Wüstite

wustite

andradite

hematite

hedenbergite

Formula: FeO
Simple oxide, periclase group
Magnesiowüstite is a variety of wüstite, FeO, that is also an iron-bearing variety of periclase, MgO

Crystal System: Isometric
Specific gravity: 5.88 measured, 5.97 calculated
Hardness: 5 to 5½
Colour: black
Environments:

Volcanic igneous environments
Metamorphic environments

Wüstite may be found in kimberlite and basalt

Alteration

Wüstite is formed as an alteration product of other iron-bearing minerals at high temperatures in a highly reducing environment.

hematite, wüstite, quartz and calcite to andradite, hedenbergite, magnetite and CO2
2Fe2O3 + 2FeO + 5SiO2 + 4CaCO3 → Ca3Fe3+2(SiO4)3 + CaFe2+Si2O6 +Fe2+Fe3+2O4 +4CO2

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