Mining Industry
Finding Ores
Before you can begin to operate a mine, you must locate a source of ores for your miners to unearth. Veins of ore can be found either by surveying or by digging exploratory tunnels.Surveying
Mining blindly into the earth will rarely strike upon valuable ores by chance. In order to find a suitable place to mine, you must first survey an area. Surveying an area of 4 square miles takes one week under ideal conditions, after which the surveyor is entitled to a Mining proficiency check. Some areas - such as those containing hardened lava or deep sand - are useless for mining. Otherwise, a successful proficiency check finds any ores in the area. Note that surveying on the surface will only reveal the presence of certain ores. Only certain ores can be found by surveying the surface - copper, lead, iron, silver, gold and gemstones.
Certain metals - tin, platinum, and mithril, to be precise - can only be found by subterranean surveys. In addition, silver and gold mines of the highest quality are only found deep underground. Performing a subterranean survey is slower - only 2 square miles of underground caverns can be surveyed per week under ideal conditions. Furthermore, underground surveying is more limited in the space available to survey. In order to survey for underground ores, you must find natural caverns to search.
Exploratory Mining
If you wish to find deep ores and have no access to natural caverns to survey, the only option is to delve exploratory passages to find traces of minerals. Whereas surveying locates any ores in the area, exploratory mining is much more hit-and miss. All that miners can do is delve a tunnel and hope that they hit a vein of ore. Once they strike ore, it is as if they found it by surveying - they can begin mining in earnest, using the normal rules for any mine.
The table below shows how many feet of passageway can be mined by a single miner in an 8 hour day. Mining passages are usually 10 feet high and 5 feet wide (or just wide enough to accomodate the miner, in the case of larger creatures).
| Miner | Packed Soil | Very Soft Stone | Hard Stone | Very Hard Stone |
| Gnoll/Halfling/Human | 15.0 | 7.5 | 5.0 | 2.5 |
| Gnome/Kobold | 16.0 | 8.0 | 6.0 | 3.0 |
| Goblin/Orc | 17.0 | 8.5 | 6.5 | 3.0 |
| Dwarf/Hobgoblin | 18.0 | 9.0 | 7.0 | 3.5 |
| Ogre | 30.0 | 15.0 | 10.0 | 5.0 |
| Hill/Stone Giant | 50.0 | 25.0 | 15.0 | 7.5 |
| Fire/Frost Giant | 60.0 | 30.0 | 20.0 | 10.0 |
Mining Ores
Once a vein of minerals has been located, roll on the following table:
| Roll (d100) | Mineral |
| 01-30 | Copper |
| 31-40 | Tin |
| 41-66 | Lead |
| 67-84 | Iron |
| 85-92 | Silver |
| 93-97 | Gold |
| 98 | Platinum |
| 99 | Possible Mithril |
| 01-30 | Gemstones |
Mithril is incredibly rare. If it is indicated, roll on the following table:
| Roll (d10) | Mineral |
| 1-5 | Silver (maximum quality) |
| 6-8 | Gold (maximum quality |
| 9 | Platinum (maximum quality) |
| 0 | Mithril |
If gemstones are indicated, roll on the following table:
| Roll (d100) | Gemstone |
| 01-25 | Ornamental |
| 26-60 | Semi-precious |
| 51-70 | Fancy |
| 71-90 | Precious |
| 91-94 | Gems |
| 95-96 | Jewels |
| 97-99 | Roll twice |
| 00 | Roll thrice |
Mine Productivity
Once you know what ores or gems the mine contains, you can randomly determine the quality of the mine's production. For ores, this is equivalent to the metal-richness of the ore. For gems, this is equivalent to the density of gemstones found. For mithril mines, use the row for platinum. The output of an ore mine is measured in coins: a copper mine with a rating of 200 would mean that 1 miner working for 1 week can produce a pile of ore that can be smelted into 200 copper pieces, for example. Unsmelted ore is worth 5%-25% of its smelted value.
For reference, 50 coins weigh one pound - a longsword weighs 4 pounds, so 200 coins of metal are required to make it. A set of plate mail, which weighs 50 pounds, requires 2500 coins of iron. Arrows heads use 5 coins apiece, while spearheads use 15. You can roll the production of an ore mine on the following table; if you roll a 10, there is a 10% chance that you have located a vein of native ore that does not require smelting.
| Metal | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | Coin Value |
| Copper | 100 | 200 | 250 | 300 | 350 | 400 | 500 | 750 | 1,000 | 2,000 | 1 cp |
| Iron | 200 | 300 | 500 | 700 | 900 | 1,200 | 1,600 | 2,000 | 3,000 | 4,000 | 3 cp |
| Silver | 25 | 50 | 100 | 200 | 300 | 400 | 500 | 750 | 1,000 | 2,000 | 1 sp |
| Gold | 10 | 25 | 50 | 100 | 200 | 300 | 400 | 500 | 750 | 1,000 | 1 gp |
| Platinum | 5 | 10 | 20 | 40 | 75 | 100 | 250 | 400 | 800 | 1,000 | 5 gp |
While the quality of ore mines is determined only once, gemstone mines fluctuate in their production from week to week. Each week, roll on the following table to determine the number of uncut stones found by each miner. There is no hard limit to the number of gemstone miners that can operate in a mine; it is limited only to the mine's capacity to support miners.
| Type of Stone | #/Miner/Week | Average Uncut Value per stone |
| Ornamental | 4d10 | 1 gp |
| Semi-Precious | 3d6 | 5 gp |
| Fancy | 1d12-1 | 10 gp |
| Precious | 1d10-1 | 50 gp |
| Gemstone | 1d6-1 | 100 gp |
| Jewel | 1d4-1 | 500 gp |
Generally speaking, a gemcutter can cut 1d10 gems per week, multiplying the value of each stone by 10. Highly-skilled gemcutters will produce higher-quality cut gems, and vice-versa. In addition to the "normal" gemstones, there is a 1% chance per miner per week of uncovering an "exceptional" gemstone. The value of an exceptional gemstone is multiplied by 1d100.
Mine Capacity
Every distribution of ores or gems is finite - most mines only have a few months or even a matter of weeks in them, but some can last years or even generations. To determine how many weeks a mine can operate for before it is depleted, roll 1d100. If you roll doubles (11, 22, 33, etc.), then it is a long-lived mine - roll 1d100 again, this time for how many months it lasts. If by unlikely chance you roll doubles again, roll for years, then decades, then 100 years, etc.
Once a mine is used up, it is not necessarily the case that you must vacate entirely. If the mine is connected to natural caverns, you can survey them for further sources of material wealth; otherwise, you can extend the mine by digging exploratory tunnels until you strike ore. Many dwarven settlements are built around networks of mines that are delved ever-deeper as the resources run out.