Larimar Cabochon Flattening & Tumbling Concerns - Expert Advice

Question
I have some pieces of larimar that were tumbled in a vibrating tumbler.  The stones are flat.  They were tumbled with boiled (soft) peanut shells.  With the density of the stone at 30 - 35, the stone seems soft and when tumbling the stones have cut into the back of each other which leaves some lines.  To continue tumbling will take more stone off, leaving the cabs small.  Am afraid to go any further.  It has been suggested to use a round tumbler, and use baking soda as the medium.  My question is, shall I buy a round tumbler, and if so, what is suggested?  There are so many on the market.  Would you suggest using baking soda? My husband carves cow bone with hand tools.  We have a belt sander, coping saw, carving tools and files, and a Dremel and Foredom.  He is also carving Jade and has a Covington sander with water flow attached.  Would you suggest we resort to "hand" work on the larimar instead of using a tumbler?

Answer
sorry I know so little on tumbling...try calling Rio Grande in Albuquerque NM...there are so many mediums to use in a tumbler but their experts may know the best...having said that i think just normal hand grinding and polishing will get you just what you want in shape and
polish...if the stone is good quality, this is the way to go....perhaps find a cutter in the DR
to do it...i know before the prices were very cheap..
regards rolfe