Glowing Obsidian

Glowing Obsidian is a block which only generates when the Nether Reactor is activated. Upon activation, the blocks that make up the reactor turn into Glowing Obsidian.

Properties
As the name suggests, Glowing Obsidian is a solid block that gives off light similar to Glowstone, but slightly dimmer. It does indeed glow, but its physical properties are closer to Obsidian. A noticeable difference is it used to require a Diamond Pickaxe (minimum) to yield resources. It takes the same amount of time to mine as Obsidian, except instead of dropping itself, it drops a normal Obsidian block. The block will emit red smoke particles within close proximity to it so long as it exists, similar to the particles Redstone creates when activated. Although in the Nether Reactor the block seems to spawn items around it, it is not the block itself that acts like this, nor will it spawn items if placed normally. The block turns into obsidian after a short amount of time. Otherwise it is simply an aesthetic block, as it has the same blast resistance as normal Obsidian. It also used to be possible to be mined with a wooden pickaxe.

Trivia

 * If the Nether Reactor Core is mined out while the Nether Reactor is active, the glowing obsidian will not turn into obsidian after the reactor deactivates. This also causes the reactor to stop spawning items.
 * Glowing Obsidian used to be mined with an Iron Pickaxe, which would still drop Obsidian. Thus, in turn made it easier to obtain.
 * It is a rare bug that a Wooden Pickaxe will also make the Glowing obsidian yield Obsidian, in older versions.

Gallery
Leuchtendes Obsidian Obsidienne lumineuse Светящийся обсидиан 发光的黑曜石