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Questioning My Purchase


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Im in need of a second opinion. I just got a J SI2 Triple Excellent GIA rated stone for my engagement ring upgrade. It is really beautiful and faces up white but I've been spooked by the HCA analysys.


Here are the specs:


Price $8400

Shape RBC

Carat 1.56

Color/Clarity J/SI2

Depth 62.4%

Table 57%

Crown angle 34.0

Crown height 14.5%

Pavilion angle 41.4

Pavillion depth 44.0%

Culet None

Fluor None


How can a diamond be Excellent across all GIA standards and BOMB the HCA test? Should I be worried?


Thank you in advance!!!

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Hum. Complicated answer to an apparently simple question.


1) When GIA created their cut grading system, they did a lot of research, involving tens of thousands of diamonds and millions of individual stone viewings by thousands of people, including cutters, retailers, consumers and non-commercial experts. They came up with a very broad definition of "excellent" - too broad, some would say - that allows for different looks, including the one like your stone's, with a relatively steep pavilion angle. GIA say that their reason for including them is that enough people in their research liked them; GIA's detractors say that GIA bowed to industry pressure, since those cut proportions retain more weight out of the rough than other "less controversial" ones (pavilion angle below 41°).


2) When Garry Holloway came up with the HCA (a good 6 years before GIA's cut grade, BTW), he worked largely through simulation/ray tracing, and using his own aesthetic preferences as a guide; aesthetic preferences that do not include stones like yours, since he felt they were (in simulation) coming up as less bright than others. Garry doesn't have to contend with industry pressure - certainly not to the extent of GIA - but is only one person and he worked on the basis of relatively few direct observations and a lot of simulations (and he never intended the HCA to be a selection tool, meaning something to be used to test stones you could see, BTW).


Hence the low HCA score while GIA says it's OK. I could go on and expand on this (and specifically why I tend to trust GIA more than the HCA), but since it has already been done better than I could ever do it, here's the link: http://www.goodoldgold.com/Technologies/AConsumersGuidetotheHCA/


At the end of the day the best test is in your first line: "It is really beautiful". If you like it, what do you care what a piece of 2001 software written by Garry Holloway "thinks" about a simulation that has approximately some of the same proportion parameters as your diamond?


If you really feel you owe it to yourself to check, then do so in the only reliable, empirical way: compare your diamond to others. If you take it to jewellers that don't know you well, warn them that you want to bring another diamond into their store - some may politely refuse the challenge, but better to not enter the store than to exit it accompanied by two burly police officers and an accusation of attempted theft.

Edited by davidelevi
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The salient point is that you really like your diamond.


If you like your diamond, you can keep it. Really.


The HCA factors the averages of 17 of the 58 facets that comprise the round brilliant diamond shape:



8 Crown facets

8 Pavilion facets


The facet angle and size of the Crown bezel facets, upper halve girdle facets, the pavilion girdle halve facts_their length and slope; all of which critically impact a diamonds light refraction; i.e.; brightness, dispersion (aka prismatic light), and scintillation (aka sparkle) are not measured.


Thus, unfortunately, many beautiful diamonds with HCA scores just beyond the 2 cut off point have never found a happy hand and home. In recent years, the focus of the HCA has changed from a pick to a reject tool which perhaps has mitigated the orphanage of some diamonds.


Of interest is that GIA does not use the HCA in their Cut grading system.


Davide offers you a good suggestion; you can visit neighboring jewelers and do a visual comparison.

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Thank you both so much. That is a lot of really good information. I did go back to jeweler and the pulled some diamonds that did pass the HCA test (2.5 ish) and for the life of us we could not see a difference. Mine scored a 4.7 which just really freaked me out. But seeing the better HCA scored diamonds and how similar they look to mine does help.

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Thanks for sharing, Newbie.


Your experience may just lead to the repatriation of many fine looking diamonds that now never see the light of day.

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I went through the same thing and looked at 5 diamonds, all GIA excellent.  I chose one in the middle of HCA scores, but only because that diamond looked better to me.  Ultimately, I realized I was worrying about nothing and any of the 5 diamonds I looked at would have been great.  The differences were very, very minor and might have even been imagined by my untrained eye.  If you love the diamond, don't look back!

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Thank you all for being so helpful and kind!! I went to the "other" diamond forum first (PS) and was shocked that everyone immediately told me to return it. I've already fallen in love with this diamond and it sparkles beautifully right up there with the "HCA approved" diamonds that I saw. I'll probably look at a few more since I'm in my return window anyway but I'm 99% sure I'm keeping my lovely diamond. :)

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Si2j here is another story to make you feel better.


I bought a very beautiful stone, GIA triple excellent that scored 2.6 on HCA. It is really beautiful. People comment on it often when they see it. I didn't know about the HCA when I bought it.


A while later I also bought another Diamond for a pendant. This time I knew about HCA so this stone was a triple excellent, 1.1 HCA. The second stone is very very nice but in my opinion the first stone is much more fiery and much nicer. There is just something a bit more magic about the first stone. My best friend whose stone is also a triple excellent, 1.8 HCA prefers my 2.6 HCA to her own stone. She's always whining that my stone is sparklier even after we scrub down both rings.


You love what you love! Enjoy your ring!

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Thank you mellowyellow! :)


Thought I'd post pictures for you all. As you can see...I tried to snap pics in lots of different lightings! Top left is full on sunlight...top right in my car on a sunny day (not driving! ;)  ) ...bottom ones on a diffused lighting/overcast day. Bottom left you can start to see the "J" showing...but I don't mind. It's still incredibly white in most all angles and lightings.


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Thanks for the photos. Particularly the last one, despite the potentially unflattering light, looks great.


BTW - do you know why the "car photo" (top right in your first four) looks darker than the others, even though there is a lot of light? The answer is "because the diamond is reflecting the sky" - which is also why it has a blue tinge (possibly further enhanced by the car's glass also being green/blue tinted). This is something that can be apparent in real life too: a well cut diamond will often look darker outside than inside.

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