Grading the rainbow: how to buy a fancy colour diamond engagement ring

Forget the four Cs of white diamonds and get to know the grading system for coloured diamonds - based on hue, tone and saturation - instead.

Boghossian pink diamond engagement ring

By Åse Anderson 

Most of us are familiar with the four Cs that are universally used to determine the quality of a white diamond, but coloured diamonds also have their own grading system based on the intensity of their hue. 

Natural coloured diamonds are known as fancy colour diamonds and are incredibly rare. They come in many different shades ranging from blue, brown or pink, to green or yellow diamonds. The fire and brilliance that is so highly prized in white diamonds is less important when it comes to fancy colour diamonds. 

While a radiance-boosting cut is arguably the most important of the four Cs for white diamonds, the most vital factor for coloured diamonds is the quality of the colour. When cutting a coloured diamond, the goal is always to maximise its hue, which is why the stones sometimes have open cutlets and large tables. This would be a complete no-no on a well-cut white diamond. Clarity is also less important, and inclusions do not usually detract from the intensity of the diamond’s colour. 

View our video guide to the four Cs here 

The GIA has developed a grading system for coloured diamonds that is used worldwide and rates their colour according to three criteria: hue; tone; and saturation. The hue is the characteristic colour of the diamond, while the tone can be either at the lighter or darker end of the spectrum, and saturation refers to the depth of colour. 

Each diamond falls into one of 27 recognised hues, which are often described using two or more colours, such as orangey yellow or purple pink. The tone and saturation are described using terms such as Fancy Light, Fancy Intense, Fancy Vivid, Fancy Dark and Fancy Deep. The difference in intensity can clearly be seen when you compare the Fancy Intense stones in the Boodles yellow diamond engagement ring with the Fancy Vivid orangey yellow diamond in the Boghossian engagement ring from its Kissing Diamonds collection.

Diamonds with a darker and more saturated colour are usually deemed to be more valuable, but lighter-coloured diamonds can add an ethereal, romantic look to a jewel, especially if the stone is set in platinum or white gold. 

Coveted both for their beauty and rarity, pink diamond engagement rings are among the most sought after in the world, although their steep price points mean their splendour is a treat reserved only for a lucky few. The luminously bright colour of the round Fancy Vivid purple pink diamond in the Graff engagement ring above is beautifully enhanced by the white diamonds on the shoulders. 

See more pink diamond engagement rings

For an unusual engagement ring with an eye-catching pop of colour, the 1888 Master Diamonds De Beers engagement rings, set with stones that have been hand-selected for their exceptionally intense hues, are among the finest in the world.

View more 1888 Master Diamonds De Beers engagement rings

The spectacular spectrum includes a Fancy Dark yellowish green emerald-cut diamond solitaire, and a round brilliant Fancy Deep brown orange diamond, both surrounded by white pavé diamonds. 

If your budget allows, when it comes to diamonds, the rainbow really is yours for the taking.

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