GIA has started providing the cut grade dimensions

[mdx]

We just received a batch of GIA stones and note that the vendor copy now includes
Total Depth
Table Size
Crown Angle
Crown Height
Pavilion angle
Pavilion Depth
Star Length
Lower Half
Then the rest of the usual stuff
The dates of the certs will the additional data are from 20th Oct 2005

The data is not included on the customer copy

A pleasant surprise, we where only expecting this in Jan2006 when the new certs are launched

Johan

 

[strmrdr]

are the numbers listed the actual numbers or the rounded versions?

 

[mdx]

Hi Storm

Looks they are rounded

Johan

 

[strmrdr]

:{
less than useful and in some cases deceptive.
another sign of the rot at GIA.

 

[Garry H (Cut Nut)]

HCA under 1 and in the AGS 0 candidates Johan, should be a very fine stone.

GIA only give it Very Good using www.facetware.gia.edu

It is going to be a crazy world.

What does it look like Johan? Can you give us a Gem Adviser etc?

 

[strmrdr]

rounded data + hca == gigo
which is why i said less than usefull and could be deceptive.

 

[mdx]

Date: 11/25/2005 11:29:58 PM
Author: Garry H (Cut Nut)
HCA under 1 and in the AGS 0 candidates Johan, should be a very fine stone.

GIA only give it Very Good using www.facetware.gia.edu

It is going to be a crazy world.

What does it look like Johan? Can you give us a Gem Adviser etc?

If the client has not collected it yet , I can scan it on Monday when back at office

Will let you know
Johan

 

[valeria101]

Date: 11/25/2005 11:38:39 PM
Author: strmrdr
rounded data + hca == gigo
which is why i said less than usefull and could be deceptive.

What are you talking about ?

 

[strmrdr]

Date: 11/26/2005 1:14:58 AM
Author: valeria101

Date: 11/25/2005 11:38:39 PM

Author: strmrdr

rounded data + hca == gigo

which is why i said less than usefull and could be deceptive.

What are you talking about ?

the numbers gia provides are badly rounded.
gigo == garbage in gabage out.

 

[valeria101]

Date: 11/26/2005 1:26:08 AM
Author: strmrdr


the numbers gia provides are badly rounded.

Strm, this calls for a reality test... in my book.


And this does not mean that it has not been done. Take a look at the rather long post by Garry on the second page of this thread. (now it is the last).

 

[strmrdr]

Date: 11/26/2005 3:02:15 AM
Author: valeria101

Date: 11/26/2005 1:26:08 AM

Author: strmrdr



the numbers gia provides are badly rounded.

Strm, this calls for a reality test... in my book.



And this does not mean that it has not been done. Take a look at the rather long post by Garry on the second page of this thread. (now it is the last).

i see nothing there that says that using numbers that can be .249 degrees off on top of any scanner error on the hca will get you any useful information.
bottom line its useless info as far as the hca is concerned.

edit: should be .249 it is rounded to the nearest .5

 

[valeria101]

Date: 11/26/2005 7:45:03 AM
Author: strmrdr


i see nothing there that says that using numbers that can be 2.49 degrees off on top of any scanner error on the hca will get you any useful information.

That is not on top of scanner error... quite the contrary (my math gone?).


Anyway,

Trying again.... if you have nothing better to do, get a perfectly symmetrical (i.e. impossibly symmetrical) DC model in the SRN input format (so that each facet can be tweaked and twisted independently by manual input) and introduce symmetry variations within the allowed GIA limits. Does it hurt? How much does it hurt? Etc.

I''ve done a bit of that, but have other things going on, no matter how dear these badly addictive things have gotten.

Also, I suspect this must have been already done by the true experts out there. Any idea about such an experiment available?

 

[strmrdr]

the rounding even mucks up there own system knocking down high end diamonds:
https://www.pricescope.com/community/threads/gia-facetware-cut-question.36119/

 

[strmrdr]

bad numbers ignore.

 

[Garry H (Cut Nut)]

Storm how did a rounding error hapen 35 to 37.4?

That is a big ask even for OGi or Sarin scanners to be that far out?

 

[strmrdr]

Date: 11/26/2005 4:15:31 PM
Author: Garry H (Cut Nut)
Storm how did a rounding error hapen 35 to 37.4?


That is a big ask even for OGi or Sarin scanners to be that far out?

good question.. fixing.

 

[strmrdr]

actual:

Selected: 61.4% depth, 57% table, 34.8° crown angle, 40.9° pavilion angle
The result is for a symmetrical diamond with a medium girdle and very good polish
HCA scores were adjusted Dec. 15, 2001 and Feb. 6, 2003.


