Minerals Topics


Mineral Identification (Part 4)


Hardness measures a mineral’s resistance to scratching.

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Moh’s Scale of Hardness is used to describe mineral hardness.  On the scale, minerals with higher numbers will scratch minerals with lower numbers. 

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

Gypsum (upper left) has a hardness of 2.  Calcite (upper right) has a hardness of 3. Fluorite (lower left) has a hardness of 4.  Orthoclase feldspar (lower right) has a hardness of 6.

Quartz (upper left) has a hardness of 7. Topaz (upper right) has a hardness of 8. Diamond (below) has a hardness of 10. (Photographs by Parvinder Sethi)

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Geologists use their fingernails, pennies, glass, and steel to measure the hardness of minerals

Scratch By comparing the hardness of common objects to minerals, geologists can determine an unknown mineral’s hardness.  The human fingernail has a hardness of 2.5.  A penny has a hardness of 3.5.  Glass and steel have a hardness of 5.5. (Photographs by Parvinder Sethi)