Editing Opal (section)

=== Virgin Valley, Nevada ===
[[File:nev opal09.jpg|thumb|Multicolored rough opal specimen from Virgin Valley, Nevada, US]]

The Virgin Valley<ref>{{cite web|url=http://www.mindat.org/loc-5881.html|title=Virgin Valley District, Humboldt Co., Nevada|website=mindat.org|url-status=live|archive-url=https://web.archive.org/web/20120430090041/http://www.mindat.org/loc-5881.html|archive-date=30 April 2012|df=dmy-all}}</ref> opal fields of [[Humboldt County, Nevada|Humboldt County]] in northern [[Nevada]] produce a wide variety of precious black, crystal, white, fire, and lemon opal. The black fire opal is the official gemstone of Nevada. Most of the precious opal is partial wood replacement. The precious opal is hosted and found ''[[In situ#Earth and atmospheric sciences|in situ]]'' within a subsurface horizon or zone of [[bentonite]], which is considered a "lode" deposit. Opals which have weathered out of the ''in situ'' deposits are alluvial and considered [[placer deposit]]s. [[Miocene]]-age opalised teeth, bones, fish, and a snake head have been found. Some of the opal has high water content and may desiccate and crack when dried. The largest producing mines of Virgin Valley have been the famous Rainbow Ridge,<ref>{{cite web|url=http://www.mindat.org/loc-19286.html|title=Rainbow Ridge Mine|website=mindat.org|url-status=live|archive-url=https://web.archive.org/web/20120430115218/http://www.mindat.org/loc-19286.html|archive-date=30 April 2012|df=dmy-all}}</ref> Royal Peacock,<ref>{{cite web|url=http://www.mindat.org/loc-30709.html|title=Royal Peacock Group Mines, Virgin Valley District, Humboldt Co., Nevada|website=mindat.org|url-status=live|archive-url=https://web.archive.org/web/20120430124208/http://www.mindat.org/loc-30709.html|archive-date=30 April 2012|df=dmy-all}}</ref> Bonanza,<ref>{{cite web|url=http://www.mindat.org/loc-8801.html|title=Bonanza Opal Workings (Virgin Opal), Virgin Valley District, Humboldt Co., Nevada|website=mindat.org|url-status=live|archive-url=https://web.archive.org/web/20120430120653/http://www.mindat.org/loc-8801.html|archive-date=30 April 2012|df=dmy-all}}</ref> Opal Queen,<ref>{{cite web|url=http://www.mindat.org/loc-213530.html|title=Opal Queen group, Virgin Valley District, Humboldt Co., Nevada|website=mindat.org|url-status=live|archive-url=https://web.archive.org/web/20120430115233/http://www.mindat.org/loc-213530.html|archive-date=30 April 2012|df=dmy-all}}</ref> and WRT Stonetree/Black Beauty<ref>{{cite web|url=http://www.mindat.org/loc-228982.html|title=Stonetree Opal Mine, WRT Stonetree group, Virgin Valley District, Humboldt Co., Nevada|website=mindat.org|url-status=live|archive-url=https://web.archive.org/web/20120430115929/http://www.mindat.org/loc-228982.html|archive-date=30 April 2012|df=dmy-all}}</ref> mines. The largest unpolished black opal in the Smithsonian Institution, known as the "Roebling opal",<ref>{{cite web|url=http://geogallery.si.edu/index.php/en/1167897/roebling-opal/1|title=Roebling Opal|publisher=National Museum of Natural History|url-status=dead|archive-url=https://web.archive.org/web/20121107052201/http://geogallery.si.edu/index.php/en/1167897/roebling-opal/1|archive-date=7 November 2012|df=dmy-all}}</ref> came out of the tunneled portion of the Rainbow Ridge Mine in 1917, and weighs {{convert|2585|carat|g oz}}. The largest polished black opal in the [[Smithsonian Institution]] comes from the Royal Peacock opal mine in the Virgin Valley, weighing {{convert|160|carat|g oz}}, known as the "Black Peacock".<ref>{{cite journal|journal=Lapidary Journal|title=Opal|date=March 1971|pages=1522, 1542}}</ref>