Factor Grade
Light Return Excellent
Fire Very Good
Scintillation Very Good
Spread
or diameter for weight Very Good
Total Visual Performance 1.8 - Excellent
within TIC range

.......................................................
rounded:
Selected: 61.4% depth, 57% table, 35° crown angle, 41° pavilion angle
The result is for a symmetrical diamond with a medium girdle and very good polish
HCA scores were adjusted Dec. 15, 2001 and Feb. 6, 2003.


Factor Grade
Light Return Very Good
Fire Very Good
Scintillation Very Good
Spread
or diameter for weight Very Good
Total Visual Performance 2.3 - Very Good - Worth buying if the price is right

....................
there thats better :}

 

[valeria101]

Date: 11/26/2005 5:30:06 PM
Author: strmrdr
actual:

Total Visual Performance 1.8 - Excellent
...Total Visual Performance 2.3 - Very Good - Worth buying if the price is right

So... is 1.8 further away from 2.3 than ... 1.5 from 2 or

Look, I think these details have already been dealt with and talked about enough.

Someone still needs to write the chapter of what is a meaningful level of precission for these cut estimates and detter hair splitting on reasonable grounds.

 

[strmrdr]

Date: 11/27/2005 5:31:23 AM
Author: valeria101

Date: 11/26/2005 5:30:06 PM

Author: strmrdr

actual:


Total Visual Performance 1.8 - Excellent

...Total Visual Performance 2.3 - Very Good - Worth buying if the price is right

So... is 1.8 further away from 2.3 than ... 1.5 from 2 or

Look, I think these details have already been dealt with and talked about enough.

where? who says? is anyone forcing you to read it?

Someone still needs to write the chapter of what is a meaningful level of precission for these cut estimates and detter hair splitting on reasonable grounds.
why? there is nothing wrong with hair splitting. If 1/2 a hair seperates the best from the second best its still a difference. technology and research has just barely touched the surface of diamond cut. By splitting enough hairs Garry''s dream of only well cut diamond being available might come true :} its worked so far.

 

[oldminer]

Rounded up numbers mean greater overall innaccuracy in a predictive model. The numbers need to be rounded as the equipment used to generate the numbers has fairly wide machine error which has not yet been cured. Someday, they may have better measuring tools in the lab.

Truthfully, we have come to a time where the numbers on lab reports alone are going to mean very little. They mean a lot to cutters, but that''s before diamonds are cut, not afterwards. If one can directly measure performance, the the numbers on lab reports are really for the sake of tradition. All these past 15 years that other labs have provided numbers has not meant that those labs dominated the market. GIA with its lack of information was dominant anyway. Now that they are going to provide the numbers, the business has advanced to a point where the numbers are not going to mean much to anyone who has a choice. My own point of view remains, that numbers help to screen stones, but should not serve as substitutes for actually seeing and appreciating how beautiful they are and how they compare to one another. Enough variance is left unmeasured that one cannot use numbers to make purely correct decisions. It ironic that at the point GIA decided to release the numbers, the market has gradually come to realize how little the numbers mean. Five years ago, it would have been a major decision, now it is ho-hum to a lot of us. They ought to have given us the numbers years ago. Nothing is in them worth hiding for so long.

 

[valeria101]

Date: 11/27/2005 10:51:48 AM
Author: strmrdr

Date: 11/27/2005 5:31:23 AM
Author: valeria101


Look, I think these details have already been dealt with and talked about enough.

where? who says? is anyone forcing you to read it?

No, no 'forcing'... What the HCA is good for, how Sarin numbers vary, how scan results are averaged and what that means, how table tilt or who-knows-what else affect scanner readings and some scarce expert comments about 'decreasing return to scale' of cut grading precision added up to my initial comment.




Someone still needs to write the chapter of what is a meaningful level of precision for these cut estimates and deter hair splitting on reasonable grounds.
why? there is nothing wrong with hair splitting. If 1/2 a hair separates the best from the second best its still a difference.

I am fond of the popular saying that the nature does not take leaps ('Natura non facit saltum' - translation?). Although to some extent this is more sophism than science, it is the exceptions to this 'gadget' rule usually that require proof, not the other way around. Since we have a model at hand, if this is a valid point may just boil down to some simple math (at least in Tolkowsky's paper, the followups are a bit much for me). The rule was gingerly upheld about Fred's 61% rule, same here - methodologically.




technology and research has just barely touched the surface of diamond cut.

I know this is recent, but is it necessary? I might be dreaming, but there is allot of suitable technology never put to use in jewelry making.




By splitting enough hairs Garry's dream of only well cut diamond being available might come true :} its worked so far.

I don't know what Garry dreams of. I'd wish!

Anyway, we don't need to agree on everything - life is better fund that way

Still (virtual) friends?

