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Does good table/depth automatically means good faceup size?

leecube

Rough_Rock
Joined
Jun 20, 2011
Messages
28
Hello all, I'm a newbie here, so any input would be appreciated. I am currently seeking a yellow diamond cushion and is considering between two, both of which are Cushion Modified Brilliant cuts. Of course, I know there are loads of other information I have to take into consideration, but I'm hoping that this topic can be gear towards the stones' face-up size, aka spread?

2.00ct
7.11 x 6.91 x 4.51
Table 62%
Depth 65.3%

2.30ct
7.56 x 7.51 x 4.83
Table 63%
Depth 64.3%

1) Do you think these face up smaller in their respective carat weight? I've been looking at diamond size charts (are these accurate at all?), and seems like a 2ct cushion should have something like 7.5mm.

2) Based on my limited knowledge, I believe both of these have "good" table and depth percentages for a cushion. For example, none of these are particularly too deep, so how come it is facing up smaller?

3) What is an accurate way to compare face up values between cushions? Do I simply multiple L x W?

4) Does the L/W ratio (whether it is more rectangular or square) affects a cushion's perceived face up size?

Many many thanks in advance for your help!!
 

tyty333

Super_Ideal_Rock
Premium
Joined
Dec 17, 2008
Messages
22,518
Re: Does good table/depth automatically means good faceup si

I'm no colored diamond expert but colored diamonds are cut with a different priority. Besides retaining weight they are also trying
to get the best color they can from stone. I dont think the relationship between carat weight and dimension is an exact science
with colored stones.

Hopefully rockdiamond will chime in and give us his opinion.
 

Stone-cold11

Super_Ideal_Rock
Joined
Sep 9, 2008
Messages
14,069
Re: Does good table/depth automatically means good faceup si

No, depth and table size does not define face up dimension. How high the crown is, is also an important factor. Even that does not completely describe the diamond.
 

RayEarth

Rough_Rock
Joined
Mar 21, 2011
Messages
46
Re: Does good table/depth automatically means good faceup si

I usually avoid x.00ct because the cutter usually compromise on something to get to the "magic mark".
 

oldminer

Ideal_Rock
Trade
Joined
Sep 3, 2000
Messages
6,451
Re: Does good table/depth automatically means good faceup si

Depth Percentage tends to define the overall spread of a diamond, BUT not in every single case. There are princess cut and other fancy shaped diamonds which are in the market that have depth percentage that don't correlate to relative spread exactly as others of the same shape do. This is due to the fact that these stones have a different pavilion configuration than their more common counterparts. Still, the greater the Depth Percentage, the less spready the stone tends to be.
 

leecube

Rough_Rock
Joined
Jun 20, 2011
Messages
28
Re: Does good table/depth automatically means good faceup si

Thanks for your replies. I don't understand then, if table and depth percentages is not a good indicator for a fancy diamond's spread. Then what is?? One only uses the dimensions (length and width)then?

Also, am I crazy, or these two stone's dimensions look small for its size? TIA!
 

Stone-cold11

Super_Ideal_Rock
Joined
Sep 9, 2008
Messages
14,069
Re: Does good table/depth automatically means good faceup si

Length and width is the spread.

Fancy color stones are usually cut deeper to better enhance the color of the stones, which is the selling point and not better light return, better face up dimension, which is the selling point for colorless stone. The chart you are referring to is probably for the colorless stones.
 

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
8,417
Re: Does good table/depth automatically means good faceup si

HI Lee,
Although it might seem like laws of physics ( shallower=more spread) there's a lot of variables that make direct correlation inaccurate.

As has already been mentioned, the cut of Fancy Colored Diamonds is generally designed to increase perceived color.
Having said that, a stone's spread is a tremendously important component of desirability- as is "liveliness"- or sparkle.

I did a little checking on cushions we've had over the years- hopefully this will help.
For example, a 2.30ct cushion we had measured as follows
MEASUREMENTS: 7.81 x 7.36 x 4.52 mm
TOTAL DEPTH: 61.4%
TABLE SIZE: 69%


A 2.21ct cushion
MEASUREMENTS: 7.93 x 7.35 x 4.64 mm
TOTAL DEPTH: 63.1% ( no table size - it was a GIA "color origin" report)
These are comparable in face up to the 2.30 you listed-

Here's a "spready" one- that looked larger than most stones in the same weight range
MEASUREMENTS: 8.20 x 7.30 x 4.24 mm
TOTAL DEPTH: 58.1%
TABLE SIZE: 62%


