H&A and Light Leakage Question

[pr0crast1nat0r]

Hi and thanks in advance for responding to this newbie. Below is a pic of a diamond I am interested in for an engagement ring that has a HCA of 1.7. My understanding is that even though the H&A looks good to my inexperienced eye, there seem to be a few areas around the edge especially that show the background (grey). Is this a bad H&A because of that?

Question to the experts: Can you see from this picture whether there is a lot of light leakage? What is your opinion of this stone? (All other C''s and $ aside)

Thanks!

 

[StevL]

Using these photos you(we) can't determine how good or bad the diamond may be. These images only tell part of the story.

To answer your question about certain areas being dark around the edges, this is very normal for H&A diamonds (branded or not). In a firescope this would show as white light, or leakage. You can get H&A diamonds with more or less of this. The Eightstar diamond will not exhibit this.

 

[pr0crast1nat0r]

Hi StevL

Thanks for the reply. So before buying, it would be recommended to do a Firescope or BrillianceScope analysis? The problem with that is, so few stores even know about those tools, forget about even having one onsite. An HCA of 1.7 is also not a clear indication?

Thanks.

 

[Garry H (Cut Nut)]

I suspect this stone has a cheated girdle.
It probably is thicker at the girdle main / bezel junctions and thin at the minor / upper girdle position.
If you wish to buy an Ideal-scope you can check for the leakage Steve refers to, but you can save your money and move on.

 

[pr0crast1nat0r]

Hi Cut Nut,

Thanks for the reply. I have asked for a Sarin report, as this will show whether it
has a cheated girdle, correct? Is there a particular variance in girdle thickness
that would constitute a cheated girdle?

 

[Garry H (Cut Nut)]

Sorry - a normal Sarin will not - we need the full .srn file which contains every facet.
But if you can only get the ordinary data we can model the stone with DiamCalc and see what is going on compared to your H&A's shot - that will probably tell us something.
But it is just easier to have a look with an ideal-scope for upper girdle leakage like this - but the same amount of table leakage may not be present.

 

[pr0crast1nat0r]

Hi,

Cut Nut, thanks for the reply.

The Sarin averages are below. Could one of the experts run this through Diam-Calc to let me know whether I should continue looking at this stone.

As soon as I receive the .srn I will upload it for more specifics.

Diameter = 6.46-6.49 x 4.03mm
Depth = 62.3%
Table = 55.0%
Pavillion Depth = 43%
Pavillion Angel = 40.9
Crown Height = 34.6%
Crown Angle = 34.6
Girdle = 1.0-1.7%
culet = 1.2%

Thank you!

 

[pr0crast1nat0r]

Crown Height = 15.5% (not 34.6----typo)

 

[Garry H (Cut Nut)]

I would ask to see a full Sarin manufacturers report and that will list the girdle bezel minimum and max and the girdle valley min amd max.
I expect the bezel thickness will be thicker on average by more than 1% than the valleys.

 

[pr0crast1nat0r]

Hi Cut Nut,




The Sarin version at this store has does not allow export into .srn. However, here is the girdle profile, that shows only a 0.5% variance. With that amount of variance can you still have a cheated girdle?




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[Garry H (Cut Nut)]

they need to open different parts of the program to show the girdle at various positions - if they can give us the HRD girdle thickness % that would get around it

 

[pr0crast1nat0r]

Hi Cut Nut.




I am amazed at how quickly you respond. I saw that the picture with the girdle graph was not pasted correctly, so here I try again. The store gemologist assures me that it does not have a cheated girdle.




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[pr0crast1nat0r]

Try 3.

 

[robbe]

hi pr0crast1nat0r, i manufacture h&a diamonds(in antwerp-belgium) as well as other cuts, shapes and cutting styles; according to the images you are showing here, i can only tell you that this stone is a very good looking h&a. what cut nut is refering to is possibly a very faint deviation in girdle (i even don't think so but the man doesn't seem to give up...). this very faint deviation (if there) is nothing the human eye can see!!! don't hesitate and go for it especially if you like the stone + if you're having a good price.
if you can clearly see consistent h&a in a nice looking pattern (like this one) + having a cert confirming highest level of polish, symetry & proportions then you've got the right h&a-diamond!
wish you the best, robbe

 

[pr0crast1nat0r]

Hartelijk dank Robbe

 

[robbe]

...this is sometning you want to avoid; the white circle in the table and also those funny looking crabclaws in between every arrow-point... the pic you showed us above is much much better !!! (de groetjes!!!) robbe

 

[Garry H (Cut Nut)]

OK - I checked by adding the depth %'s (the crown height should be 15.5% with that angle and table size - is that correct?)
the stone has a total depth % of 62.2%, and if you add up all the %'s and the average of the girdle you end up with about 60%. Add to this the normal difference between the girdle measurements at the vallley and main bezel junction (+1.7%) and there is about 0.5% of additional girdle in the main junction - so yes the stone is slightly cheated, but not a lot.

Robbe this stone has steeper upper girdle facets - about 2-3 degrees steeper - than you would expect with a diamond with a 34.6 crown angle.
Does it make a difference - yes - but not huge. a stone with a 1% cheated girdle difference suffers big time though.

Do many people know about this effect - probably a few dozen in the trade. Do many care - not even the AGS lab seems to care. GIA might.

 

[Garry H (Cut Nut)]

And btw - if you line up the girdle print out with a ruler on your screen, you can see that every second girdle peak is smaller. That is the difference between the girdles ate the valleys and the main junction.

 

[pr0crast1nat0r]

Thanks for the responses. You mentioned that different labs will have different results for this one. It has a GIA cert that shows:
Polish = Excellent
Symmetry = Excellent
Girdle = Thin to Medium, Faceted
Not sure if that matters. Would GIA provide a stone with EX/EX if it had a cheated girdle?

 

[Garry H (Cut Nut)]

Yes

 

[Richard Sherwood]

bumped for review