Find your diamond
Find your jewelry
shape
carat
color
clarity

Diamond proportions

JackSpider

Rough_Rock
Joined
Jan 31, 2016
Messages
10
Hi Guys,

I have shortlisted 2 diamonds based on TRIPLE EX and proportions.

Do you think these at least made the first cut and are worth pursuing further?

file.php?mode=view&id=456643&sid=d7b79997412e2316e270d8b1eb8bf811.jpg

Thanks!

_36362.jpg
 

Gypsy

Super_Ideal_Rock
Joined
Aug 8, 2005
Messages
40,198
Not the first one. It's way too deep.

Run the second one through the HCA.

Here's what you need to know:

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. With round diamonds even a GIA triple Excellent is not enough. And you must stick to GIA and AGS only (HPD in Europe is good as well). 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 generally, though you can. In general, AGS0 trumps HCA though as one examines the actual stone and the other does not.
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,BE, 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. Some AGS0's are better than others though, so pay attention to any ASET or IS provided.

In general with rounds, you will want a table 60% or less. A depth between 59 and 62.3. Crown angle 33.5-36. Pavilion Angle: 40.6-41 (there is a little give on this). And the crown and pavilion angles must be complimentary which is what the HCA checks for you.
 

Gypsy

Super_Ideal_Rock
Joined
Aug 8, 2005
Messages
40,198
I would be wary of an SI2 with a grade setting cloud as it is likely to impede performance. Also those far away videos don't tell you much about the inclusions and thata the biggest issue.
 

diamondseeker2006

Super_Ideal_Rock
Premium
Joined
Jan 11, 2006
Messages
55,631
I also would avoid SI2, and if this is for an engagement ring, I would go no lower than J color.

These are measurements to help you stay in ideal cut territory with a GIA excellent cut stone.

table: 54-58

depth: 60-62.3

crown angle: 34-35.0

pavilion angle: 40.6-40.9 (sometimes 41.0 if crown angle is closer to 34))
 
Be a part of the community It's free, join today!
    Three-stone engagement ring upgrade
    Three-stone engagement ring upgrade
    Vintage OEC Bracelet
    Vintage OEC Bracelet
    June’s Birthstone Trinity
    June’s Birthstone Trinity

Need Something Special?

Get a quote from multiple trusted and vetted jewelers.

Holloway Cut Advisor



Diamond Eye Candy

Click to view full-size image.
Top