Editing Gallium (section)

==Occurrence==
Gallium does not exist as a free element in the Earth's crust, and the few high-content minerals, such as gallite (CuGaS<sub>2</sub>), are too rare to serve as a primary source.<ref name="Frenzel-2016b">{{cite thesis |last1=Frenzel |first1=Max |title=The distribution of gallium, germanium and indium in conventional and non-conventional resources – Implications for global availability |date=2016 |doi=10.13140/rg.2.2.20956.18564 }}{{page needed|date=April 2024}}</ref> The abundance [[Earth#Chemical composition|in the Earth's crust]] is approximately 16.9&nbsp;[[parts per million|ppm]]. It is the 34th most abundant element in the crust.<ref name="Burton">{{cite journal |doi= 10.1016/0016-7037(59)90052-3 |title= The abundances of gallium and germanium in terrestrial materials|first= J. D.|last= Burton |author2= Culkin, F. |author3=Riley, J. P. |journal= Geochimica et Cosmochimica Acta|volume= 16|issue= 1|date= 2007 |pages= 151–180|bibcode= 1959GeCoA..16..151B}}</ref> This is comparable to the crustal abundances of [[lead]], [[cobalt]], and [[niobium]]. Yet unlike these elements, gallium does not form its own ore deposits with concentrations of > 0.1 wt.% in ore. Rather it occurs at trace concentrations similar to the crustal value in zinc ores,<ref name="Frenzel-2016b" /><ref name=FrenzelMeta-2016/> and at somewhat higher values (~ 50&nbsp;ppm) in aluminium ores, from both of which it is extracted as a by-product. This lack of independent deposits is due to gallium's geochemical behaviour, showing no strong enrichment in the processes relevant to the formation of most ore deposits.<ref name="Frenzel-2016b" />

The [[United States Geological Survey]] (USGS) estimates that more than 1&nbsp;million tons of gallium is contained in known reserves of bauxite and zinc ores.<ref name="USGSCS2008" /><ref name="USGSCS2006">{{cite web|url= https://minerals.usgs.gov/minerals/pubs/commodity/gallium/myb1-2006-galli.pdf |archive-url=https://web.archive.org/web/20080509122325/http://minerals.usgs.gov/minerals/pubs/commodity/gallium/myb1-2006-galli.pdf |archive-date=9 May 2008 |url-status=live|title= Mineral Yearbook 2006: Gallium|publisher= United States Geological Survey|access-date= 20 November 2008|first= Deborah A.|last= Kramer}}</ref> Some coal [[flue]] [[dust]]s contain small quantities of gallium, typically less than 1% by weight.<ref>{{cite journal|title= Determination of gallium in coal and coal fly ash by electrothermal atomic absorption spectrometry using slurry sampling and nickel chemical modification|author= Xiao-quan, Shan|author2= Wen, Wang|author3= Bei, Wen|name-list-style= amp |journal= [[Journal of Analytical Atomic Spectrometry]]|date= 1992|volume= 7|page= 761 |doi= 10.1039/JA9920700761|issue= 5}}</ref><ref>{{cite web|publisher= West Virginia Geological and Economic Survey |date=2 March 2002|title= Gallium in West Virginia Coals|url= http://www.wvgs.wvnet.edu/www/datastat/te/GaHome.htm |url-status=live |archive-url=https://web.archive.org/web/20020311013523/http://www.wvgs.wvnet.edu/www/datastat/te/GaHome.htm
|archive-date=11 March 2002}}</ref><ref>{{cite journal|author= Font, O|title= Recovery of gallium and vanadium from gasification fly ash|date= 2007|journal= Journal of Hazardous Materials|pmid= 16600480|volume= 139|issue= 3 |doi= 10.1016/j.jhazmat.2006.02.041|pages= 413–23|last2= Querol|first2= Xavier|last3= Juan|first3= Roberto|last4= Casado|first4= Raquel|last5= Ruiz|first5= Carmen R.|last6= López-Soler|first6= Ángel|last7= Coca|first7= Pilar|last8= Peña|first8= Francisco García|bibcode= 2007JHzM..139..413F}}</ref><ref>{{cite journal|title= Elements in Coal Ash and Their Industrial Significance |author= Headlee, A. J. W. |author2= Hunter, Richard G. |name-list-style= amp |pages= 548–551|doi= 10.1021/ie50519a028|volume= 45|date= 1953|journal= Industrial and Engineering Chemistry|issue= 3}}</ref> However, these amounts are not extractable without mining of the host materials (see below). Thus, the availability of gallium is fundamentally determined by the rate at which bauxite, zinc ores, and coal are extracted.