Ferrokesterite

General Information:
 Chemical Formula:
Cu2(Fe,Zn)SnS4
 Composition:
(Molecular Weight = 432.30 gm)
Zinc 3.78 % Zn
Iron 9.69 % Fe
Copper 29.40 % Cu
Tin 27.46 % Sn
Sulfur 29.67 % S 
 Empirical Formula:
Cu2Zn0.25Fe2+0.75SnS4
 IMA Status:
Approved IMA
Physical Properties:
 Cleavage:
[???] Good
 Color:
gray or steel gray.
 Diaphaniety:
Opaque
 Hardness:
4 - Fluorite
 Luster:
Metallic
 Streak:
black
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