# Tyrrellite

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{{Short description|Selenide mineral}}
{{Infobox mineral
| name        = Tyrrellite
| category    = [Selenide mineral](/source/Selenide_mineral) <br />[Thiospinel group](/source/Thiospinel_group) <br /><small>(Spinel structural group)</small>
| boxwidth    =
| image       =Tyrrellite, Chalcomenite, Umangite-652476.jpg
| caption     =
| formula     = {{chem2|Cu(Co,Ni)2Se4}}
| IMAsymbol   = Ty<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.DA.05
| system      = [Isometric](/source/Cubic_crystal_system)
| class       = Hexoctahedral (m{{overline|3}}m) <br/>[H-M symbol](/source/H-M_symbol): (4/m {{overline|3}} 2/m)
| symmetry    = ''F''d{{overline|3}}m
| unit cell   = a= 10.005&nbsp;Å; Z&nbsp;=&nbsp;8
| color       = light bronze
| habit       = granular
| twinning    =
| cleavage    =  {001} Distinct
| fracture    = conchoidal
| tenacity    = brittle
| mohs        = 3.5
| luster      = metallic
| refractive  =
| opticalprop =
| birefringence = 
| pleochroism = 
| streak      = black
| gravity     = 6.6 ± 0.2
| density     =
| melt        =
| fusibility  =
| diagnostic  =
| solubility  =
| diaphaneity = Opaque
| other       =
| references  = <ref name=Webmin>[http://webmineral.com/data/Tyrrellite.shtml Webmineral data]</ref><ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/tyrrellite.pdf Handbook of Mineralogy]</ref><ref name=Mindat>[http://www.mindat.org/min-4071.html Mindat.org]</ref><ref name=Rob>Robinson, S.C. and Brooker, E.J. (1952) A cobalt-nickel-copper selenide from the Goldfields District, Saskatchewan. American Mineralogist, 37, 542-544.</ref>
}}

'''Tyrrellite''' is a [selenide mineral](/source/selenide_mineral) that has a chemical formula of {{chem2|Cu(Co,Ni)2Se4}}.<ref name=Mindat/>  It has been found in the Goldfields District in northern [Saskatchewan](/source/Saskatchewan), as well as in the Petrovice deposit, [Czech Republic](/source/Czech_Republic).<ref name=HBM/> It is named after the Canadian geologist [Joseph Burr Tyrrell](/source/Joseph_Burr_Tyrrell). Joseph Tyrrell was one of the first geologists from the Geological Survey of Canada to do research in the Goldfields District.<ref name=Harris>Harris, D.C. (1970) New Data on Tyrrellite. The Canadian Mineralogist, 10, 731-735.</ref>

==Crystallography==
Tyrrellite is [isometric](/source/Cubic_crystal_system), meaning that crystallographically, it has three axes of equal length perpendicular to one another. It belongs to the space group, Fd3m.<ref name=Rob/> Because tyrrellite is isometric, it is also isotropic. Isotropic minerals are defined as follows: when light passes through an isometric mineral, the light moves in all directions with equal velocity. In contrast, for anisotropic minerals, the velocity of light passing through the mineral varies with crystallographic direction.<ref>Klein, C., Dutrow, B. (2007) The 23rd edition of the Manual of Mineral Science. John Wiley Publishers, p. 290</ref>  Tyrrellite displays a light bronze color when viewed in plane polarized light.<ref name=Harris/>  Because tyrrellite is isotropic, the light bronze color will remain constant as the mineral is rotated and viewed from different crystallographic angles. When viewed under cross polarized light, tyrrellite displays total extinction, a characteristic trait of isotropic minerals.

==Discovery and occurrence==
It was first described in 1953 for an occurrence in the Goldfields District, Saskatchewan,<ref name=Harris/> while the second occurrence was reported in Petrovice deposit, Czech Republic.<ref name=HBM/> In general, tyrrellite is veined, embayed and replaced by [umangite](/source/umangite), a primary mineral of deposits in which tyrrellite is found.<ref name=Rob/> The relative scarcity and unique occurrences of tyrrellite can give geologists considerable insight into the circumstances under which the parent rock formed.

==References==
{{Reflist}}

Category:Copper minerals
Category:Cobalt minerals
Category:Nickel minerals
Category:Selenide minerals
Category:Thiospinel group
Category:Cubic minerals
Category:Minerals in space group 227

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Adapted from the Wikipedia article [Tyrrellite](https://en.wikipedia.org/wiki/Tyrrellite) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Tyrrellite?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.