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. It is described as actinolite-talc schist and its source is the Catalina Schist, Santa Catalina Island, California. It is dated at 100 million years old. Further comments "Water goes in: the container at right shows how much water this rock contains. It formed deep in a subduction zone when the altered oceanic lithosphere began to release water." This sample is about 25cm long.
|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.
|This sample is described as magnesite-talc schist. The sample is about 15 cm wide and is from Garnet Zone, Cambrian-Ordovician Periods, Smithville, Vermont.