Cave-ins do not destroy rock at all... Go actually try this and see for yourself.
They do if you drop natural solid wall. Impact tile becomes wall, and it works same as obsidian encasing.
The rock is not destroyed tho. Sometimes it is knocked out of the way, but if it is not knocked out of the way, if you mine out the dropped stone wall, the rock is accessible again, and the whole time is being tracked and is eating its little share of FPS.
Regardless, the example was dropping a
constructed floor anyway.
OK, I got to thinking and was wondering if maybe I was off in my thinking so I did some science, and what I describe is exactly what happens.
My experiment consisted of digging out a 21x21 room and channeling a 1x1 hole in the center. I designated a dumping zone next to this and proceeded to dump all the rock from mining out the room into the hole. Then I set up to drop a 1x1x1 block into the hole with the 300+ stone in it. Before dropping the rock I made sure my book keeper was at max precision and noted down 340 stones in my stocks menu. Then I dropped the block into the hole and checked stocks and still had 340 stone. K'ing over the dropped tile just showed rough stone, however the stones in the stocks menu, when zoomed to, all zoomed to the rock wall I had dropped. I then channeled the rock back out, and all 340 rocks were back and accesible.
In short COLLAPSING STUFF ONTO STONES DOES NOT DELETE THEM, IT ONLY HIDES THEM FROM VIEW, THEY ARE STILL THERE.
By all means, if you do not believe me, try this out on your own (
here is a copy of the save for my test even). But I stand by my words that the only way to truly eliminate stone is via the means I specified in my previous reply to this topic.