Chemical and metallurgical characterisation of a serie of bronze Punic coins found at Tharros

Fifty bronze Punic coins of a serie known as the "free galloping horse", dating back to 350-320 BC and struck in the Punic settlements of Sicily and at Carthage, have been found at Tharros (Sardinia). The chemical composition and the microchemical structure of these coins have been studied as well as the provenance of the metals used to produce the alloy. In particular, the objectives of our work are twofold. One was to analyse the bronze coins for gaining knowledge into the chemical and metallurgical aspects of Punic bronze coins and further, for obtaining information on the metal ores used to produce the alloy and on the technological competency of Punics in carrying out the pyrometallurgical process, the alloying and the minting processes. Another objective is to attempt the location of the geographical sources of the lead, present as minor element in the coins, via lead isotope analyses. The results indicate that the coins have been produced using a copper based alloy characterised by a tin content ranging from 1.07 wt% to 12.8% and by a very variable amount of impurities, some of them coming probably from remelting processes. Furthermore, the results indicate that deliberate adding was used to increase the metal to fill the mould, as the addition of lead instead of the most expensive and rare tin. This large variation of the content of the alloying, minor and trace elements manifests relevant differences in the alloying and refining practices even though, a specific trend in metal composition and alloying is not yet shown. Furthermore, the microchemical structure of the inclusions entrapped in the bronze indicates the chemical nature of the ores used to produce the metals whose provenance seems to be Spain and Cyprus as suggested from the results of the lead isotope analysis.