Scientific Instruments Help Researchers Tell Gem Stories
Researchers analyze and come to conclusions about the identity of a sample gem by comparing what they find to a database of the numerous gems GIA has examined over the years. They use their expertise and knowledge to look for the distinctive characteristics that reveal a gem’s identity.
The information they gather and the instruments used to collect it can be categorized into light analysis, atomic structure analysis, chemical analysis and imaging, and additional instrumentation.
GIA has also designed and developed numerous instruments to serve our internal needs to research and analyze gemstones, as well as developing instrumentation for the trade. This page showcases the tools in our research toolbox. Many of these instruments have been designed by GIA scientists and engineers or modified by GIA to adapt them to a variety of gemstone data collection needs.
LIGHT ANALYSIS
Spectroscopy analyzes the way light interacts with the gem. Researchers can identify a gem–and often determine if it has been treated or is synthetic–by examining how it absorbs or transmits light.
Visible Absorption Spectrometer
A visible spectrometer shines a narrow beam of light through the gem by scanning through a series of wavelengths, beginning at the blue end of the spectrum through to the red end. Light wavelengths not absorbed by the sample are transmitted to the instrument’s detector. These transmitted portions can be seen by your eye as the color. The results of this analysis are displayed as a graph that shows the relative transmission (or absorption) of light versus wavelength. Researchers use the information to determine the cause of color of the material.
Dive deeper into how GIA uses spectroscopy to determine a gem’s origin and treatments: Application of UV-Vis-NIR Spectroscopy to Gemology
Available equipment:
- Wide variety of GIA-built instruments with several possible configurations including those that can be operated with fibers or integrating sphere, transmission or reflectance mode, room temperature or liquid nitrogen temperature.
- Perkin Elmer Lambda 950 UV/Vis Spectrometer
- Hitachi U-2910 UV-Vis spectrometer
- Agilent Cary 60 spectrometer with a custom-made GIA integrated sphere diffuse reflectance accessory (DRA).
Infrared Absorption Spectrometer
The infrared spectrometer measures the invisible light spectrum, known as infrared. Infrared spectra can help the researcher determine if a gem has been treated, or whether it is a type I or type II diamond.
This instrument generates radiation at wavelengths beyond the red end of the spectrum where “light” is invisible to the eye but can be felt as heat. These wavelengths can be absorbed, transmitted or reflected by the sample being analyzed.
Materials such as resin, oil, plastic and other substances used for the treatment of colored gemstones have distinct features in their infrared spectra and can be detected by the spectrometer. Infrared spectroscopy is also useful for detecting trace amounts of hydrogen species in some gems, like ruby and sapphire, which can provide clues to identify the presence or absence of artificial heat treatment in some cases.
Many minerals also have unique vibrational fingerprints that can be identified with infrared spectroscopy, aiding in their identification.
Learn how GIA scientists use infrared to identify natural and lab-grown diamonds, ruby, sapphire, emerald and jadeite: Infrared Spectroscopy and Its Use in Gemology
Available equipment:
- Thermo Scientific Nicolet iS50 FT-IR spectrometer with Drifts or KBr beam splitter accessories
- Thermo Scientific Nicolet iS5 FT-IR spectrometer with Drifts accessory (available to public with GIA analysis software as the GIA DiamondCheck)
Infrared Absorption Mapping
Available equipment:
- Thermo Scientific Nicolet iN10
Raman/Photoluminescence Spectrometer
The Raman Spectrometer uses a laser to illuminate a sample and record its Raman spectrum, helping researchers identify a gem or mineral specimen. The results, which consist of sharp peaks on a graph, are examined and compared to known spectrum library of different kinds of gem materials.
The instrument can also be used to record emission spectra of samples using a technique called photoluminescence (or PL) spectroscopy, in which the light from the laser causes the sample to emit energy at specific wavelengths to create a luminescence spectrum.
GIA researchers also use a separate instrument to collect Raman data for one specific spectral peak across a two-dimensional area. This creates a map of the spatial distribution of the atomic-level defect in a material that is the cause of that spectral peak.
These instruments are key to identifying gemstone properties. Learn how GIA researchers use these powerful tools to understand a gem’s geological history and detect synthetics:
- Raman Spectroscopy and X-Ray Diffraction: Phase Identification of Gem Minerals and Other Species
- Shining a Light on Gemstone Properties: An Exploration of Photoluminescence Spectroscopy
- Renishaw inVia spectrometer with lasers of 325, 457, 488, 514, 633, and 830 nm. Used at liquid nitrogen temperature and room temperature
- GIA custom-built PL spectrometer with 405 nm laser and used at room temperature
- Aminco Bowman Series 2 Luminescence Spectrometer for room temperature fluorescence spectra
Available equipment:
- Thermo Scientific DXRxi Raman Imaging Microscope
- Custom-built hyperspectral imaging device
Electron Paramagnetic Spectrometer
This is an advanced technique that allows GIA researchers to detect particular types of atomic-level defects with unpaired electrons in materials.
