Well, 2 and a half years after my former post on these, I would like to add that Mistmoore Granite seems to drop quite a lot near the Kitchen room (16 on eqatlas), especially from the gargs in Gargoyle Room (between rooms 11 and 16 on eqatlas), and from the 2 in rooms 17 & 18.
Saw may be 10 drops during the 90 mins I spent there.
Good thing because if you are looking for this, you might want the Dark Cauldron droping from the Ancille cook in the kitchen!
10 drops in 3 cycles of Cooks to get the 2 cauldrons, enough for all the Ronium you need for the complete set!
Actually, finding the Melatite was in my opinion much Harder...
Hope this helps
Edited, Wed Jun 28 06:36:20 2006