Mineshaft

Mineshafts are underground generated structures found in Overworld biomes. They are mazes of tunnels that may have valuable ores exposed on the walls or floor.

Generation
Mineshafts generate in the Overworld usually 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, producing larger complexes. As mineshafts intersect with other cave systems, corridors generate a bridge of oak planks or suspended under chains over empty space.

Mineshafts often generate on the surface in badlands biomes. Badlands mineshafts are composed of dark oak planks and fences with railways more complete above ground. Since badlands biomes generate gold ore often and at higher altitudes, heading to mineshafts there is sensible if the player intends to gather gold.

Structure


Mineshafts consist of the following features:
 * Starting point: each mineshaft generates a parlor with a flat, usually 10×10 dirt floor, an arched ceiling, and one to four exits, usually one in each direction.
 * Corridors: 3×3 tunnels and junctions supported by planks and fences. Some places are decorated with torches and cobwebs. On long corridors, these supports are placed four blocks away from each other while some have missing planks which may be filled up with cobwebs or blocks of stone jutting out from the top. The tunnels are connected by incomplete rail systems on the ground, on which minecarts with chests generate uncommonly. Cobwebs do not generate if they'd not be connected to solid blocks and corridors generate with oak log pillars or chains and oak fences for support if they are floating in mid-air.
 * Crossings: dual-floor, 5x5 intersections supported by wooden columns.
 * Staircases: diagonal tunnels, stair blocks are not used.
 * Abandoned passageways: accessory corridors with cobwebs concealing cave spider spawners.

Trivia

 * When generated, 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.
 * 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", a mineshaft is beneath a village.