To select:
1) Ignore ANY chart you find- there's simply no way to accurately chart out measurements in a way that will include all the good ones, and exclude the bad ones- and there'll be a huge amount of stones that some will love, and others won't. Opinion comes into play.
2) find a dealer you are comfortable with, and discuss each stone, and it's particulars.
For example, maybe a slightly stone that has a slightly smaller face up may make up for that with better color or sparkle.
 

leecube

Rough_Rock
Joined
Jun 20, 2011
Messages
28
Re: Does good table/depth automatically means good faceup si

Thanks everyone for your replies, especially to RockDiamond. Because for me, this will be my first diamond purchase, so I'm scrutinizing all the numbers. I guess I have to get it in my head that for color stones, as long as the color is spectacular, I should "let go" some of the other parameters...and this case, settle for a smaller spread. haha...but it is just so hard! Because come on, who doesn't want a stone that faces up big, right? But based on what I'm reading, I should learn to "give up" something in order to gain in color.

To RockDiamond, the 2 stones that you've listed, you said the face up value is comparable to the 2.30ct that I listed. May I ask, are you using the surface are (LxW) as measurements? For example,

Stone #one, 2.30ct cushion : 7.81L x 7.36W = 57.48mm square

Stone #two, 21ct cushion : 7.93L x 7.35W = 58.29mm square

FOR MINE, the 2.30ct cushion : 7.56L x 7.51W = 56.78mm square

The difference is 0.70 - 1.51mm....is that a very small difference? (Sorry, that sounds stupid, but I really don't know in the diamond world, whether that is consider a big or minimal difference.)

MANY MANY THANKS again!
 

NARRISHKEIT

Rough_Rock
Trade
Joined
Jul 20, 2011
Messages
98
Re: Does good table/depth automatically means good faceup si

leecube said:
Thanks everyone for your replies, especially to RockDiamond. Because for me, this will be my first diamond purchase, so I'm scrutinizing all the numbers. I guess I have to get it in my head that for color stones, as long as the color is spectacular, I should "let go" some of the other parameters...and this case, settle for a smaller spread. haha...but it is just so hard! Because come on, who doesn't want a stone that faces up big, right? But based on what I'm reading, I should learn to "give up" something in order to gain in color.

To RockDiamond, the 2 stones that you've listed, you said the face up value is comparable to the 2.30ct that I listed. May I ask, are you using the surface are (LxW) as measurements? For example,

Stone #one, 2.30ct cushion : 7.81L x 7.36W = 57.48mm square

Stone #two, 21ct cushion : 7.93L x 7.35W = 58.29mm square

FOR MINE, the 2.30ct cushion : 7.56L x 7.51W = 56.78mm square

The difference is 0.70 - 1.51mm....is that a very small difference? (Sorry, that sounds stupid, but I really don't know in the diamond world, whether that is consider a big or minimal difference.)

MANY MANY THANKS again!
Unfortunately the calculations you are attempting are inaccurate cushions are not a square and have rounded edges. The error from these edges can be quite severe overestimating the total surface area by as much as 20% so those are not accurate comparisons.

Also nothing is optimized for expensive colored rough, the cutter tries to get the most saturated color, sparkle and spread which are often trade-offs of one another are distant second considerations to saturation of color.
 

TristanC

Brilliant_Rock
Joined
Jun 6, 2011
Messages
995
Re: Does good table/depth automatically means good faceup si

I started in a similar way when i looked for a FCD too. Pursuing ideal model cuts and sizes etc based on guidelines from colourless diamonds. I love solasferas as an example.

I quickly realised that this was an exercise in futility as every single FCD was cut differently.

I think in your quest: colour, and then quality of symmetry and polish would have to be more important than spread and faceup size.

Also various shapes faceup completely differently, and with no standards in cutting for FCDs, you will run into trouble quickly.

Perhaps you'll eventually come around to my way of thinking? Use your eyes to guide you, select a gem you just find beautiful on inspection.

The colour has to be the shade you want (more saturated is more expensive, but not everyone likes every hue), the size has to be approximately large enough for the setting you envisioned. The quality of symmetry or polish is up to your own personal preferences, and then after that try to get as few inclusions as you are comfortable with.

Hard to quantify FCDs really... which is part of the joy of them actually. Every one is unique, so only the most general guidelines apply. I hope you understand what I mean to say. Good luck!
 

oldminer

Ideal_Rock
Trade
Joined
Sep 3, 2000
Messages
6,451
Re: Does good table/depth automatically means good faceup si

Play around with this tool https://www.pricescope.com/tools/aga-diamond-shape-selector and see how the bulge can change apparent size. This is important in fancy shapes since diagonal width is not discussed in most measurements. The visible surface area can be larger with the same depth percentage or it can be smaller. Table size is not very important to visual size.

