VOLBORTHITE

    Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated vanadates
    Crystal system : Monoclinic
    Chemistry : Cu3V2O7(OH)2 2H2O
    Rarity : Uncommon

Volborthite is a copper vanadate formed in the oxidation zone of hydrothermal vanadium deposits. It is a secondary mineral known as impregnations in sandstones and conglomerates. It was named in honor of the Russian paleontologist Alexander Fedorovich von Volborth who discovered the mineral in the Urals. Volborthite occurs as rosettes of hexagonal or triangular scaly crystals generally not exceeding 5 mm, as scaly encrustations, as spherulitic, fibroradiated or reticulated aggregates. Its color is dark olive green to yellow-green, brownish yellow or brown.

Main photo : Volborthite from Monument Valley, Arizona, USA © Stephan Wolfsried

3 cm volborthite and azurite from Milpillas, Sonora, Mexico © Jordy Fabre
Volborthite from Milpillas, Sonora, Mexico © Yaiba Sakaguchi
Volborthite from Kociha, Slovakia © Christian Auer
Volborthite from Kahlenberg, Eifel, Germany © Jürgen Greiner

Volborthite in the World

Volborthite is particularly present in Monument Valley (Arizona) and Richardson (Utah), where it constitutes beautiful specimens. Very nice samples come from Nizhny Tagil and Sysert in the Ural Mountains (Russia). It is also known in the Slick Rock district (Colorado) and Carlin (Nevada), but the best samples come from Milpillas (Sonora, Mexico) where it forms 3 cm rosettes associated with azurite.

Volborthite in France

In France, volborthite is reported at Chardonnet near Tignes (Savoie), France.

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 3.5
Density : 3.5 to 3.8
Fracture : Undetermined
Streak : Undetermined

TP : Translucent
RI : 1.793 to 1.816
Birefringence : 0.023
Optical character : Biaxial (+/-)
Pleochroism : Low
Fluorescence : None

Solubility : Acids

Magnetism : NoneRadioactivity : None