7 replies to this topic

[Approaching30]

Hello,

A few months ago I was on this site questioning the value of a princess cut diamond for a future engagement ring. Based on the advice I received, I scrapped the purchase and have continued my search. I am still pursuing a princess cut diamond but am interested in one with excellent/ideal cut with a GIA report (among other qualities). However, unless I am missing something, I noticed that GIA papers do not specify the "cut" quality in the grading results. That being said, how does a normal guy like me know if a certain diamond has an excellent/ideal cut? I assume the rating is based on the measurements of the diamond but how can a normal person interpret this information without a jewelers feedback? I look forward to your comments.

Thanks!

[diamondsbylauren]

All due respect, but diamonds are a specialty.
It's not brain surgery, but there is a lot to learn through experience.

There is no cut grade for princess cut diamonds, so if you want one, it would be wise to draw upon the expertise of a dealer you trust.
You may find charts that purport to answer this question, but they are worse than useless IMO

[jan]

GIA doesn't currently have a cut grade on princess cut diamonds. AGS does however, although even in the ideal cut, light performance can differ on each individual diamond.

I think the reason you want an ideal cut is that you want the stone to sparkle like mad.

We actually test all of our diamonds for light performance and see how much white light, colored light and scintillation are coming from the individual stone. Just going by outside measurements won't tell you how bright the stone will be.

If you need some help finding a real sparkler, I'll be glad to help you.

[Approaching30]

Ahhh....this makes sense now. I thought I was confused. I appreciate the help!

[blinger.mike]

jan, on Monday, Dec 1 2008, 08:13 AM, said:

GIA doesn't currently have a cut grade on princess cut diamonds. AGS does however, although even in the ideal cut, light performance can differ on each individual diamond.

I think the reason you want an ideal cut is that you want the stone to sparkle like mad.

We actually test all of our diamonds for light performance and see how much white light, colored light and scintillation are coming from the individual stone. Just going by outside measurements won't tell you how bright the stone will be.

If you need some help finding a real sparkler, I'll be glad to help you.

When I think of "cut" and all the mathematics and science that would go into setting an ideal standard. Wouldn't the AGS issue a standard that would return the most light? If I had a bunch of Mirrors in a room I would simply move them around until the light reflecting of them did what I wanted it to do. What is the variable Im missing? It just seems to me that if Carat size, clarity and color remained constant all you would have to do from there is make sure the crispness of your cuts and your measurements of all thicknesses and angles where correct then it couldn't get any better.

[davidelevi]

There's (at least) three reasons why a "mathematically precise" solution does not work:

1. Even assuming that a diamond is a perfect object and cutting can be made equally perfect, the solution to the "optimal" light return equation has more than one solution (technically, there are more degrees of freedom than constraints). In fact, it has infinite solutions. So the only way to specify "optimal" standards is through ranges and combinations anyway.

2. In the real world, there are other significant constraints in terms of rough yield / cost, inclusions, cutting tolerances and errors. This acts in two ways: a] it provides "incentives" to produce (slightly) less than perfectly cut stones, and b] it creates pressure for standard setters to accept as "top grade" even stones that are (slightly) less than perfect.

3. Because light return is not the only thing that makes a diamond beautiful - you have contrast (roughly the size of the light "chunks" that return) and the balance between reflected and refracted light to consider too - there are combinations of proportions that produce the same total amount of light being returned, but in different ways. This again causes two things: a] for each level of total light return you have (infinitely) many variations of how the light is returned, each slightly different in optical effect; b] taste enters the equation - some people like broad flashes, others like lots of little sparks; some like a lot of refracted (coloured) light, others like an icy-white reflection...

ETA: removed silly smilie with black glasses instead of b )

Edited by davidelevi, 08 December 2008 - 11:03 AM.

[jan]

The cut is the most important part of the diamond's sparkle. You won't be able to tell from a lab report only how well cut the diamond is.
Also mathmatical averages won't tell you how well cut a diamond is. Measuring the outside dimensions of the stone doesn't tell you how all the facets are working together to bring you light return to the eye.

We actually have two technologies in house that can measure light return in the diamond.

www.isee2.com
www.gemex.com


The finish grade ( polish and symmetry) is not to be confused with the cut grade.

There are broad ranges in the ideal and excellent cut grades. That is why we measure each stone individually.

Edited by jan, 08 December 2008 - 11:05 AM.

[blinger.mike]

I knew I was missing something. Great input.