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Experts, you''re opinion please

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insearchofastone

Rough_Rock
Joined
Dec 1, 2009
Messages
10
Is this loose stone worth $4,800???

GIA Report
Round Brilliant
Ct= 1.00
Color - G
Clarity = SI1
Cut Grade = Very Good
Polish = Good
Symmetry - Good
Fluorescence - None

6.27-6.32x3.98
Depth = 63.2%
Table = 54%
Crown Angle = 36.0
Crown Height = 16.5%
Pavillion Angle = 39.8
Pavillion Depth = 41.5%
Star Length = 50%
Lower half = 80%
Girdle = Med to Thick
Faceted = (5.1%)
Culet = None

Thank you!
 
Not an expert, but my 2c:

1. Pavilion angle is too shallow.
2. Good symmetry, good polish, and thick girdles are not good things. The first two show lack of care in finishing, the second is a great way to hide weight. Add to that the 63% depth and you''ve got a 1ct that faces up like a 0.9.
3. The whole point of buying a diamond is to buy a sparkly stone, if the stone doesn''t sparkle it''s not worth $4800 or $48.
 
Ditto above, the stone will look dark.
 
 
Thanks Guys! It does sparkle I have to say. My concern is how did GIA give it a Very Good cut grade?
 
It''s angles are wrong, as stated, it will have obstruction issue, check it out. Also with a Good grade in polish and symm, VG cut grade is the best it will get with GIA grading system.
 
It''s angles are wrong, as stated
Click to expand...

Yet it scores a 1.4 on the HCA. ;) The supposed 1-2 "safe zone" that''s a candidate for further inspection. I thought the HCA was supposed to eliminate poor angle combinations. But, yeah, obviously I''ll defer to the experts and based on what I''ve read, that''s definitely too shallow of a pavilion angle.
 
Isn''t VG 2nd to Excellent in the Cut Grade Scale?

If the angles and other measurements are off wouldn''t the Cut Grade have been good or Fair?

I am asking because this thing glitters like crazy and I placed it next to one rated Excellent Cut with VG polish and Excellent Symmetry and you couldn''t tell the difference except for the 1000 price tag.
 
What is 1.4 on the HCA mean?
 
Date: 12/1/2009 6:11:35 PM
Author: e5116

It''s angles are wrong, as stated
Click to expand...

Yet it scores a 1.4 on the HCA. ;) The supposed 1-2 ''safe zone'' that''s a candidate for further inspection. I thought the HCA was supposed to eliminate poor angle combinations. But, yeah, obviously I''ll defer to the experts and based on what I''ve read, that''s definitely too shallow of a pavilion angle.
Click to expand...
It scores a 1.4 which means it warrants further examination, sure, but if you inspect closer
2.gif
, you will see some things that aren''t that great. It is a deep stone so it is carrying a lot of weight in the pavilion and so it does not face up as big as it should (note the "good" score on the HCA for spread). A one carat diamond should ideally be around 6.5mm in diameter whereas this one is 6.3mm. That is a noticable size difference.

This combination of angles puts the diamond into the FIC range, this means it will have a good amount of fire but perhaps at the cost of brilliance. I am not surprised it looked great under jewelers lights, that is where a firey stone will excell. But in more typical lighting it may not be as bright, and it will look smaller than a more typically ideal cut
8.gif
 
Date: 12/1/2009 6:13:36 PM
Author: insearchofastone
Isn''t VG 2nd to Excellent in the Cut Grade Scale?

If the angles and other measurements are off wouldn''t the Cut Grade have been good or Fair?

I am asking because this thing glitters like crazy and I placed it next to one rated Excellent Cut with VG polish and Excellent Symmetry and you couldn''t tell the difference except for the 1000 price tag.
Click to expand...
Nope, GIA can be more lenient than AGS in its cut grading and sometimes diamonds that are not meeting all the ideal specs will be greaded as Excellent or perhaps good. See my previous post for more detail.

The HCA is a tool that allows you to see how your diamond''s angles may play out in terms of performance. Anything under a 2 is considered good and worth examining further. Click on tools above and you will find it.
 
