81:3.4

The widespread use of metals was a feature of this era of the early industrial and trading cities. You have already found a bronze culture in Turkestan dating before 9000 b.c., and the Andites early learned to work in iron, gold, and copper, as well. But conditions were very different away from the more advanced centers of civilization. There were no distinct periods, such as the Stone, Bronze, and Iron Ages; all three existed at the same time in different localities.