How significant are the star facets and lower girdles info?

[Midnight]

The new GIA Certs coming in 2006 will emphasize them...not sure if the info will be provided on the Certs though.
The new AGS Performance Based Certs don''t provide this info on their Certs.
GOG, NiceIce, Infinity all provide both the star facet and lower girdle info in their Sarin 3-D models.
Superbcert has OGI scan with star facet info but no lower girdle info.
Whitflash added star facet info just recently to their Sarin report but no Lower Girdle Info.

Some have argued that differences in the minor facet patterning will give a top notch diamond a different appearance as compared to another one. Thus, should this info should be provided to consumers especially by Internet Vendors if they do have Sarin/OGI Scans?

 

[strmrdr]

"Some have argued that differences in the minor facet patterning will give a top notch diamond a different appearance as compared to another one. Thus, should this info should be provided to consumers especially by Internet Vendors if they do have Sarin/OGI Scans?"

Currect and yes it would be nice if they all gave the information.
If you have an idealscope image you can get an idea of the range the LGF is in by the thickness of the arrows.
With diamcalc you can get more info but thats $280 or ask someone that has it.
It would be better if the vendors all provided a full 3d scan.

 

[JohnQuixote]

Date: 8/3/2005 11:49:57 PM
Author:Midnight
The new GIA Certs coming in 2006 will emphasize them...not sure if the info will be provided on the Certs though.
The new AGS Performance Based Certs don't provide this info on their Certs.
GOG, NiceIce, Infinity all provide both the star facet and lower girdle info in their Sarin 3-D models.
Superbcert has OGI scan with star facet info but no lower girdle info.
Whitflash added star facet info just recently to their Sarin report but no Lower Girdle Info.

Some have argued that differences in the minor facet patterning will give a top notch diamond a different appearance as compared to another one. Thus, should this info should be provided to consumers especially by Internet Vendors if they do have Sarin/OGI Scans?

Midnight,

GIAs inclusion of the lower girdles and stars is simplistic at best, since they are rounding.

I'm sure we all realize that minor facets are not new. Reputable cutters and sellers have always given them due attention. They influence the character of a diamond - particularly if the diamond has good patterning. Brian Gavin was calling for recognition of the role of lower girdle lengths long ago (back in pre-Pricescope days). He has always maintained that pavilion patterning with no yaw, and the relationships of the lgfs to the mains is key to light performance. What's taken everyone so long to get that?

Of course, it's appropriate to mention that there are a number of other unreported factors that impact diamond appearance and still don't show up on 3D scans. However, all of them can be assessed with a Hearts & Arrows viewer, an ideal-scope/ASET and experienced eyes. That is part of what you should be paying for when you choose a vendor carrying high quality goods - a level of expertise, experience and authority beyond raw data. These things were all important long before they became numbers included in a simulation. It's nice that they are being included now (even if rounded) because public awareness will improve and that makes my job easier.

As Strm said, you can tell much about lower girdles through an ideal-scope image.

Remember that GIA is rounding to the nearest 5%, so any round brilliant with LGF between 73%-87% will be measured as if it were one of these. Easy, no? Fear not... Rest assured top cutters, sellers and appraisers will be paying more attention to the dynamics of these than narrowing to a mere 5%.

[PS: Midnight - thanks for noticing we're including star info. We did it for peeps like you.

]

 

[Midnight]

Date: 8/4/2005 12:31:52 AM
Author: JohnQuixote

Date: 8/3/2005 11:49:57 PM
Author:Midnight
The new GIA Certs coming in 2006 will emphasize them...not sure if the info will be provided on the Certs though.
The new AGS Performance Based Certs don''t provide this info on their Certs.
GOG, NiceIce, Infinity all provide both the star facet and lower girdle info in their Sarin 3-D models.
Superbcert has OGI scan with star facet info but no lower girdle info.
Whitflash added star facet info just recently to their Sarin report but no Lower Girdle Info.

