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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. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is produced. By definition, schist contains more than 50% platy and elongated minerals, often finely interleaved with quartz and feldspar. Image File history File links This is a lossless scalable vector image. ... Schist Source: US Government File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Schist Source: US Government File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Quartzite, a form of metamorphic rock, from the Museum of Geology at University of Tartu collection. ... Minerals are natural compounds formed through geological processes. ... Rock with mica Mica sheet Mica flakes The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. ... Chlorite is a group of phyllosilicate minerals often classified as clays. ... Talc (derived from the Persian via Arabic talq) is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg3(SiO3)4 or Mg3Si4O10(OH)2. ... Amphibole (Hornblende) Hornblende is a complex inosilicate series of minerals. ... Graphite (named by Abraham Gottlob Werner in 1789 from the Greek γραφειν (graphein): to draw/write, for its use in pencils) is one of the allotropes of carbon. ... Quartz is one of the most common minerals in the Earths continental crust. ... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ...

The individual mineral grains in schist, drawn out into flaky scales by heat and pressure, can be seen by the naked eye. Schist is characteristically foliated, meaning the individual mineral grains split off easily into flakes or slabs. The characteristic flaky texture of schist gives rise to the adjective "schistose". Minerals are natural compounds formed through geological processes. ... Foliation is any penetrative planar fabric present in rocks. ...

Manhattan schist, from Southeastern New York

Most schists have in all probability been derived from clays and muds which have passed through a series of metamorphic processes involving the production of shales, slates and phyllites as intermediate steps. Certain schists have been derived from fine-grained igneous rocks such as basalts and tuffs. Most schists are mica schists, but graphite and chlorite schists are also common. Image File history File links Download high resolution version (1701x1845, 997 KB) Manhattan schist Manhattan Schist from Southeastern New York state, USA. Photo taken by myself on 3-13-05. ... Image File history File links Download high resolution version (1701x1845, 997 KB) Manhattan schist Manhattan Schist from Southeastern New York state, USA. Photo taken by myself on 3-13-05. ... Sample of Manhattan schist The Manhattan schist is a formation of mica schist rock that underlies much of the island of Manhattan in New York City. ... The Gay Head cliffs in Marthas Vineyard are made almost entirely of clay. ... Some dried mud with windblown stones. ... For other uses, see Shale (disambiguation). ... Slate Thick slate fragment Slate roof Slate is a fine-grained, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism. ... 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. ... Volcanic rock on North America Plutonic rock on North America Igneous rocks form when rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Basalt Basalt (IPA: ) is a common gray to black volcanic rock. ... Welded tuff at Golden Gate in Yellowstone National Park Tuff (from the Italian tufo) is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. ... Graphite (named by Abraham Gottlob Werner in 1789 from the Greek γραφειν (graphein): to draw/write, for its use in pencils) is one of the allotropes of carbon. ... The chlorite ion This discusses some chlorine compounds. ...

Schists are named for their prominent or perhaps unusual mineral constituents, such as garnet schist, tourmaline schist, glaucophane schist, etc. Garnet is a group of minerals that have been used since the Bronze Age as gemstones and abrasives. ... The tourmaline mineral group is chemically one of the most complicated groups of silicate minerals. ... Glaucophane Glaucophane is a mineral belonging to the amphibole group, chemical formula Na2(Mg,Fe)3Al2Si8O22(OH)2. ...

The word schist is derived from the Greek meaning "to split", which is in reference to the ease with which schists can be split along the plane in which the platy minerals lie.

Schists are frequently used in building houses or walls, as many are quite durable and strong. However it should be noted that many foundation problems with buildings both large and small are due to the Schist decaying or even the failure of the mortar. This in turn lets water into the joints thus weakening the schist further.

Most of the building foundations built in the 1920s and 30s within the New York city area used schist. Decorative rock walls on houses in the area also used a schist called "Yonkers Stone" which is no longer available. This schist was particularly hard and color fairly consistent.

