Archaeometric Characterisation and Assessment of Conservation State of Coins: The Case-Study of a Selection of Antoniniani from the Hoard of Cumae (Campania Region, Southern Italy)

The paper presents the first archaeometric results on a selection of ancient Roman coins (antoniniani) from a treasure found in the Roman necropolis area of ancient Cumae (Southern Italy) during archaeological campaigns by the Centre Jean Berard. A multi-analytical approach consisting of non-destructive techniques (stereomicroscopy, FESEM-EDS, pXRF, Raman, mu-CT) was implemented on the better-preserved coins of the treasure in order to investigate the chemical composition of the alloy. Chemical analysis showed that the Roman mint prepared the metal with an argentiferous lead-bronze alloy. A group of coins presents a low content of the precious metal, which is in agreement with the financial crisis of the Roman Empire of the third century. Another group of two coins shows a higher silver content, which is in agreement with their issue or with the Mediolanum mint standards. In addition, the external layers of corroded coins were analysed to explore the state of conservation of the patina and to identify the corrosion products. Some typical corrosion patinas due to post-depositional conditions were identified. The mineralogical characterisation of the corrosion products enables us to implement adequate conservation strategies, and the presence of more aggressive patinas suggests immediate interventions.