What is Pyrolusite?
Pyrolusite is manganese dioxide, a black to steel-grey oxide and one of the most important manganese ores, often forming dendritic coatings and fibrous aggregates.
Mineralogy and crystal structure
Reference formula: MnO2. Pyrolusite is tetragonal and commonly intergrows with other manganese oxides such as cryptomelane and manganite. Dendritic appearance alone does not prove pyrolusite. Pyrolusite is classified with oxides and has a tetragonal crystal system. Typical hardness is 6–6.5 on the Mohs scale and specific gravity is approximately 4.7–5.1.
Colour, lustre and habit
Typical colours include black, steel-grey, dark grey, silver-grey. The usual acicular, dendritic, massive habit and metallic, dull, earthy lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Pyrolusite forms in or is associated with supergene oxidation, sedimentary manganese deposits, hydrothermal veins and cave coatings. Important documented localities include South Africa, India, Brazil, Georgia, Germany, Australia and the United States.
Black dendrites with industrial importance
Pyrolusite is a strong guide mineral because its dramatic black forms connect collector aesthetics with the global manganese cycle and ore industry.
Collecting and care
Avoid dust and prolonged skin contact; keep dry, do not grind at home and preserve matrix for identification.
