Chardalyn

A 'Chardalyn is a type of gem, first discovered in 2654 NY by an arcanist named Elorian, who examined worthless rock brought up from the Fluvion mines by miners. 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 frenzy of mining and exploration that lasted more than 500 years.

Appearance
Chardalyns appear to be black, ordinary rocks, but are more fragile than usual. They contain natural magic. They turn to useless powder when struck hard. Explorers in abandoned Netherese cities had best step carefully.

Uses
A single chardalyn can absorb one spell, which will be released when the rock is crushed or destroyed. Thus, a fireball spell can 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 them be tossed back at the caster.