Is a GIA “Good” cut actually good?

[Texas Leaguer]

Is a GIA “Good” cut actually good?
And if it is good, who is it good for – the consumer or the manufacturer?

I love GIA, don’t get me wrong. But calling the diamond featured here a “Good Cut” is not helpful to the consumer. But it does illustrate just how broad and forgiving the GIA cut grade system is.

Just how lenient is the GIA cut grade system you ask? The diamond represented by the diagram below earns a GIA cut grade of GOOD. Granted, “good” is GIA’s third grade behind Excellent and Very Good. But you can forgive the inexperienced diamond consumer for thinking this diamond is of desirable cut quality, considering GIA’s well deserved reputation for expertise and accurate grading. But in this particular case “good” is a euphemism for “third rate”!

The very high crown and pavilion angles in particular will have bad (not good) impacts on light performance. Not only is each excessive on its own, but crown and pavilion angles work together an inverse relationship. That is, a high crown angle must be complimented by a low pavilion in order for internal reflections to result in the best light performance. And a high pavilion angle must be complimented by a low crown angle to achieve that result. When both numbers are high, the result is what is known in the trade as a “steep/deep”, and the diamond represented by this diagram is an extreme example of one. Not good!

A computer generated ASET for a diamond with these specs (left) illustrates the problems with this proportioning. Not only does the stone suffer from excessive light leakage (white), but the light it is returning is dominated by less bright low angle light (green). This will result in reduced brightness overall. A well-cut diamond (right) will have the opposite ASET signature; much more red, significantly less green, and a lot less white.

Images generate with DiamCalc software by Octonus

A broad and forgiving cut grade system benefits manufacturers because they can take liberties with cutting to get higher carat yield that can be sold for more money, while still getting a cut grade on a GIA report that looks palatable to the average consumer. But a diamond that suffers from significant deficits in light performance is certainly not “good” for the consumer.

Even the GIA Excellent grade includes some diamonds with light performance deficits. So while it establishes a decent baseline for consideration, more information needs to be ascertained in order to verify that the cut quality is really excellent. But the GIA cut grades of very good and good are really stretching the definition of those labels!

 

[0515vision]

Does this have anything to do with when the system was created? That is, at the time GIA set up good/excellent, were stones with those angles still sought after by the purchasing public? And what's below "good?" "Poor?"

Now with the internet and technological means of judging diamond fire vs brlliiance vs sparkle vs etc, the term "GIA Good" doesn't hold any weight. But historically was it a valid category?

And hope all is well in Houston, @Texas Leaguer! May it be sunny skies and calm weather from here on out!

 

[oldminer]

The timing of GIA's decision making on what names to give to levels of cut grading was in a different time, for sure. That had a real effect on their decision making. Back then, people often bought a diamond that looked "ok" and was offered at a lower price than some other diamonds that to a consumer's untrained eye, looked fairly much the same, but were probably cut better and worth the added cost.

We have done a very good job educating a wide segment of the public to seek well cut and extremely well cut diamonds over the past 20 years. Probably it is time to push hard to encourage consumers to look closely and for the diamond grading major labs to tighten up their standards so that folks really understand what to buy when they are willing to pay for a superior cut diamond. There ought to be no doubt that the lower grades of cut quality hardly deserve cut grading documents at all. A diamond is a visual product than can perform well only when cut near the best level. The economics of the business have sufficiently shifted to make buying top cut stones far less of a problem than decades ago. Weight retention now means less to educated consumers and many dealers than the beauty released by proper cutting.

There are plenty of places to buy diamonds based on lowest cost per carat along with "Good" cut grades, but they are not a premium product. If you like to pay for extra fat around your steak, or the weight of your butcher's thumb on the scale, then maybe a "Good" cut will do.

Diamond reports with a cut grade that indicates the top two levels of cut and no grade for anything lower may be a more sensible way to go. Few experts care if a round diamond is below triple EX. Tricking consumers into thinking "good" actually means "good" under common usage demeans the entire system of diamond grading.

 

[MissGotRocks]

This is why I hated to see AGS merge with GIA. At least AGS did not round angles as GIA does. Even with the cut performance from AGS attached to the GIA cert, I don’t think it provides the level of assurance that the old AGS certs did. Without huge public pressure, I can’t imagine GIA changing any of this. It benefits too many non-consumers financially.

So what is an alternative plan? A Sarin report for each diamond? However, I am guessing there is variance from machine to machine?

