The ingots from the archaic Giglio-Campese wreck: chemical and isotopic study

For a long time, archaeologists have debated the origin of the ship sunk a few hundred meters off the island of Giglio (Tuscan Archipelago, Italy), at about 50 m depth: the Giglio-Campese A wreck. The cargo of this wreck contained both Greek and Etruscan artifacts. In particular, the cargo consists of a series of luxury and functional artefacts: including, for the first, fine or decorated ceramics, and carved woods; for the latter, trade amphorae, metal ingots and weapons. These artifacts allowed to date the wreck to the early 6th century B.C.E. The identification of the provenance of the ancient metal found in the cargo, could give several issues to reconstruct the origin of this ship and improve the knowledge of technical and social aspects involved with this wreck. In fact, it is possible to locate the mining districts that supplied the ore and spread light among the ancient metal trade routes used in the archaic period. With this aim, five Cu ingots, and ten Pb ingots have been analysed in order to investigate the origin of the ore material used. The copper ingots, one of which was recovered from a recent seizure, are of the B2.2 and B2.3 types, according to Brown classification (Brown, 2011). The lead ingots are of the A3 type (Brown, 2011) and have a roughly triangular section. The methodological approach was based on optical microscope analysis, followed by SEM-EDS analysis to determine their chemical composition and morphology. Trace element composition was determined through ICP-OES, whereas lead isotopic composition was measured by TIMS (Thermal Ionization Mass Spectrometry) to investigate the metal provenance. The composition of Cu ingots has Cu contents between 87 wt% and 98 wt%, however, the analyses show an extensive corrosion, characterized by compounds of Cl and Ca, present in veins and porosity. In unaltered areas the Cu content rises. Different concentration of S, As, Pb and Ag suggests the use of different mineral charge. Sn is revealed in trace in all the Cu ingots analyzed (in the range 111 to 623 ppm). Noteworthy it is the diffuse presence of circular areas of few μm enriched in Bi. Nevertheless, it is attested a metallogenic separation between the majority of Sn and Cu deposits (Sillitoe and Lehmann, 2022). For this reason, it is possible to hypothesize a reuse of secondary material for the realization of this of ingots. The evidence is also supported by the isotopic data that reveals a signal scattered between the Greek and Italic areas. Concerning the Pb ingots, the Pb content is around 85 wt%, with minor content of Cu and Al. The presence of small quantities of S and several primary galena fragments, suggest that the ingots are the result of raw smelting from lead ores, without the reusing of other metal materials. The evidence is confirmed by isotopic data, which show a very similar Pb isotope composition and indicate a compatibility well centered on the Aegean area.