List of rock types

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.

Igneous

Adakite - a class of intermediate to felsic rocks containing low amounts of yttrium and ytterbium

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, 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 during 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 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, 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 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 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 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

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

Vogesite - a variety of lamprophyre

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 chert formation 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

Variolite - devitrified glass

See also

• List of minerals
• List of rocks on Mars
• Rock cycle
• Rock formation: for a list of unusual or culturally significant rock outcrops.

External links

• British Geological Survey rock classification scheme
• Igneous rock classification
• Rock Types Article by Encyclopaedia Britannica
• Classification of common rocks and soils
• Metamorphic Rock Classification
• Volcanic rocks
• Earth Science Education Unit virtual rock kit