World of Sharr
Blue Iron is a metal found primarily in the mountainous region that separates Oster from the rest of Espara. For all intents and purposes, Blue Iron is almost is exactly like normal iron of the typical sort but with a characteristic blue color. However, as the Church of the Daughter discovered late in the third age, Blue Iron interacts oddly with Manna, absorbing it then redistributing it back into the environment. The church originally used these properties to outfit a legion of knights with armor and weapons in order to even the playing field between them and the hedge mages during The Cleansing. Though the church no longer actively hunts magic-users, the legion is kept running and Blue Iron mined for protecting against stray magi with sadistic bents and in order to have fair chance against the Wysers in what many bishops see as a matter of time before another conflict brings them to arms against each other.