Mineshaft

Abandoned Mine Shafts are a new type of dungeon that will be added in Beta 1.8, along with strongholds. They are made up of blocks such as minecart tracks, wooden planks, torches, and cobwebs. Blue Spiders are exclusive to these areas. There are chests spread out throughout the mine that contain things such as ores, food or seeds. They can even contain diamonds and may sometimes spawn in air as a world generation glitch. Blue Spider Mob Spawners can also be found, and are coated completely in Webs, filling large parts of the air around it.