Heavy Metal

Little glowing rocks scattered about near the fissure. I found them more on the tiny hills nearby than on flat ground for reference. If you dont find them nearby, head towards Thunderaxe Fortress. All kinds near the road by there and the turn in location is just outside the fortress too.

I love the embedded pun here. Element 116, prior to being formally named, was known as ununhexium. This metal is preventing the restoration of Desolace, and is thus "un"unhexing the land. Genius, Blizzard, pure genius.

While kchunter86 in this thread mentioned it, here is more info. To start this quest you must pick up the quest Stubborn Lands from Cenarion Embassador Thunk who is located in Desolace at (oddly enough) Thunk's Abode, which also has a neutral (Cenarion Circle) flight master (Thunk's Wyvern). Thunk can be found at 70.4,33.0 or near a dry wadi, south of Sargeron but north of the Magram Territory hills. This quest sends you to a large, charcoal grey, smoldering stone at 69.3, 21.4 or due west of Sargeron (from the words on the Desolace world map) and due south of Nijel's Point (from the words on the Desolace world map.

Note: you do not need Thunk's quests to complete the Desolace quest achievement, but they do count towards Loremaster but oddly enough not towards Cenarion Circle rep.