Editing Holmium (section)

==Occurrence and production==
[[File:Gadolinitas.jpg|thumb|A specimen of [[gadolinite]] - holmium is the black part of it. ]]
Like all the other [[rare-earth element]]s, holmium is not naturally found as a [[free element]]. It occurs combined with other elements in gadolinite, [[monazite]] and other rare-earth minerals. No holmium-dominant mineral has yet been found. The main mining areas are China, United States, Brazil, India, Sri Lanka, and Australia with reserves of holmium estimated as 400,000 tonnes.<ref name="emsley225" /> The annual production of holmium metal is of about 10 tonnes per year.<ref>{{Cite web |title=Ho - Holmium |url=https://mmta.co.uk/metals/ho/ |access-date=5 December 2022 |publisher=MMTA |language=}}</ref>

Holmium makes up 1.3 parts per million of the [[Abundance of elements in Earth's crust|Earth's crust]] by mass.<ref name=CRCAbundanceTable>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> Holmium makes up 1 part per million of the [[soil]]s, 400 parts per [[Names of large numbers#Standard dictionary numbers|quadrillion]] of seawater, and almost none of [[Earth's atmosphere]], which is very rare for a lanthanide.<ref name="emsley225">{{cite book|last=Emsley|first=John|title=Nature's Building Blocks|page=225|date=2011}}</ref> It makes up 500 parts per trillion of the universe by mass.<ref>{{cite web|url=http://www.webelements.com/periodicity/abundance_universe/.|title=WebElements Periodic Table » Periodicity » Abundance in the universe » periodicity|first=Mark Winter, University of Sheffield and WebElements|last=Ltd|website=www.webelements.com|access-date=27 March 2018|archive-url=https://web.archive.org/web/20170929183039/https://www.webelements.com/periodicity/abundance_universe/|archive-date=2017-09-29}}</ref>

Holmium is commercially extracted by [[ion exchange]] from monazite sand (0.05% holmium), but is still difficult to separate from other rare earths. The element has been isolated through the [[redox|reduction]] of its [[anhydrous]] [[chloride]] or [[fluoride]] with metallic [[calcium]].<ref name="CRC" /> Its estimated abundance in the Earth's crust is 1.3&nbsp;mg/kg. Holmium obeys the [[Oddo–Harkins rule]]: as an odd-numbered element, it is less abundant than both dysprosium and erbium. However, it is the most abundant of the odd-numbered heavy [[lanthanides]]. Of the lanthanides, only [[promethium]], [[thulium]], lutetium and terbium are less abundant on Earth. The principal current source are some of the ion-adsorption clays of southern China. Some of these have a rare-earth composition similar to that found in [[xenotime]] or gadolinite. Yttrium makes up about two-thirds of the total by mass; holmium is around 1.5%.<ref name="patnaik">{{cite book|last =Patnaik|first =Pradyot|date = 2003|title =Handbook of Inorganic Chemical Compounds|publisher = McGraw-Hill|pages = 338–339| isbn =0-07-049439-8|url= https://books.google.com/books?id=Xqj-TTzkvTEC&pg=PA338|access-date = 2009-06-06|archive-url=https://archive.org/details/handbookofinorga0000patn/page/n3/mode/2up|archive-date=2023-06-14}}</ref> Holmium is relatively inexpensive for a rare-earth metal with the price about 1000&nbsp;[[USD]]/kg.<ref>{{cite news| publisher = USGS| title =Rare-Earth Metals| author = James B. Hedrick| access-date = 2009-06-06| url =http://minerals.usgs.gov/minerals/pubs/commodity/rare_earths/740798.pdf}}</ref>