Bedrock

Bedrock is one of the most common blocks in the game, however, bedrock that was not generated naturally is considerably rarer. However, it can be found at many places on the map, and is used by those few players who manage to obtain it for its extreme rarity and hardiness. Bedrock cannot be legitimately obtained in survival mode, and can only acquired through the use of exploits, or obtaining the password of an OP account. It is listed as a banned block by the "disable block" plugin, so is now extremely hard to store or use.