A mixed-cut diamond is one fashioned with a combination of brilliant-cut and step-cut faceting on the same stone. The most common diamond mixed-cut configuration is brilliant-cut crown facets over a step-cut pavilion, but the reverse arrangement and various intermediate designs are also encountered. Mixed-cut diamonds are far less common than the standard brilliant cuts in colourless round and fancy-shape work, but the format is used regularly in fancy shapes and increasingly in fancy-coloured diamonds where weight retention and colour management benefit from the flexibility.

Where mixed cuts appear in diamond

The cushion-cut diamond, particularly in its older forms (the antique cushion, or old mine cut), is the most familiar mixed-cut category. The crown is cut in a brilliant pattern with table, kite, and star facets; the pavilion follows a more step-cut pattern with main pavilion facets in step arrangement rather than the radial brilliants of a modern round-brilliant pavilion. The result is a stone with the colour and clarity emphasis of a step cut combined with some of the optical life of a brilliant.

The radiant cut, developed by Henry Grossbard in the 1970s, is an explicit modern mixed cut: the cushion or rectangular outline is faceted with brilliant-cut elements arranged in a partly radial, partly stepped pattern that produces strong light return characteristic of brilliants while retaining the rectilinear outline of step cuts. The radiant has become a standard fancy shape, particularly favoured for fancy-coloured diamonds where its high light return concentrates and intensifies the colour.

Why mixed cuts in diamond

Three factors drive mixed-cut use in diamond. First, weight retention from the rough crystal is sometimes optimised by a mixed configuration. Second, colour intensification in fancy-coloured diamonds — pink, yellow, blue, brown — is enhanced by faceting that maximises light path length through the colour-bearing volume of the stone, and mixed cuts can be designed to do this better than pure brilliants. Third, certain antique aesthetic preferences are best served by the older mixed-cut designs.

In the trade

GIA grading reports identify mixed-cut diamonds under the cut description and document the specific facet arrangement. Cut grade in the GIA framework is currently assigned only to standard round brilliants; fancy-shape and mixed-cut diamonds receive descriptive cut commentary rather than a graded assessment. Buyers of mixed-cut diamonds should evaluate the cut on criteria of brilliance, light return, and colour reading rather than against an absent grade.

Skyjems regularly handles mixed-cut diamonds in cushion and radiant shapes and treats the format as a legitimate alternative to standard brilliant cuts for buyers who prefer the aesthetic or who are working with fancy-coloured material.

Further reading

• GIA — Diamond reference and cut grading
• GIA Gems & Gemology — fancy-cut diamond articles