Constituent
Name
Alum-(K)
IMA name
Alum-(K)
Class
non-silicate mineral
Compound type
sulfate
Constituent abundance in material
Relevance
main - major
Arrangement
in multi-phases
Mass fraction
0.2 $\pm$ 0.1
Chemical composition
Formula
$KAl(SO_4)_2 \bullet 12(H_2O)$
Chemical formula
KAl(SO4)2•12(H2O)
Elemental formula
(K+) Al S2 O16 (O-)4 H24
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
$K^+$ Potassium(1+) cation element 1 constituent cation main
$Al$ Aluminium element 1 constituent element main
$(SO_4)^{2-}$ Sulfate anion chemical function 2 anionic radical main
$H_2O$ Water molecule 12 hydration main
Chemical functions
  Function Number Relevance
$(SO_4)^{2-}$ 2
$R-OH$ 2 main
Chemical bonds
  Bond Number Relevance
$-O-H$ 2 main
$\dddot - \dddot - \dddot - S \dddot - O^{-1/2}$ 4
Oxides
Formula $K_{2}O$ $Al_{2}O_{3}$ $H_{2}O$ $SO_{3}$
Mass fraction (%) 9.93 10.75 45.57 33.75

Strunz

Class
sulfates - chromates - molybdates - tungstates (07)
Division
sulfates (selenates, etc.) without additional anions, with H2O (07.C)
Family
with medium-sized and large cations (07.CC)
Code
07.CC.20

Dana

Major class
sulfates, chromates, selenates (VI)
Class
hydrated acid and sulfates (29)
Type
where AB(XO4)2.x(H2O) (29.05)
Group
Alum group (29.05.05)
Code
29.05.05.01
Phase type
crystalline
Crystal system
isometric (cubic)
Crystal class
diploidal
Crystal class symbol
m-3 (Th)
Crystal spacegroup
Pa-3
Molar mass
474.39 $g/mol$
Density
1.76 $g/cm^3$
Refringence type
isotropic
Refraction index $n_{\alpha}$
1.453
Color
colorless, white
Diaphaneity
transparent
Luster
vitreous