Mineral phase
- IMA name
- Gypsum
- Secondary names
- Selenite
- Class
- non-silicate mineral
- Compound type
- sulfate
- Comments
- commonly used non-standard space groups: A2/a, A1, I12, I2/a
- Formula
- $Ca(SO_4) \bullet 2(H_2O)$
- Chemical formula
- CaSO4.2(H2O)
- Elemental formula
- Ca S O6 H4
- Isotope mixture type
- terrestrial abundance
- Composition comments
- Slightly soluble in water. Poorly deliquescent > 99% RH at 20°C
- Oxides
-
Formula $CaO$ $SO_{3}$ $H_{2}O$ Mass fraction (%) 32.57 46.5 20.93
Strunz
- Class
- sulfates - chromates - molybdates - tungstates (07)
- Division
- sulfates (selenates, etc.) without additional anions, with H2O (07.C)
- Family
- with only large cations (07.CD)
- Code
- 07.CD.40
Dana
- Major class
- sulfates, chromates, selenates (VI)
- Class
- hydrated acid and sulfates (29)
- Type
- where AXO4.x(H2O) (29.06)
- Group
- -Gypsum- group (Dihydrates, monoclinic) (29.06.03)
- Code
- 29.06.03.01
- Phase type
- crystalline
- Crystal system
- monoclinic
- Crystal class
- prismatic
- Crystal class symbol
- 2/m (C2h)
- Crystal spacegroup
- C2/c
- Crystal sites
-
Label Nb Type Wp Specie Specie coordinence Specie occupancy Specie oxidation state Ca 1 $Ca$ 1.0 S 1 $S$ 1.0 O1 2 $O$ 1.0 O2 2 $O$ 1.0 Ow 2 $O$ 1.0 H1 2 $H$ 1.0 H2 2 $H$ 1.0 - Composition order
- ordered
- Molar mass
- 172.17 $g/mol$
- Density
- 2.31 $g/cm^3$
- State NTP
- solid
- Refringence type
- biaxial
- Refringence sign
- positive
- Birefringence
- 0.0090 - 0.0100
- Refraction index $n_{\alpha}$
- 1.519 - 1.521
- Refraction index $n_{\beta}$
- 1.522 - 1.523
- Refraction index $n_{\gamma}$
- 1.529 - 1.530
- Dispersion V
- strong
- Pure color
- colorless
- Color
- colorless, white, yellowish white, greenish white, brown
- Diaphaneity
- transparent to translucent
- Luster
- pearly