Formula: Fe2+2Fe3+O2(BO3)
Anhydrous borate, ludwigite group, and forms a series with it
Specific gravity: 4.7
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
hypersthene. Minor associates include quartz,
fluorite, zircon,
chlorite, ferroan talc,
hematite, pyrite,
chalcopyrite and goethite
(AM 46.786-811 ).
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