Drilling it is a nightmare, that's a fact. Assuming you drill a hole and it's not all warped and oblong, you win more than half the battle! I half to wonder if you were able to get past the drilling part, then you could turn it and use an electric automotive grinder instead of a chisel to grind it down as it turns. I never turned it, but sure thought all about it many times, as I do have some great pieces in my shop that I found in a dumpster. I have three windows in my shop and the sills inside are from this granite. I used a circular saw and a hose to cut the slabs to fit, basically 1 window is 3ft by 6" and the other two are about 2ft by 6" deep. I made 3 cuts and it ate 4 cutter disks, and that's using some water to help! I didn't bother sanding and polishing the edges by that time it seemed impossible, so I used wood trim to cover the front edge of the granite.
My biggest fear...lets say you pull it off, as it is possible of course...the pen gets dropped, the granite could shatter. YIKES !!!!! All that time and energy for nothing.