---
title: "Mirror-image symmetry (design): meaning in gemology"
description: "Mirror-image symmetry in a faceting design is the number of identical mirrored sections around the stone. An 8-fold mirror-image design repeats the same…"
url: https://digitalgemology.com/learn/glossary/mirror-image-symmetry
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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

# Mirror-image symmetry (design)

Also called 8-fold symmetry, design symmetry

Mirror-image symmetry in a faceting design is the number of identical mirrored sections around the stone. An 8-fold mirror-image design repeats the same pair of mirrored halves eight times.

## In more detail

It describes the design, not how precisely a real stone is cut. A round brilliant such as the T73 has 8-fold mirror-image symmetry.

## How we measure it

Our cut pages give each design's symmetry. The Hearts & Arrows Scope averages each facet over its 16 mirror and turn copies. So a cut as designed reads 100%.

## Related terms

- [Symmetry](https://digitalgemology.com/learn/glossary/symmetry): Symmetry is the report grade, from Excellent to Poor, for the exactness of a stone's outline. It also covers the shape, placement and alignment of the facets.
- [Hearts and arrows symmetry](https://digitalgemology.com/learn/glossary/hearts-and-arrows-symmetry): Hearts and arrows symmetry is the share of a hearts and arrows pattern where all sixteen halves match. Our Hearts & Arrows Scope gives it as a whole percent for each view.
- [Symmetry (light performance)](https://digitalgemology.com/learn/glossary/symmetry-light-performance): In our light-performance scores, symmetry measures how evenly the pavilion facets of each angle family are cut. It reads 100 when every facet in a family has the same angle and distance from the center.
- [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.

## Learn more

- [T73 Round Brilliant Cut](https://digitalgemology.com/cuts/t73-round-brilliant)
- [Hearts & Arrows Scope](https://digitalgemology.com/about/how-we-measure/hearts-and-arrows-scope)

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