Agni mani

Agni mani was the name given to certain tektites&mdash;glass-like objects formed when hot meteors fell from the sky and struck sand. They were typically found in Anauroch and other deserts around Faerûn.

Description
Agni mani specifically meant the black variety of these irregularly shaped objects. They were used unmodified in magic items, or bits of them were sewn into garments for their protective quality. A typical specimen had a base value of 10 gp.

Powers
This gemstone could absorb a small random portion of an explosive blast, such as produced by a fireball or beads of force, vaporizing in the process. Agni manis only protected the being that was carrying or wearing them.