Characterization of Tuyères from Lekie Division, Centre Cameroon (West Central Africa): raw materials and ironworking processes

Abstract

This paper is focused on the characterization of twelve fragments of tuyères collected from Evian and Pongsolo ironworking sites in Lekie, central Cameroon (15–19th century CE) with the aim of understanding the nature of their raw materials and the temperature reached during the ironworking processes. The analytical methods used for the study were X-ray fluorescence, X-ray diffraction, polarized optical microscopy, hydric tests and colorimetry. The studied samples were produced from silica-alumina rich clay materials with variable amounts of iron oxide, lower in Evian and higher in Pongsolo which explain their different colour (greyish in Evian and reddish in Pongsolo). The chemical correlation between the tuyères and the clays from Lekie suggested a local production of the tuyères using the clays from Lekie. Mineralogical and microstructural variations were observed in the samples from the two sites, due to the differences in temperature during ironworking or firing, and the position of the sample within the tuyère. The mineralogy of the fired clays was used to infer the temperatures the samples were exposed to in the furnace, indicating 1100 °C and 1200 °C as the peak temperatures recorded in the tuyères found in Pongsolo and Evian, respectively. The high content of quartz in the tuyères and their low amount of flux oxides indicates their refractoriness during ironworking process. Similarities in terms of typology and the characteristics of the raw materials have been observed in the tuyères from other African countries, indicating the use of a bellows-operated furnace during ironworking processes in Lekie.