Formation

During metamorphism, rocks which were originally sedimentary and rocks which were undoubtedly igneous are converted into schists and gneisses, and if originally of similar composition they may be very difficult to distinguish from one another if the metamorphism has been great. A quartz-porphyry, for example, and a fine grained feldspathic sandstone, may both be converted into a grey or pink mica-schist. Usually, however, we may distinguish between sedimentary and igneous schists and gneisses. Often the metamorphism is progressive, and if the whole district occupied by these rocks be searched for traces of bedding, of clastic structure, unconformability or other evidence may be obtained showing that we are dealing with a group of altered sediments. In other cases intrusive junctions, chilled edges, contact alteration or porphyritic structure may prove that in its original condition a metamorphic gneiss was an igneous rock. The last appeal is often to the chemistry, for there are certain rock types which occur only as sediments, while others are found only among igneous masses, and however advanced the metamorphism may be, it rarely modifies the chemical composition of the mass very greatly. Such rocks, for example, as limestones, calc-schists, dolomites, quartzites and aluminous shales have very definite chemical characters which distinguish them even when completely recrystallized. Gneiss Gneiss (IPA: ) is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. ... Quartz-porphyry, in petrology, is the name given to a group of hemi-crystalline acid rocks containing porphyritic crystals of quartz in a more fine-grained matrix which is usually of micro-crystalline or felsitic structure. ... In geology, the term clastic refers to sediments formed from fragments of pre-existing rock. ... There is a billion year gap in the geologic record where this 500 million year old dolomite unconformably overlays 1. ... Pluton redirects here. ... This article or section does not cite any references or sources. ... Dolomite crystals from Touissite, Morocco Dolomite is the name of both a carbonate rock and a mineral consisting of calcium magnesium carbonate (formula: CaMg(CO3)2) found in crystals. ... Quartzite Quartzite is a hard, metamorphic rock which was originally sandstone. ...

