Metamorphic rocks

rock arising from metamorphism of original rock under high heat and pressure

contact metamorphic rock containing lazurite (but in most cases is haüyne), pyrite and calcite, mainly

Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under pressures ranging from 2 to 15 kbar, sometimes even more, and temperatures over 300 °C (572 °F). Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct cleavage.

Anthracite, also known as hard coal and black coal, is a hard, compact variety of coal that has a submetallic lustre. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the highest ranking of coals.

thumb|A schist showing characteristic scaly schistose texture caused by platy mica|micas Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced schistosity (named for the rock). This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes or plates. This texture reflects a high content of platy minerals, such as mica, talc, chlorite, or graphite. These are often interleaved with more granular minerals, such as fel

thumb|Amphibolite from Cape Cod, [[Massachusetts]] thumb|Garnet bearing amphibolite from Val di Fleres, Italy

thumb|upright=0.5|Fulgurite

Phyllite|thumb thumb|Photomicrograph of [[thin section of phyllite (in cross polarised light)]] thumb|Fractured Duke_University#Duke_stone | Duke stone showing phyllitic texture thumb|Phyllite

right|thumb|Serpentinite from the Maurienne valley, [[Savoie, French Alps]] right|thumb|Sample of serpentinite from the Golden Gate National Recreation Area, California, United States thumb|Chromite|Chromitic serpentinite ( across), [[Styria Province, Austria. Protolith was a Proterozoic-Early Paleozoic upper mantle dunite peridotite that has been multiply metamorphosed during the Devonian, Permian, and Mesozoic.]] thumb|Tightly folded serpentinite from the Tux Alps, [[Austria. Closeup view about .]]

upright=1.35|thumb|Samples of soapstone

thumb|300px|right|Eclogite from Norway with a garnet (red) and [[omphacite (greyish-green) groundmass. The sky-blue crystals are kyanite. Minor white quartz is present, presumably from the recrystallization of coesite. A few gold-white phengite patches can be seen at the top. A coin added for scale.]]

thumb|Ptygmatic folding in migmatite on Naissaar Island, Estonia thumb|Migmatite on the coast of Saaremaa, Estonia thumb|Intricately-folded migmatite from near Geirangerfjord, Norway

right|thumb|250px|A sample of granulite-facies metamorphic rock of felsic composition, with [[garnet porphyroblasts]]

thumb|Microscopic view of skarn under crossed polarizers thumb|Hand sample of skarn containing serpentinite from the edge of the Alta Stock, [[Little Cottonwood Canyon, Utah]] Skarns or tactites are coarse-grained metamorphic rocks that form by replacement of carbonate-bearing rocks during regional or contact metamorphism and metasomatism. Skarns may form by metamorphic recrystallization of impure carbonate protoliths, bimetasomatic reaction of different lithologies, and infiltration metasomatism by magmatic-hydrothermal fluids. Skarns tend to be rich in calcium-magnesium-iron-manganese-alumin

Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a classification based on the textural appearance of the rock.

thumb|Komatiite lava at the type locality in the Komati Valley, Barberton Mountainland, South Africa, showing the distinctive "spinifex texture" formed by dendritic plates of olivine (scale shown by a hammer on the right edge of photo)

thumb|A sample of banded hornfels, formed by contact metamorphism of sandstones and [[shales by a granite intrusion]] Hornfels is the group name for a set of contact metamorphic rocks that have been baked and hardened by the heat of intrusive igneous masses and have been rendered massive, hard, splintery, and in some cases exceedingly tough and durable. These properties are caused by fine grained non-aligned crystals with platy or prismatic habits, characteristic of metamorphism at high temperature but without accompanying deformation. The term is derived from the German word Hornfels, meaning

igneous rock type

type of sedimentary rock

Wikimedia list article

repetitive layering in metamorphic rocks

thumb|An example of impactite on Earth (from Monturaqui impact crater, Chile) Impactite is rock created or modified by one or more impacts of a meteorite. Impactites are considered metamorphic rock, because their source materials were modified by the heat and pressure of the impact. On Earth, impactites consist primarily of modified terrestrial material, sometimes with pieces of the original meteorite.

