What Is Diamond Bulge & How Does It Impact a Gem’s Beauty and Value?

The ins and outs of bulging diamonds...

Most diamonds have some imperfections: inclusions, blemishes, misaligned proportions, etc. These flaws can affect a diamond’s sparkle, and their severity determines how much a diamond is impacted. Diamond bulge is no exception, and this imperfection can be difficult to see if you’re not a trained professional!

However, we can give you the tools and information to identify diamond bulge before you buy!😍 Let’s take a closer look at:

  • Diamond bulge basics
  • Different types of diamond bulge
  • How does bulging occur?
  • Ways diamond bulge impacts a gem’s value and beauty
  • Tips for inspecting diamonds for bulging
Diamond Bulge on an Emerald Cut Stone

Basics: What is diamond bulge?

Diamond bulge is a result of a diamond cutter shaping a stone with facets that curve outward rather than remaining true to its intended silhouette. It can occur in a few places on a diamond, and it’s most common in step-cut gems.

A diamond cutter may choose to craft a bulging diamond to increase its carat weight without impacting its overall size, which can increase the diamond’s price. However, diamond bulge impacts lightplay, causing light leakage that dulls the stone’s sparkle.

While diamond bulge doesn’t completely dull a diamond’s fire, brilliance, and scintillation, it does mean you’re paying more for a lower quality diamond. As such, it’s important to avoid diamond bulge if you can!

What are the different types of diamond bulge?

As previously mentioned, bulging facets can appear in a few areas on a diamond. Here are two specific locations you should inspect closely depending on the shape of the stone:

Pavilion Bulge

Bulging Pavilion of an Emerald Cut Diamond

Pavilion bulge typically occurs in step-cut stones, which feature long, rectangular facets that act almost like mirrors and reflect light back to the wearer. When looking at a high-quality, step-cut diamond, you’ll notice the pavilion elegantly slopes downward from the girdle to the culet. This delicate slope fosters a striking, mirror-like glow within the diamond and produces a slim silhouette.

⚠️When a step-cut diamond suffers from pavilion bulge, this gentle slope is much steeper. The facets between the girdle and culet bulge outward, which enhances the diamond’s weight. Unlike a high-quality cut stone, a diamond with pavilion bulge has sides that look girthy and cause light leakage that impacts its mirror-like shine.

Step-cut diamonds that are affected by pavilion bulge include emerald, Asscher, and baguette-cut gems, so be sure to inspect these shapes when shopping. This is especially important if you’re purchasing a loose diamond, as pavilion bulge can make it difficult to properly set your chosen stone!

Face-up Silhouette Bulge

While step-cut gems are most likely to suffer from diamond bulge, round and fancy cut diamonds can also experience a type of bulging called face-up silhouette bulge.

This type of diamond bulge occurs when the rounded edges of a stone expand too far outward, creating a distorted silhouette. The result is a heavier diamond that looks like a bloated version of the original shape, with bulging shoulders, wings, and more.

Face-up Silhouette Bulge: Bulging Shoulders of an Oval Cut Diamond
This oval cut diamond has bulging shoulders. | Image: Al Gilbertson / GIA

For example, as a fancy shape, the ever-popular oval diamond can sometimes fall victim to face-up silhouette bulge. In theory, the widest part of an oval diamond should be its belly, and the sides should gradually slope outward before creeping inward at the same angle.

On an oval diamond with face-up silhouette bulge, this gentle slope is almost non-existent. Consequently, the diamond has broader, squarer shoulders that make the typically slim oval look more like a cushion-cut gem.🥺

It should be noted that some wearers actually prefer the thicker look of an oval diamond with face-up silhouette bulge, and this is completely fine! What matters most is that you like the shape of your diamond and aren’t put off by the fact that you’ll pay more for such a stone.

Why does diamond bulge happen?

As you can guess, diamonds don’t just naturally bulge: any bulging is a direct result of the stone’s cut. More specifically, diamond cutters may create a poor cut or intentionally produce bulging.🤷🏻‍♂️

Like any profession, diamond cutting includes craftsmen with varying degrees of skill. Most diamond cutters would try their best to avoid unnecessary bulges in a diamond, but some utilize poor techniques that result in shapes that are too broad, very narrow, etc.

