Gemstone mines work differently from other mines.  A gemstone mine will produce uncut stones of a type determined by random roll.  These stones must be cut by a character with the Craft (Gem Cutting) proficiency.  Uncut, they are worth only 1/10th of their cut value.

To determine what class of stone comes out of the gemstone mine, roll on the Gemstone Type table.

A gemstone mine is worked by the same team as a metal mine; one master miner, two journeyman miners, four apprentice miners, and ten unskilled laborers constitutes a single team and can perform one miner-week of work per week.  Paying the mining team costs 40 gp per week.

A gemstone mine's output varies by week.  The following table shows the number of gems found per miner-week, by gemstone type.

In addition, the quality of the gems found varies by week.  For each miner-week worked, roll on the Gem Value table (ACKS core page 207).  Specific gems found may be more or less valuable than the result of your single roll, but an average is accurate enough, and the average gem found in that week will have the value rolled when cut.  Multiply the number found by the value rolled to determine the mine's output that week.  (Remember to divide by 10 for its uncut value.)

Once the gems have been mined, they must be cut.  A gem cutter may cut a value of uncut gems per month equal to his monthly gold output.  (I'm not completely sold on this as a method, because it makes gem cutting pretty super profitable if you can get a source of uncut gems to actually sell to you, but I also have a problem with the idea that it would take a master gem cutter 10 years to cut a single 5,000 gp gem.  Under this method, it only takes him a single year, which is still vastly longer than what I can find any reference to, but I can't find any good historical reference to use and 2E is no help, a dwarf with the Gem Cutting proficiency can cut 2d8 gems per day regardless of value.)  You may hire a maximum of one team of gem cutters (one master, two journeymen, and four apprentices) per gem.  (One master, two journeymen, and four apprentices working together and supervised by the master can cut 40 gp per week at a cost of 30 gp per week.  Remember that the 40 gp they can cut is the uncut value of the gems; one week of work for them will produce gems worth 400 gp.)

Gemstone mines have duration and path alterations just as all other mines do.  Head back to the main Mining page for those.