The Mohs Scale

by Felicia Davies

The Mohs Scale, named after German geologist Friedrich Mohs, is a hardness scale that characterizes the scratch resistance of gems and minerals. Minerals are scratched against other minerals of known hardness to see if they can resist a surface scratch. If the surface is left unmarred and the other known mineral gets scratched, this mineral is harder, but if the known mineral scratches the surface, the unknown mineral is softer.

The scale may have been named after Mohs the geologist, but hardness testing has been used since 300 BC when it was mentioned in On Stone, a treatis by Theophrastus.

Talc is the softest mineral on the Mohs Scale and diamond is the hardest.

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