Petrographic and spectroscopic (FT-IR) study of Western Mediterranean obsidians geological sources and of a lithic collection from Ustica Island (Sicily)

Mariangela La Monica, Silvio Giuseppe Rotolo, Franco Foresta Martin


  1. In this study we applied petrochemical methods (SEM-EDS; FT-IR) in orderto characterize a group of obsidian flakes collected at Ustica island (Sicily).Despite the absence of obsidian geological outcrops, a lot of obsidianfragments still emerging from the lands of Ustica testify that the island wasa major import center of obsidian during the prehistory. On this island,there are some prehistoric settlements, dated from the Neolithic to theMiddle Bronze Age (6000- 1200 BC), in which the use of obsidian continueduntil the beginning of metals age. Our study includes: i) Macroscopic andmicroscopic optical observations, which allowed selecting 18 obsidianflakes (starting from 50 obsidian flakes) on the base of their morphologicalcharacteristics. ii) Density measurements (hydrostatic balance). iii)Scanning electron microscope determination (SEM-EDS) of major elementsof the obsidian glasses and minerals.Results of our analyses were compared with 12 geological samplescollected in obsidian sources from Monte Arci (Sardinia), Palmarola,Lipari and Pantelleria, i.e. the four most exploited obsidian sources of theancient world in the Western-Central Mediterranean. This study confirmsthe presence of the Lipari and Pantelleria sources (Sicily) in our obsidianset. iv) We also determined (by FT-IR) the hydration degree of someobsidian flakes in order to detect a possible hydration gradient between therim 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.


Obsidian, Mediterranean obsidians, Ustica Island.

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X