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40d:Exploratory mining
Exploratory mining is the process of mining large areas in order to obtain 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.
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 stone dug out of an area, and as such, it's a percentage, between 0 and 100%.
Scarcity
Scarcity is the amount of desired material present in the rock layer. 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. Scarcity is determined by the types of materials you're after. Single tiles are the scarcest, followed by small clusters, veins and large clusters. For the classification of your desired material, see the gem and stone articles. Underground features are about as scarce as large clusters.
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 find the veins of kimberlite in a gabbro layer or the large clusters of bauxite in sedimentary layers respectively, and dig those out using one of the patterns that reveals every tile.
Visibility
Visibility is the amount of tiles that you reveal in the digging process. Excavated tiles are always visible, and so are the tiles immadiately 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. Visibility is represented by the fraction of visible tiles in the excavated area. Visibility is always a priority, but it tends to decrease in priority as scarcity decreases, because there are more tiles that need to be dug out, and not just seen.
Reusability
Exploratory mining leaves behind a monotonous, repeating landscape. 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. Reusability is subjective, and it depends on the desired layout. Reusability is represented by the largest room size achievable by digging into the solid rock left behind without rebuilding any walls. Reusability is a priority for a small fortress.
What you are looking for
Ore occurs in three forms, depending on the kind:
- Large cluster: An oval that occupies nearly half of a 48x48 block, area-wise. Only one appears per block.
- Vein: A sinuous line of the material crosses the block.
- Small cluster: A sprinkle of 5 to 10 adjacent tiles. Multiple small clusters of different materials may be in the same block.
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: ░ = Not mined, not visible ▒ = Not mined, visible (wall) . = Mined (floor)
Hollow
All tiles are excavated.
- Labor: 100% of the tiles are excavated.
- Scarcity: Any scarcity. If it exists in the layer, it will be found.
- Visibility: 100% of the tiles are visible, obviously.
- Reusability: Approaches zero. Any design other than a large hall requires reconstruction.
- Bottom line: 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, really need huge amounts of stone and don't mind the reconstruction required to make the hollow area habitable.
Rows
- Labor: 1/3 (~33%) of the tiles are excavated.
- Scarcity: Any scarcity. 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: 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, this method achieves a visibility to labor ratio of 3:1, which, among those with 100% visibility, is second only to a diagonal design. In all ways, it it more efficient than a 3×3 design.
Diagonal
- Labor: 20% of the tiles are excavated.
- Scarcity: Any scarcity. 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 the most efficient for those with 100% visibility, which doesn't use other levels to move from one spot to another but is annoying to designate.
Mine shafts
- Labor: 11.1% of the tiles are excavated (1/9).
- Scarcity: Any scarcity. 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 above it to get it started, but this method is the most efficient for those with 100% visibility, and has a great reuse value. Real dwarves' choice! It takes a lot of keypressing to designate, here is a ahk script to save your fingers
7×7 blocks
- Labor: 15/64 (~23%) of the tiles are excavated.
- Scarcity: Veins and up, as the large 5X5 space left in each unit tile can easily conceal a small cluster.
- 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. 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.
15×15 blocks
- Labor: 31/256 (~12%) of the tiles are excavated.
- Scarcity: Large clusters and up, as the large 13×13 space left in each unit tile can easily conceal quite a lot. Unless you have particularly bad luck you should also find all veins, but there is no guarantee.
- 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.