Mineral phase
IMA name
Kaolinite
Class
silicate mineral
Compound type
phyllosilicate
Formula
Al2.(Si2O5)(OH)4
Chemical formula
Al2Si2O5(OH)4
Elemental formula
Al2 Si2 O9 H4
Isotope mixture type
terrestrial abundance
  Formula Name Family Number min-max Isotope mole fraction State Relevance
Al Aluminium element 2 constituent element main
Si Silicon element 2 constituent element main
O Oxygen element 9 constituent element main
H Hydrogen element 4 constituent element main
Composition comments
Common impurities: Fe, Mg, Na, K, Ti, Ca, H2O
Chemical functions
  Function Number
(OH) 4
Chemical bonds
  Bond Number
OH 1
Oxides
Formula Al2O3 SiO2 H2O
Mass fraction (%) 39.5 46.55 13.96

Strunz

Class
silicates (09)
Division
phyllosilicate (09.E)
Family
with kaolinite layers composed of tetrahedral and octahedral nets (09.ED)
Code
09.ED.05

Dana

Major class
silicates (VIII)
Class
phyllosilicate sheets of six-membered rings (71)
Type
with 1:1 layers (71.01)
Group
Kaolinite group (71.01.01)
Code
71.01.01.02
Phase type
crystalline
Crystal system
triclinic
Crystal class
pedial
Crystal class symbol
1 (C1)
Crystal spacegroup
P1
Molar mass
258.16 g/mol
Density
2.6 g/cm3
State NTP
solid
Refringence type
biaxial
Refringence sign
negative
Birefringence
0.007
Refraction index nα
1.553 - 1.563
Refraction index nβ
1.559 - 1.569
Refraction index nγ
1.560 - 1.570
Dispersion V
r > v weak
Pure color
white
Color
white, brownish white, grayish white, yellowish white, grayish green
Diaphaneity
transparent to translucent
Luster
earthy