Microstructure and chemical composition of a Sardinian bronze axe of the Iron Age from Motya (Sicily, Italy)

A bronze axe of the Iron Age found in Motya (Sicily, Italy), in prehistoric strata dating from the 10th century BC (before the foundation of the Phoenician colony), has been characterised using Scanning Electron Microscopy (SEM-EDX), X-ray diffraction (XRD) and Electron Microprobe Analysis (EMPA). The axe was studied using micro-and invasive analyses, aiming to explore microstructure, corrosive process and to acquire quantitative chemical analysis. The results revealed that the axe is composed by a leaded-Cu-Sn alloy. The external layer is affected by a moderate porosity, decuprification and destannification processes, and Pb enrichment. The X-ray maps pictured the distribution of Cu, Pb, Sn, As, Cl, S and O and showed the features of the matrix, containing globules of Pb with different size. The corrosion products were examined using X-ray diffraction (XRD), that revealed the occurrence of cuprite (Cu2O), cassiterite (SnO2), laurionite (PbClOH), cerussite (PbCO3), litharge (PbO), anglesite (PbSO4) and plumbonacrite (Pb5O(OH)2(CO3)3). The matrix is composed by Cu 86.9–95.4 wt% and Sn 2.8–6.9 wt% with arsenic impurities (0.6–1.3 wt%).