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40d:Exploratory mining
Exploratory mining is the process of mining large areas in order to locate resources such as gems, metal ores and other types of rock. It is also used, to a lesser extent, to find the locations of hidden underground features such as chasms, underground rivers, magma and adamantine. The most straightforward method is to mark a large rectangular area for digging. Unfortunately, this method is also the least efficient. More efficient digging patterns involve digging out a smaller percentage of the stone in a given area, but still revealing a large percentage of the stone. These patterns are compromises, which depend on factors that will be described in this article. Note that exploratory mining is the process dedicated solely to discovery of resources and features. The digging process is usually separated, and not discussed here in great detail. The cheating counterpart to exploratory mining is the infamous reveal tool.
Resource Distribution
To know how you should dig, it helps to know what you are looking for. When a second material appears in a layer, depending on the type of stone, ore or gem it appears in one of three shapes, large clusters, small clusters, or veins.
(For a more complete discussion of this, see veins and clusters)
- Large cluster: An oval that occupies nearly half of a 48x48 block, area-wise. Only one appears per block. (The stones that comprise large clusters tend not to have small clusters or useful veins - see specific stone type for details.)
- Vein: A sinuous line of the material crosses the block. Multiple veins can occur in the same block.
- Small cluster: A sprinkle of 1 to 9 adjacent tiles. Multiple small clusters of the same or different materials may be in the same block, or be adjacent to each other.
Ores can appear as any of the three, depending on the specific material. Gems appear only as small clusters.
Large clusters in a block
It's recommended to first dig out a wide grid of single shafts that hit the centers of the major (48x48) area blocks - if your map is 6x6, that's 36 center-shafts (or as many area blocks as you care about to start with). With a few exceptions*, if a block has a large cluster it will not have any other veins or small clusters within it - nothing. So, depending on the stone found, blocks with large clusters can be skipped right away because they are mostly worthless. (Note that layers above or below are not influenced by each other - this may influence whether you use shafts or tunnels for your exploration.) Area blocks without a large cluster can be explored using one of the patterns mentioned below. This will save you a lot of additional work (and dug out generic stone).
- (* Exceptions include adamantine veins, which can occur in any layer or large cluster in their block; olivine clusters and chromite veins, which can contain demantoids and native platinum; and magnetite with its possible platinum veins; ...and possibly others?)
Identifying Layers
Some players may wish to first identify the layers beneath the surface of their map. If (as described immediately above) you dig exploratory shafts that hit the centers of the major (48x48) area blocks, you will hit many large clusters that give you no helpful information - for instance, many stone found in clusters are found in "any layer". The solution is to dig nearer the corners or edges, to avoid the 20x40 oval that is always close to the center of the block. However, remember that the game does make the borders between area blocks fuzzy - so the closer you get to that border, the less reliable your information.
Between this and the previous technique, a complete picture of your underground geology can be achieved, and with that information you can then concentrate where you need to.
Finding a specific ore
Often a player will have need of a specific type of metal - and that requires that you either trade for it, or find a vein of an appropriate ore. Now, it's quite possible that that necessary ore is simply not present on your map - it's rare that a map will contain every ore. But if it's there, it's usually not too hard to find, if you know where to look.
In short, ore comes in veins, which tend to be a few tile wide and very long (maybe 20-40 tiles?) and snake randomly across a layer, so you don't need to expose every tile to find them, far from it. The trick is to know where to start looking, and for that you need to identify the stone layers present on your map. First, use the two techniques described above - with the second, you're trying to see what layer stones are available to search, and with the first you're trying to see which of those layers can be skipped.
Then go to the wiki article for the specific metal you are seeking - maybe iron, maybe copper or zinc, whatever. There you will see, in the side-bar, what ore(s) will produce that metal. (Alloys take may one additional step, to find all the necessary metals to make that alloy, but the process is the same.) It's quite possible that more than one ore will produce the metal you want. Then read up on the ore(s), and see what layers it's found in. Compare that to the layers you have found on your map - where they are the same, that's where to look.
Veins tend to be quite long and sinuous and so don't require detailed exploration to find, as opposed to gems which almost demand 100% revealing techniques. Diagonal tunnels, maybe 10 or 15 apart, are a good approach, or square (E-W or N-S) tunnels dug maybe 9-wide apart, but a wider shaft pattern (on a 6 or 9 wide grid?) might get lucky as well. (These numbers are chosen so they can later be filled in for 100% reveal - but they are not carved in stone, as it were. See and compare examples below.)
- Example: You want to find iron. (Who doesn't?)
