Soul Sand

Soul Sand is also a game feature of Minecraft.
More information can be found on the Minecraft Wiki

Soul Sand
Item Details
Type	Block

Soul sand is a block found naturally only as part of the Alchemists Home. Soul sand usually slows down the movement of mobs and players walking on it. It is also used for growing nether wart and for creating a bubble column.

For further information, please refer to the Vanilla Minecraft block.