Obsidian

Obsidian is a black and dark purple block. It has a high blast resistance, second only to Bedrock. It can only be mined by using a Diamond Pickaxe.

Obtaining
Obsidian can spawn underground naturally when flowing water meets a lava source block. It can also be created by the player by a similar method. It also naturally occurs in Village blacksmith chests.

Crafting

 * 4 Obsidian + 2 Diamonds + 1 Book => 1 Enchantment Table

Other Uses
Obsidian can be used to create a Nether Portal, by placing it in a 4x5 to 23x23 block formation and lighting it with Flint and Steel.

Trivia

 * When mining Obsidian with a pickaxe other than diamond, it takes longer to break and it doesn't let The Player obtain it.
 * An Obsidian Block takes about 7-8 seconds to mine with a Diamond Pickaxe.
 * Before Update 0.13.0, it took 6.5 seconds to break.
 * Before Update 0.6.0, the structure created by activating the Nether Reactor was made out of Obsidian, but it was changed to Netherrack in Update 0.6.0.
 * Its blast resistance is 6000. This means TNT and Creepers can't damage it.
 * Before Update 0.12.1, Obsidian could be only used to protect a structure or a player from an explosion. It could also be used for decoration purposes.
 * Due to the fact that Lava is not renewable, Obsidian is also not renewable.