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Formula: (Fe2+,Mn2+)2Fe3+3(PO4)3(OH)4(H2O)
Hydrated phosphate, rockbridgeite group,
manganese-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 3.21 to 3.33 measured, 3.51 calculated for the empirical formula; the lower measured density is
attributed to the presence of sub-micrometer scale porosity
Colour: Dark green to black
Environments
Pegmatites
Hydrothermal environments
Ferrorockbridgeite is a relatively new mineral, approved in 2018.
Localities
At the type locality, the Hagendorf South Pegmatite, Hagendorf, Waidhaus, Neustadt an der Waldnaab District, Upper
Palatinate, Bavaria, Germany, ferrorockbridgeite forms as densely packed, lustrous, black blades, associated with
oxidised schoonerite group minerals,
jahnsite, idiomorphic crystals of
laueite and coatings of
mitridatite. The ferrorockbridgeite has most likely formed from
hydrothermal alteration of triphylite as well as from
zwieselite.
Ferrorockbridgeite occurs as compact intergrowths of dark green to black blades. Individual blades have lengths
up to 2 mm and are on the order of 10 microns thick
(EJM 31.2.389-397)
Ferrorockbridgeite from Hagendorf-Image
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