Cobblestone is a common block, used for creating various items, that resembles an uneven, roughly paved surface. Cobblestone only occurs naturally in Dungeons, NPC Villages, Strongholds, or when water and flowing lava come into contact (which allows for infinite cobblestone generators to be made). However, if the lava flows on top of the water from above, smooth stone will be created instead. It is commonly used to create walls for constructions with a medieval appearance such as castles, towers and roads. Cobblestone is obtained by mining stone. Cobblestone takes slightly longer to mine than normal stone, and there is an alternative version of the block known as Mossy Cobblestone. Silverfish have the ability to enter and hide in cobblestone (along with smooth stone and stone bricks).
Cobblestone is a basic building block, required for the crafting of many essential tools and items.
Cobblestone is required to craft Furnaces, Cobblestone Slabs, Stone Stairs, stone tools, Levers, Pistons, Dispensers, cobblestone walls, and Brewing Stands. Because of its fair blast resistance, immunity to Enderman griefing, and the abundance of stone, cobblestone is a very commonly-used building material. Cobblestone can be smelted back into smooth stone in a furnace.
Stone tools are easy to craft and widely available early in the game. However, they possess the lowest enchant-ability of all tool sets, surpassed even by wooden tools. Even after iron is available, stone tools and swords are cheap to the point of being "disposable". Thus they are useful for many tasks where more expensive tools would be used up in short order. Some examples include experience farms, hoeing farmland, mining, or wood farms.