Editing Zirconium (section)

===Occurrence===
{{Category see also|Zirconium minerals}}
[[File:Zirconium mineral concentrates - world production trend.svg|thumb|World production trend of zirconium mineral concentrates|upright=1.1|left]]
Zirconium has a concentration of about 130&nbsp;mg/kg within the [[abundance of elements in Earth's crust|Earth's crust]] and about 0.026&nbsp;μg/L in [[sea water]]. It is the 18th most abundant element in the crust.<ref name="argonne" /> It is not found in nature as a [[native metal]], reflecting its intrinsic instability with respect to water. The principal commercial source of zirconium is [[zircon]] (ZrSiO<sub>4</sub>), a [[silicate mineral]],<ref name="nbb" /> which is found primarily in Australia, Brazil, India, Russia, South Africa and the United States, as well as in smaller deposits around the world.<ref name="madehow" /> As of 2013, two-thirds of zircon mining occurs in Australia and South Africa.<ref name="nbb13">{{cite web|title=Zirconium and Hafnium – Mineral resources|date=2014|url=http://minerals.usgs.gov/minerals/pubs/commodity/zirconium/mcs-2014-zirco.pdf}}</ref> Zircon resources exceed 60 million [[tonne]]s worldwide<ref name="usgs2008">{{cite journal |title= Zirconium and Hafnium |journal= Mineral Commodity Summaries |pages= 192–193 |date=January 2008 |url=http://minerals.usgs.gov/minerals/pubs/commodity/zirconium/mcs-2008-zirco.pdf |access-date= 2008-02-24}}</ref> and annual worldwide zirconium production is approximately 900,000 tonnes.<ref name="argonne">{{cite book|first1=John|last1=Peterson|first2=Margaret|last2=MacDonell|contribution=Zirconium|title=Radiological and Chemical Fact Sheets to Support Health Risk Analyses for Contaminated Areas|date=2007|pages=64–65|publisher=Argonne National Laboratory|url=http://www.evs.anl.gov/pub/doc/ANL_ContaminantFactSheets_All_070418.pdf|access-date=2008-02-26|url-status=dead|archive-url=https://web.archive.org/web/20080528130257/http://www.evs.anl.gov/pub/doc/ANL_ContaminantFactSheets_All_070418.pdf|archive-date=2008-05-28}}</ref> Zirconium also occurs in more than 140 other minerals, including the commercially useful ores [[baddeleyite]] and [[eudialyte]].<ref>{{cite web|author=Ralph, Jolyon|author2=Ralph, Ida|name-list-style=amp |title=Minerals that include Zr|publisher=Mindat.org |date=2008|url=http://www.mindat.org/chemsearch.php?inc=Zr%2C&exc=&sub=Search+for+Minerals|access-date=2008-02-23}}</ref>

Zirconium is relatively abundant in [[stellar classification #Class S|S-type stars]], and has been detected in the sun and in meteorites. Lunar rock samples brought back from several [[Apollo program|Apollo]] missions to the moon have a high zirconium oxide content relative to terrestrial rocks.<ref>{{Cite journal |last1=Peckett |first1=A. |last2=Phillips |first2=R. |last3=Brown |first3=G. M. |date=March 1972 |title=New Zirconium-rich Minerals from Apollo 14 and 15 Lunar Rocks |url=https://www.nature.com/articles/236215a0 |journal=Nature |language=en |volume=236 |issue=5344 |pages=215–217 |doi=10.1038/236215a0 |bibcode=1972Natur.236..215P |issn=0028-0836}}</ref>

[[EPR spectroscopy]] has been used in investigations of the unusual 3+ valence state of zirconium. The EPR spectrum of Zr<sup>3+</sup>, which has been initially observed as a parasitic signal in Fe‐doped single crystals of ScPO<sub>4</sub>, was definitively identified by preparing single crystals of ScPO<sub>4</sub> doped with isotopically enriched (94.6%)<sup>91</sup>Zr. Single crystals of LuPO<sub>4</sub> and YPO<sub>4</sub> doped with both naturally abundant and isotopically enriched Zr have also been grown and investigated.<ref>{{Cite journal|last1=Abraham|first1=M. M.|last2=Boatner|first2=L. A.|last3=Ramey|first3=J. O.|last4=Rappaz|first4=M.|date=1984-12-20|title=The occurrence and stability of trivalent zirconium in orthophosphate single crystals|url=https://aip.scitation.org/doi/abs/10.1063/1.447678|journal=The Journal of Chemical Physics|volume=81|issue=12|pages=5362–5366|doi=10.1063/1.447678|bibcode=1984JChPh..81.5362A|issn=0021-9606}}</ref>