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Daily Wire Tip: Determine Gemstone Authenticity at Home

By on March 18, 2011
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Daily Wire Jewelry Making Tip

Question:

What are some of the ways I can tell a real gemstone from a CZ or synthetic stone? I would just like a few hints that I can use such as what to look for with a magnifying glass, to tell the difference. Can you give me a few pointers?

-Lynne in Sutherlin, Oregon

Answer:

Oh my goodness, Lynne! Really, there is no sure way to determine between the stone types you list without gemological equipment. One option is to send valuable, questionable stones to the GIA (Gemological Institute of America).

Any good gemstone identification book will tell about a natural gemstone’s properties, including any natural inclusions or flaws (such as feathers, silk, lily pads, etc.) that you can look for by using either a microscope or a 10x loupe.

Of course, there are a few home tests that are not to be counted on, such as:

  • Hold a cut stone to the sun, table toward your eye. if you can see straight through it, it is a form of glass, because glass reflects light, while gem material refracts light.
  • Weigh it: Diamonds weigh more than cubic zirconia.
  • Does it have flaws or inclusions? Lab stones (aka "synthetic") are no different than natural stones, except that lab stones are perfect: they have no flaws or inclusions.
  • The warmth test: If you hold a stone to your upper lip and it stays cold, it is a rock; if it gets warm really quickly, it’s plastic; and if it warms slowly, it’s glass.

One of the least expensive ways to help identify gemstones is to use a combination short and long wave, ultraviolet light, as described in this awesome book: Gem Identification Made Easy, by Antoinette Leonard Matlins. (If the link doesn’t pull up, go to books.google.com, and search for "Easy gemstone identification tests")

You could also find and join a local Rock and Mineral Club. There you will meet people with all types of knowledge about rocks, gems and fossils, as well as those with lapidary and jewelry making interests. Like me, they are always happy to "talk rocks."

Answer contributed by Dale "Cougar" Armstrong

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12 Comments

  1. avatar

    Pat Shepard

    March 19, 2011 at 9:31 am

    While lab gemstones often don’t have any inclusions, they can. For example:

    http://cgi.ebay.com/23-32CT-50-OFF-BLUE-SAPPHIRE-LAB-GEM-INCLUSIONS-/300520646780?pt=Loose_Gemstones_1&hash=item45f86d287c

    (Not my auction – looks pretty crummy, actually)

    Lab emeralds almost always have inclusions, lab corundum (rubies and sapphires), topaz and amethyst usually don’t, but certainly can. The inclusions in lab stones tend to look different from the inclusions in natural stones, but that’s something you’d really need training for to tell the difference.

    Also, buyer beware – often stones sold as “lab rubies” or “lab emeralds” etc. are actually cubic zirconia in the appropriate color rather than an actual synthetic gem of the appropriate type. There’s good and bad to this – CZ has more fire than any natural gem (even diamonds) but it tends to discolor over time.

    With experience that’s one way to tell CZ from a natural or real lab stone – it will appear brighter to the eye. But that requires either experience or a known real gem of the same size and cut to compare it with…

    One final test – the Too Good To Be True Test. If someone is selling a 50 carat flawless sapphire for $21:

    http://cgi.ebay.com/IF-53-CTS-HUGE-ROUND-LAB-CORUNDUM-PURPLE-SAPPHIRE-T563-/230587828241?pt=Loose_Cubic_Zirconia&hash=item35b01b0811

    (Again, not my auction – though this time it’s pretty.)

    it’s going to be a lab gem or CZ. In this case they’re up front about it, but that isn’t always true. Personally, for my jewelry, I could care less about whether my gems started in the dirt of in the lab, but it does matter in terms of real world value. Let the buyer beware!

  2. avatar

    Patricia C Vener

    March 19, 2011 at 11:45 am

    Specific gravity (or density, actually). Be Archimedes in your kitchen. ;)

    This is basically dropping the stone in water. Most stones sink. When they do, they displace an amount of water equal to their volume. The mass of the water for that volume is known because in metric 1 cubic centimeter of water is equal to 1 gram of water. Then you compare the density of the stone (its mass divided by its volume) to the density of either CZ or whatever stone you though it might be.

    See? Physics does come in handy!

