Talc

Talc (hydrated magnesium silicate) is a soft crushable mineral consisted of soft soap-like colloidal particles. The three-layer structure of talc is consisted of two tetrahedral silicate sheets and an octahedral sheets where all octahedral sites are filled with magnesium ions. The chemical bonds between the talc sheets are weaker than those between kaolinite sheets. As a result, talc is a better lubricant than kaolinite. Pure talc is white but impure talc is observed in gray, green, brown and red colors. Talc is developed as a result of changes in basic rocks and high-silicon dolomite metamorphism.