PIXE and SEM studies of gold artefacts

Gold jewellery artefacts of Tartesic origin (700-500 B.C.) have been studied using external beams for quantitative PIXE. Collimators along the incident proton beam (2.7 MeV) allowed the artefacts to be irradiated in narrow regions down to 350 μm in diameter. Special attention has been paid to the procedure of soldering in various narrow regions of the bindings of filigrees, twisted wires, narrow strips and granulations on finely decorated items. By using reference materials and thick target PIXE programs including all matrix effects (X-ray cross sections, attenuation coefficients, secondary fluorescence), relative concentrations of Au, Ag and Cu in various regions have been determined. The results seem to indicate that solderings were made by local fusion and brazing. No procedure of solid state diffusion bonding like in Etruscan jewellery has been identified. Qualitative results using imaging and EDX induced by a very narrow electron beam (SEM) give complementary information to the quantitative determinations obtained from the PIXE measurements.