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[Ultrasonic] Harmful to stones


Does anyone have a list of stones that CAN"T go in the
ultrasonic? Since we are on that subject! Thanks muchly in
advance! Mary


No emeralds, tanzanites, lapis lazuli for sure. No fracture
filled diamonds. No stones with extensive inclusions.


Dear Mary,

My gemology instructor says any stones that come from living
creatures should not go into the ultrasonic.



Mary - There’s a great poster, available from the Gemological
Institute of America, which lists all the known gemstone material
by refractive indices, specific gravity, normaly found inclusions
AND their durability to thermal shock. We have one hanging in the
shop so everyone can consult it before putting the gems into the
ultrasonic, steamer or torches. Good luck. Kim.


There are several factors here. one is that the sonic is a
highly effective cleaner. Sometimes you don’t really want that
much cleaning, such as with stones that have oil fillings or the
like. Another is that the sonic cleaner is putting considerable
energy into the solution. Some highly stressed or brittle
materials might shatter or crack, simply from that sonic energy,
kinda like that old memorex ad where Ella Fitzgerald hits the
right high note and a glass shatters… This is not common.
But it can happen to a few fragile stones. And finally, remember
that ultrasonics clean by causing cavitations, which is the
formation, expansion, and collapes of tiny bubbles. Very
rapidly, and concentrated at surfaces. The result is a rather
vigorous scrubbing action. Soft materials can literally have the
polish taken right off them. The degree to which this happens
depends on your cleaner. Many of the littler units simply don’t
have the power to do this very fast. They also, of course, take
a long time to remove even a few fingerprints… But the bigger
or more powerful units can damage some things quickly. Some
silver, especailly castings, is soft enough that the sonic will
leave frosted areas or whiteish swirl marks where it’s literally
scrubbed the polish right off. For a dramatic demonstration of
what the sonic can do, as well as a test of how effective a
sonic you have, put a piece of aluminum foil in there for a few
minutes. With a good ultrasonic, it will come out looking like a
sieve, with holes punched right through it.

for the most part, gold, platinum, and rolled/drawn/worked
silver items are OK. Most of the harder stones are also safe.
But to start your list of cautions, almost any stone you’d not
put in the pickle, probably shouldn’t spend a lot of time in the
ultrasonic. An exception to that is pearls. While pickle would
dissolve them rapidly and destructively, with the proper
cleaning solution, they won’t generally be damaged by an
ultrasonic (they’re pretty tough, actually) unless they are of
very low quality with very thin nacre. One exception to that is
mabe pearls. Some of them have very thin layers, and sometimes
an ultrasonic can destroy them. Not common, but I’ve had it

Some of this is relative. Most stones can take a brief "swish"
in the ultrasonic to remove a little rouge from the ring you just
touched up. Soaking them in it for 15 minutes might be another
thing altogether.

One of the big red flags, though, is tanzanite. Because of
stresses sometimes built up in heat treating, tanzanites have a
(deserved) reputation for cracking or even shattering in an
ultrasonic. That’s not to say they all will, or even many of
them will. But enough of them might, that it’s generally felt
they should never go in an ultrasonic, even briefly, unless
you’re quite able and prepared to replace the thing. Silly risk.
Use a boil out solution instead.

Another obvious No-no is amber, especially if the solution has
ammonia. Destroys it quickly.

Stones that are oiled or otherwise treated, as with most
emeralds, risk having the oil come out. I use an ultrasonic
regularely with many emeralds, but only after a good examination
of the stone to evaluate that risk. Highly included or
particularely valuable ones don’t go in.

Same sort of thing with opals. the little run of the mill 6x4
ovals that cost a buck or so I don’t worry about. But the big
expensive ones, I don’t put in the sonic.

While turqoise or malachite and coral probably won’t be harmed
by brief cleaning, the solutions themselves might be harmful.
Use caution with these, and other such soft or porous stones.
Malachite and coral, if left in a powerful ultrasonic for too
long, can get dulled. Quickly fixed with a brief buffing, of
course, but avoidable.

Peridot can stand a brief cleaning, but don’t leave it in there
very long. It’s a bit soft to withstand that scrubbing,
especially if you’ve got a powerful cleaner.

And watch out for assembled or coated stones, like much of what’s
in costume jewelry. Ultrasonics are pretty good at getting
things unglued, or quickly seperating a rhinestone from it’s
foiled backing, etc.

Hope this helps. It’s not a complete or extensive list, but it
will give you a start on what to look for…

Peter Rowe


if you accidently leave a malachite set in a sterling silver
wire wrap ring, over night, the stone melts. don’t ask me how
i know this…

oh, i added a few new links to my website and under protest, my
pic. i was told if my daughter, cats and dogs were featured,
then so should i. the fist under my chin is there to hide the
many many chins …

pat moses-caudel


I would limit the list of stones to only a few, just to be on
the safe side. Most stones are either dyed, treated, filled, or
in some other way enhanced, therefore, I would only recommend
placing the following stones IN the ultrasonic:

Corrundum (Ruby, Sapphire)
Aquamarine (be careful on more expensive stones)
Undyed Quartz's (Amethyst,Citrine, smokey, jaspers, agates)

If it’s not on this list (provided I did not overlook anything),
I don’t recommend it at all. Keep away from known treated
stones ( except heat-treated), stones that have noticable
fractures, or are possibly dyed. Also diamonds of any larger
size, could be treated (a lot are), use your loop when possible,
and when in doubt, keep it out!

God bless,
Tom and Donna