Erniggliite

General Information:
 Chemical Formula:
Tl2SnAs2S6
 Composition:
(Molecular Weight = 869.72 gm)
Thallium 47.00 % Tl
Tin 13.65 % Sn
Arsenic 17.23 % As
Sulfur 22.12 % S 
 Empirical Formula:
Tl2SnAs2S6
 IMA Status:
Approved IMA
Physical Properties:
 Cleavage:
[???] Perfect
 Color:
gray, black gray, or black.
 Diaphaniety:
Opaque
 Hardness:
2-3 - Gypsum-Calcite
 Luster:
Metallic
 Streak:
reddish black
More details...