Analytical Study of Overlooked Bronze Age and Iron Age Goldwork from Northwest Portugal

Abstract

To gain further insight into the use of native gold and intentional gold alloys during the Bronze Age in Northwest Portugal, jewellery in  the collections of three Portuguese museums was studied using an in-house built portable X-ray fluorescence spectrometer. Among  the analysed objects are the Late Bronze Age bracelet from Monte Airoso (Viseu) and the Iron Age tubular bracelet from Regoufe  (Aveiro). To shed more light on the manufacture of gold bracelets, have also been analysed all the components (bracelets, wires and  bands) of the hoard of Arnozela (Braga), so far incompletely studied. The results obtained show that from the Middle Bronze Age  onwards gold containing 8-11 wt.% silver is used, to which gradually increasing amounts of copper seem to have been added over  time. These results support a heterogeneous chronology for the components of the hoard of Arnozela and show that the bracelet from Monte Airoso is made from an intentional gold alloy used in the Portuguese area during the Late Bronze Age. On the contrary, the  bracelet from Regoufe is made from native gold without addition of copper. This could indicate that at least during a certain period the goldsmiths used both native gold as found and intentional alloys.
Two other objects, discussed on the light of the data obtained for the bracelets, complete the study. One of them is one of the two  Portuguese Early Bronze Age gold sheet ornaments with cut parallel bands (so-called gargantilha de tiras), found in Braga. Without obvious signs of use-wear like other ornaments of the same type, and made, as expected, with gold hammered into sheet, this  ornament is made from an alloy that seems to correspond to a later period using gold from another origin. Finally, the composition of  some of the components of the Late Bronze Age-Iron Age string from Malhada (Vila Real), a set of gold decorated plaques made from punched gold sheet by using different and asymmetrical punches, supports the addition of small amounts of copper to gold to produce intentional alloys.