Rocks

A: amphibolite, andesite, anhydrite rock, anorthosite, aplite
B: basalt
C: chert, clay
D: dacite, diatomite, diorite, dolostone, dunite
E: eclogite
G: gabbro, gneiss, granite, granodiorite, granulite, greisen, gypsum rock
H: hornfels
K: kimberlite
L: latite, limestone
M: marble, marl, monzonite, mudstone
N: norite
P: peridotite, phyllite
Q: quartzite, quartzolite
R: rhyolite, rocksalt
S: sandstone, schist, serpentinite, shale, siltstone, skarn, slate, syenite
T: tonalite, trachyte, tuff

Plutonic igneous rocks

Quartzolite

Quartzolite is a plutonic igneous rock that contains 90 - 100% quartz and 0 - 10% feldspars.
The essential constituent is quartz.
Common but not essential constituents include K-feldspars and plagioclase feldspars.

Granite

Granite is a medium- to coarse-grained silica-rich plutonic igneous rock, formed by crystallisation of a silica-rich magma in a major intrusion. It contains
80 - 100 % light coloured minerals, of which quartz is 20 - 60% and feldspars 40 - 80%. Of these feldspars 35 - 100% are K-feldspars and 0 - 65% plagioclase feldspars.
It also contains 0 - 20% dark minerals.
Essential constituents are quartz and K-feldspars (feldspars rich in potassium).
Common but not essential constituents include biotite, hornblende, muscovite and plagioclase feldspars (feldspars deficient in potassium).

Granodiorite

Granodiorite is a feldspar-rich plutonic igneous rock.
Major constituents are plagioclase feldspar, K-feldspar, quartz and mica.
Minor constituents are hornblende and augite. Oligoclase is a common constituent.
Granodiorite is the most abundant of the plutonic igneous rocks.

Tonalite

Tonalite is a plutonic igneous rock.
Major constituents are plagioclase feldspar, typically oligoclase or andesine (greater than 10%), and quartz (greater than 20%), hornblende and biotite.
Minor constituents are K-feldspars (10% or less), apatite, titanite, magnetite, ilmenite and zircon.

Syenite

Syenite is a coarse-grained plutonic igneous rock with intermediate silica content. It contains
60 - 100 % light coloured minerals of which feldspar is 80 - 100% and quartz 0 - 20% or feldspathoids 0 - 10%.
Of the feldspars, 65 - 100% are K-feldspars and 0 - 35% plagioclase feldspar feldspar (albite to anorthite).
It also contains 0 - 40% dark minerals.
The essential constituents are K-feldspars.
Common but not essential constituents include aenigmatite, amphibole, biotite, feldspathoids, hornblende, plagioclase feldspar, pyroxene, titanite and zircon (very common in nepheline syenite).

Nepheline Syenite

Nepheline syenite is a nepheline-rich syenite.
The essential constituents are K-feldspars and nepheline.
Common but not essential constituents include biotite and hornblende.

Monzonite

Monzonite is a plutonic igneous rock containing 0 to 5% quartz and 95 to 100% feldspar.
Essential constituents are K-feldspars and plagioclase feldspars.
Common but not essential minerals include amphibole and pyroxene.
Disseminated copper deposits are found frequently in monzonite.

Diorite

Diorite is a plutonic igneous rock with intermediate silica content. It contains
50 - 85% of light coloured minerals of which feldspars are 80 - 100% and quartz is 0 - 20% or feldspathoids 0 - 10%.
Of the feldspars, 65 - 100% are plagioclase feldspars and 0 - 35% are K-feldspars.
It also contains 15 - 50% dark minerals.
The essential constituent is plagioclase feldspar.
Common but not essential constituents include biotite, hornblende and quartz.