Due to the laws of physics, and the very consistent nature of the element carbon (diamond), there are some characteristics that are highly consistent with charts and measurements concerning faceted diamonds. There are other characteristics which have common relative effects but are not 100% identical in all cases. Depth percentage on fancy shapes with identical outlines and identical length and width can be useful in comparison of stones for visual size. What happens is that most diamonds are not identically shaped and measurements only go part way to explaining how they look and what weight they are compared to their visual size.

Charts and predictive tools do tell consumers some factual results, but they are not the way to select a final diamond. As screening tools they can be helpful and serve to protect consumers from those who would want to tell tall tales and to make a sale of a possibly less well cut stone. AGS and GIA both use their own charts and predictive tools to make the 000 or EX EX EX grading results that the whole body of consumers relies on. So saying that charts are "useless" is not a helpful response.
 

Rockdiamond

Ideal_Rock
Trade
Joined
Jan 7, 2009
Messages
8,417
Re: Does good table/depth automatically means good faceup si

Oldminer said:
Play around with this tool https://www.pricescope.com/tools/aga-diamond-shape-selector and see how the bulge can change apparent size. This is important in fancy shapes since diagonal width is not discussed in most measurements. The visible surface area can be larger with the same depth percentage or it can be smaller. Table size is not very important to visual size.

Due to the laws of physics, and the very consistent nature of the element carbon (diamond), there are some characteristics that are highly consistent with charts and measurements concerning faceted diamonds. There are other characteristics which have common relative effects but are not 100% identical in all cases. Depth percentage on fancy shapes with identical outlines and identical length and width can be useful in comparison of stones for visual size. What happens is that most diamonds are not identically shaped and measurements only go part way to explaining how they look and what weight they are compared to their visual size.

Charts and predictive tools do tell consumers some factual results, but they are not the way to select a final diamond. As screening tools they can be helpful and serve to protect consumers from those who would want to tell tall tales and to make a sale of a possibly less well cut stone. AGS and GIA both use their own charts and predictive tools to make the 000 or EX EX EX grading results that the whole body of consumers relies on. So saying that charts are "useless" is not a helpful response.
David- the part in red would need to be at the top of any chart designed to help consumers- and it would need to be in red, and large bold print.
The part in blue is one of the biggest reasons.
It takes people's eyes off the correct ball.
If you want to be able to tell the good sellers from the bad ones the charts are of ZERO help- and may indeed make it seem like some sellers who might have different ideas about which is the best cut- VALID ideas- and make them seem like they're trying to pull a fast one when they are not. (ie- "you are showing me this stone, telling me it's well cut, why is it not a 1a on the chart?")
Want to know who might be a bad seller- google them- the chart won't help.
I also do not believe comparing any other "chart" with GIA or AGSL cut grading is a valid comparison.
Again, if we stress to consumers that GIA or AGSL are the final word on diamond grading ( and indeed, they are)- it reinforces the idea that any seller telling folks they have a better system than GIA or AGSL is to be avoided for that reason alone.

With regards to the cut of Fancy Colored Diamonds- Tristan- you mentioned "standards of cutting". Other than GIA/AGSL round cut grading- controversial itself, yet still widely accepted- there really are no widely accepted standards for fancy shapes. Even AGSL fancy shape cut grading has never been widely accepted.

I agree, there are many cutters of Fancy Colored Diamonds putting out makes which are poor.
Having said that- there ARE Fancy Colored Diamonds that are really well cut.
Some cutters are heads and shoulders above others, in terms of quality of cut.
Personally, I'd prefer a really well cut Y-Z instead of an overly deep Fancy Light Yellow. There are cutters that feel the same way.


Leecube- to answer your question: Although other variables do come into play, actual LxW measurements are far more predictive of the size you see in person- but I do agree with NARRISHKEIT that trying to convert these measurements into square footage won't produce meaningful results.

In terms of how a small difference in size will be perceived- that's both a personal issue ( how well you see, what your idea of "big is, etc)- and also the cut , color and "layout" of the stone will also affect that.
In other words- as I mentioned LxW does indeed give a useful idea of size, sometimes we can compare two stones of identical LxW yet they still look different sizes.
I don't mean to confuse you- have you seen the stone in person?
 
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