|
|
|
|
|
|
|
|
 |
Grade 2 - Example 1 - RD16
Table: 53%
Crown >: 33.5°
Pav >: 40.6
Stars: 50%
lower gird: 75%
girdle: thin-med
culet: vsmall
depth: 61.2%
polish: G
symmetry: VG |
 |
 |
 |
| This diamond's grade is determined by brightness, scintillation, and polish. Although no one of its proportions would necessarily cause its brightness or scintillation to perform poorly, the combination of this particular set of proportions leads to increased darkness in the pavilion mains. |
Click on the graphic to download the .gem file |
 |
Rhino's Review
Extremely interesting example for this Grade 2. For those who have studied or kept abreast of our developments regarding contrast brilliance and the Isee2 technology this diamond takes a hit for what I would term a combination of angles I consider to be shallow/shallow (introduced 4th quarter 2004 as opposed to steep/deep as seen in the next GIA example). The shallow/shallow combo's (shallow/shallow means that if you couple certain crown angles with pavilion angles that are too shallow it produces too much head obstruction or darkness) produce an off balance of darks/lights with an emphasis on too many darks. GIA comments "the combination of this particular set of proportions leads to increased darkness in the pavilion mains". You can observe the results of this by comparing the brightness image (in column 2) with those in the Grade 1 classification to see what GIA is talking about. If you're looking at the IS image and scratching your head, don't be surprised. Red reflector technology can not (in most circumstances) detect the features that cause this diamond to get the Grade 2 classification. Hence an HCA score of less than 2.0 proves ineffective if you are interested in picking GIA Grade 1 diamonds. This stone scores an amazing .8 on the HCA which does not correlate with GIA's grade nor from our own testing of shallow/shallow examples. An example which we have tested can be found at this link ( 1.10ct F SI2). So ... if you're working with a company that does provide IdealScope or HCA scores, bear in mind that these tools alone are ineffective for selecting Grade 1 diamonds. The only tool we are aware of at this time to detect these features for *brightness* and *contrast* digitally is the Isee2. The LR stereo in MSU software is the lowest grade we've seen so far in the examples given and contrast is the lowest as well in the 4 examples given thus far so this is a good indicator. Of grade 2 diamonds, it is these types (the shallow/shallows) that are hardest to detect via the net and via it's Sarin measurements or most available online tools (HCA and IdealScope). Expert consultation is required to help determine these types with further tests (Isee2 & BrillianceScope). Let's see how the other Grade 2's score.
Grade 2 - Example 2 - RD07
Table: 53%
Crown >: 36.5°
Pav >: 41.4°
Stars: 55%
lower gird: 90%
girdle: thin-med
culet: None
depth: 64.1%
polish: VG
symmetry: VG |
 |
 |
 |
| This diamond's grade is determined by its fire, scintillation, and weight ratio. It has a "splintery" pattern, most likely caused by a higher crown height with a somewhat steeper crown angle, accompanied by long lower girdle facets. |
Click on the graphic to download the .gem file |
 |
Rhino's Review
This diamond falls into the Grade 2 classification for more obvious reasons. #1: It's depth falling at 64.1% is the first red flag (which would make it appear smaller than usual) and #2, the set of crown/pavilion angles falls into what would be properly termed a steep/deep combination. It is these combinations that produce the extraneous leakage you see taking place under the table in the simulated LightScope image above as indicated by the extremely pale reds & whites.There are other, less steep/deep combo's that also produce what many would be considered too much leakage but with shallower angles that I would have thought would be a better example of a Grade 2 diamond. Diamonds cut with these extremely long lower girdles (90%!) will typically have it's optical strengths in way of scintillation/fire but not brightness/contrast due to the amounts of leakage taking place within the diamond. The "splintery" effect GIA speaks of can once again be observed in the MSU Jewelry store graphic in column 2. Of these first 2 examples given for Grade 2 diamonds the first example above (RD16) would definitely be the more attractive of the 2 but the reasoning behind giving them both a Grade 2 classification is justified. These first 2 examples also show us that there will be certain Grade 2's that some may find more appealing than other Grade 2's. Also of note within this particular diamond is it's MSU contrast score which gets a whopping 1.20. This demonstrates the different nature with which MSU is grading contrast as opposed to the GIA/Isee2 way. This diamond would have less than desirable *brightness/contrast* due to it's leakage which is why we do not side with the MSU results for contrast.
Grade 2 - Example 3 - RD03
Table: 63%
Crown >: 32°
Pav >: 41°
Stars: 60%
lower gird: 80%
girdle: med-sl.thck
culet: none
depth: 58.6%
polish: G
symmetry: G |
 |
 |
 |
| This diamond's grade is determined by its brightness, scintillation and finish. There is a slight darkening within the table and along the upper girdle facets. |
Click on the graphic to download the .gem file |
 |
Rhino's Review
Another diamond that would fall under the shallow/shallow combo due to the shallow 32 degree crown angles. In this case HCA concurs with a score of 2.4 while MSU gives it a LightReturn rating comparable to some of the Grade 1 stones. If you take note the pavilion mains (arrows) are notably darker in the first pic (similar to the first Grade 2 example) except the arrows are skinnier due to longer lower girdles. This is a stone that would perform better in direct an ambient light conditions than it would in suffuse (or white hemisphere lighting).
Final thoughts on Grade 2
As we enter the Grade 2 classification we begin to see deviations in crown/pavilion angles that side with either a steep/deep or shallow/shallow combination of angles. Points of note to be taken here once again ... red reflectors and HCA scores may not be the best instruments for pre-determining these grades as diamonds with IdealScope images similar to the 1st and 3rd examples (shallow/shallow examples) are typical of stones that would generally get high recommendations from people recommending stones with these images/data via the web. The HCA is particularly useful for weeding out steep/deep combo's but not the shallow/shallows. While we do consult the results of these tools we do place a heavier emphasis on the more advanced digital technologies (namely BrillianceScope & Isee2) as many, even within our own trade do not know how to properly interpret the results they see from the red reflectors (not to mention the large variety of graphics that can be generated from these scopes from one photographer to another on the same stone!). Our advice, if you want to ensure a Grade 1 classification before the system is released by GIA, is to pursue a relationship with retailers who are offering advanced analysis on their stones and/or are familiar with what stones will constitute the Grade 1 class and the characteristics that constitute these grades.It would be my educated guess at this point that as the grades go down we'll continue to see combinations of angles that are even steeper/deeper or more shallow than the examples given in Grade 2. |
|
|
|
|
|
 |
 |
|
|
