40d:Mining

Mining is an essential part of building a fort in Dwarf Fortress. There are several reasons you might want to mine, such as gathering various stone types, or simply to create the basic tunnels and rooms in your fort. Only dwarves assigned to "Mining" will actually mine the areas you want to have mined, and then only if they have access to a pick and can physically reach the site. Mining a tile preserves both the floor and ceiling of that tile, while creating a channel removes the floor. For vertical movement between tunnels, stairs or ramps are required.

Making a dwarf a miner

1. Specify your dwarf to be a miner via view, pref, labor.
2. Select "Mining" using + or -, press enter.

A miner requires an available pick.

Designating the area to be mined

1. Press designate to bring up the Designations menu.
2. Highlight Mine (it's highlighted by default) by pressing d again.
3. Move the cursor to the starting point, press enter. You should see a green flashing cross symbol indicating that it's in Selection Mode.
4. Move the cursor to another point to define the opposite corners of a rectangle, press enter again. A yellow area should now be highlighted, indicating the area to be mined.

Mined walls

When a tile has been mined, the surrounding walls and floor will most likely be some kind of rough stone. To make these surfaces look less primitive, you can smooth and engrave them. Soils, such as loam, clay, or sand, cannot be smoothed.

Stone hauling

Any useful material such as rock or ore is deposited on the ground excavated by the tile, and while loose stone will not impede movement, it can prop open doors, slow construction, and prevent open space from being used as a stockpile; therefore it is often desirable to haul stones away. You can assign stone hauling duties to specific dwarves just like you assigned them to be a miner. Make sure you have stockpiles where all the different stone types can be stored, too. Be careful which dwarves you assign to hauling if you have a massive dig going, or they might drop whatever other important stuff they were doing just to clear the paths. Typically miners will mine out stone far faster than haulers can properly clear it, particularly if the stockpile is a distance away. It is also possible to designate stone to be dumped, although this is considered an exploit, as a 1x1 garbage dump can hold an infinite number of items.

There are alternatives to hauling. Masons or Stone crafters can build their respective workshops next to or on top of a large pile of stone for clearing, and then create items out of the stone to clear it. Masons can create furniture (which takes as much space as the original stone itself, but is at least useful); they can also create blocks, which unlike stone and furniture can be stacked in bins. Craftdwarves can create various smaller items which can also be stacked in bins. Assuming you have sufficient bins, place a stockpile right next to the worksite and your haulers will only have to take the items a very short distance to place them neatly in stacks. This is a huge timesaver on large projects. Just be careful about what you make. Stone blocks are useful, but a bin completely full of stone blocks is extremely heavy and hard to move around. Crafts of all sorts are usually very light, but certain job types make multiple products out of single stones, which will multiply your hauling problem. Stone crafts, as opposed to, for instance, mugs, will produce single, lightweight, somewhat valuable items that are easy to stack and move.

Not hauling at all is also possible. You don't have to clear the rubble.

Digging in 3D

Graphical representation of several situations. This is a cross-section. "Sky" is dug-out, even underground, green is floor, non-sky cyan is no-floor, and "rock" is rock.

The map is divided in layers. Tiles on each layer are composed by whatever is on that tile, and the floor (or absence of floor) below it. A virgin rock tile is composed of a wall of rock and a floor of rock, for example. The ceiling of a tile is the same thing as the floor of the layer above that tile.

The most basic dig action is d mine. When this option is selected you can mark areas to be hollowed out from the current layer. Mining a tile preserves both the floor and the ceiling of that tile. Channeling, by contrast, removes the current floor and mines out the level below, while stairs and ramps enable creatures to move between levels.

Indiscriminate digging may cause Cave-ins.

Dig Priority

Dwarves mine in veins: after mining a tile, a miner will pick the "next" tile (a tile that is adjacent to the one just mined). If there are several possible "next" tiles, miners use an algorithm to determine which to mine next. This can be inefficient and break a large area into a large number of veins.

To pick a vein (which is to say, a tile designated for some kind of dig job), dwarves seem to use a strategy similar to the one used for chopping trees or selecting plants to gather. Generally, they seem to pick the deepest, northwestern-most vein^[Verify]. Notably, dwarves do not pick the closest vein.

Dwarves have a priority over which side they will mine out from. Unless there is something in the way, miners will try to walk around unmined areas to reach these preferred sides, even if that path is very long. In order from most preferred to least preferred, dwarves prefer to stand on the tile to the:

West > East > North > South > NW > SW > NE > SE

of the tile being dug.

Because dwarves all use the same method to choose veins, dwarves tend to dig tiles near other dwarves. This makes having multiple dwarves dig together a bit problematic, as they will often get in each others' way.

Z-axis preferences untested, though it appears to me that dwarves prefer to dig out lower areas from a diagonally located area (i.e. not standing on the down stairs while digging out the up stairs directly below the down) ^[Verify].

These details are accurate for version 38b; they are likely to change in later versions.

In .38c the dwarves choose the lowest and northwestern of possible veins.

Map structure

If you are still confused about tunnels, floors and ceilings created by the mine command then look at the following diagram:

TOP VIEWS:      SIDE VIEW:
  LAYER 3       FROM -> 
  ██████..-     5 ██████
  ██████..-     4 ██████
->██████..-     3 ██████__
  ██████..-     2 ████  
  ██████..-     1 █████████
  
  LAYER 2
  ████████.
  ████████.
->████.....
  ████████. 
  ████████.
  
Key:
█ Solid rock
. Floor, visible from this layer
- Empty space, with a floor below
_ Ceiling (undermined section)

The Top Views try to show how digging into the mountain (on Layer 2) leaves a ceiling (floor) on the layer above. This is represented on the Side View by a thin line. Try to think of the mountain as a series of boxes where with a thin lid ontop of each. At any place the box can be filled or empty, and the lid above be there or not there. For example, you can create a wall and build a floor on top of it. (Building a wall creates a floor on the next level by default, but this doesn't stop you building another floor construction on top of it!)

Revised theory: Imagine the 3D world as a grid of boxes. Each box can have one of three states; Walled, Open space, Floor.

• Each cube can only be in one of these states.
• If a tile is Walled it is inaccessible, but the box above can be walked on (if an Open space or a Floor).
• If it is Open space, then it has no Floor and may be accessible.
• If a Floor is present, then the box is accessible.
• Additionally, floor constructions can be built in an Open space or a Floor box provided there is access from the side

--Markavian (Please discuss)

Caveats

"They eat your caves!"

• Mining into damp walls usually leads flooding. Be especially careful near large rivers and aquifers. The game will warn you before this actually occurs. Note that damp walls still occur below rivers and aquifers but will not flood unless the above floor is removed (digging ramps, etc).
• Mining into warm walls usually leads to magma flooding. The game will warn you before this occurs. Like damp walls, mining warm walls will not flood magma if you are 1 z-level below the magma unless the floor above is also removed.
• Building channels will not only remove the floor of the current level, but also mine the walls out of the level below. It is not possible to remove the floor without also creating empty space on the level below.

See also

• Map tiles – Different types of walled, floor and open spaces
• Exploratory mining – Mining focused on finding valuable stone
• Stone – A list of different types of stones and ores left behind from mining.
  
• Soil – A list of soil types.

Other digging actions

• Ramp
• Stairs
• Channel