CHAPTER VI 



SULPHO COMPOUNDS 



ZINKENITE 



Zinkenite. Sulphantimonide of lead, PbSb 2 S 4 ; Pb = 35.9, 

 Sb = 41.8, S= % 22.3; Orthorhombic ; Type, Didigonal Equato- 

 rial ; a : b : c ='.5575 : 1 : .6353 ; 100 ,110 = 29 8', 001 A 101 = 

 48 44', 001 A Oil =32 25'; Crystal forms, e (102), k (061) ; 

 Cleavage, none; Brittle, fracture uneven; H. = 3-3.5; G. = 

 5.3-5.35; Color and streak, steel-gray ; Luster, metallic. 



B.B. Fuses easily in R. F., yielding an antimony coat, and with 

 von KobelPs flux shows lead ; also yields a sulphur reaction when 

 fused with soda. Dissolves in hot HC1, yielding H 2 S and white lead 

 chloride. Crystals are columnar with faces indistinct and striated 

 lengthwise, or fibrous, also massive. 



General description. Zinkenite is a member of a series of min- 

 erals which may be represented by the general formula R"S, 

 IV'Sa, in which R" may be lead, copper, or iron and R'" may be 

 antimony, arsenic, or bismuth. They are all very similar in their 

 physical properties and crystalline habit, and as they are isomor- 

 phous, grade into each other. 



Sartorite, PbAs 2 S 4 , and galenobismuthite, PbBi 2 S 4 , are the lead 

 members. Emplectite, Cu 2 Bi 2 S 4 , and chalcostibite, CuSb 2 S 4 , are the 

 copper members ; and berthierite, FeSb 2 S 4 , is the iron member of 

 the series. Berthierite is the most common of the group. On 

 coal it fuses easily, yielding an antimony coat, sulphur dioxide 

 odor, and a magnetic residue. It occurs fibrous, plumose, or mas- 

 sive with cleavage. 



JAMESONITE 



Jamesonite. Pb 2 Sb 2 S 5 ; Pb = 50.8, Sb = 29.5, S = 19 . 7 ; 

 Orthorhombic ; Type, Didigonal Equatorial ; a : b : c = .819 : 1 

 : ? ; Cleavage, basal perfect ; Brittle, fracture uneven ; H. = 

 2-3 ; G. = 5.5-6 ; Color, steel-gray ; Streak, grayish black ; 

 Luster, metallic. 



B.B. Like zinkenite. 



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