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Friedrich Mohs

Friedrich Mohs was a German geologist who studied minerals (a mineralogist!). He lived from 1773 to 1839.

He moved to Austria in 1801 where he found a job identifying minerals in a collection owned by a wealthy banker. He used physical characteristics of the crystals to decide what they were. One of the characteristics he used to identify minerals was hardness.

He knew that some of the minerals could scratch other minerals. He decided that if a mineral could make a scratch on another, it must be harder than the mineral that was scratched. He found that all other minerals could scratch the mineral talc, so it must be very soft. He also found that diamonds were so hard that they could scratch every other mineral and could not be scratched by anything. Even today, we have not been able to find a mineral that is harder than a diamond.

About a decade later, Friedrich created a scale from one to ten to describe mineral hardness while he was a professor at an Austrian University. He assigned harder minerals larger numbers as they could scratch any mineral with a smaller number. Talc, the softest mineral, he assigned to one, the smallest number on the scale. Diamond, the hardest mineral, he assigned to 10, the largest number on the scale.

Perhaps the wealthy Austrian banker would not have been happy if he had known Friedrich was scratching the minerals in his collection, but geologists around the world appreciate Mohs. Geologists still rely on Friedrich's scale today! We call it Mohs Hardness Scale.

Last modified May 6, 2003 by Lisa Gardiner.

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The Fall 2010 issue of The Earth Scientist, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!

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