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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 '' lava) exposed at or very near the surface o ...
composed mainly of sand-sized (0.0625 to 2 mm)
silicate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, ...
grains. Sandstones comprise about 20–25% of all
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. Most sandstone is composed of
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, ...

quartz
or
feldspar Feldspars are a group of rock-forming aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity ...
(both
silicate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, ...
s) because they are the most resistant minerals to
weathering Weathering is the deterioration of rocks In 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 ...
processes at the Earth's surface. Like uncemented
sand Sand is a granular material composed of finely divided rock (geology), rock and mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer ...

sand
, sandstone may be any color due to impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other
topographic Topography is the study of the forms and features of land surfaces. The topography of an area could refer to the surface forms and features themselves, or a description (especially their depiction in maps). Topography is a field of geoscience ...
features, certain colors of sandstone have been strongly identified with certain regions. Rock formations that are primarily composed of sandstone usually allow the
percolation Fig. 2: Percolation in a square lattice (Click to animate) In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ...

percolation
of water and other fluids and are
porous Porosity or void fraction is a measure of the (i.e. "empty") spaces in a , and is a of voids over the total volume, between 0 and 1, or as a between 0% and 100%. Strictly speaking, some tests measure the "accessible void", the total amount of vo ...
enough to store large quantities, making them valuable
aquifer An aquifer is an underground layer of -bearing , rock fractures or unconsolidated materials (, , or ). can be extracted using a water . The study of water flow in aquifers and the characterization of aquifers is called . Related terms include a ...

aquifer
s and
petroleum reservoir A petroleum reservoir or oil and gas reservoir is a subsurface pool of hydrocarbons contained in Porosity, porous or fractured rock formations. Petroleum reservoirs are broadly classified as ''conventional'' and ''Unconventional oil, unconventiona ...
s. Quartz-bearing sandstone can be changed into
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
through
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 ...
, usually related to tectonic compression within
orogenic belts An orogeny is an event that leads to both structural deformation and compositional differentiation of the Earth's lithosphere A lithosphere ( grc, wikt:λίθος#Ancient Greek, λίθος [] for "rocky", and [] for "sphere") is the rigid, ...
.


Origins

Sandstones are ''clastic rock, clastic'' in origin (as opposed to either ''organic'', like
chalk Chalk is a soft, white, porous Porosity or void fraction is a measure of the (i.e. "empty") spaces in a , and is a of voids over the total volume, between 0 and 1, or as a between 0% and 100%. Strictly speaking, some tests measure the "acce ...

chalk
and
coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...

coal
, or ''chemical'', like
gypsum Gypsum is a soft sulfate mineralThe sulfate minerals are a class of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the ...

gypsum
and
jasper Jasper, an aggregate of microgranular 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 Tetrahedral molecular geometry, tetrahedra, with ...

jasper
)."A Basic Sedimentary Rock Classification", L.S. Fichter, Department of Geology/Environmental Science,
James Madison University James Madison University (also known as JMU, Madison, or James Madison) is a public In public relations and communication science, publics are groups of individual people, and the public (a.k.a. the general public) is the totality of suc ...
(JMU), Harrisonburg, Virginia, October 2000
JMU-sed-classif
(accessed: March 2009): separates clastic, chemical & biochemical (organic).
The silicate sand grains from which they form are the product of physical and chemical
weathering Weathering is the deterioration of rocks In 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 ...
of bedrock. Weathering and
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
are most rapid in areas of high relief, such as
volcanic arc A volcanic arc is a chain of es formed above a subducting plate, positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic . Generally, volcanic arcs result from the of an oceanic tectonic plate und ...
s, areas of
continental rifting 200px, Gulf of Suez Rift showing main extensional faults">extensional_fault.html" ;"title="Gulf of Suez Rift showing main extensional fault">Gulf of Suez Rift showing main extensional faults In geology, a rift is a linear zone where the lithos ...
, and
orogenic belt An orogeny is an event that leads to both structural Deformation (physics), deformation and compositional differentiation of the Earth's lithosphere (Crust (geology), crust and uppermost Mantle (geology), mantle) at Convergent boundary, converge ...
s. Eroded sand is transported by rivers or by the wind from its source areas to
depositional environment In geology, depositional environment or sedimentary environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be fo ...
s where
tectonics Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of orogeny, mountain building, the growth and behavior of the strong, old cores of contin ...
has created accommodation space for sediments to accumulate. Forearc basins tend to accumulate sand rich in lithic grains and
plagioclase Plagioclase is a series of tectosilicate 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 composition ...
. Intracontinental basins and
graben 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 ti ...

