Sarin/Cut aviser vs GIA

[jimmyc]

Hello.

For the brilliance of the stone what is a better measure; GIA or the Holloway Cut Analyser/Sarin?

I''ve found a stone which I am very interested in and the GIA certificate reads perfectly (excellent polish and symmetry, ideal proportions, no culet, and no fluorescence). Based on the GIA Cert it should be perfect

However when I put the Crown and Pavilion angles into the Holloway Cut Analyser here on PS, the stone comes out as a 3.3, "Very Good" but not excellent

What is going on here and which one should I pay more attention to? The dealer tells me that with idea proportions and excellent symmetry and polish the stone is just about perfect. However when I put the angles from the Sarin results into the Holloway Analyser it is less than perfect

I am going to the trouble or buying a flawless stone with perfectly clarity so I want to make sure I get it right.

Help please?!

Jimmy C

 

[JohnQuixote]

Jimmy - GIA doesn't give a grade for proportions. Where are you seeing the term 'ideal'?

 

[jimmyc]

Sorry, I probably wasn''t very clear.

I haven''t read "ideal" anywhere (obviously it''s not on the GIA Cert) but the dealer describes the stone as "ultra ideal" because the Cert has depth (62%) and table (57%) in the ideal range and the symmetry and polish are both excellent

 

[JohnQuixote]

The depth and table measurements are in line with traditional Ideal proportions, but the crown and pavilion angles are critical measurements. For that matter, girdle thickness is important too (included on the GIA report). Without knowing these the diamond can range anywhere from ideal to i-disaster

Unfortunately, GIA info does not include the all-important crown and pavilion angles yet - they will in their new grading system but that doesn't help you now. Does the dealer have access to a Sarin machine? A Sarin report gives all these particulars.

 

[Rhino]

Date: 7/18/2005 3:15:44 AM
Author: JohnQuixote
The depth and table measurements are in line with traditional Ideal proportions, but the crown and pavilion angles are critical measurements. For that matter, girdle thickness is important too (included on the GIA report). Without knowing these the diamond can range anywhere from ideal to i-disaster

Unfortunately, GIA info does not include the all-important crown and pavilion angles yet - they will in their new grading system but that doesn't help you now. Does the dealer have access to a Sarin machine? A Sarin report gives all these particulars.

Good advice John but one thing to bear in mind.

The general Sarin's that are being presented from the greater majority of firms offering them are now going to be incomplete if they do not contain minor facet information.

Ie. If upper girdle angles are over a certain degree, this will contribute to the darkness around the perimeter causing certain stones not to receive ideal grades. There are a certain percentage of stones that feature this negative which will prevent it from getting ideal grades now.

Also if lower girdle lengths are too short or too long this will impact contrast, dispersion and scintillation.

At this stage of the game we have reached a transition point regarding the information to garner and if minor facet information isn't included, my professional opinion is that most Sarin's are incomplete if a person is now seeking to know if a stone gets ideal grade or not.

Jimmy... continue to persue a Sarin. When you do ask if its possible to attain a 3d model.

 

[JohnQuixote]

Jon - How is this different from the way you felt a week ago?

We both know minor facets are crucial, particularly within well-patterned diamonds. You also know I'm one of the first to wave the pom poms about them. Pick up that megaphone and let's do a cheer.

But don't expect every Sarin on the planet to include the info right away.

Consider that it's been HCA, along with traditional AGS proportions grades, that has fueled the common expectation for one to have crown/pavilion angles. Once GIA comes out with their version of HCA it will ignite common demand for minor facet info as well, but that may not happen for many months. Minor facets won't be any more important then...Those of us who like to play around with 'em will just have more public info to play with.

In the meantime, the PS population will just have to continue using the standards that have evolved thus far to help others. So Jimmy, don't worry about the blitzkrieg here. If you can get crown and pavilion angles Pricescopers can help you. A 3d model would be beyond fab.


