Study of gold alloy productions from Late Bronze Age and Iron Age

• Autor(a) principal: Serrano, Sofia Pereira
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/155789
• topic: Gold; Silver; Iron Age; Iberian Peninsula; XRF; OM; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

This master’s dissertation focuses on the archaeometallurgical study and conservation of thirteen gold alloy earrings attributed to the Late Bronze Age and Iron Age from the Western Iberia. Most of the artefacts studied are from the collection "Treasures of Portuguese Archaeology" of the NationalMuseum of Archaeology (Lisboa, Portugal). Based on typological and decoration features, they were divided into two groups: eight plain gold rings, attributed to the LBA, which are bulk objects with a smooth surface, and five IA earrings with complex goldwork, like gold wires, sheets, granules and gilding. The aim of the study includes: i) the study of the alloy compositions; ii) the study of the detailed fine goldwork of the objects; iii) contribute to the understanding of technological evolutions from LBA to IA; iv) determination of heterogeneities in gold alloys at the surface level, due to corrosion, technological features or previous treatments, with an influence on their conservation. To achieve these goals complementary analytical and examination techniques were used, such as general photography, multifocus microscopy, elemental analysis by portable and micro X Ray Fluorescence Spectrometry (XRF) and microscopy and elemental analysis by Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). Results showed variations on the artefacts composition, being mostly composed by an Au-Ag alloy (8-20 wt.% Ag), with small amounts of Cu. The only exception are two IA earrings, with absence of Cu, unusual for alloys from this period. It also allowed to carry out compositional characterizations at different depths, concluding that heterogeneities exist within surface areas but can be more significant at different depths. Overall, a superficial loss in Ag was found, possibly due to corrosion phenomena, being that any conservation and restoration treatment could interfere with the final surface composition. It was found that the goldwork performed in some earrings is very fine, showing that ancient goldsmiths were able to produce wires and granules with less than 1 mm in diameter, as well as gilding. The results obtained are significant for the study of ancient technologies as well as for future conservation approaches to Proto-historic goldworks.