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Talc - Mg3 Si4 O10 (OH)2

soap stone, magnesium hydrosilicate, trioctahedral clay mineral

T Talc is known for being the softest mineral on earth. It is number 1 on the Mohs hardness scale, and can be easily scratched by a fingernail. Talc is not commonly seen in collections, as it is usually uninteresting and fairly common, although a few deeply colored and crystallized examples are known and well sought after. Also very popular are the Talc pseudomorphs. Talc forms some very interesting pseudomorphs after many different minerals, and certain localities are known for the specific minerals replaced by Talc.

Talc is a hydrous magnesium silicate mineral with a chemical composition of Mg3Si4O10 (OH) 2. Talc is actually a rock, and can come in a variety of shades other than white, including gray, pink, blue, violet, green and even black. It is resistant to heat, electricity and acids, which makes it valuable for many industrial purposes. It has a hardness rating of one, meaning it can leave a mark on paper. It feels soapy to the touch and has a luster that can be dull, Pearly or greasy.

Talc is a monoclinic mineral with a sheet structure similar to the micas. Talc has perfect cleavage that follows planes between the weakly bonded sheets. These sheets are held together only by van der Waals bonds which allows them to slip past one another easily. This characteristic is responsible for talc's extreme softness, its greasy, soapy feel and its value as a high temperature lubricant.

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