Mithril Ore

Silver-white ore out of the high peaks, cold to the touch and lighter than it has any right to be. A full sack weighs less than the same volume of iron, which is usually what tells a miner what they've found before the color does.

It takes a long time in the furnace and rewards patience. Armor made from it protects like steel at a fraction of the weight, which is why so little of it ever reaches open market.