Calling all Experts - 8 Diamond Taste Test - What are the best features of these stones?

[Eggs]

I''ve been trying to follow a number of excellent threads on this forum the last few months about diamond proportions, especially crown/pavillion angles and star/lg number in relation to brightness, scintillation and dispersion. But I''m sure like every other newbie here on this forum, I''m just overwhelmed by all the informtion.

So I thought I''d try a little taste test!

These are real premium stones listed on a number of online vendor sites.

For this Taste Test, let''s say they''re all in the 0.5 - 0.6 range, I color and SI1 clarity, are eyeclean.

1) Which is likely to have the most and larger firey flashes? Why?
2) Which is likely to have the best scintillation performance? Why?
3) Which is likely to be the brightest stone? Why?
4) Which is likley to be the best overall performer? Why?
5) Which is likely to be the worst overall performer? Why?

...and here are the choices:

 

[Eggs]

Oh Yeah - Forgot to add that these are all AGS certified stones.

 

[urseberry]

Wow, those are all really similar. I don''t know that people will be able to make clear distinctions between them. Now if you had a 60/60, a BIC, and a FIC in there among all those TICs, people could start making bold statements.

 

[urseberry]

Just noticed that number 2 stands out for it''s somewhat shallow 40.6 pavilion angle. It may be a little more susceptible to head shadow.

 

[Eggs]

Please excuse (my brain must be on vacation!)

Assume also all great Excellent cuts, symmetry and polish. Am I missing anything else?

 

[Eggs]

Hi urseberry, I see your point - thank! I''ll try to add a few more stones with different numbers. It''s been hard to find a real FIC stone to use as an example.

Since these 8 are so similar, what would you say would be the fire, scintillation and brightness of these?

 

[urseberry]

As well-cut TICs, these stones should display a good balance between fire and brightness. I don't totally understand yet how angles affect scintillation, besides the fact that longer lower girdle facets do usually increase scintillation. I know that star facets can be important too, but haven't memorized exactly what effect they have. My experience comes from reading this site - the only diamond I've had the pleasure of examining in detail is the one on my finger: 0.79 ct with 34 crown, 40.8 pavilion, 58% table, and near H&A optical symmetry. A very bright stone that still displays plenty of fire in spot lighting!

Anyway, since all of your sample stones sit inside the AGS ideal range and score under 2 on the HCA, they are likely to have excellent fire, brightness, and scintillation, with a good balance between all three factors. If I were making a purchase decision, I would ask the vendor's opinion, and consider my preferences in color, clarity, and cost, while trying to maximize size.

 

[Ellen]

Seriously, the average person would have a very hard time telling these apart.

 

[Lorelei]

Date: 2/11/2008 7:56:06 AM
Author: Ellen
Seriously, the average person would have a very hard time telling these apart.

Ditto. Possibly the seasoned diamantaire might be able to detect such subtle variations, but I know I couldn''t.

 

[Paul-Antwerp]

Date: 2/11/2008 2:05:06 AM
Author:Eggs
I''ve been trying to follow a number of excellent threads on this forum the last few months about diamond proportions, especially crown/pavillion angles and star/lg number in relation to brightness, scintillation and dispersion. But I''m sure like every other newbie here on this forum, I''m just overwhelmed by all the informtion.

So I thought I''d try a little taste test!

These are real premium stones listed on a number of online vendor sites.

For this Taste Test, let''s say they''re all in the 0.5 - 0.6 range, I color and SI1 clarity, are eyeclean.

1) Which is likely to have the most and larger firey flashes? Why?
2) Which is likely to have the best scintillation performance? Why?
3) Which is likely to be the brightest stone? Why?
4) Which is likley to be the best overall performer? Why?
5) Which is likely to be the worst overall performer? Why?

...and here are the choices:

Nobody can answer these questions with only this information. Let me explain.

