Every Facet Matters, Tests Show

[mike04456]

Just came across this item on Rapaport:

(Rapaport…December 10, 2002) Gemological Institute of
America (GIA) research has found that a diamond’s star
and lower girdle facets “greatly impact” its appearance —
more than most diamantaires believe. Estimates of diamond
appearance should not rely only on pavilion and crown
angles, table size and depth, GIA researchers say.

The whole news bit is here:

http://www.diamonds.net/news/newsitem.asp?num=7382&type=all&topic=all

 

[Rhino]

I've been saying this for a couple of years now. I've had the opportunity to discuss these things with Dr. Eileen Reinitz who is head of GIA's research and our conclusions were the same. My new page (a work in progress) will be featuring, in laymens terms (and with graphics to demonstrate) how the minor facets (particularly the star/upper girdle ratio, upper girdle angles and lower girdle facet length impact the look of, fire and brilliancy of, conrast of, and scintillation of a diamond. The beginnings of that page is here.

http://www.goodoldgold.com/minor_facets.htm

I have many graphics I've taken that will demonstrate my points (which correlate with GIA's latest research) but we are in the midst of our busy season and probably will not finish this page till early next year. It is some new and exciting stuff.

Peace,
Rhino

 

[DiamondOptics]

Hi Lawgem,


Excellent little article!

It would be interesting to see were
these studies and observations will lead.


Kirk
www.diamondoptics.com

 

[Rhino]

Also, while I am an advocate of the HCA, one of it's main weakness' is it gives no consideration to the minor facets.

We wub Gary though and I applaud the efforts he has made.

Rhino

 

[mike04456]

----------------
It would be interesting to see were
these studies and observations will lead.
----------------


I think "interesting" understates it by several orders of magnitude. If and when GIA finally gets around to putting cut grades on its reports, it's probably going to upend much of the industry. I have a feeling that there are a lot of diamond manufacturers who have to change their shorts every time GIA issues one of these press releases, especially since it's becoming clear that they are not going to endorse the traditional ideal make.

 

[Rhino]

Hi lawgem,

I don't think that they're going to knock AGS Ideal proportions but what they are saying is that they believe, like what myself and other cut geeks like Rock, Gary, Serg, etc are saying. That the AGS Ideal range is too broad and also that there are what would seemingly be unorthodox #'s, produce some beautifully brilliant stones that fall out of the traditional "ideal" range. To the credit of AGS however some of the most beautifully cut diamonds do fall within that AGS "0" zone but I'll be the first to admit that there are plenty of combination within that "0" zone that are not as brillant.

The consideration of the minor facets is a definite step in the right direction though.

Rhino

 

[mike04456]

They have indeed said much along those lines, which to my ear comes pretty darned close to saying the AGS model is flawed. What's going to be "interesting" is what happens if we get two competing, inconsistent cut grade systems (GIA vs. AGS). I can't imagine that manufacturers are going to enjoy working in that environment.

 

[Rhino]

Just curious lawgem. What about the upcoming GIA cut grading system leads you to believe that it'll be inconsistent? From what I've been reading it seems that their system will be very consistent.

Rhino

 

[lawmax]

It seems to me that 8star has been saying this for many more than a couple of years. This is new information?

 

[Rhino]

Actually information from the new studies runs counter to 8*'s philosophy on the minor facets. One in particular is on the subject of the star facets and the fact that increasing their length increases fire. 8* on the other hand cuts short stars. GIA has recently even publicly rebuked 8* for stating in their literature that out of so many thousands of diamonds that theirs was the "model" of perfection. I myself used to proudly state so and have even written it on the forums as do other 8* distributors do from time to time. GIA has flat out rebuked this teaching and stated that there is no one model as there are many combinations that produce excellent brilliancy and different models that can increase fire. And yes that is "new" information based on the latest GIA research. When I discovered these things 2 years ago I was sharply criticized by people as not being able to get certain kind of ideal cuts when in fact that was false information and I had access to various types of ideal cuts. When I was able to compare the same types of consistency within 2 different super ideal cuts it was then I started to learn and see the differences to a greater degree.