 

[Karl_K]

Honestly Im feeling for GIA on this one.
Until you have designed a grading system you have no idea of the incredible complexity it takes to make diamond cut fit in traditional and expected ranges.
You have top, a very narrow near top, and meh.
Then you have to split meh into 2 or 3 chunks or more.
That results in meh diamonds getting a good rating.
The bigger problem is the huge amount of combos that deserve meh get the top grade in the GIA system.
For that its legit to roast them.

 

[Texas Leaguer]

Honestly Im feeling for GIA on this one.
Until you have designed a grading system you have no idea of the incredible complexity it takes to make diamond cut fit in traditional and expected ranges.

100% Karl. That's really why I felt compelled to lead with "I love GIA" !

When all the technical work is done in measuring and calculating, there is still the real world observational piece. And that may be the most confounding. Especially for scientists, because it is fully in the realm of the subjective. But if you are going to devise a "grading" system (not simply a measurement system) then you are going to have to do that work.

But the real challenge GIA had in devising their system was more political in nature. That is, they had a huge existing constituency whose needs they had to consider. Billions of dollars of inventory that had been cut in the traditional way - prioritizing carat weight. Coming out with a strict system would have cost their clients mightily, making some of their goods unsellable. That was a very strong force that GIA had to contend with.

On the other hand AGSL was small and was literally born to cater to cutters striving for the Ideal cut. So they built a very strict system. But it too had limitations. For instance, as @Serg has pointed out, the ASET paradigm is monocular (or as Serg says "cyclops view"). In reality we observe diamonds with two eyes seperated by several inches, and that introduces significant complicating factors. You also have a brain in the mix that is interpolating the information it recieves visually. AGSL was of course aware of this issue when they developed their system, but the computing power necessary to factor in both eyes was not available at the time.

So, people can take pot shots at GIA and other labs (ok I'm guilty), but we should always recognize that grading systems are part science and part art.

 

[Texas Leaguer]

This is why I hated to see AGS merge with GIA. At least AGS did not round angles as GIA does. Even with the cut performance from AGS attached to the GIA cert, I don’t think it provides the level of assurance that the old AGS certs did. Without huge public pressure, I can’t imagine GIA changing any of this. It benefits too many non-consumers financially.

So what is an alternative plan? A Sarin report for each diamond? However, I am guessing there is variance from machine to machine?

@MissGotRocks , I think you are correct that not much will change with round cut grading at GIA. However, now consumers have the option of getting an AGS Ideal addendum report with any GIA report on a diamond that qualifies. This enables a finer gradation of their Excellent cut for consumers looking for elite cut quality.

But the real opportunity here for GIA with the acquisition of AGSL is to finally roll out a cut grade system for fancy shapes. It would be a game changer, just as it was a game changer when GIA finally released their cut grading system for rounds. Because of their enourmous reach, practically overnight cutting got much better with manufacturers striving for the Triple Ex grade.

One of the benefits that lab grown diamonds is bringing to the market is a better appreciation of fancy shapes. Consumers and manufactures can afford to expand their horizons. This trend creates an even greater need for a cut grading standard (even if a forgiving one) that will help consumers avoid paralysis in decision making. And a forgiving grading system gives companies who want to reach farther the opportunity to add value for those shoppers who are looking for the best of the best.

 

[Texas Leaguer]

Does this have anything to do with when the system was created? That is, at the time GIA set up good/excellent, were stones with those angles still sought after by the purchasing public? And what's below "good?" "Poor?"

Now with the internet and technological means of judging diamond fire vs brlliiance vs sparkle vs etc, the term "GIA Good" doesn't hold any weight. But historically was it a valid category?

And hope all is well in Houston, @Texas Leaguer! May it be sunny skies and calm weather from here on out!

@0515vision ,
Thank you for your well wishes. We are doing well. Of course hurricane season is upon us now

I think @oldminer posted some thoughts on the historical. And @Karl_K pointed out the dificulties of creating any cut grading system. It is very hard to create a system that will stand the test of time and changing technology. We need to give every lab that attempts this a little slack.

I hope I did not come across as bashing GIA by broaching this topic. It was more meant to be cautionary advice to newbies.

 

[Texas Leaguer]

Diamond reports with a cut grade that indicates the top two levels of cut and no grade for anything lower may be a more sensible way to go. Few experts care if a round diamond is below triple EX. Tricking consumers into thinking "good" actually means "good" under common usage demeans the entire system of diamond grading.

This is actually a sensible approach.

OK, here's my hierarchy if I was designing the labels. From bottom up:

Oh, hell no.
Nope.
Well, sort of, maybe
Sweet.
I'm having what she's having!

Zellenials might not get that last reference, but they should check it out

 

[MissGotRocks]

@0515vision ,
Thank you for your well wishes. We are doing well. Of course hurricane season is upon us now

I think @oldminer posted some thoughts on the historical. And @Karl_K pointed out the dificulties of creating any cut grading system. It is very hard to create a system that will stand the test of time and changing technology. We need to give every lab that attempts this a little slack.

