Cushion vs Round

The cushion and the round share the same fundamental light mechanics — both are brilliant cuts, both use triangular and kite-shaped facets to bounce light between the pavilion walls and return it through the crown. What separates them is character. The round is the product of a century of scientific optimisation, producing maximum brilliance and a formal grading benchmark. The cushion traces its lineage to the old mine cut and candlelight; it was designed for warmth, fire, and a softer visual temperament.

There is one thing about cushion buying that has no equivalent in the round category and that must be understood before anything else. It concerns the two types of cushion, which are sold under the same name and look entirely different in person.

Two fundamentally different stones are sold as "cushion cut diamonds." The grading report says "cushion" for both. They look completely different in person.

Cushion brilliant uses triangular facets similar to a round brilliant. It produces tight, concentrated sparkle — sharp flashes of light, high scintillation, visually similar to a round in its flash pattern. If you want a cushion that sparkles like a round, this is the subtype.

Modified brilliant (also called "chunky cushion" or "crushed ice cushion") uses an additional row of facets below the girdle. It produces a diffuse, crushed-ice optical effect — hundreds of tiny sparkle points rather than discrete flashes. The visual character is completely different: softer, more dispersed, and depending on preference, either beautiful or lacking in definition.

Neither subtype is superior. They are different aesthetics. The problem is that a buyer who purchases online based on a certificate and a static photo may receive a stone that looks nothing like what they imagined. The certificate will simply say "cushion" for both. You must ask the seller explicitly which subtype you are buying, request video that confirms the sparkle character, and ideally see both subtypes side by side before deciding.

The round leads on brilliance, scintillation, and clarity coverage — the result of its precise rotational symmetry and the century of optimisation behind it. The cushion's strongest performance metric is fire: coloured spectral light produced by dispersion. The cushion's heritage as a descendant of the old mine cut (designed for candlelight and early indoor lighting) gives it a warmth in fire that many buyers find more romantic than the clinical brightness of a well-cut round.

Size per carat is roughly similar between the two — the cushion's depth (60–67%) means it carries more weight below the girdle than it looks. A 1.00 ct cushion typically measures approximately 5.8–6.0 mm face-up versus 6.5 mm for a round. The cushion looks slightly smaller per carat than the round, unlike the oval which runs larger.

In directional light — sunlight streaming through a window, candlelight, a single overhead spot — the cushion cut produces coloured spectral flashes with notable intensity. This is fire: white light dispersed into its component wavelengths as it exits the crown. The cushion's facet arrangement and crown proportions are well-suited to producing these coloured flashes.

The round brilliant, by contrast, is optimised for brilliance — maximum white light return — at a slight cost to fire. In the same directional lighting, the round will appear brighter. The cushion will appear warmer and more colourful. In diffuse or overhead lighting (common indoors), the round's advantage in brilliance becomes more apparent.

Neither is objectively better. The question is which lighting environment the stone will primarily be worn in, and which optical character the wearer finds more appealing. Buyers who have seen both under good lighting conditions consistently describe the choice as obvious once they've made the comparison.

Cushion cut diamonds trade at roughly 10–20% below round brilliants of equivalent grade. This discount is structural: it reflects the round's dominant market position and the existence of the GIA cut grade rather than any deficiency in the cushion's optical performance. A well-cut cushion at a given grade is not an inferior stone — it is a different stone at a lower price point.

The caveat is that "equivalent grade" is harder to verify for a cushion than for a round, precisely because there is no formal cut grade. Two cushions at the same carat weight, color, and clarity can look substantially different depending on subtype, proportions, and individual cut quality. The grade comparison is less clean.

The round brilliant is the only cut with a formal GIA cut grade — Excellent, Very Good, Good, Fair, Poor. This grade is assessed against rigorous optical benchmarks and is independently verifiable. When you purchase a round with GIA Excellent cut, you have a documented assurance of optical quality that is consistent across thousands of stones.

The cushion has no equivalent. GIA assesses polish and symmetry on fancy shapes, but provides no cut grade. This means evaluating a cushion's cut quality requires direct assessment: look for proportions (depth 60–67%, table 53–65%), confirm the subtype, and request an ASET or Ideal-Scope image if possible. The absence of a cut grade is not fatal — it simply requires more diligence from the buyer.