Ziesite

Ziesite is a mineral, copper vanadate: formula βCu2V2O7. It was discovered in 1980 as monoclinic crystals around fumaroles in the crater of the Izalco Volcano, El Salvador. It is named after Emmanuel G. Zies, a mineralogist.Closely related is Blossite, also copper vanadate; its formula is given as αCu2V2O7. It forms orthorhombic crystals. Blossite is named after mineralogist F. Donald Bloss.The available literature does not explain the significance of the α/β forms other than the different crystal forms.
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General Information:
 Chemical Formula:
Cu2V+++++2O7
 Composition:
(Molecular Weight = 340.97 gm)
Vanadium 29.88 % V 
Copper 37.27 % Cu
Oxygen 32.85 % O 
 Empirical Formula:
Cu2V5+2O7
 IMA Status:
Approved IMA 1979
Physical Properties:
 Color:
black.
 Density:
3.86
 Diaphaniety:
Opaque
 Luster:
Metallic
 Streak:
red brown
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