The rock that has the highest metamorphic grade is known as ‘gneiss.’ Gneiss is a high-grade metamorphic rock that forms under extreme pressure and temperature conditions. Its composition typically includes feldspar, quartz, and biotite, giving it a distinct banded appearance.
During the metamorphic process, existing rocks such as granite or sedimentary rocks undergo significant changes, which can lead to the formation of gneiss. The conditions that create gneiss occur deep within the Earth’s crust, often in regions where tectonic activity is present, such as continental collision zones.
Gneiss is typically distinguished from lower-grade metamorphic rocks by its foliation and the presence of alternating light and dark minerals. The mineral composition and structural traits of gneiss make it an essential subject of study in geology, particularly concerning the geological history of an area.