In the level 78 Facet of Forging quest, the text dialog says:

[20:45]Iola: You remember Nee Marn? He recently told me of a special gemstone which can only be found in Il Mheg.
[20:45]Iola: It seems Voeburtite knights used to carry such a jewel to ward off hostile magicks. A talisman of sorts.
[20:45]Iola: Well, call it fate, but the city guard's vulnerability to the arcane was the last project to consume my father's attention before he died.
[20:45]Iola: He wanted to fix the flaw he perceived in their armor, and it falls to me to complete his legacy. As such, the item I would have you craft is already decided: a neckpiece set with the gemstone from Il Mheg!
[20:45]Iola: This is it, Paca, our final collaboration. I look forward to seeing what masterpiece you devise to protect our soldiers from fell sorcery!
But nothing in the quest requires anything from Il Mheg. Instead you gather Petalite from Lakeland. Il Mheg has a node item called Diaspore but I'm guessing later balancing of the quests made the required stone a higher level than the level 72 rock in Il Mheg.