Making the Grade - New Article

[coati]

New Journal Article by Garry Holloway: https://www.pricescope.com/journal/making-the-grade

"Has the GIA’s cut grading system for round brilliant diamonds made lower cut grades redundant?"

Thanks Garry for your contribution.

 

[ChunkyCushionLover]

HI Garry,

Good topic but I'm having trouble following your data and conclusions.

You used data from 1000 diamonds from which database? (PS?)

Culet – of the 311 stones with data listed, 304 had none (or were pointed), six were classified as ‘Very Small’, one was ‘Small’ and none were ‘Medium’ or ‘Large’.

You didn't look at the actual certificates, as culet data is always available on GIA reports just what was put into the database?
Were you looking for pairs of diamonds with identical 4Cs and different cut grades for pricing comparisons or somethingelse?

On answering the question of whether GIA cut grades have encouraged cutters to cut more for beauty than for weight I don't see how this can be answered from the grading report data. The poorest proportioned RBs are rarely sent to GIA. It would seem more likely that that question would be better answered by interviewing as a large a sample of manufacturers(large and small) as possible and asking them about their rough planning strategies.

Regards,
CCL

 

[oldminer]

There are markets for less well cut diamonds and for very finely cut diamonds. They rarely cross over one another. Once consumers are made aware of what cut quality means in terms of beauty how it equates to cut grading, they seem very interested in getting those kind of diamonds, but the majority in the USA seem content to buy average to lower cut quality diamonds with grading documents that are more or less worthless. Pricescopers are a large exception to the norm and growing, it would appear.

Technology is playing a part. It may well be easier to cut better makes and get an acceptable return on investment than it has ever been. Better cut diamonds that don't cost extra will surely find buyers willing to purchase them. Once a premioum is necessary, the price point game takes over most of the time.

Labs and their clients really don't want to extend cut grading to all shapes. Grading cut erodes the number of diamonds a major lab will be asked to process when the majority of fancy shapes would fail to score a high grade. Why would any dealer with a pretty diamond want a medium grade for cut on a document when currently there is no one asking for it and the stone sells based on its looks.

 

[Garry H (Cut Nut)]

HI Garry,

Good topic but I'm having trouble following your data and conclusions.

You used data from 1000 diamonds from which database? (PS?)

Culet – of the 311 stones with data listed, 304 had none (or were pointed), six were classified as ‘Very Small’, one was ‘Small’ and none were ‘Medium’ or ‘Large’.

You didn't look at the actual certificates, as culet data is always available on GIA reports just what was put into the database?
Were you looking for pairs of diamonds with identical 4Cs and different cut grades for pricing comparisons or somethingelse?

On answering the question of whether GIA cut grades have encouraged cutters to cut more for beauty than for weight I don't see how this can be answered from the grading report data. I doubt you will find anywhere in the brief article where I have drawn any conclusions CCL - I just noted some things which seem to stand out - many of which would have been very different 10 years ago The poorest proportioned RBs are rarely sent to GIA. It would seem more likely that that question would be better answered by interviewing as a large a sample of manufacturers(large and small) as possible and asking them about their rough planning strategies. I think Dave would also agree that over the past decade even the standard of the non or pretend certified stones have also improved dramatically

Regards,
CCL

Attempt to answer Dave and CCL:
This is from a 1 page article that I was asked to produce for the Aussie trade mag.
The average reader knows about 10% as much about diamonds as the average Pricescope enthusiast.
The initial word count got shrunk when they decided they needed pretty pic's. The editing was by comittee with silly deadlines.

All the data was taken from Rapnet.
I set up a search that got just over 1,000 resullts (note is on paper at home).
Of course I could not examine 1,000 reports, so used the reported data that was listed - and a lot of vendors just don't bother with things like culet (probably many don't even know that it is not a cut of meat).

 

[diagem]

Hi Garry, you wrote in your journal:
"But has cut quality really improved? Assuming that it has, is the overwhelming popularity of gem reports pushing quality improvements in the market?

To date, the GIA has not been able to offer a cut grade for fancy cuts (those other than round brilliant) due to the high number of proportion variables. Overall, there are far fewer stones in fancy shapes that would achieve an excellent grade for polish and symmetry.

There are two arguments for why this might be. The first is technical: most fancy-shaped diamonds have facets that are close to the octahedral plane and polishing in that direction is near impossible, so ‘brillianteers’ must accept a lower polish grade or adjust the facet angle, resulting in a lower symmetry grade. The second is about money: some believe the absence of cut grades for fancy shapes means manufacturers get less reward for higher standards; ie, they get away with higher yields."

Question (perhaps you know)..., what parameters are needed to achieve the Ex-Ex grade for asymmetrical fancy cuts at GIA and/or AGS. Any differences between them?
Could the deductions for symmetry & polish be based on subjective calls?

 

[Garry H (Cut Nut)]

of cut grades for fancy shapes means manufacturers get less reward for higher standards; ie, they get away with higher yields."[/i]

Question (perhaps you know)..., what parameters are needed to achieve the Ex-Ex grade for asymmetrical fancy cuts at GIA and/or AGS. Any differences between them?
Could the deductions for symmetry & polish be based on subjective calls?

Hi DG,
It would be a bit of subjective and reliance on scn rsults I guess. If you knew they might have to kill you?

http://www.octonus.com/oct/products...llustrated_report_for_marquise_2010_10_27.pdf that is an example of how a scanner can be used.
GIA GTL currently use scanners that are not accurate enough to do the same level of reporting - especially on stones with facet arrangements that they have not got programmed into their scanners for recognition. (A problem for all scanners).