- Iron has 3 ores: hematite, limonite, and magnetite. Looking at those articles, we find that magnetite is easy - it's a large cluster (about 20x40!), centered in an area block of sedimentary layer stone - check that article to see what kinds of stone layers are "sedimentary". If you have area blocks of sedimentary layers, center-punch a single shafts down through them and see. Limonite is also found in sedimentary, but in veins - this will take some exploration through the entire layer, but because we are looking for veins we don't have to reveal everything, not even close. Hematite is found in sedimentary as well, but also in Igneous extrusive layers - so that's another category of stone to check.
Not all layers contain every ore they might contain, but if they do, that's where you'll find it. If you have none of the necessary layers, there is no chance you will find veins of that ore. You don't find iron ore in metamorphic layers unless it's extending from a different, nearby type - it just isn't there, period. If you want even a chance for a specific type of ore, make sure the proper ore-bearing layer stone is present on your embark map!
(This general approach is also used to determine "where to mine next?", even if you aren't looking for anything specific. Knowing that granite or gabbro has a better chance to pay off better than diorite, and not to bother with the blocks with large clusters, gets your miners to the motherload that much faster.)
If all this is a bit overwhelming, and/or you have layers that seem "completely useless" - well, you might be right (on both counts), but The Non-Dwarf's Guide to Rock can be helpful in getting your feet back under you. It's useful to know what might be found where, and when nothing will ever be found somewhere.
Factors in exploratory mining
These are the factors we shall consider for each digging pattern. Knowing them and deciding on their priority will help you find the most suitable pattern. Most of the factors are represented by numbers, obtained by dividing two quantities. Others are more subjective.
Labor
Labor is the amount of work that goes into the digging process. Exploratory mining is a work intensive process, capable of straining even a large fortress, but the work that goes into different patterns varies greatly. A fortress with a large supply of skilled miners can afford to consider labor low priority. The labor factor is the fraction of tiles that a dwarf must dig out of an area to provide the desired result, and as such, it's a percentage, between 0 and 100%.
Target
Target refers to the size and shape of what you are hoping to find, the target material present in the rock layer as it typically appears - individual tiles, small clusters, veins, large features, whatever. It's theoretically represented by the fraction of desired material in the soil layer, but one can seldom state it accurately or even estimate it. "Target" is determined by the specific type of materials you're after - for the classification of the specific target material you are hoping to find, see the gem and stone articles. Single tiles are obviously the smallest target, followed by small clusters (at a maximum size of 3x3), veins (typically a sinuous line approximately 3 wide x 30-40 long) and large clusters (a rough oval about 20x40 centered in the area block). Underground features such as magma vents or underground pools have about the same target size as large clusters.
"Target" and "visibility" (below) are directly related. If you are after the precious gems: diamond, sapphire and ruby, you will see that these can be found only in kimberlite (diamonds) and bauxite (sapphires and rubies) respectively. So you only need to use one of the lower-visibility methods to find the veins of kimberlite in a gabbro layer or the large clusters of bauxite in sedimentary layers respectively, and then dig those out using one of the patterns that reveals every tile.
In short, if the sought-after material is a small target, you want high visibility; if large and hard to miss, lower visibility methods will work.
Visibility
Visibility is the amount of tiles that you reveal in the digging process. Excavated tiles are always visible, and so are the tiles immediately adjacent to them, including diagonals. The purpose of exploratory mining is to make a single tile of the desired material visible, allowing you to switch to conventional digging and extract it and similar material connected to it. Visibility is represented by the fraction of visible tiles in the excavated area. Perfect visibility is not always a priority - it tends to decrease in importance as the size of the target increases, because there are fewer tiles that need to be dug out for the target stone to be found.
With some patterns, it's possible to start with lower visibility, and then "fill in" for more complete visibility in the areas you wish to concentrate on.
To better understand this, see veins and clusters.
Re-usability
Re-usability is represented by the largest room size achievable by digging into the solid rock left behind without rebuilding any walls or floors. Exploratory mining typically leaves behind a monotonous, repetitive underground landscape of shafts or tunnels. The excavated level may be hard to reuse for habitation, storage or industry without additional digging and significant rebuilding efforts that leave behind inferior walls that cannot be engraved. Re-usability is subjective, and it depends on the desired layout. Re-usability is a priority for a small fortress.
Exploratory Patterns
Patterns are represented by a unit tile. This unit tile is repeated throughout the area intended for excavation to create the desired pattern. Each pattern is analyzed with the above factors in mind.
