"Here lies a peasant child scarred by the heat of battle.
Fighting not for glory but because he just wanted to live,
His despairation led him to victory."
~ Carved on the ornate stone doors leading to the large tomb.
Historically, most tombs known to have grave goods in them were robbed soon after the dead person was laid to rest. So why has the tomb that your group of adventurers broken into not already suffered this fate?
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.