Hausmannite - Encyclopedia

Class : Oxides and hydroxides
Subclass : Oxides
Crystal system : Tetragonal
Chemistry : Mn₃O₄
Rarity : Quite common

Hausmannite is a mineral typical of high-temperature hydrothermal veins and metamorphic manganese deposits, in which it frequently accompanies braunite. It is also an oxide formed during the diagenesis of hydrated manganese minerals in certain large sedimentary deposits (Nikopol, Ukraine). It was named in honor of Johan Friedrich Ludwig Hausmann, Professor of Mineralogy at the University of Göttingen (Germany) and who studied the definition sample. Hausmannite appears in octahedra, sometimes centimeter-sized with striated faces, sometimes smooth and shiny, with a strong semi-metallic luster, of a brownish black. It also forms massive grainy aggregates. In reflected light, it is easily identified thanks to its constant polysynthetic twins and its scratched appearance. It is a manganese ore.

Main photo : Hausmannite from N'Chwaning II Mine, South Africa © Xiao-Dong Xu

Hausmannite on andratite from N'Chwaning II Mine, South Africa © Dan Weinrich

Hausmannite on andratite from N'Chwaning II Mine, South Africa © Dominik Schläfli

Hausmannite on andratite from N'Chwaning II Mine, South Africa © Tony Peterson

Twinned hausmannite from N'Chwaning Mines, South Africa © Rob Lavinsky

Hausmannite in the World

The most beautiful known crystals of hausmannite come from the mines of the Hotazel manganiferous district in South Africa, notably from N'Chwaning II, from where magnificent 4.5 cm crystals, often twinned, were extracted. The German deposits of Ilmenau (Thuringia) produced beautiful centimeter-sized octahedra, as did the Miguel Burnier mine near Ouro Preto (Minas Gerais, Brazil). Hausmannite is also common in the metamorphic manganese deposits of Langban (Sweden).

Hausmannite in France

In France, hausmannite is reported at Saphoz (Haute-Saône), on the Plateau d'Ambulla (Pyrénées-Orientales) and at Plan de Labasse (Hautes-Pyrénées) as well as at Combe Brémond near Barcelonnette (Alpes-de-Haute-Provence).

Twinning

A twinning plane is known on {112} that can produce polysynthetic twins.

Fakes and treatments

No fakes recorded for this mineral species.

Hardness : 5.5
Density : 4.83 to 4.85
Fracture : Irregular
Streak : Brownish black

TP : Opaque
RI : 2.152 to 2.462
Birefringence : 0.310
Optical character : -
Pleochroism : Low
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : NoneRadioactivity : None

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