Micro-Stratigraphical Investigation on Corrosion Layers in Ancient Bronze Artefacts of Urartian Period by Scanning Electron Microscopy, Energy-Dispersive Spectrometry, and Optical Microscopy

Yeghis Keheyan,Giancarlo Lanterna

doi:10.3390/heritage4030143

Abstract

The results of the analysis on some fragments of bronze belts and a bowl discovered from southwestern Armenia at the Yegheghnadzor archaeological site are discussed. The samples are dated to the 7–6th millennium BCE from the Urartian period. The artefacts were corroded, and a multilayer structure was formed. To study the stratigraphy of layers and their composition, the samples have been analyzed using SEM-EDS (Scanning Electron Microscopy, Energy-Dispersive Spectrometry) and OM (Optical Microscopy) techniques. The bronze finds appear with the typical incrustations rich in alloy alteration compounds. Concentrations of copper and tin in the alloys were quantified by SEM-EDS: the pattern and the percentage of the alloy are the same for the belts. Regarding the bowl sample, it is constituted by two foils perfectly in contact but different in color, thickness, and composition. The results evidenced that only two elements participate in forming the alloy composition in the samples: Cu and Sn. The tin content is variable from 7.75% to 13.56%. Other elements such as Ag, As, Fe, Ni, P, Pb, Sb, and Zn make up less than 1% and can be considered as impurities.

Highlights

The results of the analysis on some fragments of bronze belts and a bowl discovered from southwestern Armenia at the Yegheghnadzor archaeological site are discussed
During the Bronze Age, Armenia was an integral part of a cultural zone between the Van, Urmia, and Sevan lakes, with contacts mainly toward the Near East
The authors of [1,2] report that metallurgy in the Southern Caucasus and Armenia in particular appears with the extraction of native copper and cold working-cum-annealing at the beginning of the 6th millennium BC

Summary

Introduction

During the Bronze Age, Armenia was an integral part of a cultural zone between the Van, Urmia, and Sevan lakes, with contacts mainly toward the Near East. Archaeometallurgical investigations in Armenia during the post-Soviet period entered a completely new stage with the application of modern analytical methods such as X-ray fluorescence analysis (XRF), instrumental neutron activation analysis (INAA), Scanning Electron Microscope with Electron Probe Micro Analyses (SEM-EPMA), and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) to study metal artifacts and ores, and researchers have been created a large database of chemical compositions and lead isotope analyses of artifacts. This is based on data from new excavations and a review of previous work. The analysis of unaltered areas carried out at SEM/EDS, even if less accurate, revealed a very different but reliable bronze composition [14]

Experimental Conditions

Results and Discussions

CConcluding Remarks