Gabbro

Gabbro is a silica-poor plutonic igneous rock. It contains
35 - 80% of light coloured minerals of which feldspars are 80 - 100% and quartz is 0 - 20% or feldspathoids 0 - 10%.
Of the feldspars, 65 - 100% are plagioclase feldspar feldspars and 0 - 35% are K-feldspars.
It also contains 20 - 65% dark minerals.
Essential constituents are plagioclase feldspars and dark minerals (mafic minerals) such as olivine and pyroxene.
Common but not essential constituents include biotite and hornblende.
Gabbro is most abundant at constructive plate margins, where tectonic plates move apart and magma wells up to fill the gap, and gabbro constitutes the lower portions of the oceanic crusts. It is also abundant in oceanic islands; these are islands without any foundation of continental rock, usually formed as the result of volcanic action.
Gabbro can also occur at destructive plate margins, where the tectonic plates are moving together, and in continental rifts, where the continental crust is thinning due to the underlying plates moving apart.
Nickel ores are associated with norites (orthopyroxene-dominated gabbros) and peridotite.

Anorthosite

Anorthosite is a plutonic igneous rock, formed by crystallisation of a silica-poor magma in a major intrusion. It contains at least 90% calcium-rich plagioclase feldspar. The remaining 10% is made up of olivine, garnet, pyroxene and iron oxides.
The essential constituent is plagioclase feldspar.
Common but not essential constituents include pyroxene.

Aplite

Aplite is a fine-grained granite consisting of only feldspar and quartz.
Essential constituents are K-feldspar, plagioclase feldspar and quartz.

Mafic and Ultramafic

Mafic rocks are rocks that are rich in dark minerals such as magnesium and iron compounds but deficient in quartz. Common rock-forming mafic minerals include olivine, pyroxene, and biotite.
Ultramafic rocks contain more than 90% mafic minerals.

Dunite

Dunite is an ultramafic plutonic igneous rock containing more than 90% of olivine.
The essential constituent is olivine.
Common but not essential constituents include magnetite and pyroxene.

Norite

Norite is a a mafic, plutonic igneous rock including more than 50% anorthite and very much more orthopyroxene than clinopyroxene. Accessory minerals include olivine, magnetite, ilmenite, apatite and chromite, with accidentals biotite, hornblende and cordierite.

Peridotite

Peridotite is an ultramafic plutonic igneous rock containing more than 40% of olivine.
The essential constituent is olivine.
Common but not essential constituents include pyroxene and chromite. Nickel ores are associated with norites (orthopyroxene-dominated gabbros) and peridotite.

Kimberlite

Kimberlite is an ultramafic igneous rock.
Essential constituents are carbonates such as calcite, together with olivine, phlogopite and pyroxene.
Common but not essential constituents include monticellite, perovskite and pyrope.

Volcanic igneous rocks

Rhyolite

Rhyolite is a fine-grained feldspar-rich volcanic igneous rock, formed from a silica-rich magma. It contains
80 - 100% light minerals of which quartz is 20 - 60% and feldspars 40 - 80%.
Of the feldspars 35 - 100% are K-feldspars and 0 - 65% are plagioclase feldspars (albite to anorthite).
It also contains 0 - 20% dark minerals.
Essential constituents are K-feldspars, plagioclase feldspars and quartz.
Common but not essential constituents include amphibole, biotite and pyroxene. Rhyolite mainly occurs as lava domes (domes resulting from the slow extrusion of viscous lava from a volcano). Rhyolite, like granite, is most commonly associated with island arc (a chain of volcanic islands, parallel with and close to a boundary between two converging tectonic plates) and mountain-building magmatism.

Dacite

Dacite is a volcanic igneous rock.
Essential constituents are plagioclase feldspars, quartz, biotite and hornblende.
Accessories are magnetite, ilmenite, sanidine, pyroxene and glass.

Latite

Latite is a volcanic igneous rock.
Essential constituents are sanidine, plagioclase feldspars, augite and hornblende.
Accessories are anorthoclase, olivine, feldspathoids, magnetite and ilmenite.

