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.
Mindat: Talc
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