Class : Silicates
    Subclass : Phyllosilicates
    Crystal system : Monoclinic
    Chemistry : Mg₃Si₄O₁₀(OH)₂
    Rarity : Common

Talc is a magnesium phyllosilicate that can appear in three ways, in different geological contexts. It can first form by hydrothermal alteration of magnesium silicates : usually olivine (forsterite) of peridotites or chrysotile and antigorite of serpentinites (themselves derived from peridotites). Talc also appears by siliceous metasomatosis of dolomites, this context giving the purest qualities, highly sought after by industrialists. And finally, talc can crystallize following the light metamorphism of magnesian rocks. It is sometimes abundant to the point of being the major constituent of certain rocks (talcschists). Its name comes from the Arabic talq (pure, white) because of the color of its powder. Talc occurs in automorphic crystals forming flexible pseudohexagonal lamellae, sometimes centimeter-sized, or in cleavable flaky masses, in rosettes or in tufts of transparent lamellae. Its color is white to greenish when mixed with chlorite, sometimes grayish in massive varieties. Its low hardness (1 on the Mohs scale, the softest of minerals) gives it a creamy feel, which is the origin of most of its uses. It is in fact used in powder form in the pharmaceutical and cosmetic industries (soaps, powders and body creams), the rubber, paint, ceramics and food industries (anti-sticking of cereal cakes intended for livestock and confectionery, insecticides). Talc is also a mineral filler widely used in papermaking, particularly for coating magazines, and plays a role in the manufacture of thermal and electrical insulators. The compact, fine-grained varieties (steatite) are a highly sought-after ornamental material for sculpting art objects, particularly in China.

Main photo : Talc from Trimouns, Luzenac, Ariège, France © Guy Bernadi

No twinning known for this mineral species.

No fakes listed for this mineral species.