Autunite
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 4.0)
Mineral NameAutunite
Chemical FormulaCa(UO2)2(PO4)2·10-12H2O
Mohs Hardness2
Crystal Systemtetragonal
Lustervitreous
Streak Colorpale yellow
Cleavageperfect on {001}
Fractureuneven
Specific Gravity3.1
Colorsyellow, yellowish-green, greenish-yellow
Transparencytransparent
Type LocalityVénachat Mine, Compreignac, Haute-Vienne, Limousin, France
Mineral GroupPhosphates
Usesuranium ore, collector
Associated Mineralsuraninite, pitchblende
Rarityuncommon
Description
This specimen features bright yellowish-green, tabular to platy crystals of autunite forming aggregates, contrasting sharply with the dark, botryoidal to massive pitchblende matrix.
Geological Context
Autunite is a secondary uranium mineral, typically forming in the oxidized zones of uranium-bearing ore deposits through the alteration of primary uranium minerals like uraninite (pitchblende). It is often found in granitic pegmatites and hydrothermal veins.
