The role of arsenic in Chalcolithic copper artefacts - insights from Vila Nova de São Pedro (Portugal)

► Association between copper alloyed with arsenic (As > 2%) and artefacts typologies. ► Final forging treatment present in artefacts with higher arsenic contents. ► Harder forging applied to the cutting edge of the artefacts leads to high hardness. ► Arsenical copper was not recognized by ancient metallurgists as harder material. ► The selection of the alloy was possibly made based on colour.