• Guerra, Maria Filomena
• Tissot, Isabel

Abstract

<p>This work is the first analytical study carried out on a representative group of early gold objects found in the region of Vila Real, situated in one of the richest gold-bearing areas in the northwest of the Iberian Peninsula. The objects were examined by optical microscopy and mobile XRF in four museums. Among them are the unique Early Bronze Age spiral ring from Vila Real (found at Fraga da Pitorca), one of the three chains of gold spirals from North Portugal and one of the few Villena-Estremoz type bracelets found in the Northwest (both from Alto da Pedisqueira). They constitute the Treasure of Chaves. Two of the three Bronze Age bracelets from Vila Real (found at Torgueda and Vinhós) have also been analysed together with typical productions of the region of Chaves, the Iron Age torcs from Rendufe, Codeçais and Paradela do Rio. Two similar torcs found in Lugo were analysed for comparison. When the earliest objects from Vila Real are compared to those found in neighbouring regions (Bragança, Minho and Galicia), they suggest regional exploitation of local gold resources. In Vila Real, native gold seems to be used as found until at least the end of the Bronze Age, but search and implementation of metallurgical practices related to several stages of production of intentional gold alloys seem to begin in the Early Iron Age. Some objects are made with gold containing a little more copper but amounts of silver within the same range as earlier objects, suggesting the addition of copper to local native gold, whereas others, particularly the torcs, contain increasing amounts of silver and copper. When copper and increasing amounts of silver are added to a gold containing 10 wt% Ag and 0.2 wt% Cu (native alloy observed at Vila Real) the theoretical debased alloys cover the chemical range defined by objects dated from the Iron Age to the early Roman period found north of Douro river, suggesting the use of well-established metallurgical practices.</p>

Topics

• impedance spectroscopy
• silver
• gold
• copper
• iron
• optical microscopy
• bronze
• X-ray fluorescence spectroscopy
• gold alloy