There was a thread a while back (or maybe this was on the map on Analander's site) that said (AFAIR) "they are all the same kind and basically in a row, from the water where you encounter the emerald slime, to the place the receptacle is".The toughest part for me in finding them (after reading that), was that the rune tends to be on the opposite side of the tree, when you go at them in that order (from pool to receptacle).
I had a weird experience getting into the Mountain Wilderness one ... thought I had touched all six runes, placed the sword ... and it disappeared, with no mushroom patch popping up. Looked around, a few times, then rechecked all the runes ... had missed one. After touching the last one, the sword "magically" appeared, sticking into the stone 
Off looking for Nebdar now, for that awesome amulet I have heard so much about.
Tools for Wizardry(r) 7