Crying Obsidian

Crying Obsidian (also known as Spawnstone, Teleblock, and Bleeding Obsidian by players) refers to a leaked, abandoned project by Jeb to implement a change-spawn obelisk.

History
This texture was added in Beta 1.3 but was never used in the game. It closely resembles obsidian, and also appears to maybe be a bedrock texture modified to look like Obsidian.

In Beta 1.5, the texture slot for Crying Obsidian was replaced by a grayscale replacement of the side of dirt blocks, which is used for biome-compliant grassy dirt block sides.

Its original purpose was to set a new respawn point, but was abandoned after the introduction of bedrock. It would have been crafted with an air block and bedrock.

On February 9th, 2012, altikat was tweeted with a request for the return of Crying Obsidian (or more colored blocks). He responded "As soon as I've made preparations for more texture space," suggesting the return of Crying Obsidian might be possible.

you can find altikat on the minecraft fourms!

Trivia

 * The Crying Obsidian texture still exists in the Minecraft Pocket Edition terrain.png file. (both platforms)
 * It also looks (very closely) like an Obsidian block overlaid with the ore pattern of Lapis Lazuli.