Color grading of fancy color diamonds

It is remarkable how fancy colored diamonds receive their color. Fancy diamonds require just the right amount of pressure, heat, radiation, and the appropriate chemical reaction in order to become colored. This set of circumstances rarely occurs in nature. In fact, only one out of ten thousand diamonds found on the earth’s surface possesses a naturally distinct color, making the evolution of these colored diamonds truly extraordinary.

This natural phenomenon also establishes the level of uniqueness of each colored diamond you see today. Unlike the pure and structurally perfect colorless diamonds, those with colors have structural imperfections and impurities that are commonly found in their make-up. The presence of the element Boron, for instance, gives a diamond a more bluish color while the element Nitrogen gives a more yellow or orange shade to the diamond. Ironically, such minor “glitches” of nature are responsible for most of the colored diamonds found on the market today.

Fancy colored diamonds are graded outside the normal color range (D-Z), with colors such as Pink, Blue, Yellow…etc’. They are graded more for their color intensity than their brilliance, the most valuable being medium saturated pinks, blues, and greens with medium to dark tones.

Grading Fancy color diamonds is highly-specialized and takes the expert eye of laboratory graders to ensure its accuracy. One of the best ways to determine the value of fancy colored diamonds is to use the grading system set out by the Gemological Institute of America (or GIA). They usually start out by looking at the face-up (table up) appearance of the colored diamond while judging these three important components: Hue, Tone, and Saturation.

Hue – Determining the actual color

Hue is the main body color together with some possible modifiers. There are seven dominant color hues that GIA uses when grading a colored diamond: Red, Purple, Orange, Violet, Blue, Green, and Yellow. Pink, which falls under the shade of Red, is not mentioned, yet has its own range on the color wheel. It can also appear as a primary or secondary color.

Brown and Gray, which are recognized as diamond colors by the GIA, are not considered dominant colors. However, they strongly affect a hue’s intensity. Cool colors, such as blue and green are modified by grey in low intensities; warm colors like red, orange, and yellow are modified by brown.

The dominant hues can be expanded into 27 hues to complete the entire spectrum of colored diamonds.


Fancy color diamonds Hue - The color grading wheel

Some of these hues are a combination of dominant and modifying colors. Modifying colors are colors that can be found in addition to the main color. For example, a Reddish-Purple diamond has a dominant Purple hue with modifying tints of Red.

To avoid confusion, keep in mind that the last color mentioned is the main color of the stone, despite the numerous colors that come before it. For example:

A “Red-Purple” diamond means that the ratio between the colors is almost balanced, with Purple having a slight edge between the two.

A “Reddish Purple” diamond means that the ratio between them is about 25% Red and 75% Purple.

A “Reddish Brownish Purple” means that the ratio is around 60-75% Purple, with around 20% – 40% of the mixture consisting of Red and Brown.

Modifying colors can dramatically affect the value of a diamond, depending upon the color. Generally, the more common ones like yellow, brown and gray can lower the price, while the more uncommon ones like orange, pink, blue, purple, and green add more value to the stone.

Tone Grading of colored diamonds

Tone expresses the lightness or darkness of a color. It is measured on a scale ranging from Faint to Dark.A pink diamond, for instance, can be “Dark Pink” or “Light Pink” depending on its tone.

Grading goes according to following categories:

1. Very Light

2. Light

3. Medium Light

4. Medium

5. Medium Dark

6. Dark

7. Very Dark


Saturation Grading

Saturation measures the strength and intensity of the primary color. For example, primary colors like Red, Yellow, and Blue are considered fully saturated, because they contain the strongest intensity — or “truest version” — of their colors.

Saturation has six categories on the GIA scale, and they range from pastel to vivid. Dark-toned diamonds, on the other hand, range from dark to deep.

Grading Colored Stones as a Whole

The interplay of hue, tone, and saturation can be challenging to decipher. Keep in mind that GIA more heavily factors in tone and saturation (less so on hue) when grading fancy colored diamonds. Their rating consists of nine categories:

Faint – lowest in terms of tone and saturation, and shows a faint and nearly undetectable hue.

Very Light – low in tone and saturation, and shows a very light, yet traceable hue.

Light – a light and almost fair tone with weaker saturation.

Fancy Light – just below the average saturation, with tones exhibiting a vibrant, yet pale hue.

Fancy – moderate amount of saturation and tone.

Fancy Dark – darker tone and weaker saturation.

Fancy Intense – more moderate tone and stronger saturation.

Fancy Deep – highest in saturation and tone.

Fancy Vivid – moderate tone, heavy saturation and intense, vibrant hue. They are considered very rare and highly valuable.


Tone and Saturation color grading of fancy color diamonds

While tone, hue, and saturation are the main aspects utilized to grade fancy colored diamonds, another factor that’s commonly used in appraising the value of a diamond is color distribution. This can range from even to uneven, and a stone’s value becomes higher depending on the evenness of the diamond’s color.

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