how much stock should i put into the 65/65 rule?

[prufrock69]

Hi, I''m purchasing a princess cut diamond: 1.01 carat, vs2, F, polish: VG and symmetry: good, with a table of 78% and a depth of 71%. I was pretty excited about it, it looks fabulous with a lot of fire. I ran this question by some guy (forget his name) that told me I shouldn''t purchase because of the 65/65 rule, which is I''m assuming 65 table and 65 depth. Is this a widely accepted rule or is this just his opinion on the matter? I''m getting the diamond for 4,000 which I thought was a great deal, but I''m having my doubts now based on what this gentleman said. Is he correct?

Thanks!

 

[moremoremore]

Freddie is wrong. Wrong wrong wrong. While your table seems a bit large, if you love it and it's got lots of fire and you are paying a fair price- well then, there is your answer. Even when the numbers are "perfect"....a stone could still be visually unappealing. You are lucky you found one that you like! :0

 

[valeria101]

Is this the only princess cut you got to see?

It is hard to judge without reference what the respective 'numbers' deliver in person. Not too many diamonds would be blatantly ugly, it is just that some happen to look better than others.

These being said, I have a hard time believing in any rule of thumb, and the simpleer, the worse.

Along the same lines, there is a 60-60 rule for round cuts and it is by no means complete. Of course, 65-65 would definitely not be better for a round cut than 60-60, but more precise rules are readily in place to describe what a diamonds shows up like in terms of brilliance. Nothing like this has been devised for princess cuts...

Now... the first 65% (depth) definitely has a point - a stone would get to look a tad bigger at this lower depth than the usual over 70%. The next 65% (table size) begs a question: what is that good for? It definitely does not pin down the geometry of the stone to determine its optics (brilliance, light return or what not). A number for pavilion height would say a bit more to justify the set of numbers. It would be best to actually have some qualification of the stone's light return, since it is not feasible to get to compare lots of stones in person.

However, both the specs and the price of your stone spell "fine" (based on THESE ranking rules) - and if you know you like it and do not care to know whether much better is out there, this is it. I would not discredit the approach at all: it is very unlikely that you would find anyone to ever critique the stone for it's light return in person. There are just not many enough princess cuts made to achieve top brilliance...

Now, you may wander why is all that table better than the 65%-65% rule. Well, for once the ranges are more reasonable and make a good survey of what professionals would think of any princess cut. There is a detailed explanation of what those numbers stand for, but as far as I understant they firstly make a 5min summary of lots of hands-on experience.

 

[Hest88]

There is no accepted rule for princesses, the way the older 60/60 rule worked for RB. If that were the case, I would think we would have seen a lot more 65/65 princesses!

 

[valeria101]

Some cared to measure how much light a princess cut delivers. mostly for the purpose to present stones online. If the respective techie details are not attractive to you, at least the resulting experiments make a good case that any rule about what set of numbers 'work' for a princess cut, is definitely not going to be that simple...


Here's one example LINK and ANOTHER...