Fancy diamonds are diamonds which are richly colored, rather than clear or white. True fancy diamonds are rare, and most of the colored diamonds on the market are artificially colored through a variety of laboratory techniques. The value of this type of diamond can range considerably, depending on the hue and intensity of the diamond, along with the cut and carat weight. The popularity of colored diamonds for formal jewelry has waxed and waned, although some of the most famous diamonds in the world, such as the Hope Diamond, are fancy.
The unique colors of fancy diamonds are naturally caused by impurities in the stone. The high pressures which diamonds are subjected to while they are forming often admit impurities, which can detract from the price if they only faintly discolor the stone. If the impurities appear in large amounts, however, the diamond will be considered fancy, and can command a very high price, especially if the color is rare. Nitrogen and boron both cause colors to appear in diamonds, as does irradiation, which causes the diamond to turn green. When artificially coloring diamonds in the lab, they are subjected to radiation, heat treatment, or high pressure.
When grading a fancy diamond, the first thing to determine is the hue of the stone. The range of colors for diamonds includes yellow, green, blue, brown, orange, pink, and red. Brown diamonds are sometimes listed as “claret” or “champagne” diamonds, because the brown color has a low sales value. After the hue of the diamond is determined, the intensity of the color is graded. Many diamond graders use the Gemological Institute of America (GIA) scale, which starts with “faint” and moves through very light, light, fancy light, fancy, fancy dark, fancy intense, fancy deep, and fancy vivid. A fancy vivid will have the richest color, and tends to be more valuable.
Like other diamonds, fancy diamonds are also graded using the four C's of cut, color, clarity, and carat weight. Carat weight is the size of the diamond; in general, a diamond with a larger carat weight will be more valuable, especially if it has a strong color. Cut is also an important evaluating tool, because a cut can make or break a diamond in the setting. If cut well, a diamond's facets will brilliantly reflect light, creating the eye dazzling impact which most consumers associate with diamonds. If poorly cut, the diamond will appear listless and dull. The shape of the cut is also important, and fancy diamonds are often cut into unusual shapes to enhance their natural beauty. Finally, the clarity of the diamond is examined. Clarity is not as important for these diamonds as it is for clear ones, but a high number of inclusions will devalue the stone.