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What do y''all think about this one (HCA)?

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Rough_Rock
Joined
Sep 23, 2002
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77
Ran this through the HCA. I'm used to seeing diamonds with smaller tables getting scores like this - but unless I'm doing something wrong, this gets in the "excellent" range. It also scored high on the Brilliance Scope, although I don't have a copy of those results.

1.3C round
VS2
G Color
Diameter: 7.19 mm avg
Depth: 57.9%
Crown Angle: 33.8 degrees or 12.5%
Pavil Angle: 40.4 degrees or 42.5%
Table Avg. Size 62.7%
Cutlet: Very Small


The measurements above came from a Sarin machine.
 

JayTee

Rough_Rock
Joined
Dec 6, 2002
Messages
62
This looks like another example of a large table stone which still scores well on the HCA due to the compensation by the shallower depth and smaller crown angle.
Take a look at recent posts about Large Table stones as well as archived posts about Mara's stone.
 

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Rough_Rock
Joined
Sep 23, 2002
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77
So what does this mean? Is this a matter of experts that disagree, i.e., HCA versus AGS "ideal" cut ranges?

Let me say that the above stone is a G color - but when I compared it to 3 "G" GIA stones, I could *easily* tell that it was whiter (you know, the good ol' folded white paper color comparison instrument :) ) Either this one is whiter than a GIA "G," or the the GIA stones are not G. I could even tell a difference amongst the G color GIA stones. Someone is obviously wrong.

Doesn't give me much faith in the value of a GIA cert, or any other, for that matter! So subjective! I'm going crazy!!!!!!
 

JayTee

Rough_Rock
Joined
Dec 6, 2002
Messages
62
Yes, there is disagreement. Many online posters have mentioned that the AGS Ideal range is too loose and includes possibilities which have a lot of light leakage.
Also, check the Garry Holloway's tutorial that explains the research behind the HCA scoring system especially this link here. This will hopefully answer some of your questions about the differences between the HCA and AGS0.

As to the stone's color, keep in mind that grading is subjective, even with the GIA. I understand that color grading is done by comparing the stone to a range of master color-defined stones, some people may see a G where others see a H color (or a F color for that matter). Also, fluorescence plays a part in the color as well. Since you did not mention any fluoresence in your stone's information, I can only guess but faint or medium fluoresence tends to make stones look whiter.

The two certs that people place the most stock in (again, general consensus of opinion) are ones from GIA and AGS. Yes, the grading can be subjective and there are differences from time to time, but that just goes with the nature of what you're buying. If you purchased a CD of music, you would take any "grade" of it with a grain of salt, because it depends on the person listening to it.

The bottom line of course is how you personally feel about your stone. If you noticed that this particular stone was more yellow than other G color stones, then it sounds like you would prefer a whiter-colored stone, and might want to consider some F color stones or other 'G's which are whiter to your observation.

Hope this helps.
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
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31,003
Yes definitely read my posts about larger tabled stones. We got a larger tabled stone, similar specs...61.4% table, 56.9% depth, but our crown angle was much shallower, yours is more inline with what it should be.. your pav is a little shallower, but it still seems in the okay range from what I have read. So this sounds fine from my non-expert point of view.

When you mention that this G stone seems whiter, I have the same thing with my G stone.I compared my G stone to an E stone and they looked *the same*. I think that maybe it is because (and please, experts weigh in)...my larger tabled stone is very very brilliant, with great light return. I feel as though it looks much whiter than other stones, in most lights. It does not return as much FIRE inside of the stone (rainbows inside), but rather returns lots of SPARKLES back to the naked eye. I think this might make the stone seem whiter than a G.

Thoughts?

If this rates well on HCA..then it is probably because its a very brilliant diamond. Maybe someone can do a diamcalc or gem advisor pic for you to see for yourself how it rates.
 

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Rough_Rock
Joined
Sep 23, 2002
Messages
77
Thanks for your help! Actually, this "G" is much whiter than the others I saw.

This stone was extremely nice...although I have to say that I haven't really seen one that has been a dog (albeit lower clarities, lower colors, and worse HCA scores). Guess that goes with being an untrained observer. I was extremely surprised (and disappointed) to see the discernible color variations between the several GIA stones (all graded G).

While I'm on the topic, the gemologist I'm dealing with showed me a Brilliance Scope scan on a particular "Hearts and Arrows" cut that rated much lower than the so-called "non-ideal" cut stone I'm considering....and it was about 15% more costly.

There are so many parameters to this study. So many variables.
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
Actually pretty interesting, ran the #'s through the HCA. I noticed that the pre-existing specs in the HCA showed that the crown angle of 33.8 is not that far off from the 34.5 that it starts you with, and the pav angle of 40.4 is only .1 off the pre-existing 40.5 that the HCA starts with. So from what I can TELL, the crown and pav angles are great in conjunction with the table and depth for this stone. The HCA results were great, giving you a TIC still as opposed to a BIC which is what I have. a TIC is more along the lines of a true ideal as opposed to a BIC which has more 'brilliance' than a good 'mix' of both brilliance and fire.

