You need to be GM miner before you can do.
You are digging up the rare ML gems without any special preparations ... only that they are realy rare. (I am getting on average 1-2 of them for each sturdy mining tool.)
To mine the classic gems, you need to read a mining book from a gargoyle in ter-mur. (They are selling these ones.) Set you shovel/pickaxe to mining gems and you will get gems among your usual ores.