Mineral phase
IMA name
Bassanite
Type
Class
non-silicate mineral
Compound type
sulfate
Chemical composition
Formula
$Ca_2(SO_4)_2 \bullet (H_2O)$
Chemical formula
Ca2(SO4)2•(H2O)
Elemental formula
(Ca2+)2 S2 O5 (O-)4 H2
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$Ca^{2+}$ Calcium cation element 2 constituent cation main
$(SO_4)^{2-}$ Sulfate anion chemical function 2 anionic radical main
$H_2O$ Water molecule 1 hydration main
Chemical functions
  Function Number
$(SO_4)^{2-}$ 2
$R-OH$ 2
Chemical bonds
  Bond Number
$-O-H$ 2
$\dddot - \dddot - \dddot - S \dddot - O^{-1/2}$ 4
Oxides
Formula $CaO$ $H_{2}O$ $SO_{3}$
Mass fraction (%) 38.63 6.21 55.16

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.45

Dana

Major class
sulfates, chromates, selenates (VI)
Class
hydrated acid and sulfates (29)
Type
where AXO4.x(H2O) (29.06)
Group
-Bassanite- group (29.06.01)
Code
29.06.01.01
Phase type
crystalline
Crystal system
monoclinic
Crystal class
sphenoidal
Crystal class symbol
2 (C2)
Crystal spacegroup
C2
Molar mass
290.30 $g/mol$
Density
2.7 $g/cm^3$
State NTP
solid
Refringence type
uniaxial
Refringence sign
positive
Birefringence
0.020
Refraction index $n_o$ (w)
1.55
Refraction index $n_e$ (e)
1.57
Pure color
colorless
Color
colorless, snow white
Diaphaneity
transparent to translucent
Luster
earthy
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