Trachyte

Trachyte is a feldspar-rich volcanic igneous rock of intermediate silica content. It contains
60 - 100% light minerals of which feldspars are 80 - 100% and quartz 0 - 20% or feldspathoids 0 - 10%.
Of the feldspars 35 - 65% are K-feldspars and 35 - 65% are plagioclase feldspars (albite to anorthite).
It also contains 0 - 40 % dark minerals.
Essential constituents are albite variety oligoclase and sanidine.
Common but not essential constituents include biotite, hornblende, nepheline, pyroxene and quartz.
Trachyte is most commonly associated with ocean island (islands without any foundation of continental rock, usually formed as the result of volcanic action) and continental rift (where the continental crust is thinning due to the underlying plates moving apart) magmatism.

Andesite

Andesite is a volcanic igneous rock with intermediate silica content. It contains
60 - 85% light minerals of which 80 - 100% are feldspars and 0 - 20% are quartz or 0 - 10% are feldspathoids.
Of the feldspars 65 - 100% are plagioclase feldspars and 0 - 35% are K-feldspars.
It also contains 15 - 40% dark minerals.
Essential constituents are plagioclase feldspars.
Common but not essential constituents include biotite, hornblende, and pyroxenes.
Andesite occurs in lava flows together with basalt and trachyte.

Basalt

Basalt is a silica-poor volcanic igneous rock, formed from a silica-poor magma. It contains
30 - 60% light minerals of which feldspars are 80 - 100% and quartz 0 - 20% or feldspathoids 0 - 10%.
Of the feldspars 65 - 100% are plagioclase feldspars and 0 - 35% are K-feldspars.
It also contains 40 - 70% dark minerals.
Essential constituents are plagioclase feldspar and pyroxenes.
Common but not essential constituents include feldspathoids, olivine and quartz
In addition, many hydrothermal minerals are found filling cavities in basalt

Clastic sedimentary rocks

Sandstone

Sandstone is a clastic sedimentary rock comprised mainly of sand-sized grains, between 0.0625 and 4 mm across. The grains can be quartz, feldspar or rock fragments. Sandstone is deposited by a wide range of processes including river and stream deposits (fluvial), floodplain or river delta deposits (alluvial), windborn deposits (aeolian) and under-water, sediment-laden currents (turbidity currents).
Essential constituents are feldspars and quartz.
A common constituent is calcite

Siltstone

Siltstone is a clastic sedimentary rock comprised mainly of grains sized 0.0039 to 0.0625 mm across.

Mudstone

Mudstone is a clastic sedimentary rock comprised mainly of grains sized less than 0.0039 mm across. Shale, clay and marl are types of mudstone. The majority of grains in mudstones are clay minerals such as montmorillonite and kaolinite.

Shale

Shale is a mudstone with a fissile parting. It is the most abundant clastic sedimentary rock in the Earth's crust, comprising about 70% of sedimentary rocks. It consists of a high percentage of clay minerals, substantial amounts of quartz and smaller amounts of carbonates, feldspar, fossils and organic matter. Shale is coloured red and purple by hematite and goethite, blue, green and black by ferrous iron, and grey or yellowish by calcite.
It is deposited by gentle currents on deep ocean floors, shallow sea basins and river floodplains.

Clay

Clay is a soft, cohesive, water-rich mudstone that is plastic when wet and hardens when fired. The majority of clays are largely composed of phyllosilicates, such as chlorite, kaolinite, mica, montmorillonite and muscovite variety illite.

Marl

Marl is a mudstone containing a great deal of carbonate.
The essential constituent is calcite.
Common but not essential constituents include dolomite and hematite.

Tuff

Tuff is a fine-grained pyroclastic rock, ie it is formed by the lithification of beds of volcanic ash and lava fragments. Such a rock may be classified as volcanic igneous, but here we group it with the sedimentary rocks.

Chemical sedimentary rocks

Rocksalt

Rocksalt is the massive rock form of the mineral halite. It is a monomineralic chemical sedimentary rock.
The essential constituent is halite, and a common but not essential constituent is anhydrite.
Rock salt often occurs in salt domes. A salt dome is a structural dome formed when a thick bed of evaporite minerals found at depth intrudes vertically into surrounding rock strata. Salt domes contain anhydrite, gypsum, and native sulphur, in addition to halite and sylvite. Rocksalt forms from the evaporation of ocean or saline lake waters. It is rarely found at the Earth's surface, except where the climate is very arid.

