Originally Posted by
Euclid440
Yes, that looks like a stone were the black and translucent transition, I have a small one more grey with black and white veins running through it. It is translucent and super finisher.
I use a steel baking sheet, glass and stone will abrade with 60 grit silicone carbide and at least you are losing half of your cutting power. Steel remains flat and will also contain the slurry, add a ½ teaspoon when you feel it is not cutting.
Stay on 60 grit until you are absolutely sure you are flat; the rest of the progression goes quickly.
Experiment with lubricants, pressure and laps, depending on how the stone face was finished and the stone, you can use more pressure that normal. Hundreds of laps are not uncommon.
If you use oil it will wash off easily with dish soap or degreaser to prevent going rancid.