Azuremite
Illegal Drug, unknown (magic)
The ruins of this sprawling city are now known as the Crystalfen Caverns. These caves are home to scattered veins of azuremite, a gorgeous blue crystal that formed from millennia of psychic energies existing near element deposits. Curious explorers who discovered the veins found that, when mined and refined into a fine dust, the azuremite powder is a strong mind-altering agent and induces temporary visions and other psychic phenomena.
While a number of small, isolated entrances to this labyrinth of tunnels have been discovered and adventuring parties have attempted to chart the mines, the caverns are so vast and deep that either they gave up for fear of becoming lost, or they were assailed by the terrible denizens of the caverns, never to return. Most who now brave the caverns are foolish treasure hunters or criminals seeking to mine more azuremite to sell on the black market.
Source: Tal’Dorei Campaign Setting Reborn p. 141