View source for Argentite

[[Image:Argentite.jpg|thumb|Argentite sample]]
[[Image:Argentite-unit-cell-3D-balls.png|thumb|The unit cell of '''argentite''']]

In [[mineralogy]], '''argentite''' ({{etymology|la|{{wikt-lang|la|argentum}}| silver}}) is [[cubic crystal system|cubic]] [[silver sulfide]] (Ag<sub>2</sub>S), which can only exist at temperatures above {{cvt|173|C|F}},<ref name=de>{{cite web |url=https://mineralienatlas.de/lexikon/index.php/MineralData?mineral=Argentit |title=Argentit |publisher=Mineralienatlas Lexikon |language=de}}</ref> {{cvt|177|C|F}},<ref name=Mindat>{{Mindat |id=326 |name=Argentite}}</ref> or {{cvt|179|C|F}}.<ref name=Webmin>{{WebMineral |url=https://webmineral.com/data/Argentite.shtml |title=Argentite Mineral Data}}</ref> When it cools to ordinary temperatures it turns into its [[monoclinic]] [[Polymorphism (materials science)|polymorph]], [[acanthite]].<ref name=Mindat/><ref name=Webmin/> The [[International Mineralogical Association]] has decided to reject argentite as a proper mineral.<ref name=Webmin/>

The name "argentite" sometimes also refers to [[pseudomorph]]s of argentite: specimens of acanthite which still display some of the outward signs of the cubic crystal form, even though their actual crystal structure is monoclinic due to the lower temperature.<ref name=Mindat/><ref name=de/> This form of acanthite is occasionally found as uneven [[cube]]s and [[octahedron|octahedra]], but more often as dendritic or earthy masses, with a blackish lead-grey color and metallic luster.{{sfn|Spencer|1911}}

Argentite belongs to the [[galena]] group. [[Cleavage (crystal)|Cleavage]], which is so prominent a feature in galena, here presents only in traces. The mineral is perfectly [[Sectility|sectile]] and has a shining streak; [[hardness]] 2.5, [[specific gravity]] is 7.2–7.4. It occurs in mineral veins, and when found in large masses, as in  [[Mexico]] and in the [[Comstock Lode]] in [[Nevada]], it forms an important [[ore]] of silver. The mineral was mentioned in 1529 by [[G. Agricola]], but the name ''argentite'' was not used till 1845 and is due to [[W. Haidinger]]. Old names for the species are ''Glaserz'', ''silver-glance'' and ''vitreous silver''. A related copper-rich mineral occurring e.g. in [[Jalpa, Zacatecas]], [[Mexico]], is known as [[jalpaite]].{{sfn|Spencer|1911}}

==References==
{{Reflist}}
*{{EB1911|first=Leonard James |last=Spencer|authorlink=Leonard James Spencer|wstitle=Argentite|volume=2|page=475}}

==External links==
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[[Category:Silver minerals]]
[[Category:Sulfide minerals]]