Mineral phase
IMA name
Kieserite
IMA Code
Ksr
Class
non-silicate mineral
Compound type
sulfate
Formula
MgSO4H2O
Chemical formula
MgSO4•H2O
Elemental formula
(Mg2+) S O3 (O-)2 H2
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
Mg2+ Magnesium(II) cation element 1 constituent cation main
(SO4)2 Sulfate anion chemical function 1 anionic radical main
H2O Water molecule 1 hydration main
Composition comments
Dissolves very slowly in water
Chemical functions
  Function Number
(SO4)2 1
ROH 2
Chemical bonds
  Bond Number
Mg2+O 2
OH 2
OH 2
4
Oxides
Formula MgO SO_{3} H_{2}O
Mass fraction (%) 29.13 57.86 13.02

Strunz

Class
sulfates - chromates - molybdates - tungstates (07)
Division
sulfates (selenates, etc.) without additional anions, with H2O (07.C)
Family
with only medium-sized cations (07.CB)
Code
07.CB.05

Dana

Major class
sulfates, chromates, selenates (VI)
Class
hydrated acid and sulfates (29)
Type
where AXO4.x(H2O) (29.06)
Group
Kieserite group (Monohydrates) (29.06.02)
Code
29.06.02.01
Phase type
crystalline
Crystal system
monoclinic
Crystal class
prismatic
Crystal class symbol
2/m (C2h)
Crystal spacegroup
C2/c
Molar mass
138.38 g/mol
Density
2.57 g/cm^3
State NTP
solid
Phase transitions
Phase transition type Other phases Temperature - Pressure
solid-solid Hexahydrite below 68°C (341 K)
solid-solid Hexahydrite above 42% RH
Refringence type
biaxial
Refringence sign
positive
Birefringence
0.064
Refraction index n_{\alpha}
1.52
Refraction index n_{\beta}
1.533
Refraction index n_{\gamma}
1.584
Dispersion V
relatively strong
Pure color
colorless
Color
colorless, white, gray white, yellowish, green yellow
Diaphaneity
transparent to translucent
Luster
vitreous