The absence of color is characteristically a marker of quality in a diamond, along with the other 3C's of diamond grading: Clarity, carat, and cut. The less color a diamond possesses, the more true color it reflects, resulting in that brilliant sparkle that has been valued since time immemorial. Colorless diamonds are typically labeled on a color scale from D to Z, with D being truly colorless and Z possessing clearly visible yellow or brown color.
Where the colorless scale ends, begins the world of colored diamonds (interchangeably referred to as “fancy color diamonds”). About one in 10,000 diamonds will fall off the color grading scale because its yellow or brown color is more intense than the Z cutoff, or, less commonly, because it displays one or more other colors, like blue, pink, green, purple, and even red.
What’s incredible about fancy colors is that under the right conditions, the same impurities that depreciate a colorless diamond result in some of the most precious, and therefore valuable, stones in the world! Fancy color diamonds are born when elements other than carbon in a diamond’s atomic structure alter its appearance and result in different colors.
To date, over 300 different hues and fancy color combinations have been discovered. From the more popular pink and yellow diamonds, to the highly prized red and green diamonds, colored diamonds can be found in every shade of the rainbow.
Unlike their colorless counterparts, which exist in fairly large quantities in nature, fancy color diamonds constitute an ever shrinking percentage of the rough diamonds mined and manufactured each year. Currently, only about .01% of all carats of diamonds mined is colored, and if trends continue, eventually the earth's supply of colored diamonds will be depleted.
Furthermore, the vast majority of fancy colors found are under one carat, compounding their worth and desirability.
Although if you hear the word “diamond” you typically think of a brilliant, colorless stone, diamonds in fact come in many different colors. The ideal colorless diamond, graded D, is completely clear because it is made of 100% pure carbon, but this is pretty much impossible to find in nature. Trace amounts of other elements such as nitrogen and boron are generally found in diamonds, and under certain conditions these trace elements can result in beautiful colors.
Fancy color diamonds are atomically and structurally identical to a colorless diamond, but the color comes from chemical impurities or structural defects within the crystal lattice work of the stone.
Fancy color diamonds are categorized in two types, depending on the quantity of nitrogen found within their atomic structure. The diamonds in each category differ in the ways that the nitrogen atoms bond with the carbon atoms in the diamond’s internal structure.
Diamonds with nitrogen in their atomic structure comprise 98% of all natural diamonds. Nitrogen absorbs blue light and can have different effects on the diamond’s appearance, depending on the way that the atoms bond with each other.
Nitrogen-containing diamonds are further categorized based on the different ways that the nitrogen atoms bond with the carbon
Diamonds in the Type Ia class contain nitrogen clusters scattered throughout their compound element structure. The majority of both colorless and colored diamonds fall into this category.
Type Ia diamonds are subdivided into two types in which the nitrogen atoms are clustered differently
The nitrogen atoms are found scattered around the carbon lattice in pairs know as A-aggregates. When the bonds are formed this way, no visible light is absorbed and the result is a totally colorless stone.
Nitrogen atoms are scattered around the carbon lattice in clusters of 4 known as B-aggregates. Similar to the Type IaA diamond, no visible light is absorbed and the color of the stone is not affected.
Most Type I diamonds are actually a combination of Type IaA and Type IaB—known as Type IaAB Diamonds. This means that the nitrogen is clustered in threes and actually does absorb some visible light, resulting in a yellow or brown color.
When the nitrogen atoms are spread evenly throughout the carbon lattice, a Type Ib Diamond is formed. They are much rarer than Type Ia, making up only about .1% of all natural colored diamonds. These diamonds absorb blue and green light, making for intense canary yellows, oranges, browns, and sometimes even greens.
Type II diamonds are different than Type I diamonds in that they are basically nitrogen free. They are extremely rare, only comprising about 2% of all natural fancy colored diamonds. They are further classified into two groups.
These diamonds are the purest diamonds that exist, containing minuscule amounts of any element other than carbon. The result is prevalently a pure colorless diamond, highly prized by collectors all over the world.
Even this pure specimen can still become a colored diamond as it endures the journey to the surface of the earth from miles underground where it was formed. The incredible pressure can twist or bend the carbon tetrahedrons out of shape. This imperfect carbon lattice does absorb some light, resulting in beautiful yellows, oranges, browns, and more rarely, even pinks, purples and reds.
Type IIb diamonds contain no nitrogen, but they are unlike Type IIa diamonds due to the addition of boron to their chemical composition. Boron absorbs red, yellow and orange light so it is the only element in a diamond that results in a natural blue or grey color.