PS: Jon, I would be more excited about the potential of this system, except you do realize that GIA still plans to ROUND the minor facet info, right?

 

[jimmyc]

Sorry guys, but you have managed to seriously confuse me!

Please use small words, for a small mind.

From what I can gather, if I put the Sarin results into the Holloway Analyser and it does not come up Excellent then perhaps the stone is not as good as it could be - is my understanding correct?

The GIA Cert says excellent, excellent and the Megascope AGS results give it a 0, however the Holloway analyser only gives it a "very good - buy if the price is right". Which one(s) should I pay more attention to?

Thanks

Jimmy

 

[belle]

they are both telling you need to get the crown and pavilion angles for an accurate assessment of the diamond.

 

[JohnQuixote]

Jimmy - No need to apologize. It got a bit tangential.

Do you know crown and pavilion angles? (you mentioned OGI Megascope) HCA is a good tool for rejection, but we can give you even better direct feedback with specifics.

Thanks Belle

 

[jimmyc]

Hi guys

The Sarin results are as follows...
Depth 62.3
Table 55.8
Crown Angle 35.5
Pavilion Angle 40.9

As I''ve said the Holloway Analyser only gives it a very good. What do you think?

J

 

[JohnQuixote]

Crown angle 35.5 is the source of your pain. Too steep.

This is one cut to the outer limits of old ideal proportions and would not likely make ideal with their new performance parameters.

 

[Rhino]

Hey budro!

My apologies for not answering sooner.

Date: 7/18/2005 3:20:55 PM
Author: JohnQuixote

Jon - How is this different from the way you felt a week ago?

We both know minor facets are crucial, particularly within well-patterned diamonds. You also know I''m one of the first to wave the pom poms about them. Pick up that megaphone and let''s do a cheer.

But don''t expect every Sarin on the planet to include the info right away.

Actually its no different than how I felt a week ago or even a few years ago. Ever since studying and learning the impact of the minors on diamond appearance I don''t ever feel 100% comfortable advising a person on a stone with the Sarin data that people post here. Matter of fact I never make solid recommendations on that alone and in my own personal buying decisions I never drop the bucks until I know lower girdles, upper girdles and star info plus the consistency to which the stone has been cut (mathetical symmetry). Yes... if a person posts some cherry angles (34.x/40.7-40.9/53-57) the chances are very high that it will be a stunner but without the information on the other 40 facets I would not recommend the stone. Not with a 100% clear conscience.

The labs (both AGS and GIA) have also confirmed this with their new cut grading systems which takes into account the optical effects of the minors (YAY). This is a graphic I have posted in the past but demonstrates the point. The basic Sarin data is identical on each of these 4 stones. The information that varies is the minor facets (actually in this example, only lower girdles, not stars or uppers).

Wouldn''t you agree ... if we are going to advise consumers on muti-thousand dollar decisions that they should get the full picture and not a partial one?

Regarding the expectations of suppliers or people in the trade having Sarin''s to include that information ... Rapnet has had Sarin''s with 3d models available online for years now. How many in the trade are *for* giving this information?!?! I think there may be 2 suppliers who can provide it. I don''t expect MOST within the trade to provide this data so my expectations are not high at all.

Consider that it''s been HCA, along with traditional AGS proportions grades, that has fueled the common expectation for one to have crown/pavilion angles. Once GIA comes out with their version of HCA it will ignite common demand for minor facet info as well, but that may not happen for many months. Minor facets won''t be any more important then...Those of us who like to play around with ''em will just have more public info to play with.

In the meantime, the PS population will just have to continue using the standards that have evolved thus far to help others. So Jimmy, don''t worry about the blitzkrieg here. If you can get crown and pavilion angles Pricescopers can help you. A 3d model would be beyond fab.


PS: Jon, I would be more excited about the potential of this system, except you do realize that GIA still plans to ROUND the minor facet info, right?

