Reassessment of the evidence for early metallurgy in Niger, West Africa

A large number of structures that appear to be forges or smelting furnaces have been excavated by D. Grébénart in the Agadez region of Niger. Many of the calibrated radiocarbon dates from these structures fall in the second and third millennia BC, more than a millennium older than the earliest previous dates for metallurgy in sub-Saharan Africa. Chemical and microstructural studies of the fused materials from these structures show that most of the samples dated prior to 1000 be are partially vitrified soil and cannot be positively associated with a metallurgical process. The only positive evidence for metallurgy in this region in the second/third millennium BC is a single radiocarbon date of 1710 ± 110 be (GIF-5176) for a copper-working furnace. This date may reflect the use of old charcoal and should be viewed with caution until thermoluminescence dates can be obtained for this furnace. After 1000 BC, native copper and copper oxide minerals were processed in non-tapping shaft furnaces. Calcite, dolomite and aluminosilicate gangue minerals have combined to produce unusual red melilite slags. The scale of production appears to have been very small. Iron smelting came into general use in this region around 500 BC, but the origins of this technology are still unclear.