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In
geology Geology (from the γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is a branch of concerned with both the liquid and , the of which it is composed, and the processes by which they change over time. Geology can ...

geology
, a rock is any naturally occurring solid mass or aggregate of
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
s or
mineraloid A mineraloid is a naturally occurring mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian is an amorph ...
matter. It is categorized by the minerals included, its
chemical composition {{Unreferenced, date=December 2017 Chemical composition refers to identity and number of the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an el ...
and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid
outer core Earth's outer core is a fluid layer about thick and composed of mostly iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transi ...
and pockets of
magma Magma () is the molten or semi-molten natural material from which all s are formed. Magma is found beneath the surface of the , and evidence of has also been discovered on other and some s. Besides molten rock, magma may also contain suspended ...

magma
in the
asthenosphere The asthenosphere ( grc, ἀσθενός 'asthenos''meaning "without strength", and thus "weak", and 'sphaira''meaning "sphere") is the highly viscous The viscosity of a fluid In physics, a fluid is a substance that continually Defor ...
. Rocks are usually grouped into three main groups:
igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock i ...
s,
sedimentary rock Sedimentary rocks are types of rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compoun ...

sedimentary rock
s and
metamorphic rock , a type of metamorphic rock Metamorphic rocks arise from the transformation of existing rock (geology), rock to new types of rock, in a process called metamorphism upright=1.35, Schematic representation of a metamorphic reaction. Abbreviat ...

metamorphic rock
s. Igneous rocks are formed when
magma Magma () is the molten or semi-molten natural material from which all s are formed. Magma is found beneath the surface of the , and evidence of has also been discovered on other and some s. Besides molten rock, magma may also contain suspended ...

magma
cools in the Earth's crust, or
lava Lava is magma once it has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fracture in the Crust (geology), crust, ...

lava
cools on the ground surface or the seabed. Sedimentary rocks are formed by
diagenesis upright=1.35, Permineralization in vertebra from ''Valgipes bucklandi'' Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after the ...
or
lithification Lithification (from the Ancient Greek word ''lithos'' meaning 'rock' and the Latin-derived suffix ''-ific'') is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithificatio ...
of
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...

sediment
s, which in turn are formed by the
weathering Weathering is the deterioration of Rock (geology), rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little o ...
, transport, and
deposition Deposition may refer to: * Deposition (law), taking testimony outside of court * List of deposed politicians, Deposition (politics), the removal of a person of authority from political power * Deposition (university), a widespread initiation ritual ...
of existing rocks. Metamorphic rocks are formed when existing rocks are subjected to such high pressures and temperatures that they are transformed—something that occurs, for example, when
continental plates upright=1.35, Diagram of the internal layering of Earth showing the lithosphere above the asthenosphere (not to scale) Plate tectonics (from the la, label=Late Latin Late Latin ( la, Latinitas serior) is the scholarly name for the written L ...
collide. The scientific study of the character and origin of rocks is called
petrology Image:LvMS-Lvm.jpg, A volcanic lithic fragment (geology), sand grain seen under the microscope, with plane-polarized light in the upper picture, and cross polarized light in the lower picture. Scale box is 0.25 mm. Petrology (from the grc, wikt: ...
, which is an essential subdiscipline of
geology Geology (from the γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is a branch of concerned with both the liquid and , the of which it is composed, and the processes by which they change over time. Geology can ...

geology
.


Classification

Rocks are composed primarily of grains of minerals, which are
crystalline solids A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinet ...
formed from atoms
chemical bond A chemical bond is a lasting attraction between atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyda ...
ed into an orderly structure. Some rocks also contain
mineraloid A mineraloid is a naturally occurring mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian is an amorph ...
s, which are rigid, mineral-like substances, such as
volcanic glass Volcanic glass is the amorphous In condensed matter physics Condensed matter physics is the field of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nat ...
, that lacks crystalline structure. The types and abundance of minerals in a rock are determined by the manner in which it was formed. Most rocks contain
silicate minerals Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide) is usually conside ...
, compounds that include silica tetrahedra in their
crystal lattice In geometry and crystallography, a Bravais lattice, named after , is an infinite array of discrete points generated by a set of Translation operator (quantum mechanics)#Discrete Translational Symmetry, discrete translation operations described in th ...
, and account for about one-third of all known mineral species and about 95% of the
earth's crust 350px, Plates in the crust of Earth Earth's crust is a thin shell on the outside of Earth, accounting for less than 1% of Earth's volume. It is the top component of the lithosphere, a division of Earth's layers that includes the Crust (geology), ...
. The proportion of
silica Silicon dioxide, also known as silica, is an oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any su ...

