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Formula: Fe2+2Fe3+O2(BO3)
Anhydrous borate, ludwigite group, and
forms a series with it
Crystal System: Orthorhombic
Specific gravity: 4.21 measured, 4.80 calculated
Hardness: 5
Streak: Black, blackish green
Colour: Black, greenish black
Solubility: Slowly soluble in acids
Common impurities: Mg,Al
Environments
Vonsenite is an uncommon high-temperature mineral occurring in
contact metamorphic
deposits (Mindat), where it occurs in boron-rich skarn associated with
magnetite, pyroxene and
pyrrhotite
(HOM, Webmin).
Localities
The type locality is the Old City Quarry, Riverside, Riverside county, California, USA.
At the Jayville magnetite deposit, At Lawrence county, New York, USA, vonsenite occurs in
skarn. Major associates are
biotite,
clinoamphiboles, Fe-rich diopside and
enstatite-ferrosilite. Minor
associates include quartz,
fluorite, zircon,
chlorite, ferroan talc,
hematite, pyrite,
chalcopyrite and goethite
(AM 46.786-811 ).
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