Wyniki badań kaolinu z Krzyżowej na Dolnym Śląsku

Abstract

RESULTS OF INVESTIGATIONS OF KAOLIN FROM KRZYŻOWA IN LOWER SILESIA

Near Krzyżowa in Lower Silesia there occurs an interesting kaolin deposit. The overburden of this deposit consists of Quaternary loams and gravels, and of plastic Miocene clays. Generally speaking, in the top part of the deposit there occurs a white kaolin underneath a yellow and red kaolin. The thickness of the white kaolin is several meters; however, locally this layer is frequently eroded and then red kaolin appears directly in the top part of the deposit. In this bed, 5 bore holes have been drilled, the deepest being 26.1 m. A map of the geological research has been given in Fig. 1. Samples of kaolin have been examined by means of a thermal differential analysis (Fig. 2), by chemical analyses (Table 2) and by microscope observations. The results of these investigations reveal that the main mineral components are kaolin and quartz. Interesting is the appearance, within this deposit, of kaolinite new growths in the shape of worms or its fragments, and of colourless scales with low interference colours descending from biotite. The mother rock of the kaolin has been gneiss which is characteristic for Sowie Góry. In some of samples the author observed the preserved texture of the mother rock. Kaolin is found in a secondary deposit too.

White kaolin from Krzyżowa seems to be also of interest for economic purposes. As raw material it shows a heat resistance equaling 34 Seeger cone, and a total drying shrinkage of 6.8%; its Fe₂O₃ content is slightly less than 1.5%. Its pellitic fraction, obtained by washing out, is about 30%. In order to ascertain the resources of this deposit, further geological-exploratory field work seems to be necessary.