In order to influence the habit of barite (BaS04) single crystals obtained by precipitation, the tailor-made additives 2-aminoethanol, 3-aminopropanol, 5-aminopentanol, 4-aminobutane sulfonic acid, and several other growth inhibitors have been tested. The crystallization experiments have been carried out in a fully automated crystallizer with reproducible educt feed rates. The kinetics of the reaction has been measured by means of the conductivity. Scanning electron microscopic analysis of the obtained crystal habits led to the result that most of the additives tested did not influence the growth form of the crystals, but the predicted, tailor-made additives resulted in a more isometric crystal form.
The morphology and fabric of kaolin weathered from a non-feldspathic mica-phyllite in Znojmo, Moravia, are illustrated in scanning electron micrographs. In contrast to accordion-like kaolinite books, or elongate halloysite(?) crystals, commonly developed from feldspar, the kaolinite from the mica-phyllite tends to be individually platy, with highly irregular edges resulting from multiple adjacent crystal comers and re-entrants. Irregular or impaired crystal growth of kaolinite from mica may be due to 'poisoning' of kaolinite crystals by vanadium that is common in mica.The morphology of kaolinite crystals, and the fabric of kaolin rocks they comprise, presumably result from the gross genetic environment during formation of the kaolin. Dominating environmental factors include parent materials (Keller, 1976), the concentrations of ions in the fluids of the kaolinizing system, and perhaps the temperature, pressure, and length of time during kaolinization. This report considers the effect of parent materials.Feldspars are well known to be the most common parent materials from which kaolins are produced. Indeed, because of the almost universal prevalence of feldspars in silicate rocks, feldspar-free rock
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