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THE MINERAL TALC Chemistry: Mg3Si4O10(OH)2, Magnesium Silicate Hydroxide Class: Silicates Subclass: phyllosilicates Group: Clays and also The Montmorillonite/Smectite Group. Uses: an ornamental and heat, acid and electrically-resistant stone (soapstone) used as counter tops, electrical switchboards, carvings, etc, used as an ingredient in paints, rubber, roofing materials, ceramics and insecticides. Most commonly known as the primary ingredient in talcum powder.PHYSICAL CHARACTERISTICS: Color is green, gray and white to almost silver. Luster is dull to pearly or greasy. Transparency crystals are translucent and masses are opaque. Crystal System is monoclinic; 2/m. Crystal Habits: never in large individual crystals, but if found are flattened tabular crystals with a hexagonal cross-section, usually talc is found in compact or lamellar masses. Cleavage is perfect in one direction, basal. Fracture is uneven to lamellar. Hardness is 1 (can leave mark on paper) Specific Gravity is 2.7 - 2.8 (average) Streak is white. Other Characteristics: cleavage flakes are slightly flexible but not elastic and talc has a soapy feel to the touch. Associated Minerals include serpentine, dolomite, magnesite, quartz, pyroxenes, olivine, biotite and amphiboles.