graben
s along continental margins are also common environments for deposition of sand.Blatt and Tracy 1996, pp. 220-227 As sediments continue to accumulate in the depositional environment, older sand is buried by younger sediments, and it undergoes
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 ...
. This mostly consists of
compaction Compaction may refer to: * Soil compaction In geotechnical engineering#REDIRECT geotechnical engineering {{Redirect category shell, 1= {{R from other capitalisation ..., soil compaction is the process in which stress applied to a soil causes ...
and
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 the sand.Blatt and Tracy 1996, pp. 265-280Boggs 2006, pp. 147-154 Early stages of diagenesis, described as ''eogenesis'', take place at shallow depths (a few tens of meters) and are characterized by
bioturbation Bioturbation is defined as the reworking of soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic m ...
and mineralogical changes in the sands, with only slight compaction. The red
hematite Hematite (), also spelled as haematite, is a common iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member o ...

hematite
that gives
red bed Red is the color at the long wavelength end of the visible spectrum of light, next to Orange (colour), orange and opposite Violet (color), violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the ...
sandstones their color is likely formed during eogenesis.Boggs 2006, p. 148 Deeper burial is accompanied by ''mesogenesis'', during which most of the compaction and lithification takes place.Boggs 2006, pp. 147-154 Compaction takes place as the sand comes under increasing pressure from overlying sediments. Sediment grains move into more compact arrangements, ductile grains (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
grains) are deformed, and pore space is reduced. In addition to this physical compaction, chemical compaction may take place via
pressure solution 350px, Schematic diagram of pressure solution accommodating compression/compaction in a clastic rock. Left box shows the situation before compaction. Red arrows indicate areas of maximum stress (= grain contacts). Blue arrows indicate the flow of d ...
. Points of contact between grains are under the greatest strain, and the strained mineral is more soluble than the rest of the grain. As a result, the contact points are dissolved away, allowing the grains to come into closer contact. Lithification follows closely on compaction, as increased temperatures at depth hasten deposition of cement that binds the grains together. Pressure solution contributes to cementing, as the mineral dissolved from strained contact points is redeposited in the unstrained pore spaces. Mechanical compaction takes place primarily at depths less than . Chemical compaction continues to depths of , and most cementation takes place at depths of . Unroofing of buried sandstone is accompanied by ''telogenesis'', the third and final stage of diagenesis. As erosion reduces the depth of burial, renewed exposure to
meteoric waterMeteoric water is the water derived from Precipitation (meteorology), precipitation (snow and rain). This includes water from lakes, rivers, and icemelts, which all originate from precipitation indirectly. While the bulk of rainwater or meltwater fro ...
produces additional changes to the sandstone, such as dissolution of some of the cement to produce secondary porosity. File:MoabAlcove.JPG, Alcove in the
Navajo Sandstone The Navajo Sandstone is a geological formation in the Glen Canyon Group that is spread across the U.S. states of southern Nevada Nevada (, ) is a U.S. state, state in the Western United States, Western region of the United States. It is bor ...
File:PetraSandStoneRock-cut tombs.jpg, Kokh-type tombs cut into the multicoloured sandstone of
Petra The Positron-Electron Tandem Ring Accelerator (PETRA) is one of the particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel electric charge, charged particles to very high speeds and energies, and to ...

