The Neolithic greenstone industry of Brignano Frascata (Italy): archaeological and archaeometric study, implications and comparison with coeval sites in the Grue, Ossona and Curone valleys

The Neolithic greenstone industry of Brignano Frascata (Province of Alessandria, Piemonte Region, Northern Italy) was investigated with an archaeometric approach involving both morpho-typological and mineral-petrographic methods, in order to reconstruct the manufacturing techniques/habits and locate the supply sources of the raw materials. The outcomes were compared with those collected on similar tools from other sites of the same region, namely in the Grue, Ossona and Curone valleys, as well as others resulting from a pilot comparative study on analogous geological specimens from close Quaternary alluvial and/or Oligocene conglomeratic deposits. This survey proved that Brignano Frascata should be considered as a local atelier for the production/trade of polished stone implements in Neolithic, devoted to daily uses with no ritual purposes. Several indicators point to an in situ manufacturing (high number of retrieved roughouts/fragmented tools, broken during production/use), which also fed trade/exchange forms on short-to-medium distances. Although displaying gross processing features and lack of finishing, these tools show an excellent selection of lithologies, marked by predominance of 'Na-pyroxene rocks'. Several mineral-petrographic resemblances are observed with analogous geological samples from local sources, as well as with coeval implements from other Northern Italy sites, suggesting a common supply source or the existence of a trade channel. By considering the mineral-chemical features of the rocks used to produce these tools, referred to the particular geologic context of discovery (eastern part of the Voltri group), the chance for the raw materials to derive from secondary deposits of close conglomeratic formations and/or alluvial beds of streams flowing in the adjoining valleys is proposed.