Spectroscopic analyses of an ancient silver fragment of the reliquary bust of St. Leo

A fragment of the silver reliquary bust of St. Leo, made in Messina, Italy, in the last of 1739 and now preserved in the church of SS. Savior of Africo Nuovo, Reggio Calabria, Italy, was investigated with spectroscopic techniques (scanning electron microscopy (SEM)+energy-dispersive X-ray (EDX), X-ray diffraction (XRD)) in order to analyze the composition of the sample in terms of elements and compounds. EDX analysis employs an electron beam that interacts with the sample, leading to the emission of characteristic X-rays as secondary radiation. In the XRD analysis, a Cu K alpha X-ray radiation is detected by a Si(Li) solid-state detector after the interaction with the sample. The chemical composition of the bulk allowed to identify the constituting metal alloy, while the detection of surface elements and compounds, closely related to the sample preservation, was useful in order to suggest to restorators the best interventions to minimize the conservation problems that could affect the durability of the precious artefact.