List of rock types

The following is a list of rock types recognized by petrologists. There is no agreed number of specific types of rocks. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe rock types. Additionally, different classification systems exist for each major type of rock. There are three major types of rock, sedimentary, metamorphic, and igneous. They are all identified by their texture, streak, and location, among other factors..

Igneous

Adakite - a class of intermediate to felsic rocks containing low amounts of yttrium and ytterbium
A sample of andesite (dark groundmass) with amygdaloidal vesicles filled with zeolite. Diameter of view is 8 cm.
Andesite - an intermediate volcanic rock
Alkali feldspar granite - a granitoid in which at least 90% of the total feldspar is in the form of alkali feldspar
Anorthosite - a mafic intrusive igneous rock composed predominantly of plagioclase
Aplite - a very fine-grained intrusive igneous rock composed of quartz and feldspar, similar composition to granite but with grains <1mm
Basalt - a volcanic rock of mafic composition
A'a - basaltic lava with a crumpled appearance
Pahoehoe - basaltic lava with a flowing, often ropy appearance
Hawaiite - a type of basalt, typically formed by ocean island (hot spot) volcanism
Basanite - a volcanic rock of mafic composition; essentially a silica-undersaturated basalt
Blairmorite - a rare volcanic rock
Boninite - a magnesium-rich basalt dominated by pyroxene
Carbonatite - a rare igneous rock composed of >50% carbonate minerals
Charnockite - a type of granite containing orthopyroxene
Enderbite - a variety of charnockite
Dacite - a felsic to intermediate volcanic rock containing hornblende and with more plagioclase than orthoclase
Diabase or dolerite - an intrusive mafic rock forming dykes or sills
Diorite - a coarse-grained intermediate plutonic rock composed of plagioclase, pyroxene and/or amphibole
Napoleonite - a variety of diorite which is characterized by orbicular structure. Also called corsite.
Dunite - a phaneritic ultramafic rock composed of more than 90% olivine
Essexite - a silica-undersaturated mafic plutonic rock (essentially a feldspathoid-bearing gabbro)
Foidolite - a plutonic igneous rock composed of >90% feldspathoid minerals
Gabbro - a coarse-grained plutonic rock composed of pyroxene and plagioclase basically equivalent to basalt
Granite - a coarse-grained plutonic rock composed of orthoclase, plagioclase and quartz
Granodiorite - a granitic plutonic rock with more plagioclase than orthoclase
Granophyre - a subvolcanic intrusive rock of granitic composition
Harzburgite - a variety of peridotite; an ultramafic cumulate rock
Hornblendite - a mafic or ultramafic cumulate rock dominated by >90% hornblende
Hyaloclastite - a volcanic rock composed primarily of glasses and glassy tuff
Icelandite - an iron-rich, aluminium-poor andesite
Ignimbrite - a fragmental volcanic rock
Ijolite - a very rare silica-undersaturated plutonic rock
Kimberlite - a rare ultramafic, ultrapotassic volcanic rock and a source of diamonds
Komatiite - an ultramafic volcanic rock with very high magnesium content
Lamproite - an ultrapotassic volcanic rock
Lamprophyre - an ultramafic, ultrapotassic intrusive rock dominated by mafic phenocrysts in a feldspar groundmass
Latite - a silica-undersaturated form of andesite
Lherzolite - an ultramafic rock, essentially a peridotite
Monzogranite - a silica-undersaturated granite with <5% normative quartz
Monzonite - a plutonic rock with <5% normative quartz
Nepheline syenite - a silica-undersaturated plutonic rock of nepheline and alkali feldspar
Nephelinite - a silica-undersaturated plutonic rock with >90% nepheline
Norite - a hypersthene-bearing gabbro
Obsidian - a type of volcanic glass
Pegmatite - an igneous rock (or metamorphic) rock with crystals >1 inch, usually granitic
Peridotite - a plutonic or cumulate ultramafic rock composed of olivine and pyroxene
Phonolite - a silica-undersaturated volcanic rock; essentially similar to nepheline syenite
Picrite - an olivine-bearing basalt
Porphyry - a rock, usually granitic, with a porphyritic texture
Pumice - a fine grained, vesicular volcanic rock
Pyroxenite - a coarse grained plutonic rock composed of >90% pyroxene
Quartz diorite - a diorite with >5% modal quartz
Quartz monzonite - an intermediate plutonic rock, essentially a monzonite with 5-10% modal quartz
Quartzolite - an intrusive rock composed mostly of quartz
Rhyodacite - a felsic volcanic rock which is intermediate between a rhyolite and a dacite
Rhyolite - a felsic volcanic rock
Comendite - a peralkaline rhyolite
Pantellerite - an alkaline rhyolite-rhyodacite with amphibole phenocrysts
Scoria - an extremely vesicular mafic volcanic rock
Sovite - a coarse-grained carbonatite rock
Syenite - a plutonic rock dominated by orthoclase feldspar; a type of granitoid
Tachylyte - essentially a basaltic glass
Tephrite - a silica-undersaturated volcanic rock
Tonalite - a plagioclase-dominant granitoid
Trachyandesite - an alkaline intermediate volcanic rock
Benmoreite - sodic trachyandesite
Basaltic trachyandesite
Mugearite - sodic basaltic trachyandesite
Shoshonite - potassic basaltic trachyandesite
Trachyte - a silica-undersaturated volcanic rock; essentially a feldspathoid-bearing rhyolite
Troctolite - a plutonic ultramafic rock containing olivine, pyroxene and plagioclase
Trondhjemite - a form of tonalite where plagioclase-group feldspar is oligoclase
Tuff - a fine-grained volcanic rock formed from volcanic ash
Websterite - a type of pyroxenite, composed of clinoproxene and orthopyroxene
Wehrlite - an ultramafic plutonic or cumulate rock, a type of peridotite, composed of olivine and clinopyroxene

