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From the EditorIn a few days I will be leaving for Europe to first attend the Geo-Raman in Nancy, France; as a consequence we will have limited office hours during the month of June but we can be reached by e-mail. We submitted a poster (950KB, PDF) “The GL Gem Raman – a powerful tool in gem and mineral identification” and will demonstrate the Raman unit during the conference. For more information visit the Geo-Raman Xth Meeting website. |
Treated fresh water pearls
The GL Gem Raman can be used to detect colour treatment of freshwater cultured pearls. Based on recent research all natural colour pearls show the two mayor Raman resonance features of polyacetylenic pigments assigned to C=C stretching at about 1530cm-1 and C-C stretching at about 1130 cm-1.
We have tested a number of strands in the C.I.G. study collection and can confirm this observation. However, the Raman features may show up in colour treated pearls if the pigments were present before treatment. Further studies will be necessary to cover those possibilities.
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GL Gem Raman Version 1.1
We have made a slight change to the way the GL Gem Raman program saves a spectrum; version 1.1. saves now the full range from 200 – 2,500 cm-1 as a [nameR].fak file (similar to the GL Gem Spectrometer). As shown in the spectral graph it is very easy to import the raw Raman spectrum into Spekwin32 for further processing and editing.
At the same time GLGemRaman saves the spectrum as a [nameR].rruff file in the range from 200 – 1,500 cm-1 as this is the most common range found in the RRUFF databases. Just clicking on the file will open the CrystalSleuth program and depending on the speed of your computer you will receive a match within less than 10 seconds.
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The GL Gem Raman spectra for a diamond and cubic zirconia samples were saved as a .fak file, imported into Spekwin32 and normalized. The Raman peaks are very distinct and allow immediate separation as the GLGemRaman program displays real-time data acquisition.
Spekwin32 is a free optical spectroscopy software (Version 1.71.6) which has been modified by its author Dr. F. Menges. for use with our spectrometers.
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Introductory price for GL Gem Raman ends
Unfortunately prices for several of the high quality optical parts for the Raman unit have gone up in the last couple of weeks. We strive to purchase the best components at the most economical prices but have no other choice than to increase the price for the GL Gem Raman as of June 1, 2012 (2 units are left for immediate shipment; delivery time if ordered by May 31 is approximately 4 weeks).
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The GL Gem Raman could quickly pay by itself in time saved when facing difficult gem and mineral identification and by avoiding mistakes in buying and appraising gems and jewellery; go to the Gemlab on-line store or download the GL Gem Raman info sheet (PDF).
For more information go to GL Gem Raman. |
Undisclosed synthetic diamonds
In a recent JCK article about “Undisclosed Synthetic Diamonds Appearing on Market” questions about detection methods were asked. CVD diamonds are type IIa and transmit UV light; one has to determine whether the diamond in question is opaque to UV or transparent to UV. Type Ia and Ib diamonds are by far the most common natural diamonds and do not transmit UV.
Though we have not received a CVD diamond in our lab as yet we have used the SSEF Diamond Spotter for detection of HPHT treated diamonds in the past; watch an on-line slide show about its use (it was made available to us by the SSEF in 2003) or download a promotional presentation (PDF). In addition to the typical columnar strain/growth seen through the microscope (using crossed polarizers) the GL Gem Raman should also be useful.
In a new book “Infrared and Raman Spectroscopy in Forensic Science” (Google Books, Feb. 2012) the following observation was made: Brown type IIa diamonds have been found to exhibit a very weak one-phonon infrared absorption that begins near the Raman energy at 1332cm-1, and increases, with decreasing wavenumber, to a maximum at 1016cm-1 with a shoulder on the high-wavenumber side at about 1050cm-1. A colourless type IIa specimen showed an even weaker absorption beginning again near 1332cm-1 and increasing to show two maxima near 1100cm-1 and 1000cm-1. These specimen also showed birefringence patterns between crossed polars that are indicative of plastic deformation. It is suggested that the infrared absorptions are caused by dislocations.
As soon as we can test CVD diamonds with the GL Gem Raman we will report about the results.
In this context read this interesting article “The Mystery of two Gemesis Companies under one hat”.
Andesine Update
In the never ending story of the Andesine scam sometimes the truth prevails ….. read “Art Garabedian/DSN lose Andesine case (Court document, PDF)”.
Pre-announcement for Vancouver, B.C.
The University of British Columbia Continuing Studies at Robson Square is offering as part of their CULTURAL ENRICHMENT program:
Discovering Gems and Jewellery – an Introduction
Gemstones have intrigued us throughout history and are reputed as symbols of wealth, power, healing and love. In this course, students explore the unique properties of gemstones that affect their value and study the locations where they are found. Participants will board a virtual tour of splendid gem collections found in museums around the world and discover the challenges in differentiating between natural and man-made gem materials. In addition, advice will be given for purchasing jewellery at various venues such as at auction.
Instructor: J. Wolf Kuehn, B.A., M.A., Dipl.oec., F.G.A., F.G.G.
WD508F12A Sat, Sep 22-Oct 27, 12:30-2:30pm; UBC Robson Square. $360+tax
WD508F12B Sat, Sep 22-Oct 27, 3-5pm; UBC Robson Square. $380+tax (Interpreted in Mandarin)
To register contact UBC Continuing Studies.
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© 2012 Gemlab Research & Technology, Vancouver, Canada