Shortwave UV fluorescence Spectrometer
The ideal excitation wavelength can effectively excite the targeted spectral features from the tested sample, and the fluorescence spectrometer records emission spectra of the sample. A 275 nm LED generating mid-wave UV is used to excite fluorescence from samples such as a pearl’s nacre. A reflection fiber probe guides the UV light to the sample and collects the fluorescence signal. A spectrometer records the signal and sends the spectra to a computer for analysis.
Available equipment:
- A GIA-built short-wave UV excitation with a 275 nm LED light source and an Avantes AvaSpec-Mini spectrometer.
CHEMICAL ANALYSIS
Researches use chemical analysis to determine what elements a gem is made of and if the gem is natural, synthetic or has been treated.
X-Ray Fluorescence (XRF)
X-Ray fluorescence helps researchers identify the chemical elements in a gem. By illuminating the sample with energy from an X-ray source, this system records the emission of X-rays of particular energies characteristic of the chemical elements present in the gem. The instrument performs a rapid, nondestructive, qualitative chemical analysis of samples that have a large, flat polished surface.
The technique can quickly tell the researcher what chemical elements are present in the sample. This technique has some applications in geographic origin determination for colored stones as well as confirming some treatments like clarity enhancement of ruby with lead glass.
These two techniques help GIA researchers identify the origins and potential treatments of colored stones. Learn more about them here: Chemical Analysis in the Gemological Laboratory: XRF and LA-ICP-MS
Available equipment:
- Thermo Scientific ARL Quant’x energy-dispersive X-ray fluorescence (EDXRF) spectrometer
- Horiba Mesa-50 XRF
X-Ray Fluorescence (XRF) Imaging
The technique is used to confirm the pearls’ growth environment. Freshwater and saltwater pearls present different luminescence reactions under x-ray excitation due to manganese content.
Freshwater pearls typically displayed moderate to strong greenish yellow luminescence due to the presence of trace amounts of manganese (Mn). Owning to very low or absence of Mn content, most natural pearls remain inert. However, bead cultured saltwater pearls with relatively thin nacre may show a weak luminescence of a freshwater shell bead nucleus underneath.
Luminescence reaction of pearls under x-ray can be displayed and recorded on a monitor using a digital camera.
Available equipment:
- A MatriX-FocalSpot Verifier PF-100 X-ray fluorescence unit (100 kV and 3.2 mA excitation) equipped with a Canon EOS REBEL T4i DSLR camera (five-second exposure, F5.0, ISO 12800)
Laser-Ablation, Inductively Coupled Plasma, Mass Spectrometer (LA-ICP-MS)
This advanced instrument helps researchers determine how much of each element is present in the sample.
A beam of light from a laser is focused on the surface of a sample and it ablates, or removes, tiny particles from the surface. These particles are moved by a flowing gas into a high-temperature plasma torch where they are broken down so that the individual atoms that can be identified by the detector. This makes it possible for the researcher to make a quantitative chemical analysis of the naturally occurring elements, even down to low concentrations in the sample. A very small part of the sample is destroyed in the process.
LA-ICP-MS is invaluable in the modern gemological laboratory for detection of beryllium diffused ruby and sapphire. The high sensitivity of LA-ICP-MS also allows researchers to measure trace elements to below the parts-per-million level, allowing a trace element fingerprint to be measured, which in many cases is crucial for geographic origin determination of many colored stones.
Available equipment:
- Thermo Fisher iCAP Q ICP-MS, coupled to an Elemental Scientific Lasers NWR 213 laser ablation system with a frequency-quintupled Nd:YAG laser (213 nm wavelength with 4 ns pulse width).
IMAGING
Photography–specifically photomicrography–offers researchers a way to capture close-up images of features or inclusions within the gem. Researchers use this information to determine the circumstances around how the gem formed and, for some gems, where it originated.
Photomicroscope
A binocular photomicroscope is used to capture photographic images of the features, or inclusions, in a gem. Researchers use this information to help identify a gem and determine if it is natural, treated, or synthetic.
Available equipment:
- Nikon Eclipse LV-100 microscope
- Nikon SMZ1500
- Leica DM750P petrographic microscope
Deep UV Fluorescence Imaging
The DiamondView instrument helps distinguish most natural and synthetic diamonds by using a short-wave ultraviolet source to produce fluorescence patterns. The instrument was developed by researchers from the De Beers Diamond Trading Company in the United Kingdom in 1996.
Learn more about the principles, mechanisms, and characteristics of luminescence that create the impressive glow of gemstones: Glowing Gems: Fluorescence and Phosphorescence of Diamonds, Colored Stones, and Pearls
Available Equipment:
- DiamondView with a suite of filters to selectively image the fluorescence
- GIA custom-built LumiSense
X-ray Imaging for Pearls
Natural and cultured pearls often display similar external appearances and occasionally cannot be confidently differentiated without examining their internal structures. X-ray imaging is an important technique used by researchers and gemological laboratories to reveal interior growth patterns of pearls for identification.
