Double layer lattice silicates

The difference in strength of inter-iayer bonding between expanding and non-expanding double layer lattice silicates may be easily observed by the following demonstration ... 

There are two major subdivisions of layer lattice silicates a single layer type based on a condensation of a hydroxide layer structure with one silica plane and a double layer unit in which a further inverted silica plane completes a sandwich-like structure above the hydroxide unit. Each layer lattice is theoretically complete within itself and although similar layers can stack above each other there can be no formal inter-layer ionic or covalent bond formation. 

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