Can you see the difference between "Good" and "EX" polish and Symmetry? Any personal experiences?

[Rockdiamond]

You're welcome Garry.
The purpose of the discussion is that it seems an important topic to revisit.
I have a lot of experience with people who equate polish and symmetry with cut quality when that is not always the case.
The tutorial is balanced in it's explainations.
But it does hold true that, like David Atlas' complaint about reading the instructions- it's possible to miss the tutorial.

Another purpose is that I am genuinely interested in knowing if a professional has the eyesight to be able to spot the size defect we're talking about.
ETA Storm excepted.....I only single out "professional" as it really does require a lot of training to spot the kind of defects we're talking about. I'm counting Storm as a yes. I have spoken to cutters who say they can spot these things naked eye.

Now that I have read the tutorial, and you are participating, there can be one more reason for the thread.
Although it is an excellent tutorial, there was one line in the tutorial I did disagree with...
"The visual effect of Good or lower Polish is that you might feel a need to clean the stone. During the GIA observation testing, it was found that observers were less inclined to prefer diamonds with Good and lesser Polish. "


The second part makes perfect sense.
If we are going to go by rough averages, instead of hand picking the "Good" stones, percentages dictate the EX/EX's would average more attractive makes.

I disagree with the first part of the statement- where you say that if a stone was "Good and lower" you might feel the need to clean it"- I would agree that with a stone of "Fair "polish might exhibit that type of deficiency.
Again- this goes to the small size and impact of the defect comprising "good" polish GIA grade.


I'm only bringing it up as it's a good conversation- I don;t mean to lessen my compliment- it's a well balanced and written tutorial IMO.

 

[Garry H (Cut Nut)]

Date: 7/9/2009 11:17:15 PM
Author: Rockdiamond

Now that I have read the tutorial, and you are participating, there can be one more reason for the thread.
Although it is an excellent tutorial, there was one line in the tutorial I did disagree with...
''The visual effect of Good or lower Polish is that you might feel a need to clean the stone. During the GIA observation testing, it was found that observers were less inclined to prefer diamonds with Good and lesser Polish. ''


The second part makes perfect sense.
If we are going to go by rough averages, instead of hand picking the ''Good'' stones, percentages dictate the EX/EX''s would average more attractive makes.

I disagree with the first part of the statement- where you say that if a stone was ''Good and lower'' you might feel the need to clean it''- I would agree that with a stone of ''Fair ''polish might exhibit that type of deficiency.
Again- this goes to the small size and impact of the defect comprising ''good'' polish GIA grade.


I''m only bringing it up as it''s a good conversation- I don;t mean to lessen my compliment- it''s a well balanced and written tutorial IMO.

David the GIA survey was reported thus:
We found, as would be expected, that apparent brightness
decreases as the color of the diamond becomes
more saturated in the GIA D-to-Z range (including
browns). Grade-determining clouds in the SI2 and I
clarity grades diminish the appearance of fire. Fair
or Poor polish causes both apparent brightness and
fire to diminish; and Fair or Poor symmetry negatively
affects apparent brightness.
http://www.gia.edu/diamondcut/pdf/cut_fall2004.pdf page 19

I have personally seen SI1 GIA graded diamonds with reduced brilliance.
As Dave has said - the ''good'' range is very wide - I also believe that Good Polish can and does include doubtful diamonds.

I am sure (as i wrote earlier in this thread) that there are very bad rules used by most labs for symmetry grading, and that Good can be very fine as per the stone that is linked to from the Symmetry tutorial. And if there are a few bad facet meet points - it rarely is an issue even though in reflected glare you may be able to see them.
The fact is that labs use rules and those rules like so many others we discuss might not meet the standards at Pricescope.

However I still believe that you are doing yourself damage because the good people here are seriously questioning your goal and the rather selective way you reply to the issues David. If I were you I would stop.

But equally

 

[Dancing Fire]

Garry
according to the chart an EX/EX stone would cost 11.6% more than a G/G stone?

 

[Rockdiamond]

HI DF- I know you asked Garry, but if I may:
It may very well be that taken as a statistic, there is an 11.6% difference in price between an EX EX and a G/G

Of course we all know that old saying- " there''s lies. damn lies, and statistics"

What I mean to say is that the cost could be far higher- and less tangible.
Say a person has eliminated "good" polish in their search.
Instead of a simple 11.6% difference in price, they may very well end up making compromises in size, color or clarity that are quite visible. Their diamond may very well be 25% less in size- or other visible aspects.

My point, unchanged since the thread began, is that the defects ( or their effects) causing the "Good" grade are not visible to the naked eye. If a person believed their diamond would look like it needed cleaning ( mentioned in the tutorial) or that "I believe than many of us could tell the difference from a low good to a very good or excellent grade stone with the naked eye " ( a quote from David Atlas on the first page of the thread)- if either or both were true, than the elimination of Good makes sense.
If , as I am saying, its'' not, then it might make sense not to eliminate stones of "Good" polish

Garry- Thank you for the advice.
As Ellen reminds all of us, integrity is not a sometimes thing.
If a point of view is unpopular, but held due to moral convictions, it makes sense to discuss it even if it might be upsetting to some.
We''re talking about diamonds- not a life and death subject, thankfully.
However I do believe that the intensity of objection shows that it is a subject which is near and dear to many people.
I''m passionate about it- which is why I''m discussing it.

