Archaeometric investigation of the Byzantine Period (Romanus III) gold coins unearthed in Diyarbakir Sur district excavations

Coins made of precious metals are at the forefront of materials that are preserved in museums and that can only be analyzed on-site. Portable X-ray fluorescence (p-XRF) spectrometry is mostly preferred for gold and silver-based coins that need to be characterized in situ and non-destructively with portable analysis devices. Within the scope of this thesis, a detailed archaeometric analysis was carried out by means of p-XRF on the coins which were found after the excavations in Melik Ahmet Street in 1992 and taken to Diyarbakır Museum Directorate through confiscation and recorded. The chemical composition of the samples was determined by analyzing 45 gold coins belonging to the Romanus III period with p-XRF without any damage. The analyzes were carried out under the supervision of museum officials, and after the study, the coins were taken back to their place in the museum by the authorities. In the analyses, the main element forming the composition for the coins of the Romanus III period is gold (93.89% on average). The most abundant element detected after gold is silver, but the highest silver rate does not exceed 9% (5.25% on average). Copper (1.05-2.46%) was found in 12 coins, and iron (0.87-6.5%) in 18 coins. Titanium, manganese, osmium, iridium, nickel and lead were detected in one sample each. Despite the fact that the elemental contents of the coins are mostly parallel to each other, hierarchical clustering analysis was carried out to see the distribution of the samples within themselves. In the classifications made with gold-silver-copper-iron and gold-silver, the coins formed three different groups. The analyses results obtained in the present study were compared with the chemical compositions of some Byzantine solidus and Byzantine period hollow gold coins (from Diyarbakır Museum) in order to make evaluations on possible changes, differences and similarities among the coins. For this purpose, hierarchical clustering analysis was carried out considering the p-XRF data of the coins in the present study (belonging to the Romanus III period), solidus samples belonging to six Byzantine period emperors who were on the throne between 457-695 and for the hollow coins belonging to four Byzantine period emperors who were on the throne between 1059-1143, and their distributions were examined. In the results of hierarchical clustering analyses for the Romanus III solidus coins respectively performed with the solidus belonging to different periods (according to the gold, silver, copper and iron contents) and with the Byzantine hollow gold coins (according to gold, silver and copper contents), it was seen that the coins were divided into 3 groups in both clustering analyzes. Considering results of the cluster analysis, it was seen that non-gold metals were preferred in the production of hollow coins produced in the following periods as an alternative to the high percentage of gold used in solidus in the Romanus III period and before. It has been determined that there were no significant changes in terms of coin metal in each emperor's own period, but there were fluctuations in the use of precious metals in coins as the emperor changed, especially in the hollow coins.