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Filtering w/ ideal proportions rejects potential good ones?

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knguyen120

Rough_Rock
Joined
Jul 27, 2014
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Hiya,

I want to get engaged within a month so time isn't on my side. I was filtering James Allen with specific proportions listed before in this site and it really narrowed down my selection a little too much. So much that I didn't find anything. Will I pass up perfectly good performing diamonds searching this way? Can a diamond perform perfectly well even if it doesn't match those proportions? If so, I would thus need an idealscope/ASET image correct?

Thanks!!!
 
Re: Filtering w/ ideal proportions rejects potential good on

Here's what is was trying to filter by:
Table: 53-57%
Total Depth: 59.5 – 61.5%
Crown angle: 34-35
Pavillion angle: 40.6-41
 
Re: Filtering w/ ideal proportions rejects potential good on

It's an interesting and important question. In short, you can think about a diamond like a tiny hall of mirrors, where the mirrors reflect light back to the eye, creating patterns of flashes are nice to look at.

Certain combinations of proportions reflect light better and create patterns that look better than others. This may seem subjective, and in a way it is, but people tend to agree on at least a baseline standard of beauty within certain categories of cut (round brilliant, princess).

The "ideal proportions" you mentioned are a relatively foolproof first step in narrowing down options that fit at least one standard of beauty.

knguyen120 said:
Can a diamond perform perfectly well even if it doesn't match those proportions? If so, I would thus need an idealscope/ASET image correct?

Thanks!!!

It depends on what combination of proportions you're talking about, and it depends on what you mean by "perfectly well."

To find any nice diamond without seeing it in person, it's always helpful to get an ASET or Idealscope to get a sense for how the diamond is dealing with light, even in those ideal proportions, and particularly as you get away from those ideal proportions.
 
Re: Filtering w/ ideal proportions rejects potential good on

For rounds. Those stats are ONLY for people buying from a vendor IN PERSON without an idealscope, or from a vendor online who does not provide an idealscope image. JA is neither of those.

This is what I filter buy at JA: I chose "true hearts" and "ideal" catagories. Pick my color and clarity range. Then THE ONLY THING I DO: set depth to 62.4 . After that I chose by sight and then I look at each stones numbers and run through HCA FOR GIA STONES. For AGS stones, an AGS0 plus idealscope is enough. No HCA needed for me.

So yes, you are being unnecessarily restrictive. You can get BEAUTIFUL stones outside that range. The HCA is restrictive enough, and as long as you are shopping at James Allen. Just use the HCA as a filter.

2.5-2.1= maybe range. Has a higher chance of not having a good idealscope. But due to GIA rounding, there could be excellent stones there too so it's not an auto-disqualify.

2.0 and under has a higher chance of having a good idealscope.

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.
 
Re: Filtering w/ ideal proportions rejects potential good on

Wow thanks for the very informative posts! I used the HCA to eliminate a big pool of diamonds. The James Allen rep told me that I should use the HCA chart to further eliminate even more diamonds (because I had still too many). Basically if the X landed within the white box I kept the diamond in my wish list.

What's funny is that this method eliminated some of the more expensive diamonds even though they had the same cut, clarity, color etc. Wonder how the pricing works.
 
Re: Filtering w/ ideal proportions rejects potential good on

I'd argue that unless you like diamonds with larger tables and low crowns, filter by table size (I prefer 55-56%) and crown angle if CA is also an option.
 
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