Editing Arsenopyrite

{{Short description|Iron-arsenic sulfide mineral}}
{{Infobox mineral
| name        = Arsenopyrite
| category    = [[Sulfide mineral]]
| boxwidth    =
| boxbgcolour  =
| image       = Arsenopyrite-117874.jpg
| imagesize   = 260px
| alt         = 
| caption     = 
| formula     = FeAsS
| strunz      = 2.EB.20
| system      = [[Monoclinic]]
| class       = Prismatic (2/m) <br/><small>(same [[H-M symbol]])</small>
| symmetry    = ''P''2<sub>1</sub>/c
| unit cell   = a = 5.744, b = 5.675 <br/>c = 5.785&nbsp;[Å]; β = 112.3°; Z&nbsp;=&nbsp;4
| colour       = Steel grey to silver white
| habit       = Acicular, off-square prismatic, stubby; striated; also compact, granular, columnar
| twinning    = Common on {100} and {001}, contact/penetration twinning on {101}
| cleavage    = 110 (distinct)
| fracture    = Subconchoidal to rough
| tenacity    = Brittle
| mohs        = 5.5–6
| lustre      = Metallic
| refractive  =
| opticalprop = Anisotropism – strong red-violet
| birefringence =
| pleochroism = Weak, white or bluish tint, faint reddish yellow
| streak      = Black
| gravity     = 5.9–6.2
| melt        =
| fusibility  = Yes
| diagnostic  =
| solubility  = Nitric acid
| diaphaneity = Opaque
| other       = Garlic odour when struck, greenish tinge when weathered, green staining of wall rocks
| references  = <ref name=Hurlbut>Hurlbut, C. S.; Klein, C., 1985, Manual of Mineralogy, 20th ed., {{ISBN|0-471-80580-7}}</ref><ref name=Handbook>[http://rruff.geo.arizona.edu/doclib/hom/arsenopyrite.pdf  Handbook of Mineralogy]</ref><ref name=Mindat>[http://www.mindat.org/min-305.html Mindat.org]</ref>
}}

'''Arsenopyrite''' ([[International Mineralogical Association|IMA]] [[List of mineral symbols|symbol]]: Apy<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>) is an iron arsenic [[sulfide]] (FeAsS). It is a hard ([[Mohs scale of mineral hardness|Mohs]] 5.5–6)<ref>{{Cite web |title=Mohs Hardness Scale: Testing the Resistance to Being Scratched |url=https://geology.com/minerals/mohs-hardness-scale.shtml |access-date=2024-04-10 |website=geology.com}}</ref> metallic, opaque, steel grey to silver white mineral with a relatively high [[specific gravity]] of 6.1.<ref name=Hurlbut/>  

When dissolved in [[nitric acid]], it releases elemental [[sulfur]].  When arsenopyrite is heated, it produces sulfur and arsenic vapor. With 46% [[arsenic]] content, arsenopyrite, along with [[orpiment]], is a principal [[ore]] of arsenic. When deposits of arsenopyrite become exposed to the atmosphere, the mineral slowly converts into  iron arsenates.  Arsenopyrite is generally an acid-consuming sulfide mineral, unlike [[pyrite|iron pyrite]] which can lead to [[acid mine drainage]].{{citation needed|date=May 2021}}

The [[crystal habit]], hardness, density, and garlic odour when struck are diagnostic. Arsenopyrite in older literature may be referred to as ''mispickel'', a name of German origin.<ref>[http://www.mindat.org/min-4652.html Mindat Mispickel]</ref> It is also sometimes referred to as [[mundic]], a word derived from [[Cornish dialect]] and which also refers to a copper ore, as well as a form of deterioration in aggregate concrete made with mine tailings.

Arsenopyrite also can be associated with significant amounts of [[gold]]. Consequently, it serves as an indicator of gold bearing reefs. Many arsenopyrite gold ores are [[refractory]], i.e. the gold is not easily cyanide leached from the mineral matrix.

Arsenopyrite is found in high temperature [[hydrothermal]] veins, in [[pegmatite]]s, and in areas of [[contact metamorphism]] or [[metasomatism]].

==Crystallography==
[[File:Arsenopyrite-176706.jpg|thumb|left|upright|Arsenopyrite crystal from the Yaogangxian Mine, Hunan, China (size: 2.7 x 2.0 x 1.7 cm)]]
Arsenopyrite crystallizes in the [[monoclinic]] [[crystal system]] and often shows prismatic crystal or columnar forms with [[Striation (geology)|striation]]s and [[Crystal twinning|twinning]] common. Arsenopyrite may be referred to in older references as [[orthorhombic]], but it has been shown to be monoclinic.  In terms of its atomic structure, each Fe center is linked to three As atoms and three S atoms.  The material can be described as Fe<sup>3+</sup> with the diatomic trianion AsS<sup>3−</sup>.  The connectivity of the atoms is more similar to that in [[marcasite]] than [[pyrite]].  The ion description is imperfect because the material is semiconducting and the Fe-As and Fe-S bonds are highly [[covalent]].<ref>Vaugn, D. J.; Craig, J. R. Mineral Chemistry of Metal Sulfides" Cambridge University Press, Cambridge: 1978. {{ISBN|0-521-21489-0}}.</ref>

[[File:Arsenopyrite by petrographic microscope NL.jpg|thumb|upright|Microscopic picture of arsenopyrite]]

==Related minerals==
Various [[Transition metal|transition]] group metals can substitute for iron in arsenopyrite. The arsenopyrite group includes the following rare minerals:
*[[Clinosafflorite]]: {{chem2|(Co,Fe,Ni)AsS}}
*[[Gudmundite]]: {{chem2|FeSbS}}
*[[Glaucodot]] or [[alloclasite]]: {{chem2|(Fe,Co)AsS}} or {{chem2|(Co,Fe)AsS}}
*[[Iridarsenite]]: {{chem2|(Ir,Ru)AsS}}
*[[Osarsite]] or [[ruarsite]]: {{chem2|(Os,Ru)AsS}} or {{chem2|(Ru,Os)AsS}}

==See also==
* {{Portal-inline|Earth sciences}}
* [[Classification of minerals (disambiguation)|Classification of minerals]]
* [[List of minerals]]

==References==
{{Reflist}}

==External links==
* {{Commons-inline}}

{{Authority control}}

[[Category:Iron minerals]]
[[Category:Sulfide minerals]]
[[Category:Arsenic minerals]]
[[Category:Monoclinic minerals]]
[[Category:Minerals in space group 14]]