Post-15th century European glass beads in southern Africa : composition and classification using pXRF and Raman spectroscopy

Abstract

A hundred and twenty-seven glass beads found at the archaeological sites in southern Africa were analysed using pXRF and Raman spectroscopy. The beads are identified as European productions on the basis of their composition and morphology. Six identified glass groups are soda-based plant ash (61%), potash-rich wood ash (14%), synthetic soda (8%), mixed alkali (4%), lead-soda (22%) and natron (4%). Except for soda-based plant ashes and natron (outliers), all the groups date back to the 19th century. Calcium antimonate (Ca2Sb2O7) detected in most of the soda-based plant ash glasses (87%) indicated that some of the beads had been imported from Europe since the 17th century.