Meta-autunite

minerals

autunite

metatyuyamunite

uraninite

Images

Formula: Ca(UO2)2(PO4)2.6H2O
Hydrated normal phosphate, meta-autunite group
Specific gravity: 3.35 to 3.55
Hardness: 2 to 2½
Streak: Pale yellow
Colour: Greenish yellow, lemon yellow
Common impurities: Ba,Mg
RADIOACTIVE
Environments:

Pegmatites
Sedimentary environments

Meta-autunite is a secondary mineral in granite pegmatites, or sedimentary bedded uranium-vanadium deposits, formed as dehydration pseudomorphs after autunite (Mindat, HOM). It is associated with autunite, and also carnotite, coffinite, columbite group minerals, metatorbernite, metatyuyamunite, phosphuranylite, schoepite group minerals, uraninite, uranophane and zircon (Mindat).

Localities

The type locality is the Daybreak mine, Mount Kit Carson, Spokane county, Washington, USA.

Alteration:

Meta-autunite is usually a dehydration product of autunite. Dehydration of autunite to meta-autunite takes place at room temperature in a dry atmosphere in a few hours, but it may re-hydrate to autunite again, depending on the humidity level. Meta-autunite forms irreversibly when autunite is heated above 80oC (Dana, Mindat, AM 45.99-128).

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