Talc is a clay mineral composed of hydrated magnesium silicate with the chemical formula H₂Mg₃(SiO₃)₄ or Mg₃Si₄O₁₀(OH)₂.

In loose form, it was one of the most widely used substances known as baby powder, along with corn starch.

Talc was often simply called talcum powder. It occurs as foliated to fibrous masses.

It has a perfect basal cleavage, and the folia are not elastic, although slightly flexible.