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Formula: Cu2+3Fe3+4(VO4)6
Anhydrous vanadate
Crystal System: Orthorhombic
Specific gravity: 4.215 calculated
Streak: Dark grey
Colour: Black
Environments
Localities
At the type locality, the Izalco Volcano, Sonsonate Department, El Salvador, lyonsite has been discovered
in the summit crater fumaroles. The mineral, which occurs with thénardite
and howardevansite, formed as a sublimate product from the volcanic
gases at up to 800oC. Lyonsite occurs as euhedral, black lathlike crystals up to 230 microns in
greatest dimension
(AM 72.1000-1005, HOM).
Lyonsite from the Izalco Volcano -
Image
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