Cabochon cutting produces a smooth, polished dome with a flat or slightly convex base. It is the standard for gems with play-of-color (opal), asterism (star sapphire, star ruby), or chatoyancy (cat's-eye chrysoberyl, tiger's-eye). The curved surface concentrates and reflects light to highlight natural phenomena that faceting would disperse or hide.
Cutters orient the rough so the optical effect aligns properly with the dome. Thickness and curvature affect the strength and centering of the phenomenon. Cabochons also suit heavily included or translucent material where faceting would emphasize flaws. Polishing uses progressively finer diamond or oxide compounds to achieve a glassy luster without flat facets.