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Autunite
Chemical Formula	Ca(UO2)2(PO4)2·10-12H2O
Species	Phosphates
Crystal System	Orthorhombic
Mohs Scale	2
Specific Gravity	3.1-3.2
Color	Lemon-yellow to sulfur-yellow, greenish yellow to pale green; may be dark green to greenish black
Streak	Pale yellow
Luster	Sub-Vitreous, Resinous, Waxy, Pearly
Refractive Index	n = 1.553 - 1.555 n = 1.575 n = 1.577 - 1.578 n = 1.575 n = 1.572
Diaphaneity	Transparent, Translucent
Cleavage	PerfectPerfect on , indistinct on
Fracture	Micaceous
Crystal Habit：Tabular crystals, foliated or scaly aggregates, and in crusts
Geological Setting：In the oxidation zone of uranium bearing rocks, including sandstones, hydrothermal veins, and granitic pegmatites.

Autunite (hydrated calcium uranyl phosphate) with formula: Ca(UO₂)₂(PO₄)₂·10-12H₂O is a yellow - greenish fluorescent mineral with a hardness of 2 - 2?. Autunite crystallizes in the orthorhombic system and often occurs as tabular square crystals. Due to the moderate uranium content of 48.27% 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. It occurs as oxidizing product of uranium minerals in granite pegmatites and hydrothermal deposits. Associate minerals include metaautunite, torbernite, phosphuranylite, saleeite, uranophane and sabugalite.

Mining

Some autunite is found near the Mount Spokane, Washington. 90,000 lbs of U₃O₈ were produced from nine properties, although most of the ore came from the Daybreak Mine.

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