What is Russellite?
Russellite is a rare bismuth tungsten oxide, usually yellow to brown, valued for unusual chemistry and occurrence in oxidised bismuth-bearing deposits.
Mineralogy and crystal structure
Reference formula: Bi2WO6. Russellite is orthorhombic and belongs to a small group of bismuth tungstates. Bismuth and tungsten make the material dense; the selected COD entry is an exact russellite model. Russellite is classified with oxides and has a orthorhombic crystal system. Typical hardness is 2.5–3 on the Mohs scale and specific gravity is approximately 8.0–8.5.
Colour, lustre and habit
Typical colours include yellow, yellow-brown, brown, greenish yellow. The usual granular, massive, crusty habit and adamantine, resinous, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Russellite forms in or is associated with oxidised hydrothermal bismuth-tungsten veins and alteration zones. Important documented localities include Cornwall in the United Kingdom, Australia, Bolivia, China and other specialised localities.
A yellow oxide from a bismuth-tungsten system
Russellite is a strong specialist specimen because its colour is modest but its chemistry is not. Matrix, locality and association with bismuth minerals make the piece legible and collectible.
Collecting and care
Keep labelled and dry, avoid dust and acids, and do not cut or grind unknown bismuth-bearing ore.
