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How to test if a zircon is genuine

I recently purchased a rough stone marketed as a certified 108 carat rough red zircon. The so-called certificate was supposedly issued be “a” GGL laboratory although as stated on the card they had not seen this particular stone but rather issued the “cert” as per the supplier’s description. The lab website that they listed also turned up a dead web address. Right away this told me the stone must be counterfeit. Is there a method in which to authenticate a zircon? The Presidium Gem tester 2 doesn’t list the zircon in its list of identifiable stones. My guess is that if the certificate is fake the stone is as well but I want to be sure in my dispute with the supplier as it could very well be a zircon only glass infused. How can I be sure?

Test for refractive index, specific gravity, and dispersion starting out.
Zircon is typically not glass infused. Glass infusion is used to enhance clarity, and gem zircon is typically very clear to begin with. The most common treatment for Zircon is heat.

The image you have provided looks like it might be red CZ. Once again, testing the above data points should verify. This link ( has an example of red CZ rough for comparision.

Agree Specific gravity as zircon is very dense. Looking at the rough there is a chip and the manner in which it is chipped to me would indicate glass. There are a lot of scammers out there and they do not care. The worst ones to my knowledge are on places like Ebay and Amazon. Sadly the platforms don’t care when you complain they are only interested in getting their commission.

In a piece that big, there ought to be clear doubling of the back edges of the stone as viewed through one axis (the C axis). So if you turn the stone all around and don’t see any doubling or blurry edges looking thru it, it can’t be zircon. I also agree that an SG measurement would help. Cubic zirconia is heavy (dense), but zircon even denser. Get a small gram scale and put a salad dressing cup or such full of water on it and tare it out to zero. Then tie a string to your rough and suspend it in the water and get a weight. Then rest the rough on the bottom of the cup and get another weight. Divide the greater weight by the lesser and get an SG the easy way. This thing looks like a boule of synthetic of some sort. All the rough zircon I have seen is water worn pebbles, altho’ it may be found in other forms…look that up. Good luck getting your money back. Please don’t buy any more ebay bargains! Buy from recognized dealers or on referral from trusted friends.


Raman and or FTIR will tell you right away… send to a lab that has this equipment and the seller will have no choice but to return $

When I did the test for specific gravity my calculations came to 1.97. So giving myself a margin for error that’s pretty darn close to glass at 2.4

How could one possibly believe that was a natural piece of anything?

Just out of curiosity, what did 108cts of zircon cost you?

Shape of your rough is classic man made cubic zirconia.

I agree to the discussion. I always test first doubling with my loupe or microscope. Almost always it is easy to find doubling for (high) zircon like red or white ones. If you find doubling - it cannot be CZ. I also test with presidium digital refractometer and Gem-n-eye in parallel. I have good experience with this procedure. But the problem which came up in the last years is India and fake certificates. I cannot understand why Ebay does not take action. If you search for certain stones you get hundreds of offers from India with fake certificates and only a couple of serious offers between. Some are easy to detect like blue rhodochrosite (!), 10 ct “natural” tanzanites for 10 – 20 USD, 4 … 10 ct “natural clean” Alexandrite for 20 USD, and recently 6 … 10 ct VVS “natural” tsavorite “from Kenia” for 10 … 20 USD or “natural” 12 ct bixbite “from Utah” for a couple of USD. Such prices are impossible because so big stones would cost hundreds or many thousands USD. Same with trapiche stones. You find trapiche emerald in the size of 2 …5 ct (and more) for a couple of dollars. In some picture you can already see that this are fakes (despite a certificate from GGL or CGL) because some have 7 sections, other are glued together in wrong direction but you find also some where you are not sure – only the size and the price tells you that it is impossible. My conclusion: be extremely careful with dealers from India. Although some serious dealers exists – most dealers have either absolutely no knowledge and sell what they have been told from dishonest partners or they are dishonest itself. Always compare size, cost, color and shape of rough crystals with other offers in the internet. Furthermore, inform yourself about size and other properties in the articles from IGS or MINDAT database.

Hello. This is not natural zircon. This is man made zircon is very high dispersion and strong doubling Facets I. Rough the formation not like this Even rough material strong doubling on axis also fluorescence completely diferente some has a long parallel inclusions very thin is a good clue and most have cloudy or smoke appearance . Crystallography formation is bipiramiidal dipyramidal. The section square we’ll terminate plan and some times twins prismatic cleavage distinct rarely gemologist observe

Prof Miguel Zenetos gg Gia

Thank you for that information.
My suggestion is: NEVER buy gems on ebay, amazon,alibaba, etc, unless you are looking for synthetics.

if it came from China it most likely a CZ

there are a lot a good e-bayers.try reading reviews and also % of satisfaction.Stick to usa

sound infomation-dweyer

Hi everyone,

I have been duped on ebay too. Londen blue Topas turned out to be Londen blue Glass, but not from a Indian seller but from a UK seller.

On the contrary I have founded an Indian seller which has not disappointed me. Real certificate 16 ct tanzaite belivable price and quality. I do believe you only get what you pay for or wors on ebay and amazon or Wish and snap ups are a thing of the past on ebay. But there are still some good sellers out there. But it’s alwais a risk.

I highly recommend the IGS Mini courses, thay heaped me a great deal.

Unfortunately there is no Zircon Mini course, but a great mini course on gemo tools and GemstoneInvestment. Absolutely great.

If an offer is to good to be true it’s most likely not true.

Best regards Johann

I have been fortunate most of the time on Ebay and buy only from sellers that have 100% rating with a return policy. Also, only from the U.S. Many stones can be evaluated by a GIA gemologist, and so I take it there to determine many stones, except ruby. Purchased a ring from Rubylane, and it was evaluated by a GIA gemologist as fake. The seller had taken the time to go to the GIA lab in NYC, a block from her store, and they said it was real. The lady allowed me to send it to GIA lab in Carlsbad, CA,(which took 3 weeks) which also confirmed the stones were natural. It’s getting so hard, even for the professionals.