Gypsum rock

Gypsum rock is a monomineralic chemical sedimentary rock with gypsum as its major constituent.
Common minor constituents are anhydrite, rocksalt, limestone and dolomite.
Gypsum rock originates by precipitation as sea water is evaporated or by the hydration of anhydrite.

Anhydrite rock

Anhydrite rock is a monomineralic chemical sedimentary rock with anhydrite as its major constituent.
Medium constituents are gypsum, calcite, dolomite, clay minerals and bitumen.
Anhydrite rock originates by precipitation from sea water or diagenetically from gypsum as a result of high temperature and thick overburden in mountain ranges.

Biogenic sedimentary rocks

Limestone

Limestone is a biogenic sedimentary rock formed in marine environments.
The essential constituent is calcite.
Common but not essential constituents include aragonite and dolomite.

Dolostone

Dolostone is a biogenic sedimentary rock formed in marine environments and consisting of more than 50% dolomite.
Most dolostone did not originally form as dolostone, but instead formed from the alteration of limestone as magnesium-rich water moved through it, altering its calcite and aragonite into dolomite. The replacement may be only partial, and most dolostone is a mixture of dolomite and calcite.
The main exception to this secondary dolostone is the rare primary dolostone that forms as a relatively late product of seawater evaporation.
The essential constituent is dolomite, almost always accompanied by calcite.
Common but not essential constituents include ankerite.

Diatomite

Diatomite is a biogenic sedimentary rock composed of diatom skeletons, consisting of about 90% opal. Diatoms are microscopic, single-celled algae that live in marine or fresh water, with skeletons made of silicon dioxide. The remaining 10% is made up of aluminium and iron oxides.

Chert

Chert is a chemical sedimentary rock consisting almost entirely of chalcedony; it may be biochemical, or formed by replacement.
Biochemical chert is formed when the siliceous skeletons of marine plankton are dissolved during diagenesis (rock formation), with silica being precipitated from the resulting solution.
Replacement chert, such as petrified wood, forms when other material is replaced by silica.
Chert occurs as nodules in limestone and dolostone as a replacement mineral. Flint is a variety of chert that occurs in chalk or marl. Agate is a type of chert that forms through direct precipitation of silica in voids within a rock. Chert also occurs in thin beds, when it is a primary deposit, and in beds and lenses of diatomite.
The essential constituent is chalcedony.
Common but not essential constituents include opal and quartz. dolomite and chert to talc and calcite
3CaMg(CO3)2 + 4SiO2 + H2O → Mg3Si4O10(OH)2 + 3CaCO3 + 3CO2
Metamorphism of siliceous carbonate rocks causes the formation of hydrous phases such as talc and tremolite. This is a very low-grade metamorphic reaction occurring at temperature between about 150oC and 250oC.

Contact metamorphic rocks

Hornfels

Hornfels is formed by contact metamorphism close to igneous intrusions at temperatures of 200 to 800oC and low to high pressure.
Common but not essential constituents include andalusite, cordierite, hornblende and plagioclase feldspar.
Hornfels is a characteristic rock of the hornblende-hornfels, albite-epidote-hornfels and pyroxene-hornfels facies.

Marble

Marble is formed by regional or contact metamorphism of limestone or dolostone at temperatures above 570oC and low to high pressure.
The essential constituent is calcite.
Common but not essential constituents include actinolite, diopside, dolomite and tremolite.

Skarn

Skarn is a metamorphic rock formed by the contact metamorphism of limestone when it is intruded by an igneous rock, often granite, at temperatures above 570oC and at low pressure.
The essential constituent is calcite and a common constituent is dolomite.

Regional metamorphic rocks

Slate

Slate is a very fine-grained, foliated rock with a pervasive fissile cleavage (splitting along flat planes) due to alignment of phyllosilicates. It is produced by the regional metamorphism of clay-rich sediments, such as shale and mudstone at about 2 kbar pressure and 500oC.
Essential constituents are feldspar, mica and quartz.
Common but not essential constituents include graphite and pyrite. Slate is typically grey to black in colour with a dull lustre, and sometimes green. It is formed by regional metamorphism of argillaceous (clay-rich) sediments.
Slate is a characteristic rock of the prehnite-pumpellyite, greenschist and blueschist facies. With increasing metamorphic grade slate transforms into phyllite.

