Formula: Fe2+2(PO4)F
Anhydrous phosphate containing halogen, triplite group, and
forms a series with it
Crystal System: Monoclinic
Specific gravity: 3.89 to 3.97 measured, 3.92 calculated
Hardness: 5 to 5½
Streak: White to tan
Colour: Dark brown, black (altered)
Solubility:
Common impurities: Mg,Ca
Environments
Zwieselite occurs as a primary phosphate in complex
zoned granite
pegmatites, associated with
triphylite,
hureaulite and
rockbridgeite
(HOM).
Localities
At the type locality, the Birkhöhe Quarry, Zwiesel, Regen District, Lower Bavaria, Bavaria, Germany,
zwieselite occurs in a granite
pegmatite
(Mindat).
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