How to Grade Diamond Colour ?

Probably the best way to learn to color grade is to ask your jeweler to show you how. He or she will have some loose diamonds, a paper or plastic white grading tray, possibly a set of graded comparison diamonds called master stones and a good diffused (not bare) light source such as a daylight-equivalent fluorescent light. You might be surprised when the jeweler places the diamond upside down on the tray and has you look at the color through the pavilion (the backside of the diamond). This, however, is the most accurate way of seeing the fine nuances of color from one grade to another.

When you're judging diamonds for color, remember the following tips:

♦ Judge diamond color against a non-reflective white background. For example, you can fold a white business card in half and lay the diamond in the crease, or you can place the diamond in a white grading tray.

♦ Use comparison diamonds to determine a precise color grade. Even professional diamond graders realize that they cannot rely only on their color memory. They need master stones. You can get a general idea of color without comparison stones. If you see an obvious yellowish tint when you view the stone through the side, then the stone is probably in the K to Z grade range.

♦ Make sure that the master stones and diamonds to be graded are clean. Dirt can affect the colour grade.

Figure 1 - Diamonds of five different color grades ranging from D (colourless) to Z (light yellow). Do not use this photo to grade the colour of your diamonds. The printing & developing processes and paper colour usually alter the true color of gems in photographs.

♦ Place your diamond both to the right and to the left of the master stones. It's normal for it to look lighter on one side than the other.

♦ Pay attention to the grading environment. Colour grading can be affected by the lighting, the color of the surroundings and your clothes, the air quality, and the country you live in (the suns rays vary according to geographical regions) and the time of day and year. Yellow from your clothes, walls, gold mountings or sunlight can be reflected within the diamond.

♦ Be careful not to mistakenly downgrade larger diamonds. They often appear darker than small master stones of the same color grade because the colour is easier to see.

♦ Remember that precise color grading can only be done with loose diamonds. The color of the metal surrounding diamonds set in jewelry influences the appearance of the diamonds. Consequently, their color can only be estimated.

Even though you should grade diamonds with a daylight equivalent fluorescent light, before buying a diamond, look at it under other lighting such as halogen spotlights, daylight by a window, overhead fluorescent lighting and light bulbs. Then you won't be disappointed when you get home and the diamond looks different than in the store. Lighting has an important impact on the appearance of gems. Smart sellers have you view stones under the most favorable lighting conditions. But you won't always be wearing your jewelry in the same environment.