The Mohs Scale of Hardness Explained

Sunday, April 5, 2020

The Mohs scale of mineral hardness is based on the ability of one mineral to scratch another mineral visibly. The Mohs' hardness scale was developed in the 1800s by Frederich Mohs, a German mineralogist. 
Hardness is a measure of a mineral’s ability to resist being scratched. He selected ten minerals of different hardness that ranged from a very soft mineral (talc) to a very hard mineral (diamond). 
When completing hardness tests of the minerals it is necessary to determine which mineral was scratched.

Let’s go through the Moh’s Scale

As you move up the scale hardness increases

1 Talc

2 Gypsum

3 Calcite

4 Fluorite CaF2

5 Apatite

6 Orthoclase feldspar

7 Quartz

8 Topaz

9 Corundum

10 Diamond

You can also use common household items to test for hardness.

  • A fingernail 2-2.5
  • Penny 3.5
  • Nail 5-6
  • Glass 5- 5.5
  • Streak plate 6 6.5
  • Quartz 7
Let's determine the hardness of a mineral. The mineral can scratch talc so it has a hardness greater than 1. However, the mineral can be scratched by calcite which has a hardness 3 so its hardness is 2.

Now I can use this information, along with a mineral field guide in order to identify the mineral.

Additional Mohs Scale Resources

Mohs scale on Youtube

Helpful Article

A very detailed list of Mineral and Hardness


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