Dervillite

General Information:
 Chemical Formula:
Ag2AsS2
 Composition:
(Molecular Weight = 354.79 gm)
Silver 60.81 % Ag
Arsenic 21.12 % As
Sulfur 18.08 % S 
 Empirical Formula:
Ag2AsS2
 IMA Status:
Approved IMA 1982
Physical Properties:
 Cleavage:
[???] Good
 Color:
brownish black.
 Diaphaniety:
Opaque
 Hardness:
1-1.5 - Talc or a little harder
 Luster:
Metallic
 Streak:
black
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