Dwarven iron
From elanthipedia
A hard type of iron with a slight blue-black tint to it, this metal is found deep in the earth alongside veins of plain iron. Dwarves make the most use of it by far, and the metal is considered a traditional icon by many members of the race. Dwarven iron is a common product of Stone Clan and is prized for weapons, armor, and rough jewelry. Normally the metal is not combined into alloys since it does not rust like normal iron does.
Dwarven iron must be provided for alterations.