Stacking Faults in the Kaolin-Group Minerals: Defect Structures of Kaolinite

Abstract

Abstract-Previous studies of the defect structure of kaolinite have examined samples having a restricted level of defects. This study examined nine kaolinite samples having a large diversity of defect contents, as indicated by Hincldey indexes ranging from 1.44 to 0.18. The samples were chosen so as to cover this range in as regular a manner as possible. The types and abundances of the defects were determined by examining the X-ray powder diffraction profiles for the 02,11 and 20,13 bands. The diffraction intensities were measured by counting for a fixed time in steps of 0.01"20. Analysis of these diffraction profiles indicatedthat (1) the major defect is the existence of a translation between adjacent layers, which is not the usual tl (approximately a/3), but is related to that translation by the pseudo-mirror plane coincident with the long diagonal of the unit cell; (2) the existence of a few C layers among the B layer stacking is a minor defect; (3) many of the samples could be accurately modeled only by assuming the existence of two kaolinite phases; (4) the existence of only a few C layers in some samples does not support the idea of a continuous series from kaolinite to dickite through disordered intermediates; and (5) the Hinckley indexes of several samples depend on the relative proportions of the two types of kaolinite in the mixture.The nine kaolinite samples fall into three groups: those having a low to moderate abundance of defects (Hinckley index > 0.43) are mixtures of two types of kaolinite (one almost free of defects, the other richer in defects); those having low Hinckley indexes (0.43 to 0.18) are single phases with different proportions of defects; and those which contain a single type of kaolinite, unlike the others in the nature of the interlayer translations and the greater abundance of C layers. The agreement between calculated and observed X-ray diffraction profiles is excellent for all specimens, except one sample (from Charentes) for which the fit is acceptable but not perfect.

Propriedades cristalográficas de caulinitas de solos do ambiente tabuleiros costeiros, Amazônia e Recôncavo Baiano

“…Os resultados dos índices R e a estimativa do padrão interno obtidos foram insatisfatórios (dados não apresentados). Dessa forma, e baseando-se na descrição da possibilidade de presença conjunta de caulinita triclínica e caulinita com caráter monoclínico (Plançon & Tchoubar, 1977;Brindley et al, 1986;Plançon et al, 1989) (Brasil, 1971).…”

“…Plançon & Tchoubar (1977) e Plançon et al (1989) relataram que esses aspectos são comuns em caulinitas com alta desordem estrutural e, conforme classificação proposta por esses autores, enquadram-se no grupo 3, o qual classifica as caulinitas com caráter monoclínico. A R. Bras.…”

Rietveld Refinement of the Kaolinite Structure at 1.5 K

“…Although Young and coworkers concluded that the non-H portion of the structure largely obeys C-centering, the important result of the P1 refinements was that OH groups that are equivalent in C1 exhibited two different orientations in P1. These orientations have important effects, for example, in vibrational spectroscopy (e.g., Brindley et aL, 1986;Johnston et al, 1990), the calculation of X-ray powder diffraction patterns (e.g., Bookin et aL, 1989;Plancon et aL, 1989), and electrostatic modeling of the structure (e.g., Abbott, 1989;Guthrie and Bish, 1991). Thus, it is crucial to examine the available evidence concerning the true space group.…”

Stability of kaolin sand from the Vyšný Petrovec deposit (south Slovakia) in an acid environment

“…Particle shape of kaolinite is regular and pseudohexagonal. One of substantial parameters affecting the utilization of kaolins is the "crystallinity" or degree of structural ordering of kaolinite (Plançon & Tchoubar 1977a,b;Plançon et al 1988Plançon et al , 1989Bookin et al 1989). The level of kaolinite ordering is usually expressed by indices calculated from their X-ray diffraction patterns (Hinckley 1963;Plançon & Zacharie 1990;Aparicio et al 2006).…”