Editing Apatite (section)

==Geology==
Apatite is very common as an [[accessory mineral]] in [[igneous]] and [[metamorphic]] rocks, where it is the most common [[phosphate mineral]]. However, occurrences are usually as small grains which are often visible only in [[thin section]]. Coarsely crystalline apatite is usually restricted to [[pegmatites]], [[gneiss]] derived from [[sediments]] rich in [[carbonate minerals]], [[skarn]]s, or [[marble]]. Apatite is also found in [[clastic]] [[sedimentary rock]] as grains eroded out of the source rock.<ref name=Nesse349>{{cite book |last1=Nesse |first1=William D. |title=Introduction to mineralogy |date=2000 |publisher=Oxford University Press |location=New York |isbn=9780195106916 |page=349}}</ref><ref>[https://www.minerals.net/mineral/apatite.aspx The Apatite Mineral Group]. minerals.net.  Retrieved on 2020-10-14.</ref> [[Phosphorite]] is a phosphate-rich [[sedimentary rock]] containing as much as 80% apatite,<ref>{{cite journal |last1=Gulbrandsen |first1=R.A |title=Chemical composition of phosphorites of the Phosphoria Formation |journal=Geochimica et Cosmochimica Acta |date=August 1966 |volume=30 |issue=8 |pages=769–778 |doi=10.1016/0016-7037(66)90131-1|bibcode=1966GeCoA..30..769G }}</ref> which is present as [[cryptocrystalline]] masses referred to as ''collophane''.<ref>{{cite journal |last1=Burnett |first1=William C. |title=Geochemistry and origin of phosphorite deposits from off Peru and Chile |journal=GSA Bulletin |date=1 June 1977 |volume=88 |issue=6 |pages=813–823 |doi=10.1130/0016-7606(1977)88<813:GAOOPD>2.0.CO;2|bibcode=1977GSAB...88..813B }}</ref> Economic quantities of apatite are also sometimes found in [[nepheline syenite]] or in [[carbonatite]]s.<ref name=Nesse349/>

Apatite is the defining mineral for 5 on the [[Mohs scale of mineral hardness|Mohs scale]].{{sfn|Nesse|2000|p=99}} It can be distinguished [[Field work|in the field]] from [[beryl]] and [[tourmaline]] by its relative softness. It is often fluorescent under [[ultraviolet light]].<ref>{{cite book |last1=Sinkankas |first1=John |title=Mineralogy for amateurs. |date=1964 |publisher=Van Nostrand |location=Princeton, N.J. |isbn=0442276249 |pages=417–418}}</ref>

Apatite is one of a few minerals produced and used by biological micro-environmental systems.<ref name=Nesse349/> Hydroxyapatite (IMA name: Hydroxylapatite), is the major component of [[tooth enamel]] and [[bone mineral]]. A relatively rare form of apatite in which most of the OH groups are absent and containing many [[carbonate]] and acid phosphate substitutions is a large component of [[bone]] material.<ref>{{cite journal |last1=Combes |first1=Christèle |last2=Cazalbou |first2=Sophie |last3=Rey |first3=Christian |title=Apatite Biominerals |journal=Minerals |date=5 April 2016 |volume=6 |issue=2 |pages=34 |doi=10.3390/min6020034|bibcode=2016Mine....6...34C |doi-access=free }}</ref>

Fluorapatite (or fluoroapatite) is more resistant to acid attack than is hydroxyapatite; in the mid-20th century, it was discovered that communities whose water supply naturally contained fluorine had lower rates of [[dental caries]].<ref name=NICDR>{{cite web |url=http://www.nidcr.nih.gov/OralHealth/Topics/Fluoride/TheStoryofFluoridation.htm |title=The story of fluoridation |publisher=National Institute of Dental and Craniofacial Research |date=2008-12-20 }}</ref> [[Fluoridated water]] allows exchange in the [[tooth|teeth]] of fluoride ions for [[Hydroxyl#Hydroxyl group|hydroxyl groups]] in apatite. Similarly, toothpaste typically contains a source of fluoride [[anions]] (e.g. sodium fluoride, [[sodium monofluorophosphate]]). Too much fluoride results in [[dental fluorosis]] and/or [[skeletal fluorosis]].<ref name=FRWG>{{cite journal | title = Recommendations for using fluoride to prevent and control dental caries in the United States. Centers for Disease Control and Prevention | journal = MMWR. Recommendations and Reports | volume = 50 | issue = RR-14 | pages = 1–42 | date = August 2001 | pmid = 11521913 | url = http://cdc.gov/mmwr/preview/mmwrhtml/rr5014a1.htm}}
*{{cite web |date=2007-08-09 |title=CDC Releases New Guidelines on Fluoride Use to Prevent Tooth Decay |website=Centers for Disease Control and Prevention |url=http://cdc.gov/fluoridation/guidelines/tooth_decay.htm |archive-url=https://web.archive.org/web/20080308203450/https://cdc.gov/fluoridation/guidelines/tooth_decay.htm |archive-date=2008-03-08}}</ref>

