A fancy yellow diamond is a naturally colored yellow diamond which emits yellow color beyond the normal D-Z color grade range. Fancy yellow diamonds are yellow because they have strong amounts of nitrogen impurities in their crystal structure causing the color yellow to permeate through the stone. Nitrogen is a naturally occurring element in almost all white diamonds, which is why most diamonds have some hint of yellow. The more yellow a diamond is, the more nitrogen present in the crystal structure.
The GIA D-Z grading scale is the industry standard for color grading white diamonds. Diamonds which fall in the lower letter ranges K-Z, exhibit faint to light yellow body color, but these are still considered in the normal diamond color range. These diamonds do not receive the title of ‘Fancy’.
Fancy yellow diamonds exhibit a tone and saturation that surpasses the Z color range. Diamonds which surpass the Z color range are then broken down further into the fancy categories: fancy light, fancy, fancy intense, fancy vivid, fancy dark, and fancy deep. The key here is that they all begin with the word fancy. Most fancy yellow diamonds sold in the market range from fancy light to fancy intense. Jewelers and auction houses will often use the name ‘Canary’ to describe yellow diamonds, which receive a color grade of fancy or better. The term canary adds to the allure of fancy yellow diamonds, but it can be misleading since every person interprets color differently. There is no gemological measurement for the term canary, but it is meant to represent a range of fancy yellow colored diamonds. Since the GIA does not recognize canary as a color grade, it is always important to refer to the actual grade received on a certificate when speaking about fancy yellow diamonds.