DrillMaster: “That’s the wrong sort of sand. The best kind is the stuff my Brother-in-Law imports; we get far fewer breakages with that and it’s not that much more expensive.”
Build a frame around it–drill through that.
Verrrrry carefully.
After this thread, I had a similar drilling challenge of my own - I had a piece of flint that I wanted to drill with a diamond holesaw, then drill with a larger holesaw concentrically, so as to cut out a hollow cylinder of stone, to make into a ring.
I did this by embedding the rock in plaster, inside a wooden box, affixed to a board - I clamped the board to the drill press (allowing me to maintain concentricity) and flooded the box with water to keep the cutting edges cool and to help flush away the cutting waste - I drilled right through the plaster and through the rock inside it. Worked a treat.
And STILL no pictures of anyone’s finished piece!
That flint ring sounds cool …
Having a drapery and window covering business for many years I drilled a lot of ceramic tile with never an issue. I think besides a good drill bit you need to take extra care making sure it is sitting absolutely flat. maybe you could put some wax paper beneath it and use some pour stone as a base below it for absolute contact.
I made a video (actually two) about the stone ring:
Slow TV version (37 minutes, no narration): https://www.youtube.com/watch?v=x2smr5kz3t8
Concise edit (2 minutes with voiceover): https://www.youtube.com/watch?v=CLbAIcdG0G8