Diamond Color
Most people, untrained in grading diamonds, think of diamonds as colorless, or perhaps white or even blue. While diamonds do come in all colors of the rainbow, those with color (as opposed to colorless), or those with color beyond the normal range of yellow to brown or gray, are generally referred to as fancy colors. The general reference to diamond color pertains to the subtle differences in the depth of the body color. Most diamonds are yellow to brown therefore the less color, the more rare the diamond. Diamonds are the only gem in which the absence of color indicates more value.
Why are there differences in color? It depends on the kinds of atoms in a diamond and how they are arranged and bonded. An ideal, and colorless diamond would be 100 percent carbon, perfectly bonded in a uniform isometric arrangement, and therefore colorless. Most gem diamonds, however, contain traces of impurity (usually less than 0.05 percent of its weight). Nitrogen, the most common impurity, colors the diamond yellow. When boron atoms are present in a diamond, the diamonds look blue. Fluorescence, another common interaction between light's energy and the atoms in a diamond can also cause bluish hue. In about one half of all gem stone diamonds fluorescence is visible under special lighting (“black lights”). Stronger fluorescence can make a yellow diamond look white under daylight, while too much fluorescence can make a diamond look oily or dirty.
In the 1950s, the Gemological Institute of America (GIA) developed a color grading scale for diamonds that is the most commonly used scale in the country today. The scale begins with D (colorless) and continues through Z (light yellow). Color depth can be analogous to adding one or more drops of yellow food coloring to a clear glass of water. Each drop deeps the tone and saturation of the water, but the hue (yellow) has not changed. Below is a sample of representation of the difference in the GIA scale.
It is important here to note that neither this photograph, nor any photograph can accurately reproduce the subtle differences between the different grades. Neither can it be reproduced on paper. The only way a diamond can be accurately graded is un-mounted, face down, on a white backing, under white light and next to certified master graded stones (stones which have been verified as a particular color grade). Every aspect of a diamond is measured in minute differences. Color is no exception. If you've ever tried to match fabric or paint at a store without a sample from home, you know how difficult a task that can be. If you saw 10 different brands of “white” paper independently from each other, you probably couldn't see a difference. If you saw those pages side by side, however, you could probably see subtle differences in color. Color, in such subtle difference, generally cannot be memorized. Jewelers would never buy diamonds without inspecting them under the correct lighting conditions without the correct tools. Why should you?
Diamond color is graded from the bottom - the pavilion. This is one reason why a mounted diamond cannot be graded accurately. A two to three grade color range is often estimated when appraisals are done on mounted diamonds. Mounted diamonds also tend to draw the color of the metal in which they are mounted. The size of a diamond also influences color, because the farther light has to travel through the stone, the more light may be absorbed and the easier it is to see the diamonds color. Color grades D through F are so slight that they are best described as differences in transparency. In diamonds .25 ct. or smaller these grades are (for all intent purposes) colorless. In stones .50 ct. (1/2 carat) and smaller, diamonds graded between G and I, generally appear colorless once mounted and viewed face-up (from the top verses the bottom [pavilion]). J-L graded diamonds weighing .50 ct., or less, viewed in yellow gold mountings face-up appear very nearly colorless. In white gold settings, however, most people can usually see some color in the J-L color grades.
