
Autunite
'Autunite' (hydrated calcium uranyl phosphate) with formula: Ca(UO
2)
2(PO
4)
2·10-12H
2O is a yellow - greenish
fluorescent mineral with a
hardness of 2 - 2½. Autunite crystallizes in the
tetragonal system and often occurs as tabular square crystals. Due to the high
uranium content it is
radioactive and also used as uranium ore. If the mineral dries out, it converts to
meta-autunite-I, which can turn into
meta-autunite-II after heating. These two subsequent minerals are very rare in nature. For scientific studies it is recommended to store the mineral in a sealed container to minimize the water loss. Museums are known to have covered the mineral with
lacquer to avoid drying of the mineral.
Autunite was discovered in 1852 near
Autun,
France.
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Mindat

Scaly Crystals of the secondary uranium phosphate mineral Autunite