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Mohs Hardness Scale

 

A material's hardness is its resistance to scratching or grinding. The scale is a standard of ten minerals by which the hardness of a mineral may be rated. A rock's hardness can be determined by its ability to scratch softer materials. A simple method for determining hardness is through the use of a glass plate, pocket knife, copper wire, or by a harder mineral. The color of a mineral's streak color is also an important tool for making mineralogical identifications.

Mohs Hardness Scale is as follows (from softest to hardest).

 

1. Talc

2. Gypsum (photo: selenite from Utah)

3. Calcite (photo: honey calcite from Florida)

(scratched by copper wire)

4. Flourite (photo: fluorite from Illinois)

5. Apatite (photo: apatite as fossil bone from Florida)

(scratched by pocket knife)

6. Orthoclase

7. Quartz (photo: quartz crystals)

(scratches glass)

8. Topaz

9. Corundum (example: ruby)

10. Diamond*

(cuts glass)

* The diamond hardness is actually better represented as 40.

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