GIA Excellent Symmetry - has the standard dropped?

[Garry H (Cut Nut)]

This stone was given XXX by GIA. It is +5ct, so scanner accuracy should not be an issue.

 

[bmfang]

What are its stats @Garry H (Cut Nut)?

 

[Karl_K]

I dont know, but we have been seeing a lot of ASETs like that.
What is the range on the pavilion mains and lower girdle angles?

 

[Rockdiamond]

I hate to say this, but GIA is definitely having some "growing and contracting pains".
We've also noticed some inconsistencies with color/clarity....

 

[denverappraiser]

 

[rockysalamander]

Its such a shame that they are letting these varying pavilion mains make it to Excellent. I concur with @Rockdiamond. I visited a family friend this past week and we were looking at diamonds. There were several GIA G's that we both raised our eyebrows at...to our eyes, they were solid H color. I hope this is a blip and not a trend.

 

[Garry H (Cut Nut)]

Neil that is a beauty mate!
Rocky Salamander I think it is more likely a combo effect of minor facets.
I have not studied the stone intensely (but I do have a .srn stl file so I can when I get tiime) and so it might be a case where the stone slipped thru, but the compounding effect gives a poor result

 

[John P]

I suggest to reverse the opera glasses, and spy on what producers are doing to keep EX.

Remember the lab 'symmetry' grade is completely blind to 3D optical precision. We imaged three diamonds with notably different levels of 3D precision to demonstrate this back in 2007. All of these diamonds earned EX or Ideal in symmetry (photos by Whiteflash).



So I don't know that the lab's standard has changed.

It begs the question: What will a diamond be penalized for? Out of round or wavy girdle, a tilted table, crown and pavilion not aligned, T/C off-center... Those things are largely avoidable today due to advances in modern girdling and auto-blocking.

What's left? Facet shape and meet points. And actually, by the book, GIA EX symmetry permits some level of minor misalignment, misshapen facets and/or extra facets to pass.

My point is that the 3D optical symmetry issues in Sir Garry's OP above (and the right two diamonds in this post) are not examined in lab graded 'symmetry.' I can tell you they're caused by angle variation within facet groups and supposedly this gets accounted for at some level (?) but I don't see it penalized, especially when a clever brillianteerer cleans up shapes and meet points on the diamond's surface - making it appear tightly knit.

You will see this regularly in commercial production because producers have learned that only the average of a facet group's 8 (or 16) measurements is used for grading. So if they're chasing a 41.0 degree PA - but some challenge limits a side of the stone to 41.5 - they can compensate by polishing another side down to 40.5... and viola! ...the average PA measurement becomes the desired 41.0, which is the only number used to calculate the cut-grade and the only number seen on the report.

 

[Karl_K]

Roughly .5 degrees variation on the mains.
Its a lot but not that huge.
The lower halves/girdle facets are another story they are twisted like pretzels.

 

[Garry H (Cut Nut)]

I think I have it.
The lower girdle the leaks the most is the steepest.
On the next reflection it bounces off one of the steepest pavilion mains, then hits the crown facet where most of the light would normally exit, but that crown facet has total internal reflection (on left side). It to is slightly steep.

End result – 3 steep deep interactions and a dead facet. In each case the variations are smaller than the boundaries GIA would have programmed in to the scanner.

So for us Cut Nut's using reflector tools makes great sense. In a half carat stone this would not be a big deal. But in a +5ct stone like this most people would see a dull spot in the stone. Size does matter!

 

[pyramid]

Its such a shame that they are letting these varying pavilion mains make it to Excellent. I concur with @Rockdiamond. I visited a family friend this past week and we were looking at diamonds. There were several GIA G's that we both raised our eyebrows at...to our eyes, they were solid H color. I hope this is a blip and not a trend.

I don't know about colour but when I began reading here in 2002, lots of the experts who were dealers were saying that clarity had taken a large nosedive from what it was, it was at this time, it was written that we need to check SI1 clarity with our eyes to see if it is eyeclean, as in the previous years SI1 was always eyeclean and that was the definition of SI1 and before they started telling us to check with our own eyes, they used to say if we could see something it was DEFINITELY not an SI1 but an SI2 or worse as SI1 is always eyeclean. It seems that the old SI1 is now VS2 or a bit higher.

 

[bmfang]

Love reading your posts @Karl_K and @John Pollard. Always come out feeling a little smarter and more knowledgeable after reading a thread that the two of you contribute to!

 

[pyramid]

Love all dealers posts.

Kudos to Garry H here though who has discovered why asset scopes are showing more leaking now and yet getting GIA excellent. The diamcalc ray tracing is THE proof of what is going on.

 

[John P]

Roughly .5 degrees variation on the mains.
Its a lot but not that huge.
The lower halves/girdle facets are another story they are twisted like pretzels.

Definitely. That's an unavoidable by-product of cross-working the mains to chase an average, not a consistent target. The ASET reveals what lurks beneath.

