Microanalytical study of copper ores from the Chalcolithic settlement of Sao Pedro (Portugal): Copper production in the south-western Iberian Peninsula

Copper ores recovered at the third millennium bce settlement of Sao Pedro, Portugal, were characterized by micro-Raman spectroscopy, micro-energy dispersive X-ray spectrometry (micro-EDXRF) and micro-particle-induced X-ray emission spectrometry (micro-PIXE). The collection shows the common presence of secondary copper minerals (malachite, pseudomalachite and libethenite) combined with iron oxyhydroxides (hematite and goethite), while arsenic-rich minerals are absent and, therefore, can be excluded as the source of arsenical copper. Overall, these copper ores suggest a primitive technology involving the exploitation of the superficial zone of ore bodies and reliant on the fortuitous finding of arsenic-rich sources to produce the arsenical copper alloy frequently present among metallic collections of the Iberian Peninsula.