CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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 Post subject: Re: Diamond proportions: Discussion after Quiz
PostPosted: Mon Jan 23, 2012 9:17 pm 
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I've read the explanation of Dr. Hanneman with attention but I still don't understand why the data given by me is irrelevant. A new criteria for diamond proportions grading were proposed, to "cut-grade" any round brilliant diamond from its certificate data, without the necessity of even looking at it". I showed that these criteria are incorrect, or at least they need additional parameters to take into account. I think these considerations are VERY relevant for every person who could be thinking to use the proposed rule.

I completely agree your data are quite relevant for anyone considering the cut grading of diamonds as they should fully understand the the fundamental principles, however, I personally don’t consider them important for dealing with the “small world” of what I consider FINE diamonds.

But first, let me make a point. While evolutionary changes can come from within, revolutionary changes always come from without, inspired by one who does not have a vested interest to maintain the status quo.

I am not affiliated with the diamond industry in any way, and have no desire to be so. I simply look at the cut grading of a diamond as an interesting problem which has existed for almost one hundred years, without the introduction of any significant improvements. My writings are my attempt to introduce some new concepts which I believe are improvements. Ideally, I need to get this information to someone like Verena Pagel-Theisen, if she is still around. Does anyone know?

Actually, relative to the current practice, all I have suggested is that cut grading reports could be made more useful by the simple addition of what I call a “cut rating” in the following form: C/P ratio:Total Height.
Granted, it is just a piece of arithmetic that anyone can calculate from the numbers from any current grading report. On the other hand, those two values completely and objectively describe the shape of any typically cut diamond and offers a shorthand description which can be used by any diamond merchant or price report to precisely describe the stone.
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You wrote, “A new criteria for diamond proportions grading were proposed, to "cut-grade" any round brilliant diamond from its certificate data, without the necessity of even looking at it".
You will note “cut-grade” is in parentheses. That is because, in the approach I advocate, the expression, C/P ratio:Total Height, is not a GRADE. It is a RATING.
This is the most important point and you are missing it. It is the basis of my whole concept. That is why it is revolutionary.

Currently, each cut grade has its own unique and SUBJECTIVE definition of certain attributes (algorithm). To be assigned a certain grade, the object must display those attributes. On the other hand, my “Universal Rating” is a completely OBJECTIVE expression consisting of two numbers which have no meaning whatsoever relative to good, bad or indifferent. That is why it can be simply added to any grading report from any grading laboratory without disrupting any current practices, and all competent laboratories will report the same values.
Quote:
We can talk a lot on different diamond grading systems. ... And other important point: one shouldn't mix proportions with finish (symmetry and polish), they should be graded separately.

I agree completely, and that is exactly why the status quo must go.

Now, how all this relates to and simplifies current Cut Grading is that it does not recognize subjective cut grades like poor, fair, good, very good, and excellent, or their equivalents. Now, there are only two grades, Fine and Commercial. These are based on appearance and as Conny wrote, “... we all recognize a well cut round brilliant when we see it.”
Quote:
Egor I know... we all recognise a well cut round brilliant when we see one but as usual no possibility of doing stuff easier. That's why I stick to the HRD nomenclature. 

Personally I wish there was not so much fuzz about cut grading, but then of course, I am one of those who love a nicely polished OMC or OEC.

Now, you have an alternative. Don’t be a slave to the status quo.
Quote:
which total depth value should we consider?

Total Depth = crown height + girdle thickness + pavilion depth

Just take a piece of X-Y graph paper and plot C/P from 0.74 to 0.94 on the ordinate and Total Depth from 57 to 56 on the abscissa and draw concentric circles around the point 0.84,61.3. You can name the different areas anything you want and create you own (subjective) grading system.

Since the results are purely objective and the angles for the best cut don’t change, Conny could use such a chart for his OMC or OEC stones. Also, when it comes to the value of a “non-ideal cut” stone, it is not a function of its cut grade or shape, but rather of its kernel weight. (That is another of my “revolutionary” concepts.) :D :D


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 Post subject: Re: Diamond proportions: Discussion after Quiz
PostPosted: Tue Jan 24, 2012 4:16 am 
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I like the idea of KISS principle implemented on diamond gading :)

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 Post subject: Re: Diamond proportions: Discussion after Quiz
PostPosted: Tue Jan 24, 2012 12:49 pm 
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Oh, too much new revolutionary concepts for me!...
Coming from Russia, I like much more evolutionary processes and changes! :D

I have nothing more to say in this discussion.

Personally, I can't understand why you defend something that was proven to not work.

Just a final consideration: imagine a person who use your rule and buy the diamond number 2 as a perfect cut diamond (it accomplishes the rule perfectly). Any grading lab of the world will give Poor cut grade to such stone and the person will lose his money.

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 Post subject: Re: Diamond proportions: Discussion after Quiz
PostPosted: Tue Jan 24, 2012 9:16 pm 
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Oh, too much new revolutionary concepts for me!...
Coming from Russia, I like much more evolutionary processes and changes! 
I have nothing more to say in this discussion.

Egor, I want to thank you for your input. Your graphics are superb and you have done a remarkable job of defending the status quo. Unfortunately, everyone knows the status quo is unsatisfactory, but they haven’t the slightest idea of what to do to make diamond evaluations easier. The answer of course, lies in my revolution. :D
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Personally, I can't understand why you defend something that was proven to not work.

Since Egor has bowed out of this discussion, The following is addressed to those with open minds and advocates of KISS
As you can see, he still believes he has proven my approach does not work, but he is mistaken. He simply doesn’t understand the philosophical concepts involved and keeps talking about “my rule” and how it doesn’t work.

There is no rule. There never has been a rule, except in his mind. There is just my recognition of the fact that the finer the diamond, the closer the C/P ratio approaches the value of 0.84. Of course there are thousands or billions of combinations of C and P which produce a ratio of 0.84, but that doesn’t matter a bit, and they are all irrelevant because saying a fine diamond has a C/P ratio of 0.84 is vastly different from saying all diamonds having that ratio are fine diamonds.

It all hangs on the definition of a “Fine” diamond, which I (as well as the GIA and probably every experienced diamond dealer in the world) have clearly defined as one which shows no remarkable features related to its polish, symmetry, and/or girdle, and exhibits an even pattern of bright and dark areas with strong contrast which guarantees an attractive appearance. Conny wrote, “... we all recognize a well cut round brilliant when we see it.” Incidentally, this only occurs when the crown angle is very close to 34.5 degrees and the pavilion angle close to 41 degrees. All other combinations do not meet those criteria, as Egor’s graphics clearly demonstrated.
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Just a final consideration: imagine a person who use your rule and buy the diamond number 2 as a perfect cut diamond (it accomplishes the rule perfectly). Any grading lab of the world will give Poor cut grade to such stone and the person will lose his money.

In my system, anyone can look at number 2 and immediately classify the stone as Commercial, and there would be no need for any measurements at all, or to assign a “Cut Grade”.

Remember, stones classified as Commercial are actually bought on the basis of their attractiveness, and that is a subjective factor. I would not be the least bit surprised if a great number of people consider number 2, to be far more attractive than many stones bearing a cut grade of “Fair” or “Good”.


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