Slags from Bronze Age copper production in Acqua Fredda

Abstract So-called “plate slags” from the archaeological Bronze Age copper smelting site Acqua Fredda were examined. What was common to all the examined slags was that their compositions, once converted and plotted on the FeO-SiO2-CaO phase diagram, were located at the phase boundary between olivine and wollastonite, resulting in melting temperatures of approx. 1100 °C for the slags. Slags with a composition which fall within the olivine region exhibit long, thin olivine crystals in a glassy matrix. Slags in the wollastonite region have a very fine-grained structure, making phase identification impossible. The copper-containing inclusions in the slag mainly consist of Fe-poor Cu2S, but FeO and SiO2 may also be present. General assertions about the local copper production in Acqua Fredda should not be made based on the slag analyses conducted in this study.