Ender Portal Frame

Air Portal Frame is a block that can be found in strongholds as of Beta 1.9 pre-release 3. It is likely that they will tie in with The Ender dimension through the creation of Air Portals. It is a non-solid block when cracked, becoming solid when repaired. They cannot be mined, however an explosion will cause them to drop as an item shaped like a Glass Pane. They have no tooltip, indicating that them dropping at all might be a bug. The player can repair a cracked Air Portal Frame by right clicking it with an Eye of Ender.

They are found in a ring shape within a room with a pool of lava and a staircase containing a Silverfish spawner. Some are naturally cracked at random.

Trivia

 * The frame block cannot be moved using pistons.