The Gem causes a Lightning Strike dealing nature damage. That said, shouldnt our mastery buff it as it does elemental force?
I feel like items like this and rune of origination will keep mastery VERY attractive to Enhancement. With the Rune we stand to gain probably 20% mastery or more per proc... Add that to this gem and all our other spells... I just can't see haste pulling ahead. (Of course this is perfect world scenario)