The captured Mine page provides only the upgrade-requirements table plus navigation, no descriptive text; by type and cost it is the ore field. It becomes buildable at Keep 11 (rows Lv1-11 list Keep 11), then each level requires the matching Keep level (Keep n per Mine n) -- the latest-unlocking of the four basic resource fields and strictly Keep-gated. Its upgrade cost is Food/Lumber/Stone -- the Ore column is blank (the ore field never costs ore). Stone enters at Lv7. Late amounts large and balanced. Construction-speed example +0% (through Lv17) to +610% at Lv50. No duty-officer or milestone section. Comments (not authoritative) indicate a build-count cap that rises with Keep level (a low-Keep alt could build 5 mines, a main 7; exact figures not given). For a bot: Mine is the ore source, first available at Keep 11, Keep-gated so its level cannot exceed the Keep, cheap early and enormous late, consuming food/lumber/stone. No ore upkeep neutralization is described. Priority: raise only to Keep minimum; ore mainly matters as an upgrade cost late-game rather than a training input.
Original research source: Evony Guide Wiki