Some have argued that differences in the minor facet patterning will give a top notch diamond a different appearance as compared to another one. Thus, should this info should be provided to consumers especially by Internet Vendors if they do have Sarin/OGI Scans?

Midnight,

GIAs inclusion of the lower girdles and stars is simplistic at best, since they are rounding.

I''m sure we all realize that minor facets are not new. Reputable cutters and sellers have always given them due attention. They influence the character of a diamond - particularly if the diamond has good patterning. Brian Gavin was calling for recognition of the role of lower girdle lengths long ago (back in pre-Pricescope days). He has always maintained that pavilion patterning with no yaw, and the relationships of the lgfs to the mains is key to light performance. What''s taken everyone so long to get that?

Of course, it''s appropriate to mention that there are a number of other unreported factors that impact diamond appearance and still don''t show up on 3D scans. However, all of them can be assessed with a Hearts & Arrows viewer, an ideal-scope/ASET and experienced eyes. That is part of what you should be paying for when you choose a vendor carrying high quality goods - a level of expertise, experience and authority beyond raw data. These things were all important long before they became numbers included in a simulation. It''s nice that they are being included now (even if rounded) because public awareness will improve and that makes my job easier.

As Strm said, you can tell much about lower girdles through an ideal-scope image.

Remember that GIA is rounding to the nearest 5%, so any round brilliant with LGF between 73%-87% will be measured as if it were one of these. Easy, no? Fear not... Rest assured top cutters, sellers and appraisers will be paying more attention to the dynamics of these than narrowing to a mere 5%.

[PS: Midnight - thanks for noticing we''re including star info. We did it for peeps like you.

]

John,

I guess I will continue to peep until WF add the LGF info to their Sarins.

Do you anticipate WF will provide this info in the near future? I am not an expert on the Sarin/OGI scans but does every single scan that is processed automatically provides the LGF on the report? One Pricescope vendor mentioned that their OGI scan can''t provide the LGF and that only the Sarin can. Thus, they had to "manually" hand measured it when it was requested. I had the impression that the OGI had this capability.

 

[Regular Guy]

Date: 8/4/2005 12:31:52 AM
Author: JohnQuixote

Some have argued that differences in the minor facet patterning will give a top notch diamond a different appearance as compared to another one. Thus, should this info should be provided to consumers especially by Internet Vendors if they do have Sarin/OGI Scans?

..... However, all of them can be assessed with a Hearts & Arrows viewer, an ideal-scope/ASET and experienced eyes.

....can''t help wanting to understand this discussion. I have an easy time when experts on this forum agree with each other...but heartburn when there is dissonance on the fundamentals.

John, regrets if I''ve misread him, but I understand Jonathan to report that viewers such as the idealscope, and presumably ASET won''t necessarily pick up the kinds of distinctions we are talking about here. In such a case, I was lead to believe that info concerning minor facets could help to tease out those distinctions. This being the case, if GIA''s effort to document these distinctions would fail, then indeed perhaps 3 D Sarin would be necessary. And thank goodness for your expert eyes to see not only these documentable things, but more as well.

From the point of view of picking a nice diamond, such niceties are subtle and may not matter a great deal, and again, for the jeweler, wanting only to have excellent diamonds...probably all will fly under the radar to suit. But, for the e-ring buyer, who will plan to buy...um...just one of these, the desire to optimize is undeniable.

Have I mis-read your colleague, do you have a disagreement on this (issue of the viewers overall ability, or lack thereof, to pick up the distinctions that minor facets might point to), or is the issue simpler than I think.

Regards,

 

[WinkHPD]

I feel some interesting comments coming on. Hey, all you vendors, rush out and buy the 25k version of this fancy machine to give me numbers to plug into software designed to make 80% of all the diamonds on the market read as excellent.

Or go get an idealscope or an ASET and look at the diamond to see what you shall see.

Methinks the more educated around here such as John Quixote might have something to say about this. Standing by for an experts opinion...

