306 MINERALOGY 



COVELL1TE 



Covellite. CuS ; Cupric sulphide ; Cu = 66.4, S = 33.6 ; Hex- 

 agonal; Type, Trigonal Holoaxial, or Monoclinic; _c = 1.1466, 

 0001 A 1011 = 52 56' ; Common forms, c (0001), r (lOll), m (1010), 

 x(1122); Cleavage, basal perfect, thin lamellae, flexible; H. = 

 1.5-2; G. = 4.59-4.64; Color, deep indigo-blue ; Streak, gray to 

 black ; Opaque. 



B.B. On coal in O. F. fuses to a globule and yields SO 2 fumes. 

 Roasted and reduced with soda yields malleable copper. 



General description. Usually in cleavable masses or in dis- 

 seminated scales, rarely in crystals ; less common in occurrence than 

 the cuprous sulphide, chalcocite, of which it is at times an alteration 

 product. 



Covellite is a sulphide of secondary origin, probably produced by 

 the interaction of chalcocite and copper sulphide in solution, result- 

 ing in covellite and metallic copper. It is associated with other 

 copper minerals, as at Butte, Montana; at the Copper Queen 

 mine, Bisbee, Arizona; and at the Rambler mine, Wyoming. 

 While its percentage of copper is high, owing to its rare occurrence 

 in quantity it is only a minor ore of copper. 



GREENOCKITE 



Greenockite. CdS ; Cadmium sulphide ; Cd = 77.7, S A = 22,3 ; 

 Hexagonal ; Type, Dihexagonal Polar ; c =J).8109 ; 0001 A lOll = 

 43 1' ; Common forms, c (0010), M (1010), p (1011) ; H. = 

 3-3.5; G. = 4.9-5.0; Cleavage, prismatic distinct, c less so; 

 Brittle, fracture conchoidal; Color, shades of yellow; Streak, 

 orange-yellow to red; Luster, adamantine to resinous; Trans- 

 parent to translucent ; co = 2.688; Optically (+). 



B.B. On coal yields a sulphur dioxide odor and a reddish 

 brown coat of cadmium oxide. Reduced with soda yields malle- 

 able buttons of cadmium. Soluble in hot HC1, yielding hydrogen 

 sulphide. 



General description. Crystals of greenockite are interesting 

 from their polar development, being combinations of the lower 

 base with the hexagonal prism of the second order, terminated 

 above with a series of hexagonal pyramids of the second order and a 



