Editing Phosphorite (section)

{{Short description|Sedimentary rock containing large amounts of phosphate minerals}}
[[File:Peloidal phosphorite Phosphoria Formation Simplot Mine Idaho.jpg|thumb|Peloidal phosphorite, [[Phosphoria Formation]], Simplot Mine, Idaho. 4.6 cm wide.]]
[[File:Fossiliferous peloidal phosphorite, Yunnan Province China.jpg|thumb|Fossiliferous peloidal phosphorite, (4.7 cm across), [[Yunnan]], [[China]]. ]]
'''Phosphorite''', '''phosphate rock''' or '''rock phosphate''' is a non-[[detrital]] [[sedimentary rock]] that contains high amounts of [[phosphate minerals]]. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4%<ref name="fao">{{cite book |last1=Zapata |first1=F. |last2=Roy |first2=R.N. |date=2004 |title=Use of Phosphate Rocks for Sustainable Agriculture |url=http://www.fao.org/3/y5053e/y5053e00.htm#Contents |chapter=Chapter 1 - Introduction: Phosphorus in the soil-plant system |chapter-url=http://www.fao.org/3/y5053e/y5053e06.htm |location=Rome |publisher=[[Food and Agriculture Organization]] |isbn=92-5-105030-9}}</ref> to 20% [[phosphorus pentoxide]] (P<sub>2</sub>O<sub>5</sub>). Marketed phosphate rock is enriched ("beneficiated") to at least 28%, often more than 30% P<sub>2</sub>O<sub>5</sub>. This occurs through washing, screening, de-liming, magnetic separation or flotation.<ref name="fao" /> By comparison, the average phosphorus content of sedimentary rocks is less than 0.2%.<ref name=Blatt>Blatt, Harvey and Robert J. Tracy, ''Petrology'', Freeman, 1996, 2nd ed. pp. 345–349 {{ISBN|0-7167-2438-3}}</ref>  

The phosphate is present as [[fluorapatite]] Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>F typically in [[cryptocrystalline]] masses (grain sizes < 1 μm) referred to as [[collophane]]-sedimentary apatite deposits of uncertain origin.<ref name=Blatt/> It is also present as [[hydroxyapatite]] Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>OH or Ca<sub>10</sub>(PO<sub>4</sub>)<sub>6</sub>(OH)<sub>2</sub>, which is often dissolved from vertebrate bones and teeth, whereas fluorapatite can originate from [[hydrothermal vein]]s. Other sources also include chemically dissolved phosphate minerals from [[igneous]] and [[metamorphic rock]]s. Phosphorite deposits often occur in extensive layers, which cumulatively cover tens of thousands of square kilometres of the [[Crust (geology)|Earth's crust]].<ref>C.Michael Hogan. 2011. [http://www.eoearth.org/article/Phosphate?topic=49557 ''Phosphate''. Encyclopedia of Earth. Topic ed. Andy Jorgensen. Ed.-in-Chief C.J.Cleveland. National Council for Science and the Environment. Washington DC]</ref>

[[Limestone]]s and [[mudstone]]s are common phosphate-bearing rocks.<ref name="Prothero">{{cite book|author1=Prothero, Donald R.  |author2=Schwab, Fred |title=Sedimentary Geology|url=https://books.google.com/books?id=vlG-BGZhZrAC|access-date=15 December 2012|date=22 August 2003|publisher=Macmillan|isbn=978-0-7167-3905-0|pages=265–269}}</ref> Phosphate-rich sedimentary rocks can occur in dark brown to black beds, ranging from centimeter-sized laminae to beds that are several meters thick. Although these thick beds can exist, they are rarely only composed of phosphatic sedimentary rocks. Phosphatic sedimentary rocks are commonly accompanied by or interbedded with [[shale]]s, [[chert]]s, limestone, [[Dolomite (rock)|dolomite]]s and sometimes [[sandstone]].<ref name="Prothero"/> These layers contain the same textures and structures as fine-grained limestones and may represent [[diagenesis|diagenetic]] replacements of [[carbonate minerals]] by phosphates.<ref name=Blatt/> They also can be composed of peloids, ooids, fossils, and clasts that are made up of apatite. There are some phosphorites that are very small and have no distinctive granular textures. This means that their textures are similar to that of collophane, or fine [[micrite]]-like texture. Phosphatic grains may be accompanied by [[organic matter]], [[clay mineral]]s, [[silt]]-sized detrital grains, and [[pyrite]]. Peloidal or pelletal phosphorites occur normally; whereas [[Oolite|oolitic]] phosphorites are not common.<ref name="Prothero"/>

Phosphorites are known from [[Proterozoic]] [[banded iron formation]]s in [[Australia]], but are more common from [[Paleozoic]] and [[Cenozoic]] sediments. The [[Permian]] [[Phosphoria Formation]] of the western [[United States]] represents some 15 million years of sedimentation. It reaches a thickness of 420 metres and covers an area of 350,000&nbsp;km<sup>2</sup>.<ref name=Blatt/> Commercially mined phosphorites occur in [[France]], [[Belgium]], [[Spain]], [[Morocco]], [[Tunisia]], [[Saudi Arabia]]<ref name="Galmed_et_al_2020">{{cite journal | title=Petrology of Early Paleogene phosphorite deposits in Hazm Al-Jalamid, Northwest Saudi Arabia | last1=Galmed | first1=M.A. | last2=Nasr | first2=M.M. | last3=Khater | first3=A.E-S.M. | journal=Arabian Journal of Geosciences | date=2020 | volume=13 | issue=17 | at=829 | doi=10.1007/s12517-020-05852-3| s2cid=221200370 }}</ref> and [[Algeria]]. In the United States phosphorites have been mined in [[Florida]], [[Tennessee]], [[Wyoming]], [[Utah]], [[Idaho]] and [[Kansas]].<ref>Klein, Cornelis and Cornelius S. Hurlbut, Jr., ''Manual of Mineralogy'', Wiley, 1985, 20th ed., p. 360, {{ISBN|0-471-80580-7}}</ref>