A Kal'gerion gem rock is a unique type of gem rock in the Kal'gerion dungeon that yield gems, rather than ore, when mined. They are the only rocks to contain uncut dragonstone. At least 50 Mining is required to mine these rocks, and they give 75 experience, regardless of the type of gem mined. The chance of mining an additional ore while wearing Varrock armour does not apply to gem rocks.
Based on a sample of 1,000 consecutively mined gems at Kal'gerion resource dungeon without a charged amulet of glory, the chance of mining each type of gem is as follows: