CIGem News Fall 2009 - ISSN 0846-3611 GEMMOLOGY CANADA - Wolf Kuehn, F.G.G., F.G.A., Editor

The Quarterly Newsletter of the Canadian Institute of Gemmology (C.I.G.)

Macro Photography

Over the years I have experimented with various setups to get a quick image of an inclusion or a decent close-up of a gemstone. After studying Bob's Rock Shop Product Review on the Raynox Video MicroExplorer and reading Jamey Swishers excellent suggestions at his Gemstone Photography: Fact and Fiction and Photography Help the following ideas present a low-cost portable solution for top quality micro-photography of gems.

As I had already the Raynox Video Explorer and the Panasonic DMC-FZ28 (upon Jamey's recommendations) I only needed to purchase another Super Macro Conversion Lens MSN-202 with adaptor providing an additional 4x macro-lens. This mounts easily onto the extension tube of the DMC-FZ28 which has produced the best imagery of gemstones and inclusions for me so far.

For illumination I use the built-in fluorescent light in the base of the explorer and/or a Schott flexible fibre-optics ring-light which is connected to a Micro Light FL-3000 with 150 W halogen bulb and directly attached to the macro lens. One can see the reflection of the ring-light in the photo below.

FZ28 immersion cell setup

For immersion photography I try to use an immersion dish with a liquid close to the R.I. of the stone. The following images of an emerald were taken (from left to right) with base light only, base light and  illumination from ring-light. A flux-grown synthetic ruby (Kashan) in a "dry" setup using the base light only (magnification 40x).

emerald emerald kasha

The same setup can be used for close-up photography; the macro conversion lens has to be exchanged for the 35x micro lens from the original video-explorer. For the following shots of various gems I used an Ott-Lite True Color flip-light. These images are shown as I took them; I did not enhance them nor crop them.

.ruby sapphire cubic zirconia spinel

The Panasonic FZ28 is a versatile camera and the superior optics of the Raynor micro/macro lenses in the above setup produce images which match results from a professional gem microscope; it takes very little time to take a picture and the system is portable.

Tables of Gemstone Identification

tables

Birgit Guenther, F.G.G., F.G.A., G.G. has announced the 3rd and updated edition (first published 1981) of her bilingual text "Tables of Gemstone Identification/Bestimmungstabellen fuer Edelsteine Synthesen Imitationen (in English and German)".

The book has 256 pages and contains 135 coloured spectra. Price 87.50 Euros. Please order the book directly from the author.

I have used the Tables of Gemstone Identification frequently during the last 35 years. This new edition is highly recommended.

UV-LEDs, Lasers and other gadgets

lasersPrices for electronic equipment are falling rapidly and many gemmologists are considering the purchase of a green or blue laser pointer to conduct gem testing. These tools are indeed very interesting but I have a number of reservations. In my opinion a laser pointer should be used for what it is designed for: in an auditorium during a presentation. The green laser is far more powerful than the red one and with the blue laser one can burn a piece of paper at a distance.

I do not recommend them for use by gemmologists for the following reasons: Green and violet/blue laser pointers emitting 5 mW or more are dangerous for the eye. It is absolutely necessary to wear the proper protective gear when aiming a laser pointer at reflective surfaces; using it through a microscope increases the risk of permanent eye damage.

Wearing the protective gear it is more difficult to see subtle fluorescence reactions; though the filter will remove the dangerous radiation of the excitation source (that's what the goggles are made for). However, to get useful data a fiber-optic spectrometer will be necessary. Digital cameras or infra-red webcams, etc. can be damaged by green and blue lasers (what is the critical angle of silicon?).

Lasers are best left to research labs where they are used for luminescence studies and tomography projects.

A much better alternative are the UV-LEDs which are now available in the SW range at lower prices (around $ 100) and with higher output. SW UV-LEDs are used with increasing demand in health care (sanitation equipment), water purification, dental applications (or curing windshield repair resins) etc. For work with the microscope or spectroscope special fibers are needed. See for related products.

As a new LW standard I recommend the Nichia 365 nm UV LED Flashlight; it produces the i-line of the mercury spectrum and sells for around $ 50. See Nichia Press Release or if you want to build your own using a stronger 365 nm chip visit candlepowerforums.com

The 254 nm UV-LEDs are available but not in a flashlight or separate probe as yet.

I have tested the common UV-LEDs with a UV meter and the radiation level is lower than that of a SW mercury lamp; regular coated eye-glasses appear to offer sufficient protection. However, UV filter (orange eye type) protection glasses are needed for the stronger Nichias.

I highly recommend the use of UV-LEDs as a new excitation source for luminescence studies. See  UV-LEDs - Setting a New Standard for Fluorescence Observations (from GIT 2008, Bangkok, Thailand Proceedings). Within the next 6 months we should have a proto-type setup for SW and LW LEDs testing in our Gemlab Research & Technology lab.

Immersion Spectroscopy

GLR&TWe have experimented using various immersion liquids to improve the quality of spectras. The optical artifacts caused by the cut of the stone are eliminated by suspending it in a bath of liquid with a refractive index that matches that of the stone.

I followed closely the "Technique for UV-visible-NIR Microspectral Analysis of Gems by CRAIC Technologies". The full article can be read here.

