Any excavated cave tile has a chance of caving in. When this happens, the tile is simply returned to its former non-excavated state and can be excavated again. If you mine a tile soon after it collapses, it won't need as many mine actions as usual to re-open. Ore veins may appear in cave-ins.
Reinforcing a cave wall with a [[support beam]] lowers the chance of cave-ins, but reinforced walls cannot be excavated or mined. Ore veins are said to count as reinforced veins for purposes of stability.
== Skill and difficulty ==