Obsidian

Obsidian is the second-strongest Block in Minecraft, after Bedrock, and is the strongest block that can be mined by players, as Bedrock can be placed but cannot be mined once it is placed.

Sources

Obsidian can only be found naturally near Lava beds that are below sea level. It is created when Water touches a lava source block, causing the lava block to turn into an obsidian block. For this reason, it is usually found very deep underground, around layer 10. However, it can still be found anywhere where water and lava meet.

To collect obsidian, a diamond Pickaxe must be used, and it will take 8.5 seconds to mine (quicker if the pickaxe is enchanted with efficiency). It takes approximately 250 seconds to break an obsidian block by hand, and about 50 seconds to break it with a pickaxe weaker than diamond, although neither will yield any obsidian.

Obsidian is a renewable resource, as the spawning platform and Ender Crystal pillars in the End (which are made of obsidian) are regenerated when a Player re-enters the dimension or re-spawns the Ender Dragon. Obsidian is also spawned when Nether Portals are created, as portal frames are also made of obsidian. The four extra corner blocks of a nether portal can be mined and used to create other nether portals, without deactivating the portal.

Players can create obsidian themselves by pouring water from a Bucket over a pool of stationary lava. If the lava is flowing, it will create Cobblestone, instead of obsidian.

When an Ender Chest is mined without a Pickaxe that's not enchanted with Silk Touch, 8 obsidian will be dropped instead.

Uses

Obsidian is required to make the frame of a Nether Portal. Prior to update 1.7, a portal could to be built in either a 4x1x5 or a 2x1x3 frame of obsidian without any blocks in the middle of the portal. Currently, the maximum size a portal can be is a 23x1x23 frame, with the middle left open. The corner blocks do not have to be included in the portal. After the portal is complete, lighting one of the bottom obsidian blocks on fire with a Fire Charge or a Flint and Steel (lava will not work) will activate the portal, and grant access to the Nether.

Obsidian is very resistant to explosions (with the exception of a Wither's skeleton skull attack). It is therefore useful for players interested in building near-indestructible rooms, which can either be used for protection against explosions outside, or as a trap for other players caught in an explosion within the room. Obsidian is therefore a common building material for defensive structures on Multiplayer servers.

Mining

Crafting

Enchantment Table				Ender Chest
None	Book	None		Obsidian	Obsidian	Obsidian
Diamond	Obsidian	Diamond		Obsidian	Eye of Ender	Obsidian
Obsidian	Obsidian	Obsidian		Obsidian	Obsidian	Obsidian

Beacon
Glass	Glass	Glass
Glass	Nether Star	Glass
Obsidian	Obsidian	Obsidian

Trivia

• While obsidian is a strong block in Minecraft, obsidian in the real world is a fragile volcanic glass. However, it is capable of reaching a sharpness equal to (if not, higher) diamond. It was for this reason that obsidian was a popular material used for arrow heads throughout earth's history.
• Changing the in-game language to "Pirate" will rename obsidian to "Rock o' Tears", possibly a reference to the unimplemented Crying Obsidian.
• Village blacksmiths and Nether Fortress Chests can rarely contain obsidian, although, between the two, it is three times as likely to be offered by a blacksmith.
• In Minecraft: Pocket Edition, Glowing Obsidian (a red-glowing variant), could be created when activating a Nether Reactor Core. However, it cannot be mined or obtained.
• Obsidian is one of only a few blocks that cannot be destroyed by an ender dragon (the others being end stone, air, and bedrock). Instead, the dragon will phase through it, and knock back any player hiding behind one of the obsidian pillars, causing damage to the player.
• Despite being one of the most durable blocks, the Wither can still break it with its attacks.
• The wither being able to break obsidian is an exception, otherwise,  its blue skull has the same strength as a black skull.
• There is a myth that enough TNT can break obsidian. Even though obsidian has a blast resistance of 6,000, TNT (minimum required blast resistance is 77.67), cannot destroy Obsidian, no matter how many are used.

