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 brittle as glass and turned into a powder when they were forcefully struck or when hurled against a solid object. Until the early 1370s DR, the rarity and fragility of chardalyns contributed to their high base value of 20,000 gp. Once techniques like gem magic became more widespread, the base value of chardalyns dropped to 8,000 gp for a large stone that could hold the most powerful magics, and even lower for smaller, more limited stones.

Powers
A single chardalyn could absorb one arcane spell, which was released when the stone was crushed or destroyed. This was a natural ability of the substance and did not require any magical preparation or treatment beforehand. The spell stayed encased in the chardalyn indefinitely, to be released minutes or centuries later. Usually, the spell is cast with the chardalyn as the target and the spell was absorbed, but an empty chardalyn had a slightly better than even chance to absorb a spell that did not target it directly, as long as it was in the spell's area of effect.

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