Wink

 

[JohnQuixote]

Date: 8/4/2005 1:30:23 PM
Author: Regular Guy

....can't help wanting to understand this discussion. I have an easy time when experts on this forum agree with each other...but heartburn when there is dissonance on the fundamentals.

John, regrets if I've misread him, but I understand Jonathan to report that viewers such as the idealscope, and presumably ASET won't necessarily pick up the kinds of distinctions we are talking about here. In such a case, I was lead to believe that info concerning minor facets could help to tease out those distinctions. This being the case, if GIA's effort to document these distinctions would fail, then indeed perhaps 3 D Sarin would be necessary. And thank goodness for your expert eyes to see not only these documentable things, but more as well.

From the point of view of picking a nice diamond, such niceties are subtle and may not matter a great deal, and again, for the jeweler, wanting only to have excellent diamonds...probably all will fly under the radar to suit. But, for the e-ring buyer, who will plan to buy...um...just one of these, the desire to optimize is undeniable.

Have I mis-read your colleague, do you have a disagreement on this (issue of the viewers overall ability, or lack thereof, to pick up the distinctions that minor facets might point to), or is the issue simpler than I think.

Regards,

Ira,

Inaccurate data won’t tease out anything. I’d be surprised if anyone was telling you that 3D scans reveal more than actual imagery. Hardware calibration and built-in measurement errors skew data. There are elements to a diamond such as facet yaw that are not picked up by Sarin/Ogi. Software calculation error is also possible.

However you slice it a software simulation is only a prediction.

Natural viewers show things distinctly and you are observing the real end result, not a prediction.

Actual assessment remains the obvious, elegant answer. It’s the same thing that guided Cardinal Mazarin, Henry Morse and Tolkowsky. Tools have evolved now. We have better scopes and new reflectors. We’re even working towards mechanical assessment (Imagem, Brilliancescope & ISee), but I still trust a master with a loupe over a computer simulation any day of the week and twice on the Sabbath.

Ideal-scope/ASET and H&A Viewers have no error. They are easily standardized for those wishing to do so. I’d also say it’s more realistic to expect an ideal-scope or ASET image than to expect every dealer in the country to run out and buy a Sarin/Ogi.

I hope that clarifies, Ira.

 

[JohnQuixote]

Date: 8/4/2005 12:52:01 PM
Author: Midnight

John,

I guess I will continue to peep until WF add the LGF info to their Sarins.

Do you anticipate WF will provide this info in the near future? I am not an expert on the Sarin/OGI scans but does every single scan that is processed automatically provides the LGF on the report? One Pricescope vendor mentioned that their OGI scan can't provide the LGF and that only the Sarin can. Thus, they had to 'manually' hand measured it when it was requested. I had the impression that the OGI had this capability.

(Hey Midnight, I hope you know ‘peeps’ meant ‘people’, not chickens!)

Short answer

As GIAs cut estimator becomes popular Whiteflash may decide to add the LGF average on our pages. Meanwhile we will continue to safeguard the consumer - just as we always have with this and many other issues of expertise. Let’s not limit our discussion to minor facets: It can be about expert analysis of durability relative to inclusions/cleavage planes, girdle treatments, patterning assessment, yaw assessment and other professional assessment a customer is hopefully paying for when he/she buys from a trusted authority.

Longer answer

(A) This information has always been important.
(B) We have always safeguarded these things for consumers.
(C) Now consumers are aware of minor facets, but because measuring devices aren’t accurate they stand to get bad information.

Since you asked about Whiteflash and minor facets: Brian Gavin’s minor facet philosophy has been available for a long time. Specific relationships between lower girdle facets and pavilion mains have been fundamental to the PATTERNING soapbox we have been shouting from since the 90s.

The labs spent 100 million dollars to figure out that minors are crucial (GIA) and that actual observation of light dynamics (AGS ASET) is critical to assessment. Meanwhile, cutters like Brian have known this for years. “It’s all in the hearts”… (we have to stop him from wearing sandwich boards and ringing a bell about this).

