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.

New insight into Bronze Age goldwork from northern Portugal. Bracelets, spirals and torcs from the region of Vila Real

“…The Treasure of Arnozela (Armbruster 2010), found in the neighbouring region of Braga (Severo 1905-8b) and comprising gold ring-shaped items, wires and bands is in the same situation. The analysis by Guerra and Tissot (2021b) of all the components of this treasure has shown the variability of the alloys and allowed to suggest the LBA-early IA as terminus post quem of the deposition.…”

“…Figure 12 -The Cu and Ag contents contained in the torcs from Vila Real compared to the objects from Vila Real analysed in this work as well as the plates from Malhada analysed by Guerra and Tissot (2021b), the EBA objects from North Portugal (in Figure 8), the Treasure of Gondeiro and the torc from Bragança analysed by Hartmann (1971), and the jewellery contained in the Treasure of Estela analysed by Armada and García-Vuelta (2021). The hypothetical alloys estimated by adding silver and copper to a native gold containing 10 wt% Ag and 0.2 wt% Cu were added to the diagram.…”

“…Although the native gold used during the earliest period in North Portugal does not seem to contain the same amounts of silver as the native gold used during the same period in Galicia, the few objects from North Portugal that were to date analysed seem to suggest an increase with time of the copper content (Guerra and Tissot 2021b). To gather further information on the production process of intentional gold alloys, and to assess the initial use of native gold containing increasing amounts of copper, it is necessary not only to analyse a larger number of objects found in the Portuguese territory, but also to take into account the geographical origin of the finds.…”

“…We plotted in Figure 10 the torcs with all the other objects from Vila Real so far analysed. In addition to those already mentioned, were considered in the diagram the six gold plates from the LBA-early IA necklace found at Malhada (Silva 1986) analysed by Guerra and Tissot (2021b), and the gold torc presumably from Chaves analysed by Alves et al (2002). The other components of the Treasure of Lebução, analysed by Hartmann (1971), have also been considered.…”

“…One tubular bracelet, one torc and two fragments of torcs are contained in the Treasure of Lebução (Valpaços), dated to the Late IA (Ladra 2009, Martins 2010, and the two other objects are the bracelets from Torgueda and Vinhós (Peso da Régua), dated to the LBA (Armbruster and Parreira 1993). More recently, one gold torc dated to the IA, presumably from Chaves, was analysed by Alves et al (2002), and six of the more than fifty plates that constitute the LBA-IA string from Malhada (Campeã) were analysed by Guerra and Tissot (2021b).…”