Shimmering Loam  

 

I've seen 1 drop in the Fear Itself mission, An Offering to Thule. Not sure which mob it was. Also several drop in uninstanced Sanctum Somnium off the human "royal" trash mobs. But I was there for about 25 hours over the past few days and only saw a few. They are very rare. Ngreth remarked in a thread on EQLive forums that they don't drop in the lower tiers. He said it in response to a complaint that the task to make Illustrious augs requires T3 access, so presumably he means the first 2 tiers which are not locked at all. And since I saw one drop in T3, I'm under the assumption they can drop in any T3 or T4 zone.