Sedimentary

Bituminous coal seam in West Virginia
Limey shale overlaid by limestone. Cumberland Plateau, Tennessee
Dolomite crystals from Touissite, Morocco
Turbidite (Gorgoglione Flysch), Miocene, South Italy
Argillite - a sedimentary rock composed primarily of clay-sized particles
Arkose - a sandstone with <25% feldspar crystals
Banded iron formation - a fine-grained chemical sedimentary rock composed of iron oxide minerals
Breccia - a sedimentary or tectonic rock composed of fragments of other, broken rocks
Calcarenite - a sedimentary rock composed of > 50% detrital carbonate grains
Chalk - a sedimentary rock composed primarily of coccolith fossils
Chert - a fine-grained chemical sedimentary rock composed of silica
Claystone - a sedimentary rock formed from clay
Coal - a sedimentary rock formed from organic matter
Conglomerate - a sedimentary rock composed of large rounded fragments of other rocks
Coquina - a sedimentary carbonate rock formed by accumulation of abundant shell fossils and fragments
Diamictite - a lithified sedimentary deposit with a wide range of grain sizes
Diatomite - sedimentary rock formed from diatom fossils
Dolomite or dolostone - a carbonate rock composed of the mineral dolomite +/- calcite
Evaporite - chemical sedimentary rock formed by accumulation of minerals after evaporation; varieties include rock salt (halitite) and rock gypsum
Flint - a form of chert
Geyserite - opaline silica deposit formed around hot springs and geysers
Greywacke - a type of sandstone with quartz, feldspar and rock fragments within a clay matrix
Gritstone - essentially a coarse sandstone formed from small pebbles
Itacolumite - porous, yellow-orange sandstone which is flexible if cut into thin strips
Jaspillite - an iron-rich chemical sedimentary rock similar to chert or banded iron formation
Laterite - residual sedimentary rock formed from a parent rock under tropical conditions
Lignite - sedimentary rock composed of 60%- 70% organic material; otherwise known as brown coal
Limestone - composed primarily of carbonate minerals
Marl - limestone with a considerable proportion of silicate material
Mudstone - clastic sedimentary rock that contains a mixture of silt- and clay-sized particles
Oil shale - sedimentary rock composed dominantly of organic material
Oolite - chemical sedimentary limestone formed from ooids, spherical grains composed of concentric layers
Sandstone - clastic sedimentary rock defined by its grain size (0.0625 mm to 2 mm)
Shale - clastic, fissile sedimentary rock defined by clay-sized particles
Siltstone - clastic sedimentary rock defined by 50% or greater silt-sized particles
Tillite - lithified glacial till
Travertine - sedimentary rock containing calcite and iron oxides
Tufa - porous limestone formed by the precipitation of carbonate minerals from ambient temperature water bodies
Turbidite - particular sequence of sedimentary rocks which form within the deep ocean environment
Wackestone - matrix-supported carbonate sedimentary rock.

