---
title: "Facet: meaning in gemology"
description: "A facet is one flat, polished face of a cut gemstone. Its angle and its direction around the stone decide where it sends light."
url: https://digitalgemology.com/learn/glossary/facet
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Cutting and files

# Facet

Also called face, facets

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](https://digitalgemology.com/learn/glossary/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](https://digitalgemology.com/learn/glossary/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](https://digitalgemology.com/learn/glossary/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](https://digitalgemology.com/learn/glossary/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](https://digitalgemology.com/learn/glossary/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](https://digitalgemology.com/learn/glossary/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.

## Learn more

- [The 3D models](https://digitalgemology.com/about/how-we-measure/3d-models)
- [Who uses our files](https://digitalgemology.com/about/files)

[All 328 terms](https://digitalgemology.com/learn/glossary)