Mineshaft

Mineshafts are large, underground generated structures found in all Overworld biomes. As their name suggests, they are maze-like complexes of tunnels which may have valuable ores exposed on the walls and floor.

Generation
Mineshafts generate naturally in the Overworld; they are usually found underground but can occasionally be found in the ocean. They are generated before chunk features such as ores. Multiple mineshafts can generate near each other and intersect, producing larger complexes. On a side note, mineshafts can intersect with other cave systems, and corridors generate a floor of wooden planks if they cross over empty space.

Mineshafts often generate on the surface in badlands biomes. Badlands mineshafts are composed of dark oak planks and fences, and generated railways are more complete above ground. Since badlands biomes generate gold ore far more often and at higher altitudes than other biomes, heading to mineshafts there is sensible if one intends to gather a lucrative gold haul for piglin bartering in the Nether.

Structure


Mineshafts consist of the following features:
 * Starting point - a large room with a flat 10x10 dirt floor, an arched ceiling and up to 4-5 exits, usually one in each direction. Each mineshaft generates one starting point.
 * Corridors - 3×3 tunnels/passageways and junctions supported by wooden reinforcements constructed with planks and fences; underground, these are built with oak wood, but in badlands biomes they are made of dark oak wood instead. On long corridors, these supports are placed four blocks away from each other, and some have missing planks which may be filled up with cobwebs or blocks of stone jutting out from the top. The passageways are connected by incomplete rail systems on the ground, on which minecarts with chests may generate.
 * Crossings - dual-floor, 5x5 intersections supported by wooden beams.
 * Staircases - diagonal tunnel sections (note that stair blocks are not used).
 * Spawner areas - certain corridors that are packed with cobweb masses and concealing cave spider spawners.

Trivia

 * When generated, abandoned mineshafts cut through the top bedrock layer(s), if they happen to generate at the bedrock layers.
 * Mineshafts can generate on top of other mineshafts. If you see two different ones intersecting each other anomalously, they are two different shafts, even if they somehow meet up perfectly elsewhere.
 * Mushrooms can be found at the bottom of mineshafts.
 * Despite it being considered a technical fault and odd generation, it is common for mineshafts to intersect ravines.
 * The dirt room of a mineshaft never generates in the same chunk as (0, 0) in any Minecraft world.

Publicity

 * In LEGO Minecraft Micro World – "The Village", an abandoned mineshaft is beneath a village.