Table/Depth Concern - Please help!

[new2dabiz]

Hello! This is my first post - although I have gathered so much helpful insight from other threads. Let me clarify that my intent of this post is to hear the truth from you guys (hopefully that this is a nice stone). Looks like a BEAUTIFUL stone and I have shopping pretty intensely and have seen probably around 50 stones. I would really appreciate input on the bolded font below.

I am on the verge of purchasing a 1.7c round brilliant (VS1/F). The dimensions are 7.98 - 7.93 x 4.59 mm. No fluorescence.

Cut Grade: Very Good
Total Depth: 57.7%
Table Width: 59%
Crown Height: 12%
Pavilion Depth: 44%
Firdle Thickness: Thin, Faceted

My main concern is this stone too shallow? It appears to have wonderful sparkle inside the store and in the natural sunlight, I just want to be reassured that the above Depth and Width percentages are ok.

Thanks so much!

 

[Gypsy]

It's not any one measurement that matters. It's how they all work together.

We usually say that GIA Very Good cut is not good enough.
GIA Ex cut is already too broad.

Here's my usually advice and knowledge blurb. Follow this, and run your stone through the HCA.

The entire purpose of faceting a diamond is to reflect light.
How well or how poorly a diamond does this determines how beautiful it is.
How well a diamond performs is determined by the angles and cutting. This is why we say cut is king.
No other factor: not color, not clarity has as much of an impact on the appearance of a diamond as its cut. An ideal H will out white a poorly cut F. And GIA Ex is not enough.
So how to we ensure that we have the right angles and cutting to get the light performance we want?
https://www.pricescope.com/wiki/diamonds/diamond-cut
Well one method is to start with a GIA Ex, and then apply the HCA to it. YOU DO NOT USE HCA for AGS0 stones.
https://www.pricescope.com/wiki/diamonds/holloway-cut-advisor
The HCA is a rejection tool. Not a selection tool. It uses 4 data points to make a rudimentary call on how the diamond may perform.
If the diamond passes then you know that you are in the right zone in terms of angles for light performance. 2 and under is a pass. Under 2.5-2.1 is a maybe. 2.6 and over is a no. No score 2 and is better than any other.
Is that enough? Not really.
So what you need is a way to check actual light performance of your actual stone.
That's what an idealscope image does. https://www.pricescope.com/wiki/diamonds/firescope-idealscope
It shows you how and wear your diamond is reflecting light, how well it is going at it, and where you are losing light return. That is why you won't see us recommending Blue Nile, as they do not provide idealscope images for their diamonds. James Allen, GOG, BGD, ERD, HPD and WF do.

The Idealscope is the 'selection tool'. Not the HCA.
So yes, with a GIA stone you need the idealscope images. Or you can buy an idealscope yourself and take it in to the jeweler you are working with to check the stones yourself. Or if you have a good return policy (full refund minimum 7 days) then you can buy the idealscope, buy the stone, and do it at home.


Now if you want to skip all that... stick to AGS0 stones and then all you have to do is pick color and clarity and you know you have a great performing diamond. Because AGS has already done the checking for you. That's why they trade at a premium.

 

[new2dabiz]

Thank you for the input. Others, please chime in!

I am simply wondering if I should be considered with the table and depth percentages. It seems to be close to approaching "shallow", but to my eye, and on paper, looks GREAT.

 

[John P]

The dimensions are 7.98 - 7.93 x 4.59 mm. No fluorescence.
Cut Grade: Very Good
Total Depth: 57.7%
Table Width: 59%
Crown Height: 12%
Pavilion Depth: 44%
Firdle Thickness: Thin, Faceted

It's not any one measurement that matters. It's how they all work together.

With those numbers the pavilion and crown angle combination will be something like 41.3 / 30.5 (+/-) which is in-line with the 12% crown height. It's what some might call a pancake. Thin girdle. Short crown. Shallow depth.

I'd suggest you compare it to a known Ideal performer or two. I'd especially check differences in dispersion in a side by side comparison with a top EX or Ideal, and look for some central darkness caused by table-reflection in diffused and softer light conditions.

