diamants synthétiques CVD et HPHT(presque-)incolores.

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Swiss Branch: GGTL Laboratories Free Zone (Opening May 2015) GGTL - GemTechLab Laboratory Aéroport Halle de fret 4bis route des Jeunes Zone Port Franc Local 1008 CH 1227 Les Acacias, Genève Voie des

and Franck Notari Next edition: September 2015 - Un diamant synthétique CVD riche en azote.

1 Swiss Branch: GGTL Laboratories Free Zone (Opening May 2015) GGTL - GemTechLab Laboratory Aéroport Halle de fret 4bis route des Jeunes Zone Port Franc Local 1008 CH 1227 Les Acacias, Genève Voie des Traz 20 SUISSE SWITZERLAND CH Genève 5 Liechtenstein Branch: GGTL - GEMLAB Laboratory Gnetsch, 42 LI 9496 Balzers LIECHTENSTEIN GGTL Laboratories Newsletter N 4 March 2015 Thomas Hainschwang and Franck Notari Next edition: September Un diamant synthétique CVD riche en azote. - Le DFI Mid-UV Laser + : détection immédiate et rapide de diamants synthétiques CVD et HPHT(presque-)incolores. xx s Our laboratory GGTL Laboratories Liechtenstein has recently detected the first CVD synthetic diamond in a parcel of melee diamonds. Surprisingly it is an as-grown (= untreated) nitrogenrich ( 175 ppm) type Ib diamond is of vivid yellow colour. Recently GGTL Laboratories has detected a vivid yellow CVD synthetic diamond in a parcel of melee diamonds originating from Hong Kong. This confirms our sentiment that the productions of Chinese provenance need to be surveyed with much attention. In fact we think that a good portion of all CVD synthetic diamonds that will be produced in the future will likely be provided through this country. In this context India is also a potential candidate. Russia which has been indicated as a major CVD producer by some is for the time being far more specialized in the production of HPHT synthetic diamonds and not CVD. This remarkable stone has been described in detail in The Journal of Gemmology LINK, Vol. 34, No. 4, 2014, pp Figure 1: The first melee-sized (1.6 mm diameter) CVD synthetic diamond, rich in nitrogen and not treated post growth. What is most spectacular about this synthetic diamond is its remarkable nitrogen content, which we have calculated at 175 ppm (± 5). This content is superior to the vast majority of natural diamonds of the same type and color. The stone also exhibits a very distinct Si centre (silicon) in photoluminescence spectroscopy which was very easily detected under 405, 473, 532 and 635 nm laser excitations (Figure 2). Main characteristics of the vivid yellow CVD diamond: - Type Ib nitrogen rich (175 ppm, a particularly high nitrogen content for a CVD diamond). - Opaque to UV. - Rich in silicon defects. - Exceptional colour, untreated («as-grown»). - Typical defects observable in infrared and photoluminescence spectroscopy. - Typical strain patterns under crossed polarizing filters. This stone was obviously opaque to shortwave Ultraviolet light, with total absorption at > 400 nm. We have forecasted this evolution in our Newsletter from September 2013 since this criterion (transparency to SWUV) is still as an important key to the identification of CVD diamonds. For the time being since we talk about type Ib CVD synthetic diamond, such SWUV opaque stones are yellow. While for now this is the only such stone that we have encountered in the many hundreds of carats of vivid yellow melee diamonds (which are ALWAYS polluted by HPHT synthetic diamonds), it remains to be

