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Orpiment

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Formula:
As
 
2
S
 
3
System:MonoclinicColour:Orange-yellow to ...
Lustre:PearlyHardness:1½ - 2
Name:From Latin "aurum", gold, and "pigmentum", pigment, in allusion to its color.


May be visually similar to uzonite.

Classification of Orpiment

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:2/F.02-70
Nickel-Strunz 10th (pending) edition ID:2.FA.30

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
F : Sulfides of arsenic, alkalies; sulfides with halide, oxide, hydroxide, H2O
A : With As, (Sb), S
Dana 8th edition ID:2.11.1.1

2 : SULFIDES
11 : AmBnXp, with (m+n):p = 2:3
Hey's CIM Ref.:3.7.8

3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
7 : Sulphides etc. of V, As, Sb and Bi
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Occurrences of Orpiment

Geological Setting:In low-temperature hydrothermal veins, hot springs and fumaroles; also commonly as an alteration product of arsenic minerals, especially realgar.

Physical Properties of Orpiment

Lustre:Pearly
Diaphaneity (Transparency):Transparent
Colour:Orange-yellow to lemon-yellow
Streak:Light lemon yellow
Hardness (Mohs):1½ - 2
Tenacity:Sectile
Cleavage:Perfect
Perfect {010} imperfect {100}
Density (measured):3.49 g/cm3
Density (calculated):3.48 g/cm3

Crystallography of Orpiment

Crystal System:Monoclinic
Class (H-M):2/m - Prismatic
Cell Parameters:a = 11.475(5) Å, b = 9.577(4) Å, c = 4.256(2) Å
β = 90.45(5)°
Ratio:a:b:c = 1.198 : 1 : 0.444
Unit Cell Volume:V 467.70 ų (Calculated from Unit Cell)
Z:4
Morphology:Commonly in foliated columnar or fibrous aggregates, with cleavages as much as 60 cm across; may be reniform or botryoidal; also granular or powdery; rarely as prismatic crystals.
Twinning:On {100}
Comment:sp. gr. P21/n
Crystal Atlas:
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Orpiment no.3 - Goldschmidt (1913-1926)
Orpiment no.13 - Goldschmidt (1913-1926)
Orpiment - Tabular {010}

About Crystal Atlas

The mindat.org Crystal Atlas allows you to view a selection of crystal drawings of real and idealised crystal forms for this mineral and, in certain cases, 3d rotating crystal objects. The 3d models and HTML5 code are kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction:
d-spacingIntensity
4.85 (100)
4.02 (50)
3.22 (30)
2.79 (30)
2.72 (30)
2.47 (40)
1.755 (40)
Comments:Baia Sprie (Felsőbánya), Romania.

Optical Data of Orpiment

Type:Biaxial (-)
RI values: nα = 2.400 nβ = 2.810 nγ = 3.020
2V:Measured: 30° to 76°, Calculated: 62°
Maximum Birefringence:δ = 0.620

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Very High
Type:Anisotropic
Anisotropism:Barely observable because of strong internal reflections
Dispersion:relatively strong r > v
Reflectivity:
400nmR1=33.0%R2= 36.5%
420nmR1=31.0%R2= 35.2%
440nmR1=28.9%R2= 33.9%
460nmR1=27.4%R2= 31.5%
480nmR1=26.0%R2= 30.3%
500nmR1=24.9%R2= 29.3%
520nmR1=24.0%R2= 28.4%
540nmR1=23.3%R2= 27.8%
560nmR1=22.8%R2= 27.3%
580nmR1=22.3%R2= 26.9%
600nmR1=22.0%R2= 26.5%
620nmR1=21.7%R2= 26.3%
640nmR1=21.5%R2= 26.0%
660nmR1=21.2%R2= 25.7%
680nmR1=21.0%R2= 25.5%
700nmR1=20.8%R2= 25.3%


Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 36.5%.
R1 shown in black, R2 shown in red
Colour in reflected light:White to pale grey
Internal Reflections:Strong
Pleochroism:Strong
Comments:white to grey white with reddish tint (reflected light)
Y=yellow, Z=greenish yellow (transmitted light)

Chemical Properties of Orpiment

Formula:
As
 
2
S
 
3
Simplified for copy/paste:As2S3
Essential elements:As, S
All elements listed in formula:As, S
Common Impurities:Hg,Ge,Sb

Relationship of Orpiment to other Species

Common Associates:
StibniteRealgarGypsumCalciteBaryte
Arsenic
Related Minerals - Nickel-Strunz Grouping):