Petra
File:CoralPinkSandDunesSand.JPG, Sand grains of
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, ...

quartz
with
hematite Hematite (), also spelled as haematite, is a common iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member o ...

hematite
coating providing an orange colour


Components


Framework grains

Framework grains are sand-sized ( diameter) detrital fragments that make up the bulk of a sandstone. Most framework grains are composed of
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, ...

quartz
or
feldspar Feldspars are a group of rock-forming aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity ...
, which are the common minerals most resistant minerals to
weathering Weathering is the deterioration of rocks In 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 ...
processes at the Earth's surface, as seen in the
Goldich dissolution series The Goldich dissolution series is a way of predicting the relative stability or weathering Weathering is the breaking down of rocks, soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago ...
. Framework grains can be classified into several different categories based on their mineral composition: * Quartz framework grains are the dominant minerals in most
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 '' lava) exposed at or very near the surface o ...
s; this is because they have exceptional physical properties, such as hardness and chemical stability. These physical properties allow the quartz grains to survive multiple recycling events, while also allowing the grains to display some degree of rounding. Quartz grains evolve from plutonic rock, which are felsic in origin and also from older sandstones that have been recycled. * Feldspathic framework grains are commonly the second most abundant mineral in sandstones. Feldspar can be divided into alkali feldspars and plagioclase feldspars, which can be distinguished under a petrographic microscope. ::*
Alkali feldspar Feldspars () are a group of rock-forming tectosilicate 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. ...
range in chemical composition from KAlSi3O8 to NaAlSi3O8. ::*
Plagioclase feldspar . (unknown scale) Plagioclase is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagiocla ...
range in composition from NaAlSi3O8 to CaAl2Si2O8. * Lithic framework grains (also called lithic fragments or lithic clasts) are pieces of ancient source rock that have yet to weather away to individual mineral grains. Lithic fragments can be any fine-grained or coarse-grained igneous, metamorphic, or sedimentary rock, although the most common lithic fragments found in sedimentary rocks are clasts of volcanic rocks. * Accessory minerals are all other mineral grains in a sandstone. These minerals usually make up just a small percentage of the grains in a sandstone. Common accessory minerals include micas (
muscovite Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'' ...

muscovite
and
biotite Biotite is a common group of phyllosilicate Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science conce ...

biotite
),
olivine The 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. R ...

olivine
,
pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming Silicate minerals#Inosilicates, inosilicate minerals found in many Igneous rock, igneous and metamorphic rock, metamorphic rock (geology), rocks. Pyroxenes have t ...
, and
corundum Corundum is a crystal A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance th ...

corundum
.Prothero, D. (2004). Sedimentary Geology. New York, NN: W.H. Freeman and Company Many of these accessory grains are more dense than the silicates that make up the bulk of the rock. These '' heavy minerals'' are commonly resistant to weathering and can be used as an indicator of sandstone maturity through the
ZTR index The ZTR index is a method of determining how weathered ''Weathered'' is the third studio album by American Rock music, rock band Creed (band), Creed, released on November 20, 2001. It was the last Creed album to be released until ''Full Circle (Cr ...
. Common heavy minerals include
zircon Zircon ( or ) is a belonging to the group of s and is a source of the metal . Its chemical name is , and its corresponding chemical formula is . A common showing some of the range of substitution in zircon is (Zr1–y, y)(SiO4)1–x(OH)4x ...

zircon
,
tourmaline Tourmaline ( ) is a crystalline boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone can be found in a wide variety of colors. Etymology The term is derived from th ...

tourmaline
,
rutile Rutile is an oxide mineral The oxide mineral class includes those mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the so ...

rutile
(hence ''ZTR''),
garnet Garnets () are a group of silicate mineral Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science c ...

garnet
,
magnetite Magnetite 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 for ...

magnetite
, or other dense, resistant minerals derived from the source rock.


