Constituent
Name
Gypsum
Class
non-silicate mineral
Compound type
sulfate
Comments
commonly used non-standard space groups: A2/a, A1, I12, I2/a
Relevance
impurity
Arrangement
complex intimate mix
Mass fraction
0.005 $\pm$ 0.004
Abundance comments
Mass fraction probably < 0.01 (for raw Swy-2 and << 0.001 for < 2µm size - Vogt 2002)
Formula
$Ca(SO_4) \bullet 2(H_2O)$
Chemical formula
CaSO4.2(H2O)
Elemental formula
O6 H4 Ca S
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$S$ Sulfur element 1 constituent element main
$Ca$ Calcium element 1 constituent element main
$O$ Oxygen element 6 constituent element main
$H$ Hydrogen element 4 constituent element main
Chemical functions
  Function Number
$\bullet (SO_4)^{2-}$ 1
Chemical bonds
  Bond Number
$\geqq S=O$ 2
$-\gg S-O^-$ 2
Oxides
Formula $SO_{3}$ $CaO$ $H_{2}O$
Mass fraction (%) 46.5 32.57 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 Wp Atom Atom coordinence Atom occupancy Atom oxidation state
H2 2  $H$ 1.0
Ca 1  $Ca$ 1.0
H1 2  $H$ 1.0
S 1  $S$ 1.0
Ow 2  $O$ 1.0
O2 2  $O$ 1.0
O1 2  $O$ 1.0
Composition order
ordered
Molar mass
172.17 $g/mol$
Density
2.31 $g/cm^3$
Refringence type
biaxial
Refringence sign
positif
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
Color
colorless, white, yellowish white, greenish white, brown
Diaphaneity
transparent to translucent
Luster
pearly