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How Much Can Number Crunching Tell You About A Diamond?


Mainer
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In looking at two diamonds of  close  to the  same ct wt does  the relationship of the diameter of the diamond to the depth, make a difference when comparing the look of a diamond?    Is it possible for a diamond of a greater ct wt have a "smaller"  look than diamond of similar or bigger  ct wt.  

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Ignoring serious outliers, depth percentage doesn't really tell you all that much.  The problem is that total depth is the sum of the crown, girdle and pavilion.  Exactly how that is made up makes all the difference.  If you're going to be looking at numbers, the angles are a much better place to be.

 

For the most part, visible 'size' means face up surface area.  There's a loose relationship between girdle diameter and weight but no, it's not direct.  Thick girdles, for example, add a lot of weight without adding diameter. 

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Yes. Totally. For 4 categories of reasons:

 

Weight is proportional to volume, so (with some adjustments for shape etc.), to the product l x w x d. Increase d, and l x w will need to decrease if weight is to remain constant. What you "see" once the stone is set is l x w.

 

Cut quality has an important effect on perceived size: a stone that is brighter will look larger; a stone that is uniformly brighter (with no large contrasting areas) will look larger; a stone that is more symmetrically patterned may also appear larger.

 

A stone that is lighter in colour will generally look larger - though this is not particularly true within the D-Z colour range, but definitely true as colour saturation increases and tone gets darker (e.g. in brown, blue or green gemstones).

 

Finally, shape and cutting style can have a big influence: just look to round vs. princess cuts: for any given weight, the round will face significantly bigger (as long as both stones are cut decently). But that's an entirely different discussion.

 

ETA - seen Neil's comment, it may seem that we are in disagreement. I don't think we are: Neil is getting into the specific of a two stone comparison; I am talking of varying one factor at a time, keeping everything else as constant as can be. In a sense, Neil is answering (closer to) the first formulation of your question (does the relationship of the diameter of the diamond to the depth, make a difference when comparing the look of a diamond?); I am answering the second (Is it possible for a diamond of a greater ct wt have a "smaller" look than diamond of similar or bigger ct wt?).

Edited by davidelevi
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If diamond size were measured in an intuitive way, size would have a unit that looks like bling per sq. mm., not weight.  That gets complicated.  “Damn girl, that's a big diamondâ€, isn't referring to weight after all.  Increasing bling (which mostly has to do with cut) would increase that, as would increasing face up surface area.  The problem here is that bling has no scale.  It includes element of light return, how even it is across the surface, and even issues like the direction of viewing and the light sources.  Taste is a big player.  That's why weight is the standard.  It's easy to measure and the units are well understood. 

 

My answer had to do with surface area.  Davide's had to do with bling.  It's two different approaches to the same question, but the question isn't as easy as it seems.

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