A review of the “foundation” of GIA’s new cut grade system
published in GIA’s Gems & Gemology Fall 2004  “Foundation for Grading the Overall Cut Quality of Round Brilliant Cut Diamonds” Thomas M. Moses et al. & 11 other Authors.

By Garry Holloway Melbourne Australia

Some 15 years ago the Gemological Institute of America began a study of diamond cut quality. The initial studies were based on computer modelling software. For the last few years they have been attempting to verify computer results with human observations. This article is the third published; brilliance (they now call it brightness) was covered in 1998 and fire in 2001. Both previous articles received plenty of criticism from their peers in the field, but by and large the GIA’s studies appear to have gone over many people in the industry’s heads; previous articles and trade summaries have either been ignored or perhaps have been difficult to interpret. This latest publication is unlikely to clarify the future cut quality grading system.

It is rumoured that some suppliers of large quantities of diamonds that are graded by the GIA Gem Trade Lab would prefer things stayed as they are; some of those companies are large contributing donors to the GIA’s funding. The GIA gives the least cut proportion information of any lab; what is included is insufficient to enable even trade experts to be confident about a diamonds cut quality and visual performance. Maintaining the status quo could suit companies who have clearly well established marketing and distribution channels.

Never the less the GIA Board of Governors has authorized the spending of an estimated $70 Million on this project (according to a well known personality).

This most recent article is, like the other two, is complex and somewhat rambling, as if it had been written by a 12 person committee. The article attempts to explain the processes used in a human observation study designed to confirm (or deny) the effectiveness of their two previously published computer based studies. A statistical method was used for this purpose; GIA claims the results were confirmed. Martin Haske has told me that he disagrees. I am not an expert in this field and invite other opinions.
Discuss...

We boarded the PoW’s in Delhi for a 1 week round trip.

In our carriage there were 4 bedroom / ensuites and a small sitting room that we shared with the other 3 cabins. Breakfast was served there by our 2 room butler guys....

We arrived in Mumbai (Bombay) on the 12^th of Feb. after our train journey on the Palace on Wheels in North India, 3 kilo's heavier and ready to buy diamonds. I have tried to capture a few of the interesting things we have seen around Mumbai....

 

ToC

1. Vegas JCK Trade Fair
2. In American Gem Society
3. Vegas' life
4. Rapaport Presentation
5. Washington, DC
6. In the Zoo
7. Smithsonian
8. Monuments, the Air and Space Museum, Botanic Garden
9. 'Fibre' Exhibition
10. Vietnam War Memorial, Arbitorium
11. Amish Village, PA
12. Back in Philly
13. Visit to Dave Atlas' lab, Imagem
14. Imagem (continued)
15. Dinner with Dave
16. New York City

With the implementation of new technologies current diamond polishing costs are about $35 per carat. Diamond grading reports run to $127 per carat. Does this seem a little strange to you?

At the start of 2006 GIA began, for the first time ever, issuing cut grades for round colorless diamonds. Evidence suggests this system, that was meant to help, could actually disadvantage many retailers and consumers.

GIA began a computer ray tracing Cut Study in 1989. In 2001 they were ready to validate computer findings with a human observation survey. But there was only a 58% correlation.

Is this where it seems they went wrong?

• Most of the observations were made by industry participants: only 7% were 'consumers'. Trade observers could be biased in favor of smaller diameter steep crown - deep pavilion diamonds with better yields & profits.
• The lighting GIA used in the survey skewed observer preferences toward deeper smaller diameter diamonds (commercially favourable).
• Diamonds were shown in a gray color tray; conventional wisdom suggests the tray should have been black. A set diamond has little or no light entering from under the stone so leakage areas look dark.

It is also possible the GIA's computer ray tracing was not up to the task (as many experts suggest) or the results would have reduced the Labs revenue (as some critics suggest, although Lab profits support GIA's other worthwhile research).

Labs grading mistakes are a diamantaires favorite topic of conversation; are mistakes myths or reality? We aim to find out.

If major labs give the same diamond 2 or more grade differences, this is more than a borderline difference of opinion. We want your help to find examples...

The Internet has bought the world a click away.  Shoppers are now offered a huge number of diamond and jewelry options from different parts of the world.  A lot more information and the specifications are available today and price and quality comparisons can be made thanks to our consumer advocate website Pricescope.com’s listings and and price comparison tools. Consumers can buy diamonds through the internet, delivered to their door step and return the goods if they are dissatisfied.  Participating vendors know they must be honest and transparent or they will be publically ‘outed’ on the forum.   

Historically ‘blue white’ fluorescent top coloured (D to F on the GIA colour grading scale) diamonds were once priced around 10% more than non fluorescent diamonds. Today D to F coloured blue fluorescent diamonds are usually discounted on wholesale markets. There are two main technical reasons why fluorescent diamonds would be discounted. The diamond’s body colour may have been ‘over-graded’ or its transparency may have been impaired.