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Formula:
Formerly the formula was given as
(Na,Ca,Mn2+,☐)2Mn2+2Al(PO4)3
but now the IMA gives it as
NaNaMn(Fe2+Al(PO4)3
Anhydrous normal phosphate, wyllieite group,
manganese-bearing mineral,
forms a series with
rosemaryite and with
ferrowyllieite
Crystal System: Monoclinic
Specific gravity: 3.61 calculated
Hardness: 4 to 4½
Streak: Dirty olive-green
Colour: Deep bluish green to deep oily green, grey-green to greenish-black
Environments
Wyllieite occurs in zoned complex granite
pegmatites
(HOM).
Localities
At the Buranga pegmatite, Muhororo, Ngororero District, Western Province, Rwanda, wyllieite is associated with
trolleite and scorzalite
(HOM).
At the type locality, the Old Mike mine, Custer, Custer Mining District, Custer county, South Dakota, USA, wyllieite
occurs as masses and crude crystals up to 10 cm in size, in zoned, complex
granite
pegmatites. Associated minerals include
quartz, muscovite,
plagioclase, graftonite and
sarcopside, also arrojadite-(KFe),
arsenopyrite, scorzalite,
ludlamite, vivianite and
garnet
(Mindat,Dana).
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