To answer the trade main needs, GGTL Laboratories has been developing instruments to improve the gemstones analysis. We focus on matters such as authentication, synthetic discrimination, treatment disclosure and origin determination.
Our UV-Vis-NIR spectrometer has been specifically designed to analyse any gemstones of all sizes, from 1.0 mm an up, at room and at low temperature (-196°C, liquid nitrogen conditions). The analysis time with this instrument is very fast; single scans takes less than 50 msec, making multi-scan acquisitions very efficient. The instrument can be supplied in various configurations that permit resolutions between 0.3 and 1.2 nm. The instrument is delivered with all accessories needed for low temperature spectroscopy and, upon request, we can supply the accessory for the acquisition of polarized spectra.
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The GGTL Photoluminator Raman/Photoluminescence spectrometer system is specifically built for the analysis of gemstones. Its main application is for low temperature photoluminescence spectroscopy of diamond. The system is adjustable with various spectrometers and lasers from 360 to 785 nm, thus allowing solutions for many budgets and uses. The standard Photoluminator system uses three lasers: a 405 nm, a 473 nm, and a 532 nm laser, which can be exchanged in less than one minute without moving the sample that is being analysed.
The sample chamber is sealed against any laser leakage as the lasers can only be operated with a closed sample chamber door; hence the instrument is classified as a class I laser product. A volume of 28x29x32 cm is available inside the chamber where the samples are moved on a motorized XYZ stage with a 50 mm motion in each direction. The stage is set up to work best with the special GGTL low temperature accessory supplied with the system.
The GGTL Photoluminator system can be coupled with a series of different spectrometers via a fibre optic cable. The standard version uses a quadruple-channel spectrometer with thermoelectrically cooled CCD detector that operates over a range of 250 to 1050 nm offering a rather high resolution of 0.30 nm. If even higher throughput is needed, then double or even single channel spectrometers with equally cooled CCD detectors can be supplied; these have a lower resolution of 0.60 nm (double channel) and 1.2 nm (single channel) but have a higher light throughput. If a higher resolution is needed, we can supply a research grade Echelle spectrograph with the GGTL Photoluminator that delivers a (average) very high resolution of 0.05 nm over the range of 350 to 1150 nm. It uses an Andor camera with a thermoelectrically cooled CMOS detector. The acquisition time using such a system is distinctly longer than with the standard spectrometers, thus more complex and requires a trained hand.
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Developed in house, the DFI is an extraordinary instrument dedicated to the identification of synthetic diamonds in parcels of colourless (D-Z) diamonds. With the necessary expertise, the DFI can be used for a large range of other analysis for coloured diamonds and coloured stones. The operating principles are the direct simultaneous observation of the luminescence under various UV and laser excitations (several excitation bands from the deep UV all the way to 405 nm), at room or at low temperature (77k) luminescence spectra and finally the Raman spectra. Currently, the DFI is the only instrument (along with the D-Tect, produced by GGTL Laboratories) able to unambiguously identify a natural or synthetic diamond and imitation without any further testing (no “refers”) ever needed. The instrument’s ingenious Spect-Ident software developed by GGTL gives an unexperienced user the possibility to conclude without need of spectral interpretation and enables a significant increase in screening speed. The DFI can be supplied with a single channel or a double channel spectrometer calibrated for absolute irradiance, which both have very high throughput and cooled CCD detectors and hence permit very rapid analysis. The single channel system has a spectral resolution of 1.3 nm while the double channel system has a resolution of about 0.3 to 0.7 nm.
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The D-Tect – the little brother of the DFI – was initially designed and produced by GGTL Laboratories for HRD Antwerp. It works similarly to the DFI but has a more limited range of excitations available. It is dedicated to the identification of colourless “D-Z” diamonds, especially the ones rejected by the M-ScreenTM - the most reliable automated instrument for the identification of suspicious stones in melee parcels today. The D-Tect instrument is now exclusively distributed by GGTL Laboratories Switzerland. Similarly to the DFI, it allows the direct and unambiguous identification of natural and synthetic diamonds imitations. It is highly unusual to encounter stones for which one cannot conclude. The D-Tect comes with the same GGTL Spect-Ident analytical software used with the DFI that automates the spectral interpretation and significantly speeds up and secures the analysis. The D-Tect is equipped with a single channel spectrometer, calibrated for absolute irradiance, with cooled CCD offering a resolution of 1.3 nm.