Cobblestone, the cracked product of mined Stone, is one of the most common Blocks in Minecraft, being found either by mining ordinary stone, or in dungeons that have been generated by the game, along with Moss Stone. It can also be found in strongholds, villages, and jungle temples. Cobblestone doesn't have physics applied to it, so it makes a very good construction material and is used to craft a Furnace. It can be smelted in a furnace to turn it back into Stone. Once Cobblestone is smelted, it becomes considerably weaker than it was before.
Cobblestone is mostly used for creating Furnaces and building shelter. Cobblestone can also be used for Tools, such as Pickaxes, Axes, Shovels, etc. Cobblestone is also used for some weapons, such as Swords. The material is also very blast resistant, being one of the easiest blast-resistant materials to obtain.
When flowing Water and flowing Lava meet, they create Cobblestone, allowing Players an infinite supply of Cobblestone, assuming the Lava and Water source blocks aren't blocked off or removed.
Cobblestone is used in 17 diferent crafting recipes.
Cobblestone is resistant to Ghast fireballs, making it useful for guarding Portals.
Cobblestone was actually introduced before Stone was.
In past versions, Cobblestone had a lighter texture to it.
Cobblestone is one of the few blocks obtained by mining a different block, Stone, in this case.