Caddellite

Caddellite is a blue mineral that is meteoric in origin. It appears in  Ultima VII.

Description
Caddellite could be only be found in the meteorites that impacted the ancient lands of Ambrosia, making it a scarce commodity. In questing to destroy the Cube Generator, the Avatar would nevertheless have cause to seek it out, as the hero needed its unique sound-dampening qualities to craft protective helmets that the construct's defenses might be penetrated.

After consulting with the Time Lord and the scholars of the Lycaeum, the Avatar's company were able to locate the last remaining cache of the rare metal, which lay under the protection of a fearsome hydra. Once obtaining sufficient quantities of Caddellite, the hero was then able to commission Zorn, the blacksmith of Minoc, to forge the mineral into helms.

Trivia

 * Caddellite is named after Michelle Caddell, Mariah's real world counterpart and Richard Garriott's personal secretary at Origin.