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The heat and pressure inside the Earth can cause chemical changes in rocks that change their characteristics.

Top: Sample of lewisian gneiss, UK. Bottom: open quarry for mining marble.

Sometimes new minerals are formed by chemical reactions when solid rocks meet magma. The rocks that are formed when these processes happen are called metamorphic rocksMarble is a metamorphic rock that was once the sedimentary rock limestone.  Quartzite is a metamorphic rock that used to be sandstone. Granite is an igneous rock that can change into gneiss from the heat and pressure inside the Earth. 

Question

Can you find any other examples of metamorphic rocks?

Slate is a metamorphic rock made from shale. Schist is a metamorphic rock formed from shale. Phyllite is a metamorphic rock that is also made from shale.

Question

What do you notice about all metamorphic rocks?

They are all made from other rock types, called "parent" rocks.