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The 'Mohs scale of mineral hardness' characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science.
Mohs based the scale on ten minerals that are all readily available. As the hardest known naturally occurring substance, diamond is at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, and/or the softest material that can scratch the given material. For example, if some material is scratched by apatite but not by fluorite, its hardness on the Mohs scale would fall between 4 and 5.
The Mohs scale is a purely ordinal scale. For example, corundum (9) is twice as hard as topaz (8), but diamond (10) almost four times as hard as corundum. The table below shows comparison with absolute hardness measured by a sclerometer.

Hardness	Mineral	Absolute Hardness
1	Talc(Mg3Si4O10(OH)2)	1
2	Gypsum (CaSO4·2H2O)	2
3	Calcite (CaCO3)	9
4	Fluorite (CaF2)	21
5	Apatite(Ca5(PO4)3(OH-,Cl-,F-))	48
6	Orthoclase Feldspar (KAlSi3O8)	72
7	Quartz (SiO2)	100
8	Topaz (Al2SiO4(OH-,F-)2)	200
9	Corundum (Al2O3)	400
10	Diamond (C)	1500

On the Mohs scale, a fingernail has hardness 2.5; a copper penny, about 3.5; a knife blade, 5.5; window glass, 5.5; steel file, 6.5.^[1] Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale.
The table below incorporates additional substances that may fall between levels:

Hardness	Substance or Mineral
1	Talc
2	Gypsum
2.5 to 3	pure Gold, Silver
3	Calcite, Copper penny
4	Fluorite
4 to 4.5	Platinum
4 to 5	Iron
5	Apatite
6	Orthoclase
6	Titanium
6.5	Iron pyrite
6 to 7	Glass, Vitreous pure silica
7	Quartz
7 to 7.5	Garnet
7 to 8	Hardened steel
8	Topaz
9	Corundum
10	Diamond
>10	Ultrahard Fullerite
>10	Aggregated diamond nanorods

Contents

Notes

References

Notes

1. "The Hardness of Minerals and Rocks" by William S. Cordua Hosted at International Lapidary Association

References

★ American Federation of Mineralogical Societies. "Mohs Scale of Mineral Hardness". Last Revised on April 21, 2007. Retrieved on August 19, 2007.

★ Cordua, William S. "The Hardness of Minerals and Rocks". ''Lapidary Digest'', c. 1998.