It scores a 1.4 which means it warrants further examination, sure, but if you inspect closer , you will see some things that aren't that great. It is a deep stone so it is carrying a lot of weight in the pavilion and so it does not face up as big as it should (note the "good" score on the HCA for spread). A one carat diamond should ideally be around 6.5mm in diameter whereas this one is 6.3mm. That is a noticable size difference.
Click to expand...

Right, my point is that we were able to eliminate it WITHOUT even visually inspecting it. That is, the HCA ideally should not have given it a good score. I realize no calculator is perfect, but this particular calculator seems to greatly favor shallow pavilion angles that can cause obstruction.
 
Date: 12/1/2009 6:34:06 PM
Author: e5116

It scores a 1.4 which means it warrants further examination, sure, but if you inspect closer , you will see some things that aren''t that great. It is a deep stone so it is carrying a lot of weight in the pavilion and so it does not face up as big as it should (note the ''good'' score on the HCA for spread). A one carat diamond should ideally be around 6.5mm in diameter whereas this one is 6.3mm. That is a noticable size difference.
Click to expand...

Right, my point is that we were able to eliminate it WITHOUT even visually inspecting it. That is, the HCA ideally should not have given it a good score. I realize no calculator is perfect, but this particular calculator seems to greatly favor shallow pavilion angles that can cause obstruction.
Click to expand...
Actually many people really like FIC stones and seek them out.
 
Depends on the GIA Ex cut stone shown to you. Also what kind of lighting conditions have you viewed it under? GIA Ex cut stones are not equal, some Ex cut have a steeper pavilion that allows light leakage making the stone look less lively.

Try this link from GIA and you will see how GIA grades your stone.
http://www2.gia.edu/facetware/
 
Is AGS better than GIA when it comes to certification?
 
Date: 12/1/2009 6:34:06 PM
Author: e5116

Right, my point is that we were able to eliminate it WITHOUT even visually inspecting it. That is, the HCA ideally should not have given it a good score. I realize no calculator is perfect, but this particular calculator seems to greatly favor shallow pavilion angles that can cause obstruction.
Click to expand...

It is stated in the usage warning and information page on how to use the HCA.
 
Date: 12/1/2009 6:42:22 PM
Author: insearchofastone
Is AGS better than GIA when it comes to certification?
Click to expand...
AGS is moderately better for cut quality grading (because of a narrower range of proportions that can be excellent), but still not perfect.
Colour and clarity are - on balance - comparable to GIA.
 
It is stated in the usage warning and information page on how to use the HCA.
Click to expand...

I understand its usage warning and how to use it. This diamond places it in the more fire region, wherein the table must be smaller to prevent fisheye (and this table is appropriately small).

My point is that a diamond with the above proportions would universally be dark, would it not? I mean, I'd eliminate this exact diamond off the bat because of only good polish and symmetry, but even if it was Ex/Ex with those specs, we all still wouldn't recommend it based on the angle combinations, right? The primary purpose of the HCA is to eliminate likely poor performers and then further analyze ones with promise. All I'm saying is that this calculator (while greatly appreciated and helpful) universally gives the benefit of the doubt to shallow stones, while harshly penalizing steep/deeps. (i.e. I personally would prefer a 33.5/41.4 diamond that scores much worse on the HCA than this one.) I'm not trying to be critical, just trying to understand the rationale behind such conclusions. Perhaps it was just Gary's personal preference for those types of stones. I'm certainly no expert and you can feel free to disagree.
 
Date: 12/1/2009 6:11:35 PM
Author: e5116


It's angles are wrong, as stated
Click to expand...

Yet it scores a 1.4 on the HCA. ;) The supposed 1-2 'safe zone' that's a candidate for further inspection. I thought the HCA was supposed to eliminate poor angle combinations. But, yeah, obviously I'll defer to the experts and based on what I've read, that's definitely too shallow of a pavilion angle.
Click to expand...
HCA does eliminate poor combinations. But it's calculations measure how "perfect" a stone can be.
Some stones are "too perfect" and they both absorb and emit the light straight out of the top. Unfortunately, that's exactly the position your head occupies and you end up looking at a reflection/silhouette of yourself and blocking light to the stone.

GIA's Excellent cut grade (and AGS's 0 cut grade) largely eliminates stones with obstruction problems. AGA's cut grade may also drop the grade of potentially obstructed stones.
 
