Some new learning stuff on the IS website

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Garry H (Cut Nut)

Aug 15, 2000
We have upgraded the website quite a bit lately.

And we will be launching a new product real soon.

Here are some sample bits.

........... The AGS future standards will stem from internal light flow analysis rather than external measurement of the diamond "Grades will reflect the degree to which a cutter has succeeded in creating perfect paths of light into, through and out the top of a stone," says EightStar''s David Federman. The perfect path of light as seen in a Firescope™ shows an eight-rayed pattern, hence the company name ''Eight Star''. According to Federman "Diamonds having a discernible pattern or signs of light leakage indicate a less beautiful, more poorly performing cut that the AGS may penalize with a lower cut grade". There have been suggestions that the AGS would review its round brilliant proportion based grading system based on the fancy shaped system.

This is what the AGS seems to have in mind. "Our grading system is dynamic and continues to evolve as our knowledge of the optical characteristics of the diamond increases," says Peter Yantzer, director of the AGS Gem Lab. "Performance-based cut grading is a quantum leap in the evolution and understanding of what makes a diamond beautiful".

. And .....Judging Brilliance, Fire and Scintillation

Brilliance - Diamonds that appear strong pink/red through the Ideal-Scope have the best light return. The less leakage the better. We have found that some diamonds with shallower crowns have very good light return.
The brightest face up performance will be seen in diamonds that do not show too much darkness. This includes diamonds with thinner dark stars which can be a result of longer lower girdle facets on the pavilion. But be careful because diamonds with very large tables also display thinner stars, and these will not be as brilliant as diamonds with tables below 62%.

Brilliance and light return are not the same thing. We will explain more in the scintillation section.

Fire - Diamonds with thick dark stars are usually more firey. However there is a trade off when it comes to light return, and indeed you must sacrifice some brightness to achieve more fire.

We know for instance that some very shallow crown diamonds display great fire. You have probably seen some old cuts like this; lousy brilliance but great flashes of fire?

Scintillation - Thick dark prominent stars reduce light return, but can enhance our perception of brilliance as the diamond is rocked from side to side, creating a ''bang bang'' sparkle effect.

A great analogy is to compare a plain piece of white paper and a chequer board. The checker board is half the brightness as the white paper, but when you move the two, the scintillating effect of the chequer board is far more eye catching. In this way we prefer to use the term ''light return'' rather than ''brilliance'' as the later term is a matter of subjective human interpretation.

There are still great debates between us ''cut nuts'' over definitions of all these terms.


Mar 21, 2002

Well done. There is Good text from 1 to 15 pages.
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