Celestite

Also called "astral gold" or "heaven's gold", this golden metal is actually harder than dwarven steel and significantly more aetherically-dense. It is very well suited for magic items, as it can channel and resist aetheric forces as well as gold while being much more durable. Unfortunately, the secret to making it has either been lost on the Mortal plane or never was known--all known examples are heavily influenced by the Astral plane or were forged there.