Manganosite

oxide

manganese

Formula: MnO
Simple oxide, periclase group, manganese mineral
Specific gravity: 5.364
Hardness: 5½
Streak: Brown
Colour: Emerald-green, darkening on exposure to black
Solubility: Dissolves with difficulty in strong hydrochloric or nitric acid to a colourless solution (Dana)
Environments:

Metamorphic environments

Manganosite occurs in metamorphosed manganese deposits as an alteration product of rhodochrosite or other manganese minerals, formed during oxygen-deficient metamorphism of manganese-bearing deposits. It also occurs in marine manganese nodules (HOM).

At Långban, Sweden, manganosite is associated with pyrochroite, manganite and dolomite.

At Nordmark, Sweden, manganosite is associated with pyrochroite, hausmannite, periclase, garnet and dolomite.

At Franklin, New Jersey, USA, manganosite is associated with franklinite, willemite, calcite and zincite.

Alteration

manganosite and O2 to hausmannite
6MnO + O2 ⇌ 2Mn2+Mn3+2O4
Increasing temperature favours the forward reaction AM80.571.

manganosite and quartz to rhodonite
MnO + SiO2 ⇌ Mn2+SiO3
AM80.561

manganosite and quartz to tephroite
2MnO + SiO2 ⇌ Mn2+2SiO4
AM80.571

manganosite and rhodonite to tephroite
MnO + Mn2+SiO3 ⇌ Mn2+2SiO4
AM80.571

rhodochrosite to manganosite and CO2
MnCO3 ⇌ MnO + CO2
Increasing temperature favours the forward reaction AM80.571.

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