the Banat. 266. BORAX (Tinkal), Na 2 2B +10H 2. Oblique prismatic, C 73 25. ooP 87&quot; ; P 122 Almost isomorphous with augite; brittle. H. =2 to 2 5; G. =17 to 1 8. Pellucid; resinous. Colour less, or yellowish, greenish, and greyish white. Taste feebly alkaline and sweetish. C.c.: 16 4 soda, 36*5 boracic acid, and 47 1 water ; but often with 2 phosphoric acid or other impurities. Shores of salt lakes in Tibet and Nepal, in California, and near Potosi. 267. BOROCALCITE, Ca2B + 6H 2. Similar to ulexite (sp. 268) ; and from same locality. Fig. 360 (sp. 266). 268. ULEXITE, Na 2 2B +2Ca2B + 18H 2. Fibrous. H. =1;G. = 1 6. White. Tasteless. Iquique and Nova Scotia. 34 (fig. 360). 269. SZAIBELYITE, 2Mg 5 2 H. = 3 5 ; G. = 2 7. Werksthal in Hungary. 270. HYDROBORACITE, 2Ca3B 3 + 2Mg3B 3 + 12H 2. Radiating and foliated. Caucasus. A similar mineral, with soda in place of magnesia, is found in Peru. 271. SUSSEXITE, (Mn, Mg) 2 B + H 2. Fibrous, silky. White. H. =3;G. =3 4. Franklin (Sussex county, New Jersey). ANHYDROUS CARBONATES. 272. CALCITE (Cole-spar, Calcareous Spar), CaC. Hexagonal and rhombohedral ; R 105 5 (fig. 101). The forms and combinations exceed those of any other mineral. Among them are more than fifty rhombohedrons, especially - |R 135 ; R ; - 2R 79 ; and 4R 66 ; with OR and ooR as limiting forms. There are one hundred and fifty-five distinct scalenohedrons, as R3 ; R2 ; JR3 ; and the second hexagonal prism ooP2. Hexagonal pyramids are among the rarer forms. Some of the most usual combinations are oo R, -|R (c, g, fig. 179) ; or -R, R, very frequent ; also &amp;lt;xR, OR ; likewise - 2R, R (/, P, fig. 107) ; R3, ooR, - 2R ; R5 (y), 113 (r), R (P), 4R (in), ooR (c) (fig. 109); R, R3 (fig. 108). Several hundred distinct combinations are known. Hemitropes and twins are not uncommon. These occur with the axes parallel (figs. 106, 146, 148, 180, 366, 367). Others Fig. 361. Fig. 362. Fig. 363. Fig. 364. are conjoined by a face of R, the axes being almost at right angles, 89 8 (figs. 183, 369) or by a face of - R, in which the chief axes form an angle of 127^; and usually many times repeated, so that the centre crystals appear in lamellae not thicker thaii paper (fig. 181) ; at an obtuse angle, as figs. 149, 363, or an acute