GIA triple ex but 4.2 HCA score

[watz]

Hi everyone

I have just recently bought a round brilliant loose diamond to put on an engagement ring once I find the right design . I was pretty happy with the stone as on paper it seemed like a good buy with a triple ex score on the GIA cert and a excellent cut based on the AGS proportion chart. However after running the specs into HCA program it has given the diamond a 4.2 score (Good). I would like to ask if anyone can shed some light into why this diamond may have a low HCA score and with the attributes listed below, what maybe some of the negative/positive aspects of this diamond? I have read on a few sites about the HCA being biased towards certain attributes but i would just like to know other peoples opinions with the specs of this particular diamond.

From looking at other diamond specs i have noticed that the crown height is quite low and the pavilion angle is pretty steep. However i am not sure if these are negative aspects of this diamond as a whole.

I have seen the diamond with my eyes however I have never been great at differentiating diamonds with my eyes and to be honest I could barely notice the differences on all the diamonds that have been shown to me. My partner however has much better eyes then i do and may notice much more. I wish i could bring her to see the diamond prior but then it wouldn't be surprise!

Measurements 7.28 - 7.34 x 4.37
Carat - 1.4
Colour - E
Clarity - IF
CUT - Excellent
Polish - Excellent
Symmetry - None
Fluorescence - None

Table - 59%
Crown height - 12.5%
Pavilion Depth - 44.5%
Total Depth - 59.8%
Crown Angle - 31.5
Pavilion Angle - 41.8
Lower girdle / half facet length - 80%
Girdle Thickness - 3%
Star length - 45%
Cutlet - None

Thanks

 

[MissGotRocks]

This stone falls into the 60/60 camp - table and depth both close to 60. Nothing wrong with that - just a different flavor of stone. It is the somewhat shallow crown angle and steeper pavilion angle that take a ding on the HCA. You'd be recommended to find a stone with a crown angle more in the range of 34-35 and a pavilion angle more like 40.6-40.9 for a more ideal cut.

However, if you like the stone and are pleased with it, then so be it. There are better cut stones to be had. A trade off might be the E color and IF clarity. I personally would not pay for either of those things - I'd prefer a G-H stone in the VS1-SI1 clarity range. You'd get a larger stone and or a better cut for about the same money.

 

[Diamond_Hawk]

Hello Watz,

MissGotRocks is on point.

There are many 60/60 diamonds which will perform on the HCA as well as “Ideal/Tolkowsky” diamonds. However the span of GIA EX proportions run outside of top HCA scores. The reason this diamond is being penalized is the very steep pavilion angle.

While the HCA score in and of itself is not going to be a perfect predictor of performance I’d say the angle combos make for such a shallow crown and steep pavilion that it will not have some of the qualities of more balanced diamonds. This does not mean, however, that the stone is a dud.  Many people like (or prefer) the way a 60/60 performs.  There are scientific methods to evaluate light performance (ASET and Idealscope pictures among others) but the final determination must be made by seeing the stone in person in multiple lighting environments. If you are still in the ‘return window’ on the diamond and want to know more about the way it performs, you can purchase an Idealscope or ASET viewer and look at it yourself since you have the stone in hand. 

E color and IF clarity are really “going for it” in terms of value and quality. My suggestion would be to get to the highest level you can in the cut-quality area as well (understanding GIA EX is very wide compared to the stricter color and clarity areas). The choice is personal, of course. The ones who need to love the diamond are you and the ultimate wearer.

 

[ebadevil]

hey, I just purchased a 60/60 diamond myself

here is something that might help you:
https://www.pricescope.com/wiki/diamonds/60-60-proportioned-diamond

it gives you a good look at 60/60 diamonds with different pavilion angles... as you can see, it starts becoming messy after 41 degrees...

based on the research that I've done, 41.2 is the upper edge of an acceptable pavilion angle for a 60/60 diamond... ideally I think you want 40.8 but 40.6 or 41 works too. if you look on the HCA, to make a 31.5 crown angle work, you really gotta be dead on there in the 40.8-41 pavilion range... 41.8 will be far too steep

 

[watz]

Thanks for your help everyone, I'll have a look to see if i can buy a ASET in Australia and ill try to post a photo of the diamond to get further feedback.

 

[Gypsy]

Read advixe posted here; [URL='https://www.pricescope.com/community/threads/triple-ex-gia-with-fair-hca.204914/']https://www.pricescope.com/community/threads/triple-ex-gia-with-fair-hca.204914/[/URL]