392 MINERALOGY G. =5 5 to 5 8. Rather dull; brighter on the streak. Blackish lead-grey, with a blue or other tarnish. B.B. colours the flame blue ; on charcoal in the oxygen flame sputters, and fuses easily ; in the red. flame becomes solid. With soda gives a grain of copper. Green solution in n. acid, leaving sulphur. C.c.: 79 8 copper, 20 2 sulphur. Fassnet Burn (Haddingtonshire), Ayrshire, Fair Island, near Redruth and Land s End in Cornwall, Saxony, Silesia, Nor way, the Banat, Siberia, and the United States. Important copper ore. 165. STROMEYERITE, Cu 2 S + AgS. Right prismatic ; isomorphous with redruthite. Crystals rare ; usually massive ; fracture flat, very sectile. H. =2 5 ; G. =6 2 to 6 3. Bright. Blackish lead-grey. C.c.: 53 1 silver, 31 2 copper, and 157 sulphur, but often indeterminate proportions of silver (3 to 53) and copper (30 to 75). Schlangenberg in Siberia, Rudelstadt in Silesia, and Catemo in Chili. 166. BERZELINITE, Cn 2 Se. Crystalline, in thin dendritic crusts, and imbedded in calcite. Silver-white with a black tarnish ; streak shining. In open tube gives a red sublimate of selenium, with white crystals of selenious acid. B.B. on charcoal fuses to a grey, slightly malleable bead, giving odour of selenious acid ; with soda a grain of copper. C. c. : 61 5 copper and 38 5 selenium. Skrikerum in Smaland, Lerbach in the Harz. 167. CROOKESITE, (CuTl) 2 Se. In crystalline grains the size of peas. H. -2 5 to 3 ; G. = 6 9. Brittle. Lead-grey. Metallic. B.B. colours the flame intense green. C.c.: 4576 copper, 371 silver, 17 25 thallium, 33 27 selenium. From Skrikerum. 168. EUKAIRITE, Cu 2 Se + AgSe. Massive and granular crystalline. Cuts with knife. Lead-grey ; streak shining. B.B. fuses to a brittle metallic grain. C.c. : 43 1 silver, 25 3 copper, and 31 "6 selenium. Skrikerum, Atacama, Chili. 169. ARGENTITE, Ag 2 S . Cubic. ooOoo ; 0; 0; and 202 (figs. 29, 56). Crystals generally misshapen, with uneven or curved faces ; in druses, or linear groups ; also arborescent, capillary, or in crusts. Cl. indistinct ; fracture hackly ; malleable and flexible. H. = 2 to 2 5 ; G. = 7 to 7 4. Rarely brilliant, more so on the streak. Blackish lead-grey, often with a black , brown, or rarely iridescent tarnish. B. B. on charcoal fuses, intumesces greatly, and leaves a grain of silver. Sol. in con. n. acid. C.c.: 87 silver and 13 sulphur. Huel Duchy, Dolcoath, Herland, and near Callington in Cornwall ; Alva in Stirlingshire : Freiberg, Marienberg, Annaberg, Schneeberg, Johann-Georgenstadt, Joachimsthal, Schemnitz and Kremnitz, Kongsberg. Common ore at Guanajuato and Zacatecas in Mexico, in Peru, and at Blagodat in Siberia. 170. ACANTHITE, AgS. Right prismatic. H. =2 5; G. = 7 33. Iron-black. C.c. like argentite, thus dimorphous. Freiberg and Clausthal, on argentite; also at Copiapo. 171. JALPAITE, 3AgS + Cu 2 S. Cubic; form 0. Cl. cubic; malleable. H. =2 5; G. = 6 88. Dark- grey. Metallic lustre. C.c.: silver 7178, copper 14 04, sulphur 14 "2. Jalpa in Mexico. 172. LAUTITE (CuAg) As.S . Granular. Iron-black. H. =3; G. =4 96. C.c.: copper 28 3, silver 12, arsenic 41 - 8, sulphur 17 86. Lauta, near Marienberg. 173. NAUMANNITE, AgSe. In thin plates and granular. Cl. hexahedral, perfect. Malleable. H. =2-5;G. =8. Iron-black. Splendent. C.c.: 73 silver and 27 selenium, with 4 91 lead. Tilkerode. 174. HESSITE, AgTe. Cubic or anorthic (?) ; massive and granular. Slightly malleable. H. = 2 5 to 3; G. =81 to 8 45. Blackish lead-grey to steel- grey. B. B. on charcoal fumes, fuses to a black grain with white spots, and leaves a brittle grain of silver. C.c.: 62 8 silver and 37 2 tellurium. Zavodinski (Altai), Nag- yag, Rezbanya, California, and Chili. 175. PETZITE, 2 AgTe + AuTe . Like hessite. Two varieties : (a) with G. =872, containing 18 per cent, of gold, from Nagyag ; (b) with G. =9 to 9-4, and 24 to 26 of gold. Calaveras and Tuolumne in Cali fornia, Colorado. 