Search Colored-Stone.com:

This month's issue

Contact Customer Service

Colored Stone Back Issues

Author Joel Arem intends to put an end to diffusion confusion in the May-June 2009 issue of Colored Stone.

by Joel Arem
All photos courtesy of the ISG.

Blue treatment material at the end of this tourmaline demonstrating an effort to artificially diffuse color into stone.

Tourmaline cross section showing the "red and yellow crud" that entered this rough stone during the treatment process.

Red and yellow filled tubes in Mozambique tourmaline with red color diffusing out into the stone.

In 1999, the International Union of Pure and Applied Chemistry (IUPAC) published a lexicon of terms for solid-state diffusion. A decade later, it is time to finally align IUPAC definitions with gemological observations of potential diffusion treatment in gems such as corundum, feldspar and tourmaline. We’ve asked author, gemologist and Ph.D. Joel Arem to make a first attempt at this crucial semantic alignment in the May-June 2009 issue of Colored Stone. Here’s why he accepted this challenging assignment.

[Joel Arem's report begins here:]

Robert James does not work for Western Union. But judging from the hostile reception the president of the International School of Gemology (ISG) received in some quarters for his Tucson presentation on what he alleges is diffusion treatment in feldspar, and possibly also in garnet, topaz and tourmaline, you would think he was the proverbial messenger shot for delivering an unpopular message. Granted, James may have been on less-then-firm semantic grounds when characterizing his controversial observations. But that was no reason to deny the reality of his observations or criticize his insistence on further investigation.

At his open seminar on February 6th, James offered striking evidence of a new treatment process being employed to enhance the color of tourmaline, precious topaz and tsavorite garnet. Observations on all three materials reveal a coating of what James calls “red crud” on the outside of both rough and cut stones, from which bundles of tubes and needles filled with opaque colored material penetrate the gem. Some of the tubes are enveloped by a visible “halo” of color in the surrounding crystalline matrix; Observations at relatively low magnification (10-50X) do not resolve the nature of this halo. James also observed “burn” marks on the exterior of a number of samples, which he interprets as damage from strong radiation.

At considerable personal expense, James contracted with several independent laboratories to perform detailed spectroscopic analyses of the ‘crud,’ as well as chemical scans of the interiors of a number of cut gemstones received from dealers in Bangkok. The results indicate abnormally high levels of calcium, iron and manganese. James also discovered that the crud is strongly magnetic. Tourmaline samples obtained directly from Nigerian and Mozambique sources did not show any unusual features. All the observed anomalies were restricted to gemstones obtained from Thailand. Similar patterns of treatment were observed on samples of tsavorite garnet and precious topaz.

The red and yellow "crud" baked onto the surface of this Nigerian tourmaline.	Unusual red and yellow material inside distended tubes inside tourmaline.

Some of James’ critics have used his debatable lump-sum characterization of the treatment process as “grain boundary diffusion” as an excuse to deny the validity of his observations as well as the soundness of his suspicions. After the seminar, Colored Stone’s editor-in-chief David Federman asked me for a report on the proceedings, to be followed by a paper, to be published in his magazine, on proper terminology to describe what James was seeing. I accepted the assignment with relish because, if qualified with correct semantics, it becomes clear that James has made important gemological discoveries. However, I insisted that this paper be allowed space to provide essential background on some basics of solid-state chemistry and color science. This background is needed to allow the gemological community to understand a new and internationally sanctioned rubric of scientific terminology, one suitable to accurately describe the various forms of treatment we are seeing. Federman agreed to publish this tutorial in the May-June issue of Colored Stone and post a fuller version of this paper as a free download at the magazine’s Web site. You will want to see this download when it appears, but here’s a sneak peek at what it says.

A red diffusion tube with yellow material at lower right inside a Nigerian tourmaline crystal.	Radiation impacts used to create needle like tubes that extend down into this topaz crystal.

A scientific approach is needed to deal with the new treatment processes that are plaguing the current gemstone industry because the art of treating gems is a scientific process. Only by adopting science as its ally can the gemstone industry maintain the ability to detect misrepresentation and provide consumers with the confidence that will insure the long-term survival of the trade itself. I believe the messenger indeed saw compelling evidence of treatment. All he needs is the scientific language to correctly identify and communicate what he saw.

This was also sent out to our Colored Stone GemMail newsletter subscribers. Want to receive the latest up-to-date information on the gemstone industry? Sign up for our free Colored Stone GemMail newsletter.

e-mail the editors of Colored Stone | About Colored Stone | Sign up for the FREE Colored Stone GemMail newsletter

This site and all of its contents are copyright Colored Stone and Interweave unless otherwise noted.
All articles, photographs, graphics, logos, and trade show floorplans are owned by Colored Stone and may not be reproduced in any form,
in print or in electronic media, without the express written permission of the publisher. Violators will be subject to legal action.