The schists and gneisses are classified according to the minerals they consist of, and this depends principally on their chemical omposition. We have, for example, a group of metamorphic limestones, marbles, calc-shists and cipolins, with crystalline dolomites; many of these contain silicate minerals such as mica, tremolite, diopside, scapolite, quartz and feldspar. They are derived from calcareous sediments of different degrees of purity. Another group is rich in quartz (quartzites, quartz schists and quartzone gneisses), with variable amounts of white and black mica, garnet, feldspar, zoisite and hornblende. These were once sandstones and arenaceous rocks. The graphitic schists may readily be believed to represent sediments once containing coaly matter or plant remains; there are also schistose ironstones (hematite-schists), but metamorphic beds of salt or gypsum are exceedingly uncommon. Among schists of igneous origin we may mention the silky calc-schists, the foliated serpentines (once ultramafic masses rich in olivine), and the white mica-schists, porphyroids and banded halleflintas, which have been derived from rhyolites, quartz-porphyries and acid tuffs. The majority of mica-shists, however, are altered clays and shales, and pass into the normal sedimentary rocks through various types of phyllite and mica-slates. They are among the most common metamorphic rocks; some of them are graphitic and others calcareous. The diversity in appearance and composition is very great, but they form a well-defined group not difficult to recognize, from the abundance of black and white micas and their thin, foliated, schistose character. As a special subgroup we have the andalusite-,staurolite-, kyanite- and sillimanite-schists, together with the cordierite-gneisses, which usually make their appearance in the vicinity of gneissose granites, and have presumably been affected by contact alteration. The more coarsely foliated gneisses are almost as frequent as the mica-schists, and present a great variety of types differing in composition and in appearance. They contain quartz, one or more varieties of feldspar, and usually mica, hornblende or augite, often garnet, iron oxides, etc. Hence in composition they resemble granite, differing principally in their foliated structure, many of them have "augen" or large elliptical crystals, mostly feldspar but sometimes quartz, which are the crushed remains of porphyritic minerals; the foliation of the matrix winds around these augen, closing in on each side. Most of these augen gneisses are metamorphic granites, but sometimes a conglomerate bed simulates a gneiss of this kind rather closely. There are onter gneisses, which were derived from feldspathic sandstones, grits, arkoses and sediments of that order; they mostly contain biotite and muscovite, but the hornblende and pyroxene gneisses are usually igneous rocks allied in composition to the hornblende-granites and quartz-diorites. The metamorphic forms of dolerite, basalt and the mafic igneous rocks generally have a distinctive facies as their pyroxene and olivine are replaced by dark green hornblende, with often epidote, garnet and biotite. These rocks have a well developed foliation, as the prismatic hornblendes lie side by side in parallel arrangement. The majority of amphibolites, hornblende-schists, foliated epidiorites and green schists belong to this group. Where they are least altered they pass through chloritic schists into sheared diabases, flaser gabbros and other rocks in which remains of the original igneous minerals and structures occur in greater or less profusion.^[1] Venus de Milo, front. ... A sample of tremolite Tremolite is a member of the amphibole group of silicate minerals with composition: Ca2Mg5Si8O22(OH)2. ... Diopside Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. ... Scapolite (Gr. ... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ... Garnet is a group of minerals that have been used since the Bronze Age as gemstones and abrasives. ... This article is about the mineral named zoisite. ... Amphibole (Hornblende) Hornblende is a complex inosilicate series of minerals. ... Black-band ironstone, 2. ... Hematite (AE) or haematite (BE) is the mineral form of Iron(III) oxide, (Fe2O3), one of several iron oxides. ... Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. // Heating gypsum to between 100°C and 150°C (302°F) partially dehydrates the mineral by driving off exactly 75% of the water contained in its chemical structure. ... Serpentine Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((Mg, Fe)3Si2O5(OH)4) minerals; it may contain minor amounts of other elements including chromium, manganese, cobalt and nickel. ... Ultramafic (or ultrabasic) rocks are igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). ... The mineral olivine (also called chrysolite and, when gem-quality, peridot) is a magnesium iron silicate with the formula (Mg,Fe)2SiO4. ... Hälleflinta (a Swedish word meaning rock-flint), a white, grey, yellow, greenish or pink, fine-grained rock consisting of an intimate mixture of quartz and feldspar. ... Rhyolite This page is about a volcanic rock. ... Welded tuff at Golden Gate in Yellowstone National Park Tuff (from the Italian tufo) is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. ... Andalusite-cordierite schist (Large brown crystals are Andalusite Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5. ... Staurolite Staurolite is a red brown to black mostly opaque nesosilicate mineral with a white streak. ... Kyanite, whose name derives from the Greek, kyanos, meaning blue, is a typically blue silicate mineral, commonly found in aluminium-rich metamorphic pegmatites and/or sedimentary rock. ... Sillimanite: Biotite gneiss (Mesozoic and Paleozoic) Sillimanite is an alumino-sillicate mineral with the chemical formula Al2SiO5. ... Cordierite is a magnesium iron aluminum cyclosilicate with associated water. ... A Gneiss with larges eye-shaped feldspars Augen are large, lenticular eye-shaped mineral grains or mineral aggregates visible in some foliated metamorphic rocks. ... Arkose is a kind of sandstone combining of quartz and with large amounts of feldspar. ... Figure 1:Mantle-peridotite xenolith with green peridot olivine and black pyroxene crystals from San Carlos Indian Reservation, Gila Co. ... It has been suggested that this article or section be merged with Diabase. ... Basalt Basalt (IPA: ) is a common gray to black volcanic rock. ... In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... Amphibolite is a gouping of rocks composed mainly of amphibole (as hornblende) and plagioclase feldspars, with little or no quartz. ...

Schist UK metal band

With the slogan REAL.TRUE.PROPER.METAL. Schistare an up and coming unsigned heavy metal band from London England, with all original songs, and style, with a bit of Pantera thrown into the mix. This article is about the capital of England and the United Kingdom. ... Motto (French) God and my right Anthem God Save the King (Queen) England() – on the European continent() – in the United Kingdom() Capital (and largest city) London (de facto) Official languages English (de facto) Government Constitutional monarchy  -  Queen Queen Elizabeth II  -  Prime Minister Tony Blair MP Unification  -  by Athelstan 967  Area... Pantera was an American heavy metal band from Arlington, Texas, that formed in 1981. ...

See also

• List of minerals
• List of rock textures

Gem animals. ... This page is intended to be a list of rock textural and morphological terms. ...

References

1. ^ This article incorporates text from the Encyclopædia Britannica Eleventh Edition article "Petrology", a publication now in the public domain.