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Granulite is a type of high-pressure metamorphic rock that is formed through the transformation of mafic and ultramafic igneous rocks under intense heat and pressure. This process typically occurs at depths of 20-50 km beneath the Earth's surface, where the rocks are subjected to temperatures ranging from 600-900°C and pressures exceeding 15 kbar.

The formation of granulite is associated with the breakdown of mafic and ultramafic lithologies, leading to the production of a distinctive rock type characterized by a coarse-grained texture and a limited range of mineral phases. These include quartz, feldspar, garnet, and pyroxene, which are arranged in a specific configuration due to the stringent conditions under which they formed.

Granulite is exceptionally common in the Earth's crust, with notable exposures found in shield areas and along ancient suture zones. The protolith (the original rock type) from which the granulite is derived often includes rocks such as tonalite, eclogite, and dunite. Mineralogists often employ the granulite facies to identify the thermal and pressure conditions at the time of rock formation.

Despite being composed primarily of a few key minerals, granulite exhibits a complexity of structure, often reflecting a history of complex detrital recycling and mantle fragmentation. Its high-pressure evolution results in distinct structural orientations and ion-breeding artifacts. Studies of granulite have also shed light on the tectonic processes that operated on a geological timescale.