- +
2.FA.05Duranusite
As
 
4
S
2.FA.10Dimorphite
As
 
4
S
 
3
2.FA.15bPararealgar
As
 
4
S
 
4
2.FA.15aRealgar
As
 
4
S
 
4
2.FA.15cUM1970-19-S:As
As
 
4
S
 
4
2.FA.15dUM1970-18-S:As
As
 
4
S
 
4
2.FA.20Alacránite
As
 
8
S
 
9
2.FA.25Uzonite
As
 
4
S
 
5
2.FA.30Laphamite
As
 
2
(Se,S)
 
3
2.FA.35Getchellite
AsSbS
 
3
2.FA.40Wakabayashilite
[(As,Sb)
 
6
S
 
9
][As
 
4
S
 
5
]
Related Minerals - Hey's Index Grouping:

- +
3.7.1Patrónite
VS
 
4
3.7.2Duranusite
As
 
4
S
3.7.3Dimorphite
As
 
4
S
 
3
3.7.4Realgar
As
 
4
S
 
4
3.7.5Pararealgar
As
 
4
S
 
4
3.7.6Alacránite
As
 
8
S
 
9
3.7.7Uzonite
As
 
4
S
 
5
3.7.9Jeromite
3.7.10Laphamite
As
 
2
(Se,S)
 
3
3.7.11Getchellite
AsSbS
 
3
3.7.12Wakabayashilite
[(As,Sb)
 
6
S
 
9
][As
 
4
S
 
5
]
3.7.13Pääkkönenite
Sb
 
2
AsS
 
2
3.7.14Stibnite
Sb
 
2
S
 
3
3.7.15Metastibnite
Sb
 
2
S
 
3
3.7.16Tellurantimony
Sb
 
2
Te
 
3
3.7.17Bismuthinite
Bi
 
2
S
 
3
3.7.18Nevskite
Bi(Se,S)
3.7.19Guanajuatite
Bi
 
2
(Se,S)
 
3
3.7.21Ikunolite
Bi
 
4
(S,Se)
 
3
3.7.22Laitakarite
Bi
 
4
Se
 
2
S
3.7.23Poubaite
PbBi
 
2
(Se,Te,S)
 
4
3.7.24Tellurobismuthite
Bi
 
2
Te
 
3
3.7.25Součekite
PbCuBi(S,Se)
 
3
3.7.26Tsumoite
BiTe
3.7.27Pilsenite
Bi
 
4
Te
 
3
3.7.28Hedleyite
Bi
 
7
Te
 
3
3.7.29Tetradymite
Bi
 
2
Te
 
2
S
3.7.30Joséite
Bi
 
4
TeS
 
2
3.7.31Joséite-B
Bi
 
4
Te
 
2
S
3.7.32Ingodite
Bi
 
2
TeS
3.7.33Sulphotsumoite
Bi
 
3
Te
 
2
S
3.7.34Kawazulite
Bi
 
2
Te
 
2
Se
3.7.36Skippenite
Bi
 
2
TeSe
 
2
3.7.37Kochkarite
PbBi
 
4
Te
 
7
3.7.38Rucklidgeite
(Bi,Pb)
 
3
Te
 
4
3.7.39Aleksite
PbBi
 
2
Te
 
2
S
 
2
3.7.40Junoite
Cu
 
2
Pb
 
3
Bi
 
8
(S,Se)
 
16

Other Names for Orpiment

Synonyms:
ArrhenicumOpermentOropimentYellow ArsenicYellow Ratsbane
Other Languages:
Catalan:Orpiment
Dutch:Orpiment
Estonian:Auripigment
French:Orpiment
Arsenic Jaune
German:Auripigment
Arsenblende
Arsenikon
Königsgelb
Rauschgelb
Greek:Αρδενικόν
Αρρενικόν
Italian:Orpimento
Japanese:石黄
Latin:Arsenicum flavum
Auripigmentum
Lithuanian:Orpimentas
Polish:Siarczek arsenu
Russian:Аурипигмент
Simplified Chinese:雌黄
Slovak:Auripigment
Spanish:Orpimente
Ukrainian:Аурипігмент

Other Information

Health Warning:Contains arsenic - always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest.

References for Orpiment

Reference List:

- +
Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 266-269.

Mullen, D.J.E. and Nowacki, W. (1972): Refinement of the crystal structures of realgar, AsS and orpiment, As2S3. Zeitschrift für Kristallographie, 136, 48-65.

Bonazzi, P. & Bindi, L. (2008): A crystallographic review of arsenic sulfides: Effects of chemical variations and changes induced by exposure to light. Zeitschrift für Kristallographie, 223, 132-147.

Internet Links for Orpiment

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  • Orpiment details from Handbook of Mineralogy (PDF)
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    Localities for Orpiment

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