Gem rock

Gem rocks can be mined through the Mining skill in Shilo Village after a player has completed the Shilo Village quest; In the Lunar Mine after Lunar Diplomacy. There is also another kind of gem rock, which appears when players play the Tai Bwo Wannai Cleanup minigame. In these rocks, the gems the player will mine are clearly visible, encrusted on the outside. When mining gem rocks, players will get 65 Mining experience per rock. After completing the hard tasks in the Karamja achievement diary a new mine becomes available with these kinds of rocks.

When gem rocks are mined, these gems are obtained instead of ores:
 * Opal
 * Jade
 * Red topaz
 * Sapphire
 * Emerald
 * Ruby
 * Diamond

The gem received is random - rocks are not bound to specific gems. Note that it's pretty rare to get high level gems such as rubies, and rare to get diamonds.

A player should carry a chisel with them as they mine gem rocks in order to cut the gems, gaining Crafting experience and Fletching experience if they are then cut into Bolt Tips.