What happens in the pavilion is of primary importance. The way that lower girdles relate to mains is a key to acquiring the best Visual Balance™. Minor facet relations were the foundation of Brian’s presentation at the International Diamond Cut Conference in Moscow more than a year ago. The absence of yaw drives optimization of light return. Yaw, something still not widely understood, can have more influence on appearance than minor facet configurations... So where is the GIA input estimator for yaw??

“It’s all in the hearts.” Repeat after me. “It’s all in the hearts.”

I showed you the only three lower girdle constants GIA will be using (above), visible via ideal-scope. I’ll post some examples of how you can determine lower girdle dynamics via hearts patterning to a much more discriminating level below.

Simply put, for our part anyway, we have a set of standards to safeguard people who buy our goods – and all of our diamonds fall within these standards. Even Expert Selection goods are cut for these standards and perform similar to ACA because of it. They may not meet our strict patterning specs of ACA, but that is why there is a difference in price.

Other vendors look out for customer interests as well - via analysis, pedigreed goods, experience and know-how, etc. Obviously not all have the same methods, but I suggest that anyone ask a seller or an appraiser what things they do to ensure that their customers are served with a level of professional expertise. The best will proudly tell you.

Whether the info is on a description page or not, cutters, sellers and appraisers with expertise and integrity will always look out for their clientele’s best interests.

 

[strmrdr]

In the end its the consumers who will decide.
Those who want the full srn file will shop with those that provide it.
Those that want all the information up front including real h&a photos will buy from a vendor that provides it.
Those that dont can look to the other vendors.

 

[JohnQuixote]

Date: 8/4/2005 7:53:44 PM
Author: Wink
I feel some interesting comments coming on. Hey, all you vendors, rush out and buy the 25k version of this fancy machine to give me numbers to plug into software designed to make 80% of all the diamonds on the market read as excellent.

Or go get an idealscope or an ASET and look at the diamond to see what you shall see.

Methinks the more educated around here such as John Quixote might have something to say about this. Standing by for an experts opinion...

Wink

Wink,

Consumers will decide what level of info they desire individually. ASET and a H&A viewer can be bought for about $200, or they can just consider that a part of the cost when they trust a vendor like you to perform the analysis.

Wink and others have been safeguarding consumers for years – even those who didn’t know major proportions (not to mention minors…rounded!).

And…For the consumers who like to read PS, acquire knowledge and give advice, I suggest you go buy an ASET and a H&A viewer and sit and sift through a few hundred diamonds, noting how useful these tools are, before you go buy that $20,000 Sarin DiaMension to give you less accurate data.

 

[JohnQuixote]

Date: 8/4/2005 9:37:30 PM
Author: strmrdr
In the end its the consumers who will decide.
Those who want the full srn file will shop with those that provide it.
Those that want all the information up front including real h&a photos will buy from a vendor that provides it.
Those that dont can look to the other vendors.

Strm - true - but it would be a shame for consumers to operate on the assumption that a srn scan and computer simulation based from such a scan provides more meaningful data than actual imagery does.

I like to play with the sims too, but they don't tell as much about a particular diamond as the actual diamond does.

 

[Regular Guy]

Me....I'll be sucking on helium and talking with a high voice.

Actually, where were you when I needed you!

I have no regrets. As the linked post concludes on a, b & c...

a) knowing the elements of beauty, and how important they are in relation to each other is a more than reasonable objective.
b) determining if your jeweler can help you understand this as well may be important
c) ditto for your appraiser.

If these are not items for discussion for Pricescope, what is?

If Jonathan has any input, it's welcome.

Your interest and indulgence are both appreciated and welcome.

with apologies for any extent to which I'm causing trouble. And I didn't even start this thread!

Regards, and p.s. with an upcoming DC gem event, I hope to try out your suggestions, John...will advise.

 

[strmrdr]

Date: 8/4/2005 9:48:20 PM
Author: JohnQuixote

Date: 8/4/2005 9:37:30 PM

Author: strmrdr

In the end its the consumers who will decide.

