The Mohs scale of mineral hardness categorises gems by the various levels of scratch resistance. The scale runs from one to ten, with diamond being the hardest mineral with a rating of ten.
Mohs Scale of Hardness:
1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
6. Orthoclase
7. Quartz
8. Topaz
9. Corundum (Ruby and Sapphire)
10. Diamond