Dictionary:

phyllite

  (fĭl'īt')

A green, gray, or red metamorphic rock, similar to slate but often having a wavy surface and a distinctive micaceous luster.

A type of metamorphic rock formed during low-grade metamorphism of clay-rich sediments called pelites. Phyllites are very fine grained rocks with a grain size barely visible in a hand specimen. They have a well-developed planar element called cleavage defined by alignment of mica grains and interlayering of quartz-rich and mica-rich domains. Typically, mica grains show the greater alignment, although other mineral components (quartz, carbonate, and feldspars) may show a preferred shape orientation. Where all minerals of a particular type show the same degree of alignment and the fabric is well developed throughout the rock, the fabric is termed a penetrative fabric. Cleavage surfaces in phyllites have a glittery, lustrous sheen due to light reflecting off grains of chlorite and muscovite. The mineralogy of phyllites is dependent on chemical composition; typical minerals in phyllites are chlorite, muscovite, and quartz. Other minerals that may be present in phyllites formed during low-grade metamorphism include chlorotoid, garnet (rarely), sodium-mica, and sulfide minerals. See also Chlorite; Muscovite; Quartz.

Phyllite is found in most regionally metamorphosed terranes in the world, including the Appalachians of eastern North America, the Scottish Highlands, and the Alps. See also Metamorphic rocks.

For more information on phyllite, visit Britannica.com.

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).

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.

The protolith (or parent rock) for a phyllite is a slate.It is very delicate, and can be broken into small sheets.

Phyllite will form under low grade metamorphic conditions. Phyllites are usually black or dark gray. The foliation is commonly crinkled or wavy in appearance.

Wikimedia Commons has media related to:

Category:Phyllite

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)