Hausmannite

manganese

jacobsite

Formula: Mn2+Mn3+2O4
Multiple oxide with a distorted spinel structure, although it is not a member of the spinel group (Mindat). Manganese mineral.
Specific gravity: 4.83 to 4.85
Hardness: 5½
Streak: Dark reddish brown, dark brown
Colour: Brown-black
Solubility: Soluble in hot hydrochloric acid with the evolution of Cl2.
Epitaxy: Hausmannite and jacobsite have been found as oriented intergrowths.
Environments:

Metamorphic environments
Hydrothermal environments

Hausmannite is a primary mineral in hydrothermal veins. It may also be produced by metamorphism of manganiferous rocks. At the type locality, Thuringia, Germany, it occurs in a manganese ore deposit.
At the Woods mine, New South Wales, Australia, hausmannite forms by oxidation and loss of SiO2 from neotocite and tephroite. (AJM 15.1&2.15)

Alteration

braunite to hausmannite, SiO2 and O2
3Mn2+Mn3+6O8(SiO4) ⇌ 7Mn2+Mn3+2O4 +3SiO2 + O2
(AM80.565)

braunite to hausmannite, rhodonite and O2
2Mn2+Mn3+6O8(SiO4) ⇌ 4Mn2+Mn3+2O4 + 2Mn2+SiO3 + O2
A higher temperature favours the forward reaction
(AM80.565).

braunite to tephroite, hausmannite and O2
3Mn2+Mn3+6O8(SiO4) ⇌ 3Mn2+2(SiO4) + 5Mn2+Mn3+2O4 + 2O2
(AM80.571)

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

hausmannite and quartz to rhodonite and O2
2Mn2+Mn3+2O4 + 6SiO2 ⇌ 6Mn2+SiO3 + O2
(AM80.571)

hausmannite and rhodonite to tephroite and O2
2Mn2+Mn3+2O4 + 6Mn2+SiO3 ⇌ 6Mn2+2SiO4 + O2
A higher temperature favours the forward reaction (AM80.565)

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

rhodochrosite and O2 to hausmannite and CO2
6MnCO3 + O2 ⇌ 2Mn2+Mn3+2O4 +6CO2
A higher temperature favours the forward reaction (AM80.571)

Common impurities: Zn,Fe,Ca,Ba,Mg

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