Blackrock

Info

Found in both the Deep Biome and Hell Biome, this block is impervious to normal mining and is vulnerable only to Bombs.

When Black Rock is within the range of a Protector it is impossible to destroy, even with the most powerful bombs.

How to Obtain

Blackrock was a Daily Loot reward once. Any players who received this were able to place blackrock. However, once place, blackrock could only be destroyed by bombs, therefore is unobtainable. Developers can mine blackrock, according to @jsonperl

History

Blackrock was added alongside the Deep Biome in late 2013.