Talc is a mineral composed of hydrated magnesium silicate with the chemical formula 3MgO4SiO2.H2O. It contains %63.5 SiO2, %31.7 MgO ve %4.8 in its ideal composition. Its color ranges from white to green and it has a distinctly greasy feel. Its hardness changes from 1.0 to 1.5 on the Mohs Hardness Scale and its specific density is between 2.6-2.8 gr/cm3. It holds monoclinic crystalline structure. It is a weak conductor of heat and electricity. It has high tolerance to fire and acids. It gets solidified and its hardness increases upon high temperature treatment. Commercial Talc is usually very different from its theoretical form. In addition to pure Talc mineral, these products could be mixture of various ratios of its paragenesis minerals such as dolomite, calcite, pyrite etc.
Most common commercaial forms of Talc:
Soapstone: It contains at least 50% talc and it has a high resistance to heat, electricity and acids.
Steatite: It is a term to describe high purity talc. Most common use is to make electricity insulators. It should not contain less than %1.5 CaO ve Fe2O3 ve %4′ ten az Al2O3.
Lava: It refers to “Block Talc” or fınal products that are produced from block talc.
Asbestine: is a mineral compound composed of nearly pure fibrous magnesium silicate, with physical characteristics between those of asbestos and talc.
Rensselaerite: It is a kind of mineral looks like Talc but not soft and greasy.
French Chalk: It is a massive form of talk usually used in paint and pencil production.
Talc is used in many industries such as paper making, plastic, paint and coatings, rubber, food, electric cable, pharmaceuticals, cosmetics, ceramics, etc. A coarse grayish-green high-talc rock is soapstone or steatite and has been used for stoves, sinks, electrical switchboards, crayons, soap, etc. It is often used for surfaces of lab counter tops and electrical switchboards because of its resistance to heat, electricity and acids. Talc finds use as a cosmetic (talcum powder), as a lubricant, and as a filler in paper manufacture. Talc is used in baby powder, an astringent powder used for preventing rashes on the area covered by a diaper. Most tailor’s chalk, or French chalk, is talc, as is the chalk often used for welding or metalworking. Talc is also used as food additive or in pharmaceutical products as a glidant. In medicine talc is used as a pleurodesis agent to prevent recurrent pleural effusion or pneumothorax. Due to its low shear strength, talc is one of the oldest known solid lubricants, there are also a limited use talc as friction reducing additive in lubricating oils. Talc is widely used in the ceramics industry in both bodies and glazes. In low-fire artware bodies it imparts whiteness and increases thermal expansion to resist crazing.