Poor HCA Score

[Diamonds102]

My diamond scored a 3.5 on the HCA system. How less "brilliant" a diamond is it? I had it appraised but forgot to ask him about this and he never mentioned that it looked less brilliant than any other diamonds. It is the only thing holding me back from purchasing.
FYI it is a G color VS1 1.8ct.

I have read all the posts about HCA and can't come to a conclusion.
Would a layman notice the difference between a HCA score less than 2 and my 3.5?

Help...

 

[yssie]

numbers? got any photos?

 

[slg47]

do you have the GIA report number?

 

[diamondseeker2006]

Can you tell us the numbers from the report? Is it GIA? I am curious as to what the cut grade is.

Most diamonds are pretty. My "good" cut original diamond is pretty and sparkles. But knowing what I know now, I'd never buy anything but GIA Excellent or AGS Ideal cut. Why spend that much money and not get a stone that is well cut?

 

[Diamonds102]

Shape: Round Brilliant
Carat Weight: 1.87
Color: G
Clarity: Vs1
Cut Grade: Excellent
Table %: 57.00
Depth %: 62.29
Girdle: Medium to Slightly Thick
Culet: N
Polish: Excellent
Symmetry: Excellent
Fluorescence: None
Measurements: 7.84-7.89x4.90
Length/Width ratio: 1.01

 

[slg47]

do you have the crown/pavilion angles (or the GIA report number?)

 

[Diamonds102]

http://www.solomonbrothers.com/Dialog.aspx?ImageUrl=http://Diamonds.net/UF/8258/Certs/RB10722.jpg

 

[slg47]

HCA score is lower due to steep pavilion angle, but the longer lower girdle facets may compensate for this somewhat. Do you see a dark ring underneath the table? also, you could put a colored piece of paper under the diamond and see if you can see it through the diamond, that would be where light is leaking.

 

[Diamonds102]

Why do you think the appraiser didn't notice this and say anything about a steep pavillion angle?

 

[slg47]

the pav is not WAY WAY steep, but HCA will penalize anything over 41.0 I think. Anyway, it is hard to judge by the numbers and I am no expert for sure. You have a GIA Ex and it is better than 99% of the diamonds out there!

ETA remember HCA only takes into account 4 numbers...it is a useful weeding tool but definitely doesn't tell the whole story.

 

[yssie]

ditto slg re. HCA not telling the full story


not sure what that scan is from but pav 40.5-41.8 seems like an overly large range even accounting for scanner error to me..

 

[Karl_K]

ditto slg re. HCA not telling the full story


not sure what that scan is from but pav 40.5-41.8 seems like an overly large range even accounting for scanner error to me..

gold star on both accounts Yssie.
the stone was tilted on the sarin scanner, probably a piece of dust under it.

If the optical symmetry is better than decent and the angles fairly tight to each other it has excellent potential by the numbers.
The down side is it is slightly smaller than some diamonds of the same weight.
Many Tiffany diamonds are in the this range, it is a bit different look than a diamond closer to tolk but it is one some experts like and sell.
If you look hard enough with one eye closed you might possibly see a tiny hint of a gray ring under the table but then again you may not.
With both eyes open it should not be visible.

The appraiser maybe didn't comment because it is the same range as some premium brands use so it didn't seem unusual to him/her.

 

[John P]

Karl gave a thorough overview.

I would only add this:

You have a GIA Ex and it is better than 99% of the diamonds out there!

For the record, 85% of configurations normally produced by the world's large manufacturers will score either GIA EX or VG.

 

[Garry H (Cut Nut)]

Sergey points out that HCA is too harsh because we have 2 eyes and 41.2 / 35 can have bright zones for alternate eyes in the leakage zones.
HCA can be too harsh.
It would not be possible to get Ex for GIA sym with the scan data reported.

 

[Diamonds102]

Sergey points out that HCA is too harsh because we have 2 eyes and 41.2 / 35 can have bright zones for alternate eyes in the leakage zones.
HCA can be too harsh.
It would not be possible to get Ex for GIA sym with the scan data reported.

So does that mean the Ex is incorrect or the scan data is incorrect? And should I buy the diamond if either of them are incorrect?

 

[yssie]

Sergey points out that HCA is too harsh because we have 2 eyes and 41.2 / 35 can have bright zones for alternate eyes in the leakage zones.
HCA can be too harsh.
It would not be possible to get Ex for GIA sym with the scan data reported.

So does that mean the Ex is incorrect or the scan data is incorrect? And should I buy the diamond if either of them are incorrect?

safe assumption that scan is incorrect.
Which means the only good info you have to go on is the GIA report
Which leads us back to the fact that the numbers on the report are averaged, then rounded, and you don't know what information is lost in the averaging & rounding w/o a professional inspection/look in-person yourself/photos & images