Man-made diamonds are fascinating objects. There are probably more scientists involved in diamond research than for all other gemstones combined. The Athens gem conference had several diamond growers in attendance and the latest information about methods to screen and detect synthetic diamonds were shared.
I received encouraging responses from several FGAs about my concerns over the misuse of the FGA designation by non-diploma holders (as expressed in the CIGem News Summer 2015 newsletter). We will obtain clarification about the proper use of the F.G.A. (Hon) designation after the new Council is in place.
Again I urge all Gem-A members to cast their vote in the upcoming election for Trustees. The choice is between a trade association headed by “Seven Disgruntled Members” or candidates who have and will support the high educational standards Gem-A has been known for decades and are able to run a modern UK professional association.
Wolf Kuehn, F.G.A. (diploma holder since 1985), F.G.G.
How to quickly identify CVD grown diamonds
During the Athens gem conference Dr. Joe Yuan from Taidiam Technology described the growth and detection methods of the most recent synthetic diamond products. I tested a Taidiam CVD grown diamond in my lab with the GL Gem Spectrometer, GL Gem Raman PL532 TEC using liquid nitrogen (LN) immersion and a binocular microscope with polarizing accessory.
I found that the SiV– optical center at 737 nm as commonly seen in CVD grown synthetic diamonds appears to be unstable. Taidiam, IIa company and Apollo/SCIO may show 737 nm line (including very few natural diamonds), Element 6, Washington and Taidiam (after my own experiment by immersing it in Liquid Nitrogen as described below) have NO 737 nm peak. Dr. Yuan confirms my findings by explaining that CVD growth is dependent on conditions of quartz bell or plate, quantity of doped Si and its detection by the type and precision of spectrometer used; even the same product may give different results.
CVD grown diamonds, however, can be quickly identified with a hand spectroscope or preferably with the GL Gem Spectrometer in order to detect any “Cape lines”.
If not present inspect the diamond under a microscope with crossed polarizers and look for abnormal birefringence and/or coarse parallel or crossed column lines indicating CVD.
According to Dr. Yuan “this approach is 100%” and I believe him. Please download more instructions here (PDF).
Usefulness of Liquid Nitrogen in Spectroscopy
For several days I have been testing diamond and gemstone samples immersed in LN (liquid nitrogen) to determine whether there are any benefits for users of the GL Gem Spectrometer and the GL Gem Raman PL532 TEC. The answer is: not really.
Low-cost LN setup for use with spectrometers.
Always follow instructions about proper use of liquid nitrogen.
A common problem is the icing up of the used low-cost glass device causing signal loss. There is no easy solution unless someone is willing to spend a larger amount of money for a dedicated LN accessory. For that reason I believe that increasing exposure times and controlling background noise is a better alternative; TEC for the Raman spectrometer makes sense when exposure rates are higher than 1,000 ms. LN will reveal stronger PL and additional peaks not seen at room temperature and narrows spectral width which can be seen only with scientific quality spectrometers.
The following show results obtained from a Taidiam CVD grown diamond before at room temperature/during and after LN immersion.
The Future of Man-Made Diamonds
During the round-table discussion there were opposing views whether synthetic diamonds have a future in jewellery stores; looking back 25 years many of the diamond producers have been unsuccessful. Now with production costs coming down considerably it will be possible to produce a diamond at 1/3 price or less than its natural counterpart. The question remains whether a young couple will accept a lab grown diamond in their engagement ring instead of the traditional solitaire. The growers are investing heavily in presses and cutting equipment; but without an effective marketing campaign to attract more jewellery buyers I am somewhat pessimistic. However, we must educate ourselves to identify these new materials for the obvious reason!
I had a chance to briefly test the largest HPHT grown and cut 10.02-carat, E, VS1, type IIa, square, emerald-cut stone produced by New Diamond Technology LLC of St. Petersburg, Russia. It is certainly a spectacular piece and displayed some orange fluorescence both under the UV lamp and a strong LED light which could be an identifying feature.