I hope I did not come across as bashing GIA by broaching this topic. It was more meant to be cautionary advice to newbies.

No, I don’t think it came across as bashing at all. I think it is very helpful and educational to try to explain the different nuances in the cut grades. So often, newcomers are looking for assurances on a stone they are considering for purchase. They are surprised to learn that a GIA 3x gets a thumbs down response. I sometimes feel that they end up questioning the reliability of member’s opinions. It is good to hear this from trade members that deal with lots of diamonds all day long.
I do understand that it can be difficult to create a grading system. However, it is even more difficult to come up with one that is transparent and fair for consumers without hurting tradespeople. I felt that AGS had done a great job with that but they did not have the world wide appeal of GIA. My greatest wish as a consumer is that GIA would not round numbers but would state them in exact measurements. Even looking at ACA diamonds more recently graded by GIA, there seems to be two sets of combinations that come up most all of the time. Whiteflash provides images and videos though that help judge, as well as offering personalized assistance through their associates. We must deal with the information provided for the time being, and I am very appreciative of the information and transparency that Whiteflash and other vendors provide in helping to make a very expensive choice!

 

[oncrutchesrightnow]

Behold the abject horror of this Excellent cut diamond:



Love it. 55/63.1, 36.5/40.6, 7.23mm for 1.5 carat. BUT I knew what I was getting — chunky fiery flashes at the cost of size and light leakage. I feel for the consumer who is making one major diamond purchase in their life and thinks “good” means “big and bright and sparkly.”

Maybe with the availability of cheap custom cut diamonds, consumers will be more likely to ask for what they want. The one with the chunky facets, the one that has that dot in the middle, the one that glows blue, the one that you can see across the room. As prices drop that might be a pathway to diamond education, especially with social media. Check out how symmetrical this diamond is, look at how poofy that diamond is, ew this other diamond has no light in the middle. Because even if you tighten GIA standards, some vendor can flood the internet with ten trillion bots calling their diamonds “Awesome cut grade.”

It also might end up being a good way to share all that inventory that isn’t moving, or encourage artists to pursue creativity and quality in cutting diamonds.

 

[Garry H (Cut Nut)]

Today listed on RapNet
551,279 Excellent cut
30,131 Good cut
431 Poor cut

When you design a cut grading system with the assistance of the foxes the hens have no chance!

Of those half a million rounds around 100,000 will be < HCA 2.0.
and when you look at how broad GIA's symmetry grade is you see things like this (from my book - get notification at GarryHolloway.com )

 

[diamonds27]

Is a GIA “Good” cut actually good?
And if it is good, who is it good for – the consumer or the manufacturer?

I love GIA, don’t get me wrong. But calling the diamond featured here a “Good Cut” is not helpful to the consumer. But it does illustrate just how broad and forgiving the GIA cut grade system is.

Just how lenient is the GIA cut grade system you ask? The diamond represented by the diagram below earns a GIA cut grade of GOOD. Granted, “good” is GIA’s third grade behind Excellent and Very Good. But you can forgive the inexperienced diamond consumer for thinking this diamond is of desirable cut quality, considering GIA’s well deserved reputation for expertise and accurate grading. But in this particular case “good” is a euphemism for “third rate”!

The very high crown and pavilion angles in particular will have bad (not good) impacts on light performance. Not only is each excessive on its own, but crown and pavilion angles work together an inverse relationship. That is, a high crown angle must be complimented by a low pavilion in order for internal reflections to result in the best light performance. And a high pavilion angle must be complimented by a low crown angle to achieve that result. When both numbers are high, the result is what is known in the trade as a “steep/deep”, and the diamond represented by this diagram is an extreme example of one. Not good!

A computer generated ASET for a diamond with these specs (left) illustrates the problems with this proportioning. Not only does the stone suffer from excessive light leakage (white), but the light it is returning is dominated by less bright low angle light (green). This will result in reduced brightness overall. A well-cut diamond (right) will have the opposite ASET signature; much more red, significantly less green, and a lot less white.

Images generate with DiamCalc software by Octonus

A broad and forgiving cut grade system benefits manufacturers because they can take liberties with cutting to get higher carat yield that can be sold for more money, while still getting a cut grade on a GIA report that looks palatable to the average consumer. But a diamond that suffers from significant deficits in light performance is certainly not “good” for the consumer.

Even the GIA Excellent grade includes some diamonds with light performance deficits. So while it establishes a decent baseline for consideration, more information needs to be ascertained in order to verify that the cut quality is really excellent. But the GIA cut grades of very good and good are really stretching the definition of those labels!

