Diamond Knowledge

Anatomy of a Round Brilliant

A round brilliant is a small piece of optical engineering. Learn its parts, and the language on a grading report — and the reasons behind a cut grade — fall into place.

← Part of the Brilliani Labs Diamond Guide

What are the main parts of a diamond?

From top to bottom: the table (the flat top facet), the crown (the upper section), the girdle (the thin band at the widest point), the pavilion (the lower section), and the culet (the point or tiny facet at the very bottom).

How many facets does a round brilliant have?

Fifty-seven, or fifty-eight if the culet is a small facet rather than a point.

What is the table?

The large flat facet on top, and the main window through which light enters and returns. Table size is given as a percentage of the diamond's diameter.

What is the crown?

The sloped upper section between the table and the girdle. Its angle and height help split light into colour (fire) and direct brilliance back to the eye.

What is the girdle?

The narrow band around the widest part of the diamond, where the crown meets the pavilion. It ranges from extremely thin to extremely thick, can be polished or faceted, and is where a report number is often laser-inscribed.

What is the pavilion?

The lower section, from the girdle down to the culet. Its angle and depth are critical: get them right and light reflects back up through the table; get them wrong and light leaks out. This is the heart of why cut beats carat.

What is the culet?

The point at the very bottom, or a tiny facet there. Ideally it is none or very small; a large culet can show as a dark spot through the table.

What is total depth, and why does it matter?

The height from table to culet, given as a percentage of the diameter. Together with table size and the crown and pavilion angles, it determines how well the diamond returns light.

Why does anatomy matter when choosing a diamond?

Because these proportions are what a cut grade measures. Understanding them is how you read a proportions diagram and understand why one round brilliant outperforms another. It is also the groundwork for how to read a grading report.