Mohs Hardness Scale

The ability of a solid substance to resist surface deformation or abrasion. In mineralogy, hardness is defined as the resistance of the smooth surface of a mineral to scratching. It is determined by the Mohs scale of hardness, named for German mineralogist Friedrich Mohs. In the Mohs scale, ten common minerals are arranged in order of increasing hardness and assigned numbers:

1. talc
2. gypsum
3. calcite, Baking Soda (3.5)
4. fluorite, Corn cob (4.5)
5. apatite
6. orthoclase ( feldspar)
7. quartz
   CRYSTAL GRIT
   Garnet
8. topaz
9. corundum
10. diamond

The hardness of a given mineral specimen is then determined by which mineral in the Mohs scale will scratch it.

In metallurgy and engineering, hardness is determined by impressing a hard material on the surface to be tested and measuring the size of the indentation. This is known as the Brinell test, after Swedish engineer Johann Brinell.