Opoka lekka (ziemia krzemionkowa) z Polanowic na Kujawach

Stanisław Romuald Krażewski



The borehole drilled in 1969 at Polanowice, Kujawy, Central Poland, revealed light, i.e., decalcified gaize of the Cretaceous age, occurring beneath Quaternary series at the depth of 38 m. The boreholes, stopped at the depth of 78 m, did not penetrate the gaize series. The gaize is light, porous, brittle, and whitening and consists of amorphous silica with recrystallized elements, quartz pelite, some coarser quartz grains, occassional grains of glauconite and pyrite, and single mica flakes. Rhoentgenographic analysis of residuum after HCl digestion shows occurrence of amorphous matter (SiO2 ) and distinct striae typical of the "cachalong" according to the test No. 261 of B. I. Michejew (1957). The results of chemical analyses are given in Table 1. The light gaize, known in the technical nomenclature as the siliceous earth, is a valuable material for fermentation industry and other branches of food industry, as well as for building industry. Comparisons of this material with requirements of the Polish norm for siliceous earth as well as with the siliceous earth known from the Piotrowice area, are positive for the deposit in question. Of course, more detailed technological and geological studies on this deposit are required. From the point of view of industrial exploitation, a relatively large depth of occurrence, ca. 40 m, would be disadvantageous. However, this does not reduce the significance of this finding for petrology, and possibly for industry.

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