Back to rock tumbling Bob. I am no expert, just the way I do this. As I said before I use nothing coarser then 220 grit silicon. Also use it on vibrating flat laps since coarser eats them up too fast. With tumbling I do use the 12 lb rotary tumbler for about a week with ceramic media to take up spaces. Then the sonic tumbler for 600 grit also with ceramic media (each step has its own ceramic) for about 4 days. Next the pre polish for 3-4 days and then the tin oxide polish with aluminum oxide pellets for 3-4 days. I have then added a burnishing step with borax for about 2 days using the same pellets as in the polish step. This last step removes any film that may be on the stones. That is what I now do but I am not telling anyone to do like this.
PS. many of the vibrating tumblers are very loud. One made of rubber or rubber liner is much better.
PSS> The Diamond Pacific Sonic tumblers are great except the small 3-4 lb containers don't work because the sides curve in and stones bind up. The
10 lb works fine. Perhaps they have redesigned the small ones, I don't know. Bob