Patty, Not sure what might have caused the chalkiness…might have
been ultrasonic or a number of other things as well. But to repolish
the surface I would use ZAM. I find it polishes all solid corals very
well. Use only a cotton muslin stitched buff and keep it well loaded
with the ZAM. Even a 1.5 inch buff in a flex-shaft will do it. Be
careful not to keep the buff in one spot as the coral will ‘burn’ and
cause a spot on the surface that will no longer take a polish.
White diamond, black emory, and some of the other polishes will work
also but ZAM gives the best polish.
Powders such as cerium oxide will do the job but are messy and will
give no better polish.
Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry.