Gneiss, which is often used as a building stone, is a metamorphic rock that is primarily made up of quartz, feldspar, and mica. It is classified as a high grade material — this means it has been subjected to a lot of heat and pressure. It is very widely distributed across most parts of the world, and can be composed of both igneous and sedimentary rocks, with granite being the most common. The grains within it are flattened and are arranged in distinct bands that can seperate easily — these are typically arranged in alternating layers of light minerals such as quartz and feldspar and dark ones such as biotite and hornblende. Gneiss can be easily confused with some types of schist.