An Introduction to Environmental Chemistry

(a) SiO 4 tetrahedron

Apex up Apex down

(b) Simplified structure for olivine

O Si

Mg2+

(c) Chain silicate

(d) Double chain silicate

(e) Sheet silicate

End view

O Si

Fig. 4.4(a) The schematic SiO 4 tetrahedron in Fig. 4.2a can be represented as a tetrahedron,
each tip representing the position of oxygen anions. The sketches represent monomer structure
in (b) and progressive polymerization of adjacent tetrahedra to form (c) chains, (d) cross-linked
double chains and (e) sheets. The cross-linked structures form hexagonal rings which can
accommodate anions such as OH-. After Gill (1996), with kind permission of Kluwer Academic
Publishers.