How to detect girdle cheating?

[layman]

Hi experts,

I have read postings regarding girdle cheating. I wonder if there is a way to detect it without a sarin report on the girdle?

Do girdle-cheated diamonds always
- Have narrower diameter for its weight?
- Has bad ideal scope images
- Any other easily identifiable symptoms?

From the AGS/GIA reports, is there any way of detecting this?

Thanks

 

[Richard Sherwood]

A cheated girdle is essentially a wider girdle which has been made to look thinner by deeper "scallops" being cut than normal.

Therefore the diameter of the diamond will ordinarily be less than normal.

It will show up on the girdle "map" of the Sarin or Megascope report, but not be indicated on a GIA report.

Since the AGS report indicates the width of the diamond at both the "peaks" and "valleys", a cheated girdle could be ascertained by the fact that the difference between the two measurements is quite a bit more than the normal +-1/7% difference.

The crown/pavilion angle relationship will determine more whether the light return performance is good or not as opposed to the cheated girdle. Many thick girdled stones can have good light return performances.

The cheated girdle is easily picked up by the eye. The wide scallops have a look similar to the Joker's smile in the Batman movie.

 

[diamondlil]

This is interesting to me, Rich, since a friend of mine just purchased a beautiful diamond with a med to thick girdle (crown and pavillion angles are excellent but the diamond appears slightly smaller due to the thick girdle). Would a cheated girdle be equally as brilliant as a thick? It seems that a cheated girdle would screw up the crown and pavillion angles since those facets that were cheated right at the girdle would be angled differently than the rest. Am I understanding this right?




What purpose would a cutter have in cheating the girdle? Is this an attempt to *disguise* what would normally be a thick girdle (which could lead to a discount in price)?




Very interesting . . .

DiamondLil

 

[Garry H (Cut Nut)]

Hi all,

Since I coined the term "Cheated Girdle" perhaps I could help here.
(Rich I think we might be at crossed purposes

)

You can see more detial about this in the thread about the GIA recent newsletter too. they call it indexing and suggest it is good. I disagree.

8* cheat the goirdle in a kinda good way. They make the upper girdle facets more shallow. This stops some leakage, but decreases the contrast the leakage causes. See the 2 most recent newsletters at www.iddeal-scope.com.

Cheated girdles are usually applied by commercial cutters having diamonds certified in USA because USA measure the girdle at the thinnest part - the area between the points where the main and minor facet junctions occur. The thin part is as Rich says, normally 1.7% thinner than the main and minor facet junctions points in a diamond with no indexing.
In European labs they measure the girdle at the main facet junction - which is normally the same as the minor facet junction. So there is no point cheating and making the facet thicker there. But an 8* with a medium girdle will be rated as very thin if graded by an European lab like HRD. So chaeting does not work in Europe and 8* would have a hard time there too (although there 8* choose a very good girdle thickness).

I call it cheating because it is a way a cutter can increase the depth and still get a top grade from AGS and a medium or slightly thick girdle from GIA even though the stone really has a thick or very thick girdle.

The problem is that the increase in upper girdle facet is usually done on stones that are on the deep side and the result is a smaller looking diamond because of loads of leakage around the edge of the diamond - more than what could help with contrast.

 

[layman]

I don't know if this makes sense to you guys.

Reading from GoG's tutorials, I come to know that if you take the Depth% - (Crown% + Pav%) you get some "bezel girdle" thickness

http://www.goodoldgold.com/the_girdle.htm

Can I use this to tell if a diamond is Girdle Cheated?

Is 1.7% from the (max. girdle - min. girdle) specified in AGS cert or from the (Bezel girdle - some? girdle) ?

Hope I am not embarrasing myself with all these jargon.

 

[Mara]

Garry...does WF cheat the girdle with their ACA's?

 

[valeria101]

Am I seeing things, or there are at least three different definitions of "cheated girdle" on this thread

What is kind of "cheating" you are asking about, Layman ?

