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