Mineshaft

An abandoned mineshaft is a generated structure found underground or underwater, having mazes of tunnels with cave spiders and ores exposed on the walls or floor regularly.

Generation
Mineshafts generate in any Overworld biome, usually underground or rarely in oceans. They are generated before chunk features such as ores. Multiple mineshafts can generate near each other, producing larger complexes. As mineshafts intersect with caves and canyons, corridors generate a bridge of planks 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


All mineshafts have:
 * Starting point: a parlor with a 10×10 dirt floor, an arched ceiling and one to four exits in each direction.
 * Corridors: some 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 would not be connected to solid blocks, while corridors generate with log pillars, chains and fences for support if they are 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.