Why Avantes for your Gemology application?
- Applications experience of the configuration needed to test the different grades of diamonds
- Wide range of Spectrometers to provide optimised & cost effective solutions.
- Custom probe manufacture (like a zero fluoresence probe)
The measurement needs of the Gemology industry are demanding for a series of reasons. Chief among these can be low signal measurement and the need for rapid measurement systems to handle the volume of gemstones measured. Avantes offers basic measurement tools as well as advanced systems to meet various gemological requirements. Measurements can be accomplished with fairly simple systems using either integrating spheres or reflection probes up to photoluminescence systems requiring lasers and TE-cooled spectrometers.
Basic Gemology Measurement
Gemologists often have two basic questions, “What are the characteristics of the stone I’m asked to measure?”, and “Are these characteristics natural?” This is because the industry has developed multiple methods to “enhance” stones to improve color and hide imperfections. Methods employed include heat treating, irradiating, resin filling, laser drilling and even simple surface medications such as petroleum product treatments. A typical basis system consists of an AvaSpec-ULS2048-USB2 spectrometer, a WS-2-GEM, white reference tile for gemology, and either an FCR-7UV200-2-BX fiber-optic reflection probe and AvaLight-HAL-Mini halogen light source or an AvaSphere-50-LS-HAL, reflection integrating sphere with Halogen illumination included. Although there are a number of possible applications, the measurement of the main chromium peaks (692.8 nm & 694.2 nm) in rubies or the determination of diamond types Ia or Ib status are frequently performed with this setup. Type Ia or colorless diamonds show strong nitrogen absorption peaks at 415 nm and 478 nm, whereas type Ib, yellow diamonds have wider distribution of nitrogen atoms eliminating these peaks. Other useful peaks are at 592 nm and 741 nm, peaks which indicate artificial coloring has occurred.
Advanced Gemology Measurements
Various entities report the use of photoluminescence systems to detect gemstone characteristics. This technique most often makes use of a laser excitation source, sample chamber, and detection system. The laser wavelength depends on the feature(s) being sought. Most often, the chamber will include provisions for cryogenic cooling. The detection system can range from simple cameras to photomultiplier tubes. Avantes has provided systems with various lasers as well as the AvaSpec-ULS2048LTEC-USB (thermoelectrically cooled) spectrometer. An AvaRaman-Probe, fiber-optic Raman probe, is required as well to filter the excitation source out of the measured data.One example of the usefulness of this
technique is the detection of high-pressure, high-temperature treatment (HPHT). HPHT is sometimes used to improve diamond color, for instance turning brown diamonds into green or yellow diamonds. Since many regulatory agencies require that all such treatments be disclosed, the chief concern is that stones could be misrepresented as natural or untreated stones. HPHT can be detected with an Avantes low-cost, high-performance photoluminescence system as it leaves a trace peak at 694 nm.