Friedrich Mohs

Friedrich Mohs is famous in the gem world as the creator of the Mohs scale of mineral hardness. His scale is still widely used today. But who was Friedrich Mohs and how did he come to create his scale?

Mohs was born to a merchant's family in the town of Gernrode in Germany in 1773. After attending school at Halle, he went on to study at the mining academy at Freiberg, where he was greatly influenced by his teacher, Abraham Werner. Werner inspired the young Mohs with a lifelong interest in mineralogy and geognosy, or the geological study of materials forming the earth.

In 1801 Friedrich Mohs moved to Austria, and began work in two different capacities. He was employed as a foreman at the Neudorf mine in the eastern Harz Mountain region, but of more interest to Mohs with his passion for rocks, was his second job - he was hired by a rich Austrian banker, J.F. van der Null who had a large mineral collection which was in need of a curator. Mohs' task was to sort the collection into categories, and to identify those materials which were still unknown.

This was a great challenge for Mohs as at the time, there was no accepted way to categorize minerals. Using the same reasoning as botanists, who sorted plants and animals with similar physical characteristics into genus groups, Mohs began examining the minerals for common properties which would allow him to group them together for identification.

Although this approach was widely criticized by the mineralogical establishment of the time, it was to ultimately bring him fame, as one of the main physical properties Mohs concentrated on was the hardness of the material in question.

Mohs noted that certain minerals could be used to scratch the surface of other minerals, so he reasoned that this scratch test could be used to rank minerals by their hardness. In this way he eventually ranked all the minerals according to their hardness. The scale ranged from the softest mineral, talc, to the hardest, diamond.

Around 1810 Mohs gave up his job as mine foreman and in 1812 became a professor of mineralogy in Gratz where he finalized his work on hardness. Creating a scale of one to ten, he assigned each mineral a value, which was to become the Mohs' Scale of Hardness.

In 1817, Mohs replaced his mentor Werner, who had died, as a tutor at the mining academy in Freiberg, where he worked for nine more years, until he was appointed as a professor of Mineralogy at the University of Vienna. Mohs ended his remarkable career as a mining advisor at the Mining University in Leoban and died aged 66, while holidaying in Italy.