Also, talcum [tal-kuh m] /ˈtæl kəm/ (Show IPA). a green-to-gray, soft mineral, hydrous magnesium silicate, Mg 3 (Si 4 O 10)(OH) 2 , unctuous to the touch, and occurring usually in foliated or compact masses, used in making lubricants, talcum powder, electrical insulation, etc.
a white, grey, brown, or pale green mineral, found in metamorphic rocks. It is used in the manufacture of talcum powder and electrical insulators. Composition: hydrated magnesium silicate. Formula: Mg3Si4O10(OH)2. Crystal structure: monoclinic