Wolf Kuehn, F.G.G., F.G.A., Editor
From the Editor
I just returned from SE Asia after travelling in Myanmar, attending “The 3nd International Gem & Jewelry Conference” GIT 2012 in Bangkok and participating in the post-conference tour to Chanthaburi and Cambodia.
More about my travel and news from Thailand in the January CIGem Newsletter Winter 2013.
In this special GL Newsletter I will report briefly about interesting topics presented during the conference as I did 3 years ago for the GIT 2008 conference.
GIT 2012 The 3nd International Gem & Jewelry Conference
Held for the third time in Bangkok, Thailand and organized by the The Gem and Jewelry Institute of Thailand GIT 2012 attracted over 500 participants from around the world. It was encouraging to see many young contributors sharing their research and work projects in oral presentations and poster sessions covering a wide scope of topics from gemmology to jewellery design.
Many thanks to Ms. Wilawan Atichat, Director of GIT and her team for a superb job in organizing this event. Over half of the contributions were dedicated to the section “Gem Identification and Treatments”.
You can download the close to 500 pages of the E-Proceedings PDF document from here (zip file, 90 MB). I will refer to them in my comments and observations below; also download our poster “Raman Spectroscopy – A Powerful Tool in Gem Identification” (PDF, 948 KB).
Diffusion of Transition Metals in Gemstones
Three years ago Yong-Kil Ahn and Jong-Wan Park, Hanyang University, Seoul, Korea submitted a research poster to GIT 2008 “Comparative study of Cr3+ diffusion in proton and electron irradiated chrysoberyl” (PDF, 325 KB). It was work in progress and I maintained contact with the authors to stay up-to-date.
In the meantime they published two other articles to be shared: “Diffusion of chromium in sapphire: The effects of electron beam irradiation” (PDF, 960 KB) and “Effects of electron-beam irradiation, a thin-Ti layer, and a BeO additive on the diffusion of titanium in synthetic sapphire” (PDF, 972 KB).
As part of their research several diffusion experiments were performed and various methods for enhancing the diffusity were attempted as demonstrated in their poster “Diffusion of Transition Metals in Gemstones using various Specimen Preparation Methods” (E-Proceedings, page 164ff). Photoluminescence results for the specimens using a 325 nm He-Cd excitation source show a clear difference between the fluorescence of sapphire before and after irradiation.
Ion Beam Treatment and Analysis
Ion beam treatment – a rather expensive method at the present time due to the high cost of the equipment – can be used to not only improve the colour but also the clarity and luster of gemstones. In their “Overview of Ion Beam Treatment of Gemstones in Thailand” (E-Proceedings, page 252ff) the Thai researchers tested and treated a variety of gemstones such as rubies, sapphires, topazes, spinels and garnets from Thailand, Myanmar (Burma), and Africa.
The ion beam technology has been recently applied for the first time in Thailand for gemstone analysis, particularly, the Proton Induced X-ray Emission (PIXE) which is an effective and nondestructive way to quantify trace elements analysis at ppm level.
The Thai researchers conducted an “Ion Beam Analysis of Spinel” (E-Proceedings, page 220ff) and introduced a “Novel Ion Beam Technique for Lead Detection in Rubies” (E-Proceedings, page 244ff).
The ion beam techniques give an advantage over conventional techniques in term of lead content detection. In summary they warned that “Rubies treated by paw-mai method contained remarkable high concentration of lead and they may be harmful to gem consumers” and unsafe for the treaters of these gem materials as well.
New Treated Sapphire
Since early 2012, a new type of treated blue sapphire has been encountered in the trade. During the post conference tour in Chanthaburi Dr. Pornsawat Wathanakul made samples available to the participants and a brochure was distributed as well.
I tested my sample under immersion in methylene iodide and found that it showed colour concentrations along the facet junctions reminding of the old “surface-diffused” sapphires. In addition, in their presentation “Newly Treated Blue Sapphire: a Preliminary Investigation” (E-Proceedings, page 264ff) they detected the presence of beryllium which may play a role in the colouration of this blue sapphire. A “Round up on Gemstone Hot Issues in 2012” (E-Proceedings, page 264ff) was given by the same group of Thai researchers.
Ted Themelis gave an oral presentation of “Lithium-Treated Gemstones” (E-Proceedings, page 228ff) with first hand knowledge of this type of treatment; it has been applied to blue sapphires, grossularites, tourmalines and other gems to improve their colour, diaphaneity and lustre since 2011.
As the outcome of the treatment in many cases is unpredictable it is difficult to know the exact mechanism involved in this treatment. It would require a complete analysis of the samples before and after treatment.
|A typical rough, untreated African grossularite used in the lithium process (left); after heating
with lithium-based additives, most stones turned reddish-orange (middle, 3.59 carats), rarely intense red (right, 22.71 carats).
Diamonds and Organic Gems
In this section several contributions were made about “CVD Synthetic Diamonds and their Proper Identification” (E-Proceedings, page 301ff) and “Research on CVD Gem Diamonds” (E-Proceedings, page 303ff).
My Canadian colleague Branko Deljanin spoke about “Screening and Identification of Coloured and Colourless Diamonds for the Synthetic Origin using the UV Lamp and the Polariscope mounted on a Microscope” (E-Proceedings, page 308ff).
In summary further research is necessary to properly identify all the treatment combinations applied to both natural and synthetic diamonds. Our own recently developed GL Gem Raman PL532 will become an important tool not only for the identification of coloured stones, but also to check for type IIa HPHT treated stones (IIa with HPHT annealing or without).
There were many more contributions such as from my Russian colleagues on “Identification of the Garnet Chemical Composition and Color Causes by Express Raman and Visible Spectroscopy” (E-Proceedings, page 214ff).
I selected the above contributions as they covered the most interesting subjects and issues for someone working in a gemmological laboratory like myself. Download and read the GIT 2012 E-Proceedings (PDF, 100 MB – large file).
Tucson Specials from the Gemlab Online Store
During January 2013 we will offer the GL Gem Spectrometer to attendants at the Tucson Gem Shows at a reduced price of $ 1,295.00 with free delivery if picked up at our booth # 31 in the Tucson Convention Centre (during the AGTA GemFair from February 5 – 10). More details here.
We also will introduce and demonstrate the new GL Gem Raman PL532.