Editing Xenotime (section)

{{Short description|Phosphate mineral}}
{{Infobox mineral
| name = Xenotime
| category = [[Phosphate minerals]]
| boxwidth =
| image = Xenotime with Rutile-08-2-78ab.jpg
| imagesize   = 260px
| caption = Xenotime with [[rutile]]
| formula = YPO<sub>4</sub>
| IMAsymbol   = Xtm<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref>
| strunz = 8.AD.35
| color = Brown, brownish yellow, gray
| habit = Prismatic, radial aggregates, granular
| system = [[Tetragonal]]
| class = Dipyramidal (4/mmm) <br/>[[H-M symbol]]: (4/m)
| symmetry = ''I''4<sub>1</sub>/a
| cleavage = Perfect [100]
| fracture = Uneven to splintery
| mohs = 4.5
| luster = Vitreous to resinous
| refractive = 1.720–1.815 
| birefringence = δ = 0.096
| pleochroism = Dichroic
| streak = Pale brown, yellowish or reddish, to white
| gravity = 4.4–5.1
| melt = 
| solubility =
| diaphaneity = Translucent to opaque
| other = Not radioactive or luminescent
| references = <ref name=Lost>{{cite book|ref=Fontani|last1=Fontani|first1=Marco| author-link= Marco Fontani|last2=Costa|first2=Mariagrazia|last3=Orna|first3=Virginia|title=The Lost Elements: The Periodic Table's Shadow Side|publisher=Oxford University Press|year=2014|page=73|url=https://books.google.com/books?id=Ck9jBAAAQBAJ|isbn=978-0199383-344}}</ref><ref name=Mindat>{{cite web|url=http://www.mindat.org/min-4333.html|title=Mindat database}}</ref><ref name=Webmineral>{{cite web|url=http://www.webmineral.com/data/Xenotime-%28Y%29.shtml|title=Xenotime|work=Webmineral}}</ref><ref name=Handbook>{{cite web|url=http://rruff.geo.arizona.edu/doclib/hom/xenotimey.pdf|title=Handbook of Mineralogy}}</ref>
}}

'''Xenotime''' is a [[rare-earth]] [[phosphate mineral]], the major component of which is [[yttrium]] orthophosphate ([[yttrium|Y]][[phosphorus|P]][[oxygen|O]]<sub>4</sub>). The phosphate ions are described by a tetrahedral shape and coordinate to the center Y<sup>3+</sup> metal ion in a way that closely resembles the structure of [[zircon]] (ZrSiO<sub>4</sub>).<ref>{{Cite journal |last1=Pagliaro |first1=Francesco |last2=Comboni |first2=Davide |last3=Battiston |first3=Tommaso |last4=Krüger |first4=Hannes |last5=Hejny |first5=Clivia |last6=Kahlenberg |first6=Volker |last7=Gigli |first7=Lara |last8=Glazyrin |first8=Konstantin |last9=Liermann |first9=Hanns-Peter |last10=Garbarino |first10=Gaston |last11=Gatta |first11=G. Diego |last12=Lotti |first12=Paolo |date=December 2024 |title=Comparative thermal and compressional behaviour of natural xenotime-(Y), chernovite-(Y) and monazite-(Ce) |url=https://www.cambridge.org/core/product/identifier/S0026461X24000707/type/journal_article |journal=Mineralogical Magazine |language=en |volume=88 |issue=6 |pages=682–697 |doi=10.1180/mgm.2024.70 |bibcode=2024MinM...88..682P |issn=0026-461X}}</ref> It forms a solid solution series with [[chernovite-(Y)]] ([[yttrium|Y]][[arsenic|As]][[oxygen|O]]<sub>4</sub>) and therefore may contain trace [[impurities]] of [[arsenic]], as well as [[silicon dioxide]] and [[calcium]]. Other iso-structural ions that undergo exchanges with PO<sub>4</sub> are VO<sub>4</sub> and NbO<sub>4</sub> ions, contributing to the list of possible co-occurring elements that may be in need of separation.<ref name="linkinghub.elsevier.com">{{Cite journal |last1=Hetherington |first1=Callum J. |last2=Jercinovic |first2=Michael J. |last3=Williams |first3=Michael L. |last4=Mahan |first4=Kevin |date=2008-09-15 |title=Understanding geologic processes with xenotime: Composition, chronology, and a protocol for electron probe microanalysis |url=https://linkinghub.elsevier.com/retrieve/pii/S0009254108001952 |journal=Chemical Geology |series=The role of accessory minerals in metamorphic and igneous processes |volume=254 |issue=3 |pages=133–147 |doi=10.1016/j.chemgeo.2008.05.020 |bibcode=2008ChGeo.254..133H |issn=0009-2541|url-access=subscription }}</ref> The [[rare-earth elements]] [[dysprosium]], [[erbium]], [[terbium]] and [[ytterbium]], as well as metal elements such as [[thorium]] and [[uranium]] (all replacing yttrium) are the expressive secondary components of xenotime. Due to uranium and thorium impurities, some xenotime specimens may be weakly to strongly [[radioactive]]. [[Lithiophyllite]], [[monazite]] and [[purpurite]] are sometimes grouped with xenotime in the informal "anhydrous phosphates" group. Xenotime is used chiefly as a source of yttrium and heavy [[lanthanide]] metals (dysprosium, ytterbium, erbium and gadolinium). Occasionally, [[gemstone]]s are also cut from the finest xenotime crystals.