Spell penetration gems
From WoWWiki
Bonuses for spell penetration can usually only be found on blue and green gems, but the [Mysterious Fire Opal] currently provides penetration as well. This is believed to have been an error in its itemization, but Blizzard has thus far made no mention of fixing it, which makes it a valuable gem for filling yellow sockets in PvP gear for DoT-based casters (who do not typically care about spell crit and may prefer spell penetration to intellect).
| Color | Name | Effect(s) | |
|---|---|---|---|
 Blue
| [Stormy Azure Moonstone] | +8 Spell Penetration | |
| [Stormy Star of Elune] | +10 Spell Penetration | ||
| [Stormy Empyrean Sapphire] | +13 Spell Penetration | ||
  Orange
| [Mysterious Fire Opal] | +5 Spell Penetration | +6 Spell Damage |
| Green
| [Radiant Deep Peridot] | +6 Spell Penetration | +3 Spell Crit |
| [Radiant Talasite] | +5 Spell Penetration | +4 Spell Crit | |
| [Radiant Seaspray Emerald] | +6 Spell Penetration | +5 Spell Crit | |
