Magnesium \Mag*ne"si*um\, n. [NL. & F. See Magnesia.]

(Chem.) 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.

Magnesium sulphate. (Chem.) Same as Epsom salts.

Source: Webster's Revised Unabridged Dictionary (1913)