I realize that most consumers come here and DO make purchasing decisions based on Sarin and HCA alone. I have seen and experienced too many lemons with many combinations that the HCA rewards. Interestingly the new GIA/AGS systems concur my feelings.

Regarding the "rounding" by GIA. I think too much of a stink is being made over this and let me explain why.

Let''s take lower girdles for example. If a lower girdle length is listed with GIA as being say 80% in length. We know that it could technically be 2.5% either way. As low as 77.5% or as high as 82.5%. The question that begs an answer John is if we put a diamond with a 80% lg length next to a diamond with a 78 or 79% lg length ... is there such a great difference in appearance between the 2... really? You know I am a nut for minor facet information but even this geek knows there is not a world of difference between this comparison. Would you agree? And the fact that GIA will also be listing this information on their reports is a MAJOR STEP FORWARD. To include it in online software is also another major step forward and demostates (as you note) the importance of having this information. I like the fact that people will not get the whole picture or even be able to use their online software if they do not have this information. If it were up to me I''d also include upper girdle angles as well and get the entire picture.

Look forward to hearing back from ya bro.

Kind regards,

 

[Maxine]

To: "J" and "J":
What WILL make the new grades????????????

Is there a way for the consumer to tell as of now?????????

 

[Rhino]

Date: 7/20/2005 10:59:37 AM
Author: Maxine
To: ''J'' and ''J'':
What WILL make the new grades????????????

Is there a way for the consumer to tell as of now?????????

No way for consumers to know at this point unless of course they are looking at a current AGS Report. What will be an interesting selling point however is that even though AGS grades a diamond as "ideal" I am seeing that not all these ideals will be the same or even look the same. Here''s a recent shot I took of a current AGS ideal next to one of ours. Two different looking ideals.

 

[Regular Guy]

Date: 7/20/2005 10:54:59 AM
Author: Rhino

The labs (both AGS and GIA) have also confirmed this with their new cut grading systems which takes into account the optical effects of the minors (YAY). This is a graphic I have posted in the past but demonstrates the point. The basic Sarin data is identical on each of these 4 stones. The information that varies is the minor facets (actually in this example, only lower girdles, not stars or uppers).

Wouldn''t you agree ... if we are going to advise consumers on muti-thousand dollar decisions that they should get the full picture and not a partial one?

Jonathan,

Referring to your graphic, and the four different diamonds with the same crown & pavilion angles otherwise, but different lower girdle data...which is your preference? Is the picture intending to communicate the preferred one; I''m not getting that. Any way you can share the nature of how much you would prefer one over the other?

Regards,

 

[Dancing Fire]

RG
i'm not rhino but,i'll bet you is the one with 80% LG.

 

[Regular Guy]

Date: 7/21/2005 12:13:50 AM
Author: Dancing Fire
RG
i''m not rhino but,i''ll bet you is the one with 80% LG.

care to annotate?

 

[belle]

let''s all try to answer questions directed to other people

it''ll be fun!

Date: 7/21/2005 12:31:50 AM
Author: Regular Guy

Date: 7/21/2005 12:13:50 AM
Author: Dancing Fire
RG
i''m not rhino but,i''ll bet you is the one with 80% LG.

care to annotate?

i''ll bet it''s because with 70-75% there is too much contrast and with 85% there is too little.
80% is juuuust right.

 

[Dancing Fire]

Date: 7/21/2005 12:31:50 AM
Author: Regular Guy

Date: 7/21/2005 12:13:50 AM
Author: Dancing Fire
RG
i'm not rhino but,i'll bet you is the one with 80% LG.

care to annotate?

RG
look at the 80% stone,notice the hot spots (little black watermelon seeds) next the arrow shafts? that style cut stones seem to get top scores on teh B-scope & Isee2 scans.Rhino believes in these high tech machines

so...how much are we betting.

okay the winner gets belle's E-ring.

 

[belle]

well, i''m going to win anyway

besides, 3cts is too big for you df.

