What is Volborthite?
Volborthite is a hydrated copper vanadate known for yellow-green platy crystals and crusts in oxidised copper-vanadium deposits.
Mineralogy and structure
Reference formula: Cu3V2O7(OH)2·2H2O. Volborthite is monoclinic and hydrated, with chemistry that can include substitutions and alteration. The exact COD 1000137 model is used; colour is not diagnostic without context. Volborthite is classified with vanadates and has monoclinic crystal symmetry. Typical hardness is 3–3.5 on the Mohs scale and specific gravity is approximately 3.3–3.4.
Colour, lustre and habit
Typical colours include yellow, olive-green, green, brown. The usual tabular, platy, crusty habit and pearly, vitreous, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Volborthite forms in or is associated with secondary oxidation zones of copper deposits, vanadium-rich sandstones and hydrothermal veins. Important documented localities include Peru, Chile, Mexico, the United States, Germany and Australia.
Olive-yellow plates from a vanadium-rich oxidation zone
Volborthite brings a strong colour story to the vanadate family. Bright crusts and platy crystals are attractive when paired with copper minerals and a documented secondary-ore setting.
Collecting and care
Protect from scratches, acids, water and dust. Keep enclosed when the specimen is friable and wash hands after handling vanadium-bearing material.
