Why in Tolkowsky Range but not in AGS Ideal Range?

[jazzshn]

I am quite confused by the question.

According to the specifications of one laboratory, "Tolkowsky Range" is as follows:
53 - 57% Table based on diamond''s overall diameter.
33 - 36¡ã Crown Angle.
40 - 41.5¡ã Pavilion Angles.
56 - 60.5% Total Depth (excluding girdle thickness) with 14 - 16.5% of the depth being comprised of the crown (top half of the diamond) and 42 - 44% representing the pavilion lower half of the diamond.

But A true "Ideal Cut Diamond" is a round brilliant cut diamond that has been cut to AGS Ideal Cut Proportions as defined in the following table:
Table Diameter 52.4 - 57.5%
Crown Angle 33.7 - 35.8¡ã
Pavilion Angle 40.2 - 41.2¡ã
Girdle Thickness Thin, Medium, Slightly Thick
Culet Size None, Pointed, Very Small, Small, Medium

Now, there is a stone I am going to buy with the following proportions, which is unfortunately falling out of AGS Ideal Range.
Depth: 60.3%
Table: 57%
Crown Angle: 33.5
Pavilion Angle: 40.8
Culet: 0
Girdle: Medium, Facted (3.0%)

My question is: Why is that? Will it affect the future value of the stone?

Thanks.

 

[yssie]

jazz, your stone is going to be beautiful. Seriously. Stop analysing

.



That much variation... is in the error margin of most scanners - won't be visible or have any effect on performance whatsoever. Yes, it might mean that your stone has lower future value if it falls outside that coveted AGS0 bracket, but your stone loses 50-80% of it's current value the minute you purchase it, so in the grand scheme of things.. unless of course you buy with a buyback or upgrade policy for the future, in which case whatever your stone is worth then doesn't matter, it's what you pay now that counts.

 

[jazzshn]

Date: 3/23/2010 1:09:24 AM
Author: yssie
jazz, your stone is going to be beautiful. Seriously. Stop analysing

.



That much variation... is in the error margin of most scanners - won''t be visible or have any effect on performance whatsoever. Yes, it might mean that your stone has lower future value if it falls outside that coveted AGS0 bracket, but your stone loses 50-80% of it''s current value the minute you purchase it, so in the grand scheme of things.. unless of course you buy with a buyback or upgrade policy for the future, in which case whatever your stone is worth then doesn''t matter, it''s what you pay now that counts.

Sorry.

As you said, if another stone is 80-82, you prefer that one. 80-82 is a weight you like or it is a goode weight for stone? Thanks.

 

[yssie]

oh - not weight, lower half

sc prefers fatter arrows (lower LGF) and bolder flash, I prefer skinny arrows (higher LGF) and splinterier flash. Total personal preference thing. The thing is, GIA rounds that number to the nearest 5, so that "75" could be 77 and the 80 could be 78, in which case you'd never see a difference.

 

[yssie]

may I ask where you're getting your ags0 info from?


the charts i'm looking at say 33.5 is the AGS0 lower-crown limit for pav 40.8.. don't think I've ever seen it specified as 33.7, that doesn't make much sense



ETA: here you go, straight from AGS (200
http://www.agslab.com/pbcg/AGSL_Proportion_Charts.pdf

 

[jazzshn]

Date: 3/23/2010 1:27:29 AM
Author: yssie
may I ask where you''re getting your ags0 info from?


the charts i''m looking at say 33.5 is the AGS0 lower-crown limit for pav 40.8.. don''t think I''ve ever seen it specified as 33.7, that doesn''t make much sense



ETA: here you go, straight from AGS (200
http://www.agslab.com/pbcg/AGSL_Proportion_Charts.pdf

I got it from here: http://www.idealcutdiamonds.com/diamond-education/diamond-cut-classifications/diamonds-tolkowsky-cut

Thanks a lot for your advices and sharing.

 

[jazzshn]

Date: 3/23/2010 1:27:29 AM
Author: yssie
may I ask where you''re getting your ags0 info from?


the charts i''m looking at say 33.5 is the AGS0 lower-crown limit for pav 40.8.. don''t think I''ve ever seen it specified as 33.7, that doesn''t make much sense



ETA: here you go, straight from AGS (200
http://www.agslab.com/pbcg/AGSL_Proportion_Charts.pdf

Can''t open the linkage...

