HCA of 0.8 but not ideal cut?

[cb1916]

Hi all,

Looking at the following stone:
Round Brilliant
7.50 - 7.54 x 4.49
Weight - 1.510ct
Total depth - 59.7%
Crown angle - 33.7
Pavil angle - 40.8
Pavil depth - 42.9%
Table size - 56.8%
Girdle thickness - 1.1% (0.8-1.2) [thin to med, faceted]
Polish/Sym: Ex/Ex
Color: F
Clarity: VS2
Culet: none
Flour: faint

As you can see, the total depth is slightly under the 60% that I believe is the low-end for the ideal cut, but the HCA score is a very solid 0.8 (EX/EX/EX/EX).

Should I have reservations given that it''s not quite ideal? Also, any worries about fain flourescence?

Thanks,
CB

 

[moremoremore]

I am firm believer that a stone doesn't have to be 'ideal' to be beautiful...as long as you are paying a good price for what you are getting, than it's all good! And there is no prob with faint flourescence.

 

[cb1916]

Thanks for your response. Based on the price quoted to me, I would basically be paying as if it were an ideal cut, which doesn't bother me too much because it looks great (have seen in person) and has a great HCA score.

 

[Icicles]

i actually like lower depth % because it'll have a bigger spread.

 

[Carmel]

Well, ironically (or I should say coincidentally) enough ~ I, too, am considering a similar stone (not the same one, mine is much smaller) with a 59.7% Table. My research led me to opinions shared by the folks at NiceIce.

As quoted and copied from the NiceIce website (I hope I’m not infringing on some FCC or Copyright Law), they actually state:

"For your convenience the parameters for the AGS IDEAL CUT proportions rating for round brilliant cut diamonds is as follows:

Table Diameter: 52.4 - 57.5%
Crown Angle: 33.7 - 35.8° degrees
Pavilion Angle: 40.15 - 41.20 degrees
Girdle Thickness: Thin, Medium, Slightly Thick
Culet Size: None, Pointed, Very Small, Small,
or Medium

Note that the Total Depth % of the diamond is not taken into account...This is because it is the Crown & Pavilion angles that control most of the brilliance and thus the Total Depth is not as important a factor. Just the same, we prefer that the total depth of a round brilliant cut diamond be somewhere between 59.0% and 61.8% with the ceiling being around 62.5% in our opinion. Although it is not uncommon to find AGS Ideal Cut diamonds with total depths as deep as 63.5% we recommend that you avoid them like the plague because they are simply too deep!"

So, I’m left to presume that there is not anything wrong with a Table percentage of that calculation – and may, perhaps, even be considered advantageous.

Just one way to analyze it, and I’m sure there are differences of opinion. I just have to think that the NiceIce folks are somewhere in the realm of being right on the money, though.

 

[Regular Guy]

This approach makes sense to me....

 

[Regular Guy]

cb1916,

Sorry to have been a sloppy reader, and so to be contrary now; if you read my post referece above, I generally think, given sufficient time, it's good to take advantage of the "spread," allowing you to take advantage of the value available, when a diamond is non-ideal (which should save you money) in measurement, but well scoring on the HCA. Also, you don't share details about the cost you're looking at, but you might want to consider this one option:

http://www.niceice.com/certcopies/gia13384746/index.htm

and also, a couple of others are only slightly more, but VS1, when you search on this site by cut quality.

Best wishes,

 

[RockDoc]

Date: 8/6/2004 3:35:12 PM
Author: Carmel
Well, ironically (or I should say coincidentally) enough ~ I, too, am considering a similar stone (not the same one, mine is much smaller) with a 59.7% Table. My research led me to opinions shared by the folks at NiceIce.

As quoted and copied from the NiceIce website (I hope I’m not infringing on some FCC or Copyright Law), they actually state:

''For your convenience the parameters for the AGS IDEAL CUT proportions rating for round brilliant cut diamonds is as follows:

Table Diameter: 52.4 - 57.5%
Crown Angle: 33.7 - 35.8° degrees
Pavilion Angle: 40.15 - 41.20 degrees
Girdle Thickness: Thin, Medium, Slightly Thick
Culet Size: None, Pointed, Very Small, Small,
or Medium

Note that the Total Depth % of the diamond is not taken into account...This is because it is the Crown & Pavilion angles that control most of the brilliance and thus the Total Depth is not as important a factor. Just the same, we prefer that the total depth of a round brilliant cut diamond be somewhere between 59.0% and 61.8% with the ceiling being around 62.5% in our opinion. Although it is not uncommon to find AGS Ideal Cut diamonds with total depths as deep as 63.5% we recommend that you avoid them like the plague because they are simply too deep!''

