Mineral phase
IMA name
Pentahydrite
Secondary names
Allenite
IMA Code
Phy
Class
non-silicate mineral
Compound type
sulfate
Formula
MgSO45H2O
Chemical formula
MgSO4•5H2O
Elemental formula
(Mg2+) S O7 (O-)2 H10
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 5 hydration main
Composition comments
common impurities: Fe, Mn, Ni, Ca
Chemical functions
  Function Number
(SO4)2 1
ROH 2
Chemical bonds
  Bond Number
Mg2+O 2
OH 10
OH 2
4
Oxides
Formula MgO SO_{3} H_{2}O
Mass fraction (%) 19.15 38.05 42.8

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.20

Dana

Major class
sulfates, chromates, selenates (VI)
Class
hydrated acid and sulfates (29)
Type
where AXO4.x(H2O) (29.06)
Group
Chalchanthite group (Pentahydrates, triclinic: P-1) (29.06.07)
Code
29.06.07.03
Phase type
crystalline
Crystal system
triclinic
Crystal class
pinacoidal
Crystal class symbol
-1 (Ci)
Crystal spacegroup
P-1
Molar mass
210.45 g/mol
Density
1.9 g/cm^3
State NTP
solid
Refringence type
biaxial
Refringence sign
negative
Birefringence
0.011 - 0.023
Refraction index n_{\alpha}
1.482 - 1.495
Refraction index n_{\beta}
1.492 - 1.512
Refraction index n_{\gamma}
1.493 - 1.518
Pure color
colorless
Color
colorless, white, light blue, light greenish blue
Diaphaneity
transparent to translucent
Luster
vitreous