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About Turqoise


#1

I’ve been told that if turquoise has been dyed, it will sweat when
you heat it. Can any of you gemologists out there tell me if that is
accurate?

Not generally true. If it’s been treated just with wax, then a
nearby hot point will indeed make it “sweat”. Don’t heat the turqoise
itself. heated turqoise reacts with an action called decripitation.
In common language, it explodes/disintigrates/ or otherwise
dramatically self destructs. Now, I’m talking about more than just
lukewarm. I mean hitting it with a torch flame. But still, you don’t
need to heat the turqoise more than holding a hot point (red hot) just
nearby. Use a loupe to see what the surface of the stone is doing
next to the point.

The most common treatments for turqoise, though, are no longer just
wax. Now it’s usually impregnated with various resins. Commonly,
epoxy or polyester resins are used. These don’t sweat. but if you
TOUCH that hot point to an inconspicous part of the stone, the plastic
burning smell will be obvious. The little speedy wax pens, you know,
those $20 buck battery operated wonders, are good for this test. Be
sure to only touch an inconspicuous part of the stone, as the point
you touch, if the stone is treated, does get a tiny burn mark. This is
a test to use only cautiously and if your other observations have not
told you what you wish to know, since in essence, it is a slightly
destructive test. But the treated turqoise is also easy buffed again,
so it’s not a serious problem if you’re careful.

This test will not tell you if the stone has been treated by the most
sophisticated means, where are also used on the best of the stones
needing treatment. In this case, the stones are impregnated with the
addition of silica, to make them denser and more impervious to
absorbing things. Raises the apparent quality. But it’s very
difficult to test for this. Bottom line here is know your sources
when buying the very best qualities of turqoise.

And the other thing the hot point test doesn’t detect well is the
addition of dye to the plastic. Much turqoise is stabilized with just
the added resins. But much really bad chalk is also given the addition
of dyes to the resins. Fortunately, most of this stuff simply looks
wrong. Too dark, or the color isn’t uniform, or you can find small
pockets of pure resin which then are colored instead of clear. So a
good examination with a loupe and a careful eye will usually tell you
what you need.

also, be aware that there are simulated and reconstituted turqoise
materials out there. Usually visual examination will tell you when
something is wrong here. But again, sometimes you have to be quite
careful.

Hope this helps.

Peter Rowe