Geffroyite

General Information:
 Chemical Formula:
(Ag,Cu,Fe)9(Se,S)8
 Composition:
(Molecular Weight = 1,342.22 gm)
Iron 3.74 % Fe
Copper 12.78 % Cu
Silver 43.40 % Ag
Selenium 35.30 % Se
Sulfur 4.78 % S 
 Empirical Formula:
Ag5.4Cu2.7Fe2+0.9Se6S2
 IMA Status:
Approved IMA 1982
Physical Properties:
 Color:
bronze brown.
 Density:
5.39
 Diaphaniety:
Opaque
 Hardness:
2.5 - Finger Nail
 Luster:
Metallic
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