The provenance of twelve un-worked blocks and one part-knapped block recovered from the surface of five Middle Neolithic sites in the vicinity of Porto Vecchio, southeastern Corsica (western Mediterranean), was determined by ion beam analysis (PIXE). This is the first such discovery on Corsica of actual raw blocks of this exotic material. Twelve of these samples come from sources associated with the Monte Arci volcanic complex of Central-West Sardinia, with six each of the SA and SC chemical types. The only possible origin for the remaining block is Lipari, a raw material previously only attested by three artifacts from a Neolithic site of NW Corsica. This piece is aberrant for its unusual facies and its poor quality, making it quite unsuitable for knapping, and by extent distinct from the high quality glassy obsidian from Lipari that was used regularly by Neolithic peoples. This raises the question of the archaeological significance of this surface find.