Cobblestone

"Cobblestone, as you’ll know if you’ve played Minecraft for more than about ten seconds, is what you get when you break stone. As a result, it’s one of the substances in the game that will fill up your storage chests faster than a diamond pick chews through sugarcane. The glut of cobblestone you obtain in the course of normal play, combined with its blast resistance, is why it’s usually the favoured building material of anyone who builds for function rather than aesthetics."

- Duncan Geere

Cobblestone is a common block, obtained from mining stone, but can also be made from clay. Its texture resembles block of stone with a largely cracked surface. Cobblestone is mainly used for crafting or as a common building block.

Obtaining
Cobblestone requires a pickaxe to be mined, in which case it will drop itself. If mined without a pickaxe, then the mining will be slower and it will drop nothing.

Stone
If stone is mined with a pickaxe that is not enchanted with silk touch, it will drop cobblestone.

Natural generation
Cobblestone occurs naturally in dungeons, strongholds, villages, jungle temples, underwater ruins and woodland mansions.

Water and lava
When water and flowing lava come into contact, the flowing lava is replaced with cobblestone. However, if the lava flows on top of the water from above, stone will be created instead.

Usage
Cobblestone can be used as a basic building block, as it is highly blast resistant and fairly common.

Silverfish
Silverfish have the ability to enter and hide in cobblestone, creating a infested block.

Repairing
Stone swords, pickaxes, axes, hoes and shovels can be repaired with cobblestone in an anvil.

Trivia

 * If a player were to turn Inverted Colors on, the cobblestone texture will look like end stone, but blue.
 * This is because the textures of end stone and cobblestone are inverted, but don't use the opposing colors matched with the High Contrasting.
 * Looking at the top of cobblestone the texture shows an L. This can be used to find north.