The cushion cut diamond is a faceted diamond whose outline is square or rectangular with softly rounded corners, producing a silhouette that recalls a cushion or pillow. It is among the oldest standardised diamond shapes still in widespread use, descending directly from the old mine cut that dominated European and American jewellery from roughly the mid-eighteenth century through the early twentieth. Today the cushion cut is one of the most commercially significant fancy shapes, valued simultaneously for its historical resonance and for the warm, dispersive fire it produces — a quality that distinguishes it perceptibly from the cooler, more mirror-like brilliance of the modern round brilliant.

Historical Development

The cushion cut's ancestry lies in the old mine cut, a hand-fashioned form that emerged as lapidaries in the seventeenth and eighteenth centuries worked to maximise the fire of diamonds under candlelight. Old mine cuts are characterised by a high crown, a small table, a large culet (the flat facet at the base of the pavilion, often large enough to be visible as a dark circle when the stone is viewed face-up), and an overall outline that is neither perfectly square nor perfectly round but distinctly cushion-shaped. Because diamonds were cleaved and bruted by hand, no two old mine cuts are identical; their charm lies partly in this individuality.

As mechanised cutting became standard in the late nineteenth and early twentieth centuries, cutters began to refine the cushion shape, gradually reducing the culet, lowering the crown, and enlarging the table to improve light return. The transition from old mine cut to what we now call the modern cushion cut was gradual rather than abrupt, and many stones from the Edwardian and early Art Deco periods occupy an intermediate position. The round brilliant, introduced in its mathematically optimised form by Marcel Tolkowsky in 1919, eventually displaced the cushion as the dominant shape for engagement rings, but the cushion never disappeared from the market entirely.

A significant revival began in the late 1990s and accelerated through the 2000s and 2010s, driven by consumer appetite for vintage-inspired jewellery and by the cushion shape's particular suitability for coloured diamonds, where its depth and facet arrangement can intensify saturation.

Facet Arrangements: Cushion Brilliant and Cushion Modified Brilliant

The Gemological Institute of America (GIA) recognises two principal facet configurations on its grading reports, and the distinction matters both optically and commercially.

• Cushion brilliant: The facet arrangement closely mirrors that of a round brilliant, with a standard set of crown and pavilion facets adapted to the cushion outline. Light return is relatively uniform, and the stone tends to display a pattern of broad, overlapping reflections.
• Cushion modified brilliant: An additional row of facets — sometimes called an extra facet row — is introduced on the pavilion, creating a distinctive visual effect often described in the trade as a "crushed ice" appearance: a scintillating, fragmented pattern of small, bright reflections rather than the larger, chunkier facet flashes of the standard cushion brilliant. Some cutters and buyers prefer this effect; others find it less legible and less reminiscent of the historical old mine cut aesthetic.

GIA's report will state which configuration applies, and buyers should be aware that the two can look markedly different in person even when all other grading parameters are identical. Neither is inherently superior; the choice is largely one of aesthetic preference.

Proportions and Light Performance

Because the cushion cut is a fancy shape rather than a round, GIA does not assign a cut grade to cushion cut diamonds on its grading reports — a fact that distinguishes it from the round brilliant, which receives an overall cut grade. Evaluating a cushion cut's light performance therefore requires direct examination or the use of angular spectrum evaluation technology (ASET) imaging and idealscope analysis, tools offered by independent laboratories and some retailers.

As a general principle, cushion cuts with a total depth percentage in the range of roughly 58 to 68 per cent and a table percentage of 58 to 68 per cent tend to perform well, though these are guidelines rather than rules, and the interaction of crown angle, pavilion angle, and culet size must be considered holistically. Cushion cuts typically return slightly less white light than an optimally cut round brilliant of equivalent diameter, but they often display stronger dispersion — the spectral fire that separates white light into its constituent colours — because their facet geometry and proportions are more tolerant of steep crown angles that enhance this effect.

Length-to-width ratio is the primary determinant of outline shape. A ratio of 1.00 to approximately 1.05 produces a square cushion; ratios above 1.10 yield a distinctly rectangular stone. Personal preference governs the choice, though square cushions have historically been more popular in solitaire engagement rings, while elongated cushions are frequently used in three-stone settings where the shape complements flanking side stones.

Colour and Clarity Considerations

The cushion cut's relatively deep pavilion and its facet arrangement mean that it tends to retain colour more readily than a round brilliant of equivalent colour grade. A stone graded H in colour may appear slightly more tinted in a cushion cut than in a round brilliant, a phenomenon that is more pronounced in larger stones. Buyers seeking a near-colourless appearance in a cushion cut often find that selecting one grade higher than they might choose in a round brilliant achieves the desired result.

Conversely, this colour retention is an advantage when working with fancy-colour diamonds. Cushion cuts are among the most popular shapes for intense and vivid yellow, pink, and blue diamonds, where depth of colour is the paramount quality criterion. Several of the world's most celebrated coloured diamonds — including historic stones that predate modern cutting — are cushion cuts or old mine cuts, a reflection of the shape's long dominance during the era when these stones were first fashioned.

With respect to clarity, the cushion modified brilliant's crushed-ice facet pattern can mask inclusions effectively, as the fragmented reflection pattern makes it harder for the eye to locate internal features. The standard cushion brilliant, with its larger, more defined facet reflections, offers somewhat less natural camouflage, though both configurations are generally more forgiving than the step cuts (emerald cut, Asscher cut) in which inclusions are highly visible.

Notable Stones and Historical Significance

Several of the most historically significant diamonds in existence are cushion cuts or old mine cuts. The Hope Diamond, now housed at the Smithsonian Institution in Washington, D.C., is a cushion antique brilliant of 45.52 carats. The Regent Diamond, part of the French Crown Jewels collection at the Louvre, is a cushion brilliant of 140.64 carats, cut in the early eighteenth century and long regarded as one of the finest large diamonds ever fashioned. The Koh-i-Noor, set in the British Crown Jewels, was recut from its original Indian form into an oval brilliant in 1852, but its predecessor shape was broadly cushion-like. These associations have contributed to the cushion cut's enduring prestige and its particular appeal to buyers drawn to jewellery with historical depth.

In the Trade

Cushion cut diamonds are graded by all major gemological laboratories, including GIA, IGI, and GCAL. As noted, GIA reports specify the facet configuration (cushion brilliant or cushion modified brilliant) but do not assign a cut grade. When purchasing a cushion cut, examining the stone in person or requesting video footage is advisable, as two stones with identical grading parameters can differ substantially in their visual character depending on their specific proportions and facet arrangement.

In the secondary and antique market, original old mine cut diamonds command a premium among collectors who value the handmade quality and the warm, candlelight-era optical character of these stones. Repolishing an old mine cut into a modern cushion brilliant is technically straightforward but results in weight loss and the permanent alteration of a historical artefact; reputable dealers and gemmologists generally advise against it unless the stone is significantly damaged.

The cushion cut's versatility — equally at home in a Georgian closed-back setting, a Victorian cluster mount, an Art Deco platinum solitaire, or a contemporary pavé halo — has made it a perennial choice across jewellery periods and styles, and its continued commercial strength suggests that its third century of prominence is well underway.

Further Reading

• GIA: Diamond Cut — gia.edu
• GIA Gems & Gemology: Grading Fancy-Shape Diamonds
• GIA: Diamond Shapes FAQ — gia.edu