Structure and Composition of the Clay Minerals and their Physical and Chemical Properties

This chapter discusses the structure and composition of the clay minerals and their physical and chemical properties. The atomic structure of the clay minerals consists of two basic units, an octahedral sheet and a tetrahedral sheet. The octahedral sheet is comprised of closely packed oxygen's and hydroxyls in which aluminum, iron, and magnesium atoms are arranged in octahedral coordination. When aluminum with a positive valence of three is the caution present in the octahedral sheet, only two-thirds of the possible positions are filled in order to balance the charges. When only two-thirds of the positions are filled, the mineral is termed dioctahedral. When magnesium with a positive charge of two is present, all three positions are filled to balance the structure and the mineral is termed trioctahedral