2 seen when and if more of such stones and possibly near colorless melee CVD diamonds enter the market. Currently it is unknown if this stone was grown on purpose with such a high single nitrogen content and also who the producer of this material is. In any case, this synthetic diamond represents an exceptional piece in respect of the fact that it is the first one of its kind detected in parcels of melee-sized natural diamonds and that it is the first CVD diamond ever described which such amazingly high nitrogen content and such vivid yellow coloration. Looking at the spectra one is immediately reminded of the recently published gray violet CVD diamonds, which also exhibit such very high Si-center content. Figure 2: The photoluminescence spectra of this yellow CVD synthetic diamond recorded with the diamond kept at C are strongly dominated by the Si center peaks, with the main peak being a doublet at and nm, typical of CVD synthetic diamond (and much weaker in some HPHT synthetic diamond). With exception of the NV center emissions all other features are characteristic of CVD diamond. A new and efficient approach to resolve the problem of the detection of synthetic diamonds: The DFI Mid-UV Laser + A flexible and high-performing instrument, designed and built by GGTL Laboratories for professionals, for the detection of (near-) colorless HPHT and CVD synthetic diamond of any size and shape Since more than a year a polemic around CVD synthetic diamonds has developed. To reply to the worries of the trade, automated screening instruments (black boxes) have appeared in the market, more or less efficient and more or less expensive. Even if the problem of CVD synthetic diamonds mixed in parcels of colorless melee diamonds is not yet a reality, GGTL Laboratories is monitoring this situation and systematically tests all submitted parcels. To be able to do so we have developed a routine screening machine: the DFI. The system specification was to efficiently and rapidly recognize (near-) colorless HPHT and CVD synthetic diamonds, in all shapes and sizes, unmounted or mounted, which today no existing automated system permits to do. The DFI was initially only destined for our three laboratories, but because of repeated demands by some of our clients we have decided to commercialize it under the name DFI Mid-UV Laser +. Caracteristics of the DFI Mid-UV Laser + : - Efficient and rapid Identification of (near) colourless CVD and HPHT synthetic diamonds. - Possible to analyse stones of all sizes, even very small (e.g. 0.5mm and less ). - Permits the analysis of unmounted and mounted diamonds (on watches, jewels etc.). - Screening capacity ([near-] colorless melee): 3000 stones per hour. - Identification of CVD synthetic diamonds eventually doped with nitrogen (opaque to UV). - Two replies: natural or synthetic. No reply: "to be sent to the laboratory".

3 We did not want to create a "black box" (automated system, by definition "blind") since we wanted to take into account that there will be a likely evolution of the production techniques, which would modify the characteristics of such synthetics. For CVD diamonds we did not want to take their UV transparency into account (since they are a priori type IIa), since it is now established that by nitrogen doping the growth speed can be increased by a factor >5, which will result in a considerable reduction of the production cost obviously of great interest for the producers. Such doped CVD would then be type Ib (hence containing single nitrogen) and can then in theory be transformed into type Ia via a properly performed HPHT treatment. Theoretically such diamonds could be near-colourless and then have properties similar to the vast majority of natural diamonds in that they would be opaque to shortwave UV. It needs to be seen, if this is commercially worthwhile and if in the future such SWUV opaque synthetic diamonds will enter the market or not. The major difference to existing instruments is that the DFI needs an operator, which has always been an obvious choice for us. The logical reason for this is that a well-trained and vigilant technician will be able to note slight anomalies which can be indications that permit to detect new production methods or treatments applied to synthetics (e.g. the "HIH" HPHT synthetic diamonds, see our newsletter from the 1 st September 2011). This is a significant advantage which no automated system will ever be able to offer. Additionally, a non-automated system permits to analyse stones of all dimensions, which is today especially in the watchmaker industry an important requirement for diamonds of small diameters. Here as well the automated systems suffer from a big handicap since they are unable to analyze really small stones. Another sss fundamental difference is that except in some very rare cases the DFI offers only two replies: "natural" or "synthetic". The option "to be sent to a laboratory" does not represent a great interest for the trade. An instrument that screens stones by giving the two possibilities "natural" and "to be sent to the laboratory" does only present limited interest as long as the machine is mainly based on type IIa determination: one can send the entire parcel to the lab directly immediately instead for a quick type IIa test, something not very difficult to achieve with the right equipment. After such a quick test the IIa s are tested in the lab and the problem is solved. In fact, in virtually all parcels composed of 100% natural diamonds one will find stones that present characteristics which will tell the automatic screening instrument that they need to be sent to the laboratory, which represents a loss of time and money. Furthermore, how can one return a parcel to a dealer several weeks after having purchased it, just because the detection of potential synthetic diamonds has taken so long? - A delicate situation and source of many problems. The traders need clear and especially rapid answers. The DFI Mid-UV Laser + : The principle of the analysis by the DFI is based on several joint techniques. The samples are excited by a beam of UV and/or a laser. Several very precise high performance filter sets allow to excite the samples with several excitations with different wavelengths. The presence/absence, colour, intensity and distribution of the fluorescence combined with the nature of the excitation are very efficient and rapid criteria for the screening of diamonds. The combined or separate use of the laser enhances the observation of certain emissions which can be very weak under UV excitation, as well as the often characteristic growth structures and distribution of defects. The system is coupled to a calibrated spectrometer using a cooled detector, which permits the simultaneous observation of the photoluminescence (PL) spectrum at room temperature or at low temperature (77K). A high resolution camera also with cooled detector permits to record high quality images of the luminescent diamonds.

