What is Uranocircite?
Uranocircite is a hydrated barium uranyl phosphate, typically yellow to greenish-yellow and associated with oxidised uranium deposits.
Mineralogy and structure
Reference formula: Ba(UO2)2(PO4)2·10H2O. Uranocircite belongs to the autunite group and can lose water to form meta-uranocircite. The structure image uses COD 1534214 as a labelled meta-uranocircite representative; the specimen's hydration state should not be assumed from colour alone. Uranocircite is classified with phosphates and has tetragonal crystal symmetry. Typical hardness is 2–2.5 on the Mohs scale and specific gravity is approximately 3.1–3.4.
Colour, lustre and habit
Typical colours include yellow, greenish-yellow, yellow-green, brownish-yellow. 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
Uranocircite forms in or is associated with secondary oxidation zones of uranium deposits, fractures and weathered phosphate-bearing uranium minerals. Important documented localities include Germany, Portugal, France, the United States, the Czech Republic and Australia.
Yellow phosphate plates from a uranium oxidation zone
Uranocircite combines bright colour with a clear secondary-ore story. Its value lies in intact plates, reliable hydration and locality data, presented with proper radiation safety.
Collecting and care
Radioactive and hydrated: keep sealed, dry and shielded as appropriate; avoid dust, water, prolonged exposure and unsupervised handling.