Metamorphic

Phyllite
Banded gneiss with a dike of granite orthogneiss
Marble
Quartzite
Manhattan Schist, from Southeastern New York
Slate
Anthracite - metamorphosed coal, between 92% - 98% organic matter
Amphibolite - a metamorphic rock composed primarily of amphibole
Blueschist - a metamorphic rock composed of sodic amphiboles with a distinct blue color
Cataclasite - a rock formed by faulting
Eclogite - an ultra-high grade metamorphosed basalt or gabbro; also a facies of metamorphic rocks
Gneiss - a high grade coarse grained metamorphic rock with light and dark alternating bands
Granulite - a high grade metamorphic rock formed from basalt; also a facies of metamorphic rocks
Greenschist - a mafic metamorphic rock dominated by green amphiboles
Hornfels - a metamorphic rock formed by heating by an igneous rock
Litchfieldite - nepheline syenite gneiss
Marble - a metamorphosed limestone
Migmatite - a high grade metamorphic rock verging upon melting into a magma
Mylonite - a metamorphic rock formed by shearing
Metapelite - a metamorphic rock with a protolith of clay-rich (siltstone) sedimentary rock
Metapsammite - a metamorphic rock with a protolith of quartz-rich (sandstone) sedimentary rock
Phyllite - a low grade metamorphic rock composed mostly of micaceous minerals
Pseudotachylite - a glass formed by melting within a fault via friction
Quartzite - a metamorphosed sandstone typically composed of >95% quartz
Schist - a low to medium grade metamorphic rock
Serpentinite - a metamorphosed ultramafic rock dominated by serpentine minerals
Skarn - a metasomatic rock
Slate - a low grade metamorphic rock formed from shale or silts
Suevite - a rock formed by partial melting during a meteorite impact
Talc carbonate - a metamorphosed ultramafic rock with talc as an essential constituent; similar to a serpentinite
Soapstone - essentially a talc schist
Whiteschist - a high pressure metamorphic rock containing talc and kyanite

Specific varieties of rocks

The following are terms for rocks that are not petrographically or genetically distinct but are defined according to various other criteria; most are specific classes of other rocks, or altered versions of existing rocks. Some archaic and vernacular terms for rocks are also included.

Adamellite - a variety of quartz monzonite
Appinite - a group of varieties of lamprophyre, mostly rich in hornblende
Aphanite - an aphanitic felsic volcanic rock which confounds identification via optical means
Borolanite - a variety of nepheline syenite from Loch Borralan, Scotland
Blue Granite - essentially larvikite, a monzonite
Epidosite - a type of metasomatite; essentially altered basalt
Felsite - an aphanitic felsic volcanic rock which confounds identification via optical means
Flint - typically a form of chert, jasper, or tuff
Ganister - a Cornish term for a lithified E horizon of a palaeosol formed from sandy soil
Gossan - the product of the weathering of a sulfide rock or ore body
Hyaloclastite – volcanic glass with basaltic composition
Ijolite - a silica-undersaturated plutonic rock associated with nepheline syenites
Jadeitite - a very rare rock formed by concentration of jadeite pyroxene; a form of serpentinite
Jasperoid - a hematite-silica metasomatite analogous to a skarn
Kenyte - a variety of phonolite, first found on Mount Kenya
Lapis lazuli - a rock composed of lazulite and other minerals
Larvikite - a variety of monzonite with microperthitic ternary feldspars from Larvik, Norway
Litchfieldite - a metamorphosed nepheline syenite occurrence near Litchfield, Maine
Llanite - a hypabyssal rhyolite with microcline and blue quartz phenocrysts from the Llano Uplift in Texas
Luxullianite - a tourmaline-bearing granite with a peculiar texture, occurring at Luxulyan, Cornwall, England
Mangerite - a hypersthene-bearing monzonite
Minette - a variety of lamprophyre
Novaculite - a type of chert found in Oklahoma, Arkansas and Texas
Pyrolite - a chemical analogue considered to theoretically represent the earth's upper mantle
Rapakivi granite - a granite containing crystals of orthoclase, which are mantled by oligoclase
Rhomb porphyry - a type of latite with euhedral rhombic phenocrysts of feldspar
Shonkinite - melitilic and kalsititic rocks
Taconite - banded iron formation, primarily used in the United States of America
Tachylite - basaltic volcanic glass
Teschenite - a silica undersaturated, analcime bearing gabbro
Theralite - a nepheline gabbro
Unakite - an altered granite
Variolite - devitrified glass
Vogesite - a variety of lamprophyre
Wad - rock rich in manganese oxide or manganese hydroxide

See also

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