Spongiolitowa forma odlewnicza ze stanowiska nr 20 w Przemyślu. Rezultaty badań

Abstract

Site No. 20 in Przemyśl, is an important research point of the early medieval city. During field works, two parts of a casting mould for the production of axes were found at the bottom of the settlement layer. No traces of copper were observed on the discovered form, but there were visible signs of burnout outside. This form is affiliated to the Mierzanowice culture. Petrographic tests have been performed using polarizing and scanning microscopes as well as microapaleontological examinations. They allow the researchers to identify the mould material as spongiolite (spiculite), most likely coming from the vicinity of Przemyśl, where the outcrops of this rock are located. With high probability, it can be stated that this material comes from the upper part of the Lgota beds covering the aforementioned lithostratigraphic units. The type of raw material used meets the conditions for using it as a casting mould. The obtained data allow for conclusion about the local production of this form.

Przemyśl 20 site is an important research point of the early medieval city. Archaeological research confirmed the existence of intensive settlement before this time. During field works, two parts of a casting mold for the production of axes, 17 cm long, 7.5 cm wide and 4 cm thick, were found at the bottom of the settlement layer. On the discovered form, no traces of copper were observed, on the outside were visible signs of burnout. This form is the only find of this type in Poland and ascibed to the Mierzanowice culture. Petrographic tests performed using polarizing and scanning microscopes as well as microapaleontological examinations allow the identification of the mold material as spongiolite (spiculite), most likely from the vicinity of Przemyśl, where the outcrops of this rock are located. Considering the results of micropaleontological research, it is not possible to unequivocally interpret whether the material from which the foundry mold was made comes from works classified as radiolar shale formations from Barnasiówka, or from silicoclastic turbidites rich in sponge spicules. With high probability it can be stated that this material comes from the upper part of the Lgota beds covering the abovementioned lithostratigraphic units. The type of raw material used meets the conditions for using it as a casting mold. The obtained data allow to conclude about the local production of this form.