Diamond sparkle comes from the way a stone handles light.

Brightness is the white light reflected back to the eye. Fire is the coloured flashes created as light disperses. Scintillation is the pattern of light and dark areas that move as the diamond turns.

Cut quality is the main driver of sparkle, but shape, proportions, polish, symmetry and cleanliness all play a role. A certified diamond with strong cut details is usually a better starting point than carat weight alone.