The documentation of coloured diamonds at the GIA Laboratory has been an integral part of the laboratory's history for six decades. Through such characterisation we are better able to understand the occurrence of colored diamonds in color space as well as the properties that determine the cause of color. It is vital to document the full range of colored diamonds, from commonly occurring colors such as yellow, to more rarely encountered ones such as red, purple and green. In our experience, rare colored diamonds are encountered in two ways. First, there are rare hue ranges, such as purple and green. Second, there are also unusually saturated diamonds in more common colors such as yellow.
The 9.03-carat Yellow Oval Modified Brilliant is an example of a more common colored diamond hue, but it is an exceptional in its saturation of color. Often when yellow diamonds attain this depth of color it is due to nitrogen replacing carbon atoms in the diamond's structure. In this instance, the color is due to aggregated nitrogen (classified as type Ia in scientific terms). It is reminiscent of a 9.00-carat pear shape from the spring 1995 sale - one of the first Fancy Vivid diamonds sold publicly.
In GIA's experience, strongly colored, so called 'Cape diamonds' (named for their geographical location in South Africa) like this example occur rarely. Typically the color saturation is much weaker and most often does not reach a depth of color that classifies the diamond as even Fancy Light Yellow in the GIA Fancy Colored Colour grading system. This diamond is free from any inclusions with exception of internal graining. The characteristic occurs more frequently in these rarely encountered strongly colored yellow diamonds. The combination of this diamond's size, cutting style, and depth of color make it an exceptional specimen.
Tom Moses, GIA Senior Vice President of Laboratory and Research