A gray-white brittle metallic element, occurring in several allotropic forms, found worldwide, especially in the ores pyrolusite and rhodochrosite and in nodules on the ocean floor. It is alloyed with steel to increase strength, hardness, wear resistance, and other properties and with other metals to form highly ferromagnetic materials. Atomic number 25; atomic weight 54.938; melting point 1,246°C; boiling point 2,061°C; specific gravity 7.21 to 7.44; valence 1, 2, 3, 4, 5, 6, 7. See Periodic Table.