Sheet Silicates (also known as phyllosilicates) are formed in a process similar to
chain silicates. Three of the four oxygens are shared with other tetrahedra: only the
upper oxygens remain charged and not connected to a Silicon atom.
Sheet silicates tend to follow their
namesake and form sheets or
layers of minerals. This gives very strong
intramolecular bonds, but extremely
weak intermolecular bonds. The bonds between molecules in a sheet silicate are a very good representation of
Van Der Waals forces.
Example:
Muscovite or any of the micas.
For more general information, see silicon tetrahedra.