How is it a diamond can look bigger than it really is?

[cute330xigrl]

I''ve seen a few posts about diamonds appearing bigger face up... like a 1ct has the same dimensions as lets say a 1.2? Is this b/c the stone is on the shallow side? Wish I could find a post so I can quote it, but can''t find ''em.

Thanks
Chris

 

[Patty]

Yes, it's because diamonds are sold by weight, not measurements.

Just like not all 120 pound women look alike...some area taller, shorter, top heavy, bottom heavy, etc.

So an ideal cut diamond that weighs one carat should measure about 6.5 mms across. But if it's cut deep, it will measure smaller across the top. If it's cut shallow, it will measure bigger across the top. But put it on a scale, and it will weigh one carat.

 

[ForteKitty]

Take a ball of play-doh that measures an inch in diameter. Now smash it flat. It still weighs the same as before, but is now much wider!

 

[Lord Summerisle]

yeah.

i''m not that well up on the correct maths of the proportions... but yes.

if you have a 1ct RB with 60% depth and a 1.1ctRB with say 65% depth - (i think) the 1ct would appear larger as the 1.1 has more weight hidden in its extra depth.

I could be way off in that respect... but bascially if you had 2 diamonds which are identical in everything but depth... then the one with lower depth % will appear larger... as more weight is in the width rather than the depth

 

[cute330xigrl]

With you all so far.... so what would be the cutting point in getting a more shallow stone? (For the purposes of this thread, we''ll just discuss a 1ct.)

If it''s shallow, lite escapes correct? So is it safe to say that something like a lightscope analysis will show a poor performing stone?

 

[Lord Summerisle]

to answers your questions...

No and Yes.

if the angles are correct - then a shallow stone can return just as much light as a one in the ideal range. and yes a lightscope (i assume you mean something like the ideal scope) will show how much and where the stone leaks.

say a stone 57% depth, 57% 28° crown and 41.4° pav would be much shallower than most ideal cuts.. but would still maintain ex light return (at least according to the HCA graph)

 

[cute330xigrl]

very very interesting. I''m in the market for a set of earrings.. want to buy .8x tcw ... just trying to have a more comprehensive understanding for my search. thank you! thank you all!

 

[windy1365]

Patty - that is a great analogy!!

 

[Patty]

Date: 2/25/2005 10

1:51 PM
Author: windy1365
Patty - that is a great analogy!!

Thank you windy!

I like the smooshed clay analogy too!