End result – 3 steep deep interactions and a dead facet. In each case the variations are smaller than the boundaries GIA would have programmed in to the scanner

Boom. You nailed it. Nicely correlated and explained with DiamCalc.

Love reading your posts @Karl_K and @John Pollard. Always come out feeling a little smarter and more knowledgeable after reading a thread that the two of you contribute to!

Well that's uplifting. Thank you @bmfang . In fact I'm going to print this and show it to my wife the next time we argue.

(I'll still lose)

 

[msop04]

I don't know about colour but when I began reading here in 2002, lots of the experts who were dealers were saying that clarity had taken a large nosedive from what it was, it was at this time, it was written that we need to check SI1 clarity with our eyes to see if it is eyeclean, as in the previous years SI1 was always eyeclean and that was the definition of SI1 and before they started telling us to check with our own eyes, they used to say if we could see something it was DEFINITELY not an SI1 but an SI2 or worse as SI1 is always eyeclean. It seems that the old SI1 is now VS2 or a bit higher.

I've never read that SI1 should be eye clean... actually, VS2 clarity isn't always eye clean. Also, the type of inclusion(s), grade-setting inclusion(s), and the placement of those inclusions play a huge role in whether or not a stone is eye clean. I've seen SI2's that were completely eye clean, but VS2's that had a visible inclusion on the table. There are a lot of factors that determine if a specific clarity graded stone will be eye clean, hence the importance of being able to see the report and stone.

 

[Garry H (Cut Nut)]

I've never read that SI1 should be eye clean... actually, VS2 clarity isn't always eye clean. Also, the type of inclusion(s), grade-setting inclusion(s), and the placement of those inclusions play a huge role in whether or not a stone is eye clean. I've seen SI2's that were completely eye clean, but VS2's that had a visible inclusion on the table. There are a lot of factors that determine if a specific clarity graded stone will be eye clean, hence the importance of being able to see the report and stone.

Us 'oldies' know that diamonds graded by GIA and other labs decades ago that have been resubmitted usually (more than often, but not always) come back with better Clarity grades today.
In maybe the 1980's I1 = eye visible - but probably only up to about 1ct. VS2 in a 100ct diamond would likely have always been eye visible.
I rarely see a +1ct SI2 that is eyeclean and if it is, then at least 90% of those will have coulds that dull the stone. Give me a few hard to see grade makers that I can put under a prong anyday over a dull diamond.

 

[whitewave]

I hate to say this, but GIA is definitely having some "growing and contracting pains".
We've also noticed some inconsistencies with color/clarity....

I get a little when somone proclaims GIA has the strictest color grading

 

[metall]

Love all dealers posts.

Kudos to Garry H here though who has discovered why asset scopes are showing more leaking now and yet getting GIA excellent. The diamcalc ray tracing is THE proof of what is going on.

I'm on the same boat. I think I lurk on the RockyTalk forum more for educational posts like this than questions regarding diamonds. Especially since I am still not experienced enough to tell a lump of coal from an ideal cut diamond just from numbers. Even with Images/IS/ASETs sometimes...I can tell minor details, but I can't tell how or why it's affecting the stone's performance.

The more I read posts like this, the more I can start seeing the reasons for the deficiency which I can only hope will translate to better future purchases.

 

[cflutist]

@Rockdiamond or @John Pollard
Isn't consistency more difficult when there are multiple locations? How many labs does GIA have around the world? Correct me if I am wrong but AGSL has one location in Las Vegas where standards can be more tightly controlled?

 

[Rockdiamond]

Us 'oldies' know that diamonds graded by GIA and other labs decades ago that have been resubmitted usually (more than often, but not always) come back with better Clarity grades today.
In maybe the 1980's I1 = eye visible - but probably only up to about 1ct. VS2 in a 100ct diamond would likely have always been eye visible.
I rarely see a +1ct SI2 that is eyeclean and if it is, then at least 90% of those will have coulds that dull the stone. Give me a few hard to see grade makers that I can put under a prong anyday over a dull diamond.

This could absolutely be attributable to our vastly different locations- but I do find plenty of eye clean SI2 diamonds that have no cloudiness issues whatsoever. Without a doubt, there's plenty of horrible SI2's- particularly in inventories that have been picked through. Looking at new productions will produce entirely different proportion of bad SI2's
We surely agree that "dull" is the kiss of death to a diamond in the eyes of most buyers.

 

[Rockdiamond]

@Rockdiamond or @John Pollard
Isn't consistency more difficult when there are multiple locations? How many labs does GIA have around the world? Correct me if I am wrong but AGSL has one location in Las Vegas where standards can be more tightly controlled?

Theoretically, it should be the case that a single location is more consistent than a lab with multiple locations- but the reality is that diamond grading is subjective. So even in a single location, different graders may come up with slightly different results.
Plus, for every stone AGSL grades GIA probably grades 1000- so there's that too.....

