Judging Brilliance, Fire and Scintillation

Brilliance  – Diamonds that appear strong pink/red through the Ideal-Scope have the best light return. The less leakage the better, but brilliance is not only about light return. Contrast has a role to play too.The dark 8 rayed star should not be too thick; too much darkness in a diamond through the Ideal-Scope means less light is returned, just like leakage. (Thick stars occur when pavilion lower girdle facets that are too short). But if the star is too thin then the diamond will lack contrast and scintillation and it will have less fire.

Excellent Edge to   Edge Brilliance

Excellent Edge to Edge Brilliance

Very Good Edge to   Edge Brilliance

Very Good Edge to Edge Brilliance

Fair Edge to   Edge Brilliance

Fair Edge to Edge Brilliance

PROS – increased fire
CONS – reduced light
return and scintillation
PROS – balanced contrast,
scintillation and fire
CONS – none
PROS – increased light return
CONS – reduced fire,
contrast and scintillation
Fire – Diamonds with thick dark stars are usually more firey. However there is a trade off when it comes to light return. Diamonds that are a little to deep, with leakage through the table region, can display more fire if they are set so that light can get in from behind.


Scintillation – Thick dark prominent stars reduce light return but as discussed in the newsletter, some contrast is needed to enhance our perception of brilliance as the diamond is rocked from side to side. The dark / bright alternating contrast creates a ‘bang bang’ sparkle effect. Small bits of leakage near the girdle often contribute to that contrast.

Ideal Cut with excellent scintillation  



Poor cut with poor scintillation




A checker board is half as bright as a sheet of white paper, but when you move the two, the scintillating effect of the checker board is far more eye catching.