Moh's Hardness Test
- The Moh's hardness scale for minerals has been used since 1822.
- It consists of 10 minerals arranged in order from 1 to 10.
- Diamond is rated as the hardest and is indexed as 10
- Talc as the softest with index number 1.
- The steps are not of equal value and the difference in hardness between 9 and 10 is much greater than between 1 and 2.
- The hardness is determined by finding which of the standard minerals the test material will scratch or not scratch; the hardness will lie between two points on the scale - the first point being the mineral which is scratched and the next point being the mineral which is not scratched.
- Some examples of the hardness of common metals in the Moh's scale are copper between 2 and 3 and tool steel between 7 and 8.
- Each mineral in the scale will scratch all those below it as follows:
Diamond 10
Corundum 9
Topaz 8
Quartz 7
Orthoclase (Feldspar) 6
Aptite 5
Fluorite 4
Calcite 3
Gypsum 2
Talc 1