Carat Weight

[Humasight]

Thank you for the opportunity to use this forum once more time!
My oval cut pink diamond weight more than my 0.75 ct. oval cut white diamond. Both have the same measurements (7x5 mm). Do Colored diamonds have different carat chart than white diamonds? The pink weighs 0.98ct.

 

[sledge]

No.

Your diamonds are cut differently. The heavier diamond will be deeper. So far you listed the length and width but no depth.

Carat weight uses a calculation that is dependent on depth.

 

[Humasight]

No.

Your diamonds are cut differently. The heavier diamond will be deeper. So far you listed the length and width but no depth.

Carat weight uses a calculation that is dependent on depth.

Thank you for the reply!
Okay I'll list the depth. What's the carat weight for a 15x12x8 oval cut diamond?

 

[diamondseeker2006]

Um, weight is weight. You can't calculate weight from diameter and depth measurements. You maybe can approximate, but that's it.

Colored gems/diamonds are often cut deeper to enhance color. The color is the primary factor whereas with colorless diamonds, cut (light return) is the primary factor.

 

[msop04]

Um, weight is weight. You can't calculate weight from diameter and depth measurements. You maybe can approximate, but that's it.

Colored gems/diamonds are often cut deeper to enhance color. The color is the primary factor whereas with colorless diamonds, cut (light return) is the primary factor.

This. You absolutely cannot calculate the carat weight of a stone based on its measurements (dimensions)... gotta put that thing on a scale. Our eyes cannot see weight - only size.

 

[cflutist]

Here is the weight estimation formula for rounds and ovals. For slightly thick or thicker girdles there is a weight adjustment based on girdle thickness and diameter (another chart).

 

[sledge]

Thank you @cflutist. I've been busy today and haven't had a chance to respond.

While I agree putting a stone on a scale will give you an exact weight, using the formulas based on length, width and depth will give you a close approximation.

Furthermore, the fact a colored stone is cut different than a colorless stone affects depth, which in return affects carat weight. If both stones were cut the same and consequently had the same L, W & D dimensions then the weights would basically be the same, regardless of color.

So yes, dimensions do determine weight but only when looked at as a whole.

 

[tyty333]

No.

Your diamonds are cut differently. The heavier diamond will be deeper. So far you listed the length and width but no depth.

Carat weight uses a calculation that is dependent on depth.

I think you and the others are not talking the same thing. You are talking about an estimation or approximation where depth would need to be known.
They (the others) are talking the exact weight of the stone. I think you meant approximate "carat weight uses a calculation that is dependent on
depth." So you are both right just not speaking the same language!

 

[mrs-b]

I can't tell you for sure what your diamond weighs...but I'd sure love to see it! That is one huge sparkly, by any estimation!

 

[sledge]

I think you and the others are not talking the same thing. You are talking about an estimation or approximation where depth would need to be known.
They (the others) are talking the exact weight of the stone. I think you meant approximate "carat weight uses a calculation that is dependent on
depth." So you are both right just not speaking the same language!

I agree that we aren't speaking the same language. Yes, the only way to get an EXACT weight is put each stone on a scale. Using a formula will only give us an APPROXIMATE weight. I did not, and still have not, said that I believe a calculated formula weight will be as accurate as putting a stone on a set of scales. If that happened, it would be coincidental at best.

However, the formula method should get us very close. More importantly is if we look at the how the formula works, we see the most logical reason to explain the difference is the depths are not identical. Furthermore, we can conclude the depths are different because the crown angle, pavilion angle and girdle thickness are different between the stones, which all directly affect the total depth.

I was being brief in my initial response, so while the L/W/D dimensions do indeed explain weight difference, apparently I failed to do a sufficient job of explaining in detail that caused confusion. For that I am sorry but hope this further clarifies my thought process.


Example:
We have two stones. Both measure 6.87 x 5.10mm in L & W, respectively. Stone A has a depth of 62.9%, or 3.21mm. Stone B has a depth of 61%, or 3.11mm. Both girdles are identical.

Stone A:

• Average diameter = (6.87mm + 5.10mm) / 2 = 5.985mm
• 5.985mm^2 x 3.21mm x 0.0062 = 0.712894118, or 0.713 carat
• Actual weight (as measured by scale) = 0.72 carat
• https://www.jamesallen.com/loose-diamonds/oval-cut/0.72-carat-e-color-i1-clarity-sku-5630686

Stone B:

• Average diameter = (6.87mm + 5.10mm) / 2 = 5.985mm
• 5.985mm^2 x 3.11mm x 0.0062 = 0.6905685578, or 0.691 carat
• Actual weight (as measured by scale) = Unknown as this is a fictitious example, but assume will be reasonably close to 0.691 carats
  

 

[cflutist]

@sledge

Since you enjoy math, this chart shows the weight estimation adjustments to be used in the formula for RB diamonds when the girdle is slightly thick or greater.

 

[Humasight]

Please help! My mother's old mine cut diamond dropped out of the setting. She does not recall the carat weight of the diamond. However, she remembered the whole ring weighed 5.2grams on a scale. I told her to weigh the setting and she did. The setting weighs 3.2grams. So the diamond is 2 grams around 10cts. She needs the carat weight in order to do a report.

 

[sledge]

You're da bomb @cflutist. Thank you!

Enjoyment of math is relative. I like the results it produces. I remember quite distinctly cussing the last time I did a 3 page hand-written calculus problem.

When I have a few minutes to kill, I might build an Excel sheet that makes it even easier.