SULPHIDES, \l;si:.\lli.s. INTIMONIDE8 



formed artificially l>y gently heating FeS \viih -ulphur. or by pass- 

 ing I1..S over oxides and chlorides of iron, heated to redne-s; also 

 by heating the mixture of ferric oxide, sulphur, and ammonium 

 chloride slowly to a temperature above which the latter volatili/.e<, 

 when culies and octahedron.- of pyrite will form. Pyrite is also 

 formed hy the action of H 2 S on ferric sulphate, as in marcasite, 

 Imt from neutral or slightly acid solutions. 



SMALTITE 



Smaltite. Diarsenide of cobalt, CoAs2; Co = 28.2, As = 71.8; 

 Isometric; Type Tesseral Central; Common forms, a (100), 

 o (111), d (110), e (210) ; Twinning plane, 111, composition face, 

 211 ; Cleavage, 111 distinct, a in* traces; Brittle, fracture uneven; 

 H = 5.5-6 ; G. = 6.4-6.6 ; Color, tin-white ; Streak, gray-black ; 

 Luster, metallic. 



B.B. On coal easily fusible, yielding a magnetic globule and an 

 arsenic odor, may yield a white coat of As2O 3 . With borax shows 

 persistent cobalt reactions. Soluble in hot nitric acid. 



General Description. Habit lie pyrite, but well-developed 

 crystals are rare; more often massive with the surface darkened 

 from tarnish. It may contain both iron and nickel, as the corre- 

 sponding diarsenide of nickel, chloanthite, is isomorphous with 

 cobaltite ; the two species grade into each other. Safflorite is an 

 orthorhombic form of CoAs2 occurring at Tunaberg, Sweden. 



Skutterudite, CoAs 3 , is a triarsenide from Modun, Norway, also 

 isometric. Smaltite occurs in veins associated with other ores of 

 cobalt, nickel, iron, and silver ; the most noted locality of America 

 is at Cobalt, Ontario. The historic European localities are Frei- 

 berg, Saxony; Joachimsthal, Bohemia ; and Tunaberg, in Sweden. 



CHLOANTHITE 



Chloanthite. Diarsenide of nickel; NiAs^ Ni = 28.1, As = 

 71.9 ; Common forms, *(100), o (111), d (110), e (210) ; Twinning 

 plane, 111; Cleavage, 111 distinct, a in traces; Brittle, fracture 

 uneven; H. = 5.5-6; G. =6.4-6.6; Color, tin-white; Streak, 

 gray-black ; Luster, metallic. 



B.B. Fuses easily on coal to a globule and yields an arsenic 

 odor, with possibly a white coat of AsjOs. Roasted and treated 

 with borax yields a persistent nickel reaction. It may contain 

 considerable cobalt. 