 

[yssie]

http://agslab.com/trade_research_and_development_proportion_based_cut_grade.php


they have the proportion grade charts in a bunch of formats at the bottom of the page




ETA: I see. The author of that article - uncredited and unaccredited as far as we know - is putting his own spin on a lot of things, isn't he? In any case, the official AGS documentation is available

 

[jazzshn]

Date: 3/23/2010 1:37:50 AM
Author: yssie
http://agslab.com/trade_research_and_development_proportion_based_cut_grade.php


they have the proportion grade charts in a bunch of formats at the bottom of the page




ETA: I see. The author of that article - uncredited and unaccredited as far as we know - is putting his own spin on a lot of things, isn''t he? In any case, the official AGS documentation is available

Thank you very much.

I also got the xls format which is very useful.

Maybe I will have more questions to ask later. lol

 

[Lorelei]

Date: 3/23/2010 1:04:39 AM
Author:jazzshn

I am quite confused by the question.

According to the specifications of one laboratory, ''Tolkowsky Range'' is as follows:
53 - 57% Table based on diamond''s overall diameter.
33 - 36¡ã Crown Angle.
40 - 41.5¡ã Pavilion Angles.
56 - 60.5% Total Depth (excluding girdle thickness) with 14 - 16.5% of the depth being comprised of the crown (top half of the diamond) and 42 - 44% representing the pavilion lower half of the diamond.

But A true ''Ideal Cut Diamond'' is a round brilliant cut diamond that has been cut to AGS Ideal Cut Proportions as defined in the following table:
Table Diameter 52.4 - 57.5%
Crown Angle 33.7 - 35.8¡ã
Pavilion Angle 40.2 - 41.2¡ã
Girdle Thickness Thin, Medium, Slightly Thick
Culet Size None, Pointed, Very Small, Small, Medium

Now, there is a stone I am going to buy with the following proportions, which is unfortunately falling out of AGS Ideal Range.
Depth: 60.3%
Table: 57%
Crown Angle: 33.5
Pavilion Angle: 40.8
Culet: 0
Girdle: Medium, Facted (3.0%)

My question is: Why is that? Will it affect the future value of the stone?

Thanks.

Hi Jazz,

Your stone has definite potential and has excellent proportions, if you can get an Idealscope image that would be a useful supplement to the numbers. What are the colour, clarity and size of the diamond please?

 

[jazzshn]

Date: 3/23/2010 6:02:06 AM
Author: Lorelei

Date: 3/23/2010 1:04:39 AM
Author:jazzshn


I am quite confused by the question.

According to the specifications of one laboratory, ''Tolkowsky Range'' is as follows:
53 - 57% Table based on diamond''s overall diameter.
33 - 36¡ã Crown Angle.
40 - 41.5¡ã Pavilion Angles.
56 - 60.5% Total Depth (excluding girdle thickness) with 14 - 16.5% of the depth being comprised of the crown (top half of the diamond) and 42 - 44% representing the pavilion lower half of the diamond.

But A true ''Ideal Cut Diamond'' is a round brilliant cut diamond that has been cut to AGS Ideal Cut Proportions as defined in the following table:
Table Diameter 52.4 - 57.5%
Crown Angle 33.7 - 35.8¡ã
Pavilion Angle 40.2 - 41.2¡ã
Girdle Thickness Thin, Medium, Slightly Thick
Culet Size None, Pointed, Very Small, Small, Medium

Now, there is a stone I am going to buy with the following proportions, which is unfortunately falling out of AGS Ideal Range.
Depth: 60.3%
Table: 57%
Crown Angle: 33.5
Pavilion Angle: 40.8
Culet: 0
Girdle: Medium, Facted (3.0%)

My question is: Why is that? Will it affect the future value of the stone?

Thanks.

Hi Jazz,

Your stone has definite potential and has excellent proportions, if you can get an Idealscope image that would be a useful supplement to the numbers. What are the colour, clarity and size of the diamond please?

