It’s been years since I’ve done any lapidary work, but back in the 90’s I cut a LOT of petosky stones and various other soft stones (corals, shell, even lapis) for a business in my home town. We used Dico Blue Buffing compound on the soft stones and it polished them beautifully. If I recall correctly, you could go right from about 600 grit to the buffing compound and come out with a highly-polished finish. I’m guessing that jet would behave the same way though I’ve never worked with it and can’t know for sure.