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. Department of Earth, Atmospheric, and Planetary Sciences
