Archaeometric investigation of bronze arrowheads from the Siege of Motya (Sicily)

Nine Phoenician bronze arrowheads were characterized by means of scanning electron microscope (SEM-EDS), electron microprobe analysis (EMPA) and X-ray diffraction (XRD). These archaeological arrowheads were recovered from the archaeological site of Motya (western Sicily, Italy) and attributed to the siege by Dionisio I, tyrant of Syracuse, in 397 B. C. In particular, scanning electron microscope (SEM-EDS) and X-ray maps was performed on cross section to characterize qualitative chemical composition of the artifacts, distribution of the alloy elements in the different layers and corrosion microstructures. Quantitative analysis from rim to core sections has been carried out using electron microprobe analysis (EMPA) to determine the composition of major and minor elements of the alloy. X-ray diffraction (XRD) was used to define the mineralogical composition of the corrosion products. This systematic study allowed the conic arrowhead to be identified as binary alloy (Cu-Sn) with complex banding corrosion layers, known as the Liesegang rings. Indeed, the bilobed and trilobed arrowheads were made by ternary alloys (Cu-Sn-Pb), showing a Cu-Sn matrix with Pb globules, which are oxidized to form lead salts on the patina. The presence of copper trihydroxichlorides seems to be strongly correlated with the size of the Pb-globules. This is the first scientific attempt to characterize the bronze arrowheads found in Motya, by relating the microstructures and the alloy compositions with their typologies and probable geographic provenances. This research gives new insight on weaponry and poliorcetics of the Syracusan army.