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)
Alluaudite is a very common secondary mineral in
pegmatites, formed by sodium metasomatism of triphylite -
lithiophilite, heterosite –
purpurite 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
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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