Key: . = Mined (floor) x = Mined (shaft) ░ = Visible, not mined (wall) ▓ = Not mined, not visible
Hollow
All tiles are excavated.
- Labor: 100% of the tiles are excavated.
- Target: Any size. If it exists in the layer, it will be found.
- Visibility: 100% of the tiles are visible, obviously.
- Reusability: Approaches zero, except for mass storage. Any design other than a large hall requires reconstruction.
- Bottom line: Easy to designate, but miners tend to be a bit chaotic in their approach to the task. Hollowing wastes labor like there's no tomorrow, but integrates extraction into the exploratory mining process. Use only if you have a lot of labor to spare, or need huge amounts of stone and don't mind the reconstruction required to make the hollow area habitable.
Rows
- Labor: 1 per every 3 tiles (~33%) of the tiles are excavated.
- Target: Any size. Clusters as small as a single tile are revealed.
- Visibility: 100%.
- Reusability: Very low. The long corridors aren't very useful, and can only be expanded to long, wide corridors.
- Bottom line: Easy to designate, and a single miner will focus on one tunnel to the end or they take a break. This method achieves the same visibility as hollowing out, but using a mere third of the labor. Ideal for hunting single-tile gems. As an added bonus, it is more efficient than a 3×3 design.
Larger "tunnel" patterns are suggested to be dug in multiples of "3" to allow for later complete revealing with minimum effort.
Diagonal every 5
- Labor: 20% of the tiles are excavated (1 per 5).
- Target: Any size. Clusters as small as a single tile are revealed.
- Visibility: 100%.
- Reusability: With a bit of imagination you can build nice 3x3 rooms
- Bottom line: This method is 2nd most efficient of those with 100% visibility. This one doesn't use other levels to move from one spot to another but is annoying to designate.
A variation would put diagonals every 10 or 20, laying the groundwork to fill them in later for higher visibility if desired.
Mine shafts, grid of every 3 tiles
- Labor: 11.1% of the tiles are excavated (1/9).
- Target: Any size. Clusters as small as a single tile are revealed.
- Visibility: 100%.
- Reusability: It's easy to make into square rooms of various sizes, the stairways can be removed and used as doorways, or just carved out as part of the rooms.
- Bottom line: You'll need to clear part of one layer to get the shafts started up or down (use one of the other methods to cover the area), but for one shaft at a time this method is, tile for tile, the most efficient for those with 100% visibility, and has a great reuse value. In practice, however, if you have more than one shaft being dug at one time, up/down-mining can cause miners to jump around between shafts, wasting time.
- It takes a lot of keypressing to designate, although you can save some effort by designating every third row (as in the rows method, except with stairways) and then removing the designations ({k|d}-{k|x}) on all but every third column. Alternately, here is a ahk script to save your fingers. For a discussion on optimizing travel times through mineshafts, see here.
- See also: Mineshaft stitching
Diagonal ramps, 1/7 grid
(Be sure you know how ramps work before trying this one!)
- Labor: 14.2% of the tiles are excavated (1/7).
- Target: Any size. Clusters as small as a single tile are revealed.
- Visibility: 100%.
- Reusability: Moderate. 3x3 spaces cannot be created until at least one up-ramp is removed or a down-ramp floored over. Ramps are less convenient than stairs for many purposes (for example, digging out the wrong tiles around a ramp can make it unusable).
- Bottom line: In some ways the most efficient method of all, but difficult to designate and somewhat inconvenient (especially around the edges of the map).
Pinwheel Shafts
- Labor: In this example about 17.3% of the tiles are being excavated.
- Target: All except single-tile targets are guaranteed to be found, and those will only rarely be missed.
- Visibility: 96.6%.
- Reusability: Workshops can be easily fitted into the unmined 3x3 areas.
- Bottom line: Very similar to Mine Shafts, but you can replace the up/down stairways with alternating up stairs and down stairs on different levels, eliminating the chance that one of your dwarves will slip and fall all the way down the shaft to their deaths.
7×7 blocks
- Labor: 15/64 (~23%) of the tiles are excavated.
- Target: Veins and up, as the large 5X5 space left in each unit tile can easily conceal a small cluster. Small clusters will be found perhaps half the time.
- Visibility: 39/64 (~61%) of the tiles are visible.
- Reusability: Medium. The 7×7 blocks can easily be converted into 5×5 rooms, suitable for individual rooms, storage or workshops. Optionally, it can be converted into a grid of connected 7x7 rooms, if you center each room on a crossroad. Easily converted into a more thorough 3×3 block patten by digging through the large blocks.
