Talc is a clay mineral composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2. Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 1 as the hardness of talc.
In loose form, it, along with corn starch, was one of the most widely used substances known as baby powder (in the case of talc, often called simply talcum powder; see litigation.)
It occurs as foliated to fibrous masses, and in an exceptionally rare crystal form. It has a perfect basal cleavage, and the folia are not elastic, although slightly flexible.
As such, talc can easily be scratched by a fingernail. Talc has a specific gravity of 2.5–2.8, a clear or dusty luster, and is translucent to opaque. Talc is not soluble in water, but is slightly soluble in dilute mineral acids
Talc’s smooth texture, ability to absorb oil, and other aesthetic properties are why it is commonly found in products as seen in the chart below.