Hey, you should check out this new site, www.yourdiamondguys.com. It’s got this cool AI that scans for inclusions and weeds out the bad ones, so you only see the best diamonds with nice imperfections. Plus, there’s tons of info on there to help you out.

 

[Garry H (Cut Nut)]

Hey, you should check out this new site, [**edited by moderator to remove spam**

The trouble is the worst inclusions are not visible with less than about 50X magnification.

 

[diamonds27]

Try it out. I think it’s super useful. Not perfect but really gets rid of a vast majority of the bad. When you go straight onto the retailers website they just feed you everything. Could be pages worth and very few have the mental energy for that. This site helps tremendously. I think.

 

[diamonds27]

I can not see whrere that service is offered unless I pay them a lot of money

The search functionality is free. The only time you have to pay something is if you want a personalized consult. Otherwise you can search as much as you want with the slider scale.

 

[Garry H (Cut Nut)]

Unimpressed.
This stone came up as one of only 2 stones in a 1-1.01ct excellent and Ideal in a D E SI2 search.
Yet the clarity picked missed a whole lot of twinning / grain at 9 oclock just inside the table. The system will only be as good as the image quality and lighting.
Worse still this "excellent cut" stone has a depth of 63.3%

 

[lovedogs]

Unimpressed.
This stone came up as one of only 2 stones in a 1-1.01ct excellent and Ideal in a D E SI2 search.
Yet the clarity picked missed a whole lot of twinning / grain at 9 oclock just inside the table. The system will only be as good as the image quality and lighting.
Worse still this "excellent cut" stone has a depth of 63.3%

They have a lot of terrible stones labeled "excellent". It's honestly just sad.

 

[diamonds27]

The site is a disaster. You have to pay for 15 minutes??? Monthly? The "guides" are just info that can be found anywhere, no real useful information given.

There is no monthly fee? Don’t know where you are seeing that?
Yes. If you want to speak with someone live you have to pay. That is not the intention of the website. There is free email and you can email someone to your hearts content for FREE.
That looks like a pretty darn nice SI2 visually. 95 percent of SI2 diamonds are black and or have massive hard inclusions. These are soft and wispy which is what everyone wants in a SI2. This is not a VS stone.
The reason you only got a couple options is because it weeded out all the poor options. Instead of the user being inundated with junk, the system correctly showed nice instead of wasting the users time.
In re: the depth. I would be willing to bet there was a red X next to the depth. Indicating this is not a perfect stone but one that should be considered because of the imperfection. Can you please send a screen shot showing the score?
Please show that shot with the green checks and red x?
Let’s make sure the users on the forum get the full picture as opposed to picking and choosing. Appreciate any feedback you may have. But in 2 minutes you found a basically eye clean SI2 which is a needle in a haystack these days for anyone who knows diamonds. It’s a nightmare out there.

 

[lovedogs]

This stone is a hot mess.

Your site gives it all green checks. Your site is unhelpful.




Here are the laughable "consult" options for people who are unlucky enough to be convinced by this nonsense.

 

[diamonds27]

You are sounding rather like schill? And on inspection - you are a very very naughty person!

That is unfortunate you feel that way.
Best of luck to you.

 

[HGar]

Sorry but I can’t take any “business” seriously when they have major spelling mistakes in plain view.

 

[Ibrakeforpossums]

The trouble is the worst inclusions are not visible with less than about 50X magnification.

Why is that? What are they?

 

[Garry H (Cut Nut)]

Why is that? What are they?

The inclusions that reduce transparency.
GIA and labs use jargon to conceal this by including them under inclusion types that are meaningless to 90% of diamond sellers and 99% of consumers.

 

[Garry H (Cut Nut)]

Rob C are you also Diamonds 27?
You have recommended the same firm every bar one post.
Boy do you guys have thick skins.
We have a guy we call Rhino here - @jonathon - you had better come here and lock your horn into this guy!!

 

[freddyboston]

A bunch of fools... Their AI actually filter's out Fluor / won't display them (advance to phase 2)

 

[Ibrakeforpossums]

Oh Lord.

 

[jjca]

Can't an admin just block these spammers? I'm so sick of reading their comments (repetitive and annoying). AI is just that "artificial" and it can't actually see what a human eye sees (a hot mess of a poorly cut diamond).

The people in the forum are too smart to fall for this - you're wasting your time. Please give up and hawk your snake oil elsewhere.

 

[Alistair Stillwell]

Great post, really interesting. Thank you

 

[glitterata]

Wow, the spammers and scammers are out in force this week. I feel bad for Ella.