 

[layman]

I guess, I am concerned about the kind of girdle cheating that Garry described. The kind that will cause leakage and cause diamonds to look bad even though they have good HCA score.

I read about this guy who showed Garry a diamond that rated very well on HCA but performed badly on a Brilliancescope

http://www.diamondtalk.com/forums/showthread.php?t=30627

It turned out that the diamond was Girdle Cheated. Since HCA would never have known about the girdle trick, it took the measurements at face value and gave a good value.

Since most people who buys from the internet relies heavily on HCA and GIA/AGS certificate, it would be disastrous for someone to buy a diamond only to realise that they have been duped.

Frankly, I am not too concerned about the 8* or Whiteflash version of the girdle trick. If the stone looks better with the unusual girdle, no problem.

But if a stone is cut for the sake of fooling all the grading mechanisms out there just so that certain individuals can make a few extra bucks, then I think it becomes a problem.

What I want to know is if there is a way for consumers to quickly identify by means of simple calculation or observation, whether a stone is Girdle Cheated.....or "Cheated Girdle"

 

[Mara]

I would say...if the IdealScope doesn't look great, then don't consider the stone. The IS will show light leakage and return. If it looks good, it's an indicator that the stone was not cheated OR is the good cheating. If it looks bad...it's not a stone you should be considering anyway. IMO.

 

[layman]

Mara, precisely what I wanted to know.

If bad girdle cheated stones always show bad IS images, then I suppose that is a simple way to detect it.

If a stone shows HCA 0.6 and performs like crap on IS, then one should know there is something fishy going on with the stone.

Assuming the HCA works perfectly all the time

- fair assumption, Garry?

 

[2Bmarried]

Mara,

When I was looking at diamonds a few weeks back, one of the stones I had narrowed it down to was an ACA diamond. I posted the IS image on the thread I started and Garry replied that it had a cheated girdle. However, it had the best IS image of those I had looked at, as far as light return. Upon speaking with Brian at WF, he told me that it (correct me if I'm wrong, Brian) will reflect light more like a headlamp & might not necessarily have the contrast that many people like, or dislike. But it did have the least amount of leakage. Garry thought the picture looked a bit fuzzy because of the cheated girdle, a good "trick", but it just looked like a slightly out-of-focus IS image. Seems to me that a stone with a cheated girdle can still have an excellent IS image. I'll leave it to the experts!!

 

[elmo]

----------------
On 3/2/2004 7:15:12 AM Richard Sherwood wrote:

Since the AGS report indicates the width of the diamond at both the 'peaks' and 'valleys', a cheated girdle could be ascertained by the fact that the difference between the two measurements is quite a bit more than the normal +-1/7% difference.
----------------

I thought the AGS girdle numbers were the min/max range for the valleys only, sort of like a GIA "thin-slightly thick" call. Am I wrong?

 

[Mara]

2BM...the 'cheated girdle' phenom from what I gathered could be good OR bad..depending.




In Garry's quote here:




"8* cheat the girdle in a kinda good way. They make the upper girdle facets more shallow. This stops some leakage, but decreases the contrast the leakage causes. See the 2 most recent newsletters at www.iddeal-scope.com."





EightStart and ACA "cheat" their girdles in a similar way.




Personally...if the light return is eye popping, I don't care if the girdle is cheated. My fiance's ACA which has a tweaked (cheated) girdle is an amazing beauty. I honestly can't imagine a better looking stone anywhere. It blows us away every time. So I've seen a cheated...and a non-cheated (in stores...like a HOF)...and they both look great in terms of being 'ideal' ...but the cheated looks stunningto me!

I, personally, would use light return as the gauge of what to buy/discard. That is what your eye SEES. Not cheated girdles or min/max's or numbers. If the numbers match up (are nice), the HCA says its good, the IS image is eye-popping....and it's an H&A...honestly that is all I need to know.