Those who want the full srn file will shop with those that provide it.

Those that want all the information up front including real h&a photos will buy from a vendor that provides it.

Those that dont can look to the other vendors.

Strm - true - but it would be a shame for consumers to operate on the assumption that a srn scan and computer simulation based from such a scan provides more meaningful data than actual imagery does.


I like to play with the sims too, but they don''t tell as much about a particular diamond as the actual diamond does.

You know what my answer is so I dont know why im writing it here :}

Its another piece of the puzzle like every other test if you rely totally on it and only on it thats a mistake but like a lot of other tests it can tell you things about the diamond.

The more info you have the better.
Lets take hearts.
As you know there are too ways to get good hearts.
Tight physical symmetry with proper angles.
Less tight physical symmetry with complementary angles.
Tell me how to tell that without a sarin?
Tell me it dont make a difference?
Having both sets of data is good and the more data one gets the better.

Also it makes it a lot harder for someone to use images that arent of that diamond.
Its a nice checks and balances situation to have both.

Now if you want to talk about the GIA cut grading issue.
Then I think we can pretty much agree its a joke.

 

[JohnQuixote]

Here is some info for those interested in a tutorial on assessment of minor facets from actual imagery.

Of course, with these examples we are talking about a high quality level of patterning. We have always cut this type of diamond because it’s our personal taste. If you don’t like orderly symmetry that’s fine, but we are into it. We believe patterning optimizes light return thanks to focused alignment of the mirrors in the pavilion ("it''s all in the hearts"). We also believe that specific minor facet relationships, along with symmetrical patterning, result in the best Visual Balance.





First, I’m revisiting the graphic from above to show GIA''s rough treatment of these details. Remember that as far as the GIA metric is concerned, ANY diamond that has lower girdles between 73% and 87% will be assessed as if it were one of these (?!).

Getting within 5%, then running a simulation? Accuracy pundits should be crying foul.

 

[JohnQuixote]

So in the GIA metric, anything between 75% and 82% will be judged as if it were 80%...

Um. Why can''t 78% be 78% and 82% be 82%? They are completely different looks. The character of a well-patterned diamond alters significantly between these numbers.

Let’s look at 78%, 80% and 82% lower girdles as they would appear. First the crown view. You can see that the differences here are, logically, less obvious than the 75-80-85 above.

 

[JohnQuixote]

Now the pavilion view. This is the view where Brian does his assessment of quality: It’s “all in the hearts.”

You can see where even the differences between 78%, 80% and 82% LGF are distinct:

78% - Robust hearts with slight separation from arrowheads above (pointing to the culet).
80% - Narrower hearts with notable separation from arrowheads. Slight splits appear at the Vs.
82% - Narrow hearts with significant separation from arrowheads. Notable splits at the Vs.

Can you tell the difference? I sure can... And the view through a H&A viewer is an actual image, not a simulation based on a 3D scan that has given inaccuracies or a cut estimation made with data rounded to 5%. Fie!

This is the method Kazumi Okuda and his contemporaries used to enable true patterning, and it's the method Brian used to design (and is still using to assess) ACA.

 

[JohnQuixote]

For fun, here is a dimmed pavilion view with crown facets wireframed in (stars at 50%).

 

[JohnQuixote]

Date: 8/4/2005 9:54:23 PM
Author: Regular Guy
Me....I''ll be sucking on helium and talking with a high voice.

Actually, where were you when I needed you!

I have no regrets. As the linked post concludes on a, b & c...

a) knowing the elements of beauty, and how important they are in relation to each other is a more than reasonable objective.
b) determining if your jeweler can help you understand this as well may be important
c) ditto for your appraiser.

If these are not items for discussion for Pricescope, what is?

If Jonathan has any input, it''s welcome.

Your interest and indulgence are both appreciated and welcome.

with apologies for any extent to which I''m causing trouble. And I didn''t even start this thread!

Regards, and p.s. with an upcoming DC gem event, I hope to try out your suggestions, John...will advise.

