Early Iron Age Metal Working at the Tsodilo Hills, Northwestern Botswana

Abstract

This paper describes Early Iron Age metal working at the sites of Divuyu and Nqoma, excavated by James Denbow and Edwin Wilmsen, in northwestern Botswana. This research represents the first metallographic analysis of a large collection of Iron Age metal artefacts from southern Africa. The artefacts studied were small articles of copper and iron, mostly items of jewellery and tools possibly used in their manufacture. They were classified and sampled representatively for metallographic and chemical analysis. Fifty-four artefacts were studied in detail and the fabrication technology reconstructed. The forging, and possibly also smelting, of iron took place at both sites during the Early Iron Age. The primary smelted product was inhomogeneous iron and steel, with typical fayalitic slag, characteristic of indigenous bloomery iron production. Forging was carried out in an oxidizing hearth. The technique used was poor, with no evident control over carbon content or the mechanical properties of the steel, and with no heat treatment other than annealing. The fabrication of artefacts involved forging square wire and flat sheets, which were cut into strips for beads, clips, chains, and fibre-cored wound ornaments. Crude round iron wire was used to make numerous finger rings. Copper was worked similarly, usually leaving the metal in its annealed state. Significant chemical variation in the copper artefacts and iron slag inclusions showed that diverse ore sources were exploited. There were stylistic similarities between individual artefacts from these sites in the Tsodilo Hills and Early Iron Age material from Zaı̈re and the northern Transvaal. Comparison of the fabrication technology with Late Iron Age material suggests that local indigenous iron and copper working technology in southern Africa has changed little since its inception.