Fancy colour diamonds
Beyond Z, colour stops being a fault and becomes the point. Pick a colour and move one diamond through GIA's fancy grades, see where each grade sits by lightness and strength, learn what gives a diamond its colour, and how a laboratory tells natural colour from treated or laboratory-grown.
Where each grade sits
GIA describes a coloured diamond's colour by its hue, its tone (how light or dark) and its saturation (how strong). The fancy grade names the combined effect of tone and saturation. The map below shows the idea; the exact boundaries are set by GIA's reference stones, not by numbers.
Every grade of this colour
The same stone at each grade, face-up. Tap one to load it above.
Graded face-up, the opposite of D to Z
D to Z: looking for the absence of colour
Near-colourless diamonds are graded table-down on a white tray against masterstones, because face-up sparkle hides faint body colour.
Fancy colour: judging the colour itself
Coloured diamonds are graded face-up, the way the colour is seen in jewellery, under controlled light in a neutral surround, and compared with GIA's reference stones to bracket hue, tone and saturation.
One of 27 hues
The grader chooses one of 27 hues (for example purplish pink or greenish yellow), then the fancy grade for tone and saturation: a report might read "Fancy Intense purplish pink".
Cut for colour
Coloured diamonds are usually cut to make the most of their colour rather than their light return. Cut styles such as the radiant can make a yellowish stone show a fancy yellow face-up. Compare three cuts of the same material below.
Same body colour and size in three cuts, ray traced. Longer light paths in the mixed cuts deepen the face-up colour. Illustration.
What gives a diamond its colour
A pure diamond is colourless. Colour comes from tiny defects in the crystal: atoms of another element, or carbon atoms out of place. The same colour can have more than one cause.
Natural, treated or laboratory-grown
Natural colour
Colour formed in the earth. GIA's coloured diamond reports state the colour origin; an identification and origin report is offered for natural-colour diamonds that have not had unstable treatments.
Treated colour
Colour changed after mining: irradiation, often followed by heating (annealing), high pressure and high temperature (HPHT), or a surface coating. Treatments range from simple to very high-tech; treated colour must be disclosed, and coatings can wear.
Laboratory-grown
Diamonds grown in a laboratory can also be yellow, blue, pink and other colours. A laboratory separates them from natural diamonds with spectroscopy and growth-pattern imaging; they are reported as laboratory-grown.
What you can and cannot see
Natural, treated and laboratory-grown colour can look identical. Only a gemmological laboratory can establish the origin of a diamond's colour. JewelLoop never values, identifies or prices stones.
Care
Warm soapy water
Always safe for a natural, untreated diamond (GIA).
Avoid sudden heat
Sudden temperature changes can cause thermal shock and create or extend fractures and cleavages (GIA).
Ask before cleaning treated stones
Coated or fracture-filled diamonds need gentler care: ultrasonic and steam cleaners can damage coatings and fillers.
Sources
Grade terms and their order: GIA, When is a colored diamond considered fancy?; GIA, Colored diamonds: a colorful anniversary (2014): Fancy Deep and Fancy Vivid added in 1994 to Faint, Very Light, Light, Fancy Light, Fancy, Fancy Dark and Fancy Intense. J. M. King, T. M. Moses, J. E. Shigley and Y. Liu, Color grading of colored diamonds in the GIA Gem Trade Laboratory, Gems & Gemology, Winter 1994.
Hue, tone and saturation, 27 hues, colour origin on reports: GIA 4Cs, Colored diamond grading. Face-up grading against reference stones, D-to-Z table-down: GIA 4Cs colour grading articles. Cut for colour, rarity of hues, black diamonds, care: GIA, Fancy color diamond buyer's guide.
Causes of colour: J. E. Shigley and C. M. Breeding, Optical defects in diamond: a quick reference chart, G&G Summer 2013; S. Eaton-Magaña et al., Natural-color blue, gray, and violet diamonds, G&G Summer 2018.
Images: ray-traced diamonds (JewelLoop renderer, diamond refractive index and dispersion). The colours are computed for display and are illustrations: GIA publishes no colour coordinates for its grades, and grading is done against physical reference stones, never from a screen.