View source for Sandstone

{{Infobox Rock
|name=Sandstone
|type=Sedimentary
|image=USDA Mineral Sandstone 93c3955.jpg
|image_caption=Prepared sample of sandstone
|composition=Typically [[quartz]] and/or [[feldspar]] (on earth); [[Lithic_Fragment_(geology)|lithic]] fragments are also common. Other minerals may be found in particularly immature sandstone.
}}
[[Image:MoabAlcove.JPG|thumb|[[Alcove]] in the [[Navajo Sandstone]]]]
{{About|the geological rock type|}}

'''Sandstone''' (sometimes known as [[arenite]]) is a [[sedimentary rock]] composed mainly of [[sand]]-sized [[mineral]]s or rock [[Particle size (grain size)|grains]].  Most sandstone is composed of [[quartz]] and/or [[feldspar]] because these are the most common minerals in the Earth's [[crust (geology)|crust]]. Like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, gray and white. Since sandstone beds often form highly visible cliffs and other [[topography|topographic]] features, certain colors of sandstone have been strongly identified with certain regions.  

Some sandstones are resistant to [[weathering]], yet are easy to work. This makes sandstone a common [[building material|building]] and [[pavement (material)|paving]] material. However, some that have been used in the past, such as the [[Collyhurst sandstone]] used in [[North West England]], have been found less resistant, necessitating repair and replacement in older buildings.<ref>[http://www.sci-eng.mmu.ac.uk/manchester_stone/images.asp?page1=2&vartype=building&id=&offset=0# Edensor, T. & Drew, I.  ''Building stone in the City of Manchester: St Ann's Church'']</ref> Because of the hardness of the individual grains, uniformity of grain size and [[friability]] of their structure, some types of sandstone are excellent materials from which to make [[grindstone (tool)|grindstone]]s, for sharpening blades and other implements. Non-friable sandstone can be used to make grindstones for grinding grain, e.g., [[gritstone]].

Rock formations that are primarily composed of sandstone usually allow [[percolation]] of water and other fluids and are [[porosity|porous]] enough to store large quantities, making them valuable [[aquifer]]s and [[petroleum reservoir]]s. Fine-grained aquifers, such as sandstones, are more apt to filter out pollutants from the surface than are rocks with cracks and crevices, such as [[limestone]] or other rocks fractured by [[earthquake|seismic activity]].

== Origins ==
[[File:CoralPinkSandDunesSand.JPG|thumb|left|Sand from [[Coral Pink Sand Dunes State Park]], [[Utah]]. These are grains of [[quartz]] with a [[hematite]] coating providing the orange color. Scale bar is 1.0 mm.]]
[[File:Millet-Seed Sandstone Macro.JPG|thumb|right|Millet-Seed sandstone macro (size: ~4 cm or ~1.6 in).]]

Sandstones are ''[[clastic rock|clastic]]'' in origin (as opposed to either ''organic'', like [[chalk]] and [[coal]], or ''chemical'', like [[gypsum]] and [[jasper]]).<ref name="LF">
  "A Basic Sedimentary Rock Classification", L.S. Fichter,
  Department of Geology/Environmental Science,
  [[James Madison University]] (JMU), Harrisonburg, Virginia,
  October 2000, webpage:
  [http://csmres.jmu.edu/geollab/fichter/SedRx/<!--
  -->sedclass.html JMU-sed-classif] (accessed: March 2009):
  separates clastic, chemical & biochemical (organic).
</ref>
They are formed from [[Cementation (geology)|cemented]] grains that may either be fragments of a pre-existing rock or be mono-minerallic [[crystal]]s. The cements binding these grains together are typically [[calcite]], [[clay]]s and [[silica]]. [[particle size (grain size)|Grain size]]s in sands are defined (in geology) within the range of 0.0625 mm to 2 mm (0.002-0.079 inches). Clays and sediments with smaller grain sizes not visible with the naked eye, including [[siltstone]]s and [[shale]]s, are typically called ''[[argillaceous minerals|argillaceous]]'' sediments; rocks with larger grain sizes, including [[breccia]]s and [[conglomerate (geology)|conglomerate]]s are termed ''rudaceous'' sediments.
[[File:Lower antelope 2 md.jpg|thumb|right|Red sandstone interior of [[Antelope Canyon|Lower Antelope Canyon]], [[Arizona]], worn smooth by erosion from [[flash flood]]ing over millions of years.]]

