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Gemstone Laboratory Testing

Gemstone Testing, The Natural Emerald Company

Beryl Quartz Emerald Zambia
A piece of Zambian emerald crystal in quartz matrix.

On this page you can learn about some of the latest equipment and challenges that gem labs face each day to positively identify gemstones so traders and consumers can buy with confidence. Gemology today is constantly focused on identifying new treatments that unscrupulous dealers apply to lower grade mine production to artificially enhance low-quality stones.

There are literally dozens of variables that need to be analyzed and carefully considered in regards to verifying the inherent quality of each and every gemstone. High tech equipment has helped speed up the processing to identify these gemstones, but it takes years (and lots of investment) to acquire the skills and experience of a master gemologist.

The Natural Emerald Company uses a wide variety of gem labs around the world. There are countless low quality or even fraudulent “labs” that exist and create worthless reports; it’s very important to know the reputation of a lab before you accept their findings. Here are some of the most common and advanced types of testing that the labs will undertake to identify and verify the emeralds that we work with.

Identification Processes

emerald fignerprint inclusion
Fingerprint inclusions in an emerald.

The most important gemological-mineralogical criteria used for the characterization of gemstones are:

Inclusion Features

These include cavity fillings, growth features, and other characteristics within the gem that are large enough to be seen with a microscope. If more information is needed than the microscope provides, some advanced equipment can be used to report on inclusions.

Chemical Fingerprinting

This is a breakdown of the major, minor, and trace mineral elements that make up the gem.

Spectral Fingerprinting

This is a detailed analysis of the way different types of light (particularly ultraviolet, visible, and near-infrared range light) interact with the stone. It can be used to determine the type of gem, its origin, and any treatments it has undergone. In order to analyze the characterization of gemstones – to determine the distinctive characteristics of natural, synthetic, and treated gem materials – advanced gemstone testing requires a variety of powerful analytical tools.

Kevin examines blue sapphire
Kevin examines a gemstone against a spectral wavelength chart.

Many gem materials and treatments can be identified using classical gemological equipment such as the binocular microscope, the spectroscope, and the refractometer, but detecting today’s increasingly sophisticated synthetic and treated gemstones with these tools is nearly impossible. New processes for creating synthetic gems and for artificially altering natural ones require updated methods and tools for detection. Today, we turn to more advanced scientific instrumentation to help us properly identify where a gem originated and what has been done to it.

When analyzing an emerald, it is extremely important that it is not damaged by the analysis. Emeralds are carefully cut to achieve their beauty and are often very valuable; damaging these precious objects can significantly reduce their value and great care must be taken when examining them. Using light waves to gather information causes no damage to the gemstone and is considered the best technique.

patrick studies sapphire microscope
Patrick studies a gemstone underneath a high-powered microscope.

Most techniques and instruments for analyzing gems do so by analyzing how these different types of light waves interact with the gemstones. Essentially, the instruments shine different kinds of light on the gem. Sensitive detectors quantify exactly how the light has passed through, reflected off of, been absorbed by, or otherwise interacted with the gem. Different aspects of the gem’s physical and chemical composition are revealed through these processes. When we combine all of the test results we are able to create a detailed description of the stone we see today and its path to formation.

Fourier Transform Infrared Spectrometer (FTIR)

Kevin tests blue sapphire FTIR
Kevin tests a gemstone in the FTIR.

A Fourier Transform Infrared (FTIR) spectrometer records the intensity of infrared light wavelengths that pass through, are absorbed by, or are reflected off when infrared light is directed at a sample. Sometimes the light is redirected by a system of mirrors to pass by the sample many times before being analyzed. The spectrum (a pattern representing the interaction of light with the sample) that results from this process represents the molecular absorption and transmission of the elements within the stone, creating a molecular “fingerprint” of the sample. Like a fingerprint, this infrared spectrum is unique to each type of material. This makes infrared spectroscopy useful for several types of analysis.

FTIR spectrometry is widely used in both research and forensic analysis in the gemological field, enabling identification of foreign substances in treated gem materials, such as oils or resins in the case of a fracture-filled emerald. A number of synthetic gems can be distinguished from their natural counterparts by differences in their infrared spectra. Type I and Type II diamonds can also be recognized.

FTIR test diagram
A diagram of how FTIR testing works.

Top quality labs use a FTIR spectrometer for the following advanced gemstone testing:

  • Detecting gems that have undergone heat treatment to alter their appearance.
  • Distinguishing between synthetic and natural gems.
  • Analyzing clarity enhancements of specific gems such as oils or resins in a fracture-filled emerald, or polymer impregnation in jadeite jade.

Energy Dispersive X-Ray Fluorescence Spectrometer (EDXRF)

Patrick tests pink sapphire EDXRF
Patrick tests a stone in the EDXRF.

The energy-dispersive X-ray fluorescence (EDXRF) system is used to determine a gem’s chemical composition. X-ray fluorescence (XRF) is the emission of characteristic “secondary” (or fluorescent) X-rays from a material that has been exposed to incoming high-energy X-rays. An X-ray beam illuminates and heats the sample, causing the material to emit specific X-rays that are characteristic of the major and minor chemical elements in the gem.

In general, EDXRF is widely used for elemental analysis and chemical analysis, particularly in the investigation of metals, glass, ceramics, and building materials, and for research in geochemistry, forensic science and archaeology.

EDXRF test diagram
A diagram of how EDXRF testing works.

Top quality labs use a EDXRF spectrometer for the following advanced gemstone testing:

  • Distinguishing between synthetic and natural emeralds.
  • Analyzing trace elements to identify the geographical origin of an emerald.

We advocate learning as much as you can about emeralds before making a purchase so you can feel confident in your decision as you shop for the best value.

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