Caddellite

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

Description
Caddellite could be only be found in the meteorites which impacted the ancient lands of Ambrosia, making it a hard to come by commodity. During their quest 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 they might penetrate the construct's defenses.

After consulting with the Time Lord and the scholars of the Lycaeum, the hero and their company were able to locate the last remaining cache of the rare metal, which lay under the protection of a fearsome hydra. Once they had obtained sufficient quantities of the metal, the Avatar was then able to commission Zorn, blacksmith of Minoc to force the material into helms.