Determination of the mineralogical composition
Due to the very fine grained sedimentary pattern it is not possible to determine the mineralogical composition by means of a microscope, but rather by x-ray diffractometry. X-ray diffractometry is a standard method, the error of about 1 % is very low and thus the obtained data are reliable. All analyses of the mineralogical composition of the slates mentioned were done after the Rietveld-procedure by the laboratory at the Mineralogical Department of the Freiberg University of Mining and Technology (Germany). All mineral analysed have been corrected and calculated as if these analysed minerals amounted 100 %. This fact has to be kept in mind while considering or comparing any results from different laboratories. In other words, if one laboratory discriminates four and the another one six minerals, the correction to 100 % is different and so has to be the interpretation. Because all results mentioned on these pages steam from one laboratory with one method they can be compared.