The American Gem Society (AGS) Laboratory is the first and foremost independent laboratory to issue numerical cut grades. This grade is based primarily on measurements taken on a Sarin Diamension machine. The highest grade is "0 Ideal." As a stone deviates from perfection, its numerical grade increases; 1 Excellent, 2 Very Good, all the way down to 10 Poor.
The AGS grades seven aspects of cut of each stone it analyses. These include the Crown Angle, Pavilion Depth, Table Diameter, Girdle Thickness, Culet Size, Polish and Symmetry. The first five of these are grouped under the term "Proportion."
The AGS gives its highest cut grade to a stone that has achieved the highest (actually lowest "0") score on all three criteria: Polish, Symmetry and Proportion. This is the origin of the terms "Triple Ideal," "Triple Zero," "Zero Cut" and "AGS 0." Remember that not all AGS Triple Ideal Cuts achieve the more precise demands of Hearts & Arrows.
AGS Lab Diamond Quality Document
GIA Certificates — The GIA is the most recognized grading lab. Unfortunately the GIA does not provide any quantitative analysis of cut. Additional information is necessary to determine the cut of diamonds graded by the GIA.
The main difference between these two labs is that the AGS has adopted a standard for the cut quality of diamonds, providing you with an idea of the overall beauty of your diamond. While the GIA provides a poor to excellent grade for finish and symmetry, it does not provide proportion information. Proportions play a major role in the brilliance, scintillation and fire in diamonds. Conversely, the AGS has 11 Cut Grades (0-10) in three different categories. In assigning a Cut Grade the AGS considers seven factors: five proportion factors, polish and symmetry. The AGS then provides three grades from 0-10 for symmetry, polish and proportions. A "0" grade is representative of the most desirable Ideal Cut and a "10" is representative of a poor cut. Diamonds that score 0 in all three cut categories are premium cut diamonds with the potential for superior brilliance and scintillation.
EGL Certificates — E.G.L. provides a detail diamond report that is sometimes not as strict as G.I.A. Because the art of diamond grading is a subjective science, two different gemological laboratories may arrive at differing opinions when assigning a diamonds color and clarity grade. E.G.L. has sometimes been known to assign a higher grade on diamonds that have grades on the border between two grades. G.I.A. usually will always give the lower grade. When purchasing a diamond with an E.G.L. quality report, it is possible to receive a lower grade if it is submitted to G.I.A. for a new diamond quality report. Diamonds with E.G.L. quality reports that are offered for prices significantly lower than equal quality G.I.A. certified diamonds have the greatest chance of not matching if submitted to G.I.A. for a new quality report. E.G.L. certifications are often reliable but one must be aware of possible inconsistencies and limitations when comparing diamond certifications between different gemological laboratories
The E.G.L. certification however does provide more proportion information than the G.I.A. diamond report by including the important pavilion and crown angles in their diamond report. Be aware that plots of internal and external blemishes on E.G.L. certifications are much less detailed than G.I.A. or A.G.S. quality reports. Many diamonds under one carat in size are are certified by E.G.L. due to the benefit of lower cost and faster service. E.G.L. also provides a economically priced miniature version of its full certification.
I.G.I. - The International Gemological Institute — I.G.I. provides a detailed certification that is not as strict as G.I.A. Like the E.G.L. the I.G.I. certification also provides more information than the G.I.A. diamond report by including the important pavilion and crown angles in their diamond report. Diamond grades rarely vary over one grade from G.I.A. Like E.G.L., I.G.I.'s diamond report cost less and is used mostly by diamond cutters for smaller diamonds although larger diamonds are also available. You must be aware that diamonds graded by E.G.L and I.G.I. can be less in price than diamonds graded equal by G.I.A. and may sometimes not match G.I.A. if resubmitted.
Laser Inscription
A laser inscription is a name or number that is burned into the diamond girdle to help identify it. The inscription is like an engraving that is not just on the surface but is etched or burned fractions of a millimeter into the diamond. The AGS Lab does our lasering and the Diamond Quality Document mentions the inscription in its "Comments" section (bottom left of DQD).
Most Hearts and ArrowsIdeal Cut diamond at Vivo Diamonds have their report number laser inscribed in the girdle. This adds a degree of security, which can be useful in case you ever need to have your jewellery cleaned or repaired.
The black that you see in the laser inscription is actually burnt carbon residual left over from the laser burning. After the diamond is mounted, the jewellery cleaning process involves ultrasonic and steam cleaning, which may remove this carbon residual, making the inscription appear white or clear. This does not change the fact that the stone is laser-inscribed. While it may become more difficult to see under a loupe, the inscription on your diamond will still be visible when viewed under a microscope.
Here are a couple of magnified images depicting the visibility of the laser inscription before and after the carbon residue has been removed from cleaning.
