With three straight or slightly curved sides, preferably of equal length, the Triangular Brilliant Cut is a generic term for a shape that today also is referred to as the Trillion, Trilliant and sometime the Trill.

The design of the cut is generally credited to the Asscher brothers in Amsterdam, and the term “Trilliant” was trademarked by the Henry Meyer Diamond Company of New York in 1962, to underline the brilliance of the triangular cut. Its patent has since expired, meaning that the various terms are now widely used to refer to most faceted triangular shaped stones, although not to the step-cut tapered baguette.

Triangular Brilliants are most often produced from flattened, triangular rough diamonds called macles. Most often they are smaller in size and are used, generally in pairs, as side stones to complement larger solitaires, or in diamond-stud earrings. Larger stones can be used as centerpieces in jewelry.

Smaller Triangular Brilliants typically have 31 facets, while larger stones feature 50 facets.

For larger diamonds being used as solitaires, the sides of the triangle are generally curved outward, or convex. Side stones generally have straight sides or are concave, with the inward curve accommodating the round shape of the centerpiece stone that they are complementing. Other alternatives are round-cornered triangular, modified shield cuts and triangular step cuts. When used as side stones, care should be taken to ensure that color of both the Triangular Brilliants and the center-stones are properly matched.

Triangular Brilliant diagram

To ensure maximum brilliance, one-third of the diamond’s weight should be in the crown, above the girdle, and two-thirds in the pavillion. When the split between the crown and girdle is relatively even, the stone will display less brilliance. The length to width ratio should be remain within 1.00 and 1.10.

Because of its shape, Triangular Brilliants require special prongs in order to be held reliably in jewelry. V-prongs, which wrap around the tips of the stone are recommended, and halo settings are also appropriate.