While we generally think of diamonds as clear and colorless the fact is that color is one of the four characteristics of diamonds that determines their value. A diamond that is perfect – i.e., chemically pure with no imperfections is transparent and has no color or hue. Most natural diamonds that are the size of gems are not perfect, however. Diamond color is affected by structural defects in the diamond’s crystal lattice and by chemical impurities. Color isn’t all bad for a diamond, however. Depending on the intensity of the color, and of the hue, the color can actually enhance its value.
Most white diamonds, for example, cost less if they have a yellow hue that the naked eye can detect. In contrast, blue or pink diamonds as so intense in color that they have a dramatic look. The Hope Diamond is one example of this.
Most diamonds that are used as gems are almost totally transparent with just a little tint. These are called white diamonds. Nitrogen is the most common diamond impurity, as it replaces a little bit of the diamond’s carbon atoms and thus gives off a brownish or yellow tint. This is a very common effect in white diamonds. A diamond is very rare if this coloration is not detected.
Diamonds are rated according to their coloration, with ratings from a high quality (low color) D to a bright yellow Z, the lowest rating and quality. This system is devised through the use of natural diamond benchmarks whose color grade is known and whose lighting is carefully controlled. Diamonds that have the higher grades of color are the rarest and thus the most costly.
What’s confusing about the grading, however, is that the lower end of the rating system, the Z diamonds, are priced comparatively high as well, because they are difficult to find. Diamonds whose ratings are D, E or F are considered to be colorless, while G, H, I and J are labeled near-colorless. A rating of K, L or M of a diamond means that it is considered slightly colored, while N, O, P, Q, R, S, T, U V, W, X or Z rating diamonds will almost always look brown or light yellow.