Sand

Sand is a natural block. It is a block that responds to gravity.

Generation
Sand can sometimes be found in regions near sea level, often lining the edges of bodies of water or appearing in submerged areas. It replaces the top layer of terrain without affecting the blocks underneath. Since Sand does not update on its own, this can rarely lead to small areas of floating sand blocks.

Behaviour
Sand blocks will fall down when they are not supported by a block which is collidable. When it is placed or updated by a neighbouring block, it will check whether the block underneath itself is a collidable block. If the block is not collidable, the Sand will move down a block, leaving an Air block where it used to be. Since this causes a block update, this will repeat once every server tick until a solid block is reached.