The presence of large and diverse quantities of iron smelting residues indicates that iron smelting was practised in Nsukka. Unfortunately most of the present inhabitants of Nsukka do not know how the residues originated. Although some of the residues are indestructible, there is urgent need to study them now as they are either being quarried away for constructions or bulldozed to give way for development projects.
Hence an attempt was made in this research to study iron smelting in· Nsukka through the analyses of the residues. Three investigation techniques were used during this research. These are ethnographic investigation, archaeological and analytical techniques. The analyses were conducted at two levels, morphological and microscopic. Carbon samples were processed to give carbon14 dates and to identify species. The dates show that iron was smelted in Nsukka from about 765 cal. BC to about 1950 cal. AD. During this period, the industry passed through three distinct technological phases.
The study of the results of the slag, iron ore and the slag-inclusion analyses show that Nsukka iron smelters smelted local goethite and haematite in shaft furnaces. Initially the high presence of Al2O3 in the iron ores enforced the use of high smelting temperatures. During the late phase, the temperature was lowered by the use of sand flux. The presence and the location of iron ores determined the site of the industry. The sites were relocated when the ores were exhausted.
Available evidence suggests that Nsukka iron smelting was conducted by a closed-caste of specialised craftsmen, who moved from one location to another as they exhausted available raw materials on each site. These craftsmen limited themselves to the production of blooms. They never refined or forged the blooms. The blooms were sold to blacksmiths who refined and forged them into tools.