Slime Block

The Slime Block is an upcoming, transparent block that resembles a Slime. If the player (or any other mob) jumps onto the block, they will bounce on it at a slightly lower height than their original jump. When they land back on the block, they will bounce at an even lower height than the previous bounce, and the cycle repeats until the player or mob is just standing on the block. The block will be introduced in the Minecraft 1.8 version for PC. Such blocks (transluscent blocks with two different transparencies) are now able to be implemented due to a new rendering system. Slime blocks also cause players to move slower while walking on it. Their speed is comparable to Sneaking, and is slower than walking on Soul Sand. Walking on a Slime Block with cake, Daylight Sensors, or slabs over it will retain the slowing effect while preventing bouncing. Carpets will still allow bouncing, however. Both players and mobs who fall onto this block will take no fall damage.

Usage
Dropped items move quite fast when in water that is flowing over Slime Blocks (although slower than they do over ice). This is particularly useful for transporting resources using water currents because items will keep sliding on Slime Blocks when they are dropped at an angle, even if water is not placed on top. Due to Slime Blocks not melting, unlike ice, Slime Blocks are a far safer and more efficient alternative.

Behavior
Slime Blocks will cause Players and Mobs to bounce at a height relative to the height at which the player/mob fell at. If the player is holding the jump key, they will perform a normal jump on contact with the Slime Block. The bounce height quickly deteriorates. A fall of 255 blocks only produces a bounce height of about 50 blocks, while a fall of 50 blocks is a bounce height of 22 blocks. Speed is also taken into account when the player hits the Slime Block. When a player hits "Terminal Velocity" in Minecraft, it means that the player can not travel any faster than he or she is already doing so. You can reach terminal velocity from a few hundred block drop. The maximum jump height is around 57.5 blocks. A fall from 6 blocks would rise a player up to 4 blocks height, while a fall from 3 blocks can rise a player up to 2 blocks height. When a single layer of water is present above Slime Blocks, a fall of 255 blocks only produces a bounce height of 37 blocks.

Placing Carpets, Rails, Trapdoors, Redstone Repeaters or Redstone Comparators on a Slime Block does not stop mobs from bouncing and not taking fall damage. Likewise, placing a Pressure Plate on a Slime Block does not stop mobs from bouncing, but the Pressure Plate will activate. Cake, Slabs, and other half blocks stop the bouncing effect.

Most mobs will bounce off of Slime Blocks except for Chickens, Ghasts, and Bats. Strangely Squid will bounce on Slime Blocks even though that mob normally spawns in water. Occasionally Horses may get stuck on a block when trying to spawn them above Slime Blocks in creative. Items, falling sand/gravel, minecarts and boats are not affected by Slime Blocks. Strangely, the item particles that appear when breaking an item are affected by Slime Blocks.

Slime Blocks are the only block that can be broken at speeds quicker than creative mode in survival without the aid of Haste II from a beacon.

Slime Blocks will also insulate explosions from TNT or Creepers when placed around those objects.

Slime Blocks are the slowest Blocks in the game, placing ice under Soul Sand is even slower than walking on a Slime Block.

Trivia

 * Slime Blocks can be mined instantly with your hand.
 * A Minecart leaving a rail onto a Slime Block will be able to continue on a rail on the opposite side, if it has sufficient momentum leaving the initial rail.
 * Because Chickens tend to land softly, they rarely if ever will bounce on the block.
 * Because it lets light pass through, a Slime Block doesn't deactivate a Beacon.
 * Any entity landing on the sides of the block will not bounce. In order to bounce, you need to land in the middle.
 * The texture of the inside block uses the 10x10 center of the 16x16 slime.png file.
 * Slime blocks under Soul Sand will make you go as slow as ice under Soul Sand.
 * Slime blocks will not allow spawning of mobs regardless of light level.