Toward Demystifying the Mohs Hardness Scale

William W. Gerberich, Roberto Ballarini, Eric D. Hintsala, Maneesh Mishra, Jean Francois Molinari, Izabela Szlufarska

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Today, the Mohs scale is used profusely throughout educational systems without any persuasive understanding of the fundamental principles. Why one mineral has a scratch hardness over the next culminating in a scale of 1 (chalk) to 10 (diamond) has no atomistic or structure-sensitive basis that explains this outcome. With modern computationally based atomistic and multiscale models, there is increasing promise of defining the pressure and rate-dependent parameters that will allow a fundamental understanding of the Mohs scale. This study principally addresses the combined fracture and plasticity parameters that qualitatively affect fracture at the nanoscale. A physical model wherein the crack tip under a scratch is shielded by dislocations is supported by molecular dynamics (MD) simulations in both ductile aluminum and brittle silicon carbide. Next, this model is applied to nanoindentation data from the literature to produce a ranking of Mohs minerals based on their fundamental properties. As such, what is presented here is a first step to address the flow and fracture parameters ultimately required to provide a figure of merit for scratch hardness and thus the Mohs scale.

Original languageEnglish (US)
Pages (from-to)2681-2688
Number of pages8
JournalJournal of the American Ceramic Society
Issue number9
StatePublished - Sep 1 2015

Bibliographical note

Publisher Copyright:
© 2015 The American Ceramic Society.


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