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
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
columbite group minerals, metatorbernite,
schoepite group minerals, uraninite,
uranophane and zircon
The type locality is the Daybreak mine, Mount Kit Carson, Spokane county, Washington, USA.
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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