Matrix

Matrix Matrix or MATRIX may refer to: Science and mathematics * Matrix (mathematics), a rectangular array of numbers, symbols, or expressions * Matrix (logic), part of a formula in prenex normal form * Matrix (biology), the material in between a eukaryoti ...
is very fine material, which is present within interstitial pore space between the framework grains. The nature of the matrix within the interstitial pore space results in a twofold classification: * Arenites are texturally ''clean'' sandstones that are free of or have very little matrix. * Wackes are texturally ''dirty'' sandstones that have a significant amount of matrix.


Cement

Cement is what binds the siliciclastic framework grains together. Cement is a secondary mineral that forms after deposition and during burial of the sandstone. These cementing materials may be either silicate minerals or non-silicate minerals, such as calcite. * Silica cement can consist of either quartz or
opal Opal is a hydrate In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, comp ...

opal
minerals. Quartz is the most common silicate mineral that acts as cement. In sandstone where there is silica cement present, the quartz grains are attached to cement, which creates a rim around the quartz grain called overgrowth. The overgrowth retains the same crystallographic continuity of quartz framework grain that is being cemented. Opal cement is found in sandstones that are rich in volcanogenic materials, and very rarely is in other sandstones. * Calcite cement is the most common carbonate cement. Calcite cement is an assortment of smaller calcite crystals. The cement adheres to the framework grains, cementing the framework grains together. * Other minerals that act as cements include:
hematite Hematite (), also spelled as haematite, is a common iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member o ...

hematite
,
limonite Limonite () is an iron ore Iron ores are rocks A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the w ...

limonite
,
feldspar Feldspars are a group of rock-forming aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity ...
s,
anhydrite Anhydrite, or anhydrous calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hyd ...

anhydrite
,
gypsum Gypsum is a soft sulfate mineralThe sulfate minerals are a class of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the ...

gypsum
,
barite Baryte, barite or barytes (, ) is a consisting of (4). Baryte is generally white or less, and is the main source of the element . The ''baryte group'' consists of baryte, (strontium sulfate), (lead sulfate), and (calcium sulfate). Baryte and c ...

barite
,
clay minerals Clay minerals are hydrous aluminium Aluminium (aluminum in American English, American and Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than thos ...
, and
zeolite Zeolites are microporous, aluminosilicate Aluminosilicate mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Eart ...

zeolite
minerals. Sandstone that becomes depleted of its cement binder through weathering gradually becomes friable and unstable. This process can be somewhat reversed by the application of tetraethyl orthosilicate (Si(OC2H5)4) which will deposit amorphous silicon dioxide between the sand grains. The reaction is as follows. :Si(OC2H5)4 (l) + 2 H2O (l) → SiO2 (s) + 4 C2H5OH (g)


Pore space

Pore space includes the open spaces within a rock or a soil.Jackson, J. (1997). Glossary of Geology. Alexandria, VA: American Geological Institute The pore space in a rock has a direct relationship to the
porosity Porosity or void fraction is a measure of the void Void may refer to: Science, engineering, and technology * Void (astronomy) Cosmic voids are vast spaces between filaments (the largest-scale structures in the universe The universe ( ...
and permeability of the rock. The porosity and permeability are directly influenced by the way the sand grains are packed together. * Porosity is the percentage of bulk volume that is inhabited by interstices within a given rock. Porosity is directly influenced by the packing of even-sized spherical grains, rearranged from loosely packed to tightest packed in sandstones. * Permeability is the rate in which water or other fluids flow through the rock. For
groundwater Groundwater is the 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 form ...

groundwater
, work permeability may be measured in gallons per day through a one square foot cross section under a unit
hydraulic gradient Fluid flows from the tank at the top to the basin at the bottom under the pressure of the hydraulic head. Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum A vertical datum, altimetric dat ...
.


