INTERRELATED FEATURES OF STRUCTURE AND STACKING OF KAOLIN MINERAL LAYERS

Abstract

Layer stackings in the ideal and real kaolinite structures are considered in terms of layer orientations i = 1, 2, . . . 6, intra- and interlayer displacements of adjacent 0- and T-sheets, s i and t k, distortions of these displacements δ 1 and δ 2, deviations of unit cell parameters η = b i2/a i2 - 3, ∈ i = γ i π/2, and normal projections c n of the axis vector c on the ab plane. The ideal monoclinic angle of dickite (c nx = -1/3) and the deviation α - π/2 ≠ 0 for kaolinite are explained by combinations of the δ 1 and δ 2 values in the sequence of symbols s i and t k defining the corresponding structures. Twenty stacking variants in the 3 successive layers of the kaolinite structure are derived, incorporating layer orientations of the same parity, displacements t +,- = [0, ± 1/3] and reflection operations in planes normal to the axis b 3. Two deformation mechanisms are proposed for the accommodation of successive layer unit cells adjusting either angular or linear parameters at the agreement of either linear or angular parameters corresponding.