Are your players running roughshod over your monsters and ransacking your dungeons? Are they disrespecting you as a Dungeon Keeper?
DungeonCo here to help, with the handy dandy Wings of Wondrous Power
Mining in a certain area turns all exposed skin (maybe just parts that are actively disturbing the chemicals that cause the reaction) of the those doing the mining to a dark blue color. Will wear off taking as many years/days spent in the mine.