Ultra Stone

Information
Ultra Stone is one of the unbreakable blocks within the game. It spawns always in 0 Altitude and above with some chances. This is deliberately used to prevent players from accidentally falling into the void in Adventure Mode. There is currently no way to break it unless you use Creation Mode / Dev Mode.

Trivia
Ultra Stone is found within the nest of the Underworld, Above the ceiling of the Underworld and below the ground in all three worlds.

To see more blocks like this one, go to this page --> Blocks