A real-time microradiography (RTX) provides the operator instant, 2D x-ray images where extremely fine detail can be focused and viewed on a monitor and images can be recorded in digital formats.
X-ray computed microtomography (μ-CT) applied to pearl testing provides high-resolution, 3D imaging of the morphological structures, allowing fine growth features to be viewed in greater detail compared to traditional X-radiography.
The RTX and μ-CT results are grayscale images in which differing shades of bright and dark grayscale intensity correspond to X-ray opacity of the materials. Mineralized materials, such as aragonite or calcite, are denser or more radiopaque than organic-rich features or voids filled with gases and/or liquid; hence, an area composed entirely of aragonite will appear lighter than an area containing organic-rich or void features, which generally appear darker.
X-ray radiography and X-ray computed microtomography play a crucial role in the identification of pearl. Learn more about these imaging techniques and their importance in gemology: Applications of X-Ray Radiography and X-Ray Computed Microtomography in Gemology
Available Equipment:
- Pacific X-ray Imaging (PXI) GenX-90P X-ray system with 4-micron microfocus, 90 kV voltage, and 0.18 mA current X-ray source combined with a PerkinElmer 1512 flat panel detector.
- Matrix-FocalSpot XT-3 real-time X-ray inspection system with a 4 microns microfocus, 90 kV voltage, and 0.18 mA current X-ray source combined with a PerkinElmer 1512 flat panel detector.
- ProCon CT-mini X-ray system with a 5-micron microfocus, 90 kV voltage, and 0.18 mA X-ray current source. Two detectors with a frame grabber card were used to capture the results: a Hamamatsu flat panel detector C7921CA-29 with 50 micropixel pitch and 1032 × 1032 pixel resolution, and a Varex 1207 flat panel detector with 74.8 micropixel pitch and 1536 × 864 pixel resolution.
Scanning Electron Microscope
This instrument uses a focused beam of electrons to produce a high-magnification image of the topography and composition of a very small surface area of a sample material.
Cathodoluminescence spectroscopy and imaging may also be collected with some additional accessories.
Available Equipment:
- Zeiss Evo MA 10 scanning electron microscope, using a variable-pressure secondary electron dectector (VPSE G4) and a Gatan MonoCL4 Swift system containing a high sensitivity photomultiplier tube (HSPMT).
Additional Instrumentation/Equipment
Chemical Vapor Deposition Reactors for Laboratory Growth of Diamond
Laser Cutting and Polishing – typically for flat-plate fabrication of diamond and other gemstones
Heated/Cooled Microscope Stage
This equipment gives precise temperature control (-196oC – 600oC) of a sample when collecting spectroscopy or collecting images.
Available equipment:
- Linkam THMS600
High-Temperature Furnace
We can use this furnace to heat gem materials to specific temperatures and particular oxidizing or reducing atmospheres to better understand the heat-treatment of gems and the thermal behavior of solid materials.
Available equipment:
- 1000-3560-FP24 Thermal Technology gas mixing furnace. Possible temperatures up to 1800oC. Possible durations up to 7 days continuous. Inert, oxidizing, and reducing atmospheres with available gases including CO2, O2, H2, N, CO.
- MTI GSL 1500X furnace with 2” OD mullite tube: room temperature -1500oC; ambient or inert environment; duration of ~12 hours or less due to lack of interlocks.
Recent Instrument Publications and Patents
Metrology at GIA
Tunable laser photoluminescence and excitation spectroscopy for gemstone analysis
Multi-excitation photoluminescence spectroscopy system for gemstone analysis
Development of a large volume line scanning, high spectral range and resolution 3D hyperspectral photoluminescence imaging microscope for diamond and other high refractive index materials
High Resolution Luminescence and Raman 3d Hyperspectral Imaging of Gemstones - Astrophysics Data System
Photochromic gemstone analysis using in situ absorption spectroscopy
Rapid gemstone mineral identification using portable Raman spectroscopy - Tsai - 2023 - Journal of Raman Spectroscopy - Wiley Online Library
Publication Number: US10641526B2
Title: Method and apparatus for rapidly cooling a gem, including two stage cooling
Publication Number: US10859505B2
Title: Fluorescence box for gemological applications
Publication Number: US11037282B2
Title: Detection of clarity markings in gemstones
Publication Number: US11915407B2
Title: Automated system and method for clarity measurements and clarity grading
Publication Number: US20240159683A1
Title: Apparatus and method for assessing optical quality of gemstones
Publication Number: US20240167955A1
Title: Apparatus and method for fluorescence grading of gemstones
Publication Number: US12135278B2
Title: Light emitting diode arrangements for gemstone evaluation
Publication Number: US20240385119A1
Title: Imaging assisted scanning spectroscopy for gem identification
Publication Number: US20240394961A1
Title: Gemstone cut analysis
Publication Number: US12196678B2
Title: Luminescence imaging for gemstone screening
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