Peace,
Rhino

 

[pricescope]

According to Serg & Co, not everything in GIA study is right.

Just keep in mind, if somebody including GIA published something it doesn't mean it is the last word in science.

 

[lawmax]

Your opinion aside Rhino, as I understand what I've read over the past 2 1/2 years, 8star has always been discussing the importance of all of the facets as they do not base their cutting on external measurements like everyone else, but on use of the Firescope TM which allows the cutters to adjust cutting to alignment of all of the facets. As far as the "rebuke" from GIA, I imagine it did not want to be seen as endorsing 8star, i.e., endorsing one particular company. What did the 1998 Fall issue of Gems and Gemology say about 8star and the diamond that most closely compared to GIA's virtual model?

 

[pricescope]

Don’t we sound smart?

"Hey, HCA is not 100% accurate because HCA does NOT analyze all the facets!"

"Look, even GIA teaches how important minor facets are!"

Let’s step back for a minute.

1. When we criticize a grading system we should compare it to existing ones. For symmetrical diamonds HCA is much more effective than AGS grading system because it has more merits while flaws remain the same.

2. None of the grading labs give any info on minor facets.

3. GIA still doesn’t give even crown and pavilion angles. Their symmetry grading doesn’t help much either.

4. AGS ideal graded stones are still cost more on the market despite the fact that everyone agrees AGS grading system is outdated.

5. Nobody gives any scientific advice about optimal proportions of those minor facets. Manufacturers of different brands claim their diamonds are the best. All those super ideal cuts are very nice but can anybody say which one is nicer? No, because it is subjective.

6. HCA was started 2 years ago and although it has the limitations it is still
a. more accurate than AGS grading system
b. easy and cheap way to weed out known poor performers

7. Minor facets vs. Relationship between Crown and Pavilion Angles. Which of these two AGS1 stones would you prefer?

 

[Garry H (Cut Nut)]

Someone point out on another thread an interesting view point about HCA on Rockdoc's page, and I agree with much of it

http://www.consumersgemlab.com/the_holloway_cut_adviser.htm

Consider the “40 mystery facets” and the GIA study. It may be in the GIA’s interest to politely discredit the AGS system which also does not consider these facets.

The actual words used in the GIA article RockDoc and Jonathon on thiss thread referred to are: “We also showed that star and lower girdle facet lengths could have a noticeable effect on WLR, our metric for brilliance”.

Much stronger words have been used and spoken by the President of the GIA and Ms Reinitz, which has been widely reported and led to a conclusion that is not supported by the study itself. (Which is why the words in the article are softer).

The range of WLR for the crown, pavilion and tables studied (with the mystery facets held constant) is from 0.245 to .315. The results for mystery facet variation in the ‘reference’ stone (near Tolkowsky) were only from 0.273 to 0.281. The reason why there is such a small variation in result is because the mystery facets are tied to the main facets. The range of angle variations is small in diamonds with good main facet proportions.

Now it is also true that cutters can cheat with the mystery facets, Jonathon bought such a stone that has AGS 0 grading and should never have been acceepted because of a decietful and deliberate abuse of AGS standards. We believe this problem will be cleared up.

It is also true that HCA can not know the symmetry of a diamond; this is a great concern. We recommend online consumers use the services of an appropriately trained and equipped appraiser, or pay a premium for diamonds of known optical symmetry like H&A’s and Ideal-Scope diamonds.

 

[mike04456]

----------------
Just curious lawgem. What about the upcoming GIA cut grading system leads you to believe that it'll be inconsistent?
----------------


I meant inconsistent with AGS, not internally inconsistent.

In reply to Leonid, no, GIA is hardly infallible, but their opinion, when it comes out, is going to carry a lot of weight in the trade. I happen to know that a lot of manufacturers are begging GIA for as much lead time as possible before issuing a cut grade so they have time to prepare stones that will get the top grade under the new system out of the gate.

