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Are there Differences between Ideal Cut Diamonds?


Apr 29

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One of the challenges that diamond buyers face online is a lack of experience regarding the subtle differences which define the different qualities of ideal cut diamonds, such as the difference between two round brilliant ideal cut diamonds which are the same approximate carat weight, color grade, clarity grade, and overall cut quality.

One example of a difference which an experienced diamond dealer will recognize as likely being due to a difference in the overall cut quality of two “comparable” diamonds, but which is likely to be overlooked by the average consumer, is one diamond being graded by the GIA Laboratory with an overall cut grade of GIA Excellent, and the other diamond being graded by the AGS Laboratory with an overall cut grade of AGS Ideal-0, which we addressed in the differences between GIA and AGS diamond grading reports.

How to interpret ASET images for AGS Ideal Cut diamonds:

how-to-interpret-aset-images-brian-gavin-diamonds-grading-tutorialsThis image contains the ASET image for two round brilliant cut diamonds, which are relatively identical in carat weight, and which are both graded by the American Gem Society Laboratory (AGSL) with an overall cut grade of AGS Ideal-0. The diamond represented at the top of the diagram is a 1.215 carat, G-color, VS-2 clarity, Brian Gavin Blue (fluorescent) diamond, which is the same clarity and color as the diamond positioned at the bottom of the graphic.

You don’t have to be a rocket scientist to see that the ideal cut diamond produced by Brian Gavin (top) is cut to a higher degree of optical symmetry, just look at how much more consistent the distribution of red, green, and blue is throughout the diamond.

The color red is used to represent the brightest light which is striking the diamond and being reflected back up towards the observer (that’s you); the color green is the second brightest light; and the color blue represents the contrast created by the shadow which is cast upon the diamond, and reflected off of the pavilion main facets, when we look upon the diamond. Notice the difference in the manner in which these two diamonds reflect light…

Now I’m going to let you in on a little secret… the crown angle for the Brian Gavin diamond pictured above(top) is 34.9 degrees, and it is offset by a pavilion angle of 40.8 degrees; while the crown angle of the second diamond (bottom) is 34.6 degrees, and offset by a pavilion angle of 40.9 degrees; thus the average diamond buyer would probably consider them to be comparable if they were considering them without the additional insight provided by the Angular Spectrum Evaluation Technology (ASET) image provided on the AGS Diamond Quality Documents for each diamond.

Evaluating the structure of pavilion mains on a diamond:

using-ideal-scope-to-evaluate-arrows-pattern-agsl-104069928021

The Ideal Scope image for the 1.215 carat, G-color, VS-2 clarity, Brian Gavin Blue diamond indicates that the arrows pattern which is created by the pavilion main facets of the diamond, are evenly shaped and exhibiting a high degree of contrast. This is important because it demonstrates that the diamond will exhibit a high level of static contrast, which our eyes will interpret as sparkle, when the diamond is being viewed in a lighting environment where the diamond would not actually be sparkling due to a lack of ultra violet light, such as a traditional office environment where illumination is provided by fluorescent lighting. Take note of how symmetrical and even the pavilion mains look in this picture.

While the vendor where we found the other AGS Ideal-0 cut diamond that we’re using as a comparison for this example, does not have the capability of providing their customers with Ideal Scope images, but we don’t really need one to know that the pavilion main facets are cut with less precision… just take another look at the ASET image provided above, and you’ll see that not only are the pavilion mains of the diamond cut thinner, but they lack consistency in shape as well.

The reason why the pavilion main facets appear like misshapen, broken spindles on that diamond, is because there is a difference in the size, shape, and length of the facets which comprise the two primary facet groups located on the underside of the diamond… the pavilion main facets, and the lower girdle facets are not symmetrical, nor is the indexing of the facets, and this will have an effect upon the volume of sparkle produced by this diamond.

While both diamonds received an overall cut grade of AGS Ideal-0 by the AGSL under the guidelines of their Proprietary Light Performance grading platform, it’s kind of like the difference between an A- and an A+ as the two diamonds represent opposite ends of the scale in terms of precision… and you don’t have to take our word for it, the proof is provided in the ASET images.

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