What is Walentaite?
Walentaite is a rare hydrated iron arsenate-phosphate found as earthy yellow to brown secondary material in oxidised ore deposits.
Mineralogy and structure
Reference formula: Fe3+3(AsO4)2(PO4)·4H2O. Walentaite is orthorhombic and its natural chemistry commonly includes variable arsenate, phosphate, calcium, manganese and tungsten. COD 9017256 is a labelled representative natural model. Walentaite is classified with phosphates and has orthorhombic crystal symmetry. Typical hardness is 2–3 on the Mohs scale and specific gravity is approximately 3.0–3.4.
Colour, lustre and habit
Typical colours include yellow, orange-yellow, brown, greenish-yellow. The usual crusty, fibrous, granular habit and pearly, vitreous, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Walentaite forms in or is associated with oxidised arsenic-phosphate veins, mine workings and secondary alteration zones. Important documented localities include Germany, the Czech Republic, Slovakia, Mexico and other European and American ore districts.
A yellow secondary mineral with complex chemistry
Walentaite is a specialist collector mineral where colour and the chemistry of an oxidised ore zone matter more than crystal size. Provenance is essential.
Collecting and care
Arsenic-bearing and fragile: keep sealed and dry, avoid dust and water, and wash hands after handling.
