HCA Result for a 60/60

[magpie2]

Hi All,

I've got a 3ct RB coming from JA soon with more or less 60/60 proportions. The specs are T61 CA 33 PA 40.9 D 59.8. It's destined for a pendant.
From a long time lurking on this very helpful forum I've pretty much got the impression that such a stone would have 'Less Fire' but 'More Brightness'. On the basis that assumption is correct, I was surprised to see, when I checked it using HCA, the result was 1.6 EX overall, with EX for Spread and Fire but just VG for light return and scintillation.
Interestingly too, it was shown marginally outside the GIA EX cut parameters, though, if I'm reading the chart correctly, it fell within the AGS 0 range.
The diamond is IGI graded EX for cut, and I'm pretty sure when I was trawling through BN looking at all the certs, I've seen GIA stones with the same (within roundings) specs receiving EX cut grades.
I've attached the IS for it. It's overlaid on the diamond and it's just a screenshot, so a little rough, but I know people like to look at pics on the forum!
I'd therefore be grateful if someone could help me understand the apparent contradiction in Fire / Light Return ratings from what I was expecting and also let me know if the cut would actually be GIA EX.
Thanks in advance for any contributions.

 

[diamondsR4eVR]

Interesting post. I’d be interested to know too as I have a 60/60 that scored under 2 in HCA and under certain lighting it’s a disco ball of fire and other times it looks very bright as normally expected.
How did you find the AGS 0 range info? Search bar?

 

[magpie2]

Hi,
Thanks for your response. I got the grading data from the HCA. Between the results / diamond specs and the diamond search section, there's a line saying 'Click her to see possible GIA / AGS grades'.

 

[diamondsR4eVR]

I think I did that before but did not understand the AGS scoring.

 

[Karl_K]

When preferring to show brightness or fire it is not how awesome the fire can be at its best its how often over all possible lighting conditions it shows fire vs brightness.
Lets say for sake of super simplification there are 1000 possible light conditions. The one favoring fire might show fire in 200 of those vs 150 for the other.

 

[magpie2]

Thanks for that Karl. Can I just clarify - are you saying that in the right lighting environment a 60/60 can have as much fire as a super ideal, it's just there are more environments where the ideal will demonstrate the property? Because I've always had the impression a smaller table meant more of the other crown facets as a % and therefore more fire vs a 60/60 period.

 

[magpie2]

I think I did that before but did not understand the AGS scoring.

I think you've just got to go by the key at the bottom of the chart showing white/grey and black lines representing the different 'scoring' areas as opposed to different colours for the GIA grades.

 

[Karl_K]

Thanks for that Karl. Can I just clarify - are you saying that in the right lighting environment a 60/60 can have as much fire as a super ideal, it's just there are more environments where the ideal will demonstrate the property?

Yes. Some it could have more.

Because I've always had the impression a smaller table meant more of the other crown facets as a % and therefore more fire vs a 60/60 period.

The ratio of different sizes of fire potential is different yes.
Which is what changes the response in different lighting conditions.
This is what makes it very complex.
Which is more fire? 5 big flashes or 10 smaller flashes?
Larger flashes are easier to see but there are more small flashes.

 

[magpie2]

That's very interesting, and I must say rather surprising given a lot of comments and indeed videos I've seen here before. It does however explain the 'Excellent for Fire' rating.
I'm still at a bit of a loss though as to why light return, which I thought would be the outstanding metric for a diamond with these proportions, only comes in at VG on HCA, especially when it appears to be a potential AGS0 make. The IS image also looked very promising for light return - to this seriously untrained eye at least.
Incidentally, I'd love to hear your thoughts on the IS in general if you could spare the time.