Bannermanite

bannermanite

scherbinaite

stoiberite

ziesite

Images

Formula: (Na,K)_xV⁴⁺_xV_6-xO₁₅ (0.5 < x < 0.9)
Vanadium oxysalt
Crystal System: Monoclinic
Specific gravity: 3.5 measured, 3.55 calculated
Streak: Dark grey-black
Colour: Black, light brown on thin edges in transmitted light
Environments

Fumeroles

Localities

The type locality, the Izalco Volcano, Sonsonate Department, El Salvador, is a basaltic composite cone that has been intermittently active since its birth in 1770.
Vanadium is a distinctive element in the minerals of the sublimate suite, which includes such vanadium minerals as shcherbinaite, stoiberite and ziesite. Bannermanite is found in the fumaroles as a black incrustation coating basaltic breccia fragments. It occurs as subhedral to euhedral crystals up to approximately 250 microns in size, and is intimately associated with shcherbinaite (AM 68.634-642). Other associated minerals include fingerite, chalcocyanite and chalcanthite (HOM).

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