Obsidian

"Strong almost beyond compare and able to stand huge blasts, glossy, black obsidian is forged in the very fires of the earth. What a block!"

- Alex Wiltshire

"Obsidian is tough to design in Minecraft because: This is obsidian. Very specular, brittle, see-through on thin edges, very dark, very smooth. texture is largely defined by specular and shape. In MC, it's a purple colored 'rock' with a few spots!"

- Jasper "JAPPA" Boerstra

Obsidian is a dark block known for its high blast resistance and strength.

Natural generation
Obsidian can be created when a Nether portal is generated in the Nether or the Overworld. This portal can then be mined, providing a way of obtaining obsidian renewably.

When a player enters the End, a platform of 25 obsidian blocks is generated for the player to spawn on. This platform can then be mined, and gets regenerated when the player reenters the End. Solid pillars of obsidian can also be found on the surface, which regenerates when the ender dragon respawns. Obsidian also generates as a part of end ship in end cities.

Obsidian also occurs naturally where underwater springs flow onto lava, often at layer 10 or lower.

Obsidian also generates in woodland mansions in a tree shape with a diamond block in the middle of it.

Lava and water
Obsidian is formed when flowing water hits a lava source block, and can be found naturally where water from a spring or lake has flowed over a nearby lava pool.

Obtaining


Obsidian drops 1 obsidian when mined with a diamond pickaxe. Otherwise, it drops nothing.

Enchanting a pickaxe with "Efficiency" and using a beacon with Haste both drastically decrease the mining time. See the obsidian farming tutorial for more information.

Ender chests
When an ender chest is mined with a pickaxe without the Silk Touch enchantment, it drops 8 obsidian.

Usage
Obsidian can be used to build explosion resistant structures. At 6,000, obsidian's explosion resistance is the highest the player can obtain in Survival mode, other than anvils, which have the same blast resistance. Obsidian cannot be pushed by pistons. Obsidian is also notoriously known in servers as a defense block. It is common in many builds as building armor and is essential for protection.

Nether portals
Obsidian can be used to create a nether portal frame, which can then be ignited using fire. The frame must be a vertical rectangle any size from 4×5 to 23×23. Note that the corners of the frame are not required.

Trivia

 * Obsidian is one of the hardest blocks to destroy in Minecraft. In reality, obsidian is glass-like in texture and quite fragile.
 * In real life, obsidian is an extrusive igneous rock like andesite, meaning that they are both formed from lava that has cooled down.
 * Destroying an obsidian block with a diamond pickaxe, while underwater, without standing on solid ground would take 3 minutes and 54 seconds (without the pickaxe, it takes 4 minutes and 10 seconds). Either way, the player runs out of air long before the block is mined (unless a potion of water breathing is used).
 * Destroying an obsidian block without a pickaxe, while underwater, without standing on solid ground, while under Mining Fatigue 3 from an Elder Guardian takes 50*5*5*5*370, or 2312500 seconds, or 26 days, 18 hours, 21 minutes, and 40 seconds. The derivation is from hardness times 5 (from not using a tool that can harvest the obsidian block) times 5 (from being underwater) times 5 (from not standing on solid ground) times 370 (from mining fatigue).
 * It is a common misconception that enough TNT can destroy obsidian. Even though its explosion resistance rating is finite, additional TNT or other explosives has no more effect on an individual block than only one (it would take 71.25 times the explosive power of TNT to destroy a block of obsidian). It is possible to hack or an explosion strong enough to destroy obsidian, but no such explosion appears naturally.
 * The Blue Wither Skull's ability to destroy obsidian is a special feature; its explosion is otherwise no stronger than a ghast's fireball.