BEYOND THE 4CS
In a white diamond, colour lowers the grade. In a fancy coloured diamond, colour is everything. How yellow, pink and blue diamonds are formed, graded and chosen for an engagement ring.
Most diamonds are graded on the D to Z scale, where less colour is better. Diamonds with colour deeper than Z, or with a colour other than yellow or brown, are called fancy coloured diamonds. Here the rule is reversed: the purer and stronger the colour, the rarer and more valuable the stone.
Colour comes from small changes in the crystal: a trace element in the carbon, or a distortion in the way the atoms are arranged.
Laboratories grade a fancy coloured diamond face up, by its hue, its tone and its saturation, and describe it in words rather than a letter:
| Grade | Character |
|---|---|
| Faint to Light | Just a hint of colour |
| Fancy Light | Soft, delicate colour |
| Fancy | Clear, definite colour |
| Fancy Intense | Strong, rich colour |
| Fancy Vivid | The most saturated and most prized |
| Fancy Deep, Fancy Dark | Deep, darker tones of the colour |
The report also names the hue, sometimes with a modifier: a Fancy Intense Yellow, for example, or a Fancy Light Purplish Pink.
Yellow diamonds owe their colour to nitrogen. They are the most widely available of the fancy colours, which makes them the natural first choice for a coloured diamond engagement ring. The strongest, purest yellows are sometimes called canary.
Radiant and cushion cuts intensify yellow, and a yellow gold setting, or yellow gold claws on a platinum band, deepens the colour further.
Pink diamonds are not coloured by an impurity. Their colour is thought to come from distortion in the crystal lattice, created by immense pressure as the diamond travelled through the earth. For decades, the Argyle mine in Western Australia was the leading source of pink diamonds. It closed in 2020, and fine natural pinks are rarer than ever.
Blue diamonds are coloured by boron and are among the rarest gems on earth. The Hope Diamond, now in the Smithsonian Institution, is the most famous of them. Natural blue diamonds of strong colour appear only rarely in the market.
Fancy colours can also be created by treatment, such as irradiation or HPHT processing, and grown in a laboratory. Each can be beautiful, and each is a very different proposition in rarity and value from a natural coloured diamond.
A report from an independent laboratory is essential. It states whether the colour is natural or treated, and whether the diamond is natural or laboratory-grown.
Put colour first: choose the strongest, most even colour you love, then think about clarity and size. Inclusions matter less in a coloured diamond than in a white one, as long as the stone looks clean and lively.
If a coloured diamond is on your mind, bring the idea to your consultation. We will talk through natural, treated and lab-grown options openly, and design the setting around the colour.
Nitrogen atoms within the crystal absorb blue light, which makes the diamond look yellow.
Pink colour is thought to come from distortion in the crystal lattice, caused by pressure as the diamond rose through the earth, rather than from an impurity.
Traces of boron in the crystal give blue diamonds their colour.
Fancy Vivid is the most saturated and most prized. Fancy Intense is also strong and rich in colour.
Ask for a report from an independent laboratory. It states whether the colour is natural or treated, and whether the diamond is natural or lab-grown.
Yellow gold, or yellow gold claws on a platinum or white gold band, deepens the yellow colour of the stone.
STILL HAVE QUESTIONS?
Bring the report, or the question, to a private appointment in central London or a video call. Consultations are complimentary.