A multi-analytical approach to gold in Ancient Egypt: Studies on provenance and corrosion

Abstract

Recent results from a three-year multi-disciplinary project on Ancient Egyptian gold jewellery revealed that items of jewellery from the Middle Kingdom to the New Kingdom were manufactured using a variety of alluvial gold alloys. These alloys cover a wide range of colours and the majority contain Platinum Group Elements inclusions. However, in all the gold foils analysed, these inclusions were found to be absent. In this work a selection of gilded wood and leather items and gold foil fragments, all from the excavations by John Garstang at Abydos (primarily from Middle Kingdom graves), were examined using Scanning Electron Microscopy-Energy Disperse Spectroscopy (SEM-EDS), X-Ray Fluorescence (μXRF), Particle Induced X-Ray Emission (µPIXE) and Double Dispersive X-Ray Fluorescence (D 2 XRF). The work allowed us to characterise the composition of the base-alloys and also to reveal the presence of Pt at trace levels, confirming the use of alluvial gold deposits. Corrosion products were also investigated in the foils where surface tarnish was visually observed. Results showed that the differences in the colour of corrosion observed for the foils are related not only to the thickness of the corrosion layer but also to a multi-layer structure containing the various corrosion products.

Preliminary investigation of the materials and techniques used in a decorated wooden stick of king Tutankhamun

“…Almost no silver (Ag) was observed. This composition with a higher level of gold purity is in agreement with the composition of other ancient Egyptian gold leaf previously determined [18][19]23]. Despite this, the gold leaf adhered to the ground layer (spots no.…”

Gold from the tomb of Scribe Beri: a comparative analytical approach to the New Kingdom gold grave goods from Riqqa (Egypt)

“…The thickness of the tarnished layer in gold objects kept in museum atmospheric conditions is generally \1 lm [19]. The analysis using PIXE, which is representative of the first 5-12 lm of gold alloys, and XRF, which reflects the composition of a deeper layer from 8 to 30 lm, should in this work provide compositions that can be considered as being close to 'bulk' analysis.…”

“…The information used for processing quantification comes from a layer whose thickness very much depends on the amount of gold (highest Z) in the alloy, the energy of the X-ray lines used for elemental quantification, and the type of incident radiation (charged particles or X-rays). Nevertheless, EDS always analyses a very thin layer, below 0.6 lm, which for untreated surfaces may suffer from the heterogeneities caused by tarnishing or corrosion during burial [18][19][20].…”

“…The few existing publications on the alloys used in the manufacture of Egyptian goldwork dating to the second millennium BC seem to indicate the use of native gold from different sources [3,9,14,19]. Different amounts of Cu were frequently added to the native gold to enhance the colour and to change the properties of the alloys.…”

“…The significance of PGEs, as they relate to the use of alluvial gold, was discussed by Ogden [33,34]. While other sources of gold cannot be ruled out, the presence of Os-rich and Os-Ir alloy minerals in the Eastern Desert [35] could contribute to the presence of PGE inclusions on the surface of objects made from local alluvial gold, given that the subgroup Ir, Os, and Ru [36] is non-soluble in gold [19].While no inclusions could be identified in Egyptian gold foils, the presence of Pt was demonstrated for gilded wood and leather items and gold foil fragments from Middle Kingdom tombs in Abydos by using the newly developed method double dispersive X-ray fluorescence (D 2 XRF) at the BAM line of synchrotron BESSY [19], confirming the use of alluvial gold.…”