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There are three primary rock types in the earth's crust. Most of the crust consists of igneous rock. Metamorphic rock is either igneous or sedimentary rock that has changed form through heating and compression. The most common type of exposed rock is sedimentary, which forms from the conglomeration of sea, lake or river sediments, or from the bodies of tiny creatures, such as corals and limestone.

As for the total number of different types, there are hundreds. As for the total number of individual rocks, this changes as rock is cemented together or breaks apart, and I'm not going to bother estimating it here.

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15y ago

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