Mohs scale

Qualitative scale characterizing scratch resistance / From Wikipedia, the free encyclopedia

The Mohs scale of mineral hardness (/mz/) is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of minerals through the ability of harder material to scratch softer material.

Open wooden box with ten compartments, each containing a numbered mineral specimen.
Mohs hardness kit, containing one specimen of each mineral on the ten-point hardness 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";[1][2] 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.[4][5][6] The Mohs scale is useful for identification of minerals in the field, but is not an accurate predictor of how well materials endure in an industrial setting.[7]

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