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omieluv

Ideal_Rock
Joined
Feb 28, 2007
Messages
2,146
Here is a newbie question. How can you tell from a diamond''s measurements how will it will "face-up" as compared to other diamonds? I am not saying that the spread of the diamond is most important to me, but if all else is being close to equal concerning optimal proportions, cut and color, I would want to go with the diamond with the best spread. I want to start practicing, so when the time is right, I will be able to pick out a great stone. Thanks!
 

boston_jeff

Brilliant_Rock
Joined
Jan 30, 2007
Messages
623
If it is a round, use the HCA tool on Pricescope.

You should also look to see if there might be "hidden weight," e.g., how deep the stone is and if it has a very/extremely think girdle.
 

belle

Super_Ideal_Rock
Joined
Nov 19, 2004
Messages
10,285
spread is determined by the dimensions (lxw) in mm. so....compare the measurements.
 

kev_800

Shiny_Rock
Joined
Jan 27, 2007
Messages
122
Also, when people say a diamond ''faces up'' larger sometimes they''re referring to the phenomenon of a smaller, more well cut diamond appearing larger than a smaller, poorly cut diamond. When a diamond is well cut, it reflects light from the very edge to the very edge, all the way around. Thus, the diamond appears larger than a diamond that is poorly cut and only reflects light out of the center portion of the diamond.

I dont know if that helps...
 

Regular Guy

Ideal_Rock
Joined
Jul 6, 2004
Messages
5,951
Note also, the column specifically labelled "spread," on the in-house set of options displayed on this board, is designed to include some calculation to that effect for you.
 

starryeyed

Ideal_Rock
Joined
Nov 6, 2006
Messages
2,398
Hi Omieluv. Perhaps this thread will help you: Carat Weight Calc from Measurements

For an ideal cut Round Brilliant (RB), the formula is: diameter * diameter * depth *0.0062 = carat weight

If you know the carat weight of the stone, but not the depth %, you could make an assumption and back-solve. For example, if a stone is cut to a Tolkowsky depth of 59.3%, then:

depth = 0.593 * diameter, and therefore

diameter^3 * 0.593 * 0.0062 = carat weight

If you are looking at a 1-carat stone and want to determine if it "faces-up" the same as a Tolkowsky with 59.3% depth, just back-solve:

diameter = {1 carat/(0.593 * 0.0062)}^(1/3)
diameter = 6.5 mm

If the diameter is greater than 6.5 mm, you know it faces up bigger, i.e. - has a larger spread. If the diameter is less than 6.5 mm, it faces up smaller, i.e. - has a smaller spread.

If the stone has a larger depth %, you can see that the diameter for the same carat weight will be smaller. Hope this helps.
 

Regular Guy

Ideal_Rock
Joined
Jul 6, 2004
Messages
5,951
several charts exist as well. This one is in FAQs.
 

omieluv

Ideal_Rock
Joined
Feb 28, 2007
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2,146
Thanks everyone for your responses. I will take time this weekend to digest the info!!
 
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