- Bottom line: This is a low-labor method great for vein-hunting. The low labor cost puts you in a position to invest more and get better coverage if desired.
If you think you may wish to later use the "rows" method (above) for 100% visibility, this could be based on a spacing of 6, 9, or 12. Wider spacing starts to risk missing even veins and possibly underground rivers, though you will still certainly find underground features such as pools and magma vents even with tunnels spaced 24 apart.
15×15 blocks
- Labor: 31/256 (~12%) of the tiles are excavated.
- Target: Large clusters are guaranteed, and unless you have particularly bad luck you should also find all veins, but there is no guarantee. veins would only rarely be hidden in the large 13×13 space left. The large 13×13 space left in each unit tile can easily conceal quite a lot.
- Visibility: 87/256 (34%) of the tiles are visible.
- Reusability: High. A 15×15 block of solid rock is extremely versatile when it comes to interior design. It's easily converted into a 7×7 block design, which may be further converted into a 3×3 block design.
- Bottom line: This method is preferable when you are low on labor or when you're after an underground feature. It can easily accommodate parts of your fort, or serve as the precursor for a more thorough search. A 12x12 or 18x18 version are also valid options, with obvious dis/advantages.
Mine Shafts on a 6-, 9-, 12-, or 15-grid
- Labor: from under 3% (1/36) for the 6-grid to less than 0.5% for the 15 grid (1/225).
- Target: Large clusters and up (as above), and magma pipes, magma pools, and underground pools. Underground rivers are only guaranteed with the 6-grid, but a wider grid could be used to start and easily get lucky.
- Visibility: extremely low.
- Reusability: High. Any area often needs a set of stairs (or more than one) leading up/down, and these would be the start of them.
- Bottom line: This method should be used when you are looking for a large underground feature, or getting a feel for the various rock layers, or just hoping to get lucky with little effort. Grids larger than 15 may start to miss even large features such as large clusters and pools, but can be used for identifying stone layers, and can always be filled back in later with shafts on a tighter grid. (See "searching for undergound water & magma, below)
With any grid pattern, a (much) wider version could be used to start and to locate specific stone layers/areas, and then filled in later in a tighter pattern where you want if you're not lucky the first pass. If you plan to use the 3-grid pattern (for a 100% tile reveal) later, create your grid with intervals that are a multiple of "3". If you are only looking for veins, features or just don't care, then do as you will and play it by ear later.
Searching for underground water & magma
While a lot of fun, underground features can be both difficult to find and dangerous to the unprepared, being as they are full of hostile creatures.
Magma is a rough circle usually about 20 tiles or more in diameter - a 12 grid is guaranteed to find one, a 15 is very unlikely to miss. Magnetite (an iron ore) is found in sedimentary layers in large clusters that are even bigger and even easier to find. Underground rivers are often only 5 tiles wide, damp stone included, and so the 6-grid may be necessary to find those.
If you noted where these features were located before embark, on the local map, that helps immensely. Each of these areas is 48 tiles across, and any feature such as a pool, pipe or river is enclosed completely within that area. Digging a single shaft for large features in the exact center pays off most of the time.
Digging
Underground features are a lot larger than veins and small clusters, so the 15x15 block method is more than sufficient to find them. If you dig tunnels rather than shafts, you only need to dig every 3rd z-level out as even the shortest feature, a cave river, can be discovered on any one of the 3 levels it influences with "warm" or "damp" stone, as shown in the side profiles below.
Over the top Reveals Hits damp Hits damp Underneath
(misses) (hits) (hits) (hits) (misses)
_______o## ######## ######### ######### ######### # Unmined stone
### ##### ___o ## #### ### #### ### #### ### ~ Water
###~~##### ####~~## __o#~~### ####~~### ####~~### _ Floor of the tunnel
########## ######## ######### ___o##### ######### o Miner
########## ######## ######### ######### _______o#
Once you encounter warm or damp stone you want to back off a couple of squares and dig an up staircase. On this new z-level dig another tunnel to where you just found damp/warm stone. Depending on how tall the feature was and whereabouts you hit it, you may need to repeat this approach. Eventually your miner will reach a z-level where he can safely dig all the way through to the "surface" of the feature.
Obsidian caps
Even when a magma pipe reaches the surface it can freeze over in cold climates, or may simply stop just short of surface. In theses case it will have a obsidian cap over it, which is easier to find: just search for any hills or mountainsides that have a circular chunk missing and/or a grey circle of stone (example on the right).
See also: