Gneiss is a type of metamorphic rock that forms from the alteration of sedimentary or igneous rock under high pressure and temperature conditions. It is characterized by a distinct banding pattern of alternating light and dark mineral layers, which gives the rock a layered appearance. The mineral composition of gneiss varies, but it typically contains feldspar, quartz, and mica minerals.
Gneiss can form from the metamorphism of shale, sandstone, or granite, and the mineral composition of the original rock can influence the mineral composition of the resulting gneiss. Gneiss may also form from the recrystallization of existing metamorphic rock.
Gneiss is a durable rock that is often found in the cores of mountain ranges, where it has been subjected to high pressure and temperature conditions. It is also commonly used as a building material, as well as for decorative purposes.
In summary, gneiss is a type of metamorphic rock that forms from the alteration of sedimentary or igneous rock under high pressure and temperature conditions. It is characterized by a distinct banding pattern and a mineral composition that varies depending on the original rock.