What is ''windowing''?

[wolftress]

I keep hearing the term ''windowing'' used to describe inferior diamonds and other precious stones. I know it refers to the cut, but what is it specifically? How does it affect the light performance of a stone?

 

[Skippy123]

This thread may help. https://www.pricescope.com/community/threads/what-is-windowing-on-the-ends-of-an-elongated-stone.44152/
another one https://www.pricescope.com/community/threads/windowing-need-answers-asap.25588/

 

[wolftress]

Thank you, Skippy! The coloured gem thread was really helpful