Iron melts at a significantly higher temperature than copper, zinc, or tin. Iron probably flowed from somebody’s hearth stones once they started using forced air from bellows to obtain higher temperatures for faster melts.
so the bellows would be key; I see iron a lot more common than those other metals in earth’s crust
If you are into iron, the confederacy ran I think 6 major iron furnaces during the war .. The smelter poured the melted iron into ingot shapes that were carved in granite. They are still there.
The furnaces were named after the commissioners daughters and family. They are Virginia parks now. I have camped at the one named Elizabeth Furnace,