The Asschers of Amsterdam, gem cutters for the British royal family, designed this striking, dramatic shape in 1902. A square with diagonally cropped corners and stepped sides, it features a high crown and sheds a gentle light. Natasha Gregson Wagner wears an antique 4.5-carat Asscher-cut diamond ring.

2.44-carat Asscher-cut diamond with diamond accents in platinum, Neil Lane, $41,000; 310-275-5015.