This doesn't exist in Minecraft; it's just fiction. It can appear in Mods though.
Black Sand is just like White Sand and a block commonly found on Possible World near water. Black Sand complies with the laws of physics, just like regular Sand and Gravel. Also, due to this fact, the player can use sand and pistons to create a gravity-powered elevator. If the player destroys a floating piece of generated sand, all sand connected to it will collapse.
The main use for Black Sand is to smelt it into Glass and crafted (in 4 blocks like for Bricks) to make Stone which does not comply with Gravity as Sand and Gravels Does.
- It looks the same as Clay Blocks but 5x Darker.