Graded Ideal but GIA Proportions Diagram indicate different?

[TeresaMarie]

I am wondering why when searching for diamonds online, when you select "ideal" as the cut - then take a look further at the diamonds proportions according to the GIA report they are not within the ideal cut guides? I.e. Table (53-5, Depth (59 - 62.3), Crown Angle, Pavilion Angle, etc. A lot of the proportions are outside of the recommended perimeters’ that I have found on various websites including price scope. Any insight / advice would be greatly appreciated.

 

[kenny]

Re: Graded Ideal but GIA Proportions Diagram indicate differ

You don't have to bother paying attention to those ranges.
Those four specs work together in ways to complex for us mortals, without advanced math degrees, to figure out.

A diamond you find within those ranges may happen to have 4 numbers that work together in the least-disadvantageous way.
The HCA below is a clever math thingie that crunches the numbers the identifies combinations of the four numbers that work together in the most-advantageous way ... for the best light performance.

Buying a round with superb cut is an easy two-step process.
HCA and Idealscope.

Plug four numbers from the GIA or AGS report into the HCA.
https://www.pricescope.com/tools/hca
Reject rounds that score over 2.0 and get an Idealscope picture on those scoring under 2.0.

https://www.pricescope.com/tools/ideal-scope

Compare the Idealscope pics to this chart. http://www.ideal-scope.com/1.using_reference_chart.asp



If your vendor can't or won't provide an Idealscope pic find another vendor or buy your own Idealscope here.
http://www.ideal-scope.com/cart_order.asp

 

[TeresaMarie]

Re: Graded Ideal but GIA Proportions Diagram indicate differ

Well must say I am glad I posted that question. I have been trying to find a diamond on james allen by putting in the table, depth, then checking the other (crown, pavilion) and if it wasn't in the perimeter thinking it wasn't good. I have been punching numbers in the HCA tool after. As for the pictures, JA doesn't seem to post them unless they are their True Hearts diamond. If I use the HCA tool alone, is that a "good enough" indicator?

 

[Texas Leaguer]

Re: Graded Ideal but GIA Proportions Diagram indicate differ

Well must say I am glad I posted that question. I have been trying to find a diamond on james allen by putting in the table, depth, then checking the other (crown, pavilion) and if it wasn't in the perimeter thinking it wasn't good. I have been punching numbers in the HCA tool after. As for the pictures, JA doesn't seem to post them unless they are their True Hearts diamond. If I use the HCA tool alone, is that a "good enough" indicator?

The HCA tool uses a limited number of rounded and averaged measurements. Think of it as a silhouette as opposed to a photo. And think of going on a blind date- would a silhouette be "good enough". Kind of depends on how demanding you are.

 

[Diamond2014]

Re: Graded Ideal but GIA Proportions Diagram indicate differ

If I were to order the Ideal-Scope, how long it usually take to get to US? Is it being shipped within US? I'm from NY, and I kept holding off the order of the Ideal-Scope, thinking it'll come from Australia, which will take quite some time

 

[Gypsy]

Re: Graded Ideal but GIA Proportions Diagram indicate differ

"ideal" is not a GIA rating. It's a meaningless vendor rating. The only time "ideal" is relevant is with an AGS lab report. Never GIA.

 

[TeresaMarie]

Re: Graded Ideal but GIA Proportions Diagram indicate differ

Lol.. so how does a someone who knows nothing about diamonds find a good one? There is such an overwhelming amount of information.

 

[Gypsy]

Re: Graded Ideal but GIA Proportions Diagram indicate differ

Lol.. so how does a someone who knows nothing about diamonds find a good one? There is such an overwhelming amount of information.

Finding PS and posting here is a great start. Then you can study up on the piles of knowledge available here. The "Knowledge" tab at the top of your screen is a great place to start.

If you are looking for a modern round brilliant then here is some information to get you started:

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. And you must stick to GIA and AGS only. EGL is a bad option: [URL='https://www.pricescope.com/community/threads/egl-certification-are-any-of-them-ok.142863/']https://www.pricescope.com/community/threads/egl-certification-are-any-of-them-ok.142863/[/URL]
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. Under 2 is a pass. Under 2.5-2.1 is a maybe. 2.6 and over is a no. No score 2 and under 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. BGD, James Allen, GOG, HPD, ERD 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.


If you are looking for a different shape let me know and I'll link you to information that shape.