Types of sandstone

Sandstones are typically classified by point-counting a
thin section vein in mica Micas ( ) are a group of minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect Cleavage (crystal) ...
using a method like the Gazzi-Dickinson Method. This yields the relative percentages of quartz, feldspar, and lithic grains and the amount of clay matrix. The composition of a sandstone can provide important information on the genesis of the sediments when used with a triangular ''Q''uartz, ''F''eldspar, ''L''ithic fragment ( QFL diagrams). However, geologist have not been able to agree on a set of boundaries separating regions of the QFL triangle. Visual aids are diagrams that allow geologists to interpret different characteristics of a sandstone. For example, a QFL chart can be marked with a
provenance Provenance (from the French ''provenir'', 'to come from/forth') is the chronology of the ownership, custody or location of a historical object. The term was originally mostly used in relation to works of art but is now used in similar senses i ...
model that shows the likely tectonic origin of sandstones with various compositions of framework grains. Likewise, the stage of textural maturity chart illustrates the different stages that a sandstone goes through as the degree of kinetic processing of the sediments increases. * A QFL chart is a representation of the framework grains and matrix that is present in a sandstone. This chart is similar to those used in igneous petrology. When plotted correctly, this model of analysis creates for a meaningful quantitative classification of sandstones.Carozzi, A. (1993). Sedimentary petrography. Englewood Cliffs, NJ: Prentice-Hall * A sandstone provenance chart is typically based on a QFL chart but allows geologists to visually interpret the different types of places from which sandstones can originate. * A stage of textural maturity chart shows the differences between immature, submature, mature, and supermature sandstones. As the sandstone becomes more mature, grains become more rounded, and there is less clay in the matrix of the rock.


Dott's classification scheme

Dott's (1964) sandstone classification scheme is one of many such schemes used by geologists for classifying sandstones. Dott's scheme is a modification of Gilbert's classification of silicate sandstones, and it incorporates R.L. Folk's dual textural and compositional maturity concepts into one classification system. The philosophy behind combining Gilbert's and R. L. Folk's schemes is that it is better able to "portray the continuous nature of textural variation from mudstone to arenite and from stable to unstable grain composition". Dott's classification scheme is based on the mineralogy of framework grains, and on the type of matrix present in between the framework grains. In this specific classification scheme, Dott has set the boundary between arenite and wackes at 15% matrix. In addition, Dott also breaks up the different types of framework grains that can be present in a sandstone into three major categories: quartz, feldspar, and lithic grains. * Arenites are types of sandstone that have less than 15% clay matrix in between the framework grains. ** Quartz arenites are sandstones that contain more than 90% of siliceous grains. Grains can include
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, ...

quartz
or
chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a preci ...

chert
rock fragments. Quartz arenites are texturally mature to supermature sandstones. These pure quartz sands result from extensive
weathering Weathering is the deterioration of rocks In 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 ...
that occurred before and during transport. This weathering removed everything but quartz grains, the most stable
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
. They are commonly affiliated with rocks that are deposited in a stable cratonic environment, such as aeolian
beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from Rock (geology), rock, such as sand, gravel, shingle beach, shingle, pebbles, etc., or biological so ...

beach
es or shelf environments. Quartz arenites emanate from multiple recycling of quartz grains, generally as sedimentary source rocks and less regularly as first-cycle deposits derived from primary
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 ...
or
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. ** Feldspathic arenites are sandstones that contain less than 90% quartz, and more feldspar than unstable lithic fragments, and minor accessory minerals. Feldspathic sandstones are commonly immature or sub-mature. These sandstones occur in association with cratonic or stable shelf settings. Feldspathic sandstones are derived from granitic-type, primary crystalline, rocks. If the sandstone is dominantly plagioclase, then it is igneous in origin. ** Lithic arenites are characterised by generally high content of unstable lithic fragments. Examples include volcanic and metamorphic clasts, though stable clasts such as chert are common in lithic arenites. This type of rock contains less than 90% quartz grains and more unstable rock fragments than feldspars. They are commonly immature to submature texturally. They are associated with fluvial conglomerates and other fluvial deposits, or in deeper water marine conglomerates. They are formed under conditions that produce large volumes of unstable material, derived from fine-grained rocks, mostly
shale Shale is a fine-grained, clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defi ...

