Traces of metallurgy in the Panormos Phoenician colony (Palermo, Italy): archaeometric characterization of iron-slags

Archaeological works carried out in Palermo (NW Sicily) by the Archaeological Section of the Soprintendenza BB.CC.AA. of Palermo, between 2011 and 2012, revealed a settlement dating back to the Ellenic age and belonging to the Panormos Phoenician colony (Aleo Nero et al., 2016). The archaeological site brought to light fragments of potteries-Punic type amphorae-shells remanents, besides iron slags and oxidized strata connected with traces of metallurgical activity. Few information exists about Sicilian metallurgy during this age, and the iron slags connected with this activity have been little studied so far. This contribution is aimed to broaden our knowledge on this class of remains, contributing to increase the archaeological information about the Phoenician metallurgy in Sicily, and overall in southern Italy. To reach these objectives, textural, mineralogical and geochemical characterization of iron slags was carried out through a multidisciplinary analytical approach including Electron Microscopy with electron-dispersive energy (SEM-EDX), X-Ray Powder Diffraction (XRPD) and X-Ray Fluorescence (XRF). The studied iron slags show pseudo-spherical shape, spongy appearance and rust color. SEM-EDS analyses evidenced the presence of a glassy matrix with variable amount of iron silicates and Ca-rich portions in which iron oxides are embedded with dendritic and/or globular habitus. XRPD investigations identified quartz, calcite, fayalite and hedenbergite, with wüstite, maghemite and magnetite as primary iron oxides, and lepidocrocite and goethite as secondary hydrated iron oxides. In terms of bulk composition, XRF analyses highlighted prevalent amounts of SiO2 (13.31-46.12 wt%), FeO (37.99 – 68.76 wt%), CaO (9.22 – 19.38 wt%), Al2O3 (2.21 – 3.17 wt%) and P2O5 (0.87 – 2.26 wt%) and minor amounts (< 2%) of MgO, K2O, SO3, TiO2, MnO and Na2O. These results indicate that the investigated samples represent metallurgical materials associated with iron smithing. Slag mineral phases include iron silicates, calcite, quartz and iron oxides as the most abundant phases. Concerning the smithing process, the significantly high amount of lime in the investigated slags leads back to the Carthaginian-type metallurgical process. The high calcium content suggests the use of a lime-based flux. This hypothesis is reinforced by the occurrence during the excavations, of recycled Murex shells, probably previously used to produce purple dye (Charlton et al., 2010). However, we can not exclude that the lime content could also derive by the use of local carbonatic lithologies, widely outcropping in the Palermo territory. Aleo Nero, C., Chiovaro, M., Sabatino, G., Di Bella, M., Marcianò, G. (2016): Un esempio di attività metallurgica di età ellenistica a Panormos. In: "La città che produce. Archeologia della produzione negli spazi urbani", Giornate Gregoriane, X edizione, Agrigento, 10-11 dicembre 2016. Charlton, M.F., Crew, P., Rehren, T., Shennan, S.J. (2010): Explaining the evolution of ironmaking recipes-an example from northwest Wales. J. Anthropol. Archaeol., 29, 352-367.