Gübelin Gem Lab’s Innovative Gemstone Ratings Driven by Pioneering Spirit

Unlike diamonds, the criteria for grading of coloured gemstones has always been complex and mysterious. While evaluation categories like colour, cut, clarity, carat weight are common with diamonds, additional factors such as origin and rarity greatly influence the perception of beauty and value for a coloured gemstone. Some may argue that the element of mystery is responsible for healthy margins in the industry. Consumers however, desire better understanding, greater transparency, and traceability of their precious gems from mine to market. Our international correspondent, Richa Goyal Sikri catches up with RAPHAEL GÜBELIN, President of the House of Gübelin, to discuss their latest initiative; an innovative rating system that aims to bring greater transparency in the coloured gemstone sector.

The Gübelin Gem Lab has continuously brought to market innovative solutions like the Provenance Proof a few years ago, which employs nano-technology to create a physical tracer for emeralds and a digital tracer via a blockchain product. And now, a new gemstone rating system. What is the motivating factor for Gübelin to introduce these initiatives? 

We are driven by the pioneering spirit of our House since 1854. For example, my great-uncle Eduard Josef Gübelin was a pioneer in gemmology and especially origin determination. Together with other gemmologists, he established the Swiss Gemmological Association. He also developed examination instruments such as the Coloriscope, Gemmolux, the Jeweller’s Spectroscope (to name a few), and further improved them. One of his greatest achievements was the study of the inner world of gemstones, through which he determined their place of origin. These were the innovations that were appropriate to meet the needs of consumers back then. Nowadays, we have other questions consumers want answered. Hence, the Gübelin Gem Lab continues his work, deploying innovative methods and latest technology. To get a deeper understanding and enable more transparency about gems and where they come from, we initiated Provenance Proof. Now, you can follow the journey of a gem from mine to market. We share these initiatives with the entire trade, might it be Provenance Proof or the Gübelin Gemstone Rating.

Raphael Gübelin President

Can you explain how the Gübelin Gemstone Rating system works? 

There are two ways to get a rating for a gemstone. You can either get it in combination with a Gübelin Gemmological Report, or you order it as a stand-alone service. Experienced and trained gemmologists perform the rating following a highly standardised assessment procedure and a methodology that we have designed and built on the basis of the data on many tens of thousands of gemstones Gübelin has seen in the almost 100 years it is in business. The rating is based on three categories. The primary one being quality, which is complemented by rarity, and salience. The main criteria – quality – consists again of colour, clarity/transparency and cut/brilliance. Colour is further broken up into hue, tone, saturation and homogeneity.

Rarity comprises the type of gemstone, the presence, absence and type of treatment, and the size of the gemstone.

Finally, the salience addresses the level of exceptionality, i.e. insofar as a gem is able to attract the attention of the observer, to stand apart from other gemstones. The overall result of the rating is expressed in an easy-to-understand numerical grade: the Gübelin Points.

Considering these three pillars of the Gübelin Gemstone Rating system (Quality, rarity, and salience), how much weightage is assigned to each? What would you say to industry stakeholders who are concerned regarding the element of subjectivity in the grading because of the salience factor?

The most important parameter is quality, followed by rarity and salience. Salience is the least scientific parameter and there is a certain level of subjectivity, but it’s based on a common perception. Let me explain why we integrated this parameter. When defining the quality criteria, we realised some gems show properties that are not exactly matching the ideal, but are highly attractive. And there are also some gems that fit well into what is considered as being ideal, but they lack a special charm or appeal. There seems to be a common consensus among gem connoisseurs about which gemstones – beyond the objective quality criteria – are highly attractive and “talk to them”. This shared perception made us introduce salience. It allows, for example, to compensate for the lower transparency rating that the typical Kashmiri sapphire with the velvety appearance will get. Or for the lower rating for colour homogeneity in the most beautiful Padparadscha sapphires that typically show a slightly uneven colour distribution.


 If a new deposit is discovered after a gemstone has been rated for rarity, would that impact the ‘rarity’ grade?

Rarity is driven by demand and supply – and this can vary over time. We carefully monitor this parameter, especially as the coloured gemstone trade is very fragmented with tens of thousands of mines, artisanal miners and mostly a lack of formal information about production. To cope with this challenge, we rely on our global network that we’ve established over decades, and our experience. We are currently defining a process to review the rarity rating. If rarity would change, we would review and revise the respective parameters.


Would you employ the same criteria for rating vintage cuts versus modern-cuts? With old-cut gems, while the colour and rarity element is strong, due to the style of cutting, they may get a lower grade. However, there is a segment of the market that values the distinctive characteristic of the old-style more than the modern-cut. How would you rate them?

This is when salience is essential as this parameter allows us to factor in old-cut stones. Salience might compensate for a somewhat lower cut rating. But it is important to understand that this rating system is merely giving orientation. The points do not make the sales process obsolete, which can emphasize the hidden facts such as a historic or local cutting style.


How would you take into account regional preferences? For example, in India customers value clarity more, whereas in the US colour reigns supreme. How would the system balance these preferences? 

We try to assess in a balanced way that fits with the entire trade, all over the world. So the Gemstone Rating can provide more orientation and comparability to the global industry. We don’t take regional preferences into consideration, nor fashions or consumer trends

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