---
title: "Cleavage: meaning in gemology"
description: "Cleavage is a mineral's tendency to split along flat planes in its crystal structure. A hard knock in a cleavage direction can split a stone."
url: https://digitalgemology.com/learn/glossary/cleavage
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Gemstone properties

# Cleavage

Also called cleavage plane, cleavage direction

Cleavage is a mineral's tendency to split along flat planes in its crystal structure. A hard knock in a cleavage direction can split a stone.

## In more detail

Diamond has cleavage, so it can split even though it is the hardest gem. Corundum has no cleavage. GIA's researchers broke a moissanite cube with a hammer: it showed curved, shell-like fractures and no cleavage.

## Related terms

- [Toughness](https://digitalgemology.com/learn/glossary/toughness): Toughness is a gem's resistance to chipping and breaking. It differs from hardness, which is resistance to scratching.
- [Hardness (Mohs)](https://digitalgemology.com/learn/glossary/hardness): Hardness is a gem's resistance to scratching. Gemologists rank it on the Mohs scale, on which diamond is 10.
- [Fracture](https://digitalgemology.com/learn/glossary/fracture): Fracture is the way a gem breaks when it does not split along a cleavage plane. Conchoidal fracture leaves curved, shell-like surfaces.
- [Durability](https://digitalgemology.com/learn/glossary/durability): Durability is a gem's ability to resist scratching, breaking, and damage from heat, light or chemicals. It has three parts: hardness, toughness and stability.
- [Crystal system](https://digitalgemology.com/learn/glossary/crystal-system): A crystal system groups crystals by the symmetry of their atomic structure. Gemologists use seven: cubic, tetragonal, hexagonal, trigonal, orthorhombic, monoclinic and triclinic.

## Learn more

- [Diamond vs moissanite properties: hardness, refractive index, dispersion, density](https://digitalgemology.com/learn/diamond-vs-moissanite/diamond-vs-moissanite-properties)
- [Moissanite vs diamond: wear, care and cleaning](https://digitalgemology.com/learn/diamond-vs-moissanite/moissanite-vs-diamond-durability-and-care)

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