Help, Why a H&A scores lower on HCA than Regular Diamond

[nowhereman17]

Hi Everyone,

I got the Crown and Pavillion angles from BlueNile and I''m comparing two diamonds in about the same price range.

One is a Hearts and Arrows (specs below) and scores 2.4 on the HCA (thanks pricescope)

The other is a regular diamond from bluenile (see specs below) and scores 0.8 on the HCA! (Excellent in all categories except VG in Spread)

Why is this? Shouldn''t a H&A diamond beat the regular on these performances?

Or am I missing something with regards to what makes an H&A so good.

H&A diamond

Shape BR
Color Grade E
Clarity Grade VVS2
Weight 0.772
Measurments 5.94 - 5.96 x 3.62 mm
Proportions
Depth 60.8%
Table 57%
Girdle 1.0-1.7
Culet PT
Crown Angle 35.200
Pavilion Angle 40.900
Polish IDEAL
Symmetry IDEAL
Fluorescence N
$4,235.96

Bluenile Regular Diamond
Carat weight: 0.80
Cut: Ideal
Color: E
Clarity: VS2
Depth %: 61.2%
Table %: 56%
Crown - 34.1
Pavillion - 40.7
Symmetry: Excellent
Polish: Excellent
Girdle: Medium, faceted
Culet: None
Fluorescence: None
Measurements: 5.98x6.04x3.68 mm
$4,246.00

What do you think of the BN stone? The size and Depth/Table all seem to be better in the Blue Nile (clarity and polish differences are minimal). Why go with the H&A?

Thanks,

Dave

 

[nicknomo]

H&A has little to do with crown and pavillion angles (which is what the HCA uses). H&A is a matter of symmetry and cutting technique... It doesn't guarentee superior proportions...

 

[quaeritur]

I wouldn't go with this particular H&A over the BN stone. And in all fairness, the BN stone looks really good. H&A occurs when facets are aligned just so. Unfortunately, the alignment can work sometimes, even when other factors are not ideal. This particular stone is a "steep and deep" combo. With a rather steep crown like this one, I'd want the pavilion to be <40.8. If you play with these #s on the HCA you'll see what I mean. In this case, with the 40.9 pavilion angle, you're going to have a stone that leaks a bit of light under the table. The HCA takes this into account, but current AGS "ideal cut" standards are not tight enough to reflect this particular unfortunate combination as less-than-ideal. You can read more about this here.

As for the second stone, it may in fact display a great H&A pattern. I really like the #s on it. I recently purchased a BN stone that I'm thrilled with, and it did turn out to be an H&A. The only thing to note about BN is that they tend to be a little pricier than some of the other excellent vendors around here, but if they have the right stone, it might be worth the extra couple of hundred to get it there.

Good luck, and kudos on doing your homework with these choices!

 

[sheckrock]

where is the H&A from? It is my understanding that, just because it says "H&A" doesn't mean that the hearts and arrows are cut perfectly. I've no doubt that there are hearts and arrows, though, the way that they are cut makes a difference. This is probably what is effecting the HCA grade.

I will refer you to this webpage just to see what I mean, I don't know much about the store, I just found this good explaination on a search.

http://www.whiteflash.com/diamond-education/visible_perfection.aspx

shecky

 

[sheckrock]

See, check out these hearts


Disclaimer:

images @whiteflash.com

 

[sheckrock]

and now these


Disclaimer:

images are @whiteflash.com

 

[quaeritur]

Yes, Shecky, but those images in and of themselves don't necessarily tell you a whole lot about the performance (light return and scintillation) of a diamond. There are amazing non H&A diamonds out there. And there are H&A duds as well.

More important in determining the performance, barring seeing the stones in person, is the combination of crown and pavilion angles.

 

[sheckrock]

I agree with quaeritur. I just wanted to illustrate that not all "H&A" have really nice "H&A".

shecky

 

[noobie]

quaeritur (does that stand for anything BTW?) gave you a good explanation. I like the specs on the BN stone better as well. Being an H&A does not necessarily mean good performance.

 

[quaeritur]

----------------
On 8/6/2004 4:34:38 PM noobie wrote:


quaeritur (does that stand for anything BTW?) ...
----------------

It's Latin for "one asks" or "one questions"... seemed appropriate with all the questions I had for PS when I joined... and still do!

 

[noobie]

----------------
On 8/6/2004 4:37:26 PM quaeritur wrote:






It's Latin for 'one asks' or 'one questions'... seemed appropriate with all the questions I had for PS when I joined... and still do!

----------------

Ahh thanks, I was going to use "Inonothing" for mine as in I Know Nothing

 

[Rhino]

Actually ... considering the 2 stones you list the first may be more beautiful in softer light conditions while the 2nd stone may be more beautiful in direct light conditions. Do not underestimate the importance of superior optical symmetry when it comes to the appearance of a diamond. IMO I would look for a stone that will display the best optics no matter what light condition you bring it into. That would be an H&A cut to a very cherry set of proportions, better than listed above.




Peace,

 

[noobie]

There you go an expert opinion. I knew I should have stuck with inonothing.

 

[quaeritur]

LOL!

 

[Rhino]

----------------
On 8/6/2004 5:37:06 PM noobie wrote:







There you go an expert opinion. I knew I should have stuck with inonothing.

----------------

Hey... your opinion is highly valued bossman. What is inonothing?

 

[Rhino]

Woops... ok... just got it. Hehe...

 

[quaeritur]

Rhino-

Just for the record, I'm not discounting the importance of optical symmetry. I'm just suggesting that this BN stone may not only be a good performer, it may actually also have the optical symmetry going for it. Impossible to tell without more info, but I also wouldn't discount it as an option.

I think this stone on your site is a good example of what I'm talking about. And I'd still rather have the good angles, even if it isn't with perfect H&A, than perfect H&A in a less complementary set of angles. That might just be my personal preference though!

 

[Rhino]

I hear ya loud and clear. Yea... more info would be useful for sure.

 

[Lynn B]

Rhino,

I have noticed that you have mentioned this before in other various threads... what do you personally consider to be "cherry" proportions... and why?

Thank you very much!

Lynn

 

[kevinng]

On the side... my girlfriend's father just bought her a 3 stone ring. They are tiny little diamonds and the ring cost less than $900, but what struck me was the amount of fire it has in soft light. I did not have any of my scopes with me, but it was really interesting to see the fire coming out of this cheap little thing.

If you look at it with the naked eye, the symmetry is obviously very very bad. However, looking at it from a distance, the ring is still quite a pretty little thing.

Tomorrow, I will try to see it in daylight... that is, if she wears it.

A good diamond must perform in all lighting conditions. This ring looks a little leaky with my naked eye. So, I don't think it will look good in daylight.

I have one of Rhino's diamonds... and I must say that it is stunningly white in daylight, while it has lots of fire in soft light. A very nice balance indeed.