Surface characterization of medieval silver coins minted by the early Piasts: FT‐IR mapping and SEM/EDX studies

An investigation of a numismatic collection of silver denarii from the early Piast dynasty was conducted using Fourier-transform infrared spectroscopy. The studied coins, minted between 995 and 1020 ad under the rules of Boleslaus the Brave and Mieszko II Lambert, belong to the collection of the National Museum in Krakow. Fourier-transform infrared spectroscopy imaging and mapping have been used for recording a visual image of the surface chemistry based on vibrational spectra and accurately representing the distribution of chemical compounds, respectively. Additionally, scanning electron microscopy coupled to energy-dispersive X-ray analysis was used to study the surface topography of the coins and characterize their elemental composition. Differences in the distribution of the identified chemical compounds were detected in heterogeneous areas of the denarii. Corrosion effects, associated to many factors including the alloy composition, the metallographic structure, the manufacturing processes, and the environment were also observed and identified.