A soft, slippery mineral composed of hydrated magnesium silicate. Talc is found in veins and masses in metamorphic rocks; large deposits occur in Austria (Tyrol), Italy (Florence), Switzerland, Germany (Bavaria), England (Cornwall), Scotland (Shetland), Canada (Quebec, Ontario), and the U.S. (New England, New York, Pennsylvania, Maryland, North Carolina, Texas). Talc, mixed with other minor minerals, occurs in the stone called steatite, or soapstone. It is usually a white, green or gray color. Talc is so soft, it can be scratched with a fingernail. It has a waxy luster and a greasy feel. Steatite was used in antiquity for small carved objects, such as cylinder seals, scarabs, amulets, bowls, boxes, beads, and statuary. After carving, some pieces were baked to dehydrate the talc and thus harden the stone. Currently, talc is often crushed and used as a filler in paper, ceramics, paint, plastics, rubber, soaps, plaster, crayons, and cosmetics. It has also been used as a lubricant, leather dressing, dusting powder, and as an insulating material. Talc is used on the inside of powdered gloves and can leave residual powder on contacted surfaces. Since soapstones are resistant to most chemical reagents, and to moderate heat, they have been used for sinks and countertops.
Synonyms and Related Terms
hydrated magnesium silicate; Pigment White 26; talc (Fr.); talk (Ned., Sven., Pol.); talco (Esp., It., Port.); Talk (Deut.); Talkum (Deut.); talkis (Gr.); talcum; soapstone; steatite; asbestine; French chalk; tailors chalk; Mistron®; Vertal; Nicron®;
Ground particles can be very small (2.0 micrometers).
Talc occurs naturally in foliated masses. Perfect cleavage in one direction producing thin laminar particles. Streak = white. Fracture = uneven. Luster = pearly, greasy.
Strongly birefringent under crossed polars
Insoluble in water, cold acids or alkalis
|Molecular Weight||mol. wt. = 379.3|
|Refractive Index||1.539; 1.589; 1.589|
Hazards and Safety
Noncombustible. Some samples may contain asbestos.
Mineralogy Database: Talc
Sources Checked for Data in Record
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- CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: density=2.7-2.8