Rusty key / golden key / copper ore?

[Maiex]

Where do I use golden key? I brought it in to crypts to a locked door that required a rusty key :(.... Also, how do you get rusty key?

[Maiex]

Also wondering where copper spawns?

[76561199698493558]

Near the top right of the goblin caves map is a mine area that usually (always?) has a copper node.