Schist is a type of foliated metamorphic rock, formed when pre-existing sedimentary or igneous rocks undergo metamorphosis due to increasing heat and directed pressure. The distinctive structural characteristic of schist is its foliation, which results from the realignment and segregation of minerals within the rock body. This metamorphic process causes minerals such as mica, chlorite, and quartz to align themselves into visible planar sheets, creating a characteristic layered or banded appearance. The specific mineral composition and degree of foliation vary widely depending on the parent rock material and the temperature and pressure conditions of the metamorphic environment, making schist a key indicator of past geological stress and transformation.