 

[Dancing Fire]

Date: 7/21/2005 1:10:31 AM
Author: belle
well, i''m going to win anyway

besides, 3cts is too big for you df.

belle

who said you were in the contest? you just put up the winner''s prize

. don''t worry, i''ll get use to a 3ct.

 

[belle]

who's thread is this we're hijacking?

i made a guess so i'm in. what are you putting up? all bets are on.

 

[Rhino]

Good guesses. DF ... haha... you are an avid student. On par with the likes of strmrdr. I have to say ... my answer to this question is not as definite as it once was. Let me explain. My answer now would be that it depends on the light condition I am examining the diamond under.

In soft hemisphere lighting where (optical) symmetry becomes more easily seen with the unaided eyes I kinda prefer lg's around the 75-76% zone. Contrast is more stark as there are less reflectors (hot spots) off the pavilion reflecting back obstruction to the viewer and an on/off/on/off effect is slightly more apparent. This could be an arguement for a certain preferred kind of "brilliance" or "brightness" in these light conditions.

When you lengthen the lower girdles you create more smaller areas of obstruction. This does not in any way decrease the beauty but it does introduce another thing to consider. More points of contrast. When evenly dispersed throughout the diamond (lights/darks) could make an arguement for higher, what would be termed dynamic scintillation. More squares on the checkerboard so to speak.

I would point out at this juncture that the Isee2 technology which digitally analyzes the balance of the lights/darks within a diamond in these lighting conditions give high marks for both types (75% and higher lower girdles) of stones because both have beautiful balance of contrast. They just display that contrast slightly different back to the eyes of the viewer.

However I don't feel hemisphere lighting flatters scintillation as much as direct lighting and this is where this concept (dynamic scintillation) really comes into play because in direct lighting, which really flatters scintillation, I would prefer lower girdles from 77-80%

. In direct lighting these stones have a slight advantage because those hot spots and the arrows (blacks under LightScope) become strong sources of intense reflection, not to mention properly angled lower girdles, produce not only strong fire but more scintillation. If any of ya'll are ever out here ask me and I'll show you a comparison of how the relationship of blacks/reds under reflector technology correllate to human eye observation. It's really cool, not only in comparing 57 facet H&A's with varying lower girdles but also in the 2nd generation super ideals too.

These are the kind of stones that are rewarded by Bscope as this technology is doing its analysis in direct light conditions.

One thing I would also point out is that IF a diamond with shorter lg's (which lacks those hot spots) is cut in such a way that there is no facet yaw, no yaw increases the intensity of light output, in a properly angled diamond, particularly through the lower girdles. I'm writing from a different lap top but I have the graphics that demonstrate this effect too, of the relationship between facet yaw and light output. In the not too distant future we'll be able to demonstrate this numerically as well.

So... in brief. In hemisphere lighting I prefer 75-76%. In direct lighting I prefer 77-80%. This is if I were sticking to H&A's. Once you go a little beyond the 80% lg arena you are no longer in Hearts & Arrows land as the hearts start forming clefts around this length. HOWEVER ... since Hearts are not seen in the face up position I must say in all sincereity, stones with lower girdles up to around the 85% zone are by no means ugly. Matter of fact they can be quite scintillating and bright. We've had stones in our inventory like this in the past (though not many) that were absolutely beautiful. A good comparison for peeps to make would be between a stone with 75%, 80% and 85% lower girdles and see which they preferred. Hrm... I see a poll coming up. Does everyone have GemAdvisor? This'll be fun.

 

[JohnQuixote]

Jonathan, I think you misunderstood my point. Maybe I wandered as I pondered. My incursion here was merely to try and avoid confusing Jimmy (it didn't work - he got bamboozled).

Now the thread has been 100% pirated. Alas. (edited to add... Avast!)

Dearest Rhino, I agree, and have always agreed, that minors are crucial, particularly in patterned diamonds. Do a PS search and see how many times I talk about balance between LGF and Mains and the resultant differences in visual 'character' (in case you don't recall you told me you liked that word - use it if'n you want - I have no copyright lol). I have always emphasized that patterning does not rely on facet alignment alone, but is a result of harmonious balance of visual properties in both major and minor configurations. You're preaching to the choir, friend.

