What I find fascinating about ancient metal working techniques is that they did a lot of processes which have the same effects as we use today in terms of hardening and working the metal into a useful tool.

I'm a metal worker and we are taught the effects our processes have down to the structure of the molecules. These guys wouldnt have benefitted from that level of knowledge but they did know how to use similar techniques to have the same effects.

In fact some people believe that some ancient metals were actually superior to todays such as true Damascus steel (not the modern recreated versions).