What is Ojuelaite?
Ojuelaite is a hydrated zinc-iron arsenate from the famous oxidised ore zone of Mapimí, Mexico, where it forms pale yellow crusts and delicate sprays.
Mineralogy and crystal structure
Reference formula: ZnFe3+2(AsO4)2(OH)2·4H2O. Ojuelaite belongs to a family of hydrated iron arsenates whose water content and morphology are sensitive to alteration. The COD model is an exact representative entry for the named mineral. Ojuelaite is classified with phosphates and has a monoclinic crystal system. Typical hardness is 2.5–3 on the Mohs scale and specific gravity is approximately 3.1–3.3.
Colour, lustre and habit
Typical colours include pale yellow, yellow, brown, white. The usual fibrous, crusty, radiating habit and vitreous, pearly, earthy lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Ojuelaite forms in or is associated with supergene oxidation of zinc-rich hydrothermal ore deposits. Important documented localities include Mapimí in Durango, Mexico, with related arsenate occurrences in the United States and Europe.
Pale yellow chemistry from a legendary mine
Ojuelaite is a classic locality mineral: its delicate colour and hydrated structure are inseparable from the oxidised workings of the Ojuela Mine.
Collecting and care
Keep sealed and dry; avoid dust and acids and handle as an arsenic-bearing mineral.