 

[new2dabiz]

Thanks for this information - it is very helpful, 'gypsy'!

I used the HCA tool (https://www.pricescope.com/tools/hca) - and received a '2.0 - Overall Very Good'. The specs resulted in all 'Very Good' and an "Excellent Spread".

This gives me a little more positive reinforcement with the fact that the stone looks incredible to me in person (indoor and outdoor light) and the price is right! Given the price, and the 4 C's (and the above tool); I will most likely move forward with this stone!!!

Now I just need to keep my mouth shut so she doesn't find out ; ) I CAN'T WAIT

 

[JulieN]

What lab graded this?

Thin girdle with that crown angle is a chip risk.

 

[new2dabiz]

Thanks - after reading 'pancake' I am worried. If we were talking breakfast I would be excited, but not a pancake ring!!!

After visually inspecting the ring inside and outside (the sparkle is wonderful), and getting positive feedback from the HCA tool above, I am feeling confident with the ring specs and dimensions. Now, my only concern is, will the stone look flat (from the side) after it is set? The good thing is her ring size is a 3, yes a 3, so the ring is going to look big.

Any thoughts on all the information/concern above?

Thanks again everyone!

 

[new2dabiz]

GIA graded!

Chip risk!? That doesn't sound good

 

[JulieN]

GIA reports will have angles, very rounded. Please post them

 

[new2dabiz]

I will post the angles when I get a chance to get my hands on the report. I had to hand over the report to my parents to lock in the safe (so my gf doesn't get her hands on it)

The percentages I posted have to be at least close to sufficient for this discussions purposes...

Is chipping a real concern? and will it look flat/shallow in its setting?

 

[John P]

Clearly you're excited about it, and no one wants to bring you down. But there are some questions.

The crown angle number is one of them. The crown height percentage puts us in a certain ballpark (thus the questions) but is not sufficient. Even the crown angle you post will be (1) an average of eight separate measurements that is (2) further rounded to the nearest half-degree. The percentage you've given (12%) is also rounded, and another layer of approximation distant.

Is chipping a real concern? and will it look flat/shallow in its setting?

GIA used to include a warning about crown angles under 32 degrees on their reports. Now, when coupled with a thin girdle, they just reduce the cut grade to VG. If the crown angle is 30-32 degrees then chipping is a danger with a thin girdle, but that's addressed by carrying insurance on your precious jewelry items - advisable for anyone.

As for flat appearance: Princess cuts, radiants and other shapes frequently have crowns 12% and under, so it won't be off-putting in that sense. But yes, next to other round brilliants the crown will seem a bit flat by comparison.

RE the HCA: It's a rejection tool, not to be used for selection. Basically any diamond 2.0 and below is worth exploring further.

 

[new2dabiz]

I am trying to calculate the (approx) crown angle. I found a few formulas on PS that tell you how to do it using the specs (percentages) listed above. I am having trouble calculating this to give me an estimated crown angle. Is anyone able to help?

It sounds like now my main concern should be the CROWN ANGLE and is likelihood of chipping. I will absolutely get insurance, regardless of what stone I pick.

 

[John P]

I am trying to calculate the (approx) crown angle. I found a few formulas on PS that tell you how to do it using the specs (percentages) listed above. I am having trouble calculating this to give me an estimated crown angle. Is anyone able to help?

Already did. The crown angle will be approximately 30.5 +/-

There is no way - full stop - no way to calculate it further without the report information. And even then the averaging and rounding makes it somewhat fuzzy: Look at the calculated carat weight, using all the data you provided before.


Clearly, rounding is afoot. There is an element somewhere, not reflected in the data-points, that accounts for the missing 0.03 cts +/-

 

[new2dabiz]

Wow, thank you for this analysis!

After doing some more research, regarding crown angle, 30.5 doesn't seem as if it should cause as much concern as if it was less than 30. What this would mean is in a general sense, that in order to see the light reflecting up, you would have to look straight at it, as opposed to a 34 degree crown angle, where the light would also reflect out at an angle.

30.5 doesn't seem like it should be of much concern.