Mohs scale

The scale was introduced in 1812 by the German geologist and mineralogist Friedrich Mohs, in his book Versuch einer Elementar-Methode zur naturhistorischen Bestimmung und Erkennung der Fossilien (English: Attempt at an elementary method for the natural-historical determination and recognition of fossils);[1][2][a] it is one of several definitions of hardness in materials science, some of which are more quantitative.

[3] The method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise On Stones, c. 300 BC, followed by Pliny the Elder in his Naturalis Historia, c. AD 77.

[8] Technically, "scratching" a material for the purposes of the Mohs scale means creating non-elastic dislocations visible to the naked eye.

While these microscopic dislocations are permanent and sometimes detrimental to the harder material's structural integrity, they are not considered "scratches" for the determination of a Mohs scale number.

[citation needed] The table below shows the comparison with the absolute hardness measured by a sclerometer, with images of the reference minerals in the rightmost column.