Aelglurn

Aelglurn is a cousin of pitgran. When mined, it resembles a chalky white rock with a faint golden sheen. It is useful as a hardening agent for steel, as a disinfectant, and makes particularly good chalk for magical sigils, particularly protective ones. It is also an extremely potent augmentator for healing potions.A relatively small amount of powdered aelglurn will neutralize a lot of poisons if ingested; it works in a manner similar to activated charcoal in the body.
It is because of these beneficial properties that aelglurn is considered holy or sacred by a number of faith traditions and cultures across Plavithen. Aelglurn is, on an essential level, extremely pure and beneficial stuff. It is non-toxic to humanoids.In particular, it is especially valuable to the Xoani and Cetorians, both holdovers from the so-called "second age" who use it instead of powdered silver to make holy water. Other cultures use it in ceremonial body paint, as a hardening agent in holy weapons or armor, and as a component of paint on important buildings.
It is somewhat ironic, then, that it is also a waste product.
Aelglurn is generated as a byproduct of the reactors that the facilities of the precursors run on. (Except the ones that run on nuclear power, mostly out in space.) At the time the reactors were invented, it was major scientific and technological news that the primary byproduct of the reactors was itself beneficial; they called them "no cost" or "no downside" reactors. In the millennia since that world fell, the reactors have continued to run, slowly accumulating deposits of aelglurn in underground venting shafts. What the current residents of Plaviten do not realize is that mining aelglurn is more beneficial than they think. Clearing it away allows the reactors to continue to "breathe." This keeps a number of underground facilities operating that would otherwise fall to decay if their reactors shut down.