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Grade 3 - Example 1 - RD22
Table: 54%
Crown >: 35.5
Pav >: 39.4
Stars: 55%
lower gird: 75%
girdle: thin
culet: none
depth: 60.6%
polish: VG
symmetry: VG |
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| This diamond's grade is limited by its scintillation. in this case, the somewhat shallow pavilion angle produces dark pavilion mains. |
Click on the graphic to download the .gem file |
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Rhino's Review
While 35.5° may seem to be a crown angle on the steep side, a pavilion angle of 39.4° is considerably too shallow for this combo producing the dark pavilion mains GIA notes and can be observed in the first graphic. Our experience shows that when you have crown angles in the mid 35 degree range, pavilion angles around the 40.4-40.6 produce the brightness necessary to cause this stone to get a Grade 1 classification. This first example given here also demonstrates how an IdealScope/LightScope image coupledwith a seemingly excellent HCA score of 1.8 may not be the best indicators for the layman, even as we go down to the Grade 3 classification and actually demonstrates some of the many of the mistakes I personally made with red reflector technology when I didn't know how to interpret what it was I was seeing through these devices. This diamond will generally have a better appearance in direct light conditions but will suffer in softer light conditions where contrast/brightness is best observed. Of all the technologies we work with, once again, the BrillianceScope and Isee2 appear to be the best tools for determining the metrics for this grade so far.
Grade 3 - Example 2 - RD11
Table: 58%
Crown >: 37°
Pav >: 42.2°
Stars: 45%
lower girds: 85%
girdle: med-sl.thick
culet: none
depth: 64.9%
polish: G
symmetry: VG |
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| This diamond's grade is determined by its fire, scintillation, and weight ratio. A some what steep crown angle, combined with a slightly steep pavilion and this total depth, lead to a diamond that displays a slightly dark ring within the table edge, as well as somewhat dark upper-girdle facets. |
Click on the graphic to download the .gem file |
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Rhino's Review
As compared to the steep/deep combo in Grade 2 (Example 2) here's an even worse combination of angles (as suspected). HCA properly grades this with a 4.6 (although it did give the Grade 2 stone an even worse score of 5.1) and MSU with .82 & .85 for light return. Our only disagreement is with the outstanding 1.10 contrast score via MSU which is rewarding this diamond with higher contrast for more leakage. The long lower girdles at 85% (also similar to Gr2Ex2) contributes to a splintery appearance making the best attributes of this stone that of fire & scintillation as observed in direct light conditions. You can observe the darkness in the upper girdles in their graphic which is more than likely due to upper girdle angles being => 44°. It is good to know that GIA will be taking this into account as well (how upper girdles impact appearance).
Grade 3 - Example 3 - RD06
Table: 56%
Crown >: 23°
Pavilion >: 42°
Stars: 60%
lower girds: 80%
girdle: med-sl.thick
culet: none
depth: 57.2%
polish: VG
symmetry: VG |
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| This diamond's grade is limited by its scintillation. the shallow crown angle and low crown height lead to a face-up appearance with a lack of contrast in its pattern and localized darkness (especially in the table area). |
Click on the graphic to download the .gem file |
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Rhino's Review
23° crown angles is the red flag here which the HCA properly comments on regarding the likelihood of this diamond chipping. HCA will not grade stones with crown angles that are too shallow. FINALLY (except we'd consider this too late in the game) do we see the results of a stone that's too shallow with regards to red reflectors as there are too many blacks under the table contributing to the darkness that GIA is talking about. As it is with the other shallow/shallow combo's the IdealScope image is seemingly excellent and MSU does reward the diamond with high marks for light return (which it is properly doing), however since the MSU software does not differentiate between the lights/darks (for contrast brilliance) this shows a general strength and weakness of the Gem Advisor software (at least this version anyhow). The strength is that the MSU software is properly showing that this diamonds facets are primarily functioning as mirrors (as opposed to windows), the weakness is that this might lead someone to think this is an excellent diamond when in fact the balance of contrast stinks (too many reflections of darks and not enough lights).
Final thoughts on Grade 3
Grade 3 represents some of the more common crappers that exist on the market that are generally found in your mall type operations. The 2nd two examples have obvious red flags even if you were only looking at total depth info (#2 has a depth of 64.9%, obviously deep while the 3rd example has a total depth of 57.2%, obviously shallow). The tricky one is the first example with a normal total depth of 60.6% which is coupled with a table of 54%. A great example of how foolish it is to make a decision based on strictly table/total depth alone. Interestingly, thus far GIA has been giving two shallow/shallow and one steep/deep in each of their 3 examples within each grade. As stated earlier the steep/deeps are pretty easy to distinguish and weed out especially with available online tools like HCA and IdealScope/LightScope. Perhaps GIA is giving us this 2/1 comparison to emphasize how neglected the metric of brightness is overlooked by those of us within the trade, especially by gemologists who incorporate these technologies into their purchasing decisions. It is also worth noting that there are certain H&A *brands* (not inexpensive either!) who do charge a premium for their product who cut their stones to these shallow/shallow combos. It may be worth reconsidering this metric (and perhaps changing their cutting) if they are to maintain top optical scores from the most well known lab in the world. BrillianceScope & Isee2 would accurately determine the grading here as well. |
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