Editing Sandstone (section)

===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.