(Chemical symbol Mg.) - Element No. 12 of the periodic system; atomic weight 24.305. Specific gravity 1.77 with a melting point of approximately 1160°F. A silver-white light malleable, ductile metallic element that occurs abundantly in nature. The metal is used in metallurgical and chemical processes; in photography, in signaling, and in the manufacture of pyrotechnics because of the intense white light it produces on burning.