Diamond Color Quality - from Perception to Reality

The Gemological Institute of America has provided a scale that enables classification (or grading) of diamonds based on their color. It goes from D, meaning colorless, up to Z meaning fancy yellow. The letters between D and Z represent a small shift in color and encompasses a small color range. For example, the grades E and F are very similar to D, and to the ordinary eye they will appear practically colorless. Even G, H, I and occasionally J will have little coloration with the table facet is in face-up position - the usual position for setting the diamond up in jewelry. (The grades are determined with the table in face-down position.) The exception might be the emerald cut diamond with its large table, in which case some color might be visible from the G grade upwards.

As the amount of yellow increases, the value of the diamond goes down, but pay attention. As soon as the fancy yellow is reached, the price dramatically goes up again, and it can be extremely high for some of the rarest fancy colors. The first substantial cost decrease is when going from D to E grades.

Fancy Color 1.13 Carats Diamond with Certificate

When talking about the fancy colors, it is important to have a feeling of how much such a stone may cost. Have in mind that the diamonds from the top of the following list are often amongst the "rarest animals" in the jewelry world, therefore reaching the very top of price ranges possible. The red fancy colored diamond with intense saturation can cost half a million dollars per carat, or more.

• 1 Red diamonds
  
• 2 Orange-yellow diamonds
  
• 3 Pink diamonds
  
• 4 Green diamonds
  
• 5 Blue diamonds
  
• 6 Yellow (canary) diamonds
  
• 7 Orange diamonds
  
• 8 Colorless (white) diamonds
  
• 9 Purple diamonds
  
• 10 Brown (cognac) diamonds
  
• 11 Black diamonds
  

The quality of the diamonds in regards to their color can be greatly influenced by a phenomenon called fluorescence. When exposed to the UV radiation from the sun, or to any other source of long wave length UV radiation, roughly one third of the gem grade clear diamonds will exhibit fluorescence. Some laws of physics tell us that a diamond is transparent as a result of its band gap, being larger than the wave length of all the visible light wave lengths. But some UV frequencies will be large enough to match the band gap energy and excite some electrons from their equilibrium positions. When coming back to equilibrium, these electrons will emit fluorescence, usually of blue light, but sometimes also of other colors. This light can be strong or less intense. Once the UV source is removed the fluorescence will usually cease.

This blue light can have a double effect. On one side, if the diamond is in the range from D to H, it might ruin the color producing a whitish background appearance. Diamonds from the lower color grade side, might appear to have less yellowish hues, in which case the bluish fluorescence actually helps.

When purchasing a diamond, along with checking one of the most important parameters which is its cut, check the fluo, it should be listed in the report. If there is one, it should be of blue nuances, not some other color. If it is blue, then it should be weak, not strong in its intensity. This can be checked, for instance testing the visual aspect in bright sun light or in various artificial lighting.

Today, more than ever it is important to distinguish fake and synthetic stones when shopping for diamonds. Some colors can be largely influenced by using synthetic metods, such as for instance those used for creating diamonds from laboratory. One of those is High pressure High temperature procedure for color enhancement. Their color can be enhanced by using irradiation and annealing techniques, in much the same way as in the artificially produced green amethysts for example. Therefore, purchasing diamonds of the desired color is a game of knowledge as much as it requires a larger amount of money.