The application of non-destructive techniques for the study of corrosion patinas of ten Roman silver coins. The case of the medieval Grosso Romanino

This work focuses on the study of ten Grosso Romanino, a silver medieval coin, minted in Rome during the 13th century CE. As the coinage of this denomination occurred during a tumultuous period of the history of Rome, the official documentation from Mint was lost. For this reason, archaeometric investigations were necessary to have an overall knowledge of the Grosso Romanino. This work represents the first attempt of archaeometric study performed on this interesting denomination. The coins were characterized by a combination of non-destructive techniques, i.e., X-ray diffraction (XRD), Scanning Electron Microscopy (SEM-EDAX), micro-Raman spectroscopy and Voltammetry of Microparticles (VIMP), aiming to investigate the external surface and its microstructure and to explore the nature of the alloy and corrosion products. The results show an Ag- rich alloy with minor amount of copper (2.1–3.1 wt%), lead (0.7–3.2 wt%) and other elements. Moreover, the rare corrosion products on the surfaces indicate the presence of a random distributed patina composed by oxides, sulfides and chlorides.