silica
in rocks and minerals is a major factor in determining their names and properties. Rocks are classified according to characteristics such as mineral and chemical composition, permeability,
texture Texture may refer to: Science and technology * Surface texture, the texture means smoothness, roughness, or bumpiness of the surface of an object * Texture (roads), road surface characteristics with waves shorter than road roughness * Texture (co ...
of the constituent particles, and
particle size Particle size is a notion introduced for comparing dimension thumb , 236px , The first four spatial dimensions, represented in a two-dimensional picture. In physics Physics is the natural science that studies matter, its Elemen ...
. These physical properties are the result of the processes that formed the rocks. Over the course of time, rocks can be transformed from one type into another, as described by a geological model called the
rock cycle The rock cycle is a basic concept in geology that describes transitions through geologic time among the three main rock (geology), rock types: sedimentary, metamorphic rock, metamorphic, and igneous. Each rock type is altered when it is forced ...

rock cycle
. This transformation produces three general classes of rock:
igneous Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the p ...
,
sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentatio ...

sedimentary
and
metamorphic Metamorphic rocks arise from the transformation of existing rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the mineral ...

metamorphic
. Those three classes are subdivided into many groups. There are, however, no hard-and-fast boundaries between allied rocks. By increase or decrease in the proportions of their minerals, they pass through gradations from one to the other; the distinctive structures of one kind of rock may thus be traced, gradually merging into those of another. Hence the definitions adopted in rock names simply correspond to selected points in a continuously graduated series.


Igneous rock

Igneous rock (derived from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

Latin
word ''igneus,'' meaning ''of fire,'' from ''ignis'' meaning ''fire)'' is formed through the cooling and
solidification Freezing is a phase transition In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, ...

solidification
of
magma Magma () is the molten or semi-molten natural material from which all s are formed. Magma is found beneath the surface of the , and evidence of has also been discovered on other and some s. Besides molten rock, magma may also contain suspended ...

magma
or
lava Lava is magma once it has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fracture in the Crust (geology), crust, ...

lava
. This magma may be derived from partial melts of pre-existing rocks in either a
planet A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilibrium, rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and ...

planet
's
mantle Mantle may refer to: *Mantle (geology) A mantle is a layer inside a planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a n ...
or crust. Typically, the melting of rocks is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Igneous rocks are divided into two main categories: *
Plutonic Intrusive rock is formed when magma Magma () is the molten or semi-molten natural material from which all s are formed. Magma is found beneath the surface of the , and evidence of has also been discovered on other and some s. Besides molt ...
or
intrusive Intrusive may refer to: * Intrusiveness, a typically unwelcome behavior, interrupting and disturbing to others * Intrusive rock; intrusion of molten magma leaving behind igneous rock * Saltwater intrusion, the movement of saline water into freshwa ...

intrusive
rocks result when magma cools and
crystallizes Crystallization or crystallisation is the process by which a solid forms, where the Atom, atoms or molecules are highly organized into a Crystal structure, structure known as a crystal. Some of the ways by which crystals form are Precipitation ( ...

crystallizes
slowly within the
Earth's crust 350px, Plates in the crust of Earth Earth's crust is a thin shell on the outside of Earth, accounting for less than 1% of Earth's volume. It is the top component of the lithosphere, a division of Earth's layers that includes the Crust (geology), ...
. A common example of this type is
granite Granite () is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cool ...