The formation of sandstone involves two principal stages. First, a layer or layers of sand accumulates as the result of [[sedimentation]], either from water (as in a river, lake, or sea) or from air (as in a desert). Typically, sedimentation occurs by the sand settling out from suspension; i.e., ceasing to be rolled or bounced along the bottom of a body of water (e.g., seas or rivers) or ground surface (e.g., in a desert or [[erg]]). Finally, once it has accumulated, the sand becomes sandstone when it is [[Compaction (geology)|compacted]] by pressure of overlying deposits and cemented by the precipitation of minerals within the pore spaces between sand grains.

The most common cementing materials are silica and [[calcium carbonate]], which are often derived either from dissolution or from alteration of the sand after it was buried. Colors will usually be tan or yellow (from a blend of the clear quartz with the dark amber feldspar content of the sand). A predominant additional colorant in the southwestern United States is [[iron oxide]], which imparts reddish tints ranging from pink to dark red ([[terracotta]]), with additional [[manganese]] imparting a purplish [[hue]]. Red sandstones are also seen in the Southwest and West of [[England]] and [[Wales]], as well as central [[Europe]] and [[Mongolia]]. The regularity of the latter favors use as a source for [[masonry]], either as a primary building material or as a facing stone, over other construction.

The environment where it is deposited is crucial in determining the characteristics of the resulting sandstone, which, in finer detail, include its ''grain size'', ''sorting'' and ''composition'' and, in more general detail, include the rock geometry and sedimentary structures. Principal [[Sedimentary depositional environment|environments of deposition]] may be split between terrestrial and marine, as illustrated by the following broad groupings:

* Terrestrial environments
[[File:Stadtroda Sandstein.jpg|thumb|right|Sandstone near [[Stadtroda]], [[Germany]].]]
# [[River]]s ([[levee]]s, point bars, channel sands)
# [[Alluvial fan]]s
# [[Glacial outwash]]
# [[Lake]]s 
# [[Deserts]] ([[sand dune]]s and [[Erg (landform)|erg]]s)

* Marine environments
# [[River delta|Deltas]]
# [[Beach]] and shoreface sands
# [[Tidal flat]]s
# Offshore bars and sand waves
# Storm deposits (tempestites)
# [[Turbidite]]s (submarine channels and fans)

== Types ==
[[File:Sandstone(quartz)USGOV.jpg|thumb|Sandstone composed mainly of quartz grains]]
[[File:LvMS-Lvm.jpg|thumb|Photomicrograph of a [[volcanic]] [[sand grain]]; upper picture is plane-polarized light, bottom picture is cross-polarized light, scale box at left-center is 0.25 [[millimeter]]. This type of grain would be a main component of a lithic sandstone.]]
Sandstones fall into several major groups based on their [[mineralogy]] and texture.  Below is a partial list of common sandstone types.
* [[quartz arenites]] are made up almost entirely of [[quartz]] grains, usually well sorted and rounded. These pure quartz sands result from extensive [[weathering]] that occurred before and during transport and removed everything but quartz, the most stable [[mineral]].  They are common in [[beach]] environments.
* [[arkose]]s are more than 25 percent [[feldspar]].<ref name=LF/> 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]] and [[Metamorphic rock|metamorphic]] [[terrain]]s where [[chemical weathering]] is [[subordinate]] to [[physical weathering]].
* [[lithic sandstones]] contain many [[Lithic_Fragment_(geology)|lithic fragments]] derived from fine-grained rocks, mostly [[shales]], [[volcanic]] rocks, and fine-grained [[metamorphic rock]]s.
* [[graywacke]] is a [[heterogeneous]] mixture of [[Lithic_Fragment_(geology)|lithic fragments]] and angular grains of quartz and feldspar, and/or grains surrounded by a fine-grained [[clay]] [[Matrix (geology)|matrix]]. Much of this matrix is formed by relatively soft fragments, such as [[shale]] and some volcanic rocks, that are chemically altered and physically compacted after deep burial of the sandstone formation.
*[[Eolianite]] is a term used for a rock which is composed of sand grains that show signs of significant transportation by wind.  These have usually been deposited in [[Deserts|desert]] environments.  They are commonly extremely well sorted and rich in quartz.
*[[Oolite]] is more a limestone than a sandstone, but is made of sand-sized carbonate ooids, and is common in saline beaches with gentle wave action.

