- A hardness scale from 1 to 10, based on ten commonly occurring minerals. It is utilized to determine if one substance can scratch another. Talc is a 1 on the scale, quartz is a 7, corundum a 9, diamond is a 10, to name a few. Any material with a higher number can scratch that with a lower number, so diamond can scratch quartz, but quartz can not scratch diamond. Other materials may have values between the reference minerals. Also called Mohs hardness scale.