GL Newsletter May 2014

logo21-150x150 From the editor

As we are approaching the busy months of this year just a few reminders:

There are few places left during our Spring 2014 PDP (Professional Development Program) at the Sandman Signature Hotel – Vancouver Airport, May 31 – June 3. More info here.

The program for the 11th International GeoRaman Conference (June 15 – 19) in St. Louis, MO USA has been published; download program (PDF file which contain links to abstracts).

Please read our abstract (PDF, 356 KB).

GL Gem Spectrometer and GL Gem Raman Workshops

For present and interested future users of our advanced gem testing instruments we offer a free 3-hour review and hands-on session during the Spring 2014 Workshops on Tuesday, June 3 from 2:00 – 5:00 p.m.; the workshop is limited to 5 participants. Please contact us at gemlab@cigem.ca to reserve your space.

We also have an advanced 3 1/2 hour workshop scheduled for Tuesday, June 3, 2014 from 6:00 – 9:30 p.m.; please register on-line by May 20.

GL Gem Raman PL 532 Upgrade

After successful testing of a protoype we have implemented the GL Gem Raman Band Pass Filter (GLBPF) for suppression of fluorescence in Raman mode. It consists of a holder with a dielectric filter which is inserted into the GL Gem Raman case when needed. This simple solution allows the upgrade of all GL Gem Raman units previously sold for a reasonable price (dielectric filters are not inexpensive!); all users will be contacted when the filter assemblies become available (in early June 2014).

The official introduction of the the upgraded GL Gem Raman PL532 TEC (which will be slightly lighter weighing less than 8 kgs) will take place at the GeoRaman Conference (June 15 – 19) in St. Louis, MO USA; as an official sponsor of this event we have a display booth and will be demonstrating the new GL Gem Raman PL532 TEC in the 2014 GeoRaman Exhibition Hall.

After band pass filter for fluorescence suppression

Band pass filters are used in more expensive commercial Raman systems in a number of applications. The introduction of a suitable band pass filter for suppression of fluorescence will greatly improve the detection of Raman signals when previously overwhelmed by fluorescence. We received surprisingly good results with spinels, rubies and sapphires, emeralds and other gemstones affected by fluorescence. In many cases valuable Raman information could be obtained to positively identify the sample in the RRUFF database. However, very strongly fluorescent materials such as synthetic flame fusion ruby could not be identified; for these materials a UV laser in a gated system will be necessary.

The filter assembly can also be used with other filters. As we are able to produce the filter assembly in larger quantities the price of the complete GL Gem Raman PL 532 TEC system has not changed and will be under US$ 8,500 (Can$ 9,300, EUR 6.200). More info about the GL Gem Raman PL532 here.

New Advisor to the GLR&T Team

We welcome J M Dereppe, Ph.D. (Professor Emeritus, Physical Chemistry Department), University of Louvain, Belgium to the Gemlab R&T Development and Support Team. Jean-Marie is running his own research lab and is an experienced spectroscopist who purchased the GL Gem Raman PL532 TEC last year; he is also our European contact person.

Jean-Marie’s work was was crucial in finding a solution to overcoming the fluorescence problems common in Raman spectroscopy. After testing a number of filters he presented me with the idea of a bandpass filter which we now include in all new GL Gem Raman units as the “GL Gem Raman Band Pass Filter (GLBPF) for suppression of fluorescence in Raman mode”.

Articles about Testing HPHT Reated and CVD Grown Diamonds

We were able to test a number of diamond samples and the work is still ongoing (and probablay will for a while). Until now there is no 100% answer as to the type or combination of treatments used on synthetic diamonds (either HPHT or CVD grown); as these materials will become more common in the near future scientist struggle to come up with solutions. As a start an excellent scientific book is by “Inga A. Dobrinets, Victor G. Vins, Alexander M. Zaitsev (2013) HPHT-treated Diamonds”; sample pages can be downloaded from here.

Personally I would be cautious with all devices claiming 100% reliability and repeatability based on a large reference base: only one sample which has not been properly identified will make the whole database useless.

I believe there will be several approaches in the future with analysis of photolouminescence features perhaps the most promising. In this context the PL feature of the GL Gem Raman PL532 will be very useful in future research; the state of the art will be presented during our poster session at the GeoRaman 2014 conference. Below one example of our findings:

Raman PL spectrum (room temp.) indicating HPHT treatment in synth. diamond

Raman PL spectrum (room temp.) indicating HPHT treatment in synth. diamond

The graph above left illustrates a synthetic HPHT treated diamond (non CVD) with a nitrogen-vacancy defect at 637 nm; it also shows the surpression of the 558, 566 and 576nm bands which usually indicate an untreated diamond if the 637 nm peak is missing as well.

Strong silicon-vacancy peak at about 737nm may indicate CVD (chemical vapour deposition) grown synthetic diamond; there are natural diamonds with similar features but they can be recognized by their inclusions. However, the detection of the SiV optical center at 736.6/736.9 nm SHOULD NOT be considered proof of CVD synthesis (see recent article in Gems & Gemology, Spring 2014); more research is necessary.

The analysis of Gr1 and SiV centres in CVD-grown yellow diamonds and the comparison with existing published data indicate that other impurities like Xe, Ni or Cr may produce other colours as well; see “Contributions to Gemology #14 (2014) New Generation of Synthetic Diamonds Reaches the Market, 41 – 55” published by GRS Gemresearch Swisslab.

Exotic Gems, Volume 3 by Renee Newman

Exotic Gems Vol 3 How to Identify, Evaluate, Select and Care For Matrix Opal, Fire Agate , Blue Chalcedony, Rubellite, Indicolite, Paraiba and Other Tourmalines.

This book and other volumes can be purchased at our Gemlab Books on-line store.

I would like to thank Renee for the authographed copy she presented me during the last AGTA Gem Show in Tucson, Arizona; as always a solid work with lots of beautiful images.