Volborthite

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Volborthite
Volborthite-263832.jpg
Volborthite crystals from the Ridenaur Mine, Prospect Canyon District, Coconino County, Arizona (size: 5.8 x 4.5 x 4.2 cm)
General
Category Polyvanadate minerals
Formula
(repeating unit)
Cu3V2O7(OH)2·2H2O
Strunz classification 8.FD.05
Dana classification 40.03.10.01
Crystal system Monoclinic
Crystal class Prismatic (2/m)
Unit cell a = 10.610(2) Å, b = 5.866(1) Å
c = 7.208(1) Å; β = 95.04(2)°; Z = 2
Identification
Color Olive-green, yellow-green; green to yellow-green in transmitted light
Crystal habit Aggregates of scaly crystals, rosettes
Crystal symmetry Monoclinic
H-M symbol: (2/m)
Space group: C2/m
Cleavage Perfect
Mohs scale hardness
Luster Vitreous, waxy, greasy, pearly
Streak light green
Diaphaneity Translucent
Specific gravity 3.5 - 3.8
Optical properties Biaxial (+/-)
Refractive index nα = 1.793 nβ = 1.801 nγ = 1.816
Birefringence δ = 0.023
Pleochroism Weak
2V angle Measured: 63° to 83°
Dispersion Translucent to Subtranslucent
Ultraviolet fluorescence Non-fluorescent
Solubility Soluble in acids
References [1][2][3]

Volborthite is a mineral containing copper and vanadium, with the formula Cu3V2O7(OH)2·2H2O. Found originally in 1838 in the Urals, it was first named knaufite but was later changed to volborthite for Alexander von Volborth (1800–1876), a Russian paleontologist.[4]

Tangeite (synonym: calciovolborthite), CaCuVO4(OH), is closely related.

Occurrence[edit]

Volborthite was first described in 1837 for an occurrence in the Sofronovskii Mine, Yugovskii Zavod, Perm, Permskaya Oblast, Middle Urals, Russia.[2]

It occurs as an uncommon oxidation mineral in vanadium bearing hydrothermal copper ores. It is associated with brochantite, malachite, atacamite, tangeite, chrysocolla, baryte and gypsum.[1]

References[edit]