Mineral phase
IMA name
Hexahydrite
IMA Code
Hhy
Class
non-silicate mineral
Compound type
sulfate
Formula
MgSO46H2O
Chemical formula
MgSO4•6H2O
Elemental formula
(Mg2+) S O8 (O-)2 H12
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 6 hydration main
Chemical functions
  Function Number
(SO4)2 1
ROH 2
Chemical bonds
  Bond Number
Mg2+O 2
OH 12
OH 2
4
Oxides
Formula MgO SO_{3} H_{2}O
Mass fraction (%) 17.64 35.05 47.31

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.25

Dana

Major class
sulfates, chromates, selenates (VI)
Class
hydrated acid and sulfates (29)
Type
where AXO4.x(H2O) (29.06)
Group
Hexahydrite group (Hexahydrates, monoclinic: C2/c) (29.06.08)
Code
29.06.08.01
Phase type
crystalline
Crystal system
monoclinic
Crystal class
prismatic
Crystal class symbol
2/m (C2h)
Crystal spacegroup
C2/c
Molar mass
228.46 g/mol
Density
1.76 g/cm^3
State NTP
solid
Phase transitions
Phase transition type Other phases Temperature - Pressure
solid-solid Kieserite below 42% RH
solid-solid Epsomite above 51% RH
Phase transitions comments
hydrates to Epsomite in humid air
Refringence type
biaxial
Refringence sign
negative
Birefringence
0.030
Refraction index n_{\alpha}
1.426
Refraction index n_{\beta}
1.453
Refraction index n_{\gamma}
1.456
Pure color
colorless
Color
colorless, white, greenish
Diaphaneity
transparent to opaque
Luster
vitreous