Fancy colored diamonds are natural diamonds with distinct color, such as yellow, blue, pink, green, orange or red. Colors come from trace elements like nitrogen and boron, from distortions in the crystal lattice, or from natural radiation. Strong natural color is rare, and fancy colored diamonds are graded on a separate system from the D-to-Z scale, with color dominating their value.
Where fancy color begins
White diamonds are graded on the D-to-Z scale covered in the diamond color guide. Yellow and brown diamonds with more color than a Z master stone move into the fancy category. For any other hue, such as blue, pink or green, even a faint trace of color puts the stone in the fancy color system.
Most fancy colored diamonds sold are yellow or brown. Pink, blue and green stones are much rarer, and natural red diamonds are among the rarest gems of any kind.
What causes color in diamonds
Each color has its own cause, usually tied to an impurity or a defect in the carbon lattice. The diamond chemistry and formation page explains the diamond types mentioned here.
| Color | Usual cause |
|---|---|
| Yellow | Nitrogen. Clustered nitrogen (N3 centers) gives pale Cape yellow; isolated nitrogen in Type Ib stones gives intense canary yellow |
| Orange | Nitrogen-related defects that absorb blue and some green light |
| Brown | Plastic deformation of the lattice, which distorts the crystal |
| Pink and red | Plastic deformation, seen as colored bands of graining |
| Purple | Related to plastic deformation, often with hydrogen |
| Blue | Boron in Type IIb diamonds; some gray-blue stones owe color to hydrogen |
| Green | Exposure to natural radiation, which knocks carbon atoms out of place |
| Black | Dense dark inclusions, such as graphite, or heavy fracturing |
| Gray | Hydrogen or boron, or fine dark inclusions |
Yellow from nitrogen
Nitrogen absorbs light at the blue end of the spectrum, and the eye reads what remains as yellow. Most yellow diamonds are Type Ia, where nitrogen sits in clusters. The deepest canary yellows often come from Type Ib stones with isolated nitrogen atoms.
Blue from boron
Boron atoms in the lattice absorb red, orange and yellow light, leaving blue. Boron-bearing Type IIb diamonds also conduct electricity, a property labs use to confirm natural blue color.
Pink, red and brown from deformation
Pink, red and brown diamonds usually owe their color to plastic deformation, a twisting of the lattice under pressure and heat in the mantle. The color often appears in parallel bands called graining. Western Australia's former Argyle mine, which closed in 2020, was the best-known source of pink diamonds, and it produced large amounts of brown diamond as well.
Green from radiation
Natural radiation from nearby radioactive minerals, over very long periods, displaces carbon atoms and creates a defect called the GR1 center, which absorbs red light. Often the radiation reaches only a thin surface layer, so many natural green diamonds show their color as a green skin on the rough. Cutters sometimes leave bits of that skin on the girdle as evidence of natural color.
How fancy color is graded
GIA grades fancy color with the diamond face-up, the way it will be worn, comparing it against color references under controlled light. The grade has three parts:
- Hue, the main color, such as yellow, pink or blue.
- Tone, how light or dark the color is.
- Saturation, how strong or pure the color is.
These combine into a grade description from the list below, ordered roughly from weakest to strongest color:
- Faint
- Very Light
- Light
- Fancy Light
- Fancy
- Fancy Intense
- Fancy Vivid
- Fancy Deep (strong color, darker tone)
- Fancy Dark (darker tone, less saturation)
The report names the hue with any modifying colors, such as "Fancy Intense Purplish Pink" or "Fancy Vivid Yellow." Modifiers matter: a pure pink and a brownish pink with the same intensity term can differ greatly in value. Some hues, such as red, rarely occur in light tones, so the grade descriptions available depend on the color.
Cut and clarity matter less for fancy colors than for white diamonds. Cutters often choose radiant, cushion and other mixed cuts that intensify color face-up instead of maximizing brilliance, so a fancy colored stone with modest clarity can still be highly prized. The diamond clarity guide covers clarity grading.
Famous fancy colored diamonds
Several famous diamonds are fancy colors.
- The Hope diamond, about 45.52 carats, is a gray-blue Type IIb stone. It has a long history traced back to a larger blue diamond sold by the traveler Jean-Baptiste Tavernier to Louis XIV in the 1660s, and the Smithsonian has held it since Harry Winston donated it in 1958. Under ultraviolet light it glows red-orange for some time after the light is switched off.
- The Dresden Green, about 41 carats, is the best-known natural green diamond. Its color comes from natural radiation, and it has been held in Dresden since the 18th century.
- The Tiffany Yellow, about 128.5 carats, was cut from a rough crystal found at the Kimberley mines in South Africa in the late 1870s.
The diamond mines of the Golconda region produced several historic colored stones, including blue diamonds connected to the Hope's history.
Treated color
Diamonds can be treated to add or change color, and treated stones sell for a fraction of natural color equivalents. The main methods are:
- Irradiation, often followed by heating (annealing), which can produce green, blue, yellow, pink, red or purple.
- HPHT processing, which can turn some brown Type Ia stones yellow or greenish yellow, and some Type IIa stones pink or blue.
- Coatings, thin films on the surface that add color and can wear or scratch.
- Multi-step processes that combine HPHT, irradiation and annealing.
Gem labs identify treated color mainly with spectroscopy, which detects defects created by treatment. Color zoning patterns, such as color concentrated near the culet or along facet edges, can also give treatment away. Grading reports state when color is treated. The diamond treatments page covers each method.
Lab-grown colored diamonds
Laboratories can grow diamonds in many colors. HPHT growth with nitrogen yields yellow, adding boron produces blue, and post-growth treatment produces pink and other colors. These stones have the same chemistry as natural colored diamonds and need lab testing to identify. The lab-grown diamonds page explains how they are made and detected.
Frequently asked questions
What is the rarest diamond color?
Natural red is generally considered the rarest, followed by colors such as green, purple and blue in strong saturations.
What makes a pink diamond pink?
Most pink diamonds owe their color to plastic deformation of the crystal lattice, which creates color bands called graining.
Are yellow diamonds rare?
Pale yellow diamonds are common. Intense and vivid yellows are much rarer and are graded as fancy colors.
How can I tell if a colored diamond is treated?
You need a report from a gem lab. Spectroscopy and microscopic examination of color zoning reveal most treatments.