Soapstone powder is also written as H2Mg3(SiO3)4 (Magnesium Silicate), 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, seerpentine, dunite and chlorite. In pulverized form it is whiter in appearance. The compact variety of soapstone powder is called steatite or soapstone. The word soapstone powder 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 soapstone powder of pure white quality which forms the base for many cosmetics and toilet preparations. Talcum powder 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. Soapstone powder 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 srpentine and carbonates. Fibrous variety is slightly difficult to grind.
Talc
Specifications:
Mesh : 300 to 1200
Partical Size : Upto 10 Microns d97
Appearance : White Powder
Water solubility : 0.09% to 0.10%
Oil Absorption :25 to 42.5
Brightness : 78 to 97%
CaCO3 : 1 to 6%
Industrial Applications:
Pulverized soapstone powder has wide industrial applications as filler in rubber, textile, plastic, linoleum, asbestos products, polishes and soaps; as a loading agent for paper of all kinds; as a carrier of insecticidal and pesticidal dusts and for coating calcium ammonium fertiliser. Most of the rubber manufacturers use soapstone powder as a lubricant to prevent ungalvanized rubber goods from sticking. The purer variety of steatite after calcination, industrially called 'Lava' is used in the manufacture of low loss ceramic materials required for high frequency insulations in all kinds of radio, television and related instruments. Bricks made out of crushed steatite bonded by sodium silicate are used for ssthe manufacture of furnaces in which argentiferous lead is softened before desilverising. Paper industry accounts for about 50% of the total consumption, in the domestic industry, 15% is shared by the insecticide and pesticide industries and only 3% by talcum powder manufacturers. The remaining quantity is consumed in textile, ceramics, paints, rubber, foundry facing and other industries.
