The Occurrence of Brochantite on Archaeological Bronzes: A Case Study from Lofkeend, Albania

摘要

A technical study was conducted on a group of copper alloy artifacts excavated from the burial tumulus of Lofkend (fourteenth-ninth century BCE) to identify the alloy compositions and methods of manufacture. The surface corrosion was also examined in order to understand the diagenetic processes affecting the preservation of the finds and their condition. Portable X-ray fluorescence spectroscopy, metallographic examination, and X-ray powder diffraction (XRD) analysis were used to characterize the alloy composition and identify the corrosion products present. XRD analysis showed the presence of brochantite (Cu4SO4(OH)(6)) on five of the metallic artifacts. Brochantite is not commonly reported on archaeological bronzes from terrestrial sites, but is more readily found on copper alloy objects exposed to sulfur pollutants in the air or soil. The possible conditions that could have led to the formation of this corrosion on the bronzes from Lofkend are discussed in the context of the particular burial environment found at the tumulus.