Sanmartinite

General Information:
 Chemical Formula:
(Zn,Fe++)WO4
 Composition:
(Molecular Weight = 310.85 gm)
Zinc 15.78 % Zn
Iron 4.49 % Fe
Tungsten 59.14 % W 
Oxygen 20.59 % O 
 Empirical Formula:
Zn0.75Fe2+0.25(WO4)
Physical Properties:
 Cleavage:
[010] Perfect
 Color:
brownish black or dark brown.
 Density:
6.7
 Diaphaniety:
Transparent to Opaque
 Hardness:
4-4.5 - Between Fluorite and Apatite
 Luster:
Resinous
 Streak:
red brown
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