Soul Sand

Soul sand is a block that can be found in the nether. Any players or mobs will move much slower while walking on soul sand.

Natural generation
Soul sand generates around lava oceans in the nether like sand around water on beaches in the overworld. It can be found a couple layers above and a few layers below the surface of the lava ocean, but not directly under lava.

Breaking
Soul sand can be broken with any item or by hand, but using a shovel is faster.