Editing Orpiment (section)

{{Short description|Orange-yellow arsenic sulfide mineral}}
{{infobox mineral
| name        = Orpiment
| category    = [[Sulfide mineral]]
| boxwidth    = 
| boxbgcolor  = 
| image       = Orpiment-148270.jpg
| imagesize   =
| alt         =
| caption     = Orpiment crystal from Twin Creeks Mine, Potosi District, [[Humboldt County, Nevada]], United States (Size: 3.3 cm × 2.1 cm × 2.1 cm)
| formula     = As<sub>2</sub>S<sub>3</sub>
| IMAsymbol   = Orp<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.FA.30
| dana        =
| system      = [[Monoclinic]]
| class       = Prismatic (2/m) <br /><small>(same [[H-M symbol]])</small>
| symmetry    = ''P''2<sub>1</sub>/n
| unit cell   = a = 11.475(5), b = 9.577(4) <br />c = 4.256(2)&nbsp;[Å], β = 90.45(5)°; Z&nbsp;=&nbsp;4
| color       = Lemon-yellow to golden or brownish yellow
| colour      = 
| habit       = Commonly in foliated columnar or fibrous aggregates; may be reniform or botryoidal; also granular or powdery; rarely as prismatic crystals
| twinning    = On {100}
| cleavage    = Perfect on {010}, imperfect on {100};
| fracture    = 
| tenacity    = [[Sectility|Sectile]]
| mohs        = 1.5–2
| luster      = Resinous, pearly on cleavage surface
| streak      = Pale lemon-yellow
| diaphaneity = Transparent
| gravity     = 3.49
| density     = 
| polish      = 
| opticalprop = Biaxial (−)
| refractive  = n<sub>α</sub> = 2.400 n<sub>β</sub> = 2.810 n<sub>γ</sub> = 3.020
| birefringence = δ = 0.620
| pleochroism = In reflected light, strong, white to pale gray with reddish tint; in transmitted light, Y = yellow, Z = greenish yellow 
| 2V          = Measured: 30° to 76°, Calculated: 62°
| dispersion  = r > v, strong
| extinction  = 
| length fast/slow =
| fluorescence= 
| absorption  =
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| other       = 
| alteration  = 
| references  =<ref name=Handbook>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Orpiment |url=http://www.handbookofmineralogy.org/pdfs/orpiment.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=14 March 2022 |date=2005}}</ref><ref name=Mindat>{{mindat|id=3021|title=Orpiment|accessdate=26 May 2022}}</ref><ref name=Webmin>{{WebMineral|url=http://webmineral.com/data/Orpiment.shtml|name=Orpiment|accessdate=26 May 2022}}</ref>
}}
'''Orpiment''', also known as ″'''yellow [[arsenic blende]]'''″ is a deep-colored, orange-yellow [[arsenic]] [[sulfide mineral]] with formula {{chem|As|2|S|3}}. It is found in volcanic [[fumarole]]s, low-temperature [[hydrothermal]] veins, and [[hot spring]]s and may be formed through [[sublimation (phase transition)|sublimation]].

Orpiment takes its name from the Latin ''auripigmentum'' (''aurum'', "gold" + ''pigmentum'', "[[pigment]]"), due to its deep-yellow color. Orpiment once was widely used in artworks, medicine, and other applications. Because of its toxicity and instability, its usage has declined.