Structure of Important Clay Minerals

Clay minerals consist of hexagonal networks of Si04 tetrahedra. The basal planes of the tetrahedra are in the plane of the sheet silicate network, and their tips point 

in three-layer sheet silicates, part of the Si in the tetrahedral layer is substituted by Al, then negative surface charges will occur that are compensated for by alkali cations, rather weakly bound between the three-layer stacks. In that way the large group of mica is formed. On the other hand, the formal partial substitution of Al by Mg in the pyrophyllite lattice produces a charge deficiency that will be compensated for by monovalent or divalent atoms such as Na or Ca to create the minerals of the smectite group. 

The group of chlorite shown in Table 2.2 is sometimes referred to as a four-layer structure, as they are composed of modified three-layered talc units connected by a brudte-type layer. However, it may be more appropriate to call them mixed-layer structures with ordered intermediate layers.  

Dioctahedral (with gibbsite layers) Trioctahedral (with brudte layers) 

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That clay is an extremely important raw material will be clear from the fact that chapter 8 is entirely devoted to it. This chapter explains how clay is formed in nature, which composition it has, the structure of important clay minerals and the properties of clay. One property is highlighted here and that is the very varied composition of clay and the relatively large number of substances - apart from the clay minerals - which are present in clay. For most products made of clay the complex composition of this clay poses no problems in the production process nor for the final product properties. In this respect, these... 

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