| Category | Resources |
| Alias | Zuggs Gallstones |
| Type | natural stone |
| Source | abundant, widespread in the Underdark |
Any rock that is radioactive is commonly called a deep rock. The effects of these rocks vary, but prolonged exposure can cause sickness, mutations or even death.
In the Creation War (1486 DE - 8777 DE), an army of dwarves was captured and sent to Cruharr. In this fiery Underdark region, the dwarves were put to work mining deep rocks. Their exposure over generations turned them into a new Dwarf sub-race named the Azer.
In the Demon Spawn War (89 GE - 269 GE), a slave force under Zuggtmoy was put to work in the mines of Siolix. In rich mines surrounded by veins of deep rock, those that survived, mutated, becoming a a new Giant sub-race named the Fomorian.
Some Drow civilizations use deep rocks in making of adamantine items with a pseudo magic. Two races that have been "genetically-altered" by exposure to deep rocks are the Derro and the Mutant of Undercity.
Some of the deep rocks beneath Gandûm-Thûr have properties that enhance psionics and help in "opening up" those with psionic potential.
Deep rock can be used to add a special property to magic items. An enchanter with sufficient skill and ingredients can give the item an alignment focus that reflects that of his wielder, such that a lawful good wielder makes the item effective in overcoming a damage reduction of 5/evil or chaos, 10/evil and chaos, and so on. If the creature is true neutral then they benefit from it being able to overcome all damage reductions that are based on an alignment value. The Alignment Focus property adds +1 to the items market price.
A deep rock item that has been magicked no longer has mutative effects.