First, you are offering the choice between 8 stones that have average proportions and angles, that are in a very tight area. Little difference there.
But do note that these are averages, and that this average might hide big differences in the actual proportions and angles. Each average number here comes from 8 individual numbers, and nobody can deduct this from this chart.

Second, optical symmetry has an effect, especially when looking at your exact questions number 1 and 2. Now, I must say that what I am going to explain you about this, is deducted from observation, and not scientifically confirmed yet. So, please be aware that this is my personal observation, and that others might chime in and say exactly the opposite. Don''t let this confuse you.

Scintillation and the observation of fire both depend highly on optical symmetry. I should add, in case of average size stones. Extremely big stones in a standard round brilliant could benefit from an asymmetric setup, but a better solution would probably be a faceting-pattern with more than 57 facets. How is that?

Well, when we observe a diamond, we see a lot of virtual facets, each returning light in a different way. When moving the stone, we observe scintillation in these virtual facets. The sharpness of that scintillation depends on the crispness of these virtual facets, and this is benefit number one of optical symmetry.

When observing scintillation, it is important to have a nice distribution of different sizes of virtual facets. Most difficult to obtain are relatively big virtual facets. Asymmetry creates a number of extra virtual facets, all very small, which make the big virtual facets smaller again. In that way, optical symmetry avoids unnecessary small virtual facets, and maintains the size of the big virtual facets. Benefit number 2.

The big virtual facets are important again in observing fire. A stone may exhibit fire, but the size of the virtual facets decides whether you can observe this as fire, or not. Small virtual facets exhibiting a fiery flash, will not be observed as fire. When you have small size melee-stones, round brilliant, it is very difficult to see their fire, simply because their virtual facets are too small. Because of this, optical symmetry is important again, since the size of the bigger virtual facets will be maintained.

So, when your first two questions are about fire and scintillation, and question 4 and 5 actually also are, you cannot in any way answer this without going into more detail about the actual angles and proportions (not the averages) and without studying the optical symmetry of the stone.

Live long,

 

[Rhino]

LOL... yes to reiterate what has already been said ... there are a number of nuances that go through my mind as I review each set of criteria and the time it would take to type that all out could in the end be completely moot due to the points that Paul brought out concerning optical symmetry. Alot of the answers to your questions just simply *can't* be answered because even if you were able to detect these nuances with your eyes, your personal preference for beauty may be different from from the person who shares a different preference.

Take 2 diamonds for example with superior optical symmetry ...

Both have tables in the mid 50's, one has 34.5 crown angles with a 41.0 pavilion angle and a lower girdle length of 81% with 55% stars and the other has 40.6 pavilion angles with a 34.5 pavilion angle, 75% lower girdles and 50% stars.

Depending on your focal length, the first diamond in diffuse lighting will have pavilion mains that are more likely to light up and be less noticeable while the 2nd diamond stands a greater chance of reflecting back dark reflections of the observer standing before the diamond forming darker arrows in a practical observation. One person may prefer the appearance of one over the other although both perhaps may make AGS Ideal/GIA Ex and both I might add would be beautiful stones.

Take the same two diamonds into spot lighting and each can form different sparkle patterns. The former may produce more pin fire flash mixed with broad while the latter may emphasize moreso the broad. Again, the preference is up to the individual.

In each scenario it is your pavilion angle/crown combo *and* lower girdle facet length that are the main contributors to the differing appearances and as Paul noted ... alter the optical symmetry by either variances from the min to main angles and/or azimuth angles and it throws these nuances off to be completely different. It's one reason why professional's will generally never buy until they see and also depends upon how selective that individual is. For some all they need to see is a piece of paper. For others, we want more details that are not conveyed on paper alone. Folks like Paul and myself are of the latter.

