Talc is a soft mineral, measuring about 1 on the Mohs hardness scale. The softest of the common minerals, it can be scratched with a fingernail. This sample is on display at the Smithsonian Museum of Natural History.
Talc has the composition Mg3Si3O10(OH)3 as a silicate of magnesium. This talc sample is about 12x4 cm and is from Schabry, Ekaterinburg, Urals, Russia.