Obsidain is so rare because of the lack of lava in the game. However, if lava does spawn, water almost never touches a lava source block. Instead, flowing lava and water are more likely to meet, creating cobblestone. Obsidian can also be obtained by creating a nether reactor, as when the core of the reactor stops, obsidian forms around it. In the earlier version, the structure created by activating the nether reactor was made out of obsidian.
- In the seed "herobrine" if the player finds the unaturally placed cobblestone and continues to mine it as it keeps forming, a piece of obsidian will eventually appear next to the stone.
- In computer, if the player doesn't put the lava and the water together correctly, normal stone will spawn, not cobblestone.