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Cleaning blue zircon


#1

Hey there orchid gem junkies…

We sell a lot of blue zircon at the store where I work. We call it
"Glacier Ice" (this is Alaska marketing, okay?).

Anyway, we sold a white gold pendant with an emerald cut, maybe a
carat, carat and a half blue zircon the other day. Boss (a GG,
incidently) wants it polished up and cleaned before boxing, etc. So
I polish it, swish it in the ultrasonic (this is a little ultrasonic,
no heater, slightly warmed by the action…) rinse in room
temperature beaker of water, Boss says, “you should never do that
with zircon, the temperature change could shatter the stone.” He
then proceeds to steam clean the piece, putting the gemdirectly
underneath the nozzle…

“Steam cleaning is okay,” he says…

Now, my question is: It would seem the temperature change from room
temperature to direct steam (assuming steam temp is minimum 212
degrees f.,) is greater than the temperature change from a slightly
warm ultrasonic (maybe 90 degrees?) to room temperature water (72?
76?). What is the greater potential for damaging this stone? Is there
some gemological principle I am missing here?

Help me, Obi Wan, you are my only hope…
BK in AK


#2

Hi there,

I’m no gem expert but I do have some experience with blue zircon.

I have always been told that ultrasonic or very hot water were risky
with zircon.

Blue zircon is a beautiful stone that has a few problems. It is very
susceptible to facet abrasion and should never in my opinion be set
in a ring. I have seen zircon in rings that were nearly
unrecognizable as a faceted stone with just a year or two of wear. I
have a pile of blue zircons that all have facet abrasion that aren’t
worth repolishing, they might make nice fish tank gravel someday.
Regardless, and somebody correct me if I’m wrong, but this property
is caused because of the fact that zircon is not the same hardness
throughout the crystal. This is caused by radioactive decay of the
uranium atoms inside the crystal, leaving gaps in the crystal
stucture. I have always assumed that zircon should be kept out of an
ultrasonic due to the chance of facet abrasion while being vibrated
around in the solution, but I can’t confirm it, everyone just says
don’t put it into an ultrasonic.

Heat is another thing with zircon. Hot water or steam are not thermal
shock issue, but blue zircon can revert to it’s pre heat-treated
brown color sometimes with just minimal heat. I have seen stones turn
from a beautiful deep blue to dirty brown in a few hours in the sun.
I believe that sunlight is much more likely to cause a color change
but I have heard that even very hot water can change the color of the
stone. All of this makes for a stone that one might only want to sell
to people that they’ll never see again, because when the customer
comes back after a few years and their stone is now devoid of any
facets and it has turned an ugly brown color it’s not a happy
experience. If however the price is right and the customers are fully
informed of the care and hazards of zircon then everyone ends up
happy.

Oh, and “glacier ice”? Funny name for a Cambodian stone. I suppose
it’s mined from the glaciers there? haha just kidding, I hope all
this helps, good luck with your boss.

Doug