Originally posted by Fzanco:

I wonder if there is an above ground boss stone for the queen? There are those derelict ruins that seem to have no purpose, maybe they have a stone on the rare chance

I've never seen one in a ruin, only in the mines. Yagluth stones are still harder to find. I think in 900+ hours over multiple characters I have found maybe 3 stones in total, maybe less.

If you are desperate, look up your map online though it kinda spoils things.