Mineral phase
IMA name
Alum-(K)
Type
Class
non-silicate mineral
Compound type
sulfate
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
$(SO_4)^{2-}$ 2
$R-OH$ 2
Chemical bonds
  Bond Number
$-O-H$ 2
$\dddot - \dddot - \dddot - S \dddot - O^{-1/2}$ 4
Oxides
Formula $K_{2}O$ $Al_{2}O_{3}$ $H_{2}O$ $SO_{3}$
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 $g/cm^3$
State NTP
solid
Refringence type
isotropic
Refraction index $n_{\alpha}$
1.453
Pure color
colorless
Color
colorless, white
Diaphaneity
transparent
Luster
vitreous
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