# Corderoite

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{{Short description|Extremely rare mercury sulfide chloride mineral}}
{{Infobox mineral
| name        = Corderoite
| category    = Halide mineral
| image       = Corderoite-Cinnabar-226331.jpg
| alt         = 
| caption     = Dark red bands of [cinnabar](/source/cinnabar) alternate with layers of tan [limonite](/source/limonite). The corderoite are the yellow-tan microcrystals.
| formula     = Hg<sub>3</sub>S<sub>2</sub>Cl<sub>2</sub>
| IMAsymbol   = Cde<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.FC.15a
| dana        =
| system      = [Cubic](/source/Cubic_crystal_system)
| class       = Tetartoidal (23) <br/><small>(same [H-M symbol](/source/H-M_symbol))</small>
| symmetry    = ''I2''<sub>1</sub>3
| unit cell   = a = 8.940(5)&nbsp;Å; Z&nbsp;=&nbsp;4
| color       = Pale orange-pink to salmon-pink; on exposure to light, rapidly darkening to pale gray, then black
| colour      = 
| habit       = Rare as cubic crystals; as rims and replacements of cinnabar
| twinning    = 
| cleavage    = 
| fracture    = 
| tenacity    =
| mohs        = 3
| luster      = 
| streak      = 
| diaphaneity = Transparent
| gravity     = 6.845 calc.
| density     = 
| polish      = 
| opticalprop = Isotropic
| refractive  = n > 2.5
| birefringence = 
| pleochroism = 
| 2V          = 
| dispersion  = 
| extinction  = 
| length fast/slow =
| fluorescence= 
| absorption  =
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| other       = 
| alteration  = 
| references  = <ref name=Handbook>http://rruff.geo.arizona.edu/doclib/hom/corderoite.pdf Handbook of Mineralogy</ref><ref name=Mindat>http://www.mindat.org/min-1127.html Mindat with location data</ref><ref name=Webmin>http://www.webmineral.com/data/Corderoite.shtml Webmineral data</ref>
}}
'''Corderoite''' is an extremely rare [mercury](/source/mercury_(element)) [sulfide](/source/sulfide) [chloride](/source/chloride) mineral with formula Hg<sub>3</sub>S<sub>2</sub>Cl<sub>2</sub>. It crystallizes in the [isometric](/source/Cubic_(crystal_system)) crystal system. It is soft, 1.5 to 2 on the Mohs scale, and varies in color from light gray to black and rarely pink or yellow.

It was first described in 1974 for occurrences in the McDermitt Mercury mine in [Humboldt County, Nevada](/source/Humboldt_County%2C_Nevada). The name is from the old name of the mine, the ''Old Cordero Mine.''<ref>{{Cite web |title=McDermitt Mine, Opalite Mining District, Humboldt County, Nevada, USA |url=http://www.mindat.org/loc-4206.html |access-date=2025-08-13 |website=www.mindat.org |language=en}}</ref>

== Structure ==
The structure of {{chem2|Hg3S2Cl2}} was determined in the 1960s before it was found in nature.<ref name=Foord/>
It has crankshaft chains that are crosswise linked by additional Hg²+.{{cn|date=July 2023}}
The crystals are [chiral](/source/chiral) (existing in two [enantiomorphic](/source/enantiomorphic) forms), in [space group](/source/space_group) I2{{sub|1}}3 (no. 199). The chloride ions form a lattice similar to a primitive cubic lattice (but with the ions slightly displaced along three-fold axes), and the sulfide ions form a similar lattice by occupying positions near the centres of the cubes of chloride ions, also on three-fold rotation axes. This gives eight chloride and eight sulfide ions per unit cell. The mercury ions are located on two-fold rotation axes that do not intersect the three-fold rotation axes. They occupy positions close to the centres of the faces of the chloride cubes, but only half of such positions are occupied, giving 12 mercury ions per unit cell. The closest neighbors of a mercury ion are two sulfide ions, at a distance of 2.422 [Å](/source/%C3%85ngstr%C3%B6m), the S-Hg-S angle being 165.1°. Each sulfide ion has three mercury ions near it, with the Hg-S-Hg angles being 94.1°. The nearest neighbors of a chloride ion are six mercury ions, at two somewhat different distances. A diagram can be seen on line, with blue balls representing mercury, green chlorine, and yellow sulfur.<ref>{{cite web |title=Corderoite |url=http://rruff.geo.arizona.edu/AMS/result.php?key=_database_code_amcsd%200009337&viewing=html |website=American Mineralogist Crystal Structure Database}} Click on "View JMOL 3-D Structure".</ref> Various sulfide halides of
Hg share the feature of being face-sharing [HgS<sub>2</sub>X<sub>4</sub>]{{sup|−6}} polyhedral, with X=Cl in the case of corderoite.

== Geologic occurrence ==
The main occurrence of corderoite in the [type locality](/source/Type_locality_(geology)) is in the Upper [Miocene](/source/Miocene) [playa](/source/Sink_(geography)) sediments within a thick zone, around {{convert|5|–|7|m|abbr=on}}, sub parallel to bedding. Lake sediments including altered [rhyolitic](/source/Rhyolite) [tuff](/source/tuff) and [ash](/source/Volcanic_ash) were deposited on the Tertiary rhyolitic volcanic rocks. Corderoite occurs as isolated grains or with cinnabar as replacements. Corderoite  occurs as a low temperature [supergene](/source/Supergene_(geology)) mineral.<ref name=Foord>Berendsen P., Foord E. E., and Storey L. O. (1974) "Corderoite, first natural occurrence of Hg<sub>3</sub>S<sub>2</sub>Cl<sub>2</sub>, from the Cordero mercury deposit, Humboldt County, Nevada". ''American Mineralogist'', 59, 652–655 http://www.minsocam.org/ammin/AM59/AM59_652.pdf</ref>

==References==
{{Reflist}}

*Grenchischev O. K. and Vasil'ev V. I. (1978) "First find of Corderoite (Hg<sub>3</sub>S<sub>2</sub>Cl<sub>2</sub>) in mercury ores of USSR". Doklady. 246/1-6, 145.
*Keller P., Lissner F., and Schleid T. (2005) "Single-crystal structure determination of Perroudite, Hg<sub>5</sub>Ag<sub>4</sub>S<sub>5</sub> (I,Br)<sub>2</sub>Cl<sub>2</sub>, from Tsumeb (Namiba), and its structural relationships to other sulfide halides of mercury and cinnabar." Stuttgart 181/1, 1–9.
*Lavrent'ev Y. G. and Vasil'ev V. I. (1986) "New finds and data on the composition of corderoite (Hg<sub>3</sub>S<sub>2</sub>Cl<sub>2</sub>)". ''Soviet Geology and Geophysics'', 27/12, 117–121.
*Modreski P. J. (1998) "Eugene Edward Foord, 1946–1998". ''The Canadian Mineralogist'', 36/2, 251–254.

Category:Sulfide minerals
Category:Chloride minerals
Category:Mercury(II) minerals
Category:Cubic minerals
Category:Minerals in space group 199
Category:Minerals described in 1974

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