Trade Alert on Professional Melee Identification


The following is a Trade Alert on Professional Diamond Melee Identification, written by Dusan Simic and Wendelin Weingartner, from AG&J Laboratory in New York:

New York, NY. October 29th, 2013. Lately there has been an increasing concern in the diamond industry about melee lab-grown diamonds mixed into natural parcels. There is also a widely held discussion in the industry on how to counter this challenge. As we have dedicated years of research exactly to this topic, we want to contribute to the discussion by refuting some recent misunderstandings and definitions without going into technical detail regarding diamond identification.

It is important to be able to differentiate between professional and non-professional services, as well as to be able to identify when laboratories do not use adequate instrumentation to identify lab-grown or treated diamonds within melee parcels-a subject we hope to shed clarity on.

First, one has to understand that today’s lab-grown diamonds are different from those created as recently as only two years ago. Growing processes and post treatments are developing quickly; this is a very dynamic process. Therefore, detection methods have to be improved and refined as well. Today, for example, using XRF or a magnet is not enough to detect HPHT lab-grown diamonds.

Unfortunately, detection methods have to become more advanced and involve more expensive research and instrumentation as the methods of growing diamonds develop. The only solution we see is to use automation and sophisticated software to integrate highly complex identification methods into a system that is still fast, yet offers a low cost method to identify every single stone in a parcel. We want to emphasize that every single stone in a parcel needs to be identified. “Screening” a parcel, an often-misused term, does not mean that every diamond is identified.

Additionally, we want to list a few shortcomings and misunderstandings that we often encounter in our industry, and feel need some clarification:

  1. Misuse of the words “screening” and “identification”:

Commonly, gemological professionals consider “screening” a parcel as consisting of looking over samples by using only one method. Identification of a stone is much more involved, because at least two methods have to be used to achieve a final identification. Therefore, it is important to specifically request identification of every single stone when submitting a parcel to a laboratory.

  1. Identification with a laser pen—does not work in most cases today
  2. FT-IR spectroscopy or UV photometer (D screen) —these are well-established and very useful screening methods, but by themselves are not enough for a final identification.
  3. Diamond Sure and Diamond View—also widely used in gemological laboratories, but technically not suitable for pointer size diamonds.
  4. Magnetism—modern HPHT growing processes leave no traces in diamonds that can be detected with a magnet.
  5. Characteristic luminescence under DUV excitation — today, most lab grown diamonds don’t show cross patterns or red luminescence anymore.
  6. Characteristic birefringence under CPF — can be used for screening but not for a final identification.

In conclusion, we want to make our industry aware of the complexity of the professional identification of melee diamonds. We at AG&J use a combination of photoluminescence using different light sources, Raman spectroscopy and UV-Vis-NIR-FTIR absorption, primarily using customized instruments and software.

There are no simple solutions, be aware of anyone who offers these!