GIA publish 1998 Brilliance and 2001 Fire papers online

[Garry H (Cut Nut)]

http://www.gia.edu/pdfs/Fall_1998_Cut.pdf

http://www.gia.edu/pdfs/Fall_2001_Cut.pdf

Now all you guys who never read them can get your snarling and snapping teeth into the GIA.

It is great bed time reading.

 

[Garry H (Cut Nut)]

This chart is a little old (Jasper Paulsen did it a year or 2 back) and the HCA scores for shallow stones have been made tougher. Red is best.

GIA light return (WLR) and the range of best fire between the two DCLR lines are my interpreted best estimates from those 2 papers.

 

[Boulder]

Thanks for pointing this out! This indeed looks like good bedtime reading.

 

[Hest88]

Wonderful! Thanks Garry.

 

[Garry H (Cut Nut)]

Bump
Did any of you read these?

It might become more relevant if we are correct - see the latest newsletter at
http://www.ideal-scope.com/newsletter_issue_current.asp
New GIA & AGS Cut grade systems

Recently Gemological Institute of America (GIA) announced that a Cut Grade could be seen on GIA certs later this year or early in 2005.

It is likely GIA will release the proportions (possibly as early as 17th April at the Basel GemFest) so diamond polishers can begin producing stones that will get a better cut grade. After +ten years of GIA research this is good news for consumers and, in the long term, for the industry as a whole. But it will come as a huge shock for many industry dinosaurs.

Consumers will be happy if the grade is simple grade like color (‘D’, ‘E’, ‘F’, etc) and clarity (‘FL’, ‘SI2’, etc).

At Ideal-Scope we know that there are many different sets of proportions that produce beautiful diamonds. Garry Holloway was the first to develop the terms BIC and FIC that describe more Brilliant or more Firey ideal cuts; truly beautiful looking diamonds even though some have AGS10 proportions. We will be happy when the leading authority vindicates our long held position J.

As an Ideal-Scope owner or user have you found any diamonds with very shallow crowns and deep pavilions, or very steep crown angles and shallow pavilions, that look great through the Ideal-Scope? Were you amazed at how beautiful they look to your naked eye? It was this observation, 20 years ago with a Firescope™, that started Garry’s interest in diamond cut.

We have no doubt that a GIA ‘A’ grade diamond will:

¨ look great through an Ideal-Scope

¨ score well on the Holloway Cut Advisor

¨ score well on DiamCalc

More effective cut grading by lab’s will give diamond cutters more incentive to produce better looking diamonds. Removing the ‘smoke and mirrors, will give people confidence to pay more for better cut diamonds.

The immediate impact on diamond cutters? They will only send the better cut stones to GIA. At present GIA often get the worst proportioned diamonds. Why? A GIA report gives the least proportion cut quality information of any lab in the world. This means the GIA will lose a lot of business unless they can convince cutters that they will get better yields on many pieces of rough diamond because (like our BIC – FIC’s) the wider range of proportions results in increased yields.

Hopefully this long awaited shot in the arm for the diamond industry will come sooner rather than later.

Follow this link to read the full details on this latest GIA presentation by Peggy Jo Donahue (Professional Jeweller).




AGS to discuss new cut grade system at Moscow conference

The American Gem Society has been studying diamond cut for several years. Our goal is to develop practical, performance-based cut grading systems for fancy shape diamonds, round brilliants and round fancies.” Peter Yantzer

Few people are aware the AGS are changing their Tolkowsky based grading system. Among the new approach is an Ideal-Scope type colored reflection photographic system.

Demand for conference attendance has led to an early closing of registration. Major labs are well represented, except for GIA, who are concerned about anti trust collusion charges. However Sergey and I have been invited to attend formal functions at Basel.

Follow this link to learn all about the 1st International Diamond Cut Conference 2004 to be held in late April in Russia.

Back to top


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

Got something to say?

Tell us about your experience using the Ideal-Scope? Have you found it easy to use?

Has it helped you appreciate and buy better cut diamonds?

Is there anything that you don’t like about the Ideal-Scope?

Maybe you have some suggestions for future topics for this newsletter.

Click here to send us an email with your comments or ideas.

Back to top

 

[valeria101]

" This means the GIA will lose a lot of business unless they can convince cutters that they will get better yields on many pieces of rough diamond because (like our BIC – FIC’s) the wider range of proportions results in increased yields. "

It is said that the HCA gives green light to about 5% of the diamonds available at present. If the majority are to comply with some cut standard compatible with the HCA selection, this still means that 95% of cut decisions would change... This is quite a number!

 

[valeria101]

----------------
On 4/11/2004 6:31:37 AM Cut Nut wrote:

Removing the smoke and mirrors, will give people confidence to pay more for better cut diamonds.

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

Gee...

it is sooo temting to kep guessing scenarios with all these changes in sight

Here's one

Adding one more grading criteria on the GIA cert will shift the overall 'score' (which determiens price, ultimately) for stones prices accordint to the current categories. I suppose more off-color and/or badly included stones would get better cuts (as some branded ones today) - since the overall bad mark of these duds would clearly benefit from one more criteria on the cert to beef it up. Some more weight loss in these stones with lower cost per carat makes them nice candidates for the comming top cut grades, I suppose. Conversely, the value of badly cut pieces with high colors and clarity will get hit by the new cut grades...

Since fire and brilliance are both 'good' but emphasized by different types of cut proportions, maybe these will become major excuses to keep a variety of stones labeled "well cut", avoiding the constraining narrow H&A (and/or HCA<2) interval.

Well, if such considerations hold, the new cut grade will make up for very different diamond buying choices... as far as I understand (probably not much).

 

[Garry H (Cut Nut)]

Not so Ana.

Look at the HCA charts and think about the range of proportions where most diamonds are cut to.

It probably centers around 32-36 crown and 40.5 to 42 pavilion angle (with tales averaging about 61-62%).

Now look at HCA - it could extend to 25 degree crwon angles and it can go to below 39.5 pavilion angles with 37 - 38 crown angles.

If GIA sanction that range they will achieve the type of change that I would like to see in this diansaur industry.

It will increase cutters yields - not decrease them!

 

[valeria101]

----------------
On 4/11/2004 4:14:55 PM Cut Nut wrote:



Now look at HCA - it could extend to 25 degree crwon angles and it can go to below 39.5 pavilion angles with 37 - 38 crown angles.

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

Your explanation is much welcome. Thanks!

I would surely like to look at the respective 3D chart that is