Raman and XRF classification of Asian and European glass beads recovered at Mutamba, a southern African Middle Iron Age site

Abstract

Twenty-eight representative beads found at the thirteenth-fourteenth century AD site of Mutamba in southern Africa were classified morphologically and then analysed with pXRF. Eighteen beads were selected from four identified series of K2-IP, EC-IP, Mapungubwe Oblate and European for Raman spectroscopy. The results show corrosion has a great effect on the composition and nanostructure of Mapungubwe series with lixiviation of alkalis. In corroded K2-IP beads elevated amounts of potassium recorded on the surface layer compared to less corroded IP beads. Despite these changes pXRF and Raman spectroscopy were successful in discriminating of the bead series by considering the concentration of trace elements (Zr, U), detected pigments (lead tin yellow (II), red lead), opacifiers (SnO 2 , calcium antimoniate) and colorants (Fe, Cu, Co) and their concentrations in the beads.

The Reliquary Bust of Saint Lambert from the Liège Cathedral, Belgium: Gemstones and Glass Beads Analysis by pXRF and Raman Spectroscopy

“…These spectra are in good agreement with all Raman signatures spectra of "Na 2 O + K 2 O + CaO" glasses from Colomban et al (2006). The bands between 300 and 600 cm À1 correspond to the symmetric bending vibrations of the SiO 4 4À tetrahedra, while the bands between 900 and 1300 cm À1 are assigned to the stretching vibrations of mainly depolymerised silicate (Robinet et al 2008, Koleini et al 2017. The band around 1000 cm À1 is also certainly influenced by a fluorescence phenomenon because of the dark colour of the stones (Jehlička et al 2011).…”

“…, Koleini et al . ). The band around 1000 cm −1 is also certainly influenced by a fluorescence phenomenon because of the dark colour of the stones (Jehlička et al .…”

Glass Beads, Markers of Ancient Trade in Sub-Saharan Africa: Methodology, State of the Art and Perspectives

“…An advantage of XRF is the existence of portable instruments which are much cheaper than laboratory based ones and therefore more available to archaeologists. However, the first problem with portable XRF instruments is that elements lighter than magnesium cannot be measured, but calculation and comparison with references can identify different types of glass [82][83][84]. The second problem with non-destructive XRF analyses with portable instruments on unprepared samples is the lack of flat (corrosion-free) surfaces and the difficulty to minimise the distance between the artefact and the instrument as well as keeping it constant.…”

The Chronology of Insiza Cluster Khami‐Phase Sites in South‐Western Zimbabwe: Compositional Insights from pXRF and Raman Analysis of Excavated Exotic Glass Finds

“…; Koleini et al . ,b, ,b). The results of the XRF and Raman measurements can be summarized as follows: The first group is a mineral soda glass with high alumina (>7.9 wt%) and low magnesia (<1 wt%).…”

“…Recent studies of glass beads conducted with the aid of a combination of pXRF and Raman spectroscopy have demonstrated the efficiency of these mobile techniques in defining the chronological sequences of traded glass bead series in southern Africa (Koleini et al . ,b; ,b). Following the method reported in Koleini et al .…”