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 |
Mineral |
Associations and Uses |
| 1 |
Talc |
Talcum powder |
| 2 |
Gypsum |
Plaster of Paris. Gypsum is formed when
seawater evaporates from the Earth's surface |
| 3 |
Calcite |
Limestone and most shells contain calcite |
| 4 |
Fluorite |
Fluorine in fluorite prevents tooth decay |
| 5 |
Apatite |
When your are hungry, you have a big "appetite" |
| 6 |
Orthoclase |
Orthoclase is a feldspar, and in German, "feld"
means "field" |
| 7 |
Quartz |
|
| 8 |
Topaz |
The November birthstone. Emerald and
aquamarine are varieties of beryl with a hardness of 8. |
| 9 |
Corundum |
Sapphire and ruby are varieties of corundum.
Twice as hard as topaz. |
| 10 |
Diamond |
Used in jewelry and cutting tools. Four
times as hard as corundum. |
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
| 
