Sandstone Blocks

Sandstone Blocks are found naturally-placed in the Underground Desert biome. Sandstone blocks don't affect whether an area qualifies as an Underground Desert biome. The only qualification for such a biome's enemies to spawn is a naturally generated sandstone wall. Like Sand and Hardened Sand, it is a corruptable block in Hardmode, and has Corruption, Crimson, and Hallowed counterparts: Ebonsandstone, Crimsandstone, and Pearlsandstone respectively.

It can be crafted into Smooth Sandstone, which then can be crafted into various furniture items.

Trivia

 * Oddly enough, it cannot be used to make Sandstone Brick and Sandstone Slab, despite the similarity in names.