  3. avatar

    mary

    March 21, 2011 at 1:57 pm

    Pat:

    Oh dear, I want some of those just to have sitting around in a bowl…LOL Too good to be true…but pretty. :-)

  4. avatar

    Suz

    April 12, 2012 at 9:10 am

    Thanks so much for the incredibly helpful info. I’ve bought some real ( ha ha) “duds” sold as “authentic, natural, real, etc,,,,) on EBay. I’ve learned the long, hard way to really do my research through books, classes, and articles free for the taking some of them, off of the Internet.
    Buyer beware , number 1, and number 2, you REALLY DO get what you pay for!
    Thanks so much WS!

  5. avatar

    Merry Pringle

    July 3, 2012 at 4:47 pm

    Is a Ruby Corundum a lab Ruby? They look beautiful.But if I use them I have to be able to tell buyers what they are getting. Thank-you so much Merry

    • avatar

      Rose

      July 24, 2012 at 9:08 am

      Hi Merry, our Ruby Corundums are lab-made rubies. So they have the same chemical composition as natural rubies, but are much more accessible :)

      • avatar

        Brian

        August 3, 2013 at 7:32 am

        Why are your “Ruby Corundums” listed under Cubic Zirconia on your site? They can’t be both.

  6. avatar

    Melanie Johnson

    February 7, 2013 at 8:07 am

    Corundum is the scientific name of the family of stones that Ruby is in. It has NOTHING to do with an indicator of natural or lab-created stone. It should perhaps be mentioned that Synthetic stones are true ARTIFICIAL COPIES while Lab-Created stones are grown from “seeds” of natural stones in a lab environment resulting in a chemically scientifically & optically equivalent stone. Also in the Corundum family is Sapphire.

  7. avatar

    Liz

    July 31, 2013 at 5:38 am

    I have the book “Gem Identification Made Easy,” along with several others. I use the book as my first reference, then do a little comparison. I didn’t buy the books at the beginning – I checked some out from my local library for a “test drive.” This book, though, is a great resource!

  8. avatar

    pas

    January 3, 2014 at 9:00 pm

    what if it is attached to a ring?

  9. avatar

    Wilford Bickel

    July 10, 2014 at 6:40 am

    There are several ways to make sure you are buying properly identified stones. First the book on Identification listed above is good – another one I would recommend is “Gemstones of the World” by Walter Schumann, 4th edition. I have probably 10 different books on gems and gem identification used as references when doing ID work. Once you study these books and you learn proper naming you can tell real quick the dealers that are listing stones with improper names or cannot tell you the species of stone (such as Corrundum is the Species and contains both Rubies and Sapphires) – a dead give away that you DON’T want to deal with them. The FTC has a listing and it was in a previous tip on the way to properly list natural, lab created and synthetics (ie: CZ stones) – as a seller you need to study this and make sure you follow them.

    Then you will have to set up a small ID lab – The Gem Identification book by Antoinette Leonard Matlins has a basic list of equipment you need to get started. I would recommend an electronic unit that can determine diamond and moissanite from CZ and other stones, a second or combined unit that can then tell diamond from Moissanite, a reflective index unit with chemical, a 10X triplet color corrected loupe (lots of loupes on the market do not have color correction). A chelsea filter for ruby and emeralds, scales for caret weight, a polarizer, a darkfield loupe and both short and long wave length Infrared light. To start seperating lab created from natural a microscope with minimum 60x magnification (some good digital ones on the market now at a good price). I am sure without pulling all equipment out there are a couple of other items that I am missing.

    Also, find somewhere online to take a some courses – I have done so and while I have not completed a certification I do feel secure that I can ID stones and protect myself from fakes. ID of stones is not cheap but certainly not overly expensive when you consider what just a few fake stones can cost you.

    Good luck to all – it is actually fun to stop making jewelry and do some ID work just with the beautiful stones!!!

  10. avatar

    Kenna

    November 10, 2014 at 8:37 am

    If you don’t want to go to the effort of learning identification, I recommend stopping by a lapidary group, as was mentioned. I am very fortunate that my local lapidary club has all the best books and dvds to borrow, some identification equipment and many experienced “experts” who are happy to look at my stones and tell me what they are and whether they are “any good” or not. I took a short workshop on gem identification and the instructor taught us some basic methods (ultraviolet for eg) and low cost equipment options. Anything more than that was beyond my time or financial availability. Gemologists and others study this for years and still have difficulty determining a lab gem from a natural gem, so it is not the kind of thing you can learn well easily, as you have probably gathered by the comments. Best of luck.