Hydrated normal phosphate, meta-autunite group. Rapid dehydration of uranocircite in dry atmospheres at normal temperature results in metauranocircite (Mindat).
Specific gravity: 3.94
Hardness: 2 to 2½
Streak: Yellowish white
Colour: Greenish yellow, yellowish green
Metauranocircite occurs typically as a secondary mineral derived from phosphatic
uraninite deposits in the oxidised zone of some uranium deposits; it may be
primary in low-temperature veins, and it also occurs in
granite pegmatites. Associated minerals include autunite,
uranophane-β and zippeite group minerals
(HOM, Webmin, Mindat).
The type locality is the Krunkelbach Valley Uranium deposit, Menzenschwand, St Blasien, Waldshut, Freiburg Region, Baden-Württemberg, Germany.
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