Buying a cushion cut diamond is a fundamentally different process from buying a round brilliant. With a round, the GIA cut grade does a significant portion of the evaluative work for you. With a cushion cut, no such grade exists. The GIA issues colour and clarity grades for fancy shape diamonds, but it does not assess cut. That responsibility falls to you — and to the jeweller you choose to work with.

This is not a disadvantage. It is, in fact, one of the things that makes cushion cut shopping more interesting. But it does mean that you need to approach the process with more tools and more knowledge than you might bring to a round brilliant purchase. At Dalila Diamond, we believe an informed buyer makes a better purchase — and this guide is designed to give you everything you need to make a confident, well-considered decision.

Step One: Establish Your Ratio

Before you evaluate any other quality factor, decide what length-to-width ratio you are looking for. The ratio determines whether you are buying a square cushion (1.00–1.09) or an elongated cushion (1.10–1.30). This is not a minor stylistic preference — it is a fundamental shape decision that affects how the ring looks on the hand, how large the stone appears, and which setting styles are appropriate.

If you are unsure, our recommendation at Dalila Diamond is to request side-by-side images of the same carat weight at three different ratios: 1.05, 1.15, and 1.25. Most buyers find that viewing these three options simultaneously makes their preference immediately clear. The ideal ratio for most buyers looking for an elongated cushion falls between 1.20 and 1.25.

 Step Two: Evaluate Proportions

In the absence of a GIA cut grade, the proportions listed on the diamond's certificate become your primary quality indicators. The two most important numbers are the depth percentage and the table percentage.

The depth percentage — the height of the stone expressed as a percentage of its width — should fall between 60 and 67 percent. A stone cut deeper than 67 percent retains excessive weight in its base: it will appear smaller face-up than its carat weight suggests, and may show a dark, shadowy centre when viewed from above. This is sometimes called the 'nail head' effect, and it is a reliable sign that the stone was cut to maximise carat weight at the expense of optical performance.

The table percentage — the size of the flat top facet expressed as a percentage of the stone's width — should sit between 58 and 68 percent. Within the recommended range, personal preference governs: a larger table tends to produce more brilliance; a smaller table tends to produce more fire and scintillation.

Step Three: Understand the Cut Pattern

The cushion cut is available in two primary internal facet arrangements, and the difference between them is significant enough to be visible to the naked eye — even in photographs.

The Cushion Brilliant Pattern

Features larger, more defined facets that produce identifiable flashes of light as the stone moves. The internal pattern shows clear, chunky facet reflections — almost like a windmill or pinwheel shape at the centre. This pattern tends to look best in natural and warm light. It is the more traditiona cushion cut.

The Crushed-Ice Pattern

Has a much denser arrangement of smaller facets below the girdle. The result is an internal texture that appears almost liquid or finely crushed, without the clear facet reflections of the brilliant pattern. This creates a different kind of visual character: less dramatic in individual flashes, but more constantly alive with scattered light in all directions. The crushed-ice look is considered more contemporary and has become increasingly popular with younger buyers.

Step Four: Assess Colour in Context

The cushion cut retains colour more readily than round brilliants and some other fancy shapes. This is a consequence of the cut's geometry: the larger facets and deeper crown hold colour in a way that the round brilliant's many small, precisely angled facets do not. In practical terms, it means that a colour grade that looks perfectly white in a round brilliant may read slightly warmer in an identically graded cushion cut.

In a platinum or white gold setting, we recommend prioritising a colour grade of H or above for buyers who want a clearly white stone. In a yellow gold or rose gold setting, the warmth of the metal renders colour in the I and J range effectively invisible to the eye, and buyers can realistically invest in a lower colour grade without visible compromise.

Evaluate colour in multiple lighting conditions before committing. Natural daylight is the harshest and most revealing — a stone that appears acceptably white under LED showroom lighting can read distinctly warm in sunlight. Ask your jeweller to show you any stone you are considering in a variety of lighting environments before making a final decision.

Step Five: Clarity — Finding the Sweet Spot

The cushion cut's facet structure is reasonably forgiving of inclusions. In either pattern, the goal is to find a stone that is eye-clean — meaning no inclusions are visible to the naked eye at a normal viewing distance of approximately 25 centimetres.

For most buyers, this goal is achievable at the VS2 or SI1 clarity grade. Stones in this range offer excellent value: they carry no visible inclusions under normal viewing conditions, yet they are priced significantly below flawless or VVS stones that offer no practical visual advantage.

Avoid inclusions near the centre: Inclusions positioned beneath the table facet are most visible. Those near the girdle edge are far less so.

Check inclusion type: Crystal inclusions are less visible than black carbon spots. Feathers are usually invisible unless they affect structural integrity.

Trust video over grading reports: A GIA clarity grade tells you what grade a diamond is. The video tells you what it actually looks like.

Step Six: Always Buy from Video

This bears repeating because it is the most important practical advice we can offer. The cushion cut — unlike the round brilliant — has no standardised cut grade. Two cushion cuts with identical certificates can look dramatically different in person. The only way to assess a cushion cut accurately is to see it moving — in high-definition video, rotating under standardised lighting.

At Dalila Diamond, every stone we present to clients is accompanied by high-resolution video footage under both natural and LED lighting. We encourage clients to take as long as they need with that footage — to watch the stone move, to look at the internal pattern, to assess the colour and the clarity with their own eyes before making any commitment.

Q1: Why doesn't the GIA issue a cut grade for cushion cut diamonds? 

The GIA only issues cut grades for standard round brilliant diamonds, because the round brilliant has a mathematically defined ideal against which every stone can be measured. Fancy shape diamonds — including cushion cuts — come in too many variations of ratio, facet pattern, and proportion to be assessed against a single standard. This means cushion cut buyers must evaluate cut quality themselves using proportion data and, most importantly, high-quality video of the stone in motion.

Q2: What depth and table percentage should I look for in a cushion cut diamond? 

At Dalila Diamond, we recommend a depth percentage between 60 and 67% and a table percentage between 58 and 68%. Stones outside these ranges are often cut to retain maximum carat weight at the expense of optical performance — producing diamonds that look smaller or duller than their carat weight suggests. Staying within these ranges consistently produces the best balance of brilliance, fire, and face-up size.

Q3: What is the difference between the cushion brilliant and crushed-ice cut pattern? 

The cushion brilliant pattern has larger, more defined facets that produce clear, identifiable flashes of light — almost like a pinwheel or windmill shape when viewed from above. The crushed-ice pattern has a much denser arrangement of smaller facets that creates a scattered, liquid-looking internal texture with no single dominant flash. Neither is better — they suit different aesthetics. The brilliant pattern is more traditional and reads best in warm light; the crushed-ice is more contemporary and looks especially striking in elongated cushion cuts.

Q4: What colour grade should I choose for a cushion cut diamond? 

The cushion cut retains colour more readily than a round brilliant, so colour grade selection matters more here than with other shapes. In platinum or white gold, Dalila Diamond recommends H colour or above for a stone that reads as clearly white. In yellow gold or rose gold, the warmth of the metal masks colour effectively, and I or J colour diamonds are excellent value. Always evaluate colour in natural daylight before committing — LED showroom lighting can flatter a stone more than real-world conditions.