Silverfish are small, bug-like hostile mobs which have silver skin and black eyes that hide in Monster Eggs most often found in strongholds, but occasionally found beneath extreme hills and extreme hills edge biomes. There are three types of Monster Eggs: Stone, Cobblestone, and Stone Brick Monster Eggs. Each of them look identical to normal blocks, but take slightly more time to mine than normal with a pickaxe, and will take noticeably less time to mine without one. When the block is mined, the silverfish pops out and attacks. Destroying the blocks via Creepers or TNT simply kills the silverfish. In regular gameplay, Silverfish are only found in strongholds and rarely in extreme hills biome. If left alone, silverfish can re-enter some blocks, namely cobblestone, regular stone, and stone bricks.