Autunite Locality: Les Oudots Quarry, Grury, Issy-l'Evêque, Saône-et-Loire, Burgundy, France:: Taille : 30 x 15 x 7 cm — Photo: Didier Descouens · CC BY-SA 4.0
Autunite
Also known as: Lime uranium mica.
Autunite (hydrated calcium uranyl phosphate), with formula Ca(UO2)2(PO4)2·10–12H2O, is a yellow-greenish fluorescent phosphate mineral with a hardness of 2–2+1⁄2. Autunite crystallizes in the orthorhombic system and often occurs as tabular square crystals, commonly in small crusts or in fan-like masses. Due to the moderate uranium content of 48.27% it is radioactive and also used as uranium ore. Autunite fluoresces bright green to lime green under UV light. The mineral is also called calco-uranite, but this name is rarely used and effectively outdated.
Intro adapted from Wikipedia (CC BY-SA).
Autunite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca(UO₂)₂(PO₄)₂·10-12H₂O.
It crystallizes in the orthorhombic crystal system (space group Pnma). It is a member of the Autunite structural group.
Key properties: Mohs hardness 2–2.5; specific gravity 3.05–3.2; typically yellow or green; Pale yellow streak; Vitreous, pearly on {001} luster; refractive index 1.568; optically uniaxial.
IMA symbol Aut, grandfathered status — known before the IMA’s founding, named in 1852.
A secondary mineral derived from primary uranium-bearing minerals under oxidizing conditions, in hydrothermal veins, granite pegmatites, etc.
It is found associated with Meta-autunite, torbernite, phosphuranylite, saléeite, uranophane, uranophane-beta, sabugalite.
The name refers to Autun, France, near to which the first specimens to be analyzed were collected.
Collections: Collector Favorites, Fluorescent & Glowing, Rare & Remarkable.