This list is centered around raid tanking stats, thus why it's focused on avoidance and defensive effects. I left off the spell damage gems, assuming that folks are getting it from gear + chants. White gems are
left off because, who the hell sockets white quality gems. Shame on you.
I just pulled these off of WoWWiki. I hate picking through the entire gem list in order to find just the tanking ones. So for the sake of reference, all of the tanking gems are broken down by color.
Red Gems
Effect
Source
Flashing Living Ruby+8 Parry
Crafted
World drop
Flashing Crimson Spinel+10 Parry
CraftedSSO Rep
Suble
Living Ruby+8 Dodge
CraftedWorld dropSubtle Crimson Spinel+10 Dodge
CraftedSSO Rep
Yellow Gems Effect Source
Thick Golden Draenite
+6 DefCrafted, Vendor
Consortium Honored
Thick Dawnstone+8 DefCrafted
World Drop
Thick Lionseye
+10 Def
CraftedSSO RepFacet of Eternity
+12 Def
JC Only
KoT Honored
Blue Gems
EffectSource Solid Azure Moonstone
+9 StaCrafted, Vendor
Solid Star of Elune
+12 StaCrafted
World Drop
Eye of the Sea
+15 StaFishing Daily
Bag of Fishing Treasures
Solid Empyrean Saphire
+15 Sta
Crafted
SSO Rep
Charmed Amani Jewel
+15 StaZA Quest
Quest: Playin' With Dolls
Falling Star
+18 Sta
JC Only
LC Revered
Green Gems
Effect
Source
Enduring Green Peridot
+3 Def, +4 Sta
Crafted, Vendor
HH Friendly
Enduring Talasite
+4 Def, +6 Sta
Crafted
World Drop
Enduring Chrysoprase
+6 Def, +5 Sta
Drop
Heroic Durn
Enduring Seaspray Emerald
+5 Def, +7 Sta
Crafted
SSO RepPurple Gems
Effect
Source
Regal Nightseye
+4 Dodge, +6 Sta
Crafted
SSO Rep
Regal Tanzanite
+5 Dodge, +6 Sta
Drop
Heroic SLabs
Defender's Tanzanite
+5 Parry, +6 Sta
Drop
Heroic Mech
Orange Gems
EffectSource Stalwart
Fire Opal +4 Dodge, +5 Def
Drop
Heroic SethekkGlimmering Fire Opal
+5 Parry, +4 Def
Drop
Heroic BM
Remember: If the socket bonus is crap, don't bother worrying about the gem colors. Just maximize HP, mitigation, or whatever you need.Last updated 8/14/2008 (Added tables, updated list) �BC: Healing Gems up
Article Source: www.hokage.org.