384 MINERALOGY 39. FLUELLITE, A1 2 F 3 . Right prismatic. In acute rhombic octahedrons with truncated apex. Polar edges 109 6 and 82 12 , middle 144. H. =3. Lustre vitreous. Colour white; transparent. Stenna-gwyn in Cornwall. 40. CRYOLITE, 3NaF + A1 2 F 3 . Anorthic ; but mostly in cleav- able masses. Sf:T9l5T; P:T 90 2 ; P-.M 90 40 . Cl. P perfect, M and T imperfect ; brittle. H. = 2 -5 ; G. = 2 -9 to 3 08. Vitreous, somewhat pearly on P. Translucent ; after immersion in water transparent. Colourless and snow-white ; but when deep-seated brown to black. Melts even in flame of candle to a white enamel. In open tube traces of hydrofluoric acid. Sol. in s. acid. C.c. : alumi nium 13, sodium 32 8, fluorine 54 2. Arksutfiord, Greenland ; Miask, Siberia. Used for manufacture of a white glass, and extraction of aluminium. 41. ARKSUTITK, (CaNa) 2 F + Al 2 F 3 . Ca :Na = l : 3. Massive granular. H. = 2 5; G. =3 03 to 3 18. C l. one distinct. Vitreous; white; translucent. C.c.: aluminium 18 6, sodium 23 3, calcium 6 8, fluorine 51 - 3. Arksutfiord. 42. CHIOLITE, 3NaF + 2Al 2 F 3 . Pyramidal, and twins (fig. 272). Middle edge 111 14 . Mostly granu lar. Cl. imperfect. H. = 4 ; G. = 2 "84 to 2 9. Resinous ; white. Fuses more easily than cryolite ; evolves hydro fluoric acid. C.c. : aluminium 18 6, sodium 23 - 4, fluorine 58. llmeri Mts. near Miask. Fig. 272 (species 42). 43. CHODNEFFITE, 2NaF + A1 2 F 3 . G. = 3. Other characters like chiolite, and from same locality. 44. PACHNOLITE, 3(CaNa)F + Al 2 F 3 + 2H 2 0. Ca:Na = 3:2. Oblique prismatic. ooP 98 34 ; always twins. Vitreous ; white ; semitransparent. C.c. : aluminium 12 3, calcium 16 1, sodium 12 4, fluorine 51 - 1, water 8 1. Evolves water with crackling, when heated ; other characters like cryolite, along with which it occurs in Greenland. 45. THOMSENOLITE, 2(CaNa)F + A1 2 F 3 + 2H 2 0. Ca:Na = 7:3. Oblique prismatic. Prismatic planes striated; ooP 89 (fig. 273). Cl. basal, perfect. H. =2 5 to 4 ; G. =274 to 276. Vitreous ; cleav age face pearly. White with yellow crust; translu cent. C.c. : aluminium 15, calcium 15 "4, sodium 7 6, fluorine 52 - 2, water 9 8. B. B. fuses more easily than cryolite to clear glass, decrepitating violently. Along with cryolite in Greenland. 46. GEARKSUTITE, Ca 2 F + Al 2 F 3 + 4H 2 0. Earthy. H. =2. White; dull ; opaque. C.c.: aluminium 15 5, calcium 19 3, sodium 2 - 5, fluorine 41 2, water 20 3. Along with cryolite. 47. EVIGTOKITE, 2CaF 2 -f A1 2 F 6 + 2H 2 . Crystalline. Soft; brittle; like kaolin. C.c.: calcium 22 39, aluminium 16 23, sodium -43, fluorine 55 24, water 571. Arksutfiord, Green- Fi S- 273 (sp. 45). land. 48. PROSOPITE. Oblique prismatic. A hydrated silico-fluoride of aluminium and calcium. H. =4; G. =2 89. Colourless imbedded crystals. From the tin- mines of Altenberg. 49. CALOMEL, Hg 2 Cl . Pyramidal ; P 135 50 (fig. 274). H. =1 to 2 ; G. = 6 4to6 5. Translucent; adamantine. Yel lowish white to grey. Sublimes unchanged inclosed tube ; with soda yields mercury. Insol. in n. acid. C.c.: mercury 85, chlorine 15. Moschellandsberg, Idria, Almaden. 50. SYLVITE, KC1. Cubic (figs. 26, 30); also massive. Cl. cubic. H. =2; G- 1-9 to 2. White or colourless. Vitreous; soluble; taste like common salt. * > <274 (sp. 49). C.c. : potassium 52 - 5, chlorine 47 5. B.B. fuses, and colours flame violet. Crater of Vesuvius, and salt beds of Stassfurt. 51. HALITE (Common Salt, Rock-salt), NaCl. Cubic (fig. 21) ; generally granular, sometimes fibrous. Cl. cubic. H. =2; G. =2 1 to 2 - 2. Transparent to translucent ; vitreous. Colourless or white ; but often coloured red, yellow, or blue. Taste saline. B.B. fuses and partly evaporates; colours flame yellow. C.c. : sodium 39 3, chlorine 607. In great beds at Wieliezka, Salzburg, Bex, &c., on the Continent; Cheshire in England. As an efflorescence in Brazil, Abyssinia, the Caspian and Aral Seas. As a sublimation among lavas at Vesuvius and other volcanoes. 