Part of the EASP Geology Walk Gneiss is a metamorphic rock formed by changing schist, granite, or volcanic rocks through intense heat and pressure. Gneiss is foliated, which means that it has layers of lighter and darker minerals. These layers are of different densities and come about as a result of the intense pressure used to form gneiss. Gneiss is made up of coarse-grained minerals such as quartz and feldspar. Granitic gneiss has a mineral composition similar to that of granite. Schist is a metamorphic rock usually formed originally from shale. It is a step above gneiss in the metamorphic process, meaning schist has been subjected to less intense heat and pressure. After metamorphism, the schist is very foliated (the minerals of the rock are arranged in layers). It can be easily split into thin, flakey pieces. Schists often have a high luster (they are very shiny) due to large crystals within the rock. Department of Earth, Atmospheric, and Planetary Sciences
