1º_ Magnesium silicate, a mineral that is used in cosmetics when powdered. From the Old Arabic Voice 1591; 1604; 1602; (talq), which took it from Persian 1578; 1575; 1604; 1705; (talk). 2º_ By association with the powder, it is called "talcum powder". . . " or " . . . in talc" to finely ground products, such as powdered sugar or even, ironically, cocaine powder.