When people talk about diamonds, we often hear terms like brilliance, cut, or clarity—but underneath it all is something more fundamental: a diamond’s anatomy. Every diamond is made up of distinct parts, each one influencing how the stone interacts with light, how it’s graded, and ultimately how it looks.
Understanding diamond anatomy gives you a better sense of why cut matters, why proportions make such a difference, and how gemologists evaluate quality.
In this guide, we’ll walk through the major parts of a diamond, explain how they work together, and show you what to look for when comparing stones side by side.
Note: While there are many different diamond shapes—each with its own unique anatomy—this guide will focus on the round brilliant cut. As the most popular and widely studied shape, it serves as the standard reference for explaining diamond anatomy.
The Foundation: Facets
Before we talk about diamond anatomy, we first have to understand what facets are. Facets are the flat, polished surfaces that cover a diamond’s exterior. They act like tiny mirrors, catching and reflecting light back to your eye. In a round brilliant diamond, there are typically 57 or 58 facets, each precisely arranged to maximize brilliance, fire, and scintillation. The exact placement and angles of these facets are what determine how light travels through the stone. Well-cut facets create lively sparkle and balance, while poorly aligned ones can cause uneven light return or dark spots. In many ways, facets are the building blocks of a diamond’s beauty.
The Table
The table is the flat surface on the very top of a diamond. It’s the largest facet, and it acts as the main entry point for light. Light comes in through the table, reflects off the internal facets, and returns to your eye.
If the table is too large or too small compared to the rest of the stone, it affects how much light is returned. A well-proportioned table helps balance brightness (brilliance) with flashes of color (fire).
The Crown
The crown is the upper section of the diamond that sits just below the table and extends down to the girdle. It’s made up of angled facets that help bend, reflect, and disperse light into the diamond internally, giving off brightness and fire.
The crown’s angle and height influence how vivid the internal reflections appear. Too shallow, and light play can be muted; too steep, and the stone may lose some brightness.
The Girdle
The girdle is the thin band that runs around the widest part of the diamond. It separates the crown and the pavilion.
The girdle doesn’t directly affect sparkle, but it plays an important role in durability.
A girdle that’s too thin can chip, while one that’s too thick adds unnecessary weight without making the diamond look bigger. With this in mind, you may probably recall pieces of jewelry with bezels around the stone. The bezels in these cases protect the girdle.
The Pavilion
The pavilion is the bottom portion of the diamond, stretching from the girdle down to the culet. This area is critical for how light bounces around inside the stone.
If the pavilion is cut too deep, light escapes from the bottom, making the diamond look dark in the center. Too shallow, and light leaks out the sides. The right proportions allow light to reflect back through the table, creating brightness and life.
The Culet
At the very bottom is the culet. It’s a super tiny facet at the tip of the pavilion. The reason it exists is not necessarily for light/optical reasons, but rather to add durability to the diamond. Having an incredibly small point at the bottom of a diamond makes it pretty fragile and prone to breaking.
The idea here is that with a flat surface present, the stone is more durable against chipping.
This all being said, ideally the culet is so small you can’t see it. Larger culets can make the diamond have a black spot when looking straight down through the table.
Today, most well-cut diamonds have either no culet or one that is graded “very small.”
How Anatomy Shapes Beauty
When you put these parts together—facets, table, crown, girdle, pavilion, and culet—you get the structure that determines how a diamond handles light. Proportions between these areas are what gemologists evaluate when assigning a cut grade.
For example, the relationship between table size and crown angle influences fire, while pavilion depth affects brilliance. Even small adjustments in anatomy can mean the difference between a diamond that looks dull and one that sparkles vividly.
Seeing It for Yourself
Charts and reports are helpful, but the best way to understand diamond anatomy is to see it in person. Tilting the stone in different lighting will show you how the parts interact. You can see how the diamond does with regards to brilliance, scintillation, and fire.
More specifically, with the help of a professional you’ll be able to identify how the table catches light, how the crown disperses color, and how the pavilion reflects brightness back to your eye.
At Paul’s Jewelers, we’ve been helping clients in Milwaukee and beyond choose diamonds for over 55 years. With one of the largest jewelry manufacturing operations in the state, our team includes GIA-trained gemologists that can show you exactly how diamond anatomy influences its appearance, and price.
Whether you’re shopping for an engagement ring, upgrading a family heirloom, or designing a one-of-a-kind masterpiece, we’ll walk you through the details so you feel confident in your choice.
Stop by our showroom to see how every part of a diamond comes together to create beauty that’s sure to be enjoyed for years to come.