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Google makes me worries - Too deep on the cut??

AC1010

Rough_Rock
Joined
Jun 5, 2016
Messages
2
Hi All...

I just bought a solitaire ring with a brilliant cut diamond, after going through some study and visited a couple shops. Details of the stones are:

0.9 carat
Table - 57%
Depth - 64.3%
Crown angle - 36.5%
Pavilion angle - 41.2%
Girdle - slightly thick - thick (faceted, 5.0%)
Measurement - 6.03 - 6.07x3.89mm

I thought I got a good bargain initially and happily in the preparation to ask the important question. But a friend of mine showed me her stone yesterday of 0.75carat and her stone appears to be pretty similar size to mine!!! Further study over the night makes me realised depth of 64.3% and the thick girdle might be the key of the visual difference. Also, 6.03-6.07 measurement seem a bit too small for a 0.9carat stone, compare to 63mm average that I saw from James Allen website. 0.3 might not sound much but it is 5% smaller in term of overall diameter of the stone and it is good enough to put an engineer in dilemma.

My question is should I return the stone to get a different one with shallower depth? Appreciate if you help with my dilemma.
Thanks...
 

tyty333

Super_Ideal_Rock
Premium
Joined
Dec 17, 2008
Messages
21,685
Good on you for doing your research...yes, return it. NoT only is it deep, but the angles do not compliment each other so you are not getting optimal light return along with brilliance and fire. If you let us know your budget we can show you what you can/ should get.
 

MissGotRocks

Super_Ideal_Rock
Premium
Joined
Jun 23, 2005
Messages
12,221
Yes, I would return it. Not only is it too deep, but the crown and pavilion angles are both too deep as well. This stone will face up smaller than a .90 with excellent chance of light leakage. Use these parameters to find another stone:

Depth up to 62.2%

Table 55-58

Crown 34 - 35

Pavilion 40.6 - 40.9

Plug these numbers from a specific diamond into the HCA - found under the Tools tab at the top of the page. You are looking for a stone to score less than 2 on the HCA. The HCA helps to weed out poor performers.
 

fair75

Rough_Rock
Joined
May 28, 2015
Messages
87
Ditto on the others' advice to return it. I will just add that I personally prefer pavilion angle to be between 40.6 and 40.8, table % between 54 and 57, & total depth % between 60 and 61.9. HCA is nice, but it's only a rejection tool, not a selection tool. Remember to ask for a photo if you are buying online.
 

Gypsy

Super_Ideal_Rock
Joined
Aug 8, 2005
Messages
40,198
Way too deep.
 

AC1010

Rough_Rock
Joined
Jun 5, 2016
Messages
2
Thanks for the advice! I spoke to the jeweler and he agreed to exchange the stone for me, going to meet him next week.

Another dummy question, the current is a 'very good' cut under GIA. Does it mean that I need to go for 'Excellent' cut to meet the depth/angles suggested?
 

Gypsy

Super_Ideal_Rock
Joined
Aug 8, 2005
Messages
40,198
Yes, the above is IN ADDITION TO, Excellent cut.

Here is a round diamond tutorial:

Round Diamonds 101:

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: 40.6-40.9 (there is a little give on this). And the crown and pavilion angles must be complimentary which is what the HCA checks for you.
 

Wink

Ideal_Rock
Trade
Joined
May 3, 2001
Messages
7,475
AC1010|1465285356|4041089 said:
Thanks for the advice! I spoke to the jeweler and he agreed to exchange the stone for me, going to meet him next week.

Another dummy question, the current is a 'very good' cut under GIA. Does it mean that I need to go for 'Excellent' cut to meet the depth/angles suggested?
No, it means you need to know what to look for in angles and measurements. GIA is notorious amongst us cut fanatics for allowing steep deep measurements even in their (so called) excellent cut grade. The excellent rating will in no way assure you of getting the angles suggested to you.

Some of the GIA excellent cut grade diamonds are indeed beautiful and fantastic, and sadly, some of them are definitely NOT. Your chosen jeweler has already proved that he either does not understand proper cutting, or worse, he does not care, since selling a poorly cut diamond allows him to make more money while having you think you are getting a great bargain.

Since he is willing to do a trade with you, you must be sure that you know what you will accept as a trade. Be sure to visit other local jewelers and see some well cut diamonds if you can. Then you will understand why so many people have learned to insist on proper cutting so that you can have a diamond that will always be beautiful.

Wink
 
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