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Cuprite
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{{Short description|Oxide mineral}} {{Infobox mineral | name = Cuprite | category = [[Oxide mineral]] | boxwidth = | boxbgcolor =#982e27 | boxtextcolor = #fff | image = CupriteUSGOV.jpg | alt = | caption = Cuprite from [[Morenci, Arizona]] | formula = Cu<sub>2</sub>O | IMAsymbol=Cpr<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = | strunz = 4.AA.10 | dana = 4.1.1.1 | system = [[Cubic crystal system|Cubic]] | class = Hexoctahedral (m{{overline|3}}m) <br/>[[H-M symbol]]: (4/m {{overline|3}} 2/m) | symmetry = ''P''n{{overline|3}}m | unit cell = a = 4.2685 Å; V = 77.77 Å<sup>3</sup>; Z = 2 | color = Dark red to cochineal red, sometimes almost black | colour = | habit = Cubic, octahedral, and dodecahedral crystals; as hairlike capillary forms, earthy, compact granular and massive | twinning = Penetration twins | cleavage = Fair in four directions forming octahedrons | fracture = Conchoidal to uneven | tenacity = Brittle | mohs = 3.5 to 4 | luster = Adamantine, sub-metallic, earthy | streak = Shining metallic brownish-red | diaphaneity = Transparent, translucent | gravity = 6.14 | density = | polish = | opticalprop = Isotropic | refractive = n = 2.849 | birefringence = | pleochroism = Visible | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = | alteration = | references = <ref name=Mindat>{{cite web|url=http://www.mindat.org/min-1172.html|title=Cuprite|publisher=Mindat|accessdate=2010-07-10}}</ref><ref name=Webmin>{{cite web|url=http://www.webmineral.com/data/Cuprite.shtml|title=Cuprite|publisher=Webmineral data|accessdate=2010-07-10}}</ref><ref name=Handbook>[http://rruff.geo.arizona.edu/doclib/hom/cuprite.pdf Handbook of Mineralogy]</ref> }} '''Cuprite''' is an [[oxide mineral]] composed of [[copper(I) oxide]] Cu<sub>2</sub>O, and is a minor [[ore]] of [[copper]].<ref name=EB1911>{{cite EB1911 |wstitle=Cuprite |volume=12 |page=635 |first=Leonard James |last=Spencer |authorlink=Leonard James Spencer}}</ref> [[File:Cuprite-66649.jpg|thumb|left|Cuprite from Tsumeb Mine (size:2.3 x 2.1 x 1.2 cm]] Its dark crystals with red internal reflections are in the [[Cubic crystal system|isometric]] system hexoctahedral class, appearing as cubic, octahedral, or dodecahedral forms, or in combinations. Penetration [[Crystal twinning|twins]] frequently occur. In spite of its nice color, it is rarely used for [[jewelry]] because of its low [[Mohs hardness]] of 3.5 to 4. It has a relatively high [[specific gravity]] of 6.1, imperfect cleavage and is brittle to conchoidal fracture. The luster is sub-metallic to brilliant adamantine. The "chalcotrichite" (from <span title="chalkós thríx trichós">{{langx|grc|χαλκός θρίξ τριχός}}, "plush copper ore")</span><ref name=EB1911/> variety typically shows greatly elongated (parallel to [001]) capillary or needle like crystals forms. [[Image:Chalcotrichite.jpg|thumb|left|Chalcotrichite from Ray, Arizona]] It is a secondary mineral which forms in the oxidized zone of copper sulfide deposits. It frequently occurs in association with [[native copper]], [[azurite]], [[chrysocolla]], [[malachite]], [[tenorite]] and a variety of [[iron oxide]] minerals.<ref name=Hurlbut>Hurlbut, Cornelius S.; Klein, Cornelis, 1985, ''Manual of Mineralogy,'' 20th ed., Wiley, p. 299-300 {{ISBN|0-471-80580-7}}</ref> It is known as ''ruby copper'' due to its distinctive red color. Cuprite was first described by [[Wilhelm Karl Ritter von Haidinger]] in 1845 and the name derives from the [[Latin]] ''cuprum'' for its copper content.<ref name=EB1911/><ref name=Webmin/> Cuprite is found in the [[Ural Mountains]], [[Altai Mountains]], and [[Sardinia]], and in more isolated locations in [[Cornwall]], [[France]], [[Arizona]], [[Chile]], [[Bolivia]], and [[Namibia]].<ref>Joel E. Arem, Ph.D., F.G.A., ''Color Encyclopedia of Gemstones'', 1977, Van Nostrand Reinhold Company</ref> == As a gemstone == Though almost all crystals of cuprite are far too small to yield faceted [[gemstone]]s, one unique deposit from Onganja in [[Seeis]], [[Namibia]], which was discovered in the 1970s, has produced crystals which were both large and gem quality. Virtually every faceted stone over one carat (0.2 g) in weight is from this single deposit, which has long since been mined out. The number of faceted gems over two carats (0.4 g) is difficult to estimate, but according to Joel Arem, one-time curator for the [[Smithsonian]] [[National Gem and Mineral Collection]] in [[Washington, D.C.]], faceted cuprite of any size is considered one of the most collectible and spectacular gems in existence, with its deep garnet coloring and higher brilliance than a diamond. Only the gem's soft nature prevents it from being among the most valuable jewelry stones. ==See also== *[[Bornite]] *[[Tennantite]] *[[Tenorite]] CuO *[[Tetrahedrite]] ==References== {{Wiktionary}} {{Reflist}} [[Category:Copper ores]] [[Category:Alchemical substances]] [[Category:Oxide minerals]] [[Category:Cubic minerals]] [[Category:Minerals in space group 224]] [[Category:Luminescent minerals]] [[Category:Minerals described in 1845]]
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