Mohs Scale of Mineral Hardness

In 1812 the Mohs scale of mineral hardness was devised by the German mineralogist Frederich Mohs (1773-1839), who selected the ten minerals because they were common or readily available. The scale is not a linear scale, but somewhat arbitrary.

Hardness	Key Stone	Comments
10	Diamond	Hardest mineral known to man
9	Corundum (Sapphire/Ruby)	Harder than Topaz
8	Topaz	Harder than Quartz
7	Quartz	Scratches Glass
6	Microcline	Suitable for gems
5	Apatite	About the hardness of teeth
4	Fluorite	Cannot be scratched with a nail
3	Calcite	Difficult to scratch with a nail
2	Gypsum	Easily scratched with nail
1	Talc	Very soft, chalk-like

   

Mohs Hardness Scale
Hardness	Name of Mineral		Comparison	Level
1	Talc	Can be scratched by fingernail		SOFTEST
2	Gypsum	Can be scratched by fingernail		↓
3	Calcite	Can be scratched by a coin		↓
4	Fluorite	Can be scratched by a knife blade		↓
5	Apatite	Can be scratched by a knife blade		↓
6	Orthoclase Feldspar	Harder than Steel		↓
7	Quartz	Harder than Steel		↓
8	Topaz	Harder than Steel		↓
9	Corundum	Harder than Steel		↓
10	Diamond	Harder than Steel		HARDEST
Table / Scale

Hardness of some other items:

2.5	Fingernail
2.5–3	Gold, Silver
3	Copper penny
4-4.5	Platinum
4-5	Iron
5.5	Knife blade
6-7	Glass
6.5	Iron pyrite
7+	Hardened steel file