The Totem of Nehual is something of a Maltese Falcon. Many have spent long periods of their life searching for it, spending vast sums of money, and in the end never finding it, or only finding it long enough to lose it.
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. ... meeting a party of blue-skinned humans armed with pick-axes etc. Strange disease? Demon offspring? Curse? If they meet only one ex-worker, they will very carefully listen to any stories he says, no matter if drunken or insane, or just makes up to get a beer.