Although you and I- and David Atlas and I share a lot in the way we look at diamonds, I do believe the subject of Polish is still a fertile ground for discussion.
One that still needs more clarification.
For example- the quote you posted this morning - in blue- clearly stated that "Fair or Poor polish causes both apparent brightness and
fire to diminish; and Fair or Poor symmetry negatively affects apparent brightness. "Good" is not mentioned.

Garry, you suggested that there are books that might document what I am asking to see.
That may or may not be true- but the reason I''m asking to see it here is that we are all aware of how photos can be taken by people posting here- or on websites. We have a point of reference.
To "prove" or disprove that Good polish, or the resultant effects of "good " polish may be visible to the naked eye, the type of photos we''ve seen here many times documenting clarities- or faceting are needed.

 

[oldminer]

Check out this .pdf.

http://www.gia.edu/diamondcut/pdf/polish_and_symmetry.pdf

Toward the end of the article it really gets to the meat of the issue and has PHOTOGRAPHS of examples and a bit on how finish is graded. This shows that photos could be used if anyone wanted to point out problems and not benefits.

 

[Rockdiamond]

Thank you David!
Excellent referrence!
To bolster the side of this conversation that says visible problems are possible, that''s what GIA says.
The definition of "Good" polish- from the GIA page states:
"Noticeable polish features are seen face up at 10x magnification.
The luster of the diamond may be affected when viewed wtih the naked eye"

Based on that definition, it would seem that there are stones that have eye visible polish defects rated as "good" polish.
In terms of photos, the GIA page does have some - however they are extreme close up detail shots- as opposed to a more realistic photo showing the entire diamond.
This still leaves doubt in my mind- I can''t recall ever seeing a stone rated "good" that did have eye visble luter deficits based on the grade.

Of course I defer to GIA in an overall sense... but as Garry has written- there are many in the trade who do quesiton someof the methods used to ascertain these finish grades.

It may just be realistic photos showing these problems in relation to a diamond as a whole do not exist- or it may be that such stones are incredibly rare. I still feel that it''s important to document this in such a way that people can see the effects.
I''d like to see the effects!

 

[Judah Gutwein]

Re: My own limitations..

Good to Excellent Polish is something I cannot distinguish with my naked eye.
Good to Excellent Symmetry, is something I can distinguish most of the time without a loupe.

 

[Diamond Explorer]

Date: 7/10/2009 1:23:02 PM
Author: oldminer
Check out this .pdf.


http://www.gia.edu/diamondcut/pdf/polish_and_symmetry.pdf


Toward the end of the article it really gets to the meat of the issue and has PHOTOGRAPHS of examples and a bit on how finish is graded. This shows that photos could be used if anyone wanted to point out problems and not benefits.

Great PDF, This is the best visual to display what we are talking about!

 

[whatmeworry]

Date: 7/10/2009 1:23:02 PM
Author: oldminer
Check out this .pdf.


http://www.gia.edu/diamondcut/pdf/polish_and_symmetry.pdf


Toward the end of the article it really gets to the meat of the issue and has PHOTOGRAPHS of examples and a bit on how finish is graded. This shows that photos could be used if anyone wanted to point out problems and not benefits.

Interesting link Dave, I find it interesting that the GIA symmetry grade seems to actually take crown and pavilion angle deviations into account. This seems somewhat different from what other experts have said here.

 

[Garry H (Cut Nut)]

David you have flogged the horse to death now.

I suggest that in this case, you do the research, you are after all close by to a market with a huge number of diamonds. Write and submit a Journal article (there are plenty of us here who will happily provide editorial review assistance) with the approriate photo''s.
In this case you can choose to be neutral or opinionated.
Then there will be a pinned discussion at the top of this forum where everyone can continue the discussion. I will petition I suggest that this thread die now, until that time, and then be added to the new post journal article.

 

[Modified Brilliant]

Date: 7/8/2009 4:51:23 PM
Author: Richard Sherwood


I usually can''t spot the difference between Good and Excellent polish with the naked eye, but I usually can spot the difference between Good and Excellent symmetry.

Copy and "ditto" that. Rich... why do you have to explain things in such easy to understand and simple terms?

www.metrojewelryappraisers.com

 

[Rockdiamond]

Date: 7/10/2009 4:42:41 PM
Author: Judah Gutwein
Re: My own limitations..

Good to Excellent Polish is something I cannot distinguish with my naked eye.
Good to Excellent Symmetry, is something I can distinguish most of the time without a loupe.

Ditto Judah!

I think a lot of us are on the same page.
In person, talking to dealers, Judah''s answer is basically what I''ve encountrered

Jeff, Rich and some of our esteeemed appraisers basically feel that they ususally can''t spot the "Good reasons" by eye.

Garry''s idea is a good one.
I will obtain diamonds of "good" polish, and plots on the downgrade reasons from GIA to see if I can document some of them photographically.