Understand Certificates
Information to consider before selecting your diamond…
1. Two diamonds (certified by the same gem lab) with identical weight, color and clarity are probably not equal in value. One could be worth considerably more than the other, and value should be assessed with the guidance of an expert.
There are many subtleties beyond the information provided by any laboratory [including the GIA.]
2. Remember, diamond laboratories certify any diamond submitted for grading whether they are beautiful or not. The laboratory function is simply to provide an opinion on color and clarity… while recording measurements and weight.
3. Color and clarity grading is not an exact science, and grades may change if a diamond is submitted to the same laboratory more than once.
4. Inclusion location, size and type influence value. Stones with black center inclusions or inclusions that break the surface are less valuable than diamonds with delicate inclusions off to the side… even though they may have the same clarity grade.
5. Traces of brown, gray or green make a diamond less valuable and this is rarely mentioned in a GIA report.
6. For the same value one may select a larger [lower color / clarity] diamond rather than a smaller [finer quality] stone, and succeed in owning a beautiful, brilliant diamond and sound investment. A properly cut diamond has the same refractive index of light [brilliance] irrespective of the color grade.
7. Fluorescence decreases value in proportion to the effect on brilliance (if any). Very strong fluorescence should be avoided however faint to medium fluorescence has little impact on value and actually enhances color and value in medium and lower color grades.
8. Carat weight is typically a buyer's first priority and this drives cutters to leave extra weight on the girdle, crown and pavilion of stones. Additional weight in these areas succeeds only in making the stone heavier, but not larger where it adds to the face size and value.
Most diamonds on the market today have excess weight in the wrong places and should be avoided.
9. This leads us to a critical issue: Proportion and brilliance.
For many years the 'Tolkowsky cut’ diamond has been marketed as having 'ideal' proportion. A recent GIA study [done over a fifteen year period] has come to a different conclusion:
"The Tolkowsky cut rates only 'moderately bright' when compared to diamonds cut with different proportion criteria.” The GIA study goes on to describes in detail the best proportion for a round stone and states: “Proportion providing ‘best brilliance’ should have a 61%; table: 42.5 degree pavilion, and 26.3 degree crown. These proportions produce a larger 'face size’ to ‘weight' ratio providing the informed and discerning buyer with a larger, as well as more brilliant stone.
10. In order to truly understand the value of diamonds one needs technical knowledge combined with years of active trading.
There is a great deal to know and share about this most intriguing and brilliant of gemstones.