On the Mohs scale, talc has the lowest hardness rating, 1.
Talc is a hydrated magnesium silicate with the chemical formula Mg₃Si₄O₁₀(OH)₂. Its crystal structure consists of weakly bonded layers, allowing the layers to slide easily past one another. This makes talc exceptionally soft and gives it a characteristic soapy or greasy feel.
Talc is widely used in ceramics, paints, plastics, paper, and cosmetics. Finely powdered talc was historically used in body powders, although concerns about possible asbestos contamination have led to stricter testing and changing product practices. Pure talc itself is not asbestos, but both can occur in some geological settings.
The Mohs scale is ordinal rather than evenly spaced: a mineral rated 4 is not simply twice as hard as one rated 2. Talc can be scratched by every other reference mineral on the traditional ten-point scale, while diamond occupies the opposite extreme at 10.