Permanently Charged 21 Phyllosilicate Minerals

In the description of 2 1 phyllosilicates, they have been divided into two broad parts in this section, we will consider those minerals that have a relatively low permanent charge, which does not suffer noticeable changes upon heating or other processes such as ionic exchange. These minerals form the pyrophyllite-talc group. 

The least reactive type of surface site found on clay minerals is the neutral siloxane surface. Features associated with this type of site include no charge, no permanent dipole moment, and weak interactions with the hydrogen-bonded network of water molecules. Hydrophobic surfaces occur on 2 1 phyllosilicates, where there is no isomorphic substitution (e.g., talc and pyrophyllite), and also on the siloxane side of the kaolinite 1 1 TO unit. There is currently some question about the structural microscopic hydrophilicity of talclike surfaces (43) however, from a... 

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