Additionally, some diamond cutters choose to create diamond bulge in their products. As we’ve mentioned, diamond bulge is an easy way to artificially enhance the carat weight of a diamond without actually making it appear larger. A diamond cutter may create a diamond with significant bulge so that it will garner a higher price, despite it not actually looking as large as its weight implies.

How does diamond bulge impact a diamond’s beauty and value?

So how exactly does diamond bulge impact the beauty and value of a particular gem? There are several ways diamond bulge may affect your purchase, but here’s a brief breakdown of the major impacts of bulging stones:


Bulging can impact the overall beauty of your diamond by creating a less-than-desirable silhouette. Ovals with shoulder bulge, overly rounded hearts, and puffy emeralds that carry more weight than they should are just a few ways diamonds can be visibly impacted.

Furthermore, diamond bulging impacts a stone’s fire, brilliance, and scintillation by inducing both windowing and extinction.

  • Windowing occurs when a diamond is too shallow or disproportionate, which allows light to leak completely though the table of the stone and out the other side. If you place your finger behind a diamond and can easily see the color of your skin, the diamond suffers from windowing.
  • In contrast, extinction is the presence of dark patches within a diamond, which indicates a blockage of light. Extinction is common in diamonds with high depth percentages as well as stones with bulging pavilion facets.

Issues that decrease a diamond’s fire, brilliance, and scintillation lead to dull diamonds that don’t sparkle under any lighting. If you prefer a dull diamond, more power to you, but most shoppers will feel cheated if they bring home a diamond that doesn’t sparkle!


Diamond bulge also impacts the value of your chosen stone. Some bulging can be seen from the top of the stone, but many silhouettes—such as emerald cuts—carry their weight below the girdle line.

In this case, diamond bulge produces “unseen” weight, and by that we mean a diamond with a higher carat weight that actually appears smaller. As a result, you’ll pay more money for a visually smaller, less appealing diamond than if you had searched for a proper stone without diamond bulge.

How to inspect and avoid diamond bulge?

There are a few ways you can avoid buying a stone with diamond bulge, but you’ll have to be vigilant!🔔 Diamond reports do not detail any information regarding diamond bulge, so you’ll have to do the hard work yourself to identify it.

First, make good use of high-resolution 360° videos and images to closely inspect a diamond from all angles. Checking the diamond yourself can help you discern whether the stone has bulging edges, a heavy pavilion, and more.

James Allen and Blue Nile are two major diamond retailers that offer 360° videos and imaging so you can inspect diamonds from the comfort of your own home. James Allen even offers up to 40x magnification for a close-up look at the inner workings of any diamond!

Additionally, James Allen provides complimentary, real-time diamond inspections with non-commissioned gemologists who can answer your questions about diamond bulge and help you find a stone with an ideal silhouette.

Next, while a diamond report may not detail any bulging, it CAN tell you a lot about the stone’s silhouette. Look at the diamond’s length, width, and other cut qualities to see if they fall within the ideal parameters for the stone’s shape. If a diamond seems to fall within the parameters but has a strange, puffy effect, be careful: bulging may be the cause.

Finally, if you have a nice budget to play with, consider perusing the premier diamonds of A CUT ABOVE by Whiteflash. This particular collection of diamonds was cut with the utmost care and precision, utilizing top-notch techniques for enhanced light performance. Diamonds like these typically avoid issues like bulging altogether, so you’ll pay a bit more but won’t have to worry about optical performance!

Beating diamond bulge: Final thoughts

With the right approach, you can avoid diamond bulge while shopping on your own. When it comes to a diamond, optical performance is everything, and bulging can directly impact your chosen stone’s lovely sparkle. As such, commit yourself to carefully inspecting each diamond you come across for the telltale signs of diamond bulge.

There are several imperfections you can actually identify by yourself when shopping for a diamond, and being able to do so can save you money in the long run! If you’re looking at diamonds with elongated silhouettes, be sure to read more about “the bow-tie effect” here before choosing a gem.

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