observers head causing dark center

[slippy1]

Can someone think of a reason why when observing two stones, side by side, only one would show a dark center under the table due to the observers head blocking light? Perhpas a shallow cut would prevent the second one from showing it?

I guess what I am asking is, why dont all diamonds have this "problem" (if i can call it that).

 

[Garry H (Cut Nut)]

I have done a good simple explanation of why shallow and very deep diamonds do this - it is in one of the newsletters (about 003 or 004 I think) at www.ideal-scope.com

You will see the link at the top of the page.

 

[slippy1]

That was a good read. Thanks.