shale
s,
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. Like all rock types, the concept of volcanic rock is artificial, and in nature vo ...

volcanic 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
. * Wackes are sandstones that contain more than 15% clay matrix between framework grains. ** Quartz wackes are uncommon because quartz arenites are texturally mature to supermature. ** Felspathic wackes are feldspathic sandstone that contain a matrix that is greater than 15%. ** Lithic wacke is a sandstone in which the matrix greater than 15%. *
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
sandstones are more than 25 percent
feldspar Feldspars are a group of rock-forming aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity ...
. The grains tend to be poorly rounded and less well sorted than those of pure quartz sandstones. These feldspar-rich sandstones come from rapidly eroding
granitic A granitoid is a generic term for a diverse category of phanerite, coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich lsyenites and ...
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
terrain Relief map of Sierra Nevada, Spain Terrain or relief (also topographical Topography is the study of the forms and features of land surfaces. The topography of an area could refer to the surface forms and features themselves, or a desc ...

terrain
s where
chemical weathering Weathering is the breaking down of rocks, soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive maps of ...
is
subordinate A hierarchy (from the Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) in which the items are represented as being "above", "below", or "at the same level as" one another. Hierarch ...
to
physical weathering Weathering is the breaking down of rocks A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the way in wh ...
. *
Greywacke Photomicrograph of a lithic wacke (sandstone). Top image is in plane polarized light (PPL); bottom image is in cross polarized light (XPL). Blue epoxy fills pore spaces. Greywacke or graywacke ( German ''grauwacke'', signifying a grey, earthy r ...

Greywacke
sandstones are a
heterogeneous Homogeneity and heterogeneity are concepts often used in the sciences Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally ...
mixture of lithic fragments and angular grains of quartz and feldspar or grains surrounded by a fine-grained
clay Clay is a type of fine-grained natural soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic m ...
matrix Matrix or MATRIX may refer to: Science and mathematics * Matrix (mathematics), a rectangular array of numbers, symbols, or expressions * Matrix (logic), part of a formula in prenex normal form * Matrix (biology), the material in between a eukaryoti ...
. Much of this matrix is formed by relatively soft fragments, such as
shale Shale is a fine-grained, clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defi ...

shale
and some volcanic rocks, that are chemically altered and physically compacted after deep burial of the sandstone formation.


Quartzite

When sandstone is subjected to the great heat and pressure associated with
regional metamorphism Image:Metamorphic reaction EN.svg, upright=1.35, Schematic representation of a metamorphic reaction. Abbreviations of minerals: act = actinolite; chl = Chlorite group, chlorite; ep = epidote; gt = garnet; hbl = hornblende; plag = plagioclase. Two m ...
, the individual quartz grains recrystallize along with the former cementing material. Most or all of the original texture and sedimentary structures of the sandstone are erased by the metamorphism. The grains are so tightly interlocked that when the rock is broken, it fractures through the grains to form an irregular or conchoidal fracture. Geologists had recognized by 1941 that some rocks show the macroscopic characteristics of quartzite, even though they have not undergone metamorphism at high pressure and temperature. These rocks have been subject only to the much lower temperatures and pressures associated with
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 ...
of sedimentary rock, but diagenesis has cemented the rock so thoroughly that microscopic examination is necessary to distinguish it from metamorphic quartize. The term ''orthoquartzite'' is used to distinguish such sedimentary rock from ''metaquartzite'' produced by metamorphism. By extension, the term ''orthoquartzite'' has occasionally been more generally applied to any quartz-cemented
quartz arenite Quartz arenite makes up the Prospect Mountain Quartzite on top of Doso Doyabi, Nevada ">Nevada.html" ;"title="Doso Doyabi, Nevada">Doso Doyabi, Nevada A quartz arenite or quartzarenite is a sandstone composed of greater than 90% detrital quartz, ...
. Orthoquartzite (in the narrow sense) is often 99% SiO2 with only very minor amounts of iron oxide and trace resistant minerals such as
zircon Zircon ( or ) is a belonging to the group of s and is a source of the metal . Its chemical name is , and its corresponding chemical formula is . A common showing some of the range of substitution in zircon is (Zr1–y, y)(SiO4)1–x(OH)4x ...

