Pricing a fancy colour diamond is a difficult formula to capture due to the number of variables involved. The cost will be an approximation based on a combined reading of the diamond’s gemmological parameters with more subjective aspects of its aesthetic value.
A nuanced understanding of how a fancy colour diamond will be appreciated by the end market is fundamental to pricing a diamond correctly.
The rules of supply and demand
As with any other commodity, demand & available supply are the factors which govern the price of fancy colour diamonds; their value will change over time as these trends evolve. It is for this reason that some stones – despite their size or rarity – may not be as highly valued as others because they may be difficult to incorporate into wearable jewellery, or the colour could be undesirable at the time of sale.
It is vital for fancy colour diamond buyers to place greater significance on certain qualities when looking at the price of a stone. These qualities have been ranked in order of importance.
The quality of colour is by far the most important factor. The stronger the saturation level and brighter the tone, the rarer the stone. Diamonds that showcase vibrant colour will obtain significant premiums on their price. Colour saturation is measured from levels “Faint” to “Fancy Vivid”.
Colour dispersion refers to how evenly distributed the colour is through the diamond. There are several levels of colour dispersion, which allows for a wide range of quality even when the grade on the certificate is ‘Even’. The dispersion of colour throughout the stone is crucial to its value. A high level of colour dispersion is sought after as, more typically, dispersion is somewhat patchy or may exhibit a black, colourless frame. Stones without colourless patches are considerably more valuable.
In the fancy colour diamond sphere, we look for vibrant colour, saturation and character – the role of clarity is more important for colourless diamonds than for fancy colour diamonds. Clarity has little impact on the price of a coloured diamond, especially for very rare stones.
For example, there is a much bigger impact on price for a 5 carat Fancy Yellow in the VVS2-SI1 range, compared to a 1 carat Vivid Pink in the same range, where the clarity grade is inconsequential because Vivid Pink stones are so rare.
Naturally occurring fluorescence is a unique quality that some fancy colour diamonds possess, whereby they ‘glow’ another colour when exposed to UV light. More than 90% of diamonds that fluoresce produce a blue colour, and on rare occasions they may fluoresce yellow, orange or green.
Fluorescence in low to medium doses has no aesthetic impact on the stone and therefore should not detract from its value. In some cases, when the colour of fluorescence compliments the body of the stone, it may generate a stronger, more vibrant colour and drive up the price of the stone.
Some sources maintain that fluorescence gives the stone a hazy quality and reduces the value. However, less than 0.1% of diamonds that fluoresce exhibit these qualities. Pink diamonds in particular tend to fluoresce more strongly & frequently, and price is not negatively impacted by this factor.
Polish & Symmetry
The value of a fancy colour diamond primarily lies in facet alignment verses facet symmetry, as facet alignment can enhance the stone’s colour intensity. For colourless diamonds symmetry is an important quality, but in a fancy colour diamond symmetry will not create an aesthetically pleasing appearance. Fancy colour diamonds are often cut “free-style” to avoid issues that may arise with poorer colour dispersion and lower yield from the rough (meaning how much of the rough diamond is lost during cutting). The importance of polish and symmetry is frequently overrated for fancy colour diamonds.
The depth of a diamond refers to the height of a stone divided by its width. Fancy colour diamonds with low depth percentage are greatly valued as they look larger than their actual weight (this is true as long as the colour distribution of the stone is not compromised because of the shallowness of the diamond). Very shallow stones earn a premium because of their rarity. Most fancy colour diamonds are cut with a high depth percentage, so when we see a shallow stone with excellent colour retention, it deserves a premium.