Bow-Tie Effect: The dark shadow in the oval stone
Why some oval diamonds, moissanites, and lab-grown diamonds appear dark in the centre—and when you should take a closer look.
The bow-tie effect is one of those details you often don’t notice until it’s too late when buying your first ring. Everything looks fine on the certificate. The carat weight is right. The colour is right. The clarity is right. Then you turn the stone in the light, and suddenly there’s a dark shadow in the centre.
When it comes to oval stones, this isn’t a minor issue. Precisely because oval engagement rings are in such high demand, it’s important to know how a “bow tie” effect develops and how much of it still looks good. In short: It’s not about avoiding every shadow. It’s about recognizing the wrong kind of shadow.
In a nutshell
The bow-tie effect is a dark, bow-tie-shaped shadow area in the centre of elongated gemstones such as ovals, marquises, or teardrops. A slight bow-tie effect is normal and can add contrast; a distinct black bar makes the stone appear darker and should be carefully examined before purchase.
What is the bow-tie effect?
The bow-tie effect describes a dark zone that runs across the centre of a stone. When viewed from above, it resembles a bow tie. That’s where the name comes from.
Important: This is not an inclusion. Not a crack. Not dust. The shadow is not a flaw in the material, but is caused by the way light travels through the stone. Or rather: by light that does not reach the eye clearly.
"When it comes to elongated stones, we never just look at the carat weight and the certificate. The stone has to be able to move. You can only tell from the video whether a 'bow tie' is alive or just sits there dark."
Velur Editorial Team
That is exactly why two oval stones with very similar specifications look completely different. One appears open, bright, and lively. The other has a dark bar in the centre that immediately catches the eye.
Why does the bow-tie effect occur?
A diamond appears bright when light enters the stone, is reflected off the facets, and returns to the top. With elongated shapes, this path is more challenging than with round brilliant-cut diamonds. The centre is longer, the facets are arranged differently, and small differences in depth, symmetry, or angle are more noticeable.
Sometimes people refer to it as "light loss." Other times, they call it "light blockage." Both terms describe the same problem from different perspectives: The eye receives less light in certain areas. The visible effect is a dark spot in the centre.
A certificate can provide information on colour, clarity, and dimensions. However, it does not reliably tell you how beautiful an oval stone will look in everyday life. The GIA itself points out that there is currently no internationally accepted system for evaluating the visual appearance of fancy-cut diamonds.
That's why a report is just the beginning. To get the full picture, you need photos, video, and changes in lighting—daylight, ambient light, and movement from the side. Only then can you see whether the shadow is softly illuminated or remains a solid black line.
Which stones does Bow Tie display most often?
| Cut | Bow-Tie Risk | What You Should Keep in Mind |
|---|---|---|
| Oval | Frequently | The shadow is usually positioned right across the centre. When there is movement, it should become lighter and not look like a bar. |
| Marquise | Very common | The long, pointed shape accentuates shadows in the centre. It's worth taking a close look at the video here. |
| Drops | Frequently | The shadow often appears in the rounded central area. Symmetry is very important here. |
| Rectangular Cushion | Medium | The shadows are often softer, but can become visible when shapes are highly elongated. |
| Round | Low | Round brilliant-cut diamonds have different proportion systems. A classic "bow tie" is not the main focus here. |
When is a bow tie still attractive, and when does it become a distraction?
A stone without any dark areas doesn't automatically look better. Brilliance requires contrast. Light and dark facets should alternate; otherwise, the stone looks flat. A subtle bow tie can therefore be perfectly fine.
The problem arises when the shadow becomes too dominant—when, at first glance, you don't see the stone but only the dark streak, and when the area barely lightens even when you tilt it. That's when the "bow tie" takes away from the stone's presence.
Our criterion is simple: If the shadow defines the stone, it’s too strong. If it only flashes briefly and is part of the interplay of facets, it can stay.
The Velur Shopping Guide: How to Check Out a Bow Tie
You don't have to be a gemologist to see that. But you need more than just a photo. A single product photo might hide the bow tie or make it look too big. Video beats photos.
