Diamondillium

Diamondillium is an ultra hard mineral created by Dr. Ogden Wernstrom. It was used to encase the Earth to protect it against the Electromatter tentacles, but failed.

There was a contest of Deathball between Farnsworth and Wernstrom to decide wether Diamondium or Diamondillium (respectively) would be used to protect Earth from the tentacles, Ogden Wernstrom was the victor, so Diamondillium was used.