Triangle-Cut

The triangle and the trillion get used interchangeably and should not be. A triangle keeps its sides dead straight and its three corners crisp; a trillion bows its sides outward for a fuller, rounder face. Straight sides give the sharper, more architectural look and a flat edge that sits tight against a neighboring stone.

Three sharp corners is three things to protect, so a triangle is usually bezeled or set with prongs that cap each point. Standard millimeter sizes, and like the trillion it works in pairs as a flanker.