Estudo arqueometalúrgico de artefactos provenientes do Castro de Vila Nova de São Pedro (Azambuja, Portugal)

Abstract

The Castro de Vila Nova de São Pedro (VNSP) is an emblematic settlement located at Azambuja, Portugal. It was predominantly occupied during the Chalcolithic period (III Millennium BC). A diversified collection of 53 copper-based artefacts (mostly in a fragmentary condition), belonging to the extensive metallic collection of VNSP deposited at MAC, was studied using micro-EDXRF spectrometry, optical microscopy, SEM-EDS and Vickers microhardness measurements. Results show that the artefacts collection is mainly composed of copper or arsenical copper, being 38% made of copper alloyed with arsenic (As > 2%). A statistically significant association was found between copper alloyed with arsenic and artefacts classified as tools/weapons (blades, arrowheads and daggers). Microstructural analyses show that the majority of this group (73%) was shaped with forging plus annealing operation cycles and 23% received a final cold hammering. An association between the presence of a final forging treatment and artefacts presenting higher arsenic contents was identified. Nevertheless, no direct correlation was found between the arsenic content of the alloy and/or a final forging treatment and artefacts hardness. However, it was observed that a harder forging was applied to the cutting edge of the artefacts and despite the arsenic content in the alloy a high hardness was obtained in this area.