Talc

Talc (from the Arabic talk) is a silicate mineral, a type of clay. It is the standard for grade 1 in the Mohs scale of mineral hardness. A fingernail can easily scratch it. Talc is composed of hydrated magnesium silicate with the chemical formula Mg₃Si₄O₁₀(OH)₂. Talc and pyrophyllite are very similar, but pyrophyllite may be slightly harder.

Talc has a greasy feel and a translucent, soapy look. In loose form, it is the widely used substance known as talcum powder. Steatite, also called soapstone, is a rock with a lot of talc.

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