Ira - Hehe... Years down the road we might have accurate automation, but right now I still trust the jedi masters over the ''droids.

Sorry I wasn''t in your corner in yon thread (must''ve been grilling).
You know I am but a PM away, friend.

Do you have an IS, ASET and H&A viewer to take to DC?

 

[Rhino]

Interesting thread. I have a bit to add but I''m gettin ready to hit the sack so it''ll have to wait till tomorrow.

There are 3, no 4 tools that show the results of absence or presence of facet yaw and only one that measures it.

1. LightScope shows results of presence or absence of facet yaw. This can not be determined in other red reflectors or H&A viewers that I know of. If it can I''d love to see how.
2. BrillianceScope accurately shows the results of precision cut diamonds that have presence or absence of facet yaw. As John pointed out, no yaw = light transmitted at higher intensity. The BrillianceScope is sensitive to this phenomena and rewards or discounts accordingly.
3. An *accurate* Sarin 3d model imported into DiamCalc whose results can be observed via...
4. Gem Advisor.
5. Helium is the only scanner that can measure this phenomena and provide the "numbers" confirming all of the above.

I''m working on a web page that demonstrates how these tools do it and show it graphically but I am waiting for one last piece of lab equipment before I finish the entire article.

When I post tomorrow I''ll provide some examples as time allows, if it allows.

Peace,

 

[Rhino]

Hi Midnight,

Actually the OGI does report lower girdle info. It really depends on how old or new the software is that the vendor is running. We have both scanners here. One key factor to bear in mind is that the OGI measures lower girdle height (measured on the vertical plane) while Sarin measure lower girdle length (along the horizontal plane). Helium gives both measurements. DiamCalc and AGS will be using lower girdle height (when they discuss this metric) while Sarin & GIA use lower girdle length. Neither is right or wrong, just different ways for getting similar information. On another thread I posted a conversion chart for those using DiamCalc who are looking at Sarins and wanted the conversion numbers.

 

[WinkHPD]

I had an interesting conversation with Senor Quixote one time and he made a comment that sticks with me.

I had commented that I was not satisfied with any of the current affordable measuring devices. ( I do not consider 20-25k affordable for the average jeweler) I had also commented that the ASET made mincemeat of a lot of the data as you could now instantly see what you needed to see, leakage, return and even from where the return came from in a manner that would mean a lot more than 75%, 78%, 83.9768765321% or whatever would ever mean to the average consumer or jeweler.

His comment:

"Wink, 3d imaging is nice, but when you have the real diamond to look at, it is sort of like having a world class sprinter in a room with you and then inputing his measurements into a computer and watching his computerized image run when you could have just asked him to run for you."

Given the FACT that the 3d imaging available today will not give us all the measurements including yaw and gee and twist and shout accurately that a simple idealscope or ASET picture will give us the visual results of instantly and repeatably, is it any wonder that so many of us prefer to use the $1000 table sized ASET viewer than the $25,000 mostly accurate sometimes when it feels like it provided your stone is perfectly clean and centered Sarin or OGI machine?

Wink

 

[JohnQuixote]

Date: 8/4/2005 11:40:01 PM
Author: Rhino
Interesting thread. I have a bit to add but I'm gettin ready to hit the sack so it'll have to wait till tomorrow.

There are 3, no 4 tools that show the results of absence or presence of facet yaw and only one that measures it.

1. LightScope shows results of presence or absence of facet yaw. This can not be determined in other red reflectors or H&A viewers that I know of. If it can I'd love to see how.
2. BrillianceScope accurately shows the results of precision cut diamonds that have presence or absence of facet yaw. As John pointed out, no yaw = light transmitted at higher intensity. The BrillianceScope is sensitive to this phenomena and rewards or discounts accordingly.
3. An *accurate* Sarin 3d model imported into DiamCalc whose results can be observed via...
4. Gem Advisor.
5. Helium is the only scanner that can measure this phenomena and provide the 'numbers' confirming all of the above.

