Moh's Scale Of Hardness

Author: Brian Boyle   Date Posted:27 April 2015 




Mohs Scale Of Hardness

The hardness of any material is defined as its resistance to scratching by other materials. Materials of any particular type  are usually fairly consistant in hardness regardless of the locale where they were found.

MINERAL                       HARDNESS

 Diamond                       10

 Corundum                     9

Topaz                            8

Feldspar (Orthoclase)   6

Apatite                          5

              Opal                              5.5 to 6.5

Flourite                         4

Calcite                          3

Gypsum                       2

Talc                              1

The relative hardness of any mineral, gemstone or rock in their rough state (finished stones would be severly damaged) can be determined by comparitive scratch test to determine its position in Mohs scale.


The following is a list of materials that can be used for testing stones for their hardness.

MATERIAL                     HARDNESS

  Silicon Carbide               9.25

    Steel File                        6 to 7

Window Glass                5.5

Steel Knife Blade            5.5

Fingernail                        2.5