This mining snippet has mines separated by type and includes the use of a mining skill. Your players will need to have a pick and be holding
it to mine. Rooms will need to have a vein object reset into them for
players to mine. Once the ore is mined, they will be told that there
is none there. I find it best to have the ore scattered throughout the
mines and being unseen.

You will need to create the following:
Skills:
mine
Object Types:
silvervein
goldvein
gemvein
pick
Specific Objects:
gemstone - declared in your game as a specific vnum
Room Types:
goldmine
silvermine
gemmine

Feel free to use this snippet as you see fit, but please keep the tag at the top to give me credit for the time spent on it, especially if you plant to post the code to a web site or ftp site. The DOT license forbids profit made from this code.