magnesite

magnesite măg´nəsīt [key], mineral, magnesium carbonate, MgCO 3, white, yellow, or gray in color. It originates through the alteration of olivine or of serpentine by waters carrying carbon dioxide through the replacement of calcium by magnesium in calcareous rocks, sometimes limestone but more often dolomite and through precipitation from waters rich in magnesium that have undergone reaction with sodium carbonate. Caustic magnesite is not thoroughly calcined, 3% to 4% of carbon dioxide being left mixed with magnesium chloride it makes oxychloride cement, which is extensively used for floorings and as a stucco. Dead-burned magnesite is calcined in kilns until it contains less than 1% of carbon dioxide it is made into an excellent firebrick . Magnesite is also used in the manufacture of Epsom salts, face powder, boiler wrappings, and disinfectants.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

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