Description :

Hydrated Magnesium Silicate ( 3Mgo, 4SiO2, H2O )

TALC is also written as H2Mg3(SiO3)4, which corresponds to 4.8% H2O; 31.7% MgO and 63.5% SiO2. It is essentially a secondary mineral formed by the hydrothermal actions and regional metamorphism of magnesium rich rocks like dolomite, pyroxenite, amphibolite, serpentine, dunite and chlorite.

In pulverized form it is whiter in appearance. The compact variety of talc is called steatite or soapstone. The word soapstone has been named probably due to its soapy feel. The impure and hard variety is called potstone, which is mainly utilized for making carvings, models, decorative vases, utensils, pots and the like and hence the name potstone.

French-chalk is the trade name of pulverized talc of pure white quality which forms the base for many cosmetics and toilet preparations. Talc is valued for its extreme softness, smoothness, high lubricating and hiding power and ability to absorb oil and grease. It is chemically inert to acids and alkalies.

It has been found to be an excellent filler. It can withstand temperatures upto 1300ºC. It has low electrical and thermal conductivity. Above all it can be easily powdered, cut and sawn into any shape and size. These properties in talc are of extreme value for various industrial applications described later in this chapter.

Talc is found in three forms, fibrous, nonfibrous and massive. The fibrous variety consists of rich proportions of tremolite, anthophyllite, and serpentine. The nonfibrous variety contains mostly of serpentine and carbonates. Fibrous variety is slightly difficult to grind.