Tungsten Bar

The two ores are interchangeable for nearly everything, but one real difference exists and it favors casters. A tungsten pickaxe can break meteorite. The silver one cannot. A tungsten world therefore lets you walk straight to a fallen meteor and assemble the magic armor set well ahead of schedule, while a silver world makes you upgrade your pickaxe first. If you are planning a mage run and get to pick your world, this is the ore you want.

The word is Swedish for heavy stone, which fits an element notorious for refusing to melt. A furnace like the one in game would never get near the temperature real tungsten needs, and the real metal is closer to white than the sprite color suggests.