A light silver-white metallic element, malleable and
   ductile, quite permanent in dry air but tarnishing in moist air. It
   burns, forming (the oxide) magnesia, with the production of a blinding
   light (the so-called magnesium light) which is used in signaling, in
   pyrotechny, or in photography where a strong actinic illuminant is
   required. Its compounds occur abundantly, as in dolomite, talc,
   meerschaum, etc. Symbol Mg. Atomic weight, 24.4. Specific gravity,
   1.75.