By the first millennium BC , ironworking had been introduced in Northern Africa .
By the first millennium BC , ironworking had been quickly spread across the Sahara into the northern parts of sub-Saharan Africa , and by 500 BC , metalworking began to become commonplace in West Africa .
By the first millennium BC , ironworking had been introduced in Northern Africa and quickly spread across the Sahara into the northern parts of sub-Saharan Africa , and by 500 BC , metalworking began to become commonplace in West Africa .