granite
. * Volcanic or
extrusive A volcanic rock from Italy with a relatively large six-sided phenocryst (diameter about 1 mm) surrounded by a fine-grained groundmass, as seen in thin section under a petrographic microscope Extrusive rock refers to the mode of igneous volcanic ...
rocks result from magma reaching the surface either as lava or ''fragmental ejecta'', forming minerals such as
pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a formed from erupted from a . In other words, it differs from other by being of origin. ...

pumice
or
basalt Basalt (, ) is a fine-grained extrusive A volcanic rock from Italy with a relatively large six-sided phenocryst (diameter about 1 mm) surrounded by a fine-grained groundmass, as seen in thin section under a petrographic microscope Extr ...

basalt
. Magmas tend to become richer in silica as they rise towards the Earth's surface, a process called ''
magma differentiation In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, Intrusive rock, emplacement, or volcanic erup ...
''. This occurs both because minerals low in silica crystallize out of the magma as it begins to cool (
Bowen's reaction series Within the field of geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of whic ...

Bowen's reaction series
) and because the magma assimilates some of the crustal rock through which it ascends (''
country rock Country rock is a subgenre of , formed from the fusion of and . It was developed by rock musicians who began to record country-flavored records in the late 1960s and early 1970s. These musicians recorded rock records using country themes, vocal ...
''), and crustal rock tends to be high in silica. Silica content is thus the most important chemical criterion for classifying igneous rock. The content of
alkali metal oxide The alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origi ...
s is next in importance. About 65% of the Earth's crust by volume consists of igneous rocks. Of these, 66% are basalt and
gabbro Gabbro () is a phaneritic (coarse-grained), mafic intrusion, intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a crystallinity, holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coa ...

gabbro
, 16% are granite, and 17%
granodiorite Granodiorite () is a coarse-grained (phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from grani ...
and
diorite Diorite ( ) is an intrusive rock, intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is Intermediate composition, inter ...

diorite
. Only 0.6% are
syenite Image:Nepheline-syenite-2005.jpg, Leucocratic variety of nepheline syenite from Sweden (särnaite) Syenite is a coarse-grained Intrusion, intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, ...

syenite
and 0.3% are
ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch o ...
. The
oceanic crust The oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates This is a list of tectonic plates on Earth's surface. Tectonic plates are pieces of Earth's crust 350px, Plates in the crust of Earth Earth's crust i ...
is 99% basalt, which is an igneous rock of
mafic A mafic mineral or rock is a silicate mineral Silicate minerals are rock-forming mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composit ...
composition. Granite and similar rocks, known as granitoids, dominate the
continental crust Continental crust is the layer of igneous Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the ...
.


Sedimentary rock

Sedimentary rocks are formed at the earth's surface by the accumulation and cementation of fragments of earlier rocks, minerals, and organisms or as chemical precipitates and organic growths in water (
sedimentation Sedimentation is the deposition of sediments Sediment is a naturally occurring material that is broken down by processes of weathering Weathering is the deterioration of rocks In geology Geology (from the Ancient Greek γ ...
). This process causes
clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals In geology Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Gre ...
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...

sediment
s (pieces of rock) or
organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or ...
particles (
detritus In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms ...

detritus
) to settle and accumulate or for minerals to chemically
precipitate In aqueous solution, precipitation is the process of transforming a dissolved substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a de ...
(
evaporite An evaporite () is a water-soluble Solubility is the property of a solid, liquid or gaseous chemical substance called ''solution, solute'' to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depend ...
) from a
solution Solution may refer to: * Solution (chemistry) Image:SaltInWaterSolutionLiquid.jpg, upMaking a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The salt is the solute and the water the solvent. In chemistry ...
. The particulate matter then undergoes compaction and cementation at moderate temperatures and pressures (
diagenesis upright=1.35, Permineralization in vertebra from ''Valgipes bucklandi'' Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after the ...
). Before being deposited, sediments are formed by
weathering Weathering is the deterioration of Rock (geology), rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little o ...
of earlier rocks by
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
in a source area and then transported to the place of deposition by
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

water
,
wind Wind is the natural movement of air or other gases relative to a planet's surface. Wind occurs on a range of scales, from thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by th ...

wind
,
ice Ice is water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , eve ...

