Newbie question about HCA :)

[TabitaW]

Hi all,

I am a newbie here, have been lurking here for a while but now I would like to get some of you're experts help please (if anyone would bother for my little diamond ). I have a 0.40 carat RB which I am very pleased with (it's a real sparky one!). I bought it a while ago and it's the first loose diamond I bought on my own. (But certainly not the last. ). It's a GIA certified diamond so I have the specifications, thats why I now want your help on how to read the HCA results I got. (Thanks to Pricscope I now know there are lots of more to find out!)
I got a quite good result on the HCA (better than expected), but I'm not sure I got it right, mostly since the HCA says "The result is for a symmetrical diamond with a medium girdle and very good polish". My diamond have a girdle "Thin to thick, 4%" so I don't know if that's bad?
Here are the specs for my stone if you could help me:
RB 0.40 ct
Color: J
SI 1 (a feather inclusion, totally eyeclean, I can hardly see it with a loupe but I'm not an expert)
4.69-4.74 x 2.94 mm
Polish: Very Good
Symmetry: Very Good
Cut: Very Good
Depht: 62.2%
Table: 57%
Crown Angle: 34.0 (degrees)
Crown Height: 14.5%
Pavillion Angle: 41.0 (degrees)
Pavillion Depht: 43.5 %
Girdle: Thin to thick, 4%
Star Length: 50%
Lower Half: 75 %
Culet: None
Fluoresence: None

The HCA score I got was "1.5 - Excellent" - but I'm very uncertain regarding the girdle. When I compared the specs with the AGS "ideal cut" It's very close to be an ideal cut also. That's why I am a bit confused if I got something wrong since GIA are rating it as "Very Good" and not "Excellent". Could you please also help me to point out what it is that makes it that way I would be very glad. (Please remember I'm a newbie... ) Many thanks in advance!

 

[John P]

Welcome to Pricescope Tabita.

Your diamond has a nice HCA score. No worries on the comments. Your girdle runs to "Thick" - which is the reason for the VG cut grade by the way - but it's only holding a bit of extra weight and will not impact the visual performance. The symmetry comment is there because diamonds cut with sub-par 3D optical precision may have reduced performance qualities. Although we'd need more information to make that assessment about your specific diamond, I wouldn't worry about it unless the diamond looks sleepy or does not pop.

More about the HCA:

It's a great tool which uses a few critical data points to predict - in general terms - how light is likely to be returned (or not returned) to the viewer's eye. It's relevant but also kind of like using someone's age, height and weight to predict - in general terms - that "This person can dunk a basketball" or "This person cannot dunk a basketball."

Diamonds scoring under 2.0 are those Garry Holloway has observed to be strong performers, all things being equal. But, again, this is a general result. If the diamond has sub-par cut-precision, if the minor facets are out of bounds, if there is deleterious painting or digging, if there are inclusions clouding the performance (etc.), the result may not be valid.

 

[TabitaW]

Thanks for your kind help!

I'm not worried about my diamond, I just got a little confused since I bought it on the GIA-specs and didn't have the highest expectations (I got it quite cheap and we all know we usually get what we pay for... ) and when I got it and saw it IRL I was surprised (in a good way). The jeweller that helped me to set it in my weddingring wouldn't beleive I got it for what I paid (he actually were a little "disappointed" because he couldn't find diamonds that cheap). Anyway, it sparkle a LOT and got lots of "fire" and seems very bright (I had lower expectations on it being graded J too) so I decided to try and find out why, try to learn what to look for next time (this .40 ct is just temporary until I have saved enough to get something in the 1 ct range ). And I really got stuck on this HCA-thing, realizing I have lot to learn, but heavy knowledge is no burden!