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Formula: Ca(UO2)2(PO4)2.6H2O
Hydrated normal phosphate, meta-autunite group,
uranyl mineral
Crystal System: Tetragonal
Specific gravity: 3.35 to 3.55 measured, 3.31 calculated
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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