Player's Handbook[]
A character with mining proficiency is needed to site and supervise the operations of any mine. First, the character can attempt to determine what types of ores or gems can be found in a given area. To do this, he must spend at least a week searching a four-square-mile area. The DM may rule that more area must be searched to find anything of value and may thus increase the amount of time required. At the end of the search, the character can say what is likely to be found in this area. After this, the character can site the mine. On a successful proficiency check (made secretly by the DM), the character has found a good site to begin mining for any minerals that may be in the area. The check does not guarantee a successful mine, only that a particular site is the best choice in a given area. The DM must determine what minerals, if any, are to be found in the region of the mine. On a failed check, the character only thinks he has found a good site. Much effort is spent before the character is proved wrong, of course.
Once the mine is in operation, a character with mining proficiency must remain on site to supervise all work. Although this is a steady job, most player characters will find it better to hire an NPC for this purpose.
Player's Option: Skills & Powers[]
Mining: A character with the mining proficiency can select the site of a mine and supervise its excavation and operation. Mining proficiency checks are best made for a player by the DM, since the character will not learn for some time whether his suppositions about a potential mine were accurate.
The Player's Handbook contains a more detailed description of how to role-play a miner's proficiency use.
The Complete Book of Dwarves[]
The Player's Handbook provides basic information on mining and this proficiency is described in detail in Chapter 8. Mining operations are usually at the heart of dwarf strongholds.
Campaign Option: Council of Wyrms Setting[]
For dragons, the Mining proficiency allows a dragon to determine the types of ores and gems that may be found in a given area, as well as the best mining sites. As described in the Player's Handbook, a week of examination typically covers a four-square-mile area, and a successful check finds the best site. Dragons will not use the proficiency to supervise a working mine (as they prefer to leave such work to their vassals). Hatchlings can't select this proficiency.