Total amount of white light returned to the eye from the gem material as the result of internal and external reflections. The major factors that affect the amount of brilliancy in a gem are refractive index, proportions, polish and transparency.
The amount of light the eye views from the stone as a result of the facets and gridle.
The total amount of light reflected from both the interior and exterior surfaces of a gemstone. The amount of brilliancy also depends on the cutting, transparency, facet angles, proportions and polish.