shape
carat
color
clarity

How can you tell...?

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omieluv

Ideal_Rock
Joined
Feb 28, 2007
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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!
 
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.
 
spread is determined by the dimensions (lxw) in mm. so....compare the measurements.
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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...
 
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.
 
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.
 
several charts exist as well. This one is in FAQs.
 
Thanks everyone for your responses. I will take time this weekend to digest the info!!
 
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