A fancy coloured diamond is valued for the colour it shows face-up. Whether it is natural or laboratory-grown, a gemmological laboratory examines the diamond and documents its colour and identifying characteristics. The grading process helps you understand what you are shopping for, how the colour is described, and whether the diamond’s colour is natural, treated, or associated with laboratory growth.
What makes a diamond “fancy coloured”?
Most diamonds with little or no visible colour are described on the familiar D-to-Z scale. A diamond with colour outside that range such as a vivid pink, blue, green, or a more saturated yellow or brown may be described as fancy coloured. Coloured diamonds come in many hues, from subtle champagne and cognac shades to vivid pink, blue, green, yellow, and red.
Fancy colour grading works differently from the D-to-Z scale. D-to-Z grading measures the relative absence of colour. Fancy colour grading describes the colour that is present.
The three main parts of fancy colour grading
Gemologists assess a fancy coloured diamond in controlled lighting and describe three related features:
- Hue: The colour family, such as pink, blue, yellow, or green. A diamond may also have a secondary hue, such as greenish yellow or purplish pink.
- Tone: How light or dark the colour appears.
- Saturation: How strong or vivid the colour appears.
The laboratory combines these observations into a colour description or grade. Depending on the grading system and the diamond, report terms can include grades such as Fancy Light, Fancy, Fancy Intense, Fancy Vivid, Fancy Deep, or Fancy Dark. The exact terms and presentation can vary by laboratory, so it is helpful to read the report issued for the specific diamond.
Gemologists also consider how evenly the colour is distributed across the stone. A colour that appears strong and balanced face-up may be described differently from one that is uneven or concentrated in certain areas. Cut can affect the colour we see: fancy coloured diamonds are often fashioned to bring out their face-up colour, even when that means choosing different proportions from those typically sought in a colourless diamond.
How natural fancy coloured diamonds are assessed
Natural diamonds acquire colour through conditions and trace elements present as they form in the earth. A gem laboratory first identifies the diamond and evaluates its colour. It may also assess whether the colour is natural or the result of a treatment. Treatments can alter or intensify a diamond’s appearance, so the report’s comments about colour origin and any detected treatment are important parts of the description.
A natural fancy coloured diamond report may include its colour grade, carat weight, measurements, clarity characteristics, polish, symmetry, and other details. Some reports also include a plotted clarity diagram or information about geographic origin, depending on the report type and laboratory service. Geographic origin is different from colour origin: one refers to where a natural diamond came from, while the other describes whether its colour is natural or treated.
How lab-grown fancy coloured diamonds are assessed
Lab-grown diamonds have the same essential chemical composition and crystal structure as natural diamonds, but they are created using technology rather than forming in the earth. Their origin is identified through laboratory testing, not by appearance alone.
For a lab-grown fancy coloured diamond, a grading report can describe the colour and other gemological characteristics while identifying the diamond as laboratory-grown. Depending on the laboratory and report, it may also state the growth method such as HPHT or CVD and whether post-growth treatment was detected. Some lab-grown diamonds develop colour during growth; others may receive a post-growth treatment that changes or enhances their colour. The report helps explain what the laboratory was able to determine about that particular stone.
The colour vocabulary may resemble that used for natural fancy coloured diamonds, but a report’s scope depends on the issuing laboratory and the service selected. Check that the report clearly states the diamond’s origin and provides the colour details you need.
Does the grading process differ between natural and lab-grown diamonds?
The basic colour characteristics hue, tone, saturation, and distribution are relevant to both natural and lab-grown fancy coloured diamonds. The main additional questions are about origin and colour formation. For a natural diamond, the report can address whether its colour is natural or treated. For a lab-grown diamond, it identifies laboratory growth and may describe the growth method and any post-growth treatment.
Grading terminology and report formats are not identical across every laboratory. When comparing two diamonds, look at the actual report details rather than relying on a single grade word or a seller’s description.
What else should you look for on a report?
Colour is often the most influential quality factor for a fancy coloured diamond, but it is not the only one. Review the report for:
- Natural or laboratory-grown origin
- The colour description and grade
- Any comments about colour treatment or post-growth treatment
- Carat weight and measurements
- Clarity characteristics, if included
- Cut, polish, and symmetry information, where provided
- The issuing laboratory and report number
A grading report is an independent gemological assessment. It describes a diamond; it is not an appraisal or a guarantee of resale value. You can usually verify a report number through the issuing laboratory’s report-check service.
Choosing a fancy coloured diamond
The best colour is the one you enjoy seeing. Compare diamonds in person or through clear, well-lit product images, and consider how the hue and intensity look from different angles. Read the grading report alongside the photographs, since a grade description cannot fully capture the way an individual diamond appears to your eye.
Explore Jacob Mercari’s fancy coloured diamonds and loose diamond collection to compare available natural and lab-grown options online. Each diamond has its own colour, character, and report details to review before you choose.
References:
https://www.gia.edu/fancy-color-diamond-quality-factor
https://www.gia.edu/fancy-color-diamond/buyers-guide
