Dimly glowing cave crystals that nearly completely cover the walls of the Crystal Caverns. So far from experimentation the following properties have been discovered:
brittle crystal
if droppped it'll likely break
a type of rock
can be ground down into a coarse powder(or finer)
does not dissolve in water
appears to be silicon based
still emitting a glow. glowed brighter in hideaway
crushed up it can be used to reveal things that are magically invisible