176. DISCRASITE, Ag.jSb ; Ag 3 Sb ; and Ag 6 Sb. Right prismatic ; P with polar edges 132 42 and 92; ooP 120 Fig. 335 (sp. 176). nearly (figs. 335, 336). Crystals short prismatic, or thick tabular, Fig. 337. and vertically striated (fig. 335) ; twins united by a face of ooP ; often in stellar groups (fig. 336) ; also massive or granular. Cl. basal and Poo , distinct ; ooP imperfect ; rather brittle, and slightly malleable. H. =3 5; G. =9 4 to 9 8. Silver- white to tin-white, with a yellow or blackish tarnish. B.B. fuses easily, fumes staining the charcoal white, and leaves a grain of silver. Sol. in n. acid. C.c.: 64 to 84 silver, and 36 to 16 antimony. Andreas- berg, Allemont in Dauphine, Spain, and Ar- queras in Coquimbo (Chili). A valuable ore of silver. A variety from Chili contains 94 2 silver and 5 8 antimony, and is Ag ]8 Sb. 177. BLENDE, ZnS. Cubic and tetrahedral (figs. 152, 153, 337). Twins remarkably common, united by a face of 0, and several times repeated ; fre quently massive and granular. Cl. oo 0, perfect; very brittle. H. = 3 5 to 4 ; G. =3 9 to 4 2. Semitransparent to opaque ; adamantine and resinous. Brown or black, also red, yellow, and green, rarely colour less or white. B.B. decrepitates, often violently, but only fuses on very thin edges. Sol. in con. n. acid, leaving sulphur. C.c.: 67 zinc and 33 sulphur ; but generally in the darker varieties with 1 to 15 iron, to 3 cadmium. Very abundant. Glen Gairn (bright yellow and highly phosphorescent), Leadhills. Tyndrum, Cornwall, Derby shire, Cumberland, the Harz, Freiberg, Przibram, Schemnitz, Kapnik, North America, Peru. Used for producing zinc vitriol and sulphur, and as an ore of zinc. Lithium, indium, thallium, and gallium have all been found in blende. 178. WURTZITE, 6ZnS + FeS. Hexagonal ; ooP, P, with well-marked horizontal striae. Cl. basal, and prismatic. H. =3 5 to 4; G. =3 9 to 4 1. Brownish black; streak light brown. C.c.: like blende, which is thus dimor phous. Oruro in Bolivia, and Przibram (radiated and cadmiferous). 179. GREENOCKITE, CdS. Hexagonal, and generally hemimorphic. P 86 21 ; 2P 123 54 . Crystals 2P, OP, ooP, P; orP, 2P, ooP; attached singly. Cl. ool , imperfect; basal perfect. H. =3 to 3 "5 lucent; brilliant resinous, or adaman tine. Honey- or orange-yellow, rarely brown ; streak yellow. B. B. decrepitates, and becomes carmine- red, but again yellow when cold ; fused with soda forms a reddish brown coating on charcoal. Sol. in h. acid. C.c. : 77 6 cadmium, and 22 4 sulphur. Bishopton in Renfrewshire, Przibram, and Friedensville in Pennsylvania. 180. ALABANDINE, MnS . Cubic ; and ooQoo ; usually massive and granular. Cl. hexa hedral, perfect; fracture uneven; rather brittle. H. =3 5 to 4; G. =3 9 to 4. Opaque; semi-metallic. Iron-black to dark steel- grey, brownish black tarnish ; streak dark green. B.B. fuses on thin edges to a brown slag. Sol. in h. acid. C c. : 63 manganese and 37 sulphur. Nagyag, Kapnik, Alabanda in Caria, Mexico, and Brazil. 181. MILLERITE, NiS . Hexagonal rhombohedral ; R 144 8 ; in fine acicular prisms of ooP2, R. Brittle. H. =3 5 ; G. =4 6 (or 5 26 to 5 65). Brass- or bronze-yellow, with a grey or iridescent tarnish. B.B. fuses easily to a blackish metallic globule, which boils and sputters. In nitro-hydrochloric acid forms a green solution. C.c. : 64 4 nickel and 35 6 sulphur. Morven (Argyllshire), Chapel (Fife), Ayrshire, near St Austell in Cornwall, at Merthyr-Tydvil, Johann-Georgen stadt, Joachimsthal, Przibram, Camsdorf, Riechelsdorf, Pennsyl vania. 182. PENTLANDITE (EisennickelTcies), 2FeS + NiS . Cubic ; massive and granular ; fracture uneven ; brittle. H. = 3 5 to 4; G. =4 6. Light pinchbeck-brown, with darker streak. Not magnetic. B.B. acts in general like pyrrhotite ; the roasted powder forms with borax in the red. flame a blnck opaque glass. C.c. : 36 sulphur, 42 iron, and 22 nickel ; but mixed with pyrrhotite and chalcopyrite. Lillehammer in southern Norway. Inverarite, 5FeS + NiS, with 11 of nickel, from near Inveraray, is a variety. 183. NICKELITE (Copper Nickel), NiAs. Hexagonal ; P 86 50 . Crystals ooP, OP ; rare. Arborescent, reniform, and massive ; fracture conchoidal and uneven ; brittle. H. = 5 5 ; G. = 7 "5 to 7 7. Light copper-red, with a blackish tarnish. It forms no sublimate in the closed tube. B. B. fuses with strong
G. =4-8 to 4 9. Trans-