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Analytical Capabilities
All kinds of diamonds, colored stones, and pearls are examined as part of our ongoing gemstone research program. In many cases, an important goal of our research program is to develop practical criteria to identify those gem materials that have been synthesized in the laboratory, or have been treated to improve their color and/or appearance. Accurate gem identification is essential to support the jeweler's ability to disclose information on the gemstones that they sell to their customers. Our examination of gemstones begins with standard gemological instruments, and includes more advanced analytical equipment.
Standard Instrumentation
As visual examination of color and other aspects of the appearance of a gemstone is fundamental, the most important piece of standard gemological equipment is the binocular microscope. This instrument is used with various illumination techniques to observe inclusions and other distinctive features in gemstones. An important part of our documentation of gemstones is photography of visual characteristics seen with the microscope. Additional instruments, such as a refractometer, spectroscope, polariscope, electronic balance (for calculating the specific gravity), and ultraviolet lamps, allow us to document basic gemological properties, such as refractive index, absorption spectra, optic character, specific gravity, and ultraviolet fluorescence. In some cases, this information is supplemented by results from testing with simple instruments that can measure properties such as thermal or electrical conductivity or surface reflectivity.
Advanced Instrumentation
When necessary, we use analytical instruments to provide additional information on the identity of gemstones. Such instrumentation includes spectrophotometers to record ultraviolet, visible, infrared and luminescence spectra, and X-ray equipment to provide images, diffraction data, and non-destructive chemical analyses. We use a laser Raman microspectrometer to help identify tiny inclusions in gemstones. Luminescence reactions are documented with cathodoluminescence and with various ultraviolet lamps that provide excitation over a range of wavelengths. On rare occasions when a reactor-treated or natural gemstone emits a small amount of residual radioactivity, this can be detected with gamma spectroscopy equipment. An electron microprobe for quantitative chemical analysis, and a scanning electron microscope for observing structural features, are available to us at a nearby university.
This advanced instrumentation provides important information for identifying gemstones. However, the most effective use of this equipment occurs when there are gemstones of known origin to study that allow the compilation of a database of more accurate gemological information. Here at GIA, research on gemstones extends back for almost 50 years, and we continue to document new gem materials to add to our ever-expanding database.
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