List of rock types

A list of all unique rock types recognized by petrologists. Names of non-rock types and archaic rock types are given as appendices.

Igneous

A sample of andesite (dark groundmass) with amygdaloidal vesicules 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 - an intrusive igneous felsic rock composed predominantly of plagioclase

Aplite - a very fine grained intrusive igneous rock composed of quartz and feldspar

Basalt - a volcanic rock of mafic composition

Adakite - a class of basaltic rocks containing low amounts of yttrium and ytterbium

Hawaiite - a class of basalts formed from ocean island (hot spot) volcanism

Basanite - a volcanic rock of mafic composition; essentially a silica-undersaturated basalt

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 plagioclase > 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

Dunite - a phaneritic ultramafic rock composed of more than 90% olivine, usually forsteritic

Essexite - a silica undersaturated mafic plutonic rock (essentially a foid-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 plagioclase > 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 - a volcanic rock

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 ancient ultramafic volcanic rock with very high MgO 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 with nepheline replacing orthoclase

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 giant sized crystals

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, extremely 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

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

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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 sedimentary rock similar to sandstone

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

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 poorly sorted conglomerate

Diatomite - a sedimentary rock formed from diatom fossils

Dolomite or dolostone - a carbonate rock composed of the mineral dolomite +/- calcite

Evaporite - a chemical sedimentary rock formed by accumulation of minerals after evaporation; varieties include rock salt (halitite) and rock gypsum

Flint - a form of chert

Greywacke - an immature 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 - a residual sedimentary rock formed from a parent rock under tropical conditions

Lignite - a sedimentary rock composed of organic material; otherwise known as Brown Coal

Limestone - a sedimentary rock composed primarily of carbonate minerals

Marl - a limestone with a considerable proportion of silicate material

Mudstone - a sedimentary rock composed of clay and muds

Oil shale - a sedimentary rock composed dominantly of organic material

Oolite - a chemical sedimentary limestone

Sandstone - a clastic sedimentary rock defined by its grain size

Shale - a clastic sedimentary rock defined by its grain size

Siltstone - a clastic sedimentary rock defined by its grain size

Travertine - a sedimentary rock containing calcite and iron oxides

Turbidite - a particular sequence of sedimentary rocks which form within the deep ocean environment

Wackestone - a matrix-supported carbonate sedimentary rock.

Metamorphic

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Phyllite

Banded gneiss with a dike of granite orthogneiss

Marble

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Quartzite

Manhattan Schist, from Southeastern New York

Slate

Anthracite - a type of coal

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 coarse grained metamorphic rock

Gossan - the product of the weathering of a sulfide rock or ore body

Granulite - a high grade metamorphic rock formed from basalt; also a facies of metamorphic rocks

Greenschist - a mafic metamorphic rock dominated by green amphiboles

Greenstone

Hornfels - a metamorphic rock formed by heating by an igneous rock

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

Phyllite - a low grade metamorphic rock composed mostly of micaceous minerals

Metapsammite - a metamorphic rock with a protolith of quartz-rich (sandstone) sedimentary rock

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 palaeosol formed on sandstone

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