Burning Crusade Classic Protection Paladin Guide : Gems

General Gem Theory

If you still need to reach the Uncrushable breakpoint, use your gem slots to get there. If you're already at the Uncrushable breakpoint, gem for stamina. Gear is a better place to get mitigation and avoidance.

Gemming for threat with gems is not as powerful as other uses of your gem slots. Don't gem for spell damage, hit, spell hit, etc. Consumables and your weapon are better places to look at it to increase your threat generation.

Not all of the gems will release in Phase One. Some of them will unlock in a later phase.

Gems

Solid Star of Elune (12 stamina, Blue)

This gem gives the largest bonus to effective health of all gem options prior to the Phase 3 BT/Hyjal gems becoming available. If you are uncrushable by a solid margin, this will give you the most survivability of any gem option.

Enduring Talasite (4 Defense Rating and 6 Stamina, Blue/Yellow)

The best yellow hybrid available, giving both a modicum of avoidance and stamina. 

In Phase 4, this will be a solid choice for filling the defense gap in the 2.3 badge/ZA gear. This gem is best used to complete socket bonuses in gear, especially gear that has a stamina socket bonus. Completing a socket bonus for 6 stamina on a 3 socket piece is worth it most of the time, even if you lose 6 stamina for a R/B/Y socket color set (as is the case with a number of good epic tanking pieces). The defense rating is worth ~1.66 defense, which is adjusted based on your total defense, making it either .16 avoidance or .32, based on how much defense rating you have.

Glowing Nightseye (5 spell damage and 6 stamina, Red/Blue)

If you feel slightly low on spell power and have a red socket to fill, this is a good option. Generally, however, this is inferior to Solid Star given that a weapon can give sufficient spell power to hold threat for a long time in terms of raid progression. As with the Enduring Talasite, this is a choice gem for completing socket bonuses.

Shifting Nightseye (4 agility and 6 stamina, Red/Blue)

 Another red gem option, giving slightly more avoidance in lieu of threat. The agility is worth .16 dodge.

Subtle Living Ruby (8 dodge rating, Red) The best straight red gem available for conversion. If you're short avoidance and need a red gem, this is a good gem to choose. Each gem is worth .42 dodge.

Thick Dawnstone (8 defense rating, Yellow)

The only straight yellow gem worth considering whatsoever. The defense rating is equivalent to ~3.33 Defense, which rounds based on your total defense rating. It is approximately either .48 or .64 avoidance.

Meta Gems

Powerful Earthstorm Diamond (18 stamina and stun resist)

Extremely potent for a gem slot. After Kings and talents, you're looking at closer to 23 stamina from this gem, for 230 health. It has a relative  easy requirement of at least 3 blue gems. You're going to have 3 blue gems anyway.

Tenacious Earthstorm Diamond (12 Defense Rating and restore health on hit) 

12 Defense Rating = .6% avoidance, .8% for Uncrushable, 5 defense. The health restore effect is bonus threat. Requires 5 blue gems, which shouldn't be a stretch in most gear setups. If you're not Uncrushable, this is a good gem choice.

Eternal Earthstorm Diamond (12 Defense Rating and +10% Block Value, 2.4 recipe)

12 Defense Rating = .6% avoidance, .8% for Uncrushable, 5 Defense skill. The beauty of this is the block value. The requirements are only 2 blues and 1 yellow, which are easily attainable in any tanking gear set. Since it's scales, this gem has the potential to be far more powerful than any other Meta.