Metamorphic rock are the result of the transformation of a pre-existing rock type, the protolith, in a process is called metamorphism. The nature of the protolith can be either sedimentary, igneous or older metamorphic rocks.
Metamorphic rocks can be classified according texture or mineral assembly (metamorphic facies).
Basically, they are formed when igneous or sedimentary are changed by going through profound physical and/or chemical change under extreme heat (>2000 degrees Celsius) and pressure.
there are two types of metamorphic rocks: Foliated and Non-foliated. For the foliated rocks, the minerals are segregated in wavy bands through metamorphism.
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