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AGTA GTC's Laboratory Update for August 15, 2006

In this message…

  1. Upcoming Lectures
  2. Sapphire Reports With and Without LIBS from the AGTA GTC
  3. Upcoming Articles on Tajik Ruby & Spinel and Russian Emerald and Alexandrite

Upcoming lectures

The staff of the AGTA GTC has several lectures coming up in the near future.

San Diego, CA, Aug. 26–29, 2006GIA Symposium Logo

Many of the AGTA GTC's gemological staff will be participating in the GIA International Gemological Symposium 2006 and the associated Research Conference, as follows:

Poster Sessions

Lecture

Panels

Toronto, Canada, October 28, 2006Canadian Gemmological Association logo

The AGTA GTC's Richard Hughes will be delivering the keynote address at the Canadian Gemmological Association's 2006 Conference and Graduation.

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Sapphire Reports with and without LIBS Analysis from AGTA GTC

by Garry Du Toit

In mid-2001, unusual orange sapphires began appearing in Thai gemstone markets. It was later proven that these gemstones were actually pink sapphires with an artificially-colored rim created by diffusing beryllium into the gemstone. After further study it was discovered that some blue, red, orange and yellow sapphires were being treated in a similar manner.

In some cases this type of treatment can be detected by examining the gemstone in a gemological microscope while immersed in methylene iodide. When this is not possible, further analysis is needed using a newly acquired Laser-Induced Breakdown Spectrometer (LIBS).

The LIBS technique involves focusing a laser pulse onto a surface. The energy from the pulse heats, vaporizes, atomizes and then ionizes the material on the surface, resulting in emission of elements in a hot plasma. The atoms and ions in the plasma emit light which is then detected. The unique spectral signatures allow elements in the plasma to be identified. As a result of this type of analysis, a small eye-visible pit is left on the surface of the gemstone. LIBS analysis is normally done on or just below the girdle so that it is difficult to see. Minor repolishing will remove the pit (http://www.agta-gtc.org/2006-06-23_libs.htm).

It is for this reason that AGTA GTC requests prior authorization in writing by the client to perform LIBS analysis on all sapphires that are submitted for identification or origin reports which have been heated and are considered at risk of having been lattice diffused with elements from an outside source. The possibility that a heat treated sapphire may have been lattice diffused and the need for prior authorization will be explained to the client by our take-in staff at the time the gemstone is submitted beginning in July 2006. AGTA GTC will not perform LIBS analysis on any gemstone without the client’s written consent. Prompt attention to this detail will insure that the client will receive the normal five to seven day turnaround time without any unnecessary delays.

AGTA GTC report with LIBS analysis on Sapphire Identification or Origin Reports

If it is determined that no lattice diffusion has taken place, the report will be the same as the present report with the exception that the LIBS box will be marked in the lower right side of the report.

Enhancement:1 Indications of heating1, TE
Species: NATURAL CORUNDUM
Variety:  SAPPHIRE
Comment:1 1Corundum is usually heated to improve its appearance, unheated stones are unusual. This report has been prepared in accordance with the standardized language and criteria set out by the Laboratory Manual Harmonization Committee (LMHC); see reverse.
Tests Box

If it is determined that lattice diffusion has taken place, the report will read as follows:

Enhancement:1 Indications of heating, TE. Color induced by lattice diffusion of a chemical element from an external source.1
Species: NATURAL CORUNDUM
Variety:  SAPPHIRE
Comment:1 1LIBS analyses confirm the presence of beryllium. See LMHC Paper #2 for further important information. This report has been prepared in accordance with the standardized language and criteria set out by the Laboratory Manual Harmonization Committee (LMHC); see reverse.
Tests Box

AGTA GTC report without LIBS analysis on Sapphire ID or Origin Report

If it is determined that the gemstone is at risk of being lattice diffused and the client declines LIBS analysis, the report will read as follows:

Enhancement:1 Indications of heating1, TE
Species: NATURAL CORUNDUM
Variety:  ORANGE SAPPHIRE
Comment:1 1Further advanced analysis is required to determine whether or not a foreign element has been introduced. See LMHC Paper #2 for further important information. This report has been prepared in accordance with the standardized language and criteria set out by the Laboratory Manual Harmonization Committee (LMHC); see reverse.
Tests Box

Keystone Fees for LIBS Analysis

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Upcoming articles

In July 2006, the AGTA GTC's Richard Hughes undertook a lengthy journey to Central Asia, visiting ruby and spinel localities in Tajikistan's remote Badakhshan region, joined by AIGS Lab Director, Vincent Pardieu, AIGS student, Guillaume Soubiraa, and AGTA member, Dana Schorr. In addition, at the invitation of Canada's Tsar Emerald Corp., Richard visited the famous Malysheva emerald and alexandrite deposit outside Yekaterinburg, Russia. Look for reports on these localities in future issues, along with gemological research on the Malysheva emeralds and alexandrites.

Richard Hughes at Kuh-i-lal

The AGTA GTC's Richard Hughes at Tajikistan's storied Kuh-i-Lal spinel deposit. These mines have been worked for some 1500 years and are believed to be the source of the famous "balas rubies" (spinels) of yore, including the Black Prince's Ruby. In the background one can see the Pamir (Pandzh) River, which forms the border between Afghanistan and Tajikistan. Photo: Dana Schorr.