goldsmiths • jewelers • gemologists




Boldly Going Where No Lab-Rat Has Gone Before; Lab Games Part II

by Richard W. Wise, G.G.
©2007


Gem Science: Playing Catch-up:

In a very informative post on Gemologyonline.com Vincent Pardieu former Director of the AIGS gem laboratory in Bangkok tells a interesting story:

In 1995, a man from Chanthaburi, Thailand who specialized in heat treating yellow sapphire discovered that he could dramatically improve the color by using a powdered form of a mineral known as ploy nua oon in the Thai language. In 1999 when a new strike of pink and yellow sapphire from Ilakaka, Madagascar started entering the market he found that by using the same method he could turn the pinks an attractive pinkish orange or padparadscha color. http://gemologyonline.com/Forum/phpBB2/viewtopic.php?t=679&start=30

"Ploy Nua On" is the Thai name for a stone known in English as chrysoberyl. The burner just discovered in 1995 how to use a beryllium rich atmosphere to lower the blue content in sapphire and create in some cases an additional yellow color and by 1999 the first Beryllium treated padparadscha were in the market. .The dreaded Beryllium diffusion treatment was born.

What is Beryllium diffusion and how does it differ from plain old heat treatment? The key word is diffusion, a foreign element, beryllium is added to the stone. With traditional low-temperature heating nothing is added. This type of heat treatment has been going on for several thousand years. High temperature heating began in the 1970s and does actually involve hydrogen diffusion but on grading reports it is typically called “heat only” , has been accepted as “traditional” by the market and has dramatically less effect on price than Beryllium diffusion.

The AGTA laboratory put out a warning in January, 2002 http://www.agta.org/consumer/gtclab/orangesapphirealert.htm just before the big Tucson shows but it was not until the September 2003 Hong Kong show the full impact of this treatment hit the market. Sapphire prices dipped 20-40%. I recall dealers running for the hills willing to unload treated sapphire at almost any price. Were all these stones beryllium treated? No one quite knew.

This is a perfect example of the catch-up game that gemologists must play. Technology improves, new treatment methods are discovered by accident or on purpose and the laboratories first must determine that something is being done and then what is being done. In this case with a time lag of seven years.

Boldly going where No Lab-rat has gone before.

Gemological Laboratories are under increasing pressure to add quality grading to their traditional role of determining origin and treatment of gemstones. One laboratory, AGL had been doing this for several years. However, recently under the aegis of the Lab Harmonizing Committee several of the leading labs have decided to aggressively go where no lab has gone before into the world of marketing. Gem Labs have entered the nomenclature business and into a firestorm of controversy .

The question of nomenclature is often more about tradition than science. You can study internal inclusions and make a determination about treatments and point out what specific anomalies led to your conclusions but how do you decide what to name a gem? The recent flap over Mozambique cuprian tourmaline that I covered in an earlier post is an excellent example. http://gemwiseblogspotcom.blogspot.com/2006_06_01_archive.html

Traditionally we name a gemstone based on species and variety but what happens in the case of a gem that is of the species corundum but derives its name strictly from a mix of colors? What gem am I thinking of? I’ll give you a hint; padparadscha sapphire.

In my book Secrets Of The Gem Trade, The Connoisseur’s Guide To Precious Gemstones, www.secretsofthegemtrade.com , following the late great GIA gemologist Richard Liddicoat, I define padparadscha as a light to medium tone of pinkish orange to orangey pink. Up until recently, labs have avoided the issue by simply calling the colors; “pinkish orange” and so forth.

A consortium of gem labs under the title: The Laboratory Manual Harmonization Committee (LMHC) met in Milan and has drawn up a standardized definition of padparadscha. The LMHC consists of seven of the world’s major laboratories (AGTA Gem Testing Center, CISGEM (Milan), GAAJ (Japan), GIA (USA), Gemological Institute of Thailand, Gübelin Gem Lab (Switzerland) and SSEF Swiss Gemmological Institute (Switzerland). Some of these labs, excluding for the moment GIA-GTL, have begun to call and consumers have begun to demand a lab certificate that uses the term padparadscha to describe the stone. The question is, where is this definition coming from and is this the beginning of a brave new world wherein laboratory gemologists begin to dictate to dealers and connoisseurs?

“Well”, I can hear you say, “somebody’s got to cut through all the confusion.” and I agree. But, be careful what you wish for. Leaving aside the question of how this definition was arrived at, like it or not, once established the criteria determined by the labs will become the accepted definition. Are we ready for this and what in the training of a gemologist prepares them for this role? I received my Graduate Gemologist diploma some years back and I can tell that what a neophyte Graduate Gemologist doesn’t know about quality in gemstones would fill many volumes. A newly minted G.G. is little more than an apprentice scientist. Oh sure, he learns the GIA diamond grading system but…

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According to Richard Hughes well known author and gemologist with the AGTA gem laboratory which makes him one of the most prominent lab-rats, laboratories have no business making such calls. He was particularly upset by the fact that the LMHC did not

include a representative from Sri Lanka at the meetings where the decision was made (I mean where does the term come from?). Hughes also had problems with the adoption of a printed color chart developed by Franck Notari (GIA Geneva). Hughes makes the point that the definition of padparadscha is fuzzy at best and he feels that the insistence on hard a fast definitions is not appropriate. As proof of this assertion, Hughes did an analysis and discovered that the magnificent 20.84 carat padparadscha (pictured above left) that sold last year at Christies falls outside the parameters as defined by the chart adopted by the LMHC.

 

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