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Does my beautiful diamond get a great HCA score, too?

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Dougie

Rough_Rock
Joined
Feb 22, 2003
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16
Dear Garry Holloway:

I just bought a diamond engagement ring for my fiancee, and I think it is very beautiful -- brilliant, and full of fire and scintillation. But because I am not an expert at looking at hundreds of diamonds, it's possible that I just don't know what a truly beautiful diamond looks like. Could you tell me whether my diamond (an AGS Ideal 0 Cut grade) has measurements that you think would qualify it as a beautiful diamond? I thank you so very much for your very informative website, and for your help on this. You provide a great service!

Here's the AGSL DQD info for my diamond:

Round Brilliant
Measurements: 7.49 - 7.55 x 4.53 mm H color VS1 clarity 1.550 carats
Flourescence: Inert

Polish: Ideal
Symmetry: Ideal
Proportions: Ideal

Table: 57 %
Total Depth: 60.2 % Crown Height: 14.9 % Pavilion Depth: 42.7 %
Crown Angle: 34.7 degrees
Pavilion Angle: 40.7 degrees
Girdle: Faceted 0.7 - 1.5 %
Culet: Pointed

Is my diamond as beautiful as I think it is Garry? Thank you for your help!
 

Dougie

Rough_Rock
Joined
Feb 22, 2003
Messages
16
Thanks Garry for your help, and for confirming that the diamond I bought was truly beautiful! Is it possible to elaborate just a little on what you mean when you say it is "a beautiful stone" ? Thanks. Did you use the exact same HCA "calculator" that all visitors to your website can use, or did you use a more advanced "private" version?

Anyway, thanks again!

P.S. I've seen different ranges for the AGS Ideal Proportions CROWN HEIGHT percentage. Some websites say the AGS standard for Crown Height is 15.0 - 16.2 %, while others say the AGS standard is 14.4 - 16.2 %. Which is the correct AGS Ideal range? Thanks Garry.
 

Giangi

Ideal_Rock
Joined
Jan 23, 2003
Messages
2,530
I'm not Garry
but I think I can answer your question...
AGS hasn't a standard for crown height %... They use the crown angle, which should be between 33.7' and 35.8' to receive an AGS 0 rating. If you do a bit of research, you'll discover that crown height is between about 14% and 17%, but again, AGS doesn't use this data...
BTW, your new diamond is beautiful
!!!!!
 

Dougie

Rough_Rock
Joined
Feb 22, 2003
Messages
16
Dear Giangi:

Thanks for the info! I guess that explains the inconsistent ranges seen on the various websites -- I suppose they were all completely wrong in suggesting that AGS had a set range for crown height, as opposed to crown ANGLE. Anyway, thanks.

Oh, and thanks for saying my "new diamond is beautiful." Can you tell me what you based your conclusion on? Were you plugging the figures I gave you into the HCA, or were you using some other system? Thanks Giangi!
 

Dougie

Rough_Rock
Joined
Feb 22, 2003
Messages
16
By the way, when AGS says a girdle should range from thin to slightly thick, what girdle percentage does "thin" range from? And what girdle percentage would be considered "too thin"?
 

Giangi

Ideal_Rock
Joined
Jan 23, 2003
Messages
2,530
If my memory serves me correctly AGS 0 min 0.5% (Thin) max 2.95% (Sl.Thick)...

Be advised that AGS uses the average... This means that if a diamond has '0' crown ht and pavilion and has a 0.0(Ext thin) to 3.4(thick) girdle --which are both outside 0 rating--, but the girdle average is 1.9 (which is AGS 0), then the rating it's 0. It's all about average numbers...
I hope it's clear enough to be understood...
 

Dougie

Rough_Rock
Joined
Feb 22, 2003
Messages
16
Thanks so much Giangi! You really know your diamonds! I noticed that the AGS certificate lists a girdle RANGE of 0.7 to 1.5 %, so perhaps the girdle figure is the one figure that is NOT an average? Although I suppose you're saying that all the other figures (crown and pavilion angles and percentages, as well as total depth and table percentages) are averages.

Could I ask you again Giangi how you concluded that the diamond I bought was "beautiful." I'm just curious.
Thanks!!!
 

Giangi

Ideal_Rock
Joined
Jan 23, 2003
Messages
2,530
Thank you!!!!!

Yes, they list min and max, but they use average...
Why am I saying that your diamond is so beautiful???
Because it's H, which is fine and VS 1, which is beautifully clean. I may add that VS 1s are so boring to look at under a microscope
!
Second, the proportions you stated suggest a beautiful make...
It's OK now??


Enjoy your beautiful new rock
!!!!

Giangi
 

Dougie

Rough_Rock
Joined
Feb 22, 2003
Messages
16
Thanks Giangi! My fiancee IS enjoying it! You're right, I can't find the inclusions even using a 10x loupe. I guess I have to look harder!
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,273
Numbers look good Dougie. Here is a possible simulated IdealScope image of a stone with those dimensions. Please note however that the minor facets can alter the look of the stone from this image and this is only a possibility.

Peace,
Rhino

dougie02is.gif
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,273
And while I'm in a playful mood ... here are 2 other possibilities using the same measurements on the AGS DQD but changing the minor facets.

