Discriminating the origin of obsidian fragments in archaeological contexts based on morphological features and geochemical data: the Breccia Museo (Campanian Ignimbrite eruption, Italy) case study

A recent archaeological discovery on Vivara, the small islet next to Procida (Campania region, Italy), has documented the prehistoric use of finely crushed obsidian fragments as abrasive powder for polishing wooden artifacts. These fragments originated from a local deposit known as Breccia Museo – whose exploitation in prehistoric times had not been previously attested – and were found mixed with obsidian tools sourced from other well‑known Italian deposits widely used throughout prehistory. To develop effective methods for discriminating obsidian provenance, as required in this case, we carried out geochemical, isotopic, and mineralogical analyses on obsidian samples collected from the Breccia Museo outcrop at Punta della Lingua (~4 km NE of Vivara), one of the richest and most accessible deposit on Procida Island. The results were compared with those obtained from Breccia Museo obsidians from other local (Campi Flegrei) outcrops, as well as with reference samples from the major obsidian sources exploited in the Central‑Western Mediterranean during prehistory (Monte Arci, Palmarola, Lipari, and Pantelleria). In addition, a micromorphological and microanalytical study was performed to identify further distinctive features useful for recognizing Breccia Museo obsidian across different archaeological contexts. This interdisciplinary investigation highlights the potential of combining relatively rapid major/minor element analyses, mineralogical and morphological characterization, with more time‑consuming but highly precise isotopic measurements (87Sr/86Sr, 143Nd/144Nd) to achieve robust provenance discrimination.