Would love to see a diamcalc/gem advisor pic on this stone. I bet it's pretty brilliant. Was checking out my file again as compared to some of the ones that have been posted lately and I am proud to say that my larger tabled, AGS 7 non ideal stone looks pretty darn good!
 

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Rough_Rock
Joined
Sep 23, 2002
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Mara, thank you for sharing your advice and diamond specs. When you compared your stone to other G colored stones, did you compare it by flipping it (face down) and comparing the pavilion colors from the side? This is how I was able to discern the color differences easily. Face up, it was difficult. Then again, it was difficult for me to tell the difference between an E and an H in the face up position.
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
For the most part we just viewed them face up, and side by side face up. We viewed their pavilions side by side in different tweezers, but not side by side on the white paper. They literally looked the same. Plus with the brilliance and sparkles you have going on, half the time its hard to see ANYTHING but that. But I was very happy that I couldn't see a difference between the E and G. This diamond is very white though, it reminds me somewhat of a crystal, so clear.
 

JayTee

Rough_Rock
Joined
Dec 6, 2002
Messages
62
A jeweler also explained to me that it is easier to see color grade differences through the pavilion (when the stone is sitting upside-down on its table). If you flip it over, you can still see the color difference, but it is much more subtle.
 

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Rough_Rock
Joined
Sep 23, 2002
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77
Yes, those little suckers are dazzling. What do you think about the spread on the stone I've looked at above?
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
I would estimate that the spread give you a diamond look similar to a diamond of around 1.35-1.4c. Mine is a 1.23c and the spread is .13, looking like a 1.35: diameter is 7.15-7.19. Yours is 7.19 diameter and a 1.3c. Would think from the rough #'s that the spread is adding about .5-.10 for you. Anyone know for sure?
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,274
What are you minimum/maximum diameter measurements and total depth measurement in millimeters?
 

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Rough_Rock
Joined
Sep 23, 2002
Messages
77
Rhino,

According to the Sarin data, the min is 7.15 mm and max is 7.27 mm.

The depth is 4.16 mm.

Thanks for your help.
 

RockDoc

Ideal_Rock
Joined
Aug 15, 2000
Messages
2,509
Do you really want to know about the characteristics of this diamond?

Get an expert to give you an opinion based on seeing and testing it.


No one can evaluate diamonds by proportion comparison.

I have seen diamonds with the same proportions look vastly different in person.

Buying putting 100% reliance in opinion that is not based on seeing and testing the stone, is rolling the dice.

Get it checked

Rockdoc
 

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Rough_Rock
Joined
Sep 23, 2002
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I am getting it checked by an independent (heeding advice I've seen on this forum many times). My appointment is not yet set, however, and I want to learn as much as possible in the interim. I have an engineering mind - anything scientific interests me. So, I want to receive as much input as possible.
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,274
I'd have to ditto Bill. The symmetry sounds like it may be wacky and while the stone does have some serious spread the numbers you gave will not allow itself to be input into the DiamCalc software. I could show you possible examples of FireScope images of what you may have but the minor facets can change the whole story and make the diamond appear totally different than the software could represent. I like to fool around with the software and it is great but when I make virtual models for my clients it is based upon actual measurements of the stone which go beyond the information you'll get on a Sarin or even a MegaScope report.

If I get a chance I'll try and show you some hypothetical possibilities but first I gotta finish alot of work related stuff. If you send it to an appraiser like Bill you won't be working with hypothetical possibilities though ... you'll be working with facts and that of course is the best.

Bill ... how do you like my new little pic icon? :)

Peace,
Rhino
 

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Rough_Rock
Joined
Sep 23, 2002
Messages
77
Thanks for the offer. I'd love to see some hypotheticals when you get a chance. Not sure why the numbers are whacky on the Sarin results. Maybe the Sarin operator was enjoying a few cocktails whilst measuring. If he/she was, I want that job!

On the cert, it reads differently: 7.16 X 7.22 X 4.18. Maybe these figures will be allowable by the software?
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,623
You have got lots of good advice here from pros and professional shoppers alike.

Yes this stone makes it as one of my big spread BIC / TIC border line stones.
You are getting about .1mm extra, or .10cts - I suspect the girdle is a little thick? You did not post that data.
Certainly worth getting a second opinion on the stone.
It will not look as good from 12 inches as it will from 15 inches. Symmetry might be an issue.
If the picture comes out - you may have to click the icons? -you will see what it should look like in the Ideal-Scope.

www.ideal-scope.com will explain more.

RT Dec2002.jpg
 

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Rough_Rock
Joined
Sep 23, 2002
Messages
77
Thanks CutNut! Is symmetry an issue if the dimensions turn out to be 7.16 X 7.22 X 4.18 (as the cert says) as opposed to the wider Sarin data at the top of this thread?

The girdle is thin.
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
CutNut--what do you mean when you say it will not look as good from 12 inches as it will 15? You mean in up-close viewing of the stone in person?

Interesting picture..the arrows look very prominent, but it looks as though there is a bit of a lack of dark reds in the ideal-scope image. The reds look bright or pale, but no darks. Or it could just be my monitor!
 
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