What is Uranophane?
Uranophane is a yellow hydrated calcium uranium silicate that forms delicate fibres and crusts as a secondary mineral in oxidised uranium deposits.
Mineralogy and structure
Reference formula: Ca(UO2)2(SiO3OH)2·5H2O. Uranophane is commonly divided into alpha- and beta-polymorphs in mineralogical references. This page uses the monoclinic alpha-uranophane structure from COD 9011364 as a clearly labelled representative model; natural material is radioactive and hydrated. Uranophane is classified with silicates and has monoclinic crystal symmetry. Typical hardness is 2.5–3 on the Mohs scale and specific gravity is approximately 3.8–4.0.
Colour, lustre and habit
Typical colours include yellow, lemon-yellow, orange-yellow, brownish-yellow. The usual fibrous, radiating, crusty habit and silky, vitreous, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Uranophane forms in or is associated with oxidation zones of uranium ores, fractures, mine dumps and weathered primary uranium minerals. Important documented localities include the United States, Germany, France, the Czech Republic, Australia, Canada and Namibia.
Golden-yellow fibres from an oxidised uranium vein
Uranophane shows how groundwater can reorganise uranium and silica after the primary ore has weathered. Its bright colour and fine fibres are attractive, but safe containment and provenance come first.
Collecting and care
Radioactive and fragile: keep enclosed, dry and away from children, pets and food; do not generate dust or use water and handle according to radiation-safety procedures.