The choice of the immersion liquid plays an important role in the results obtained from the spectrometer. Glycerin may be an effective immersion liquid for this purpose though it may not match the RI of the stone closely. As a consequence the signal-to-noise ratio was lower and spectral artifacts may still appear; however, glycerin does not degrade over time and has a spectral range which extends deep into the ultraviolet region, it is water soluble and can easily be removed from the gemstone.

The use of an OceanOptics NIR 256-2.5 spectrometer for gem identification.

We have just started some research into the feasibility of NIR spectrometers in gem identification. Near-infrared Spectroscopy (NIRS) is molecular spectroscopy and has been neglected in favour of colourimetry, mid-infrared spectroscopy and techniques based on other special regions. The primary advantage of the NIR region is that absorbencies are lower than in neighbouring regions and generally obey the Beer/Lambert law, i.e., absorbance increases linearly with concentration. This is because NIR absorptions are generally 10-100 times weaker in intensity than the fundamental mid-IR absorption bands. A crucial step in achieving success is ensuring that the samples have been analyzed as accurately and precisely as conventional techniques allow; these analyses are termed reference analyses. For gem materials this will require calibrations for a select group of specimen such as emerald; once calibrations are obtained unlike most conventional analytical methods, NIRS is non-destructive, requires little or no sample preparation, does not use chemicals and can be operated by non-chemists.

The following absorption spectrum was obtained from a synthetic flux grown emerald in air and in an immersion liquid (R = 1.65).

synth emerald

Case before Human Rights Tribunal dismissed

Former C.I.G. student Augusto Duminuco filed a complaint against the Canadian Institute of Gemmology before the British Columbia Human Rights Tribunal. An application to dismiss the complaint was not granted (see decision dated October 1, 2008 ). However, the complaint was withdrawn a few weeks before the scheduled 2-day public hearing in September.

This action has cost not only the school but also the tax-payer a substantial amount of money. I am glad it is over and I want to thank all of you who have supported me from the very beginning.

Other News

In the C.I.G. News Bulletin I often link to websites where differing views are offered; this allows readers to form their own opinions. There are always ongoing reports about the Andesine/Lasazine saga, the Paraiba and tourmaline controversy and other topics. In one of the more recent studies done on andesine (see GIA Special Issue on Red Feldspar), however, a comment by one of the researchers struck me: "Any reasonable person, seeing only the evidence from the mine, would conclude the site must be real." If I'd given similar advise to the numerous callers who inherited "Alexandrite" from a great-great uncle in Tsarist Russia and claim "it must be genuine" I could fill a museum display by now. A professional gemmologist should always be looking for direct evidence and not trust circumstantial evidence provided by a third party. To get to the truth in the andesine/lasazine case an independent team of geologists will have to travel to Tibet and inspect the alleged mine source.

For comprehensive information about the real Oregon Sunstone go to Welcome to Plush Sunstone.

Just for fun I used the FZ28 to produce a short YouTube movie of a synthetic red spinel crystal (1993, Russian production).

 

CIG

Accredited Gemmologist (C.I.G.) Professional Development Program

Vancouver C.I.G. courses and workshops - Fall 2009


 Introduction to Diamonds -PLEASE REGISTER BY October 10- More info here

  • Course 130-3 (Introduction to Diamonds), Fri, October 23, 6:15 - 9:00 p.m., Sat/Sun, October 24/25, 10 a.m - 4:30 p.m. (weekend class, Vancouver) $ 495 includes text-book and exam fee (no GST), study materials with binder will be shipped upon registration

    In this course you will learn everything you need to know about diamonds. Sell more and answer customer questions with confidence. Introduction to diamond grading and jewellery fashion.

    Course Content: 1. Diamonds. How they are created. 2. The Beauty of Diamonds 3. Weight and Colour of Diamonds. 4. Judging the Clarity of Diamonds. 5. Judging the Cut of Diamonds. 6. Diamond or Imitation? Gold, Platinum. 7. Choosing an Appropriate Style. 8. Choosing a Diamond Ring, Judging Craftmanship.

    Pearls, Opal and Jade - PLEASE REGISTER BY October 30- More info here

  • Course 160-2 Fri, November 6, 6:15 - 9:00 p.m., Sat/Sun, November 7/8, 10 a.m - 4:30 p.m. (weekend class, Vancouver) $ 495 includes text-book and exam fee (no GST), study materials with binder will be shipped upon registration

    In this course you will learn about pearl types and shapes, how to judge luster, thickness, colour and size of pearls. The identification and evaluation of South Sea, black and freshwater pearls and other organic gems are also covered. There will be one session on opal and its evaluation. Another session will cover the jades - oriental jadeite and nephrite.

    For more information about Vancouver courses go here.

    We have reduced the price for several books to clear our inventory. Go to Specials or visit gemlab Books and Instruments.

    Past issues of C.I.Gem News: Click on the edition you want to read:Special GIT 2008 edition - Spring 2009 - Summer 2009 . The next newsletter will be published December 21, 2009.


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    Unless indicated otherwise images 2009 J. Wolf Kuehn and Canadian Institute of Gemmology. Users may View/Download images for their own private, non-commercial use.

    The articles in CIGem News express the opinions of the editor and do not necessarily reflect those of the Canadian Institute of Gemmology (C.I.G.). The included links are provided for educational purposes. Copyright and content responsibility remains with the linked organization and do not represent any endorsement by the author.

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