GIA-GTL would be under considerable pressure from benefactors and clients who submit large quantities of diamonds for grading to be liberal one the one hand. On the other hand they are an ethical and honourable institution charged with protecting the public and promoting the industry. The second stone (RD33) in this category is so poor that it is hard to imagine the need for a lower grade?
RD37
Worthy of note: The Liddicoat depth estimation is a commonly used and GIA taught method of pavilion depth estimation. By estimating the width of the table reflection compared to the width of the table, a reckoning of the pavilion depth % is made (add 1/10th of the % to 40 = estimated pavilion depth). In this case the table reflection is 1/3rd the table width. This would lead us to believe the pavilion depth is 43.3%, but the depth is actually only 42.3%. The Rapid Sight method works with a relatively small range of table sizes and is also affected by girdle thickness and crown height. In this case a 1% over estimation of depth percentage would indicate the stone had a 40,9° pavilion; knowing the pavilion was only 40.2° might influence a buyers decisions.
Category 5
I question the validity of this grade that would apply to the worst 1% of certified diamonds based on a survey conducted on Rapnet on 11/19/2004. There were only 441 plus 1.00ct rounds with depth % greater than 69% listed out of approximately 40,000 round stones searched by the same criteria. Surely the lowest grade in a 5 grade system should be set to reflect around 10 to 20% of the goods in the market?
It would also have been instructive to see more than one example of a diamond downgraded for other than having an overly thick girdle.
The optical performance of RD39 appears to be as good, or better, than some stones in Categories 3 and 4. Aside from the extremely thick girdle (which does not have a major impact on optical performance) the crown and pavilion angles represent the steepest and deepest AGS 0 angles; was the inclusion of this stone a political choice?