Bone Block

Bone Blocks are blocks that are placed by the Bone Wand at the cost of 1 Bone per block.

In, mining them will drop Bones. There is no way to obtain the block as an item as of 1.4.

Trivia

 * On the, despite them being unobtainable in worlds and characters created in 1.4 or later, creating a world in 1.3.5 or earlier, collecting some bone blocks and then saving them in either the player's inventory or a storage device, it is possible to import them over to 1.4. However, despite them being researchable in Journey Mode, they can only be brought to those worlds with Third Party Programs. If a player does this, bone blocks can be freely duplicated in Journey Mode, however this is largely pointless aside from collectability, as bones and the Bone Wand can both be duplicated.
 * The Bone Block item appears to be a skull while the center block in a 3x3 square (as shown above) could possibly be bone marrow, which is in real life bones.

History
骨块 뼈다귀 블록 Bloc d'os