[[Fission track dating|Fission tracks]] in apatite are commonly used to determine the thermal histories of [[orogenic belt]]s and of [[Sedimentary rock|sediments]] in [[sedimentary basin]]s.<ref>{{Cite book|date=2019|editor-last=Malusà|editor-first=Marco G.|editor2-last=Fitzgerald|editor2-first=Paul G.|title=Fission-Track Thermochronology and its Application to Geology|series=Springer Textbooks in Earth Sciences, Geography and Environment |publisher=Springer Textbooks in Earth Sciences, Geography and Environment|doi=10.1007/978-3-319-89421-8|issn=2510-1307|isbn=978-3-319-89419-5|s2cid=146467911}}</ref> [[Helium dating|(U-Th)/He dating]] of apatite is also well established from noble gas diffusion studies<ref>{{Cite journal|last1=Zeitler|first1=P.K.|last2=Herczeg|first2=A.L.|last3=McDougall|first3=I.|last4=Honda|first4=M.|date=October 1987|title=U-Th-He dating of apatite: A potential thermochronometer|journal=Geochimica et Cosmochimica Acta|volume=51|issue=10|pages=2865–2868|doi=10.1016/0016-7037(87)90164-5|issn=0016-7037|bibcode=1987GeCoA..51.2865Z}}</ref><ref>{{Cite journal|last1=Wolf|first1=R.A.|last2=Farley|first2=K.A.|last3=Silver|first3=L.T.|date=November 1996|title=Helium diffusion and low-temperature thermochronometry of apatite|journal=Geochimica et Cosmochimica Acta|volume=60|issue=21|pages=4231–4240|doi=10.1016/s0016-7037(96)00192-5|issn=0016-7037|bibcode=1996GeCoA..60.4231W}}</ref><ref>{{Cite journal|last1=Warnock|first1=A.C.|last2=Zeitler|first2=P.K.|last3=Wolf|first3=R.A.|last4=Bergman|first4=S.C.|date=December 1997|title=An evaluation of low-temperature apatite U Th/He thermochronometry|journal=Geochimica et Cosmochimica Acta|volume=61|issue=24|pages=5371–5377|doi=10.1016/s0016-7037(97)00302-5|issn=0016-7037|bibcode=1997GeCoA..61.5371W}}</ref><ref>{{Cite journal|last=Farley|first=K. A.|date=2000-02-10|title=Helium diffusion from apatite: General behavior as illustrated by Durango fluorapatite|journal=Journal of Geophysical Research: Solid Earth|volume=105|issue=B2|pages=2903–2914|doi=10.1029/1999jb900348|issn=0148-0227|bibcode=2000JGR...105.2903F|url=https://authors.library.caltech.edu/37451/1/1999JB900348.pdf|doi-access=free}}</ref><ref>{{Cite journal|last1=Shuster|first1=David L.|last2=Flowers|first2=Rebecca M.|last3=Farley|first3=Kenneth A.|date=September 2006|title=The influence of natural radiation damage on helium diffusion kinetics in apatite|journal=Earth and Planetary Science Letters|volume=249|issue=3–4|pages=148–161|doi=10.1016/j.epsl.2006.07.028|issn=0012-821X|bibcode=2006E&PSL.249..148S}}</ref><ref>{{Cite journal|last1=Idleman|first1=Bruce D.|last2=Zeitler|first2=Peter K.|last3=McDannell|first3=Kalin T.|date=January 2018|title=Characterization of helium release from apatite by continuous ramped heating|journal=Chemical Geology|volume=476|pages=223–232|doi=10.1016/j.chemgeo.2017.11.019|issn=0009-2541|bibcode=2018ChGeo.476..223I}}</ref><ref>{{Cite journal|last1=McDannell|first1=Kalin T.|last2=Zeitler|first2=Peter K.|last3=Janes|first3=Darwin G.|last4=Idleman|first4=Bruce D.|last5=Fayon|first5=Annia K.|date=February 2018|title=Screening apatites for (U-Th)/He thermochronometry via continuous ramped heating: He age components and implications for age dispersion|journal=Geochimica et Cosmochimica Acta|volume=223|pages=90–106|doi=10.1016/j.gca.2017.11.031|issn=0016-7037|bibcode=2018GeCoA.223...90M}}</ref> for use in determining thermal histories<ref>{{Cite journal|last1=House|first1=M.A.|last2=Wernicke|first2=B.P.|last3=Farley|first3=K.A.|last4=Dumitru|first4=T.A.|date=October 1997|title=Cenozoic thermal evolution of the central Sierra Nevada, California, from (UTh)/He thermochronometry|journal=Earth and Planetary Science Letters|volume=151|issue=3–4|pages=167–179|doi=10.1016/s0012-821x(97)81846-8|issn=0012-821X}}</ref><ref>{{Cite journal|last1=Ehlers|first1=Todd A.|last2=Farley|first2=Kenneth A.|date=January 2003|title=Apatite (U–Th)/He thermochronometry: methods and applications to problems in tectonic and surface processes|journal=Earth and Planetary Science Letters|volume=206|issue=1–2|pages=1–14|doi=10.1016/s0012-821x(02)01069-5|issn=0012-821X|bibcode=2003E&PSL.206....1E}}</ref> and other, less typical applications such as paleo-wildfire dating.<ref>{{Cite journal|last1=Reiners|first1=P. W.|last2=Thomson|first2=S. N.|last3=McPhillips|first3=D.|last4=Donelick|first4=R. A.|last5=Roering|first5=J. J.|date=2007-10-12|title=Wildfire thermochronology and the fate and transport of apatite in hillslope and fluvial environments|journal=Journal of Geophysical Research|volume=112|issue=F4|pages=F04001|doi=10.1029/2007jf000759|issn=0148-0227|bibcode=2007JGRF..112.4001R|doi-access=free}}</ref>