Manganese metals dissolve in acid and corrode in moist air.
Pyrolusite is the principal ore or manganese. Manganese is used mainly in the form of alloys with iron. One of these alloys, ferromanganese, is used in steelmaking. Safes are made of manganese steel. Pyrolusite is used as a depolarizer in dry cells and is also used to decolorize glass that is colored green by impurities of iron.