I finally finished turning my 3 lb chunk of rock into a bench stone. Holy moly, I am never going to do this again.
How NOT to shape and lap very hard, uncut Arkansas stone:
1. Buy a carbide grit hacksaw blade. Haha, this was a long shot, and it would probably work on soft ark. But unless you want this to be a year long project, I don't recommend it.
2. Proceed to use a way undersized 4" tile cutting saw to shape it. This way you can cut only about 1" deep into the stone, at best. Then after cutting all the way around the rock, you can hammer wooden wedges all the way around the cut until the rock splits. Leaving huge quarter inch high protrusion in the center which will takes hours to nip away.
3. Instead of buying the correct tool, chip away at the surface using tile cutting saw. Be sure to do this in your garage, so that when you're done, everything is covered with a layer of hazardous white dust.
4. When you get it as close to even as possible, using your bare hands and the edge of the tile saw, begin hand lapping with SiC grit and your Norton coarse India way too soon.
5. Give up when you realize that the 12 mil low spot is going to take 200 hours to reach, given the 18 square inch surface area.
Light bulb finally went on. I turned my tile saw into a single tooth "rock jointer." Sheet of plywood. Cut slit. Put it on tile saw. Shim it until the top of the blade barely pokes out the top (at peak of its wobble). Run the rock back and forth over this. Works best if you don't stop with rock over the blade. Pass all the way across without stopping. Using this technique, I was able to reach the low spot in just 15 minutes, leaving a super even uneven surface, about 4 or 5 mils high/low points, and lapping took only a few hours.
*Where I cut it, the stone has streaks bordering true hard white, but it's mostly slightly grey translucent. It's gonna be pretty aggressve until the surface burnishes in, but the edge it makes is already delicious.