Arcubisite

Arcubisite (Ag6CuBiS4) is a mineral found in Greenland.
See more at Wikipedia.org...

General Information:
 Chemical Formula:
Ag6CuBiS4
 Composition:
(Molecular Weight = 1,048.00 gm)
Copper 6.06 % Cu
Silver 61.76 % Ag
Bismuth 19.94 % Bi
Sulfur 12.24 % S 
 Empirical Formula:
Ag6CuBiS4
 IMA Status:
Approved IMA 1973
 Locality:
Ivigtut, Greenland.
 Name Origin:
Named for the composition.
Physical Properties:
 Color:
steel gray.
 Diaphaniety:
Opaque
 Luster:
Metallic
More details...