 

[niceice]

The fact that all of them have a crown and pavilion angle combination likely to work well together is a great start. But as Paul has pointed out, it is impossible to accurately access the potential of the diamond off of the average measurements alone, the next step would be to obtain a facet-by-facet report from a Sarin / OGI / Helium to determine the consistency of the facet structure. It will be important to take the consistency of ALL facet segments into account, not just the bezel and pavilion main facets which comprise the average crown and pavilion angle measurements stated on the lab report diagrams. Once the degree of symmetry / consistency has been determined for the individual sections which make up the structure of the diamond, it will be easier to get an idea of which diamond is more likely to exhibit superior visual performance. The concept behind this method of evaluating a diamond is one of the reasons behind why the AGS Laboratory updated their cut grade system in 2005. There were a few cutters at the time who were taking advantage of the fact that the average crown and pavilion angles were used to determine whether a diamond met the criteria for the zero ideal cut rating and were cutting their diamonds with a rather broad stroke to retain more rough during the cutting process and still create an average crown and pavilion angle within the selection criteria. The reality is that a low of 33.5 degrees and a high of 35.5 degrees will still produce an average of 34.5 degrees, but the odds are that the outer perimeter of the diamond will be shadowed (the upper girdle facets will be darker) instead of being as visually pleasing and bright as they would be if the range were tighter, such as a low of 34.3 degrees and a high of 34.8 degrees (which would produce the same average of 34.5 degrees). The same concept holds true for the pavilion...

 

[WinkHPD]

Date: 2/11/2008 2:05:06 AM
Author:Eggs
I've been trying to follow a number of excellent threads on this forum the last few months about diamond proportions, especially crown/pavillion angles and star/lg number in relation to brightness, scintillation and dispersion. But I'm sure like every other newbie here on this forum, I'm just overwhelmed by all the informtion.

So I thought I'd try a little taste test!

These are real premium stones listed on a number of online vendor sites.

For this Taste Test, let's say they're all in the 0.5 - 0.6 range, I color and SI1 clarity, are eyeclean.

1) Which is likely to have the most and larger firey flashes? Why?
2) Which is likely to have the best scintillation performance? Why?
3) Which is likely to be the brightest stone? Why?
4) Which is likley to be the best overall performer? Why?
5) Which is likely to be the worst overall performer? Why?

...and here are the choices:

I would agree with what Paul said, and I would go just a little further.

One, you are probably trying to go too deep unless you intend to make a career of the diamond field. Very few diamond sellers would have a clue what you are talking about. That in itself is very unfortunate, but a sad reality of our trade. I admire your determination and your desire to know every thing that you can about this diamond you are about to purchase.

Two, I have an entirely different take on the color and clarity issue that your relatives in the business have taken. I have come to agree completely with one of Paul's other vendors who argues that there is only one C of diamond clarity and that is cut. The other C's are diamond rarity, and while they have a great deal, probably 80-85% to do with the price of the stone, it is the cut that gives it beauty, and thus value.

Having recently sold gems that were in the price range that you desire. albeit of lower color and clarity but of Paul's ourtanding cutting, I can tell you that they were stunningly beautiful, and in fact one of them, a J-I1 when compared to a much higher rarity E-VVS1 diamond of similar size that was only of moderate cut, blew it out of the water. Thats an EVVS1 blown out of water by a J-I1, no misprint, but just a plain fact!

Cutting truly is the great equalizer. I have had that E-VVS1 here for years and can not sell it against the stones that I carry from Paul.

You would do yourself and your signifiant other a real favor if you found someone local who could show you some truly well cut diamonds, then you would both understand that cut really is the most important of the C's, and since it is the only one that man has any control over, the only one that I consider a quality issue. If you have the budget to purchase rarity, then by all means do so, but if it is beauty you want, look to cut!

Wink

 

[Ellen]

Eggs, you said these were all AGS stones. As in, AGS0? (newer grading, with light performance)

 

[niceice]

Date: 2/11/2008 1:28:20 PM
Author: Ellen
Eggs, you said these were all AGS stones. As in, AGS0? (newer grading, with light performance)

The clarification would help... Above Eggs said:

"Assume also all great Excellent cuts, symmetry and polish. Am I missing anything else?"

So there is wiggle room (for all) in the perceived definition of ideal.