- a hard, brittle, grayish-white, metallic element, an oxide of which, MnO2(manganese dioxide ), is a valuable oxidizing agent: used chiefly as an alloying agent in steel to give it toughness. Symbol: Mn; atomic weight: 54.938; atomic number: 25; specific gravity: 7.2 at 20°C.
- a brittle greyish-white metallic element that exists in four allotropic forms, occurring principally in pyrolusite and rhodonite: used in making steel and ferromagnetic alloys. Symbol: Mn; atomic no: 25; atomic wt: 54.93805; valency: 1, 2, 3, 4, 6, or 7; relative density: 7.21–7.44; melting pt: 1246±3°C; boiling pt: 2062°C
