Question

Q4-B In terms of silicate molecular structures and electrostatic forces, briefly explain why kaolinite clay feels so slippery when moistened with water. You may also choose to use diagrams to illustrate your answer. [50 marks]

Answer 1

Plastic behavior when wet and ability to adsorb water and ions in solution, can be attributed to small crystal size, high surface area. slippery feel of Kaolinite is the result of cleavage along the weak van der Waals bonds between the layers. Kaolinite is a phyllosilicate mineral that cleaves into thin sheets. Phyllosilicate structure consists of sheets of hydrated SiO₄ rings and an octahedral sheet consisting AlO or SiO. These sheets are held together only by van der Waals bonds, which allows them to easily slip past one another.

STRUCTURE OF A KAOLINITE LAYER O OH Al Si

Image source - Grim(1962)