But as an expert - is my comment about th trade off between polish and symmetry relevant and accurate?

 

[diagem]

of cut grades for fancy shapes means manufacturers get less reward for higher standards; ie, they get away with higher yields."[/i]

Question (perhaps you know)..., what parameters are needed to achieve the Ex-Ex grade for asymmetrical fancy cuts at GIA and/or AGS. Any differences between them?
Could the deductions for symmetry & polish be based on subjective calls?

Hi DG,
It would be a bit of subjective and reliance on scn rsults I guess. If you knew they might have to kill you?

http://www.octonus.com/oct/products...llustrated_report_for_marquise_2010_10_27.pdf that is an example of how a scanner can be used.
GIA GTL currently use scanners that are not accurate enough to do the same level of reporting - especially on stones with facet arrangements that they have not got programmed into their scanners for recognition. (A problem for all scanners).

But as an expert - is my comment about th trade off between polish and symmetry relevant and accurate?

Garry, we all know scanner limitation when it comes to symmetry facet meet points/junctions. Simply unreliable especially at X1000 the size on the screen..., please tell me GIA/AGS dont set symmetry grades based on scans only(do GIA and/or AGS admit at using Helium?)

As far as your trade off comment..., its accuracy depends on specific facet design and shape and the level of accuracy expectancy. In Step-Cuts cut for specific LP (eg Octavia) there is no room for error period, even scan error (+/- 0.3 deg in the latest models) will screw up the symmetry to a certain level (especially on computer screens).
Rounds & other symmetrical shapes also have almost no play and the trade off is painful although tools make cutters life much easier reaching the wanted results. The cutting of asymmetrical fancy shapes (which can enjoy a more forgiving trade off) is a completly different world! I dont think they are even comparable at this time of age..., way more complicated!

The reason I asked you the question originaly was I couldnt find a common ground on why some Ex/Ideal grades get symmetry deductions..., I have been trying to pick up some of my faults comparing scans to Lab's symmetry grades..., I have witnessed quite a few less accurate symmetry stones earn Ideal/EX while some more accurate stones get penalized for reasons I could not point my finger at.

 

[Garry H (Cut Nut)]

of cut grades for fancy shapes means manufacturers get less reward for higher standards; ie, they get away with higher yields."[/i]

Question (perhaps you know)..., what parameters are needed to achieve the Ex-Ex grade for asymmetrical fancy cuts at GIA and/or AGS. Any differences between them?
Could the deductions for symmetry & polish be based on subjective calls?

Hi DG,
It would be a bit of subjective and reliance on scn rsults I guess. If you knew they might have to kill you?

http://www.octonus.com/oct/products...llustrated_report_for_marquise_2010_10_27.pdf that is an example of how a scanner can be used.
GIA GTL currently use scanners that are not accurate enough to do the same level of reporting - especially on stones with facet arrangements that they have not got programmed into their scanners for recognition. (A problem for all scanners).

But as an expert - is my comment about th trade off between polish and symmetry relevant and accurate?

Garry, we all know scanner limitation when it comes to symmetry facet meet points/junctions. Simply unreliable especially at X1000 the size on the screen..., please tell me GIA/AGS dont set symmetry grades based on scans only(do GIA and/or AGS admit at using Helium?)

As far as your trade off comment..., its accuracy depends on specific facet design and shape and the level of accuracy expectancy. In Step-Cuts cut for specific LP (eg Octavia) there is no room for error period, even scan error (+/- 0.3 deg in the latest models) will screw up the symmetry to a certain level (especially on computer screens).
Rounds & other symmetrical shapes also have almost no play and the trade off is painful although tools make cutters life much easier reaching the wanted results. The cutting of asymmetrical fancy shapes (which can enjoy a more forgiving trade off) is a completly different world! I dont think they are even comparable at this time of age..., way more complicated!

The reason I asked you the question originaly was I couldnt find a common ground on why some Ex/Ideal grades get symmetry deductions..., I have been trying to pick up some of my faults comparing scans to Lab's symmetry grades..., I have witnessed quite a few less accurate symmetry stones earn Ideal/EX while some more accurate stones get penalized for reasons I could not point my finger at.

I suggest you always ask telling them you will repolish for a higher grade.

Then
1. they will tell you
2. they may change their mind

 

[diagem]

I suggest you always ask telling them you will repolish for a higher grade.

Then
1. they will tell you
2. they may change their mind

Thank you for your suggestion.
I thought you asked already and so will save me correspondents

 

[Garry H (Cut Nut)]

I suggest you always ask telling them you will repolish for a higher grade.

Then
1. they will tell you
2. they may change their mind

Thank you for your suggestion.
I thought you asked already and so will save me correspondents

Then you can tell me / us please Yoram

 

[diagem]

I suggest you always ask telling them you will repolish for a higher grade.

Then
1. they will tell you
2. they may change their mind

Thank you for your suggestion.
I thought you asked already and so will save me correspondents

Then you can tell me / us please Yoram

Just sent them an email, hope I hear some soon.

 

[MakingTheGrade]

Heh, I saw my screen name in the headline and was uber confused as to why Coati was calling me out to read an article.

 

[coati]

Heh, I saw my screen name in the headline and was uber confused as to why Coati was calling me out to read an article.

I thought of you when I made the post!