Diamonds 101...ok just a little scary here...need help on a few key ?''s

[shuston]

Hi gang,
First let me say I like deals..seriously. But I also like quality, both would be great but I don''t want to drop 2 dimes on an engagement ring. That said, I could use your help...

1. AGS, H, VS2, 1.8 ct, polish/symetry/proportions all ''ideal'', fluoresence is negligible, girdle is .8-1%, table is 54%, depth is 62.2%, crown angle is 35% and pavilion angle is 41.2%. Price is $12,555. Good price? Also, is this a good cut or is 54% a little low?

2. Is that a better deal than the following: GIA, H, 1.86 ct, SI-2 (no visible flaw to naked eye), 62.1% depth, 58% table, good polish, very good symetry, no fluoresence...$11K. (no other info available)? Which cut is better, #1 above or #2?

3. What is the absolutely best cut - table, depth, crown angle, pavilion angle, etc....that gives you a great mix of white light and fire? Everybody throws out "ideal" cut but nobody can ever tell me what that means?? You''d think they''d have standards for that type of thing, but what do I know...Oh, and how important are symetry, polish and proportion?

4. Why does nobody every distinguish if a diamond is an H1 vs an H5? Doesn''t this make a difference?

Too much involved here!!! Sheesh, and I thought I was just buying a type of stone...

THANK YOU!

 

[aljdewey]

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On 11/22/2003 1:43:50 AM shuston wrote:

1. AGS, H, VS2, 1.8 ct, polish/symetry/proportions all 'ideal', fluoresence is negligible, girdle is .8-1%, table is 54%, depth is 62.2%, crown angle is 35% and pavilion angle is 41.2%. Price is $12,555. Good price? Also, is this a good cut or is 54% a little low?

************This cut is okay, but it only scores a "good" on fire and scintillation....rates a 3.6 on HCA. The crown/pavil angle combo suggests it might leak light under the table a bit.

2. Is that a better deal than the following: GIA, H, 1.86 ct, SI-2 (no visible flaw to naked eye), 62.1% depth, 58% table, good polish, very good symetry, no fluoresence...$11K. (no other info available)? Which cut is better, #1 above or #2?

************You don't given enough information on #2 to make any comparison....you need crown/pav angles.

3. What is the absolutely best cut - table, depth, crown angle, pavilion angle, etc....that gives you a great mix of white light and fire? Everybody throws out 'ideal' cut but nobody can ever tell me what that means?? You'd think they'd have standards for that type of thing, but what do I know...Oh, and how important are symetry, polish and proportion?

************Actually, we can tell you what that means. You might have the best success staying within these tolerances:

Total depth: 59 - 61.8%
Table: 55 - 56%
Crown angle: 34.3 - 34.8 degrees
Pavilion angle: 40.5 - 40.9 degrees*
Girdle: 1% thin to 1.7% medium, preferably faceted.
Culet: none or pointed (same thing, different lab description)

Polish, symm....etc. .....most people feel okay as long as they are "very good" or better.

4. Why does nobody every distinguish if a diamond is an H1 vs an H5? Doesn't this make a difference?

************No, it doesn't make a difference. Labs don't grade that way.....that kind of distinction comes only from using a colorimeter. Because it doesn't impact price at all, no one uses it.

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[shuston]

Thanks aljdewey. I'll get more info on rock #2. In the meantime could you explain what you mean when you say, "This cut is okay, but it only scores a "good" on fire and scintillation....rates a 3.6 on HCA"....

How are you ranking it on fire and scintillation? Also, what's the HCA ranking? Where can I get access to these rankings?

Thanks.

 

[Colored Gemstone Nut]

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On 11/22/2003 9:10:55 AM shuston wrote:





Thanks aljdewey. I'll get more info on rock #2. In the meantime could you explain what you mean when you say, 'This cut is okay, but it only scores a 'good' on fire and scintillation....rates a 3.6 on HCA'....

How are you ranking it on fire and scintillation? Also, what's the HCA ranking? Where can I get access to these rankings?

Thanks.
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Shuston....

The HCA stands for the Holloway Cut Advisor which was created by Garry Holloway. You can enter the sarin data of any given stone and get a -pre-liminary outlook on whether the diamond you are considering might be a good performer.

Here is the Link....

www.pricescope.com/cutadviser.asp

The system gives generates independent results each of the three categorie (the highest being excellent)

In diamonds the most critical characteristic affecting light return is the crown angle & Pav. angle relationship.

In your stone the diamond is being penalized because of the steep pav. angle.....If you were to trim it down to 40.5 the results are affected dramatically......

Slight variations in the critical angle relationship can make or break a stone as far as being a real top contender...

 

[shuston]

Do you think rock #1 is a good buy at $12,500? I tried getting more info on rock #2 but the jeweler didn't have it on hand...apparently GIA doesn't always provide that info on their cert cards?? (weird)

 

[Rhino]

One reason why Al and myself would councel against the 1st stone is because that particular crown/pavilion/table combo is one that guarantees a lot of light leakage under the table.




Here is a simulated LightScope (or red reflector tech.) image of such a stone. The white under the table is areas of light leakage to demonstrate the point. I have a tutorial on our website that explains how to interpret these kind of images in more depth if you're interested in learning more.




/idealbb/files/35412angles.jpg

Kind regards,

Rhino