Corundum

(From left to right) Aquamarine, Peridot, Diamond, and Sapphire Corundum rocks

Corundum refers to a collection of rocks which can be mined at mining level 30. The rocks are embedded with brightly-colored crystals, which indicate the gem associated with the rock. When mined, each rock has a chance to yield its gem, depending on the player's Mining level. Otherwise, the player will receive the corresponding gem dust. Note that using a Mattock will prevent any chance of receiving gems. The player will be awarded between 85 - 680 XP regardless of the outcome.

These rocks spawn infrequently in underwater caves beneath The Heartlands.

Gem probability

The probability of obtaining Gems from Corundum scales linearly with the player's Mining level. This can be increased with a Chisel, though at the cost of a longer mining time.

Gem	Dust	Level 30	Level 40	Level 50
Diamond	Diamond Dust	57%	75%	94%
Ruby	Ruby Dust	54%	71%	89%
Sapphire	Sapphire Dust	45%	61%	76%
Emerald	Emerald Dust	43%	57%	71%
Peridot	Peridot Dust	42%	56%	70%
Garnet	Garnet Dust	39%	53%	66%
Aquamarine	Aquamarine Dust	25%	33%	42%