Tales of Tolgard
This extremely rare white metal is named for its long-ago dwarf discoverer and is found only in scattered, but very rich, deposits deep in the Underdark as a soft, greenish-gray claylike ore or a flaky mud. Its preparation is complex, and it is a secret known only to a very few senior dwarven smiths and elders. If even a single element of the process is wrong, the hizagkuur remains mud and not a usable metal. If successfully transformed into a metal, hizagkuur must be cast, worked, or forged into final form within a day and thereafter can never be worked again.
Hizagkuur is unsuitable for use in the crafting of magical items or items that are to be worn because once it has cooled and hardened after being worked, it reflects all magic cast at it back at the source as well as delivering a shock to anyone touching it as long as they are in contact with it. It sees most use as a sheathing for fortress gates, vault doors, and seals on coffers or hatches of crucial importance.