Phyllite

Phyllite is a type of foliated metamorphic rock primarily composed of quartz, sericite mica, and chlorite; the rock represents a gradiation in the degree of metamorphism between slate and mica schist. Minute crystals of graphite, sericite, or chlorite impart a silky, sometimes golden sheen to the surfaces of cleavage (or schistosity). Phyllite Source: US Government File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Phyllite Source: US Government File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Foliation is any penetrative planar fabric present in rocks. ... Quartzite, a form of metamorphic rock, from the Museum of Geology at University of Tartu collection. ... Quartz is amongst one of the most common minerals in the Earths continental crust. ... Sericite is a fine grained mica, either muscovite, illite, or paragonite. ... rock with mica Mica sheet mica flakes The mica group of minerals includes several closely related materials having highly perfect basal cleavage. ... Chlorite is a group of phyllosilicate minerals often classified as clays. ... Slate Slate is a fine-grained, homogeneous, metamorphic rock derived from an original sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism. ... Schist The schists form a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. ... Graphite (named by Abraham Gottlob Werner in 1789 from the Greek γραφειν: to draw/write, for its use in pencils) is one of the allotropes of carbon. ...

Its constituent platy minerals are larger than those in slate but are not visible with the naked eye.

Phyllites are said to have a "phyllitic texture" and are usually classified as having a low grade on the Barrovian Sequence.

They are regional metamorphic.