Color Grading of Rio Tinto
As a responsible consumer, having a certificate or a diamond grading report is important. Unfortunately, it is difficult to understand a word of what is on that diamond grading report, unless one is a jeweler.
In general, color grading scales D, E, and F mean that the diamond has no color. G, H, and I mean that it has very little color. J, K, and L mean that the diamond has a slight yellow color. Scales from P to X means that the diamond is a darker shade of yellow. Z denotes the diamond has a fancy color other than white or yellow. It is important to note however, that on the color grading scale, D is the most valuable while X is the least valuable. However, diamonds receiving a Z rating are the rarest and most expensive diamonds in the world.
In the case of brown diamonds however, a color grading system (C1 to C7) created by Argyle Diamonds grades the darker and rarer cognacs are the most expensive gems within the range, the fairest being a light champagne color. Rio Tinto’s Argyle Diamond Mine in the remote east Kimberley region of Western Australia and is the world’s largest producer of champagne diamonds, which have been becoming popular over the past few years.
The Argyle diamond mine, owned by Rio Tinto has devised its own color-grading scale, ranging from C1 to C7, designated as “light champagne” to “cognac”. The grading scale is an attempt to bypass the widely respected and recognized Gemological Institute of America (GIA) grading system solely to boost sales on its brown and yellow stones.
Grading brown diamonds established by the GIA would end up looking not too good for brown diamonds. This is because the GIA grading scale grades white diamonds ranging from D to Z. As the scale goes down, stones appear gradually tinted and off-color. In other words, the lower the color grade, the lower the valuation. In the case of brown diamonds, The C1-C2 “light champagnes” would be at the lowest of the GIA’s scale for white diamonds and the “cognacs”, C3-C7, would also be at the lower end of the GIA’s colored diamonds, or fancies.