Girdle impact on brilliance

[Matt1120]

The sarin scan on a brilliant cut diamond I am looking to purchase shows very good to excellent proportions in all areas except the girdle and I am concerned this will impact brilliance/fire. The scan shows a range of 0.5 to 3% for the girdle (rated "good") on a 0.93ct stone - should I be concerned?

Any advice/comments would be appreciated.

 

[valeria101]

As long as the angles are "correct", the slightly thick girdle would not affect brilliance - just the aparent size (spread) of the stone. You may find some reference about the matter down THIS link

I am not very familiar with what each comment ("good" or whatever) on the Sarin report mena, but it takes a combination of crown and pavilion angles, table size and symmetry to determine to what degree a cut diamond reflects light. It could well be that the (well known) relationship is already taken into account by the Sarin grading system, but it would be worth checking anyway.

Just my 0.2, of course.

 

[Garry H (Cut Nut)]

If that was an even graduation then the symmetry would be a bit out of whack. But what is more common is the stone has a thin spot in one area and the rest is say 2.5% to 3%.

What setting / lab was used for the scan?
3% is just into thick for AGS where they measure, but it is medium where HRD and many other labs measure (-1.8%).

 

[Matt1120]

The sarin scan was done at the jewellery store I plan to purchase the ring at. I unfortunately do not have specific details on the "setting" you refer to... if you are asking about the ring setting, I plan to go with four platinum prongs to hold the 0.93 brilliant cut and surround it with 2 0.27carat matched pairs of equal colour (E) and clarrity (SI1).

Thank you for the input!!!!

 

[valeria101]

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On 6/18/2004 5:49:43 PM Matt1120 wrote:




I unfortunately do not have specific details on the 'setting' you refer to...

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Each lab has it's own convention on where to measure those girdles, I bet this is what "setting" means. Silly I didn't see that 0.5%-3% variation when writing my previous post

This may account for less than greta symmetry of the cut, or not much - as Garry says. Would it be possible to either have the stone checked by an appraiser of get the girdle outline (if available from scanning) ? Do you have the complete Sarin report (something like the "manufacturer" view on the reports posted by GoodOldGold) ?

 

[diamonddoll]

0.5 to 3% is an awfully big spread. Can't they narrow it down more for you? The basic thing about the girdle is if it's think then you're pyaing for wieght in the diamond that you can't see. I mean, you want the diameter of the face of the diamond to be large enough without being shallow. Otherwise, you might be abkle to drop down in size, save money and possible get the same diameter so the diamond looks just as big on the finger.

 

[Matt1120]

Although not on me, I do have the complete sarin report... the report is very comprehensive as it gives ranges and target values for each component of the cut proportions (e.g. table ranges from 56.1 to 56.5%).

I plan to put the diamond in a gemscope and will try to see if I notice a gradutation in the symmetry across the girdle or a small dip in one area. Failing this, I will bring it in for a proper appraisal.

Thank you for the website link it was very helpful and educational

 

[Garry H (Cut Nut)]

what is a gemscope?

 

[Paul-Antwerp]

Sorry, off-topic,

Garry,

Did you alreade arrive in Antwerp?

Paul

 

[Matt1120]

Garry,

I may have the terminology mixed up but a gemscope is merely a microscope with a mount (holder) for the stone being examined. Much easier to look at the stone in detail than with a loop.

Matt