Mohs scale of hardness

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Mohs' scale of hardness The scale is not regular. Diamond, the hardest known natural substance, is 90 times harder than corundum.

Mineral

Hardness

Simple hardness test

Talc

1.0

Crushed by fingernail

Gypsum

2.0

Scratched by fingernail

Calcite

3.0

Scratched by copper coin

Fluorspar

4.0

Scratched by glass

Apatite

5.0

Scratched by knife blade

Feldspar

6.0

Scratched by quartz

Quartz

7.0

Scratched by steel file

Topaz

8.0

Scratched by corundum

Corundum

9.0

Scratched by diamond

Diamond

10.0

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