Most people are familiar with the mineral talc. It can be crushed into a white powder that is widely known as "talcum powder". This powder has the ability to absorb moisture, absorb oils, absorb odor, serve as a lubricant and produce an astringent effect with human skin. These properties make talcum powder an important ingredient in many baby powders, foot powders, first aid powders and a variety of cosmetics.
Talc is also called steatite – or, in chemical terms, hydrated magnesium silicate. It is the main component of soapstone. Its crystals usually develop massive, leafy aggregates with laminar particles. Ground talc is called talcum.
Although talcum powder and soapstone are two of the more visible uses of talc they account for a very small fraction of talc consumption. Its hidden uses are far more common. Talc's unique properties make it an important ingredient for making ceramics, paint, paper, roofing materials, plastics, rubber, insecticides and many other products.
Talc is a hydrous magnesium silicate mineral with a chemical composition of Mg3Si4O10(OH)2. Although the composition of talc usually stays close to this generalized formula, some substitution occurs. Small amounts of Al or Ti can substitute for Si; small amounts of Fe, Mn and Al can substitute for Mg; and, very small amounts of Ca can substitute for Mg. When large amounts of Fe substitute for Mg the mineral is known as minnesotaite. When large amounts of Al substitute for Mg the mineral is known as pyrophyllite.
Talc is usually green, white, gray, brown or colorless. It is a translucent mineral with a pearly luster. It is the softest known mineral and is assigned a hardness of 1 on the Mohs Hardness scale.
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.
Talc has a high capacity for absorbing organic substances. The opposite applies to water: talc is hydrophobic and insoluble. It is also acid-resistant, chemically inert and non-toxic. Talc has neither aroma nor taste.