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Help a new buyer with a diamond! Any response helps :)

Kc10f

Rough_Rock
Joined
Apr 12, 2016
Messages
24

Gypsy

Super_Ideal_Rock
Joined
Aug 8, 2005
Messages
40,198
Hi. The angles are not complimentary.

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 62.4. Crown angle 33.5-35. Pavilion Angle: 40.6-40.8 (there is a little give on this). And the crown and pavilion angles must be complimentary which is what the HCA checks for you.
 

Kc10f

Rough_Rock
Joined
Apr 12, 2016
Messages
24
Thanks for the reply. That was a very informative post. I requested for an ideal scope of that particular diamond. Of course now, it seems like I may be better continuing my search and trying to find something with an HCA score <2. Are their exceptions to the HCA rule? Can a diamond still perform great without being in the les than 2 range? I have read mixed things on the forum.
 

flyingpig

Ideal_Rock
Premium
Joined
Nov 7, 2015
Messages
2,171
Kc10f|1460548584|4018654 said:
Thanks for the reply. That was a very informative post. I requested for an ideal scope of that particular diamond. Of course now, it seems like I may be better continuing my search and trying to find something with an HCA score <2. Are their exceptions to the HCA rule? Can a diamond still perform great without being in the les than 2 range? I have read mixed things on the forum.
It depends on how you define "great".
Super ideal performance? Highly unlikely from 57/35.5/40.8 combo.
But, AGS ideal level light performance? Therr is a chance.

Wait for the IS image. 35.5/40.8 combo varies alot in light performance.

There are exceptions. One is a stone graded by AGS with ideal light performance. Such stone is 3D ray traced.But your stone is GIA.

There is no reason to go for a stone that scores poorly on HCA, unless the IS confirms no issue. There are plenty of stones with super ideal proportions at great price.
 

Kc10f

Rough_Rock
Joined
Apr 12, 2016
Messages
24
Thanks flyingpig. I will put the ideal scope images up when I have them. Should be a day or two. Is there anything to look for in the diamond pictures james Allen post? When I spoke with their customer service, they seemed to be looking at the diamond picture and liked this one because of the "8 pointed" star being defined and dark to the edges. Is there some type of logic to viewing the images to determine brilliance, fire, etc?
 

Kc10f

Rough_Rock
Joined
Apr 12, 2016
Messages
24
While I am waiting to get the ideal scope images back for the above diamond I thought maybe it would be a good idea to pick out a couple others and go ahead and request the ideal scope on those. I would like to be around a G-H color. A VS2 or above. I could compromise with and SI1 if looked like it would be eye clean. I would like to be around .7 ct give or take some. Price below $3,000 for diamond. Other than the HCA being below 2, what should I look for to narrow it down to 2 diamonds to request ideal scopes on? I am preferring to go with James Allen.

Thanks again!
 

Sagefemme

Shiny_Rock
Joined
Oct 8, 2015
Messages
291
These measurements have been listed, and relisted, and relisted here a thousand times. I'm not even sure whose version this is, just pasted it from another similar thread. These are the angles/percents that result in the best light performance. This forum is great for educating yourself about diamonds. Just start reading (start with the knowledge tab above).

quote]depth - 60 - 62%
table - 54- 57%
crown angle - 34- 35 degrees
pavilion angle - 40.6- 41 degrees
girdle - avoid extremes, look for thin to slightly thick, thin to medium etc
polish and symmetry - very good and above

note - with crown and pavilion angles at the shallower ends ( CA 34- PA 40.6) and steeper ( CA 35- PA 41) check to make sure these angles complement in that particular diamond - eyeballs, Idealscope, trusted vendor input - check as appropriate! [/quote]

Or, name your budget and preferences for a setting and some of the experts here will find you a group of great stones to choose from. They can find them in 1/100 the time it takes the rest of us.
 

Kc10f

Rough_Rock
Joined
Apr 12, 2016
Messages
24
Sage,

Thanks for the reply. As I mentioned, I appreciate all the help I can get. I have been studying those angles for HCA a lot! Lol. I basically put the characteristics I mentioned about then do an advance filter for depth 60-62 and table 54-57. Then it shows maybe 6 or so diamonds in my criteria listed above.

This is where I struggle. Other than looking for blatant inclusions on 20x magnification I don't know how to narrow down to 2 for ideal scopes on.

I want the best cut I can get under 3k and would like for an eye clean diamond close to G/H and around .7 ct give or take. I am thinking a round in a cushion rose gold setting. Thanks for your feedback!

Edit: I forgot to mention once I get my search narrowed to 6 or so I then do HCA calculation to see its score. Usually the advanced filter turns up mainly HCA scores less than 2
 

Sagefemme

Shiny_Rock
Joined
Oct 8, 2015
Messages
291
Have you thought about which setting and your budget for the whole project? That could influence the diamond choice.
 

Kc10f

Rough_Rock
Joined
Apr 12, 2016
Messages
24
Sage,

I am currently looking at about 4,300 for the full project. The setting I am looking at is the 14k rose gold cushion halo priced at 1,350.
 
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