Johillerite

General Information:
 Chemical Formula:
Na(Mg,Zn)3Cu(AsO4)3
 Composition:
(Molecular Weight = 607.02 gm)
Sodium 3.79 % Na
Magnesium 9.01 % Mg
Zinc 8.08 % Zn
Copper 10.47 % Cu
Arsenic 37.03 % As
Oxygen 31.63 % O 
 Empirical Formula:
NaMg2.25Zn0.75Cu(AsO4)3
 IMA Status:
Approved IMA 1982
Physical Properties:
 Cleavage:
[010] Perfect, [100] Good, [001] Good
 Color:
violet.
 Density:
4.15
 Diaphaniety:
Transparent
 Hardness:
3 - Calcite
 Luster:
Vitreous (Glassy)
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