DEFINITION

Talc is a powdered, selected, natural, hydrated magnesium silicate. Pure talc has the formula Mg₃Si₄O₁₀(OH)₂. It may contain variable amounts of associated minerals among which chlorites (hydrated aluminum and magnesium silicates), magnesite (magnesium carbonate), calcite (calcium carbonate), and dolomite (calcium and magnesium carbonate) are predominant. Talc containing (detectable) asbestos is not pharmaceutical grade.