I imagine part of the challenge would be undercutting the resulting cylindrical rock (still attached to bedrock at the bottom). Also there's the significant iss

I imagine part of the challenge would be undercutting the resulting cylindrical rock (still attached to bedrock at the bottom). Also there's the significant issue of removing the cut rock from 10k feet below ground. This is much easier to do with sand which gets picked up in a mud slurry.