Gem rocks

Gem Rocks yield gems when mined instead of ore. They give 65 Mining experience per rock, regardless of what gem is mined. 40 mining is required to mine these rocks.

The types of gems that can be mined are:


 * Opal
 * Jade
 * Red topaz
 * Sapphire
 * Emerald
 * Ruby
 * Diamond

The gem received is random - rocks are not bound to specific gems. (Except for the rocks found during The Tale of the Muspah) It is rare to receive more expensive gems such as rubies and diamonds. Gems are mined at a faster rate while wearing a fully charged Amulet of glory.

Respawn time is about a minute, though the rate changes depending on how many players are connected to the server.

A popular technique when mining these rocks is to bring a chisel and cut and fletch the gems into bolt tips thus reducing the need to bank.

Another popular technique is to drop the less valuable gems such as jades and opals to maximise the amount of money made.

Can be used with the Gem Bag reward from Dungeoneering for minimal banking by fletching the cheaper gems to bolt tips and saving the more expensive gems.

Based on a sample of 1084 consecutively mined gems at Shilo Village (with Rune pickaxe & Amulet of glory), the chance of mining each type of gem is as follows:



Based on the above table, this means on average the player will earn coins per rock mined,  if the player drops all opal, jade, and red topaz gems.



Locations

 * Shilo Village after completing the Shilo Village quest.
 * Shilo Village Underground Gem Mine after completing hard tasks of Karamja Diary.
 * Lunar Mine after completing Lunar Diplomacy.
 * Ice cave, found during The Tale of the Muspah (Only contains sapphires, no xp is gained from these rocks and cannot be mined again).

Tai Bwo Wannai Cleanup Minigame


Gem rocks can be found randomly while hacking jungle in the Tai Bwo Wannai Cleanup minigame. When a player discovers one, a message will appear saying: "The jungle parts to reveal a gem-rich rock". These rocks have gems encrusted on the surface, which disappear as the player mines it. The rock may be mined three times before disappearing. The colours of these gems are not an indication of which gems the player will actually mine.

Trivia.

 * The rocks appear to only contain only red gems, such as Red Topaz, but they actually give you many different coloured gems.
 * According to a popular myth and 2,430 successfully mined gems, the 4 ores in the South produce a higher number of precious gems than the 3 ores in the North. Although this has not yet been properly proven.

Though not proven it seems that if two players begin mining a gem rock at the same time occasionally both will receive a gem for it.(test)