Mohs's Hardness Scale - A Physical Interpretation

The Mohs hardness scale consists of ten minerals arranged in increasing order of hardness such that each mineral will scratch the one on the scale below it, but will not scratch the one above it. Although these minerals are generally considered to be brittle, experiments show that under local indentation and during sliding their behaviour is primarily determined by the plastic properties of the minerals. This suggests that there should be some relation between the Mohs hardness and the indentation hardness of the minerals.