Hardness is the ability of a mineral to resist abrasion. Hard substances tend to have a strong internal structure.

The hardest minerals are usually members of the silicate and oxide groups.

Sulphates and borates tend to be very soft.

Minerals are classified on the Mohs scale. This is a scale from 1 to 10 with 10 being the hardest. Each level has a description of it's ability to be abrased.

The Mohs Scale

1. Softest-can be scratched by a fingernail	e.g. talc
2. Can be scratched by a fingernail but less easily	e.g. gypsum
3. Can be scratched by a sharper item e.g. a coin	e.g. calcite
4. Can be scratched with a knife	e.g. flourite
5. Can be scratched with a needle	e.g. apatite
6. Can scratch glass	e.g. orphoclase
7. Can scratch fairly easily	e.g. quartz
8. Can scratch quartz easily	e.g. topaz
9. Can scratch quartz and harder substances	e.g. corundum
10. The hardest	e.g. diamond