 

[pricescope]

----------------
In reply to Leonid, no, GIA is hardly infallible, but their opinion, when it comes out, is going to carry a lot of weight in the trade. I happen to know that a lot of manufacturers are begging GIA for as much lead time as possible before issuing a cut grade so they have time to prepare stones that will get the top grade under the new system out of the gate.
----------------
Agreed.

However, if GIA will release another flawed system, it will lower its authority one step further.

People in the trade already report that GIA gradings today are not as strict as they use to be.

 

[mike04456]

----------------
However, if GIA will release another flawed system, it will lower its authority one step further.
----------------


Which is why, I suspect, it will be years before we see this hypothetical GIA cut grade system. I think they know they need to do it right or not at all.

 

[Rhino]

Excellent points Leonid. I agree 100%. Your points however should not dismiss current and even further research into the effects of the minor facets which do make up 40 out of the 57 facets.

Hi lawmax!

While I was an 8* distributor we were told and touted that out of 67,000 diamonds the 8* was the "one" that matched GIA's model of perfection or was the one that most closely resembled it. Here is the article word for word quoted directly from the National Jeweler Website ...

--------------------------------------------------------------------------

http://www.nationaljeweler.com/nationaljeweler/search/search_display.jsp?vnu_content_id=1467801

GIA Corrects Erroneous Statement

APRIL 01, 2002 - Carlsbad, Calif. -- The Gemological Institute of America (GIA) has issued a correction to an erroneous statement made in an EightStar Diamond Co. press release, dated Jan. 31, concerning commentary in the GIA quarterly journal, Gems & Gemology.

The EightStar press release stated that GIA, in two studies from 1998 and 2001, "looked at 67,000 diamonds in an attempt to find stones whose symmetry matched that of a perfect diamond it had created on a computer. Only one real-world diamond equaled GIA's cyber-diamond for perfection of shape and faceting: the EightStar diamond."

On Feb. 26, GIA responded with a statement of its own, saying "There was never an intent—stated or implied—in either of studies to 'attempt to find stones whose symmetry matched that of a perfect diamond ... created in a computer,' as stated in the EightStar press release. Furthermore, GIA has never said it was searching for a perfect diamond."

GIA did confirm that the EightStar diamond was used as part of its research, but only "to satisfy the need for a stone with high symmetry to illustrate the appearance of a diamond in fully diffused lighting, not to serve as a model of a 'perfect' diamond." This was further substantiated by the article acknowledgments in the Fall 1998 Gems & Gemology, which said that the EightStar diamond "approximated the symmetry of the (computer) model."

Moreover, GIA said that neither the 1998 study nor the 2001 study indicated that the EightStar diamond "equaled GIA's cyber-diamond for perfection of shape and faceting."

---------------------------------------------------------------------------

Now PLEASE ... I am NOT saying that 8*'s aren't a beautiful stone. I am not saying that nor am I trying to argue with you. Just pointing out what is and isn't meant from the GIA studies concerning what's been said on the boards vs what GIA truly means in their statements. It's important not to read things into the commentary that aren't there to begin with.

Peace,
Rhino

 

[Rhino]

Here is the press release on some of the more recent studies.

24Hour Diamond News.com

http://www.24news.org/new_page_17.htm

GIA Research Conducts Largest-Ever Series of Observation Tests on Diamond Appearance


Carlsbad, Calif. – December 11, 2002 – Using a groundbreaking approach to the evaluation of diamond appearance, research scientists at the Gemological Institute of America (GIA) have studied how human observers describe and judge diamonds of various proportions under a variety of conditions. Diamond dealers, retailers, consumers, and trained observers have all taken part in this ongoing series of observation tests of diamond appearance.

Over the past eighteen months, GIA has collected nearly 40,000 observations of more than 1,000 diamonds in a variety of controlled environments as well as in typical trade settings. No cut-evaluation methodology currently used in the trade has been empirically tested in this manner.

“We work on the premise that computer modeling must always be validated by real-world observations,” said Thomas C. Yonelunas, CEO of the GIA Gem Trade Laboratory. “We are pleased to confirm that the observations gathered in this phase of our study strongly support computer-modeled results for brilliance and fire.”

