Which term describes the overall effect of light from a diamond's internal and external reflections?

• A. Luster
• B. Brightness
• C. Luminescence
• D. Dispersion

Answer: (B)

Brightness describes the overall light return of a diamond—the amount of white light that leaves the stone and reaches your eyes, coming from both how light reflects off the facets (external reflections) and how it bounces inside the gem (internal reflections). A well-cut diamond is designed to maximize this light return, giving a lively, scintillating appearance, while a poor cut can let light leak away and reduce brightness. Luster is the surface sheen, luminescence is light emission under stimulation (glow), and dispersion is the splitting of light into colors (fire). So the best term for the combined effect of internal and external reflections is brightness.