ice
,
mass movement A mass movement denotes a political party or movement which is supported by large segments of a population. Political movements that typically advocate the creation of a mass movement include the ideologies of communism Communism (from La ...
or
glacier A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abunda ...

glacier
s (agents of
denudation , Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At 8.5 million square kilometers (3.2 million square miles) and with over ...
). About 7.9% of the crust by volume is composed of sedimentary rocks, with 82% of those being shales, while the remainder consists of limestone (6%), sandstone and
arkose Arkose () is a detritalDetritus (; adjective ''detrital'' ) is particles of rock derived from pre-existing rock through processes of weathering Weathering is the breaking down of rocks, soil Soil (often stylized as SOiL) is an American roc ...

arkose
s (12%). Sedimentary rocks often contain
fossil A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication used by humans, inc ...

fossil
s. Sedimentary rocks form under the influence of gravity and typically are deposited in horizontal or near horizontal layers or
strata In geology and related fields, a stratum (plural: strata) is a layer of sedimentary rock or soil, or igneous rock that was formed at the Earth's surface, with internally consistent characteristics that distinguish it from other layers. The "str ...
, and may be referred to as stratified rocks.


Metamorphic rock

Metamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous rock or another older metamorphic rock—to different
temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concept ...

temperature
and
pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mass to change its velocity (e.g. moving fr ...

pressure
conditions than those in which the original rock was formed. This process is called
metamorphism Metamorphism is the change of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs nat ...
, meaning to "change in form". The result is a profound change in physical properties and chemistry of the stone. The original rock, known as the
protolith A protolith (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: ...
, transforms into other mineral types or other forms of the same minerals, by recrystallization. The temperatures and pressures required for this process are always higher than those found at the Earth's surface: temperatures greater than 150 to 200 °C and pressures greater than 1500 bars. Metamorphic rocks compose 27.4% of the crust by volume. The three major classes of metamorphic rock are based upon the formation mechanism. An intrusion of magma that heats the surrounding rock causes contact metamorphism—a temperature-dominated transformation. Pressure metamorphism occurs when sediments are buried deep under the ground; pressure is dominant, and temperature plays a smaller role. This is termed burial metamorphism, and it can result in rocks such as
jade Jade is a mineral, much used in some cultures as jewellery and for ornaments, mostly known for its green varieties, though it appears naturally in other colors as well, notably yellow and white. Jade can refer to either of two different silica ...

jade
. Where both heat and pressure play a role, the mechanism is termed regional metamorphism. This is typically found in mountain-building regions. Depending on the structure, metamorphic rocks are divided into two general categories. Those that possess a texture are referred to as foliated; the remainders are termed non-foliated. The name of the rock is then determined based on the types of minerals present.
Schist Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fair ...

Schist
s are foliated rocks that are primarily composed of lamellar minerals such as
mica Micas ( ) are a group of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs natural ...

mica
s. A
gneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. Gneiss is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous Igneous rock (derived from the Latin Latin (, or ...

gneiss
has visible bands of differing
lightness Lightness is a visual perception of the luminance (L) of an object. It is often judged relative to a similarly lit object. In colorimetry and color appearance models, lightness is a prediction of how an illuminated color will appear to a stand ...

lightness
, with a common example being the granite gneiss. Other varieties of foliated rock include
slate Slate is a fine-grained, foliated, homogeneous metamorphic rock , a type of metamorphic rock Metamorphic rocks arise from the transformation of existing rock (geology), rock to new types of rock, in a process called metamorphism uprigh ...

slate
s,
phyllite Photomicrograph of thin section of phyllite (in cross Polarization (waves), polarised light) Phyllite is a type of Foliation (geology), foliated metamorphic rock created from slate that is further metamorphosed so that very fine grained white mic ...

phyllite
s, and
mylonite Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse" ...

mylonite
. Familiar examples of non-foliated metamorphic rocks include
marble Marble is a metamorphic rock , a type of metamorphic rock Metamorphic rocks arise from the transformation of existing rock (geology), rock to new types of rock, in a process called metamorphism upright=1.35, Schematic representation of ...

