Bixbyite

minerals

topaz

rhodochrosite

hausmannite

Formula: Mn3+2O3
Simple oxide, manganese mineral
Specific gravity: 4.945
Hardness: 6 to 6½
Streak: Black
Colour: Black
Common impurities: Al,Mg,Si,Ti
Environments:

Volcanic igneous environments
Metamorphic environments
Hydrothermal environments

At Långban, Sweden, bixbyite occurs in metamorphosed manganese ores (Dana).

At the Black Range tin district, New Mexico, USA, bixbyite occurs in rhyolite (Dana).

At Topaz Mountain, Utah, USA, bixbyite occurs in cavities in rhyolite associated with topaz, spessartine, beryl variety red beryl and hematite, also with fluorite (Dana).

Alteration

bixbyite and O2 to pyrolusite
2Mn2O3 + O2 ⇌ 4MnO2
Increasing temperature favours the forward reaction (AM80.571).

bixbyite and quartz to braunite and O2
14Mn2O3 + 4SiO2 ⇌ 4Mn2+Mn3+6O8(SiO4) + O2
(AM80.571)

hausmannite and O2 to bixbyite
4Mn2+Mn3+2O4 + O2 ⇌ 6Mn2O3 (AM80.560-575)

rhodochrosite and O2 to bixbyite and CO2
4MnCO3 + O2 ⇌ 2Mn3+2O3 +4CO2
Increasing temperature favours the forward reaction (AM80.571).

The diagram below is a Pourbaix diagram for manganese (GSJ). It shows the relationship between akhtenskite MnO2, bixbyite Mn2O3 and hausmannite Mn3O4.

Pourbaix manganese.jpg
























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