I'm working on a web page that demonstrates how these tools do it and show it graphically but I am waiting for one last piece of lab equipment before I finish the entire article.

When I post tomorrow I'll provide some examples as time allows, if it allows.

Peace,

It's exciting that these recent threads have begun, since Brian introduced this information years ago and has been patiently waiting.

Rhino, you know I have great respect for your expertise, but I need to correct some of your comments regarding facet yaw.

Lightscope and H&A Viewers

I suspect only the crown of the diamond is surrounded by reflecting material in your lightscope, correct? If this is so, a 3D view of distortions and angles of incidence is not possible in the pavilion. Even if it's not so, the pavilion view is the only view that fully discloses yaw. Do you have examples of what you are taking about?

I imagine it's possible to assess reduction of optimization (less robust and even light return) and some stray reflections DUE to yaw in lightscope. This is also possible with ASET and Ideal-scope.

The full extent of yaw can only be assessed in a H&A viewer. The hearts view of a diamond fully ensconced in the reflecting element shows distortions, angles of incidence and stray reflections, since it is an all-inclusive 3D view. I'll attach images below.

Brilliancescope

Brilliancescope shows robustness of light return in its metric. ASET and Ideal-scope/lightscope also do this. BS does have photos and you can see symptoms of yaw in those, but you cannot actually see the extent of yaw, the distortions or the angles of incidence.

Jon, you may be interested to know that yaw can be responsible for some of your 'hot spots' on BS, so it's rewarding an undesirable diamond quality.

While on that topic, diamonds with LGF > 80% are also rewarded by BS, even though they are not as visually balanced through a range of lighting as those with LGF just under or at 80%

Sarin/Ogi

This is not correct. Sarin and Ogi do not detect yaw. Sarin measures angles. OGI, because of patents, establishes points and then deducts angles. In both cases the machines work from point to point seeing flat facets in 2D shadow of the diamond. If the rotation of the machine table doesn't match the azimuth of the facet (as it does not with yaw - see diagram below) the slope indications are incorrect.

Edited to add: Extreme yaw shows itself as azimuth shift and is measured by Sarin/Ogi and represented in a 3D model. Jon, maybe that is what you're seeing?

Helium

Brian was one of the only Americans at the IDCC in Moscow, and had the privilege of an introduction to Helium's fundamentals. Very impressive! Garry has also described the system to me and it uses different axes than Sarin/Ogi. We are hopeful it measures yaw and waiting for evidence. Jon, any info you can add would be welcome.


Also, Jon, before you complete your web page about this you may want to consult with Brian, who is the identifier of yaw. We have dedicated considerable research along with Bruce Harding who, self-admittedly, had his CAD skills pushed to the max on this project. Peer review is always a good thing, friend.

Lest any think I am Rhino-hunting, I'm not (and besides, he has thick skin)

I want to be clear that I think highly of Jonathan and his enthusiasm for all aspects of dia-knowledge.

 

[JohnQuixote]

For anyone we haven’t yet lost… (I’ll do a tap-dance if AGBF is still reading)

Here is a diagram explaining the yaw phenomenon. It happens either by sloppy cutting, or when a cutter cannot polish a facet in the conventional manner (girdle to culet or culet to girdle) and must adjust the ‘cheater’ screw to take that facet from ‘east to west.’ Brian Gavin identified facet yaw years ago. In the last year Brian, Paul Slegers, Bruce Harding, Garry and I have had many exchanges about its cause and effect. Bruce is a master of AutoCAD and has designed gem software. I diagramed yaw for Brian in a rudimentary way and Bruce made art out of my scribblings. In addition to being a foremost diamond authority, Bruce is also a prince of a guy - one of the truly wonderful people in this trade.

