Silt Block

Silt Blocks were added in 1.1, and falls under the soils category, and like sand are subject to gravity. They deal damage to any player or mob they fall on.

Location
Below the cavern level

Uses
Silt acts like sand, so you can use it like sand to fill in lava and such. You take damage when it falls on you, so you can make traps with it.

Crafting
It has no use what so ever.