marble
,
soapstone Soapstone (also known as steatite or soaprock) is a talc- schist, which is a type of metamorphic rock. It is composed largely of the magnesium Magnesium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic ...
, and
serpentine Serpentine may refer to: Music * Serpentine (album), ''Serpentine'' (album), a 2002 goth metal album by Flowing Tears * Serpentine (song), "Serpentine" (song), a 2011 country song by Tiffany * Serpentines (Ingrid Laubrock album), ''Serpentines'' ( ...
. This branch contains
quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecto ...

quartzite
—a metamorphosed form of
sandstone Sandstone is a clastic sedimentary rock of a clast (sand grain), derived from a basalt Basalt (, ) is a fine-grained extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ('' mafic ' ...

sandstone
—and
hornfels Hornfels is the group name for a set of contact metamorphic rocks that have been baked and hardened by the heat of intrusive Intrusive may refer to: * Intrusiveness, a typically unwelcome behavior, interrupting and disturbing to others * Intrusi ...

hornfels
.


Human use

The use of rock has had a huge impact on the cultural and technological development of the human race. Rock has been used by humans and other
hominids The Hominidae (), whose members are known as great apes or hominids (), are a taxonomic Family (biology), family of primates that includes eight Neontology#Extant taxa versus extinct taxa, extant species in four Genus, genera: ''Orangutan, Pon ...
for at least 2.5 million years.
Lithic technology In archaeology Archaeology or archeology is the study of human activity through the recovery and analysis of material culture. Archaeology is often considered a branch of socio-cultural anthropology, but archaeologists also draw from biolo ...
marks some of the oldest and continuously used technologies. The
mining Mining is the extraction of valuable mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occu ...

mining
of rock for its
metal A metal (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appro ...

metal
content has been one of the most important factors of human advancement, and has progressed at different rates in different places, in part because of the kind of metals available from the rock of a region.


Building

Rock varies greatly in strength, from
quartzites Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms. The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahed ...
having a
tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle tensi ...
in excess of 300
MPa MPA or mPa may refer to: Academia Academic degrees * Master of Performing Arts * Master of Professional Accountancy * Master of Public Administration * Master of Public Affairs Schools * Mesa Preparatory Academy * Morgan Park Academy * Mounds ...
to sedimentary rock so soft it can be crumbled with bare fingers (that is, it is ''
friable Friability ( ), the condition of being friable, describes the tendency of a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and c ...
''). (For comparison,
structural steel Structural steel is a category of steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, ...
has a tensile strength of around 350 MPa.) Relatively soft, easily worked sedimentary rock was quarried for construction as early as 4000 BCE in Egypt, and stone was used to build fortifications in
Inner Mongolia Inner Mongolia, officially the Inner Mongolia Autonomous Region, is a landlocked autonomous region An autonomous administrative division (also referred to as an autonomous area, entity, unit, region, subdivision, or territory) is a subnati ...

Inner Mongolia
as early as 2800 BCE. The soft rock,
tuff Tuff is a type of Rock (geology), rock made of volcanic ash ejected from a Volcano, vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is consider ...

tuff
, is common in Italy, and the
Romans Roman or Romans usually refers to: *Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, ...
used it for many buildings and bridges.
Limestone Limestone is a common type of carbonate In chemistry, a carbonate is a salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its na ...

Limestone
was widely used in construction in the Middle Ages in Europe and remained popular into the 20th century.


Mining

Mining is the extraction of valuable
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
s or other
geological Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processes by which th ...

geological
materials from the earth, from an
ore ore – psilomelane Psilomelane is a group name for hard black manganese oxides including hollandite and romanechite. Psilomelane consists of hydrous manganese Manganese is a chemical element Image:Simple Periodic Table Chart- ...

ore
body,
vein Veins are blood vessels The blood vessels are the components of the circulatory system The circulatory system, also called the cardiovascular system or the vascular system, is an organ system An organ system is a biological system A b ...
or seam. The term also includes the removal of soil. Materials recovered by mining include
base metals A base metal is a common and inexpensive metal A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast ...
,
precious metals Precious metals are rare, naturally occurring metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance ...
,
iron Iron () is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behav ...

