Graded angles are averages of all angles?

[MRBXXXFVVS1]

I learned that the graded angles on diamond reports are actually averages of all the angles, therefore there could be a bit of variation throughout the cut. Does the overall cut and symmetry account for this? Of course, an Idealscope and ASET will show how the diamond performs in terms of light return.

 

[headlight]

On GIA reports, proportions are rounded which is a huge bone of contention on this forum. GIA doesn't feel it has an impact. So, yes, in answer to your question, there can be variation. The averages then yield the value that will fall where it may in the GIA Cut Grading charts and the cut grade is based on that. Yes, images will give a fuller picture. So will seeing the diamond in person in various lighting settings. AGS (which is preferred here) have stricter tolerances for their cut grades. GIA accepts a much wider range for their Excellent grade. They also approach it that there are many combinations that will yield an attractive diamond. I personally do feel there is merit to this. Is it the be all, end all?... Does it get it right every time?... Apparently not. Also, you have to keep in mind that some diamonds have different looks and people are attracted to specific ones. Here on PS there is a certain look that is preferred. Is that the only way to go? I would say not, but each person has to decide for themselves. Many people here consider cut to be the ultimate sole determination. However, I approach it as a total package... looking at a stone's cut, clarity, color, personality, carat wt, and price as a COLLECTIVE. I place a lot of value on color so, while no one wants a poorly cut stone, I feel that the color plays an important role. But that's me, although I know I am not alone in this. Often on this forum the term "frozen spit" (which I think is a repulsive term) is used to describe diamonds that are not ideal cuts. I think that's a bit extreme... there are many stones that fall between those two boundaries. There are many beautiful stones that are near ideals. Add to that D or E (and even F) color and you've got something pretty special IMO. A good majority of participants here who have super ideal cuts have J color. I would rather have near ideal and colorless (of course, I would love to have it all lol but that would only happen if I went below a size that was my minimum). But not everyone agrees with me and I accept that. I think each stone needs to be evaluated on its own merit, as opposed to going solely by images. On that note, I don't think a slight area of light leakage on an image is going to translate adversely in real life viewing. Many here feel if it isn't solid red the stone should be rejected. I respect this. So here you have a viewpoint that is not so popular but I think that is what makes this a great forum, to get the input from many.

 

[Dancing Fire]

On GIA reports, proportions are rounded which is a huge bone of contention on this forum. GIA doesn't feel it has an impact. So, yes, in answer to your question, there can be variation. The averages then yield the value that will fall where it may in the GIA Cut Grading charts and the cut grade is based on that.

Here's a GIA stone I wouldn't mind wearing...

Distinctive Gem | The Synergy of Science & Beauty

Known for our August Vintage cut, DG is a family owned & operated online diamond business built on customer service. While we accommodate almost all jewelry requests and custom work, we specialize in ideal cut vintage and modern diamonds that are comprised of the highest optical performance you...

august-vintage-inc.myshopify.com

 

[Karl_K]

AGSL rounds then averages the numbers on the report but the light performance grade is based on a computer model using the full scan data.

Gia rounds then averages then grossly rounds the numbers to put on the report and those numbers are used to assign a cut grade.
This leads to a huge variation between 2 diamonds with the exact same numbers on the report and leaves a ton of room for cheating.

Why Advanced Images Matter...A Bad 34.5/40.8...

I'm just as guilty as anyone. Helping someone find a stone and run across one with that 34.5/40.8 combo. You smile. You then run through the rest of the proportions.... 57 table, 61.7 depth, 75 LGF's, 50 stars and medium-slightly thick girdle....check, check, check,check and check You...

www.pricescope.com

 

[Garry H (Cut Nut)]

As everyone has written, yes, angles are averaged and there can be big variations.
But many years ago I discovered this diamond which had a huge variation AND reasonable H&A's patterning.
The reason probably was a little bit of dust or dirt on the table of the diamond when it was placed in the dop holder during polishing. It was a very fine stone with GIA symmetry grading of "Good".

As a result even though there was a big difference in the crown and the pavilion angles, when accounting for the variation as per the axis of the diamond, the difference as per the OctoNus Theory developed for this scenario was relatively small.
We wrote the stone up here http://www.octonus.lgg.ru/cut/english/symmetry/_6.htm


In a perfect world labs would give you more info and not round as much, but, hey, it is not a perfect world.