I'm going to step out on a limb here, and I would like to preface it
by telling everyone NOT to do what I recommend here unless you can
afford to replace the stone you're cleaning.
I have never, in more than 20 years of cleaning stones in both an
ultrasonic and a steamer ever had a stone be negatively impacted by
the cleaning methods used. I have put every fragile stone known to
man in at some time or another and never had anything break, or be
impacted by the cleaning methods (I can't say the same thing about
applying heat to stones however--including stones like sapphire that
are supposedly "heat resistant").
I generally try to keep stones like emeralds and opals in the
ultrasonic for a brief period of time (usually I hold the piece in
with tweezers and swish it around a bit for less than a minute). I
also have used a steamer in a somewhat similar fashion by trying to
direct the steam around the sides of the stone as opposed to coming
down on the top of it.
I think the bigger problem with these cleaning methods is that people
tend to (especially with the ultrasonic) dump stuff in and forget
about it for 20 minutes by which time something could have actually
happened to the stones. The other thing you can do is make the
cleaning solution in the ultrasonic as strong as possible so that it
cleans the piece relatively quickly.
I don't know what other people use but we use ammonia, ivory liquid
and water. If I need a piece to clean up quickly because I don't
want to let it sit in the solution, I'll just add some extra ammonia
so the cleaning action is sped up. However as I stated before I
wouldn't ever do any of this to a stone I couldn't afford to replace
and yes, I have worked with some customer's emeralds that were way
out of my budget range, and I never did anything but use an ammonia,
ivory liquid, water mixture with a soft brush.
If you brush the whole piece with the cleaning brush you can
sometimes achieve a slightly softer look to the metal that isn't bad
and then it doesn't look like a mistake because only part of the
piece looks that way.
Daniel R. Spirer, G.G.
Daniel R. Spirer Jewelers, LLC
1780 Massachusetts Ave.
Cambridge, MA 02140