Judging The Brilliance Of Coloured Stones

[pwsg07]

How to judge the brilliance of the coloured stones? I have read Secrets of the Gem Trade: The connoisseur's Guide to Precious Gemstones. I still don't understand how to judge the brilliance. In a stone, there are reflections with brighter colour and darker colour but not black. Does the darker colour but not black reflections consider brilliance as well? How to judge the round brilliant shape stone? Thank you.

 

[normanintheskywithsapphires]

To me brilliancy is the amount of light thrown back from the stone. If for example has a window that does not reflect any light and makes 50% of the stone. Then the rest 50% would be the maximum brilliancy.
As for black, I never consider it a color but the lack of light so it can't be brilliancy, right?

 

[chrono]

Brilliancy is how well it sparkles. In short, you want to see a lot of brightness in the stone and it must be almost evenly spread across the crown of the stone.

 

[MichaelDavid]

Hopefully I can post this link here, this is a great article that may help the poster out.

http://www.ruby-sapphire.com/brilliance_windows_extinction.htm

Keep in mind with color stones the stones actual color is the most important factor, which is certainly associated with the cut. Also note cuts like a step cut will never have much brilliance so a stones value wouldn't really be affected by its level of brilliance.