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HOW DO I TELL A DIAMOND FROM A CUBIC ZIRCONIA (A CZ)?

I 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.