Mohs scale

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

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.[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]

  1. ^ a b von Groth, Paul Heinrich (1926). Entwicklungsgeschichte der Mineralogischen Wissenschaften [History of the development of the mineralogical sciences] (in German). Berlin: Springer. p. 250. ISBN 9783662409107.
  2. ^ "Mohs hardness". Encyclopædia Britannica (online ed.).
  3. ^ "Mohs scale of hardness". Mineralogical Society of America. Retrieved 10 February 2021.
  4. ^ Theophrastus. Theophrastus on Stones. Retrieved 10 December 2011 – via Farlang.com.
  5. ^ Pliny the Elder. "Book 37, Chap. 15". Naturalis Historia. Adamas: Six varieties of it. Two remedies.
  6. ^ Pliny the Elder. "Book 37, Chap. 76". Naturalis Historia. The methods of testing precious stones.
  7. ^ "Hardness". Materials Mechanical Hardness. Non-Destructive Testing Resource Center. Archived from the original on 14 February 2014.


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