Editing Hafnium (section)

===Occurrence===
[[File:Zircão.jpeg|thumb|left|Zircon crystal (2×2 cm) from [[Tocantins]], [[Brazil]]]]

Hafnium is estimated to make up about between 3.0 and 4.8 [[Parts per million|ppm]] of the [[Earth]]'s upper [[crust (geology)|crust]] by mass.<ref>{{Cite book |last1=Haygarth |first1=John C. |url=https://onlinelibrary.wiley.com/doi/10.1002/9781118788417.ch1 |title=Zirconium and Hafnium |last2=Graham |first2=Ronald A. |date=2013-09-30 |publisher=John Wiley & Sons, Inc. |isbn=978-1-118-78841-7 |editor-last=Mishra |editor-first=Brajendra |location=Hoboken, NJ, USA |pages=1–71 |language=en |doi=10.1002/9781118788417.ch1}}</ref>{{rp|5}} <ref name=CRC>ABUNDANCE OF ELEMENTS IN THE EARTH’S CRUST AND IN THE SEA, ''CRC Handbook of Chemistry and Physics,'' 97th edition (2016–2017), p. 14-17</ref> It does not exist as a free element on Earth, but is found combined in [[solid solution]] with zirconium in natural [[zirconium]] compounds such as [[zircon]], ZrSiO<sub>4</sub>, which usually has about 1–4% of the Zr replaced by Hf. Rarely, the Hf/Zr ratio increases during crystallization to give the isostructural mineral [[hafnon]] {{chem2|(Hf,Zr)SiO4}}, with atomic Hf > Zr.<ref>{{cite book|title = The Rock-Forming Minerals: Orthosilicates|first1 = William Alexander|last1 = Deer |author-link1=William Alexander Deer|last2 = Howie|first2= Robert Andrew |author-link2=Robert A. Howie|last3=Zussmann|first3=Jack|isbn=978-0-582-46526-8|date = 1982|publisher = [[Longman|Longman Group Limited]]|pages=418–442|volume=1A|url=https://books.google.com/books?id=Yi0SAQAAMAAJ&q=9780582465268}}</ref> An obsolete name for a variety of zircon containing unusually high Hf content is ''alvite''.<ref>{{cite journal|title = The Mineralogy of Hafnium|first = O. Ivan|last = Lee|journal = [[Chemical Reviews]]|date = 1928|volume = 5|issue=1|pages=17–37|doi = 10.1021/cr60017a002|url=https://archive.org/details/in.ernet.dli.2015.27353/page/n23/mode/2up}}</ref>

A major source of zircon (and hence hafnium) ores is [[heavy mineral sands ore deposits]], [[pegmatite]]s, particularly in [[Brazil]] and [[Malawi]], and [[carbonatite]] intrusions, particularly the Crown Polymetallic Deposit at [[Mount Weld]], [[Western Australia]]. A potential source of hafnium is [[Trachyte|trachyte tuffs]] containing rare zircon-hafnium silicates [[eudialyte]] or [[armstrongite]], at [[Dubbo]] in [[New South Wales]], Australia.<ref>{{cite web|url = http://www.alkane.com.au/projects/nsw/dubbo/DZP%20Summary%20June07.pdf|title = The Dubbo Zirconia Project |last=Chalmers|first=Ian|date = June 2007|publisher = Alkane Resources Limited|access-date = 2008-09-10|archive-url = https://web.archive.org/web/20080228054038/http://www.alkane.com.au/projects/nsw/dubbo/DZP%20Summary%20June07.pdf|archive-date = 2008-02-28}}</ref>