Mohs' Scale of Hardness

Mohs' scale of hardness is a scale of grading materials based on their hardness.  It is based on the ability of one material to scratch another material.  The scale was developed by the German geologist, Friedrich Mohs.

The scale is from 1 to 10, 1 being the hardest and 10, the softest. Talc, a soft mineral used for making powders, is at scale 10.  All minerals will be able to scratch talc.  Talc cannot scratch any other mineral.  Diamond, being the hardest mineral, is at position 1.  Diamond can scratch all materials.  No mineral will be able to scratch diamond.

To find the Mohs' value for an unknown mineral, the mineral is used to scratch a mineral of known value, say glass.  It is able to scratch glasss, its value is more than that of the glass, which is 5.  The mineral can be made to scratch minerals upper in the ranking.  The Mohs' value can thus be found.