What Exactly Does GIA Excellent Cut Grade Mean?

Q:

Hi Liz,

Great website! Can you help me with some diamond recommendations? I’m looking for a diamond with GIA excellent cut grade. Here are the details of what I’m looking for:

Shape: Round Diamond
Color: H/I/J
Clarity: VS2/SI1/SI2
Carat: 1.5ct
Cut: Excellent/Ideal
Budget $10K

I am most concerned about the diamond being eye-clean. I also don’t want to see any noticeable yellow tint. I looked at some J color ideal cut diamonds this weekend and they looked fine to me but I have also seen some I color diamonds which showed some yellow tint. I want to ensure they look near colorless.

Thanks,

Thom

A:

Hello Thom,

Thank you for contacting me and letting me know your diamond requirements and budget.

To address your first concern, I only recommend diamonds that are ‘eye-clean’. Depending on your color sensitivity you may be able to detect some color in a “J” diamond from the side-view or pavilion angle. As you know, ideal cut diamonds reflect the maximum amount of light thereby facing up visually bigger and brighter. As long as you stick with an ideal cut diamond a J color will not be an issue.

If you are looking to maximize carat weight for your budget, I recommend the following diamond: http://www.ritani.com/diamonds/round-diamond-1-52-Carat-J-color-GIA-certified/D-Z1NSJM

This is a gorgeous 1.52ct J VS2 for $9,381.00 available at Ritani. There is a nice HD video that shows this 1.52ct from all angles and the magnified image shows no obvious visual inclusions. It is a GIA excellent cut grade diamond and has AGS ideal cut proportions. I would say this is an excellent choice for you.

Please let me know what you think and if you have any questions about this diamond or anything else.

Kind Regards,

Liz

Q:

Thanks Liz. I did a quick search and found this diamond for $7,908.00 what do you think? Sames specs as the one you recommended but more than $1k cheaper. http://www.ritani.com/diamonds/round-diamond-1-56-Carat-J-color-GIA-certified/D-ZYH1HQ

Thom

A:

Hi Thom,

The 1.56ct J VS2 that you have chosen has no actual magnified picture of the diamond (the picture on the website is a stock/sample image). I still prefer the first stone for you as the cut is better.

Kind Regards,

Liz

Q:

Hi Liz,

I totally understand the need for a diamond picture however this diamond has a GIA excellent cut grade. If both stones are graded ‘excellent’ is there a specific reason you don’t think the second choice is good?

Thom

Why Two Diamonds With GIA Excellent Cut Grade Have A $1500 Price Difference

A:

Hi Thom,

Diamonds are crystals that are cut by humans to further enhance their beauty. Humans have determined certain popular angles with geometry that produces the best internal light reflection. Each lab has their own way of assessing how well a diamond is cut.

GIA uses a 5 grade hierarchy for cut: Excellent, Very Good, Good, Fair and Poor. A GIA report can list overall cut grade as Excellent with either or both polish and symmetry grades being at least Very Good. GIA’s approach to diamond cut grade is a proportion-based quality system for round brilliant colorless diamonds. This technology relies upon a 2-dimensional system to determine a diamond’s cut grade. Most people are satisfied and feel safe in purchasing a diamond that has a GIA excellent cut grade.

1.52ct J VS2 from Ritani with GIA excellet cut grade and also AGS ideal cut proportions

However, another lab that is well known and respected is AGS Laboratories. AGS uses a 0-10 grading scale with 0 representing Ideal. AGS utilizes a more advanced 3-dimensional system to determine a diamond’s cut. Additionally, AGS includes human analysis, angular spectrum evaluation tool (ASET), and optical physics ray-tracing software to determine the quantity and quality of light that is returned to the observer (in motion as well as in a face-up static position).

Each gem lab evaluates diamond cut differently. The two most popular diamond labs are GIA and AGS in the USA. GIA’s ‘Excellent’ cut grade includes AGS’s ‘Ideal and Excellent’ which means it includes a wider variance of diamond cut proportions. For more information please visit diamond grading.

All of these tools help to give AGS an overall summary of the interaction of light within any given diamond and therefore is used to determine if a diamond’s cut is AGS “Ideal Light Performance” grade. Because the AGS cut evaluation process is very stringent and exact, (given to less than 1% of all diamonds in shapes where cut is graded), the AGS 0 ‘Ideal’ grade is the world’s strictest laboratory standard for cut. AGS light performance based reports require that a diamond have Ideal light performance, Ideal polish, and Ideal Symmetry in order to receive the coveted grade known in the trade as The Triple Zero®.

Cut Is Queen – Why Cut Proportions Will Always Reign As Most Important ‘C’ For Diamonds

So, back to your original question of why one diamond with a GIA excellent cut grade is preferred over the other simply has to do with cut proportions and angles. Your second diamond from Ritani is indeed a GIA Excellent cut grade but wouldn’t make it as part of AGS’s ideal cut grade. It is cut slightly too deep which translates to light leakage. In other words, the diamond will not be as bright white or brilliant as it could be because of the error in cut. This is exactly why the price difference is nearly $1500.00. There is always a reason why a diamond is priced as it is.

When it comes to buying diamonds, investing in an ideal cut diamond (bright white brilliance coupled with lots of sparkle) is really what matters most.

I hope this clears up some questions for you. Please let me know if I can help out further.

Kind Regards,

Q:

Hi Liz,

Thanks for the detailed explanation! I had no idea diamond cut was so detailed! I’m going to talk to Ritani about your recommended 1.52ct J VS2. Thanks again!

Thom