You have learned how to harness the essence of different gem stones to gain elemental abilities

Gem Focus

At 3rd level, you gain the ability to draw the essence from gems to make your attacks more powerful. You can spend a ki point as a bonus action to activate a gem to deal elemental damage with your attacks or other effects. This lasts fort 1 minute. Different gems can imbue your attacks with different elemental damage based on the type of gem used. If the gem is damages, then it cannot be activated and needs to be either replaced or repaired. You gain proficiency with a jeweler's kit.

Ruby: Fire

Sapphire: Cold

Emerald: Poison

Amethyst: Lightning

Obsidian: Necrotic

Pearl: Radiant

Topaz/Tourmalain: Thunder

Diamond: AC increase

The amount of damage is dependent on the users level and value of the gem, with a max of 1d6 at 4th level.

50gp: 1d4

100gp: 1d6

250gp: 1d8

500gp: 1d10

1000gp: 1d12

Gem Defense

At 6th level, the max damage increases to 1d8, and you gain the ability to gain elemental resistance in stead of dealing damage when activating this ability.

Dual-Weilding Gems

At 11th level, the max damage increases to 1d10. You can now have 2 gems activated at the same time.

Multi-tasking Gems

At 17th level, the max damage increases to 1d12. You can now gain both damage and resistance from your gems at the same time.