Depth 15 is pretty deep, but not the deepest. Our mine is currently at
depth 17 (we just got 10 iron). I figure that if we keep going we might not
get gate crystals, but we should end up right near Yellowleaf.
This is our third mine in the same province and we have yet to hit a gate
crystal. Overall we have mined 10 mines with a total depth of 65. That's
195 mining attempts. Zero gate crystals. Anyone wanna buy some mithril?