Dogtooth calcite
Click on image for full size
Courtesy of Corel Photography

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.

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

What Is a Mineral?

Minerals occur naturally on rocky planets and form the building blocks of rocks. They are non-living, solid, and, like all matter, are made of atoms of elements. There are many different types of minerals...more

Whatís That Mineral?

Each type of mineral is made of a unique group of elements that are arranged in a unique pattern. However, to identify minerals you donít need to look at the elements with sophisticated chemical tests....more


Quartz is the second most common mineral in Earthís crust. It is a member of the quartz group, which includes less common minerals such as opal, crystobalite, and coesite. Silica (Si) and Oxygen (O) are...more

Mica Minerals

Mica minerals make some rocks sparkle! They are often found in igneous rocks such as granite and metamorphic rocks such as schist. They sparkle because light is reflected on their flat surfaces, which...more


Feldspar is the most common mineral in the Earthís crust, so you are very likely to find it in the rocks you collect! It is found it all of the three rock types, but is most common in intrusive igneous...more


Olivine looks like little green crystals. It is typically found in some igneous and metamorphic rocks. Often the crystals are so small that you need to use your hand lens or magnifying glass to see them...more

Type of Minerals

So far, over 2000 minerals have been found, and every year new ones are discovered. This is a pretty overwhelming number of different types of minerals, however, you don't need to know them all to be...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA