Mohs hardness

What is the Mohs hardness? Definition and explanation ...

The Mohs hardness is a relative hardness value of minerals and named after the German mineralogist Friedrich Mohs (1773 - 1839). Mohs experimented with the external resistance of minerals. For this purpose, he practically always scored two different minerals against each other, observed which mineral is damaged or remains undamaged and consequently ordered them according to their hardness on a scale. The principle is very simple: If mineral A scratches mineral B, mineral A is harder than B. Mineral B itself can not damage mineral A. Put into practice is an extreme example, for example, the comparison of plaster and diamond. The plaster can not nearly damage the diamond. In contrast, the diamond easily cuts through the plaster. So diamond is harder than plaster.
The Mohs hardness on a Ordinalskala a range of values ​​from 1 to 10. As just mentioned, it is a relative hardness value. A mineral with the Mohs hardness 2 is therefore not twice as hard as a mineral with the Mohs hardness 1. For a better overview in the lower table also the absolute grinding hardness values ​​(after August Rosiwal) are listed, in order to make clear that the actual hardness is not linear with the Mohs hardness increases. Furthermore, the table also lists additional intermediate values ​​(e.g., Mohs hardness 1.5). These can not be found in the original allocation of Mohs, but should do justice to a more precise differentiation of minerals and elements.
An approximate guideline for assessing Mohs hardness:
1 - 2 = soft
3 - 5 = medium
6 - 10 = hard

Table of Mohs hardness with examples:

Mohs hardnessExamplesAbsolute grinding hardness
1talc 0,03
1,5Lead, graphite, tin 0,9
2plaster 1,2
2,5Aluminum, gold, silver 2,5
3calcite 4,5
3,5Iron, platinum, nickel 4,7
4fluorite 5,0
4,5steel 6,0
5Apatite, opal 6,5
5,5Glass 20
6orthoclase 40
6,5Silicon, Opal, Quartz 55
7quartz 120
7,5Emerald, tungsten 155
8topaz 175
8,5chrome 400
9corundum 1000
9,5titanium ???
10diamond 140.000