I've used abalone and paua shell inlays on some of my artwork, and prepare it like this. It isn't easy, and it does generate a lot of toxic dust, but the results are nice. Definately do it with good ventilation (outside on a breezy day or in front of a HEPA filtered vacuum hose) and a particle mask.
Once the ants have finished, knock the barnackes off with a small wooden mallet (improvised if necessary). Using a medium grit sandpaper, remove the crusty outer shell. Once that tedious process is done, use a fine grit sandpaper to remove the scratches. Then use a super-fine grit sandpaper to remove those scratches. Repeat with an even finer paper. If you go to an automotive supply store, you should be able to find 1500 grit wet-dry finishing sandpaper. Using that, you can polish it to to a glassy finish that looks beautiful.
I suspect there's a better/faster way, but I don't know it and this works... eventually.