4 Figure 3: The DFI Mid-UV Laser + installed in one of our laboratories is a very flexible and efficient tool for the analysis of melee-sized diamonds. It is based on a combination of fluorescence imaging and spectroscopy and solves virtually all problems encountered in the detection of synthetic diamonds. Baguette shaped diamonds and diamonds of other cutting styles are not immune against the pollution by synthetics. With the DFI the stones can be of any shape any size, since the samples are manipulated by the technician and not the machine. For the same reason, the analysis of mounted diamonds is possible without any problem. The DFI is not only the instrument, but its principle bases on an alert network. Every client receives a secured address, with which he can not only receive real-time technical support, but with which he also receives the possibility to send analysis documents (spectra and Images, up to 50 Mb for each mail). This system permits to launch a quasi-immediate alert when, for example, a technician discovers CVD synthetic diamonds in a parcel of melee diamonds. Upon acquisition of a DFI, a three day hands-on training (invoiced) is performed for the client or his technician in our laboratory in Liechtenstein under the supervision of Dr Hainschwang. After this training, the trained person will be able to efficiently identify colorless and near colorless HPHT and CVD synthetic diamonds. Besides the normal use of certain components, the annual maintenance costs of the DFI do not exceed 1000 USD. Upon delivery the instrument can be mounted and adjusted by a member of the staff of GGTL Laboratories at the client s office, and at this occasion a supplementary short training is given. The machine is under warranty for one year. Only a limited quantity of the DFI will be produced. Price upon request: Fr, En: emeline.bulut@ggtl-ab.org Fr, En, Es, De: aurelie-fleur.fourre@ggtl-lab.org

5 You are not convinced yet? Just compare: Capability DFI Your Instrument Minimum dimensions: < 0,40 mm. Maximum dimensions: without limit. Baguettes. s Other fancy cuts. Rough diamonds. Detection of (near-) colorless CVD synthetic diamonds. Detection of (near-) colorless HPHT synthetic diamonds. Analysis of mounted diamonds (watches, jewels ). Hourly screening capacity for (near-) colorless melee: 3000 p/h Detection of imitations. Immediate identification (synthetic or natural). Necessity to send analysed diamonds to a laboratory for additional testing. Your GGTL Laboratories team GGTL Laboratories Newsletter, N 4, March 2015 Contact: laboratory@ggtl-lab.org Our website: Links to earlier Newsletters:

Raman Spectroscopy and Photoluminescence Mapping. of Diamonds with Multiple Fluorescence Zones

WE DREAM, WE DEVELOP, WE DELIVER. MD Technical Review Letter - Raman Spectroscopy and Photoluminescence Mapping of Diamonds with Multiple Fluorescence Zones Charis W.Y. LEE, J. CHENG, K. W. CHENG and Tony