Is an oval diamond just as brilliant as a round one?

No. Not quite. A round brilliant is the benchmark for white-light return because its facet pattern was engineered for it. A well-cut oval can get surprisingly close-and in some lighting, it can look even more dramatic-but on average, across a range of cuts, the round wins. The reason isn't poetry. It's facet geometry.

Rounds are symmetrical in every direction. A round with an excellent cut grade from GIA or AGS has been optimized so that pavilion main facets act like mirrors, bouncing light back up through the crown. When I hold a true triple-excellent round next to an oval, the round almost always has more life across the entire face of the stone. The oval will have a dark area across the middle-the bowtie-and that area reduces the total amount of light hitting your eye. A good cutter can minimize the bowtie, but they can't eliminate it. The facet layout on an oval (a modified brilliant, usually) creates shadow zones by design.

Last April a client named Marcus brought in two stones he'd bought online: a 1.01 carat G/VS2 round and a 1.20 carat F/VS1 oval. He wanted to see which one was "brighter" before picking a setting. We put them under the same north-facing window, side by side, on white paper. The round was a little firecracker-consistent sparkle from edge to edge. The oval had a pretty obvious bowtie right across the belly, two dark triangles. In direct sun, the oval threw big flashes of light that the round didn't, but in the office, the round won. Marcus went with the round. I think he made the right call, but I also know that three feet away on a dance floor, the oval would have flashed harder. That's the trade-off.

Here's the thing about brilliance. Most clients mean "sparkle," and sparkle has two parts: brightness (white light return) and fire (spectral colors). Rounds are designed to balance both. Ovals tend to favor fire, especially in longer stones. The elongated shape and larger facets break light into rainbows more easily. So if you love a fiery, disco-ball effect, a high-quality oval might actually feel more alive to you than a round. It won't be as uniformly brilliant, but it can be more exciting in quick flashes.

Cut quality for an oval matters more than almost any other factor, and it's harder to assess. There's no standardized "ideal cut" for fancy shapes. GIA doesn't assign a cut grade to ovals. AGS does for some fancy shapes, but many ovals aren't AGS-graded. You have to rely on your eyes, the dimensions, and the bowtie. A depth percentage between 58 and 62 percent, a table between 53 and 63 percent, and a ratio you like (1.35 to 1.50 is the sweet spot for most) help, but they don't guarantee brilliance. I've seen ovals with perfect numbers on paper that looked dead because the cutter left a heavy bowtie to retain carat weight.

That's the other ugly truth: weight retention kills light performance. A diamond cutter loses more rough when aiming for a round brilliant than for an oval. With an oval, you can save a lot of the original crystal, so cutters are incentivized to produce ovals that hit a magic carat mark even if the angles are compromised. A 1.50 carat oval with a sloppy pavilion and a dark bowtie will sell faster online than a 1.30 carat oval with optimised light return, because most buyers shop by carat first. It's a problem.

So, if you're after maximum all-purpose brilliance, go round. If you want the elongated silhouette and are willing to hunt for an oval with a barely-there bowtie-and to pay a premium for that-you can get a stone that's 90% as brilliant, with bigger fire and a more distinctive look. My test is simple: hold the stone over a piece of text. If the words are readable, light is passing straight through without returning to your eye. You want the text to be obscured because light is bouncing back. For an oval, move your hand and watch whether the text disappears evenly. If a bowtie-shaped area stays transparent, keep looking.

I've set plenty of both. My personal favorite is an old European cut, which is a round with less predictable sparkle. I don't need perfectly uniform brilliance. But if a client asks me this question across the bench, I hand them a calibrated round and a high-quality oval under my lamp and let them decide. Almost always, they see what Marcus saw.