A manganese oxide mineral that's a key ore for manganese that forms as a weathering product of other manganese minerals, or as concretions or nodules deposited by groundwater or lake water.

Pyrolusite is used in the production of steel and manganese bronze, as a decoloring agent in glass, and in dry cells.

Pyrolusite can be toxic to the blood, nervous system, liver, and central nervous system. Repeated or prolonged exposure can cause organ damage. The dry powder pigment can be inhaled, so care should be taken when handling it.