Grading Natural Fancy Yellow Color Diamond

Diagram of Fancy Colored Diamonds(Canary)

Range from Vivid to Light

Diagram of Non-fancy Diamond
Range from Z - U
 

Most diamonds used as gemstones are basically transparent with little tint, or white diamonds. The most common impurity, nitrogen, replaces a small proportion of carbon atoms in a diamond's structure and causes a yellowish to brownish tint.

Beautiful yellow diamonds exist in tones from light yellow to fancy intense vivid yellow, also named Canary Yellow, depending on the concentration of nitrogen when the crystal is formed. Yellow diamonds are more desirable than white diamonds, due to their warm color. In fancy diamonds, inclusions are mostly not noticeable to the naked eye because of its rich color, inclusions does not affect the look or its sparkles not like in clear diamonds.

Natural fancy coloured diamonds are very rare and expensive. Most people believe that yellow diamonds are less desirable and valuable than white diamonds. While this is true of faintly coloured or off-white diamonds, intensely coloured diamonds are very attractive, rare and expensive. The Kimberley Octahedron is the largest diamond in the world at about 616 carats, and is yellow.
 

Grading fancy color diamonds

Yellow or brown color diamonds having color more intense than "Z", as well as diamonds exhibiting color other than yellow or brown are considered fancy colored diamonds. These diamonds are graded using separate systems which indicate the characteristics of the color, and not just its presence. These color grading systems are similar to those used for other colored gemstones, such as ruby, sapphire, or emerald, than they are to the system used for white diamonds.
 

GIA colored diamond grading system

The GIA issues grading a Colored Diamond Grading Report for colors that are not in the normal color range of diamonds. Formal GIA terms used to describe natural yellow diamonds:

Fancy Vivid Yellow- Vivid yellow diamonds are the rarest and most unique diamonds. These characteristics make it the most expensive kind from any other range. This range has the richest and most intense hue of all.

Fancy Intense Yellow- Intensity color range for diamonds have richer color and quality. Values of this kind of diamond are higher.

Fancy Yellow- This color range has yellow hue but less saturated. These stones are very beautiful but less expensive than intense and vivid range.

Light Fancy Yellow- There is slight yellow tint that can be detected by human eye on this color range. The buyer perception of color for yellow diamonds is confident, intelligent and wordly. Lighter shades are a great value because they still look yellow, yet you can have more size for the money.

Gran Colorimeter

Color can also be determined using a device called the Gran Colorimeter, manufactured by Sarin Technologies. It measures from D to Z to Fancy Intense with an accuracy within ±½ of a color grade on loose stones from 0.25 to 10 carats (as low as .15 carat or as high as 20 carats with reduced accuracy), and you can specify which grading scale it should use (GIA, GEM, IGI, AGS, HRD, and others). The accuracy is within ±1 color grade for mounted stones. If you diamond is a "G" color it will tell you whether it's a "high G" or a "low G." The Gran colorimeter was first developed by Paul Gran in 1972 at Gran Computer Industries Ltd.