HCA vg-vg-vg VS ex-ex-ex

[optimizedlife]

Would this difference matter? My criteria, because I'm a perfectionist has been 3xEx for light/fire/scintillation.

If one of those is VG instead of Excellent, would that EVER be realistically noticable? I'm guessing not.

 

[drk14]

I assume that by "vg-vg-vg" and "ex-ex-ex" you are referring to GIA grades on cut, polish and symmetry. FYI, even GIA ex-ex-ex is not sufficient to guarantee the best light/fire/scintillation. The "HCA" in yout topic title doesn't make sense in this context, but maybe that was a typo.

You will need to look at the diamond's specific proportion and angles, at the very least, and to make a more informed decision you will at least need an IdealScope image.

If you're a perfectionist, as you say, then you should carefully read all of the excellent information available under the "Knowledge" tab at the top of the page, especially the "Advanced Tutorial" section.

Good luck!

 

[diamondseeker2006]

No, he is referring to the HCA. It provides scoring of light return, fire, and scintillation (and spread, but that is generally always very good on ideal cut stones).

My view is that if I am spending thousands of dollars, I am going to be aiming for three excellents in those areas. It doesn't guarantee a perfect stone, as you know, but from there you can compare others with excellent scores using idealscope images and magnified images of the stones.

 

[optimizedlife]

Oh I've read everything in Knowledge I'm an engineer and a perfectionist.

I was just kind of asking from a 'meta' point of view if there would realistically be any visible light return differences.

 

[optimizedlife]

Oops completely forgot to refer to your main thing. diamondseeker is correct, that was not in reference to GIA or grading, but with regards to the HCA return values for Fire, Scintillation, and Light Return.

eg:
Factor Grade
Light Return Excellent
Fire Excellent
Scintillation Excellent
Spread or diameter for weight Excellent
Total Visual Performance 0.4 - Excellent
within TIC range

 

[drk14]

ok I stand corrected

I assume that HCA<2 always corresponds ex-ex-ex-ex, then, in which case I would agree with diamondseeker 2006 (if I was in the market for an RB).

Still probably a good idea to get IS images for final selection.

 

[optimizedlife]

You can have an HCA < 2 and not all EX.

And yes of course to images/etc

 

[Tourmaline]

I assume that HCA<2 always corresponds ex-ex-ex....

Nope.

 

[drk14]

Nope.

LOL, ok then. So, going by the commonly repeated heuristic that HCA>2 is useful as a rejection tool but for HCA<2, HCA is not to be used a selection tool, wouldn't the answer to OP's original question be that having one or more non-Excellent HCA grades may not matter, as long as HCA<=2?

 

[Gypsy]

Nope.

LOL, ok then. So, going by the commonly repeated heuristic that HCA>2 is useful as a rejection tool but for HCA<2, HCA is not to be used a selection tool, wouldn't the answer to OP's original question be that having one or more non-Excellent HCA grades may not matter, as long as HCA<=2?

Yes.

 

[Garry H (Cut Nut)]

What are the parameters of the stone, and what is its symmetry grade from a lab, or does it have H&A's and I will enter it into the new Android app.

 

[optimizedlife]

Thanks, although this wasn't about a specific stone, just a general question.

What Android app?