I've recently read Things Fall Apart by Chinua Achebe. In the story it is evident that the people of Umuofia have metal tools and I was wondering, for how long had African horticulturalist societies worked metal. I understand that Africans had been trading with cultures who made metal for a very long time. At what point did Africans begin to make metal and was this trade widespread by the 15th century AD. Another question is regarding the firearms they possessed, would they have had rifles, repeaters and revolvers or would they have been simpler muskets.
West Africa is probably one of the places where metallurgy was independently invented, meaning they probably did not learn how to make metal from contact with those who did, unlike, say the Europeans. UNESCO published a book about it around ten years ago, and recent research further supports the local innovation theory. There are furnaces in the Aïr in Niger that predate Carthage, for example.
With the specific case of southern Nigeria I know that people have been continuously smelting iron in the Nsukka division, which is in Igboland like the fictional village of Umuofia, since around 760 BC (maybe earlier now - I haven't really kept track of new research). So the region of Igboland had been working iron for more than 26 centuries by the time Things Fall Apart is set.