Figure 1. The colours of a diamond courtesy of https://www.diamonds.pro/wp-content/uploads/diamond_color_chart1.gif

What Is A Fancy Coloured Diamond?

Fancy coloured diamonds are any colour of diamond that is not colourless, or if yellow, is darker than colour grade Z on the GIA colour grading scale. Although we tend to think of diamonds as being colourless and rare, there are many different colours of diamond. The various colours of diamonds come from trace impurities in the diamond or from slight changes to the crystalline structure due to immense pressure and heat below the Earth's surface.

Coloured diamonds are much rarer than regular diamonds. It is estimated that for every 10,000 colourless diamonds there is only one fancy coloured diamond. So rare are some coloured diamonds that only six red diamonds graded by the GIA as fancy red have ever been mined!

Is It Real?

Perhaps because natural fancy coloured diamonds are exceedingly rare, techniques have been developed to create coloured diamonds from low-grade brown or clear diamonds using irradiation. Although such diamonds have been treated with radiation, there is no residual radiation, and such diamonds are entirely safe. Irradiation is a permanent measure.

A lower-cost, but less permanent way to create coloured diamonds is to coat the diamond with a coating that changes or adds colour to the stone.

High pressure and high temperature (HPHT) have been found to both make diamonds colourless and to add colour.

Treated Diamonds Have Lower Value

The value of diamonds receiving these treatments is much lower than for natural fancy coloured diamonds. While reputable sellers will disclose treated diamonds, some buyers have been misled by such practices. Fraud is profitable since it enables low-grade stones to be passed off as rare and valuable natural diamonds.

You Can Detect A Fake

While some colour treatments or enhancements are hard to detect, the most common form, HPHT, is quite recognisable. The saturation of the colour will be so intense that, rather than looking like a diamond, the stone will look like a semi-precious gem. GIA assessment reports provide information about the origin of the colour, natural or treated, making GIA certification a requirement when buying a fancy coloured diamond.

How Are Fancy Coloured Diamonds Graded?

Fancy Coloured Diamond Colour Grading

The most important aspect of a fancy coloured diamond is its colour. Colour grading for coloured diamonds is much more complicated than for colourless gems because the colour of every diamond is unique. The grading of fancy coloured diamonds is carried out by highly skilled graders who specialise in coloured gemstones.

There are three criteria for grading colour:

1. Hue: the actual colour of the diamond using a range of 27 descriptions
2. Tone: how light or dark the colour is
3. Saturation: the strength of the colour

Hue is usually a combination of at least two colours where the dominant colour comes second as a noun, and the secondary colour comes first as an adjective. For example, 'Greenish Blue' would be a blue diamond with greenish tones modifying the purity of the blue.

If colours are equally strong, then the colour is shown as two nouns as 'Green Blue'. In the rare case of a pure colour, then there is no secondary adjective or noun, and the diamond would be shown as being 'Blue'.

Pure colours are very rare indeed and command very high prices.

GIA Fancy Diamond Colour Grades

The grading report takes all the information about colour, tone and saturation and gives each diamond a one- or two-word term to describe the tone and saturation. The range of terms is as follows:

Light coloured diamonds: Faint, VL or Very Light, Light, FL or Fancy Light,

Medium: Fancy

Dark: FD or Fancy Deep, FD or Fancy Dark, FI or Fancy Intense, FV or Fancy Vivid

Fancy Intense and Fancy Vivid are the rarest forms.