Determining Gemstone Authenticity with Laboratory Analysis

Shutterstock | Victor Moussa

Shutterstock | Victor Moussa

The demand for gemstones is increasing, and fake gemstones are becoming a prominent and difficult-to-tackle problem in the jewelry and gemstone industries. Synthetic, fake, and enhanced gemstones can be identified quickly and with confidence by using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Specac’s MiniDiff accessory has been pre-configured for instant DRIFTS experiments, providing jewelers with an effective and easy way of assessing the authenticity of gemstones.

Gemstones, such as pearls, sapphires, tourmalines, diamonds, opals, and tanzanite, are naturally occurring mineral crystals that have been cut and then polished.

Since ancient times, gemstones and the jewelry they adorn have been a part of human society. Throughout history, gemstones and jewelry have been used for signifying wealth and status. Today, global urbanization means that the popularity of gemstones continues to increase. With the emergence of wealthy middle classes in rapidly growing economies such as Brazil and China, there is a huge demand for gemstones but regulation has struggled to keep up with this demand. As a result, the sale of fraudulent and fake gemstones has skyrocketed and there is a need for an effective and fast way of determining authenticity.

The price of gems relies on their identity, color, clarity, weight (carat), size, origin, shape, treatments, cut, and polish. Some of the rarest gemstones, such as the red diamond, are capable of fetching up to $1 million per carat.

Naturally occurring, flawless, large gemstones are often the most valuable but are also the rarest. With natural, unenhanced gemstones fetching such increased price tags, analytical methods capable of identifying fraudulent gemstones are in great demand.

What Makes a Gemstone Fraudulent?

Fraudulent gemstones range from outright fakes developed from glass or plastic, which are usually effortlessly identified by experts, to synthetic or treated gemstones which can be tougher to spot.

Synthetic gemstones share the chemical, physical, and optical properties of natural gemstones but they have been grown in a laboratory rather than developed naturally. There are synthetic versions of all the popular gemstones, and it is difficult to identify them. Synthetic gemstones are mostly perfectly clear, without inclusions, and have a deep color. Synthetic gemstones can be equally as beautiful as their natural counterparts; however, they can be distinguished from natural gemstones by the lack of inclusions present in natural gemstones.

Enhancements or treatments can be carried out on gemstones in order to enhance their appearance. A few enhancements are common place in the gem industry. For instance, most sapphires and rubies are heat treated, which is probably considered to be the most common form of gem enhancement. Other methods of gem enhancement include diffusion treatments, irradiation, dyeing, bleaching, impregnation with resins, filling, oiling, and coating.

Synthetic and treated gemstones are still popular, high-value commodities as long as their origins are completely disclosed. Improving gemstones can modify their value either up or down. For instance, if by modification an unusable gemstone becomes useable and attractive the value will possibly increase, in spite of the fact that the gem has been improved. However, ‘useable’ untreated gemstones tend to have much greater values than treated gemstones. For this reason, it is easy to understand why fraudsters may attempt to pass off enhanced or synthetic gemstones as untreated, natural gems.

Some enhancements are extensively accepted within the gemstone industry and by consumers, but these improvements must always be disclosed to guarantee that a sale is not considered as fraudulent.

Modifications that occur without the consumer’s knowledge are considered as fraudulent. Such misleading practices are immensely prevalent in growing economies and can take place on a large scale. For instance, in 2001, huge quantities of a rare, pink-orange sapphire called padparadscha started to appear in the Asian gemstone markets. Scientists identified that the gems were, in fact, cheaper sapphires that had been treated with beryllium and then fraudulently sold as padparadscha. A scandal followed, and the sapphire market took a serious hit.

How are Fraudulent Gemstones Identified?

Gemologists make use of tools including jeweler’s microscopes, loupes, or measurement of the refractive index in order to identify synthetic gemstones or those that have been improved. A jeweler’s loupe is a magnifying device that allows inclusions and blemishes to be seen. Microscopes offer further magnification and can be employed for detecting heat treatments and various other clarity enhancements.

However, these techniques all need a trained gemologist to perform the analysis, and the decision always includes human error. Furthermore, synthetic gems and enhancements are becoming immensely sophisticated making standard methods unreliable. As a result, sophisticated methods of gemstone analysis, which are borrowed from analytical chemistry, are indeed becoming popular.

Infrared Spectroscopy for Gemstone Analysis

Identifying synthetic, improved, and fraudulent gemstones can now be attained rapidly and easily using affordable equipment. Vibrational spectroscopy is becoming increasingly vital in the field of gemology. Reflectance infrared spectroscopy techniques, such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), are mainly useful for gemstone analysis as they are simple, rapid, and highly accurate and the equipment required is robust and low-cost.

DRIFTS permits the intrinsic structural vibrations of gemstones to be observed by reflecting an infrared beam off the surface of the material and then detecting the reflected infrared light. The analysis is non-destructive and can also be carried out on mounted gemstones. The obtained infrared spectra are compared with the reference spectra in order to identify gemstones, determine whether the stone is natural or synthetic, and identify the presence of waxes, coatings, dyes, polymers, or oils employed during enhancements.

DRIFTS Accessories for Gemstone Analysis

Reflection infrared spectroscopy is usually conducted with the help of an FTIR spectrometer along with an accessory that enables measuring reflectance. Specac offers a variety of reliable reflectance FTIR accessories that are ideal for gemstone analysis including the MiniDiff and Selector DRIFTS accessories.

The Selector is a flexible DRIFTS accessory, while the MiniDiff is an economic, pre-aligned DRIFTS accessory that allows easy analysis. The Selector and the MiniDiff offer universal, easy, and simple solutions for gemstone analysis.

The MiniDiff DRIFTS accessory from Specac

The MiniDiff DRIFTS accessory from Specac

The fraudulent sale of gemstones is a growing problem that needs affordable, robust, and simple analysis techniques. No analytical technique can detect every gem enhancement or solve every problem, but DRIFTS can provide simple, rapid analysis of gemstones and offer an indication of whether a gemstone is natural, fake, synthetic, or improved.

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References and further reading:

  1. ‘What are Gemstone Enhancements?’ https://www.gemsociety.org/article/gemstone-treatment-and-enhancement/
  2. ‘Selector | Diffuse Reflectance Accessory’ https://www.specac.com/en/products/ftir-acc/reflect/diffuse/selector
  3. ‘MiniDiff Plus DRIFTS accessory’ https://www.specac.com/en/products/ftir-acc/reflect/diffuse/minidiff-plus
  4. ‘Finding a real gem’ — Rachel A. Petkewich, Analytical Chemistry, 2003.
  5. ‘Specular reflectance infrared spectroscopy – a review and update of a little exploited method for gem identification’ — Thomas Hainschwang and Franck Notari, The Journal of Gemmology, 2008.
  6. ‘Thai Beryllium Scandal’ https://www.gemselect.com/other-info/beryllium-scandal.php

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This information has been sourced, reviewed and adapted from materials provided by Specac.

For more information on this source, please visit Specac.

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