 

[JohnQuixote]

That diagram is just one choice for yaw. There are many combinations. In the above illustration the height of the meets are 50%. Tips of scallops at usual azimuths. The main is yawed 4.82 degrees, and the half on the right is only 6.21 degrees from its correct main index, so the azimuth angle between them is only 1.39 degrees. You can see this in the similar direction of the shading lines, parallel to the girdle plane. The two reflections would be almost simultaneous in the diamond. If you rotate both halves counterclockwise, the far left one would have gotten wider and far right narrower unless you shifted its azimuth too and that would look more distored.

 

[JohnQuixote]

This was one of my rudimentary drawings when I was first trying to grasp the EFFECT of yaw - not the cause or the 3-dimensional realities, which Bruce rendered.

This is very simplistic as I was only working in 2D, but the concept of how reflections can occur at different angles of incidence than intended is plain here.

 

[JohnQuixote]

Here is a diamond with some yaw and lower girdle facets >80%

The pavilion (hearts) view displays moderate yaw in almost every pattern and lower girdle facets well over 80%.
The arrows (crown) view displays some of the effects of yaw in the same diamond (under the table), but as you can see the hearts view is significantly more telling about the cut.

(Jon - this is why I''m curious about your lightscope statement)

 

[JohnQuixote]

Next are some examples of yaw within patterned diamonds:

I want to be clear that the definition of “POOR” pavilion patterning refers to these diamonds compared to Brian Gavin's standards of true patterning.

These are diamonds that are patterned better than average makes. Elements of yaw appear in the H&A viewer, though they are not visible in crown views.

 

[JohnQuixote]

These near-true examples show elements of yaw (orange), lower girdles > 80% (green) and lower girdles on the bottom right example < 75%.

A 3D scan done by Sarin/Ogi could pick up the lower girdle data – some error possible - but would not pick up all yaw.

 

[JohnQuixote]

These are absent of yaw, with lower girdles averaging 80% (first 2) and 79% (last). No magic, I did that analysis all with my little hearts & arrows viewer – without a given error

 

[JohnQuixote]

Date: 8/5/2005 1:11:28 AM
Author: Wink
I had an interesting conversation with Senor Quixote one time and he made a comment that sticks with me.

I had commented that I was not satisfied with any of the current affordable measuring devices. ( I do not consider 20-25k affordable for the average jeweler) I had also commented that the ASET made mincemeat of a lot of the data as you could now instantly see what you needed to see, leakage, return and even from where the return came from in a manner that would mean a lot more than 75%, 78%, 83.9768765321% or whatever would ever mean to the average consumer or jeweler.

His comment:

'Wink, 3d imaging is nice, but when you have the real diamond to look at, it is sort of like having a world class sprinter in a room with you and then inputing his measurements into a computer and watching his computerized image run when you could have just asked him to run for you.'

Given the FACT that the 3d imaging available today will not give us all the measurements including yaw and gee and twist and shout accurately that a simple idealscope or ASET picture will give us the visual results of instantly and repeatably, is it any wonder that so many of us prefer to use the $1000 table sized ASET viewer than the $25,000 mostly accurate sometimes when it feels like it provided your stone is perfectly clean and centered Sarin or OGI machine?

Wink

LOL. Wink, it's nice that you remembered that.

I am a huge fan of people learning as much as possible - that's why I work to post this information.
I want to be clear about this though.

A bombardment of numbers or yaw illustrations such as I have posted here does not serve the average consumer. (read again 'average')

The goal here should be to best serve all clients as they are, not convert every one into measurement analysts.

Our pro consumers like Strm and Ira are rare. Sure there will be others, but just as surely there are many who would rather not deal with an unexpectedly steep learning curve... They just want to get a nice diamond.

Back in 'the day,' Lazare Kaplan adopted Tolkowsky's proportions and sold diamonds that cost more to create because he was an expert who recognized an elite product. Customers back then didn't know a thing about proportions, but he looked out for their interests with his expertise.

I am all for consumer enthusiasts - or anyone - who want to learn the ropes and measures. I'm here to help them on the phone, in emails and in such threads as this that 'go deep.' However, I am against bombarding newbie readers with demands for 3D scans - and scaring them into thinking they have to become experts themselves to make a purchase.