Internal Structure of Kaolinite Group

The clay minerals of kaolinite group have dioctahedral t-o structure. This type of structure consists of three planes of anions. On one side, there is a plane of bridging 0 of the r-sheet, on the other side there is a plane of OH . The middle anionic plane consists of the non-bridging oxygens of the f-sheets and OH . In the o-sheet, each octahedral cation is surrounded by three OH from the plane of OH , one OH and two non-bridging oxygens from the middle plane. 

The t-o layers are electrically neutral, and bonded to one another by weak Van der Waals bond or hydrogen bond. The basal spaeing (repeat distance from one layer to the next) is about 7 A. 

Halloysite has a characteristic property of absorbing water. The water molecules are arranged in a sheet in the interlayer space, i.e. in between two 

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