Editing Chert (section)

{{Short description|Hard, fine-grained sedimentary rock composed of cryptocrystalline silica}}
{{for multi|the Spanish municipality|Xert|an evil spirit in Slavic folklore|Chort}}
{{Use dmy dates|date=February 2019}}
{{Infobox rock
|name=Chert
|type=Sedimentary
|image=ChertUSGOV.jpg
|alt=Chert hand sample
|caption=A hand sample of chert
|composition=[[Microcrystalline]] or [[cryptocrystalline]] [[quartz]]
}}

'''Chert''' ({{IPAc-en|tʃ|ɜr|t}}) is a hard, fine-grained [[sedimentary rock]] composed of [[microcrystalline]] or [[cryptocrystalline]] [[quartz]],<ref name=Knauth1979>{{cite journal |last1=Knauth |first1=L. Paul |title=A model for the origin of chert in limestone |journal=Geology |date=1 June 1979 |volume=7 |issue=6 |pages=274–77 |doi=10.1130/0091-7613(1979)7<274:AMFTOO>2.0.CO;2|bibcode=1979Geo.....7..274K }}</ref> the mineral form of [[silicon dioxide]] (SiO<sub>2</sub>).<ref name=":0">{{cite web |url=https://geology.com/rocks/chert.shtml |title=Chert: Sedimentary Rock - Pictures, Definition, Formation |website=geology.com |access-date=2018-05-12}}</ref> Chert is characteristically of biological origin, but may also occur inorganically as a [[precipitation (chemistry)|chemical precipitate]] or a [[diagenesis|diagenetic]] replacement, as in [[petrified wood]].<ref>{{cite book |title=Dictionary of Geological Terms |edition=3rd |editor-last1=Bates |editor-first1=R. L. |editor-last2=Jackson |editor-first2=J. |year=1984 |publisher=[[American Geological Institute]]/[[Doubleday (publisher)|Doubleday]] |isbn=0385181019 |page=85 |oclc=465393210}}</ref>

Chert is typically composed of the petrified remains of [[siliceous ooze]], the biogenic sediment that covers large areas of the deep ocean floor, and which contains the silicon skeletal remains of [[diatom]]s, [[Dictyochales|silicoflagellates]], and [[radiolaria]]ns.<ref name="boggs-2006-208-210">{{cite book |last=Boggs |first=Sam |title=Principles of sedimentology and stratigraphy |date=2006 |publisher=[[Pearson Prentice Hall]] |location=[[Upper Saddle River, New Jersey]] |isbn=0131547283 |pages=208–10 |edition=4th}}</ref> [[Precambrian]] cherts are notable for the presence of fossil [[cyanobacteria]].<ref>{{cite journal |last1=Golubic |first1=Stjepko |last2=Seong-Joo |first2=Lee |title=Early cyanobacterial fossil record: preservation, palaeoenvironments and identification |journal=European Journal of Phycology |date=October 1999 |volume=34 |issue=4 |pages=339–48 |doi=10.1080/09670269910001736402|doi-access=free |bibcode=1999EJPhy..34..339G }}</ref> In addition to [[Micropaleontology|microfossils]],<ref name="boggs-2006-208-210"/> chert occasionally contains [[macrofossil]]s.<ref>{{cite journal |last1=Bonde |first1=Suresh D. |last2=Kumaran |first2=K. P. N. |title=The oldest macrofossil record of the mangrove fern Acrostichum L. from the Late Cretaceous Deccan Intertrappean beds of India |journal=[[Cretaceous Research]] |date=February 2002 |volume=23 |issue=1 |pages=149–52 |doi=10.1006/cres.2001.0307|bibcode=2002CrRes..23..149B }}</ref><ref>{{cite journal |last1=Kotyk |first1=M. E. |last2=Basinger |first2=J. F. |last3=Gensel |first3=P. G. |last4=de Freitas |first4=T. A. |title=Morphologically complex plant macrofossils from the Late Silurian of Arctic Canada |journal=[[American Journal of Botany]] |date=1 June 2002 |volume=89 |issue=6 |pages=1004–13 |doi=10.3732/ajb.89.6.1004|pmid=21665700 |doi-access=free }}</ref> However, some chert is devoid of any fossils.{{sfn|Boggs|2006|p=207}}

Chert varies greatly in color, from white to black, but is most often found as gray, brown, grayish brown and light green to rusty red<ref name="roberts-etal-1990">W.L. Roberts, T.J. Campbell, G.R. Rapp Jr., "Encyclopedia of Mineralogy, Second Edition", 1990. {{ISBN|0-442-27681-8}}</ref><ref name="mitchell-1985">R.S. Mitchell, "Dictionary of Rocks", 1985. {{ISBN|0-442-26328-7}}</ref> and occasionally as dark green.<ref>{{cite journal |last1=McBride |first1=E.F. |last2=Folk |first2=R.L. |title=The Caballos Novaculite Revisited: Part II: Chert and Shale Members and Synthesis |journal=SEPM Journal of Sedimentary Research |date=1977 |volume=47 |doi=10.1306/212F731A-2B24-11D7-8648000102C1865D}}</ref> Its color is an expression of trace elements present in the rock. Both red and green are most often related to traces of iron in its [[redox|oxidized and reduced]] forms, respectively.<ref name="boggs-2006-208-210"/><ref>{{cite journal |last1=Thurston |first1=Diana R. |title=Studies on bedded cherts |journal=Contributions to Mineralogy and Petrology |date=1972 |volume=36 |issue=4 |pages=329–334 |doi=10.1007/BF00444339|bibcode=1972CoMP...36..329T |s2cid=128745664 }}</ref>