Mohs Hardness Scale

The Mohs scale ranks minerals based upon hardness. Hardness is ranked on a scale from 1 to 10, an example of 1 being talc (like the powder) and 10 being diamond.

German mineralogist Friedrich Mohs introduced the scale to identify minerals using a simple field test. It is easy to administer, minerals higher on the Mohs scale are harder and will scratch softer, lower-ranked ones.

The Mohs hardness scale is how Professor Riordan likes to arrange his rock collection, and the Clypeate carefully reproduces this arrangement in his Willard hotel suite.

Mohs testing kit with sample rocks of different Mohs score