Just had something kind of strange happen. While mining in one particular location, the ore changed from bronze to copper during the same visit to that location. As you can see from the journal in the screen shot below, my miner got some iron ore, a piece of bronze stone, more iron ore, more bronze ore, and then more bronze stone. At that point, I clicked on the pack llama's bar to open it in anticipation of throwing the stone in there when I finished mining that spot. Since I wasn't quite finished with the spot, I used my last object/last target macro to keep mining, forgetting that the macro was kind of botched because of opening up the llama's backpack. After getting that squared away and resuming the mining, all of a sudden I was getting copper ore. Just thought this was odd enough to want to document it for anyone else trying to figure out just what triggers a change in the ore.