Constituent
- Name
- Orpiment
- IMA name
- Orpiment
- Class
- non-silicate mineral
- Compound type
- sulfide
- Comments
- Common impurities: Hg, Ge, Sb
- Relevance
- main - minor
- Arrangement
- in multi-phases
- Formula
- $As_2S_3$
- Chemical formula
- As2S3
- Elemental formula
- As2 S3
- Isotope mixture type
- terrestrial abundance
- Oxides comments
- As: 60.9%, S: 39.1%
Strunz
- Class
- sulfides - sufosalts (02)
- Division
- sulfides of arsenic, alkalies; sulfides with halide, oxide, hydroxide, H2O (02.F)
- Family
- With As, (Sb), S (02.FA)
- Code
- 02.FA.30
Dana
- Major class
- sulfides (II)
- Class
- sulfides - including selenides and tellurides (02)
- Type
- where Am Bn Xp, with (m+n):p=2:3 (02.11)
- Group
- Orpiment group (02.11.01)
- Code
- 02.11.01.01
- Phase type
- crystalline
- Crystal system
- monoclinic
- Crystal class
- prismatic
- Crystal class symbol
- 2/m (C2h)
- Crystal spacegroup
- P2(1)/m
- Molar mass
- 246.04 $g/mol$
- Density
- 3.49 - 3.56 $g/cm^3$
- Refringence type
- biaxial
- Refringence sign
- negative
- Birefringence
- 0.620
- Refraction index $n_{\alpha}$
- 2.40
- Refraction index $n_{\beta}$
- 2.81
- Refraction index $n_{\gamma}$
- 3.02
- Dispersion V
- r > v strong
- Color
- lemon yellow, brownish yellow, orange yellow
- Diaphaneity
- transparent to translucent
- Luster
- pearly