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Formula: NaNaFe2+(Fe2+Al)(PO4)3
Phosphate, wyllieite group,
alluaudite supergroup, forms series with
wyllieite and with
rosemaryite
Crystal system: Monoclinic
Specific gravity: 3.601 measured, 3.68 calculated
Hardness: 4
Streak: Light grey
Colour: Greenish black, also dark bluish green, dark greenish grey, dark green, dark brown
Luminescence: Not fluorescent under UV
Environments
Ferrowyllieite occurs as a primary phosphate in zoned
granite
pegmatites
(HOM).
Localities
At the type locality, the Victory Mine, Custer, Custer Mining District, Custer County, South Dakota, USA,
ferrowyllieite occurs as crude euhedral crystals, to 10 cm in size, in interlocking aggregates in large pods
in the granite
pegmatite. Associated minerals include
arrojadite-(KFe),
muscovite, schorl,
plagioclase and quartz
(HOM, Mindat).
Ferrowyllieite from the Victory Mine -
Image
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