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Polishing iolite


Hi. Cutting my first piece of iolite. Any advice on best lap and polishing compound to use? I have a BATT lap and a copper lap, diamond powder, cerium oxide plus a few of the various wax sticks I got with the BATT lap.



Cerium on BATT would be a great choice. If you have a cerium wax stick from gearloose, that would probably work well and the wax sticks tend to prevent scratching that you might get with a slurry.


My preference is to use tin/lead and 50,000 diamond powder.
Bat laps work with diamond pretty well as does cast aluminium laps with lindeA slurry.
Must be kept wet at all times. Keep dripper on.
Another good lap to use with diamond is type metal.


Thanks for the advice. Forgot to ask about lap speed but found that initially 200rpm using cerium oxide wax stick on the BATT lap worked well but still was a little scratchy, so then tried it at a dead stop and it came up a treat quite quickly. I’m sure others already tried and knew this but thought I would say in case some haven’t tried before.




Not to disagree for the sake, but, particularly on stones below 8 in hardness, the oxides are often thought to give a better polish. Some even use them on harder stones after 50K to “kiss” the polish and really bring it up. Some describe the diamond polish on these stones as being greasy or a bit cloudy. I’m surprised to hear of scratches with the wax sticks, as they are designed to eliminate the scratching that you get with slurries that get too dry. It’s possible with iolite to be on or near a cleavage plane which can cause problems with polishing, and polishing at a stop is often the cure for that. The other possibility with scratches is that there was some subsurface damage that wasn’t eliminated in the prepolish. In that case it isn’t the cerium stick that is scratching, but the fact that it is polishing and revealing the scratches that weren’t eliminated in the prepolish. Prepolishing a little longer would eliminate that. Just my two cents, but if you google for discussions on this, I think you will find what I say about oxides being best for anything but corundum and chrysoberyl being repeated elsewhere. Hope this helps.