Analysis of lattice fringe images appeared on ultrathin sections of intergradient clay minerals in soils

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An intergradient clay mineral, "chloritized" vermiculite, present in a Korean Ultisol was studied by ultrathin sectioning and by examining 001 lattice fringe images using high-resolution electron microscopy: 1. Typical mineral particles (diameter, 0.3-0.5<micrn>m; thikness, 0.07-0.14 <micrn>m) are spindle-shaped. Lattice fringes with 14-, 11-12-, 10- and 7-8-<ang> spacinges appear in the samples saturated with K^+ and dried at 25-60゜C. Among these lattice fringes, those with 14-and 11-12-<Ang> spacings are predominant. The lattice fringes are not always straight but are often curved, waved and discontinuous. 2. One particle consists of stacked several "crystals". These "crystals" are packets of silicate layers in which their stacking is more uniform. The "crystals" consist of a kind of silicate layer of more than two kinds of interstratifying silicate layers. There is a tendency for the 7-8-<Ang> layers to be segregated in the portion near to the particle surface. 3. The lattice fringe images do not appear in some portions between the "crystals" and near to the ends of the spindle-shaped particles."Chloritized" vermiculite has been considered vermiculite whose interlayer is partially filled up with hydroxy-Al polymer. The interlayer material dissolved from the mineral had, however, a composition of kaolin mineral, and a partial transformation of each vermiculite layer into kaolin layers was suggested. The electron micrographs which support this suggestion were not obtained, but those suggesting the dissolution of material, which did not show the lattice fringe images and was present between the "crystals" and near to the ends of the spindleshaped particles, were obtained.