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Standard hydrated talc is one of a family of insoluble mineral magnesium silicates. It is a soft, greasy, granular or fibrous mineral. The mineral itself can range in color from white and silver-white to apple-green and even black. It shines with a pearly luster and its cleavage is basal perfect and it can be easily cut. Clay bodies containing talc also have a soft, soapy feel and talc in glazes tends to form a film on the surface of the slurry.
Talc is a common mineral and occurs in large beds of crystalline schists together with serpentine, dolomite, and chlorite. Talc is most often found in metamorphic rocks in a foliated or granular compact form known as steatite or soapstone. Thus, commercial talcs normally contain traces of iron, aluminum, and calcium; and they vary widely in composition from one geological deposit to another (and even within the same deposit). Some talc deposits are quite uniform consisting almost entirely of platiform (flat) talc crystals, others can be a conglomeration of crystal types and fibers and many different related minerals involved in their formation.
Talc is formed by the conversion of magnesium-bearing igneous rocks by various geologic means. High quality deposits form through hydrothermal alteration of dolomitic stone by Si/Mg-bearing fluids or by contact metamorphism of dolomitic rock by granite. Tremolite or actinolite containing rocks can also be converted to talc by Si-bearing fluids.
Geologically talc is closely related to chrysotile asbestos and soapstone.
Out Bound Links
- (Minerals - Related)
Dolomitic Limestone, Dolostone
Dolomite as a mineral exists as layers of predominantly calcium, carbonate and magnesium rock. Manufacturers blend these layers in a controlled fashion to produce a consistent product approximating th...
- (Minerals - Related)
Limestone, Calcium Carbonate
Also called GCC (Ground Calcium Carbonate), limestone is a very common sedimentary rock. Calcite and Aragonite minerals are the pure crystalline forms of CaCO3 (limestone contains them), but limestone...
Talc at Wikipedia
What is Talc at SpecialtyMinerals.com
Talc micrograph at minersoc.org
- (URLs - Technical Information)
By Tony Hansen