Soul Sand

Soul Sand (also known as Slow sand, Quick sand, Mud, Hell mud or Nethermud) is a brown-grey dirt-type block, only naturally found in The Nether, usually near large bodies of lava in deposits similar to gravel deposits. It is commonly mistaken that the best tool for harvesting soul sand is to be a shovel because harvesting it makes the same sound as dirt, gravel and sand. However, shovels make no effect in speeding up the process. Swords can harvest it slightly faster, but this costs two uses of the sword instead of one.

This material has looks somewhat similar to a Dirt block, but it has some unique features. It slows the movement of any player or mob, and players sink slightly into the block while walking on it. It is only 15/16 the height of a normal block, so the player cannot walk from a block of soul sand to a slab without jumping. This also means that you can not get off of soul sand while holding down the sneak key, unless the player jumps.

Uses
This slowing effect is much greater when the Soul Sand block is placed in water and is useful for making drowning traps more effective against mobs. This block will also prevent water currents from transporting items over it. For example, it is often used in a cannon to stop water from moving the TNT too quickly. When placed directly over an ice block, soul sand's slow effect is greatly increased, affecting both mobs and players. The slowing effect can also be used to stop large amounts of mobs at once, making them vulnerable to attacks with a bow.

Soul sand suppresses the impact from boats when colliding to it at the angle of approximately 6° to 174°, making it an effective building material when creating a dock.

As of the Beta 1.9 Pre-release it can be used to grow a plant known as Nether Wart

One-way and Minecart-only gates


When placed on the ground in front of a two-block high doorway, soul sand prevents players from going through it from that direction,which can be useful for building one-way passages or invisible barriers. This affects mobs too as they have to jump to get out of the slowing effects of the block, thus are unable to get through the door.

However, it is possible to avoid the sand trap by jumping over the soul sand and squeezing into the one way door or continuing to jump when trying to go through the entry way. Since you do not sink into the soul sand in this case, it is like jumping over an empty space. It is possible for a mob to avoid the trap in this way, but unlikely, since a mob usually only jumps when there is a block one level higher than the mob. For that reason, these kinds of one-way doors will be best served by covering a large (4x9 centered in front of the door itself) rectangle with soul sand, such that players and entities will not be able to merely jump over it.

Because rails can be laid on soul sand like most other block materials, the slowing ability can be exploited to create minecart-only gates (by placing soul sand on both sides of the doorway). This is one of the few ways to allow rails to go directly inside a secure area without risking wandering mobs getting in.

Using the same idea underground, one can create a tunnel trap for wandering mobs and players. By digging out one block of the ceiling of a 1x2 tunnel and placing soul sand underneath, players will be unable to easily leave the soul sand block without destroying blocks.

Trivia

 * The texture resembles a collage of creeper-like faces. This could explain the "soul" in soul sand.
 * The first appearance of this block was on Notch's blog.
 * When first released, Sneaking on a soul sand block would not prevent the player from falling off the block. This bug was fixed in the 1.2.1 Alpha patch.