Anatomy of a diamond
The parts of a diamond, and how light moves through them.
Knowing the parts of a diamond makes a grading report easier to read and explains why cut matters so much. Every term below appears on reports and in conversations with a jeweller.
From the CTJ Jewellery team, led by founder Greg Ward
- Table
- The large flat facet on top. Light enters here.
- Crown
- The upper section between the table and the girdle. Its angles create fire.
- Girdle
- The thin outer edge. Graded diamonds carry their laser-inscribed report number here.
- Pavilion
- The lower section. Its angles reflect light back up through the table.
- Culet
- The point or tiny facet at the base.
- Facets
- The flat polished surfaces. A round brilliant cut has 57 or 58.
How a diamond handles light
A well-cut diamond takes in light through the table, reflects it off the pavilion and returns it through the top. When the angles are off, light leaks out of the sides and base and the diamond looks darker.
- Brilliance
- The white light a diamond returns.
- Fire
- Flashes of spectral colour as light splits.
- Scintillation
- The sparkle and pattern of light and dark as the diamond moves.
Proportions that affect sparkle
Grading laboratories measure table and depth as a percentage of the diamond’s width. For a round brilliant, these ranges are widely associated with strong light return. We still judge every diamond by eye.
| Measurement | What it is | Commonly preferred for rounds |
|---|---|---|
| Table % | Table width as a share of total width | About 53% to 58% |
| Depth % | Total depth as a share of width | About 59% to 62.5% |
| Girdle | Thickness of the outer edge | Thin to slightly thick |
| Culet | The point at the base | None or very small |
How cut affects light
- Too shallow: light leaks out through the pavilion, and the centre looks glassy
- Too deep: light escapes through the sides, and the centre looks dark
- Well cut: light reflects off the pavilion and returns through the table