Hi master,
The information you want as follows:
Carat Weight: 0.74ct
Measurement: 5.85-5.89 x 3.54 mm
Color Grade: E
Clarity Grade: VS1
I just got a result of AGA calculaor as attached, which depressed me.

 

[stone-cold11]

Stop over thinking...

AGA 1A cut consists of a very small range of proportions. 1B grade is good enough.

 

[Rhino]

Date: 3/23/2010 1:04:39 AM
Author:jazzshn

I am quite confused by the question.

According to the specifications of one laboratory, ''Tolkowsky Range'' is as follows:
53 - 57% Table based on diamond''s overall diameter.
33 - 36¡ã Crown Angle.
40 - 41.5¡ã Pavilion Angles.
56 - 60.5% Total Depth (excluding girdle thickness) with 14 - 16.5% of the depth being comprised of the crown (top half of the diamond) and 42 - 44% representing the pavilion lower half of the diamond.

But A true ''Ideal Cut Diamond'' is a round brilliant cut diamond that has been cut to AGS Ideal Cut Proportions as defined in the following table:
Table Diameter 52.4 - 57.5%
Crown Angle 33.7 - 35.8¡ã
Pavilion Angle 40.2 - 41.2¡ã
Girdle Thickness Thin, Medium, Slightly Thick
Culet Size None, Pointed, Very Small, Small, Medium

Now, there is a stone I am going to buy with the following proportions, which is unfortunately falling out of AGS Ideal Range.
Depth: 60.3%
Table: 57%
Crown Angle: 33.5
Pavilion Angle: 40.8
Culet: 0
Girdle: Medium, Facted (3.0%)

My question is: Why is that? Will it affect the future value of the stone?

Thanks.

Why is that? : Becuase that angle combination combined with a 60.3 depth is on the cusp of what AGS would consider as having dark contrast. Ie. too much head/body shadow. It may or may not get Ideal light performance based on a combo of angle measurements and azimuth angles of the facets (cutting to the east/west orientation). Only a physical analysis and running it through AGS PGS or sending it to AGS themselves would you know for sure.

Will it affect future value?: Round diamonds that fall into the rarest category (pertaining to cut) have a combination of precise optical symmetry combined with light performance specs that fall into the zenith of the GIA Ex/AGS Ideal range. This is unknown about this diamond so can''t say.

There''s a strong chance you''ll look at it alongside of an AGS Ideal and see little or no difference. Only one way to know for sure and that would be for you to make that comparison if you want to make sure.

 

[Todd Gray]

Date: 3/23/2010 1:37:50 AM
Author: yssie
http://agslab.com/trade_research_and_development_proportion_based_cut_grade.php

they have the proportion grade charts in a bunch of formats at the bottom of the page

ETA: I see. The author of that article - uncredited and unaccredited as far as we know - is putting his own spin on a lot of things, isn''t he? In any case, the official AGS documentation is available

Apologies... The Ideal Cut Diamonds site is a new design prototype for what will probably become the next site design for Nice Ice and I didn''t get a chance to go through every article when I transferred files from the older site to the new site, it''s a work in progress and apparently that page has not yet been edited to reflect the updated AGS proportions data from June of 2005 - which might sound a bit strange at first glance since it''s been five years and all, but try to keep in mind that I''ve spent most of that time tied up in litigation pertaining to Robin''s estate and am just now getting back in the game - the site is about 100 articles deep, so it takes awhile to go through

 

[oldminer]

The 1A grade is very narrow as I felt that truly top proportions deserve their own category of recognition. However, diamonds which score 1B are still produced in relatively limited numbers although more commion today than in the 1990''s when I created the AGA Cut Class charts. 1B diamonds are still highly prized and nearly all will be very well cut and highly attractive stones. You should never be displeased enough with a stone that scores 1B not to want to see it in person and consider buying it. It will be a very high grade stone in nearly every possible instance.

Many 2A and 2B diamonds look very fine and the vast majority of consumers buy these grades as the best ones they are shown or they select grade 3 and 4 becuase that is what the store sells.

 

[jazzshn]

Dear masters,

Thank you all for you valuable advices. I will go shopping soon and report my purchase.