Magnesium Ores

natural mineral formations that contain magnesium in sufficient quantity to make extraction economically feasible. Magnesium is a component of more than 100 minerals, among them brucite, Mg(OH)₂, containing 41.7 per-cent Mg; magnesite, MgCO₃ (28.8 percent Mg); dolomite, MgCO₃.CaCO₃ (18.2 percent Mg); kieserite, MgSO₄.H₂O (17.6 percent Mg); bischofite, MgCl₂.6H₂O( 12.0 percent Mg); langbeinite, 2MgSO₄.K₂SO₄ (11.7 percent Mg); epsomite, MgS04-7H20 (9.9 percent Mg); kainite, MgSO₄.KC1.3H₂O (9.8 percent Mg); carnallite, MgCl₂.KCl-6H₂O (8.8 percent Mg); astrakanite, MgSO₄.Na₂SO₄.4H₂O (7.3 percent Mg); and polyhalite, MgSO₄.2CaSO4-K₂SO₄.2H₂O (4.2 percent Mg).

The principal magnesium ores are found in mineral deposits of magnesia-potassium salts. Large magnesite beds are found in metamorphosed dolomites. Bodies of brucite (the raw material with the highest magnesia content) form in cases of contact metamorphism of magnesite. Natural mineral brines and salt springs are formed as a result of leaching of magnesia salts by subterranean waters. Modern salt deposits (brines and sediments) occur in inland gulfs (for example, Kara-Bogaz-Gol in the USSR) and in intracontinental drainage basins (Lakes Baskunchak and El’ton in the USSR; the Great Salt Lake in the USA). Another increasingly used magnesium source is seawater (4 percent Mg in dry residue), with its stable composition and unlimited resources.

The USSR has very large magnesia-potassium salt basins, which include the Verkhniaia Kama deposit (Permian) in Cisuralia, the Pripiat’ deposit (Devonian) in the Byelorussian SSR, and the Kalush deposit (Neocene) in Ciscarpathia. Other well-known areas are the Permian Stassfurt salt basin (Federal Republic of Germany and German Democratic Republic) and deposits in the southern USA.