Grading Polished Diamonds For Color
When we speak of color in diamonds, most people think of the beautiful reds, blues, and yellows we see when a diamond flashes in the sun light. In fact grading a diamond for color means deciding by which amount the diamond's "body color" deviates from the whitest possible (water like colorless) color. Nature provides a continuous darkening in the tints from white to yellow, white to brown, and white to green. Divisions are determined by the ability of the human eye to separate one tint from an adjacent one that is slightly lighter or darker. This concept should not be confused with the sparkle, brilliance, or scintillation of the diamond.
Because of the diamond's high brilliance and dispersion of light, the color grade cannot be accurately determined by looking at the stone from the top (face up) position. It is best to observe color by examining the stone through the side of the pavilion (bottom of the stone) with the diamond upside down in a white paper grading trough. Please note in the illustration below the stone can be examined in several positions to obtain an accurate color grade.
GIA Gemological Institute of America pioneered the universal grading system in the early 1940's to supersede all confusing grading systems in use at that time. The GIA color grading classification starts from D, the finest color (colorless), and proceeds through the alphabet to z getting progressively more yellow. A set of master comparison stones calibrated to the exact color of every-other color: E, G, I ... is the most reliable method of grading diamonds for color. When compared in a standard viewing box or white folded paper the master stones are placed on either side of the diamond until the stones are sorted into the proper descending color values. This allow for the accurate color grading of the diamond.
The grades D, E, F are exceptionally fine white diamonds being the only grades referred to colorless. E color diamonds are extremely close to D color diamonds, however the color variance can only be detected in a controlled grading environment. The variance in price per carat between D and E color is significant at the wholesale level reflecting the rarity of the diamonds in the market. The chart below illustrates the shift in pricing.
Price movement as diamond color diminishes, while holding all other quality classifications constant. Prices are New York 47th Street Wholesale prices 12/27/02.
Knowing the subtle differences between the sub-groups in the color grading classification system and the major impact these changes have on the wholesale price, it is imperative the client requires a Diamond Grading Report from an independently recognized company. The cost of a Diamond Certificate is a small price to pay to insure the diamond quality you pay for is the diamond quality you receive.