Initial observation tests allowed researchers to further define relevant environmental and observational parameters, leading to refined metrics for brilliance (brightness) and fire. These new calculated predictions of brilliance and fire were then verified by “real world” brilliance and fire differences seen in diamonds. Recently, GIA conducted observation tests to determine how the two appearance aspects of brilliance and fire contribute to overall appearance. Among those who participated in the tests were diamond dealers in both New York and Antwerp. They observed the test diamonds both in their own offices, where they make similar judgments every day, and in controlled viewing environments at GIA offices.

Trade members were given the opportunity to learn the diamonds’ proportions after their observation tests were completed. Some participants indicated their surprise at the performance of a number of diamonds specially cut to proportions considered outside standard cutting parameters. This further supported GIA’s contention that “every facet matters.” GIA has found that variations in the lengths of star and lower-girdle facets greatly impact the visual appearance of a diamond. Thus, estimates of appearance cannot rely only on pavilion angle, crown angle, table size, and total depth.

Retailers and consumers were also tested in various controlled and natural environments at other times throughout this phase of the research. In addition, thousands of observation tests have been conducted at GIA in controlled environments using experienced laboratory observers.

Research scientists at GIA are currently examining other possible appearance aspects, such as scintillation, to understand how they also might interact with brilliance and fire to determine overall appearance.

The goal of GIA’s long-term research project is to provide a scientific basis for evaluating cut in diamonds. Not only will this help members of the trade reach a consensus on a cut system, but ultimately it will also provide consumers with a higher level of confidence and comfort in their diamond purchases.

GIA plans to incorporate the findings from these observation tests into expanded cut quality information on GIA Diamond Grading Reports.

For more on GIA’s cut research project, visit the GIA Web site at www.gia.edu.

---------------------------------------------------------------------------

Peace,
Rhino

 

[Rhino]

I would also add that 8* is to be applauded for it's work in the minor facets. Richard and I have alot in common and are what I would consider *extremeists* in what we do. He is an artist and I for one really do love and appreciate the contributions he has made to this field. His product is not done by chance while there are many that are. He knows exactly what the product is to be and what comes off that wheel is it or it goes back.

Many times while burning the midnight oil, putting in those extra hours, his was one of the only other names I'd see on my buddy list burning the oil with me. We've shared many great times and I've often woke up the rest of my family laughing so hard at his jokes. He really has a great sense of humor when you get him going.

hehe

Peace,
Rhino

 

[Rhino]

Lawgem,

What you say is VERY TRUE. Whether GIA is right or wrong, what they say carries much weight, waaay more than what anyone here says that's for sure.

Peace,
Rhino

 

[Garry H (Cut Nut)]

GIA can have it both ways, because they are special - if they claim this:
“We are pleased to confirm that the observations gathered in this phase of our study strongly support computer-modeled results for brilliance and fire.”

The results of their copmuter study (noted above) show a small variation from minor facets,

That measn this or the other statement is wrong:

"This further supported GIA’s contention that “every facet matters.” GIA has found that variations in the lengths of star and lower-girdle facets greatly impact the visual appearance of a diamond. Thus, estimates of appearance cannot rely only on pavilion angle, crown angle, table size, and total depth."

Is this politics gone mad?

 

[Rhino]

Actually Gary ... it can also mean that what may seemingly be minor changes to some can mean more major impacts on the appearance and look of the diamond. When we talk angles and percentages in diamonds you know as well as I do that 1 or 2 degrees, while seemingly minor, can impact the look of the diamond if it goes 1 or 2 degrees in the wrong direction. Minor changes can sometimes mean major results optically. I believe that's the point being made. From what I understand about what I am reading concerning GIA's research it is more in line with the fundamental aspects of the HCA (ie. there are many sets of proportions that produce excellent brilliancy) except GIA is taking it to the next level and taking into account the minor facets. I sincerely believe they're heading in the right direction. There isn't any evidence that I've seen which proves otherwise especially when you have guys like Al Gilbertson, etc. who are participating and contributing in this research.

Peace,
Rhino

 

[Garry H (Cut Nut)]

C'mon Rhino!
You can do better than that

You boot lick'in?

