Alluaudite

triphylite

lithiophilite

Formula: (Na,Ca)(Mn,Mg,Fe2+)(Fe3+,Mn2+)2(PO4)3
Anhydrous normal phosphate, forms a series with ferroalluaudite.
Specific gravity: 3.45
Hardness: 5½ to 6
Streak: Dirty yellow
Colour: Dirty yellow to brownish yellow, greyish green, black
Solubility: Soluble in acids
Melting point: Approximately 1000oC (AM 50.1647)
Environments

Pegmatites

Alluaudite is a very common secondary mineral in granite pegmatites, formed by sodium metasomatism of triphylite - lithiophilite, heterositepurpurite or ferrisicklerite (Webmin, Dana, HOM). It is an alteration product of varulite and arrojadite-(KFe) (Mindat), and it alters to heterosite and purpurite with leaching of sodium Na and oxidation of iron Fe and manganese Mn (Dana). It also occurs in phosphatic nodules in shale (HOM).
Associated minerals include triphylite, arrojadite, satterlyite, wicksite, wolfeite and pyrite (HOM).

The type locality is Varuträsk, Skellefte mining district, Skellefteå, Västerbotten County, Sweden.

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