Mohs scale of mineral hardness
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The '''Mohs scale of mineral hardness''' characterizes the scratch resistance of various [[mineral]]s through the ability of a harder material to scratch a softer material. It was created in 1812 by the German [[Mineralogy|mineralogist]] [[Friedrich Mohs]] and is one of several definitions of [[Hardness (materials science)|hardness]] in [[materials science]]. The method however, is of great antiquity, and is first mentioned by [[Pliny the Elder]] in his [[Naturalis Historia]] first published in about 77 AD.
==Minerals==
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 [[Level of measurement#Ordinal measurement|ordinal]] scale. For example, [[corundum]] (9) is twice as hard as [[topaz]] (8), but diamond (10) is almost four times as hard as corundum. The table below shows comparison with [[absolute hardness]] measured by a [[sclerometer]], with pictorial examples.
{| class="wikitable sortable"
|-
!Hardness
!Mineral
!Absolute Hardness
!Image
|-
|align="center"|1
|[[Talc]] (Mg<sub>3</sub>Si<sub>4</sub>O<sub>10</sub>(OH)<sub>2</sub>)
|align="center"|1
|[[Image:Talc block.jpg|100px]]
|-
|align="center"|2
|[[Gypsum]] (CaSO<sub>4</sub>·2H<sub>2</sub>O)
|align="center"|2
|[[Image:Gypsum Australia.jpg|100px]]
|-
|align="center"|3
|[[Calcite]] (CaCO<sub>3</sub>)
|align="center"|9
|[[Image:Calcite-sample2.jpg|100px]]
|-
|align="center"|4
|[[Fluorite]] (CaF<sub>2</sub>)
|align="center"|21
|[[Image:Fluorite with Iron Pyrite.jpg|100px]]
|-
|align="center"|5
|[[Apatite]] (Ca<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>(OH-,Cl-,F-)
|align="center"|48
|[[Image:Apatite crystals.jpg|100px]]
|-
|align="center"|6
|[[Orthoclase]] (KAlSi<sub>3</sub>O<sub>8</sub>)
|align="center"|72
|[[Image:Mineraly.sk - ortoklas.jpg|100px]]
|-
|align="center"|7
|[[Quartz]] (SiO<sub>2</sub>)
|align="center"|100
|[[Image:USDA Mineral Quartz Crystal 93c3951.jpg|100px]]
|-
|align="center"|8
|[[Topaz]] (Al<sub>2</sub>SiO<sub>4</sub>(OH-,F-)<sub>2</sub>)
|align="center"|200
|[[Image:Topaz cut.jpg|100px]]
|-
|align="center"|9
|[[Corundum]] (Al<sub>2</sub>O<sub>3</sub>)
|align="center"|400
|[[Image:Cut Ruby.jpg|100px]]
|-
|align="center"|10
|[[Diamond]] (C)
|align="center"|1500
|[[Image:Rough diamond.jpg|100px]]
|}
On the Mohs scale, a pencil lead has a hardness of 1; a [[fingernail]] has hardness 2.5; a copper penny, about 3.5; a knife blade, 5.5; window glass, 5.5; steel [[file (tool)|file]], 6.5.<ref>{{cite web|url= http://www.gemcutters.org/LDA/hardness.htm|date= 1998 |accessdate=2007-08-19 | title= "The Hardness of Minerals and Rocks" by William S. Cordua|work= Lapidary Digest}} Hosted at [http://www.gemcutters.org/ International Lapidary Association]</ref> Using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale.
==Intermediate hardness==
The table below incorporates additional substances that may fall between levels::
{| class="wikitable"
|-
!Hardness
!Substance or Mineral
|-
|align="center"|1
|[[Talc]]
|-
|align="center"|2
|[[Gypsum]]
|-
|align="center"|2.5 to 3
|pure [[gold]], [[silver]], [[aluminium]]
|-
|align="center"|3
|[[Calcite]], [[copper]] [[penny]]
|-
|align="center"|4
|[[Fluorite]]
|-
|align="center"|4 to 4.5
|[[Platinum]]
|-
|align="center"|4 to 5
|[[Iron]]
|-
|align="center"|5
|[[Apatite]]
|-
|align="center"|6
|[[Orthoclase]]
|-
|align="center"|6
|[[Titanium]]
|-
|align="center"|6.5
|[[Iron pyrite]]
|-
|align="center"|6 to 7
|[[Glass]], [[Fused quartz|Vitreous pure silica]]
|-
|align="center"|7
|[[Quartz]]
|-
|align="center"|7 to 7.5
|[[Garnet]]
|-
|align="center"|7 to 8
|[[Hardened steel]]
|-
|align="center"|8
|[[Topaz]]
|-
|align="center"|9
|[[Corundum]]
|-
|align="center"|9 to 9.5
|[[Carborundum]]
|-
|align="center"|<10
|Ultrahard [[fullerite]]
|-
|align="center"|10
|[[Diamond]]
|-
|align="center"|>10
|[[Aggregated diamond nanorods]]
|}
==See also==
*[[hardness]]
*[[Brinell hardness]]
*[[Vickers hardness]]
==References==
{{reflist}}
*American Federation of Mineralogical Societies. [http://www.amfed.org/t_mohs.htm "Mohs Scale of Mineral Hardness"]. Last Revised on [[April 21]], [[2007]]. Retrieved on [[August 19]], [[2007]].
*Cordua, William S. [http://www.gemcutters.org/LDA/hardness.htm "The Hardness of Minerals and Rocks"]. ''Lapidary Digest'', c. 1990.
{{ Mineral identification}}
[[Category:Materials science]]
[[Category:Mineralogy]]
[[Category:Scales]]
[[af:Mohs se hardheidskaal]]
[[ar:مقياس موس]]
[[bg:Скала на Моос]]
[[ca:Duresa Mohs]]
[[cs:Mohsova stupnice tvrdosti]]
[[de:Härte#H.C3.A4rtepr.C3.BCfung_nach_Mohs]]
[[et:Mohsi astmik]]
[[es:Escalas de dureza]]
[[eo:Mohs-skalo]]
[[eu:Mohs eskala]]
[[fr:Échelle de Mohs]]
[[gl:Escala de Mohs]]
[[ko:모스 굳기계]]
[[hr:Mohsova skala]]
[[id:Skala Mohs]]
[[is:Mohs kvarði]]
[[it:Scala di Mohs]]
[[he:סולם מוס]]
[[jv:Skala Mohs]]
[[lv:Mosa skala]]
[[lt:Moso skalė]]
[[hu:Mohs-féle keménységi skála]]
[[mn:Моссын шатлал]]
[[nl:Hardheidsschaal van Mohs]]
[[ja:モース硬度]]
[[no:Mohs skala]]
[[nn:Mohs hardleiksskala]]
[[nds:Mohshard]]
[[pl:Twardość w skali Mohsa]]
[[pt:Escala de Mohs]]
[[ru:Шкала Мооса]]
[[sk:Mohsova stupnica tvrdosti]]
[[sl:Mohsova trdotna lestvica]]
[[sr:Тврдоћа по Мосовој скали]]
[[sh:Tvrdoća po Mosovoj skali]]
[[fi:Mohsin kovuus]]
[[sv:Mohs hårdhetsskala]]
[[th:สเกลของโมส์]]
[[vi:Thang độ cứng Mohs]]
[[uk:Шкала Мооса]]
[[zh:摩氏硬度]]