Comparative archaeometrical study of Roman silver coins by prompt gamma activation analysis and SEM-EDX

A selected set of 115 Roman silver denarii, minted during the period 119 A. D. to 194 A. D. have been examined in order to determine their silver and copper contents. All these denarii have been found at Romanow near Krasnystaw in Poland. The total excavated hoard contained 700 denarii from the period 112 A.D. to 195 A.D. Since the Roman currency in principle was based on pure silver, chemical analyses of a representative collection enables the archaeologists to follow the debasement of the coinage, and to assess the course of inflation. Prompt gamma activation analysis (PGAA) and comparative energy dispersive X-ray fluorescence (SEM-EDX) as non-destructive methods were chosen to study a large number of samples. Contrary to the shallow penetrating SEM-EDX, PGAA is an ideal method for non-destructive determination of bulk composition. The Cu/Ag mass ratios were determined for the detection of debasement and ancient counterfeiting of coins.