Most diamonds are graded on the absence of colour, running from D at colourless down to Z. Fancy coloured diamonds sit outside that scale entirely. Here, colour is the point rather than the flaw, and everything about how they are graded and priced works differently.
The intensity scale
Fancy colours are graded on saturation rather than absence. The ladder runs from Faint, through Very Light, Light, Fancy Light, Fancy, Fancy Intense, up to Fancy Vivid, with Fancy Deep and Fancy Dark describing stones where tone rather than saturation dominates.
Fancy Vivid is the top of the intensity scale, describing the most saturated expression of a hue. Grading is done under controlled lighting, assessing hue, tone and saturation together.
Hue modifiers matter too. A purplish modifier on a pink generally adds appeal, a brownish modifier generally reduces it, and an orangy one is broadly neutral. This is why a report says something like Fancy Vivid Purplish Pink rather than just pink.
Where the colours come from
Different mechanisms produce different hues, and they are not all understood equally well.
Blue comes from boron in the crystal lattice, which also makes the stone a semiconductor.
Yellow comes from nitrogen.
Pink and red are the odd ones. The colour appears to come from plastic deformation of the crystal lattice during formation, distorting the structure in a way that absorbs certain wavelengths. The mechanism is still not fully understood, which is part of why these hues are so scarce in nature.
The 4Cs work differently here
This is the part that surprises people who have bought a colourless diamond before.
Colour dominates. Intensity drives value far more than any other factor. A smaller stone at a higher intensity grade can be worth more than a larger stone at a lower one.
Clarity matters much less. Inclusions that would seriously damage the value of a colourless stone are often accepted in a fancy colour, because colour is what is being bought.
Cut is optimised for colour, not brilliance. A colourless diamond is cut to maximise light return. A fancy colour is cut to present the strongest face-up colour, which is why cushion, radiant and emerald cuts are common in this category. They concentrate hue rather than sparkle.
Our guide to the 4Cs covers how these work for colourless stones.
Natural and lab grown coloured diamonds are different markets
This distinction matters more for coloured stones than for colourless ones, and it is worth being blunt about.
Natural fancy colours, particularly pinks, blues and reds, are extraordinarily scarce. The Argyle mine in Western Australia, the world's dominant source of pink diamonds, closed permanently in November 2020, and that supply has not been replaced. Natural stones in these hues sit in a collector market with prices to match.
Laboratory grown fancy colours are real diamonds with genuine colour, produced through controlled growth conditions. They give you the visual result at a small fraction of the natural price, and for anyone who wants a vivid coloured stone to wear, they are the accessible route.
What they do not carry is the scarcity of a natural stone, and nobody should buy one expecting it to behave like one. As with lab grown colourless diamonds, prices in this category have fallen as production has expanded. Buy it because you want the stone.
Our comparison of lab grown and natural diamonds covers this in more depth.
Certification is not optional
For fancy colours a report does more work than it does for colourless stones.
It states the hue, any modifiers and the intensity grade, all of which are subjective judgements that need an independent assessor. Critically, it also states whether the colour is natural or the result of treatment, since irradiation and high pressure high temperature processing can both induce or alter colour. And it states whether the stone is natural or laboratory grown.
Without a report from a recognised laboratory, none of that is verifiable. Our guide to diamond certification covers how to read and verify one.
Frequently asked questions
What does Fancy Vivid mean?
The highest intensity grade on the fancy colour scale, describing the most saturated expression of a hue.
Why are pink diamonds so rare?
Pink colour appears to come from plastic deformation of the crystal lattice, a mechanism that is uncommon and still not fully understood. The Argyle mine, the dominant source, closed in 2020.
Does clarity matter for coloured diamonds?
Much less than for colourless stones. Colour intensity is the dominant value factor, and inclusions are more readily accepted.
Are lab grown coloured diamonds real?
Yes. They are real diamonds with genuine colour. They do not carry the scarcity of natural coloured stones and are priced accordingly.
Can diamond colour be treated?
Yes. Irradiation and high pressure high temperature treatment can induce or alter colour. A grading report from a recognised laboratory will disclose this.
Our coloured stones
We hold a 1.06ct laboratory grown Fancy Vivid Pink, IGI certified, alongside colourless lab grown and natural stones. See the range or visit the showroom at 124 Peterborough Street, Christchurch.