52. SALMIAC, NH 4 C1. Cubic (figs. 30, 40, and 41 with 26, 33, 40). Cl. octahedral ; also stalactitic, globular, and as an efflorescence. H. = 1 5 to 2 ; G. = 1 5 to 1 6. Pellucid; vitreous. Colourless, but sometimes staineii. Taste pungent. B.B. directly volatile ; in copper colours flame blue-green. C.c.: 32 ammonia, 6Q 4 chlorine. A sublimate on active volcanoes. Vesuvius, island of Volcano, Iceland. Near coal-seams which have taken fire, in Scotland and at Newcastle. 53. CHLORO-CALCITE, CuCl + (KCl, NaCl). Cubic. Vesuvian bombs. 54. CERARGYRITE, AgCl . Cubic (fig. 26). Twins on octahedral face. No cl. ; chiefly massive in crusts. H. =1 to 1 5; G. =5 5 to 5 6. Fracture con- choidal. Malleable. Translucent; adamantine to resinous. Grey, yellowish, and greenish. B.B. fuses easily to a dark bead, reduced in inner flame. Soluble in ammonia. C.c.: silver 75, chlorine 25. Johann-Georgenstadt, Mexico, Peru. 55. EMBOLITE, 2AgBr + 3AgCl. Cubic (fig. 29) ; also massive or concretionary. H. = 1 to 1 5 ; G. ==5 8. Adamantine to resinous. Green and yellowish green. C.c. : silver 67, chlorine 13, bromine 20. Chili, Mexico, Honduras. 56. BROMITE, AgBr . Cubic (figs. 26, 30). H. = 1 to 2; G. =5 8 to 6. Splendent. Yellow to olive-green; streak siskin -green. B.B. fusible easily. C.c.: silver 57 5, bromine 42 5. San Onofro and Plateros (Mexico). 57. IODITE, Agl . Hexagonal. Cl. basal ; also massive, and in crystalline plates some inches in width ; these are flexible. H. = 1 to 1 5 ; G. = 5 5to 57. Translucent; adamantine. Citron and sulphur-yellow; streak yellow. B.B. fusible, colours the flame purple-red, and leaves button of silver. C.c.: silver 46, iodine 54. Zacatecas in Mexico, Algodones in Chili, Arizona, rarely in Spain. 58. COCCINITE, HgI 2 . In grains of an adamantine lustre, from Casas-Viejas in Mexico. Colour red to yellow ; in acute rhombic prisms. Also from Zimapan and Culebras. 59. TOCORNACLITE, Agl + Hg 2 I . Amorphous, yellow, soft. Chanarcillo in Chili. 60. COTUNNITE, PbCl. Right prismatic. H. =2; G. = 5 238. Transparent; high ada mantine to pearly. White. C.c. : lead 74, chlorine 26. Crater of Vesuvius. 61. MOLYSITE, Fe 2 Cl 3 . Incrusting. Brownish red and yellow. On lavas of Vesuvius. C.c. : iron 34 5, chlorine 65 5. 62. CARNALLITE, KCl + 2MgCl + 12H 2 0. Right prismatic. Noel. Conchoidal fracture. H. =2 to 2 5 ; G. = 1 6. Colourless, generally red from iron. C.c.: 34 2 chloride of magnesium, 26 9 chloride of potassium, 38 9 water. Stassfurt, Galicia, Persia. 63. TACHHYDRITE, CaCl + 2MgCl + 12H 2 0. Massive. Yellow, translucent, very deliquescent. In anhydrite. C.c. : calcium 7 46, magnesium 9 51, chlorine 40 34, water 42 69. Stassfurt. 64. KUEMERSITE, KC1 + NH 4 C1 + Fe 2 Cl 3 + 3H 2 . Cubic ; in octahedra. Ruby-red. Soluble. Fumaroles of Vesuvius. 65. ERITHROSIDERITE, 2KCl + Fe 2 Cl :i + 2H.jO. Right prismatic. Vesuvian lava. 66. MATLOCKITE, PbCl + PbO . Pyramidal; P 136 17 . Crystals tabular. Cl. basal; fracture conchoidal. H. =2 5; G. =7 21. Translucent; adamantine. Yellowish white. B. B. fuses easily with decrepitation ; colours flame blue. C.c. : chloride of lead 55 "5, oxide of lead 44 f>. Cromford in Derbyshire. 67. MENDIPITK, PbCl + 2PbO. Right prismatic; chiefly massive. Cl. ooP perfect 102 36 . H.=2 5 to 3 ; G.=7 to7 l. Fracture conchoidal. Translucent; adaman
tine to pearly. Yellowish or greyish white. BB. decrepitates, fuses