A light, silvery-white, moderately hard metallic element that in ribbon or powder form burns with a brilliant white flame. Obtained chiefly from magnesite, dolomite, and bodies of salt water, it is used in structural alloys, pyrotechnics, flash photography, and incendiary bombs. Atomic number 12; atomic weight 24.305; melting point 650°C; boiling point 1,090°C; specific gravity 1.738 (at 20°C); valence 2. See Periodic Table.