Obsidian

Obsidian is a deep purple block that was first released into the game in version 0.30. Obsidian may be found on rare occasions, when there is flowing Water and source Lava blocks nearby. Obsidian is created when flowing water hits a lava "source block"; when water and runoff lava collide, cobblestone is created. Obsidian never actually spawns with the chunk, but is created by the environment. Obsidian can only be successfully mined with a diamond pickaxe. Each obsidian block takes 15 seconds to mine when using a diamond pick. It can be broken with a non-diamond pickaxe, but this takes 50 seconds and will not yield a collectible block.



Obsidian in the wild is somewhat rare and difficult to mine since it usually rests on top of a Lava block. Obsidian farming is thus the preferred way to acquire large quantities. A basic Obsidian farm is composed of a trough seven blocks long into which seven blocks of Lava are poured using the Bucket. A water block is then placed on top of one end of the trough so that it flows onto the lava and converts it into Obsidian.

As of the Halloween Update, Obsidian can be used to create portals to The Nether. This requires at least 10 blocks of Obsidian (14 for a full frame) and a Flint and Steel.

Current Uses

 * Portals to The Nether
 * Decoration
 * Bunkers. At 6,000, Obsidian's explosion resistance rating is second only to Bedrock.  It is therefore an exceptionally desirable construction material for making defensive structures, in both PvE or PvP, as it is effectively impervious to both lava and explosions. It also takes longer to mine than any other blocks, so it's good at keeping other players out.

History
Obsidian was available for use since Classic mode. It is generally used for making dark things, or the black lines of Pixel Art.

In Survival Test mode, Obsidian was extremely tough to break and would drop one or two Cobblestone blocks when broken.

Obsidian was removed in Indev and brought back in Infdev. Obsidian was used to mark the positions of the cardinal directions. This created two intersecting planes extending just above the surface of the solid material that surrounds them. This has since been removed.

Possible Future
Notch has mentioned he may require floating islands to have obsidian in the future:

Later, when asked about making floating blocks fall, he answered:

Farming and Casting
On the 16th of March 2011, a new way to farm obsidian involving redstone as the only irretrievable source (rather than lava) was discovered. The process involves having a row of running water with a line of redstone next to it and pouring the lava onto the redstone, in-turn, replacing it with obsidian. This is currently the only known way to create numerous blocks of obsidian without using multiple buckets of lava. This method still works in 1.4, even though Notch knows about it.

Redstone-to-Obsidian Converter basic tutorial

Obsidian generator different building method

Obsidian can also be easily farmed through the creation of nether portals. Since a portal is created in the Nether to mimic the overworld, by creating pairs of portals one can destroy the first portal and run back through the second.

Basic Obsidian Farm

Structures can be constructed out of Obsidian without the use of a diamond pickaxe by creating a mold and placing the lava source within it, then running water over the lava. This will form the obsidian in place, but without diamonds it is quite hard to get rid of. Casting is recommended over mining when having a lot of buckets and still lava is nearby.

A more advanced form of casting for large structures can be made by building "scaffolding" to create a frame two away from the desired location of the Obsidian - then using this to create an artificial waterfall flowing through the square next to where Obsidian is wanted. It is then possible to stand next to the waterfall and repeatedly jump while placing buckets of lava at your feet: they will turn into obsidian before they can set anything on fire or do any damage. This has the advantage of not needing to be built up and have the water moved with every new row, and allows the maximum of 36 buckets of lava to be converted at once.

Advanced Obsidian Creation

Safe(er) Mining
Obsidian, if found in the wild, is typically directly above a lava source block, making it dangerous and difficult to mine. This can be overcome, however by placing a water spring block directly over the block you are currently mining. This will convert any lava around the obsidian block into more obsidian, so it's less likely to fall into lava.

An equally effective way is to find the edge of the obsidian "lake", dig a one block deep hole under which there is no lava, and place the water source in this hole. Then, start mining the obsidian bording the water spring. When it breaks, the fast-moving water will fill the void faster than the liberated obsidian block can drop into the lava. The player can continue mining outward from the spring as far as the water will travel. This method relies on the same properties of water as the first strategy, but does not require the player to battle against running water while mining.

Trivia

 * Even though Obsidian is the second hardest block to destroy, in reality, obsidian is glasslike, made by volcanoes, and is actually quite fragile. The misconception is probably due to obsidian being able to reach a sharpness comparable to diamond while being easier to produce, therefore being a favored material during the Stone Age for use as blades and arrow tips.
 * Obsidian portals created by the game always have corner blocks, so you can make portals without corner blocks to get four free blocks of obsidian, however, if an exit portal is floating in midair, the game will add two blocks of obsidian to each side along the bottom row, increasing the free obsidian from a new portal to eight.
 * It is a common misconception that enough TNT will destroy Obsidian. However, even though its explosion resistance rating IS finite, there is a rule within the code that if one block of TNT next to a block will not destroy the block, no amount will. However, this rule only applies to bedrock, water, lava and obsidian so far, because one block of TNT next to any other block will destroy that block. Were Notch to release an explosive with 6,000 explosive power, Obsidian could be destroyed by that explosive; as of now, it can only be destroyed by mining through it.

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