Inconsistency on GIA Grading Certificates.
To diamond dealers and everyone associated with the diamond and fine jewelry trade, there is perhaps no thing more disturbing in recent times than the extreme inconsistency in GIA diamond grading reports.
While there has always been some level of inconsistency in diamond grading itself, today there are 10 GIA laboratories around the world. It is obvious to knowledgeable Diamantaires that several of the GIA laboratories are significantly off the mark from the established standards of traditional GIA diamond grading.
The diamond buying public consumer must understand that diamond grading reports are not based on any scientific method of evaluating a diamond. The color characteristic is perhaps more consistent than the clarity characteristic. This is because color is based on master color samples. In a perfect world these master color samples used by the ten laboratories are all uniform and consistent. Clarity, on the other hand, is based on “standards” such as “a minor inclusion somewhat easily seen under magnification” or “somewhat difficult to see under magnification”. There is no hard fast standard that determines one clarity grade from another. It is just the grader’s subjective opinion of the level of visibility of the inclusions within the diamond!
As a result of the “blurry lines’ that are inherent in GIA diamond grading, there has always been pricing differentials of diamonds within any particular GIA grade. For instance, two 1.00 carat round brilliant diamonds that are graded “H/SI2” may be priced 25% more or less than the other because one might have a black carbon inclusion in the center whereas the other might contain a white feather located near the girdle. Obviously, this second diamond is more desirable and valuable than the black center included diamond.