thumb|300px|right| Late-stage charnockite dike (geology)|dykes cutting [[anorthosite, Rogaland, Norway]] thumb|Job Charnock's Mausoleum at St John's Church compound, [[Kolkata]]

thumb|Small-scale boudinage thumb|Boudinaged quartz vein within [[blueschist, Samos, Greece.]] thumb|Boudinage in Greenland near [[Kangerlussuaq]] thumb|upright|Boudinaged Vein (geology)|quartz vein in shear foliation, Starlight Pit, Fortnum Gold Mine, [[Western Australia.]] thumb|upright|Foliation (geology)|Banded [[gneiss with dike of granite orthogneiss; competent banded gneiss is boudinaged by ductile shear.]] thumb|Boudin on the Island of Uto, Stockholm Archipelago, [[Sweden]] thumb|Chocolate-tablet boudinage structures in a low grade metasedimentary rock outcropping in Deception Pass, Wa

geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms, or columns

right|thumb|400px| L-S tectonite viewed in the plane of the S fabric right|thumb|400px| L-S tectonite viewed perpendicular to the plane of the S fabric thumb|Deformed conglomerate (geology)|conglomerate showing no strain in one plane (at left) and strong stretching in the other (at right) – an L-tectonite Tectonites are metamorphic or tectonically deformed rocks whose fabric reflects the history of their deformation, or rocks with fabric that clearly displays coordinated geometric features that indicate continuous solid (ductile) flow during formation. Planar foliation results from a parallel

thumb|Fenite from Russia Fenite is a metasomatic alteration associated particularly with carbonatite intrusions and created, very rarely, by advanced carbon dioxide alteration (carbonation) of felsic and mafic rocks. It is characterised by the presence of alkali feldspar, sodic pyroxene and sodic amphibole. Fenite alteration is known, but restricted in distribution, around high-temperature metamorphic talc carbonates, generally in the form of an aureole around ultramafic rocks. Such examples include biotite-rich zones, amphibolite-calcite-scapolite alteration and other unusual skarn assemblage

thumb|Rodingite from Maryland Rodingite is a metasomatic rock composed of grossular-andradite garnet, calcic pyroxene, vesuvianite, epidote and scapolite. Rodingites are common where mafic rocks are in proximity to serpentinized ultramafic rocks. The mafic rocks are altered by high pH, Ca2+ and OH− fluids, which are a byproduct of the serpentinization process, and become rodingites. The mineral content of rodingites is highly variable, their high calcium, low silicon and environment of formation being their defining characteristic. Rodingites are common in ophiolites, serpentinite mélanges, oc

pseudofossil

thumb|Cataclasite under a petrographic microscope. The rock in part of the Malm Formation of the [[Helvetic nappes; sample found in a landslide near Engelberg in the Swiss Alps.]] thumb|Thin section image of a cataclasite in both plane polarized light (right) and crossed polarized light (left). Contact between highly fractured wall rock (right) and clast supported cataclasite (left) is outlined in red. This rock is from the [[San Andreas Fault at Elizabeth Lake, California.]] Cataclasite is a cohesive granular fault rock. Comminution, also known as cataclasis, is an important process in formin

thumb|A quarry of listwanite in the region of [[Aosta Valley, in Italy]] thumb|upright|A quarry of listwanite in the region of Aosta Valley, in Italy Listwanite (also sometimes spelled listvenite, listvanite, or listwaenite) is a rock type that forms when the groundmass of ultramafic rocks, most commonly mantle peridotites, is partially altered to carbonate minerals and cut by ubiquitous carbonate veins containing one or more of magnesite, calcite, dolomite, ankerite, and/or siderite. Original pyroxene and olivine in the peridotite are commonly altered to Mg- or Ca-carbonate and hydrous Mg-sil

In a geological context, crenulation or crenulation cleavage is a fabric formed in metamorphic rocks such as phyllite, schist and some gneiss by two or more stress directions causing the formation of the superimposed foliations.

Supercrustal rock are rocks that were deposited on the existing basement rocks of the crzst, hence the name. They may be further metamorphosed from both sedimentary and volcanic rocks.

thumb|Anyolite from Mundarara Mine, Tanzania. Red colored ruby inclusions are visible. Anyolite is a metamorphic rock composed of intergrown green zoisite, black/dark green pargasite and ruby. It has been found in the Arusha Region of Tanzania and in Austria. It is sometimes incorrectly advertised as a variety of the mineral zoisite. The term anyolite is, however, not an officially accepted term for a metamorphic rock. Its name derives from the Maasai word anyoli, meaning "green". Anyolite is also referred to as ruby in zoisite, ruby zoisite, ruby-zoisite or Tanganyika artstone.

thumb|right|Porcellanite from the Czech Republic

thumb|A Neolithic polished jadeitite axe head found at [[Colomiers in southern France]] Jadeitite is a metamorphic rock found in blueschist-grade metamorphic terranes. It is found in isolated metasomatically altered rock units within serpentinite associated with subduction zone environments. Jadeitite consists almost entirely of the pyroxene mineral jadeite and is typically mined as a source of the ornamental rock or gemstone, jade. Occurrences include Myanmar, Guatemala, Japan, Kazakhstan and in the Coast Ranges of western North America.

thumb|Andalusite crystals in Dalradian (Southern Highland Group) metamorphic rock at Boyndie Bay, north-east Scotland

metamorphic rock from a volcanic precursor

Nuummite is a rare metamorphic rock that consists of the amphibole minerals gedrite and anthophyllite. It is named after the area of Nuuk in Greenland, where it was found.