One of the major divisions of the mineral facies classification of metamorphic rocks, encompassing the rocks that formed under fairly low temperatures (480660 °F, or 250350 °C) and pressure conditions and usually produced by regional metamorphism .
The minerals commonly found in such rocks include quartz, orthoclase, muscovite, chlorite, serpentine, talc, and epidote; carbonate minerals and amphibole (actinolite) may also be present.