Cut registry › Jewellery cuts › Square radiant
Jewellery cuts · Square brilliant
The one with the right pavilion.
Same family as the elongated radiant, same faceting idea, and a very different result. The difference between the two is almost entirely one angle, and no report records it.
The short version
A square radiant cut diamond is a square stone with truncated corners and brilliant-style faceting throughout, carrying 49 facets on our measurement.
It is the square form of the radiant, and on our census it performs considerably better than our elongated reference radiant does.
Definition
The radiant was developed by Henry Grossbard in 1977 to put a brilliant’s light return inside a step cut’s outline. It is cut both square and elongated, and the two are usually discussed as though the only difference were the silhouette.
They are not the same stone. The square radiant is a more compact shape with a shorter path from table to pavilion, and the pavilion angle a cutter reaches for is different as a result.
Its cut corners give it the same durability advantage the elongated radiant has: no sharp point to chip, unlike a princess. It is the most robust square brilliant in common production.
Proportions
Trade description on the left, our measured reference stone on the right. The pavilion figure is the one that matters, and it is the one no grading report records.
| Measure | Commonly cited | Our reference stone | What it does |
|---|---|---|---|
| Length-to-width | 1.00 to 1.05 | 1.00 | Square by definition. |
| Depth | 60% to 70% | 60.1% | Well inside the usual window. |
| Table | 60% to 70% | 65.0% | The flat top, as a share of the width. |
| Pavilion angle | not commonly published | 55.6° | The difference between this stone and a leaky one. |
| Facets | ~70 commonly cited | 49 | Counted as facets that actually reach the surface. |
GIA issues no cut-quality grade for radiants of any proportion, which matters more here than on most shapes. The radiant family is unusually sensitive to pavilion angle, and the report will not tell you what yours is.
Light
Measured on the census that runs on every cut on this site: 3,200 rays face-up, 2,200 at 20° tilt, on exact facet geometry, against T57 as the standard.
| Material | Useful light | Leak | Fire | Scintillation | Global | vs the standard |
|---|---|---|---|---|---|---|
| Diamond | 72.42% | 12.37% | 62.12 | 66.34 | 76.82 | −11.78 |
| Moissanite | 70.92% | 10.97% | 92.55 | 66.34 | 82.29 | −7.53 |
| Cubic zirconia | 74.36% | 12.67% | 81.22 | 66.34 | 82.63 | −9.14 |
| T57 standard, diamond | 92.28% | 1.88% | 78.85 | 71.82 | 88.61 | 0.00 |
The square radiant returns 72.42% of entering light usefully and leaks 12.37%, for 76.82 Global against the standard’s 88.61, placing it eighth of the twenty-one jewellery cuts we publish.
Set that against our elongated radiant, which returns 31.55% and leaks 41.49%. Same family, same faceting principle, and roughly a third of the leakage. The elongated reference stone carries a shallow pavilion; this one does not. That single difference is worth more than eleven points of Global.
This is the clearest demonstration on the site of a point that applies to every fancy shape: the pavilion angle decides light return, and no grading report records it. Two stones described identically on paper can sit either side of this gap.
Its weak term is fire, at 62.12 against the standard’s 78.85, the lowest of the square brilliants we publish. It holds 89.86 under tilt against 90.41.
Where the light is: useful return across the face
Five equal bands across the stone. The square radiant returns 87.6% at the centre against 77.8% at the edges, against the round-brilliant control’s 99.1% and 98.1%. Unlike the princess, whose corners measurably darken, this cut keeps its light fairly evenly spread.
Against the standard
Light return. 72.42% against the standard’s 92.28%, a Global gap of 11.78 points.
Against the elongated radiant. 76.82 against 65.14, and 12.37% of leak against 41.49%. If you are choosing between the two, this is the comparison that matters.
Fire. 62.12 against 78.85, and the weakest figure among the square brilliants here. The crushed-ice scatter that hides inclusions also averages colour back towards white.
Durability. Truncated corners, so no protective setting is needed. Safer than a princess and safer than a carré.
Colour. Like every radiant it concentrates body colour rather than dispersing it, so a white stone usually wants a higher colour grade than a round would.
The baseline for all of this is the round brilliant itself. Its facet plan is set out in the anatomy of a round brilliant, and the measured standard we compare against is T57, the stone Tolkowsky published in 1919.
Materials
In moissanite it returns 70.92% for 82.29 Global, with fire climbing to 92.55 from 62.12 in diamond. On a cut whose weakest term is fire, a high-dispersion material is the obvious answer.
In cubic zirconia it returns 74.36% for 82.63 Global.
Compare it with the elongated radiant in the Index.
Trade-offs
Questions
The questions buyers actually ask, answered in full. Where the answer is ours to prove, the figure is measured on the Index; where it is an established gemological fact, it is stated as one.
A square radiant cut diamond is a square stone with truncated corners and brilliant-style faceting throughout, carrying around 70 facets. It is the square form of the radiant, which Henry Grossbard developed in 1977 to give a step-cut outline the light return of a brilliant.
On our reference geometries, substantially. The square radiant returns 72.42% of entering light and leaks 12.37%, for 76.82 Global; our elongated radiant returns 31.55% and leaks 41.49%. The difference is almost entirely pavilion angle rather than outline, and no grading report records it.
Corners and pattern. A square radiant has truncated corners, which makes it far more durable; a princess has sharp uncut corners that sit on cleavage planes and chip. A well-cut princess shows a readable X through the table, where a radiant gives a continuous crushed-ice glitter with no pattern.
Usually higher than for a round of the same size. Radiant faceting concentrates body colour rather than dispersing it, which is exactly why the cut is preferred for fancy yellows and exactly why a white one shows warmth sooner.
Yes, and they are among the most durable square shapes available. The truncated corners remove the exposed points that make a princess or a carré vulnerable, so no protective setting is required.
Deep enough to hold the light, and that is not a number you will find on a report. Our square reference stone sits at 55.6° and leaks 12.37%; our elongated reference stone has a much shallower pavilion and leaks 41.49%. On a radiant this is the variable that decides everything, and it is invisible on paper.
Well. The many small pavilion facets scatter light into a continuous glitter with no calm windows in it, so inclusions have plenty of visual noise to hide behind. A radiant of either proportion is forgiving on clarity.
No. GIA issues cut grades for round brilliants only, and a radiant will be described on a report as a cut-cornered square modified brilliant. That absence matters more here than on most shapes, because the radiant family is unusually sensitive to pavilion angle.
Next
See the whole set on the jewellery cuts index, or the measured house and historic cuts in the cut registry.
Method
Monte-Carlo on exact facet geometry: 3,200 rays face-up plus 2,200 at 20° tilt, cosine-weighted from a 7° near-vertical cone. Useful light is what exits through the crown within 64° of vertical. The same protocol runs on every cut on this site, so the figures are comparable to each other.
They measure our reference geometry for the shape at the proportions listed above, not an average of stones on the market. A square radiant cut to different proportions will read differently. Treat them as a like-for-like comparison between shapes, not as a grade for any individual stone.
Engine estimates, ±2 points, not lab-certified grades. We do not publish the Index symmetry axis on these pages: it scores facet regularity within each pavilion family, which is meaningful for a round brilliant and misleading for a shape whose pavilion is deliberately irregular.
66.34 here against the standard’s 71.82. The term is 100(1−e−n/45) on the count of facets that actually reach the surface, so it is a pure function of facet count and nothing else.