Serpentinite

Serpentinite is a regional metamorphic rock formed mainly from ultramafic parent rocks (protoliths) at about 5 kbar pressure and 400oC. It is a common component of oceanic crust at a convergent plate boundary where the oceanic crust is forced down beneath the continental crust. Serpentinite forms by the transformation of olivine and pyroxene in peridotite to serpentine. Relicts of olivine and pyroxene are often present in the serpentinite. Dehydration of serpentinite at high temperature produces talc, tremolite and forsterite.
The essential constituent is serpentine.

Phyllite

Phyllite is formed by regional metamorphism of argillaceous (clay-rich) sediments, such as shale and mudstone, at about 5 kbar pressure and 400oC. It is a characteristic rock of the greenschist facies, and it is also a rock of the amphibolite facies.
Essential constituents are biotite, chlorite and muscovite.
Common but not essential constituents include feldspar, graphite and quartz.

Quartzite

Quartzite is a high-temperature metamorphic rock produced by regional metamorphism of sandstone. It is composed mainly of quartz, with mica, kyanite and sillimanite as accessories.

Schist

Schist is formed by regional metamorphism of a wide range of fine-grained sediments, including argillaceous (clay-rich) and arenaceous (sandy) sediments, mixed silica-rich and carbonate sediments, and igneous rocks, at about 4 to 15 kbar pressure and 450 to 700oC.
It is a characteristic rock of the greenschist and blueschist facies, and it is also a rock of the amphibolite facies.
Essential constituents are feldspar, usually albite or its variety oligoclase, mica and quartz.
Common but not essential constituents include actinolite, garnet, graphite, hornblende and kyanite.

Mica schists are derived mainly from argillaceous (clay-rich) protoliths, quartz- and feldspar-rich schists have protoliths with a more significant arenaceous (sandy) component, graphite schists typically form from carbon-rich argillaceous (clay-rich) sediments and calc-silicate schists form from clay-rich limestone or calcite-rich mudstone, and often contain diopside and wollastonite.

Greisen

Greisen is a medium-temperature metamorphic rock resulting from the alteration of granite by hot vapour from magma. It is composed mostly of light-coloured mica and quartz, commonly with topaz, fluorite and tourmaline as accessories.

Gneiss

Gneiss is a metamorphic rock formed by high grade regional metamorphism of rocks containing quartz and feldspar at about 6 kbar pressure and 700oC. It is a characteristic rock of the granulite facies and it is also a rock of the amphibolite facies.
The precursor rock (original rock before metamorphism) may be granite, granodiorite, silica-rich igneous volcanic rocks, mudstone, siltstone or shale.
Common but not essential constituents include amphibole, feldspar, mica and quartz.

Amphibolite

Amphibolite is a metamorphic rock formed by regional metamorphism of silica-poor igneous rocks such as gabbro, at temperatures 500 - 750oC and pressure 8 - 70 kbar (medium-grade metamorphism).
Essential constituents are amphiboles such as hornblende, tremolite and actinolite, and plagioclase feldspar (albite to anorthite).
Common but not essential constituents include epidote, garnet, biotite, clinopyroxene, scapolite, quartz and titanite.
Amphibolite is the characteristic rock of the amphibolite facies.

Granulite

Granulite is a metamorphic rock formed by high-grade regional metamorphism of silica-poor igneous and sedimentary rocks at temperature 500 - 750oC, pressure 8 - 70 kbar.
It is the characteristic rock of the granulite facies.
Essential minerals are feldspars.
Common but not essential minerals include cordierite, amphibole, quartz and pyroxene.

Eclogite

Eclogite is formed by regional metamorphism at about 20 kbar pressure and 700oC.
Essential constituents are omphacite and pyrope.
Common but not essential constituents include kyanite, paragonite, pyroxene, quartz and rutile.