Magnesioferrite

oxide

magnetite

Formula: MgFe3+2O4
Multiple oxide, spinel group, magnesioferrite-magnetite series
Specific gravity: 4.6
Hardness: 6 to 6½
Streak: Black or dark red
Colour: Black, reddish-brown in transmitted light
Environments:

Metamorphic environments

Magnesioferrite is most commonly found in fumeroles where it probably formed by the reaction at high temperature of steam and ferric chloride with magnesian material . It is also found in sanidinite facies combustion-metamorphosed marl and burning coal heaps, and in metamorphosed dolostone. It is an accessory mineral in some kimberlite, gabbro and carbonatites.
Magnesioferrite is associated with hematite, titanium-rich magnetite, iron-rich diopside and dolomite, and at Långban, Sweden, occasionally with bromellite.

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