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Confused over Cut

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deathgleaner

Rough_Rock
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Oct 16, 2008
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I found an e-diamond with a table% of 55 and a depth% of 61.9. I know that, usually, with those numbers a diamond should be an Ideal Cut, but it is said to be a GIA Very Good Cut. Is this because of the pavillion and/or crown? How important are numbers for pavillion and crown?

I am also looking at the chart in HCA results regarding "The Green dot outline is the GIA Excellent ''candidates'' The White outline is the AGS Ideal ''candidates''" Ideally, where should a diamond be in that chart? In the middle of the green dot outline or the white dot outline?

Thanks so much. This forum has been most helpful.
 
It is a F VS2 round brilliant of 0.9 Carat, medium to slightly thick girdle, excellent symmetry and polish. I have a budget of about $5000. I know that cut is more important than weight and it will cost a premium to get to the magic number of 1 Carat, so I am not that fussed over weight. I want a diamond with a lot of fire and with a good cut such that it looks about the same size as a 1 Carat. Thank you again.
 
It takes more than just depth and table information to determine if a stone actually falls within "ideal" cut parameters. You'd need crown/pavilion info as well, and girdle info would be great.

Beyond that, each grading lab has defined what its parameters are for earning a top cut grade. AGS's system differs a bit from GIA's and is traditionally viewed as the more stringent system.

GIA's cut grade system penalizes stones with brillianteering (even if that brillianteering has a positive impact instead of a negative impact on the stone), so it's possible for a stone to earn top cut grade under AGS and perhaps earn only a VG in GIA's system.

It's more common, though, for AGS's top-cut requirements to be far more stringent than GIA's.

Where a diamond should fall on the HCA chart relative to GIA/AGS top make candidates is a matter of preference, but most folks on here would most highly recommend stones that fall within the area common to both labs.

The stone's numbers suggest it has potential; I'm sure folks can give you more input if you're able to secure an Idealscope or ASET image for it. The HCA is a wonderful tool as a potential weeding aide, but it's speculative and therefore less impactful than an image of the actual stone.
 
What are the actual values of the crown and pavilion angle?
 
Thanks so much. The crown is 35.5 and the pavillion is 40.6. I had put these numbers into the HCA and came up with:

Light Return Excellent
Fire Excellent
Scintillation Excellent
Spread or diameter for weight Very Good
Total Visual Performance 1.3 - Excellent within TIC range

It has excellent polish and excellent symmetry also. So, now, I am even more confused as to what is wrong with this diamond such that it is only a Very Good Cut and not an Ideal Cut.

Its price is Cdn$5542.

Any thoughts would be much appreciated.
 
Date: 10/16/2008 7:17:23 PM
Author: deathgleaner
Thanks so much. The crown is 35.5 and the pavillion is 40.6. I had put these numbers into the HCA and came up with:


Light Return Excellent

Fire Excellent

Scintillation Excellent

Spread or diameter for weight Very Good

Total Visual Performance 1.3 - Excellent within TIC range


It has excellent polish and excellent symmetry also. So, now, I am even more confused as to what is wrong with this diamond such that it is only a Very Good Cut and not an Ideal Cut.


Its price is Cdn$5542.


Any thoughts would be much appreciated.

First of all GIA doesn't use the term ideal. Second, GIA isn't known for grading cut well...

Your diamond falls into both GIA and AGS ranges on the HCA, so I would ask for an idealscope image, and if that looks good, you should have a beautiful stone on your hands!

Ideally you'd love for the diamond to be in the white outline AND the green outline, but if only 1, then the white outline is more important IMO.
 
Ditto what neat said.

Did the cert say anything about cut downgraded for brillianteering?

The only other possibility is the rounding of numbers by GIA. As you can see from the HCA plot, the location of your stone is near the edge of what GIA considered to be excellent. They could have rounded up the numbers to get you to your current HCA score. The only way to know is to get an independent appraiser with a Helium scanner to scan for the dimensions of the round.
 
It could be because of the girdle. How thin/thick is the girdle listed?
 
I would not buy a gia VG cut without an ideal-scope or ASET image.
 
