Trade Wind Beads: An Interim Report of Chemical Studies

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

“…A Raman spectroscopic study in combination with XRF analysis of the Mapungubwe oblates (Prinsloo and Colomban, 2008) classified the glass as typical soda/lime/potash glass with a similar Raman spectrum as Islamic glass from the 8th century (Ommayad) (Colomban, 2004), but with higher levels of aluminium, iron and magnesium. This is in accordance with the previous results obtained from XRF, NAA and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses (Davison and Clark, 1974;Davison, 1973;Saitowitz, 1996;Robertshaw et al, 2010). The turquoise, bright green, bright yellow and orange colours were obtained by utilising a combination of cassiterite (SnO 2 ) and lead tin yellow type II (PbSn 1Àx Si x O 3 ).…”

“…Employing both X-ray fluorescence (XRF) and neutron activation analysis (NAA), both novel techniques in the 1970's, Davison found that the beads were chemically different to the beads excavated in eastern Africa and at that time known as "trade wind beads" (Van der Sleen, 1956). She named the beads the Mapungubwe oblates and also found that the beads from the K2 site (M1 layer at Mapungubwe) were chemically in a separate group and after Gardner named it the M1 group (Davison and Clark, 1974;Davison, 1973). Extensive studies using X-ray powder diffraction (XRD), rare earth elemental analysis (REE) and XRF measurements of some of the burial beads and the beads excavated by Meyer and Eloff (later excavations) were undertaken by Saitowitz who proposed Fustat as the origin of some of the beads based upon REE analysis, but gave inconclusive scientific evidence (Robertshaw et al, 2010;Wood, 2000Wood, , 2005.…”

The Trading of Ancient Glass Beads: New Analytical Data From South Asian and East African Soda–alumina Glass Beads*

“…It seems that this second type of glass is more recent and that it circulated between the east coast of Africa and Madagascar and the west coast of India, possibly with Chaul as a trading port to Africa, over a period ranging from the ninth to the 19th centuries ade. It is quite likely that the high-uranium glass samples identified by Davison (1972) and Davison and Clark (1974) are part the hU-lBa glass group, even if this would need to be verified by determining barium, strontium and zirconium concentrations in the samples. If we take Davison's results into account, the region of occurrence of the hU-lBa glass could be extended in Africa to the two Kenyan sites of Fort Jesus and Gedi, and would encompass Mozambique, Zimbabwe, Zambia, South Africa (eastern part), the site of Vohémar in Madagascar and the site of Maski in India.…”

“…In previous studies (Davison 1972;Davison and Clark 1974; Popelka et al 2005), relatively high uranium concentrations were measured in m-Na-Al glass found in Sub-Saharan Africa. Figure 5 shows the repartition of the uranium concentrations for each Kenyan site, Chaul and for South India and Sri Lanka.…”

Maritime Community Settlement History in Pangani Bay, Tanga Coastal Region, Tanzania

“…According to Davidson and Clarke (1974), glasshouses, probably located in India produced enormous quantities of beads from c. 1000-1700 AD, for sale everywhere along the Indian Ocean. The recovery of glass beads in Pangani Bay shows that Swahili traders played an important role in the acquisition and commercial supply of these beads to the neighbouring Swahili towns and immediate hinterlands.…”