Use-wear analyses and provenance determination of pitchstone artefacts: a pilot study from western Scotland

Pitchstone (a volcanic glass similar to obsidian) from geological outcrops on the west coast of Scotland circulated widely among Neolithic communities in northern Britain and Ireland, representing an exchange network that in its areal extent rivalled those that developed around obsidian sources in continental Europe and the Mediterranean. While the archaeological distribution of pitchstone within the British Isles is now well documented, rather less is known about which sources were used or the functions of pitchstone tools found in archaeological contexts. Here we report the results of a pilot study, the main objectives of which were to: (1) assess if we could discriminate between pitchstone sources and assign archaeological finds to sources using non-destructive chemical analysis, and (2) determine how use-wear manifests itself on pitchstone artefacts. We undertook pXRF analyses of pitchstone samples from two geological outcrops on the Isle of Arran and five archaeological assemblages from Neolithic sites on Arran and mainland Scotland. We also conducted analyses of wear patterns on pitchstone artefacts from all five archaeological assemblages. To aid interpretation of the wear patterns observed on archaeological pieces, experiments were conducted in which natural pitchstone flakes and replicated artefacts were used in various tasks (processing of dry and fresh wood, pig hide, reed, and fresh meat and bones) followed by microscopic examination to assess the kinds of use-wear produced. The results of the pXRF analyses suggest that the pitchstone found at each of the archaeological sites examined was obtained from more than one source. The results of the use-wear analyses were equivocal. Microfractures and striations were identified on both archaeological and experimental artefacts. But it proved difficult to distinguish taphonomic from use damage on the archaeological pieces.