X-ray fluorescence analysis and the x-ray spectral microanalysis of late Bosporan staters from the Phanagorian and Gai-Kodzor hoards: technical aspects and possible copper ore sources

The Bosporan staters of AD 285/286-341/342 were investigated at their surfaces by X-ray fluorescence analysis (XRF) and at the cross-sections by X-ray spectral microanalysis in the scanning electron microscope (SEM/EDXMA) in order to determine the chemical composition of the alloy and proposal sources of copper raw materials for coin production. It is established that the Bosporan mint used a wide range of copper alloys: copper, lead-, tin-, tin-lead and multicomponent bronzes, as well as copper alloys with silver additives. When there was a deficit of pure copper, the mint used copper scrap containing other non-ferrous metals. Archaeometric studies allow us to trace the dynamics of degradation of coinage alloys over the years of emissions caused by high rates of inflation during the reign of Thothorses to Rhescuporis VI. The ‘damage' of the copper coin is caused by the state's intense search for money to fight the barbarians. The obtained data shed new light on a little-known feature of the Later Bosporan Kingdom coin production.