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ideal cut, but not ideal size?

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diamluvr

Rough_Rock
Joined
Jun 12, 2003
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16
Hi everyone I''m new here!
I hope someone can enlighten me on this. I don''t have the GIA report (it''s at my fiances), but I do know that my 1.35 ct. RB stone is cut within the ideal proportions. Anyway, my diamond''s diameter is listed as an average of 7.1 mm, but I''ve been viewing different charts that state it should actually be about a 7.23 mm.. why is that? I know it''s not a huge difference, but that one-tenth mm is driving me crazy!
Thanks!
 

dimonbob

Brilliant_Rock
Trade
Joined
Dec 12, 2000
Messages
670
Hi diamluvr, welcome to the forum.

To answer your question correctly, we would need a lot more information on your diamond and what charts you are referring to.

One explination is, and you say it is cut within ideal proportions, the three parts of the total depth are not set numbers but are a range of numbers. If the pavilion depth, the girdle thickness and the crown height were all at the maximum edge of the ideal numbers than the diameter would be smaller. Do you know how small 1/10 of a mm is? A sheet of copy paper is thicker. Do not worry about it!
 

niceice

Brilliant_Rock
Joined
Jan 29, 2003
Messages
1,792

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On 6/12/2003 10:45
4 PM dimonbob wrote:

Do you know how small 1/10 of a mm is? A sheet of copy paper is thicker. Do not worry about it!

----------------

We'll second that! If the diamond you have has ideal proportions, you've won 90% of the battle... Beyond that you can begin to drive yourself nuts! Hardly a day goes by where we don't find ourselves chuckling because some poor fellow is trying to find the perfect Tolkowsky cut diamond... 34.5 degree crown angle / 40.75 degree pavilion angle when the poor guy doesn't realize that he's never going to find that 40.75 degree crown angle simply because the machines that measure the diamonds round that measurement off... If the average of the eight pavilion main facets that create the pavilion angle measurement displayed on the Sarin or OGI results is 40.74 degrees then the machine is going to round off the pavilion angle to 40.7 degrees and if it actually measured 40.75 degrees the machine is going to round it off to 40.8 degrees... And this poor guy has been looking for the "perfect" diamond for the past six months and who knows how many wonderful diamonds he passed up simply because he didn't understand part of a concept that may have been poorly explained on a web site somewhere or in a book... Assuming that your diamond doesn't have a total depth of 63.5% or something off the charts like that, we wouldn't stay up at night worrying about it too much... But there is nothing wrong with doing a little homework to set your mind at ease... Get the measurements for the diamond including the crown and pavilion angles and put them up for all to see and we'll all be happy to toss in our two cents for what it may be worth
 

diamluvr

Rough_Rock
Joined
Jun 12, 2003
Messages
16
OKay, thanks everyone, I'll try to sneak a peek at the GIA again. (He likes to hide it from me because he knows how I am about diamonds)
BTW, does the GIA actually list the crown and pavillion measurements? I don't recall that off-hand..
 

niceice

Brilliant_Rock
Joined
Jan 29, 2003
Messages
1,792
Unfortunately the GIA does not list the crown and pavilion angle measurements on their lab reports, they only provide the minimum and maximum measurements for the outside diameter; the millimeter depth of the diamond; the total depth percent; the table diameter percent and the girdle thickness... But if you're lucky, there might be a Sarin / OGI proportions analysis sticker on the GIA report if it was purchased from one of the more reputable internet dealers...
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
-----------
Anyway, my diamond's diameter is listed as an
average of 7.1 mm, but I've been viewing different
charts that state it should actually be about a 7.23
mm.
----------

Hi DiamLuvr. Don't worry, be happy. The DiamCalc's default "1A" profile shows a diameter measurement of 7.18 for a 1.35 carat stone, which is only .08 mm different from your measurement.
 

diamluvr

Rough_Rock
Joined
Jun 12, 2003
Messages
16
Thanks Rich! Would you be able to tell me the diameter of an ideal-cut 1.6 ct. RB stone? That was the runner-up and I'd like to know if there'd be a substantial difference. Thanks again!
 

niceice

Brilliant_Rock
Joined
Jan 29, 2003
Messages
1,792

----------------
On 6/15/2003 8:50
3 AM diamluvr wrote:
Would you be able to tell me the diameter of an ideal-cut 1.6 ct. RB stone
----------------
Here are the measurements for an ideal cut, 1.60 carat, F, VS-2 that we have listed on our site...

Measurements: 7.59 - 7.61 x 4.59 mm
Total Depth: 60.4%
Table Diameter: 57%
Crown Angle: 34.1 degrees
Pavilion Angle: 40.7 degrees
Girdle: thin to medium, faceted
Culet: none
 
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