So, I’m left to presume that there is not anything wrong with a Table percentage of that calculation – and may, perhaps, even be considered advantageous.

Just one way to analyze it, and I’m sure there are differences of opinion. I just have to think that the NiceIce folks are somewhere in the realm of being right on the money, though.

The AGS "number" for an ideal are changing.

On the new AGS reports, AGS has changed their Ideal paramters. I recently saw a new AGS report where a stone with a little broader proportions is graded as ideal. I think it had a 58% table.

Their software for grading purposes for members and independent appraisers is supposed to be finished soon. AGS is putting more "weight" in their consideration of light return from a iamond.

There is also a change in the required equipment used to grade proportions as well which to the best information that I have is going to be a requiisite to obtaining and using the software when it is released. I think that will happen in the quarter of 2006.

AGS has released cutting guidelines, but these are for cutters, and not necessarilly for use in grading applications.

Rockdoc

 

[Garry H (Cut Nut)]

Date: 12/9/2005 8:17:11 PM
Author: RockDoc

Date: 8/6/2004 3:35:12 PM
Author: Carmel
Well, ironically (or I should say coincidentally) enough ~ I, too, am considering a similar stone (not the same one, mine is much smaller) with a 59.7% Table. My research led me to opinions shared by the folks at NiceIce.

As quoted and copied from the NiceIce website (I hope I’m not infringing on some FCC or Copyright Law), they actually state:

''For your convenience the parameters for the AGS IDEAL CUT proportions rating for round brilliant cut diamonds is as follows:

Table Diameter: 52.4 - 57.5%
Crown Angle: 33.7 - 35.8° degrees
Pavilion Angle: 40.15 - 41.20 degrees
Girdle Thickness: Thin, Medium, Slightly Thick
Culet Size: None, Pointed, Very Small, Small,
or Medium

Note that the Total Depth % of the diamond is not taken into account...This is because it is the Crown & Pavilion angles that control most of the brilliance and thus the Total Depth is not as important a factor. Just the same, we prefer that the total depth of a round brilliant cut diamond be somewhere between 59.0% and 61.8% with the ceiling being around 62.5% in our opinion. Although it is not uncommon to find AGS Ideal Cut diamonds with total depths as deep as 63.5% we recommend that you avoid them like the plague because they are simply too deep!''

So, I’m left to presume that there is not anything wrong with a Table percentage of that calculation – and may, perhaps, even be considered advantageous.

Just one way to analyze it, and I’m sure there are differences of opinion. I just have to think that the NiceIce folks are somewhere in the realm of being right on the money, though.

The AGS ''number'' for an ideal are changing.

On the new AGS reports, AGS has changed their Ideal paramters. I recently saw a new AGS report where a stone with a little broader proportions is graded as ideal. I think it had a 58% table.

Their software for grading purposes for members and independent appraisers is supposed to be finished soon. AGS is putting more ''weight'' in their consideration of light return from a iamond.

There is also a change in the required equipment used to grade proportions as well which to the best information that I have is going to be a requiisite to obtaining and using the software when it is released. I think that will happen in the quarter of 2006.

AGS has released cutting guidelines, but these are for cutters, and not necessarilly for use in grading applications.

Rockdoc

AGS''s new guide for cutters would indicate this stone has the potential to be AGS0.

 

[solange]

I would prefer a stone that is very slightly shallower rather than one that is a little too deep because you get the extra spread. If you have seen the stone and it looks good to you, I do not think that tiny difference in depth will have much effect on the appearance of the stone to anyone but an expert and you will have a stone that has maximum spread.

 

[Mara]

Part of the reason it could score well and also looks so great to your eye is that the angles seem to correspond well with the table and depth numbers, so the stone seems like attention was definitely given to turn this stone into a winner even though it has a slightly lower depth than some would consider ideal.

Bottom line it's not as though the depth were 57% in which case it might have more of a red flag, those numbers and the HCA score (with an EX on spread, yay), plus your eyes having loved it, to me say that this stone should definitely be a contender in your final decision...I wouldn't just throw it out for that one little blip. Now if it was an entirely virtual stone and you would not be able to see it before you buy, I might advise differently but in this case your eye loved it, so you are already ahead in that sense. Just be sure you are fully educated so that you don't have any regrets after purchase!

