Assorted Augment Gems

An assorted augment gem is a small gem, crystal, or similar object that provides a magical effect when affixed to a ring, amulet, wand or any other item thats is equipped but not considered arms or apparel. Each item can hold a single augment crystal, but an attached crystal can be swapped for another one at any time. Attaching an augment crystal to (or removing it from) an item requires a move action that doesn’t provoke attacks of opportunity. Effectively, each eligible item has a single “slot” that can be filled by any appropriate augment crystal.

Crystals can come in 3 forms, Lesser, Moderate and Greater. You must meet the level of a crystal to be able to use it.
Lesser Gems – 3rd Level
Moderate Gems – 9th Level
Greater Gems – 15th Level
You get the effect listed for your rarity of gem plus the effects for the lower rarity gems. (ie. a greater gem gets the moderate and lesser effect) HOWEVER bonuses of the same kind do not stack, so you cannot wear two gems of warding to get a higher DR, but you can wear two gems of elemental defense provided they are for different elements.

NOTE – 2 indentical gems can be fused to create a gem of the rarity up. (ie two lessers make a moderate.)

Gem of Enhancement.

Each of these gems are connected to a different stat, and provide a bonus score to them,
Lesser – Gain a +1 to the associated score.
Moderate – Instead gain a +2 to the associated score.
Greater – Instead gain a +3 to the associated score.

Gem of Protection

This gem is enchanted to ward you against particular types of attacks. Each is attuned to a different saving throw.
Lesser – Increase the associated save by +1.
Moderate – Instead increase the associated save by +3.
Greater – Additionally the gem gains a secondary save and gives +3 to that save.

Gem of Reserve Power

A gem of reserve power can hold magical, spiritual or just about any other type of energy in it. Each is associated to a different type of pool.
Lesser – Increase your pool by 3 points, OR hold 1 channel divinity (or similar).
Moderate – Increase your pool by 5 points, OR hold 2 channel divinity (or similar).
Greater – Increase your pool by 7 points, OR hold 3 channel divinity (or similar).

Gem of Spell Critical

This gem is infused with magical energy and causes spells to hit with more precision.
Lesser – Increase your spell crit range by +1.
Moderate – You instead gain a +2 to your spell crit range, and a +1 to save dc.
Greater – Additionally, you increase your spell crit multiplier by +1, and increase your save dc by another +1.

Gem of Spell Power

This gem is infused with magical energy, and empowers your spells.
Lesser – You gain +1 to spell attacks and save dc.
Moderate – You instead gain +2 to spell attacks and save dc.
Greater – You instead gain +3 to spell attacks and save dc.

Image – https://www.curseforge.com/minecraft/mc-mods/gems-jewels