- magnesium, Mg, atomic number 12 - a light silver-white ductile bivalent metallic element; in pure form it burns with brilliant white flame; occurs naturally only in combination (as in magnesite and dolomite and carnallite and spinel and olivine)
--1 is a kind of metallic element, metal
--1 is a substance ofcarnallite; dolomite; magnesite; olivine; periclase, magnesia, magnesium oxide; spinel