In an attempt to clarify Rusty's Fan-like post...
The base (original) tier of the gear piece you "extracted" (stoned) the listed stats from is what counts. If the gear piece was *originally* tier 3, you will get a tier 3 mana stone out of the AT when you "extract" the stats with a Purified Fusion Stone in the AT. It makes no difference whatsoever what tier the stats were on their native gear pieces. X stats come from blue level 75, tier 4 gear. When extracted, the stats become tier 5 mana stones.
So, if you used the X runes to stat up a tier 3 gear piece, it would become a tier 5 piece. But, if you extract the stats, they become tier 3 mana stones *because* the base tier of the gear piece was tier 3.
Is that a bit less murky?
God, I miss Murky!