Orpiment Mineral Data

General Orpiment Information

Chemical Formula:

As2S3

Composition:

Molecular Weight = 246.04 gm

Arsenic 60.90 % As

Sulfur 39.10 % S

______

100.00 %

Empirical Formula:

As₂S₃

Environment:

Low temperature hydrothermal veins, hot springs, and fumaroles; also commony as an alteration product of arsenic minerals, especially realgar.

IMA Status:

Valid Species (Pre-IMA) 1747

Locality:

Common world wide. Link to MinDat.org Location Data.

Name Origin:

From the Latin, auripigmentum, in allusion to the vivid golden hue.

Name Pronunciation:

Orpiment

Synonym:

ICSD 15239

PDF 24-75

Orpiment Image

Images:

Orpiment

Comments: Deep orange-colored orpiment crystal aggregate.
Location: Twin Creeks mine, 62 bench, north of Winnemucca, Humboldt County, Nevada. USA. Scale: 6.5 x 5.5 cm.
© Fabre Minerals

Orpiment Crystallography

Axial Ratios:

a:b:c =1.1981:1:0.4431

Cell Dimensions:

a = 11.49, b = 9.59, c = 4.25, Z = 4; beta = 90.45° V = 468.29 Den(Calc)= 3.49

Crystal System:

Monoclinic - Prismatic H-M Symbol (2/m) Space Group: P 2₁/n

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 4.82(1), 2.7(0.53), 4(0.47),

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Forms: ( 0 1 0) ( 1 2 0) ( 1 1 1) ( 1 0 1)

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Physical Properties of Orpiment

Cleavage:

{010} Perfect

Color:

Lemon yellow, Brownish yellow, Orange yellow.

Density:

3.49 - 3.56, Average = 3.52

Diaphaneity:

Transparent to translucent

Fracture:

Sectile - Curved shavings or scrapings produced by a knife blade, (e.g. graphite).

Habit:

Foliated - Two dimensional platy forms.

Habit:

Massive - Fibrous - Distinctly fibrous fine-grained forms.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Hardness:

1.5-2 - Talc-Gypsum

Luminescence:

Non-fluorescent.

Luster:

Pearly

Streak:

pale yellow

Optical Properties of Orpiment

Optical Data:

Biaxial (-), a=2.4, b=2.81, g=3.02, bire=0.6200, 2V(Calc)=62, 2V(Meas)=76. Dispersion r > v strong.

Pleochroism (x):

yellow.

Pleochroism (y):

yellow.

Pleochroism (z):

greenish yellow.

RL Anisotrophism:

Bearly observable because of the strong internal reflections.

RL Pleochroism:

Strong, white to gray-white with a reddish tint.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Orpiment in Air**
λ	R₁	R₂	∑ R₁(λ)	∑ R₂(λ)
400 nm	29.80	39.90
420 nm	27.60	36.80
440 nm	25.40	33.70
460 nm	23.60	31.20
480 nm	22.30	29.50
500 nm	21.40	28.40
520 nm	20.90	27.70
540 nm	20.50	27.20
560 nm	20.10	26.70
580 nm	19.70	26.40
600 nm	19.40	25.90
620 nm	19.10	25.60
640 nm	19.00	25.40
660 nm	18.80	25.20
680 nm	18.70	25.10
700 nm	18.60	25.00

**Calculated Relative Intensity Colors of Orpiment in Air**
Relative Intensity	0%	50%	100%	150%	200%	250%	300%	350%	400%	440%
R₁
R₂

Calculated Properties of Orpiment

Electron Density:

Bulk Density (Electron Density)=3.23 gm/cc
note: Specific Gravity of Orpiment =3.49 gm/cc.

Fermion Index:

Fermion Index = 0.0029323747
Boson Index = 0.9970676253

Photoelectric:

PE_Orpiment= 44.66 barns/electron
U=PE_Orpiment x rElectron Density= 144.44 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Orpiment is Not Radioactive

Orpiment Classification

Dana Class:

02.11.01.01 (02)Sulfides - Including Selenides and Tellurides

(02.11)where Am Bn Xp, with (m+n):p=2:3

(02.11.01)Orpiment Group

02.11.01.01 Orpiment As2S3 P 2₁/n 2/m

02.11.01.02 Getchellite AsSbS3 P 2₁/a 2/m

Strunz Class:

02.FA.30 02 - SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulf

02.F - Sulfides of Arsenic, Alkalies; Sulfides with Halide, Oxide, Hydroxide, H2O

02.FA -With As, (Sb), S

02.FA.30 Orpiment As2S3 P 2₁/n 2/m

02.FA.30 Laphamite As2(Se,S)3 P 2₁/n 2/m

Other Orpiment Information

References:

NAME( AntBidBlaNic1) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic1)

See Also:

Links to other databases for Orpiment :
1 - Am. Min. Crystal Structure Database
2 - Amethyst Galleries' Mineral Gallery
3 - Athena
4 - EUROmin Project
5 - Ecole des Mines de Paris
6 - GeoScienceWorld
7 - Google Images
8 - Google Scholar
9 - Handbook of Mineralogy (MinSocAm)
10 - Handbook of Mineralogy (UofA)
11 - MinDAT
12 - Mineralienatlas (Deutsch)
13 - Online Mineral Museum
14 - Philatelic Mineralogy
15 - QUT Mineral Atlas
16 - Ruff.Info
17 - WWW-MINCRYST
18 - theimage

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Print or Cut-and-Paste your Orpiment Specimen Label here :

Orpiment

As2S3
Dana No: 02.11.01.01 Strunz No: 02.FA.30
Locality:

Notes:

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