Hardness

Hardness, measure of the resistance of a substance to being scratched by another substance. Resistance to scratching is measured on a scale named for Friedrich Mohs (1773–1839), who chose 10 minerals as reference points, ranging from talc (hardness 1) to diamond (10). A modified Mohs scale is now usually used, with 5 additional reference points. Resistance to indentation is also measured by other scales as well, such as the Brinell, Rockwell, and Vickers scales.