Mohs Hardness Test

Let's Have Some Moh Fun

Kids have fun analyzing minerals with the Mohs hardness test.

Worksheet and suggested activities below

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Mohs Hardness MatchCard

Objective: Apply Moh's hardness test to identify the hardness of minerals.

MatchCard: Download below.

MatchCard Information Pieces describe the different steps of Mohs Test. Ideas for projects are listed on the instructor's page and below.

Print Mohs Hardness MatchCard

This is MatchCard #5 of the Geology Unit Study. Look below for more information on MatchCards and the MatchCard Science curriculum.

How Moh's Hardness Test Works

Moh's Hardness is a scale from 1 to 10 listing minerals from the softest (1) to the hardest (10).

A rock or mineral can only be scratched by an object with a higher ranking on the scale. Therefore, if you know what a mineral is, you can use it to help identify the hardness of other minerals. That will help identify the mineral itself.

There are also other common items such as glass, steel, copper, and even fingernails, that can be used in place of other minerals to identify the hardness of a particular rock or mineral.

Using A Moh's Kit

You can either buy a Moh's Kit like the one above, or make one buy acquiring ten specimens of common minerals.

The most commonly used minerals are:

• 10. Diamond
• 9. Corundum
• 8. Topaz
• 7. Quartz
• 6. Feldspar
• 5. Apatite
• 4. Fluorite
• 3. Calcite
• 2. Gypsum
• 1. Talc

Most kits, whether purchased or made, do not have a diamond, which is the hardest level. Of course, you can always borrow someone's wedding ring to do this test. However, for students one can probably perform tests with specimens 1 through 9 and get the point across without using a real diamond.

To perform the test, give the students the minerals without any identification. They must see what minerals will scratch the other minerals.

By trial and error, the students arrange the specimens in order of hardest to softest.

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Identify Unknown Specimens

After students have performed the first test, they can now use the known minerals to identify the hardness of unknown minerals.

Give the students 5 to 6 specimens of other rocks and minerals. Let them experiment to identify the hardness on the Mohs Scale.

Once the hardness is identified, let them use a rock guide to see if they can find the name of their specimen.

If a rock is being tested, once it is found in the field guide the student should also identify if it is a Igenous, Sedimentary, or Metamorphic rock.

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Use Common Tools

For this final rock identification activity, we will use common tools instead of known specimens.

• Fingernail
• Copper penny
• Nail
• Steel knife (does not need to be sharp)
• Steel file
• Glass (pocket sized mirror will work)

In addition you will need a variety of rocks and minerals. You may use the specimens used in the previous activity. (Unless they have already memorized the identify of the specimens.)

With the assortment of specimens, they start at the bottom test of hardness (fingernail), and if it does scratch the surface of the rock, they move to the next hardest test.

• 10. The hardest mineral
• 9. Can only be scratched by a diamond
• 8. Rock can scratch glass
• 7. Rock can scratch steel
• 6. Scratched by a steel file
• 5. Scratched by a steel knife
• 4. Scratched by a nail
• 3. Scratched by a copper penny
• 2. Scratched by a fingernail
• 1. Easily scratched by a fingernail

Again, it is helpful to check your rocks and minerals field guide to verify the correct specimen.