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talc

talc, mineral ranging in color from white through various shades of gray and green to the red and brown of impure specimens, translucent to opaque, and having a greasy, soapy feel. It is a hydrous silicate of magnesium, Mg3Si4O10(OH)2, and usually contains small quantities of nickel, iron, and aluminum as impurities. It occurs commonly in folia (thin layers), but is also found in coarsely granular, finely granular, or cryptocrystalline masses. Soapstone, or steatite, is a massive, granular form of talc. French chalk is a fine-grained variety. Talc is usually associated with chlorite schists, serpentine, dolomite, and other metamorphic rocks; it is apparently a secondary mineral formed by the alteration of other magnesium silicates. There are important deposits of talc in Austria, Italy, France, and Canada and in the United States in California, North Carolina, Texas, Georgia, and Montana. Talc is used in making paper (as a filler), paints, face and talcum powder, soap, fireproof roofing, foundry facings, lubricants, linoleum and oilcloth, electrical insulation, and pottery.

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

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