Free Mine
The Free Mine is the ore operation controlled by the New Camp. Where the Old Mine funnels its ore to the Crown through the Old Camp's trade, the Free Mine keeps its ore inside the New Camp and pushes it toward the Water Mages' Barrier research.
Defence
The mine is worked by New Camp members rather than by drafted diggers, and it is defended by Lee's Mercenaries. That makes it a more tightly-held operation than the Old Mine, and one that is directly tied to the camp's long-term plans for escape.