 

[strmrdr]

Date: 11/27/2005 12:14:19 PM
Author: oldminer
Rounded up numbers mean greater overall innaccuracy in a predictive model. The numbers need to be rounded as the equipment used to generate the numbers has fairly wide machine error which has not yet been cured. Someday, they may have better measuring tools in the lab.


Truthfully, we have come to a time where the numbers on lab reports alone are going to mean very little. They mean a lot to cutters, but that''s before diamonds are cut, not afterwards. If one can directly measure performance, the the numbers on lab reports are really for the sake of tradition. All these past 15 years that other labs have provided numbers has not meant that those labs dominated the market. GIA with its lack of information was dominant anyway. Now that they are going to provide the numbers, the business has advanced to a point where the numbers are not going to mean much to anyone who has a choice. My own point of view remains, that numbers help to screen stones, but should not serve as substitutes for actually seeing and appreciating how beautiful they are and how they compare to one another. Enough variance is left unmeasured that one cannot use numbers to make purely correct decisions. It ironic that at the point GIA decided to release the numbers, the market has gradually come to realize how little the numbers mean. Five years ago, it would have been a major decision, now it is ho-hum to a lot of us. They ought to have given us the numbers years ago. Nothing is in them worth hiding for so long.

At this point I prefer numbers over any of the so called diamond grading machines.
The only one im willing to 100% accept is the ideal-scope and the aset eventualy within the limits they are useful.
Any closed black box will never be the ultimate answer to diamond performance grading.
It might be a part of the puzzle but never the final answer and all the dreaming in the world isnt going to change that :}

Right now accurate numbers as we can get and ideal-scope images are the best tools we consumers have.
Rounded numbers is a step in the wrong direction.

 

[strmrdr]

Val, yep still friends :}

It comes down to science vs art.
Diamond cutting and jewelery making has until recent times been a craft and an art.
It is becoming a science and a lot of people dont like that.
Some feel it takes the soul out of it but others like me find its far more intresting :}

In the end the consumers win because they can take advantage of both the science and the art.
............
My bottom line is that I dont see how adding error into the numbers serves anyone.

 

[JohnQuixote]

Date: 11/27/2005 12:14:19 PM
Author: oldminer
Rounded up numbers mean greater overall innaccuracy in a predictive model. The numbers need to be rounded as the equipment used to generate the numbers has fairly wide machine error which has not yet been cured. Someday, they may have better measuring tools in the lab.

Truthfully, we have come to a time where the numbers on lab reports alone are going to mean very little. They mean a lot to cutters, but that''s before diamonds are cut, not afterwards. If one can directly measure performance, the the numbers on lab reports are really for the sake of tradition. All these past 15 years that other labs have provided numbers has not meant that those labs dominated the market. GIA with its lack of information was dominant anyway. Now that they are going to provide the numbers, the business has advanced to a point where the numbers are not going to mean much to anyone who has a choice. My own point of view remains, that numbers help to screen stones, but should not serve as substitutes for actually seeing and appreciating how beautiful they are and how they compare to one another. Enough variance is left unmeasured that one cannot use numbers to make purely correct decisions. It ironic that at the point GIA decided to release the numbers, the market has gradually come to realize how little the numbers mean. Five years ago, it would have been a major decision, now it is ho-hum to a lot of us. They ought to have given us the numbers years ago. Nothing is in them worth hiding for so long.

This is one thread that might make Ira happy, as I think there is agreement on a few things here.

1. Numbers on a lab report are a start and can indicate zones of ''traditional success.''
2. Using HCA to get a prediction - not treated as ultimate, just as a ''nod'' - can help with sight-unseen decisions.
(at this time, for several reasons, I find HCA more useful than Facetware)
3. A reflector image, IS or ASET, provides reliable direct assessment of broad overall light return potential.

For further assessment there are different approaches. Some are science-based and some are taste-based (art, to a degree).

Mechanical devices:

Machines like the SAS, Gran and Imagem arguably measure color in a diamond better than humans do. Similarly, there are mechanical ways to approach clarity grading. These decisions are not taste-based, so if scientific metrics and tolerances could ever be agreed upon it''s likely the future of color/clarity grading will be mechanical.

Imagem, Brilliancescope and Isee also give light performance evaluations. These are harder to accept unilaterally, as results vary depending on the company that designed the machine. This makes those judgments taste-based. Nevertheless, they are consumer-friendly, and the marketing appeal of the reports is undeniable, so they will continue to gain popularity. Taken in perspective and not used as ''absolute'' such machines provide interesting supplemental information, but a static natural reflector image is more objective.

Virtual modeling:

I hope Ana does not mind my taking a quote from another thread to use here:

Date: 11/27/2005 2:14:47 AM
Author: valeria101

After a bit of using GemAdviser and Diam Calc... as an amateur, I would describe the GA is a great analytic & research tool. Not realistic enough to be used leisurely and truly ''played'' with, great to understand the techie talk on this forum and elsewhere.

