What kind of rock is formed when existing rock types are changed by heat and pressure?



When the original rock is subjected to extreme heat and pressure, profound physical and chemical changes can occur. The three main types of rocks are metamorphic, igneous, and sedimentary.
Metamorphic rocks make up a large part of the Earth's crust. Common metamorphic rocks include marble, slate, gneiss, quartzite, and schist.

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