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

Abstract

Fourteen glass beads and one glass fragment from Khami-period (AD 1400-1830) sites of Danamombe, Naletale, Gomoremhiko, Nharire and Zinjanja, in Zimbabwe, were analysed by pXRF and Raman spectroscopy with the intention of correlating the results with associated radiocarbon dates. The results show that Zinjanja and an earlier part of the Danamombe stratigraphic context had Khami Indo-Pacific beads (15th-17th centuries) corresponding with Torwa occupational layers. Other European beads and one bottle fragment [high-lime, lowalkali (HLLA) glass] dating from the 16th to the 19th centuries were confined to the top stratigraphic layers of Danamombe and Naletale, which coincide with the later Rozvi occupational layers. Gomoremhiko had one Mapungubwe-Zimbabwe bead series (13th-15th centuries), which suggests that it was probably earlier than the other sites. All European beads are made of soda-lime plant-ash glass with high alumina, which makes them comparable with glass produced through the Mediterranean traditions in Southern Europe.

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

“…Blue (cobalt) beads of the IP series type were imported for the first time during the Khami period. This period coincides with the arrival of the European traders (first the Portuguese, then the Dutch merchants) but the number of European beads is very low as observed at Baranda and Danamombe sites in Zimbabwe [83,95] as the early European traders also initially sourced their beads in India. It is only in the mid-17th century that a rise in European bead numbers as well as a variety of colours and compositions is documented [94,127].…”

“…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.…”

“…For instance, analysis of the bibliography (almost exhaustive) compiled by the Society of Bead Researchers lists 243 articles that were published between 1981 and 2016 [93] (summarised in Table 3 based on locations in Africa). Figure 2 shows the variety of size, shape and colour of beads excavated at different archaeological sites in Southern Africa (Botswana, South Africa and Zimbabwe) with occupation dates from around the 10th to 19th centuries AD [78,82,83,94,95]. [96][97][98].…”

On-Site Raman Spectroscopic Study of Beads from the Necropolis of Vohemar, Northern Madagascar (>13th C.)

“…The subtraction of the baseline following the established procedure allowed the comparison of spectra recorded with different instruments [44]. Once a convenient quality, a processed spectrum was obtained, if possible, following previously established categorization criteria [44][45][46][47][48][49][50][51][52][53], to assign the spectra to a particular mineral or a family of glass bead. Broad components at ~500 and 1000 cm −1 were characteristic of the bending and stretching bands of the SiO4 vibrational unit forming the silicate amorphous framework (Figure 3).…”

Application of Raman Spectroscopy to Ancient Materials: Models and Results from Archaeometric Analyses

“…Based on this vectorial model, many studies were able to successfully examine the graphical spread of single material whose contribution had different geographical provenance. The work proposed by Koleini et al [40], for example, analyzed fourteen glass beads and one glass fragment from Khami-period (AD 1400-1830) sites of Danamombe, Naletale, Gomoremhiko, Nharire, and Zinjanja, in Harare, Zimbabwe. The intent was to assign the occupation domain of that land basing the analysis on jewels provenance.…”