There are a number of stones that should NEVER be placed in an
ultrasonic cleaner; oiled, highly included & those showing
fractures. There's a large list of stones that even if they are
(or appear) perfect should never be put in an ultrasonic, most
I'd like to give an example for emerald. I recently made up a
large 18k lady's ring and set it with her 5 carat gem pear shape
emerald. I gave it a few second swish through a warm and gentle
ultrasonic, then, with my thumb over the emerald, gave it a few
shots of steam from several inches away.
I heard later from the dealer that sold it to her the oil had
come out and some fractures were showing. hmmm, I was
devastated, I thought I had ruined her stone and no way could I
afford to replace it. The dealer simply had it re-oiled and it
was fine, but what a lesson for me. It's the tooth brush from
now on, and no steam under any circumstances...
By the way, I just started the GIA colored stone course on my
way to a GG cert. I no longer have any excuse to screw up stones!