Pyrolusiitti

Pyrolusiitti is the mineral form of manganese dioxide, with the chemical formula MnO2. It is one of the most common and important manganese minerals, serving as the primary ore of manganese. The name pyrolusiitti comes from the Greek words "pyr" meaning fire and "lousis" meaning washing, referring to its historical use in glassmaking to decolorize glass.

This mineral typically occurs in earthy or powdery masses, but can also form prismatic crystals. Its color is typically dark gray to black, and it has a metallic luster. Pyrolusiitti is relatively soft, with a Mohs hardness of 2 to 2.5, and a specific gravity of about 5.06. It is insoluble in water but soluble in hydrochloric acid, producing chlorine gas.

Pyrolusiitti is found in a variety of geological environments, commonly in sedimentary deposits associated with iron and manganese ores, and as a secondary mineral in oxidized zones of manganese deposits. It is also found in hydrothermal veins. Major deposits are located in South Africa, Australia, China, Gabon, and India.

The principal use of pyrolusiitti is in the production of manganese metal and alloys, particularly ferromanganese and silicomanganese, which are essential for the steel industry. It is also used in batteries, particularly dry cell batteries, as a depolarizer. Other applications include the production of chemicals, dyes, and in water purification.