Page 70 - Fundamentals of Geomorphology

( ) Kaolinite
a
Tetrahedral
sheet 1:1 layer
Octahedral 7.2 Å thick
sheet

Basal oxygen plane
Silicon plane
Octahedral cation plane
Octahedral anion plane

( ) Illite
b

2:1 layer
9.4 Å thick

( ) Smectite
c

2:2 layer
14.4 Å thick

Figure 3.1 Clay mineral structure. (a) Kaolinite, a 1 : 1 dioctahedral layer silicate. (b) Illite, a 2 : 1 layer silicate,
consisting of one octahedral sheet with two flanking tetrahedral sheets. (c) Smectite, a 2 : 2 layer silicate, consisting
of 2 : 1 layers with octahedral sheets between. Å stands for an angstrom, a unit of length (1Å = 10 −8 cm).
Source: After Taylor and Eggleton (2001, 59, 61)