Welcome to AGTA GTC's Laboratory Update for May 10, 2005


  1. Current Turnaround Time
  2. Seeing in the Dark: UV Fluorescence as a Gem Dealer’s Tool
  3. Testifyin’: Pala International’s Josh Hall
  4. The AGTA GTC in Las Vegas
  5. Testing Mounted Gems?

Current turnaround time
Over the past three months, the AGTA GTC staff has worked hard to reduce the time it takes for a Lab Report to be issued. We now have the turnaround time down to five to seven business days. With the upcoming JCK show in Las Vegas, now is an excellent time to submit your stones for testing. See our full rate sheet at this link.

Seeing in the dark:
UV fluorescence as a gem dealer’s tool

One of the greatest challenges facing gem dealers is being able to accurately determine if a gemstone has been heat treated. While a 100% reliable answer to that question is a job for a major gem lab, there is a simple and inexpensive tool that can often give an important indication.
     So what is this miracle tool? I speak of the lowly ultraviolet light.
     It wasn’t long ago that ultraviolet (UV) fluorescence was considered the poor stepchild of the gem lab, a pint-sized pea shooter when compared with the high-caliber cannons available in major labs. But with the rising importance of treatment detection, the humble UV lamp is making a comeback.

Many heat-treated rubies and sapphires will display chalky short-wave (SW) fluorescence. This reaction is practically never found in untreated corundums. It is actually the colorless portions of the gemstone that fluoresce (a reaction similar to Verneuil synthetic sapphires). Since colorless areas follow the original crystal’s growth structure, the fluorescence will follow the same pattern as the gem’s color zoning. Figures 2, 3 and 4 illustrate this in both sapphire and ruby.

Figure 1. Tufted love
When a sapphire is subjected to high-temperature heat treatment, a chalky blue to blue-green SW fluorescence is often created. As seen above, this reaction is confined to certain zones in the gem. These “tufted” fluorescent zones follow the crystallographic structure of the gem.
Photo: Richard W. Hughes/AGTA GTC

Figure 2. Ring around the collar
Flipping the same sapphire from Figure 1 over reveals a distinct bluish (‘chalky’) fluorescent ring, corresponding to the colorless portions of the gem when viewed in immersion. When seen, this strong chalky blue SW fluorescence is an extremely strong indication that the gem has been subjected to high-temperature heat treatment. Photo: Richard W. Hughes/AGTA GTC

Figure 3. Let it glow
In this heat-treated and flux-healed ruby from Möng Hsu, Burma, thin zoned patches of chalky blue fluorescence float on top of the chromium-based red body fluorescence. These chalky blue zones are a strong indication of high-temperature heat treatment. Photo: Richard W. Hughes/AGTA GTC

Show and tell
So how does one go about checking for this reaction? The first step is to obtain a combination LW/SW lamp. You will also need a pair of protective glasses (SW light can burn your eyes with prolonged exposure). A viewing cabinet is also a plus. Finally, you will need a small lens to magnify the gemstone. Figure 4 shows the author’s setup.
     The idea is to hold the gemstone with tweezers and bring it as close as possible to the lamp and view it under magnification. Examine the gemstone from all angles; many times the key chalky areas are confined to tiny portions of the gemstone.

Figure 4.
The author’s setup for close-up examination of UV fluorescence. A small piece of blutac or clay inserted between the UV lamp and the viewing cabinet creates a small gap. This allows the gemstone to be viewed while positioned extremely close to the lamp, greatly increasing the ability to catch weak reactions. A lens is positioned to magnify the gemstone during viewing. The masking tape keeps the lamp from tipping off the cabinet. Special UV protection glasses such as those in front of the cabinet should be worn to protect the eyes from harmful SW radiation. Photo: Richard W. Hughes/AGTA GTC

This test does require a bit of knowledge. If a ruby or sapphire shows a chalky fluorescence in SW, it is probably heat treated. If it is inert, that does not mean it’s not heated.
Also be careful that the gemstone is clean. Soap and other chemicals can also produce chalky fluorescence.
     And finally, while this test is a tool that can be extremely useful, it is not a substitute for a complete gemological examination in a fully-equipped laboratory.

Summing up
With UV fluorescence, we have something all too rare in gemology today: an inexpensive instrument that is as sensitive as even bomb-science level analytical equipment.
     Now what does this mean for a gem dealer? With a small UV lamp, one can quickly check potential purchases. Any stones that show a chalky SW fluorescence are most likely heat treated. Total equipment outlay? The lamp alone costs less than $300. Heh, heh, heh, I can already see you smiling.

Testifyin’: Pala International’s Josh Hall

“We have used the AGTA gem lab since its inception and have been thoroughly pleased with the professionalism, speed and accuracy of their services.
     “The reports are easy to read and understand and we particularly like the option of the photograph on the report.
     “But above and beyond all that, is the fact that AGTA has the advanced laboratory equipment and expertise to certify a stone as to its location. That ability alone has put money in our till.
     “We will continue to use the lab and encourage all who see this to do the same. You will not be disappointed!”

Josh Hall
Vice President
Pala International


The AGTA GTC in Las Vegas
Once again, the AGTA GTC will be participating in the Las Vegas JCK Show, offering a range of gemological services, such as:

  • Identification reports for all kinds of gems, including the identification of clarity enhancement fillers
  • Country-of-Origin reports for ruby, sapphire and emerald

Note that the AGTA Pavilion opens and closes one day before the main JCK show. So the AGTA-GTC mobile lab is open Thursday, June 2 to Monday, June 6, 2005. The hours are 10:00 am to 6:00 pm on June 2nd and 9:00am to 6:00pm on June 36. The mobile lab is planning to deliver the report to the client within 12 days and the services are going to be available during the show time. 
    But even better than submitting stones during the show is to submit them to our NY office prior to the show, so you’ll have the stones in your showcase, ready for sale with reports. Stones submitted by Wednesday, May 18, have a good chance to be back in your hands by May 27 just before the show. So hurry up!

Can you test mounted gems?
One of our customers’ most frequent questions is whether or not we can test mounted gems. The answer is quite simple. Yes, we can and do produce identification and origin reports on mounted gems.

There is, however, a caveat. Because some mountings block important features of the gemstone, in such cases we may have to ask that the gemstone be removed before issuing a report. But such situations are rare. So if you’ve got mounted pieces, bring ‘em on.

The AGTA Gemological Testing Center provides the industry and the public with a complete range of lab services, including gemstone identification, origin determination and pearl identification. Located in New York City, the laboratory is equipped with the latest, technologically advanced, investigative equipment. The AGTA GTC is committed to providing excellent service, superior value and outstanding quality. A complete list of services and detailed pricing information is available on our website, www.agta-gtc.org. Please contact us with any questions.

American Gem Trade Assocation Gemological Testing Center
18 East 48th St., Suite 502
New York, NY 10017, USA
Tel: 212-752-1717; Fax: 212-750-0930
E-Mail: info@agta-gtc.org; Web: www.agta-gtc.org
© 1999–2006 American Gem Trade Assocation Gemological Testing Center. All rights reserved. Users may download this information for their own private, non-commercial use. Any other reproduction of this document (text or graphics) without the express written consent of the AGTA GTC is strictly prohibited.
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