Metamorphic granite is a metamorphic rock which forms when granite undergoes deep metamorphism due to high temperature or pressure. It is mainly made up of plagioclase, quartz and biotite, similar to the minerals of granite. The initial metamorphic granite rock is trondhjemite, formed 726 million years ago and which underwent high pressure metamorphism 230 million years ago. Trondhjemite is characterized by containing aegirine, aegirine augite and garnet.

Metamorphic granite

Microscope image of metamorphic granite

Formation of metamorphic granite