The composition of roman metals from Moinho do Castelinho and Quinta da Bolacha (Portugal)

Abstract

The work involved the elemental characterisation by micro energy-dispersive X-ray fluorescence spectrometry of copper-based objects recovered during archaeological works at the neighbouring roman sites of Moinho do Castelinho and Quinta da Bolacha (Lusitania province). The set of 9 artefacts comprised ornaments, tools and implements of different type (fibula, shroud pin, punches, spatula, hook and nail), in addition to small fragments of unknown functionality (a fragmented handle and a small bar). Micro-EDXRF point analyses identified a diversified metallurgy including copper, bronze and leaded bronze, in addition to iron, nickel, arsenic and antimony as minor elements. Furthermore, micro-EDXRF elemental mappings identified the presence of Pb-rich inclusions in the bronze alloys with higher lead content. The composition of these roman artefacts suggests a selection of alloys according to the functionality of the artefact, as evidenced by a nail composed of copper, a handle with a more complex shape made with leaded bronze and a bronze fibula with a higher amount of tin. Finally, the choice of distinct alloys for everyday objects was viewed in the light of technological, symbolic and economic concerns, and compared with the use pattern of roman sites in the western end of the Iberian Peninsula.