Dragon Egg

The Dragon Egg is a block that spawns on top of the Bedrock portal created by the defeat of the Enderdragon in The End. They currently have no explicit purpose, but are tricky to collect and are the only non-opaque falling block.

Behavior
Clicking on the egg causes it to teleport to a place nearby (up to five blocks vertically and fifteen blocks horizontally), creating the same particles as Endermen and Nether Portals. It may teleport into the air and subsequently fall to ground.

Like Sand and Gravel, Dragon Eggs fall when unsupported, and if they land in the cube of another block (such as a Torch or Slab) they will drop as a resource. Since they are not opaque blocks, they cannot suffocate the player by falling onto them.

To obtain the dragon egg, the player may left click on any block near to the egg, and before the block breaks, move the cross-hairs to the egg, which will then begin to break. Other methods include pushing one with a piston, detonating it with TNT, or placing a torch or slab under the block the egg rests on and then destroying that block so the egg falls onto it. It is possible for the player to hit one while it is still moving to the point it breaks, however this is difficult. The player may block with their sword and begin breaking the egg, which does not cause it to teleport.

Attempting to break the egg with a hacked sword to do more than 20 hearts of damage will crash minecraft.

if you are in creative mode and place 2 on a block above you, you will not suffocate, hence the Dragon Egg is somewhat like glass

History
The Dragon Egg is an item first mentioned by Notch on the 27th of October, 2011 on which Notch was supposedly working before the feature freeze, though it seems to have been worked on during it.

The Dragon Egg was first introduced in Beta 1.9 Pre-release 6 (November 11th 2011).

As of Minecraft 1.0, the Dragon Egg has no crafting use.

Trivia

 * Destroying its accompanying Overworld Portal with water or lava will also cause it to drop as a resource.
 * Enderdragons destroy Dragon Eggs when passing through them.
 * The writer of the Minecraft comic WonderCraft, Samcube, was requested by Mojang to create official Minecraft posters for possible purchase. In part of these works, one can see an area with an Enderdragon and a chicken on top of a Huge Mushroom. In the same scene is a purple, egg-shaped block like entity near the chicken - this was the Dragon Egg. However, it is unknown why Mojang would give Samcube information about the Dragon Egg before anyone else.
 * The End achievement features a Dragon Egg as its icon.
 * When hit with flint and steel (left click) it might break with one hit or teleport and appear in a new position, but still broken.
 * If you try to mine the egg with a hacked pickaxe (effectivity enchantment level 126), the game will crash.
 * If you jump on the Egg while left clicking, it will start to mine. If you use a Diamond Pickaxe, it will drop Obsidian.
 * You can break a dragon egg in the overworld by clicking then moving your mouse onto the egg, you can pick it up regardless of the tool you use.