Hardness is the power a mineral has to resist scratching (abrasion)
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 you 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 |