One of the major divisions of the mineral facies classification of metamorphic rocks, encompassing the rocks that formed under fairly low temperatures (480–660 kF, or 250–350 kC) 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.