Chardalyn

A chardalyn was a rare, naturally occurring substance mined in nugget form in the northern and northwestern regions of Faerûn.

Description
When first discovered, these black stones   were described as "useless rocks" by miners, but their affinity for magic was soon discovered. These nuggets were as fragile as glass and turned into a powder when they were forcefully struck or when hurled against a solid object.

History
First discovered in the Plain of Standing Stones in -1205 DR (2654 NY) by an arcanist named Elorian, who examined worthless rock brought up from the Fluvion mines. She was amazed at the degree of magic the stones seemed to possess. Before long, she realized that the fragile gems could hold a single spell that was cast into them, later releasing the magic when it was crushed. This discovery launched Netheril into a frenzy of mining and exploration that lasted more than 500 years.

Appearance
Chardalyns appeared to be black, ordinary rocks, but were more fragile than usual. They contained natural magic. They turned to useless powder when struck forcefully. Explorers in abandoned Netherese cities were advised to step carefully.

Uses
A single chardalyn could absorb one spell, which was released when the rock was crushed or destroyed. Thus, a fireball spell could be cast into the stone and be released by simply tossing the stone at an enemy.

If the chardalyn was empty, it could absorb an incoming spell and then be tossed back at the caster.