

SULPHIDES, ARSENIDES, ANTIMONIDES 297 



0001 A lOlO = 65? 35' ; Crystal forms, c (0001), m (10TO) ; Cleavage, 

 c perfect, lamina flexible lut inelastic; H. = 1-1.5; G. = 4.7-4.8; 

 ( \tlor, lead-gray to bluish gray to bluish black, marks paper, ami 

 ft vis greasy; Streak, bluish gray; Luster, metallic ; Opaque. 



B.B. Infusible in the forceps, but yields a green flame. The 

 p< > \vdered mineral on coal in O. F. yields a white coat. In the open 

 tube yields SC>2. Decomposed with HNO 2 , moistened with H 2 SO4.. 

 ami evaporated in a porcelain crucible, yields a blue residue on cool- 

 ing. 



General description. Crystals are tabular, parallel to the base, 

 and six-sided, with the prism faces irregularly striated and furrowed 

 horizontally. Several prisms have been described, but good faces 

 are rare. Usually much like graphite in appearance. In flat scales 

 disseminated through granite and pegmatites, as at Cooper, Maine. 

 It occurs also in gneiss, schist, gabbro, granular limestones, and in 

 quartz veins, as at Chelan County, Washington, and Beaverhead 

 County, Montana. Crystals two to three inches across have been 

 found in Okanogan County, Washington, and at Aldfield, Pontiac 

 County, Quebec. 



While molybdenite occurs in many localities in the United 

 States, they are all small deposits, two of which are at present mined, 

 that at Cooper, Maine, and in Washington, even though molyb- 

 denite is the principal ore of the metal and is quoted as being 

 valued at $1.50 per pound. 



The metal is used in making tool steel ; as ammonium molyb- 

 date in the determination and separation of phosphoric acid in iron 

 ores ; in the staining of leather, and as sodium molybdate in the 

 coloring of pottery blue. Artificial crystals of molybdenite have 

 been formed by fusing the oxide with sulphur and potassium car- 

 bonate. 



ARGENTITE 



Argentite. Silver glance ; Ag2S ; Sulphide of silver ; 

 Ag = 87.1 ; 8 = 12.9; Isometric; Type, Ditesseral Central; 

 Common forms, o(lll), a (001), d(110); Twinning plane, 111, 

 interpenetrating; Cleavage, a and d in traces; Sectile and malle- 

 able ; H. = 2-2.5 ; G. = 7.2-7.35 ; Color, dark lead-gray ; Streak, 

 gray, shining ; Luster, metallic ; Opaque. 



B.B. Fuses with intumescence in O. F. on coal, yielding a 

 globule of silver and a sulphur dioxide odor. 



