Palladium Ore

Palladium Ore is a new Hardmode Ore that was introduced in the 1.2 patch.

Hardmode Ores are generated upon destroying a Demon Altar or Crimson Altar with a Pwnhammer. They are immune to all types of explosions.

Palladium is the replacement for Cobalt.

Palladium requires Molten Pickaxe to mine.

Trivia
In reality, palladium is an element that is chemically similar to platinum. Though elemental palladium is silvery-white in color, it forms several compounds with orange or red-brown color. It has a wide range of applications including jewelery and electronics, but its most common use is as a chemical catalyst.