The clay furnace, with a mortared stone chimney. The lid is open and what is hopefully chalcocite ore, Cu2S, is roasting on a rock in the center. This roasting in open air will replace the sulphur with oxygen, leaving cuprite, Cu2O, which can be reduced to pure copper in a yellow hot charcoal fire. The ore changes from vibrant purple to dull brown, and stinks pungently like sulphur dioxide- so I can at least be sure I’m working with a sulphur compound