Vancouver Gem & Mineral Show, August 14 – 16
|Visit us a the C.I.G. (Canadian Institute of Gemmology) booth; books and small gem testing instruments will be on sale.|
Please bring interesting gems and minerals (2 per visitor) and have them identified with our GL Gem Raman PL532 TEC while you wait and watch.
Location: Kitsilano Rink
2690 Larch St, Vancouver, BC V6K 4K9
Friday, August 14th 2015, 12:00-8pm
Saturday, August 15th 2015, 10am-6pm
Sunday, August 16th 2015, 10am-5p
Adults: $7, Seniors/Students: $5, Children 12 and under free (with adults)
In this advanced course students will learn state-of-the-art techniques (including immersion-scope, gemstone magnetism, IR-VIS-NIR and Raman spectroscopy), etc. designed to identify confidently any gemstone encountered in the market place. Between 100 and 120 challenging gems including the most recent synthetics and treatments are available for testing. Max 5 participants.
- Fee: $ 995 includes comprehensive study guide and materials (copy of Gemstone Inclusion Library), use of lab equipment and study stones. Recommended text-book: Gemology by Peter Read. Download course flyer (PDF).
- GEM 250 – 3: Mon – Thu, November 9 – 12, 9:30 a.m. – 4:30 p.m. RESERVED
- GEM 250 – 4: Sat – Tue, November 14 – 17, 9:30 a.m. – 4:30 p.m. SPACE AVAILABLE
- Location: Sandman Signature Hotel – Vancouver Airport, Richmond B.C. (special room rate). Please register by October 15.
- To keep costs down no lunch or beverage services are offered, lunch break 12:30 – 1:30 p.m
- Prerequisites: A.G. (C.I.G.) diploma or equivalent (please contact us)
Here a brief list of man-made gems in our study collection: Chatham, Kashan, Ramaura, Knischka, Lechleitner, Regency, Biron, Lenix, Gilson, Tairus rubies, sapphires, emeralds, alexandrite, opal, moissanite, synthetic CVD and HPHT grown and treated diamonds and many others. Gem enhancement techniques such as polymer impregnation (jadeite), heat-alteration, surface colour diffusion, irradiation, HPHT and glass filling are studied.
GEM 270 GL Gem Spectrometer and Raman Workshop
This course is for current or future users of the GL Gem Spectrometer and GL Gem Raman system.
Using PowerPoint presentations the development and use of advanced spectrometers is introduced.
Learning step-by-step testing method for the GL Gem Spectrometer and use of the GLGemRaman software and searchable database.
Practical testing of a number of interesting gem materials by the participants under supervision of the workshop facilitator; most up-to-date information on synthetic diamonds including CVD, HPHT and irradiation treatments and their detection.
Prerequisite: previous practical experience with spectroscope/spectrometer and good understanding of advanced spectroscopy.
Presenter: Wolf Kuehn, B.A., M.A., Dipl.oec, FGA, FGG
GEM 270-3 Friday, Nov 13 from 9:00 – 1:00 p.m. (4 hours); limited to 3 participants.
GEM 270-4 Friday, Nov 13 from 2:00 – 6:00 p.m. (4 hours); limited to 3 participants. RESERVED
Sandman Signature Hotel – Vancouver Airport, Richmond B.C. (special room rate). Please register by October 15.
Fee: $ 295 (free for purchasers of the GL Gem Spectrometer or Raman PL532 TEC*); to keep costs down no lunch or beverage services are offered.
Please wait with travel arrangements until final confirmation.
*Participants who will purchase the GL Gem Spectrometer or GL Gem Raman system within one month will receive a $ 295 refund/discount.
Wolf Kuehn, B.A., M.A., PDP (SFU), Dipl.oec, F.G.A., F.G.G. – GLR&T Project Manager
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