For stones serving purposes other than as a ring stone, such as for pendant/ear-ring stone. Also, shallower stones are less likely to be affected by dirt.
 
Where can I find the HCA calculator? Does it mean that if the result is between 1 and 2 it is a bad diamond? In my case a 1.4?
I''m trying to follow you guys.... Basically I should not consider this stone eventhough it is 4800 and really sparkles?
 
Date: 12/1/2009 8:02:59 PM
Author: insearchofastone
Where can I find the HCA calculator? Does it mean that if the result is between 1 and 2 it is a bad diamond? In my case a 1.4?
I''m trying to follow you guys.... Basically I should not consider this stone eventhough it is 4800 and really sparkles?
Click to expand...
For a ring (rather than earrings or a pendant, and frankly even then) this is exactly what we''re saying. You can do better.
 
I just went to the HCA calculator and scored an excellent?! I''m confused.

See the grades below
 
Date: 12/1/2009 8:02:59 PM
Author: insearchofastone
Where can I find the HCA calculator? Does it mean that if the result is between 1 and 2 it is a bad diamond? In my case a 1.4?
I''m trying to follow you guys.... Basically I should not consider this stone eventhough it is 4800 and really sparkles?
Click to expand...
For any round diamond to be graded below "very good" polish and symmetry, it doesn''t show much pride in their work on the part of the cutter.
Absolute minimum acceptable is very good - and Excellent is preferred.

Notice also that a typcal 1ct stone measures about 6.5mm. Your stone "faces up" somewhat smaller.

The smaller size, greater depth and lower polish/symm would get downgraded by AGA''s grading system.

Basically, to be fairly confident that obstruction won''t be an issue, look at GIA Excellent cut, or AGS 0 ideal cut.
 
Date: 12/1/2009 8:18:07 PM
Author: insearchofastone
I just went to the HCA calculator and scored an excellent?! I'm confused.

See the grades below
Click to expand...
Maybe this illustration will help:

A standard ideal cut stone is on the left. A stone with proportions similar to yours is on the right. Notice the very prominent black middle.

Underneath the pictures is a life-size (ish) representation of the stones. Notice how the one similar to yours looks very dark in the middle (under the table). There's a good chance that the darkness will never go away.

0 0 0 0 0 10a2.jpg
 
Date: 12/1/2009 6:29:38 PM
Author: dreamer_dachsie

Date: 12/1/2009 6:11:35 PM
Author: e5116


It''s angles are wrong, as stated
Click to expand...

Yet it scores a 1.4 on the HCA. ;) The supposed 1-2 ''safe zone'' that''s a candidate for further inspection. I thought the HCA was supposed to eliminate poor angle combinations. But, yeah, obviously I''ll defer to the experts and based on what I''ve read, that''s definitely too shallow of a pavilion angle.
Click to expand...
It scores a 1.4 which means it warrants further examination, sure, but if you inspect closer
2.gif
, you will see some things that aren''t that great. It is a deep stone so it is carrying a lot of weight in the pavilion and so it does not face up as big as it should (note the ''good'' score on the HCA for spread). A one carat diamond should ideally be around 6.5mm in diameter whereas this one is 6.3mm. That is a noticable size difference.

This combination of angles puts the diamond into the FIC range, this means it will have a good amount of fire but perhaps at the cost of brilliance. I am not surprised it looked great under jewelers lights, that is where a firey stone will excell. But in more typical lighting it may not be as bright, and it will look smaller than a more typically ideal cut
8.gif
Click to expand...
OP, read this, it tells you why your stone scored well but may not be a good one.
 
Date: 12/1/2009 6:01:28 PM
Author: insearchofastone
Thanks Guys! It does sparkle I have to say. My concern is how did GIA give it a Very Good cut grade?
Click to expand...
It got a VG cut grade because of the pavilion angle, polish and symmetry. This is not a suitable diamond for a ring due to the high chance of obstruction ( visible darkening of the diamond when viewed at close scrutiny). In other words if this diamond is set in a ring it could look dark when the wearer brings the hand closer to admire it and it could look a bit like a doughnut with a darker centre sometimes due to the obstruction.
 
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