teh 20% rule or something? is it true?

[enibas]

if you have two diamonds of the exact same quality (CUT, color, clarity) -- they will look the same "size" to the naked eye as long as the heavier one is no more than 20% larger than the smaller one...this has been paraphrased, but true or false?

 

[Garry H (Cut Nut)]

A larger diamond will look larger.

How exact can 2 cuts be. I have seen very close, but never exactly the same.

 

[mike04456]

Sounds like some kind of promotional tactic to me...

In reality, you're never going get two identical diamonds. Like fingerprints and snowflakes, no two are ever exactly the same. Even two stones cut from the same rough can look dramatically different.

 

[Richard Sherwood]

I would have to answer "false".

I think the average person could easily spot a 20% difference in carat weight.

A 1.00 versus a 1.20, for example. Pretty easy to see. You're talking an approximate 6.5 mm spread versus a 6.9 mm spread. The eye and the brain, a duo of magnificent measuring instruments, can easily pick up a 4/10th's millimeter difference in spread.

Most experienced diamond people could spot a 1/10th mm difference in spread.

Rich, GG
Sarasota Gemological Laboratory