Impact on Oval Brilliance

[abbeyld]

I am addicted to this forum! The information is invaluable to us diamond seekers. THANKS!

I am looking to buy an oval. I think I have read as much as possible, viewed the AGA charts for fancies, and know the bottom line in fancies is to see the stone in person. In buying on-line though, it''s hard to compare multiple stones side by side.

Now my question:

Is there any general opinion PS can provive on the impact of the potential brilliance on:

1. L/W Ratio - For example a stone that has a 1:1.39 versus a stone that has a 1:1:65.
2. Table - For example, a stone that has a 59% table versus a 54%.

THANKS!!!

 

[valeria101]

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On 4/18/2004 10:10:48 AM abbeyld wrote:




Is there any general opinion PS can provive on the impact of the potential brilliance on:

1. L/W Ratio - For example a stone that has a 1:1.39 versus a stone that has a 1:1:65.
2. Table - For example, a stone that has a 59% table versus a 54%.


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Actually no... There are many details at play once L/W, table and total depth are set. Brilliance and the extent of the bow-tie effect would be determined by the arangement of pavilion facets, and the coordination between those and the rest of cut details. I don't think anyone has yet attempted to devise a way to predict brilliance from a minimum of cut details in ovals - as it has been done for rounds. I doubt this is feasible, since the cut model itself is not standardizes. For example, a few extra facets are sometimes cut on the middle section to minimize the bow-tie - but this is not the norm and some stones with equally fine brilliance accross the board (literally) would have just the shape, size and angles of the traditional facets modified, not the number of facets.

The one way to deal with this is to use some direct test of brilliance on the stone itself (Ideal Scope , B Scope... for EXAMPLE).

The AGA charts (LINK) for ovals contain a good aray of common-sense criteria to avoid stones not so desirable for other reasons BUT brilliance. That remains undetermined by using the AGAs without some extra test.

To make things worse, those % are calculated relative to the width of the stone, so if you want an elongated oval you would need to keep in mind that the respective +65% depth does not mean allot of weight under girdle but a thin stone!

Hopefully, buying an oval stone with some test of brilliance in place does not sound impossible...