From the Editor
I wish you a Merry Christmas Season with a Happy and Successful 2012 and hope to see you in Tucson, Arizona in February.
GL Gem Raman Developments:
We finished testing the proto-type of the GL Gem Raman and have started designing a production unit combined with software development. We hope to have the first units for sale at the AGTA GemFair show in Tucson, Arizona in February 2012 or earlier.
Here a few comments about the advantages (and disadvantages) of a Raman over other advanced gem testing instruments such as FTIR, UV-VIS-NIR spectrometer, etc:
We have chosen a 300 mW 532nm laser as excitation source as commercial units are now available at economical prices. These devices use diode lasers to “pump” a Nd-YAG laser which operates at 1064 nm. The light from this laser is frequency-doubled to give green 532 nm light. This wavelength is about optimum for both Raman efficiency and the detector operating range. The Raman spectral range is from 200 – 2,500 cm-1 and output under 200 mW is usually sufficient and safe for the sample.
Raman spectroscopy is scattering-based, not transmission/reflection; i.e. no need for sample preparation. Only a small sample area is required; there are no movable optical parts and maintenance is minimal.
The Raman can quickly tell the difference between diamond, cubic zirconia and zircon, distinguish jadeite from nephrite, separate real from faux pearls, tell whether it is ivory or plastic. There is great potential for detecting treatments and colour enhancements in gemstones; it will help in the determination of the nature and colour origin of diamonds and other gemstones.
The GL Gem Raman has a sample compartment big enough to accomodate larger specimen and single pieces of jewellery.
Large reference databases are available on-line such as at the RRUFF Project; GL R&T together with other GL Gem Raman users will build a reference database for the 532nm excitation laser used in the instrument.
Sphene or Sphalerite?
From RUFF Project
In the C.I.G. study gem collection we have one stone marked “sphene (over the limit)”. As I did not get results with the refractometer we checked the stone with the GL Gem Raman; as shown above we could match the stone with the RUFF reference for sphalerite.
BTW: The GL Gem Spectrometer would have provided a (less expensive) answer; both transmission spectra for sphene (titanite) and sphalerite were recorded by Dr. Bill Hanneman with the GLGemSpec in his book “Pragmatic Spectroscopy for Gemologists“. Below the normalized absoprtion spectrum of sphalerite (obtained with our GLGemSpec) and the Caltech reference (Mineral Spectroscopy Server) for sphene (titanite); they do not have a reference spectrum for sphalerite:
GL Gem Spectrometer
If you want to join other GLGemSpec users in over 15 countries you must order your unit soon to receive it before Christmas; see detailed product information here. We also have a demo unit for sale ($ 200 savings).
In the last 12 months since introduction we have improved the firmware and software to make the spectrometer very efficient for use with or without the GL Halogen 10W Holder.
Experienced users have developed their own illumination setups for use with larger samples and individual jewellery pieces.
As part of our commitment we offer a generous warranty and upgrade policy.
Please order here.
“A comparison study of corundum using the GL Gem Spectrometer” by the World Gem Society; download (PDF) here.
AGTA GemFair Tucson 2012 – January 31 to February 5
Get ready for the big event and visit us at booth # 31 on the Galleria Level
We will have all the details about the new GL Gem Raman and like last year the portable GL Gem Spectrometer will be demonstrated. I also will be giving a workshop and presentation – to be announced soon.
C.I.G. Vancouver Courses 2012
We have posted the schedule for Courses/Workshops in the coming new year here.
World Gem Society
For a nominal fee you can access a variety of resources available to gemmologists and appraisers.
Wolf Kuehn, B.A., M.A., Dipl.oec, F.G.A., F.G.G. – GLR&T Project Manager
© 2011 Gemlab Research & Technology, Vancouver, Canada – www.gemlab.ws
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