View source for Chalcocite

{{Short description|Sulfide mineral}}
{{Infobox mineral
| name        = Chalcocite
| category    = [[Sulfide minerals]]
| boxwidth    = 
| boxbgcolor  = 
| image       = Chalcocite-253980.jpg
| caption     = Chalcocite from [[Cornwall]]
| formula     = [[copper]](I) [[sulfide]]: Cu<sub>2</sub>S
| IMAsymbol   = Cc<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      = 2.BA.05a
| system      = [[Monoclinic]]
| class       = Prismatic (2/m) <br/><small>(same [[H-M symbol]])</small>
| symmetry    = ''P2''<sub>1</sub>/c
| unit cell   = a = 15.246(4)&nbsp;Å, <br/>b = 11.884(2)&nbsp;Å, <br/>c = 13.494(3)&nbsp;Å; <br/>β = 116.35(1)°; Z&nbsp;=&nbsp;48
| color       = Dark gray to black
| habit       = Tabular to prismatic crystals also massive to granular, (pseudo-orthorhombic)
| twinning    = Common on {110} yielding pseudohexagonal stellate forms
| cleavage    = Indistinct on {110}
| fracture    = Conchoidal
| tenacity    = Brittle to [[Sectility|sectile]]
| mohs        = {{frac|2|1|2}}&ndash;3
| luster      = Metallic
| refractive  = 
| opticalprop = 
| birefringence = 
| pleochroism = 
| streak      = Shiny black to lead gray
| gravity     = 5.5&ndash;5.8
| melt        = 
| fusibility  = 2&ndash;2.5
| diagnostic  = 
| solubility  = 
| diaphaneity = Opaque
| other       = 
| references  = <ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Chalcocite Mineralienatlas]</ref><ref name=Mindat>[http://www.mindat.org/min-962.html Mindat.org]</ref><ref name=Webmin>[https://webmineral.com/data/Chalcocite.shtml Webmineral.com]</ref><ref name=HBM>[https://rruff.geo.arizona.edu/doclib/hom/chalcocite.pdf Handbook of Mineralogy]</ref>
}}

'''Chalcocite''' ({{IPAc-en|'|k|æ|l|k|ə|ˌ|s|aɪ|t}}),<ref>{{cite Collins Dictionary|chalcocite}}</ref><ref>{{cite Dictionary.com|chalcocite}}</ref> [[copper(I) sulfide]] (Cu<sub>2</sub>S), is an important [[copper]] [[ore]] [[mineral]]. It is [[opacity (optics)|opaque]] and dark gray to black, with a metallic [[lustre (mineralogy)|luster]]. It has a hardness of 2.5&ndash;3 on the [[Mohs scale]].  It is a [[sulfide]] with a [[monoclinic]] crystal system.

The term ''chalcocite'' from the [[Greek language|Greek]] ''khalkos'', meaning "copper". It is also known as '''redruthite''', '''vitreous copper''', or '''copper-glance'''.<ref>{{cite EB1911|wstitle=Copper-glance|volume=7|page=110}}</ref>

==Occurrence==
Chalcocite is sometimes found as a primary [[vein (geology)|vein]] mineral in [[hydrothermal]] veins. However, most chalcocite occurs in the [[Supergene (geology)|supergene]] enriched environment below the oxidation zone of copper deposits as a result of the leaching of copper from the oxidized minerals. It is also often found in [[sedimentary rock]]s.

It has been mined for centuries and is one of the most profitable copper ores. The reasons for this is its high copper content (66.7% atomic ratio and nearly 80% by weight) and the ease at which copper can be separated from [[sulfur]]. 

Since chalcocite is a secondary mineral that forms from the alteration of other minerals, it has been known to form [[pseudomorph]]s of many different minerals. A pseudomorph is a mineral that has replaced another mineral atom by atom, but it leaves the original mineral's crystal shape intact. Chalcocite has been known to form pseudomorphs of the minerals [[bornite]], [[covellite]], [[chalcopyrite]], [[pyrite]], [[enargite]], millerite, [[galena]] and [[sphalerite]].

[[File:Chalcocite-139819.jpg|thumb|left|Chalcocite crystals from the Mammoth Mine, Mount Isa – Cloncurry area, Queensland, Australia (size: 3.0 x 2.9 x 2.4 cm)]]

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==See also==
*[[Copper(I) sulfide]]
*[[Copper monosulfide]]

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==References==
{{Reflist}}
*Dana's Manual of Mineralogy {{ISBN|0-471-03288-3}}
*[https://web.archive.org/web/20041013111535/http://mineral.galleries.com/minerals/sulfides/chalcoci/chalcoci.htm Mineral Galleries]


{{Commons category|Chalcocite|position=left}}

{{Ores}}

[[Category:Copper ores]]
[[Category:Sulfide minerals]]
[[Category:Monoclinic minerals]]
[[Category:Minerals in space group 14]]