“So any metal had to be an alloy of these
Plus any crap they didn’t refine away.”
Knowing metals... I would say this all depended on knowledge of temperatures. The reason iron came later is because they couldn’t figure out how to reach the temperatures needed to smelt the ore. You can actually separate different metals with controlled temps.
Oh, if only they had a decent prism...
Fractional distillation just popped into my old brain.