Phase Composition and Its Spatial Distribution in Antique Copper Coins: Neutron Tomography and Diffraction Studies.

Bulat Bakirov,Nikolay Sudarev,Irina Saprykina,Sergey Kichanov,Denis Kozlenko,Roman Mimokhod

doi:10.3390/jimaging7080129

Abstract

The chemical and elementary composition, internal arrangement, and spatial distribution of the components of ancient Greek copper coins were studied using XRF analysis, neutron diffraction and neutron tomography methods. The studied coins are interesting from a historical and cultural point of view, as they are “Charon’s obol’s”. These coins were discovered at the location of an ancient Greek settlement during archaeological excavations on the “Volna-1” necropolis in Krasnodar Region, Russian Federation. It was determined that the coins are mainly made of a bronze alloy, a tin content that falls in the range of 1.1(2)–7.9(3) wt.%. All coins are highly degraded; corrosion and patina areas occupy volumes from ~27 % to ~62 % of the original coin volumes. The neutron tomography method not only provided 3D data of the spatial distribution of the bronze alloy and the patina with corrosion contamination inside coin volumes, but also restored the minting pattern of several studied coins. Taking into account the obtained results, the origin and use of these coins in the light of historical and economic processes of the Bosporan Kingdom are discussed.

Highlights

IntroductionA detailed study of the chemical composition of ancient numismatic materials using structurally non-destructive diagnostic methods has gradually occupied its niche in the archeological natural-scientific research approaches [1,2,3]
The analysis of the chemical composition of the coin surfaces was performed without mechanical removal of the patina materials
It was found that all studied coins were made from copper-based alloys

Summary

Introduction

A detailed study of the chemical composition of ancient numismatic materials using structurally non-destructive diagnostic methods has gradually occupied its niche in the archeological natural-scientific research approaches [1,2,3]. Coins are being intensely investigated by means of non-destructive physical methods, such as traditional techniques like metallography or X-ray diffraction [1,3,9]. In this context, we should mention the neutron radiography [10,11,12] and neutron diffraction [12,13,14] methods as relatively modern structural non-destructive experimental approaches [1,15,16]. Neutron structural methods were applied to determine the bulk composition hidden by corrosion [11,14] for coin identification [11], for the reconstruction of coinage technologies and sources of mining materials for coins [19] and for the description of coins’ degradation like internal corrosion tracks [11,20] and deterioration areas [18,21]

Methods

Results

Conclusion