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Mohs Scale of Hardness
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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

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 from fluorite prevents tooth decay.

5

Apatite Apatite is a mineral in vertebrate bones and teeth.

6

Orthoclase Orthoclase is a feldspar, and in German, "feld" means "field".

7

Quartz Quartz is the most common mineral in the Earth's crust.

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
>10 Wurtzite Boron Nitride
>10 Lonsdaleite (Hexagonal Diamond)

 

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