HCA help

[inverse121]

I let my jeweler pick out my stone and I am very happy with the look. I know that is all that matters, but after what I have learned here, I have a question.

Can the HCA be "wrong?"

My paperwork all says AGS Ideal 0, but the HCA does not show it as such.

Depth 62.8%
Table 53%
Crown Angle 34.9*
Crown % 16.4%
Pavilion Angle 41.1*
Pavilion % 43.4%
Culet Pointed

My GIA paperwork says GIA excellent

Depth % 63
Table % 53
Crown Angle 35
Crown Height 16
Pavilion Depth % 43
Girdle Medium
Culet V Small

I guess I didn''t learn enough to understand. That being said, it really looks great, albeit small for this site at .62

 

[Regular Guy]

One thing...review this, and determine...is your AGS0 a newer one, marking AGS0 for light performance?

The author of the HCA tool would tend to suggest AGS0 trumps HCA, and we have seen the unusual HCA 4 here with an AGS 0. But, if the older cert, not so clear.

 

[:)]

Inverse, did your diamond come with BOTH AGS and GIA reports? There are different types of AGS reports, not all are light perfromance based.

That said, what really matters is how it looks to you and your fiancee. If you both love it then don''t get too wrapped up in the numbers.

 

[inverse121]

RG, thanks, I must have missed that in the past. I have the old style cert issued August of 2005. I trusted my jeweler to pick it out for me. She said she would pick the right stone for my ring. She saved me money, too. I would have blindly paid more if she had not been up front an honest. The price was the same as the prices given at any of the reputable online retailers for stones with similar numbers.

I know only looking at the numbers is a mistake. I couldn''t be any happier with the way it came out visually. I just wanted to understand why the HCA didn''t put it in the box.

 

[inverse121]

Yes, it came with both reports, the old style AGS.
Interestingly they differ on some items.
Culet Pointed (AGS) vs Culet V Small (GIA)
Flourescence Negligible (AGS) vs Faint (GIA)

Then I have some "Diamond Grading Report" that I think is just a marketing paper from a GG using a
DC3000 Gran Diamond Colorimeter
Mettler CB203 electronic balance
OGI systems megascope proportion analyzer
GIA diamond lite illumination box
Gem instruments Mark VI gemolite binocular microscope with darkfield illumination
that states the everything the GIA states plus
Brightness EXCELLENT
Fire EXCELLENT
Scintillation EXCELLENT
GIA-EXCELLENT
and the AGS inscription number

Regardless of all the paperwork, I trusted the jeweler and am happy, I posted a pic in the Beverly K thread.

 

[hartfordmd]

I think the "differences" in the certs are just related to semantic (word choice) differences between the 2 labs. Faint and negligible probably describe the same thing, as do pointed and very small. As another example, for polish and symmetry AGS's top grade is "ideal" but GIA's top grade is "excellent." Just a difference in words, not necessarily inconsistencies. Congrats on the stone!!!

 

[phoenixgirl]

It's the higher pavilion angle coupled with the higher crown angle. Each angle individually could be a winner, but they are not as desirable together. If you look at the HCA result box, you'll see that lowering either of them would have pulled you back into the excellent category.

 

[Garry H (Cut Nut)]

it is possible the next release of HCA will move the steep deep boundary to cover stones with these proportions.

But at these proportions the sym and upper and lower facets must be very tight

 

[inverse121]

Phoenixgirl, I did notice that the minute differences in measurement made significant changes. Using the GIA numbers (rounded) vs the AGS numbers or combinations of them can "pull it into the box" also using % vs Angle and an approximation on the Culet for pointed or very small changes things.

Garry, I was hoping you would chime in, yet, I am still a little perplexed.

Do I have this right? The HCA can be used as a tool to narrow the ones choices, but the proof is in the pudding, and sometimes there are stones that do not fall in the boxes can be real performers?

 

[JulieN]

Date: 11/16/2006 7:00:32 AM
Author: inverse121

Do I have this right? The HCA can be used as a tool to narrow the ones choices, but the proof is in the pudding, and sometimes there are stones that do not fall in the boxes can be real performers?

Yes, but HCA is not just performance. There are four factors; one is spread. This stone is small for its weight. If two stones are both nice, but spreads less, you would not choose it.

 

[inverse121]

JulieN. You may have hit the nail on the head as for the reason my jeweler picked this stone. I knew I would learn more. My GF wanted a small stone, set low as she works with her hands. She can have whatever she wants, but I wanted a very particular setting that has a platinum carved band and the stone needed to be approximately .5cts My instructions were to find the best stone for this setting (and preferably the biggest without looking awkward). She said the stone had to be 5.4 or smaller and she had found a perfect .624ct that would fit and "fill up" the mount horizontally and vertically. So I went with it.

I am just amazed at how changing one of the numbers input to HCA by just a tenth can change the location of the X. Sounds like a the HCA could be used for some serious internet marketing by rounding the numbers. Using the following from my GIA, I land dead center in the AGS 0 box.
Depth 63%
Table 53%
Crown Angle 35
Crown Height 16
Pavilion Depth % 43
Culet .4
Using the AGS numbers, I am out on the fringe of the GIA dotted line in the green.
You can see it face up in the Beverly K thread. Here is the side view.