zircon
,
rutile Rutile is an oxide mineral The oxide mineral class includes those mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the so ...

rutile
and
magnetite Magnetite 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 for ...

magnetite
. Although few
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 are normally present, the original texture and
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
structures are preserved. The typical distinction between a true orthoquartzite and an ordinary quartz sandstone is that an orthoquartzite is so highly cemented that it will fracture across grains, not around them. This is a distinction that can be recognized in the
field Field may refer to: Expanses of open ground * Field (agriculture), an area of land used for agricultural purposes * Airfield, an aerodrome that lacks the infrastructure of an airport * Battlefield * Lawn, an area of mowed grass * Meadow, a grassl ...

field
. In turn, the distinction between an orthoquartzite and a metaquartzite is the onset of recrystallization of existing grains. The dividing line may be placed at the point where strained quartz grains begin to be replaced by new, unstrained, small quartz grains, producing a ''mortar texture'' that can be identified in thin sections under a polarizing microscope. With increasing grade of metamorphism, further recrystallization produces ''foam texture'', characterized by polygonal grains meeting at triple junctions, and then ''porphyroblastic texture'', characterized by coarse, irregular grains, including some larger grains ( porphyroblasts.)


Uses

Sandstone has been used since prehistoric times for construction, decorative art works and tools. It has been widely employed around the world in constructing temples, churches, homes and other buildings, and in civil engineering. Although its resistance to
weathering Weathering is the deterioration of rocks In 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 ...
varies, sandstone is easy to work. That makes it a common building material, building and pavement (material), paving material, including in asphalt concrete. However, some types that have been used in the past, such as the Collyhurst sandstone used in North West England, have had poor long-term weather resistance, necessitating repair and replacement in older buildings. Because of the hardness of individual grains, uniformity of grain size and friability of their structure, some types of sandstone are excellent materials from which to make grindstone (tool), grindstones, for sharpening blades and other implements. Non-friable sandstone can be used to make grindstones for grinding grain, e.g., gritstone. A type of pure quartz sandstone, orthoquartzite, with more of 90–95 percent of quartz, has been proposed for nomination to the Global Heritage Stone Resource. In some regions of Argentina, the orthoquartzite-stoned facade is one of the main features of the Mar del Plata style bungalows.


See also

* * * * * *


Notes


Bibliography

* Folk, R.L., 1965
''Petrology of sedimentary rocks'' PDF version
Austin: Hemphill's Bookstore. 2nd ed. 1981, . * Francis J. Pettijohn, Pettijohn F. J., P.E. Potter and R. Siever, 1987, ''Sand and sandstone'', 2nd ed. Springer-Verlag. . * Scholle, P.A., 1978, ''A Color illustrated guide to constituents, textures, cements, and porosities of sandstones and associated rocks'', American Association of Petroleum Geologists Memoir no. 28. . * Scholle, P.A., and D. Spearing, 1982, ''Sandstone depositional environments: clastic terrigenous sediments '', American Association of Petroleum Geologists Memoir no. 31. .
USGS Minerals Yearbook: Stone, Dimension
Thomas P. Dolley, U.S. Dept. of the Interior, 2005 (format: PDF).


Further reading

* Webb, Jonathan.
Sandstone shapes 'forged by gravity'
' (July 2014), BBC {{Authority control Sandstone, Industrial minerals Building stone