A facet is one flat, polished face of a cut gemstone. Its angle and its direction around the stone decide where it sends light.
In more detail
Facets are grouped into the crown above the girdle, the girdle, and the pavilion below it. In a faceting design, each facet has an angle and an index position on the gear. We measure facet angles from the girdle plane.
How we measure it
Our models are closed solids of flat facets. The tools trace each convex cut as the intersection of one half-space per facet.
Related terms
- Planar facet: A planar facet is a facet that lies exactly in one flat plane. Real cut stones and our models have planar facets; curved or smoothed display models do not.
- Tier: A tier is a set of facets cut at the same angle, at several index positions around the stone. A faceting design lists its tiers in cutting order.
- Facet count: The facet count is the number of facets on a cut. On our cut pages, it is the number of planar faces of the cut's STEP solid.
- Index gear: An index gear is the toothed wheel on a faceting machine that sets each facet's direction around the stone. Each index is one tooth of the gear.
- Crown: The crown is the part of a cut stone above the girdle. On a standard round brilliant it has 33 facets: the table, 8 stars, 8 bezels and 16 upper halves.
- Pavilion: The pavilion is the cone-shaped part of a cut stone below the girdle. A standard round brilliant has 24 pavilion facets: 8 mains and 16 lower halves.