Chemical composition and lead isotopy of copper and bronze from Nuragic Sardinia

Abstract

We present data on the chemical and lead isotope composition of copper and bronze objects from Nuragic Sardinia. The sample suite comprises, inter alia, objects from the hoard finds at Arzachena (21 objects), Bonnanaro (10), Ittireddu (34), and Pattada (20), all in northern Sardinia. With one exception, all ingot fragments (49) consist of unalloyed copper; the exception comes from Ittireddu and contains 11 per cent tin. In contradistinction, all implements (21) are made from standard bronze with a mean tin content of 10.8 per cent. A dozen sword fragments from the Arzachena hoard, all of fairly uniform small size, are pieces of a large number of different swords. The low tin content of only about 1 per cent would have made for poor weapons, confirming the archaeological identification of the fragments as pieces of votive swords. Scrap metal from Arzachena is remarkable for its wide range of trace element contents and lead isotope abundance ratios. It is dissimilar to all other metal samples investigated, possibly representing metal from local smelting experiments using a variety of different copper ores. Lead isotope data and trace element patterns, alone or in conjunction, do not allow us to tell oxhide ingots from plano-convex (bun) ingots. Most ingot fragments have a lead isotope signature similar to those of Cypriot copper ores but there are also a number of ingots whose lead isotope fingerprints are fully compatible with them being local products. Of the bronzes, none has lead with an isotopic composition characteristic of copper ingots from Cyprus. All contain local lead, suggesting the bronze implements were manufactured locally. Isotopically-fitting lead is found in copper and lead ore deposits from the Iglesiente-Sulcis district in south-west Sardinia and from Funtana Raminosa in central Sardinia.