Saturday, 4 April 2015

Schist

Schist

Schist is a metamorphic rock formed from phyllite subjected to pressure and temperature by regional metamorphism. Schist is a medium grade metamorphic rock intermediate between phyllite and gneiss with medium to large, flat, sheet like grains in a preferred orientation. Schist comes in almost infinitive variety and its characteristics are described by its name, schist comes from Greek word meaning "split".

Schist composition

Schist have more than 50% platy and elongated minerals often finely interleaved with quartz and feldspar. The flat and planar minerals of the schist includes mica, chlorite, talc, hornblende, graphite and other minerals. Quartz often occurs in such an extent that a particular form called quartz schist and is also often garentiferous. 

Schist varieties

Schist are mostly named after its minerals constituents which are abundant in a single type. Schist rich in mica are called mica schist which have biotite or muscovite. Mostly mica schist is abundant but graphite and chlorite schist are also commonly occurred in Earth. Other schist varieties are named after the unusual mineral constituent such as garnet schist, tourmaline schist and glaucophane schist.

Schist characteristics

The individual mineral grains in schist are shaped into flakes by heat and pressure which can be seen with naked eye. Schist characteristics is its foliation, minerals are aligned by the metamorphism where it can split along the foliation. These foliations are thus named as schistose which is the characteristic of schist.

Uses

Schist are frequently used as a dimension stone by cutting it into specific shape and size.

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