What is Vauquelinite?
Vauquelinite is a rare lead copper chromate phosphate, usually green to brown and found as a secondary mineral in oxidised lead deposits.
Mineralogy and structure
Reference formula: Pb2Cu(CrO4)(PO4)(OH). Vauquelinite is monoclinic and contains both chromate and phosphate groups. The exact COD 9008142 structure is used. Lead and chromium require protected handling and clear labelling. Vauquelinite is classified with chromates and has monoclinic crystal symmetry. Typical hardness is 2.5–3 on the Mohs scale and specific gravity is approximately 5.5–5.8.
Colour, lustre and habit
Typical colours include green, olive-green, brown, yellow. The usual tabular, granular, crusty habit and resinous, vitreous, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Vauquelinite forms in or is associated with oxidation zones of lead-copper ores, chromate-bearing veins and secondary cavities. Important documented localities include the Urals, Romania, France, Germany, the United States, Mexico and Chile.
Green chemistry in a lead-ore oxidation zone
Vauquelinite is a high-interest micromount and cabinet mineral because colour, rarity and complex chemistry align. A documented paragenesis is more persuasive than an isolated green crust.
Collecting and care
Keep enclosed, dry and away from dust, food and children. Do not cut, grind or acid-test; wash hands after handling.
