"Copper ore? Why not just exchange it for pure copper, isn't the price of pure copper quite high?"
"Hmm... pure copper is a metal material, and its price is 50 times higher! By taking the copper ore back for smelting, you can get the most metal and also have high variability.
Moreover, most of the copper we currently use is mainly for building city walls, constructing secret defenses, or expanding the Holy City.
A city wall only needs 50% copper content to isolate 'life outside the city', so there's no need to use pure copper... On the contrary, by integrating other metals or special stones on the basis of 50%, the hardness and toughness of the city walls can be greatly increased."
"Smelting technology...sounds quite advanced."
"In the Holy City, there's a dedicated alchemy team. Smelting metal is not difficult."