iron
,
uranium Uranium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

uranium
,
coal Coal is a combustible , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German language, German , ...

coal
,
diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. At Standard conditions for temperature and pressure, room temperature and pressure, another solid form of ...

diamond
s,
limestone Limestone is a common type of carbonate In chemistry, a carbonate is a salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its na ...

limestone
,
oil shale Oil shale is an organic-rich containing (a solid mixture of ) from which liquid s can be produced, called . Shale oil is a substitute for conventional crude oil; however, extracting shale oil is costlier than the production of conventional ...

oil shale
,
rock salt Halite ( or ), commonly known as rock salt, is a type of salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a cry ...
,
potash Potash () includes various mined and manufactured salts In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structu ...
,
construction aggregate Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction Construction is a general term meaning the and to form , , or ,"Construction" def. 1.a. 1.b. ...
and
dimension stone Dimension stone is natural stone or Rock (geology), rock that has been selected and finished (e.g., trimmed, cut, drilled, ground, or other) to specific sizes or shapes. Color, Texture (geology), texture and pattern, and surface finish of the st ...
. Mining is required to obtain any material that cannot be grown through
agricultural Agriculture is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary behaviors such as watching tele ...

agricultural
processes, or created
artificially Artificiality (the state of being artificial or man-made) is the state of being the product of intentional human manufacture, rather than occurring nature, naturally through processes not involving or requiring human activity. Connotations Artifici ...
in a
laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testabl ...

laboratory
or
factory A factory, manufacturing plant or a production plant is an Industry (manufacturing), industrial site, often a complex consisting of several buildings filled with Outline of industrial machinery, machinery, where workers manufacturing, manufactu ...

factory
. Mining in a wider sense comprises extraction of any
resource Resource refers to all the materials available in our environment which help us to satisfy our needs and wants. Resources can broadly be classified upon their availability — they are classified into renewable A renewable resource, also know ...

resource
(e.g.
petroleum Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isoc ...

petroleum
,
natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consisting of methane and commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carbon dioxid ...

natural gas
,
salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure fo ...

salt
or even
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

water
) from the earth. Mining of rock and metals has been done since
prehistoric Prehistory, also known as pre-literary history, is the period of human history Human history, or world history, is the narrative of Human, humanity's past. It is understood through archaeology, anthropology, genetics, and linguistics, ...
times. Modern mining processes involve
prospecting Prospecting is the first stage of the geological analysis (followed by exploration Exploration is the act of searching for the purpose of discovery Discovery may refer to: * Discovery (observation) Discovery is the act of detecting s ...
for mineral deposits, analysis of the profit potential of a proposed mine, extraction of the desired materials, and finally reclamation of the land to prepare it for other uses once mining ceases. Mining processes may create negative impacts on the environment both during the mining operations and for years after mining has ceased. These potential impacts have led to most of the world's nations adopting regulations to manage negative effects of mining operations.


See also

*
Building material Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, and wood, even twigs and leaves, have been used to construct buildings. Apart from naturally occurring materials, many man-mad ...
*
History of Earth The history of Earth concerns the development of planet A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilibrium, rounded by its own gravity ...
*
Geologic time scale The geologic time scale (GTS) is a system of chronological dating Chronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located in a previously establi ...

Geologic time scale
*
Geomorphology Geomorphology (from Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek ...

Geomorphology
*
Boulder In geology Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speake ...

Boulder
*
List of rock types The following is a list of rock types recognized by geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes the Earth and other terrestrial planets, as well as the processes that shape them. Geol ...
*
Oldest rock 200px, A sample of Acasta River area of Canada). This sample has been dated at 4.03 billion years old. The oldest dated rocks formed on Earth, as an Aggregate (geology), aggregate of minerals that have not been subsequently broken down by erosion ...
*
Stone industry Stone industry refers to the part of the primary sector of the economy, similar to the mining industry, but concerned with excavations of stones, in particular granite, marble, slate and sandstone. Other products of the industry include crushed s ...


References


External links

* * * {{DEFAULTSORT:Rock (Geology) Petrology Materials