Watch the video: When the stone rotates, the dark area should move with the light and not remain stationary.
Examine the stone under several light sources: daylight, soft indoor lighting, and direct light reveal different aspects of the stone.
Look at the centre: If your eyes are immediately drawn to a black bar, it’s better to compare.
Don't just go by the measurements: depth, surface, and proportions help with the initial selection. But you can still see the beauty in the stone itself.
| Signal | The Right Direction | Warning Signal |
|---|---|---|
| Exercise | The shadow changes and brightens at times. | The dark bar remains almost the same in every position. |
| Contrast | Dark and light facets alternate visibly. | The centre appears permanently matte or black. |
| Overall impression | First, you notice the shape, the sparkle, and the proportions. | You'll see the bow tie first. |
As a rough preliminary screening process, the depth, table, and length-to-width ratio of oval stones are often examined. While these measurements can be helpful, they are no substitute for visual selection. A stone may look impressive on paper but disappoint in person. Conversely, there are stones with measurements that don’t meet textbook standards but look outstanding on the finger.
If you're torn between two oval stones, don't automatically choose the larger one. Choose the stone that looks brighter when it's in motion. If you're unsure, send us the video via WhatsApp and we'll give you our honest opinion on what we'd look for.
Does the bow-tie effect also occur with moissanite and lab-grown diamonds?
Yes. The "bow tie" effect is not related to a diamond's origin. A natural diamond, a lab-grown diamond, and a moissanite can all exhibit a central shadow if the cut and light path interact in an unfavorable way.
Another thing you'll notice about moissanite is that it has a different fire than a diamond. This can make some shadows appear softer, but it can't make them disappear. The same rule applies here: Don't buy based solely on specifications. Take a look at the stone.
With lab-grown diamonds, the advantage is often the selection. Because you have more flexibility within the same budget, you can be more selective: it’s better to choose a slightly smaller stone with beautiful brilliance than a larger stone with a dark centre. If you’re still undecided about which type of stone to choose, our comparison of moissanite, lab-grown diamonds, and natural diamonds will help you.
This is especially true for you if you're looking for an oval engagement ring, a pear-shaped cut, or a marquise cut. With these shapes, it's not just the carat weight that matters—it's also very much a matter of how well the stone reflects light.
Our sincere recommendation
Don't avoid every bow tie. Avoid the bow tie that dominates the stone.
An oval stone can have depth. It can have facets. It can be slightly darker in the centre when it moves. What you don't want: a black area that makes the stone look smaller, duller, or unbalanced.
When you buy an engagement ring online, don't just focus on size and price when choosing from the Velur engagement ring collection. Ask about the stone. Ask about the video. Ask about the light. This isn't just a detail for nerds. It's the difference between a stone that looks good on paper and a ring you'll love to look at every day.
Frequently Asked Questions About the Bow-Tie Effect
The bow-tie effect is a dark area that can run across the centre of a gemstone and resembles a bow tie. It is caused by the way light behaves within the cut, not by an inclusion or a crack in the stone.
No. A light-coloured bow tie can create a normal contrast and add depth to an oval stone. It becomes a problem when the shadow is wide, black, and remains visible even when the stone is in motion.
It is most commonly seen in elongated brilliant cuts: oval, marquise, and pear. Elongated cushion or radiant shapes may also exhibit shadow zones, though they are usually distributed differently.
Generally speaking, no. According to the GIA, there is currently no internationally accepted system for visually evaluating the appearance of fancy cuts. That’s why video, daylight, and expert advice are more important than just the numbers in the report.
Yes, moissanites can also exhibit bow-tie zones. This effect depends primarily on the cut, the symmetry, and the way light is reflected within the stone.
Watch a 360-degree video. If the dark bar stays firmly in the centre as you pan and barely brightens, it’s best to be cautious. If the dark areas flash and disappear, the stone usually looks more lifelike.
Sources: GIA 4Cs Guide to Oval-Cut Diamonds, GIA FAQ on Fancy-Cut Diamonds, International Gem Society Oval-Cut Guide.
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