Sandstone [[composition]] is (generally) based on the make up of the framework, or sand-sized grains in the sandstone.  This is typically done by [[point-counting]] a [[thin section]] of the sandstone using a method like the [[Gazzi-Dickinson Method]].  The composition of a sandstone can have important information regarding the genesis of the sediment when used with [[QFL diagrams]].

== See also ==
{| width=580px
|
* [[Bargate stone]]
* [[Beaver river sandstone]]
* [[Brownstone]]
* [[Dimension stone]]
* [[Geology]]
|<!--next column-->
* [[Hummelstown brownstone]]
* [[List of minerals]]
* [[List of stone]]
* [[Old Red Sandstone]]
* [[New Red Sandstone]]
|<!--next column-->
* [[Sarsen]]
* [[Sedimentary basin]]s
* [[Yorkstone]]
* [[Dells of the Wisconsin River|Wisconsin Dells]]
* [[Uluru]]
|}
{{commonscat}}<br clear=all>

== Notes ==
{{Reflist}}

== References ==
{{refbegin}}
* Boggs, J.R., 2000, ''Principles of sedimentology and stratigraphy'', 3rd ed. Toronto: Merril Publishing Company. ISBN 0-13-099696-3.
* Folk, R.L., 1965, [http://www.lib.utexas.edu/geo/folkready/folkprefrev.html ''Petrology of sedimentary rocks'' PDF version]. Austin: Hemphill’s Bookstore. 2nd ed. 1981, ISBN 0-914696-14-9.
* Pettijohn, F.J., P.E. Potter and R. Siever, 1987, ''Sand and sandstone'', 2nd ed. Springer-Verlag. ISBN 0-387-96350-2.
* 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. ISBN 0-89181-304-7.
* Scholle, P.A., and D. Spearing, 1982, ''Sandstone depositional environments: clastic terrigenous sediments '', American Association of Petroleum Geologists Memoir no. 31. ISBN 0-89181-307-1.
* [http://minerals.usgs.gov/minerals/pubs/commodity/<!--
  -->stone_dimension/dstonmyb05.pdf USGS Minerals Yearbook: Stone, Dimension], Thomas P. Dolley, U.S. Dept. of the Interior, 2005 (format: PDF).
{{refend}}

[[Category:Sedimentary rocks]]
[[Category:Stone]]
[[Category:Building materials]]
[[Category:Sandstone|*]]

[[ar:حجر رملي]]
[[bg:Пясъчник]]
[[ca:Gres (geologia)]]
[[cs:Pískovec]]
[[cy:Tywodfaen]]
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[[et:Liivakivi]]
[[es:Arenisca]]
[[eo:Grejso]]
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[[gl:Arenita]]
[[ko:사암]]
[[hr:Pješčenjak]]
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[[id:Batu pasir]]
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[[it:Arenaria (roccia)]]
[[he:אבן חול]]
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[[oc:Gres]]
[[pl:Piaskowiec]]
[[pt:Arenito]]
[[ro:Gresie]]
[[ru:Песчаник]]
[[simple:Sandstone]]
[[sk:Pieskovec]]
[[sl:Peščenjak]]
[[sr:Пешчар]]
[[sh:Peščar]]
[[fi:Hiekkakivi]]
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