GIA Excellent Cut = Idealscope Excellent

[chictomato]

Hi there, I am not really in diamonds. But would like to get the beat quality diamond possible. I understand from the forum that a Idealscope image is essential to know if a diamond has light leakage, if it has good light return and symmetry (pls correct me if i am wrong). However, I do not have a idealscope. By purchasing a GIA Excellent Cut diamond is it equivalent to a excellent score with the Idealscope? meaning that it has a minimal leakage and excellent light return? tks!

 

[stone-cold11]

No, not necessary. GIA Ex cut allows for some steep deep combination that leaks light and the averaging and round of numbers in the report means that even if the numbers looks good on paper it may not perform well which is why we need to see an IS image.

 

[Lorelei]

Date: 8/24/2009 4:09:17 AM
Author:chictomato
Hi there, I am not really in diamonds. But would like to get the beat quality diamond possible. I understand from the forum that a Idealscope image is essential to know if a diamond has light leakage, if it has good light return and symmetry (pls correct me if i am wrong). However, I do not have a idealscope. By purchasing a GIA Excellent Cut diamond is it equivalent to a excellent score with the Idealscope? meaning that it has a minimal leakage and excellent light return? tks!

No, one of the topics which has been widely discussed here is that the GIA Excellent cut grade allows for what are called steep deep angled diamonds. Sometimes with these they leak light which is undesirable, you want the light bouncing back out of the diamond and hitting you in the eye! So really a GIA Excellent will not always show an excellent IS image. To further cloud the issue, GIA round the numbers so what might appear to be a potentially leaky steep deep on paper might not be in an image, especially if the proportion averages are tight and those proportions are actually shallower than the angles suggest.

This thread goes into greater detail.

https://www.pricescope.com/community/threads/consumer-advisory-gia-cut-grade-rounding-problems.39401/

 

[Paul-Antwerp]

What is more, the idealscope-pic is of the actual diamond, while the GIA-grade is based on averages, even rounded averages. A lack of precision will not influence the GIA-grade, while it does have an effect on the actual idealscope of the stone.

Live long,

 

[oldminer]

Just to provide balance to the responses, a diamond may look superb to untrained eyes well down the scale of appearance levels noticeable by expert observers. A consumer may find a diamond that they really love, graded GIA Excellent or even Very Good which would not have a perfected Ideal-Scope image or be what one of the experts might choose on a grading basis, but one which simply looks good to their untrained eyes. The GIA cast a broader net over their top range grade than AGS did. In doing so, the GIA made a smart business decision and gets a larger share of the diamond grading business. As far as consumers are concerned, AGS is more on the consumer''s side of information, but which lab wins is partly determined by which lab has the most business and not which lab is the strictest. There are conflicting goals which are very difficult to resolve, but one can understand the different points of view.

Grading a mounted diamond accompanied by a Sarin file, is easy enough with DiamCalc. Such software helps make sense out of the numbers involved in measuring a diamond.