6 Cs of Sapphire

The 4 Cs of diamonds represents the main characteristics of a diamond which defines its beauty, perfection, and value. More importantly, it serves as the protocol of communication between the sellers and buyers. Also, it enables fair price comparisons, inventory classifications and many other instruments in the trade.

However, we do not have a similar grading system for Sapphire grading. Many experts have attempted to standardize this, but we have failed to establish an industry-accepted classification for sapphires. We believe that NGE can fill this void and provide tools to standardize the sapphire trade. In this attempt, we take a more practical path than try to achieve perfection. Therefore we judge these instruments by how effectively and efficiently they are serving the trade rather than their theoretical foundation them.

"6 Cs of Sapphires" have been successfully used in the high-end fine jewellery market. Here, the first 4 Cs are similar to the 4 Cs of diamonds and two new Cs have been introduced to address another two main factors 'Curing" and "Country of Origin" which define the characteristics and the quality of natural sapphires. The 6Cs of Sapphire is not a grading system but a collection of protocols to improve communication among traders.

Not only these new Cs but also all other Cs need to be well tailored for the Sapphires. Even some companies try to use the same definitions and guidelines from Cut and Clarity, they also need to be tailored for Sapphires. The only "C" which can be used as-is is obviously the "Carat".


The "Color" in the 4Cs diamond grading system is an indicator of how colorless a diamond is. According to GIA, "diamonds are color-graded by comparing them to stones of known color under controlled lighting and precise viewing conditions". Sapphires come in every color you can imagine. Here are some of the colors found in the NGE inventory. Every single sapphire has its own unique color. And describing this color is not a simple task. The color characteristics of sapphire can be further broken down into three color properties, hue, saturation, and tone.

Hue is simply the obvious color difference you see in the stone. For example, consider the four blue sapphire gemstones in the below picture. They all are blue but you can see a clear difference in each of their blues. There are numerous naming conventions to identify different hues such as navy blue, sky blue, denim blue etc. However, there is no consistency in these naming conventions. Therefore, we use NGE color cards to identify the hue of sapphire gemstones.

Saturation is how well the color is distributed across the body of the gemstone and how vibrant the color is expressed. The best stones have a vivid saturation and the opposite is a dull saturation.

Tone is the relative lightness or darkness of the color. For example, two sapphires can have the same color but one can be lighter and another can be darker based on how much grey color is mixed with its main hue.

As we stated earlier, at NGE we are trying to keep things less complicated unless it is really necessary to go for extra classification. In most cases, the color properties can be fairly well observed via photographs and videos. We use NGE color cards to identify the hue correctly so that the photographs and videos along with NGE color card codes can communicate the color information adequately. Visit this page to learn more about NGE color cards.


Sapphire Rainbow of Colors


Diamond clarity is the absence of any inclusions and blemishes. Natural gemstones, especially sapphires have inclusions. In contrast to diamonds, some inclusions can add value to the sapphires by enhancing the beauty of the gemstone. Therefore, clarity is another complicated characteristic of sapphires. If inclusions are not visible to the naked eye we call them eye-clean sapphires and if they any inclusions are not visible with a 10X magnification we call them loupe-clean sapphires.

We need to understand that most of these grading protocols were developed in the times when shooting high-magnified photos and videos and sending them across were not possible. Now, with the right instruments, we can communicate the clarity information very accurately.


The quality of the cut of sapphire is also not as same as the cut or a round brilliant diamond where the GIA grading is defined. The ultimate idea of grading the cut of a gemstone is to determine the glitter and brilliance that comes off the gemstone when interacts with light rays. It is very difficult to establish a clear guideline as to how the geometric dimensions and proportions of the cut lead to the visual appearance of sapphire because, unlike diamonds, this characteristic highly interacts with the colour and clarity of the sapphire. Sometimes Sapphire gemstones are cut out of proportions resulting in the gemstone becomes deep or shallow to maintain and get the optimum color. In such circumstances, the perfection of geometry and symmetry does not mean a better cut. We are expecting to work in this area and come up with some best practices for the industry.


Curing refers to various treatments and enhancements carried out to improve the properties of sapphires as well as hiding or healing the defects. The most common sapphire treatment is heat treatment. Heat treatments are the process of exposing the gemstones to high heat for a long duration so that it speeds up the transformations which will take millions of years to happen naturally. Heating is an accepted treatment for sapphires as, except for very few, the majority of sapphires are heat treated.

Undesirable techniques such as filling, dying etc. are used by some but these sapphires are not valued in the trade.

"C"ountry of Origin

The last "C" of the 6 Cs of Sapphire is the country of origin. Sapphires for different regions have different characteristics. Not only the characteristics but also other factors such as whether the mining is carried out in an environment-friendly manner or whether the trade is conflict-free can be important in the trade. Therefore, we believe capturing this information is very important in the sapphire trade.

 This is a short but comprehensive overview of the 6 Cs of sapphires. But we provide additional training and resources to our members to properly grade their sapphire gemstones.

Rafael Green

David Middleton

Natural Gem Exchange's training and education department is dedicated to provide international standard trainging and eduction to all it's stakeholders including customers, partners, and employees.

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