recently received this interesting question from a Mrs. Gottrocks
shopper. To be honest, the answer to the question of how to tell a
diamond from a CZ isn't as simple as it might be for the layman. There
are many indications jewelers and gemologists use in combination to
make that determination, and it is always preferable to have a seasoned
professional make the identification for you to be sure. Here are
a couple of the methods jewelers use.
The Stone Is Too Clean: As a jeweler, the number one red
flag, besides plain ol' experience, is if, at first glance, the stone
is too "clean". This means that with a 10-power jewelers loupe or
other magnification, the stone has no apparent inclusions within it.
"Inclusions" is the label given to the various natural features found
within minerals such as diamond. An apparently internally flawless
stone is always a red flag, as in general, fewer consumers purchase
expensive Flawless, Internally Flawless, or Very Very Slightly Included
(VVS) diamonds, preferring less expensive diamonds which have inclusions
relatively easy to see with a loupe (VS, SI and I stones).
Diamond Testers: Once a sure fire way to identify a diamond,
a diamond tester is a little gadget which, when pressed against the
stone, says yes or no to the question, "Is this a diamond?." It won't
tell you what it is if its not a diamond, but it will indicate if
it is. It is important to not touch a prong or other metal with the
tip while testing, to try to press against the middle of the top of
the stone, and to make sure the stone is very clean. Unfortunately,
there is now a synthetic stone which will test positive on a diamond
tester, so you can no longer rely on this method alone. You should
always use a diamond tester in conjunction with another method, such
as checking for doubling.
Magnification and Doubling: This means that if you look through
the stone while it is magnified (microscope is best, but loupe, with
practice, will do) while it is face up, and you focus through the
stone to the facet edges furthest away from you, you will see that
they are doubled (you can see two of each line, as if your vision
was blurred). Again, you need to be sure to clean the stone very well.
If you see doubling, it is not a diamond. However, not all diamond
simulants exhibit doubling, so you can't use this method alone.
Bottom Line - Seek Professional Help: Most jewelers will
give you a quick opinion on "CZ or diamond" at little or no charge,
and if the stone is questionable, will recommend you send the stone
to a gem lab for definite identification. Make sure you have a definite
ID before you make that purchase or sale, and get at least two professional
opinions to rule out any unskilled or disreputable jewelers.
Please feel free to email us
with your questions, or with suggestions for future topics.