Radiant Cut — The Mixed Brilliant-Step Hybrid Patented in 1977
Radiant Cut — The Mixed Brilliant-Step Hybrid Patented in 1977
A rectangular or square cut combining brilliant-cut crown facets with step-cut pavilion geometry
The radiant cut is a rectangular or square mixed-cut diamond style combining brilliant-cut faceting on the crown with step-cut faceting on the pavilion, conceived to deliver the brilliance of a brilliant cut from the rectangular outline traditionally associated with step cuts. It was patented in 1977 by the New York cutter Henry Grossbard, who had spent more than two decades cutting emerald-shaped diamonds and sought a way to bring brilliant-cut life to the same outline. The design has remained one of the few protected modern diamond cuts to enter sustained commercial use.
Geometry
The standard radiant cut comprises 70 facets — 25 on the crown including the table, 8 on the girdle, and 37 on the pavilion including the culet — though variants exist with slightly different facet counts. The corners are cut square or with a small chamfer that gives the radiant its characteristic clipped-corner outline; the elongated rectangular form retains a length-to-width ratio that may run from 1.00 (nominally square) to 1.50 or higher (long rectangular).
The crown is faceted on the brilliant-cut model: a flat table surrounded by star and bezel facets, with upper girdle facets meeting the girdle. The pavilion is the technical innovation — step-cut horizontal facets running parallel to the girdle, but interrupted by additional facets at the corners and at the culet area, generating brilliant-cut light return rather than the broader flashes of a true step cut. The 1977 patent (US Patent 4,083,352) described the precise facet arrangement.
Optical performance
The radiant cut delivers more brilliance and fire than the emerald cut and conceals inclusions more effectively because the brilliant-cut crown facets break up internal reflections rather than presenting the long, open table-and-step view of an emerald cut. This is the practical advantage of the design: a stone that would grade at SI clarity in an emerald cut may face up cleanly as a radiant. The trade-off is that the radiant has neither the dramatic flash of a brilliant nor the architectural calm of an emerald cut, occupying an aesthetic middle ground that suits buyers who want a rectangular outline without the clarity premium of a step cut.
Application to fancy colour diamonds
The radiant cut is particularly significant in fancy-colour diamond cutting. The combination of brilliant-cut pavilion facets and the rectangular outline intensifies perceived body colour by both increasing internal light path length and by recycling colour through multiple internal reflections. Yellow diamonds in particular benefit: a fancy yellow stone cut as a radiant may face up with significantly more apparent saturation than the same rough cut as a round brilliant or an emerald cut. Most of the famous large fancy yellow diamonds of the past forty years have been cut as radiants for this reason.
In the trade
Radiant cuts are routinely available in commercial weights from approximately 0.50 carat upward. Length-to-width ratio is the principal aesthetic variable beyond the 4Cs and is often specified by buyers; ratios in the 1.10-to-1.30 range are most popular for centre stones in three-stone settings, while squarer ratios of 1.00-to-1.05 compete with cushion and princess cuts. Pricing tracks the standard diamond grading factors closely, with no significant cut premium or discount relative to other fancy shapes in conventional commercial qualities.