A Raman spectroscopic study of glass trade beads excavated at Mapungubwe hill and K2, two archaeological sites in southern Africa, raises questions about the last occupation date of the hill

Thousands of glass trade beads were excavated over a 75 year period on Mapungubwe Hill and at K2, two archaeological sites in the Limpopo valley, South Africa. An assemblage of 175 beads that appeared to be different in shape, size and colour (red, yellow, green, blue, white, black, pink, plum) was studied with Raman scattering. At least seven different chromophores or pigments (lazurite, lead tin yellow type II, Ca/Pb arsenate, chromate, calcium antimonate, Fe–S “amber” and a spinel) have been identified. Pigment identification allows the recognition of specific productions and indicated that many of the pigments colouring the beads excavated on Mapungubwe hill were manufactured after the 13th century, confirming the presence of modern beads in the archaeological record, some dating from the 19th century. This date is in agreement with the last occupation date for the hill suggested by the earlier excavators and raises questions about the revision of this date to 1290 AD by archaeologists in the 1970’s.

► 175 glass trade beads analysed with Raman spectroscopy.
► The glass matrix was classified into two main sub-groups.
► Seven pigments or chromophores identified.
► Some pigments were manufactured after the 13 c.
► This conflicts with last occupation date (1290 AD) of the site obtained with carbon dating.