Schist is a type of metamorphic rock in which lamellar minerals, such as muscovite, biotite, and chlorite, or prismatic minerals, such as hornblende and tremolite, are oriented parallel to a secondary platy or laminated structure termed the schistosity. The mineral grains in many examples are large enough to be recognized in hand specimens. Schist breaks easily into thin layers parallel to the schistosity. Schists are commonly rich in quartz and contain some feldspars and carbonates. The specific mineral composition of a schist is indicated by placing the name or names of significant subordinate minerals in front of the word schist; commonly occurring types include biotite schist, muscovite-chlorite schist, garnet-mica schist, staurolite kyanite schist, and hornblende schist. A general composition or texture of the schist can be indicated by prefixing; examples include calc-silicate schist and spotted schist. The mineral assemblages and textures of the schist change with the temperature and pressure of recrystallization. With increasing metamorphism, the grain size usually increases and, depending on appropriate chemical availability, minerals such as chloritoid, garnet, staurolite, cordierite, andalusite, and kyanite crystallize as large crystals (called porphyroblasts) in a foliated micaceous matrix. Many porphyroblasts contain inclusions, indicating that they crystallized by replacement of some other mineral or rock.