Editing Sandstone (section)

==Components==

===Framework grains===
[[File:(1)Saunders Quarry-1.jpg|thumb|upright=1.1|Paradise Quarry, [[Sydney]], Australia]]
[[File:GrusSand.JPG|thumb|left|[[grus (geology)|Grus]] sand and the granitoid from which it is derived]]
Framework grains are sand-sized ({{convert|0.0625|to|2|mm|in|adj=on|sp=us}} diameter) detrital fragments that make up the bulk of a sandstone.<ref name="Stow">{{cite book |author=Dorrik A. V. Stow|title=Sedimentary Rocks in the Field: A Colour Guide|url=https://books.google.com/books?id=CRfXEf0Q9q8C|access-date=11 May 2012|year=2005|publisher=Manson Publishing|isbn=978-1-874545-69-9}}{{Dead link |date=May 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="Pettijohn">{{cite book |author1=Francis John Pettijohn |author2=Paul Edwin Potter |author3=Raymond Siever |title=Sand and Sandstone |url=https://books.google.com/books?id=QnpYqGksckwC|access-date=11 May 2012 |year=1987 |publisher=Springer |isbn=978-0-387-96350-1}}</ref> Most framework grains are composed of [[quartz]] or [[feldspar]], which are the common minerals most resistant to [[weathering]] processes at the Earth's surface, as seen in the [[Goldich dissolution series]].<ref>{{cite book |last=Prothero & Schwab |first=Donald R. & Fred |title=Sedimentary Geology |year=1996 |publisher=W. H. Freeman |isbn=0-7167-2726-9|pages=24}}</ref> 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]]s; this is because they have exceptional physical properties, such as [[hardness]] and chemical stability.<ref name="boggs-2006-119-135"/> These physical properties allow the quartz grains to survive multiple recycling events, while also allowing the grains to display some degree of rounding.<ref name="boggs-2006-119-135"/> 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.<ref name="boggs-2006-119-135"/> Feldspar can be divided into alkali feldspars and plagioclase feldspars, which can be distinguished under a petrographic microscope.<ref name="boggs-2006-119-135"/>

::*[[Alkali feldspar]] range in chemical composition from KAlSi<sub>3</sub>O<sub>8</sub> to NaAlSi<sub>3</sub>O<sub>8</sub>.<ref name="boggs-2006-119-135"/>

::*[[Plagioclase feldspar]] range in composition from NaAlSi<sub>3</sub>O<sub>8</sub> to CaAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub>.<ref name="boggs-2006-119-135"/>
[[File:LvMS-Lvm.jpg|thumb|Photomicrograph of a [[volcanic]] sand grain; upper picture is plane-polarised light, bottom picture is cross-polarised light, scale box at left-centre is 0.25 millimeter. This type of [[Sand grain|grain]] would be a main component of a lithic sandstone.]]
* 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.<ref name="boggs-2006-119-135"/> Lithic fragments can be any fine-grained or coarse-grained igneous, metamorphic, or sedimentary rock,<ref name="boggs-2006-119-135"/> although the most common lithic fragments found in sedimentary rocks are clasts of volcanic rocks.<ref name="boggs-2006-119-135"/>
* 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]] and [[biotite]]), [[olivine]], [[pyroxene]], and [[corundum]].<ref name="boggs-2006-119-135"/><ref name="Prothero">Prothero, D. (2004). Sedimentary Geology. New York, NN: W.H. Freeman and Company</ref> Many of these accessory grains are more dense than the silicates that make up the bulk of the rock. These ''[[heavy mineral]]s'' are commonly resistant to weathering and can be used as an indicator of sandstone maturity through the [[ZTR index]].<ref>Prothero, D. R. and Schwab, F., 1996, Sedimentary Geology, p. 460, {{ISBN|0-7167-2726-9}}</ref> Common heavy minerals include [[zircon]], [[tourmaline]], [[rutile]] (hence ''ZTR''), [[garnet]], [[magnetite]], or other dense, resistant minerals derived from the source rock.

===Matrix===
[[Matrix (geology)|Matrix]] is very fine material, which is present within interstitial pore space between the framework grains.<ref name="boggs-2006-119-135"/> 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.<ref name="Prothero"/>
* Wackes are texturally ''dirty'' sandstones that have a significant amount of matrix.<ref name="Pettijohn"/>

===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.<ref name="boggs-2006-119-135"/> These cementing materials may be either silicate minerals or non-silicate minerals, such as calcite.<ref name="boggs-2006-119-135"/>
* Silica cement can consist of either quartz or [[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 [[volcano]]genic materials, and very rarely is in other sandstones.<ref name="boggs-2006-119-135"/>
* 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.<ref name="boggs-2006-119-135"/>
* Other minerals that act as cements include: [[hematite]], [[limonite]], [[feldspar]]s, [[anhydrite]], [[gypsum]], [[barite]], [[clay minerals]], and [[zeolite]] minerals.<ref name="boggs-2006-119-135"/>

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(OC<sub>2</sub>H<sub>5</sub>)<sub>4</sub>) which will deposit amorphous silicon dioxide between the sand grains.<ref>{{cite journal |last1=Zárraga |first1=Ramón |last2=Alvarez-Gasca |first2=Dolores E. |last3=Cervantes |first3=Jorge |title=Solvent effect on TEOS film formation in the sandstone consolidation process |journal=Silicon Chemistry |date=1 September 2002 |volume=1 |issue=5 |pages=397–402 |doi=10.1023/B:SILC.0000025602.64965.e7|s2cid=93736643 }}</ref> The reaction is as follows.

:Si(OC<sub>2</sub>H<sub>5</sub>)<sub>4</sub> (l) + 2 H<sub>2</sub>O (l) → SiO<sub>2</sub> (s) +  4 C<sub>2</sub>H<sub>5</sub>OH (g)

===Pore space===
Pore space includes the open spaces within a rock or a soil.<ref name="Jackson">Jackson, J. (1997). Glossary of Geology. Alexandria, VA: American Geological Institute {{ISBN|3-540-27951-2}}</ref> The pore space in a rock has a direct relationship to the [[porosity]] and [[permeability (earth sciences)|permeability]] of the rock. The porosity and permeability are directly influenced by the way the sand grains are packed together.<ref name="boggs-2006-119-135"/>
* Porosity is the percentage of bulk volume that is inhabited by interstices within a given rock.<ref name="Jackson"/> Porosity is directly influenced by the packing of even-sized spherical grains, rearranged from loosely packed to tightest packed in sandstones.<ref name="boggs-2006-119-135"/>
* Permeability is the rate in which water or other fluids flow through the rock. For [[groundwater]], work permeability may be measured in gallons per day through a one square foot cross section under a unit [[hydraulic gradient]].<ref name="Jackson"/>