Mohs hardness


Mohs hardness
Rough measure of the resistance of a smooth surface to scratching or abrasion, expressed in terms of a scale devised by German mineralogist Friedrich Mohs in 1812.

Minerals are ranked in comparison with the Mohs scale, which is made up of 10 minerals that have been given arbitrary hardness values on a scale from 1 (least hard, or talc) to 10 (hardest, or diamond).

* * *

      rough measure of the resistance of a smooth surface to scratching or abrasion, expressed in terms of a scale devised (1812) by the German mineralogist Friedrich Mohs. The Mohs hardness of a mineral is determined by observing whether its surface is scratched by a substance of known or defined hardness.

       Mohs hardness scale and observations on hardness of some additional materialsTo give numerical values to this physical property, minerals are ranked along the Mohs scale, which is composed of 10 minerals that have been given arbitrary hardness values. The minerals contained in the scale are shown in the Table (Mohs hardness scale and observations on hardness of some additional materials); also shown are other materials that approximate the hardness of some of the minerals. As is indicated by the ranking in the scale, if a mineral is scratched by orthoclase but not by apatite, its Mohs hardness is between 5 and 6. In the determination procedure it is necessary to be certain that a scratch is actually made and not just a “chalk” mark that will rub off. If the species being tested is fine-grained, friable, or pulverulent, the test may only loosen grains without testing individual mineral surfaces; thus certain textures or aggregate forms may hinder or prevent a true hardness determination. For this reason the Mohs test, while greatly facilitating the identification of minerals in the field, is not suitable for accurately gauging the hardness of industrial materials such as steel or ceramics. (For these materials a more precise measure is to be found in the Vickers hardness or Knoop hardness; qq.v.) Another disadvantage of the Mohs scale is that it is not linear; that is, each increment of one in the scale does not indicate a proportional increase in hardness. For instance, the progression from calcite to fluorite (from 3 to 4 on the Mohs scale) reflects an increase in hardness of approximately 25 percent; the progression from corundum to diamond, on the other hand (9 to 10 on the Mohs scale), reflects a hardness increase of more than 300 percent.

* * *


Universalium. 2010.

Look at other dictionaries:

  • Mohs hardness — Mohs hardness. См. Твердость по Моосу. (Источник: «Металлы и сплавы. Справочник.» Под редакцией Ю.П. Солнцева; НПО Профессионал , НПО Мир и семья ; Санкт Петербург, 2003 г.) …   Словарь металлургических терминов

  • Mohs hardness scale and observations on hardness of some additional materials — ▪ Table Mohs hardness scale and observations on hardness of some additional materials mineral Mohs hardness other materials observations on the minerals talc   1 very easily scratched by the fingernail; has a greasy feel gypsum   2 Mohs hardness… …   Universalium

  • Mohs hardness scale — Moso skalė statusas T sritis Standartizacija ir metrologija apibrėžtis Mineralų kietumo skalė, kurią sudaro 10 kietumo etalonų, pvz., talko kietumas – 1, deimanto – 10. atitikmenys: angl. Mohs hardness scale; Mohs scale vok. Härteskala nach Mohs …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • Mohs hardness scale —    a 1 10 scale for estimating the hardness of a mineral, introduced by the German geologist Friedrich Mohs (1773 1839) in 1812. To apply the scale, one attempts to scratch the mineral with standard minerals assigned hardness numbers as follows:… …   Dictionary of units of measurement

  • Mohs scale of mineral hardness — 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 geologist and mineralogist Friedrich Mohs and… …   Wikipedia

  • hardness — /hahrd nis/, n. 1. the state or quality of being hard: the hardness of ice. 2. a relative degree or extent of this quality: wood of a desirable hardness. 3. that quality in water that is imparted by the presence of dissolved salts, esp. calcium… …   Universalium

  • Hardness of prominent abrasive materials — ▪ Table Hardness of prominent abrasive materials abrasive materials hardness Mohs scale (Mohs hardness) Vickers scale (Vickers hardness) Knoop scale (Knoop hardness) Natural abrasives industrial diamond 10 10,000 8,000 corundum 9 2,200 1,600… …   Universalium

  • hardness tester — ▪ device       device that indicates the hardness of a material, usually by measuring the effect on its surface of a localized penetration by a standardized rounded or pointed indenter of diamond, carbide, or hard steel.       Brinell hardness is …   Universalium

  • Mohs scale — Moso skalė statusas T sritis Standartizacija ir metrologija apibrėžtis Mineralų kietumo skalė, kurią sudaro 10 kietumo etalonų, pvz., talko kietumas – 1, deimanto – 10. atitikmenys: angl. Mohs hardness scale; Mohs scale vok. Härteskala nach Mohs …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • Mohs-Härtskala — Moso skalė statusas T sritis Standartizacija ir metrologija apibrėžtis Mineralų kietumo skalė, kurią sudaro 10 kietumo etalonų, pvz., talko kietumas – 1, deimanto – 10. atitikmenys: angl. Mohs hardness scale; Mohs scale vok. Härteskala nach Mohs …   Penkiakalbis aiškinamasis metrologijos terminų žodynas


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.