Hardness is a gem's resistance to scratching. Gemologists rank it on the Mohs scale, on which diamond is 10.
In more detail
Diamond is 10, moissanite 9.25, ruby and sapphire 9, and cubic zirconia 8 to 8.5. Emerald is 7.5 to 8 and amethyst 7. Mohs is a ranking, not a ruler: diamond is far harder than corundum. Hardness is not toughness, so a hard stone can still chip.
How we measure it
Our gemstone pages give each stone's Mohs hardness.
Related terms
- Mohs scale: The Mohs scale ranks minerals from 1 to 10 by which can scratch which. Diamond is 10 and corundum is 9.
- Toughness: Toughness is a gem's resistance to chipping and breaking. It differs from hardness, which is resistance to scratching.
- 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.
- Cleavage: 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.
- Scratch: A scratch is a thin, dull white line across the surface with no clear depth at 10x.
Learn more
- Diamond vs moissanite properties: hardness, refractive index, dispersion, density
- Moissanite vs diamond: wear, care and cleaning
- Diamond 3D models and cutting files
- Ruby 3D models and cutting files
- Emerald 3D models and cutting files
- Amethyst 3D models and cutting files
- Cubic Zirconia 3D models and cutting files