 

[lawmax]

----------------
On 12/12/2002 8:11:15 PM

Excellent points Leonid. I agree 100%. Your points however should not dismiss current and even further research into the effects of the minor facets which do make up 40 out of the 57 facets.

Hi lawmax!

While I was an 8* distributor we were told and touted that out of 67,000 diamonds the 8* was the "one" that matched GIA's model of perfection or was the one that most closely resembled it. Here is the article word for word quoted directly from the National Jeweler Website ...

--------------------------------------------------------------------------

http://www.nationaljeweler.com/nationaljeweler/search/search_display.jsp?vnu_content_id=1467801

GIA Corrects Erroneous Statement

APRIL 01, 2002 - Carlsbad, Calif. -- The Gemological Institute of America (GIA) has issued a correction to an erroneous statement made in an EightStar Diamond Co. press release, dated Jan. 31, concerning commentary in the GIA quarterly journal, Gems & Gemology.

The EightStar press release stated that GIA, in two studies from 1998 and 2001, "looked at 67,000 diamonds in an attempt to find stones whose symmetry matched that of a perfect diamond it had created on a computer. Only one real-world diamond equaled GIA's cyber-diamond for perfection of shape and faceting: the EightStar diamond."

On Feb. 26, GIA responded with a statement of its own, saying "There was never an intent—stated or implied—in either of studies to 'attempt to find stones whose symmetry matched that of a perfect diamond ... created in a computer,' as stated in the EightStar press release. Furthermore, GIA has never said it was searching for a perfect diamond."

GIA did confirm that the EightStar diamond was used as part of its research, but only "to satisfy the need for a stone with high symmetry to illustrate the appearance of a diamond in fully diffused lighting, not to serve as a model of a 'perfect' diamond." This was further substantiated by the article acknowledgments in the Fall 1998 Gems & Gemology, which said that the EightStar diamond "approximated the symmetry of the (computer) model."

Moreover, GIA said that neither the 1998 study nor the 2001 study indicated that the EightStar diamond "equaled GIA's cyber-diamond for perfection of shape and faceting."

---------------------------------------------------------------------------

Now PLEASE ... I am NOT saying that 8*'s aren't a beautiful stone. I am not saying that nor am I trying to argue with you. Just pointing out what is and isn't meant from the GIA studies concerning what's been said on the boards vs what GIA truly means in their statements. It's important not to read things into the commentary that aren't there to begin with.

Peace,
Rhino
----------------


The former employee who wrote the press release may have erred in his writing by being overly exuberant, but the 8star commentary was based on whatever it says in the 1998 Fall issue of Gems and Gemology.

 

[lawmax]

----------------
On 12/13/2002 5:54:37 AM

C'mon Rhino!
You can do better than that

You boot lick'in?
----------------


ROFL!

 

[Rhino]

And what is that commentary that GIA wrote about the 8* in their article that you are referring to? Please enlighten me.

Rhino

 

[lawmax]

----------------
On 12/13/2002 9:38:27 PM

And what is that commentary that GIA wrote about the 8* in their article that you are referring to? Please enlighten me.

Rhino
----------------


Enlighten you? You will have to seek enlightenment on your own. I don't have that kind of power.

 

[Garry H (Cut Nut)]

This is a 4 year old thread

Now that GIA has released its system, and we can use the their www.facetware.gia.edu software to check the validity of these minor facet claims it seems that what I said back then is valid - minor facets have a minor impact.

Using the default stone on their web page these are the ranges of minors that get Excellent:

Lower Girdles: 70, 75, 80 and 85%
Upper gridles / Stars: 40, 45, 50, 55, 60 and 65%

Since this covers the range of more than 90% of all diamonds on the market, the chance that a minor facet would result in a GIA downgrade is even more minor than I expected.

Thank you Rocdoc for bringing this old thread to light again.

 

[strmrdr]

Garry,

How can I put this nicely...
When you disagree with gia its a garbage system but they agree with you in one area and now your right because the same system says so?
Which is it,,,, a flawed system or the greatest thing since sliced bread?