Chemical Analysis Of Ancient African Glass Beads

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Glass beads have been found at innumerable archaeological sites in sub-Saharan Africa. However, obtaining information from glass beads found on sites that date to before European contact has proven difficult. Since glass was not manufactured from raw materials in sub-Saharan Africa (with one possible exception), archaeologists know that glass beads were trade items that linked large parts of the Old World in an early version of the global economy. If archaeologists could establish where the glasses used to make particular beads were manufactured, then they could study patterns of trade that linked Africa to the wider world over the last two millennia. Experience has shown that the only way to discover the sources of the glass is through chemical analysis. This was tried thirty years ago but without much success because of imprecise analytical techniques and a lack of comparative data from glass-making centers outside Africa. However, much has now changed: accurate chemical analyses have been undertaken of ancient European and Asian glasses, including material found at glass factories, while a new technique, laser-ablation inductively-coupled-plasma mass-spectrometry, has been developed that permits quantitative analysis of numerous chemical elements found in glass beads without damage to the beads themselves. With National Science Foundation support, Dr. Peter Robertshaw, with the assistance of scientists at the federally funded University of Missouri Research Reactor Center, will analyze about 1000 glass beads from sites throughout sub-Saharan Africa to answer two sets of questions of central importance in understanding the African past. First, they will examine beads found at sites along the coast of eastern Africa and in the southern African interior to answer several questions: Where did the glass come from - north Africa, southwest Asia, India, China, or southeast Asia? What changes in patterns of Indian Ocean trade occurred in the millennium preceding the arrival of the Portuguese in East Africa? Did different African ports obtain their glass from different sources? Did sites in the interior of Africa, such as Great Zimbabwe, receive beads from many ports and many sources? Did patterns of trade between the interior and the coast change through time? Second, Robertshaw and colleagues will seek to discover the trade routes that connected Igbo-Ukwu in southeastern Nigeria to the wider world. Igbo-Ukwu is famous for its ninth-century bronze vessels of local manufacture. Here too were discovered 160,000 glass beads. Nobody knows how this wealth was amassed and in which direction lay the trade route that connected Igbo-Ukwu with the likely glass manufacturing centers. Some scholars think that the beads came across the Sahara from the north African coast (Islamic Ifriqiya) or even Spain, others argue for an origin in Cairo via the Christian kingdoms of the Sudan, or perhaps India. This research will investigate these competing hypotheses and also explore whether some of the glass was manufactured by an indigenous African glass industry, possibly in northern Nigeria. The results of the research will permit historians to place Africa more firmly within the context of a global economy that existed prior to European expansion.