These differences CAN and DO indeed affect scintillation within the diamond (increasing or decreasing it) and only a qualified gemologist can measure the minor facets as this is not done on most measuring devices. It's safe to say that the stone has good overall brilliancy based on the numbers but to get down to the specifics of how fiery, how scintillating etc. knowing the details on the 40 minor facets is a must.

Hope this helps and most of all ... CONGRATS on your engagement!

Peace,
Rhino

dougie01.gif
 

Lugus

Shiny_Rock
Joined
Jan 17, 2003
Messages
213
Nice work on those pictures Jonathon. It's amazing how much the minor facets really affect light return, yet there is little talk about them. Any theories why this is?
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,273
Yes. Thanks for asking Lugus. One primary reason is because most measuring devices today do not give the measurements on the minor facets including most Sarin and OGI machines.

The most recent updates to their software packages do give star/upper girdle ratios and we have been featuring that data on most of the stones we publish today. Attached to this post is an example of one using the OGI showing a stone with 61% star length (upper girdles being 39% length). I personally LOVE the longer star/lower girdle ratios and prefer them over the shorter star/lg's however BOTH are gorgeous. That is my personal preference though.

While this is helpful information Lugus, knowing the star facet length alone without knowing the lower girdle facet length is almost moot information as the lower girdle measurements are equally if not more crucial because certain star lengths with certain lower girdles produce very pleasing results while other combo's are not so pleasing. For example having long stars by themselves is no guarantee ... however couple those longer stars with the proper lower girdles and BAMMO you have some serious action.
I personally have the means by which to measure both so I am able to conduct studies using the equipment I have to see what combos have what affects in relation to the diamonds light output.

One reason why I beleive there is very little talk about them is because

a. most people can't measure them.
b. if they could it is VERY TIME consuming
c. most people do not have the means to meausure and observe light output to the capacity & quality that we do in our lab.

My converstaion with Dr. Eileen Reinitz, brief with Al Gilbertson (two of the leaders in GIA research on brilliance & fire) proved fruitful as we have both arrived at the same conclusions about the minor facets using different means. They are primarily working with ray trace software and in other studies real diamonds (as published recently in some of the trade journals, Dr. Reinitz even recommended the DiamCalc software for those interested in the research) whily my studies have primarily been with all real diamonds and using the optical devices I have and use in my lab.

Funny thing ... when I first published my page on how to interpret LightScope images I was getting some sharp criticism from certain camps on the forums. Shortly after I was contacted by a scientist within the AGS labs who reads these forums and told me personally "DO NOT BUDGE ONE INCH, what you are saying is RIGHT ON and after future research is published about the minor facets you will be justified." Time has proven my contact right. Now that V-day is over I hope to have more time to finish the page I started on the minor facets as it answers many questions that were also raised in the thread that scorpionrioux started in the HCA/BrillianceScope thread.

Thanks for asking Lugus. Hope that was of some help.

Peace,
Rhino
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,273
oops ... here's the graphic showing the star facet length.

BR100DVVS2GirdFull.gif
 

Dougie

Rough_Rock
Joined
Feb 22, 2003
Messages
16
Hey Rhino, thanks a lot for the simulated Ideal-Scope images of the diamond I bought for my fiancee. That's really cool, and quite interesting. And thanks for the congrats on my engagement!

By the way, will the Ideal-Scope work at all on a diamond that is already mounted in a ring setting -- I've assumed all along that it only works on unmounted diamonds. My fiancee's diamond is mounted in a six-prong platinum setting that lifts the diamond up off the ring, like the Tiffany's style setting. Is there any device -- or other method or clever trick -- I can use on an already mounted diamond to get some idea about the light return characteristics of the diamond?

Thanks!
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,404
Yes you can use the Ideal-Scope on a set stone - there is a page of instructions on the website.

Jonathon Sarins latest software release for Diamension multi lens models measures lower girdle facet length. Sarin already measured star facet length for many years.

Diamonds with cheated girdle effects cause far more problems than the normally encountered range of star and lower girdle facets.
 

Dougie

Rough_Rock
Joined
Feb 22, 2003
Messages
16
Thanks Garry. Could you tell me again how you concluded that the diamond I bought was a "beautiful stone"? Thanks.
 

BetsyA

Rough_Rock
Joined
Feb 21, 2003
Messages
28
Garry,

Could you give me a little information on what cheated girdle effects is? Thanks.



Betsy
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,404
http://www.goodoldgold.com/_60ct_i_si1_h&a.htm

Thick at main facets, thin at minor facet or half facet junctions.

The crown angle is shallower and the minor facets are 5 degrees steeper than they wwould otherwise be. The AGS and GIA measure the girdle thickness in the half facet thin part - so this stone passes as slightly thick, but actually the girdle is 'thick' in 8 places - 5% - not the measurements quoted on the Ogi report.
 

DiehardSearcher

Rough_Rock
Joined
May 27, 2002
Messages
94
Can you explain what the cheated girdle effect negatively impacts?

Is it the inobvious variation in girdle thickness, or the thickness itself causing the problem?
 

Lugus

Shiny_Rock
Joined
Jan 17, 2003
Messages
213
what a great thread. This is probably more than any consumer should know, but I still love reading it


Jonathon, thx for the super information.
 
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