Editing Popigai impact structure (section)

== Diamond deposits ==
[[File:Popigai nanodiamonds.jpg|thumb|right|330px|Popigai diamonds are about 1 mm in size and consist of [[nanodiamond]] agglomerates.<ref>{{cite journal|doi=10.1038/srep14702|pmid=26424384|pmc=4589680|title=Natural occurrence of pure nano-polycrystalline diamond from impact crater|journal=Scientific Reports|volume=5|pages=14702|year=2015|last1=Ohfuji|first1=Hiroaki|last2=Irifune|first2=Tetsuo|last3=Litasov|first3=Konstantin D.|last4=Yamashita|first4=Tomoharu|last5=Isobe|first5=Futoshi|last6=Afanasiev|first6=Valentin P.|last7=Pokhilenko|first7=Nikolai P.|bibcode=2015NatSR...514702O}}</ref>]]
Most modern industrial diamonds are produced [[Synthetic diamond|synthetically]]. The diamond deposits at Popigai have not been mined because of the remote location and lack of infrastructure, and are unlikely to be competitive with synthetic diamonds.<ref name=geonews>{{cite news|title=Diamonds Beneath the Popigai Crater -- Northern Russia|url=http://geology.com/articles/popigai-crater-diamonds/|access-date=24 September 2012|date=23 September 2012|publisher=geology.com}}</ref>  Many of the diamonds at Popigai contain [[crystal lattice|crystalline]] [[lonsdaleite]], an [[allotrope of carbon]] that has a hexagonal lattice.<ref name=itartass>{{cite news|title=Russia declassifies deposit of impact diamonds|url=http://pda.itar-tass.com/en/c154/521362.html|publisher=ITAR-TASS|access-date=17 September 2012|date=17 September 2012|archive-url=https://web.archive.org/web/20120920221513/http://pda.itar-tass.com/en/c154/521362.html|archive-date=20 September 2012|url-status=dead}}</ref> Pure, laboratory-created lonsdaleite is up to 58% harder than ordinary diamonds.<ref name=theory>{{cite journal|author1=Pan, Zicheng |author2=Sun, Hong |author3=Zhang, Yi |author4=Chen, Changfeng  |name-list-style=amp |title=Harder than Diamond: Superior Indentation Strength of Wurtzite BN and Lonsdaleite |journal=Physical Review Letters|issue= 5|pages=055503|year=2009 |doi= 10.1103/PhysRevLett.102.055503|volume=102|pmid=19257519|bibcode=2009PhRvL.102e5503P}}
*{{cite news |author=Lisa Zyga |date=12 February 2009 |title=Scientists Discover Material Harder Than Diamond |work=Phys.org |url=http://www.physorg.com/news153658987.html}}</ref><ref name=geonews /> These types of diamonds are known as "impact diamonds" because they are thought to be produced when a meteorite strikes a graphite deposit at high velocity.<ref name=itartass/>  They may have industrial uses but are unsuitable as [[gem]]s.<ref>[http://www.rough-polished.com/en/digest/68330.html Pros and cons of extraterrestrial diamonds] {{Webarchive|url=https://web.archive.org/web/20141222224902/http://www.rough-polished.com/en/digest/68330.html |date=2014-12-22 }}, from "Rough&Polished&ndash;information and analytics on diamond and jewellery markets."</ref>

Additionally, carbon [[polymorphism (materials science)|polymorphs]], a combination of diamond and lonsdaleite even harder than pure lonsdaleite, have been discovered in the crater.<ref>{{cite journal |doi=10.1016/j.crte.2003.07.001|title=A new natural, super-hard, transparent polymorph of carbon from the Popigai impact crater, Russia|journal=Comptes Rendus Geoscience|volume=335|issue=12|pages=889|year=2003|last1=El Goresy|first1=Ahmed|last2=Dubrovinsky|first2=Leonid S|last3=Gillet|first3=Philippe|last4=Mostefaoui|first4=Smail|last5=Graup|first5=Günther|last6=Drakopoulos|first6=Michael|last7=Simionovici|first7=Alexandre S|last8=Swamy|first8=Varghese|last9=Masaitis|first9=Victor L|bibcode=2003CRGeo.335..889E|url=https://comptes-rendus.academie-sciences.fr/geoscience/articles/10.1016/j.crte.2003.07.001/ }}</ref><ref>{{Cite journal|last1=Baek|first1=Woohyeon|last2=Gromilov|first2=Sergey A.|last3=Kuklin|first3=Artem V.|last4=Kovaleva|first4=Evgenia A.|last5=Fedorov|first5=Alexandr S.|last6=Sukhikh|first6=Alexander S.|last7=Hanfland|first7=Michael|last8=Pomogaev|first8=Vladimir A.|last9=Melchakova|first9=Iuliia A.|last10=Avramov|first10=Paul V.|last11=Yusenko|first11=Kirill V.|date=2019-03-13|title=Unique Nanomechanical Properties of Diamond–Lonsdaleite Biphases: Combined Experimental and Theoretical Consideration of Popigai Impact Diamonds|journal=Nano Letters|volume=19|issue=3|pages=1570–1576|doi=10.1021/acs.nanolett.8b04421|pmid=30735045|bibcode=2019NanoL..19.1570B|s2cid=73443676 |issn=1530-6984}}</ref>