Editing Diamond (section)

=== Color ===
{{Main|Diamond color}}
[[File:National Museum of Natural History Gold Colored Diamonds.JPG|alt=A museum display of jewelry items. Three brooches each consist of a large brown central gem surrounded by many clear small stones. A necklace has a large brown gem at its bottom and its string is all covered with small clear gems. A cluster-shaped decoration contains many brown gems.|upright=1.35|thumb|Brown diamonds at the [[National Museum of Natural History]] in [[Washington, D.C.]]]]
[[File:The Hope Diamond - SIA.jpg|thumb|right|upright=1.35|alt=Picture of a diamond|The most famous colored diamond, the [[Hope Diamond]]]]
Diamond has a wide [[band gap]] of {{val|5.5|ul=eV}} corresponding to the deep [[ultraviolet]] wavelength of 225{{nbsp}}nanometers. This means that pure diamond should transmit visible light and appear as a clear colorless crystal. Colors in diamond originate from lattice defects and impurities. The diamond crystal lattice is exceptionally strong, and only atoms of [[nitrogen]], [[boron]], and [[hydrogen]] can be introduced into diamond during the growth at significant concentrations (up to atomic percents). Transition metals [[nickel]] and [[cobalt]], which are commonly used for growth of synthetic diamond by high-pressure high-temperature techniques, have been detected in diamond as individual atoms; the maximum concentration is 0.01% for nickel<ref>{{cite journal | vauthors = Collins AT, Kanda H, Isoya J, Ammerlaan CA, Van Wyk JA |title=Correlation between optical absorption and EPR in high-pressure diamond grown from a nickel solvent catalyst |journal=Diamond and Related Materials |volume=7 |pages=333–338 |year=1998 |doi=10.1016/S0925-9635(97)00270-7 |issue=2–5 |bibcode=1998DRM.....7..333C }}</ref> and even less for cobalt. Virtually any element can be introduced to diamond by ion implantation.<ref>{{cite journal |doi=10.1103/PhysRevB.61.12909 |title=Vibronic spectra of impurity-related optical centers in diamond |year=2000 | vauthors = Zaitsev AM |journal=Physical Review B |volume=61 |pages=12909–12922 |issue=19 |bibcode=2000PhRvB..6112909Z}}</ref>

Nitrogen is by far the most common impurity found in gem diamonds and is responsible for the yellow and brown color in diamonds. Boron is responsible for the blue color.<ref>{{cite journal| vauthors = Walker J |title=Optical absorption and luminescence in diamond|journal=Reports on Progress in Physics|volume=42|pages=1605–1659|year=1979|doi=10.1088/0034-4885/42/10/001|issue=10|bibcode=1979RPPh...42.1605W|url=http://accreditedgemologists.org/lightingtaskforce/OpticalAbsorptionand.pdf |archive-url=https://web.archive.org/web/20150906142645/http://accreditedgemologists.org/lightingtaskforce/OpticalAbsorptionand.pdf |archive-date=September 6, 2015 |url-status=live|citeseerx=10.1.1.467.443|s2cid=250857323 }}</ref> Color in diamond has two additional sources: irradiation (usually by alpha particles), that causes the color in green diamonds, and [[plastic deformation]] of the diamond crystal lattice. Plastic deformation is the cause of color in some brown<ref>{{cite journal| vauthors = Hounsome LS, Jones R, Shaw MJ, Briddon PR, Öberg S, Briddon P, Öberg S |title=Origin of brown coloration in diamond |journal=[[Physical Review B]] |volume=73 |page=125203|year=2006|doi=10.1103/PhysRevB.73.125203 |issue=12|bibcode=2006PhRvB..73l5203H}}</ref> and perhaps pink and red diamonds.<ref>{{cite book| vauthors = Wise RW |title=Secrets Of The Gem Trade, The Connoisseur's Guide To Precious Gemstones|publisher=Brunswick House Press|pages=223–224|year=2001|isbn=978-0-9728223-8-1}}</ref> In order of increasing rarity, yellow diamond is followed by brown, colorless, then by blue, green, black, pink, orange, purple, and red.<ref name=harlow/> "Black", or [[carbonado]], diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamond impurities replace a carbon atom in the [[crystal lattice]], known as a [[carbon flaw]]. The most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen present.<ref name=harlow/> The [[Gemological Institute of America]] (GIA) classifies low saturation yellow and brown diamonds as diamonds in the ''normal color range'', and applies a grading scale from "D" (colorless) to "Z" (light yellow). Yellow diamonds of high color saturation or a different color, such as pink or blue, are called ''fancy colored'' diamonds and fall under a different grading scale.<ref name=harlow/>

In 2008, the [[Wittelsbach Diamond]], a {{convert|35.56|carat|g|adj=on}} [[blue diamond]] once belonging to the King of Spain, fetched over US$24&nbsp;million at a Christie's auction.<ref>{{cite news |vauthors=Khan U |title=Blue-grey diamond belonging to King of Spain has sold for record 16.3{{nbsp}}GBP |url=https://www.telegraph.co.uk/culture/3703861/Blue-grey-diamond-belonging-to-King-of-Spain-has-sold-for-record-16.3m.html |work=[[The Daily Telegraph]] |location=London |date=December 10, 2008 |access-date=March 31, 2010 |archive-date=February 7, 2009 |archive-url=https://web.archive.org/web/20090207212758/http://www.telegraph.co.uk/culture/3703861/Blue-grey-diamond-belonging-to-King-of-Spain-has-sold-for-record-16.3m.html |url-status=live }}</ref> In May 2009, a {{convert|7.03|carat|g|adj=on}} [[blue diamond]] fetched the highest price per carat ever paid for a diamond when it was sold at auction for 10.5&nbsp;million Swiss francs (6.97&nbsp;million euros, or US$9.5&nbsp;million at the time).<ref>{{cite news|vauthors=Nebehay S|title=Rare blue diamond sells for record $9.5&nbsp;million|url=https://www.reuters.com/article/artsNews/idUSTRE54B6O020090512|work=Reuters|date=May 12, 2009|access-date=May 13, 2009|archive-date=May 16, 2009|archive-url=https://web.archive.org/web/20090516234031/http://www.reuters.com/article/artsNews/idUSTRE54B6O020090512|url-status=live}}</ref> That record was, however, beaten the same year: a {{convert|5|carat|g|adj=on}} vivid pink diamond was sold for US$10.8&nbsp;million in Hong Kong on December 1, 2009.<ref>{{cite news|url=https://www.reuters.com/article/idUSTRE5B02P620091201|title=Vivid pink diamond sells for record $10.8&nbsp;million|work=Reuters|date=December 1, 2009|vauthors=Pomfret J|access-date=July 1, 2017|archive-date=December 2, 2020|archive-url=https://web.archive.org/web/20201202103252/https://www.reuters.com/article/idUSTRE5B02P620091201|url-status=live}}</ref>