Agreed 100%, and I know Ana does not mean this as a criticism. On the contrary, the DC software is revolutionary and simply amazing. I use it every day for work and for play. I believe that 3D scans are a great way for vendors and experts to trade info and observations about diamonds in a broad sense, but no simulation is yet a substitute for observation of the actual diamond, or reflector images of the actual diamond. Supplement? Yes. One of the best thing about DC remains its usefulness to cutters and those developing proprietary cuts.

Though we may differ slightly, I think I have heard Dave, Strm and Ana saying the same things in this thread: While useful, numbers alone are not definitive. That means HCA and FW cannot be definitive. Direct assessment of the actual diamond (for Strm/Ana/myself that means ideal-scope/ASET at present - perhaps Dave alludes to Imagem) is the way of the future.

 

[RockDoc]

Perfect Symmetry??????

I hae yet to see a stone where all the indiividual facet group angles were exactly the same.

I believe this is impossible to achieve due to grain orientation in the stone itself.

The non contact imaging machines generally ignore the yaw angle, which is yet another entry into the "how many times do you want to split the hair" considerations.

I will admit that there are variable tolerances in the OGI, Sarin and probably Helium scanners, which can skew the reported results, and until that is honed in a lot further the reliance on just how accurately the data is reported is a major consideration.

I''ve been writing for the past number of years how important information concerning each of the facets are rather than averages and rounding up. IMO GIA''s rounding up numbers are way out of line.

I think the GIA''s analysis of cut grade is far from being representative in the most accurate consideration of the cut quality and light return performance.

Lighting environment is equally critical as well. Marty, Sir John and I are equaly concerned about this as well.

Rockdoc

 

[adamasgem]

Date: 11/26/2005 1:26:08 AM
Author: strmrdr


the numbers gia provides are badly rounded.
gigo == garbage in gabage out.

Regarding FARCEWARE(TM)..

First read the disclaimer you sign when you download it, so I won''t try it out.. Leaves me free to comment openly

"PUBLICITY. Licensee will not issue any press release or make any statement or announcement to the press, the public or any third party (including, without limitation, Licensee’s customers) which (i) reflects unfavorably on the Software or the performance of the Software, (ii) is false or misleading about GIA or the Software or (iii) is damaging to the reputation of GIA or the Software. This paragraph shall survive the termination of this Agreement.”



First they average and then they round.. , to the level of accuracy of the worst Of Heliium, then comes Sarin, OGI, Levererage Guage, eyeball sequence.. Ever look at the internal "rounding" and the quantization..

As you say GIGO.. But what do you expect when the object was to make most stones VG to EX cut on paper.., hence they sell more paper and get more $$$$$..

 

[valeria101]

Date: 11/27/2005 2:28:06 PM
Author: JohnQuixote


Virtual modeling:

[...] Ana does not mean this as a criticism. On the contrary, the DC software is revolutionary and simply amazing.

Thanks for the mention. This is precisely what the respective post was meant to say

Direct assessment of the actual diamond (for Strm/Ana/myself that means ideal-scope/ASET at present - perhaps Dave alludes to Imagem) is the way of the future.

Interestingly

that ''way of the future'' is pretty darn old.

 

[valeria101]

Date: 11/27/2005 3:52:31 PM
Author: adamasgem





First they average and then they round.. ,

[...]

But what do you expect when the object was to make most stones VG to EX cut on paper.., hence they sell more paper and get more $$$$$..

This is a bit of rhetorical Q... mosty because I am somewhat lost in details.

Is the respective averaging & rounding mostly to blame for the overly lax grading? Or is it more in the scores associated with those measurements?

In other words, can those numbers be interpreted to obtain a more realistic 'top quality' cut off or that can only be gotten with other measurements than GIA's and they have extracted all information there is from the numbers reported.

 

[JohnQuixote]

Date: 11/27/2005 4:02:04 PM
Author: valeria101

Interestingly that ''way of the future'' is pretty darn old.

Waaaaay off-topic, but relevant... My first drum teacher used to have me practice velocity and endurance exercises on a pillow way back in the day. As times progressed, new synthetic practice pads were created. New substances, better emulating head surfaces and correlated tension, even electronic measuring devices to gauge velocity and quality of stroke vis a vis mylar and kevlar and innovations a-plenty. I sunk several hundreds of dollars into better drumming mousetraps. And yet, to this day, the best method for building velocity and endurance remains practicing on a pillow.

 

[valeria101]

Date: 11/27/2005 1:16:11 PM
Author: strmrdr

Val, ...

It comes down to science vs art.

I am very fond of the classics and the Renaissance hunt for metrics of beauty