Browsing by Author "Reid, David L"

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    Glass beads as indicators of contact and trade in Southern Africa ca. AD 900 - AD 1250
    (1996) Saitowitz, Sharma Jeanette; Van der Merwe, Nikolaas J; Reid, David L
    Luxury goods, used in mediaeval long distance trade ca. AD 900-1250, found an important market among the Iron Age peoples of southern Africa. Indirect evidence of this trade can be seen in the form of archaeological collections of glass beads at sites throughout Africa and Southeast Asia. Thousands of beads have been found at Iron Age sites in the eastern Transvaal Lowveld and at inland sites along the Limpopo Valley and in Botswana. Similar looking types of beads, referred to as small seed beads, were also used in the Muslim mercantile networks and maritime trade in the Indian Ocean, and have been found at coeval sites throughout Southeast Asia, particularly at entrepot ports in India, eastern and western Malaysia and Thailand. At the commencement of the Iron Age occupation of southern African sites, glass beads of any kind were very rare. From ca. AD 900-1000, Islamic influences spread southward along the African east coast. This coincided with the marked increase of glass beads found in southern Africa. Their presence is direct evidence of foreign industry, external trade and contact. The beads are widely believed to have originated in India, and to have been distributed through Arab traders in the Indian Ocean. Exports would have included gold, possibly ivory, and other raw materials. Archaeology has much to contribute towards documenting these activities. The identity and location of the bead sources is important to an understanding of early contact and economic and political developments in southern Africa. The trade connection coincided with the beginning of a critical sequence of events in the cultural history of southern Africa, which culminated in the formation of an incipient state at Great Zimbabwe (AD 1250-1450) from precursors at Mapungubwe and related sites. This period corresponds in time with an important episode in Islamic history, when Muslims conquered Egypt and the Fatimids moved their capital eastwards, in AD 969, from Tunisia to al-Qahira (Cairo) next to the well-established cosmopolitan port entrepot of al- Fustat (now old Cairo). Texts, chronicles, glass weights, scribal notes and receipts confirm that it was already a successful industrial centre with a history of glass-making when the Fatimids gained control of Egypt. In this thesis I have addressed two aspects of research to investigate the trade networks associated with internal and foreign contact: (1) the manufacturing origins of the beads, and, (2) who brought them to southern Africa. Glass material from Egypt, Palestine, Syria and Southeast Asia was used for comparison, and as possible source material. Scientific techniques were used to confirm these operations. The beads were described, classified, and sampled selectively for physical and chemical analysis. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine the rare earth elements (REE) composition. The results show that a particular glass, used to make beads in Egypt, is the same as that used to make some of the beads found at sites in the northern and eastern Transvaal. They document the existence of a trade link with the Mediterranean via the Red Sea 1000 years ago. Until now, both the origin of this contact and the extent of indigenous responses were largely unknown. These findings cast a different light on maritime trade along the east coast of Africa from a millennium ago. Bibliography: pages 175-190.
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    Mineralogical characterization of South African mine tailings with aim of evaluating their potential for the purposes of mineral carbonation
    (2017) Amponsah-Dacosta, Maxwell; Reid, David L
    South Africa is an energy intensive economy which primarily relies on the burning of fossil fuel such as coal. The South African coal energy sector accounts for approximately 420 million metric tonnes of carbon dioxide emitted per annum. With present alarming concerns with regards to the ever-increasing atmospheric carbon dioxide concentrations resulting in global warming and climate change, several mitigation strategies have to be implemented. A majority of Carbon Capture and Storage (CCS) technologies require monitoring from potential leakages, making the process expensive. However, a benign technology exists to permanently store away anthropogenic CO₂ with products obtained instantaneously. This CCS technology is known as Mineral Carbonation. The fundamental procedure is a reaction between (magnesium - calcium - iron) silicates and CO₂ to form carbonates. The products of from the reaction require no monitoring and the fear of leakage of CO₂ is eliminated. Moreover, the carbonates from this technology are useful in the road, agriculture and building industries. The CO₂ storage capacity in mineral carbonation exceeds other CCS techniques. The South African mineral industry annually produce immense tonnages of ultramafic mine tailings. Due to the generally fine nature of the tailings, no further cost would be incurred in grinding the material. The platinum group metal (PGM), nickel and copper companies are examples of industries that produce massive tonnages of which could serve as potential feedstock for the purposes of mineral carbonation. Recent studies have shown that, the potential feedstock could sequester close of 70% of the annual CO₂ produced at Secunda, South Africa. A mineralogical investigation into the mineral carbonation potential of mine tailings was conducted using samples from seven mining companies. Four of the mining operations considered (Impala, Rustenburg, Amandelbult and Mogalakwena) are PGM operations mining the Merensky, Upper Group 2 (UG-2) and Platreef. Nkomati was another operation selected for the study, with samples collected from the Main Mineralised Zone (MMZ) and Chromititic Peridotite Mineralized Zone (PCMZ). Tailings material from the dormant O'okiep operation was the seventh, chosen for the study. To determine the suitability of these tailings for mineral carbonation, the particle size, surface area and mineral for each individual operation was accounted using Malvern, BET analysis, XRF, QXRD and QEMSCAN respectively. The overall fine-grained nature of the mine tailings was manifested in the particle size distribution results were sizes ranged from d(0.5) = 33.67 (Nkomati) to d(0.5) = 231.45 (Impala). The range in surface area was 1.45 m²/g (Amandelbult) to 5.89 m²/g (Nkomati). A theoretical carbonation capacity ranking scheme was developed where the seven mining companies selected for this study were graded based on their suitability for mineral carbonation. Three distinct factors made up the classification criteria of the ranking scheme. The first was the carbonation capacity. This was determined by the mineralogy, the Rco2 value and the tonnage of mine waste produced annually. The second major factor was the reactivity (ignoring kinetics) of the tailings. In this case, the particle size distribution and surface area of the respective mine tailings were considered. Thirdly, the distance from the CO₂ (Secunda) source was taken into account as the cost of transporting CO₂ to the mineral carbonation facility should be weighed up. In using these principles, Nkomati was unquestionably ranked first while O'okiep was rated last priority among the seven operations. The motive behind was to improve upon the theoretical carbonation capacity ranking scheme and in turn examining a variety of South African mine tailings for the purposes of detailed mineral carbonation studies in South Africa.