Archaeometric investigations of Sasanian silver drachmas (6th-7th century AD) using X-ray fluorescence analysis

X-Ray Fluorescence (XRF) analysis is widely employed in the field of cultural heritage due to its non-destructive nature. µ-EDXRF was used to study 29 Sasanian drachmas from a private collection at the Department of Humanities, University of Trieste. The coins were issued between 499 and 628 AD, during the reigns of four Sasanian kings (Kawad I, Khosrow I, Hormizd IV, and Khosrow II). This study aimed to determine the elemental composition of the alloy's surface, assess the coins’ fineness, and identify potential forgeries or signs of devaluation. Eight XRF spectra were acquired for each sample, revealing a primary composition of Ag, with traces of Cu, Au, and Pb. Semi-quantitative analysis showed Ag content exceeding 95% in nearly all coins, with two suspected forgeries identified (coin no. 13 minted during the reign of Hormizd IV and coin no. 18 from the reign of Khosrow II). Five drachmas from Khosrow II's reign, marked with the inscription “afid”, exhibited Ag content above 99 %, supporting the historical hypothesis of superior quality compared to other drachmas from the same period. Finally, the %Au and the presence of Pb provided further indications on the origin of Ag, allowing hypotheses on the mineral sources.