I just had bad ass Forgotten beast spawn in the underworld caverns. He killed a guy who was very slowly dragging a demon corpse to the butcher when the FB hurled a fireball at him and he burned to death. That demon corpse weighed more than a slade boulder. 19 Metric tons vs 14 Metric tons.
I don't think adamantine floors(made out of wafers) changes the unrevealed stone to raw adamantine. going to try raw adamantine stone next. I have to mine some more, I already processed all I had.
I'm starting to believe that the unrevealed slade changing stone type may only work once. So you would need to floor over as much area as possible on your first go. I'm going to revert to an older save and try it again. I need to figure out what causes the ground to change.
I tried collapsing a plain constructed floor. It didnt change anything.
I tried collapsing another magma flow, it didn't change anything.
So I am going to go back to the old save and replace some of those floor tiles with raw adamantine. Or Its just possible that raw adamantine can't be duped like this. That would suck though.
UPDATE:
It DOES work. I have created Raw Adamantine under the Slade floor. I guess The trick only works once. You will need to floor over the entire area you want to convert and mine before you dig through the Eerie pit
On my map, there are 4 layers on unrevealed stone under the slade floor. the top layer stays slade, but the lower 3 change into whatever is above them. So by paving the floor with a 4x4 section of adamantine, you quadruple it. 3 new layers to mine, plus you can deconstruct the paved floors after its done. You could dig out bedroom apartments in hell made from pure raw adamantine. The only catch is you need a lot of the stuff to pave the initial area. But you will get much more back.
Also, the stuff about adamantine wafers not working might not be true, since only the first cave in appears to trigger the transformation.