Editing Structural geology (section)

===Hardness===
Hardness is difficult to quantify. It is a measure of resistance to deformation, specifically permanent deformation. There is precedent for hardness as a surface quality, a measure of the abrasiveness or surface-scratching resistance of a material. If the material being tested, however, is uniform in composition and structure, then the surface of the material is only a few atomic layers thick, and measurements are of the bulk material. Thus, simple surface measurements yield information about the bulk properties. Ways to measure hardness include:

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* [[Mohs Scale]]
* [[Dorry abrasion test]]
* [[Deval abrasion test]]
* [[Indentation hardness]]
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Indentation hardness is used often in metallurgy and materials science and can be thought of as resistance to penetration by an indenter.