Date: 10/16/2008 8:02:47 PM
Author: Stone-cold11
The only way to know is to get an independent appraiser with a Helium scanner to scan for the dimensions of the round.
yuck yuck...
 
Date: 10/16/2008 8:02:47 PM
Author: Stone-cold11
The only way to know is to get an independent appraiser with a Helium scanner to scan for the dimensions of the round.
You should know, I believe, that Jonathan at G0G...along probably with AGS...are probably the only owners of a helum in the US of A. I believe.

And...I pinned him down. Jonathan would consider serviing as an appraiser in the most unusual of circumstances.
 
Thank you everyone!! I don''t think there is anything wrong with the girdle; it is medium to slightly thick. It is a bluenile diamond and they do not give an idealscope image. Bluenile has a return policy, but returning would mean losing the shipping and handling, etc.

Given that the diamond has the following stats:

Carat weight: 0.90
Cut: Very Good
Colour: F
Clarity: VS2
Price per carat: C$6,158
Depth %: 61.9%
Table %: 55%
Crown: 35.5
Pavilion: 40.6
Symmetry: Excellent
Polish: Excellent
Girdle: Medium to slightly thick
Culet: None
Fluorescence: None
Measurements: 6.23 x 6.15 x 3.83 mm

According to the HCA:

Light Return: Excellent
Fire: Excellent
Scintillation: Excellent
Spread or diameter for weight: Very Good
Total Visual Performance: 1.3 - Excellent within TIC range

The GIA certificate also shows a crystal on the table, a feather at the edge, a pinpoint at the back (in the diagram), and existence of cloud and cavity that are not shown on the diagram. There are no other comments on the certificate.

Is the price of $5,542 a good buy? I have a budget of about $5000. I am just wondering whether there is anything wrong with the diamond because the cut is only Very Good.

I know it is not supposed to be important, but I am around people at work who have 1-carat tiffany rings that cost about $20K. I just don''t want my ring to look significantly worst than their rings; people can be mean and snooty. I know I am only spending a quarter of what they spent, but I figure tiffany has huge mark-ups and it costs a premium to get to the magic number of 1-carat.

Any thoughts? Thanks.
 
Can you give the crown and pavilion height too? I am thinking it is probably due to the rounding of pavilion angle, if that is the case, even with a drop of 0.2 degree in pavilion angle, it is still within AGS0 guideline. I would think it is a good performer anyway and probably worth it to give it a shot. Maybe someone else can chip in...

By the way, have you bought it? I check out BN and it is not available for purchase.
 
I think they are 16% for top and 42.5% for bottom. What kind of numbers should a good diamond have for the vertical top and bottom measurements?

No, I have not purchased it. Bluenile rep called me and explained to me that I should think more about whether a cavity in the diamond would bother me since it can create problems when setting the stone and dirt can get trapped in the cavity and make it look like an inclusion. I probably won''t be buy it because of the cavity. I don''t know....
 
Date: 10/17/2008 12:29:31 PM
Author: deathgleaner
I think they are 16% for top and 42.5% for bottom. What kind of numbers should a good diamond have for the vertical top and bottom measurements?

No, I have not purchased it. Bluenile rep called me and explained to me that I should think more about whether a cavity in the diamond would bother me since it can create problems when setting the stone and dirt can get trapped in the cavity and make it look like an inclusion. I probably won''t be buy it because of the cavity. I don''t know....
It could be a nice diamond but as Karl mentions Idealscope images, he is right in as much as it would be very useful to properly assess this diamond, and BN do not offer such services. Also by getting the best cut diamond you can, it will most likely outshine those diamonds belonging to your colleagues, it is cut which makes a diamond beautiful.
 
Crown and pavilion angles are VERY imprtant. I had a GIA excellent cut with poor crown and pavilion proportions and would up getting it recut because it performed so poorly. AGS''s cut grading is MUCH more reliable!
 
I just read that you have friends with 1ct tiffany rings that cost $20K. You did say that you weren''t overly concerned with hitting the 1 ct. mark, but you could hit that within budget if you went with a G or H color. My H is icy white and Tiffany''s sells diamonds down to I color. In a really great cut, you won''t see ANY color in a G. Just a thought
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