I am fortunate in that when I am working with our inventory Brian designed the entire signature line, so those minor facet configurations are fashioned to his specs. As a matter of fact, with ACA both minor facet configuration and girdle particulars are emphasized. True H&A patterning relies on such relationships as a fundamental for robust optimization.

Brian is the one who taught me the basics (among others, as you well know)

so I'm sure you can appreciate that I am as excited as anyone to see them recognized.

My caution is that the machinery moves slow. Predict for me when you believe demand for minor facet info will reach the jewelers that PS consumers are interacting with (who are NOT like me and you and a dog named Boo). I think asking Jimmy to seek out minor information, while well-intended, was perhaps not practical. But that's never stopped us before, yo?







Part Two

Rounding. Simply this. Put two diamond images together: One with LGF 77.5% and another at 82.4% Compare the differences in those, both in basic appearance - as you have done above - but more importantly through different metrics for dispersion and scintillation.

Talk to me.

 

[JohnQuixote]

Date: 7/21/2005 2:05:04 AM
Author: Rhino

One thing I would also point out is that IF a diamond with shorter lg''s (which lacks those hot spots) is cut in such a way that there is no facet yaw, no yaw increases the intensity of light output, in a properly angled diamond, particularly through the lower girdles. I''m writing from a different lap top but I have the graphics that demonstrate this effect too, of the relationship between facet yaw and light output. In the not too distant future we''ll be able to demonstrate this numerically as well.

So... in brief. In hemisphere lighting I prefer 75-76%. In direct lighting I prefer 77-80%. This is if I were sticking to H&A''s. Once you go a little beyond the 80% lg arena you are no longer in Hearts & Arrows land as the hearts start forming clefts around this length. HOWEVER ... since Hearts are not seen in the face up position I must say in all sincereity, stones with lower girdles up to around the 85% zone are by no means ugly. Matter of fact they can be quite scintillating and bright. We''ve had stones in our inventory like this in the past (though not many) that were absolutely beautiful. A good comparison for peeps to make would be between a stone with 75%, 80% and 85% lower girdles and see which they preferred. Hrm... I see a poll coming up. Does everyone have GemAdvisor? This''ll be fun.

I concur absolutely. I would only caution the 85% figure to say that in halogens they are the bomb, while in very soft light they bomb

Rhino, have you talked to Marty about his musings on physical symmetry and dispersion? Also, are you familiar with dynamic fire and dynamic contrast definitions? I have been anxious to start a thread about these significant (potential) baselines for the first meaningful measure of scint.

 

[Garry H (Cut Nut)]

Date: 7/18/2005 6:00:54 PM
Author: jimmyc
Sorry guys, but you have managed to seriously confuse me!

Please use small words, for a small mind.

From what I can gather, if I put the Sarin results into the Holloway Analyser and it does not come up Excellent then perhaps the stone is not as good as it could be - is my understanding correct?

The GIA Cert says excellent, excellent and the Megascope AGS results give it a 0, however the Holloway analyser only gives it a ''very good - buy if the price is right''. Which one(s) should I pay more attention to?

Thanks

Jimmy

Jimmy GIA''s new yet to be released HCA style grading system will probably give that stone Excellent. aGS would give it about AGS 2 with their new HCA style parameters for predicting a diamonds performance with their 3D scanned real stone computer grading system.
And I am sticking with 3.3.

 

[Rhino]

Date: 7/21/2005 7:56:58 AM
Author: Garry H (Cut Nut)

Jimmy GIA''s new yet to be released HCA style grading system will probably give that stone Excellent. aGS would give it about AGS 2 with their new HCA style parameters for predicting a diamonds performance with their 3D scanned real stone computer grading system.
And I am sticking with 3.3.

