Princess cut.

The princess cut is a square or slightly rectangular shape introduced in 1980. It uses a brilliant-cut facet pattern (chevrons of triangular facets) to mimic round-brilliant sparkle in a square outline.

Pricing runs 15-20% below round at the same color/clarity/weight. You get more visual surface for the dollar — a 1.0ct princess looks slightly larger than a 1.0ct round face-up.

The trade-off is structural. Princess cuts have four sharp corners that concentrate stress and chip easily if hit. Settings need to protect the corners (V-shaped prongs are standard). A bezel or half-bezel mount is more secure than four solitaire prongs.

Best in modern, geometric settings. Looks dated in vintage-style mounts.