An Etymological Dictionary of Astronomy and Astrophysics

A white, grey, or pale green soft → mineral with a greasy feel consisting of → hydrated  → magnesium  → silicate, Mg₃Si₄O₁₀(OH)₂.

See also: From M.Fr. talc, from M.L. talcus, talcum, from Ar. talq, from Pers. talk “talc.”