Excavations at several archaeological sites in and around Gao have resulted in the recovery of thousands of glass beads presumed to have been acquired from glass bead-producing centers through trade. The bead assemblages cover the period from the eighth to the fourteenth century CE. Here we report on the results of compositional analysis by LA-ICP-MS of 100 beads, permitting comparison with the growing corpus of chemical analyses for glass from African and Near Eastern sites. In this analysis, several compositional groupings are recognized. These include two types of plant-ash soda-lime-silica glass (v-Na-Ca), a mineral soda-lime-silica glass (m-Na-Ca), a high-lime high-alumina (HLHA) glass, a mineral soda-high alumina (m-Na-Al), glass, a plant ash soda-high alumina (v-Na-Al) glass and a high lead composition glass. The reconstruction and dating of depositional contexts suggests a shift in glass sources at the end of the tenth century CE. The issue of source identification is discussed and occurrences at other African sites are mapped, providing new data towards an understanding of trade and exchange networks.
We report the preliminary results of chemical analysis by laser ablation-inductively coupled plasma-mass spectrometry of 156 glass beads from sites in southern Africa. Almost all of these beads can be grouped in two chemical types based on oxide compositions and glass recipes. Glasses of these types were manufactured in south and/or southeast Asia. These are the first results of a project that will analyse about 1000 beads from African archaeological sites.
Chemical analysis of 31 glass beads from the sites of Mahilaka and Sandrakatsy in Madagascar, which date to approximately the 9th to 15th centuries CE, reveals the presence of two main types of glass: mineral- soda glasses and plant-ash glasses. Most of these glasses were probably made in South Asia.