Gübelin Gem Lab’s New Rating System

Responding to a long-standing need in the trade, Gübelin Gem Lab has created a standard for the grading of important coloured gemstones. Pietra Communications Founder, Olga González FGA DGA, explains the three factors that the lab uses in its assessments in the Spring 2021 issue of Gems & Jewellery Magazine, a Gemmological Association of Great Britain member publication.


While diamonds have the 4Cs and the precious metals in fine jewellery use a hallmarking system, coloured gemstones have long needed a consumer-friendly rating system. Gübelin Gem Lab (GGL) has stepped in to fill the gap.

Inspired by the Parker Wine Rating used for scoring wines — which is itself based on the American standardised grading system — the laboratory developed the Gübelin Gemstone Rating. Converting quality, rarity and allure into a numerical value, Gübelin Points rate the desirability of important gemstones on a scale between 75–100. According to Dr. Daniel Nyfeler, Managing Director of GGL, “In a more digital world a [numerical] rating makes it easier to select the right stone and allow a better comparison, even without having the gem in hand.” Nyfeler indicated that the system empowers consumers by giving orientation and direction. “With the Rating, we intend to quantitatively assess some of the key characteristics of this space and reduce the complexity by concentrating to a single figure.”

The Gübelin Gemstone Rating is based on the following three factors, in descending order:

• With a focus on the visual, Quality is assessed using the gemstone’s colour, clarity, transparency, cut and brilliance.

• The variety type, the availability of a given gemstone variety on the market, as well as its size, all impact the Rarity. Treatments, such as ‘classic’ heat treatment (exclusive of lead-glass and diffusion treatment) and clarity enhancement with oil or resin are also considered in this ranking.

• The most subjective of the three factors, Salience, is best described by the lab: “Addresses the extent of exceptionality and attractiveness of a gemstone beyond the objective characteristics of the quality category. It is best seen as the gemstone’s capability to stick out of the crowd.”

The Points comprise several ranges. They find that 75–79.9 is ‘fair’, 80–84.9 is ‘good’, 85–89.9 is ‘fine’, 90–92.4 is ‘superior’, 92.5–94.9 is ‘excellent’, 95–97.4 is ‘outstanding’, and 97.7–100 is ‘exceptional’.

Dr. Nyfeler notes, “Standardisation, formalisation and virtualisation are the response to changing expectations and habits of consumers. The current limitations to travel have only accelerated this trend. Our rating system follows and supports this trend, and helps communication within the trade, and with the final customer.”

As with diamond grading, the Gübelin Gemstone Rating is discerned by trained experts following a set of developed standards, but the final number remains subjective and can therefore lead to shifting grading results.

By removing client names from the stone before grading and by providing supplemental software and tools, GGL has developed a system that minimalises risk of personal preference throughout the grading process. For criteria such as rarity, the lab recognises that supply and demand can fluctuate. Select parameters for grading will need to be reviewed and could potentially adjust over time.

Even with their subjective aspects, for GGL the namesake rating system is an ingenious marketing tool. It promotes their laboratory services and offers something extra that gemstone dealers and designers can use when speaking about a specific gemstone to a client. The end consumer benefits from an easy-to-read value that sets a gemstone within the lexicon of distinction while engaging industry trust.

“Our Gemstone Rating attempts to give direction by reducing complexity. It does not tell the full story of a gemstone or exhaustively explain its beauty, appeal and rarity. It is best seen as complementing and enriching the storytelling, rather than substituting it,” said Dr. Nyfeler.

At this time, only natural, non-synthetic gemstones that are faceted or polished may receive a Gübelin Gemstone Rating. The gemstones that can be rated are: ruby, emerald, sapphire (including fancy colours), padparadscha, Paraíba tourmaline, rubellite, red-pink spinel, alexandrite and chrysoberyl, aquamarine, morganite, and heliodor, demantoid, tsavorite and mandarin garnets, tanzanite; and Imperial, red-pink topaz. The rating does not consider origin.

GGL will offer complimentary GemstoneRating Requests with their Gemmological Reports until the end of 2021. For more information, visit gubelingemlab.com/en/.

For more information about The Gemmological Association of Great Britain, and their member publications, visit https://gem-a.com/.

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