 

[RockDoc]

Date: 12/9/2005 11:08:42 PM
Author: Garry H (Cut Nut)

Date: 12/9/2005 8:17:11 PM
Author: RockDoc

Date: 8/6/2004 3:35:12 PM
Author: Carmel
Well, ironically (or I should say coincidentally) enough ~ I, too, am considering a similar stone (not the same one, mine is much smaller) with a 59.7% Table. My research led me to opinions shared by the folks at NiceIce.

As quoted and copied from the NiceIce website (I hope I’m not infringing on some FCC or Copyright Law), they actually state:

''For your convenience the parameters for the AGS IDEAL CUT proportions rating for round brilliant cut diamonds is as follows:

Table Diameter: 52.4 - 57.5%
Crown Angle: 33.7 - 35.8° degrees
Pavilion Angle: 40.15 - 41.20 degrees
Girdle Thickness: Thin, Medium, Slightly Thick
Culet Size: None, Pointed, Very Small, Small,
or Medium

Note that the Total Depth % of the diamond is not taken into account...This is because it is the Crown & Pavilion angles that control most of the brilliance and thus the Total Depth is not as important a factor. Just the same, we prefer that the total depth of a round brilliant cut diamond be somewhere between 59.0% and 61.8% with the ceiling being around 62.5% in our opinion. Although it is not uncommon to find AGS Ideal Cut diamonds with total depths as deep as 63.5% we recommend that you avoid them like the plague because they are simply too deep!''

So, I’m left to presume that there is not anything wrong with a Table percentage of that calculation – and may, perhaps, even be considered advantageous.

Just one way to analyze it, and I’m sure there are differences of opinion. I just have to think that the NiceIce folks are somewhere in the realm of being right on the money, though.

The AGS ''number'' for an ideal are changing.

On the new AGS reports, AGS has changed their Ideal paramters. I recently saw a new AGS report where a stone with a little broader proportions is graded as ideal. I think it had a 58% table.

Their software for grading purposes for members and independent appraisers is supposed to be finished soon. AGS is putting more ''weight'' in their consideration of light return from a iamond.

There is also a change in the required equipment used to grade proportions as well which to the best information that I have is going to be a requiisite to obtaining and using the software when it is released. I think that will happen in the quarter of 2006.

AGS has released cutting guidelines, but these are for cutters, and not necessarilly for use in grading applications.

Rockdoc

AGS''s new guide for cutters would indicate this stone has the potential to be AGS0.

Hi Garry

Since I do take things rather literally when AGS or GIA says them, yes I agree that the stone has the POTENTIAL of being an AGS 0, but "potential" is a sort of dangerous terminology, should for some reason the grading paramters are changed back again.

Additionally, if AGS says they are for cuttng guidelines only I have to assume there is some viable reason for them saying that. Inside, I wonder why they have issued cutting standards where cutters adhere to the proportions, yet there is the chance of the stone being graded lower in their final grading analysis.

Even further I am puzzled as to why the ASET image isn''t part of their grading report, especially assuming that the image from the ASET is used in helping to determine the light performance rating along with the ray tracing methodology that have said they are using.

I really look forward to the final grading version of the software, and perhaps a little more clear explanation of what characteristics in the ray tracing would result in the different cut gradies and light performance grades.

Regards

Rockdoc

 

[Garry H (Cut Nut)]

Date: 12/10/2005 5:23:02 PM
Author: RockDoc


Hi Garry

Since I do take things rather literally when AGS or GIA says them, yes I agree that the stone has the POTENTIAL of being an AGS 0, but ''potential'' is a sort of dangerous terminology, should for some reason the grading paramters are changed back again. there is also the potential that a stone can be well made with good minor facets and maybe some of the right girdle digging / painting for its proportion set, and actually fall outside their cutters guide - an ideal-scope or ASET will give us an excellent guide to that potential.

Additionally, if AGS says they are for cuttng guidelines only I have to assume there is some viable reason for them saying that. Inside, I wonder why they have issued cutting standards where cutters adhere to the proportions, yet there is the chance of the stone being graded lower in their final grading analysis.

Even further I am puzzled as to why the ASET image isn''t part of their grading report, especially assuming that the image from the ASET is used in helping to determine the light performance rating along with the ray tracing methodology that have said they are using.
I think the reason is that ASET is used across a range of rotation angles - ratehr like this demo that I did years ago for how to use the Ideal-scope with fancy cuts - it is in the fancy cut section at www.ideal-scope.com
I really look forward to the final grading version of the software, and perhaps a little more clear explanation of what characteristics in the ray tracing would result in the different cut gradies and light performance grades.

Regards

Rockdoc