Hardness

Commonly, hardness refers to the resistance of the substance to surface abrasion. The harder of two substances will scratch the other, as diamond scratches glass. The well-known Mohs Scale of Hardness for minerals exemplifies this property. In metallurgy and engineering, hardness is determined by methods based on resistance to penetration by an indenter harder than the material being tested. In studying historical metals, the Vickers scale is often used.