What is Hausmannite?
Hausmannite is a manganese oxide with dark brown to black crystals, an important component of some manganese ore assemblages.
Mineralogy and structure
Reference formula: Mn3O4. Hausmannite has a tetragonal oxide structure related to the spinel family and contains manganese in more than one oxidation state. Fine-grained material may resemble other dark manganese oxides. Hausmannite belongs to the oxides and has a tetragonal crystal system. Typical hardness is 5–5.5 on the Mohs scale and specific gravity is approximately 4.7–4.9.
Colour and appearance
Typical colours include brown-black, black, dark brown. The usual tabular, prismatic, granular habit and metallic, sub-metallic lustre are useful descriptive features, but colour alone is not diagnostic.
Formation and localities
Hausmannite forms in or is associated with manganese-rich metamorphic rocks, hydrothermal veins and contact-metamorphic deposits. Important documented localities include Germany, Sweden, South Africa, Brazil, India and the United States.
Collecting and care
Keep labelled and dry; avoid cutting or grinding unknown manganese ore and protect crystal faces from abrasion.
