Brilliance – The Gemmologist Handbook

The sparkling, shimmering diamond is due to the effect of brilliance, which is a luminous phenomenon in the form of sparkling reflections. 

What is brilliance?

Brilliance is the fact that the lower part of a polished stone functions as a mirror. The rays of light falling on the surface of the stone refract into its depths and fall on the base. Reflecting off the base, they return to the face of the stone, where they have refracted again. By rotating the polished stone, the light effects change, giving the impression of shimmering reflections. 
The shimmering effect of the stone is greater the more precisely it is cut. A properly selected and executed cut should help to achieve the best optical effects with maximum economy of raw material. 
 

What are the types of brilliance?

Four types of brilliance can be distinguished:

• external brilliance – the brilliance of the stone, which is caused by the reflection of light from the surface of the crown,
• internal brilliance – the life of a stone, caused by the total internal reflection of light from the facets of the lower part of the stone
• diffuse brilliance – the play of colour, caused by the splitting of light on the structure of the stone,
• scintillation brilliance – the sparkling of the stone on rotation.