Bog iron ore – experimental testing of the impact of ore roasting on the smelting process and the end product

Dosadašnja istraživanja lokaliteta s prostora Podravine na kojima su se odvijale aktivnosti vezane uz proizvodnju željeza (Hlebine – Velike Hlebine i Dedanovice, Virje – Sušine i Volarski breg) ukazala su da je močvarna željezna ruda lokalnoga podrijetla bila temeljna sirovina za proizvodnju željeza tijekom kasne antike i ranoga srednjeg vijeka. Na osnovi mineraloških analiza uzoraka rude (XRD) pretpostavljene su razlike u načinu priprema ruda za taljenje koje su vidljive između lokaliteta različite vremenske i prostorne pripadnosti. Eksperiment prikazan u ovome radu je osmišljen kako bi se testirala jedna varijanta idejne rekonstrukcije talioničkih peći te različit način pripreme rude u svrhu usporedbe utjecaja ove varijable na postupak taljenja i krajnji proizvod. Talionička peć rekonstruirana je na osnovi podataka s arheoloških istraživanja i obrade nalaza, a pripada tipu samostojećih peći s vratima, kod kojih se u tijeku postupka ispuštala zgura. Izvedena su dva ekperimentalna taljenja u rekonstriranoj peći, koristeći rudu sa i bez pirometalurške pripreme, prženja.Earlier research of the sites in the Podravina region where iron production activities took place (Hlebine – Velike Hlebine and Dedanovice, Virje – Sušine, and Volarski Breg) indicated that bog iron ore of local origin was the basic raw material for iron production in Late Antiquity and the Early Middle Ages. On the basis of mineralogical analyses of ore samples (XRD), differences in the method of preparing ore for smelting were identified between sites from different periods and spatial distribution. The experiment presented in this paper was designed to test one variant of the conceptual reconstruction of smelting furnaces and different methods of ore preparation in order to compare the impact of this variable on the smelting process and the end product. The smelting furnace was reconstructed on the basis of data from archaeological research and the analysis of finds; it belongs to the type of free-standing shaft furnaces with a door where slag is tapped during the procedure. Two smelting experiments were carried out in the reconstructed furnace, using the ore with and without the pyrometallurgical preparation, roasting