Dave:

Note that the grit ratings on stones and sandpaper are not compareable. 2000 grit sandpaper feels like... paper. You can't see or feel the abrasive. It creates a mirror surface on metal. Also, it's critical that the base be as flat and smooth as possible. While the granite will certainly not flex, it will probably have a lot of small pits, even when polished. I know my kitchen countertop does, anyway. Maybe a piece of glass (smooth) on top of a piece of granite (flat and stiff)? CB.