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Orpiment

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Twin Creeks Mine, Potosi District, Humboldt Co., Nevada, USA
© 2001 John H. Betts

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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.
This page provides mineralogical data about Orpiment.

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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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
Twinning:On {100}
Crystal Atlas:
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Orpiment no.3 - Goldschmidt (1913-1926)
Orpiment no.13 - Goldschmidt (1913-1926)
Orpiment - Tabular {010}

About Crystal Atlas

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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. You need Java to see these. You can download Java for free - click here to download Java

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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: Peaks:
Data courtesy of RRUFF project at University of Arizona, used with permission.

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
Dispersion:relatively strong r > v
Internal Reflections:Strong
Pleochroism:Strong
Comments:white to gray white with reddish tint (reflected light)
Y=yellow, Z=greenish yellow (transmitted light)

Chemical Properties of Orpiment

Formula:
As
 
2
S
 
3
Essential elements:As, S
All elements listed in formula:As, S
Common Impurities:Hg,Ge,Sb

Relationship of Orpiment to other Species

Related Minerals - Nickel-Strunz Grouping):
2.FA.05Duranusite
As
 
4
S
2.FA.10Dimorphite
As
 
4
S
 
3
2.FA.15Pararealgar
As
 
4
S
 
4
2.FA.15Realgar
As
 
4
S
 
4
2.FA.20Alacránite
As
 
8
S
 
9
2.FA.25Uzonite
As
 
4
S
 
5
2.FA.30Laphamite
As
 
2
(S,Se)
 
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
(S,Se)
 
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 Arsenic
French names:
Arsenic Jaune
German names:
ArsenblendeArsenikonAuripigmentKönigsgelbRauschgelb
Greek names:
ΑρρενικόνΑρδενικόν
Italian names:
Orpimento
Japanese names:
石黄
Latin names:
Arsenicum flavumAuripigmentum
Russian names:
Аурипигмент
Spanish names:
Orpimente

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.

Zeitschrift für Kristallographie (1972): 136: 48-65.

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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