If there is only one tetrahedral and one octahedral group in each layer the clay is known that the tetrahedral sheet becomes corrugated or twisted, causing ditrigonal distortion to the hexagonal array, and the octahedral sheet is flattened.
The tetrahedral sheet becomes corrugated or twisted, causing ditrigonal distortion to the hexagonal array. This was what the clay is known. There is only one tetrahedral. There is one octahedral group in each layer. The octahedral sheet is flattened.