Editing Corundum (section)

==Geology and occurrence==
[[File:Corindon azulEZ.jpg|thumb|left|180px|Corundum from [[Brazil]], size about {{convert|2|×|3|cm|in|sigfig=1|abbr=on}}]]
Corundum occurs as a mineral in mica [[schist]], [[gneiss]], and some [[marble]]s in [[metamorphic]] [[terrane]]s. It also occurs in low-silica [[igneous]] [[syenite]] and [[nepheline syenite]] [[intrusive rock|intrusive]]s. Other occurrences are as masses adjacent to [[ultramafic]] intrusives, associated with [[lamprophyre]] [[dike (geology)|dikes]] and as large crystals in [[pegmatite]]s.<ref name=Hurlbut/> It commonly occurs as a [[detrital]] mineral in stream and beach sands because of its hardness and resistance to weathering.<ref name=Hurlbut/> The largest documented single crystal of corundum measured about {{convert|65|×|40|×|40|cm|in|abbr=on}}, and weighed {{convert|152|kg|lb|abbr=on}}.<ref>{{cite journal |author=Rickwood, P. C. |year=1981 |title=The largest crystals |journal=American Mineralogist |volume=66 |pages=885–907 |url=http://www.minsocam.org/ammin/AM66/AM66_885.pdf |archive-url=https://web.archive.org/web/20090620081033/http://www.minsocam.org/ammin/AM66/AM66_885.pdf |archive-date=2009-06-20 |url-status=live}}</ref> The record has since been surpassed by certain synthetic [[boule (crystal)|boules]].<ref>{{cite web |url=http://www.ledinside.com/news/2009/4/Rubicon_Technology_Grows_Super_boule_of_200kg_Weight_20090421 |title=Rubicon Technology grows 200&nbsp;kg "super boule" |website=LED Inside |date=April 21, 2009 |df=dmy-all}}</ref>

Corundum for [[abrasive]]s is mined in Zimbabwe, Pakistan, Afghanistan, Russia, Sri Lanka, and India. Historically it was mined from deposits associated with [[dunite]]s in [[North Carolina]], US, and from a nepheline syenite in [[Craigmont, Ontario]].<ref name=Hurlbut/> [[Emery (mineral)|Emery]]-grade corundum is found on the [[list of islands of Greece|Greek island]] of [[Naxos]] and near [[Peekskill, New York]], US. Abrasive corundum is synthetically manufactured from [[bauxite]].<ref name=Hurlbut/>

Four corundum axes dating to 2500&nbsp;BC from the [[Liangzhu culture]] and Sanxingcun culture (the latter of which is located in [[Jintan District]]) have been discovered in China.<ref>{{cite web |url=http://news.bbc.co.uk/2/hi/science/nature/4555235.stm |title=Chinese made first use of diamond |publisher=BBC |date=May 2005 |work=BBC News}}</ref><ref>{{cite web |last1=Alexandra |first1=Goho |title=In the Buff: Stone Age tools may have derived luster from diamond |url=https://www.sciencenews.org/article/buff-stone-age-tools-may-have-derived-luster-diamond#:~:text=He%20found%20that%20all%20four,Earth%3B%20only%20diamond%20is%20harder |website=Science News |date=16 February 2005 }}</ref>