Gallery

Blocks
Natural	Air • Stone • Granite • Andesite • Diorite • Bedrock • Clay( Terracotta) • Cobblestone ( Moss) • Cobweb • Dirt • Gravel • Coarse Dirt • Bone • Ice • Monster Spawner • Sand ( Red) • Sandstone ( Red) • Obsidian • Snow • Sponge • Wet Sponge • Stone Brick ( Cracked • Moss • Chiseled) • Prismarine ( Dark • Brick) • Sea Lantern • Pumpkin • Bee Nest • Snowier Snow • Nether Grass • Nether Fungi • Nether Mushrooms • Nether Vines • Soul Soil • Basalt
Manufactured	Bookshelf • Brick • Wool ( Carpet) • Concrete( Powder) • Conduit • Dried Kelp Block • Fence • Glass ( Pane) • Stained Glass ( Pane) • Glazed Terracotta • Hay Bale • Iron Bars • Jack-O-Lantern • Ladder • Painting • Scaffolding • Slab • Smooth Stone • Cut Sandstone • Smooth Quartz • Smooth Red Sandstone • Slime • Snow • Stairs • Walls • Wood Planks • Bee Hive • Honey Block • Honeycomb Block • Diamond Ore • Emerald Ore • Gold Ore • Iron Ore • Lapis Lazuli Ore • Redstone Ore Nether Quartz Ore
Mineral Blocks	Block of Diamond • Block of Emerald • Block of Gold • Block of Iron • Lapis Lazuli Block • Block of Quartz • Block of Redstone • Block of Coal
Utility	Bed • Brewing Stand • Cake • Cauldron • Chest • Shulker Box • Crafting Table • Enchantment Table • Furnace • Jukebox • TNT • Anvil • Blast Furnace • Barrel • Bell • Campfire • Cartography Table • Compost • Fletching Table • Grindstone • Lantern • Lectern • Loom • Smithing Table • Smoker • Stonecutter • Dispenser • Redstone Lamp • Door • Fence Gate • Lever • Note • Piston ( Sticky) • Pressure Plate • Rail ( Powered • Detector • Activator) • Redstone ( Wire • Torch • Repeater • Comparator) • Trapdoor • Trapped Chest • Hopper • Dropper • Daylight Detector • Tripwire Hook • Observer
Plants	Cactus • Dead Bush • Chorus Plant • Flowers • Grass ( Grass • Fern) • Leaves • Lily Pad • Melon • Mushrooms ( Huge)  • Mycelium • Podzol • Nether Grass • Pumpkin • Saplings • Sugar Cane • Vines • Wheat • Log • Corals • Kelp • Sweet Berry Bush • Nether Fungi • Nether Mushrooms • Nether Vines
Liquids	Lava • Water
Non-Solid	Fire • Blue Fire • Sign • Torch • Banner
The Nether	Glowstone • Unnamed Light Block • Netherrack • Nether Grass • Nether Brick ( Fence)  • Nether Quartz • Nether Wart • Nether Fungi • Nether Mushrooms • Soul Sand • Soul Soil • Basalt • Magma Block
The End	Dragon Egg • End Stone • Purpur( Purpur Pillar) • Endstone Brick • End Rod • Dragon Head • Ender Crystal
Creative only	Barrier • Structure Block • Jigsaw
Bedrock Edition only	Stonecutter (old) • Nether Reactor • Light Block
Technical	Piston Arm • Block 36 • Burning Furnace • Glowing Redstone Ore • Off-state Redstone Torch • Active Redstone Repeater • Flowing Water • Flowing Lava • Farmland • Pumpkin Stem • Melon Stem • Block 97 • Portal • End Portal Frame • End Portal
Unused	Locked Chest
Removed	Gear • Dirt Slab • Cyan Flower • Camera(BE)
Unimplemented	Crying Obsidian
Education Edition only	Element Constructor • Compound Creator • Hardened Glass • Border