Mineshaft

Abandoned mine shafts are generated structures that generate in the Overworld.

Generation
Abandoned mine shafts generate naturally in the Overworld, they are usually found underground but some can be found in the ocean. They are generated before chunk features such as ores. As with other features, multiple abandoned mine shafts can generate near each other and intersect, producing larger complexes. They can also intersect with other cave systems. Corridors will often generate a floor of wooden planks if they cross over empty space.

In Pocket Edition, they can spawn on the surface in mesa biomes. These are composed of dark oak planks and fences, rather than oak.

Structure
Abandoned mine shafts consist of:
 * A starting point - a large room with a flat dirt floor, an arched ceiling and up to four exits (one in each direction, although, sometimes it generates in a way for up to five entrances.)
 * Corridors - 3×3 block corridors featuring supports made from oak fences and wood planks (sometimes complementary with torches), broken rails, minecarts with chests (containing resources) and cave spider spawners surrounded by cobwebs.
 * Crossings - intersections with wooden pillars, sometimes two floors tall.
 * Staircases - diagonal sections of tunnel.

Trivia

 * At bedrock layer, abandoned mine shafts will cut through the top bedrock layer(s).
 * Mine shafts can generate on top of other mine shafts. If you see two different ones intersecting each other anomalously, they are two different shafts, even if they somehow meet up perfectly elsewhere.
 * Mineshafts are less common near the origin of the world (0,0).
 * Mushrooms can be found at the bottom of mineshafts.

Publicity

 * In LEGO Minecraft Micro World- The Village, an abandoned mine shaft is beneath the village.

Odd generation
Mine Puits de mine abandonné 廃坑 버려진 수직 갱도 Verlaten mijnschacht Opuszczona kopalnia Заброшенная шахта 废弃矿井