Home Metamorphic Rocks Foliated Metamorphic Rocks Schist

Schist

Schist is faliated medium grade metamorphic rock. It formed by metamorphosis of mudstone and shale or some form of igneous rock. It usually has better crystallisation of mica minerals. They are biotite, chlorite and muscovite so this called schistosity texture. There are many types of this rock so they may be named for mineral comprising the rock.e.G. Mica schist, green schist , garnet schist etc.

Type: Medium-grade metamorphic rock

Texture – Foliated, Foliation, Schistosity Texture

Grain size – Fine to medium grained; can often see crystals with the naked eye.

Hardness –Hard.

Colour – Usually alternating lighter and darker bands, often shiny.

MineralogyMica minerals ( biotite, chlorite, muscovite), quartz and plagioclase often present as monomineralic bands, garnet porphyroblasts common.

Other features –Smoothish to touch.

Name origin: The name is derived from the Greek word that means “to split.”

Schist Classification

The classification depend on their mineral content. There are some types a group of metamorphic limestones, marbles, calc-shists and cipolins, with crystalline dolomites and It has contain silicate minerals such as mica, tremolite, diopside, scapolite, quartz and feldspar

After a crystallization sequence It is separate group is rich in quartz ith variable amounts of white and black mica, garnet, feldspar, zoisite and hornblende. These were once sandstones and arenaceous rocks.

The graphitic schists may represent sediments once containing coaly matter or plant remains. There are also schistose ironstones (hematite-schists)

Origin of the schist include calc-schists, the foliated serpentines, which are once ultramafic masses rich in olivine. The white mica-schists, porphyroids and banded halleflintas, which have been derived from acid tuffs, quartz-porphyries and rhyolites

The most of the mica-schists are altered clays and shales so It is into the normal sedimentary rocks through various types of phyllite and mica-slates.They are among the most common metamorphic rocks.

A special subgroup consists of the andalusite-, staurolite-, kyanite-, and sillimanite-schists, together with the cordierite-gneisses. They usually appear in the vicinity of gneissose granites and have presumably been affected by contact alteration.

Schist Composition

Schist has a flat, large and sheet-like grains and It have flat and elongated minerals such as talc or micas.It has quartz and feldspar minerals are intertwined.These lamellar (flat, planar) minerals include micas, chlorite, talc, hornblende, graphite, and others. Banding in it is typically poorly developed. Most of this rock has these minerals such as muscovite, chlorite, talc, sericite, biotite, and graphite; feldspar and quartz. The green colour of many schists and their formation under a certain range of temperature and pressure has led to a distinction of the greenschist facies in the mineral facies classification of metamorphic rocks.Schist forms at a higher temperature and has larger grains than phyllite. Geological foliation (metamorphic arrangement in layers) with medium to large grained flakes in a preferred sheetlike orientation is called schistosity.

Formation

During metamorphism, rocks which had been firstly sedimentary, igneous or metamorphic are converted into schists and gneisses. If the composition of the rocks was firstly similar, they may be very tough to differentiate from one another if the metamorphism has been excellent. A quartz-porphyry, for example, and a quality grained feldspathic sandstone, may additionally both be transformed into a gray or crimson mica-schist. Usually, but, it’s miles feasible to differentiate among sedimentary and igneous schists and gneisses. If, for example, the complete district occupied by using these rocks has strains of bedding, clastic structure, or unconformability, then it could be a sign that the original rock become sedimentary. In different instances intrusive junctions, chilled edges, touch alteration or porphyritic structure might also prove that in its original condition a metamorphic gneiss became an igneous rock. The closing enchantment is often to the chemistry, for there are certain rock kinds which occur simplest as sediments, at the same time as others are determined only among igneous masses, and but advanced the metamorphism can be, it hardly ever modifies the chemical composition of the mass very substantially. Such rocks as limestones, dolomites, quartzites and aluminous shales have very specific chemical characteristics which distinguish them even when completely recrystallized.

Where is the Schist Found

Schists are mostly the precambrian ages rocks. It usually occurs the regional metamorphism of existing rock. These are usually sedimentary or simetimes igneous rocks. It could therefore be found where eroded mountains reveal the rock, or in areas of glacial deposition of eroded schist.

Schist Uses

  • It is used in building houses or walls. Because of it is strong and durable.
  • It has been previously used to make decorative rock walls.
  • Presently, It is used as a decorative stone as well as for jewelry.
  • In Australia, houses that were built using schist in the 1800s are still standing today.
  • Mica Schist is a very interesting rock. Some uses for this rock isare decorative rock wall, pillars, paint fillers, and roofingmaterial.

Conclusion

  • Schist and slate are very similar in that they are made from the same rock types except it is subjected to more heat and pressure.
  • It is often referred to as schistosity because of its large mica flakes.
  • Large crystals cause schist rocks to reflect lots of light which gives it a very shiny appearance.
  • The large crystals in schist indicate the amount of pressure and temperature that was used to make the rock.
  • Specific this rocks are named for the dominant mineral that is a part of its make-up.
  • Most of these rocks originate as some type of clay or mud.
  • Most of the this rock contains the mineral mica and is called mica schist.
  • It is often used as a guide to measure specific sizes and dimensions of objects.
  • Before the 18th century, schist, shale, and slate were used interchangeably to describe the same rock.
  • There are various features that distinguish schist rocks made from sedimentary rocks or those made from igneous.
  • It can be found in many countries including Brazil, parts of the US and Ireland.

Quastions and Answers about Schist

What is the difference between schist and gneiss?

Both are foliated metamorphic rocks in which individual minerals can be seen with the naked eye. The difference is that gneiss is generally more coarsely crystalline and has color banding and schist smells bad.

What is the hardness of schist?

From 4 to 5 on the Moh’s scale, which is only indicative of its relative hardness against other rocks and minerals.

What is schist made of?

When a volcano erupts the magma (lava) runs down into the holes and hardens making schist. AKA: schist is made of magma. (lava)

What is the parent rock of mica schist?

Mica schist, the most common schistose rock and the second most common metamorphic rock, is composed mostly of mica (usually biotite or muscovite) and smaller amounts of quartz.

The original parent rock (or protolith) of mica schist is shale. Phyllite could also be considered the parent rock as mica schist is a more highly metamorphosed phyllite.

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