The MOHS Hardness Scale

Hardness is measured using the MOHS Hardness Scale. A substance's hardness value indicates the resistance to scratching and grades minerals on a relative scale from 1 (which is very soft) to 10 (which is very hard).. In the MOHS scale, a mineral of a given hardness rating will scratch other minerals of the same rating, as well as any minerals of a lower rating. For example, sapphires and rubies have a MOHS rating of 9 and will scratch each other, as well as any mineral with a rating lower than 9. However, they will not scratch diamonds, which are rated 10. The MOHS scale of mineral hardness was devised by the German mineralogist Frederich MOHS (1773-1839) in 1812.

Hardness Mineral Hardness Common Objects
1 Talc Soft Softest known mineral a fingernail can scratch it so it flakes
2 Gypsum 2.5 Fingernail
3 Calcite 2.5-3 Gold, Silver
4 Fluorite 3 Copper coin
5 Apatite 5.5 Knife blade, window glass
6 Feldspar 5.5 Glass
7 Quartz 6.5 Hardened steel file
8 Topaz
Can scratch Quartz
9 Corundum
Can scratch Topaz
10 Diamond
Hardest known mineral. Diamond can scratch all other substances


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