On turn 238, got the Great Admiral that gives a free Ironclad(Yi Sun Sin). On Turn 239, I used a builder to place a mine on a hill. It unlocked the Eureka for Steel (Build a coal mine and an Ironclad). However, I haven't discovered Industrialisation yet (Haven't revealed coal). I'm convinced that when I do reveal coal, it will be on that tile. My issue, the Eureka should not be given until coal is revealed.