Mineral Species: Pyrolusite

Chemical Formula: MnO2

Chemical Name: Managnese Oxide

Mineral Class: Oxide

Mineral Notes: Pyrolusite is the most common manganese mineral and is an important ore of the metal. The mineral is an oxidation product of weathered manganese minerals and often replaces Rhodochrosite and Hausmannite. Pyrolusite has some interesting habits including fern-like patterns on the surfaces of rocks, often mistaken for fossil plants. Another habit is its acicular or hair-like aggregates that produce tufts of black  fibers. These are rare. Often specimens of Pyrolusite are difficult to distinguish from other manganese oxides. Thus the mineral name tends to be given to any black, hair-like manganese crystals or powdery black alteration products.

Description: Superbly formed crystals of black Pyrolusite on matrix. These are highly lustrous and extremely unusual because the mineral rarely occurs in such excellent crystalline form. A very good example of Pyrolusite in crystalline form. 

Location: Kokuriki Mine, Tokoro District, Hokkaido, Japan.