Sandstone

Sandstone
Sedimentary rock
USDA Mineral Sandstone 93c3955.jpg
Cut slab of sandstone showing Liesegang banding
Composition
Typically quartz and feldspar; lithic fragments are also common. Other minerals may be found in particularly mature sandstone.
Devonian Sandstone at Suur Taevaskoda, Põlva County, Estonia
Kokh-type tombs cut into the multicoloured sandstone of Petra, Jordan

Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) mineral particles or rock fragments.

Most sandstone is composed of quartz or feldspar (both silicates) because they are the most resistant minerals to weathering processes at the Earth's surface, as seen in Bowen's reaction series. Like uncemented 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 features, certain colors of sandstone have been strongly identified with certain regions.

Rock formations that are primarily composed of sandstone usually allow the percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Fine-grained aquifers, such as sandstones, are better able to filter out pollutants from the surface than are rocks with cracks and crevices, such as limestone or other rocks fractured by seismic activity.

Quartz-bearing sandstone can be changed into quartzite through metamorphism, usually related to tectonic compression within orogenic belts.

Origins

Sand from Coral Pink Sand Dunes State Park, Utah. These are grains of quartz with a hematite coating providing the orange colour. Scale bar is 1.0 mm.

Sandstones are clastic in origin (as opposed to either organic, like chalk and coal, or chemical, like gypsum and jasper).[1] They are formed from cemented grains that may either be fragments of a pre-existing rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, clays, and silica. Grain sizes in sands are defined (in geology) within the range of 0.0625 mm to 2 mm (0.0025–0.08 inches). Clays and sediments with smaller grain sizes not visible with the naked eye, including siltstones and shales, are typically called argillaceous sediments; rocks with larger grain sizes, including breccias and conglomerates, are termed rudaceous sediments.

Red sandstone interior of Lower Antelope Canyon, Arizona, worn smooth by erosion from flash flooding over thousands 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 stream, 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 or ground surface (e.g., in a desert or erg). Finally, once it has accumulated, the sand becomes sandstone when it is compacted by the 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 colourant 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 Britain, as well as central Europe and Mongolia. The regularity of the latter favours use as a source for masonry, either as a primary building material or as a facing stone, over other forms of 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 environments of deposition may be split between terrestrial and marine, as illustrated by the following broad groupings:

  • Terrestrial environments
  1. Rivers (levees, point bars, channel sands)
  2. Alluvial fans
  3. Glacial outwash
  4. Lakes
  5. Deserts (sand dunes and ergs)
  • Marine environments
  1. Deltas
  2. Beach and shoreface sands
  3. Tidal flats
  4. Offshore bars and sand waves
  5. Storm deposits (tempestites)
  6. Turbidites (submarine channels and fans)
Other Languages
Afrikaans: Sandsteen
العربية: حجر رملي
aragonés: Piedra d'arena
asturianu: Gres
беларуская: Пясчанік
беларуская (тарашкевіца)‎: Пяшчанік
български: Пясъчник
Boarisch: Sandstoa
català: Gres
čeština: Pískovec
Cymraeg: Tywodfaen
dansk: Sandsten
Deutsch: Sandstein
eesti: Liivakivi
Ελληνικά: Ψαμμίτης
español: Arenisca
Esperanto: Grejso
euskara: Hareharri
فارسی: ماسه‌سنگ
Gàidhlig: Clach-ghainmhich
galego: Arenita
한국어: 사암
հայերեն: Ավազաքար
हिन्दी: बलुआ पत्थर
hrvatski: Pješčenjak
Ido: Greso
Bahasa Indonesia: Batupasir
íslenska: Sandsteinn
italiano: Arenaria
עברית: אבן חול
ქართული: ქვიშაქვა
Кыргызча: Кумдук
latviešu: Smilšakmens
Lëtzebuergesch: Sandsteen
lietuvių: Smiltainis
Limburgs: Zandjsjtein
magyar: Homokkő
Bahasa Melayu: Batu pasir
Nederlands: Zandsteen
日本語: 砂岩
norsk: Sandstein
norsk nynorsk: Sandstein
occitan: Gres
oʻzbekcha/ўзбекча: Qumtosh
پنجابی: ریتلا پتھر
polski: Piaskowiec
português: Arenito
русский: Песчаник
Scots: Saundstane
Simple English: Sandstone
slovenčina: Pieskovec
slovenščina: Peščenjak
српски / srpski: Пешчар
srpskohrvatski / српскохрватски: Peščar
suomi: Hiekkakivi
svenska: Sandsten
தமிழ்: மணற்கல்
ᏣᎳᎩ: ᏃᏯᏅᏯ
Türkçe: Kumtaşı
українська: Пісковик
Tiếng Việt: Cát kết
Võro: Liivakivi
中文: 砂岩