Flaming stone with a propane torch is good way to take off the unnaturally smooth looking surface that a saw leaves on a stone, in order to give it a rougher texture.
Sometimes, when you have special stones or doing special fits, you have to make a difficult decision. In this case this limestone slab was one of the last long throughstones I had available but it needed some work done to it. Do I risk shaping it and breaking it with the hammer ? The stone didn't have any kind of face on it and I needed to have a flat face showing flush on one side of the dry stone wall I was building. So Yes, I got out the noisy dusty evil stone saw.
The problem with saws too is they leave horrible telltale saw marks. It's sometimes 'dodgy' trying to rough up (or 'dress' ) these sawn stones with a hammer and chisel (called a pitcher) if you want to get rid of the saw marks, and yes, you do need to !
The solution - bring in the propane torch and like magic the surface of most stones can be roughened up.