Growth Conditions and Genesis of Spherical and Platy Kaolinite

Abstract

Abstract--Spherical and platy kaolinite crystals were prepared under several hydrothermal conditions. Spherical kaolinite was produced mainly at high solid/water ratio (1/4) and at low temperatures (150 ~ 200~ Platy kaolinite predominated in products from experiments with intermediate solid/water ratios (1/256-1/16) and at high temperatures. Boehmite predominated at low solid/water ratios (1/4096) at all experimental temperatures (180"-220"C). The results indicate that the growth of the spherical kaolinite was favored at high degrees of supersaturation, whereas the growth of the platy kaolinite was favored at relatively low degrees of supersaturation.

Origin and Clay-Mineral Genesis of the Cretaceous/Tertiary Boundary Unit, Western Interior of North America

“…In contrast, the host glass of the claystone layer of the K/T boundary unit altered to finer-sized (0.2-2 /~m), poorly developed, hydrated, spherulitic crystals ( Figures 11D-F), some of which resemble immature or "embryonic-like" stages of kaolin clay precipitation ( Figures 12A and 12B). Such fine, poor-or immature-crystal development as spheroids also suggests formation from precursor amorphous, allophane-like (.9) particles or aggregates, and perhaps alteration of the glass to clay through an amorphous gel stage (Pollastro and Pillmore, 1987) by a rapid dissolution-precipitation mechanism (Tomura et al, 1985). Fine homogeneous gain size and poor crystal habit of the clay forms in the claystone layer are also consistent with rapid devitrification of the host glass.…”

2H NMR Study of Hydrogen Bonding in Deuterated Kaolinite

“…Tomura et al have succeeded in preparation of synthetic kaolinite (Tomura et al 1983(Tomura et al , 1985. Deuterated kaolinite was synthesized according to the procedure described previously (Miyawaki et al 1991), where D20 was used instead ofH20 (Akiba et a!…”

Effects of the Structure of Silica-Alumina Gel on the Hydrothermal Synthesis of Kaolinite

“…Tomura et al (1983) reported the synthesis of spherical kaolinite and its mineralogical properties. Tomura et al (1985) also reported that the spherical kaolinite was mainly produced at higher solid to water ratio (1/4) and at lower temperatures (1500-200 ~ C) than the conditions for the synthesis of platy kaolinite. Miyawaki et al (1991) revealed that the addition of Li salt into the reaction system of the synthesis improved the crystallization of kaolinite along the (001) direction.…”

“…The transition from the intermediate amorphous to kaolinite started as early as 1 -day reaction. Tomura et al (1985) showed that spherical kaolinite was produced in a highly supersaturated solution of silica and alumina. It can, therefore, be presumed that the spherical kaolinite in this study should be precipitated owing to the supersaturation of a silica-alumina cluster derived from the intermediate phase.…”