Near Loewenburg in Swiss Jura the silex of upper Kimmeridge is outcropping in the upper part of a slope beneath Neumuhlefeld. Tectonical influences have geologically isolated this place in the region. A good W-E passage through a valley nearby was used bei Mousterian and Upper Palaeolithic hunters to come to this place. The palaeolithical sites all around the outcropping silex are remarkable by a great number of nuclei – always a sign for a napping place. The using of this isolated source of raw material begins in Mousterian and ends in early Neolithic time.