 

[pyramid]

msop It definitely was said that SI1 was always eyeclean. This is why I got paranoid about my own SI1 I had a the time and although it was a small stone I was told I should not be able to see anything in it and I could. It may have been the predecessor of Pricescope board I was on, but all the dealers were there at the time and they all agreed SI1 should be eyeclean. Then as the years went by, they started saying 'may not be eyeclean' so the standard changed, they even said the old GIA standards were more strict than they are now.

 

[Rockdiamond]

msop It definitely was said that SI1 was always eyeclean. This is why I got paranoid about my own SI1 I had a the time and although it was a small stone I was told I should not be able to see anything in it and I could. It may have been the predecessor of Pricescope board I was on, but all the dealers were there at the time and they all agreed SI1 should be eyeclean. Then as the years went by, they started saying 'may not be eyeclean' so the standard changed, they even said the old GIA standards were more strict than they are now.

You know, they say the memory is the first thing to go. I disagree the first thing that went on me was.....wait, what was I saying?

Seriously- IMO it was never an accurate statement that "SI1 is always eye clean". It's the nature, size and number of imperfections, as opposed to their visibility- and IMO it's always been that way.
I might agree that grading overall has gotten a bit softer, because my memory is so darn....what was I saying?

 

[cflutist]

Theoretically, it should be the case that a single location is more consistent than a lab with multiple locations- but the reality is that diamond grading is subjective. So even in a single location, different graders may come up with slightly different results.
Plus, for every stone AGSL grades GIA probably grades 1000- so there's that too.....

@Rockdiamond Dave
Did you ever find out if 3 GIA graders had to agree like the old days before a lab report is issued? I posted an old report of one of my diamonds with 3 sets of initials on it on another thread.

 

[Rockdiamond]

@Rockdiamond Dave
Did you ever find out if 3 GIA graders had to agree like the old days before a lab report is issued? I posted an old report of one of my diamonds with 3 sets of initials on it on another thread.

I will make sure to check my service rep tomorrow....been a bit crazy round here In a good way

 

[Karl_K]

What I find fascinating is the perceptions of different people in the diamond trade based on what they are seeing in their location and how much it varies.

For example lets say a dealer buys every eye clean si1 of a certain make that a supplier shows them.
The supplier being a smart person notices this and shows the person more eye clean si1 diamonds.
As time goes by the dealer starts thinking wow there are a lot more eye clean si1 because I am rejecting so few of them.

Some markets sadly have traditionally been a dumping ground.
The supplier has something that was rejected in other markets will then sell it into one those markets.
That colors the opinions of those dealers and they may be thinking there are no eye clean si1s anymore.

Two different opinions, both true for them but not representative of the entire market.

With more and more diamonds being bought off large lists and much shorter pipelines that is changing but it still holds somewhat true.

 

[bmfang]

Thought: it would be good if current GIA grading reports specify which of the GIA labs around the world have done the grading. I seem to recall that IGI graded stones do mention which IGI lab has graded the stone on the report.

If this is done, you could easily ID which lab has been potentially “softer” on colour and clarity. But not so much with cut grade given the exceedingly wide range of GIA XXX.

 

[msop04]

msop It definitely was said that SI1 was always eyeclean. This is why I got paranoid about my own SI1 I had a the time and although it was a small stone I was told I should not be able to see anything in it and I could. It may have been the predecessor of Pricescope board I was on, but all the dealers were there at the time and they all agreed SI1 should be eyeclean. Then as the years went by, they started saying 'may not be eyeclean' so the standard changed, they even said the old GIA standards were more strict than they are now.

Maybe you just had a bad SI1.

 

[msop04]

What I find fascinating is the perceptions of different people in the diamond trade based on what they are seeing in their location and how much it varies.

For example lets say a dealer buys every eye clean si1 of a certain make that a supplier shows them.
The supplier being a smart person notices this and shows the person more eye clean si1 diamonds.
As time goes by the dealer starts thinking wow there are a lot more eye clean si1 because I am rejecting so few of them.

Some markets sadly have traditionally been a dumping ground.
The supplier has something that was rejected in other markets will then sell it into one those markets.
That colors the opinions of those dealers and they may be thinking there are no eye clean si1s anymore.

Two different opinions, both true for them but not representative of the entire market.

With more and more diamonds being bought off large lists and much shorter pipelines that is changing but it still holds somewhat true.

I hadn't thought about this scenario... very interesting indeed, @Karl_K.

 

[Rockdiamond]

Karl makes a great point. My take is slightly different.
The largest cutters move the inventory from market to market based on volume and trade shows. So I don't find it's the geographical location. A sharp dealer understands how to pick eye clean SI goods in any location.
The lists make the majority of goods available to consumers on large websites. The manner of display on these sites does not allow users to pick eye clean stones. In some cases a stone looks like it will be eye clean as it spins on the pavilion but in person the imperfections are easy to see. In other cases a stone looks bad in the video but good in person.
Of course once the stone is actually delivered the bad ones get sent back.
Over time this makes te pool of SI diamonds on the virtual lists less and less eye clean.
It does give dealers who can select in person an advantage on SI goods.