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Formula: Fe2+2Fe3+O2(BO3)
Anhydrous monoborate,
ludwigite group, forms a series with
ludwigite
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.
Vonsenite from the Old City Quarry - Image
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 ).
Vonsenite from Jayville - Image
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