The Anatomy of a Diamond

Every cut diamond, whatever its shape, is built from the same parts:

Table

The large flat facet on top. It is the window into the stone, and the facet you see most.

Crown

The angled upper section between the table and the girdle. Its facets break light into flashes of colour, the diamond’s fire.

Girdle

The thin edge around the widest part of the stone, where the setting holds it. It can be polished, faceted or left slightly rough.

Pavilion

The lower, pointed section beneath the girdle. Its angles reflect light back up through the top of the stone.

Culet

The point, or tiny facet, at the very bottom. In modern diamonds it is usually a point or very small; in antique cuts it is often large enough to see.

Light enters through the table and crown, travels down to the pavilion, and should be reflected back up to your eye. If the pavilion is too deep, light escapes through the sides and the centre looks dark. If it is too shallow, light leaks out through the bottom and the stone looks glassy and lifeless. This is what the cut grade measures.

Two numbers on a report describe the proportions. Depth percentage is the stone’s height divided by its width. Table percentage is the width of the table divided by the width of the stone. There is no single perfect figure, and the ideal ranges differ by shape, but numbers far outside the usual range are worth a closer look.

The report describes the girdle’s thickness, from extremely thin to extremely thick. A very thin girdle can chip; a very thick one adds hidden weight that makes the stone look smaller than its carat weight suggests. Medium to slightly thick is a sensible range.

The culet is usually listed as none or pointed in modern stones. A large culet shows as a small dark circle when you look down through the table, which is part of the charm of an old mine cut and usually unwanted in a modern brilliant.

You do not need to memorise angles. But knowing the parts helps you read a report, understand why two diamonds of the same carat can look different in size, and ask the right questions about a stone before it is set.