Metal artifacts are among the most common materials in the Cultural Heritage as they have been used in several fields of everyday life. The study of composition of alloy and its patina in archaeological metallic objects can provide indications about the metal provenance and the involved manufacturing procedures, leading to important conclusions regarding the state of conservation, trade routes and technological background. In our case, coins are important for studying provenance materials, dating, minting and corrosion processes as well as the stratigraphy of the archaeological sites.
The aim of this proposal is to investigate the microstructure and the composition of the alloy with a micro-invasive approach using FIB-FESEM-EDX along with traditional techniques (Raman spectroscopy, EMPA). Commonly, to investigate the composition of metal core are necessary the application of invasive and destructive techniques, therefore the developing a method with minimal damage of artifact can be of a great interest. FIB-FESEM-EDX analysis provides information about the composition, structure and thickness of the metal patina as well as the composition and microstructure of the metallic core without the need to dissect the sample to investigate deeper layers. Recently, FIB-FESEM-EDX was used as a complementary technique but it is never been applied systematically on a large set of samples. In addition, the comparison with EMPA data will be innovative and essential for the validation of the technique. Moreover, crossing the information coming from other techniques allows understanding the technological aspects of minting. As a result, FIB-FESEM-EDX features yield information for the diagnostic, authentication, technologies and historical context in which the coins were produced.
The proposal is innovative in the field of Science Applied to the Cultural Heritage as FIB-FESEM-EDX has never been used as main analytical methodology with archaeological finds. In addition to the progress of analytical techniques in the diagnostic, archaeometric implications will be a fundamental result after the validation of FIB-FESEM-EDX on samples. Indeed, metal core contains information useful for the aims before described and until now acquired primarily with destructive techniques. FIB-FESEM-EDX can be considered as micro-destructive technique but the damage is not visible at macro-level so the integrity of the sample is assured according to the philosophy of restoration too. However, thanks to these trenches it is possible to understand how the coins were produced, analysing the composition of the alloy layer by layer. Technologies and raw materials information will be crossed with the archaeological issue, resolving problems such as production, trade, use of the artefact as well as its burial history. This last information is fundamental too: it can help in the reconstruction of the archaeological site and its environmental features studying the surface corrosion products. The study of a metal artefact, from the core to the surface, will bind the analytical advances in the field with the resolution of the main archaeological problems.