Mineshaft

Abandoned Mine Shafts are a new type of structure that was added in Beta 1.8, along with strongholds.

Structure
Abandoned mine shafts are series of straight intersecting tunnels that are 3 blocks wide and with an uneven ceiling with the height of 2-3 blocks. Wooden planks make up the supports of these tunnels. Incomplete sections of minecart tracks can be found at the floor of these shafts and torches are occasionally placed on walls. Cobwebs can be found here and there. Cave Spider spawners can also be found, and are surrounded completely by Cobwebs.

Cave Spiders are exclusive to these areas. There are chests spread throughout the mine that contain things such as gold and iron ingots, ores, food or seeds. They can even contain diamonds or pickaxes and may sometimes spawn in air as a world generation glitch. It is also possible but rare to have it spawn in a ocean so the Abandoned Mine Shaft is flooded. Abandoned Mine Shafts are also rich with ores such as Iron, Gold, and rarely Lapis Lazuli and/or Diamonds. As the 'shafts' are made of wooden planks, Abandoned Mine Shafts actually in turn provide very good source of wood while prospecting underground.

Obtainable items:
 * Diamond
 * Coal
 * Lapis Lazuli
 * Iron Ingot
 * Gold Ingot
 * Melon seeds
 * Pumpkin Seeds
 * Bread
 * Rails
 * Iron Pickaxe

Abandoned Mineshafts may be large, and may be akin to labyrinths during exploration, making it difficult to keep bearings. The poisonous Cave Spiders are very common and make exploration dangerous unless prepared.

Minecart tracks may be generated floating in the air from a world generation glitch. These tracks behave similarly to floating snow in that all adjacent glitched blocks will pop out when one is mined.