is a mineral
composed of hydrated
magnesium silicate with the chemical formula H2
. It occurs as foliated to fibrous masses, its monoclinic crystals
being so rare as to be almost unknown. It has a perfect basal cleavage, the folia non-elastic
although slightly flexible. It is sectile and very soft, with a hardness
of 1. It has a specific gravity
of 2.5-2.8, a waxlike or pearly lustre, and is translucent to opaque. Its color ranges from white
and it has a distinctly greasy feel.
Talc is a metamorphic mineral resulting from the alteration of silicates of magnesium such as pyroxenes, amphiboles, olivine and other similar minerals. It is usually found in metamorphic rocks, often of a basic type due to the alteration of the minerals mentioned above.
A coarse grayish-green talc has been called soapstone or steatite and has been used for stoves, sinks, electrical switchboards, etc. Talc finds use as a cosmetic (talcum powder), as a lubricant, and as a filler in paper manufacture. Most tailor's chalk is talc.
The origin of the name derives from the Persian via Arabic.
See also: List of minerals