Arsenical copper and bronze metallurgy during Late Bronze Age of north-eastern Iran: evidences from Shahrak-e Firouzeh archaeological site

Abstract

Despite the importance of copper-base metallurgy during Iran’s Bronze Age, limited systematic scientific data exist on the alloying patterns and processes of the period. While it seems that tin bronze metallurgy existed in the Early Bronze Age in western Iran and it was widespread through the Middle and Late Bronze Age, tin bronze technology was less common in eastern Iranian Plateau during Bronze Age. In this paper, a multianalytical study has been undertaken on a series of copper alloy objects excavated from the Late Bronze Age site of Shahrak-e Firouzeh, Neyshabur, located in north-eastern Iran. The study was performed using inductively coupled plasma-optical emission spectroscopy (ICP-OES) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), as well as optical microscopy (metallography) methods. Results revealed that the prevalent copper-base metallurgy in the site was unalloyed and arsenical copper in general, with objects manufactured by a partially simple procedure, including cold working and annealing (not enough to remove the original coring occurred during solidification of the metallic ingots or pieces). These findings, coupled with comparative and descriptive interpretations, also showed that while tin bronze was made in Early Bronze Age of western Iran, arsenical copper was the main metallic material used in other parts of the country, in central and eastern Iran in particular.