(Magnesia, district in Thessaly) Compounds of magnesium have long been known. Blackrecognized magnesium as an element in 1755. Davy isolated it in 1808 and Bussy prepared itin coherent form in 1831. Magnesium is the eighth most abundant element in the earth'scrust. It does not occur uncombined, but is found in large deposits in the form ofmagnesite, dolomite, and other minerals.

The metal is now principally obtained in the U.S. by electrolysis of fused magnesiumchloride derived from brines, wells, and sea water.