Editing Crookesite

{{Short description|Selenide of copper, thallium and silver}}
{{Infobox mineral
| name        = Crookesite
| category    = Selenide mineral
| boxwidth    = 
| boxbgcolor  = 
| image       =  File:Crookesite.jpg 
| imagesize   = 
| caption     = 
| formula     = {{chem|[[Copper|Cu]]|7|([[Thallium|Tl]]|, [[Silver|Ag]])|[[Selenium|Se]]|4}}
| IMAsymbol=Crk<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.BD.50
| system      = [[Tetragonal]]
| class       = Disphenoidal ({{overline|4}}) <br/>[[H-M symbol]]: ({{overline|4}})
| symmetry    = ''I''{{overline|4}}
| color       = Lead-gray
| habit       = As finely divided, disseminated specks, and as small veinlets.
| twinning    = 
| cleavage    = Good, two at right angles
| fracture    = Brittle
| mohs        = 2.5–3
| luster      = Metallic
| refractive  = 
| opticalprop = 
| birefringence = 
| pleochroism = 
| streak      = 
| gravity     = 6.90
| density     = 
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| diaphaneity = Opaque
| other       = 
| references  = <ref name=Webmin>[http://webmineral.com/data/Crookesite.shtml Webmineral site]</ref><ref>[http://rruff.geo.arizona.edu/doclib/hom/crookesite.pdf Handbook of Mineralogy]
</ref>
}}

'''Crookesite''' is a [[selenide]] [[mineral]] composed of [[copper]] and [[selenium]] with variable [[thallium]] and [[silver]].

==Characteristics==
Its chemical formula is reported either as {{chem|[[Copper|Cu]]|7|([[Thallium|Tl]]|, [[Silver|Ag]])|[[Selenium|Se]]|4}} or {{chem|([[Copper|Cu]]|, [[Thallium|Tl]]|, [[Silver|Ag]])|2|[[Selenium|Se]]}}.<ref>http://www.mindat.org/min-1159.html Mindat</ref> It is formed by precipitation from [[hydrothermal]] fluids, and contains by mass: 16.3%&nbsp;Tl, 47.3%&nbsp;Cu, 2.9%&nbsp;Ag, and 33.6%&nbsp;Se.<ref name=Webmin/>

Crookesite is an opaque, bluish grey to pink toned brown metallic mineral crystallizing in the [[tetragonal]] system. It has a [[Mohs hardness]] of 2.5 to 3 and a [[specific gravity]] of 6.9.

==Name and discovery==
It was discovered in 1866 in Skrikerum, Sweden and named for Sir [[William Crookes]] (1832–1919), the discoverer of the element thallium.<ref name=Webmin/>

==See also==
* [[List of minerals]]
* [[List of minerals named after people]]
* {{Annotated link|Sabatierite}}

==References==
{{Reflist}}
{{Refbegin}}
* {{cite journal | doi = 10.1007/BF00815324 | title = Characterization of TlCu<sub>7</sub>S<sub>4</sub>, a crookesite analogue | year = 1987 | last1 = Berger | first1 = Rolf A. | last2 = Sobott | first2 = Robert J. | journal = Monatshefte für Chemie | volume = 118 | issue = 8–9 | pages = 967–972| s2cid = 102058943 }}
* {{cite journal | doi = 10.1524/zkri.1987.181.1-4.241 | url = http://rruff.geo.arizona.edu/doclib/zk/vol181/ZK181_241.pdf | title =Crookesite and sabatierite in a new light. A crystallographer's comment | first =   R..A. | last =  Berger | journal = Zeitschrift für Kristallographie | year = 1987 | volume = 181| issue = 1–4 | pages = 241–249|bibcode = 1987ZK....181..241B }}
{{Refend}}

[[Category:Silver minerals]]
[[Category:Copper(I) minerals]]
[[Category:Thallium minerals]]
[[Category:Selenide minerals]]
[[Category:Tetragonal minerals]]
[[Category:Minerals in space group 82]]


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