Plano-convex ingots and precious metalwork in northwestern Iberia during the Late Iron Age and early Roman period: an analytical approach

Abstract

The archaeological study of ingots has gained in importance in recent years due to their links with metallurgical production, pre-monetary exchange and the emergence of weighing systems. However, in the northwestern Iberian Peninsula, which has one of the most outstanding protohistoric precious metalworking traditions in Western Europe, little attention has been paid to this method of accumulating raw material. This article provides the first systematic approach to the chemical composition of the precious metal ingots from this geographical area, based on the elemental analyses of 40 examples datable to the Late Iron Age and the early Roman presence. Two types of ingot composition have been identified: gold-silver-copper alloy and silver. In general, the former do not coincide with those documented in the jewellery from the hillforts (c. fourth–first centuries BC). This means that they could belong to the latest period of this metalworking tradition (c. first century BC–first century AD), when there was frequent use of cores of less valuable metals. In addition to their metallurgical function, silver ingots appear to have played an important role in the proto-monetary economy that characterised the early Roman presence. We propose that the different geographical distribution of these types of ingot was related to the diverse interactional dynamics generated between the local communities and the Romans during the long process of their conquest of this territory (138–19 BC).