La Monica, Mariangela

This paper provides new petrochemical and paleomagnetic data from obsidian sub-sources on the island of Pantelleria, exploited since the Neolithic. Data has been obtained from 14 obsidian samples from 4 locations: Fossa della Pernice (2 sites), Salto la Vecchia and Balata dei Turchi. Here, we aim to better characterize these obsidians using a cross-disciplinary and multi-analytical approach, to further understand their archaeological significance. Major element analyses (EMP) have enabled two compositional super-groups to be distinguished: (i) Fossa della Pernice, less peralkaline and (ii) Balata dei Turchi–Salto la Vecchia, distinctly more peralkaline and having almost identical chemical patterns. Trace element analyses (LA-ICP-MS) corroborate major element groupings, with the Balata dei Turchi–Salto la Vecchia super-group being further characterized by a pronounced negative europium anomaly. Glass H2O contents (FT-IR) reveal an overlap among all the sub-sources (H2O = 0.1–0.3 wt. %). Magnetic methods have refined the petrochemical groupings, permitting further distinction between Balata dei Turchi–Salto La Vecchia and the Fossa della Pernice super-groups. The occurrence of sub-microscopic (< 1 μm) ferromagnetic minerals results in different magnetic susceptibility and Natural Remanent Magnetization values and allows the best distinction among the products from the chosen sites. When compared with obsidian tools excavated from Bronze-age settlements on the island of Ustica (230 km NE of Pantelleria), 12% are distinctly peralkaline, indicating their provenance to be from the Balata dei Turchi sub-source.

In this study we applied petrochemical methods (SEM-EDS; FT-IR) in order to characterize a group of obsidian flakes collected at Ustica island (Sicily). Despite the absence of obsidian geological outcrops, a lot of obsidian fragments still emerging from the lands of Ustica testify that the island was a major import center of obsidian during the prehistory. On this island, there are some prehistoric settlements, dated from the Neolithic to the Middle Bronze Age (6000- 1200 BC), in which the use of obsidian continued until the beginning of metals age. Our study includes: i) Macroscopic and microscopic optical observations, which allowed selecting 18 obsidian flakes (starting from 50 obsidian flakes) on the base of their morphological characteristics. ii) Density measurements (hydrostatic balance). iii) Scanning electron microscope determination (SEM-EDS) of major elements of the obsidian glasses and minerals. Results of our analyses were compared with 12 geological samples collected in obsidian sources from Monte Arci (Sardinia), Palmarola, Lipari and Pantelleria, i.e. the four most exploited obsidian sources of the ancient world in the Western-Central Mediterranean. This study confirms the presence of the Lipari and Pantelleria sources (Sicily) in our obsidian set. iv) We also determined (by FT-IR) the hydration degree of some obsidian flakes in order to detect a possible hydration gradient between the rim and the core of the flake sample. The width of the hydration rim, if any, can be used for an approximate evaluation of the age of the tool.

Volcanism has produced a natural glass called obsidian that during prehistoric times, from Neolithic to the Metal Ages, was considered a valuable raw material in order to produce efficient cutting tools. Ustica, a small and solitary island in the southwestern Tyrrhenian Sea, despite being volcanic, did not generate any obsidian. Yet the island's soils return large quantities of obsidian fragments, residues of prehistoric use. Where did this material, defined by some archaeologists as the Black Gold of prehistory, come from? This article reviews the archaeometric studies on Ustica’s obsidians, carried out since the middle of the 1990s, to answer this question. The obsidians of Ustica have become a tracer of commercial and cultural exchanges in the heart of the Mediterranean Sea. The geochemical fingerprint of Ustica obsidians is revealing a network of relations and exchanges not only with neighboring Lipari but also with the most distant Pantelleria and Palmarola islands. A fact that, for a tiny island that was completely devoid of spring water resources, appears surprising, in relation to the prehistoric context.