Tangeite

Tangeite, also known as calciovolborthite, is a calcium, copper vanadate mineral with formula: CaCu(VO4)(OH). It occurs as a secondary mineral that can be found in sandstone and also in the oxidized zones of vanadium bearing deposits.

Tangeite
General
CategoryPhosphate mineral
Formula
(repeating unit)
CaCu(VO4)(OH)
Strunz classification8.BH.35
Dana classification41.05.01.06
Crystal systemOrthorhombic
Crystal classDisphenoidal (222)
H-M symbol: (2 2 2)
Space groupP212121
Unit cella = 7.45 Å, b = 9.26 Å
c = 5.91 Å; Z = 4
Identification
ColorYellow, yellow-green, olive green, green to dark green
Crystal habitRarely as short prismatic crystals, commonly as fibrous to botryoidal encrustations
CleavagePerfect on {010}, good on {001}
TenacityBrittle
Mohs scale hardness3.5
LusterVitreous, pearly on cleavage faces
StreakLight yellow green
DiaphaneityTransparent, Translucent
Specific gravity3.75 - 3.84
Optical propertiesBiaxial (-)
Refractive indexnα = 2.010 nβ = 2.050 nγ = 2.090
Birefringence0.08
2V angle83° (measured)
References[1][2][3]

It was named in 1925 by Aleksandr Evgenievich Fersman for its discovery locality in the Tange Gorge, Ferghana Valley, Alai Mountains, Kyrgyzstan.[1]

References

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