[wincy]

I didn’t realize how easy native copper smelting was until I watched some of those primitive YouTube channels where they make a water filtration system and smelt some copper using a hand made smelter. Linked below if anyone is interested.

https://youtube.com/watch?v=f0BjU20kU5E

[ummonk]

It's not exactly easy - requires good quality coal, and fine tuning to get the right airflow to coal ratio to create a sufficiently hot furnace without becoming oxidizing. Those guys describe having to try multiple times before working out a successful process to produce copper, documenting a couple of their experiments in videos. They've nicely fully documented their final configuration in this video - some high quality experimental archeology work: https://www.youtube.com/watch?v=KYaJuab5riE

Keep in mind that you have to be wary of poisonous fumes - hopefully the elements giving their copper alloy a brassy appearance don't include lead, or worse, arsenic.