I''m not so sure about this mate. We recently scanned in a 34.4 crown, 41 pavilion angle (you know this 41 threshold), 55 table and the software suggested reducing the crown angle to slightly under 34 degrees to compliment that angle. I know you would personally concur with that as would I.

 

[Rhino]

JimmyC ... apologies for veering off the beaten path. The reason the HCA and the rest of us counsel against this stone is because those angles produce extraneous lekage under the table which hurts every metric (brilliance, fire, scintillation, contrast). While we don''t know the minor facet info nor the variances this graphic demonstrates the point.

 

[Rhino]

For your edification, there are 2 ways to fix such a stone. One is what Sir John has suggested. The crown angle of 35.5 when coupled with 40.9 produces undesired results. Trimming that crown angle down to the mid 34.x range would alleviate that problem. Another would be to trim down the pavilion angle. When you have crown angles in the mid 35.x range, pavilion angles at or under 40.6 is the better compliment. Here''s the results when we trim those pavilion angles to 40.5.

 

[Rhino]

Hey bossman,

Thanks for the quick feedback.

Date: 7/21/2005 2:27:03 AM
Author: JohnQuixote
Jonathan, I think you misunderstood my point. Maybe I wandered as I pondered. My incursion here was merely to try and avoid confusing Jimmy (it didn''t work - he got bamboozled).

D''oh... hence the reason for my last post to Jim.

Date: 7/21/2005 2:27:03 AM
Author: JohnQuixote

Dearest Rhino, I agree, and have always agreed, that minors are crucial, particularly in patterned diamonds. Do a PS search and see how many times I talk about balance between LGF and Mains and the resultant differences in visual ''character'' (in case you don''t recall you told me you liked that word - use it if''n you want - I have no copyright lol). I have always emphasized that patterning does not rely on facet alignment alone, but is a result of harmonious balance of visual properties in both major and minor configurations. You''re preaching to the choir, friend.

Heh... I know that. Being that the labs are moving in this direction I think its about time we all do.

Date: 7/21/2005 2:27:03 AM
Author: JohnQuixote

I am fortunate in that when I am working with our inventory Brian designed the entire signature line, so those minor facet configurations are fashioned to his specs. As a matter of fact, with ACA both minor facet configuration and girdle particulars are emphasized. True H&A patterning relies on such relationships as a fundamental for robust optimization.

Brian is the one who taught me the basics (among others, as you well know)

so I''m sure you can appreciate that I am as excited as anyone to see them recognized.

Date: 7/21/2005 2:27:03 AM
Author: JohnQuixote

My caution is that the machinery moves slow. Predict for me when you believe demand for minor facet info will reach the jewelers that PS consumers are interacting with (who are NOT like me and you and a dog named Boo). I think asking Jimmy to seek out minor information, while well-intended, was perhaps not practical. But that''s never stopped us before, yo?

HELL YO!

John, this will quickly become standard practice now. I predict demand for minor facet information will increase SHARPLY over the next 3 months. Hey... when online folks CAN''T get results from the GIA Calcutor without lower girdle and star data ... GUESS WHAT JOHN Q. PUBLIC (heck especially PS folk) WILL BE ASKING FOR?!?!?!?

Also... regarding online grading software put out by GIA and AGS, GIA''s will actually be easier for most folks as they''ll only have to input that data. AGS''s will require even more (which I am happy about). Yes the trade will be slow, EXTREMELY SLOW in bringing thier technologies up to speed but with the major labs headed in this direction, demand for the details will be even greater. 3d models will be playing a more prominent role in online trading.

Date: 7/21/2005 2:27:03 AM
Author: JohnQuixote

Part Two

Rounding. Simply this. Put two diamond images together: One with LGF 77.5% and another at 82.4% Compare the differences in those, both in basic appearance - as you have done above - but more importantly through different metrics for dispersion and scintillation.

Talk to me.

We''ll play with these. Gotta run for now but upon my return we''ll make some models and play.

Peace out,