Barbara Cohrssen Ms Cih Charles H Powell ScD CIH

1.1 Chemical and Physical Properties

Talc has a hardness of 1 on the Mohs scale of hardness; a density of 2.58 to 2.83; is commonly composed of thin tabular crystals up to 1 cm wide and is usually massive, fine-grained, and compact. It is also found as foliated or fibrous masses or in globular stellate groups (3).

Talc is a natural single-phase mineral ideally composed of 31.88% magnesium oxide, 63.37% silicon dioxide and 4.75% water. Formation is said to have occurred by hydrothermal alteration of rocks rich in magnesium and iron and low grade thermal metamorphism of siliceous dolomites (4). It is an odorless, solid material that varies in color depending upon the minerals that are found with it. Talc may be pale green to dark green or greenish gray; brownish; translucent; white to grayish white; or pearly, greasy, or dull.

The term talc in the mineralogical connotation denotes a specific rock-forming mineral of the sheet silicate category. However, when talc is referenced in the industrial or commercial sense, it may represent a varied mixture of associated minerals that have physical properties similar to the mineral talc (5).

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