Deep Rock

Deep Rock is a naturally occurring tile found in the Deep Forest Caves and Deep Swamp Caves. It can be obtained with a Shovel or crafted, and the block can be placed on terrain tiles.

In practice, Deep Rock functions as a basic environmental material from the deeper cave layers rather than a special-use crafted block. Because it is placeable, it can be collected and reused for building or terrain modification if you want to match the look of the deep cave biomes.